[mcs] Resolve nullable expression before unwrapping. Fixes #32054

[mono.git] / mcs / mcs / expression.cs

//
// expression.cs: Expression representation for the IL tree.
//
// Author:
//   Miguel de Icaza (miguel@ximian.com)
//   Marek Safar (marek.safar@gmail.com)
//
// Copyright 2001, 2002, 2003 Ximian, Inc.
// Copyright 2003-2008 Novell, Inc.
// Copyright 2011 Xamarin Inc.
//

using System;
using System.Collections.Generic;
using System.Linq;
using SLE = System.Linq.Expressions;
using System.Text;

#if STATIC
using MetaType = IKVM.Reflection.Type;
using IKVM.Reflection;
using IKVM.Reflection.Emit;
#else
using MetaType = System.Type;
using System.Reflection;
using System.Reflection.Emit;
#endif

namespace Mono.CSharp
{
        //
        // This is an user operator expression, automatically created during
        // resolve phase
        //
        public class UserOperatorCall : Expression {
                protected readonly Arguments arguments;
                protected readonly MethodSpec oper;
                readonly Func<ResolveContext, Expression, Expression> expr_tree;

                public UserOperatorCall (MethodSpec oper, Arguments args, Func<ResolveContext, Expression, Expression> expr_tree, Location loc)
                {
                        this.oper = oper;
                        this.arguments = args;
                        this.expr_tree = expr_tree;

                        type = oper.ReturnType;
                        eclass = ExprClass.Value;
                        this.loc = loc;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return arguments.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        if (expr_tree != null)
                                return expr_tree (ec, new TypeOfMethod (oper, loc));

                        Arguments args = Arguments.CreateForExpressionTree (ec, arguments,
                                new NullLiteral (loc),
                                new TypeOfMethod (oper, loc));

                        return CreateExpressionFactoryCall (ec, "Call", args);
                }

                protected override void CloneTo (CloneContext context, Expression target)
                {
                        // Nothing to clone
                }
                
                protected override Expression DoResolve (ResolveContext ec)
                {
                        //
                        // We are born fully resolved
                        //
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        var call = new CallEmitter ();
                        call.Emit (ec, oper, arguments, loc);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        arguments.FlowAnalysis (fc);
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
#if STATIC
                        return base.MakeExpression (ctx);
#else
                        return SLE.Expression.Call ((MethodInfo) oper.GetMetaInfo (), Arguments.MakeExpression (arguments, ctx));
#endif
                }
        }

        public class ParenthesizedExpression : ShimExpression
        {
                public ParenthesizedExpression (Expression expr, Location loc)
                        : base (expr)
                {
                        this.loc = loc;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        var res = expr.Resolve (ec);
                        var constant = res as Constant;
                        if (constant != null && constant.IsLiteral)
                                return Constant.CreateConstantFromValue (res.Type, constant.GetValue (), expr.Location);

                        return res;
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
                {
                        return expr.DoResolveLValue (ec, right_side);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }

                public override bool HasConditionalAccess ()
                {
                        return expr.HasConditionalAccess ();
                }
        }
        
        //
        //   Unary implements unary expressions.
        //
        public class Unary : Expression
        {
                public enum Operator : byte {
                        UnaryPlus, UnaryNegation, LogicalNot, OnesComplement,
                        AddressOf,  TOP
                }

                public readonly Operator Oper;
                public Expression Expr;
                ConvCast.Mode enum_conversion;

                public Unary (Operator op, Expression expr, Location loc)
                {
                        Oper = op;
                        Expr = expr;
                        this.loc = loc;
                }

                // <summary>
                //   This routine will attempt to simplify the unary expression when the
                //   argument is a constant.
                // </summary>
                Constant TryReduceConstant (ResolveContext ec, Constant constant)
                {
                        var e = constant;

                        while (e is EmptyConstantCast)
                                e = ((EmptyConstantCast) e).child;
                        
                        if (e is SideEffectConstant) {
                                Constant r = TryReduceConstant (ec, ((SideEffectConstant) e).value);
                                return r == null ? null : new SideEffectConstant (r, e, r.Location);
                        }

                        TypeSpec expr_type = e.Type;
                        
                        switch (Oper){
                        case Operator.UnaryPlus:
                                // Unary numeric promotions
                                switch (expr_type.BuiltinType) {
                                case BuiltinTypeSpec.Type.Byte:
                                        return new IntConstant (ec.BuiltinTypes, ((ByteConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.SByte:
                                        return new IntConstant (ec.BuiltinTypes, ((SByteConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.Short:
                                        return new IntConstant (ec.BuiltinTypes, ((ShortConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.UShort:
                                        return new IntConstant (ec.BuiltinTypes, ((UShortConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.Char:
                                        return new IntConstant (ec.BuiltinTypes, ((CharConstant) e).Value, e.Location);
                                
                                // Predefined operators
                                case BuiltinTypeSpec.Type.Int:
                                case BuiltinTypeSpec.Type.UInt:
                                case BuiltinTypeSpec.Type.Long:
                                case BuiltinTypeSpec.Type.ULong:
                                case BuiltinTypeSpec.Type.Float:
                                case BuiltinTypeSpec.Type.Double:
                                case BuiltinTypeSpec.Type.Decimal:
                                        return e;
                                }
                                
                                return null;
                                
                        case Operator.UnaryNegation:
                                // Unary numeric promotions
                                switch (expr_type.BuiltinType) {
                                case BuiltinTypeSpec.Type.Byte:
                                        return new IntConstant (ec.BuiltinTypes, -((ByteConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.SByte:
                                        return new IntConstant (ec.BuiltinTypes, -((SByteConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.Short:
                                        return new IntConstant (ec.BuiltinTypes, -((ShortConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.UShort:
                                        return new IntConstant (ec.BuiltinTypes, -((UShortConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.Char:
                                        return new IntConstant (ec.BuiltinTypes, -((CharConstant) e).Value, e.Location);

                                // Predefined operators
                                case BuiltinTypeSpec.Type.Int:
                                        int ivalue = ((IntConstant) e).Value;
                                        if (ivalue == int.MinValue) {
                                                if (ec.ConstantCheckState) {
                                                        ConstantFold.Error_CompileTimeOverflow (ec, loc);
                                                        return null;
                                                }
                                                return e;
                                        }
                                        return new IntConstant (ec.BuiltinTypes, -ivalue, e.Location);

                                case BuiltinTypeSpec.Type.Long:
                                        long lvalue = ((LongConstant) e).Value;
                                        if (lvalue == long.MinValue) {
                                                if (ec.ConstantCheckState) {
                                                        ConstantFold.Error_CompileTimeOverflow (ec, loc);
                                                        return null;
                                                }
                                                return e;
                                        }
                                        return new LongConstant (ec.BuiltinTypes, -lvalue, e.Location);

                                case BuiltinTypeSpec.Type.UInt:
                                        UIntLiteral uil = constant as UIntLiteral;
                                        if (uil != null) {
                                                if (uil.Value == int.MaxValue + (uint) 1)
                                                        return new IntLiteral (ec.BuiltinTypes, int.MinValue, e.Location);
                                                return new LongLiteral (ec.BuiltinTypes, -uil.Value, e.Location);
                                        }
                                        return new LongConstant (ec.BuiltinTypes, -((UIntConstant) e).Value, e.Location);


                                case BuiltinTypeSpec.Type.ULong:
                                        ULongLiteral ull = constant as ULongLiteral;
                                        if (ull != null && ull.Value == 9223372036854775808)
                                                return new LongLiteral (ec.BuiltinTypes, long.MinValue, e.Location);
                                        return null;

                                case BuiltinTypeSpec.Type.Float:
                                        FloatLiteral fl = constant as FloatLiteral;
                                        // For better error reporting
                                        if (fl != null)
                                                return new FloatLiteral (ec.BuiltinTypes, -fl.Value, e.Location);

                                        return new FloatConstant (ec.BuiltinTypes, -((FloatConstant) e).Value, e.Location);

                                case BuiltinTypeSpec.Type.Double:
                                        DoubleLiteral dl = constant as DoubleLiteral;
                                        // For better error reporting
                                        if (dl != null)
                                                return new DoubleLiteral (ec.BuiltinTypes, -dl.Value, e.Location);

                                        return new DoubleConstant (ec.BuiltinTypes, -((DoubleConstant) e).Value, e.Location);

                                case BuiltinTypeSpec.Type.Decimal:
                                        return new DecimalConstant (ec.BuiltinTypes, -((DecimalConstant) e).Value, e.Location);
                                }

                                return null;
                                
                        case Operator.LogicalNot:
                                if (expr_type.BuiltinType != BuiltinTypeSpec.Type.Bool)
                                        return null;
                                
                                bool b = (bool)e.GetValue ();
                                return new BoolConstant (ec.BuiltinTypes, !b, e.Location);
                                
                        case Operator.OnesComplement:
                                // Unary numeric promotions
                                switch (expr_type.BuiltinType) {
                                case BuiltinTypeSpec.Type.Byte:
                                        return new IntConstant (ec.BuiltinTypes, ~((ByteConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.SByte:
                                        return new IntConstant (ec.BuiltinTypes, ~((SByteConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.Short:
                                        return new IntConstant (ec.BuiltinTypes, ~((ShortConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.UShort:
                                        return new IntConstant (ec.BuiltinTypes, ~((UShortConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.Char:
                                        return new IntConstant (ec.BuiltinTypes, ~((CharConstant) e).Value, e.Location);
                                
                                // Predefined operators
                                case BuiltinTypeSpec.Type.Int:
                                        return new IntConstant (ec.BuiltinTypes, ~((IntConstant)e).Value, e.Location);
                                case BuiltinTypeSpec.Type.UInt:
                                        return new UIntConstant (ec.BuiltinTypes, ~((UIntConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.Long:
                                        return new LongConstant (ec.BuiltinTypes, ~((LongConstant) e).Value, e.Location);
                                case BuiltinTypeSpec.Type.ULong:
                                        return new ULongConstant (ec.BuiltinTypes, ~((ULongConstant) e).Value, e.Location);
                                }
                                if (e is EnumConstant) {
                                        var res = TryReduceConstant (ec, ((EnumConstant)e).Child);
                                        if (res != null) {
                                                //
                                                // Numeric promotion upgraded types to int but for enum constant
                                                // original underlying constant type is needed
                                                //
                                                if (res.Type.BuiltinType == BuiltinTypeSpec.Type.Int) {
                                                        int v = ((IntConstant) res).Value;
                                                        switch (((EnumConstant) e).Child.Type.BuiltinType) {
                                                                case BuiltinTypeSpec.Type.UShort:
                                                                res = new UShortConstant (ec.BuiltinTypes, (ushort) v, e.Location);
                                                                break;
                                                                case BuiltinTypeSpec.Type.Short:
                                                                res = new ShortConstant (ec.BuiltinTypes, (short) v, e.Location);
                                                                break;
                                                                case BuiltinTypeSpec.Type.Byte:
                                                                res = new ByteConstant (ec.BuiltinTypes, (byte) v, e.Location);
                                                                break;
                                                                case BuiltinTypeSpec.Type.SByte:
                                                                res = new SByteConstant (ec.BuiltinTypes, (sbyte) v, e.Location);
                                                                break;
                                                        }
                                                }

                                                res = new EnumConstant (res, expr_type);
                                        }
                                        return res;
                                }
                                return null;
                        }
                        throw new Exception ("Can not constant fold: " + Oper.ToString());
                }
                
                protected virtual Expression ResolveOperator (ResolveContext ec, Expression expr)
                {
                        eclass = ExprClass.Value;

                        TypeSpec expr_type = expr.Type;
                        Expression best_expr;

                        TypeSpec[] predefined = ec.BuiltinTypes.OperatorsUnary [(int) Oper];

                        //
                        // Primitive types first
                        //
                        if (BuiltinTypeSpec.IsPrimitiveType (expr_type)) {
                                best_expr = ResolvePrimitivePredefinedType (ec, expr, predefined);
                                if (best_expr == null)
                                        return null;

                                type = best_expr.Type;
                                Expr = best_expr;
                                return this;
                        }

                        //
                        // E operator ~(E x);
                        //
                        if (Oper == Operator.OnesComplement && expr_type.IsEnum)
                                return ResolveEnumOperator (ec, expr, predefined);

                        return ResolveUserType (ec, expr, predefined);
                }

                protected virtual Expression ResolveEnumOperator (ResolveContext ec, Expression expr, TypeSpec[] predefined)
                {
                        TypeSpec underlying_type = EnumSpec.GetUnderlyingType (expr.Type);
                        Expression best_expr = ResolvePrimitivePredefinedType (ec, EmptyCast.Create (expr, underlying_type), predefined);
                        if (best_expr == null)
                                return null;

                        Expr = best_expr;
                        enum_conversion = Binary.GetEnumResultCast (underlying_type);
                        type = expr.Type;
                        return EmptyCast.Create (this, type);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return Expr.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        return CreateExpressionTree (ec, null);
                }

                Expression CreateExpressionTree (ResolveContext ec, Expression user_op)
                {
                        string method_name;
                        switch (Oper) {
                        case Operator.AddressOf:
                                Error_PointerInsideExpressionTree (ec);
                                return null;
                        case Operator.UnaryNegation:
                                if (ec.HasSet (ResolveContext.Options.CheckedScope) && user_op == null && !IsFloat (type))
                                        method_name = "NegateChecked";
                                else
                                        method_name = "Negate";
                                break;
                        case Operator.OnesComplement:
                        case Operator.LogicalNot:
                                method_name = "Not";
                                break;
                        case Operator.UnaryPlus:
                                method_name = "UnaryPlus";
                                break;
                        default:
                                throw new InternalErrorException ("Unknown unary operator " + Oper.ToString ());
                        }

                        Arguments args = new Arguments (2);
                        args.Add (new Argument (Expr.CreateExpressionTree (ec)));
                        if (user_op != null)
                                args.Add (new Argument (user_op));

                        return CreateExpressionFactoryCall (ec, method_name, args);
                }

                public static TypeSpec[][] CreatePredefinedOperatorsTable (BuiltinTypes types)
                {
                        var predefined_operators = new TypeSpec[(int) Operator.TOP][];

                        //
                        // 7.6.1 Unary plus operator
                        //
                        predefined_operators [(int) Operator.UnaryPlus] = new TypeSpec [] {
                                types.Int, types.UInt,
                                types.Long, types.ULong,
                                types.Float, types.Double,
                                types.Decimal
                        };

                        //
                        // 7.6.2 Unary minus operator
                        //
                        predefined_operators [(int) Operator.UnaryNegation] = new TypeSpec [] {
                                types.Int,  types.Long,
                                types.Float, types.Double,
                                types.Decimal
                        };

                        //
                        // 7.6.3 Logical negation operator
                        //
                        predefined_operators [(int) Operator.LogicalNot] = new TypeSpec [] {
                                types.Bool
                        };

                        //
                        // 7.6.4 Bitwise complement operator
                        //
                        predefined_operators [(int) Operator.OnesComplement] = new TypeSpec [] {
                                types.Int, types.UInt,
                                types.Long, types.ULong
                        };

                        return predefined_operators;
                }

                //
                // Unary numeric promotions
                //
                static Expression DoNumericPromotion (ResolveContext rc, Operator op, Expression expr)
                {
                        TypeSpec expr_type = expr.Type;
                        if (op == Operator.UnaryPlus || op == Operator.UnaryNegation || op == Operator.OnesComplement) {
                                switch (expr_type.BuiltinType) {
                                case BuiltinTypeSpec.Type.Byte:
                                case BuiltinTypeSpec.Type.SByte:
                                case BuiltinTypeSpec.Type.Short:
                                case BuiltinTypeSpec.Type.UShort:
                                case BuiltinTypeSpec.Type.Char:
                                        return Convert.ImplicitNumericConversion (expr, rc.BuiltinTypes.Int);
                                }
                        }

                        if (op == Operator.UnaryNegation && expr_type.BuiltinType == BuiltinTypeSpec.Type.UInt)
                                return Convert.ImplicitNumericConversion (expr, rc.BuiltinTypes.Long);

                        return expr;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (Oper == Operator.AddressOf) {
                                return ResolveAddressOf (ec);
                        }

                        Expr = Expr.Resolve (ec);
                        if (Expr == null)
                                return null;

                        if (Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                Arguments args = new Arguments (1);
                                args.Add (new Argument (Expr));
                                return new DynamicUnaryConversion (GetOperatorExpressionTypeName (), args, loc).Resolve (ec);
                        }

                        if (Expr.Type.IsNullableType)
                                return new Nullable.LiftedUnaryOperator (Oper, Expr, loc).Resolve (ec);

                        //
                        // Attempt to use a constant folding operation.
                        //
                        Constant cexpr = Expr as Constant;
                        if (cexpr != null) {
                                cexpr = TryReduceConstant (ec, cexpr);
                                if (cexpr != null)
                                        return cexpr;
                        }

                        Expression expr = ResolveOperator (ec, Expr);
                        if (expr == null)
                                Error_OperatorCannotBeApplied (ec, loc, OperName (Oper), Expr.Type);
                        
                        //
                        // Reduce unary operator on predefined types
                        //
                        if (expr == this && Oper == Operator.UnaryPlus)
                                return Expr;

                        return expr;
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression right)
                {
                        return null;
                }

                public override void Emit (EmitContext ec)
                {
                        EmitOperator (ec, type);
                }

                protected void EmitOperator (EmitContext ec, TypeSpec type)
                {
                        switch (Oper) {
                        case Operator.UnaryPlus:
                                Expr.Emit (ec);
                                break;
                                
                        case Operator.UnaryNegation:
                                if (ec.HasSet (EmitContext.Options.CheckedScope) && !IsFloat (type)) {
                                        if (ec.HasSet (BuilderContext.Options.AsyncBody) && Expr.ContainsEmitWithAwait ())
                                                Expr = Expr.EmitToField (ec);

                                        ec.EmitInt (0);
                                        if (type.BuiltinType == BuiltinTypeSpec.Type.Long)
                                                ec.Emit (OpCodes.Conv_U8);
                                        Expr.Emit (ec);
                                        ec.Emit (OpCodes.Sub_Ovf);
                                } else {
                                        Expr.Emit (ec);
                                        ec.Emit (OpCodes.Neg);
                                }
                                
                                break;
                                
                        case Operator.LogicalNot:
                                Expr.Emit (ec);
                                ec.EmitInt (0);
                                ec.Emit (OpCodes.Ceq);
                                break;
                                
                        case Operator.OnesComplement:
                                Expr.Emit (ec);
                                ec.Emit (OpCodes.Not);
                                break;
                                
                        case Operator.AddressOf:
                                ((IMemoryLocation)Expr).AddressOf (ec, AddressOp.LoadStore);
                                break;
                                
                        default:
                                throw new Exception ("This should not happen: Operator = "
                                                     + Oper.ToString ());
                        }

                        //
                        // Same trick as in Binary expression
                        //
                        if (enum_conversion != 0) {
                                using (ec.With (BuilderContext.Options.CheckedScope, false)) {
                                        ConvCast.Emit (ec, enum_conversion);
                                }
                        }
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        if (Oper == Operator.LogicalNot)
                                Expr.EmitBranchable (ec, target, !on_true);
                        else
                                base.EmitBranchable (ec, target, on_true);
                }

                public override void EmitSideEffect (EmitContext ec)
                {
                        Expr.EmitSideEffect (ec);
                }

                public static void Error_Ambiguous (ResolveContext rc, string oper, TypeSpec type, Location loc)
                {
                        rc.Report.Error (35, loc, "Operator `{0}' is ambiguous on an operand of type `{1}'",
                                oper, type.GetSignatureForError ());
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        FlowAnalysis (fc, false);
                }

                public override void FlowAnalysisConditional (FlowAnalysisContext fc)
                {
                        FlowAnalysis (fc, true);
                }

                void FlowAnalysis (FlowAnalysisContext fc, bool conditional)
                {
                        if (Oper == Operator.AddressOf) {
                                var vr = Expr as VariableReference;
                                if (vr != null && vr.VariableInfo != null)
                                        fc.SetVariableAssigned (vr.VariableInfo);

                                return;
                        }

                        if (Oper == Operator.LogicalNot && conditional) {
                                Expr.FlowAnalysisConditional (fc);

                                var temp = fc.DefiniteAssignmentOnTrue;
                                fc.DefiniteAssignmentOnTrue = fc.DefiniteAssignmentOnFalse;
                                fc.DefiniteAssignmentOnFalse = temp;
                        } else {
                                Expr.FlowAnalysis (fc);
                        }
                }

                //
                // Converts operator to System.Linq.Expressions.ExpressionType enum name
                //
                string GetOperatorExpressionTypeName ()
                {
                        switch (Oper) {
                        case Operator.OnesComplement:
                                return "OnesComplement";
                        case Operator.LogicalNot:
                                return "Not";
                        case Operator.UnaryNegation:
                                return "Negate";
                        case Operator.UnaryPlus:
                                return "UnaryPlus";
                        default:
                                throw new NotImplementedException ("Unknown express type operator " + Oper.ToString ());
                        }
                }

                static bool IsFloat (TypeSpec t)
                {
                        return t.BuiltinType == BuiltinTypeSpec.Type.Double || t.BuiltinType == BuiltinTypeSpec.Type.Float;
                }

                //
                // Returns a stringified representation of the Operator
                //
                public static string OperName (Operator oper)
                {
                        switch (oper) {
                        case Operator.UnaryPlus:
                                return "+";
                        case Operator.UnaryNegation:
                                return "-";
                        case Operator.LogicalNot:
                                return "!";
                        case Operator.OnesComplement:
                                return "~";
                        case Operator.AddressOf:
                                return "&";
                        }

                        throw new NotImplementedException (oper.ToString ());
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        var expr = Expr.MakeExpression (ctx);
                        bool is_checked = ctx.HasSet (BuilderContext.Options.CheckedScope);

                        switch (Oper) {
                        case Operator.UnaryNegation:
                                return is_checked ? SLE.Expression.NegateChecked (expr) : SLE.Expression.Negate (expr);
                        case Operator.LogicalNot:
                                return SLE.Expression.Not (expr);
                        case Operator.OnesComplement:
                                return SLE.Expression.OnesComplement (expr);
                        default:
                                throw new NotImplementedException (Oper.ToString ());
                        }
                }

                Expression ResolveAddressOf (ResolveContext ec)
                {
                        if (!ec.IsUnsafe)
                                UnsafeError (ec, loc);

                        Expr = Expr.DoResolveLValue (ec, EmptyExpression.UnaryAddress);
                        if (Expr == null || Expr.eclass != ExprClass.Variable) {
                                ec.Report.Error (211, loc, "Cannot take the address of the given expression");
                                return null;
                        }

                        if (!TypeManager.VerifyUnmanaged (ec.Module, Expr.Type, loc)) {
                                return null;
                        }

                        IVariableReference vr = Expr as IVariableReference;
                        bool is_fixed;
                        if (vr != null) {
                                is_fixed = vr.IsFixed;
                                vr.SetHasAddressTaken ();

                                if (vr.IsHoisted) {
                                        AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, vr, loc);
                                }
                        } else {
                                IFixedExpression fe = Expr as IFixedExpression;
                                is_fixed = fe != null && fe.IsFixed;
                        }

                        if (!is_fixed && !ec.HasSet (ResolveContext.Options.FixedInitializerScope)) {
                                ec.Report.Error (212, loc, "You can only take the address of unfixed expression inside of a fixed statement initializer");
                        }

                        type = PointerContainer.MakeType (ec.Module, Expr.Type);
                        eclass = ExprClass.Value;
                        return this;
                }

                Expression ResolvePrimitivePredefinedType (ResolveContext rc, Expression expr, TypeSpec[] predefined)
                {
                        expr = DoNumericPromotion (rc, Oper, expr);
                        TypeSpec expr_type = expr.Type;
                        foreach (TypeSpec t in predefined) {
                                if (t == expr_type)
                                        return expr;
                        }
                        return null;
                }

                //
                // Perform user-operator overload resolution
                //
                protected virtual Expression ResolveUserOperator (ResolveContext ec, Expression expr)
                {
                        CSharp.Operator.OpType op_type;
                        switch (Oper) {
                        case Operator.LogicalNot:
                                op_type = CSharp.Operator.OpType.LogicalNot; break;
                        case Operator.OnesComplement:
                                op_type = CSharp.Operator.OpType.OnesComplement; break;
                        case Operator.UnaryNegation:
                                op_type = CSharp.Operator.OpType.UnaryNegation; break;
                        case Operator.UnaryPlus:
                                op_type = CSharp.Operator.OpType.UnaryPlus; break;
                        default:
                                throw new InternalErrorException (Oper.ToString ());
                        }

                        var methods = MemberCache.GetUserOperator (expr.Type, op_type, false);
                        if (methods == null)
                                return null;

                        Arguments args = new Arguments (1);
                        args.Add (new Argument (expr));

                        var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
                        var oper = res.ResolveOperator (ec, ref args);

                        if (oper == null)
                                return null;

                        Expr = args [0].Expr;
                        return new UserOperatorCall (oper, args, CreateExpressionTree, expr.Location);
                }

                //
                // Unary user type overload resolution
                //
                Expression ResolveUserType (ResolveContext ec, Expression expr, TypeSpec[] predefined)
                {
                        Expression best_expr = ResolveUserOperator (ec, expr);
                        if (best_expr != null)
                                return best_expr;

                        foreach (TypeSpec t in predefined) {
                                Expression oper_expr = Convert.ImplicitUserConversion (ec, expr, t, expr.Location);
                                if (oper_expr == null)
                                        continue;

                                if (oper_expr == ErrorExpression.Instance)
                                        return oper_expr;

                                //
                                // decimal type is predefined but has user-operators
                                //
                                if (oper_expr.Type.BuiltinType == BuiltinTypeSpec.Type.Decimal)
                                        oper_expr = ResolveUserType (ec, oper_expr, predefined);
                                else
                                        oper_expr = ResolvePrimitivePredefinedType (ec, oper_expr, predefined);

                                if (oper_expr == null)
                                        continue;

                                if (best_expr == null) {
                                        best_expr = oper_expr;
                                        continue;
                                }

                                int result = OverloadResolver.BetterTypeConversion (ec, best_expr.Type, t);
                                if (result == 0) {
                                        if ((oper_expr is UserOperatorCall || oper_expr is UserCast) && (best_expr is UserOperatorCall || best_expr is UserCast)) {
                                                Error_Ambiguous (ec, OperName (Oper), expr.Type, loc);
                                        } else {
                                                Error_OperatorCannotBeApplied (ec, loc, OperName (Oper), expr.Type);
                                        }

                                        break;
                                }

                                if (result == 2)
                                        best_expr = oper_expr;
                        }
                        
                        if (best_expr == null)
                                return null;
                        
                        //
                        // HACK: Decimal user-operator is included in standard operators
                        //
                        if (best_expr.Type.BuiltinType == BuiltinTypeSpec.Type.Decimal)
                                return best_expr;

                        Expr = best_expr;
                        type = best_expr.Type;
                        return this;                    
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Unary target = (Unary) t;

                        target.Expr = Expr.Clone (clonectx);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }

        }

        //
        // Unary operators are turned into Indirection expressions
        // after semantic analysis (this is so we can take the address
        // of an indirection).
        //
        public class Indirection : Expression, IMemoryLocation, IAssignMethod, IFixedExpression {
                Expression expr;
                LocalTemporary temporary;
                bool prepared;
                
                public Indirection (Expression expr, Location l)
                {
                        this.expr = expr;
                        loc = l;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public bool IsFixed {
                        get { return true; }
                }

                public override Location StartLocation {
                        get {
                                return expr.StartLocation;
                        }
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Indirection target = (Indirection) t;
                        target.expr = expr.Clone (clonectx);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        throw new NotImplementedException ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Error_PointerInsideExpressionTree (ec);
                        return null;
                }
                
                public override void Emit (EmitContext ec)
                {
                        if (!prepared)
                                expr.Emit (ec);
                        
                        ec.EmitLoadFromPtr (Type);
                }

                public void Emit (EmitContext ec, bool leave_copy)
                {
                        Emit (ec);
                        if (leave_copy) {
                                ec.Emit (OpCodes.Dup);
                                temporary = new LocalTemporary (expr.Type);
                                temporary.Store (ec);
                        }
                }
                
                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
                {
                        prepared = isCompound;
                        
                        expr.Emit (ec);

                        if (isCompound)
                                ec.Emit (OpCodes.Dup);
                        
                        source.Emit (ec);
                        if (leave_copy) {
                                ec.Emit (OpCodes.Dup);
                                temporary = new LocalTemporary (source.Type);
                                temporary.Store (ec);
                        }
                        
                        ec.EmitStoreFromPtr (type);
                        
                        if (temporary != null) {
                                temporary.Emit (ec);
                                temporary.Release (ec);
                        }
                }
                
                public void AddressOf (EmitContext ec, AddressOp Mode)
                {
                        expr.Emit (ec);
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
                {
                        return DoResolve (ec);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        expr = expr.Resolve (ec);
                        if (expr == null)
                                return null;

                        if (!ec.IsUnsafe)
                                UnsafeError (ec, loc);

                        var pc = expr.Type as PointerContainer;

                        if (pc == null) {
                                ec.Report.Error (193, loc, "The * or -> operator must be applied to a pointer");
                                return null;
                        }

                        type = pc.Element;

                        if (type.Kind == MemberKind.Void) {
                                Error_VoidPointerOperation (ec);
                                return null;
                        }

                        eclass = ExprClass.Variable;
                        return this;
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }
        
        /// <summary>
        ///   Unary Mutator expressions (pre and post ++ and --)
        /// </summary>
        ///
        /// <remarks>
        ///   UnaryMutator implements ++ and -- expressions.   It derives from
        ///   ExpressionStatement becuase the pre/post increment/decrement
        ///   operators can be used in a statement context.
        ///
        /// FIXME: Idea, we could split this up in two classes, one simpler
        /// for the common case, and one with the extra fields for more complex
        /// classes (indexers require temporary access;  overloaded require method)
        ///
        /// </remarks>
        public class UnaryMutator : ExpressionStatement
        {
                class DynamicPostMutator : Expression, IAssignMethod
                {
                        LocalTemporary temp;
                        Expression expr;

                        public DynamicPostMutator (Expression expr)
                        {
                                this.expr = expr;
                                this.type = expr.Type;
                                this.loc = expr.Location;
                        }

                        public override Expression CreateExpressionTree (ResolveContext ec)
                        {
                                throw new NotImplementedException ("ET");
                        }

                        protected override Expression DoResolve (ResolveContext rc)
                        {
                                eclass = expr.eclass;
                                return this;
                        }

                        public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
                        {
                                expr.DoResolveLValue (ec, right_side);
                                return DoResolve (ec);
                        }

                        public override void Emit (EmitContext ec)
                        {
                                temp.Emit (ec);
                        }

                        public void Emit (EmitContext ec, bool leave_copy)
                        {
                                throw new NotImplementedException ();
                        }

                        //
                        // Emits target assignment using unmodified source value
                        //
                        public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
                        {
                                //
                                // Allocate temporary variable to keep original value before it's modified
                                //
                                temp = new LocalTemporary (type);
                                expr.Emit (ec);
                                temp.Store (ec);

                                ((IAssignMethod) expr).EmitAssign (ec, source, false, isCompound);

                                if (leave_copy)
                                        Emit (ec);

                                temp.Release (ec);
                                temp = null;
                        }
                }

                [Flags]
                public enum Mode : byte {
                        IsIncrement    = 0,
                        IsDecrement    = 1,
                        IsPre          = 0,
                        IsPost         = 2,
                        
                        PreIncrement   = 0,
                        PreDecrement   = IsDecrement,
                        PostIncrement  = IsPost,
                        PostDecrement  = IsPost | IsDecrement
                }

                Mode mode;
                bool is_expr, recurse;

                protected Expression expr;

                // Holds the real operation
                Expression operation;

                public UnaryMutator (Mode m, Expression e, Location loc)
                {
                        mode = m;
                        this.loc = loc;
                        expr = e;
                }

                public Mode UnaryMutatorMode {
                        get {
                                return mode;
                        }
                }
                
                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public override Location StartLocation {
                        get {
                                return (mode & Mode.IsPost) != 0 ? expr.Location : loc;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return expr.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        return new SimpleAssign (this, this).CreateExpressionTree (ec);
                }

                public static TypeSpec[] CreatePredefinedOperatorsTable (BuiltinTypes types)
                {
                        //
                        // Predefined ++ and -- operators exist for the following types: 
                        // sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal
                        //
                        return new TypeSpec[] {
                                types.Int,
                                types.Long,

                                types.SByte,
                                types.Byte,
                                types.Short,
                                types.UInt,
                                types.ULong,
                                types.Char,
                                types.Float,
                                types.Double,
                                types.Decimal
                        };
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        expr = expr.Resolve (ec);
                        
                        if (expr == null || expr.Type == InternalType.ErrorType)
                                return null;

                        if (expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                //
                                // Handle postfix unary operators using local
                                // temporary variable
                                //
                                if ((mode & Mode.IsPost) != 0)
                                        expr = new DynamicPostMutator (expr);

                                Arguments args = new Arguments (1);
                                args.Add (new Argument (expr));
                                return new SimpleAssign (expr, new DynamicUnaryConversion (GetOperatorExpressionTypeName (), args, loc)).Resolve (ec);
                        }

                        if (expr.Type.IsNullableType)
                                return new Nullable.LiftedUnaryMutator (mode, expr, loc).Resolve (ec);

                        return DoResolveOperation (ec);
                }

                protected Expression DoResolveOperation (ResolveContext ec)
                {
                        eclass = ExprClass.Value;
                        type = expr.Type;

                        if (expr is RuntimeValueExpression) {
                                operation = expr;
                        } else {
                                // Use itself at the top of the stack
                                operation = new EmptyExpression (type);
                        }

                        //
                        // The operand of the prefix/postfix increment decrement operators
                        // should be an expression that is classified as a variable,
                        // a property access or an indexer access
                        //
                        // TODO: Move to parser, expr is ATypeNameExpression
                        if (expr.eclass == ExprClass.Variable || expr.eclass == ExprClass.IndexerAccess || expr.eclass == ExprClass.PropertyAccess) {
                                expr = expr.ResolveLValue (ec, expr);
                        } else {
                                ec.Report.Error (1059, loc, "The operand of an increment or decrement operator must be a variable, property or indexer");
                        }

                        //
                        // Step 1: Try to find a user operator, it has priority over predefined ones
                        //
                        var user_op = IsDecrement ? Operator.OpType.Decrement : Operator.OpType.Increment;
                        var methods = MemberCache.GetUserOperator (type, user_op, false);

                        if (methods != null) {
                                Arguments args = new Arguments (1);
                                args.Add (new Argument (expr));

                                var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
                                var method = res.ResolveOperator (ec, ref args);
                                if (method == null)
                                        return null;

                                args[0].Expr = operation;
                                operation = new UserOperatorCall (method, args, null, loc);
                                operation = Convert.ImplicitConversionRequired (ec, operation, type, loc);
                                return this;
                        }

                        //
                        // Step 2: Try predefined types
                        //

                        Expression source = null;
                        bool primitive_type;

                        //
                        // Predefined without user conversion first for speed-up
                        //
                        // Predefined ++ and -- operators exist for the following types: 
                        // sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal
                        //
                        switch (type.BuiltinType) {
                        case BuiltinTypeSpec.Type.Byte:
                        case BuiltinTypeSpec.Type.SByte:
                        case BuiltinTypeSpec.Type.Short:
                        case BuiltinTypeSpec.Type.UShort:
                        case BuiltinTypeSpec.Type.Int:
                        case BuiltinTypeSpec.Type.UInt:
                        case BuiltinTypeSpec.Type.Long:
                        case BuiltinTypeSpec.Type.ULong:
                        case BuiltinTypeSpec.Type.Char:
                        case BuiltinTypeSpec.Type.Float:
                        case BuiltinTypeSpec.Type.Double:
                        case BuiltinTypeSpec.Type.Decimal:
                                source = operation;
                                primitive_type = true;
                                break;
                        default:
                                primitive_type = false;

                                // ++/-- on pointer variables of all types except void*
                                if (type.IsPointer) {
                                        if (((PointerContainer) type).Element.Kind == MemberKind.Void) {
                                                Error_VoidPointerOperation (ec);
                                                return null;
                                        }

                                        source = operation;
                                } else {
                                        Expression best_source = null;
                                        foreach (var t in ec.BuiltinTypes.OperatorsUnaryMutator) {
                                                source = Convert.ImplicitUserConversion (ec, operation, t, loc);

                                                // LAMESPEC: It should error on ambiguous operators but that would make us incompatible
                                                if (source == null)
                                                        continue;

                                                if (best_source == null) {
                                                        best_source = source;
                                                        continue;
                                                }

                                                var better = OverloadResolver.BetterTypeConversion (ec, best_source.Type, source.Type);
                                                if (better == 1)
                                                        continue;

                                                if (better == 2) {
                                                        best_source = source;
                                                        continue;
                                                }

                                                Unary.Error_Ambiguous (ec, OperName (mode), type, loc);
                                                break;
                                        }

                                        source = best_source;
                                }

                                // ++/-- on enum types
                                if (source == null && type.IsEnum)
                                        source = operation;

                                if (source == null) {
                                        expr.Error_OperatorCannotBeApplied (ec, loc, Operator.GetName (user_op), type);
                                        return null;
                                }

                                break;
                        }

                        var one = new IntConstant (ec.BuiltinTypes, 1, loc);
                        var op = IsDecrement ? Binary.Operator.Subtraction : Binary.Operator.Addition;
                        operation = new Binary (op, source, one);
                        operation = operation.Resolve (ec);
                        if (operation == null)
                                throw new NotImplementedException ("should not be reached");

                        if (operation.Type != type) {
                                if (primitive_type)
                                        operation = Convert.ExplicitNumericConversion (ec, operation, type);
                                else
                                        operation = Convert.ImplicitConversionRequired (ec, operation, type, loc);
                        }

                        return this;
                }

                void EmitCode (EmitContext ec, bool is_expr)
                {
                        recurse = true;
                        this.is_expr = is_expr;
                        ((IAssignMethod) expr).EmitAssign (ec, this, is_expr && (mode == Mode.PreIncrement || mode == Mode.PreDecrement), true);
                }

                public override void Emit (EmitContext ec)
                {
                        //
                        // We use recurse to allow ourselfs to be the source
                        // of an assignment. This little hack prevents us from
                        // having to allocate another expression
                        //
                        if (recurse) {
                                ((IAssignMethod) expr).Emit (ec, is_expr && (mode == Mode.PostIncrement || mode == Mode.PostDecrement));

                                EmitOperation (ec);

                                recurse = false;
                                return;
                        }

                        EmitCode (ec, true);
                }

                protected virtual void EmitOperation (EmitContext ec)
                {
                        operation.Emit (ec);
                }

                public override void EmitStatement (EmitContext ec)
                {
                        EmitCode (ec, false);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        expr.FlowAnalysis (fc);
                }

                //
                // Converts operator to System.Linq.Expressions.ExpressionType enum name
                //
                string GetOperatorExpressionTypeName ()
                {
                        return IsDecrement ? "Decrement" : "Increment";
                }

                bool IsDecrement {
                        get { return (mode & Mode.IsDecrement) != 0; }
                }


#if NET_4_0 || MOBILE_DYNAMIC
                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        var target = ((RuntimeValueExpression) expr).MetaObject.Expression;
                        var source = SLE.Expression.Convert (operation.MakeExpression (ctx), target.Type);
                        return SLE.Expression.Assign (target, source);
                }
#endif

                public static string OperName (Mode oper)
                {
                        return (oper & Mode.IsDecrement) != 0 ? "--" : "++";
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        UnaryMutator target = (UnaryMutator) t;

                        target.expr = expr.Clone (clonectx);
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }

        }

        //
        // Base class for the `is' and `as' operators
        //
        public abstract class Probe : Expression
        {
                public Expression ProbeType;
                protected Expression expr;
                protected TypeSpec probe_type_expr;
                
                protected Probe (Expression expr, Expression probe_type, Location l)
                {
                        ProbeType = probe_type;
                        loc = l;
                        this.expr = expr;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return expr.ContainsEmitWithAwait ();
                }

                protected Expression ResolveCommon (ResolveContext rc)
                {
                        expr = expr.Resolve (rc);
                        if (expr == null)
                                return null;

                        ResolveProbeType (rc);
                        if (probe_type_expr == null)
                                return this;

                        if (probe_type_expr.IsStatic) {
                                rc.Report.Error (7023, loc, "The second operand of `is' or `as' operator cannot be static type `{0}'",
                                        probe_type_expr.GetSignatureForError ());
                                return null;
                        }
                        
                        if (expr.Type.IsPointer || probe_type_expr.IsPointer) {
                                rc.Report.Error (244, loc, "The `{0}' operator cannot be applied to an operand of pointer type",
                                        OperatorName);
                                return null;
                        }

                        if (expr.Type == InternalType.AnonymousMethod || expr.Type == InternalType.MethodGroup) {
                                rc.Report.Error (837, loc, "The `{0}' operator cannot be applied to a lambda expression, anonymous method, or method group",
                                        OperatorName);
                                return null;
                        }

                        return this;
                }

                protected virtual void ResolveProbeType (ResolveContext rc)
                {
                        probe_type_expr = ProbeType.ResolveAsType (rc);
                }

                public override void EmitSideEffect (EmitContext ec)
                {
                        expr.EmitSideEffect (ec);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        expr.FlowAnalysis (fc);
                }

                public override bool HasConditionalAccess ()
                {
                        return expr.HasConditionalAccess ();
                }

                protected abstract string OperatorName { get; }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Probe target = (Probe) t;

                        target.expr = expr.Clone (clonectx);
                        target.ProbeType = ProbeType.Clone (clonectx);
                }

        }

        /// <summary>
        ///   Implementation of the `is' operator.
        /// </summary>
        public class Is : Probe
        {
                Nullable.Unwrap expr_unwrap;
                MethodSpec number_mg;
                Arguments number_args;

                public Is (Expression expr, Expression probe_type, Location l)
                        : base (expr, probe_type, l)
                {
                }

                protected override string OperatorName {
                        get { return "is"; }
                }

                public LocalVariable Variable { get; set; }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        if (Variable != null)
                                throw new NotSupportedException ();

                        Arguments args = Arguments.CreateForExpressionTree (ec, null,
                                expr.CreateExpressionTree (ec),
                                new TypeOf (probe_type_expr, loc));

                        return CreateExpressionFactoryCall (ec, "TypeIs", args);
                }

                Expression CreateConstantResult (ResolveContext rc, bool result)
                {
                        if (result)
                                rc.Report.Warning (183, 1, loc, "The given expression is always of the provided (`{0}') type",
                                        probe_type_expr.GetSignatureForError ());
                        else
                                rc.Report.Warning (184, 1, loc, "The given expression is never of the provided (`{0}') type",
                                        probe_type_expr.GetSignatureForError ());

                        var c = new BoolConstant (rc.BuiltinTypes, result, loc);
                        return expr.IsSideEffectFree ?
                                ReducedExpression.Create (c, this) :
                                new SideEffectConstant (c, this, loc);
                }

                public override void Emit (EmitContext ec)
                {
                        if (probe_type_expr == null) {
                                if (ProbeType is WildcardPattern) {
                                        expr.EmitSideEffect (ec);
                                        ProbeType.Emit (ec);
                                } else {
                                        EmitPatternMatch (ec);
                                }
                                return;
                        }

                        EmitLoad (ec);

                        if (expr_unwrap == null) {
                                ec.EmitNull ();
                                ec.Emit (OpCodes.Cgt_Un);
                        }
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        if (probe_type_expr == null) {
                                EmitPatternMatch (ec);
                        } else {
                                EmitLoad (ec);
                        }

                        ec.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
                }

                void EmitPatternMatch (EmitContext ec)
                {
                        var no_match = ec.DefineLabel ();
                        var end = ec.DefineLabel ();

                        if (expr_unwrap != null) {
                                expr_unwrap.EmitCheck (ec);

                                if (ProbeType.IsNull) {
                                        ec.EmitInt (0);
                                        ec.Emit (OpCodes.Ceq);
                                        return;
                                }

                                ec.Emit (OpCodes.Brfalse_S, no_match);
                                expr_unwrap.Emit (ec);
                                ProbeType.Emit (ec);
                                ec.Emit (OpCodes.Ceq);
                                ec.Emit (OpCodes.Br_S, end);
                                ec.MarkLabel (no_match);
                                ec.EmitInt (0);
                                ec.MarkLabel (end);
                                return;
                        }

                        if (number_args != null && number_args.Count == 3) {
                                var ce = new CallEmitter ();
                                ce.Emit (ec, number_mg, number_args, loc);
                                return;
                        }

                        var probe_type = ProbeType.Type;

                        Expr.Emit (ec);
                        ec.Emit (OpCodes.Isinst, probe_type);
                        ec.Emit (OpCodes.Dup);
                        ec.Emit (OpCodes.Brfalse, no_match);

                        bool complex_pattern = ProbeType is ComplexPatternExpression;
                        Label prev = ec.RecursivePatternLabel;
                        if (complex_pattern)
                                ec.RecursivePatternLabel = ec.DefineLabel ();

                        if (number_mg != null) {
                                var ce = new CallEmitter ();
                                ce.Emit (ec, number_mg, number_args, loc);
                        } else {
                                if (TypeSpec.IsValueType (probe_type))
                                        ec.Emit (OpCodes.Unbox_Any, probe_type);

                                ProbeType.Emit (ec);
                                if (complex_pattern) {
                                        ec.EmitInt (1);
                                } else {
                                        ec.Emit (OpCodes.Ceq);
                                }
                        }
                        ec.Emit (OpCodes.Br_S, end);
                        ec.MarkLabel (no_match);

                        ec.Emit (OpCodes.Pop);

                        if (complex_pattern)
                                ec.MarkLabel (ec.RecursivePatternLabel);

                        ec.RecursivePatternLabel = prev;

                        ec.EmitInt (0);
                        ec.MarkLabel (end);
                }

                void EmitLoad (EmitContext ec)
                {
                        Label no_value_label = new Label ();

                        if (expr_unwrap != null) {
                                expr_unwrap.EmitCheck (ec);

                                if (Variable == null)
                                        return;

                                ec.Emit (OpCodes.Dup);
                                no_value_label = ec.DefineLabel ();
                                ec.Emit (OpCodes.Brfalse_S, no_value_label);
                                expr_unwrap.Emit (ec);
                        } else {
                                expr.Emit (ec);

                                // Only to make verifier happy
                                if (probe_type_expr.IsGenericParameter && TypeSpec.IsValueType (expr.Type))
                                        ec.Emit (OpCodes.Box, expr.Type);

                                ec.Emit (OpCodes.Isinst, probe_type_expr);
                        }

                        if (Variable != null) {
                                bool value_on_stack;
                                if (probe_type_expr.IsGenericParameter || probe_type_expr.IsNullableType) {
                                        ec.Emit (OpCodes.Dup);
                                        ec.Emit (OpCodes.Unbox_Any, probe_type_expr);
                                        value_on_stack = true;
                                } else {
                                        value_on_stack = false;
                                }

                                Variable.CreateBuilder (ec);
                                Variable.EmitAssign (ec);

                                if (expr_unwrap != null) {
                                        ec.MarkLabel (no_value_label);
                                } else if (!value_on_stack) {
                                        Variable.Emit (ec);
                                }
                        }
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        if (ResolveCommon (rc) == null)
                                return null;

                        type = rc.BuiltinTypes.Bool;
                        eclass = ExprClass.Value;

                        if (probe_type_expr == null)
                                return ResolveMatchingExpression (rc);

                        var res = ResolveResultExpression (rc);
                        if (Variable != null) {
                                if (res is Constant)
                                        throw new NotImplementedException ("constant in type pattern matching");

                                Variable.Type = probe_type_expr;
                                var bc = rc as BlockContext;
                                if (bc != null)
                                        Variable.PrepareAssignmentAnalysis (bc);
                        }

                        return res;
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        base.FlowAnalysis (fc);

                        if (Variable != null)
                                fc.SetVariableAssigned (Variable.VariableInfo, true);
                }

                protected override void ResolveProbeType (ResolveContext rc)
                {
                        if (!(ProbeType is TypeExpr) && rc.Module.Compiler.Settings.Version == LanguageVersion.Experimental) {
                                if (ProbeType is PatternExpression) {
                                        ProbeType.Resolve (rc);
                                        return;
                                }

                                //
                                // Have to use session recording because we don't have reliable type probing
                                // mechanism (similar issue as in attributes resolving)
                                //
                                // TODO: This is still wrong because ResolveAsType can be destructive
                                //
                                var type_printer = new SessionReportPrinter ();
                                var prev_recorder = rc.Report.SetPrinter (type_printer);

                                probe_type_expr = ProbeType.ResolveAsType (rc);
                                type_printer.EndSession ();

                                if (probe_type_expr != null) {
                                        type_printer.Merge (rc.Report.Printer);
                                        rc.Report.SetPrinter (prev_recorder);
                                        return;
                                }

                                var vexpr = ProbeType as VarExpr;
                                if (vexpr != null && vexpr.InferType (rc, expr)) {
                                        probe_type_expr = vexpr.Type;
                                        rc.Report.SetPrinter (prev_recorder);
                                        return;
                                }

                                var expr_printer = new SessionReportPrinter ();
                                rc.Report.SetPrinter (expr_printer);
                                ProbeType = ProbeType.Resolve (rc);
                                expr_printer.EndSession ();

                                if (ProbeType != null) {
                                        expr_printer.Merge (rc.Report.Printer);
                                } else {
                                        type_printer.Merge (rc.Report.Printer);
                                }

                                rc.Report.SetPrinter (prev_recorder);
                                return;
                        }

                        base.ResolveProbeType (rc);
                }

                Expression ResolveMatchingExpression (ResolveContext rc)
                {
                        var mc = ProbeType as Constant;
                        if (mc != null) {
                                if (!Convert.ImplicitConversionExists (rc, ProbeType, Expr.Type)) {
                                        ProbeType.Error_ValueCannotBeConverted (rc, Expr.Type, false);
                                        return null;
                                }

                                if (mc.IsNull)
                                        return new Binary (Binary.Operator.Equality, Expr, mc).Resolve (rc);

                                var c = Expr as Constant;
                                if (c != null) {
                                        c = ConstantFold.BinaryFold (rc, Binary.Operator.Equality, c, mc, loc);
                                        if (c != null)
                                                return c;
                                }

                                if (Expr.Type.IsNullableType) {
                                        expr_unwrap = new Nullable.Unwrap (Expr);
                                        expr_unwrap.Resolve (rc);
                                        ProbeType = Convert.ImplicitConversion (rc, ProbeType, expr_unwrap.Type, loc);
                                } else if (ProbeType.Type == Expr.Type) {
                                        // TODO: Better error handling
                                        return new Binary (Binary.Operator.Equality, Expr, mc, loc).Resolve (rc);
                                } else if (ProbeType.Type.IsEnum || (ProbeType.Type.BuiltinType >= BuiltinTypeSpec.Type.Byte && ProbeType.Type.BuiltinType <= BuiltinTypeSpec.Type.Decimal)) {
                                        var helper = rc.Module.CreatePatterMatchingHelper ();
                                        number_mg = helper.NumberMatcher.Spec;

                                        //
                                        // There are actually 3 arguments but the first one is already on the stack
                                        //
                                        number_args = new Arguments (3);
                                        if (!ProbeType.Type.IsEnum)
                                                number_args.Add (new Argument (Expr));

                                        number_args.Add (new Argument (Convert.ImplicitConversion (rc, ProbeType, rc.BuiltinTypes.Object, loc)));
                                        number_args.Add (new Argument (new BoolLiteral (rc.BuiltinTypes, ProbeType.Type.IsEnum, loc)));
                                }

                                return this;
                        }

                        if (ProbeType is PatternExpression) {
                                if (!(ProbeType is WildcardPattern) && !Convert.ImplicitConversionExists (rc, ProbeType, Expr.Type)) {
                                        ProbeType.Error_ValueCannotBeConverted (rc, Expr.Type, false);
                                }

                                return this;
                        }

                        // TODO: Better error message
                        rc.Report.Error (150, ProbeType.Location, "A constant value is expected");
                        return this;
                }

                Expression ResolveResultExpression (ResolveContext ec)
                {
                        TypeSpec d = expr.Type;
                        bool d_is_nullable = false;

                        //
                        // If E is a method group or the null literal, or if the type of E is a reference
                        // type or a nullable type and the value of E is null, the result is false
                        //
                        if (expr.IsNull || expr.eclass == ExprClass.MethodGroup)
                                return CreateConstantResult (ec, false);

                        if (d.IsNullableType) {
                                var ut = Nullable.NullableInfo.GetUnderlyingType (d);
                                if (!ut.IsGenericParameter) {
                                        d = ut;
                                        d_is_nullable = true;
                                }
                        }
                                
                        TypeSpec t = probe_type_expr;
                        bool t_is_nullable = false;
                        if (t.IsNullableType) {
                                var ut = Nullable.NullableInfo.GetUnderlyingType (t);
                                if (!ut.IsGenericParameter) {
                                        t = ut;
                                        t_is_nullable = true;
                                }
                        }

                        if (t.IsStruct) {
                                if (d == t) {
                                        //
                                        // D and T are the same value types but D can be null
                                        //
                                        if (d_is_nullable && !t_is_nullable) {
                                                expr_unwrap = Nullable.Unwrap.Create (expr, true);
                                                return this;
                                        }
                                        
                                        //
                                        // The result is true if D and T are the same value types
                                        //
                                        return CreateConstantResult (ec, true);
                                }

                                var tp = d as TypeParameterSpec;
                                if (tp != null)
                                        return ResolveGenericParameter (ec, t, tp);

                                //
                                // An unboxing conversion exists
                                //
                                if (Convert.ExplicitReferenceConversionExists (d, t))
                                        return this;

                                //
                                // open generic type
                                //
                                if (d is InflatedTypeSpec && InflatedTypeSpec.ContainsTypeParameter (d))
                                        return this;
                        } else {
                                var tps = t as TypeParameterSpec;
                                if (tps != null)
                                        return ResolveGenericParameter (ec, d, tps);

                                if (t.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                        ec.Report.Warning (1981, 3, loc,
                                                "Using `{0}' to test compatibility with `{1}' is identical to testing compatibility with `object'",
                                                OperatorName, t.GetSignatureForError ());
                                }

                                if (TypeManager.IsGenericParameter (d))
                                        return ResolveGenericParameter (ec, t, (TypeParameterSpec) d);

                                if (TypeSpec.IsValueType (d)) {
                                        if (Convert.ImplicitBoxingConversion (null, d, t) != null) {
                                                if (d_is_nullable && !t_is_nullable) {
                                                        expr_unwrap = Nullable.Unwrap.Create (expr, false);
                                                        return this;
                                                }

                                                return CreateConstantResult (ec, true);
                                        }
                                } else {
                                        if (Convert.ImplicitReferenceConversionExists (d, t)) {
                                                var c = expr as Constant;
                                                if (c != null)
                                                        return CreateConstantResult (ec, !c.IsNull);

                                                //
                                                // Do not optimize for imported type or dynamic type
                                                //
                                                if (d.MemberDefinition.IsImported && d.BuiltinType != BuiltinTypeSpec.Type.None &&
                                                        d.MemberDefinition.DeclaringAssembly != t.MemberDefinition.DeclaringAssembly) {
                                                        return this;
                                                }

                                                if (d.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
                                                        return this;
                                                
                                                //
                                                // Turn is check into simple null check for implicitly convertible reference types
                                                //
                                                return ReducedExpression.Create (
                                                        new Binary (Binary.Operator.Inequality, expr, new NullLiteral (loc), Binary.State.UserOperatorsExcluded).Resolve (ec),
                                                        this).Resolve (ec);
                                        }

                                        if (Convert.ExplicitReferenceConversionExists (d, t))
                                                return this;

                                        //
                                        // open generic type
                                        //
                                        if ((d is InflatedTypeSpec || d.IsArray) && InflatedTypeSpec.ContainsTypeParameter (d))
                                                return this;
                                }
                        }

                        return CreateConstantResult (ec, false);
                }

                Expression ResolveGenericParameter (ResolveContext ec, TypeSpec d, TypeParameterSpec t)
                {
                        if (t.IsReferenceType) {
                                if (d.IsStruct)
                                        return CreateConstantResult (ec, false);
                        }

                        if (expr.Type.IsGenericParameter) {
                                if (expr.Type == d && TypeSpec.IsValueType (t) && TypeSpec.IsValueType (d))
                                        return CreateConstantResult (ec, true);

                                expr = new BoxedCast (expr, d);
                        }

                        return this;
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        class WildcardPattern : PatternExpression
        {
                public WildcardPattern (Location loc)
                        : base (loc)
                {
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        eclass = ExprClass.Value;
                        type = rc.BuiltinTypes.Object;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ec.EmitInt (1);
                }
        }

        class RecursivePattern : ComplexPatternExpression
        {
                MethodGroupExpr operator_mg;
                Arguments operator_args;

                public RecursivePattern (ATypeNameExpression typeExpresion, Arguments arguments, Location loc)
                        : base (typeExpresion, loc)
                {
                        Arguments = arguments;
                }

                public Arguments Arguments { get; private set; }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        type = TypeExpression.ResolveAsType (rc);
                        if (type == null)
                                return null;

                        var operators = MemberCache.GetUserOperator (type, Operator.OpType.Is, true);
                        if (operators == null) {
                                Error_TypeDoesNotContainDefinition (rc, type, Operator.GetName (Operator.OpType.Is) + " operator");
                                return null;
                        }

                        var ops = FindMatchingOverloads (operators);
                        if (ops == null) {
                                // TODO: better error message
                                Error_TypeDoesNotContainDefinition (rc, type, Operator.GetName (Operator.OpType.Is) + " operator");
                                return null;
                        }

                        bool dynamic_args;
                        Arguments.Resolve (rc, out dynamic_args);
                        if (dynamic_args)
                                throw new NotImplementedException ("dynamic argument");

                        var op = FindBestOverload (rc, ops);
                        if (op == null) {
                                // TODO: better error message
                                Error_TypeDoesNotContainDefinition (rc, type, Operator.GetName (Operator.OpType.Is) + " operator");
                                return null;
                        }

                        var op_types = op.Parameters.Types;
                        operator_args = new Arguments (op_types.Length);
                        operator_args.Add (new Argument (new EmptyExpression (type)));

                        for (int i = 0; i < Arguments.Count; ++i) {
                                // TODO: Needs releasing optimization
                                var lt = new LocalTemporary (op_types [i + 1]);
                                operator_args.Add (new Argument (lt, Argument.AType.Out));

                                if (comparisons == null)
                                        comparisons = new Expression[Arguments.Count];

                                int arg_comp_index;
                                Expression expr;

                                var arg = Arguments [i];
                                var named = arg as NamedArgument;
                                if (named != null) {
                                        arg_comp_index = op.Parameters.GetParameterIndexByName (named.Name) - 1;
                                        expr = Arguments [arg_comp_index].Expr;
                                } else {
                                        arg_comp_index = i;
                                        expr = arg.Expr;
                                }

                                comparisons [arg_comp_index] = ResolveComparison (rc, expr, lt);
                        }

                        operator_mg = MethodGroupExpr.CreatePredefined (op, type, loc);

                        eclass = ExprClass.Value;
                        return this;
                }

                List<MethodSpec> FindMatchingOverloads (IList<MemberSpec> members)
                {
                        int arg_count = Arguments.Count + 1;
                        List<MethodSpec> best = null;
                        foreach (MethodSpec method in members) {
                                var pm = method.Parameters;
                                if (pm.Count != arg_count)
                                        continue;

                                // TODO: Needs more thorough operator checks elsewhere to avoid doing this every time
                                bool ok = true;
                                for (int ii = 1; ii < pm.Count; ++ii) {
                                        if ((pm.FixedParameters [ii].ModFlags & Parameter.Modifier.OUT) == 0) {
                                                ok = false;
                                                break;
                                        }
                                }

                                if (!ok)
                                        continue;

                                if (best == null)
                                        best = new List<MethodSpec> ();

                                best.Add (method);
                        }

                        return best;
                }

                MethodSpec FindBestOverload (ResolveContext rc, List<MethodSpec> methods)
                {
                        for (int ii = 0; ii < Arguments.Count; ++ii) {
                                var arg = Arguments [ii];
                                var expr = arg.Expr;
                                if (expr is WildcardPattern)
                                        continue;

                                var na = arg as NamedArgument;
                                for (int i = 0; i < methods.Count; ++i) {
                                        var pd = methods [i].Parameters;

                                        int index;
                                        if (na != null) {
                                                index = pd.GetParameterIndexByName (na.Name);
                                                if (index < 1) {
                                                        methods.RemoveAt (i--);
                                                        continue;
                                                }
                                        } else {
                                                index = ii + 1;
                                        }

                                        var m = pd.Types [index];
                                        if (!Convert.ImplicitConversionExists (rc, expr, m))
                                                methods.RemoveAt (i--);
                                }
                        }

                        if (methods.Count != 1)
                                return null;

                        return methods [0];
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        operator_mg.EmitCall (ec, operator_args, false);
                        ec.Emit (OpCodes.Brfalse, target);

                        base.EmitBranchable (ec, target, on_true);
                }

                static Expression ResolveComparison (ResolveContext rc, Expression expr, LocalTemporary lt)
                {
                        if (expr is WildcardPattern)
                                return new EmptyExpression (expr.Type);

                        var recursive = expr as RecursivePattern;
                        expr = Convert.ImplicitConversionRequired (rc, expr, lt.Type, expr.Location);
                        if (expr == null)
                                return null;

                        if (recursive != null) {
                                recursive.SetParentInstance (lt);
                                return expr;
                        }

                        // TODO: Better error handling
                        return new Binary (Binary.Operator.Equality, lt, expr, expr.Location).Resolve (rc);
                }

                public void SetParentInstance (Expression instance)
                {
                        operator_args [0] = new Argument (instance);
                }
        }

        class PropertyPattern : ComplexPatternExpression
        {
                LocalTemporary instance;

                public PropertyPattern (ATypeNameExpression typeExpresion, List<PropertyPatternMember> members, Location loc)
                        : base (typeExpresion, loc)
                {
                        Members = members;
                }

                public List<PropertyPatternMember> Members { get; private set; }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        type = TypeExpression.ResolveAsType (rc);
                        if (type == null)
                                return null;

                        comparisons = new Expression[Members.Count];

                        // TODO: optimize when source is VariableReference, it'd save dup+pop
                        instance = new LocalTemporary (type);

                        for (int i = 0; i < Members.Count; i++) {
                                var lookup = Members [i];

                                var member = MemberLookup (rc, false, type, lookup.Name, 0, Expression.MemberLookupRestrictions.ExactArity, loc);
                                if (member == null) {
                                        member = MemberLookup (rc, true, type, lookup.Name, 0, Expression.MemberLookupRestrictions.ExactArity, loc);
                                        if (member != null) {
                                                Expression.ErrorIsInaccesible (rc, member.GetSignatureForError (), loc);
                                                continue;
                                        }
                                }

                                if (member == null) {
                                        Expression.Error_TypeDoesNotContainDefinition (rc, Location, Type, lookup.Name);
                                        continue;
                                }

                                var pe = member as PropertyExpr;
                                if (pe == null || member is FieldExpr) {
                                        rc.Report.Error (-2001, lookup.Location, "`{0}' is not a valid pattern member", lookup.Name);
                                        continue;
                                }

                                // TODO: Obsolete checks
                                // TODO: check accessibility
                                if (pe != null && !pe.PropertyInfo.HasGet) {
                                        rc.Report.Error (-2002, lookup.Location, "Property `{0}.get' accessor is required", pe.GetSignatureForError ());
                                        continue;
                                }

                                var expr = lookup.Expr.Resolve (rc);
                                if (expr == null)
                                        continue;

                                var me = (MemberExpr)member;
                                me.InstanceExpression = instance;

                                comparisons [i] = ResolveComparison (rc, expr, me);
                        }

                        eclass = ExprClass.Value;
                        return this;
                }

                static Expression ResolveComparison (ResolveContext rc, Expression expr, Expression instance)
                {
                        if (expr is WildcardPattern)
                                return new EmptyExpression (expr.Type);

                        return new Is (instance, expr, expr.Location).Resolve (rc);
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        instance.Store (ec);

                        base.EmitBranchable (ec, target, on_true);
                }
        }

        class PropertyPatternMember
        {
                public PropertyPatternMember (string name, Expression expr, Location loc)
                {
                        Name = name;
                        Expr = expr;
                        Location = loc;
                }

                public string Name { get; private set; }
                public Expression Expr { get; private set; }
                public Location Location { get; private set; }
        }

        abstract class PatternExpression : Expression
        {
                protected PatternExpression (Location loc)
                {
                        this.loc = loc;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        throw new NotImplementedException ();
                }
        }

        abstract class ComplexPatternExpression : PatternExpression
        {
                protected Expression[] comparisons;

                protected ComplexPatternExpression (ATypeNameExpression typeExpresion, Location loc)
                        : base (loc)
                {
                        TypeExpression = typeExpresion;
                }

                public ATypeNameExpression TypeExpression { get; private set; }

                public override void Emit (EmitContext ec)
                {
                        EmitBranchable (ec, ec.RecursivePatternLabel, false);
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        if (comparisons != null) {
                                foreach (var comp in comparisons) {
                                        comp.EmitBranchable (ec, target, false);
                                }
                        }
                }
        }

        /// <summary>
        ///   Implementation of the `as' operator.
        /// </summary>
        public class As : Probe {

                public As (Expression expr, Expression probe_type, Location l)
                        : base (expr, probe_type, l)
                {
                }

                protected override string OperatorName {
                        get { return "as"; }
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = Arguments.CreateForExpressionTree (ec, null,
                                expr.CreateExpressionTree (ec),
                                new TypeOf (probe_type_expr, loc));

                        return CreateExpressionFactoryCall (ec, "TypeAs", args);
                }

                public override void Emit (EmitContext ec)
                {
                        expr.Emit (ec);

                        ec.Emit (OpCodes.Isinst, type);

                        if (TypeManager.IsGenericParameter (type) || type.IsNullableType)
                                ec.Emit (OpCodes.Unbox_Any, type);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (ResolveCommon (ec) == null)
                                return null;

                        type = probe_type_expr;
                        eclass = ExprClass.Value;
                        TypeSpec etype = expr.Type;

                        if (!TypeSpec.IsReferenceType (type) && !type.IsNullableType) {
                                if (TypeManager.IsGenericParameter (type)) {
                                        ec.Report.Error (413, loc,
                                                "The `as' operator cannot be used with a non-reference type parameter `{0}'. Consider adding `class' or a reference type constraint",
                                                probe_type_expr.GetSignatureForError ());
                                } else {
                                        ec.Report.Error (77, loc,
                                                "The `as' operator cannot be used with a non-nullable value type `{0}'",
                                                type.GetSignatureForError ());
                                }
                                return null;
                        }

                        if (expr.IsNull && type.IsNullableType) {
                                return Nullable.LiftedNull.CreateFromExpression (ec, this);
                        }

                        // If the compile-time type of E is dynamic, unlike the cast operator the as operator is not dynamically bound
                        if (etype.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                return this;
                        }
                        
                        Expression e = Convert.ImplicitConversionStandard (ec, expr, type, loc);
                        if (e != null) {
                                e = EmptyCast.Create (e, type);
                                return ReducedExpression.Create (e, this).Resolve (ec);
                        }

                        if (Convert.ExplicitReferenceConversionExists (etype, type)){
                                if (TypeManager.IsGenericParameter (etype))
                                        expr = new BoxedCast (expr, etype);

                                return this;
                        }

                        if (InflatedTypeSpec.ContainsTypeParameter (etype) || InflatedTypeSpec.ContainsTypeParameter (type)) {
                                expr = new BoxedCast (expr, etype);
                                return this;
                        }

                        if (etype != InternalType.ErrorType) {
                                ec.Report.Error (39, loc, "Cannot convert type `{0}' to `{1}' via a built-in conversion",
                                        etype.GetSignatureForError (), type.GetSignatureForError ());
                        }

                        return null;
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }
        
        //
        // This represents a typecast in the source language.
        //
        public class Cast : ShimExpression {
                Expression target_type;

                public Cast (Expression cast_type, Expression expr, Location loc)
                        : base (expr)
                {
                        this.target_type = cast_type;
                        this.loc = loc;
                }

                public Expression TargetType {
                        get { return target_type; }
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        expr = expr.Resolve (ec);
                        if (expr == null)
                                return null;

                        type = target_type.ResolveAsType (ec);
                        if (type == null)
                                return null;

                        if (type.IsStatic) {
                                ec.Report.Error (716, loc, "Cannot convert to static type `{0}'", type.GetSignatureForError ());
                                return null;
                        }

                        if (type.IsPointer && !ec.IsUnsafe) {
                                UnsafeError (ec, loc);
                        }

                        eclass = ExprClass.Value;
                        
                        Constant c = expr as Constant;
                        if (c != null) {
                                c = c.Reduce (ec, type);
                                if (c != null)
                                        return c;
                        }

                        var res = Convert.ExplicitConversion (ec, expr, type, loc);
                        if (res == expr)
                                return EmptyCast.Create (res, type);

                        return res;
                }
                
                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Cast target = (Cast) t;

                        target.target_type = target_type.Clone (clonectx);
                        target.expr = expr.Clone (clonectx);
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class ImplicitCast : ShimExpression
        {
                bool arrayAccess;

                public ImplicitCast (Expression expr, TypeSpec target, bool arrayAccess)
                        : base (expr)
                {
                        this.loc = expr.Location;
                        this.type = target;
                        this.arrayAccess = arrayAccess;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        expr = expr.Resolve (ec);
                        if (expr == null)
                                return null;

                        if (arrayAccess)
                                expr = ConvertExpressionToArrayIndex (ec, expr);
                        else
                                expr = Convert.ImplicitConversionRequired (ec, expr, type, loc);

                        return expr;
                }
        }

        public class DeclarationExpression : Expression, IMemoryLocation
        {
                LocalVariableReference lvr;

                public DeclarationExpression (FullNamedExpression variableType, LocalVariable variable)
                {
                        VariableType = variableType;
                        Variable = variable;
                        this.loc = variable.Location;
                }

                public LocalVariable Variable { get; set; }
                public Expression Initializer { get; set; }
                public FullNamedExpression VariableType { get; set; }

                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        Variable.CreateBuilder (ec);

                        if (Initializer != null) {
                                lvr.EmitAssign (ec, Initializer, false, false);
                        }

                        lvr.AddressOf (ec, mode);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        var target = (DeclarationExpression) t;

                        target.VariableType = (FullNamedExpression) VariableType.Clone (clonectx);

                        if (Initializer != null)
                                target.Initializer = Initializer.Clone (clonectx);
                }

                public override Expression CreateExpressionTree (ResolveContext rc)
                {
                        rc.Report.Error (8046, loc, "An expression tree cannot contain a declaration expression");
                        return null;
                }

                bool DoResolveCommon (ResolveContext rc)
                {
                        var var_expr = VariableType as VarExpr;
                        if (var_expr != null) {
                                type = InternalType.VarOutType;
                        } else {
                                type = VariableType.ResolveAsType (rc);
                                if (type == null)
                                        return false;
                        }

                        if (Initializer != null) {
                                Initializer = Initializer.Resolve (rc);

                                if (var_expr != null && Initializer != null && var_expr.InferType (rc, Initializer)) {
                                        type = var_expr.Type;
                                }
                        }

                        Variable.Type = type;
                        lvr = new LocalVariableReference (Variable, loc);

                        eclass = ExprClass.Variable;
                        return true;
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        if (DoResolveCommon (rc))
                                lvr.Resolve (rc);

                        return this;
                }

                public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
                {
                        if (lvr == null && DoResolveCommon (rc))
                                lvr.ResolveLValue (rc, right_side);

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        throw new NotImplementedException ();
                }
        }
        
        //
        // C# 2.0 Default value expression
        //
        public class DefaultValueExpression : Expression
        {
                Expression expr;

                public DefaultValueExpression (Expression expr, Location loc)
                {
                        this.expr = expr;
                        this.loc = loc;
                }

                public Expression Expr {
                        get {
                                return this.expr; 
                        }
                }

                public override bool IsSideEffectFree {
                        get {
                                return true;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (2);
                        args.Add (new Argument (this));
                        args.Add (new Argument (new TypeOf (type, loc)));
                        return CreateExpressionFactoryCall (ec, "Constant", args);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        type = expr.ResolveAsType (ec);
                        if (type == null)
                                return null;

                        if (type.IsStatic) {
                                ec.Report.Error (-244, loc, "The `default value' operator cannot be applied to an operand of a static type");
                        }

                        if (type.IsPointer)
                                return new NullLiteral (Location).ConvertImplicitly (type);

                        if (TypeSpec.IsReferenceType (type))
                                return new NullConstant (type, loc);

                        Constant c = New.Constantify (type, expr.Location);
                        if (c != null)
                                return c;

                        eclass = ExprClass.Variable;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        LocalTemporary temp_storage = new LocalTemporary(type);

                        temp_storage.AddressOf(ec, AddressOp.LoadStore);
                        ec.Emit(OpCodes.Initobj, type);
                        temp_storage.Emit(ec);
                        temp_storage.Release (ec);
                }

#if (NET_4_0 || MOBILE_DYNAMIC) && !STATIC
                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        return SLE.Expression.Default (type.GetMetaInfo ());
                }
#endif

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        DefaultValueExpression target = (DefaultValueExpression) t;
                        
                        target.expr = expr.Clone (clonectx);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Binary operators
        /// </summary>
        public class Binary : Expression, IDynamicBinder
        {
                public class PredefinedOperator
                {
                        protected readonly TypeSpec left;
                        protected readonly TypeSpec right;
                        protected readonly TypeSpec left_unwrap;
                        protected readonly TypeSpec right_unwrap;
                        public readonly Operator OperatorsMask;
                        public TypeSpec ReturnType;

                        public PredefinedOperator (TypeSpec ltype, TypeSpec rtype, Operator op_mask)
                                : this (ltype, rtype, op_mask, ltype)
                        {
                        }

                        public PredefinedOperator (TypeSpec type, Operator op_mask, TypeSpec return_type)
                                : this (type, type, op_mask, return_type)
                        {
                        }

                        public PredefinedOperator (TypeSpec type, Operator op_mask)
                                : this (type, type, op_mask, type)
                        {
                        }

                        public PredefinedOperator (TypeSpec ltype, TypeSpec rtype, Operator op_mask, TypeSpec return_type)
                        {
                                if ((op_mask & Operator.ValuesOnlyMask) != 0)
                                        throw new InternalErrorException ("Only masked values can be used");

                                if ((op_mask & Operator.NullableMask) != 0) {
                                        left_unwrap = Nullable.NullableInfo.GetUnderlyingType (ltype);
                                        right_unwrap = Nullable.NullableInfo.GetUnderlyingType (rtype);
                                } else {
                                        left_unwrap = ltype;
                                        right_unwrap = rtype;
                                }

                                this.left = ltype;
                                this.right = rtype;
                                this.OperatorsMask = op_mask;
                                this.ReturnType = return_type;
                        }

                        public bool IsLifted {
                                get {
                                        return (OperatorsMask & Operator.NullableMask) != 0;
                                }
                        }

                        public virtual Expression ConvertResult (ResolveContext rc, Binary b)
                        {
                                Constant c;

                                var left_expr = b.left;
                                var right_expr = b.right;

                                b.type = ReturnType;

                                if (IsLifted) {
                                        if (rc.HasSet (ResolveContext.Options.ExpressionTreeConversion)) {
                                                b.left = Convert.ImplicitConversion (rc, b.left, left, b.left.Location);
                                                b.right = Convert.ImplicitConversion (rc, b.right, right, b.right.Location);
                                        }

                                        if (right_expr.IsNull) {
                                                if ((b.oper & Operator.EqualityMask) != 0) {
                                                        if (!left_expr.Type.IsNullableType && BuiltinTypeSpec.IsPrimitiveType (left_expr.Type))
                                                                return b.CreateLiftedValueTypeResult (rc, left_expr.Type);
                                                } else if ((b.oper & Operator.BitwiseMask) != 0) {
                                                        if (left_unwrap.BuiltinType != BuiltinTypeSpec.Type.Bool)
                                                                return Nullable.LiftedNull.CreateFromExpression (rc, b);
                                                } else {
                                                        b.left = Convert.ImplicitConversion (rc, b.left, left, b.left.Location);
                                                        b.right = Convert.ImplicitConversion (rc, b.right, right, b.right.Location);

                                                        if ((b.Oper & (Operator.ArithmeticMask | Operator.ShiftMask)) != 0)
                                                                return Nullable.LiftedNull.CreateFromExpression (rc, b);

                                                        return b.CreateLiftedValueTypeResult (rc, left);
                                                }
                                        } else if (left_expr.IsNull) {
                                                if ((b.oper & Operator.EqualityMask) != 0) {
                                                        if (!right_expr.Type.IsNullableType && BuiltinTypeSpec.IsPrimitiveType (right_expr.Type))
                                                                return b.CreateLiftedValueTypeResult (rc, right_expr.Type);
                                                } else if ((b.oper & Operator.BitwiseMask) != 0) {
                                                        if (right_unwrap.BuiltinType != BuiltinTypeSpec.Type.Bool)
                                                                return Nullable.LiftedNull.CreateFromExpression (rc, b);
                                                } else {
                                                        b.left = Convert.ImplicitConversion (rc, b.left, left, b.left.Location);
                                                        b.right = Convert.ImplicitConversion (rc, b.right, right, b.right.Location);

                                                        if ((b.Oper & (Operator.ArithmeticMask | Operator.ShiftMask)) != 0)
                                                                return Nullable.LiftedNull.CreateFromExpression (rc, b);

                                                        return b.CreateLiftedValueTypeResult (rc, right);
                                                }
                                        }
                                }

                                //
                                // A user operators does not support multiple user conversions, but decimal type
                                // is considered to be predefined type therefore we apply predefined operators rules
                                // and then look for decimal user-operator implementation
                                //
                                if (left.BuiltinType == BuiltinTypeSpec.Type.Decimal) {
                                        b.left = Convert.ImplicitConversion (rc, b.left, left, b.left.Location);
                                        b.right = Convert.ImplicitConversion (rc, b.right, right, b.right.Location);

                                        return b.ResolveUserOperator (rc, b.left, b.right);
                                }

                                c = right_expr as Constant;
                                if (c != null) {
                                        if (c.IsDefaultValue) {
                                                //
                                                // Optimizes
                                                // 
                                                // (expr + 0) to expr
                                                // (expr - 0) to expr
                                                // (bool? | false) to bool?
                                                //
                                                if (b.oper == Operator.Addition || b.oper == Operator.Subtraction ||
                                                        (b.oper == Operator.BitwiseOr && left_unwrap.BuiltinType == BuiltinTypeSpec.Type.Bool && c is BoolConstant)) {
                                                        b.left = Convert.ImplicitConversion (rc, b.left, left, b.left.Location);
                                                        return ReducedExpression.Create (b.left, b).Resolve (rc);
                                                }

                                                //
                                                // Optimizes (value &/&& 0) to 0
                                                //
                                                if ((b.oper == Operator.BitwiseAnd || b.oper == Operator.LogicalAnd) && !IsLifted) {
                                                        Constant side_effect = new SideEffectConstant (c, b.left, c.Location);
                                                        return ReducedExpression.Create (side_effect, b);
                                                }
                                        } else {
                                                //
                                                // Optimizes (bool? & true) to bool?
                                                //
                                                if (IsLifted && left_unwrap.BuiltinType == BuiltinTypeSpec.Type.Bool && b.oper == Operator.BitwiseAnd) {
                                                        return ReducedExpression.Create (b.left, b).Resolve (rc);
                                                }
                                        }

                                        if ((b.oper == Operator.Multiply || b.oper == Operator.Division) && c.IsOneInteger)
                                                return ReducedExpression.Create (b.left, b).Resolve (rc);

                                        if ((b.oper & Operator.ShiftMask) != 0 && c is IntConstant) {
                                                b.right = new IntConstant (rc.BuiltinTypes, ((IntConstant) c).Value & GetShiftMask (left_unwrap), b.right.Location);
                                        }
                                }

                                c = b.left as Constant;
                                if (c != null) {
                                        if (c.IsDefaultValue) {
                                                //
                                                // Optimizes
                                                // 
                                                // (0 + expr) to expr
                                                // (false | bool?) to bool?
                                                //
                                                if (b.oper == Operator.Addition ||
                                                        (b.oper == Operator.BitwiseOr && right_unwrap.BuiltinType == BuiltinTypeSpec.Type.Bool && c is BoolConstant)) {
                                                        b.right = Convert.ImplicitConversion (rc, b.right, right, b.right.Location);
                                                        return ReducedExpression.Create (b.right, b).Resolve (rc);
                                                }

                                                //
                                                // Optimizes (false && expr) to false
                                                //
                                                if (b.oper == Operator.LogicalAnd && c.Type.BuiltinType == BuiltinTypeSpec.Type.Bool) {
                                                        // No rhs side-effects
                                                        Expression.Warning_UnreachableExpression (rc, b.right.StartLocation);
                                                        return ReducedExpression.Create (c, b);
                                                }

                                                //
                                                // Optimizes (0 & value) to 0
                                                //
                                                if (b.oper == Operator.BitwiseAnd && !IsLifted) {
                                                        Constant side_effect = new SideEffectConstant (c, b.right, c.Location);
                                                        return ReducedExpression.Create (side_effect, b);
                                                }
                                        } else {
                                                //
                                                // Optimizes (true & bool?) to bool?
                                                //
                                                if (IsLifted && left_unwrap.BuiltinType == BuiltinTypeSpec.Type.Bool && b.oper == Operator.BitwiseAnd) {
                                                        return ReducedExpression.Create (b.right, b).Resolve (rc);
                                                }

                                                //
                                                // Optimizes (true || expr) to true
                                                //
                                                if (b.oper == Operator.LogicalOr && c.Type.BuiltinType == BuiltinTypeSpec.Type.Bool) {
                                                        // No rhs side-effects
                                                        Expression.Warning_UnreachableExpression (rc, b.right.StartLocation);
                                                        return ReducedExpression.Create (c, b);
                                                }
                                        }

                                        if (b.oper == Operator.Multiply && c.IsOneInteger)
                                                return ReducedExpression.Create (b.right, b).Resolve (rc);
                                }

                                if (IsLifted) {
                                        var lifted = new Nullable.LiftedBinaryOperator (b);

                                        TypeSpec ltype, rtype;
                                        if (b.left.Type.IsNullableType) {
                                                lifted.UnwrapLeft = new Nullable.Unwrap (b.left);
                                                ltype = left_unwrap;
                                        } else {
                                                ltype = left;
                                        }

                                        if (b.right.Type.IsNullableType) {
                                                lifted.UnwrapRight = new Nullable.Unwrap (b.right);
                                                rtype = right_unwrap;
                                        } else {
                                                rtype = right;
                                        }

                                        lifted.Left = b.left.IsNull ?
                                                b.left :
                                                Convert.ImplicitConversion (rc, lifted.UnwrapLeft ?? b.left, ltype, b.left.Location);

                                        lifted.Right = b.right.IsNull ?
                                                b.right :
                                                Convert.ImplicitConversion (rc, lifted.UnwrapRight ?? b.right, rtype, b.right.Location);

                                        return lifted.Resolve (rc);
                                }

                                b.left = Convert.ImplicitConversion (rc, b.left, left, b.left.Location);
                                b.right = Convert.ImplicitConversion (rc, b.right, right, b.right.Location);

                                return b;
                        }

                        public bool IsPrimitiveApplicable (TypeSpec ltype, TypeSpec rtype)
                        {
                                //
                                // We are dealing with primitive types only
                                //
                                return left == ltype && ltype == rtype;
                        }

                        public virtual bool IsApplicable (ResolveContext ec, Expression lexpr, Expression rexpr)
                        {
                                // Quick path
                                if (left == lexpr.Type && right == rexpr.Type)
                                        return true;

                                return Convert.ImplicitConversionExists (ec, lexpr, left) &&
                                        Convert.ImplicitConversionExists (ec, rexpr, right);
                        }

                        public PredefinedOperator ResolveBetterOperator (ResolveContext ec, PredefinedOperator best_operator)
                        {
                                if ((OperatorsMask & Operator.DecomposedMask) != 0)
                                        return best_operator;

                                if ((best_operator.OperatorsMask & Operator.DecomposedMask) != 0)
                                        return this;

                                int result = 0;
                                if (left != null && best_operator.left != null) {
                                        result = OverloadResolver.BetterTypeConversion (ec, best_operator.left_unwrap, left_unwrap);
                                }

                                //
                                // When second argument is same as the first one, the result is same
                                //
                                if (right != null && (left != right || best_operator.left != best_operator.right)) {
                                        result |= OverloadResolver.BetterTypeConversion (ec, best_operator.right_unwrap, right_unwrap);
                                }

                                if (result == 0 || result > 2)
                                        return null;

                                return result == 1 ? best_operator : this;
                        }
                }

                sealed class PredefinedStringOperator : PredefinedOperator
                {
                        public PredefinedStringOperator (TypeSpec type, Operator op_mask, TypeSpec retType)
                                : base (type, type, op_mask, retType)
                        {
                        }

                        public PredefinedStringOperator (TypeSpec ltype, TypeSpec rtype, Operator op_mask, TypeSpec retType)
                                : base (ltype, rtype, op_mask, retType)
                        {
                        }

                        public override Expression ConvertResult (ResolveContext ec, Binary b)
                        {
                                //
                                // Use original expression for nullable arguments
                                //
                                Nullable.Unwrap unwrap = b.left as Nullable.Unwrap;
                                if (unwrap != null)
                                        b.left = unwrap.Original;

                                unwrap = b.right as Nullable.Unwrap;
                                if (unwrap != null)
                                        b.right = unwrap.Original;

                                b.left = Convert.ImplicitConversion (ec, b.left, left, b.left.Location);
                                b.right = Convert.ImplicitConversion (ec, b.right, right, b.right.Location);

                                //
                                // Start a new concat expression using converted expression
                                //
                                return StringConcat.Create (ec, b.left, b.right, b.loc);
                        }
                }

                sealed class PredefinedEqualityOperator : PredefinedOperator
                {
                        MethodSpec equal_method, inequal_method;

                        public PredefinedEqualityOperator (TypeSpec arg, TypeSpec retType)
                                : base (arg, arg, Operator.EqualityMask, retType)
                        {
                        }

                        public override Expression ConvertResult (ResolveContext ec, Binary b)
                        {
                                b.type = ReturnType;

                                b.left = Convert.ImplicitConversion (ec, b.left, left, b.left.Location);
                                b.right = Convert.ImplicitConversion (ec, b.right, right, b.right.Location);

                                Arguments args = new Arguments (2);
                                args.Add (new Argument (b.left));
                                args.Add (new Argument (b.right));

                                MethodSpec method;
                                if (b.oper == Operator.Equality) {
                                        if (equal_method == null) {
                                                if (left.BuiltinType == BuiltinTypeSpec.Type.String)
                                                        equal_method = ec.Module.PredefinedMembers.StringEqual.Resolve (b.loc);
                                                else if (left.BuiltinType == BuiltinTypeSpec.Type.Delegate)
                                                        equal_method = ec.Module.PredefinedMembers.DelegateEqual.Resolve (b.loc);
                                                else
                                                        throw new NotImplementedException (left.GetSignatureForError ());
                                        }

                                        method = equal_method;
                                } else {
                                        if (inequal_method == null) {
                                                if (left.BuiltinType == BuiltinTypeSpec.Type.String)
                                                        inequal_method = ec.Module.PredefinedMembers.StringInequal.Resolve (b.loc);
                                                else if (left.BuiltinType == BuiltinTypeSpec.Type.Delegate)
                                                        inequal_method = ec.Module.PredefinedMembers.DelegateInequal.Resolve (b.loc);
                                                else
                                                        throw new NotImplementedException (left.GetSignatureForError ());
                                        }

                                        method = inequal_method;
                                }

                                return new UserOperatorCall (method, args, b.CreateExpressionTree, b.loc);
                        }
                }

                class PredefinedPointerOperator : PredefinedOperator
                {
                        public PredefinedPointerOperator (TypeSpec ltype, TypeSpec rtype, Operator op_mask)
                                : base (ltype, rtype, op_mask)
                        {
                        }

                        public PredefinedPointerOperator (TypeSpec ltype, TypeSpec rtype, Operator op_mask, TypeSpec retType)
                                : base (ltype, rtype, op_mask, retType)
                        {
                        }

                        public PredefinedPointerOperator (TypeSpec type, Operator op_mask, TypeSpec return_type)
                                : base (type, op_mask, return_type)
                        {
                        }

                        public override bool IsApplicable (ResolveContext ec, Expression lexpr, Expression rexpr)
                        {
                                if (left == null) {
                                        if (!lexpr.Type.IsPointer)
                                                return false;
                                } else {
                                        if (!Convert.ImplicitConversionExists (ec, lexpr, left))
                                                return false;
                                }

                                if (right == null) {
                                        if (!rexpr.Type.IsPointer)
                                                return false;
                                } else {
                                        if (!Convert.ImplicitConversionExists (ec, rexpr, right))
                                                return false;
                                }

                                return true;
                        }

                        public override Expression ConvertResult (ResolveContext ec, Binary b)
                        {
                                if (left != null) {
                                        b.left = EmptyCast.Create (b.left, left);
                                } else if (right != null) {
                                        b.right = EmptyCast.Create (b.right, right);
                                }

                                TypeSpec r_type = ReturnType;
                                Expression left_arg, right_arg;
                                if (r_type == null) {
                                        if (left == null) {
                                                left_arg = b.left;
                                                right_arg = b.right;
                                                r_type = b.left.Type;
                                        } else {
                                                left_arg = b.right;
                                                right_arg = b.left;
                                                r_type = b.right.Type;
                                        }
                                } else {
                                        left_arg = b.left;
                                        right_arg = b.right;
                                }

                                return new PointerArithmetic (b.oper, left_arg, right_arg, r_type, b.loc).Resolve (ec);
                        }
                }

                [Flags]
                public enum Operator {
                        Multiply        = 0 | ArithmeticMask,
                        Division        = 1 | ArithmeticMask,
                        Modulus         = 2 | ArithmeticMask,
                        Addition        = 3 | ArithmeticMask | AdditionMask,
                        Subtraction = 4 | ArithmeticMask | SubtractionMask,

                        LeftShift       = 5 | ShiftMask,
                        RightShift      = 6 | ShiftMask,

                        LessThan        = 7 | ComparisonMask | RelationalMask,
                        GreaterThan     = 8 | ComparisonMask | RelationalMask,
                        LessThanOrEqual         = 9 | ComparisonMask | RelationalMask,
                        GreaterThanOrEqual      = 10 | ComparisonMask | RelationalMask,
                        Equality        = 11 | ComparisonMask | EqualityMask,
                        Inequality      = 12 | ComparisonMask | EqualityMask,

                        BitwiseAnd      = 13 | BitwiseMask,
                        ExclusiveOr     = 14 | BitwiseMask,
                        BitwiseOr       = 15 | BitwiseMask,

                        LogicalAnd      = 16 | LogicalMask,
                        LogicalOr       = 17 | LogicalMask,

                        //
                        // Operator masks
                        //
                        ValuesOnlyMask  = ArithmeticMask - 1,
                        ArithmeticMask  = 1 << 5,
                        ShiftMask               = 1 << 6,
                        ComparisonMask  = 1 << 7,
                        EqualityMask    = 1 << 8,
                        BitwiseMask             = 1 << 9,
                        LogicalMask             = 1 << 10,
                        AdditionMask    = 1 << 11,
                        SubtractionMask = 1 << 12,
                        RelationalMask  = 1 << 13,

                        DecomposedMask  = 1 << 19,
                        NullableMask    = 1 << 20
                }

                [Flags]
                public enum State : byte
                {
                        None = 0,
                        Compound = 1 << 1,
                        UserOperatorsExcluded = 1 << 2
                }

                readonly Operator oper;
                Expression left, right;
                State state;
                ConvCast.Mode enum_conversion;

                public Binary (Operator oper, Expression left, Expression right, bool isCompound)
                        : this (oper, left, right, State.Compound)
                {
                }

                public Binary (Operator oper, Expression left, Expression right, State state)
                        : this (oper, left, right)
                {
                        this.state = state;
                }

                public Binary (Operator oper, Expression left, Expression right)
                        : this (oper, left, right, left.Location)
                {
                }

                public Binary (Operator oper, Expression left, Expression right, Location loc)
                {
                        this.oper = oper;
                        this.left = left;
                        this.right = right;
                        this.loc = loc;
                }

                #region Properties

                public bool IsCompound {
                        get {
                                return (state & State.Compound) != 0;
                        }
                }

                public Operator Oper {
                        get {
                                return oper;
                        }
                }

                public Expression Left {
                        get {
                                return this.left;
                        }
                }

                public Expression Right {
                        get {
                                return this.right;
                        }
                }

                public override Location StartLocation {
                        get {
                                return left.StartLocation;
                        }
                }

                #endregion

                /// <summary>
                ///   Returns a stringified representation of the Operator
                /// </summary>
                string OperName (Operator oper)
                {
                        string s;
                        switch (oper){
                        case Operator.Multiply:
                                s = "*";
                                break;
                        case Operator.Division:
                                s = "/";
                                break;
                        case Operator.Modulus:
                                s = "%";
                                break;
                        case Operator.Addition:
                                s = "+";
                                break;
                        case Operator.Subtraction:
                                s = "-";
                                break;
                        case Operator.LeftShift:
                                s = "<<";
                                break;
                        case Operator.RightShift:
                                s = ">>";
                                break;
                        case Operator.LessThan:
                                s = "<";
                                break;
                        case Operator.GreaterThan:
                                s = ">";
                                break;
                        case Operator.LessThanOrEqual:
                                s = "<=";
                                break;
                        case Operator.GreaterThanOrEqual:
                                s = ">=";
                                break;
                        case Operator.Equality:
                                s = "==";
                                break;
                        case Operator.Inequality:
                                s = "!=";
                                break;
                        case Operator.BitwiseAnd:
                                s = "&";
                                break;
                        case Operator.BitwiseOr:
                                s = "|";
                                break;
                        case Operator.ExclusiveOr:
                                s = "^";
                                break;
                        case Operator.LogicalOr:
                                s = "||";
                                break;
                        case Operator.LogicalAnd:
                                s = "&&";
                                break;
                        default:
                                s = oper.ToString ();
                                break;
                        }

                        if (IsCompound)
                                return s + "=";

                        return s;
                }

                public static void Error_OperatorCannotBeApplied (ResolveContext ec, Expression left, Expression right, Operator oper, Location loc)
                {
                        new Binary (oper, left, right).Error_OperatorCannotBeApplied (ec, left, right);
                }

                public static void Error_OperatorCannotBeApplied (ResolveContext ec, Expression left, Expression right, string oper, Location loc)
                {
                        if (left.Type == InternalType.ErrorType || right.Type == InternalType.ErrorType)
                                return;

                        string l, r;
                        l = left.Type.GetSignatureForError ();
                        r = right.Type.GetSignatureForError ();

                        ec.Report.Error (19, loc, "Operator `{0}' cannot be applied to operands of type `{1}' and `{2}'",
                                oper, l, r);
                }
                
                void Error_OperatorCannotBeApplied (ResolveContext ec, Expression left, Expression right)
                {
                        Error_OperatorCannotBeApplied (ec, left, right, OperName (oper), loc);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        //
                        // Optimized version when on-true/on-false data are not needed
                        //
                        if ((oper & Operator.LogicalMask) == 0) {
                                left.FlowAnalysis (fc);
                                right.FlowAnalysis (fc);
                                return;
                        }

                        left.FlowAnalysisConditional (fc);
                        var left_fc_ontrue = fc.DefiniteAssignmentOnTrue;
                        var left_fc_onfalse = fc.DefiniteAssignmentOnFalse;

                        fc.DefiniteAssignmentOnTrue = fc.DefiniteAssignmentOnFalse = fc.DefiniteAssignment = new DefiniteAssignmentBitSet (
                                oper == Operator.LogicalOr ? left_fc_onfalse : left_fc_ontrue);
                        right.FlowAnalysisConditional (fc);

                        if (oper == Operator.LogicalOr)
                                fc.DefiniteAssignment = (left_fc_onfalse | (fc.DefiniteAssignmentOnFalse & fc.DefiniteAssignmentOnTrue)) & left_fc_ontrue;
                        else
                                fc.DefiniteAssignment = (left_fc_ontrue | (fc.DefiniteAssignmentOnFalse & fc.DefiniteAssignmentOnTrue)) & left_fc_onfalse;
                }

                public override void FlowAnalysisConditional (FlowAnalysisContext fc)
                {
                        if ((oper & Operator.LogicalMask) == 0) {
                                base.FlowAnalysisConditional (fc);
                                return;
                        }

                        left.FlowAnalysisConditional (fc);
                        var left_fc_ontrue = fc.DefiniteAssignmentOnTrue;
                        var left_fc_onfalse = fc.DefiniteAssignmentOnFalse;

                        fc.DefiniteAssignmentOnTrue = fc.DefiniteAssignmentOnFalse = fc.DefiniteAssignment = new DefiniteAssignmentBitSet (
                                oper == Operator.LogicalOr ? left_fc_onfalse : left_fc_ontrue);
                        right.FlowAnalysisConditional (fc);

                        var lc = left as Constant;
                        if (oper == Operator.LogicalOr) {
                                fc.DefiniteAssignmentOnFalse = left_fc_onfalse | fc.DefiniteAssignmentOnFalse;
                                if (lc != null && lc.IsDefaultValue)
                                        fc.DefiniteAssignmentOnTrue = fc.DefiniteAssignmentOnFalse;
                                else
                                        fc.DefiniteAssignmentOnTrue = new DefiniteAssignmentBitSet (left_fc_ontrue & (left_fc_onfalse | fc.DefiniteAssignmentOnTrue));
                        } else {
                                fc.DefiniteAssignmentOnTrue = left_fc_ontrue | fc.DefiniteAssignmentOnTrue;
                                if (lc != null && !lc.IsDefaultValue)
                                        fc.DefiniteAssignmentOnFalse = fc.DefiniteAssignmentOnTrue;
                                else
                                        fc.DefiniteAssignmentOnFalse = new DefiniteAssignmentBitSet ((left_fc_ontrue | fc.DefiniteAssignmentOnFalse) & left_fc_onfalse);
                        }
                }

                //
                // Converts operator to System.Linq.Expressions.ExpressionType enum name
                //
                string GetOperatorExpressionTypeName ()
                {
                        switch (oper) {
                        case Operator.Addition:
                                return IsCompound ? "AddAssign" : "Add";
                        case Operator.BitwiseAnd:
                                return IsCompound ? "AndAssign" : "And";
                        case Operator.BitwiseOr:
                                return IsCompound ? "OrAssign" : "Or";
                        case Operator.Division:
                                return IsCompound ? "DivideAssign" : "Divide";
                        case Operator.ExclusiveOr:
                                return IsCompound ? "ExclusiveOrAssign" : "ExclusiveOr";
                        case Operator.Equality:
                                return "Equal";
                        case Operator.GreaterThan:
                                return "GreaterThan";
                        case Operator.GreaterThanOrEqual:
                                return "GreaterThanOrEqual";
                        case Operator.Inequality:
                                return "NotEqual";
                        case Operator.LeftShift:
                                return IsCompound ? "LeftShiftAssign" : "LeftShift";
                        case Operator.LessThan:
                                return "LessThan";
                        case Operator.LessThanOrEqual:
                                return "LessThanOrEqual";
                        case Operator.LogicalAnd:
                                return "And";
                        case Operator.LogicalOr:
                                return "Or";
                        case Operator.Modulus:
                                return IsCompound ? "ModuloAssign" : "Modulo";
                        case Operator.Multiply:
                                return IsCompound ? "MultiplyAssign" : "Multiply";
                        case Operator.RightShift:
                                return IsCompound ? "RightShiftAssign" : "RightShift";
                        case Operator.Subtraction:
                                return IsCompound ? "SubtractAssign" : "Subtract";
                        default:
                                throw new NotImplementedException ("Unknown expression type operator " + oper.ToString ());
                        }
                }

                static CSharp.Operator.OpType ConvertBinaryToUserOperator (Operator op)
                {
                        switch (op) {
                        case Operator.Addition:
                                return CSharp.Operator.OpType.Addition;
                        case Operator.BitwiseAnd:
                        case Operator.LogicalAnd:
                                return CSharp.Operator.OpType.BitwiseAnd;
                        case Operator.BitwiseOr:
                        case Operator.LogicalOr:
                                return CSharp.Operator.OpType.BitwiseOr;
                        case Operator.Division:
                                return CSharp.Operator.OpType.Division;
                        case Operator.Equality:
                                return CSharp.Operator.OpType.Equality;
                        case Operator.ExclusiveOr:
                                return CSharp.Operator.OpType.ExclusiveOr;
                        case Operator.GreaterThan:
                                return CSharp.Operator.OpType.GreaterThan;
                        case Operator.GreaterThanOrEqual:
                                return CSharp.Operator.OpType.GreaterThanOrEqual;
                        case Operator.Inequality:
                                return CSharp.Operator.OpType.Inequality;
                        case Operator.LeftShift:
                                return CSharp.Operator.OpType.LeftShift;
                        case Operator.LessThan:
                                return CSharp.Operator.OpType.LessThan;
                        case Operator.LessThanOrEqual:
                                return CSharp.Operator.OpType.LessThanOrEqual;
                        case Operator.Modulus:
                                return CSharp.Operator.OpType.Modulus;
                        case Operator.Multiply:
                                return CSharp.Operator.OpType.Multiply;
                        case Operator.RightShift:
                                return CSharp.Operator.OpType.RightShift;
                        case Operator.Subtraction:
                                return CSharp.Operator.OpType.Subtraction;
                        default:
                                throw new InternalErrorException (op.ToString ());
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return left.ContainsEmitWithAwait () || right.ContainsEmitWithAwait ();
                }

                public static void EmitOperatorOpcode (EmitContext ec, Operator oper, TypeSpec l, Expression right)
                {
                        OpCode opcode;

                        switch (oper){
                        case Operator.Multiply:
                                if (ec.HasSet (EmitContext.Options.CheckedScope)) {
                                        if (l.BuiltinType == BuiltinTypeSpec.Type.Int || l.BuiltinType == BuiltinTypeSpec.Type.Long)
                                                opcode = OpCodes.Mul_Ovf;
                                        else if (!IsFloat (l))
                                                opcode = OpCodes.Mul_Ovf_Un;
                                        else
                                                opcode = OpCodes.Mul;
                                } else
                                        opcode = OpCodes.Mul;
                                
                                break;
                                
                        case Operator.Division:
                                if (IsUnsigned (l))
                                        opcode = OpCodes.Div_Un;
                                else
                                        opcode = OpCodes.Div;
                                break;
                                
                        case Operator.Modulus:
                                if (IsUnsigned (l))
                                        opcode = OpCodes.Rem_Un;
                                else
                                        opcode = OpCodes.Rem;
                                break;

                        case Operator.Addition:
                                if (ec.HasSet (EmitContext.Options.CheckedScope)) {
                                        if (l.BuiltinType == BuiltinTypeSpec.Type.Int || l.BuiltinType == BuiltinTypeSpec.Type.Long)
                                                opcode = OpCodes.Add_Ovf;
                                        else if (!IsFloat (l))
                                                opcode = OpCodes.Add_Ovf_Un;
                                        else
                                                opcode = OpCodes.Add;
                                } else
                                        opcode = OpCodes.Add;
                                break;

                        case Operator.Subtraction:
                                if (ec.HasSet (EmitContext.Options.CheckedScope)) {
                                        if (l.BuiltinType == BuiltinTypeSpec.Type.Int || l.BuiltinType == BuiltinTypeSpec.Type.Long)
                                                opcode = OpCodes.Sub_Ovf;
                                        else if (!IsFloat (l))
                                                opcode = OpCodes.Sub_Ovf_Un;
                                        else
                                                opcode = OpCodes.Sub;
                                } else
                                        opcode = OpCodes.Sub;
                                break;

                        case Operator.RightShift:
                                if (!(right is IntConstant)) {
                                        ec.EmitInt (GetShiftMask (l));
                                        ec.Emit (OpCodes.And);
                                }

                                if (IsUnsigned (l))
                                        opcode = OpCodes.Shr_Un;
                                else
                                        opcode = OpCodes.Shr;
                                break;
                                
                        case Operator.LeftShift:
                                if (!(right is IntConstant)) {
                                        ec.EmitInt (GetShiftMask (l));
                                        ec.Emit (OpCodes.And);
                                }

                                opcode = OpCodes.Shl;
                                break;

                        case Operator.Equality:
                                opcode = OpCodes.Ceq;
                                break;

                        case Operator.Inequality:
                                ec.Emit (OpCodes.Ceq);
                                ec.EmitInt (0);
                                
                                opcode = OpCodes.Ceq;
                                break;

                        case Operator.LessThan:
                                if (IsUnsigned (l))
                                        opcode = OpCodes.Clt_Un;
                                else
                                        opcode = OpCodes.Clt;
                                break;

                        case Operator.GreaterThan:
                                if (IsUnsigned (l))
                                        opcode = OpCodes.Cgt_Un;
                                else
                                        opcode = OpCodes.Cgt;
                                break;

                        case Operator.LessThanOrEqual:
                                if (IsUnsigned (l) || IsFloat (l))
                                        ec.Emit (OpCodes.Cgt_Un);
                                else
                                        ec.Emit (OpCodes.Cgt);
                                ec.EmitInt (0);
                                
                                opcode = OpCodes.Ceq;
                                break;

                        case Operator.GreaterThanOrEqual:
                                if (IsUnsigned (l) || IsFloat (l))
                                        ec.Emit (OpCodes.Clt_Un);
                                else
                                        ec.Emit (OpCodes.Clt);
                                
                                ec.EmitInt (0);
                                
                                opcode = OpCodes.Ceq;
                                break;

                        case Operator.BitwiseOr:
                                opcode = OpCodes.Or;
                                break;

                        case Operator.BitwiseAnd:
                                opcode = OpCodes.And;
                                break;

                        case Operator.ExclusiveOr:
                                opcode = OpCodes.Xor;
                                break;

                        default:
                                throw new InternalErrorException (oper.ToString ());
                        }

                        ec.Emit (opcode);
                }

                static int GetShiftMask (TypeSpec type)
                {
                        return type.BuiltinType == BuiltinTypeSpec.Type.Int || type.BuiltinType == BuiltinTypeSpec.Type.UInt ? 0x1f : 0x3f;
                }

                static bool IsUnsigned (TypeSpec t)
                {
                        switch (t.BuiltinType) {
                        case BuiltinTypeSpec.Type.Char:
                        case BuiltinTypeSpec.Type.UInt:
                        case BuiltinTypeSpec.Type.ULong:
                        case BuiltinTypeSpec.Type.UShort:
                        case BuiltinTypeSpec.Type.Byte:
                                return true;
                        }

                        return t.IsPointer;
                }

                static bool IsFloat (TypeSpec t)
                {
                        return t.BuiltinType == BuiltinTypeSpec.Type.Float || t.BuiltinType == BuiltinTypeSpec.Type.Double;
                }

                public Expression ResolveOperator (ResolveContext rc)
                {
                        eclass = ExprClass.Value;

                        TypeSpec l = left.Type;
                        TypeSpec r = right.Type;
                        Expression expr;
                        bool primitives_only = false;

                        //
                        // Handles predefined primitive types
                        //
                        if ((BuiltinTypeSpec.IsPrimitiveType (l) || (l.IsNullableType && BuiltinTypeSpec.IsPrimitiveType (Nullable.NullableInfo.GetUnderlyingType (l)))) &&
                                (BuiltinTypeSpec.IsPrimitiveType (r) || (r.IsNullableType && BuiltinTypeSpec.IsPrimitiveType (Nullable.NullableInfo.GetUnderlyingType (r))))) {
                                if ((oper & Operator.ShiftMask) == 0) {
                                        if (!DoBinaryOperatorPromotion (rc))
                                                return null;

                                        primitives_only = BuiltinTypeSpec.IsPrimitiveType (l) && BuiltinTypeSpec.IsPrimitiveType (r);
                                }
                        } else {
                                // Pointers
                                if (l.IsPointer || r.IsPointer)
                                        return ResolveOperatorPointer (rc, l, r);

                                // User operators
                                if ((state & State.UserOperatorsExcluded) == 0) {
                                        expr = ResolveUserOperator (rc, left, right);
                                        if (expr != null)
                                                return expr;
                                }

                                bool lenum = l.IsEnum;
                                bool renum = r.IsEnum;
                                if ((oper & (Operator.ComparisonMask | Operator.BitwiseMask)) != 0) {
                                        //
                                        // Enumerations
                                        //
                                        if (IsEnumOrNullableEnum (l) || IsEnumOrNullableEnum (r)) {
                                                expr = ResolveSingleEnumOperators (rc, lenum, renum, l, r);

                                                if (expr == null)
                                                        return null;

                                                if ((oper & Operator.BitwiseMask) != 0) {
                                                        expr = EmptyCast.Create (expr, type);
                                                        enum_conversion = GetEnumResultCast (type);

                                                        if (oper == Operator.BitwiseAnd && left.Type.IsEnum && right.Type.IsEnum) {
                                                                expr = OptimizeAndOperation (expr);
                                                        }
                                                }

                                                left = ConvertEnumOperandToUnderlyingType (rc, left, r.IsNullableType);
                                                right = ConvertEnumOperandToUnderlyingType (rc, right, l.IsNullableType);
                                                return expr;
                                        }
                                } else if ((oper == Operator.Addition || oper == Operator.Subtraction)) {
                                        if (IsEnumOrNullableEnum (l) || IsEnumOrNullableEnum (r)) {
                                                //
                                                // Enumerations
                                                //
                                                expr = ResolveEnumOperators (rc, lenum, renum, l, r);

                                                //
                                                // We cannot break here there is also Enum + String possible match
                                                // which is not ambiguous with predefined enum operators
                                                //
                                                if (expr != null) {
                                                        left = ConvertEnumOperandToUnderlyingType (rc, left, false);
                                                        right = ConvertEnumOperandToUnderlyingType (rc, right, false);

                                                        return expr;
                                                }
                                        } else if (l.IsDelegate || r.IsDelegate) {
                                                //
                                                // Delegates
                                                //
                                                expr = ResolveOperatorDelegate (rc, l, r);

                                                // TODO: Can this be ambiguous
                                                if (expr != null)
                                                        return expr;
                                        }
                                }
                        }
                        
                        //
                        // Equality operators are more complicated
                        //
                        if ((oper & Operator.EqualityMask) != 0) {
                                return ResolveEquality (rc, l, r, primitives_only);
                        }

                        expr = ResolveOperatorPredefined (rc, rc.BuiltinTypes.OperatorsBinaryStandard, primitives_only);
                        if (expr != null)
                                return expr;

                        if (primitives_only)
                                return null;

                        //
                        // Lifted operators have lower priority
                        //
                        return ResolveOperatorPredefined (rc, rc.Module.OperatorsBinaryLifted, false);
                }

                static bool IsEnumOrNullableEnum (TypeSpec type)
                {
                        return type.IsEnum || (type.IsNullableType && Nullable.NullableInfo.GetUnderlyingType (type).IsEnum);
                }


                // at least one of 'left' or 'right' is an enumeration constant (EnumConstant or SideEffectConstant or ...)
                // if 'left' is not an enumeration constant, create one from the type of 'right'
                Constant EnumLiftUp (ResolveContext ec, Constant left, Constant right)
                {
                        switch (oper) {
                        case Operator.BitwiseOr:
                        case Operator.BitwiseAnd:
                        case Operator.ExclusiveOr:
                        case Operator.Equality:
                        case Operator.Inequality:
                        case Operator.LessThan:
                        case Operator.LessThanOrEqual:
                        case Operator.GreaterThan:
                        case Operator.GreaterThanOrEqual:
                                if (left.Type.IsEnum)
                                        return left;
                                
                                if (left.IsZeroInteger)
                                        return left.Reduce (ec, right.Type);
                                
                                break;
                                
                        case Operator.Addition:
                        case Operator.Subtraction:
                                return left;
                                
                        case Operator.Multiply:
                        case Operator.Division:
                        case Operator.Modulus:
                        case Operator.LeftShift:
                        case Operator.RightShift:
                                if (right.Type.IsEnum || left.Type.IsEnum)
                                        break;
                                return left;
                        }

                        return null;
                }

                //
                // The `|' operator used on types which were extended is dangerous
                //
                void CheckBitwiseOrOnSignExtended (ResolveContext ec)
                {
                        OpcodeCast lcast = left as OpcodeCast;
                        if (lcast != null) {
                                if (IsUnsigned (lcast.UnderlyingType))
                                        lcast = null;
                        }

                        OpcodeCast rcast = right as OpcodeCast;
                        if (rcast != null) {
                                if (IsUnsigned (rcast.UnderlyingType))
                                        rcast = null;
                        }

                        if (lcast == null && rcast == null)
                                return;

                        // FIXME: consider constants

                        var ltype = lcast != null ? lcast.UnderlyingType : rcast.UnderlyingType;
                        ec.Report.Warning (675, 3, loc,
                                "The operator `|' used on the sign-extended type `{0}'. Consider casting to a smaller unsigned type first",
                                ltype.GetSignatureForError ());
                }

                public static PredefinedOperator[] CreatePointerOperatorsTable (BuiltinTypes types)
                {
                        return new PredefinedOperator[] {
                                //
                                // Pointer arithmetic:
                                //
                                // T* operator + (T* x, int y);         T* operator - (T* x, int y);
                                // T* operator + (T* x, uint y);        T* operator - (T* x, uint y);
                                // T* operator + (T* x, long y);        T* operator - (T* x, long y);
                                // T* operator + (T* x, ulong y);       T* operator - (T* x, ulong y);
                                //
                                new PredefinedPointerOperator (null, types.Int, Operator.AdditionMask | Operator.SubtractionMask),
                                new PredefinedPointerOperator (null, types.UInt, Operator.AdditionMask | Operator.SubtractionMask),
                                new PredefinedPointerOperator (null, types.Long, Operator.AdditionMask | Operator.SubtractionMask),
                                new PredefinedPointerOperator (null, types.ULong, Operator.AdditionMask | Operator.SubtractionMask),

                                //
                                // T* operator + (int y,   T* x);
                                // T* operator + (uint y,  T *x);
                                // T* operator + (long y,  T *x);
                                // T* operator + (ulong y, T *x);
                                //
                                new PredefinedPointerOperator (types.Int, null, Operator.AdditionMask, null),
                                new PredefinedPointerOperator (types.UInt, null, Operator.AdditionMask, null),
                                new PredefinedPointerOperator (types.Long, null, Operator.AdditionMask, null),
                                new PredefinedPointerOperator (types.ULong, null, Operator.AdditionMask, null),

                                //
                                // long operator - (T* x, T *y)
                                //
                                new PredefinedPointerOperator (null, Operator.SubtractionMask, types.Long)
                        };
                }

                public static PredefinedOperator[] CreateStandardOperatorsTable (BuiltinTypes types)
                {
                        TypeSpec bool_type = types.Bool;

                        return new [] {
                                new PredefinedOperator (types.Int, Operator.ArithmeticMask | Operator.BitwiseMask | Operator.ShiftMask),
                                new PredefinedOperator (types.UInt, Operator.ArithmeticMask | Operator.BitwiseMask),
                                new PredefinedOperator (types.Long, Operator.ArithmeticMask | Operator.BitwiseMask),
                                new PredefinedOperator (types.ULong, Operator.ArithmeticMask | Operator.BitwiseMask),
                                new PredefinedOperator (types.Float, Operator.ArithmeticMask),
                                new PredefinedOperator (types.Double, Operator.ArithmeticMask),
                                new PredefinedOperator (types.Decimal, Operator.ArithmeticMask),

                                new PredefinedOperator (types.Int, Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (types.UInt, Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (types.Long, Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (types.ULong, Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (types.Float, Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (types.Double, Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (types.Decimal, Operator.ComparisonMask, bool_type),

                                new PredefinedStringOperator (types.String, Operator.AdditionMask, types.String),
                                // Remaining string operators are in lifted tables

                                new PredefinedOperator (bool_type, Operator.BitwiseMask | Operator.LogicalMask | Operator.EqualityMask, bool_type),

                                new PredefinedOperator (types.UInt, types.Int, Operator.ShiftMask),
                                new PredefinedOperator (types.Long, types.Int, Operator.ShiftMask),
                                new PredefinedOperator (types.ULong, types.Int, Operator.ShiftMask)
                        };

                }
                public static PredefinedOperator[] CreateStandardLiftedOperatorsTable (ModuleContainer module)
                {
                        var types = module.Compiler.BuiltinTypes;

                        //
                        // Not strictly lifted but need to be in second group otherwise expressions like
                        // int + null would resolve to +(object, string) instead of +(int?, int?)
                        //
                        var string_operators = new [] {
                                new PredefinedStringOperator (types.String, types.Object, Operator.AdditionMask, types.String),
                                new PredefinedStringOperator (types.Object, types.String, Operator.AdditionMask, types.String),
                        };

                        var nullable = module.PredefinedTypes.Nullable.TypeSpec;
                        if (nullable == null)
                                return string_operators;

                        var bool_type = types.Bool;

                        var nullable_bool = nullable.MakeGenericType (module, new[] { bool_type });
                        var nullable_int = nullable.MakeGenericType (module, new[] { types.Int });
                        var nullable_uint = nullable.MakeGenericType (module, new[] { types.UInt });
                        var nullable_long = nullable.MakeGenericType (module, new[] { types.Long });
                        var nullable_ulong = nullable.MakeGenericType (module, new[] { types.ULong });
                        var nullable_float = nullable.MakeGenericType (module, new[] { types.Float });
                        var nullable_double = nullable.MakeGenericType (module, new[] { types.Double });
                        var nullable_decimal = nullable.MakeGenericType (module, new[] { types.Decimal });

                        return new[] {
                                new PredefinedOperator (nullable_int, Operator.NullableMask | Operator.ArithmeticMask | Operator.BitwiseMask | Operator.ShiftMask),
                                new PredefinedOperator (nullable_uint, Operator.NullableMask | Operator.ArithmeticMask | Operator.BitwiseMask),
                                new PredefinedOperator (nullable_long, Operator.NullableMask | Operator.ArithmeticMask | Operator.BitwiseMask),
                                new PredefinedOperator (nullable_ulong, Operator.NullableMask | Operator.ArithmeticMask | Operator.BitwiseMask),
                                new PredefinedOperator (nullable_float, Operator.NullableMask | Operator.ArithmeticMask),
                                new PredefinedOperator (nullable_double, Operator.NullableMask | Operator.ArithmeticMask),
                                new PredefinedOperator (nullable_decimal, Operator.NullableMask | Operator.ArithmeticMask),

                                new PredefinedOperator (nullable_int, Operator.NullableMask | Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (nullable_uint, Operator.NullableMask | Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (nullable_long, Operator.NullableMask | Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (nullable_ulong, Operator.NullableMask | Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (nullable_float, Operator.NullableMask | Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (nullable_double, Operator.NullableMask | Operator.ComparisonMask, bool_type),
                                new PredefinedOperator (nullable_decimal, Operator.NullableMask | Operator.ComparisonMask, bool_type),

                                new PredefinedOperator (nullable_bool, Operator.NullableMask | Operator.BitwiseMask, nullable_bool),

                                new PredefinedOperator (nullable_uint, nullable_int, Operator.NullableMask | Operator.ShiftMask),
                                new PredefinedOperator (nullable_long, nullable_int, Operator.NullableMask | Operator.ShiftMask),
                                new PredefinedOperator (nullable_ulong, nullable_int, Operator.NullableMask | Operator.ShiftMask),

                                string_operators [0],
                                string_operators [1]
                        };
                }

                public static PredefinedOperator[] CreateEqualityOperatorsTable (BuiltinTypes types)
                {
                        TypeSpec bool_type = types.Bool;

                        return new[] {
                                new PredefinedEqualityOperator (types.String, bool_type),
                                new PredefinedEqualityOperator (types.Delegate, bool_type),
                                new PredefinedOperator (bool_type, Operator.EqualityMask, bool_type),
                                new PredefinedOperator (types.Int, Operator.EqualityMask, bool_type),
                                new PredefinedOperator (types.UInt, Operator.EqualityMask, bool_type),
                                new PredefinedOperator (types.Long, Operator.EqualityMask, bool_type),
                                new PredefinedOperator (types.ULong, Operator.EqualityMask, bool_type),
                                new PredefinedOperator (types.Float, Operator.EqualityMask, bool_type),
                                new PredefinedOperator (types.Double, Operator.EqualityMask, bool_type),
                                new PredefinedOperator (types.Decimal, Operator.EqualityMask, bool_type),
                        };
                }

                public static PredefinedOperator[] CreateEqualityLiftedOperatorsTable (ModuleContainer module)
                {
                        var nullable = module.PredefinedTypes.Nullable.TypeSpec;

                        if (nullable == null)
                                return new PredefinedOperator [0];

                        var types = module.Compiler.BuiltinTypes;
                        var bool_type = types.Bool;
                        var nullable_bool = nullable.MakeGenericType (module, new [] { bool_type });
                        var nullable_int = nullable.MakeGenericType (module, new[] { types.Int });
                        var nullable_uint = nullable.MakeGenericType (module, new[] { types.UInt });
                        var nullable_long = nullable.MakeGenericType (module, new[] { types.Long });
                        var nullable_ulong = nullable.MakeGenericType (module, new[] { types.ULong });
                        var nullable_float = nullable.MakeGenericType (module, new[] { types.Float });
                        var nullable_double = nullable.MakeGenericType (module, new[] { types.Double });
                        var nullable_decimal = nullable.MakeGenericType (module, new[] { types.Decimal });

                        return new [] {
                                new PredefinedOperator (nullable_bool, Operator.NullableMask | Operator.EqualityMask, bool_type),
                                new PredefinedOperator (nullable_int, Operator.NullableMask | Operator.EqualityMask, bool_type),
                                new PredefinedOperator (nullable_uint, Operator.NullableMask | Operator.EqualityMask, bool_type),
                                new PredefinedOperator (nullable_long, Operator.NullableMask | Operator.EqualityMask, bool_type),
                                new PredefinedOperator (nullable_ulong, Operator.NullableMask | Operator.EqualityMask, bool_type),
                                new PredefinedOperator (nullable_float, Operator.NullableMask | Operator.EqualityMask, bool_type),
                                new PredefinedOperator (nullable_double, Operator.NullableMask | Operator.EqualityMask, bool_type),
                                new PredefinedOperator (nullable_decimal, Operator.NullableMask | Operator.EqualityMask, bool_type)
                        };
                }

                //
                // 7.2.6.2 Binary numeric promotions
                //
                bool DoBinaryOperatorPromotion (ResolveContext rc)
                {
                        TypeSpec ltype = left.Type;
                        if (ltype.IsNullableType) {
                                ltype = Nullable.NullableInfo.GetUnderlyingType (ltype);
                        }

                        //
                        // This is numeric promotion code only
                        //
                        if (ltype.BuiltinType == BuiltinTypeSpec.Type.Bool)
                                return true;

                        TypeSpec rtype = right.Type;
                        if (rtype.IsNullableType) {
                                rtype = Nullable.NullableInfo.GetUnderlyingType (rtype);
                        }

                        var lb = ltype.BuiltinType;
                        var rb = rtype.BuiltinType;
                        TypeSpec type;
                        Expression expr;

                        if (lb == BuiltinTypeSpec.Type.Decimal || rb == BuiltinTypeSpec.Type.Decimal) {
                                type = rc.BuiltinTypes.Decimal;
                        } else if (lb == BuiltinTypeSpec.Type.Double || rb == BuiltinTypeSpec.Type.Double) {
                                type = rc.BuiltinTypes.Double;
                        } else if (lb == BuiltinTypeSpec.Type.Float || rb == BuiltinTypeSpec.Type.Float) {
                                type = rc.BuiltinTypes.Float;
                        } else if (lb == BuiltinTypeSpec.Type.ULong || rb == BuiltinTypeSpec.Type.ULong) {
                                type = rc.BuiltinTypes.ULong;

                                if (IsSignedType (lb)) {
                                        expr = ConvertSignedConstant (left, type);
                                        if (expr == null)
                                                return false;
                                        left = expr;
                                } else if (IsSignedType (rb)) {
                                        expr = ConvertSignedConstant (right, type);
                                        if (expr == null)
                                                return false;
                                        right = expr;
                                }

                        } else if (lb == BuiltinTypeSpec.Type.Long || rb == BuiltinTypeSpec.Type.Long) {
                                type = rc.BuiltinTypes.Long;
                        } else if (lb == BuiltinTypeSpec.Type.UInt || rb == BuiltinTypeSpec.Type.UInt) {
                                type = rc.BuiltinTypes.UInt;

                                if (IsSignedType (lb)) {
                                        expr = ConvertSignedConstant (left, type);
                                        if (expr == null)
                                                type = rc.BuiltinTypes.Long;
                                } else if (IsSignedType (rb)) {
                                        expr = ConvertSignedConstant (right, type);
                                        if (expr == null)
                                                type = rc.BuiltinTypes.Long;
                                }
                        } else {
                                type = rc.BuiltinTypes.Int;
                        }

                        if (ltype != type) {
                                expr = PromoteExpression (rc, left, type);
                                if (expr == null)
                                        return false;

                                left = expr;
                        }

                        if (rtype != type) {
                                expr = PromoteExpression (rc, right, type);
                                if (expr == null)
                                        return false;

                                right = expr;
                        }

                        return true;
                }

                static bool IsSignedType (BuiltinTypeSpec.Type type)
                {
                        switch (type) {
                        case BuiltinTypeSpec.Type.Int:
                        case BuiltinTypeSpec.Type.Short:
                        case BuiltinTypeSpec.Type.SByte:
                        case BuiltinTypeSpec.Type.Long:
                                return true;
                        default:
                                return false;
                        }
                }

                static Expression ConvertSignedConstant (Expression expr, TypeSpec type)
                {
                        var c = expr as Constant;
                        if (c == null)
                                return null;

                        return c.ConvertImplicitly (type);
                }

                static Expression PromoteExpression (ResolveContext rc, Expression expr, TypeSpec type)
                {
                        if (expr.Type.IsNullableType) {
                                return Convert.ImplicitConversionStandard (rc, expr,
                                        rc.Module.PredefinedTypes.Nullable.TypeSpec.MakeGenericType (rc, new[] { type }), expr.Location);
                        }

                        var c = expr as Constant;
                        if (c != null)
                                return c.ConvertImplicitly (type);

                        return Convert.ImplicitNumericConversion (expr, type);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (left == null)
                                return null;

                        if ((oper == Operator.Subtraction) && (left is ParenthesizedExpression)) {
                                left = ((ParenthesizedExpression) left).Expr;
                                left = left.Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.Type);
                                if (left == null)
                                        return null;

                                if (left.eclass == ExprClass.Type) {
                                        ec.Report.Error (75, loc, "To cast a negative value, you must enclose the value in parentheses");
                                        return null;
                                }
                        } else
                                left = left.Resolve (ec);

                        if (left == null)
                                return null;

                        right = right.Resolve (ec);
                        if (right == null)
                                return null;

                        Constant lc = left as Constant;
                        Constant rc = right as Constant;

                        // The conversion rules are ignored in enum context but why
                        if (!ec.HasSet (ResolveContext.Options.EnumScope) && lc != null && rc != null && (left.Type.IsEnum || right.Type.IsEnum)) {
                                lc = EnumLiftUp (ec, lc, rc);
                                if (lc != null)
                                        rc = EnumLiftUp (ec, rc, lc);
                        }

                        if (rc != null && lc != null) {
                                int prev_e = ec.Report.Errors;
                                Expression e = ConstantFold.BinaryFold (ec, oper, lc, rc, loc);
                                if (e != null || ec.Report.Errors != prev_e)
                                        return e;
                        }

                        // Comparison warnings
                        if ((oper & Operator.ComparisonMask) != 0) {
                                if (left.Equals (right)) {
                                        ec.Report.Warning (1718, 3, loc, "A comparison made to same variable. Did you mean to compare something else?");
                                }
                                CheckOutOfRangeComparison (ec, lc, right.Type);
                                CheckOutOfRangeComparison (ec, rc, left.Type);
                        }

                        if (left.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic || right.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
                                return DoResolveDynamic (ec);

                        return DoResolveCore (ec, left, right);
                }

                Expression DoResolveDynamic (ResolveContext rc)
                {
                        var lt = left.Type;
                        var rt = right.Type;
                        if (lt.Kind == MemberKind.Void || lt == InternalType.MethodGroup || lt == InternalType.AnonymousMethod ||
                                rt.Kind == MemberKind.Void || rt == InternalType.MethodGroup || rt == InternalType.AnonymousMethod) {
                                Error_OperatorCannotBeApplied (rc, left, right);
                                return null;
                        }

                        Arguments args;

                        //
                        // Special handling for logical boolean operators which require rhs not to be
                        // evaluated based on lhs value
                        //
                        if ((oper & Operator.LogicalMask) != 0) {
                                Expression cond_left, cond_right, expr;

                                args = new Arguments (2);

                                if (lt.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                        LocalVariable temp = LocalVariable.CreateCompilerGenerated (lt, rc.CurrentBlock, loc);

                                        var cond_args = new Arguments (1);
                                        cond_args.Add (new Argument (new SimpleAssign (temp.CreateReferenceExpression (rc, loc), left).Resolve (rc)));

                                        //
                                        // dynamic && bool => IsFalse (temp = left) ? temp : temp && right;
                                        // dynamic || bool => IsTrue (temp = left) ? temp : temp || right;
                                        //
                                        left = temp.CreateReferenceExpression (rc, loc);
                                        if (oper == Operator.LogicalAnd) {
                                                expr = DynamicUnaryConversion.CreateIsFalse (rc, cond_args, loc);
                                                cond_left = left;
                                        } else {
                                                expr = DynamicUnaryConversion.CreateIsTrue (rc, cond_args, loc);
                                                cond_left = left;
                                        }

                                        args.Add (new Argument (left));
                                        args.Add (new Argument (right));
                                        cond_right = new DynamicExpressionStatement (this, args, loc);
                                } else {
                                        LocalVariable temp = LocalVariable.CreateCompilerGenerated (rc.BuiltinTypes.Bool, rc.CurrentBlock, loc);

                                        if (!Convert.ImplicitConversionExists (rc, left, temp.Type) && (oper == Operator.LogicalAnd ? GetOperatorFalse (rc, left, loc) : GetOperatorTrue (rc, left, loc)) == null) {
                                                rc.Report.Error (7083, left.Location,
                                                        "Expression must be implicitly convertible to Boolean or its type `{0}' must define operator `{1}'",
                                                        lt.GetSignatureForError (), oper == Operator.LogicalAnd ? "false" : "true");
                                                return null;
                                        }

                                        args.Add (new Argument (temp.CreateReferenceExpression (rc, loc).Resolve (rc)));
                                        args.Add (new Argument (right));
                                        right = new DynamicExpressionStatement (this, args, loc);

                                        //
                                        // bool && dynamic => (temp = left) ? temp && right : temp;
                                        // bool || dynamic => (temp = left) ? temp : temp || right;
                                        //
                                        if (oper == Operator.LogicalAnd) {
                                                cond_left = right;
                                                cond_right = temp.CreateReferenceExpression (rc, loc);
                                        } else {
                                                cond_left = temp.CreateReferenceExpression (rc, loc);
                                                cond_right = right;
                                        }

                                        expr = new BooleanExpression (new SimpleAssign (temp.CreateReferenceExpression (rc, loc), left));
                                }

                                return new Conditional (expr, cond_left, cond_right, loc).Resolve (rc);
                        }

                        args = new Arguments (2);
                        args.Add (new Argument (left));
                        args.Add (new Argument (right));
                        return new DynamicExpressionStatement (this, args, loc).Resolve (rc);
                }

                Expression DoResolveCore (ResolveContext ec, Expression left_orig, Expression right_orig)
                {
                        Expression expr = ResolveOperator (ec);
                        if (expr == null)
                                Error_OperatorCannotBeApplied (ec, left_orig, right_orig);

                        if (left == null || right == null)
                                throw new InternalErrorException ("Invalid conversion");

                        if (oper == Operator.BitwiseOr)
                                CheckBitwiseOrOnSignExtended (ec);

                        return expr;
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        return MakeExpression (ctx, left, right);
                }

                public SLE.Expression MakeExpression (BuilderContext ctx, Expression left, Expression right)
                {
                        var le = left.MakeExpression (ctx);
                        var re = right.MakeExpression (ctx);
                        bool is_checked = ctx.HasSet (BuilderContext.Options.CheckedScope);

                        switch (oper) {
                        case Operator.Addition:
                                return is_checked ? SLE.Expression.AddChecked (le, re) : SLE.Expression.Add (le, re);
                        case Operator.BitwiseAnd:
                                return SLE.Expression.And (le, re);
                        case Operator.BitwiseOr:
                                return SLE.Expression.Or (le, re);
                        case Operator.Division:
                                return SLE.Expression.Divide (le, re);
                        case Operator.Equality:
                                return SLE.Expression.Equal (le, re);
                        case Operator.ExclusiveOr:
                                return SLE.Expression.ExclusiveOr (le, re);
                        case Operator.GreaterThan:
                                return SLE.Expression.GreaterThan (le, re);
                        case Operator.GreaterThanOrEqual:
                                return SLE.Expression.GreaterThanOrEqual (le, re);
                        case Operator.Inequality:
                                return SLE.Expression.NotEqual (le, re);
                        case Operator.LeftShift:
                                return SLE.Expression.LeftShift (le, re);
                        case Operator.LessThan:
                                return SLE.Expression.LessThan (le, re);
                        case Operator.LessThanOrEqual:
                                return SLE.Expression.LessThanOrEqual (le, re);
                        case Operator.LogicalAnd:
                                return SLE.Expression.AndAlso (le, re);
                        case Operator.LogicalOr:
                                return SLE.Expression.OrElse (le, re);
                        case Operator.Modulus:
                                return SLE.Expression.Modulo (le, re);
                        case Operator.Multiply:
                                return is_checked ? SLE.Expression.MultiplyChecked (le, re) : SLE.Expression.Multiply (le, re);
                        case Operator.RightShift:
                                return SLE.Expression.RightShift (le, re);
                        case Operator.Subtraction:
                                return is_checked ? SLE.Expression.SubtractChecked (le, re) : SLE.Expression.Subtract (le, re);
                        default:
                                throw new NotImplementedException (oper.ToString ());
                        }
                }

                //
                // D operator + (D x, D y)
                // D operator - (D x, D y)
                //
                Expression ResolveOperatorDelegate (ResolveContext ec, TypeSpec l, TypeSpec r)
                {
                        if (l != r && !TypeSpecComparer.Variant.IsEqual (r, l)) {
                                Expression tmp;
                                if (right.eclass == ExprClass.MethodGroup || r == InternalType.AnonymousMethod || r == InternalType.NullLiteral) {
                                        tmp = Convert.ImplicitConversionRequired (ec, right, l, loc);
                                        if (tmp == null)
                                                return null;
                                        right = tmp;
                                        r = right.Type;
                                } else if (left.eclass == ExprClass.MethodGroup || (l == InternalType.AnonymousMethod || l == InternalType.NullLiteral)) {
                                        tmp = Convert.ImplicitConversionRequired (ec, left, r, loc);
                                        if (tmp == null)
                                                return null;
                                        left = tmp;
                                        l = left.Type;
                                } else {
                                        return null;
                                }
                        }

                        MethodSpec method = null;
                        Arguments args = new Arguments (2);
                        args.Add (new Argument (left));
                        args.Add (new Argument (right));

                        if (oper == Operator.Addition) {
                                method = ec.Module.PredefinedMembers.DelegateCombine.Resolve (loc);
                        } else if (oper == Operator.Subtraction) {
                                method = ec.Module.PredefinedMembers.DelegateRemove.Resolve (loc);
                        }

                        if (method == null)
                                return new EmptyExpression (ec.BuiltinTypes.Decimal);

                        Expression expr = new UserOperatorCall (method, args, CreateExpressionTree, loc);
                        return new ClassCast (expr, l);
                }

                //
                // Resolves enumeration operators where only single predefined overload exists, handles lifted versions too
                //
                Expression ResolveSingleEnumOperators (ResolveContext rc, bool lenum, bool renum, TypeSpec ltype, TypeSpec rtype)
                {
                        //
                        // bool operator == (E x, E y);
                        // bool operator != (E x, E y);
                        // bool operator < (E x, E y);
                        // bool operator > (E x, E y);
                        // bool operator <= (E x, E y);
                        // bool operator >= (E x, E y);
                        //
                        // E operator & (E x, E y);
                        // E operator | (E x, E y);
                        // E operator ^ (E x, E y);
                        //
                        Expression expr;
                        if ((oper & Operator.ComparisonMask) != 0) {
                                type = rc.BuiltinTypes.Bool;
                        } else {
                                if (lenum)
                                        type = ltype;
                                else if (renum)
                                        type = rtype;
                                else if (ltype.IsNullableType && Nullable.NullableInfo.GetUnderlyingType (ltype).IsEnum)
                                        type = ltype;
                                else
                                        type = rtype;
                        }

                        if (ltype == rtype) {
                                if (lenum || renum)
                                        return this;

                                var lifted = new Nullable.LiftedBinaryOperator (this);
                                lifted.Left = left;
                                lifted.Right = right;
                                return lifted.Resolve (rc);
                        }

                        if (renum && !ltype.IsNullableType) {
                                expr = Convert.ImplicitConversion (rc, left, rtype, loc);
                                if (expr != null) {
                                        left = expr;
                                        return this;
                                }
                        } else if (lenum && !rtype.IsNullableType) {
                                expr = Convert.ImplicitConversion (rc, right, ltype, loc);
                                if (expr != null) {
                                        right = expr;
                                        return this;
                                }
                        }

                        //
                        // Now try lifted version of predefined operator
                        //
                        var nullable_type = rc.Module.PredefinedTypes.Nullable.TypeSpec;
                        if (nullable_type != null) {
                                if (renum && !ltype.IsNullableType) {
                                        var lifted_type = nullable_type.MakeGenericType (rc.Module, new[] { rtype });

                                        expr = Convert.ImplicitConversion (rc, left, lifted_type, loc);
                                        if (expr != null) {
                                                left = expr;
                                                right = Convert.ImplicitConversion (rc, right, lifted_type, loc);
                                        }

                                        if ((oper & Operator.BitwiseMask) != 0)
                                                type = lifted_type;

                                        if (left.IsNull) {
                                                if ((oper & Operator.BitwiseMask) != 0)
                                                        return Nullable.LiftedNull.CreateFromExpression (rc, this);

                                                return CreateLiftedValueTypeResult (rc, rtype);
                                        }

                                        if (expr != null) {
                                                var lifted = new Nullable.LiftedBinaryOperator (this);
                                                lifted.Left = expr;
                                                lifted.Right = right;
                                                return lifted.Resolve (rc);
                                        }
                                } else if (lenum && !rtype.IsNullableType) {
                                        var lifted_type = nullable_type.MakeGenericType (rc.Module, new[] { ltype });

                                        expr = Convert.ImplicitConversion (rc, right, lifted_type, loc);
                                        if (expr != null) {
                                                right = expr;
                                                left = Convert.ImplicitConversion (rc, left, lifted_type, loc);
                                        }

                                        if ((oper & Operator.BitwiseMask) != 0)
                                                type = lifted_type;

                                        if (right.IsNull) {
                                                if ((oper & Operator.BitwiseMask) != 0)
                                                        return Nullable.LiftedNull.CreateFromExpression (rc, this);

                                                return CreateLiftedValueTypeResult (rc, ltype);
                                        }

                                        if (expr != null) {
                                                var lifted = new Nullable.LiftedBinaryOperator (this);
                                                lifted.Left = left;
                                                lifted.Right = expr;
                                                return lifted.Resolve (rc);
                                        }
                                } else if (rtype.IsNullableType && Nullable.NullableInfo.GetUnderlyingType (rtype).IsEnum) {
                                        Nullable.Unwrap unwrap = null;
                                        if (left.IsNull || right.IsNull) {
                                                if (rc.HasSet (ResolveContext.Options.ExpressionTreeConversion))
                                                        left = Convert.ImplicitConversion (rc, left, rtype, left.Location);

                                                if ((oper & Operator.RelationalMask) != 0)
                                                        return CreateLiftedValueTypeResult (rc, rtype);

                                                if ((oper & Operator.BitwiseMask) != 0)
                                                        return Nullable.LiftedNull.CreateFromExpression (rc, this);

                                                if (right.IsNull)
                                                        return CreateLiftedValueTypeResult (rc, left.Type);

                                                // Equality operators are valid between E? and null
                                                expr = left;
                                                unwrap = new Nullable.Unwrap (right);
                                        } else {
                                                expr = Convert.ImplicitConversion (rc, left, Nullable.NullableInfo.GetUnderlyingType (rtype), loc);
                                                if (expr == null)
                                                        return null;
                                        }

                                        if (expr != null) {
                                                var lifted = new Nullable.LiftedBinaryOperator (this);
                                                lifted.Left = expr;
                                                lifted.Right = right;
                                                lifted.UnwrapRight = unwrap;
                                                return lifted.Resolve (rc);
                                        }
                                } else if (ltype.IsNullableType && Nullable.NullableInfo.GetUnderlyingType (ltype).IsEnum) {
                                        Nullable.Unwrap unwrap = null;
                                        if (right.IsNull || left.IsNull) {
                                                if (rc.HasSet (ResolveContext.Options.ExpressionTreeConversion))
                                                        right = Convert.ImplicitConversion (rc, right, ltype, right.Location);

                                                if ((oper & Operator.RelationalMask) != 0)
                                                        return CreateLiftedValueTypeResult (rc, ltype);

                                                if ((oper & Operator.BitwiseMask) != 0)
                                                        return Nullable.LiftedNull.CreateFromExpression (rc, this);

                                                if (left.IsNull)
                                                        return CreateLiftedValueTypeResult (rc, right.Type);

                                                // Equality operators are valid between E? and null
                                                expr = right;
                                                unwrap = new Nullable.Unwrap (left);
                                        } else {
                                                expr = Convert.ImplicitConversion (rc, right, Nullable.NullableInfo.GetUnderlyingType (ltype), loc);
                                                if (expr == null)
                                                        return null;
                                        }

                                        if (expr != null) {
                                                var lifted = new Nullable.LiftedBinaryOperator (this);
                                                lifted.Left = left;
                                                lifted.UnwrapLeft = unwrap;
                                                lifted.Right = expr;
                                                return lifted.Resolve (rc);
                                        }
                                }
                        }

                        return null;
                }

                static Expression ConvertEnumOperandToUnderlyingType (ResolveContext rc, Expression expr, bool liftType)
                {
                        TypeSpec underlying_type;
                        if (expr.Type.IsNullableType) {
                                var nt = Nullable.NullableInfo.GetUnderlyingType (expr.Type);
                                if (nt.IsEnum)
                                        underlying_type = EnumSpec.GetUnderlyingType (nt);
                                else
                                        underlying_type = nt;
                        } else if (expr.Type.IsEnum) {
                                underlying_type = EnumSpec.GetUnderlyingType (expr.Type);
                        } else {
                                underlying_type = expr.Type;
                        }

                        switch (underlying_type.BuiltinType) {
                        case BuiltinTypeSpec.Type.SByte:
                        case BuiltinTypeSpec.Type.Byte:
                        case BuiltinTypeSpec.Type.Short:
                        case BuiltinTypeSpec.Type.UShort:
                                underlying_type = rc.BuiltinTypes.Int;
                                break;
                        }

                        if (expr.Type.IsNullableType || liftType)
                                underlying_type = rc.Module.PredefinedTypes.Nullable.TypeSpec.MakeGenericType (rc.Module, new[] { underlying_type });

                        if (expr.Type == underlying_type)
                                return expr;

                        return EmptyCast.Create (expr, underlying_type);
                }

                Expression ResolveEnumOperators (ResolveContext rc, bool lenum, bool renum, TypeSpec ltype, TypeSpec rtype)
                {
                        //
                        // U operator - (E e, E f)
                        // E operator - (E e, U x)  // Internal decomposition operator
                        // E operator - (U x, E e)      // Internal decomposition operator
                        //
                        // E operator + (E e, U x)
                        // E operator + (U x, E e)
                        //

                        TypeSpec enum_type;

                        if (lenum)
                                enum_type = ltype;
                        else if (renum)
                                enum_type = rtype;
                        else if (ltype.IsNullableType && Nullable.NullableInfo.GetUnderlyingType (ltype).IsEnum)
                                enum_type = ltype;
                        else
                                enum_type = rtype;

                        Expression expr;
                        if (!enum_type.IsNullableType) {
                                expr = ResolveOperatorPredefined (rc, rc.Module.GetPredefinedEnumAritmeticOperators (enum_type, false), false);
                                if (expr != null) {
                                        if (oper == Operator.Subtraction)
                                                expr = ConvertEnumSubtractionResult (rc, expr);
                                        else
                                                expr = ConvertEnumAdditionalResult (expr, enum_type);

                                        enum_conversion = GetEnumResultCast (expr.Type);

                                        return expr;
                                }

                                var nullable = rc.Module.PredefinedTypes.Nullable;

                                //
                                // Don't try nullable version when nullable type is undefined
                                //
                                if (!nullable.IsDefined)
                                        return null;

                                enum_type = nullable.TypeSpec.MakeGenericType (rc.Module, new[] { enum_type });
                        }

                        expr = ResolveOperatorPredefined (rc, rc.Module.GetPredefinedEnumAritmeticOperators (enum_type, true), false);
                        if (expr != null) {
                                if (oper == Operator.Subtraction)
                                        expr = ConvertEnumSubtractionResult (rc, expr);
                                else
                                        expr = ConvertEnumAdditionalResult (expr, enum_type);

                                enum_conversion = GetEnumResultCast (expr.Type);
                        }

                        return expr;
                }

                static Expression ConvertEnumAdditionalResult (Expression expr, TypeSpec enumType)
                {
                        return EmptyCast.Create (expr, enumType);
                }

                Expression ConvertEnumSubtractionResult (ResolveContext rc, Expression expr)
                {
                        //
                        // Enumeration subtraction has different result type based on
                        // best overload
                        //
                        TypeSpec result_type;
                        if (left.Type == right.Type) {
                                var c = right as EnumConstant;
                                if (c != null && c.IsZeroInteger && !right.Type.IsEnum) {
                                        //
                                        // LAMESPEC: This is quite unexpected for expression E - 0 the return type is
                                        // E which is not what expressions E - 1 or 0 - E return
                                        //
                                        result_type = left.Type;
                                } else {
                                        result_type = left.Type.IsNullableType ?
                                                Nullable.NullableInfo.GetEnumUnderlyingType (rc.Module, left.Type) :
                                                EnumSpec.GetUnderlyingType (left.Type);
                                }
                        } else {
                                if (IsEnumOrNullableEnum (left.Type)) {
                                        result_type = left.Type;
                                } else {
                                        result_type = right.Type;
                                }

                                if (expr is Nullable.LiftedBinaryOperator && !result_type.IsNullableType)
                                        result_type = rc.Module.PredefinedTypes.Nullable.TypeSpec.MakeGenericType (rc.Module, new[] { result_type });
                        }

                        return EmptyCast.Create (expr, result_type);
                }

                public static ConvCast.Mode GetEnumResultCast (TypeSpec type)
                {
                        if (type.IsNullableType)
                                type = Nullable.NullableInfo.GetUnderlyingType (type);

                        if (type.IsEnum)
                                type = EnumSpec.GetUnderlyingType (type);

                        switch (type.BuiltinType) {
                        case BuiltinTypeSpec.Type.SByte:
                                return ConvCast.Mode.I4_I1;
                        case BuiltinTypeSpec.Type.Byte:
                                return ConvCast.Mode.I4_U1;
                        case BuiltinTypeSpec.Type.Short:
                                return ConvCast.Mode.I4_I2;
                        case BuiltinTypeSpec.Type.UShort:
                                return ConvCast.Mode.I4_U2;
                        }

                        return 0;
                }

                //
                // Equality operators rules
                //
                Expression ResolveEquality (ResolveContext ec, TypeSpec l, TypeSpec r, bool primitives_only)
                {
                        Expression result;
                        type = ec.BuiltinTypes.Bool;
                        bool no_arg_conv = false;

                        if (!primitives_only) {

                                //
                                // a, Both operands are reference-type values or the value null
                                // b, One operand is a value of type T where T is a type-parameter and
                                // the other operand is the value null. Furthermore T does not have the
                                // value type constraint
                                //
                                // LAMESPEC: Very confusing details in the specification, basically any
                                // reference like type-parameter is allowed
                                //
                                var tparam_l = l as TypeParameterSpec;
                                var tparam_r = r as TypeParameterSpec;
                                if (tparam_l != null) {
                                        if (right is NullLiteral) {
                                                if (tparam_l.GetEffectiveBase ().BuiltinType == BuiltinTypeSpec.Type.ValueType)
                                                        return null;

                                                left = new BoxedCast (left, ec.BuiltinTypes.Object);
                                                return this;
                                        }

                                        if (!tparam_l.IsReferenceType)
                                                return null;

                                        l = tparam_l.GetEffectiveBase ();
                                        left = new BoxedCast (left, l);
                                } else if (left is NullLiteral && tparam_r == null) {
                                        if (TypeSpec.IsReferenceType (r))
                                                return this;

                                        if (r.Kind == MemberKind.InternalCompilerType)
                                                return null;
                                }

                                if (tparam_r != null) {
                                        if (left is NullLiteral) {
                                                if (tparam_r.GetEffectiveBase ().BuiltinType == BuiltinTypeSpec.Type.ValueType)
                                                        return null;

                                                right = new BoxedCast (right, ec.BuiltinTypes.Object);
                                                return this;
                                        }

                                        if (!tparam_r.IsReferenceType)
                                                return null;

                                        r = tparam_r.GetEffectiveBase ();
                                        right = new BoxedCast (right, r);
                                } else if (right is NullLiteral) {
                                        if (TypeSpec.IsReferenceType (l))
                                                return this;

                                        if (l.Kind == MemberKind.InternalCompilerType)
                                                return null;
                                }

                                //
                                // LAMESPEC: method groups can be compared when they convert to other side delegate
                                //
                                if (l.IsDelegate) {
                                        if (right.eclass == ExprClass.MethodGroup) {
                                                result = Convert.ImplicitConversion (ec, right, l, loc);
                                                if (result == null)
                                                        return null;

                                                right = result;
                                                r = l;
                                        } else if (r.IsDelegate && l != r) {
                                                return null;
                                        }
                                } else if (left.eclass == ExprClass.MethodGroup && r.IsDelegate) {
                                        result = Convert.ImplicitConversionRequired (ec, left, r, loc);
                                        if (result == null)
                                                return null;

                                        left = result;
                                        l = r;
                                } else {
                                        no_arg_conv = l == r && !l.IsStruct;
                                }
                        }

                        //
                        // bool operator != (string a, string b)
                        // bool operator == (string a, string b)
                        //
                        // bool operator != (Delegate a, Delegate b)
                        // bool operator == (Delegate a, Delegate b)
                        //
                        // bool operator != (bool a, bool b)
                        // bool operator == (bool a, bool b)
                        //
                        // LAMESPEC: Reference equality comparison can apply to value/reference types when
                        // they implement an implicit conversion to any of types above. This does
                        // not apply when both operands are of same reference type
                        //
                        if (r.BuiltinType != BuiltinTypeSpec.Type.Object && l.BuiltinType != BuiltinTypeSpec.Type.Object) {
                                result = ResolveOperatorPredefined (ec, ec.BuiltinTypes.OperatorsBinaryEquality, no_arg_conv);  
                                if (result != null)
                                        return result;

                                //
                                // Now try lifted version of predefined operators
                                //
                                if (no_arg_conv && !l.IsNullableType) {
                                        //
                                        // Optimizes cases which won't match
                                        //
                                } else {
                                        result = ResolveOperatorPredefined (ec, ec.Module.OperatorsBinaryEqualityLifted, no_arg_conv);
                                        if (result != null)
                                                return result;
                                }

                                //
                                // The == and != operators permit one operand to be a value of a nullable
                                // type and the other to be the null literal, even if no predefined or user-defined
                                // operator (in unlifted or lifted form) exists for the operation.
                                //
                                if ((l.IsNullableType && right.IsNull) || (r.IsNullableType && left.IsNull)) {
                                        var lifted = new Nullable.LiftedBinaryOperator (this);
                                        lifted.Left = left;
                                        lifted.Right = right;
                                        return lifted.Resolve (ec);
                                }
                        }

                        //
                        // bool operator != (object a, object b)
                        // bool operator == (object a, object b)
                        //
                        // An explicit reference conversion exists from the
                        // type of either operand to the type of the other operand.
                        //

                        // Optimize common path
                        if (l == r) {
                                return l.Kind == MemberKind.InternalCompilerType || l.Kind == MemberKind.Struct ? null : this;
                        }

                        if (!Convert.ExplicitReferenceConversionExists (l, r) &&
                                !Convert.ExplicitReferenceConversionExists (r, l))
                                return null;

                        // Reject allowed explicit conversions like int->object
                        if (!TypeSpec.IsReferenceType (l) || !TypeSpec.IsReferenceType (r))
                                return null;

                        if (l.BuiltinType == BuiltinTypeSpec.Type.String || l.BuiltinType == BuiltinTypeSpec.Type.Delegate || l.IsDelegate || MemberCache.GetUserOperator (l, CSharp.Operator.OpType.Equality, false) != null)
                                ec.Report.Warning (253, 2, loc,
                                        "Possible unintended reference comparison. Consider casting the right side expression to type `{0}' to get value comparison",
                                        l.GetSignatureForError ());

                        if (r.BuiltinType == BuiltinTypeSpec.Type.String || r.BuiltinType == BuiltinTypeSpec.Type.Delegate || r.IsDelegate || MemberCache.GetUserOperator (r, CSharp.Operator.OpType.Equality, false) != null)
                                ec.Report.Warning (252, 2, loc,
                                        "Possible unintended reference comparison. Consider casting the left side expression to type `{0}' to get value comparison",
                                        r.GetSignatureForError ());

                        return this;
                }


                Expression ResolveOperatorPointer (ResolveContext ec, TypeSpec l, TypeSpec r)
                {
                        //
                        // bool operator == (void* x, void* y);
                        // bool operator != (void* x, void* y);
                        // bool operator < (void* x, void* y);
                        // bool operator > (void* x, void* y);
                        // bool operator <= (void* x, void* y);
                        // bool operator >= (void* x, void* y);
                        //
                        if ((oper & Operator.ComparisonMask) != 0) {
                                Expression temp;
                                if (!l.IsPointer) {
                                        temp = Convert.ImplicitConversion (ec, left, r, left.Location);
                                        if (temp == null)
                                                return null;
                                        left = temp;
                                }

                                if (!r.IsPointer) {
                                        temp = Convert.ImplicitConversion (ec, right, l, right.Location);
                                        if (temp == null)
                                                return null;
                                        right = temp;
                                }

                                type = ec.BuiltinTypes.Bool;
                                return this;
                        }

                        return ResolveOperatorPredefined (ec, ec.BuiltinTypes.OperatorsBinaryUnsafe, false);
                }

                //
                // Build-in operators method overloading
                //
                Expression ResolveOperatorPredefined (ResolveContext ec, PredefinedOperator [] operators, bool primitives_only)
                {
                        PredefinedOperator best_operator = null;
                        TypeSpec l = left.Type;
                        TypeSpec r = right.Type;
                        Operator oper_mask = oper & ~Operator.ValuesOnlyMask;

                        foreach (PredefinedOperator po in operators) {
                                if ((po.OperatorsMask & oper_mask) == 0)
                                        continue;

                                if (primitives_only) {
                                        if (!po.IsPrimitiveApplicable (l, r))
                                                continue;
                                } else {
                                        if (!po.IsApplicable (ec, left, right))
                                                continue;
                                }

                                if (best_operator == null) {
                                        best_operator = po;
                                        if (primitives_only)
                                                break;

                                        continue;
                                }

                                best_operator = po.ResolveBetterOperator (ec, best_operator);

                                if (best_operator == null) {
                                        ec.Report.Error (34, loc, "Operator `{0}' is ambiguous on operands of type `{1}' and `{2}'",
                                                OperName (oper), l.GetSignatureForError (), r.GetSignatureForError ());

                                        best_operator = po;
                                        break;
                                }
                        }

                        if (best_operator == null)
                                return null;

                        return best_operator.ConvertResult (ec, this);
                }

                //
                // Optimize & constant expressions with 0 value
                //
                Expression OptimizeAndOperation (Expression expr)
                {
                        Constant rc = right as Constant;
                        Constant lc = left as Constant;
                        if ((lc != null && lc.IsDefaultValue) || (rc != null && rc.IsDefaultValue)) {
                                //
                                // The result is a constant with side-effect
                                //
                                Constant side_effect = rc == null ?
                                        new SideEffectConstant (lc, right, loc) :
                                        new SideEffectConstant (rc, left, loc);

                                return ReducedExpression.Create (side_effect, expr);
                        }

                        return expr;
                }

                //
                // Value types can be compared with the null literal because of the lifting
                // language rules. However the result is always true or false.
                //
                public Expression CreateLiftedValueTypeResult (ResolveContext rc, TypeSpec valueType)
                {
                        if (rc.HasSet (ResolveContext.Options.ExpressionTreeConversion)) {
                                type = rc.BuiltinTypes.Bool;
                                return this;
                        }

                        // FIXME: Handle side effect constants
                        Constant c = new BoolConstant (rc.BuiltinTypes, Oper == Operator.Inequality, loc);

                        if ((Oper & Operator.EqualityMask) != 0) {
                                rc.Report.Warning (472, 2, loc, "The result of comparing value type `{0}' with null is always `{1}'",
                                        valueType.GetSignatureForError (), c.GetValueAsLiteral ());
                        } else {
                                rc.Report.Warning (464, 2, loc, "The result of comparing type `{0}' with null is always `{1}'",
                                        valueType.GetSignatureForError (), c.GetValueAsLiteral ());
                        }

                        return c;
                }

                //
                // Performs user-operator overloading
                //
                Expression ResolveUserOperator (ResolveContext rc, Expression left, Expression right)
                {
                        Expression oper_expr;

                        var op = ConvertBinaryToUserOperator (oper);
                        var l = left.Type;
                        if (l.IsNullableType)
                                l = Nullable.NullableInfo.GetUnderlyingType (l);
                        var r = right.Type;
                        if (r.IsNullableType)
                                r = Nullable.NullableInfo.GetUnderlyingType (r);

                        IList<MemberSpec> left_operators = MemberCache.GetUserOperator (l, op, false);
                        IList<MemberSpec> right_operators = null;

                        if (l != r) {
                                right_operators = MemberCache.GetUserOperator (r, op, false);
                                if (right_operators == null && left_operators == null)
                                        return null;
                        } else if (left_operators == null) {
                                return null;
                        }

                        Arguments args = new Arguments (2);
                        Argument larg = new Argument (left);
                        args.Add (larg);        
                        Argument rarg = new Argument (right);
                        args.Add (rarg);

                        //
                        // User-defined operator implementations always take precedence
                        // over predefined operator implementations
                        //
                        if (left_operators != null && right_operators != null) {
                                left_operators = CombineUserOperators (left_operators, right_operators);
                        } else if (right_operators != null) {
                                left_operators = right_operators;
                        }

                        const OverloadResolver.Restrictions restr = OverloadResolver.Restrictions.ProbingOnly |
                                OverloadResolver.Restrictions.NoBaseMembers | OverloadResolver.Restrictions.BaseMembersIncluded;

                        var res = new OverloadResolver (left_operators, restr, loc);

                        var oper_method = res.ResolveOperator (rc, ref args);
                        if (oper_method == null) {
                                //
                                // Logical && and || cannot be lifted
                                //
                                if ((oper & Operator.LogicalMask) != 0)
                                        return null;

                                //
                                // Apply lifted user operators only for liftable types. Implicit conversion
                                // to nullable types is not allowed
                                //
                                if (!IsLiftedOperatorApplicable ())
                                        return null;

                                // TODO: Cache the result in module container
                                var lifted_methods = CreateLiftedOperators (rc, left_operators);
                                if (lifted_methods == null)
                                        return null;

                                res = new OverloadResolver (lifted_methods, restr | OverloadResolver.Restrictions.ProbingOnly, loc);

                                oper_method = res.ResolveOperator (rc, ref args);
                                if (oper_method == null)
                                        return null;

                                MethodSpec best_original = null;
                                foreach (MethodSpec ms in left_operators) {
                                        if (ms.MemberDefinition == oper_method.MemberDefinition) {
                                                best_original = ms;
                                                break;
                                        }
                                }

                                if (rc.HasSet (ResolveContext.Options.ExpressionTreeConversion)) {
                                        //
                                        // Expression trees use lifted notation in this case
                                        //
                                        this.left = Convert.ImplicitConversion (rc, left, oper_method.Parameters.Types[0], left.Location);
                                        this.right = Convert.ImplicitConversion (rc, right, oper_method.Parameters.Types[1], left.Location);
                                }

                                var ptypes = best_original.Parameters.Types;

                                if (left.IsNull || right.IsNull) {
                                        //
                                        // The lifted operator produces a null value if one or both operands are null
                                        //
                                        if ((oper & (Operator.ArithmeticMask | Operator.ShiftMask | Operator.BitwiseMask)) != 0) {
                                                type = oper_method.ReturnType;
                                                return Nullable.LiftedNull.CreateFromExpression (rc, this);
                                        }

                                        //
                                        // The lifted operator produces the value false if one or both operands are null for
                                        // relational operators.
                                        //
                                        if ((oper & Operator.RelationalMask) != 0) {
                                                //
                                                // CSC BUG: This should be different warning, csc reports CS0458 with bool? which is wrong
                                                // because return type is actually bool
                                                //
                                                return CreateLiftedValueTypeResult (rc, left.IsNull ? ptypes [1] : ptypes [0]);
                                        }

                                        if ((oper & Operator.EqualityMask) != 0 && ((left.IsNull && !right.Type.IsNullableType) || !left.Type.IsNullableType)) {
                                                return CreateLiftedValueTypeResult (rc, left.IsNull ? ptypes [1] : ptypes [0]);
                                        }
                                }

                                type = oper_method.ReturnType;
                                var lifted = new Nullable.LiftedBinaryOperator (this);
                                lifted.UserOperator = best_original;

                                if (left.Type.IsNullableType && !ptypes[0].IsNullableType) {
                                        lifted.UnwrapLeft = new Nullable.Unwrap (left);
                                }

                                if (right.Type.IsNullableType && !ptypes[1].IsNullableType) {
                                        lifted.UnwrapRight = new Nullable.Unwrap (right);
                                }

                                lifted.Left = Convert.ImplicitConversion (rc, lifted.UnwrapLeft ?? left, ptypes[0], left.Location);
                                lifted.Right = Convert.ImplicitConversion (rc, lifted.UnwrapRight ?? right, ptypes[1], right.Location);

                                return lifted.Resolve (rc);
                        }
                        
                        if ((oper & Operator.LogicalMask) != 0) {
                                // TODO: CreateExpressionTree is allocated every time           
                                oper_expr = new ConditionalLogicalOperator (oper_method, args, CreateExpressionTree,
                                        oper == Operator.LogicalAnd, loc).Resolve (rc);
                        } else {
                                oper_expr = new UserOperatorCall (oper_method, args, CreateExpressionTree, loc);
                        }

                        this.left = larg.Expr;
                        this.right = rarg.Expr;

                        return oper_expr;
                }

                bool IsLiftedOperatorApplicable ()
                {
                        if (left.Type.IsNullableType) {
                                if ((oper & Operator.EqualityMask) != 0)
                                        return !right.IsNull;

                                return true;
                        }

                        if (right.Type.IsNullableType) {
                                if ((oper & Operator.EqualityMask) != 0)
                                        return !left.IsNull;

                                return true;
                        }

                        if (TypeSpec.IsValueType (left.Type))
                                return right.IsNull;

                        if (TypeSpec.IsValueType (right.Type))
                                return left.IsNull;

                        return false;
                }

                List<MemberSpec> CreateLiftedOperators (ResolveContext rc, IList<MemberSpec> operators)
                {
                        var nullable_type = rc.Module.PredefinedTypes.Nullable.TypeSpec;
                        if (nullable_type == null)
                                return null;

                        //
                        // Lifted operators permit predefined and user-defined operators that operate
                        // on non-nullable value types to also be used with nullable forms of those types.
                        // Lifted operators are constructed from predefined and user-defined operators
                        // that meet certain requirements
                        //
                        List<MemberSpec> lifted = null;
                        foreach (MethodSpec oper in operators) {
                                TypeSpec rt;
                                if ((Oper & Operator.ComparisonMask) != 0) {
                                        //
                                        // Result type must be of type bool for lifted comparison operators
                                        //
                                        rt = oper.ReturnType;
                                        if (rt.BuiltinType != BuiltinTypeSpec.Type.Bool)
                                                continue;
                                } else {
                                        if (!TypeSpec.IsNonNullableValueType (oper.ReturnType))
                                                continue;

                                        rt = null;
                                }

                                var ptypes = oper.Parameters.Types;
                                if (!TypeSpec.IsNonNullableValueType (ptypes [0]) || !TypeSpec.IsNonNullableValueType (ptypes [1]))
                                        continue;

                                //
                                // LAMESPEC: I am not sure why but for equality operators to be lifted
                                // both types have to match
                                //
                                if ((Oper & Operator.EqualityMask) != 0 && ptypes [0] != ptypes [1])
                                        continue;

                                if (lifted == null)
                                        lifted = new List<MemberSpec> ();

                                //
                                // The lifted form is constructed by adding a single ? modifier to each operand and
                                // result type except for comparison operators where return type is bool
                                //
                                if (rt == null)
                                        rt = nullable_type.MakeGenericType (rc.Module, new[] { oper.ReturnType });

                                var parameters = ParametersCompiled.CreateFullyResolved (
                                        nullable_type.MakeGenericType (rc.Module, new [] { ptypes[0] }),
                                        nullable_type.MakeGenericType (rc.Module, new [] { ptypes[1] }));

                                var lifted_op = new MethodSpec (oper.Kind, oper.DeclaringType, oper.MemberDefinition,
                                        rt, parameters, oper.Modifiers);

                                lifted.Add (lifted_op);
                        }

                        return lifted;
                }

                //
                // Merge two sets of user operators into one, they are mostly distinguish
                // except when they share base type and it contains an operator
                //
                static IList<MemberSpec> CombineUserOperators (IList<MemberSpec> left, IList<MemberSpec> right)
                {
                        var combined = new List<MemberSpec> (left.Count + right.Count);
                        combined.AddRange (left);
                        foreach (var r in right) {
                                bool same = false;
                                foreach (var l in left) {
                                        if (l.DeclaringType == r.DeclaringType) {
                                                same = true;
                                                break;
                                        }
                                }

                                if (!same)
                                        combined.Add (r);
                        }

                        return combined;
                }

                void CheckOutOfRangeComparison (ResolveContext ec, Constant c, TypeSpec type)
                {
                        if (c is IntegralConstant || c is CharConstant) {
                                try {
                                        c.ConvertExplicitly (true, type);
                                } catch (OverflowException) {
                                        ec.Report.Warning (652, 2, loc,
                                                "A comparison between a constant and a variable is useless. The constant is out of the range of the variable type `{0}'",
                                                type.GetSignatureForError ());
                                }
                        }
                }

                /// <remarks>
                ///   EmitBranchable is called from Statement.EmitBoolExpression in the
                ///   context of a conditional bool expression.  This function will return
                ///   false if it is was possible to use EmitBranchable, or true if it was.
                ///
                ///   The expression's code is generated, and we will generate a branch to `target'
                ///   if the resulting expression value is equal to isTrue
                /// </remarks>
                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        if (ec.HasSet (BuilderContext.Options.AsyncBody) && right.ContainsEmitWithAwait ()) {
                                left = left.EmitToField (ec);

                                if ((oper & Operator.LogicalMask) == 0) {
                                        right = right.EmitToField (ec);
                                }
                        }

                        //
                        // This is more complicated than it looks, but its just to avoid
                        // duplicated tests: basically, we allow ==, !=, >, <, >= and <=
                        // but on top of that we want for == and != to use a special path
                        // if we are comparing against null
                        //
                        if ((oper & Operator.EqualityMask) != 0 && (left is Constant || right is Constant)) {
                                bool my_on_true = oper == Operator.Inequality ? on_true : !on_true;
                                
                                //
                                // put the constant on the rhs, for simplicity
                                //
                                if (left is Constant) {
                                        Expression swap = right;
                                        right = left;
                                        left = swap;
                                }
                                
                                //
                                // brtrue/brfalse works with native int only
                                //
                                if (((Constant) right).IsZeroInteger && right.Type.BuiltinType != BuiltinTypeSpec.Type.Long && right.Type.BuiltinType != BuiltinTypeSpec.Type.ULong) {
                                        left.EmitBranchable (ec, target, my_on_true);
                                        return;
                                }
                                if (right.Type.BuiltinType == BuiltinTypeSpec.Type.Bool) {
                                        // right is a boolean, and it's not 'false' => it is 'true'
                                        left.EmitBranchable (ec, target, !my_on_true);
                                        return;
                                }

                        } else if (oper == Operator.LogicalAnd) {

                                if (on_true) {
                                        Label tests_end = ec.DefineLabel ();
                                        
                                        left.EmitBranchable (ec, tests_end, false);
                                        right.EmitBranchable (ec, target, true);
                                        ec.MarkLabel (tests_end);                                       
                                } else {
                                        //
                                        // This optimizes code like this 
                                        // if (true && i > 4)
                                        //
                                        if (!(left is Constant))
                                                left.EmitBranchable (ec, target, false);

                                        if (!(right is Constant)) 
                                                right.EmitBranchable (ec, target, false);
                                }
                                
                                return;
                                
                        } else if (oper == Operator.LogicalOr){
                                if (on_true) {
                                        left.EmitBranchable (ec, target, true);
                                        right.EmitBranchable (ec, target, true);
                                        
                                } else {
                                        Label tests_end = ec.DefineLabel ();
                                        left.EmitBranchable (ec, tests_end, true);
                                        right.EmitBranchable (ec, target, false);
                                        ec.MarkLabel (tests_end);
                                }
                                
                                return;

                        } else if ((oper & Operator.ComparisonMask) == 0) {
                                base.EmitBranchable (ec, target, on_true);
                                return;
                        }
                        
                        left.Emit (ec);
                        right.Emit (ec);

                        TypeSpec t = left.Type;
                        bool is_float = IsFloat (t);
                        bool is_unsigned = is_float || IsUnsigned (t);
                        
                        switch (oper){
                        case Operator.Equality:
                                if (on_true)
                                        ec.Emit (OpCodes.Beq, target);
                                else
                                        ec.Emit (OpCodes.Bne_Un, target);
                                break;

                        case Operator.Inequality:
                                if (on_true)
                                        ec.Emit (OpCodes.Bne_Un, target);
                                else
                                        ec.Emit (OpCodes.Beq, target);
                                break;

                        case Operator.LessThan:
                                if (on_true)
                                        if (is_unsigned && !is_float)
                                                ec.Emit (OpCodes.Blt_Un, target);
                                        else
                                                ec.Emit (OpCodes.Blt, target);
                                else
                                        if (is_unsigned)
                                                ec.Emit (OpCodes.Bge_Un, target);
                                        else
                                                ec.Emit (OpCodes.Bge, target);
                                break;

                        case Operator.GreaterThan:
                                if (on_true)
                                        if (is_unsigned && !is_float)
                                                ec.Emit (OpCodes.Bgt_Un, target);
                                        else
                                                ec.Emit (OpCodes.Bgt, target);
                                else
                                        if (is_unsigned)
                                                ec.Emit (OpCodes.Ble_Un, target);
                                        else
                                                ec.Emit (OpCodes.Ble, target);
                                break;

                        case Operator.LessThanOrEqual:
                                if (on_true)
                                        if (is_unsigned && !is_float)
                                                ec.Emit (OpCodes.Ble_Un, target);
                                        else
                                                ec.Emit (OpCodes.Ble, target);
                                else
                                        if (is_unsigned)
                                                ec.Emit (OpCodes.Bgt_Un, target);
                                        else
                                                ec.Emit (OpCodes.Bgt, target);
                                break;


                        case Operator.GreaterThanOrEqual:
                                if (on_true)
                                        if (is_unsigned && !is_float)
                                                ec.Emit (OpCodes.Bge_Un, target);
                                        else
                                                ec.Emit (OpCodes.Bge, target);
                                else
                                        if (is_unsigned)
                                                ec.Emit (OpCodes.Blt_Un, target);
                                        else
                                                ec.Emit (OpCodes.Blt, target);
                                break;
                        default:
                                throw new InternalErrorException (oper.ToString ());
                        }
                }
                
                public override void Emit (EmitContext ec)
                {
                        if (ec.HasSet (BuilderContext.Options.AsyncBody) && right.ContainsEmitWithAwait ()) {
                                left = left.EmitToField (ec);

                                if ((oper & Operator.LogicalMask) == 0) {
                                        right = right.EmitToField (ec);
                                }
                        }

                        //
                        // Handle short-circuit operators differently
                        // than the rest
                        //
                        if ((oper & Operator.LogicalMask) != 0) {
                                Label load_result = ec.DefineLabel ();
                                Label end = ec.DefineLabel ();

                                bool is_or = oper == Operator.LogicalOr;
                                left.EmitBranchable (ec, load_result, is_or);
                                right.Emit (ec);
                                ec.Emit (OpCodes.Br_S, end);
                                
                                ec.MarkLabel (load_result);
                                ec.EmitInt (is_or ? 1 : 0);
                                ec.MarkLabel (end);
                                return;
                        }

                        //
                        // Optimize zero-based operations which cannot be optimized at expression level
                        //
                        if (oper == Operator.Subtraction) {
                                var lc = left as IntegralConstant;
                                if (lc != null && lc.IsDefaultValue) {
                                        right.Emit (ec);
                                        ec.Emit (OpCodes.Neg);
                                        return;
                                }
                        }

                        EmitOperator (ec, left, right);
                }

                public void EmitOperator (EmitContext ec, Expression left, Expression right)
                {
                        left.Emit (ec);
                        right.Emit (ec);

                        EmitOperatorOpcode (ec, oper, left.Type, right);

                        //
                        // Emit result enumerable conversion this way because it's quite complicated get it
                        // to resolved tree because expression tree cannot see it.
                        //
                        if (enum_conversion != 0)
                                ConvCast.Emit (ec, enum_conversion);
                }

                public override void EmitSideEffect (EmitContext ec)
                {
                        if ((oper & Operator.LogicalMask) != 0 ||
                                (ec.HasSet (EmitContext.Options.CheckedScope) && (oper == Operator.Multiply || oper == Operator.Addition || oper == Operator.Subtraction))) {
                                base.EmitSideEffect (ec);
                        } else {
                                left.EmitSideEffect (ec);
                                right.EmitSideEffect (ec);
                        }
                }

                public override Expression EmitToField (EmitContext ec)
                {
                        if ((oper & Operator.LogicalMask) == 0) {
                                var await_expr = left as Await;
                                if (await_expr != null && right.IsSideEffectFree) {
                                        await_expr.Statement.EmitPrologue (ec);
                                        left = await_expr.Statement.GetResultExpression (ec);
                                        return this;
                                }

                                await_expr = right as Await;
                                if (await_expr != null && left.IsSideEffectFree) {
                                        await_expr.Statement.EmitPrologue (ec);
                                        right = await_expr.Statement.GetResultExpression (ec);
                                        return this;
                                }
                        }

                        return base.EmitToField (ec);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Binary target = (Binary) t;

                        target.left = left.Clone (clonectx);
                        target.right = right.Clone (clonectx);
                }

                public Expression CreateCallSiteBinder (ResolveContext ec, Arguments args)
                {
                        Arguments binder_args = new Arguments (4);

                        MemberAccess sle = new MemberAccess (new MemberAccess (
                                new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Linq", loc), "Expressions", loc);

                        CSharpBinderFlags flags = 0;
                        if (ec.HasSet (ResolveContext.Options.CheckedScope))
                                flags = CSharpBinderFlags.CheckedContext;

                        if ((oper & Operator.LogicalMask) != 0)
                                flags |= CSharpBinderFlags.BinaryOperationLogical;

                        binder_args.Add (new Argument (new EnumConstant (new IntLiteral (ec.BuiltinTypes, (int) flags, loc), ec.Module.PredefinedTypes.BinderFlags.Resolve ())));
                        binder_args.Add (new Argument (new MemberAccess (new MemberAccess (sle, "ExpressionType", loc), GetOperatorExpressionTypeName (), loc)));
                        binder_args.Add (new Argument (new TypeOf (ec.CurrentType, loc)));                                                                      
                        binder_args.Add (new Argument (new ImplicitlyTypedArrayCreation (args.CreateDynamicBinderArguments (ec), loc)));

                        return new Invocation (new MemberAccess (new TypeExpression (ec.Module.PredefinedTypes.Binder.TypeSpec, loc), "BinaryOperation", loc), binder_args);
                }
                
                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        return CreateExpressionTree (ec, null);
                }

                public Expression CreateExpressionTree (ResolveContext ec, Expression method)           
                {
                        string method_name;
                        bool lift_arg = false;
                        
                        switch (oper) {
                        case Operator.Addition:
                                if (method == null && ec.HasSet (ResolveContext.Options.CheckedScope) && !IsFloat (type))
                                        method_name = "AddChecked";
                                else
                                        method_name = "Add";
                                break;
                        case Operator.BitwiseAnd:
                                method_name = "And";
                                break;
                        case Operator.BitwiseOr:
                                method_name = "Or";
                                break;
                        case Operator.Division:
                                method_name = "Divide";
                                break;
                        case Operator.Equality:
                                method_name = "Equal";
                                lift_arg = true;
                                break;
                        case Operator.ExclusiveOr:
                                method_name = "ExclusiveOr";
                                break;                          
                        case Operator.GreaterThan:
                                method_name = "GreaterThan";
                                lift_arg = true;
                                break;
                        case Operator.GreaterThanOrEqual:
                                method_name = "GreaterThanOrEqual";
                                lift_arg = true;
                                break;
                        case Operator.Inequality:
                                method_name = "NotEqual";
                                lift_arg = true;
                                break;
                        case Operator.LeftShift:
                                method_name = "LeftShift";
                                break;
                        case Operator.LessThan:
                                method_name = "LessThan";
                                lift_arg = true;
                                break;
                        case Operator.LessThanOrEqual:
                                method_name = "LessThanOrEqual";
                                lift_arg = true;
                                break;
                        case Operator.LogicalAnd:
                                method_name = "AndAlso";
                                break;
                        case Operator.LogicalOr:
                                method_name = "OrElse";
                                break;
                        case Operator.Modulus:
                                method_name = "Modulo";
                                break;
                        case Operator.Multiply:
                                if (method == null && ec.HasSet (ResolveContext.Options.CheckedScope) && !IsFloat (type))
                                        method_name = "MultiplyChecked";
                                else
                                        method_name = "Multiply";
                                break;
                        case Operator.RightShift:
                                method_name = "RightShift";
                                break;
                        case Operator.Subtraction:
                                if (method == null && ec.HasSet (ResolveContext.Options.CheckedScope) && !IsFloat (type))
                                        method_name = "SubtractChecked";
                                else
                                        method_name = "Subtract";
                                break;

                        default:
                                throw new InternalErrorException ("Unknown expression tree binary operator " + oper);
                        }

                        Arguments args = new Arguments (2);
                        args.Add (new Argument (left.CreateExpressionTree (ec)));
                        args.Add (new Argument (right.CreateExpressionTree (ec)));
                        if (method != null) {
                                if (lift_arg)
                                        args.Add (new Argument (new BoolLiteral (ec.BuiltinTypes, false, loc)));

                                args.Add (new Argument (method));
                        }
                        
                        return CreateExpressionFactoryCall (ec, method_name, args);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }

        }
        
        //
        // Represents the operation a + b [+ c [+ d [+ ...]]], where a is a string
        // b, c, d... may be strings or objects.
        //
        public class StringConcat : Expression
        {
                Arguments arguments;
                
                StringConcat (Location loc)
                {
                        this.loc = loc;
                        arguments = new Arguments (2);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return arguments.ContainsEmitWithAwait ();
                }

                public static StringConcat Create (ResolveContext rc, Expression left, Expression right, Location loc)
                {
                        if (left.eclass == ExprClass.Unresolved || right.eclass == ExprClass.Unresolved)
                                throw new ArgumentException ();

                        var s = new StringConcat (loc);
                        s.type = rc.BuiltinTypes.String;
                        s.eclass = ExprClass.Value;

                        s.Append (rc, left);
                        s.Append (rc, right);
                        return s;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Argument arg = arguments [0];
                        return CreateExpressionAddCall (ec, arg, arg.CreateExpressionTree (ec), 1);
                }

                //
                // Creates nested calls tree from an array of arguments used for IL emit
                //
                Expression CreateExpressionAddCall (ResolveContext ec, Argument left, Expression left_etree, int pos)
                {
                        Arguments concat_args = new Arguments (2);
                        Arguments add_args = new Arguments (3);

                        concat_args.Add (left);
                        add_args.Add (new Argument (left_etree));

                        concat_args.Add (arguments [pos]);
                        add_args.Add (new Argument (arguments [pos].CreateExpressionTree (ec)));

                        var methods = GetConcatMethodCandidates ();
                        if (methods == null)
                                return null;

                        var res = new OverloadResolver (methods, OverloadResolver.Restrictions.NoBaseMembers, loc);
                        var method = res.ResolveMember<MethodSpec> (ec, ref concat_args);
                        if (method == null)
                                return null;

                        add_args.Add (new Argument (new TypeOfMethod (method, loc)));

                        Expression expr = CreateExpressionFactoryCall (ec, "Add", add_args);
                        if (++pos == arguments.Count)
                                return expr;

                        left = new Argument (new EmptyExpression (method.ReturnType));
                        return CreateExpressionAddCall (ec, left, expr, pos);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        return this;
                }
                
                void Append (ResolveContext rc, Expression operand)
                {
                        //
                        // Constant folding
                        //
                        StringConstant sc = operand as StringConstant;
                        if (sc != null) {
                                if (arguments.Count != 0) {
                                        Argument last_argument = arguments [arguments.Count - 1];
                                        StringConstant last_expr_constant = last_argument.Expr as StringConstant;
                                        if (last_expr_constant != null) {
                                                last_argument.Expr = new StringConstant (rc.BuiltinTypes, last_expr_constant.Value + sc.Value, sc.Location);
                                                return;
                                        }
                                }
                        } else {
                                //
                                // Multiple (3+) concatenation are resolved as multiple StringConcat instances
                                //
                                StringConcat concat_oper = operand as StringConcat;
                                if (concat_oper != null) {
                                        arguments.AddRange (concat_oper.arguments);
                                        return;
                                }
                        }

                        arguments.Add (new Argument (operand));
                }

                IList<MemberSpec> GetConcatMethodCandidates ()
                {
                        return MemberCache.FindMembers (type, "Concat", true);
                }

                public override void Emit (EmitContext ec)
                {
                        // Optimize by removing any extra null arguments, they are no-op
                        for (int i = 0; i < arguments.Count; ++i) {
                                if (arguments[i].Expr is NullConstant)
                                        arguments.RemoveAt (i--);
                        }

                        var members = GetConcatMethodCandidates ();
                        var res = new OverloadResolver (members, OverloadResolver.Restrictions.NoBaseMembers, loc);
                        var method = res.ResolveMember<MethodSpec> (new ResolveContext (ec.MemberContext), ref arguments);
                        if (method != null) {
                                var call = new CallEmitter ();
                                call.EmitPredefined (ec, method, arguments, false);
                        }
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        arguments.FlowAnalysis (fc);
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        if (arguments.Count != 2)
                                throw new NotImplementedException ("arguments.Count != 2");

                        var concat = typeof (string).GetMethod ("Concat", new[] { typeof (object), typeof (object) });
                        return SLE.Expression.Add (arguments[0].Expr.MakeExpression (ctx), arguments[1].Expr.MakeExpression (ctx), concat);
                }
        }

        //
        // User-defined conditional logical operator
        //
        public class ConditionalLogicalOperator : UserOperatorCall
        {
                readonly bool is_and;
                Expression oper_expr;

                public ConditionalLogicalOperator (MethodSpec oper, Arguments arguments, Func<ResolveContext, Expression, Expression> expr_tree, bool is_and, Location loc)
                        : base (oper, arguments, expr_tree, loc)
                {
                        this.is_and = is_and;
                        eclass = ExprClass.Unresolved;
                }
                
                protected override Expression DoResolve (ResolveContext ec)
                {
                        AParametersCollection pd = oper.Parameters;
                        if (!TypeSpecComparer.IsEqual (type, pd.Types[0]) || !TypeSpecComparer.IsEqual (type, pd.Types[1])) {
                                ec.Report.Error (217, loc,
                                        "A user-defined operator `{0}' must have each parameter type and return type of the same type in order to be applicable as a short circuit operator",
                                        oper.GetSignatureForError ());
                                return null;
                        }

                        Expression left_dup = new EmptyExpression (type);
                        Expression op_true = GetOperatorTrue (ec, left_dup, loc);
                        Expression op_false = GetOperatorFalse (ec, left_dup, loc);
                        if (op_true == null || op_false == null) {
                                ec.Report.Error (218, loc,
                                        "The type `{0}' must have operator `true' and operator `false' defined when `{1}' is used as a short circuit operator",
                                        type.GetSignatureForError (), oper.GetSignatureForError ());
                                return null;
                        }

                        oper_expr = is_and ? op_false : op_true;
                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        Label end_target = ec.DefineLabel ();

                        //
                        // Emit and duplicate left argument
                        //
                        bool right_contains_await = ec.HasSet (BuilderContext.Options.AsyncBody) && arguments[1].Expr.ContainsEmitWithAwait ();
                        if (right_contains_await) {
                                arguments[0] = arguments[0].EmitToField (ec, false);
                                arguments[0].Expr.Emit (ec);
                        } else {
                                arguments[0].Expr.Emit (ec);
                                ec.Emit (OpCodes.Dup);
                                arguments.RemoveAt (0);
                        }

                        oper_expr.EmitBranchable (ec, end_target, true);

                        base.Emit (ec);

                        if (right_contains_await) {
                                //
                                // Special handling when right expression contains await and left argument
                                // could not be left on stack before logical branch
                                //
                                Label skip_left_load = ec.DefineLabel ();
                                ec.Emit (OpCodes.Br_S, skip_left_load);
                                ec.MarkLabel (end_target);
                                arguments[0].Expr.Emit (ec);
                                ec.MarkLabel (skip_left_load);
                        } else {
                                ec.MarkLabel (end_target);
                        }
                }
        }

        public class PointerArithmetic : Expression {
                Expression left, right;
                readonly Binary.Operator op;

                //
                // We assume that `l' is always a pointer
                //
                public PointerArithmetic (Binary.Operator op, Expression l, Expression r, TypeSpec t, Location loc)
                {
                        type = t;
                        this.loc = loc;
                        left = l;
                        right = r;
                        this.op = op;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        throw new NotImplementedException ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Error_PointerInsideExpressionTree (ec);
                        return null;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        eclass = ExprClass.Variable;

                        var pc = left.Type as PointerContainer;
                        if (pc != null && pc.Element.Kind == MemberKind.Void) {
                                Error_VoidPointerOperation (ec);
                                return null;
                        }
                        
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        TypeSpec op_type = left.Type;
                        
                        // It must be either array or fixed buffer
                        TypeSpec element;
                        if (TypeManager.HasElementType (op_type)) {
                                element = TypeManager.GetElementType (op_type);
                        } else {
                                FieldExpr fe = left as FieldExpr;
                                if (fe != null)
                                        element = ((FixedFieldSpec) (fe.Spec)).ElementType;
                                else
                                        element = op_type;
                        }

                        int size = BuiltinTypeSpec.GetSize(element);
                        TypeSpec rtype = right.Type;
                        
                        if ((op & Binary.Operator.SubtractionMask) != 0 && rtype.IsPointer){
                                //
                                // handle (pointer - pointer)
                                //
                                left.Emit (ec);
                                right.Emit (ec);
                                ec.Emit (OpCodes.Sub);

                                if (size != 1){
                                        if (size == 0)
                                                ec.Emit (OpCodes.Sizeof, element);
                                        else 
                                                ec.EmitInt (size);
                                        ec.Emit (OpCodes.Div);
                                }
                                ec.Emit (OpCodes.Conv_I8);
                        } else {
                                //
                                // handle + and - on (pointer op int)
                                //
                                Constant left_const = left as Constant;
                                if (left_const != null) {
                                        //
                                        // Optimize ((T*)null) pointer operations
                                        //
                                        if (left_const.IsDefaultValue) {
                                                left = EmptyExpression.Null;
                                        } else {
                                                left_const = null;
                                        }
                                }

                                left.Emit (ec);

                                var right_const = right as Constant;
                                if (right_const != null) {
                                        //
                                        // Optimize 0-based arithmetic
                                        //
                                        if (right_const.IsDefaultValue)
                                                return;

                                        if (size != 0)
                                                right = new IntConstant (ec.BuiltinTypes, size, right.Location);
                                        else
                                                right = new SizeOf (new TypeExpression (element, right.Location), right.Location);
                                        
                                        // TODO: Should be the checks resolve context sensitive?
                                        ResolveContext rc = new ResolveContext (ec.MemberContext, ResolveContext.Options.UnsafeScope);
                                        right = new Binary (Binary.Operator.Multiply, right, right_const).Resolve (rc);
                                        if (right == null)
                                                return;
                                }

                                right.Emit (ec);
                                switch (rtype.BuiltinType) {
                                case BuiltinTypeSpec.Type.SByte:
                                case BuiltinTypeSpec.Type.Byte:
                                case BuiltinTypeSpec.Type.Short:
                                case BuiltinTypeSpec.Type.UShort:
                                        ec.Emit (OpCodes.Conv_I);
                                        break;
                                case BuiltinTypeSpec.Type.UInt:
                                        ec.Emit (OpCodes.Conv_U);
                                        break;
                                }

                                if (right_const == null && size != 1){
                                        if (size == 0)
                                                ec.Emit (OpCodes.Sizeof, element);
                                        else 
                                                ec.EmitInt (size);
                                        if (rtype.BuiltinType == BuiltinTypeSpec.Type.Long || rtype.BuiltinType == BuiltinTypeSpec.Type.ULong)
                                                ec.Emit (OpCodes.Conv_I8);

                                        Binary.EmitOperatorOpcode (ec, Binary.Operator.Multiply, rtype, right);
                                }

                                if (left_const == null) {
                                        if (rtype.BuiltinType == BuiltinTypeSpec.Type.Long)
                                                ec.Emit (OpCodes.Conv_I);
                                        else if (rtype.BuiltinType == BuiltinTypeSpec.Type.ULong)
                                                ec.Emit (OpCodes.Conv_U);

                                        Binary.EmitOperatorOpcode (ec, op, op_type, right);
                                }
                        }
                }
        }

        //
        // A boolean-expression is an expression that yields a result
        // of type bool
        //
        public class BooleanExpression : ShimExpression
        {
                public BooleanExpression (Expression expr)
                        : base (expr)
                {
                        this.loc = expr.Location;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        // TODO: We should emit IsTrue (v4) instead of direct user operator
                        // call but that would break csc compatibility
                        return base.CreateExpressionTree (ec);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        // A boolean-expression is required to be of a type
                        // that can be implicitly converted to bool or of
                        // a type that implements operator true

                        expr = expr.Resolve (ec);
                        if (expr == null)
                                return null;

                        Assign ass = expr as Assign;
                        if (ass != null && ass.Source is Constant) {
                                ec.Report.Warning (665, 3, loc,
                                        "Assignment in conditional expression is always constant. Did you mean to use `==' instead ?");
                        }

                        if (expr.Type.BuiltinType == BuiltinTypeSpec.Type.Bool)
                                return expr;

                        if (expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                Arguments args = new Arguments (1);
                                args.Add (new Argument (expr));
                                return DynamicUnaryConversion.CreateIsTrue (ec, args, loc).Resolve (ec);
                        }

                        type = ec.BuiltinTypes.Bool;
                        Expression converted = Convert.ImplicitConversion (ec, expr, type, loc);
                        if (converted != null)
                                return converted;

                        //
                        // If no implicit conversion to bool exists, try using `operator true'
                        //
                        converted = GetOperatorTrue (ec, expr, loc);
                        if (converted == null) {
                                expr.Error_ValueCannotBeConverted (ec, type, false);
                                return null;
                        }

                        return converted;
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class BooleanExpressionFalse : Unary
        {
                public BooleanExpressionFalse (Expression expr)
                        : base (Operator.LogicalNot, expr, expr.Location)
                {
                }

                protected override Expression ResolveOperator (ResolveContext ec, Expression expr)
                {
                        return GetOperatorFalse (ec, expr, loc) ?? base.ResolveOperator (ec, expr);
                }
        }
        
        /// <summary>
        ///   Implements the ternary conditional operator (?:)
        /// </summary>
        public class Conditional : Expression {
                Expression expr, true_expr, false_expr;

                public Conditional (Expression expr, Expression true_expr, Expression false_expr, Location loc)
                {
                        this.expr = expr;
                        this.true_expr = true_expr;
                        this.false_expr = false_expr;
                        this.loc = loc;
                }

                #region Properties

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public Expression TrueExpr {
                        get {
                                return true_expr;
                        }
                }

                public Expression FalseExpr {
                        get {
                                return false_expr;
                        }
                }

                #endregion

                public override bool ContainsEmitWithAwait ()
                {
                        return Expr.ContainsEmitWithAwait () || true_expr.ContainsEmitWithAwait () || false_expr.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (3);
                        args.Add (new Argument (expr.CreateExpressionTree (ec)));
                        args.Add (new Argument (true_expr.CreateExpressionTree (ec)));
                        args.Add (new Argument (false_expr.CreateExpressionTree (ec)));
                        return CreateExpressionFactoryCall (ec, "Condition", args);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        expr = expr.Resolve (ec);
                        true_expr = true_expr.Resolve (ec);
                        false_expr = false_expr.Resolve (ec);

                        if (true_expr == null || false_expr == null || expr == null)
                                return null;

                        eclass = ExprClass.Value;
                        TypeSpec true_type = true_expr.Type;
                        TypeSpec false_type = false_expr.Type;
                        type = true_type;

                        //
                        // First, if an implicit conversion exists from true_expr
                        // to false_expr, then the result type is of type false_expr.Type
                        //
                        if (!TypeSpecComparer.IsEqual (true_type, false_type)) {
                                Expression conv = Convert.ImplicitConversion (ec, true_expr, false_type, loc);
                                if (conv != null && true_type.BuiltinType != BuiltinTypeSpec.Type.Dynamic) {
                                        //
                                        // Check if both can convert implicitly to each other's type
                                        //
                                        type = false_type;

                                        if (false_type.BuiltinType != BuiltinTypeSpec.Type.Dynamic) {
                                                var conv_false_expr = Convert.ImplicitConversion (ec, false_expr, true_type, loc);
                                                //
                                                // LAMESPEC: There seems to be hardcoded promotition to int type when
                                                // both sides are numeric constants and one side is int constant and
                                                // other side is numeric constant convertible to int.
                                                //
                                                // var res = condition ? (short)1 : 1;
                                                //
                                                // Type of res is int even if according to the spec the conversion is
                                                // ambiguous because 1 literal can be converted to short.
                                                //
                                                if (conv_false_expr != null) {
                                                        if (conv_false_expr.Type.BuiltinType == BuiltinTypeSpec.Type.Int && conv is Constant) {
                                                                type = true_type;
                                                                conv_false_expr = null;
                                                        } else if (type.BuiltinType == BuiltinTypeSpec.Type.Int && conv_false_expr is Constant) {
                                                                conv_false_expr = null;
                                                        }
                                                }

                                                if (conv_false_expr != null) {
                                                        ec.Report.Error (172, true_expr.Location,
                                                                "Type of conditional expression cannot be determined as `{0}' and `{1}' convert implicitly to each other",
                                                                        true_type.GetSignatureForError (), false_type.GetSignatureForError ());
                                                }
                                        }

                                        true_expr = conv;
                                        if (true_expr.Type != type)
                                                true_expr = EmptyCast.Create (true_expr, type);
                                } else if ((conv = Convert.ImplicitConversion (ec, false_expr, true_type, loc)) != null) {
                                        false_expr = conv;
                                } else {
                                        if (false_type != InternalType.ErrorType) {
                                                ec.Report.Error (173, true_expr.Location,
                                                        "Type of conditional expression cannot be determined because there is no implicit conversion between `{0}' and `{1}'",
                                                        true_type.GetSignatureForError (), false_type.GetSignatureForError ());
                                        }
                                        return null;
                                }
                        }

                        Constant c = expr as Constant;
                        if (c != null) {
                                bool is_false = c.IsDefaultValue;

                                //
                                // Don't issue the warning for constant expressions
                                //
                                if (!(is_false ? true_expr is Constant : false_expr is Constant)) {
                                        // CSC: Missing warning
                                        Warning_UnreachableExpression (ec, is_false ? true_expr.Location : false_expr.Location);
                                }

                                return ReducedExpression.Create (
                                        is_false ? false_expr : true_expr, this,
                                        false_expr is Constant && true_expr is Constant).Resolve (ec);
                        }

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        Label false_target = ec.DefineLabel ();
                        Label end_target = ec.DefineLabel ();

                        expr.EmitBranchable (ec, false_target, false);
                        true_expr.Emit (ec);

                        //
                        // Verifier doesn't support interface merging. When there are two types on
                        // the stack without common type hint and the common type is an interface.
                        // Use temporary local to give verifier hint on what type to unify the stack
                        //
                        if (type.IsInterface && true_expr is EmptyCast && false_expr is EmptyCast) {
                                var temp = ec.GetTemporaryLocal (type);
                                ec.Emit (OpCodes.Stloc, temp);
                                ec.Emit (OpCodes.Ldloc, temp);
                                ec.FreeTemporaryLocal (temp, type);
                        }

                        ec.Emit (OpCodes.Br, end_target);
                        ec.MarkLabel (false_target);
                        false_expr.Emit (ec);
                        ec.MarkLabel (end_target);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        expr.FlowAnalysisConditional (fc);
                        var expr_true = fc.DefiniteAssignmentOnTrue;
                        var expr_false = fc.DefiniteAssignmentOnFalse;

                        fc.BranchDefiniteAssignment (expr_true);
                        true_expr.FlowAnalysis (fc);
                        var true_fc = fc.DefiniteAssignment;

                        fc.BranchDefiniteAssignment (expr_false);
                        false_expr.FlowAnalysis (fc);

                        fc.DefiniteAssignment &= true_fc;
                }

                public override void FlowAnalysisConditional (FlowAnalysisContext fc)
                {
                        expr.FlowAnalysisConditional (fc);
                        var expr_true = fc.DefiniteAssignmentOnTrue;
                        var expr_false = fc.DefiniteAssignmentOnFalse;

                        fc.DefiniteAssignmentOnTrue = fc.DefiniteAssignmentOnFalse = fc.DefiniteAssignment = new DefiniteAssignmentBitSet (expr_true);
                        true_expr.FlowAnalysisConditional (fc);
                        var true_fc = fc.DefiniteAssignment;
                        var true_da_true = fc.DefiniteAssignmentOnTrue;
                        var true_da_false = fc.DefiniteAssignmentOnFalse;

                        fc.DefiniteAssignmentOnTrue = fc.DefiniteAssignmentOnFalse = fc.DefiniteAssignment = new DefiniteAssignmentBitSet (expr_false);
                        false_expr.FlowAnalysisConditional (fc);

                        fc.DefiniteAssignment &= true_fc;
                        fc.DefiniteAssignmentOnTrue = true_da_true & fc.DefiniteAssignmentOnTrue;
                        fc.DefiniteAssignmentOnFalse = true_da_false & fc.DefiniteAssignmentOnFalse;
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Conditional target = (Conditional) t;

                        target.expr = expr.Clone (clonectx);
                        target.true_expr = true_expr.Clone (clonectx);
                        target.false_expr = false_expr.Clone (clonectx);
                }
        }

        public abstract class VariableReference : Expression, IAssignMethod, IMemoryLocation, IVariableReference
        {
                LocalTemporary temp;

                #region Abstract
                public abstract HoistedVariable GetHoistedVariable (AnonymousExpression ae);
                public abstract void SetHasAddressTaken ();

                public abstract bool IsLockedByStatement { get; set; }

                public abstract bool IsFixed { get; }
                public abstract bool IsRef { get; }
                public abstract string Name { get; }

                //
                // Variable IL data, it has to be protected to encapsulate hoisted variables
                //
                protected abstract ILocalVariable Variable { get; }
                
                //
                // Variable flow-analysis data
                //
                public abstract VariableInfo VariableInfo { get; }
                #endregion

                public virtual void AddressOf (EmitContext ec, AddressOp mode)
                {
                        HoistedVariable hv = GetHoistedVariable (ec);
                        if (hv != null) {
                                hv.AddressOf (ec, mode);
                                return;
                        }

                        Variable.EmitAddressOf (ec);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        HoistedVariable hv = GetHoistedVariable (ec);
                        if (hv != null)
                                return hv.CreateExpressionTree ();

                        Arguments arg = new Arguments (1);
                        arg.Add (new Argument (this));
                        return CreateExpressionFactoryCall (ec, "Constant", arg);
                }

                public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
                {
                        if (IsLockedByStatement) {
                                rc.Report.Warning (728, 2, loc,
                                        "Possibly incorrect assignment to `{0}' which is the argument to a using or lock statement",
                                        Name);
                        }

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        Emit (ec, false);
                }

                public override void EmitSideEffect (EmitContext ec)
                {
                        // do nothing
                }

                //
                // This method is used by parameters that are references, that are
                // being passed as references:  we only want to pass the pointer (that
                // is already stored in the parameter, not the address of the pointer,
                // and not the value of the variable).
                //
                public void EmitLoad (EmitContext ec)
                {
                        Variable.Emit (ec);
                }

                public void Emit (EmitContext ec, bool leave_copy)
                {
                        HoistedVariable hv = GetHoistedVariable (ec);
                        if (hv != null) {
                                hv.Emit (ec, leave_copy);
                                return;
                        }

                        EmitLoad (ec);

                        if (IsRef) {
                                //
                                // If we are a reference, we loaded on the stack a pointer
                                // Now lets load the real value
                                //
                                ec.EmitLoadFromPtr (type);
                        }

                        if (leave_copy) {
                                ec.Emit (OpCodes.Dup);

                                if (IsRef) {
                                        temp = new LocalTemporary (Type);
                                        temp.Store (ec);
                                }
                        }
                }

                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy,
                                        bool prepare_for_load)
                {
                        HoistedVariable hv = GetHoistedVariable (ec);
                        if (hv != null) {
                                hv.EmitAssign (ec, source, leave_copy, prepare_for_load);
                                return;
                        }

                        New n_source = source as New;
                        if (n_source != null) {
                                if (!n_source.Emit (ec, this)) {
                                        if (leave_copy) {
                                                EmitLoad (ec);
                                                if (IsRef)
                                                        ec.EmitLoadFromPtr (type);
                                        }
                                        return;
                                }
                        } else {
                                if (IsRef)
                                        EmitLoad (ec);

                                source.Emit (ec);
                        }

                        if (leave_copy) {
                                ec.Emit (OpCodes.Dup);
                                if (IsRef) {
                                        temp = new LocalTemporary (Type);
                                        temp.Store (ec);
                                }
                        }

                        if (IsRef)
                                ec.EmitStoreFromPtr (type);
                        else
                                Variable.EmitAssign (ec);

                        if (temp != null) {
                                temp.Emit (ec);
                                temp.Release (ec);
                        }
                }

                public override Expression EmitToField (EmitContext ec)
                {
                        HoistedVariable hv = GetHoistedVariable (ec);
                        if (hv != null) {
                                return hv.EmitToField (ec);
                        }

                        return base.EmitToField (ec);
                }

                public HoistedVariable GetHoistedVariable (ResolveContext rc)
                {
                        return GetHoistedVariable (rc.CurrentAnonymousMethod);
                }

                public HoistedVariable GetHoistedVariable (EmitContext ec)
                {
                        return GetHoistedVariable (ec.CurrentAnonymousMethod);
                }

                public override string GetSignatureForError ()
                {
                        return Name;
                }

                public bool IsHoisted {
                        get { return GetHoistedVariable ((AnonymousExpression) null) != null; }
                }
        }

        //
        // Resolved reference to a local variable
        //
        public class LocalVariableReference : VariableReference
        {
                public LocalVariable local_info;

                public LocalVariableReference (LocalVariable li, Location l)
                {
                        this.local_info = li;
                        loc = l;
                }

                public override VariableInfo VariableInfo {
                        get { return local_info.VariableInfo; }
                }

                public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
                {
                        return local_info.HoistedVariant;
                }

                #region Properties

                //              
                // A local variable is always fixed
                //
                public override bool IsFixed {
                        get {
                                return true;
                        }
                }

                public override bool IsLockedByStatement {
                        get {
                                return local_info.IsLocked;
                        }
                        set {
                                local_info.IsLocked = value;
                        }
                }

                public override bool IsRef {
                        get { return false; }
                }

                public override string Name {
                        get { return local_info.Name; }
                }

                #endregion

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        VariableInfo variable_info = VariableInfo;
                        if (variable_info == null)
                                return;

                        if (fc.IsDefinitelyAssigned (variable_info))
                                return;

                        fc.Report.Error (165, loc, "Use of unassigned local variable `{0}'", Name);
                        variable_info.SetAssigned (fc.DefiniteAssignment, true);
                }

                public override void SetHasAddressTaken ()
                {
                        local_info.SetHasAddressTaken ();
                }

                void DoResolveBase (ResolveContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = local_info.Type;

                        //
                        // If we are referencing a variable from the external block
                        // flag it for capturing
                        //
                        if (ec.MustCaptureVariable (local_info)) {
                                if (local_info.AddressTaken) {
                                        AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, this, loc);
                                } else if (local_info.IsFixed) {
                                        ec.Report.Error (1764, loc,
                                                "Cannot use fixed local `{0}' inside an anonymous method, lambda expression or query expression",
                                                GetSignatureForError ());
                                }

                                if (ec.IsVariableCapturingRequired) {
                                        AnonymousMethodStorey storey = local_info.Block.Explicit.CreateAnonymousMethodStorey (ec);
                                        storey.CaptureLocalVariable (ec, local_info);
                                }
                        }
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        local_info.SetIsUsed ();

                        DoResolveBase (ec);

                        if (local_info.Type == InternalType.VarOutType) {
                                ec.Report.Error (8048, loc, "Cannot use uninitialized variable `{0}'",
                                        GetSignatureForError ());

                                type = InternalType.ErrorType;
                        }

                        return this;
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression rhs)
                {
                        //
                        // Don't be too pedantic when variable is used as out param or for some broken code
                        // which uses property/indexer access to run some initialization
                        //
                        if (rhs == EmptyExpression.OutAccess || rhs.eclass == ExprClass.PropertyAccess || rhs.eclass == ExprClass.IndexerAccess)
                                local_info.SetIsUsed ();

                        if (local_info.IsReadonly && !ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.UsingInitializerScope)) {
                                if (rhs == EmptyExpression.LValueMemberAccess) {
                                        // CS1654 already reported
                                } else {
                                        int code;
                                        string msg;
                                        if (rhs == EmptyExpression.OutAccess) {
                                                code = 1657; msg = "Cannot pass `{0}' as a ref or out argument because it is a `{1}'";
                                        } else if (rhs == EmptyExpression.LValueMemberOutAccess) {
                                                code = 1655; msg = "Cannot pass members of `{0}' as ref or out arguments because it is a `{1}'";
                                        } else if (rhs == EmptyExpression.UnaryAddress) {
                                                code = 459; msg = "Cannot take the address of {1} `{0}'";
                                        } else {
                                                code = 1656; msg = "Cannot assign to `{0}' because it is a `{1}'";
                                        }
                                        ec.Report.Error (code, loc, msg, Name, local_info.GetReadOnlyContext ());
                                }
                        }

                        if (eclass == ExprClass.Unresolved)
                                DoResolveBase (ec);

                        return base.DoResolveLValue (ec, rhs);
                }

                public override int GetHashCode ()
                {
                        return local_info.GetHashCode ();
                }

                public override bool Equals (object obj)
                {
                        LocalVariableReference lvr = obj as LocalVariableReference;
                        if (lvr == null)
                                return false;

                        return local_info == lvr.local_info;
                }

                protected override ILocalVariable Variable {
                        get { return local_info; }
                }

                public override string ToString ()
                {
                        return String.Format ("{0} ({1}:{2})", GetType (), Name, loc);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        // Nothing
                }
        }

        /// <summary>
        ///   This represents a reference to a parameter in the intermediate
        ///   representation.
        /// </summary>
        public class ParameterReference : VariableReference
        {
                protected ParametersBlock.ParameterInfo pi;

                public ParameterReference (ParametersBlock.ParameterInfo pi, Location loc)
                {
                        this.pi = pi;
                        this.loc = loc;
                }

                #region Properties

                public override bool IsLockedByStatement {
                        get {
                                return pi.IsLocked;
                        }
                        set     {
                                pi.IsLocked = value;
                        }
                }

                public override bool IsRef {
                        get { return (pi.Parameter.ModFlags & Parameter.Modifier.RefOutMask) != 0; }
                }

                bool HasOutModifier {
                        get { return (pi.Parameter.ModFlags & Parameter.Modifier.OUT) != 0; }
                }

                public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
                {
                        return pi.Parameter.HoistedVariant;
                }

                //
                // A ref or out parameter is classified as a moveable variable, even 
                // if the argument given for the parameter is a fixed variable
                //              
                public override bool IsFixed {
                        get { return !IsRef; }
                }

                public override string Name {
                        get { return Parameter.Name; }
                }

                public Parameter Parameter {
                        get { return pi.Parameter; }
                }

                public override VariableInfo VariableInfo {
                        get { return pi.VariableInfo; }
                }

                protected override ILocalVariable Variable {
                        get { return Parameter; }
                }

                #endregion

                public override void AddressOf (EmitContext ec, AddressOp mode)
                {
                        //
                        // ParameterReferences might already be a reference
                        //
                        if (IsRef) {
                                EmitLoad (ec);
                                return;
                        }

                        base.AddressOf (ec, mode);
                }

                public override void SetHasAddressTaken ()
                {
                        Parameter.HasAddressTaken = true;
                }

                bool DoResolveBase (ResolveContext ec)
                {
                        if (eclass != ExprClass.Unresolved)
                                return true;

                        type = pi.ParameterType;
                        eclass = ExprClass.Variable;

                        //
                        // If we are referencing a parameter from the external block
                        // flag it for capturing
                        //
                        if (ec.MustCaptureVariable (pi)) {
                                if (Parameter.HasAddressTaken)
                                        AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, this, loc);

                                if (IsRef) {
                                        ec.Report.Error (1628, loc,
                                                "Parameter `{0}' cannot be used inside `{1}' when using `ref' or `out' modifier",
                                                Name, ec.CurrentAnonymousMethod.ContainerType);
                                }

                                if (ec.IsVariableCapturingRequired && !pi.Block.ParametersBlock.IsExpressionTree) {
                                        AnonymousMethodStorey storey = pi.Block.Explicit.CreateAnonymousMethodStorey (ec);
                                        storey.CaptureParameter (ec, pi, this);
                                }
                        }

                        return true;
                }

                public override int GetHashCode ()
                {
                        return Name.GetHashCode ();
                }

                public override bool Equals (object obj)
                {
                        ParameterReference pr = obj as ParameterReference;
                        if (pr == null)
                                return false;

                        return Name == pr.Name;
                }
        
                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                        // Nothing to clone
                        return;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        HoistedVariable hv = GetHoistedVariable (ec);
                        if (hv != null)
                                return hv.CreateExpressionTree ();

                        return Parameter.ExpressionTreeVariableReference ();
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (!DoResolveBase (ec))
                                return null;

                        return this;
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
                {
                        if (!DoResolveBase (ec))
                                return null;

                        if (Parameter.HoistedVariant != null)
                                Parameter.HoistedVariant.IsAssigned = true;

                        return base.DoResolveLValue (ec, right_side);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        VariableInfo variable_info = VariableInfo;
                        if (variable_info == null)
                                return;

                        if (fc.IsDefinitelyAssigned (variable_info))
                                return;

                        fc.Report.Error (269, loc, "Use of unassigned out parameter `{0}'", Name);
                        fc.SetVariableAssigned (variable_info);
                }
        }

        /// <summary>
        ///   Invocation of methods or delegates.
        /// </summary>
        public class Invocation : ExpressionStatement
        {
                public class Predefined : Invocation
                {
                        public Predefined (MethodGroupExpr expr, Arguments arguments)
                                : base (expr, arguments)
                        {
                                this.mg = expr;
                        }

                        protected override MethodGroupExpr DoResolveOverload (ResolveContext rc)
                        {
                                if (!rc.IsObsolete) {
                                        var member = mg.BestCandidate;
                                        ObsoleteAttribute oa = member.GetAttributeObsolete ();
                                        if (oa != null)
                                                AttributeTester.Report_ObsoleteMessage (oa, member.GetSignatureForError (), loc, rc.Report);
                                }

                                return mg;
                        }
                }

                protected Arguments arguments;
                protected Expression expr;
                protected MethodGroupExpr mg;
                bool conditional_access_receiver;
                
                public Invocation (Expression expr, Arguments arguments)
                {
                        this.expr = expr;               
                        this.arguments = arguments;
                        if (expr != null) {
                                loc = expr.Location;
                        }
                }

                #region Properties
                public Arguments Arguments {
                        get {
                                return arguments;
                        }
                }
                
                public Expression Exp {
                        get {
                                return expr;
                        }
                }

                public MethodGroupExpr MethodGroup {
                        get {
                                return mg;
                        }
                }

                public override Location StartLocation {
                        get {
                                return expr.StartLocation;
                        }
                }

                #endregion

                public override MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
                {
                        if (MethodGroup == null)
                                return null;

                        var candidate = MethodGroup.BestCandidate;
                        if (candidate == null || !(candidate.IsStatic || Exp is This))
                                return null;

                        var args_count = arguments == null ? 0 : arguments.Count;
                        if (args_count != body.Parameters.Count)
                                return null;

                        var lambda_parameters = body.Block.Parameters.FixedParameters;
                        for (int i = 0; i < args_count; ++i) {
                                var pr = arguments[i].Expr as ParameterReference;
                                if (pr == null)
                                        return null;

                                if (lambda_parameters[i] != pr.Parameter)
                                        return null;

                                if ((lambda_parameters[i].ModFlags & Parameter.Modifier.RefOutMask) != (pr.Parameter.ModFlags & Parameter.Modifier.RefOutMask))
                                        return null;
                        }

                        var emg = MethodGroup as ExtensionMethodGroupExpr;
                        if (emg != null) {
                                var mg = MethodGroupExpr.CreatePredefined (candidate, candidate.DeclaringType, MethodGroup.Location);
                                if (candidate.IsGeneric) {
                                        var targs = new TypeExpression [candidate.Arity];
                                        for (int i = 0; i < targs.Length; ++i) {
                                                targs[i] = new TypeExpression (candidate.TypeArguments[i], MethodGroup.Location);
                                        }

                                        mg.SetTypeArguments (null, new TypeArguments (targs));
                                }

                                return mg;
                        }

                        return MethodGroup;
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Invocation target = (Invocation) t;

                        if (arguments != null)
                                target.arguments = arguments.Clone (clonectx);

                        target.expr = expr.Clone (clonectx);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        if (arguments != null && arguments.ContainsEmitWithAwait ())
                                return true;

                        return mg.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Expression instance = mg.IsInstance ?
                                mg.InstanceExpression.CreateExpressionTree (ec) :
                                new NullLiteral (loc);

                        var args = Arguments.CreateForExpressionTree (ec, arguments,
                                instance,
                                mg.CreateExpressionTree (ec));

                        return CreateExpressionFactoryCall (ec, "Call", args);
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        if (!rc.HasSet (ResolveContext.Options.ConditionalAccessReceiver)) {
                                if (expr.HasConditionalAccess ()) {
                                        conditional_access_receiver = true;
                                        using (rc.Set (ResolveContext.Options.ConditionalAccessReceiver)) {
                                                return DoResolveInvocation (rc);
                                        }
                                }
                        }

                        return DoResolveInvocation (rc);
                }

                Expression DoResolveInvocation (ResolveContext ec)
                {
                        Expression member_expr;
                        var atn = expr as ATypeNameExpression;
                        if (atn != null) {
                                member_expr = atn.LookupNameExpression (ec, MemberLookupRestrictions.InvocableOnly | MemberLookupRestrictions.ReadAccess);
                                if (member_expr != null) {
                                        var name_of = member_expr as NameOf;
                                        if (name_of != null) {
                                                return name_of.ResolveOverload (ec, arguments);
                                        }

                                        member_expr = member_expr.Resolve (ec);
                                }
                        } else {
                                member_expr = expr.Resolve (ec);
                        }

                        if (member_expr == null)
                                return null;

                        //
                        // Next, evaluate all the expressions in the argument list
                        //
                        bool dynamic_arg = false;
                        if (arguments != null)
                                arguments.Resolve (ec, out dynamic_arg);

                        TypeSpec expr_type = member_expr.Type;
                        if (expr_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
                                return DoResolveDynamic (ec, member_expr);

                        mg = member_expr as MethodGroupExpr;
                        Expression invoke = null;

                        if (mg == null) {
                                if (expr_type != null && expr_type.IsDelegate) {
                                        invoke = new DelegateInvocation (member_expr, arguments, conditional_access_receiver, loc);
                                        invoke = invoke.Resolve (ec);
                                        if (invoke == null || !dynamic_arg)
                                                return invoke;
                                } else {
                                        if (member_expr is RuntimeValueExpression) {
                                                ec.Report.Error (Report.RuntimeErrorId, loc, "Cannot invoke a non-delegate type `{0}'",
                                                        member_expr.Type.GetSignatureForError ());
                                                return null;
                                        }

                                        MemberExpr me = member_expr as MemberExpr;
                                        if (me == null) {
                                                member_expr.Error_UnexpectedKind (ec, ResolveFlags.MethodGroup, loc);
                                                return null;
                                        }

                                        ec.Report.Error (1955, loc, "The member `{0}' cannot be used as method or delegate",
                                                        member_expr.GetSignatureForError ());
                                        return null;
                                }
                        }

                        if (invoke == null) {
                                mg = DoResolveOverload (ec);
                                if (mg == null)
                                        return null;
                        }

                        if (dynamic_arg)
                                return DoResolveDynamic (ec, member_expr);

                        var method = mg.BestCandidate;
                        type = mg.BestCandidateReturnType;
                        if (conditional_access_receiver)
                                type = LiftMemberType (ec, type);

                        if (arguments == null && method.DeclaringType.BuiltinType == BuiltinTypeSpec.Type.Object && method.Name == Destructor.MetadataName) {
                                if (mg.IsBase)
                                        ec.Report.Error (250, loc, "Do not directly call your base class Finalize method. It is called automatically from your destructor");
                                else
                                        ec.Report.Error (245, loc, "Destructors and object.Finalize cannot be called directly. Consider calling IDisposable.Dispose if available");
                                return null;
                        }

                        IsSpecialMethodInvocation (ec, method, loc);
                        
                        eclass = ExprClass.Value;
                        return this;
                }

                protected virtual Expression DoResolveDynamic (ResolveContext ec, Expression memberExpr)
                {
                        Arguments args;
                        DynamicMemberBinder dmb = memberExpr as DynamicMemberBinder;
                        if (dmb != null) {
                                args = dmb.Arguments;
                                if (arguments != null)
                                        args.AddRange (arguments);
                        } else if (mg == null) {
                                if (arguments == null)
                                        args = new Arguments (1);
                                else
                                        args = arguments;

                                args.Insert (0, new Argument (memberExpr));
                                this.expr = null;
                        } else {
                                if (mg.IsBase) {
                                        ec.Report.Error (1971, loc,
                                                "The base call to method `{0}' cannot be dynamically dispatched. Consider casting the dynamic arguments or eliminating the base access",
                                                mg.Name);
                                        return null;
                                }

                                if (arguments == null)
                                        args = new Arguments (1);
                                else
                                        args = arguments;

                                MemberAccess ma = expr as MemberAccess;
                                if (ma != null) {
                                        var inst = mg.InstanceExpression;
                                        var left_type = inst as TypeExpr;
                                        if (left_type != null) {
                                                args.Insert (0, new Argument (new TypeOf (left_type.Type, loc).Resolve (ec), Argument.AType.DynamicTypeName));
                                        } else if (inst != null) {
                                                //
                                                // Any value type has to be pass as by-ref to get back the same
                                                // instance on which the member was called
                                                //
                                                var mod = inst is IMemoryLocation && TypeSpec.IsValueType (inst.Type) ?
                                                        Argument.AType.Ref : Argument.AType.None;
                                                args.Insert (0, new Argument (inst.Resolve (ec), mod));
                                        }
                                } else {        // is SimpleName
                                        if (ec.IsStatic) {
                                                args.Insert (0, new Argument (new TypeOf (ec.CurrentType, loc).Resolve (ec), Argument.AType.DynamicTypeName));
                                        } else {
                                                args.Insert (0, new Argument (new This (loc).Resolve (ec)));
                                        }
                                }
                        }

                        return new DynamicInvocation (expr as ATypeNameExpression, args, loc).Resolve (ec);
                }

                protected virtual MethodGroupExpr DoResolveOverload (ResolveContext ec)
                {
                        return mg.OverloadResolve (ec, ref arguments, null, OverloadResolver.Restrictions.None);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        if (mg.IsConditionallyExcluded)
                                return;

                        mg.FlowAnalysis (fc);

                        if (arguments != null)
                                arguments.FlowAnalysis (fc);

                        if (conditional_access_receiver)
                                fc.ConditionalAccessEnd ();
                }

                public override string GetSignatureForError ()
                {
                        return mg.GetSignatureForError ();
                }

                public override bool HasConditionalAccess ()
                {
                        return expr.HasConditionalAccess ();
                }

                //
                // If a member is a method or event, or if it is a constant, field or property of either a delegate type
                // or the type dynamic, then the member is invocable
                //
                public static bool IsMemberInvocable (MemberSpec member)
                {
                        switch (member.Kind) {
                        case MemberKind.Event:
                                return true;
                        case MemberKind.Field:
                        case MemberKind.Property:
                                var m = member as IInterfaceMemberSpec;
                                return m.MemberType.IsDelegate || m.MemberType.BuiltinType == BuiltinTypeSpec.Type.Dynamic;
                        default:
                                return false;
                        }
                }

                public static bool IsSpecialMethodInvocation (ResolveContext ec, MethodSpec method, Location loc)
                {
                        if (!method.IsReservedMethod)
                                return false;

                        if (ec.HasSet (ResolveContext.Options.InvokeSpecialName) || ec.CurrentMemberDefinition.IsCompilerGenerated)
                                return false;

                        ec.Report.SymbolRelatedToPreviousError (method);
                        ec.Report.Error (571, loc, "`{0}': cannot explicitly call operator or accessor",
                                method.GetSignatureForError ());
        
                        return true;
                }

                public override void Emit (EmitContext ec)
                {
                        if (mg.IsConditionallyExcluded)
                                return;

                        if (conditional_access_receiver)
                                mg.EmitCall (ec, arguments, type, false);
                        else
                                mg.EmitCall (ec, arguments, false);
                }
                
                public override void EmitStatement (EmitContext ec)
                {
                        if (mg.IsConditionallyExcluded)
                                return;

                        if (conditional_access_receiver)
                                mg.EmitCall (ec, arguments, type, true);
                        else
                                mg.EmitCall (ec, arguments, true);
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        return MakeExpression (ctx, mg.InstanceExpression, mg.BestCandidate, arguments);
                }

                public static SLE.Expression MakeExpression (BuilderContext ctx, Expression instance, MethodSpec mi, Arguments args)
                {
#if STATIC
                        throw new NotSupportedException ();
#else
                        var instance_expr = instance == null ? null : instance.MakeExpression (ctx);
                        return SLE.Expression.Call (instance_expr, (MethodInfo) mi.GetMetaInfo (), Arguments.MakeExpression (args, ctx));
#endif
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        //
        // Implements simple new expression 
        //
        public class New : ExpressionStatement, IMemoryLocation
        {
                protected Arguments arguments;

                //
                // During bootstrap, it contains the RequestedType,
                // but if `type' is not null, it *might* contain a NewDelegate
                // (because of field multi-initialization)
                //
                protected Expression RequestedType;

                protected MethodSpec method;

                public New (Expression requested_type, Arguments arguments, Location l)
                {
                        RequestedType = requested_type;
                        this.arguments = arguments;
                        loc = l;
                }

                #region Properties
                public Arguments Arguments {
                        get {
                                return arguments;
                        }
                }

                //
                // Returns true for resolved `new S()' when S does not declare parameterless constructor
                //
                public bool IsGeneratedStructConstructor {
                        get {
                                return arguments == null && method == null && type.IsStruct && GetType () == typeof (New);
                        }
                }

                public Expression TypeExpression {
                        get {
                                return RequestedType;
                        }
                }

                #endregion

                /// <summary>
                /// Converts complex core type syntax like 'new int ()' to simple constant
                /// </summary>
                public static Constant Constantify (TypeSpec t, Location loc)
                {
                        switch (t.BuiltinType) {
                        case BuiltinTypeSpec.Type.Int:
                                return new IntConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.UInt:
                                return new UIntConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.Long:
                                return new LongConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.ULong:
                                return new ULongConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.Float:
                                return new FloatConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.Double:
                                return new DoubleConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.Short:
                                return new ShortConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.UShort:
                                return new UShortConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.SByte:
                                return new SByteConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.Byte:
                                return new ByteConstant (t, 0, loc);
                        case BuiltinTypeSpec.Type.Char:
                                return new CharConstant (t, '\0', loc);
                        case BuiltinTypeSpec.Type.Bool:
                                return new BoolConstant (t, false, loc);
                        case BuiltinTypeSpec.Type.Decimal:
                                return new DecimalConstant (t, 0, loc);
                        }

                        if (t.IsEnum)
                                return new EnumConstant (Constantify (EnumSpec.GetUnderlyingType (t), loc), t);

                        if (t.IsNullableType)
                                return Nullable.LiftedNull.Create (t, loc);

                        return null;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return arguments != null && arguments.ContainsEmitWithAwait ();
                }

                //
                // Checks whether the type is an interface that has the
                // [ComImport, CoClass] attributes and must be treated
                // specially
                //
                public Expression CheckComImport (ResolveContext ec)
                {
                        if (!type.IsInterface)
                                return null;

                        //
                        // Turn the call into:
                        // (the-interface-stated) (new class-referenced-in-coclassattribute ())
                        //
                        var real_class = type.MemberDefinition.GetAttributeCoClass ();
                        if (real_class == null)
                                return null;

                        New proxy = new New (new TypeExpression (real_class, loc), arguments, loc);
                        Cast cast = new Cast (new TypeExpression (type, loc), proxy, loc);
                        return cast.Resolve (ec);
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args;
                        if (method == null) {
                                args = new Arguments (1);
                                args.Add (new Argument (new TypeOf (type, loc)));
                        } else {
                                args = Arguments.CreateForExpressionTree (ec,
                                        arguments, new TypeOfMethod (method, loc));
                        }

                        return CreateExpressionFactoryCall (ec, "New", args);
                }
                
                protected override Expression DoResolve (ResolveContext ec)
                {
                        type = RequestedType.ResolveAsType (ec);
                        if (type == null)
                                return null;

                        eclass = ExprClass.Value;

                        if (type.IsPointer) {
                                ec.Report.Error (1919, loc, "Unsafe type `{0}' cannot be used in an object creation expression",
                                        type.GetSignatureForError ());
                                return null;
                        }

                        if (arguments == null) {
                                Constant c = Constantify (type, RequestedType.Location);
                                if (c != null)
                                        return ReducedExpression.Create (c, this);
                        }

                        if (type.IsDelegate) {
                                return (new NewDelegate (type, arguments, loc)).Resolve (ec);
                        }

                        var tparam = type as TypeParameterSpec;
                        if (tparam != null) {
                                //
                                // Check whether the type of type parameter can be constructed. BaseType can be a struct for method overrides
                                // where type parameter constraint is inflated to struct
                                //
                                if ((tparam.SpecialConstraint & (SpecialConstraint.Struct | SpecialConstraint.Constructor)) == 0 && !TypeSpec.IsValueType (tparam)) {
                                        ec.Report.Error (304, loc,
                                                "Cannot create an instance of the variable type `{0}' because it does not have the new() constraint",
                                                type.GetSignatureForError ());
                                }

                                if ((arguments != null) && (arguments.Count != 0)) {
                                        ec.Report.Error (417, loc,
                                                "`{0}': cannot provide arguments when creating an instance of a variable type",
                                                type.GetSignatureForError ());
                                }

                                return this;
                        }

                        if (type.IsStatic) {
                                ec.Report.SymbolRelatedToPreviousError (type);
                                ec.Report.Error (712, loc, "Cannot create an instance of the static class `{0}'", type.GetSignatureForError ());
                                return null;
                        }

                        if (type.IsInterface || type.IsAbstract){
                                if (!TypeManager.IsGenericType (type)) {
                                        RequestedType = CheckComImport (ec);
                                        if (RequestedType != null)
                                                return RequestedType;
                                }
                                
                                ec.Report.SymbolRelatedToPreviousError (type);
                                ec.Report.Error (144, loc, "Cannot create an instance of the abstract class or interface `{0}'", type.GetSignatureForError ());
                                return null;
                        }

                        bool dynamic;
                        if (arguments != null) {
                                arguments.Resolve (ec, out dynamic);
                        } else {
                                dynamic = false;
                        }

                        method = ConstructorLookup (ec, type, ref arguments, loc);

                        if (dynamic) {
                                arguments.Insert (0, new Argument (new TypeOf (type, loc).Resolve (ec), Argument.AType.DynamicTypeName));
                                return new DynamicConstructorBinder (type, arguments, loc).Resolve (ec);
                        }

                        return this;
                }

                void DoEmitTypeParameter (EmitContext ec)
                {
                        var m = ec.Module.PredefinedMembers.ActivatorCreateInstance.Resolve (loc);
                        if (m == null)
                                return;

                        var ctor_factory = m.MakeGenericMethod (ec.MemberContext, type);
                        ec.Emit (OpCodes.Call, ctor_factory);
                }

                //
                // This Emit can be invoked in two contexts:
                //    * As a mechanism that will leave a value on the stack (new object)
                //    * As one that wont (init struct)
                //
                // If we are dealing with a ValueType, we have a few
                // situations to deal with:
                //
                //    * The target is a ValueType, and we have been provided
                //      the instance (this is easy, we are being assigned).
                //
                //    * The target of New is being passed as an argument,
                //      to a boxing operation or a function that takes a
                //      ValueType.
                //
                //      In this case, we need to create a temporary variable
                //      that is the argument of New.
                //
                // Returns whether a value is left on the stack
                //
                // *** Implementation note ***
                //
                // To benefit from this optimization, each assignable expression
                // has to manually cast to New and call this Emit.
                //
                // TODO: It's worth to implement it for arrays and fields
                //
                public virtual bool Emit (EmitContext ec, IMemoryLocation target)
                {
                        bool is_value_type = type.IsStructOrEnum;
                        VariableReference vr = target as VariableReference;

                        if (target != null && is_value_type && (vr != null || method == null)) {
                                target.AddressOf (ec, AddressOp.Store);
                        } else if (vr != null && vr.IsRef) {
                                vr.EmitLoad (ec);
                        }

                        if (arguments != null) {
                                if (ec.HasSet (BuilderContext.Options.AsyncBody) && (arguments.Count > (this is NewInitialize ? 0 : 1)) && arguments.ContainsEmitWithAwait ())
                                        arguments = arguments.Emit (ec, false, true);

                                arguments.Emit (ec);
                        }

                        if (is_value_type) {
                                if (method == null) {
                                        ec.Emit (OpCodes.Initobj, type);
                                        return false;
                                }

                                if (vr != null) {
                                        ec.MarkCallEntry (loc);
                                        ec.Emit (OpCodes.Call, method);
                                        return false;
                                }
                        }
                        
                        if (type is TypeParameterSpec) {
                                DoEmitTypeParameter (ec);
                                return true;
                        }

                        ec.MarkCallEntry (loc);
                        ec.Emit (OpCodes.Newobj, method);
                        return true;
                }

                public override void Emit (EmitContext ec)
                {
                        LocalTemporary v = null;
                        if (method == null && type.IsStructOrEnum) {
                                // TODO: Use temporary variable from pool
                                v = new LocalTemporary (type);
                        }

                        if (!Emit (ec, v))
                                v.Emit (ec);
                }

                public override void EmitStatement (EmitContext ec)
                {
                        LocalTemporary v = null;
                        if (method == null && TypeSpec.IsValueType (type)) {
                                // TODO: Use temporary variable from pool
                                v = new LocalTemporary (type);
                        }

                        if (Emit (ec, v))
                                ec.Emit (OpCodes.Pop);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        if (arguments != null)
                                arguments.FlowAnalysis (fc);
                }

                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        EmitAddressOf (ec, mode);
                }

                protected virtual IMemoryLocation EmitAddressOf (EmitContext ec, AddressOp mode)
                {
                        LocalTemporary value_target = new LocalTemporary (type);

                        if (type is TypeParameterSpec) {
                                DoEmitTypeParameter (ec);
                                value_target.Store (ec);
                                value_target.AddressOf (ec, mode);
                                return value_target;
                        }

                        value_target.AddressOf (ec, AddressOp.Store);

                        if (method == null) {
                                ec.Emit (OpCodes.Initobj, type);
                        } else {
                                if (arguments != null)
                                        arguments.Emit (ec);

                                ec.Emit (OpCodes.Call, method);
                        }
                        
                        value_target.AddressOf (ec, mode);
                        return value_target;
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        New target = (New) t;

                        target.RequestedType = RequestedType.Clone (clonectx);
                        if (arguments != null){
                                target.arguments = arguments.Clone (clonectx);
                        }
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
#if STATIC
                        return base.MakeExpression (ctx);
#else
                        return SLE.Expression.New ((ConstructorInfo) method.GetMetaInfo (), Arguments.MakeExpression (arguments, ctx));
#endif
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        //
        // Array initializer expression, the expression is allowed in
        // variable or field initialization only which makes it tricky as
        // the type has to be infered based on the context either from field
        // type or variable type (think of multiple declarators)
        //
        public class ArrayInitializer : Expression
        {
                List<Expression> elements;
                BlockVariable variable;

                public ArrayInitializer (List<Expression> init, Location loc)
                {
                        elements = init;
                        this.loc = loc;
                }

                public ArrayInitializer (int count, Location loc)
                        : this (new List<Expression> (count), loc)
                {
                }

                public ArrayInitializer (Location loc)
                        : this (4, loc)
                {
                }

                #region Properties

                public int Count {
                        get { return elements.Count; }
                }

                public List<Expression> Elements {
                        get {
                                return elements;
                        }
                }

                public Expression this [int index] {
                        get {
                                return elements [index];
                        }
                }

                public BlockVariable VariableDeclaration {
                        get {
                                return variable;
                        }
                        set {
                                variable = value;
                        }
                }

                #endregion

                public void Add (Expression expr)
                {
                        elements.Add (expr);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        throw new NotSupportedException ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        var target = (ArrayInitializer) t;

                        target.elements = new List<Expression> (elements.Count);
                        foreach (var element in elements)
                                target.elements.Add (element.Clone (clonectx));
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        var current_field = rc.CurrentMemberDefinition as FieldBase;
                        TypeExpression type;
                        if (current_field != null && rc.CurrentAnonymousMethod == null) {
                                type = new TypeExpression (current_field.MemberType, current_field.Location);
                        } else if (variable != null) {
                                if (variable.TypeExpression is VarExpr) {
                                        rc.Report.Error (820, loc, "An implicitly typed local variable declarator cannot use an array initializer");
                                        return EmptyExpression.Null;
                                }

                                type = new TypeExpression (variable.Variable.Type, variable.Variable.Location);
                        } else {
                                throw new NotImplementedException ("Unexpected array initializer context");
                        }

                        return new ArrayCreation (type, this).Resolve (rc);
                }

                public override void Emit (EmitContext ec)
                {
                        throw new InternalErrorException ("Missing Resolve call");
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        throw new InternalErrorException ("Missing Resolve call");
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   14.5.10.2: Represents an array creation expression.
        /// </summary>
        ///
        /// <remarks>
        ///   There are two possible scenarios here: one is an array creation
        ///   expression that specifies the dimensions and optionally the
        ///   initialization data and the other which does not need dimensions
        ///   specified but where initialization data is mandatory.
        /// </remarks>
        public class ArrayCreation : Expression
        {
                FullNamedExpression requested_base_type;
                ArrayInitializer initializers;

                //
                // The list of Argument types.
                // This is used to construct the `newarray' or constructor signature
                //
                protected List<Expression> arguments;
                
                protected TypeSpec array_element_type;
                int num_arguments;
                protected int dimensions;
                protected readonly ComposedTypeSpecifier rank;
                Expression first_emit;
                LocalTemporary first_emit_temp;

                protected List<Expression> array_data;

                Dictionary<int, int> bounds;

#if STATIC
                // The number of constants in array initializers
                int const_initializers_count;
                bool only_constant_initializers;
#endif
                public ArrayCreation (FullNamedExpression requested_base_type, List<Expression> exprs, ComposedTypeSpecifier rank, ArrayInitializer initializers, Location l)
                        : this (requested_base_type, rank, initializers, l)
                {
                        arguments = new List<Expression> (exprs);
                        num_arguments = arguments.Count;
                }

                //
                // For expressions like int[] foo = new int[] { 1, 2, 3 };
                //
                public ArrayCreation (FullNamedExpression requested_base_type, ComposedTypeSpecifier rank, ArrayInitializer initializers, Location loc)
                {
                        this.requested_base_type = requested_base_type;
                        this.rank = rank;
                        this.initializers = initializers;
                        this.loc = loc;

                        if (rank != null)
                                num_arguments = rank.Dimension;
                }

                //
                // For compiler generated single dimensional arrays only
                //
                public ArrayCreation (FullNamedExpression requested_base_type, ArrayInitializer initializers, Location loc)
                        : this (requested_base_type, ComposedTypeSpecifier.SingleDimension, initializers, loc)
                {
                }

                //
                // For expressions like int[] foo = { 1, 2, 3 };
                //
                public ArrayCreation (FullNamedExpression requested_base_type, ArrayInitializer initializers)
                        : this (requested_base_type, null, initializers, initializers.Location)
                {
                }

                public ComposedTypeSpecifier Rank {
                        get {
                                return this.rank;
                        }
                }
                
                public FullNamedExpression TypeExpression {
                        get {
                                return this.requested_base_type;
                        }
                }
                
                public ArrayInitializer Initializers {
                        get {
                                return this.initializers;
                        }
                }

                bool CheckIndices (ResolveContext ec, ArrayInitializer probe, int idx, bool specified_dims, int child_bounds)
                {
                        if (initializers != null && bounds == null) {
                                //
                                // We use this to store all the data values in the order in which we
                                // will need to store them in the byte blob later
                                //
                                array_data = new List<Expression> (probe.Count);
                                bounds = new Dictionary<int, int> ();
                        }

                        if (specified_dims) { 
                                Expression a = arguments [idx];
                                a = a.Resolve (ec);
                                if (a == null)
                                        return false;

                                a = ConvertExpressionToArrayIndex (ec, a);
                                if (a == null)
                                        return false;

                                arguments[idx] = a;

                                if (initializers != null) {
                                        Constant c = a as Constant;
                                        if (c == null && a is ArrayIndexCast)
                                                c = ((ArrayIndexCast) a).Child as Constant;

                                        if (c == null) {
                                                ec.Report.Error (150, a.Location, "A constant value is expected");
                                                return false;
                                        }

                                        int value;
                                        try {
                                                value = System.Convert.ToInt32 (c.GetValue ());
                                        } catch {
                                                ec.Report.Error (150, a.Location, "A constant value is expected");
                                                return false;
                                        }

                                        // TODO: probe.Count does not fit ulong in
                                        if (value != probe.Count) {
                                                ec.Report.Error (847, loc, "An array initializer of length `{0}' was expected", value.ToString ());
                                                return false;
                                        }

                                        bounds[idx] = value;
                                }
                        }

                        if (initializers == null)
                                return true;

                        for (int i = 0; i < probe.Count; ++i) {
                                var o = probe [i];
                                if (o is ArrayInitializer) {
                                        var sub_probe = o as ArrayInitializer;
                                        if (idx + 1 >= dimensions){
                                                ec.Report.Error (623, loc, "Array initializers can only be used in a variable or field initializer. Try using a new expression instead");
                                                return false;
                                        }

                                        // When we don't have explicitly specified dimensions, record whatever dimension we first encounter at each level
                                        if (!bounds.ContainsKey(idx + 1))
                                                bounds[idx + 1] = sub_probe.Count;

                                        if (bounds[idx + 1] != sub_probe.Count) {
                                                ec.Report.Error(847, sub_probe.Location, "An array initializer of length `{0}' was expected", bounds[idx + 1].ToString());
                                                return false;
                                        }

                                        bool ret = CheckIndices (ec, sub_probe, idx + 1, specified_dims, child_bounds - 1);
                                        if (!ret)
                                                return false;
                                } else if (child_bounds > 1) {
                                        ec.Report.Error (846, o.Location, "A nested array initializer was expected");
                                } else {
                                        Expression element = ResolveArrayElement (ec, o);
                                        if (element == null)
                                                continue;
#if STATIC
                                        // Initializers with the default values can be ignored
                                        Constant c = element as Constant;
                                        if (c != null) {
                                                if (!c.IsDefaultInitializer (array_element_type)) {
                                                        ++const_initializers_count;
                                                }
                                        } else {
                                                only_constant_initializers = false;
                                        }
#endif                                  
                                        array_data.Add (element);
                                }
                        }

                        return true;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        foreach (var arg in arguments) {
                                if (arg.ContainsEmitWithAwait ())
                                        return true;
                        }

                        return InitializersContainAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args;

                        if (array_data == null) {
                                args = new Arguments (arguments.Count + 1);
                                args.Add (new Argument (new TypeOf (array_element_type, loc)));
                                foreach (Expression a in arguments)
                                        args.Add (new Argument (a.CreateExpressionTree (ec)));

                                return CreateExpressionFactoryCall (ec, "NewArrayBounds", args);
                        }

                        if (dimensions > 1) {
                                ec.Report.Error (838, loc, "An expression tree cannot contain a multidimensional array initializer");
                                return null;
                        }

                        args = new Arguments (array_data == null ? 1 : array_data.Count + 1);
                        args.Add (new Argument (new TypeOf (array_element_type, loc)));
                        if (array_data != null) {
                                for (int i = 0; i < array_data.Count; ++i) {
                                        Expression e = array_data [i];
                                        args.Add (new Argument (e.CreateExpressionTree (ec)));
                                }
                        }

                        return CreateExpressionFactoryCall (ec, "NewArrayInit", args);
                }               
                
                void UpdateIndices (ResolveContext rc)
                {
                        int i = 0;
                        for (var probe = initializers; probe != null;) {
                                Expression e = new IntConstant (rc.BuiltinTypes, probe.Count, Location.Null);
                                arguments.Add (e);
                                bounds[i++] = probe.Count;

                                if (probe.Count > 0 && probe [0] is ArrayInitializer) {
                                        probe = (ArrayInitializer) probe[0];
                                } else if (dimensions > i) {
                                        continue;
                                } else {
                                        return;
                                }
                        }
                }

                protected override void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
                {
                        ec.Report.Error (248, loc, "Cannot create an array with a negative size");
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        foreach (var arg in arguments)
                                arg.FlowAnalysis (fc);

                        if (array_data != null) {
                                foreach (var ad in array_data)
                                        ad.FlowAnalysis (fc);
                        }
                }

                bool InitializersContainAwait ()
                {
                        if (array_data == null)
                                return false;

                        foreach (var expr in array_data) {
                                if (expr.ContainsEmitWithAwait ())
                                        return true;
                        }

                        return false;
                }

                protected virtual Expression ResolveArrayElement (ResolveContext ec, Expression element)
                {
                        element = element.Resolve (ec);
                        if (element == null)
                                return null;

                        if (element is CompoundAssign.TargetExpression) {
                                if (first_emit != null)
                                        throw new InternalErrorException ("Can only handle one mutator at a time");
                                first_emit = element;
                                element = first_emit_temp = new LocalTemporary (element.Type);
                        }

                        return Convert.ImplicitConversionRequired (
                                ec, element, array_element_type, loc);
                }

                protected bool ResolveInitializers (ResolveContext ec)
                {
#if STATIC
                        only_constant_initializers = true;
#endif

                        if (arguments != null) {
                                bool res = true;
                                for (int i = 0; i < arguments.Count; ++i) {
                                        res &= CheckIndices (ec, initializers, i, true, dimensions);
                                        if (initializers != null)
                                                break;
                                }

                                return res;
                        }

                        arguments = new List<Expression> ();

                        if (!CheckIndices (ec, initializers, 0, false, dimensions))
                                return false;
                                
                        UpdateIndices (ec);
                                
                        return true;
                }

                //
                // Resolved the type of the array
                //
                bool ResolveArrayType (ResolveContext ec)
                {
                        //
                        // Lookup the type
                        //
                        FullNamedExpression array_type_expr;
                        if (num_arguments > 0) {
                                array_type_expr = new ComposedCast (requested_base_type, rank);
                        } else {
                                array_type_expr = requested_base_type;
                        }

                        type = array_type_expr.ResolveAsType (ec);
                        if (array_type_expr == null)
                                return false;

                        var ac = type as ArrayContainer;
                        if (ac == null) {
                                ec.Report.Error (622, loc, "Can only use array initializer expressions to assign to array types. Try using a new expression instead");
                                return false;
                        }

                        array_element_type = ac.Element;
                        dimensions = ac.Rank;

                        return true;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (type != null)
                                return this;

                        if (!ResolveArrayType (ec))
                                return null;

                        //
                        // validate the initializers and fill in any missing bits
                        //
                        if (!ResolveInitializers (ec))
                                return null;

                        eclass = ExprClass.Value;
                        return this;
                }

                byte [] MakeByteBlob ()
                {
                        int factor;
                        byte [] data;
                        byte [] element;
                        int count = array_data.Count;

                        TypeSpec element_type = array_element_type;
                        if (element_type.IsEnum)
                                element_type = EnumSpec.GetUnderlyingType (element_type);

                        factor = BuiltinTypeSpec.GetSize (element_type);
                        if (factor == 0)
                                throw new Exception ("unrecognized type in MakeByteBlob: " + element_type);

                        data = new byte [(count * factor + 3) & ~3];
                        int idx = 0;

                        for (int i = 0; i < count; ++i) {
                                var c = array_data[i] as Constant;
                                if (c == null) {
                                        idx += factor;
                                        continue;
                                }

                                object v = c.GetValue ();

                                switch (element_type.BuiltinType) {
                                case BuiltinTypeSpec.Type.Long:
                                        long lval = (long) v;

                                        for (int j = 0; j < factor; ++j) {
                                                data[idx + j] = (byte) (lval & 0xFF);
                                                lval = (lval >> 8);
                                        }
                                        break;
                                case BuiltinTypeSpec.Type.ULong:
                                        ulong ulval = (ulong) v;

                                        for (int j = 0; j < factor; ++j) {
                                                data[idx + j] = (byte) (ulval & 0xFF);
                                                ulval = (ulval >> 8);
                                        }
                                        break;
                                case BuiltinTypeSpec.Type.Float:
                                        var fval = SingleConverter.SingleToInt32Bits((float) v);

                                        data[idx] = (byte) (fval & 0xff);
                                        data[idx + 1] = (byte) ((fval >> 8) & 0xff);
                                        data[idx + 2] = (byte) ((fval >> 16) & 0xff);
                                        data[idx + 3] = (byte) (fval >> 24);
                                        break;
                                case BuiltinTypeSpec.Type.Double:
                                        element = BitConverter.GetBytes ((double) v);

                                        for (int j = 0; j < factor; ++j)
                                                data[idx + j] = element[j];

                                        // FIXME: Handle the ARM float format.
                                        if (!BitConverter.IsLittleEndian)
                                                System.Array.Reverse (data, idx, 8);
                                        break;
                                case BuiltinTypeSpec.Type.Char:
                                        int chval = (int) ((char) v);

                                        data[idx] = (byte) (chval & 0xff);
                                        data[idx + 1] = (byte) (chval >> 8);
                                        break;
                                case BuiltinTypeSpec.Type.Short:
                                        int sval = (int) ((short) v);

                                        data[idx] = (byte) (sval & 0xff);
                                        data[idx + 1] = (byte) (sval >> 8);
                                        break;
                                case BuiltinTypeSpec.Type.UShort:
                                        int usval = (int) ((ushort) v);

                                        data[idx] = (byte) (usval & 0xff);
                                        data[idx + 1] = (byte) (usval >> 8);
                                        break;
                                case BuiltinTypeSpec.Type.Int:
                                        int val = (int) v;

                                        data[idx] = (byte) (val & 0xff);
                                        data[idx + 1] = (byte) ((val >> 8) & 0xff);
                                        data[idx + 2] = (byte) ((val >> 16) & 0xff);
                                        data[idx + 3] = (byte) (val >> 24);
                                        break;
                                case BuiltinTypeSpec.Type.UInt:
                                        uint uval = (uint) v;

                                        data[idx] = (byte) (uval & 0xff);
                                        data[idx + 1] = (byte) ((uval >> 8) & 0xff);
                                        data[idx + 2] = (byte) ((uval >> 16) & 0xff);
                                        data[idx + 3] = (byte) (uval >> 24);
                                        break;
                                case BuiltinTypeSpec.Type.SByte:
                                        data[idx] = (byte) (sbyte) v;
                                        break;
                                case BuiltinTypeSpec.Type.Byte:
                                        data[idx] = (byte) v;
                                        break;
                                case BuiltinTypeSpec.Type.Bool:
                                        data[idx] = (byte) ((bool) v ? 1 : 0);
                                        break;
                                case BuiltinTypeSpec.Type.Decimal:
                                        int[] bits = Decimal.GetBits ((decimal) v);
                                        int p = idx;

                                        // FIXME: For some reason, this doesn't work on the MS runtime.
                                        int[] nbits = new int[4];
                                        nbits[0] = bits[3];
                                        nbits[1] = bits[2];
                                        nbits[2] = bits[0];
                                        nbits[3] = bits[1];

                                        for (int j = 0; j < 4; j++) {
                                                data[p++] = (byte) (nbits[j] & 0xff);
                                                data[p++] = (byte) ((nbits[j] >> 8) & 0xff);
                                                data[p++] = (byte) ((nbits[j] >> 16) & 0xff);
                                                data[p++] = (byte) (nbits[j] >> 24);
                                        }
                                        break;
                                default:
                                        throw new Exception ("Unrecognized type in MakeByteBlob: " + element_type);
                                }

                                idx += factor;
                        }

                        return data;
                }

#if NET_4_0 || MOBILE_DYNAMIC
                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
#if STATIC
                        return base.MakeExpression (ctx);
#else
                        var initializers = new SLE.Expression [array_data.Count];
                        for (var i = 0; i < initializers.Length; i++) {
                                if (array_data [i] == null)
                                        initializers [i] = SLE.Expression.Default (array_element_type.GetMetaInfo ());
                                else
                                        initializers [i] = array_data [i].MakeExpression (ctx);
                        }

                        return SLE.Expression.NewArrayInit (array_element_type.GetMetaInfo (), initializers);
#endif
                }
#endif
#if STATIC
                //
                // Emits the initializers for the array
                //
                void EmitStaticInitializers (EmitContext ec, FieldExpr stackArray)
                {
                        var m = ec.Module.PredefinedMembers.RuntimeHelpersInitializeArray.Resolve (loc);
                        if (m == null)
                                return;

                        //
                        // First, the static data
                        //
                        byte [] data = MakeByteBlob ();
                        var fb = ec.CurrentTypeDefinition.Module.MakeStaticData (data, loc);

                        if (stackArray == null) {
                                ec.Emit (OpCodes.Dup);
                        } else {
                                stackArray.Emit (ec);
                        }

                        ec.Emit (OpCodes.Ldtoken, fb);
                        ec.Emit (OpCodes.Call, m);
                }
#endif

                //
                // Emits pieces of the array that can not be computed at compile
                // time (variables and string locations).
                //
                // This always expect the top value on the stack to be the array
                //
                void EmitDynamicInitializers (EmitContext ec, bool emitConstants, StackFieldExpr stackArray)
                {
                        int dims = bounds.Count;
                        var current_pos = new int [dims];

                        for (int i = 0; i < array_data.Count; i++){

                                Expression e = array_data [i];
                                var c = e as Constant;

                                // Constant can be initialized via StaticInitializer
                                if (c == null || (c != null && emitConstants && !c.IsDefaultInitializer (array_element_type))) {

                                        var etype = e.Type;

                                        if (stackArray != null) {
                                                if (e.ContainsEmitWithAwait ()) {
                                                        e = e.EmitToField (ec);
                                                }

                                                stackArray.EmitLoad (ec);
                                        } else {
                                                ec.Emit (OpCodes.Dup);
                                        }

                                        for (int idx = 0; idx < dims; idx++) 
                                                ec.EmitInt (current_pos [idx]);

                                        //
                                        // If we are dealing with a struct, get the
                                        // address of it, so we can store it.
                                        //
                                        if (dims == 1 && etype.IsStruct && !BuiltinTypeSpec.IsPrimitiveType (etype))
                                                ec.Emit (OpCodes.Ldelema, etype);

                                        e.Emit (ec);

                                        ec.EmitArrayStore ((ArrayContainer) type);
                                }
                                
                                //
                                // Advance counter
                                //
                                for (int j = dims - 1; j >= 0; j--){
                                        current_pos [j]++;
                                        if (current_pos [j] < bounds [j])
                                                break;
                                        current_pos [j] = 0;
                                }
                        }

                        if (stackArray != null)
                                stackArray.PrepareCleanup (ec);
                }

                public override void Emit (EmitContext ec)
                {
                        var await_field = EmitToFieldSource (ec);
                        if (await_field != null)
                                await_field.Emit (ec);
                }

                protected sealed override FieldExpr EmitToFieldSource (EmitContext ec)
                {
                        if (first_emit != null) {
                                first_emit.Emit (ec);
                                first_emit_temp.Store (ec);
                        }

                        StackFieldExpr await_stack_field;
                        if (ec.HasSet (BuilderContext.Options.AsyncBody) && InitializersContainAwait ()) {
                                await_stack_field = ec.GetTemporaryField (type);
                                ec.EmitThis ();
                        } else {
                                await_stack_field = null;
                        }

                        EmitExpressionsList (ec, arguments);

                        ec.EmitArrayNew ((ArrayContainer) type);
                        
                        if (initializers == null)
                                return await_stack_field;

                        if (await_stack_field != null)
                                await_stack_field.EmitAssignFromStack (ec);

#if STATIC
                        //
                        // Emit static initializer for arrays which contain more than 2 items and
                        // the static initializer will initialize at least 25% of array values or there
                        // is more than 10 items to be initialized
                        //
                        // NOTE: const_initializers_count does not contain default constant values.
                        //
                        if (const_initializers_count > 2 && (array_data.Count > 10 || const_initializers_count * 4 > (array_data.Count)) &&
                                (BuiltinTypeSpec.IsPrimitiveType (array_element_type) || array_element_type.IsEnum)) {
                                EmitStaticInitializers (ec, await_stack_field);

                                if (!only_constant_initializers)
                                        EmitDynamicInitializers (ec, false, await_stack_field);
                        } else
#endif
                        {
                                EmitDynamicInitializers (ec, true, await_stack_field);
                        }

                        if (first_emit_temp != null)
                                first_emit_temp.Release (ec);

                        return await_stack_field;
                }

                public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType, TypeSpec parameterType)
                {
                        // no multi dimensional or jagged arrays
                        if (arguments.Count != 1 || array_element_type.IsArray) {
                                base.EncodeAttributeValue (rc, enc, targetType, parameterType);
                                return;
                        }

                        // No array covariance, except for array -> object
                        if (type != targetType) {
                                if (targetType.BuiltinType != BuiltinTypeSpec.Type.Object) {
                                        base.EncodeAttributeValue (rc, enc, targetType, parameterType);
                                        return;
                                }

                                if (enc.Encode (type) == AttributeEncoder.EncodedTypeProperties.DynamicType) {
                                        Attribute.Error_AttributeArgumentIsDynamic (rc, loc);
                                        return;
                                }
                        }

                        // Single dimensional array of 0 size
                        if (array_data == null) {
                                IntConstant ic = arguments[0] as IntConstant;
                                if (ic == null || !ic.IsDefaultValue) {
                                        base.EncodeAttributeValue (rc, enc, targetType, parameterType);
                                } else {
                                        enc.Encode (0);
                                }

                                return;
                        }

                        enc.Encode (array_data.Count);
                        foreach (var element in array_data) {
                                element.EncodeAttributeValue (rc, enc, array_element_type, parameterType);
                        }
                }
                
                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        ArrayCreation target = (ArrayCreation) t;

                        if (requested_base_type != null)
                                target.requested_base_type = (FullNamedExpression)requested_base_type.Clone (clonectx);

                        if (arguments != null){
                                target.arguments = new List<Expression> (arguments.Count);
                                foreach (Expression e in arguments)
                                        target.arguments.Add (e.Clone (clonectx));
                        }

                        if (initializers != null)
                                target.initializers = (ArrayInitializer) initializers.Clone (clonectx);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }
        
        //
        // Represents an implicitly typed array epxression
        //
        class ImplicitlyTypedArrayCreation : ArrayCreation
        {
                TypeInferenceContext best_type_inference;

                public ImplicitlyTypedArrayCreation (ComposedTypeSpecifier rank, ArrayInitializer initializers, Location loc)
                        : base (null, rank, initializers, loc)
                {                       
                }

                public ImplicitlyTypedArrayCreation (ArrayInitializer initializers, Location loc)
                        : base (null, initializers, loc)
                {
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (type != null)
                                return this;

                        dimensions = rank.Dimension;

                        best_type_inference = new TypeInferenceContext ();

                        if (!ResolveInitializers (ec))
                                return null;

                        best_type_inference.FixAllTypes (ec);
                        array_element_type = best_type_inference.InferredTypeArguments[0];
                        best_type_inference = null;

                        if (array_element_type == null ||
                                array_element_type == InternalType.NullLiteral || array_element_type == InternalType.MethodGroup || array_element_type == InternalType.AnonymousMethod ||
                                arguments.Count != rank.Dimension) {
                                ec.Report.Error (826, loc,
                                        "The type of an implicitly typed array cannot be inferred from the initializer. Try specifying array type explicitly");
                                return null;
                        }

                        //
                        // At this point we found common base type for all initializer elements
                        // but we have to be sure that all static initializer elements are of
                        // same type
                        //
                        UnifyInitializerElement (ec);

                        type = ArrayContainer.MakeType (ec.Module, array_element_type, dimensions);
                        eclass = ExprClass.Value;
                        return this;
                }

                //
                // Converts static initializer only
                //
                void UnifyInitializerElement (ResolveContext ec)
                {
                        for (int i = 0; i < array_data.Count; ++i) {
                                Expression e = array_data[i];
                                if (e != null)
                                        array_data [i] = Convert.ImplicitConversion (ec, e, array_element_type, Location.Null);
                        }
                }

                protected override Expression ResolveArrayElement (ResolveContext ec, Expression element)
                {
                        element = element.Resolve (ec);
                        if (element != null)
                                best_type_inference.AddCommonTypeBound (element.Type);

                        return element;
                }
        }       
        
        sealed class CompilerGeneratedThis : This
        {
                public CompilerGeneratedThis (TypeSpec type, Location loc)
                        : base (loc)
                {
                        this.type = type;
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        eclass = ExprClass.Variable;

                        var block = rc.CurrentBlock;
                        if (block != null) {
                                var top = block.ParametersBlock.TopBlock;
                                if (top.ThisVariable != null)
                                        variable_info = top.ThisVariable.VariableInfo;

                        }

                        return this;
                }

                public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
                {
                        return DoResolve (rc);
                }

                public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
                {
                        return null;
                }
        }
        
        /// <summary>
        ///   Represents the `this' construct
        /// </summary>

        public class This : VariableReference
        {
                sealed class ThisVariable : ILocalVariable
                {
                        public static readonly ILocalVariable Instance = new ThisVariable ();

                        public void Emit (EmitContext ec)
                        {
                                ec.EmitThis ();
                        }

                        public void EmitAssign (EmitContext ec)
                        {
                                throw new InvalidOperationException ();
                        }

                        public void EmitAddressOf (EmitContext ec)
                        {
                                ec.EmitThis ();
                        }
                }

                protected VariableInfo variable_info;

                public This (Location loc)
                {
                        this.loc = loc;
                }

                #region Properties

                public override string Name {
                        get { return "this"; }
                }

                public override bool IsLockedByStatement {
                        get {
                                return false;
                        }
                        set {
                        }
                }

                public override bool IsRef {
                        get { return type.IsStruct; }
                }

                public override bool IsSideEffectFree {
                        get {
                                return true;
                        }
                }

                protected override ILocalVariable Variable {
                        get { return ThisVariable.Instance; }
                }

                public override VariableInfo VariableInfo {
                        get { return variable_info; }
                }

                public override bool IsFixed {
                        get { return false; }
                }

                #endregion

                void CheckStructThisDefiniteAssignment (FlowAnalysisContext fc)
                {
                        //
                        // It's null for all cases when we don't need to check `this'
                        // definitive assignment
                        //
                        if (variable_info == null)
                                return;

                        if (fc.IsDefinitelyAssigned (variable_info))
                                return;

                        fc.Report.Error (188, loc, "The `this' object cannot be used before all of its fields are assigned to");
                }

                protected virtual void Error_ThisNotAvailable (ResolveContext ec)
                {
                        if (ec.IsStatic && !ec.HasSet (ResolveContext.Options.ConstantScope)) {
                                ec.Report.Error (26, loc, "Keyword `this' is not valid in a static property, static method, or static field initializer");
                        } else if (ec.CurrentAnonymousMethod != null) {
                                ec.Report.Error (1673, loc,
                                        "Anonymous methods inside structs cannot access instance members of `this'. " +
                                        "Consider copying `this' to a local variable outside the anonymous method and using the local instead");
                        } else {
                                ec.Report.Error (27, loc, "Keyword `this' is not available in the current context");
                        }
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        CheckStructThisDefiniteAssignment (fc);
                }

                public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
                {
                        if (ae == null)
                                return null;

                        AnonymousMethodStorey storey = ae.Storey;
                        return storey != null ? storey.HoistedThis : null;
                }

                public static bool IsThisAvailable (ResolveContext ec, bool ignoreAnonymous)
                {
                        if (ec.IsStatic || ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.BaseInitializer | ResolveContext.Options.ConstantScope))
                                return false;

                        if (ignoreAnonymous || ec.CurrentAnonymousMethod == null)
                                return true;

                        if (ec.CurrentType.IsStruct && !(ec.CurrentAnonymousMethod is StateMachineInitializer))
                                return false;

                        return true;
                }

                public virtual void ResolveBase (ResolveContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = ec.CurrentType;

                        if (!IsThisAvailable (ec, false)) {
                                Error_ThisNotAvailable (ec);
                                return;
                        }

                        var block = ec.CurrentBlock;
                        if (block != null) {
                                var top = block.ParametersBlock.TopBlock;
                                if (top.ThisVariable != null)
                                        variable_info = top.ThisVariable.VariableInfo;

                                AnonymousExpression am = ec.CurrentAnonymousMethod;
                                if (am != null && ec.IsVariableCapturingRequired && !block.Explicit.HasCapturedThis) {
                                        //
                                        // Hoisted this is almost like hoisted variable but not exactly. When
                                        // there is no variable hoisted we can simply emit an instance method
                                        // without lifting this into a storey. Unfotunatelly this complicates
                                        // things in other cases because we don't know where this will be hoisted
                                        // until top-level block is fully resolved
                                        //
                                        top.AddThisReferenceFromChildrenBlock (block.Explicit);
                                        am.SetHasThisAccess ();
                                }
                        }
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        ResolveBase (ec);
                        return this;
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
                {
                        if (eclass == ExprClass.Unresolved)
                                ResolveBase (ec);

                        if (type.IsClass){
                                if (right_side == EmptyExpression.UnaryAddress)
                                        ec.Report.Error (459, loc, "Cannot take the address of `this' because it is read-only");
                                else if (right_side == EmptyExpression.OutAccess)
                                        ec.Report.Error (1605, loc, "Cannot pass `this' as a ref or out argument because it is read-only");
                                else
                                        ec.Report.Error (1604, loc, "Cannot assign to `this' because it is read-only");
                        }

                        return this;
                }

                public override int GetHashCode()
                {
                        throw new NotImplementedException ();
                }

                public override bool Equals (object obj)
                {
                        This t = obj as This;
                        if (t == null)
                                return false;

                        return true;
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        // Nothing
                }

                public override void SetHasAddressTaken ()
                {
                        // Nothing
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Represents the `__arglist' construct
        /// </summary>
        public class ArglistAccess : Expression
        {
                public ArglistAccess (Location loc)
                {
                        this.loc = loc;
                }

                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                        // nothing.
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = ec.Module.PredefinedTypes.RuntimeArgumentHandle.Resolve ();

                        if (ec.HasSet (ResolveContext.Options.FieldInitializerScope) || !ec.CurrentBlock.ParametersBlock.Parameters.HasArglist) {
                                ec.Report.Error (190, loc,
                                        "The __arglist construct is valid only within a variable argument method");
                        }

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ec.Emit (OpCodes.Arglist);
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Represents the `__arglist (....)' construct
        /// </summary>
        public class Arglist : Expression
        {
                Arguments arguments;

                public Arglist (Location loc)
                        : this (null, loc)
                {
                }

                public Arglist (Arguments args, Location l)
                {
                        arguments = args;
                        loc = l;
                }

                public Arguments Arguments {
                        get {
                                return arguments;
                        }
                }

                public MetaType[] ArgumentTypes {
                    get {
                                if (arguments == null)
                                        return MetaType.EmptyTypes;

                                var retval = new MetaType[arguments.Count];
                                for (int i = 0; i < retval.Length; i++)
                                        retval[i] = arguments[i].Expr.Type.GetMetaInfo ();

                        return retval;
                    }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        throw new NotImplementedException ();
                }
                
                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        ec.Report.Error (1952, loc, "An expression tree cannot contain a method with variable arguments");
                        return null;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = InternalType.Arglist;
                        if (arguments != null) {
                                bool dynamic;   // Can be ignored as there is always only 1 overload
                                arguments.Resolve (ec, out dynamic);
                        }

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        if (arguments != null)
                                arguments.Emit (ec);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        Arglist target = (Arglist) t;

                        if (arguments != null)
                                target.arguments = arguments.Clone (clonectx);
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class RefValueExpr : ShimExpression, IAssignMethod, IMemoryLocation
        {
                FullNamedExpression texpr;

                public RefValueExpr (Expression expr, FullNamedExpression texpr, Location loc)
                        : base (expr)
                {
                        this.texpr = texpr;
                        this.loc = loc;
                }

                public FullNamedExpression TypeExpression {
                        get {
                                return texpr;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        expr.Emit (ec);
                        ec.Emit (OpCodes.Refanyval, type);
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        expr = expr.Resolve (rc);
                        type = texpr.ResolveAsType (rc);
                        if (expr == null || type == null)
                                return null;

                        expr = Convert.ImplicitConversionRequired (rc, expr, rc.Module.PredefinedTypes.TypedReference.Resolve (), loc);
                        eclass = ExprClass.Variable;
                        return this;
                }

                public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
                {
                        return DoResolve (rc);
                }

                public override void Emit (EmitContext ec)
                {
                        expr.Emit (ec);
                        ec.Emit (OpCodes.Refanyval, type);
                        ec.EmitLoadFromPtr (type);
                }

                public void Emit (EmitContext ec, bool leave_copy)
                {
                        throw new NotImplementedException ();
                }

                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
                {
                        expr.Emit (ec);
                        ec.Emit (OpCodes.Refanyval, type);
                        source.Emit (ec);

                        LocalTemporary temporary = null;
                        if (leave_copy) {
                                ec.Emit (OpCodes.Dup);
                                temporary = new LocalTemporary (source.Type);
                                temporary.Store (ec);
                        }

                        ec.EmitStoreFromPtr (type);

                        if (temporary != null) {
                                temporary.Emit (ec);
                                temporary.Release (ec);
                        }
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class RefTypeExpr : ShimExpression
        {
                public RefTypeExpr (Expression expr, Location loc)
                        : base (expr)
                {
                        this.loc = loc;
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        expr = expr.Resolve (rc);
                        if (expr == null)
                                return null;

                        expr = Convert.ImplicitConversionRequired (rc, expr, rc.Module.PredefinedTypes.TypedReference.Resolve (), loc);
                        if (expr == null)
                                return null;

                        type = rc.BuiltinTypes.Type;
                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        expr.Emit (ec);
                        ec.Emit (OpCodes.Refanytype);
                        var m = ec.Module.PredefinedMembers.TypeGetTypeFromHandle.Resolve (loc);
                        if (m != null)
                                ec.Emit (OpCodes.Call, m);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class MakeRefExpr : ShimExpression
        {
                public MakeRefExpr (Expression expr, Location loc)
                        : base (expr)
                {
                        this.loc = loc;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        throw new NotImplementedException ();
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        expr = expr.ResolveLValue (rc, EmptyExpression.LValueMemberAccess);
                        type = rc.Module.PredefinedTypes.TypedReference.Resolve ();
                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ((IMemoryLocation) expr).AddressOf (ec, AddressOp.Load);
                        ec.Emit (OpCodes.Mkrefany, expr.Type);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Implements the typeof operator
        /// </summary>
        public class TypeOf : Expression {
                FullNamedExpression QueriedType;
                TypeSpec typearg;

                public TypeOf (FullNamedExpression queried_type, Location l)
                {
                        QueriedType = queried_type;
                        loc = l;
                }

                //
                // Use this constructor for any compiler generated typeof expression
                //
                public TypeOf (TypeSpec type, Location loc)
                {
                        this.typearg = type;
                        this.loc = loc;
                }

                #region Properties

                public override bool IsSideEffectFree {
                        get {
                                return true;
                        }
                }

                public TypeSpec TypeArgument {
                        get {
                                return typearg;
                        }
                }

                public FullNamedExpression TypeExpression {
                        get {
                                return QueriedType;
                        }
                }

                #endregion


                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        TypeOf target = (TypeOf) t;
                        if (QueriedType != null)
                                target.QueriedType = (FullNamedExpression) QueriedType.Clone (clonectx);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (2);
                        args.Add (new Argument (this));
                        args.Add (new Argument (new TypeOf (new TypeExpression (type, loc), loc)));
                        return CreateExpressionFactoryCall (ec, "Constant", args);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (eclass != ExprClass.Unresolved)
                                return this;

                        if (typearg == null) {
                                //
                                // Pointer types are allowed without explicit unsafe, they are just tokens
                                //
                                using (ec.Set (ResolveContext.Options.UnsafeScope)) {
                                        typearg = QueriedType.ResolveAsType (ec, true);
                                }

                                if (typearg == null)
                                        return null;

                                if (typearg.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                        ec.Report.Error (1962, QueriedType.Location,
                                                "The typeof operator cannot be used on the dynamic type");
                                }
                        }

                        type = ec.BuiltinTypes.Type;

                        // Even though what is returned is a type object, it's treated as a value by the compiler.
                        // In particular, 'typeof (Foo).X' is something totally different from 'Foo.X'.
                        eclass = ExprClass.Value;
                        return this;
                }

                static bool ContainsDynamicType (TypeSpec type)
                {
                        if (type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
                                return true;

                        var element_container = type as ElementTypeSpec;
                        if (element_container != null)
                                return ContainsDynamicType (element_container.Element);

                        foreach (var t in type.TypeArguments) {
                                if (ContainsDynamicType (t)) {
                                        return true;
                                }
                        }

                        return false;
                }

                public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType, TypeSpec parameterType)
                {
                        // Target type is not System.Type therefore must be object
                        // and we need to use different encoding sequence
                        if (targetType != type)
                                enc.Encode (type);

                        if (typearg is InflatedTypeSpec) {
                                var gt = typearg;
                                do {
                                        if (InflatedTypeSpec.ContainsTypeParameter (gt)) {
                                                rc.Module.Compiler.Report.Error (416, loc, "`{0}': an attribute argument cannot use type parameters",
                                                        typearg.GetSignatureForError ());
                                                return;
                                        }

                                        gt = gt.DeclaringType;
                                } while (gt != null);
                        }

                        if (ContainsDynamicType (typearg)) {
                                Attribute.Error_AttributeArgumentIsDynamic (rc, loc);
                                return;
                        }

                        enc.EncodeTypeName (typearg);
                }

                public override void Emit (EmitContext ec)
                {
                        ec.Emit (OpCodes.Ldtoken, typearg);
                        var m = ec.Module.PredefinedMembers.TypeGetTypeFromHandle.Resolve (loc);
                        if (m != null)
                                ec.Emit (OpCodes.Call, m);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        sealed class TypeOfMethod : TypeOfMember<MethodSpec>
        {
                public TypeOfMethod (MethodSpec method, Location loc)
                        : base (method, loc)
                {
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (member.IsConstructor) {
                                type = ec.Module.PredefinedTypes.ConstructorInfo.Resolve ();
                        } else {
                                type = ec.Module.PredefinedTypes.MethodInfo.Resolve ();
                        }

                        if (type == null)
                                return null;

                        return base.DoResolve (ec);
                }

                public override void Emit (EmitContext ec)
                {
                        ec.Emit (OpCodes.Ldtoken, member);

                        base.Emit (ec);
                        ec.Emit (OpCodes.Castclass, type);
                }

                protected override PredefinedMember<MethodSpec> GetTypeFromHandle (EmitContext ec)
                {
                        return ec.Module.PredefinedMembers.MethodInfoGetMethodFromHandle;
                }

                protected override PredefinedMember<MethodSpec> GetTypeFromHandleGeneric (EmitContext ec)
                {
                        return ec.Module.PredefinedMembers.MethodInfoGetMethodFromHandle2;
                }
        }

        abstract class TypeOfMember<T> : Expression where T : MemberSpec
        {
                protected readonly T member;

                protected TypeOfMember (T member, Location loc)
                {
                        this.member = member;
                        this.loc = loc;
                }

                public override bool IsSideEffectFree {
                        get {
                                return true;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (2);
                        args.Add (new Argument (this));
                        args.Add (new Argument (new TypeOf (type, loc)));
                        return CreateExpressionFactoryCall (ec, "Constant", args);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        bool is_generic = member.DeclaringType.IsGenericOrParentIsGeneric;
                        PredefinedMember<MethodSpec> p;
                        if (is_generic) {
                                p = GetTypeFromHandleGeneric (ec);
                                ec.Emit (OpCodes.Ldtoken, member.DeclaringType);
                        } else {
                                p = GetTypeFromHandle (ec);
                        }

                        var mi = p.Resolve (loc);
                        if (mi != null)
                                ec.Emit (OpCodes.Call, mi);
                }

                protected abstract PredefinedMember<MethodSpec> GetTypeFromHandle (EmitContext ec);
                protected abstract PredefinedMember<MethodSpec> GetTypeFromHandleGeneric (EmitContext ec);
        }

        sealed class TypeOfField : TypeOfMember<FieldSpec>
        {
                public TypeOfField (FieldSpec field, Location loc)
                        : base (field, loc)
                {
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        type = ec.Module.PredefinedTypes.FieldInfo.Resolve ();
                        if (type == null)
                                return null;

                        return base.DoResolve (ec);
                }

                public override void Emit (EmitContext ec)
                {
                        ec.Emit (OpCodes.Ldtoken, member);
                        base.Emit (ec);
                }

                protected override PredefinedMember<MethodSpec> GetTypeFromHandle (EmitContext ec)
                {
                        return ec.Module.PredefinedMembers.FieldInfoGetFieldFromHandle;
                }

                protected override PredefinedMember<MethodSpec> GetTypeFromHandleGeneric (EmitContext ec)
                {
                        return ec.Module.PredefinedMembers.FieldInfoGetFieldFromHandle2;
                }
        }

        /// <summary>
        ///   Implements the sizeof expression
        /// </summary>
        public class SizeOf : Expression {
                readonly Expression texpr;
                TypeSpec type_queried;
                
                public SizeOf (Expression queried_type, Location l)
                {
                        this.texpr = queried_type;
                        loc = l;
                }

                public override bool IsSideEffectFree {
                        get {
                                return true;
                        }
                }

                public Expression TypeExpression {
                        get {
                                return texpr;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Error_PointerInsideExpressionTree (ec);
                        return null;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        type_queried = texpr.ResolveAsType (ec);
                        if (type_queried == null)
                                return null;

                        if (type_queried.IsEnum)
                                type_queried = EnumSpec.GetUnderlyingType (type_queried);

                        int size_of = BuiltinTypeSpec.GetSize (type_queried);
                        if (size_of > 0) {
                                return new IntConstant (ec.BuiltinTypes, size_of, loc);
                        }

                        if (!TypeManager.VerifyUnmanaged (ec.Module, type_queried, loc)){
                                return null;
                        }

                        if (!ec.IsUnsafe) {
                                ec.Report.Error (233, loc,
                                        "`{0}' does not have a predefined size, therefore sizeof can only be used in an unsafe context (consider using System.Runtime.InteropServices.Marshal.SizeOf)",
                                        type_queried.GetSignatureForError ());
                        }
                        
                        type = ec.BuiltinTypes.Int;
                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ec.Emit (OpCodes.Sizeof, type_queried);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Implements the qualified-alias-member (::) expression.
        /// </summary>
        public class QualifiedAliasMember : MemberAccess
        {
                readonly string alias;
                public static readonly string GlobalAlias = "global";

                public QualifiedAliasMember (string alias, string identifier, Location l)
                        : base (null, identifier, l)
                {
                        this.alias = alias;
                }

                public QualifiedAliasMember (string alias, string identifier, TypeArguments targs, Location l)
                        : base (null, identifier, targs, l)
                {
                        this.alias = alias;
                }

                public QualifiedAliasMember (string alias, string identifier, int arity, Location l)
                        : base (null, identifier, arity, l)
                {
                        this.alias = alias;
                }

                public string Alias {
                        get {
                                return alias;
                        }
                }

                public FullNamedExpression CreateExpressionFromAlias (IMemberContext mc)
                {
                        if (alias == GlobalAlias)
                                return new NamespaceExpression (mc.Module.GlobalRootNamespace, loc);

                        int errors = mc.Module.Compiler.Report.Errors;
                        var expr = mc.LookupNamespaceAlias (alias);
                        if (expr == null) {
                                if (errors == mc.Module.Compiler.Report.Errors)
                                        mc.Module.Compiler.Report.Error (432, loc, "Alias `{0}' not found", alias);

                                return null;
                        }

                        return expr;
                }

                public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments)
                {
                        expr = CreateExpressionFromAlias (mc);
                        if (expr == null)
                                return null;

                        return base.ResolveAsTypeOrNamespace (mc, allowUnboundTypeArguments);
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        return ResolveAsTypeOrNamespace (rc, false);
                }

                public override string GetSignatureForError ()
                {
                        string name = Name;
                        if (targs != null) {
                                name = Name + "<" + targs.GetSignatureForError () + ">";
                        }

                        return alias + "::" + name;
                }

                public override bool HasConditionalAccess ()
                {
                        return false;
                }

                public override Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restrictions)
                {
                        if ((restrictions & MemberLookupRestrictions.InvocableOnly) != 0) {
                                rc.Module.Compiler.Report.Error (687, loc,
                                        "The namespace alias qualifier `::' cannot be used to invoke a method. Consider using `.' instead",
                                        GetSignatureForError ());

                                return null;
                        }

                        return DoResolve (rc);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        // Nothing 
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Implements the member access expression
        /// </summary>
        public class MemberAccess : ATypeNameExpression
        {
                protected Expression expr;

                public MemberAccess (Expression expr, string id)
                        : base (id, expr.Location)
                {
                        this.expr = expr;
                }

                public MemberAccess (Expression expr, string identifier, Location loc)
                        : base (identifier, loc)
                {
                        this.expr = expr;
                }

                public MemberAccess (Expression expr, string identifier, TypeArguments args, Location loc)
                        : base (identifier, args, loc)
                {
                        this.expr = expr;
                }

                public MemberAccess (Expression expr, string identifier, int arity, Location loc)
                        : base (identifier, arity, loc)
                {
                        this.expr = expr;
                }

                public Expression LeftExpression {
                        get {
                                return expr;
                        }
                }

                public override Location StartLocation {
                        get {
                                return expr == null ? loc : expr.StartLocation;
                        }
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        var e = LookupNameExpression (rc, MemberLookupRestrictions.ReadAccess);
                        if (e != null)
                                e = e.Resolve (rc, ResolveFlags.VariableOrValue | ResolveFlags.Type | ResolveFlags.MethodGroup);

                        return e;
                }

                public override Expression DoResolveLValue (ResolveContext rc, Expression rhs)
                {
                        var e = LookupNameExpression (rc, MemberLookupRestrictions.None);

                        if (e is TypeExpr) {
                                e.Error_UnexpectedKind (rc, ResolveFlags.VariableOrValue, loc);
                                return null;
                        }

                        if (e != null)
                                e = e.ResolveLValue (rc, rhs);

                        return e;
                }

                protected virtual void Error_OperatorCannotBeApplied (ResolveContext rc, TypeSpec type)
                {
                        if (type == InternalType.NullLiteral && rc.IsRuntimeBinder)
                                rc.Report.Error (Report.RuntimeErrorId, loc, "Cannot perform member binding on `null' value");
                        else
                                expr.Error_OperatorCannotBeApplied (rc, loc, ".", type);
                }

                public override bool HasConditionalAccess ()
                {
                        return LeftExpression.HasConditionalAccess ();
                }

                public static bool IsValidDotExpression (TypeSpec type)
                {
                        const MemberKind dot_kinds = MemberKind.Class | MemberKind.Struct | MemberKind.Delegate | MemberKind.Enum |
                                MemberKind.Interface | MemberKind.TypeParameter | MemberKind.ArrayType;

                        return (type.Kind & dot_kinds) != 0 || type.BuiltinType == BuiltinTypeSpec.Type.Dynamic;
                }

                public override Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restrictions)
                {
                        var sn = expr as SimpleName;
                        const ResolveFlags flags = ResolveFlags.VariableOrValue | ResolveFlags.Type;

                        if (sn != null) {
                                expr = sn.LookupNameExpression (rc, MemberLookupRestrictions.ReadAccess | MemberLookupRestrictions.ExactArity);

                                //
                                // Resolve expression which does have type set as we need expression type
                                // with disable flow analysis as we don't know whether left side expression
                                // is used as variable or type
                                //
                                if (expr is VariableReference || expr is ConstantExpr || expr is Linq.TransparentMemberAccess || expr is EventExpr) {
                                        expr = expr.Resolve (rc);
                                } else if (expr is TypeParameterExpr) {
                                        expr.Error_UnexpectedKind (rc, flags, sn.Location);
                                        expr = null;
                                }
                        } else {
                                bool resolved = false;
                                if (!rc.HasSet (ResolveContext.Options.ConditionalAccessReceiver)) {
                                        if (expr.HasConditionalAccess ()) {
                                                resolved = true;
                                                using (rc.Set (ResolveContext.Options.ConditionalAccessReceiver)) {
                                                        expr = expr.Resolve (rc, flags);
                                                }
                                        }
                                }

                                if (!resolved)
                                        expr = expr.Resolve (rc, flags);
                        }

                        if (expr == null)
                                return null;

                        var ns = expr as NamespaceExpression;
                        if (ns != null) {
                                var retval = ns.LookupTypeOrNamespace (rc, Name, Arity, LookupMode.Normal, loc);

                                if (retval == null) {
                                        ns.Error_NamespaceDoesNotExist (rc, Name, Arity, loc);
                                        return null;
                                }

                                if (Arity > 0) {
                                        if (HasTypeArguments)
                                                return new GenericTypeExpr (retval.Type, targs, loc);

                                        targs.Resolve (rc, false);
                                }

                                return retval;
                        }

                        MemberExpr me;
                        TypeSpec expr_type = expr.Type;
                        if (expr_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                me = expr as MemberExpr;
                                if (me != null)
                                        me.ResolveInstanceExpression (rc, null);

                                Arguments args = new Arguments (1);
                                args.Add (new Argument (expr));
                                return new DynamicMemberBinder (Name, args, loc);
                        }

                        var cma = this as ConditionalMemberAccess;
                        if (cma != null) {
                                if (!IsNullPropagatingValid (expr.Type)) {
                                        expr.Error_OperatorCannotBeApplied (rc, loc, "?", expr.Type);
                                        return null;
                                }

                                if (expr_type.IsNullableType) {
                                        expr = Nullable.Unwrap.Create (expr.Resolve (rc), true);
                                        expr_type = expr.Type;
                                }
                        }

                        if (!IsValidDotExpression (expr_type)) {
                                Error_OperatorCannotBeApplied (rc, expr_type);
                                return null;
                        }

                        var lookup_arity = Arity;
                        bool errorMode = false;
                        Expression member_lookup;
                        while (true) {
                                member_lookup = MemberLookup (rc, errorMode, expr_type, Name, lookup_arity, restrictions, loc);
                                if (member_lookup == null) {
                                        //
                                        // Try to look for extension method when member lookup failed
                                        //
                                        if (MethodGroupExpr.IsExtensionMethodArgument (expr)) {
                                                var methods = rc.LookupExtensionMethod (Name, lookup_arity);
                                                if (methods != null) {
                                                        var emg = new ExtensionMethodGroupExpr (methods, expr, loc);
                                                        if (HasTypeArguments) {
                                                                if (!targs.Resolve (rc, false))
                                                                        return null;

                                                                emg.SetTypeArguments (rc, targs);
                                                        }

                                                        if (cma != null)
                                                                emg.ConditionalAccess = true;

                                                        // TODO: it should really skip the checks bellow
                                                        return emg.Resolve (rc);
                                                }
                                        }
                                }

                                if (errorMode) {
                                        if (member_lookup == null) {
                                                var dep = expr_type.GetMissingDependencies ();
                                                if (dep != null) {
                                                        ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
                                                } else if (expr is TypeExpr) {
                                                        base.Error_TypeDoesNotContainDefinition (rc, expr_type, Name);
                                                } else {
                                                        Error_TypeDoesNotContainDefinition (rc, expr_type, Name);
                                                }

                                                return null;
                                        }

                                        if (member_lookup is MethodGroupExpr || member_lookup is PropertyExpr) {
                                                // Leave it to overload resolution to report correct error
                                        } else if (!(member_lookup is TypeExpr)) {
                                                // TODO: rc.SymbolRelatedToPreviousError
                                                ErrorIsInaccesible (rc, member_lookup.GetSignatureForError (), loc);
                                        }
                                        break;
                                }

                                if (member_lookup != null)
                                        break;

                                lookup_arity = 0;
                                restrictions &= ~MemberLookupRestrictions.InvocableOnly;
                                errorMode = true;
                        }

                        TypeExpr texpr = member_lookup as TypeExpr;
                        if (texpr != null) {
                                if (!(expr is TypeExpr) && (sn == null || expr.ProbeIdenticalTypeName (rc, expr, sn) == expr)) {
                                        rc.Report.Error (572, loc, "`{0}': cannot reference a type through an expression. Consider using `{1}' instead",
                                                Name, texpr.GetSignatureForError ());
                                }

                                if (!texpr.Type.IsAccessible (rc)) {
                                        rc.Report.SymbolRelatedToPreviousError (member_lookup.Type);
                                        ErrorIsInaccesible (rc, member_lookup.Type.GetSignatureForError (), loc);
                                        return null;
                                }

                                if (HasTypeArguments) {
                                        return new GenericTypeExpr (member_lookup.Type, targs, loc);
                                }

                                return member_lookup;
                        }

                        me = member_lookup as MemberExpr;

                        if (sn != null && me.IsStatic && (expr = me.ProbeIdenticalTypeName (rc, expr, sn)) != expr) {
                                sn = null;
                        }

                        if (cma != null) {
                                me.ConditionalAccess = true;
                        }

                        me = me.ResolveMemberAccess (rc, expr, sn);

                        if (Arity > 0) {
                                if (!targs.Resolve (rc, false))
                                        return null;

                                me.SetTypeArguments (rc, targs);
                        }

                        return me;
                }

                public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext rc, bool allowUnboundTypeArguments)
                {
                        FullNamedExpression fexpr = expr as FullNamedExpression;
                        if (fexpr == null) {
                                expr.ResolveAsType (rc);
                                return null;
                        }

                        FullNamedExpression expr_resolved = fexpr.ResolveAsTypeOrNamespace (rc, allowUnboundTypeArguments);

                        if (expr_resolved == null)
                                return null;

                        var ns = expr_resolved as NamespaceExpression;
                        if (ns != null) {
                                FullNamedExpression retval = ns.LookupTypeOrNamespace (rc, Name, Arity, LookupMode.Normal, loc);

                                if (retval == null) {
                                        ns.Error_NamespaceDoesNotExist (rc, Name, Arity, loc);
                                } else if (Arity > 0) {
                                        if (HasTypeArguments) {
                                                retval = new GenericTypeExpr (retval.Type, targs, loc);
                                                if (retval.ResolveAsType (rc) == null)
                                                        return null;
                                        } else {
                                                targs.Resolve (rc, allowUnboundTypeArguments);

                                                retval = new GenericOpenTypeExpr (retval.Type, loc);
                                        }
                                }

                                return retval;
                        }

                        var tnew_expr = expr_resolved.ResolveAsType (rc);
                        if (tnew_expr == null)
                                return null;

                        TypeSpec expr_type = tnew_expr;
                        if (TypeManager.IsGenericParameter (expr_type)) {
                                rc.Module.Compiler.Report.Error (704, loc, "A nested type cannot be specified through a type parameter `{0}'",
                                        tnew_expr.GetSignatureForError ());
                                return null;
                        }

                        var qam = this as QualifiedAliasMember;
                        if (qam != null) {
                                rc.Module.Compiler.Report.Error (431, loc,
                                        "Alias `{0}' cannot be used with `::' since it denotes a type. Consider replacing `::' with `.'",
                                        qam.Alias);

                        }

                        TypeSpec nested = null;
                        while (expr_type != null) {
                                nested = MemberCache.FindNestedType (expr_type, Name, Arity);
                                if (nested == null) {
                                        if (expr_type == tnew_expr) {
                                                Error_IdentifierNotFound (rc, expr_type);
                                                return null;
                                        }

                                        expr_type = tnew_expr;
                                        nested = MemberCache.FindNestedType (expr_type, Name, Arity);
                                        ErrorIsInaccesible (rc, nested.GetSignatureForError (), loc);
                                        break;
                                }

                                if (nested.IsAccessible (rc))
                                        break;

                                //
                                // Keep looking after inaccessible candidate but only if
                                // we are not in same context as the definition itself
                                //
                                if (expr_type.MemberDefinition == rc.CurrentMemberDefinition)
                                        break;

                                expr_type = expr_type.BaseType;
                        }
                        
                        TypeExpr texpr;
                        if (Arity > 0) {
                                if (HasTypeArguments) {
                                        texpr = new GenericTypeExpr (nested, targs, loc);
                                } else {
                                        targs.Resolve (rc, allowUnboundTypeArguments && !(expr_resolved is GenericTypeExpr));

                                        texpr = new GenericOpenTypeExpr (nested, loc);
                                }
                        } else if (expr_resolved is GenericOpenTypeExpr) {
                                texpr = new GenericOpenTypeExpr (nested, loc);
                        } else {
                                texpr = new TypeExpression (nested, loc);
                        }

                        if (texpr.ResolveAsType (rc) == null)
                                return null;

                        return texpr;
                }

                public void Error_IdentifierNotFound (IMemberContext rc, TypeSpec expr_type)
                {
                        var nested = MemberCache.FindNestedType (expr_type, Name, -System.Math.Max (1, Arity));

                        if (nested != null) {
                                Error_TypeArgumentsCannotBeUsed (rc, nested, expr.Location);
                                return;
                        }

                        var any_other_member = MemberLookup (rc, false, expr_type, Name, 0, MemberLookupRestrictions.None, loc);
                        if (any_other_member != null) {
                                Error_UnexpectedKind (rc, any_other_member, "type", any_other_member.ExprClassName, loc);
                                return;
                        }

                        rc.Module.Compiler.Report.Error (426, loc, "The nested type `{0}' does not exist in the type `{1}'",
                                Name, expr_type.GetSignatureForError ());
                }

                protected override void Error_InvalidExpressionStatement (Report report, Location loc)
                {
                        base.Error_InvalidExpressionStatement (report, LeftExpression.Location);
                }

                public override void Error_TypeDoesNotContainDefinition (ResolveContext ec, TypeSpec type, string name)
                {
                        if (ec.Module.Compiler.Settings.Version > LanguageVersion.ISO_2 && !ec.IsRuntimeBinder && MethodGroupExpr.IsExtensionMethodArgument (expr)) {
                                ec.Report.SymbolRelatedToPreviousError (type);

                                var cand = ec.Module.GlobalRootNamespace.FindExtensionMethodNamespaces (ec, name, Arity);
                                string missing;
                                // a using directive or an assembly reference
                                if (cand != null) {
                                        missing = "`" + string.Join ("' or `", cand.ToArray ()) + "' using directive";
                                } else {
                                        missing = "an assembly reference";
                                }

                                ec.Report.Error (1061, loc,
                                        "Type `{0}' does not contain a definition for `{1}' and no extension method `{1}' of type `{0}' could be found. Are you missing {2}?",
                                        type.GetSignatureForError (), name, missing);
                                return;
                        }

                        base.Error_TypeDoesNotContainDefinition (ec, type, name);
                }

                public override string GetSignatureForError ()
                {
                        return expr.GetSignatureForError () + "." + base.GetSignatureForError ();
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        MemberAccess target = (MemberAccess) t;

                        target.expr = expr.Clone (clonectx);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class ConditionalMemberAccess : MemberAccess
        {
                public ConditionalMemberAccess (Expression expr, string identifier, TypeArguments args, Location loc)
                        : base (expr, identifier, args, loc)
                {
                }

                public override bool HasConditionalAccess ()
                {
                        return true;
                }
        }

        /// <summary>
        ///   Implements checked expressions
        /// </summary>
        public class CheckedExpr : Expression {

                public Expression Expr;

                public CheckedExpr (Expression e, Location l)
                {
                        Expr = e;
                        loc = l;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return Expr.ContainsEmitWithAwait ();
                }
                
                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        using (ec.With (ResolveContext.Options.AllCheckStateFlags, true))
                                return Expr.CreateExpressionTree (ec);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        using (ec.With (ResolveContext.Options.AllCheckStateFlags, true))
                                Expr = Expr.Resolve (ec);
                        
                        if (Expr == null)
                                return null;

                        if (Expr is Constant || Expr is MethodGroupExpr || Expr is AnonymousMethodExpression || Expr is DefaultValueExpression)
                                return Expr;
                        
                        eclass = Expr.eclass;
                        type = Expr.Type;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        using (ec.With (EmitContext.Options.CheckedScope, true))
                                Expr.Emit (ec);
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        using (ec.With (EmitContext.Options.CheckedScope, true))
                                Expr.EmitBranchable (ec, target, on_true);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        Expr.FlowAnalysis (fc);
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        using (ctx.With (BuilderContext.Options.CheckedScope, true)) {
                                return Expr.MakeExpression (ctx);
                        }
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        CheckedExpr target = (CheckedExpr) t;

                        target.Expr = Expr.Clone (clonectx);
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Implements the unchecked expression
        /// </summary>
        public class UnCheckedExpr : Expression {

                public Expression Expr;

                public UnCheckedExpr (Expression e, Location l)
                {
                        Expr = e;
                        loc = l;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return Expr.ContainsEmitWithAwait ();
                }
                
                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        using (ec.With (ResolveContext.Options.AllCheckStateFlags, false))
                                return Expr.CreateExpressionTree (ec);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        using (ec.With (ResolveContext.Options.AllCheckStateFlags, false))
                                Expr = Expr.Resolve (ec);

                        if (Expr == null)
                                return null;

                        if (Expr is Constant || Expr is MethodGroupExpr || Expr is AnonymousMethodExpression || Expr is DefaultValueExpression)
                                return Expr;
                        
                        eclass = Expr.eclass;
                        type = Expr.Type;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        using (ec.With (EmitContext.Options.CheckedScope, false))
                                Expr.Emit (ec);
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        using (ec.With (EmitContext.Options.CheckedScope, false))
                                Expr.EmitBranchable (ec, target, on_true);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        Expr.FlowAnalysis (fc);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        UnCheckedExpr target = (UnCheckedExpr) t;

                        target.Expr = Expr.Clone (clonectx);
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   An Element Access expression.
        ///
        ///   During semantic analysis these are transformed into 
        ///   IndexerAccess, ArrayAccess or a PointerArithmetic.
        /// </summary>
        public class ElementAccess : Expression
        {
                public Arguments Arguments;
                public Expression Expr;

                public ElementAccess (Expression e, Arguments args, Location loc)
                {
                        Expr = e;
                        this.loc = loc;
                        this.Arguments = args;
                }

                public bool ConditionalAccess { get; set; }

                public override Location StartLocation {
                        get {
                                return Expr.StartLocation;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return Expr.ContainsEmitWithAwait () || Arguments.ContainsEmitWithAwait ();
                }

                //
                // We perform some simple tests, and then to "split" the emit and store
                // code we create an instance of a different class, and return that.
                //
                Expression CreateAccessExpression (ResolveContext ec, bool conditionalAccessReceiver)
                {
                        Expr = Expr.Resolve (ec);
                        if (Expr == null)
                                return null;

                        type = Expr.Type;

                        if (ConditionalAccess && !IsNullPropagatingValid (type)) {
                                Error_OperatorCannotBeApplied (ec, loc, "?", type);
                                return null;
                        }

                        if (type.IsArray)
                                return new ArrayAccess (this, loc) {
                                        ConditionalAccess = ConditionalAccess,
                                        ConditionalAccessReceiver = conditionalAccessReceiver
                                };

                        if (type.IsPointer)
                                return Expr.MakePointerAccess (ec, type, Arguments);

                        FieldExpr fe = Expr as FieldExpr;
                        if (fe != null) {
                                var ff = fe.Spec as FixedFieldSpec;
                                if (ff != null) {
                                        return Expr.MakePointerAccess (ec, ff.ElementType, Arguments);
                                }
                        }

                        var indexers = MemberCache.FindMembers (type, MemberCache.IndexerNameAlias, false);
                        if (indexers != null || type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                var indexer = new IndexerExpr (indexers, type, this) {
                                        ConditionalAccess = ConditionalAccess
                                };

                                if (conditionalAccessReceiver)
                                        indexer.SetConditionalAccessReceiver ();

                                return indexer;
                        }

                        Error_CannotApplyIndexing (ec, type, loc);

                        return null;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = Arguments.CreateForExpressionTree (ec, Arguments,
                                Expr.CreateExpressionTree (ec));

                        return CreateExpressionFactoryCall (ec, "ArrayIndex", args);
                }

                public static void Error_CannotApplyIndexing (ResolveContext rc, TypeSpec type, Location loc)
                {
                        if (type != InternalType.ErrorType) {
                                rc.Report.Error (21, loc, "Cannot apply indexing with [] to an expression of type `{0}'",
                                        type.GetSignatureForError ());
                        }
                }

                public override bool HasConditionalAccess ()
                {
                        return ConditionalAccess || Expr.HasConditionalAccess ();
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        Expression expr;
                        if (!rc.HasSet (ResolveContext.Options.ConditionalAccessReceiver)) {
                                if (HasConditionalAccess ()) {
                                        using (rc.Set (ResolveContext.Options.ConditionalAccessReceiver)) {
                                                expr = CreateAccessExpression (rc, true);
                                                if (expr == null)
                                                        return null;

                                                return expr.Resolve (rc);
                                        }
                                }
                        }

                        expr = CreateAccessExpression (rc, false);
                        if (expr == null)
                                return null;

                        return expr.Resolve (rc);
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression rhs)
                {
                        var res = CreateAccessExpression (ec, false);
                        if (res == null)
                                return null;

                        return res.ResolveLValue (ec, rhs);
                }
                
                public override void Emit (EmitContext ec)
                {
                        throw new Exception ("Should never be reached");
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        Expr.FlowAnalysis (fc);

                        if (ConditionalAccess)
                                fc.BranchConditionalAccessDefiniteAssignment ();

                        Arguments.FlowAnalysis (fc);
                }

                public override string GetSignatureForError ()
                {
                        return Expr.GetSignatureForError ();
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        ElementAccess target = (ElementAccess) t;

                        target.Expr = Expr.Clone (clonectx);
                        if (Arguments != null)
                                target.Arguments = Arguments.Clone (clonectx);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   Implements array access 
        /// </summary>
        public class ArrayAccess : Expression, IDynamicAssign, IMemoryLocation {
                //
                // Points to our "data" repository
                //
                ElementAccess ea;

                LocalTemporary temp;
                bool prepared;
                bool? has_await_args;
                
                public ArrayAccess (ElementAccess ea_data, Location l)
                {
                        ea = ea_data;
                        loc = l;
                }

                public bool ConditionalAccess { get; set; }

                public bool ConditionalAccessReceiver { get; set; }

                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        var ac = (ArrayContainer) ea.Expr.Type;

                        if (!has_await_args.HasValue && ec.HasSet (BuilderContext.Options.AsyncBody) && ea.Arguments.ContainsEmitWithAwait ()) {
                                LoadInstanceAndArguments (ec, false, true);
                        }

                        LoadInstanceAndArguments (ec, false, false);

                        if (ac.Element.IsGenericParameter && mode == AddressOp.Load)
                                ec.Emit (OpCodes.Readonly);

                        ec.EmitArrayAddress (ac);
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        if (ConditionalAccess)
                                Error_NullShortCircuitInsideExpressionTree (ec);

                        return ea.CreateExpressionTree (ec);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return ea.ContainsEmitWithAwait ();
                }

                public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
                {
                        if (HasConditionalAccess ())
                                Error_NullPropagatingLValue (ec);

                        return DoResolve (ec);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        // dynamic is used per argument in ConvertExpressionToArrayIndex case
                        bool dynamic;
                        ea.Arguments.Resolve (ec, out dynamic);

                        var ac = ea.Expr.Type as ArrayContainer;
                        int rank = ea.Arguments.Count;
                        if (ac.Rank != rank) {
                                ec.Report.Error (22, ea.Location, "Wrong number of indexes `{0}' inside [], expected `{1}'",
                                          rank.ToString (), ac.Rank.ToString ());
                                return null;
                        }

                        type = ac.Element;
                        if (type.IsPointer && !ec.IsUnsafe) {
                                UnsafeError (ec, ea.Location);
                        }

                        if (ConditionalAccessReceiver)
                                type = LiftMemberType (ec, type);

                        foreach (Argument a in ea.Arguments) {
                                var na = a as NamedArgument;
                                if (na != null)
                                        ElementAccess.Error_NamedArgument (na, ec.Report);

                                a.Expr = ConvertExpressionToArrayIndex (ec, a.Expr);
                        }
                        
                        eclass = ExprClass.Variable;

                        return this;
                }

                protected override void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
                {
                        ec.Report.Warning (251, 2, loc, "Indexing an array with a negative index (array indices always start at zero)");
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        ea.FlowAnalysis (fc);
                }

                public override bool HasConditionalAccess ()
                {
                        return ConditionalAccess || ea.Expr.HasConditionalAccess ();
                }

                //
                // Load the array arguments into the stack.
                //
                void LoadInstanceAndArguments (EmitContext ec, bool duplicateArguments, bool prepareAwait)
                {
                        if (prepareAwait) {
                                ea.Expr = ea.Expr.EmitToField (ec);
                        } else {
                                var ie = new InstanceEmitter (ea.Expr, false);
                                ie.Emit (ec, ConditionalAccess);

                                if (duplicateArguments) {
                                        ec.Emit (OpCodes.Dup);

                                        var copy = new LocalTemporary (ea.Expr.Type);
                                        copy.Store (ec);
                                        ea.Expr = copy;
                                }
                        }

                        var dup_args = ea.Arguments.Emit (ec, duplicateArguments, prepareAwait);
                        if (dup_args != null)
                                ea.Arguments = dup_args;
                }

                public void Emit (EmitContext ec, bool leave_copy)
                {
                        if (prepared) {
                                ec.EmitLoadFromPtr (type);
                        } else {
                                if (!has_await_args.HasValue && ec.HasSet (BuilderContext.Options.AsyncBody) && ea.Arguments.ContainsEmitWithAwait ()) {
                                        LoadInstanceAndArguments (ec, false, true);
                                }

                                if (ConditionalAccessReceiver)
                                        ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());

                                var ac = (ArrayContainer) ea.Expr.Type;
                                LoadInstanceAndArguments (ec, false, false);
                                ec.EmitArrayLoad (ac);

                                if (ConditionalAccessReceiver)
                                        ec.CloseConditionalAccess (type.IsNullableType && type != ac.Element ? type : null);
                        }       

                        if (leave_copy) {
                                ec.Emit (OpCodes.Dup);
                                temp = new LocalTemporary (this.type);
                                temp.Store (ec);
                        }
                }
                
                public override void Emit (EmitContext ec)
                {
                        Emit (ec, false);
                }

                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
                {
                        var ac = (ArrayContainer) ea.Expr.Type;
                        TypeSpec t = source.Type;

                        has_await_args = ec.HasSet (BuilderContext.Options.AsyncBody) && (ea.Arguments.ContainsEmitWithAwait () || source.ContainsEmitWithAwait ());

                        //
                        // When we are dealing with a struct, get the address of it to avoid value copy
                        // Same cannot be done for reference type because array covariance and the
                        // check in ldelema requires to specify the type of array element stored at the index
                        //
                        if (t.IsStruct && ((isCompound && !(source is DynamicExpressionStatement)) || !BuiltinTypeSpec.IsPrimitiveType (t))) {
                                LoadInstanceAndArguments (ec, false, has_await_args.Value);

                                if (has_await_args.Value) {
                                        if (source.ContainsEmitWithAwait ()) {
                                                source = source.EmitToField (ec);
                                                isCompound = false;
                                                prepared = true;
                                        }

                                        LoadInstanceAndArguments (ec, isCompound, false);
                                } else {
                                        prepared = true;
                                }

                                ec.EmitArrayAddress (ac);

                                if (isCompound) {
                                        ec.Emit (OpCodes.Dup);
                                        prepared = true;
                                }
                        } else {
                                LoadInstanceAndArguments (ec, isCompound, has_await_args.Value);

                                if (has_await_args.Value) {
                                        if (source.ContainsEmitWithAwait ())
                                                source = source.EmitToField (ec);

                                        LoadInstanceAndArguments (ec, false, false);
                                }
                        }

                        source.Emit (ec);

                        if (isCompound) {
                                var lt = ea.Expr as LocalTemporary;
                                if (lt != null)
                                        lt.Release (ec);
                        }

                        if (leave_copy) {
                                ec.Emit (OpCodes.Dup);
                                temp = new LocalTemporary (this.type);
                                temp.Store (ec);
                        }

                        if (prepared) {
                                ec.EmitStoreFromPtr (t);
                        } else {
                                ec.EmitArrayStore (ac);
                        }
                        
                        if (temp != null) {
                                temp.Emit (ec);
                                temp.Release (ec);
                        }
                }

                public override Expression EmitToField (EmitContext ec)
                {
                        //
                        // Have to be specialized for arrays to get access to
                        // underlying element. Instead of another result copy we
                        // need direct access to element 
                        //
                        // Consider:
                        //
                        // CallRef (ref a[await Task.Factory.StartNew (() => 1)]);
                        //
                        ea.Expr = ea.Expr.EmitToField (ec);
                        ea.Arguments = ea.Arguments.Emit (ec, false, true);
                        return this;
                }

                public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
                {
                        return SLE.Expression.ArrayAccess (ea.Expr.MakeExpression (ctx), MakeExpressionArguments (ctx));
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
                        return SLE.Expression.ArrayIndex (ea.Expr.MakeExpression (ctx), MakeExpressionArguments (ctx));
                }

                SLE.Expression[] MakeExpressionArguments (BuilderContext ctx)
                {
                        using (ctx.With (BuilderContext.Options.CheckedScope, true)) {
                                return Arguments.MakeExpression (ea.Arguments, ctx);
                        }
                }
        }

        //
        // Indexer access expression
        //
        class IndexerExpr : PropertyOrIndexerExpr<IndexerSpec>, OverloadResolver.IBaseMembersProvider
        {
                IList<MemberSpec> indexers;
                Arguments arguments;
                TypeSpec queried_type;
                
                public IndexerExpr (IList<MemberSpec> indexers, TypeSpec queriedType, ElementAccess ea)
                        : this (indexers, queriedType, ea.Expr, ea.Arguments, ea.Location)
                {
                }

                public IndexerExpr (IList<MemberSpec> indexers, TypeSpec queriedType, Expression instance, Arguments args, Location loc)
                        : base (loc)
                {
                        this.indexers = indexers;
                        this.queried_type = queriedType;
                        this.InstanceExpression = instance;
                        this.arguments = args;
                }

                #region Properties

                protected override Arguments Arguments {
                        get {
                                return arguments;
                        }
                        set {
                                arguments = value;
                        }
                }

                protected override TypeSpec DeclaringType {
                        get {
                                return best_candidate.DeclaringType;
                        }
                }

                public override bool IsInstance {
                        get {
                                return true;
                        }
                }

                public override bool IsStatic {
                        get {
                                return false;
                        }
                }

                public override string KindName {
                        get { return "indexer"; }
                }

                public override string Name {
                        get {
                                return "this";
                        }
                }

                #endregion

                public override bool ContainsEmitWithAwait ()
                {
                        return base.ContainsEmitWithAwait () || arguments.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        if (ConditionalAccess) {
                                Error_NullShortCircuitInsideExpressionTree (ec);
                        }

                        Arguments args = Arguments.CreateForExpressionTree (ec, arguments,
                                InstanceExpression.CreateExpressionTree (ec),
                                new TypeOfMethod (Getter, loc));

                        return CreateExpressionFactoryCall (ec, "Call", args);
                }
        
                public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
                {
                        LocalTemporary await_source_arg = null;

                        if (isCompound) {
                                emitting_compound_assignment = true;
                                if (source is DynamicExpressionStatement) {
                                        Emit (ec, false);
                                } else {
                                        source.Emit (ec);
                                }
                                emitting_compound_assignment = false;

                                if (has_await_arguments) {
                                        await_source_arg = new LocalTemporary (Type);
                                        await_source_arg.Store (ec);

                                        arguments.Add (new Argument (await_source_arg));

                                        if (leave_copy) {
                                                temp = await_source_arg;
                                        }

                                        has_await_arguments = false;
                                } else {
                                        arguments = null;

                                        if (leave_copy) {
                                                ec.Emit (OpCodes.Dup);
                                                temp = new LocalTemporary (Type);
                                                temp.Store (ec);
                                        }
                                }
                        } else {
                                if (leave_copy) {
                                        if (ec.HasSet (BuilderContext.Options.AsyncBody) && (arguments.ContainsEmitWithAwait () || source.ContainsEmitWithAwait ())) {
                                                source = source.EmitToField (ec);
                                        } else {
                                                temp = new LocalTemporary (Type);
                                                source.Emit (ec);
                                                temp.Store (ec);
                                                source = temp;
                                        }
                                }

                                arguments.Add (new Argument (source));
                        }

                        var call = new CallEmitter ();
                        call.InstanceExpression = InstanceExpression;
                        if (arguments == null)
                                call.InstanceExpressionOnStack = true;

                        call.Emit (ec, Setter, arguments, loc);

                        if (temp != null) {
                                temp.Emit (ec);
                                temp.Release (ec);
                        } else if (leave_copy) {
                                source.Emit (ec);
                        }

                        if (await_source_arg != null) {
                                await_source_arg.Release (ec);
                        }
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        base.FlowAnalysis (fc);
                        arguments.FlowAnalysis (fc);

                        if (conditional_access_receiver)
                                fc.ConditionalAccessEnd ();
                }

                public override string GetSignatureForError ()
                {
                        return best_candidate.GetSignatureForError ();
                }
                
                public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
                {
#if STATIC
                        throw new NotSupportedException ();
#else
                        var value = new[] { source.MakeExpression (ctx) };
                        var args = Arguments.MakeExpression (arguments, ctx).Concat (value);
#if NET_4_0 || MOBILE_DYNAMIC
                        return SLE.Expression.Block (
                                        SLE.Expression.Call (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo (), args),
                                        value [0]);
#else
                        return args.First ();
#endif
#endif
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
#if STATIC
                        return base.MakeExpression (ctx);
#else
                        var args = Arguments.MakeExpression (arguments, ctx);
                        return SLE.Expression.Call (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo (), args);
#endif
                }

                protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
                {
                        if (best_candidate != null)
                                return this;

                        eclass = ExprClass.IndexerAccess;

                        bool dynamic;
                        arguments.Resolve (rc, out dynamic);

                        if (indexers == null && InstanceExpression.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                dynamic = true;
                        } else {
                                var res = new OverloadResolver (indexers, OverloadResolver.Restrictions.None, loc);
                                res.BaseMembersProvider = this;
                                res.InstanceQualifier = this;

                                // TODO: Do I need 2 argument sets?
                                best_candidate = res.ResolveMember<IndexerSpec> (rc, ref arguments);
                                if (best_candidate != null)
                                        type = res.BestCandidateReturnType;
                                else if (!res.BestCandidateIsDynamic)
                                        return null;
                        }

                        //
                        // It has dynamic arguments
                        //
                        if (dynamic) {
                                Arguments args = new Arguments (arguments.Count + 1);
                                if (IsBase) {
                                        rc.Report.Error (1972, loc,
                                                "The indexer base access cannot be dynamically dispatched. Consider casting the dynamic arguments or eliminating the base access");
                                } else {
                                        args.Add (new Argument (InstanceExpression));
                                }
                                args.AddRange (arguments);

                                best_candidate = null;
                                return new DynamicIndexBinder (args, loc);
                        }

                        //
                        // Try to avoid resolving left expression again
                        //
                        if (right_side != null)
                                ResolveInstanceExpression (rc, right_side);

                        return this;
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        IndexerExpr target = (IndexerExpr) t;

                        if (arguments != null)
                                target.arguments = arguments.Clone (clonectx);
                }

                public void SetConditionalAccessReceiver ()
                {
                        conditional_access_receiver = true;
                }

                public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
                {
                        Error_TypeArgumentsCannotBeUsed (ec, "indexer", GetSignatureForError (), loc);
                }

                #region IBaseMembersProvider Members

                IList<MemberSpec> OverloadResolver.IBaseMembersProvider.GetBaseMembers (TypeSpec baseType)
                {
                        return baseType == null ? null : MemberCache.FindMembers (baseType, MemberCache.IndexerNameAlias, false);
                }

                IParametersMember OverloadResolver.IBaseMembersProvider.GetOverrideMemberParameters (MemberSpec member)
                {
                        if (queried_type == member.DeclaringType)
                                return null;

                        var filter = new MemberFilter (MemberCache.IndexerNameAlias, 0, MemberKind.Indexer, ((IndexerSpec) member).Parameters, null);
                        return MemberCache.FindMember (queried_type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as IParametersMember;
                }

                MethodGroupExpr OverloadResolver.IBaseMembersProvider.LookupExtensionMethod (ResolveContext rc)
                {
                        return null;
                }

                #endregion
        }

        //
        // A base access expression
        //
        public class BaseThis : This
        {
                public BaseThis (Location loc)
                        : base (loc)
                {
                }

                public BaseThis (TypeSpec type, Location loc)
                        : base (loc)
                {
                        this.type = type;
                        eclass = ExprClass.Variable;
                }

                #region Properties

                public override string Name {
                        get {
                                return "base";
                        }
                }

                #endregion

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        ec.Report.Error (831, loc, "An expression tree may not contain a base access");
                        return base.CreateExpressionTree (ec);
                }

                public override void Emit (EmitContext ec)
                {
                        base.Emit (ec);

                        if (type == ec.Module.Compiler.BuiltinTypes.ValueType) {
                                var context_type = ec.CurrentType;
                                ec.Emit (OpCodes.Ldobj, context_type);
                                ec.Emit (OpCodes.Box, context_type);
                        }
                }

                protected override void Error_ThisNotAvailable (ResolveContext ec)
                {
                        if (ec.IsStatic) {
                                ec.Report.Error (1511, loc, "Keyword `base' is not available in a static method");
                        } else {
                                ec.Report.Error (1512, loc, "Keyword `base' is not available in the current context");
                        }
                }

                public override void ResolveBase (ResolveContext ec)
                {
                        base.ResolveBase (ec);
                        type = ec.CurrentType.BaseType;
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        /// <summary>
        ///   This class exists solely to pass the Type around and to be a dummy
        ///   that can be passed to the conversion functions (this is used by
        ///   foreach implementation to typecast the object return value from
        ///   get_Current into the proper type.  All code has been generated and
        ///   we only care about the side effect conversions to be performed
        ///
        ///   This is also now used as a placeholder where a no-action expression
        ///   is needed (the `New' class).
        /// </summary>
        public class EmptyExpression : Expression
        {
                sealed class OutAccessExpression : EmptyExpression
                {
                        public OutAccessExpression (TypeSpec t)
                                : base (t)
                        {
                        }

                        public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
                        {
                                rc.Report.Error (206, right_side.Location,
                                        "A property, indexer or dynamic member access may not be passed as `ref' or `out' parameter");

                                return null;
                        }
                }

                public static readonly EmptyExpression LValueMemberAccess = new EmptyExpression (InternalType.FakeInternalType);
                public static readonly EmptyExpression LValueMemberOutAccess = new EmptyExpression (InternalType.FakeInternalType);
                public static readonly EmptyExpression UnaryAddress = new EmptyExpression (InternalType.FakeInternalType);
                public static readonly EmptyExpression EventAddition = new EmptyExpression (InternalType.FakeInternalType);
                public static readonly EmptyExpression EventSubtraction = new EmptyExpression (InternalType.FakeInternalType);
                public static readonly EmptyExpression MissingValue = new EmptyExpression (InternalType.FakeInternalType);
                public static readonly Expression Null = new EmptyExpression (InternalType.FakeInternalType);
                public static readonly EmptyExpression OutAccess = new OutAccessExpression (InternalType.FakeInternalType);

                public EmptyExpression (TypeSpec t)
                {
                        type = t;
                        eclass = ExprClass.Value;
                        loc = Location.Null;
                }

                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        throw new NotSupportedException ("ET");
                }
                
                protected override Expression DoResolve (ResolveContext ec)
                {
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        // nothing, as we only exist to not do anything.
                }

                public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                }

                public override void EmitSideEffect (EmitContext ec)
                {
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }
        
        sealed class EmptyAwaitExpression : EmptyExpression
        {
                public EmptyAwaitExpression (TypeSpec type)
                        : base (type)
                {
                }
                
                public override bool ContainsEmitWithAwait ()
                {
                        return true;
                }
        }
        
        //
        // Empty statement expression
        //
        public sealed class EmptyExpressionStatement : ExpressionStatement
        {
                public static readonly EmptyExpressionStatement Instance = new EmptyExpressionStatement ();

                private EmptyExpressionStatement ()
                {
                        loc = Location.Null;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        return null;
                }

                public override void EmitStatement (EmitContext ec)
                {
                        // Do nothing
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        eclass = ExprClass.Value;
                        type = ec.BuiltinTypes.Object;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        // Do nothing
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class ErrorExpression : EmptyExpression
        {
                public static readonly ErrorExpression Instance = new ErrorExpression ();

                private ErrorExpression ()
                        : base (InternalType.ErrorType)
                {
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        return this;
                }

                public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
                {
                        return this;
                }

                public override void Error_ValueAssignment (ResolveContext rc, Expression rhs)
                {
                }

                public override void Error_UnexpectedKind (ResolveContext ec, ResolveFlags flags, Location loc)
                {
                }

                public override void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
                {
                }

                public override void Error_OperatorCannotBeApplied (ResolveContext rc, Location loc, string oper, TypeSpec t)
                {
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class UserCast : Expression {
                MethodSpec method;
                Expression source;
                
                public UserCast (MethodSpec method, Expression source, Location l)
                {
                        if (source == null)
                                throw new ArgumentNullException ("source");

                        this.method = method;
                        this.source = source;
                        type = method.ReturnType;
                        loc = l;
                }

                public Expression Source {
                        get {
                                return source;
                        }
                        set {
                                source = value;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return source.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (3);
                        args.Add (new Argument (source.CreateExpressionTree (ec)));
                        args.Add (new Argument (new TypeOf (type, loc)));
                        args.Add (new Argument (new TypeOfMethod (method, loc)));
                        return CreateExpressionFactoryCall (ec, "Convert", args);
                }
                        
                protected override Expression DoResolve (ResolveContext ec)
                {
                        ObsoleteAttribute oa = method.GetAttributeObsolete ();
                        if (oa != null)
                                AttributeTester.Report_ObsoleteMessage (oa, GetSignatureForError (), loc, ec.Report);

                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        source.Emit (ec);
                        ec.MarkCallEntry (loc);
                        ec.Emit (OpCodes.Call, method);
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        source.FlowAnalysis (fc);
                }

                public override string GetSignatureForError ()
                {
                        return TypeManager.CSharpSignature (method);
                }

                public override SLE.Expression MakeExpression (BuilderContext ctx)
                {
#if STATIC
                        return base.MakeExpression (ctx);
#else
                        return SLE.Expression.Convert (source.MakeExpression (ctx), type.GetMetaInfo (), (MethodInfo) method.GetMetaInfo ());
#endif
                }
        }

        //
        // Holds additional type specifiers like ?, *, []
        //
        public class ComposedTypeSpecifier
        {
                public static readonly ComposedTypeSpecifier SingleDimension = new ComposedTypeSpecifier (1, Location.Null);

                public readonly int Dimension;
                public readonly Location Location;

                public ComposedTypeSpecifier (int specifier, Location loc)
                {
                        this.Dimension = specifier;
                        this.Location = loc;
                }

                #region Properties
                public bool IsNullable {
                        get {
                                return Dimension == -1;
                        }
                }

                public bool IsPointer {
                        get {
                                return Dimension == -2;
                        }
                }

                public ComposedTypeSpecifier Next { get; set; }

                #endregion

                public static ComposedTypeSpecifier CreateArrayDimension (int dimension, Location loc)
                {
                        return new ComposedTypeSpecifier (dimension, loc);
                }

                public static ComposedTypeSpecifier CreateNullable (Location loc)
                {
                        return new ComposedTypeSpecifier (-1, loc);
                }

                public static ComposedTypeSpecifier CreatePointer (Location loc)
                {
                        return new ComposedTypeSpecifier (-2, loc);
                }

                public string GetSignatureForError ()
                {
                        string s =
                                IsPointer ? "*" :
                                IsNullable ? "?" :
                                ArrayContainer.GetPostfixSignature (Dimension);

                        return Next != null ? s + Next.GetSignatureForError () : s;
                }
        }

        // <summary>
        //   This class is used to "construct" the type during a typecast
        //   operation.  Since the Type.GetType class in .NET can parse
        //   the type specification, we just use this to construct the type
        //   one bit at a time.
        // </summary>
        public class ComposedCast : TypeExpr {
                FullNamedExpression left;
                ComposedTypeSpecifier spec;
                
                public ComposedCast (FullNamedExpression left, ComposedTypeSpecifier spec)
                {
                        if (spec == null)
                                throw new ArgumentNullException ("spec");

                        this.left = left;
                        this.spec = spec;
                        this.loc = left.Location;
                }

                public override TypeSpec ResolveAsType (IMemberContext ec, bool allowUnboundTypeArguments)
                {
                        type = left.ResolveAsType (ec);
                        if (type == null)
                                return null;

                        eclass = ExprClass.Type;

                        var single_spec = spec;

                        if (single_spec.IsNullable) {
                                type = new Nullable.NullableType (type, loc).ResolveAsType (ec);
                                if (type == null)
                                        return null;

                                single_spec = single_spec.Next;
                        } else if (single_spec.IsPointer) {
                                if (!TypeManager.VerifyUnmanaged (ec.Module, type, loc))
                                        return null;

                                if (!ec.IsUnsafe) {
                                        UnsafeError (ec.Module.Compiler.Report, loc);
                                }

                                do {
                                        type = PointerContainer.MakeType (ec.Module, type);
                                        single_spec = single_spec.Next;
                                } while (single_spec != null && single_spec.IsPointer);
                        }

                        if (single_spec != null && single_spec.Dimension > 0) {
                                if (type.IsSpecialRuntimeType) {
                                        ec.Module.Compiler.Report.Error (611, loc, "Array elements cannot be of type `{0}'", type.GetSignatureForError ());
                                } else if (type.IsStatic) {
                                        ec.Module.Compiler.Report.SymbolRelatedToPreviousError (type);
                                        ec.Module.Compiler.Report.Error (719, loc, "Array elements cannot be of static type `{0}'",
                                                type.GetSignatureForError ());
                                } else {
                                        MakeArray (ec.Module, single_spec);
                                }
                        }

                        return type;
                }

                void MakeArray (ModuleContainer module, ComposedTypeSpecifier spec)
                {
                        if (spec.Next != null)
                                MakeArray (module, spec.Next);

                        type = ArrayContainer.MakeType (module, type, spec.Dimension);
                }

                public override string GetSignatureForError ()
                {
                        return left.GetSignatureForError () + spec.GetSignatureForError ();
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        class FixedBufferPtr : Expression
        {
                readonly Expression array;

                public FixedBufferPtr (Expression array, TypeSpec array_type, Location l)
                {
                        this.type = array_type;
                        this.array = array;
                        this.loc = l;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        throw new NotImplementedException ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Error_PointerInsideExpressionTree (ec);
                        return null;
                }

                public override void Emit(EmitContext ec)
                {
                        array.Emit (ec);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        type = PointerContainer.MakeType (ec.Module, type);
                        eclass = ExprClass.Value;
                        return this;
                }
        }


        //
        // This class is used to represent the address of an array, used
        // only by the Fixed statement, this generates "&a [0]" construct
        // for fixed (char *pa = a)
        //
        class ArrayPtr : FixedBufferPtr
        {
                public ArrayPtr (Expression array, TypeSpec array_type, Location l):
                        base (array, array_type, l)
                {
                }

                public override void Emit (EmitContext ec)
                {
                        base.Emit (ec);
                        
                        ec.EmitInt (0);
                        ec.Emit (OpCodes.Ldelema, ((PointerContainer) type).Element);
                }
        }

        //
        // Encapsulates a conversion rules required for array indexes
        //
        public class ArrayIndexCast : TypeCast
        {
                public ArrayIndexCast (Expression expr, TypeSpec returnType)
                        : base (expr, returnType)
                {
                        if (expr.Type == returnType) // int -> int
                                throw new ArgumentException ("unnecessary array index conversion");
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        using (ec.Set (ResolveContext.Options.CheckedScope)) {
                                return base.CreateExpressionTree (ec);
                        }
                }

                public override void Emit (EmitContext ec)
                {
                        child.Emit (ec);

                        switch (child.Type.BuiltinType) {
                        case BuiltinTypeSpec.Type.UInt:
                                ec.Emit (OpCodes.Conv_U);
                                break;
                        case BuiltinTypeSpec.Type.Long:
                                ec.Emit (OpCodes.Conv_Ovf_I);
                                break;
                        case BuiltinTypeSpec.Type.ULong:
                                ec.Emit (OpCodes.Conv_Ovf_I_Un);
                                break;
                        default:
                                throw new InternalErrorException ("Cannot emit cast to unknown array element type", type);
                        }
                }
        }

        //
        // Implements the `stackalloc' keyword
        //
        public class StackAlloc : Expression {
                TypeSpec otype;
                Expression texpr;
                Expression count;
                
                public StackAlloc (Expression type, Expression count, Location l)
                {
                        texpr = type;
                        this.count = count;
                        loc = l;
                }

                public Expression TypeExpression {
                        get {
                                return texpr;
                        }
                }

                public Expression CountExpression {
                        get {
                                return this.count;
                        }
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        count = count.Resolve (ec);
                        if (count == null)
                                return null;
                        
                        if (count.Type.BuiltinType != BuiltinTypeSpec.Type.UInt){
                                count = Convert.ImplicitConversionRequired (ec, count, ec.BuiltinTypes.Int, loc);
                                if (count == null)
                                        return null;
                        }

                        Constant c = count as Constant;
                        if (c != null && c.IsNegative) {
                                ec.Report.Error (247, loc, "Cannot use a negative size with stackalloc");
                        }

                        if (ec.HasAny (ResolveContext.Options.CatchScope | ResolveContext.Options.FinallyScope)) {
                                ec.Report.Error (255, loc, "Cannot use stackalloc in finally or catch");
                        }

                        otype = texpr.ResolveAsType (ec);
                        if (otype == null)
                                return null;

                        if (!TypeManager.VerifyUnmanaged (ec.Module, otype, loc))
                                return null;

                        type = PointerContainer.MakeType (ec.Module, otype);
                        eclass = ExprClass.Value;

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        int size = BuiltinTypeSpec.GetSize (otype);

                        count.Emit (ec);

                        if (size == 0)
                                ec.Emit (OpCodes.Sizeof, otype);
                        else
                                ec.EmitInt (size);

                        ec.Emit (OpCodes.Mul_Ovf_Un);
                        ec.Emit (OpCodes.Localloc);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        StackAlloc target = (StackAlloc) t;
                        target.count = count.Clone (clonectx);
                        target.texpr = texpr.Clone (clonectx);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        //
        // An object initializer expression
        //
        public class ElementInitializer : Assign
        {
                public readonly string Name;

                public ElementInitializer (string name, Expression initializer, Location loc)
                        : base (null, initializer, loc)
                {
                        this.Name = name;
                }

                public bool IsDictionaryInitializer {
                        get {
                                return Name == null;
                        }
                }
                
                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        ElementInitializer target = (ElementInitializer) t;
                        target.source = source.Clone (clonectx);
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (2);
                        FieldExpr fe = target as FieldExpr;
                        if (fe != null)
                                args.Add (new Argument (fe.CreateTypeOfExpression ()));
                        else
                                args.Add (new Argument (((PropertyExpr) target).CreateSetterTypeOfExpression (ec)));

                        string mname;
                        Expression arg_expr;
                        var cinit = source as CollectionOrObjectInitializers;
                        if (cinit == null) {
                                mname = "Bind";
                                arg_expr = source.CreateExpressionTree (ec);
                        } else {
                                mname = cinit.IsEmpty || cinit.Initializers[0] is ElementInitializer ? "MemberBind" : "ListBind";
                                arg_expr = cinit.CreateExpressionTree (ec, !cinit.IsEmpty);
                        }

                        args.Add (new Argument (arg_expr));
                        return CreateExpressionFactoryCall (ec, mname, args);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (source == null)
                                return EmptyExpressionStatement.Instance;

                        if (!ResolveElement (ec))
                                return null;

                        if (source is CollectionOrObjectInitializers) {
                                Expression previous = ec.CurrentInitializerVariable;
                                ec.CurrentInitializerVariable = target;
                                source = source.Resolve (ec);
                                ec.CurrentInitializerVariable = previous;
                                if (source == null)
                                        return null;
                                        
                                eclass = source.eclass;
                                type = source.Type;
                                return this;
                        }

                        return base.DoResolve (ec);
                }
        
                public override void EmitStatement (EmitContext ec)
                {
                        if (source is CollectionOrObjectInitializers)
                                source.Emit (ec);
                        else
                                base.EmitStatement (ec);
                }

                protected virtual bool ResolveElement (ResolveContext rc)
                {
                        var t = rc.CurrentInitializerVariable.Type;
                        if (t.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
                                Arguments args = new Arguments (1);
                                args.Add (new Argument (rc.CurrentInitializerVariable));
                                target = new DynamicMemberBinder (Name, args, loc);
                        } else {

                                var member = MemberLookup (rc, false, t, Name, 0, MemberLookupRestrictions.ExactArity, loc);
                                if (member == null) {
                                        member = Expression.MemberLookup (rc, true, t, Name, 0, MemberLookupRestrictions.ExactArity, loc);

                                        if (member != null) {
                                                // TODO: ec.Report.SymbolRelatedToPreviousError (member);
                                                ErrorIsInaccesible (rc, member.GetSignatureForError (), loc);
                                                return false;
                                        }
                                }

                                if (member == null) {
                                        Error_TypeDoesNotContainDefinition (rc, loc, t, Name);
                                        return false;
                                }

                                var me = member as MemberExpr;
                                if (me is EventExpr) {
                                        me = me.ResolveMemberAccess (rc, null, null);
                                } else if (!(member is PropertyExpr || member is FieldExpr)) {
                                        rc.Report.Error (1913, loc,
                                                "Member `{0}' cannot be initialized. An object initializer may only be used for fields, or properties",
                                                member.GetSignatureForError ());

                                        return false;
                                }

                                if (me.IsStatic) {
                                        rc.Report.Error (1914, loc,
                                                "Static field or property `{0}' cannot be assigned in an object initializer",
                                                me.GetSignatureForError ());
                                }

                                target = me;
                                me.InstanceExpression = rc.CurrentInitializerVariable;
                        }

                        return true;
                }
        }
        
        //
        // A collection initializer expression
        //
        class CollectionElementInitializer : Invocation
        {
                public class ElementInitializerArgument : Argument
                {
                        public ElementInitializerArgument (Expression e)
                                : base (e)
                        {
                        }
                }

                sealed class AddMemberAccess : MemberAccess
                {
                        public AddMemberAccess (Expression expr, Location loc)
                                : base (expr, "Add", loc)
                        {
                        }

                        public override void Error_TypeDoesNotContainDefinition (ResolveContext ec, TypeSpec type, string name)
                        {
                                if (TypeManager.HasElementType (type))
                                        return;

                                base.Error_TypeDoesNotContainDefinition (ec, type, name);
                        }
                }

                public CollectionElementInitializer (Expression argument)
                        : base (null, new Arguments (1))
                {
                        base.arguments.Add (new ElementInitializerArgument (argument));
                        this.loc = argument.Location;
                }

                public CollectionElementInitializer (List<Expression> arguments, Location loc)
                        : base (null, new Arguments (arguments.Count))
                {
                        foreach (Expression e in arguments)
                                base.arguments.Add (new ElementInitializerArgument (e));

                        this.loc = loc;
                }

                public CollectionElementInitializer (Location loc)
                        : base (null, null)
                {
                        this.loc = loc;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (2);
                        args.Add (new Argument (mg.CreateExpressionTree (ec)));

                        var expr_initializers = new ArrayInitializer (arguments.Count, loc);
                        foreach (Argument a in arguments)
                                expr_initializers.Add (a.CreateExpressionTree (ec));

                        args.Add (new Argument (new ArrayCreation (
                                CreateExpressionTypeExpression (ec, loc), expr_initializers, loc)));
                        return CreateExpressionFactoryCall (ec, "ElementInit", args);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        CollectionElementInitializer target = (CollectionElementInitializer) t;
                        if (arguments != null)
                                target.arguments = arguments.Clone (clonectx);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        base.expr = new AddMemberAccess (ec.CurrentInitializerVariable, loc);

                        return base.DoResolve (ec);
                }
        }

        class DictionaryElementInitializer : ElementInitializer
        {
                readonly Arguments args;

                public DictionaryElementInitializer (Arguments arguments, Expression initializer, Location loc)
                        : base (null, initializer, loc)
                {
                        this.args = arguments;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        ec.Report.Error (8074, loc, "Expression tree cannot contain a dictionary initializer");
                        return null;
                }

                protected override bool ResolveElement (ResolveContext rc)
                {
                        var init = rc.CurrentInitializerVariable;
                        var type = init.Type;

                        if (type.IsArray) {
                                target = new ArrayAccess (new ElementAccess (init, args, loc), loc);
                                return true;
                        }

                        if (type.IsPointer) {
                                target = init.MakePointerAccess (rc, type, args);
                                return true;
                        }

                        var indexers = MemberCache.FindMembers (type, MemberCache.IndexerNameAlias, false);
                        if (indexers == null && type.BuiltinType != BuiltinTypeSpec.Type.Dynamic) {
                                ElementAccess.Error_CannotApplyIndexing (rc, type, loc);
                                return false;
                        }

                        target = new IndexerExpr (indexers, type, init, args, loc).Resolve (rc);
                        return true;
                }
        }
        
        //
        // A block of object or collection initializers
        //
        public class CollectionOrObjectInitializers : ExpressionStatement
        {
                IList<Expression> initializers;
                bool is_collection_initialization;

                public CollectionOrObjectInitializers (Location loc)
                        : this (new Expression[0], loc)
                {
                }

                public CollectionOrObjectInitializers (IList<Expression> initializers, Location loc)
                {
                        this.initializers = initializers;
                        this.loc = loc;
                }

                public IList<Expression> Initializers {
                        get {
                                return initializers;
                        }
                }
                
                public bool IsEmpty {
                        get {
                                return initializers.Count == 0;
                        }
                }

                public bool IsCollectionInitializer {
                        get {
                                return is_collection_initialization;
                        }
                }

                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                        CollectionOrObjectInitializers t = (CollectionOrObjectInitializers) target;

                        t.initializers = new List<Expression> (initializers.Count);
                        foreach (var e in initializers)
                                t.initializers.Add (e.Clone (clonectx));
                }

                public override bool ContainsEmitWithAwait ()
                {
                        foreach (var e in initializers) {
                                if (e.ContainsEmitWithAwait ())
                                        return true;
                        }

                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        return CreateExpressionTree (ec, false);
                }

                public Expression CreateExpressionTree (ResolveContext ec, bool inferType)
                {
                        var expr_initializers = new ArrayInitializer (initializers.Count, loc);
                        foreach (Expression e in initializers) {
                                Expression expr = e.CreateExpressionTree (ec);
                                if (expr != null)
                                        expr_initializers.Add (expr);
                        }

                        if (inferType)
                                return new ImplicitlyTypedArrayCreation (expr_initializers, loc);

                        return new ArrayCreation (new TypeExpression (ec.Module.PredefinedTypes.MemberBinding.Resolve (), loc), expr_initializers, loc); 
                }
                
                protected override Expression DoResolve (ResolveContext ec)
                {
                        List<string> element_names = null;
                        for (int i = 0; i < initializers.Count; ++i) {
                                Expression initializer = initializers [i];
                                ElementInitializer element_initializer = initializer as ElementInitializer;

                                if (i == 0) {
                                        if (element_initializer != null) {
                                                element_names = new List<string> (initializers.Count);
                                                if (!element_initializer.IsDictionaryInitializer)
                                                        element_names.Add (element_initializer.Name);
                                        } else if (initializer is CompletingExpression) {
                                                initializer.Resolve (ec);
                                                throw new InternalErrorException ("This line should never be reached");
                                        } else {
                                                var t = ec.CurrentInitializerVariable.Type;
                                                // LAMESPEC: The collection must implement IEnumerable only, no dynamic support
                                                if (!t.ImplementsInterface (ec.BuiltinTypes.IEnumerable, false) && t.BuiltinType != BuiltinTypeSpec.Type.Dynamic) {
                                                        ec.Report.Error (1922, loc, "A field or property `{0}' cannot be initialized with a collection " +
                                                                "object initializer because type `{1}' does not implement `{2}' interface",
                                                                ec.CurrentInitializerVariable.GetSignatureForError (),
                                                                ec.CurrentInitializerVariable.Type.GetSignatureForError (),
                                                                ec.BuiltinTypes.IEnumerable.GetSignatureForError ());
                                                        return null;
                                                }
                                                is_collection_initialization = true;
                                        }
                                } else {
                                        if (is_collection_initialization != (element_initializer == null)) {
                                                ec.Report.Error (747, initializer.Location, "Inconsistent `{0}' member declaration",
                                                        is_collection_initialization ? "collection initializer" : "object initializer");
                                                continue;
                                        }

                                        if (!is_collection_initialization && !element_initializer.IsDictionaryInitializer) {
                                                if (element_names.Contains (element_initializer.Name)) {
                                                        ec.Report.Error (1912, element_initializer.Location,
                                                                "An object initializer includes more than one member `{0}' initialization",
                                                                element_initializer.Name);
                                                } else {
                                                        element_names.Add (element_initializer.Name);
                                                }
                                        }
                                }

                                Expression e = initializer.Resolve (ec);
                                if (e == EmptyExpressionStatement.Instance)
                                        initializers.RemoveAt (i--);
                                else
                                        initializers [i] = e;
                        }

                        type = ec.CurrentInitializerVariable.Type;
                        if (is_collection_initialization) {
                                if (TypeManager.HasElementType (type)) {
                                        ec.Report.Error (1925, loc, "Cannot initialize object of type `{0}' with a collection initializer",
                                                type.GetSignatureForError ());
                                }
                        }

                        eclass = ExprClass.Variable;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        EmitStatement (ec);
                }

                public override void EmitStatement (EmitContext ec)
                {
                        foreach (ExpressionStatement e in initializers) {
                                // TODO: need location region
                                ec.Mark (e.Location);
                                e.EmitStatement (ec);
                        }
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        foreach (var initializer in initializers) {
                                if (initializer != null)
                                        initializer.FlowAnalysis (fc);
                        }
                }
        }
        
        //
        // New expression with element/object initializers
        //
        public class NewInitialize : New
        {
                //
                // This class serves as a proxy for variable initializer target instances.
                // A real variable is assigned later when we resolve left side of an
                // assignment
                //
                sealed class InitializerTargetExpression : Expression, IMemoryLocation
                {
                        NewInitialize new_instance;

                        public InitializerTargetExpression (NewInitialize newInstance)
                        {
                                this.type = newInstance.type;
                                this.loc = newInstance.loc;
                                this.eclass = newInstance.eclass;
                                this.new_instance = newInstance;
                        }

                        public override bool ContainsEmitWithAwait ()
                        {
                                return false;
                        }

                        public override Expression CreateExpressionTree (ResolveContext ec)
                        {
                                // Should not be reached
                                throw new NotSupportedException ("ET");
                        }

                        protected override Expression DoResolve (ResolveContext ec)
                        {
                                return this;
                        }

                        public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
                        {
                                return this;
                        }

                        public override void Emit (EmitContext ec)
                        {
                                Expression e = (Expression) new_instance.instance;
                                e.Emit (ec);
                        }

                        public override Expression EmitToField (EmitContext ec)
                        {
                                return (Expression) new_instance.instance;
                        }

                        #region IMemoryLocation Members

                        public void AddressOf (EmitContext ec, AddressOp mode)
                        {
                                new_instance.instance.AddressOf (ec, mode);
                        }

                        #endregion
                }

                CollectionOrObjectInitializers initializers;
                IMemoryLocation instance;
                DynamicExpressionStatement dynamic;

                public NewInitialize (FullNamedExpression requested_type, Arguments arguments, CollectionOrObjectInitializers initializers, Location l)
                        : base (requested_type, arguments, l)
                {
                        this.initializers = initializers;
                }

                public CollectionOrObjectInitializers Initializers {
                        get {
                                return initializers;
                        }
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        base.CloneTo (clonectx, t);

                        NewInitialize target = (NewInitialize) t;
                        target.initializers = (CollectionOrObjectInitializers) initializers.Clone (clonectx);
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return base.ContainsEmitWithAwait () || initializers.ContainsEmitWithAwait ();
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        Arguments args = new Arguments (2);
                        args.Add (new Argument (base.CreateExpressionTree (ec)));
                        if (!initializers.IsEmpty)
                                args.Add (new Argument (initializers.CreateExpressionTree (ec, initializers.IsCollectionInitializer)));

                        return CreateExpressionFactoryCall (ec,
                                initializers.IsCollectionInitializer ? "ListInit" : "MemberInit",
                                args);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        Expression e = base.DoResolve (ec);
                        if (type == null)
                                return null;

                        if (type.IsDelegate) {
                                ec.Report.Error (1958, Initializers.Location,
                                        "Object and collection initializers cannot be used to instantiate a delegate");
                        }

                        Expression previous = ec.CurrentInitializerVariable;
                        ec.CurrentInitializerVariable = new InitializerTargetExpression (this);
                        initializers.Resolve (ec);
                        ec.CurrentInitializerVariable = previous;

                        dynamic = e as DynamicExpressionStatement;
                        if (dynamic != null)
                                return this;

                        return e;
                }

                public override void Emit (EmitContext ec)
                {
                        if (method == null && TypeSpec.IsValueType (type) && initializers.Initializers.Count > 1 && ec.HasSet (BuilderContext.Options.AsyncBody) && initializers.ContainsEmitWithAwait ()) {
                                var fe = ec.GetTemporaryField (type);

                                if (!Emit (ec, fe))
                                        fe.Emit (ec);

                                return;
                        }

                        base.Emit (ec);
                }

                public override bool Emit (EmitContext ec, IMemoryLocation target)
                {
                        //
                        // Expression is initialized into temporary target then moved
                        // to real one for atomicity
                        //
                        IMemoryLocation temp_target = target;

                        LocalTemporary temp = null;
                        bool by_ref = false;
                        if (!initializers.IsEmpty) {
                                temp_target = target as LocalTemporary;
                                if (temp_target == null)
                                        temp_target = target as StackFieldExpr;

                                if (temp_target == null) {
                                        var vr = target as VariableReference;
                                        if (vr != null && vr.IsRef) {
                                                vr.EmitLoad (ec);
                                                by_ref = true;
                                        }
                                }

                                if (temp_target == null)
                                        temp_target = temp = new LocalTemporary (type);
                        }

                        bool left_on_stack;
                        if (dynamic != null) {
                                dynamic.Emit (ec);
                                left_on_stack = true;
                        } else {
                                left_on_stack = base.Emit (ec, temp_target);
                        }

                        if (initializers.IsEmpty)
                                return left_on_stack;

                        StackFieldExpr sf = null;

                        // Move a new instance (reference-type) to local temporary variable
                        if (left_on_stack) {
                                if (by_ref) {
                                        temp_target = temp = new LocalTemporary (type);
                                }

                                if (temp != null)
                                        temp.Store (ec);

                                if (ec.HasSet (BuilderContext.Options.AsyncBody) && initializers.ContainsEmitWithAwait ()) {
                                        if (temp == null)
                                                throw new NotImplementedException ();

                                        sf = ec.GetTemporaryField (type);
                                        sf.EmitAssign (ec, temp, false, false);
                                        temp_target = sf;
                                        temp.Release (ec);
                                        left_on_stack = false;
                                }
                        }

                        instance = temp_target;

                        initializers.Emit (ec);

                        ((Expression)temp_target).Emit (ec);

                        if (temp != null)
                                temp.Release (ec);

                        if (sf != null)
                                sf.IsAvailableForReuse = true;

                        return true;
                }

                protected override IMemoryLocation EmitAddressOf (EmitContext ec, AddressOp Mode)
                {
                        instance = base.EmitAddressOf (ec, Mode);

                        if (!initializers.IsEmpty)
                                initializers.Emit (ec);

                        return instance;
                }

                public override void FlowAnalysis (FlowAnalysisContext fc)
                {
                        base.FlowAnalysis (fc);
                        initializers.FlowAnalysis (fc);
                }

                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class NewAnonymousType : New
        {
                static readonly AnonymousTypeParameter[] EmptyParameters = new AnonymousTypeParameter[0];

                List<AnonymousTypeParameter> parameters;
                readonly TypeContainer parent;
                AnonymousTypeClass anonymous_type;

                public NewAnonymousType (List<AnonymousTypeParameter> parameters, TypeContainer parent, Location loc)
                         : base (null, null, loc)
                {
                        this.parameters = parameters;
                        this.parent = parent;
                }

                public List<AnonymousTypeParameter> Parameters {
                        get {
                                return this.parameters;
                        }
                }

                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                        if (parameters == null)
                                return;

                        NewAnonymousType t = (NewAnonymousType) target;
                        t.parameters = new List<AnonymousTypeParameter> (parameters.Count);
                        foreach (AnonymousTypeParameter atp in parameters)
                                t.parameters.Add ((AnonymousTypeParameter) atp.Clone (clonectx));
                }

                AnonymousTypeClass CreateAnonymousType (ResolveContext ec, IList<AnonymousTypeParameter> parameters)
                {
                        AnonymousTypeClass type = parent.Module.GetAnonymousType (parameters);
                        if (type != null)
                                return type;

                        type = AnonymousTypeClass.Create (parent, parameters, loc);
                        if (type == null)
                                return null;

                        int errors = ec.Report.Errors;
                        type.CreateContainer ();
                        type.DefineContainer ();
                        type.Define ();
                        if ((ec.Report.Errors - errors) == 0) {
                                parent.Module.AddAnonymousType (type);
                                type.PrepareEmit ();
                        }

                        return type;
                }

                public override Expression CreateExpressionTree (ResolveContext ec)
                {
                        if (parameters == null)
                                return base.CreateExpressionTree (ec);

                        var init = new ArrayInitializer (parameters.Count, loc);
                        foreach (var m in anonymous_type.Members) {
                                var p = m as Property;
                                if (p != null)
                                        init.Add (new TypeOfMethod (MemberCache.GetMember (type, p.Get.Spec), loc));
                        }

                        var ctor_args = new ArrayInitializer (arguments.Count, loc);
                        foreach (Argument a in arguments)
                                ctor_args.Add (a.CreateExpressionTree (ec));

                        Arguments args = new Arguments (3);
                        args.Add (new Argument (new TypeOfMethod (method, loc)));
                        args.Add (new Argument (new ArrayCreation (CreateExpressionTypeExpression (ec, loc), ctor_args, loc)));
                        args.Add (new Argument (new ImplicitlyTypedArrayCreation (init, loc)));

                        return CreateExpressionFactoryCall (ec, "New", args);
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (ec.HasSet (ResolveContext.Options.ConstantScope)) {
                                ec.Report.Error (836, loc, "Anonymous types cannot be used in this expression");
                                return null;
                        }

                        if (parameters == null) {
                                anonymous_type = CreateAnonymousType (ec, EmptyParameters);
                                RequestedType = new TypeExpression (anonymous_type.Definition, loc);
                                return base.DoResolve (ec);
                        }

                        bool error = false;
                        arguments = new Arguments (parameters.Count);
                        var t_args = new TypeSpec [parameters.Count];
                        for (int i = 0; i < parameters.Count; ++i) {
                                Expression e = parameters [i].Resolve (ec);
                                if (e == null) {
                                        error = true;
                                        continue;
                                }

                                arguments.Add (new Argument (e));
                                t_args [i] = e.Type;
                        }

                        if (error)
                                return null;

                        anonymous_type = CreateAnonymousType (ec, parameters);
                        if (anonymous_type == null)
                                return null;

                        type = anonymous_type.Definition.MakeGenericType (ec.Module, t_args);
                        method = (MethodSpec) MemberCache.FindMember (type, MemberFilter.Constructor (null), BindingRestriction.DeclaredOnly);
                        eclass = ExprClass.Value;
                        return this;
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

        public class AnonymousTypeParameter : ShimExpression
        {
                public readonly string Name;

                public AnonymousTypeParameter (Expression initializer, string name, Location loc)
                        : base (initializer)
                {
                        this.Name = name;
                        this.loc = loc;
                }
                
                public AnonymousTypeParameter (Parameter parameter)
                        : base (new SimpleName (parameter.Name, parameter.Location))
                {
                        this.Name = parameter.Name;
                        this.loc = parameter.Location;
                }               

                public override bool Equals (object o)
                {
                        AnonymousTypeParameter other = o as AnonymousTypeParameter;
                        return other != null && Name == other.Name;
                }

                public override int GetHashCode ()
                {
                        return Name.GetHashCode ();
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        Expression e = expr.Resolve (ec);
                        if (e == null)
                                return null;

                        if (e.eclass == ExprClass.MethodGroup) {
                                Error_InvalidInitializer (ec, e.ExprClassName);
                                return null;
                        }

                        type = e.Type;
                        if (type.Kind == MemberKind.Void || type == InternalType.NullLiteral || type == InternalType.AnonymousMethod || type.IsPointer) {
                                Error_InvalidInitializer (ec, type.GetSignatureForError ());
                                return null;
                        }

                        return e;
                }

                protected virtual void Error_InvalidInitializer (ResolveContext ec, string initializer)
                {
                        ec.Report.Error (828, loc, "An anonymous type property `{0}' cannot be initialized with `{1}'",
                                Name, initializer);
                }
        }

        public class CatchFilterExpression : BooleanExpression
        {
                public CatchFilterExpression (Expression expr, Location loc)
                        : base (expr)
                {
                        this.loc = loc;
                }
        }

        public class InterpolatedString : Expression
        {
                readonly StringLiteral start, end;
                List<Expression> interpolations;
                Arguments arguments;

                public InterpolatedString (StringLiteral start, List<Expression> interpolations, StringLiteral end)
                {
                        this.start = start;
                        this.end = end;
                        this.interpolations = interpolations;
                        loc = start.Location;
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        InterpolatedString target = (InterpolatedString) t;

                        if (interpolations != null) {
                                target.interpolations = new List<Expression> ();
                                foreach (var interpolation in interpolations) {
                                        target.interpolations.Add (interpolation.Clone (clonectx));
                                }
                        }
                }

                public Expression ConvertTo (ResolveContext rc, TypeSpec type)
                {
                        var factory = rc.Module.PredefinedTypes.FormattableStringFactory.Resolve ();
                        if (factory == null)
                                return null;

                        var ma = new MemberAccess (new TypeExpression (factory, loc), "Create", loc);
                        var res = new Invocation (ma, arguments).Resolve (rc);
                        if (res != null && res.Type != type)
                                res = Convert.ExplicitConversion (rc, res, type, loc);

                        return res;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        if (interpolations == null)
                                return false;

                        foreach (var expr in interpolations) {
                                if (expr.ContainsEmitWithAwait ())
                                        return true;
                        }

                        return false;
                }

                public override Expression CreateExpressionTree (ResolveContext rc)
                {
                        var best = ResolveBestFormatOverload (rc);
                        if (best == null)
                                return null;
                        
                        Expression instance = new NullLiteral (loc);
                        var args = Arguments.CreateForExpressionTree (rc, arguments, instance, new TypeOfMethod (best, loc));
                        return CreateExpressionFactoryCall (rc, "Call", args);  
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        string str;

                        if (interpolations == null) {
                                str = start.Value;
                                arguments = new Arguments (1);
                        } else {
                                for (int i = 0; i < interpolations.Count; i += 2) {
                                        var ipi = (InterpolatedStringInsert)interpolations [i];
                                        ipi.Resolve (rc);
                                }
        
                                arguments = new Arguments (interpolations.Count);

                                var sb = new StringBuilder (start.Value);
                                for (int i = 0; i < interpolations.Count; ++i) {
                                        if (i % 2 == 0) {
                                                sb.Append ('{').Append (i / 2);
                                                var isi = (InterpolatedStringInsert)interpolations [i];
                                                if (isi.Alignment != null) {
                                                        sb.Append (',');
                                                        var value = isi.ResolveAligment (rc);
                                                        if (value != null)
                                                                sb.Append (value.Value);
                                                }

                                                if (isi.Format != null) {
                                                        sb.Append (':');
                                                        sb.Append (isi.Format);
                                                }

                                                sb.Append ('}');
                                                arguments.Add (new Argument (interpolations [i]));
                                        } else {
                                                sb.Append (((StringLiteral)interpolations [i]).Value);
                                        }
                                }

                                sb.Append (end.Value);
                                str = sb.ToString ();
                        }

                        arguments.Insert (0, new Argument (new StringLiteral (rc.BuiltinTypes, str, start.Location)));

                        eclass = ExprClass.Value;
                        type = rc.BuiltinTypes.String;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        // No interpolation, convert to simple string result (needs to match string.Format unescaping)
                        if (interpolations == null) {
                                var str = start.Value.Replace ("{{", "{").Replace ("}}", "}");
                                if (str != start.Value)
                                        new StringConstant (ec.BuiltinTypes, str, loc).Emit (ec);
                                else
                                        start.Emit (ec);

                                return;
                        }

                        var best = ResolveBestFormatOverload (new ResolveContext (ec.MemberContext));
                        if (best == null)
                                return;

                        var ca = new CallEmitter ();
                        ca.Emit (ec, best, arguments, loc);
                }

                MethodSpec ResolveBestFormatOverload (ResolveContext rc)
                {
                        var members = MemberCache.FindMembers (rc.BuiltinTypes.String, "Format", true);
                        var res = new OverloadResolver (members, OverloadResolver.Restrictions.NoBaseMembers, loc);
                        return res.ResolveMember<MethodSpec> (rc, ref arguments);
                }
        }

        public class InterpolatedStringInsert : CompositeExpression
        {
                public InterpolatedStringInsert (Expression expr)
                        : base (expr)
                {
                }

                public Expression Alignment { get; set; }
                public string Format { get; set; }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        var target = (InterpolatedStringInsert)t;
                        if (Alignment != null)
                                target.Alignment = Alignment.Clone (clonectx);
                }

                protected override Expression DoResolve (ResolveContext rc)
                {
                        var expr = base.DoResolve (rc);
                        if (expr == null)
                                return null;

                        //
                        // For better error reporting, assumes the built-in implementation uses object
                        // as argument(s)
                        //
                        return Convert.ImplicitConversionRequired (rc, expr, rc.BuiltinTypes.Object, expr.Location);
                }

                public int? ResolveAligment (ResolveContext rc)
                {
                        var c = Alignment.ResolveLabelConstant (rc);
                        if (c == null)
                                return null;
                        
                        c = c.ImplicitConversionRequired (rc, rc.BuiltinTypes.Int);
                        if (c == null)
                                return null;
                        
                        var value = (int) c.GetValueAsLong ();
                        if (value > 32767 || value < -32767) {
                                rc.Report.Warning (8094, 1, Alignment.Location, 
                                        "Alignment value has a magnitude greater than 32767 and may result in a large formatted string");
                        }

                        return value;
                }
        }
}