2005-11-18 Marek Safar <marek.safar@seznam.cz>

[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@seznam.cz)
//
// (C) 2001, 2002, 2003 Ximian, Inc.
// (C) 2003, 2004 Novell, Inc.
//
#define USE_OLD

namespace Mono.CSharp {
        using System;
        using System.Collections;
        using System.Reflection;
        using System.Reflection.Emit;
        using System.Text;

        /// <summary>
        ///   This is just a helper class, it is generated by Unary, UnaryMutator
        ///   when an overloaded method has been found.  It just emits the code for a
        ///   static call.
        /// </summary>
        public class StaticCallExpr : ExpressionStatement {
                ArrayList args;
                MethodInfo mi;

                public StaticCallExpr (MethodInfo m, ArrayList a, Location l)
                {
                        mi = m;
                        args = a;

                        type = m.ReturnType;
                        eclass = ExprClass.Value;
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        //
                        // We are born fully resolved
                        //
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        if (args != null) 
                                Invocation.EmitArguments (ec, mi, args, false, null);

                        ec.ig.Emit (OpCodes.Call, mi);
                        return;
                }
                
                static public StaticCallExpr MakeSimpleCall (EmitContext ec, MethodGroupExpr mg,
                                                         Expression e, Location loc)
                {
                        ArrayList args;
                        MethodBase method;
                        
                        args = new ArrayList (1);
                        Argument a = new Argument (e, Argument.AType.Expression);

                        // We need to resolve the arguments before sending them in !
                        if (!a.Resolve (ec, loc))
                                return null;

                        args.Add (a);
                        method = Invocation.OverloadResolve (
                                ec, (MethodGroupExpr) mg, args, false, loc);

                        if (method == null)
                                return null;

                        return new StaticCallExpr ((MethodInfo) method, args, loc);
                }

                public override void EmitStatement (EmitContext ec)
                {
                        Emit (ec);
                        if (TypeManager.TypeToCoreType (type) != TypeManager.void_type)
                                ec.ig.Emit (OpCodes.Pop);
                }
                
                public MethodInfo Method {
                        get { return mi; }
                }
        }

        public class ParenthesizedExpression : Expression
        {
                public Expression Expr;

                public ParenthesizedExpression (Expression expr)
                {
                        this.Expr = expr;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        Expr = Expr.Resolve (ec);
                        return Expr;
                }

                public override void Emit (EmitContext ec)
                {
                        throw new Exception ("Should not happen");
                }

                public override Location Location
                {
                        get {
                                return Expr.Location;
                        }
                }
        }
        
        /// <summary>
        ///   Unary expressions.  
        /// </summary>
        ///
        /// <remarks>
        ///   Unary implements unary expressions.   It derives from
        ///   ExpressionStatement becuase the pre/post increment/decrement
        ///   operators can be used in a statement context.
        /// </remarks>
        public class Unary : Expression {
                public enum Operator : byte {
                        UnaryPlus, UnaryNegation, LogicalNot, OnesComplement,
                        Indirection, AddressOf,  TOP
                }

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

                /// <summary>
                ///   Returns a stringified representation of the Operator
                /// </summary>
                static public 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 "&";
                        case Operator.Indirection:
                                return "*";
                        }

                        return oper.ToString ();
                }

                public static readonly string [] oper_names;

                static Unary ()
                {
                        oper_names = new string [(int)Operator.TOP];

                        oper_names [(int) Operator.UnaryPlus] = "op_UnaryPlus";
                        oper_names [(int) Operator.UnaryNegation] = "op_UnaryNegation";
                        oper_names [(int) Operator.LogicalNot] = "op_LogicalNot";
                        oper_names [(int) Operator.OnesComplement] = "op_OnesComplement";
                        oper_names [(int) Operator.Indirection] = "op_Indirection";
                        oper_names [(int) Operator.AddressOf] = "op_AddressOf";
                }

                void Error23 (Type t)
                {
                        Report.Error (23, loc, "Operator `{0}' cannot be applied to operand of type `{1}'",
                                OperName (Oper), TypeManager.CSharpName (t));
                }

                /// <remarks>
                ///   The result has been already resolved:
                ///
                ///   FIXME: a minus constant -128 sbyte cant be turned into a
                ///   constant byte.
                /// </remarks>
                static Expression TryReduceNegative (Constant expr)
                {
                        Expression e = null;

                        if (expr is IntConstant)
                                e = new IntConstant (-((IntConstant) expr).Value, expr.Location);
                        else if (expr is UIntConstant){
                                uint value = ((UIntConstant) expr).Value;

                                if (value < 2147483649)
                                        return new IntConstant (-(int)value, expr.Location);
                                else
                                        e = new LongConstant (-value, expr.Location);
                        }
                        else if (expr is LongConstant)
                                e = new LongConstant (-((LongConstant) expr).Value, expr.Location);
                        else if (expr is ULongConstant){
                                ulong value = ((ULongConstant) expr).Value;

                                if (value < 9223372036854775809)
                                        return new LongConstant(-(long)value, expr.Location);
                        }
                        else if (expr is FloatConstant)
                                e = new FloatConstant (-((FloatConstant) expr).Value, expr.Location);
                        else if (expr is DoubleConstant)
                                e = new DoubleConstant (-((DoubleConstant) expr).Value, expr.Location);
                        else if (expr is DecimalConstant)
                                e = new DecimalConstant (-((DecimalConstant) expr).Value, expr.Location);
                        else if (expr is ShortConstant)
                                e = new IntConstant (-((ShortConstant) expr).Value, expr.Location);
                        else if (expr is UShortConstant)
                                e = new IntConstant (-((UShortConstant) expr).Value, expr.Location);
                        else if (expr is SByteConstant)
                                e = new IntConstant (-((SByteConstant) expr).Value, expr.Location);
                        else if (expr is ByteConstant)
                                e = new IntConstant (-((ByteConstant) expr).Value, expr.Location);
                        return e;
                }

                // <summary>
                //   This routine will attempt to simplify the unary expression when the
                //   argument is a constant.  The result is returned in `result' and the
                //   function returns true or false depending on whether a reduction
                //   was performed or not
                // </summary>
                bool Reduce (EmitContext ec, Constant e, out Expression result)
                {
                        Type expr_type = e.Type;
                        
                        switch (Oper){
                        case Operator.UnaryPlus:
                                if (expr_type == TypeManager.bool_type){
                                        result = null;
                                        Error23 (expr_type);
                                        return false;
                                }
                                
                                result = e;
                                return true;
                                
                        case Operator.UnaryNegation:
                                result = TryReduceNegative (e);
                                return result != null;
                                
                        case Operator.LogicalNot:
                                if (expr_type != TypeManager.bool_type) {
                                        result = null;
                                        Error23 (expr_type);
                                        return false;
                                }
                                
                                BoolConstant b = (BoolConstant) e;
                                result = new BoolConstant (!(b.Value), b.Location);
                                return true;
                                
                        case Operator.OnesComplement:
                                if (!((expr_type == TypeManager.int32_type) ||
                                      (expr_type == TypeManager.uint32_type) ||
                                      (expr_type == TypeManager.int64_type) ||
                                      (expr_type == TypeManager.uint64_type) ||
                                      (expr_type.IsSubclassOf (TypeManager.enum_type)))){

                                        result = null;
                                        if (Convert.ImplicitConversionExists (ec, e, TypeManager.int32_type)){
                                                result = new Cast (new TypeExpression (TypeManager.int32_type, loc), e, loc);
                                                result = result.Resolve (ec);
                                        } else if (Convert.ImplicitConversionExists (ec, e, TypeManager.uint32_type)){
                                                result = new Cast (new TypeExpression (TypeManager.uint32_type, loc), e, loc);
                                                result = result.Resolve (ec);
                                        } else if (Convert.ImplicitConversionExists (ec, e, TypeManager.int64_type)){
                                                result = new Cast (new TypeExpression (TypeManager.int64_type, loc), e, loc);
                                                result = result.Resolve (ec);
                                        } else if (Convert.ImplicitConversionExists (ec, e, TypeManager.uint64_type)){
                                                result = new Cast (new TypeExpression (TypeManager.uint64_type, loc), e, loc);
                                                result = result.Resolve (ec);
                                        }

                                        if (result == null || !(result is Constant)){
                                                result = null;
                                                Error23 (expr_type);
                                                return false;
                                        }

                                        expr_type = result.Type;
                                        e = (Constant) result;
                                }

                                if (e is EnumConstant){
                                        EnumConstant enum_constant = (EnumConstant) e;
                                        Expression reduced;
                                        
                                        if (Reduce (ec, enum_constant.Child, out reduced)){
                                                result = new EnumConstant ((Constant) reduced, enum_constant.Type);
                                                return true;
                                        } else {
                                                result = null;
                                                return false;
                                        }
                                }

                                if (expr_type == TypeManager.int32_type){
                                        result = new IntConstant (~ ((IntConstant) e).Value, e.Location);
                                } else if (expr_type == TypeManager.uint32_type){
                                        result = new UIntConstant (~ ((UIntConstant) e).Value, e.Location);
                                } else if (expr_type == TypeManager.int64_type){
                                        result = new LongConstant (~ ((LongConstant) e).Value, e.Location);
                                } else if (expr_type == TypeManager.uint64_type){
                                        result = new ULongConstant (~ ((ULongConstant) e).Value, e.Location);
                                } else {
                                        result = null;
                                        Error23 (expr_type);
                                        return false;
                                }
                                return true;

                        case Operator.AddressOf:
                                result = this;
                                return false;

                        case Operator.Indirection:
                                result = this;
                                return false;
                        }
                        throw new Exception ("Can not constant fold: " + Oper.ToString());
                }

                Expression ResolveOperator (EmitContext ec)
                {
                        //
                        // Step 1: Default operations on CLI native types.
                        //

                        // Attempt to use a constant folding operation.
                        if (Expr is Constant){
                                Expression result;
                                
                                if (Reduce (ec, (Constant) Expr, out result))
                                        return result;
                        }

                        //
                        // Step 2: Perform Operator Overload location
                        //
                        Type expr_type = Expr.Type;
                        Expression mg;
                        string op_name;
                        
                        op_name = oper_names [(int) Oper];

                        mg = MemberLookup (ec, expr_type, op_name, MemberTypes.Method, AllBindingFlags, loc);
                        
                        if (mg != null) {
                                Expression e = StaticCallExpr.MakeSimpleCall (
                                        ec, (MethodGroupExpr) mg, Expr, loc);

                                if (e == null){
                                        Error23 (expr_type);
                                        return null;
                                }
                                
                                return e;
                        }

                        // Only perform numeric promotions on:
                        // +, - 

                        if (expr_type == null)
                                return null;
                        
                        switch (Oper){
                        case Operator.LogicalNot:
                                if (expr_type != TypeManager.bool_type) {
                                        Expr = ResolveBoolean (ec, Expr, loc);
                                        if (Expr == null){
                                                Error23 (expr_type);
                                                return null;
                                        }
                                }
                                
                                type = TypeManager.bool_type;
                                return this;

                        case Operator.OnesComplement:
                                if (!((expr_type == TypeManager.int32_type) ||
                                      (expr_type == TypeManager.uint32_type) ||
                                      (expr_type == TypeManager.int64_type) ||
                                      (expr_type == TypeManager.uint64_type) ||
                                      (expr_type.IsSubclassOf (TypeManager.enum_type)))){
                                        Expression e;

                                        e = Convert.ImplicitConversion (ec, Expr, TypeManager.int32_type, loc);
                                        if (e != null)
                                                goto ok;
                                        e = Convert.ImplicitConversion (ec, Expr, TypeManager.uint32_type, loc);
                                        if (e != null)
                                                goto ok;
                                        e = Convert.ImplicitConversion (ec, Expr, TypeManager.int64_type, loc);
                                        if (e != null)
                                                goto ok;
                                        e = Convert.ImplicitConversion (ec, Expr, TypeManager.uint64_type, loc);
                                        if (e != null)
                                                goto ok;
                                        Error23 (expr_type);
                                        return null;
                                ok:
                                        Expr = e;
                                        expr_type = e.Type;
                                }

                                type = expr_type;
                                return this;

                        case Operator.AddressOf:
                                if (!ec.InUnsafe) {
                                        UnsafeError (loc); 
                                        return null;
                                }
                                
                                if (!TypeManager.VerifyUnManaged (Expr.Type, loc)){
                                        return null;
                                }

                                IVariable variable = Expr as IVariable;
                                bool is_fixed = variable != null && variable.VerifyFixed ();

                                if (!ec.InFixedInitializer && !is_fixed) {
                                        Error (212, "You can only take the address of unfixed expression inside " +
                                               "of a fixed statement initializer");
                                        return null;
                                }

                                if (ec.InFixedInitializer && is_fixed) {
                                        Error (213, "You cannot use the fixed statement to take the address of an already fixed expression");
                                        return null;
                                }

                                LocalVariableReference lr = Expr as LocalVariableReference;
                                if (lr != null){
                                        if (lr.local_info.IsCaptured){
                                                AnonymousMethod.Error_AddressOfCapturedVar (lr.Name, loc);
                                                return null;
                                        }
                                        lr.local_info.AddressTaken = true;
                                        lr.local_info.Used = true;
                                }

                                // According to the specs, a variable is considered definitely assigned if you take
                                // its address.
                                if ((variable != null) && (variable.VariableInfo != null)){
                                        variable.VariableInfo.SetAssigned (ec);
                                }

                                type = TypeManager.GetPointerType (Expr.Type);
                                return this;

                        case Operator.Indirection:
                                if (!ec.InUnsafe){
                                        UnsafeError (loc);
                                        return null;
                                }
                                
                                if (!expr_type.IsPointer){
                                        Error (193, "The * or -> operator must be applied to a pointer");
                                        return null;
                                }
                                
                                //
                                // We create an Indirection expression, because
                                // it can implement the IMemoryLocation.
                                // 
                                return new Indirection (Expr, loc);
                        
                        case Operator.UnaryPlus:
                                //
                                // A plus in front of something is just a no-op, so return the child.
                                //
                                return Expr;

                        case Operator.UnaryNegation:
                                //
                                // Deals with -literals
                                // int     operator- (int x)
                                // long    operator- (long x)
                                // float   operator- (float f)
                                // double  operator- (double d)
                                // decimal operator- (decimal d)
                                //
                                Expression expr = null;

                                //
                                // transform - - expr into expr
                                //
                                if (Expr is Unary){
                                        Unary unary = (Unary) Expr;
                                        
                                        if (unary.Oper == Operator.UnaryNegation)
                                                return unary.Expr;
                                }

                                //
                                // perform numeric promotions to int,
                                // long, double.
                                //
                                //
                                // The following is inneficient, because we call
                                // ImplicitConversion too many times.
                                //
                                // It is also not clear if we should convert to Float
                                // or Double initially.
                                //
                                if (expr_type == TypeManager.uint32_type){
                                        //
                                        // FIXME: handle exception to this rule that
                                        // permits the int value -2147483648 (-2^31) to
                                        // bt wrote as a decimal interger literal
                                        //
                                        type = TypeManager.int64_type;
                                        Expr = Convert.ImplicitConversion (ec, Expr, type, loc);
                                        return this;
                                }

                                if (expr_type == TypeManager.uint64_type){
                                        //
                                        // FIXME: Handle exception of `long value'
                                        // -92233720368547758087 (-2^63) to be wrote as
                                        // decimal integer literal.
                                        //
                                        Error23 (expr_type);
                                        return null;
                                }

                                if (expr_type == TypeManager.float_type){
                                        type = expr_type;
                                        return this;
                                }
                                
                                expr = Convert.ImplicitConversion (ec, Expr, TypeManager.int32_type, loc);
                                if (expr != null){
                                        Expr = expr;
                                        type = expr.Type;
                                        return this;
                                } 

                                expr = Convert.ImplicitConversion (ec, Expr, TypeManager.int64_type, loc);
                                if (expr != null){
                                        Expr = expr;
                                        type = expr.Type;
                                        return this;
                                }

                                expr = Convert.ImplicitConversion (ec, Expr, TypeManager.double_type, loc);
                                if (expr != null){
                                        Expr = expr;
                                        type = expr.Type;
                                        return this;
                                }
                                
                                Error23 (expr_type);
                                return null;
                        }

                        Error (187, "No such operator '" + OperName (Oper) + "' defined for type '" +
                               TypeManager.CSharpName (expr_type) + "'");
                        return null;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        if (Oper == Operator.AddressOf) {
                                Expr = Expr.DoResolveLValue (ec, new EmptyExpression ());

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

                        eclass = ExprClass.Value;
                        return ResolveOperator (ec);
                }

                public override Expression DoResolveLValue (EmitContext ec, Expression right)
                {
                        if (Oper == Operator.Indirection)
                                return DoResolve (ec);

                        return null;
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        switch (Oper) {
                        case Operator.UnaryPlus:
                                throw new Exception ("This should be caught by Resolve");
                                
                        case Operator.UnaryNegation:
                                if (ec.CheckState) {
                                        ig.Emit (OpCodes.Ldc_I4_0);
                                        if (type == TypeManager.int64_type)
                                                ig.Emit (OpCodes.Conv_U8);
                                        Expr.Emit (ec);
                                        ig.Emit (OpCodes.Sub_Ovf);
                                } else {
                                        Expr.Emit (ec);
                                        ig.Emit (OpCodes.Neg);
                                }
                                
                                break;
                                
                        case Operator.LogicalNot:
                                Expr.Emit (ec);
                                ig.Emit (OpCodes.Ldc_I4_0);
                                ig.Emit (OpCodes.Ceq);
                                break;
                                
                        case Operator.OnesComplement:
                                Expr.Emit (ec);
                                ig.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 ());
                        }
                }

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

                public override string ToString ()
                {
                        return "Unary (" + Oper + ", " + Expr + ")";
                }
                
        }

        //
        // 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, IVariable {
                Expression expr;
                LocalTemporary temporary;
                bool prepared;
                
                public Indirection (Expression expr, Location l)
                {
                        this.expr = expr;
                        type = TypeManager.HasElementType (expr.Type) ? TypeManager.GetElementType (expr.Type) : expr.Type;
                        eclass = ExprClass.Variable;
                        loc = l;
                }
                
                public override void Emit (EmitContext ec)
                {
                        if (!prepared)
                                expr.Emit (ec);
                        
                        LoadFromPtr (ec.ig, Type);
                }

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

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

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

                public override Expression DoResolve (EmitContext ec)
                {
                        //
                        // Born fully resolved
                        //
                        return this;
                }
                
                public override string ToString ()
                {
                        return "*(" + expr + ")";
                }

                #region IVariable Members

                public VariableInfo VariableInfo {
                        get {
                                return null;
                        }
                }

                public bool VerifyFixed ()
                {
                        // A pointer-indirection is always fixed.
                        return true;
                }

                #endregion
        }
        
        /// <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 {
                [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 = false;
                bool recurse = false;
                
                Expression expr;

                //
                // This is expensive for the simplest case.
                //
                StaticCallExpr method;
                        
                public UnaryMutator (Mode m, Expression e, Location l)
                {
                        mode = m;
                        loc = l;
                        expr = e;
                }

                static string OperName (Mode mode)
                {
                        return (mode == Mode.PreIncrement || mode == Mode.PostIncrement) ?
                                "++" : "--";
                }
                
                /// <summary>
                ///   Returns whether an object of type `t' can be incremented
                ///   or decremented with add/sub (ie, basically whether we can
                ///   use pre-post incr-decr operations on it, but it is not a
                ///   System.Decimal, which we require operator overloading to catch)
                /// </summary>
                static bool IsIncrementableNumber (Type t)
                {
                        return (t == TypeManager.sbyte_type) ||
                                (t == TypeManager.byte_type) ||
                                (t == TypeManager.short_type) ||
                                (t == TypeManager.ushort_type) ||
                                (t == TypeManager.int32_type) ||
                                (t == TypeManager.uint32_type) ||
                                (t == TypeManager.int64_type) ||
                                (t == TypeManager.uint64_type) ||
                                (t == TypeManager.char_type) ||
                                (t.IsSubclassOf (TypeManager.enum_type)) ||
                                (t == TypeManager.float_type) ||
                                (t == TypeManager.double_type) ||
                                (t.IsPointer && t != TypeManager.void_ptr_type);
                }

                Expression ResolveOperator (EmitContext ec)
                {
                        Type expr_type = expr.Type;

                        //
                        // Step 1: Perform Operator Overload location
                        //
                        Expression mg;
                        string op_name;
                        
                        if (mode == Mode.PreIncrement || mode == Mode.PostIncrement)
                                op_name = "op_Increment";
                        else 
                                op_name = "op_Decrement";

                        mg = MemberLookup (ec, expr_type, op_name, MemberTypes.Method, AllBindingFlags, loc);

                        if (mg != null) {
                                method = StaticCallExpr.MakeSimpleCall (
                                        ec, (MethodGroupExpr) mg, expr, loc);

                                type = method.Type;
                        } else if (!IsIncrementableNumber (expr_type)) {
                                Error (187, "No such operator '" + OperName (mode) + "' defined for type '" +
                                       TypeManager.CSharpName (expr_type) + "'");
                                   return null;
                        }

                        //
                        // 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
                        //
                        type = expr_type;
                        if (expr.eclass == ExprClass.Variable){
                                LocalVariableReference var = expr as LocalVariableReference;
                                if ((var != null) && var.IsReadOnly) {
                                        Error (1604, "cannot assign to `" + var.Name + "' because it is readonly");
                                        return null;
                                }
                        } else if (expr.eclass == ExprClass.IndexerAccess || expr.eclass == ExprClass.PropertyAccess){
                                expr = expr.ResolveLValue (ec, this, Location);
                                if (expr == null)
                                        return null;
                        } else {
                                expr.Error_UnexpectedKind (ec, "variable, indexer or property access", loc);
                                return null;
                        }

                        return this;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        expr = expr.Resolve (ec);
                        
                        if (expr == null)
                                return null;

                        eclass = ExprClass.Value;
                        return ResolveOperator (ec);
                }

                static int PtrTypeSize (Type t)
                {
                        return GetTypeSize (TypeManager.GetElementType (t));
                }

                //
                // Loads the proper "1" into the stack based on the type, then it emits the
                // opcode for the operation requested
                //
                void LoadOneAndEmitOp (EmitContext ec, Type t)
                {
                        //
                        // Measure if getting the typecode and using that is more/less efficient
                        // that comparing types.  t.GetTypeCode() is an internal call.
                        //
                        ILGenerator ig = ec.ig;
                                                     
                        if (t == TypeManager.uint64_type || t == TypeManager.int64_type)
                                LongConstant.EmitLong (ig, 1);
                        else if (t == TypeManager.double_type)
                                ig.Emit (OpCodes.Ldc_R8, 1.0);
                        else if (t == TypeManager.float_type)
                                ig.Emit (OpCodes.Ldc_R4, 1.0F);
                        else if (t.IsPointer){
                                int n = PtrTypeSize (t);
                                
                                if (n == 0)
                                        ig.Emit (OpCodes.Sizeof, t);
                                else
                                        IntConstant.EmitInt (ig, n);
                        } else 
                                ig.Emit (OpCodes.Ldc_I4_1);

                        //
                        // Now emit the operation
                        //
                        if (ec.CheckState){
                                if (t == TypeManager.int32_type ||
                                    t == TypeManager.int64_type){
                                        if ((mode & Mode.IsDecrement) != 0)
                                                ig.Emit (OpCodes.Sub_Ovf);
                                        else
                                                ig.Emit (OpCodes.Add_Ovf);
                                } else if (t == TypeManager.uint32_type ||
                                           t == TypeManager.uint64_type){
                                        if ((mode & Mode.IsDecrement) != 0)
                                                ig.Emit (OpCodes.Sub_Ovf_Un);
                                        else
                                                ig.Emit (OpCodes.Add_Ovf_Un);
                                } else {
                                        if ((mode & Mode.IsDecrement) != 0)
                                                ig.Emit (OpCodes.Sub_Ovf);
                                        else
                                                ig.Emit (OpCodes.Add_Ovf);
                                }
                        } else {
                                if ((mode & Mode.IsDecrement) != 0)
                                        ig.Emit (OpCodes.Sub);
                                else
                                        ig.Emit (OpCodes.Add);
                        }

                        if (t == TypeManager.sbyte_type){
                                if (ec.CheckState)
                                        ig.Emit (OpCodes.Conv_Ovf_I1);
                                else
                                        ig.Emit (OpCodes.Conv_I1);
                        } else if (t == TypeManager.byte_type){
                                if (ec.CheckState)
                                        ig.Emit (OpCodes.Conv_Ovf_U1);
                                else
                                        ig.Emit (OpCodes.Conv_U1);
                        } else if (t == TypeManager.short_type){
                                if (ec.CheckState)
                                        ig.Emit (OpCodes.Conv_Ovf_I2);
                                else
                                        ig.Emit (OpCodes.Conv_I2);
                        } else if (t == TypeManager.ushort_type || t == TypeManager.char_type){
                                if (ec.CheckState)
                                        ig.Emit (OpCodes.Conv_Ovf_U2);
                                else
                                        ig.Emit (OpCodes.Conv_U2);
                        }
                        
                }
                
                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));
                                if (method == null)
                                        LoadOneAndEmitOp (ec, expr.Type);
                                else
                                        ec.ig.Emit (OpCodes.Call, method.Method);
                                recurse = false;
                                return;
                        }
                        
                        EmitCode (ec, true);
                }
                
                public override void EmitStatement (EmitContext ec)
                {
                        EmitCode (ec, false);
                }
        }

        /// <summary>
        ///   Base class for the `Is' and `As' classes. 
        /// </summary>
        ///
        /// <remarks>
        ///   FIXME: Split this in two, and we get to save the `Operator' Oper
        ///   size. 
        /// </remarks>
        public abstract class Probe : Expression {
                public Expression ProbeType;
                protected Expression expr;
                protected Type probe_type;
                
                public Probe (Expression expr, Expression probe_type, Location l)
                {
                        ProbeType = probe_type;
                        loc = l;
                        this.expr = expr;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        TypeExpr texpr = ProbeType.ResolveAsTypeTerminal (ec, false);
                        if (texpr == null)
                                return null;
                        probe_type = texpr.ResolveType (ec);

                        expr = expr.Resolve (ec);
                        if (expr == null)
                                return null;
                        
                        if (expr.Type.IsPointer) {
                                Report.Error (244, loc, "\"is\" or \"as\" are not valid on pointer types");
                                return null;
                        }
                        return this;
                }
        }

        /// <summary>
        ///   Implementation of the `is' operator.
        /// </summary>
        public class Is : Probe {
                public Is (Expression expr, Expression probe_type, Location l)
                        : base (expr, probe_type, l)
                {
                }

                enum Action {
                        AlwaysTrue, AlwaysNull, AlwaysFalse, LeaveOnStack, Probe
                }

                Action action;
                
                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;

                        expr.Emit (ec);

                        switch (action){
                        case Action.AlwaysFalse:
                                ig.Emit (OpCodes.Pop);
                                IntConstant.EmitInt (ig, 0);
                                return;
                        case Action.AlwaysTrue:
                                ig.Emit (OpCodes.Pop);
                                IntConstant.EmitInt (ig, 1);
                                return;
                        case Action.LeaveOnStack:
                                // the `e != null' rule.
                                ig.Emit (OpCodes.Ldnull);
                                ig.Emit (OpCodes.Ceq);
                                ig.Emit (OpCodes.Ldc_I4_0);
                                ig.Emit (OpCodes.Ceq);
                                return;
                        case Action.Probe:
                                ig.Emit (OpCodes.Isinst, probe_type);
                                ig.Emit (OpCodes.Ldnull);
                                ig.Emit (OpCodes.Cgt_Un);
                                return;
                        }
                        throw new Exception ("never reached");
                }
                
                public override void EmitBranchable (EmitContext ec, Label target, bool onTrue)
                {
                        ILGenerator ig = ec.ig;

                        switch (action){
                        case Action.AlwaysFalse:
                                if (! onTrue)
                                        ig.Emit (OpCodes.Br, target);
                                
                                return;
                        case Action.AlwaysTrue:
                                if (onTrue)
                                        ig.Emit (OpCodes.Br, target);
                                
                                return;
                        case Action.LeaveOnStack:
                                // the `e != null' rule.
                                expr.Emit (ec);
                                ig.Emit (onTrue ? OpCodes.Brtrue : OpCodes.Brfalse, target);
                                return;
                        case Action.Probe:
                                expr.Emit (ec);
                                ig.Emit (OpCodes.Isinst, probe_type);
                                ig.Emit (onTrue ? OpCodes.Brtrue : OpCodes.Brfalse, target);
                                return;
                        }
                        throw new Exception ("never reached");
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        Expression e = base.DoResolve (ec);

                        if ((e == null) || (expr == null))
                                return null;

                        Type etype = expr.Type;
                        bool warning_always_matches = false;
                        bool warning_never_matches = false;

                        type = TypeManager.bool_type;
                        eclass = ExprClass.Value;

                        //
                        // First case, if at compile time, there is an implicit conversion
                        // then e != null (objects) or true (value types)
                        //
                        e = Convert.ImplicitConversionStandard (ec, expr, probe_type, loc);
                        if (e != null && !(e is NullCast)){
                                expr = e;
                                if (etype.IsValueType)
                                        action = Action.AlwaysTrue;
                                else
                                        action = Action.LeaveOnStack;

                                warning_always_matches = true;
                        } else if (Convert.ExplicitReferenceConversionExists (etype, probe_type)){
                                //
                                // Second case: explicit reference convresion
                                //
                                if (expr is NullLiteral)
                                        action = Action.AlwaysFalse;
                                else
                                        action = Action.Probe;
                        } else {
                                action = Action.AlwaysFalse;
                                warning_never_matches = true;
                        }
                        
                        if (warning_always_matches)
                                Report.Warning (183, 1, loc, "The given expression is always of the provided (`{0}') type", TypeManager.CSharpName (probe_type));
                        else if (warning_never_matches){
                                if (!(probe_type.IsInterface || expr.Type.IsInterface))
                                        Report.Warning (184, 1, loc, "The given expression is never of the provided (`{0}') type", TypeManager.CSharpName (probe_type));
                        }

                        return this;
                }                               
        }

        /// <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)
                {
                }

                bool do_isinst = false;
                Expression resolved_type;
                
                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;

                        expr.Emit (ec);

                        if (do_isinst)
                                ig.Emit (OpCodes.Isinst, probe_type);
                }

                static void Error_CannotConvertType (Type source, Type target, Location loc)
                {
                        Report.Error (39, loc, "Cannot convert type `{0}' to `{1}' via a built-in conversion",
                                TypeManager.CSharpName (source),
                                TypeManager.CSharpName (target));
                }
                
                public override Expression DoResolve (EmitContext ec)
                {
                        if (resolved_type == null) {
                                resolved_type = base.DoResolve (ec);

                                if (resolved_type == null)
                                        return null;
                        }

                        type = probe_type;
                        eclass = ExprClass.Value;
                        Type etype = expr.Type;

                        if (TypeManager.IsValueType (probe_type)){
                                Report.Error (77, loc, "The as operator must be used with a reference type (`" +
                                              TypeManager.CSharpName (probe_type) + "' is a value type)");
                                return null;
                        
                        }
                        
                        Expression e = Convert.ImplicitConversion (ec, expr, probe_type, loc);
                        if (e != null){
                                expr = e;
                                do_isinst = false;
                                return this;
                        }

                        if (Convert.ExplicitReferenceConversionExists (etype, probe_type)){
                                do_isinst = true;
                                return this;
                        }

                        Error_CannotConvertType (etype, probe_type, loc);
                        return null;
                }                               
        }
        
        /// <summary>
        ///   This represents a typecast in the source language.
        ///
        ///   FIXME: Cast expressions have an unusual set of parsing
        ///   rules, we need to figure those out.
        /// </summary>
        public class Cast : Expression {
                Expression target_type;
                Expression expr;
                        
                public Cast (Expression cast_type, Expression expr)
                        : this (cast_type, expr, cast_type.Location)
                {
                }

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

                public Expression TargetType {
                        get {
                                return target_type;
                        }
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                        set {
                                expr = value;
                        }
                }
                
                public override Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        expr = expr.DoResolveLValue (ec, right_side);
                        if (expr == null)
                                return null;

                        return ResolveRest (ec);
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        expr = expr.Resolve (ec);
                        if (expr == null)
                                return null;

                        return ResolveRest (ec);
                }

                Expression ResolveRest (EmitContext ec)
                {
                        TypeExpr target = target_type.ResolveAsTypeTerminal (ec, false);
                        if (target == null)
                                return null;

                        type = target.ResolveType (ec);

                        if (type.IsAbstract && type.IsSealed) {
                                Report.Error (716, loc, "Cannot convert to static type `{0}'", TypeManager.CSharpName (type));
                                return null;
                        }

                        eclass = ExprClass.Value;

                        Constant c = expr as Constant;
                        if (c != null) {
                                c = c.TryReduce (ec, type, loc);
                                if (c != null)
                                        return c;
                        }

                        if (type.IsPointer && !ec.InUnsafe) {
                                UnsafeError (loc);
                                return null;
                        }
                        expr = Convert.ExplicitConversion (ec, expr, type, loc);
                        return expr;
                }
                
                public override void Emit (EmitContext ec)
                {
                        //
                        // This one will never happen
                        //
                        throw new Exception ("Should not happen");
                }
        }

        /// <summary>
        ///   Binary operators
        /// </summary>
        public class Binary : Expression {
                public enum Operator : byte {
                        Multiply, Division, Modulus,
                        Addition, Subtraction,
                        LeftShift, RightShift,
                        LessThan, GreaterThan, LessThanOrEqual, GreaterThanOrEqual, 
                        Equality, Inequality,
                        BitwiseAnd,
                        ExclusiveOr,
                        BitwiseOr,
                        LogicalAnd,
                        LogicalOr,
                        TOP
                }

                Operator oper;
                Expression left, right;

                // This must be kept in sync with Operator!!!
                public static readonly string [] oper_names;
                
                static Binary ()
                {
                        oper_names = new string [(int) Operator.TOP];

                        oper_names [(int) Operator.Multiply] = "op_Multiply";
                        oper_names [(int) Operator.Division] = "op_Division";
                        oper_names [(int) Operator.Modulus] = "op_Modulus";
                        oper_names [(int) Operator.Addition] = "op_Addition";
                        oper_names [(int) Operator.Subtraction] = "op_Subtraction";
                        oper_names [(int) Operator.LeftShift] = "op_LeftShift";
                        oper_names [(int) Operator.RightShift] = "op_RightShift";
                        oper_names [(int) Operator.LessThan] = "op_LessThan";
                        oper_names [(int) Operator.GreaterThan] = "op_GreaterThan";
                        oper_names [(int) Operator.LessThanOrEqual] = "op_LessThanOrEqual";
                        oper_names [(int) Operator.GreaterThanOrEqual] = "op_GreaterThanOrEqual";
                        oper_names [(int) Operator.Equality] = "op_Equality";
                        oper_names [(int) Operator.Inequality] = "op_Inequality";
                        oper_names [(int) Operator.BitwiseAnd] = "op_BitwiseAnd";
                        oper_names [(int) Operator.BitwiseOr] = "op_BitwiseOr";
                        oper_names [(int) Operator.ExclusiveOr] = "op_ExclusiveOr";
                        oper_names [(int) Operator.LogicalOr] = "op_LogicalOr";
                        oper_names [(int) Operator.LogicalAnd] = "op_LogicalAnd";
                }

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

                public Operator Oper {
                        get {
                                return oper;
                        }
                        set {
                                oper = value;
                        }
                }
                
                public Expression Left {
                        get {
                                return left;
                        }
                        set {
                                left = value;
                        }
                }

                public Expression Right {
                        get {
                                return right;
                        }
                        set {
                                right = value;
                        }
                }


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

                        return oper.ToString ();
                }

                public override string ToString ()
                {
                        return "operator " + OperName (oper) + "(" + left.ToString () + ", " +
                                right.ToString () + ")";
                }
                
                Expression ForceConversion (EmitContext ec, Expression expr, Type target_type)
                {
                        if (expr.Type == target_type)
                                return expr;

                        return Convert.ImplicitConversion (ec, expr, target_type, loc);
                }

                public static void Error_OperatorAmbiguous (Location loc, Operator oper, Type l, Type r)
                {
                        Report.Error (
                                34, loc, "Operator `" + OperName (oper) 
                                + "' is ambiguous on operands of type `"
                                + TypeManager.CSharpName (l) + "' "
                                + "and `" + TypeManager.CSharpName (r)
                                + "'");
                }

                bool IsOfType (EmitContext ec, Type l, Type r, Type t, bool check_user_conversions)
                {
                        if ((l == t) || (r == t))
                                return true;

                        if (!check_user_conversions)
                                return false;

                        if (Convert.ImplicitUserConversionExists (ec, l, t))
                                return true;
                        else if (Convert.ImplicitUserConversionExists (ec, r, t))
                                return true;
                        else
                                return false;
                }

                //
                // Note that handling the case l == Decimal || r == Decimal
                // is taken care of by the Step 1 Operator Overload resolution.
                //
                // If `check_user_conv' is true, we also check whether a user-defined conversion
                // exists.  Note that we only need to do this if both arguments are of a user-defined
                // type, otherwise ConvertImplict() already finds the user-defined conversion for us,
                // so we don't explicitly check for performance reasons.
                //
                bool DoNumericPromotions (EmitContext ec, Type l, Type r, Expression lexpr, Expression rexpr, bool check_user_conv)
                {
                        if (IsOfType (ec, l, r, TypeManager.double_type, check_user_conv)){
                                //
                                // If either operand is of type double, the other operand is
                                // conveted to type double.
                                //
                                if (r != TypeManager.double_type)
                                        right = Convert.ImplicitConversion (ec, right, TypeManager.double_type, loc);
                                if (l != TypeManager.double_type)
                                        left = Convert.ImplicitConversion (ec, left, TypeManager.double_type, loc);
                                
                                type = TypeManager.double_type;
                        } else if (IsOfType (ec, l, r, TypeManager.float_type, check_user_conv)){
                                //
                                // if either operand is of type float, the other operand is
                                // converted to type float.
                                //
                                if (r != TypeManager.double_type)
                                        right = Convert.ImplicitConversion (ec, right, TypeManager.float_type, loc);
                                if (l != TypeManager.double_type)
                                        left = Convert.ImplicitConversion (ec, left, TypeManager.float_type, loc);
                                type = TypeManager.float_type;
                        } else if (IsOfType (ec, l, r, TypeManager.uint64_type, check_user_conv)){
                                Expression e;
                                Type other;
                                //
                                // If either operand is of type ulong, the other operand is
                                // converted to type ulong.  or an error ocurrs if the other
                                // operand is of type sbyte, short, int or long
                                //
                                if (l == TypeManager.uint64_type){
                                        if (r != TypeManager.uint64_type){
                                                if (right is IntConstant){
                                                        IntConstant ic = (IntConstant) right;
                                                        
                                                        e = Convert.TryImplicitIntConversion (l, ic);
                                                        if (e != null)
                                                                right = e;
                                                } else if (right is LongConstant){
                                                        long ll = ((LongConstant) right).Value;

                                                        if (ll >= 0)
                                                                right = new ULongConstant ((ulong) ll, right.Location);
                                                } else {
                                                        e = Convert.ImplicitNumericConversion (ec, right, l);
                                                        if (e != null)
                                                                right = e;
                                                }
                                        }
                                        other = right.Type;
                                } else {
                                        if (left is IntConstant){
                                                e = Convert.TryImplicitIntConversion (r, (IntConstant) left);
                                                if (e != null)
                                                        left = e;
                                        } else if (left is LongConstant){
                                                long ll = ((LongConstant) left).Value;
                                                
                                                if (ll > 0)
                                                        left = new ULongConstant ((ulong) ll, right.Location);
                                        } else {
                                                e = Convert.ImplicitNumericConversion (ec, left, r);
                                                if (e != null)
                                                        left = e;
                                        }
                                        other = left.Type;
                                }

                                if ((other == TypeManager.sbyte_type) ||
                                    (other == TypeManager.short_type) ||
                                    (other == TypeManager.int32_type) ||
                                    (other == TypeManager.int64_type))
                                        Error_OperatorAmbiguous (loc, oper, l, r);
                                else {
                                        left = ForceConversion (ec, left, TypeManager.uint64_type);
                                        right = ForceConversion (ec, right, TypeManager.uint64_type);
                                }
                                type = TypeManager.uint64_type;
                        } else if (IsOfType (ec, l, r, TypeManager.int64_type, check_user_conv)){
                                //
                                // If either operand is of type long, the other operand is converted
                                // to type long.
                                //
                                if (l != TypeManager.int64_type)
                                        left = Convert.ImplicitConversion (ec, left, TypeManager.int64_type, loc);
                                if (r != TypeManager.int64_type)
                                        right = Convert.ImplicitConversion (ec, right, TypeManager.int64_type, loc);
                                
                                type = TypeManager.int64_type;
                        } else if (IsOfType (ec, l, r, TypeManager.uint32_type, check_user_conv)){
                                //
                                // If either operand is of type uint, and the other
                                // operand is of type sbyte, short or int, othe operands are
                                // converted to type long (unless we have an int constant).
                                //
                                Type other = null;
                                
                                if (l == TypeManager.uint32_type){
                                        if (right is IntConstant){
                                                IntConstant ic = (IntConstant) right;
                                                int val = ic.Value;
                                                
                                                if (val >= 0){
                                                        right = new UIntConstant ((uint) val, ic.Location);
                                                        type = l;
                                                        
                                                        return true;
                                                }
                                        }
                                        other = r;
                                } else if (r == TypeManager.uint32_type){
                                        if (left is IntConstant){
                                                IntConstant ic = (IntConstant) left;
                                                int val = ic.Value;
                                                
                                                if (val >= 0){
                                                        left = new UIntConstant ((uint) val, ic.Location);
                                                        type = r;
                                                        return true;
                                                }
                                        }
                                        
                                        other = l;
                                }

                                if ((other == TypeManager.sbyte_type) ||
                                    (other == TypeManager.short_type) ||
                                    (other == TypeManager.int32_type)){
                                        left = ForceConversion (ec, left, TypeManager.int64_type);
                                        right = ForceConversion (ec, right, TypeManager.int64_type);
                                        type = TypeManager.int64_type;
                                } else {
                                        //
                                        // if either operand is of type uint, the other
                                        // operand is converd to type uint
                                        //
                                        left = ForceConversion (ec, left, TypeManager.uint32_type);
                                        right = ForceConversion (ec, right, TypeManager.uint32_type);
                                        type = TypeManager.uint32_type;
                                } 
                        } else if (l == TypeManager.decimal_type || r == TypeManager.decimal_type){
                                if (l != TypeManager.decimal_type)
                                        left = Convert.ImplicitConversion (ec, left, TypeManager.decimal_type, loc);

                                if (r != TypeManager.decimal_type)
                                        right = Convert.ImplicitConversion (ec, right, TypeManager.decimal_type, loc);
                                type = TypeManager.decimal_type;
                        } else {
                                left = ForceConversion (ec, left, TypeManager.int32_type);
                                right = ForceConversion (ec, right, TypeManager.int32_type);

                                bool strConv =
                                        Convert.ImplicitConversionExists (ec, lexpr, TypeManager.string_type) &&
                                        Convert.ImplicitConversionExists (ec, rexpr, TypeManager.string_type);
                                if (strConv && left != null && right != null)
                                        Error_OperatorAmbiguous (loc, oper, l, r);

                                type = TypeManager.int32_type;
                        }

                        return (left != null) && (right != null);
                }

                static public void Error_OperatorCannotBeApplied (Location loc, string name, Type l, Type r)
                {
                        Error_OperatorCannotBeApplied (loc, name, TypeManager.CSharpName (l), TypeManager.CSharpName (r));
                }

                public static void Error_OperatorCannotBeApplied (Location loc, string name, string left, string right)
                {
                        Report.Error (19, loc, "Operator `{0}' cannot be applied to operands of type `{1}' and `{2}'",
                                name, left, right);
                }
                
                void Error_OperatorCannotBeApplied ()
                {
                        Error_OperatorCannotBeApplied (Location, OperName (oper), left.GetSignatureForError (), right.GetSignatureForError ());
                }

                static bool is_unsigned (Type t)
                {
                        return (t == TypeManager.uint32_type || t == TypeManager.uint64_type ||
                                t == TypeManager.short_type || t == TypeManager.byte_type);
                }

                static bool is_user_defined (Type t)
                {
                        if (t.IsSubclassOf (TypeManager.value_type) &&
                            (!TypeManager.IsBuiltinType (t) || t == TypeManager.decimal_type))
                                return true;
                        else
                                return false;
                }

                Expression Make32or64 (EmitContext ec, Expression e)
                {
                        Type t= e.Type;
                        
                        if (t == TypeManager.int32_type || t == TypeManager.uint32_type ||
                            t == TypeManager.int64_type || t == TypeManager.uint64_type)
                                return e;
                        Expression ee = Convert.ImplicitConversion (ec, e, TypeManager.int32_type, loc);
                        if (ee != null)
                                return ee;
                        ee = Convert.ImplicitConversion (ec, e, TypeManager.uint32_type, loc);
                        if (ee != null)
                                return ee;
                        ee = Convert.ImplicitConversion (ec, e, TypeManager.int64_type, loc);
                        if (ee != null)
                                return ee;
                        ee = Convert.ImplicitConversion (ec, e, TypeManager.uint64_type, loc);
                        if (ee != null)
                                return ee;
                        return null;
                }
                                        
                Expression CheckShiftArguments (EmitContext ec)
                {
                        Expression e;

                        e = ForceConversion (ec, right, TypeManager.int32_type);
                        if (e == null){
                                Error_OperatorCannotBeApplied ();
                                return null;
                        }
                        right = e;

                        if (((e = Convert.ImplicitConversion (ec, left, TypeManager.int32_type, loc)) != null) ||
                            ((e = Convert.ImplicitConversion (ec, left, TypeManager.uint32_type, loc)) != null) ||
                            ((e = Convert.ImplicitConversion (ec, left, TypeManager.int64_type, loc)) != null) ||
                            ((e = Convert.ImplicitConversion (ec, left, TypeManager.uint64_type, loc)) != null)){
                                left = e;
                                type = e.Type;

                                if (type == TypeManager.int32_type || type == TypeManager.uint32_type){
                                        right = new Binary (Binary.Operator.BitwiseAnd, right, new IntConstant (31, loc));
                                        right = right.DoResolve (ec);
                                } else {
                                        right = new Binary (Binary.Operator.BitwiseAnd, right, new IntConstant (63, loc));
                                        right = right.DoResolve (ec);
                                }

                                return this;
                        }
                        Error_OperatorCannotBeApplied ();
                        return null;
                }

                //
                // This is used to check if a test 'x == null' can be optimized to a reference equals,
                // i.e., not invoke op_Equality.
                //
                static bool EqualsNullIsReferenceEquals (Type t)
                {
                        return t == TypeManager.object_type || t == TypeManager.string_type ||
                                t == TypeManager.delegate_type || t.IsSubclassOf (TypeManager.delegate_type);
                }

                static void Warning_UnintendedReferenceComparison (Location loc, string side, Type type)
                {
                        Report.Warning ((side == "left" ? 252 : 253), 2, loc,
                                "Possible unintended reference comparison; to get a value comparison, " +
                                "cast the {0} hand side to type `{1}'.", side, TypeManager.CSharpName (type));
                }

                Expression ResolveOperator (EmitContext ec)
                {
                        Type l = left.Type;
                        Type r = right.Type;

                        if (oper == Operator.Equality || oper == Operator.Inequality){
                                //
                                // Optimize out call to op_Equality in a few cases.
                                //
                                if ((l == TypeManager.null_type && EqualsNullIsReferenceEquals (r)) ||
                                    (r == TypeManager.null_type && EqualsNullIsReferenceEquals (l))) {
                                  
                                        Type = TypeManager.bool_type;
                                        
                                        return this;
                                }

                                // IntPtr equality
                                if (l == TypeManager.intptr_type && r == TypeManager.intptr_type) {
                                        Type = TypeManager.bool_type;
                                        
                                        return this;
                                }
                        }

                        //
                        // Do not perform operator overload resolution when both sides are
                        // built-in types
                        //
                        Expression left_operators = null, right_operators = null;
                        if (!(TypeManager.IsPrimitiveType (l) && TypeManager.IsPrimitiveType (r))){
                                //
                                // Step 1: Perform Operator Overload location
                                //
                                string op = oper_names [(int) oper];
                                
                                MethodGroupExpr union;
                                left_operators = MemberLookup (ec, l, op, MemberTypes.Method, AllBindingFlags, loc);
                                if (r != l){
                                        right_operators = MemberLookup (
                                                ec, r, op, MemberTypes.Method, AllBindingFlags, loc);
                                        union = Invocation.MakeUnionSet (left_operators, right_operators, loc);
                                } else
                                        union = (MethodGroupExpr) left_operators;
                                
                                if (union != null) {
                                        ArrayList args = new ArrayList (2);
                                        args.Add (new Argument (left, Argument.AType.Expression));
                                        args.Add (new Argument (right, Argument.AType.Expression));
                                        
                                        MethodBase method = Invocation.OverloadResolve (
                                                ec, union, args, true, Location.Null);

                                        if (method != null) {
                                                MethodInfo mi = (MethodInfo) method;
                                                
                                                return new BinaryMethod (mi.ReturnType, method, args);
                                        }
                                }
                        }
                        
                        //
                        // Step 0: String concatenation (because overloading will get this wrong)
                        //
                        if (oper == Operator.Addition){
                                //
                                // If any of the arguments is a string, cast to string
                                //
                                
                                // Simple constant folding
                                if (left is StringConstant && right is StringConstant)
                                        return new StringConstant (((StringConstant) left).Value + ((StringConstant) right).Value, left.Location);
                                
                                if (l == TypeManager.string_type || r == TypeManager.string_type) {

                                        if (r == TypeManager.void_type || l == TypeManager.void_type) {
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                        
                                        // try to fold it in on the left
                                        if (left is StringConcat) {

                                                //
                                                // We have to test here for not-null, since we can be doubly-resolved
                                                // take care of not appending twice
                                                //
                                                if (type == null){
                                                        type = TypeManager.string_type;
                                                        ((StringConcat) left).Append (ec, right);
                                                        return left.Resolve (ec);
                                                } else {
                                                        return left;
                                                }
                                        }
                                        
                                        // Otherwise, start a new concat expression
                                        return new StringConcat (ec, loc, left, right).Resolve (ec);
                                }

                                //
                                // Transform a + ( - b) into a - b
                                //
                                if (right is Unary){
                                        Unary right_unary = (Unary) right;

                                        if (right_unary.Oper == Unary.Operator.UnaryNegation){
                                                oper = Operator.Subtraction;
                                                right = right_unary.Expr;
                                                r = right.Type;
                                        }
                                }
                        }

                        if (oper == Operator.Equality || oper == Operator.Inequality){
                                if (l == TypeManager.bool_type || r == TypeManager.bool_type){
                                        if (r != TypeManager.bool_type || l != TypeManager.bool_type){
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                        
                                        type = TypeManager.bool_type;
                                        return this;
                                }

                                if (l.IsPointer || r.IsPointer) {
                                        if (l.IsPointer && r.IsPointer) {
                                                type = TypeManager.bool_type;
                                                return this;
                                        }

                                        if (l.IsPointer && r == TypeManager.null_type) {
                                                right = new EmptyCast (NullPointer.Null, l);
                                                type = TypeManager.bool_type;
                                                return this;
                                        }

                                        if (r.IsPointer && l == TypeManager.null_type) {
                                                left = new EmptyCast (NullPointer.Null, r);
                                                type = TypeManager.bool_type;
                                                return this;
                                        }
                                }

                                //
                                // operator != (object a, object b)
                                // operator == (object a, object b)
                                //
                                // For this to be used, both arguments have to be reference-types.
                                // Read the rationale on the spec (14.9.6)
                                //
                                if (!(l.IsValueType || r.IsValueType)){
                                        type = TypeManager.bool_type;

                                        if (l == r)
                                                return this;
                                        
                                        //
                                        // Also, a standard conversion must exist from either one
                                        //
                                        bool left_to_right =
                                                Convert.ImplicitStandardConversionExists (ec, left, r);
                                        bool right_to_left = !left_to_right &&
                                                Convert.ImplicitStandardConversionExists (ec, right, l);

                                        if (!left_to_right && !right_to_left) {
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }

                                        if (left_to_right && left_operators != null &&
                                            RootContext.WarningLevel >= 2) {
                                                ArrayList args = new ArrayList (2);
                                                args.Add (new Argument (left, Argument.AType.Expression));
                                                args.Add (new Argument (left, Argument.AType.Expression));
                                                MethodBase method = Invocation.OverloadResolve (
                                                        ec, (MethodGroupExpr) left_operators, args, true, Location.Null);
                                                if (method != null)
                                                        Warning_UnintendedReferenceComparison (loc, "right", l);
                                        }

                                        if (right_to_left && right_operators != null &&
                                            RootContext.WarningLevel >= 2) {
                                                ArrayList args = new ArrayList (2);
                                                args.Add (new Argument (right, Argument.AType.Expression));
                                                args.Add (new Argument (right, Argument.AType.Expression));
                                                MethodBase method = Invocation.OverloadResolve (
                                                        ec, (MethodGroupExpr) right_operators, args, true, Location.Null);
                                                if (method != null)
                                                        Warning_UnintendedReferenceComparison (loc, "left", r);
                                        }

                                        //
                                        // We are going to have to convert to an object to compare
                                        //
                                        if (l != TypeManager.object_type)
                                                left = new EmptyCast (left, TypeManager.object_type);
                                        if (r != TypeManager.object_type)
                                                right = new EmptyCast (right, TypeManager.object_type);

                                        //
                                        // FIXME: CSC here catches errors cs254 and cs252
                                        //
                                        return this;
                                }

                                //
                                // One of them is a valuetype, but the other one is not.
                                //
                                if (!l.IsValueType || !r.IsValueType) {
                                        Error_OperatorCannotBeApplied ();
                                        return null;
                                }
                        }

                        // Only perform numeric promotions on:
                        // +, -, *, /, %, &, |, ^, ==, !=, <, >, <=, >=
                        //
                        if (oper == Operator.Addition || oper == Operator.Subtraction) {
                                if (l.IsSubclassOf (TypeManager.delegate_type)){
                                        if (((right.eclass == ExprClass.MethodGroup) ||
                                             (r == TypeManager.anonymous_method_type))){
                                                if ((RootContext.Version != LanguageVersion.ISO_1)){
                                                        Expression tmp = Convert.ImplicitConversionRequired (ec, right, l, loc);
                                                        if (tmp == null)
                                                                return null;
                                                        right = tmp;
                                                        r = right.Type;
                                                }
                                        }
                                        
                                        if (r.IsSubclassOf (TypeManager.delegate_type)){
                                                MethodInfo method;
                                                ArrayList args = new ArrayList (2);
                                                
                                                args = new ArrayList (2);
                                                args.Add (new Argument (left, Argument.AType.Expression));
                                                args.Add (new Argument (right, Argument.AType.Expression));
                                                
                                                if (oper == Operator.Addition)
                                                        method = TypeManager.delegate_combine_delegate_delegate;
                                                else
                                                        method = TypeManager.delegate_remove_delegate_delegate;
                                                
                                                if (l != r) {
                                                        Error_OperatorCannotBeApplied ();
                                                        return null;
                                                }
                                                
                                                return new BinaryDelegate (l, method, args);
                                        }
                                }
                                
                                //
                                // Pointer arithmetic:
                                //
                                // T* operator + (T* x, int y);
                                // T* operator + (T* x, uint y);
                                // T* operator + (T* x, long y);
                                // T* operator + (T* x, ulong y);
                                //
                                // T* operator + (int y,   T* x);
                                // T* operator + (uint y,  T *x);
                                // T* operator + (long y,  T *x);
                                // T* operator + (ulong y, T *x);
                                //
                                // T* operator - (T* x, int y);
                                // T* operator - (T* x, uint y);
                                // T* operator - (T* x, long y);
                                // T* operator - (T* x, ulong y);
                                //
                                // long operator - (T* x, T *y)
                                //
                                if (l.IsPointer){
                                        if (r.IsPointer && oper == Operator.Subtraction){
                                                if (r == l)
                                                        return new PointerArithmetic (
                                                                false, left, right, TypeManager.int64_type,
                                                                loc).Resolve (ec);
                                        } else {
                                                Expression t = Make32or64 (ec, right);
                                                if (t != null)
                                                        return new PointerArithmetic (oper == Operator.Addition, left, t, l, loc).Resolve (ec);
                                        }
                                } else if (r.IsPointer && oper == Operator.Addition){
                                        Expression t = Make32or64 (ec, left);
                                        if (t != null)
                                                return new PointerArithmetic (true, right, t, r, loc).Resolve (ec);
                                }
                        }
                        
                        //
                        // Enumeration operators
                        //
                        bool lie = TypeManager.IsEnumType (l);
                        bool rie = TypeManager.IsEnumType (r);
                        if (lie || rie){
                                Expression temp;

                                // U operator - (E e, E f)
                                if (lie && rie){
                                        if (oper == Operator.Subtraction){
                                                if (l == r){
                                                        type = TypeManager.EnumToUnderlying (l);
                                                        return this;
                                                }
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                }
                                        
                                //
                                // operator + (E e, U x)
                                // operator - (E e, U x)
                                //
                                if (oper == Operator.Addition || oper == Operator.Subtraction){
                                        Type enum_type = lie ? l : r;
                                        Type other_type = lie ? r : l;
                                        Type underlying_type = TypeManager.EnumToUnderlying (enum_type);
                                        
                                        if (underlying_type != other_type){
                                                temp = Convert.ImplicitConversion (ec, lie ? right : left, underlying_type, loc);
                                                if (temp != null){
                                                        if (lie)
                                                                right = temp;
                                                        else
                                                                left = temp;
                                                        type = enum_type;
                                                        return this;
                                                }
                                                        
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }

                                        type = enum_type;
                                        return this;
                                }
                                
                                if (!rie){
                                        temp = Convert.ImplicitConversion (ec, right, l, loc);
                                        if (temp != null)
                                                right = temp;
                                        else {
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                } if (!lie){
                                        temp = Convert.ImplicitConversion (ec, left, r, loc);
                                        if (temp != null){
                                                left = temp;
                                                l = r;
                                        } else {
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                }

                                if (oper == Operator.Equality || oper == Operator.Inequality ||
                                    oper == Operator.LessThanOrEqual || oper == Operator.LessThan ||
                                    oper == Operator.GreaterThanOrEqual || oper == Operator.GreaterThan){
                                        if (left.Type != right.Type){
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                        type = TypeManager.bool_type;
                                        return this;
                                }

                                if (oper == Operator.BitwiseAnd ||
                                    oper == Operator.BitwiseOr ||
                                    oper == Operator.ExclusiveOr){
                                        if (left.Type != right.Type){
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                        type = l;
                                        return this;
                                }
                                Error_OperatorCannotBeApplied ();
                                return null;
                        }
                        
                        if (oper == Operator.LeftShift || oper == Operator.RightShift)
                                return CheckShiftArguments (ec);

                        if (oper == Operator.LogicalOr || oper == Operator.LogicalAnd){
                                if (l == TypeManager.bool_type && r == TypeManager.bool_type) {
                                        type = TypeManager.bool_type;
                                        return this;
                                }

                                if (l != r) {
                                        Error_OperatorCannotBeApplied ();
                                        return null;
                                }

                                Expression e = new ConditionalLogicalOperator (
                                        oper == Operator.LogicalAnd, left, right, l, loc);
                                return e.Resolve (ec);
                        } 

                        //
                        // operator & (bool x, bool y)
                        // operator | (bool x, bool y)
                        // operator ^ (bool x, bool y)
                        //
                        if (l == TypeManager.bool_type && r == TypeManager.bool_type){
                                if (oper == Operator.BitwiseAnd ||
                                    oper == Operator.BitwiseOr ||
                                    oper == Operator.ExclusiveOr){
                                        type = l;
                                        return this;
                                }
                        }
                        
                        //
                        // Pointer comparison
                        //
                        if (l.IsPointer && r.IsPointer){
                                if (oper == Operator.LessThan || oper == Operator.LessThanOrEqual ||
                                    oper == Operator.GreaterThan || oper == Operator.GreaterThanOrEqual){
                                        type = TypeManager.bool_type;
                                        return this;
                                }
                        }
                        
                        //
                        // This will leave left or right set to null if there is an error
                        //
                        bool check_user_conv = is_user_defined (l) && is_user_defined (r);
                        DoNumericPromotions (ec, l, r, left, right, check_user_conv);
                        if (left == null || right == null){
                                Error_OperatorCannotBeApplied (loc, OperName (oper), l, r);
                                return null;
                        }

                        //
                        // reload our cached types if required
                        //
                        l = left.Type;
                        r = right.Type;
                        
                        if (oper == Operator.BitwiseAnd ||
                            oper == Operator.BitwiseOr ||
                            oper == Operator.ExclusiveOr){
                                if (l == r){
                                        if (((l == TypeManager.int32_type) ||
                                             (l == TypeManager.uint32_type) ||
                                             (l == TypeManager.short_type) ||
                                             (l == TypeManager.ushort_type) ||
                                             (l == TypeManager.int64_type) ||
                                             (l == TypeManager.uint64_type))){
                                                type = l;
                                        } else {
                                                Error_OperatorCannotBeApplied ();
                                                return null;
                                        }
                                } else {
                                        Error_OperatorCannotBeApplied ();
                                        return null;
                                }
                        }

                        if (oper == Operator.Equality ||
                            oper == Operator.Inequality ||
                            oper == Operator.LessThanOrEqual ||
                            oper == Operator.LessThan ||
                            oper == Operator.GreaterThanOrEqual ||
                            oper == Operator.GreaterThan){
                                type = TypeManager.bool_type;
                        }

                        return this;
                }

                Constant EnumLiftUp (EmitContext 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 is EnumConstant)
                                                return left;

                                        if (left.IsZeroInteger)
                                                return new EnumConstant (left, 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 is EnumConstant || left is EnumConstant)
                                                break;
                                        return left;
                        }
                        Error_OperatorCannotBeApplied (loc, Binary.OperName (oper), left.Type, right.Type);
                        return null;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        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) {
                                        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;

                        Constant lc = left as Constant;
                        if (lc != null && lc.Type == TypeManager.bool_type && 
                                ((oper == Operator.LogicalAnd && (bool)lc.GetValue () == false) ||
                                 (oper == Operator.LogicalOr && (bool)lc.GetValue () == true))) {

                                // TODO: make a sense to resolve unreachable expression as we do for statement
                                Report.Warning (429, 4, loc, "Unreachable expression code detected");
                                return left;
                        }

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

                        eclass = ExprClass.Value;
                        Constant rc = right as Constant;

                        // The conversion rules are ignored in enum context but why
                        if (!ec.InEnumContext && lc != null && rc != null && (TypeManager.IsEnumType (left.Type) || TypeManager.IsEnumType (right.Type))) {
                                left = lc = EnumLiftUp (ec, lc, rc);
                                if (lc == null)
                                        return null;

                                right = rc = EnumLiftUp (ec, rc, lc);
                                if (rc == null)
                                        return null;
                        }

                        if (oper == Operator.BitwiseAnd) {
                                if (rc != null && rc.IsZeroInteger) {
                                        return lc is EnumConstant ?
                                                new EnumConstant (rc, lc.Type):
                                                rc;
                                }

                                if (lc != null && lc.IsZeroInteger) {
                                        return rc is EnumConstant ?
                                                new EnumConstant (lc, rc.Type):
                                                lc;
                                }
                        }
                        else if (oper == Operator.BitwiseOr) {
                                if (lc is EnumConstant &&
                                    rc != null && rc.IsZeroInteger)
                                        return lc;
                                if (rc is EnumConstant &&
                                    lc != null && lc.IsZeroInteger)
                                        return rc;
                        } else if (oper == Operator.LogicalAnd) {
                                if (rc != null && rc.IsDefaultValue && rc.Type == TypeManager.bool_type)
                                        return rc;
                                if (lc != null && lc.IsDefaultValue && lc.Type == TypeManager.bool_type)
                                        return lc;
                        }

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

                        // Comparison warnings
                        if (oper == Operator.Equality || oper == Operator.Inequality ||
                            oper == Operator.LessThanOrEqual || oper == Operator.LessThan ||
                            oper == Operator.GreaterThanOrEqual || oper == Operator.GreaterThan){
                                if (left.Equals (right)) {
                                        Report.Warning (1718, 3, loc, "Comparison made to same variable; did you mean to compare something else?");
                                }
                                CheckUselessComparison (lc, right.Type);
                                CheckUselessComparison (rc, left.Type);
                        }

                        return ResolveOperator (ec);
                }

                private void CheckUselessComparison (Constant c, Type type)
                {
                        if (c == null || !IsTypeIntegral (type)
                                || c is StringConstant
                                || c is BoolConstant
                                || c is CharConstant
                                || c is FloatConstant
                                || c is DoubleConstant
                                || c is DecimalConstant
                                )
                                return;

                        long value = 0;

                        if (c is ULongConstant) {
                                ulong uvalue = ((ULongConstant) c).Value;
                                if (uvalue > long.MaxValue) {
                                        if (type == TypeManager.byte_type ||
                                            type == TypeManager.sbyte_type ||
                                            type == TypeManager.short_type ||
                                            type == TypeManager.ushort_type ||
                                            type == TypeManager.int32_type ||
                                            type == TypeManager.uint32_type ||
                                            type == TypeManager.int64_type)
                                                WarnUselessComparison (type);
                                        return;
                                }
                                value = (long) uvalue;
                        }
                        else if (c is ByteConstant)
                                value = ((ByteConstant) c).Value;
                        else if (c is SByteConstant)
                                value = ((SByteConstant) c).Value;
                        else if (c is ShortConstant)
                                value = ((ShortConstant) c).Value;
                        else if (c is UShortConstant)
                                value = ((UShortConstant) c).Value;
                        else if (c is IntConstant)
                                value = ((IntConstant) c).Value;
                        else if (c is UIntConstant)
                                value = ((UIntConstant) c).Value;
                        else if (c is LongConstant)
                                value = ((LongConstant) c).Value;

                        if (value != 0) {
                                if (IsValueOutOfRange (value, type))
                                        WarnUselessComparison (type);
                                return;
                        }
                }

                private bool IsValueOutOfRange (long value, Type type)
                {
                        if (IsTypeUnsigned (type) && value < 0)
                                return true;
                        return type == TypeManager.sbyte_type && (value >= 0x80 || value < -0x80) ||
                                type == TypeManager.byte_type && value >= 0x100 ||
                                type == TypeManager.short_type && (value >= 0x8000 || value < -0x8000) ||
                                type == TypeManager.ushort_type && value >= 0x10000 ||
                                type == TypeManager.int32_type && (value >= 0x80000000 || value < -0x80000000) ||
                                type == TypeManager.uint32_type && value >= 0x100000000;
                }

                private static bool IsTypeIntegral (Type type)
                {
                        return type == TypeManager.uint64_type ||
                                type == TypeManager.int64_type ||
                                type == TypeManager.uint32_type ||
                                type == TypeManager.int32_type ||
                                type == TypeManager.ushort_type ||
                                type == TypeManager.short_type ||
                                type == TypeManager.sbyte_type ||
                                type == TypeManager.byte_type;
                }

                private static bool IsTypeUnsigned (Type type)
                {
                        return type == TypeManager.uint64_type ||
                                type == TypeManager.uint32_type ||
                                type == TypeManager.ushort_type ||
                                type == TypeManager.byte_type;
                }

                private void WarnUselessComparison (Type type)
                {
                        Report.Warning (652, 2, loc, "Comparison to integral constant is useless; the constant is outside the range of type `{0}'",
                                TypeManager.CSharpName (type));
                }

                /// <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 onTrue)
                {
                        ILGenerator ig = ec.ig;

                        //
                        // 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.Equality || oper == Operator.Inequality) && (left is Constant || right is Constant)) {
                                bool my_on_true = oper == Operator.Inequality ? onTrue : !onTrue;
                                
                                //
                                // put the constant on the rhs, for simplicity
                                //
                                if (left is Constant) {
                                        Expression swap = right;
                                        right = left;
                                        left = swap;
                                }
                                
                                if (((Constant) right).IsZeroInteger) {
                                        left.Emit (ec);
                                        if (my_on_true)
                                                ig.Emit (OpCodes.Brtrue, target);
                                        else
                                                ig.Emit (OpCodes.Brfalse, target);
                                        
                                        return;
                                } else if (right is BoolConstant) {
                                        left.Emit (ec);
                                        if (my_on_true != ((BoolConstant) right).Value)
                                                ig.Emit (OpCodes.Brtrue, target);
                                        else
                                                ig.Emit (OpCodes.Brfalse, target);
                                        
                                        return;
                                }

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

                                if (onTrue) {
                                        Label tests_end = ig.DefineLabel ();
                                        
                                        left.EmitBranchable (ec, tests_end, false);
                                        right.EmitBranchable (ec, target, true);
                                        ig.MarkLabel (tests_end);                                       
                                } else {
                                        left.EmitBranchable (ec, target, false);
                                        right.EmitBranchable (ec, target, false);
                                }
                                
                                return;
                                
                        } else if (oper == Operator.LogicalOr){
                                if (onTrue) {
                                        left.EmitBranchable (ec, target, true);
                                        right.EmitBranchable (ec, target, true);
                                        
                                } else {
                                        Label tests_end = ig.DefineLabel ();
                                        left.EmitBranchable (ec, tests_end, true);
                                        right.EmitBranchable (ec, target, false);
                                        ig.MarkLabel (tests_end);
                                }
                                
                                return;
                                
                        } else if (!(oper == Operator.LessThan        || oper == Operator.GreaterThan ||
                                     oper == Operator.LessThanOrEqual || oper == Operator.GreaterThanOrEqual ||
                                     oper == Operator.Equality        || oper == Operator.Inequality)) {
                                base.EmitBranchable (ec, target, onTrue);
                                return;
                        }
                        
                        left.Emit (ec);
                        right.Emit (ec);

                        Type t = left.Type;
                        bool isUnsigned = is_unsigned (t) || t == TypeManager.double_type || t == TypeManager.float_type;
                        
                        switch (oper){
                        case Operator.Equality:
                                if (onTrue)
                                        ig.Emit (OpCodes.Beq, target);
                                else
                                        ig.Emit (OpCodes.Bne_Un, target);
                                break;

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

                        case Operator.LessThan:
                                if (onTrue)
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Blt_Un, target);
                                        else
                                                ig.Emit (OpCodes.Blt, target);
                                else
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Bge_Un, target);
                                        else
                                                ig.Emit (OpCodes.Bge, target);
                                break;

                        case Operator.GreaterThan:
                                if (onTrue)
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Bgt_Un, target);
                                        else
                                                ig.Emit (OpCodes.Bgt, target);
                                else
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Ble_Un, target);
                                        else
                                                ig.Emit (OpCodes.Ble, target);
                                break;

                        case Operator.LessThanOrEqual:
                                if (onTrue)
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Ble_Un, target);
                                        else
                                                ig.Emit (OpCodes.Ble, target);
                                else
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Bgt_Un, target);
                                        else
                                                ig.Emit (OpCodes.Bgt, target);
                                break;


                        case Operator.GreaterThanOrEqual:
                                if (onTrue)
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Bge_Un, target);
                                        else
                                                ig.Emit (OpCodes.Bge, target);
                                else
                                        if (isUnsigned)
                                                ig.Emit (OpCodes.Blt_Un, target);
                                        else
                                                ig.Emit (OpCodes.Blt, target);
                                break;
                        default:
                                Console.WriteLine (oper);
                                throw new Exception ("what is THAT");
                        }
                }
                
                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        Type l = left.Type;
                        OpCode opcode;

                        //
                        // Handle short-circuit operators differently
                        // than the rest
                        //
                        if (oper == Operator.LogicalAnd) {
                                Label load_zero = ig.DefineLabel ();
                                Label end = ig.DefineLabel ();
                                                                
                                left.EmitBranchable (ec, load_zero, false);
                                right.Emit (ec);
                                ig.Emit (OpCodes.Br, end);
                                
                                ig.MarkLabel (load_zero);
                                ig.Emit (OpCodes.Ldc_I4_0);
                                ig.MarkLabel (end);
                                return;
                        } else if (oper == Operator.LogicalOr) {
                                Label load_one = ig.DefineLabel ();
                                Label end = ig.DefineLabel ();

                                left.EmitBranchable (ec, load_one, true);
                                right.Emit (ec);
                                ig.Emit (OpCodes.Br, end);
                                
                                ig.MarkLabel (load_one);
                                ig.Emit (OpCodes.Ldc_I4_1);
                                ig.MarkLabel (end);
                                return;
                        }

                        left.Emit (ec);
                        right.Emit (ec);

                        bool isUnsigned = is_unsigned (left.Type);
                        
                        switch (oper){
                        case Operator.Multiply:
                                if (ec.CheckState){
                                        if (l == TypeManager.int32_type || l == TypeManager.int64_type)
                                                opcode = OpCodes.Mul_Ovf;
                                        else if (isUnsigned)
                                                opcode = OpCodes.Mul_Ovf_Un;
                                        else
                                                opcode = OpCodes.Mul;
                                } else
                                        opcode = OpCodes.Mul;

                                break;

                        case Operator.Division:
                                if (isUnsigned)
                                        opcode = OpCodes.Div_Un;
                                else
                                        opcode = OpCodes.Div;
                                break;

                        case Operator.Modulus:
                                if (isUnsigned)
                                        opcode = OpCodes.Rem_Un;
                                else
                                        opcode = OpCodes.Rem;
                                break;

                        case Operator.Addition:
                                if (ec.CheckState){
                                        if (l == TypeManager.int32_type || l == TypeManager.int64_type)
                                                opcode = OpCodes.Add_Ovf;
                                        else if (isUnsigned)
                                                opcode = OpCodes.Add_Ovf_Un;
                                        else
                                                opcode = OpCodes.Add;
                                } else
                                        opcode = OpCodes.Add;
                                break;

                        case Operator.Subtraction:
                                if (ec.CheckState){
                                        if (l == TypeManager.int32_type || l == TypeManager.int64_type)
                                                opcode = OpCodes.Sub_Ovf;
                                        else if (isUnsigned)
                                                opcode = OpCodes.Sub_Ovf_Un;
                                        else
                                                opcode = OpCodes.Sub;
                                } else
                                        opcode = OpCodes.Sub;
                                break;

                        case Operator.RightShift:
                                if (isUnsigned)
                                        opcode = OpCodes.Shr_Un;
                                else
                                        opcode = OpCodes.Shr;
                                break;
                                
                        case Operator.LeftShift:
                                opcode = OpCodes.Shl;
                                break;

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

                        case Operator.Inequality:
                                ig.Emit (OpCodes.Ceq);
                                ig.Emit (OpCodes.Ldc_I4_0);
                                
                                opcode = OpCodes.Ceq;
                                break;

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

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

                        case Operator.LessThanOrEqual:
                                Type lt = left.Type;
                                
                                if (isUnsigned || (lt == TypeManager.double_type || lt == TypeManager.float_type))
                                        ig.Emit (OpCodes.Cgt_Un);
                                else
                                        ig.Emit (OpCodes.Cgt);
                                ig.Emit (OpCodes.Ldc_I4_0);
                                
                                opcode = OpCodes.Ceq;
                                break;

                        case Operator.GreaterThanOrEqual:
                                Type le = left.Type;
                                
                                if (isUnsigned || (le == TypeManager.double_type || le == TypeManager.float_type))
                                        ig.Emit (OpCodes.Clt_Un);
                                else
                                        ig.Emit (OpCodes.Clt);
                                
                                ig.Emit (OpCodes.Ldc_I4_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 Exception ("This should not happen: Operator = "
                                                     + oper.ToString ());
                        }

                        ig.Emit (opcode);
                }
        }

        //
        // Object created by Binary when the binary operator uses an method instead of being
        // a binary operation that maps to a CIL binary operation.
        //
        public class BinaryMethod : Expression {
                public MethodBase method;
                public ArrayList  Arguments;
                
                public BinaryMethod (Type t, MethodBase m, ArrayList args)
                {
                        method = m;
                        Arguments = args;
                        type = t;
                        eclass = ExprClass.Value;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        if (Arguments != null) 
                                Invocation.EmitArguments (ec, method, Arguments, false, null);
                        
                        if (method is MethodInfo)
                                ig.Emit (OpCodes.Call, (MethodInfo) method);
                        else
                                ig.Emit (OpCodes.Call, (ConstructorInfo) method);
                }
        }
        
        //
        // Represents the operation a + b [+ c [+ d [+ ...]]], where a is a string
        // b, c, d... may be strings or objects.
        //
        public class StringConcat : Expression {
                ArrayList operands;
                bool invalid = false;
                bool emit_conv_done = false;
                //
                // Are we also concating objects?
                //
                bool is_strings_only = true;
                
                public StringConcat (EmitContext ec, Location loc, Expression left, Expression right)
                {
                        this.loc = loc;
                        type = TypeManager.string_type;
                        eclass = ExprClass.Value;
                
                        operands = new ArrayList (2);
                        Append (ec, left);
                        Append (ec, right);
                }
                
                public override Expression DoResolve (EmitContext ec)
                {
                        if (invalid)
                                return null;
                        
                        return this;
                }
                
                public void Append (EmitContext ec, Expression operand)
                {
                        //
                        // Constant folding
                        //
                        if (operand is StringConstant && operands.Count != 0) {
                                StringConstant last_operand = operands [operands.Count - 1] as StringConstant;
                                if (last_operand != null) {
                                        operands [operands.Count - 1] = new StringConstant (last_operand.Value + ((StringConstant) operand).Value, last_operand.Location);
                                        return;
                                }
                        }
                        
                        //
                        // Conversion to object
                        //
                        if (operand.Type != TypeManager.string_type) {
                                Expression no = Convert.ImplicitConversion (ec, operand, TypeManager.object_type, loc);
                                
                                if (no == null) {
                                        Binary.Error_OperatorCannotBeApplied (loc, "+", TypeManager.string_type, operand.Type);
                                        invalid = true;
                                }
                                operand = no;
                        }
                        
                        operands.Add (operand);
                }

                public override void Emit (EmitContext ec)
                {
                        MethodInfo concat_method = null;
                        
                        //
                        // Do conversion to arguments; check for strings only
                        //
                        
                        // This can get called multiple times, so we have to deal with that.
                        if (!emit_conv_done) {
                                emit_conv_done = true;
                                for (int i = 0; i < operands.Count; i ++) {
                                        Expression e = (Expression) operands [i];
                                        is_strings_only &= e.Type == TypeManager.string_type;
                                }
                                
                                for (int i = 0; i < operands.Count; i ++) {
                                        Expression e = (Expression) operands [i];
                                        
                                        if (! is_strings_only && e.Type == TypeManager.string_type) {
                                                // need to make sure this is an object, because the EmitParams
                                                // method might look at the type of this expression, see it is a
                                                // string and emit a string [] when we want an object [];
                                                
                                                e = new EmptyCast (e, TypeManager.object_type);
                                        }
                                        operands [i] = new Argument (e, Argument.AType.Expression);
                                }
                        }
                        
                        //
                        // Find the right method
                        //
                        switch (operands.Count) {
                        case 1:
                                //
                                // This should not be possible, because simple constant folding
                                // is taken care of in the Binary code.
                                //
                                throw new Exception ("how did you get here?");
                        
                        case 2:
                                concat_method = is_strings_only ? 
                                        TypeManager.string_concat_string_string :
                                        TypeManager.string_concat_object_object ;
                                break;
                        case 3:
                                concat_method = is_strings_only ? 
                                        TypeManager.string_concat_string_string_string :
                                        TypeManager.string_concat_object_object_object ;
                                break;
                        case 4:
                                //
                                // There is not a 4 param overlaod for object (the one that there is
                                // is actually a varargs methods, and is only in corlib because it was
                                // introduced there before.).
                                //
                                if (!is_strings_only)
                                        goto default;
                                
                                concat_method = TypeManager.string_concat_string_string_string_string;
                                break;
                        default:
                                concat_method = is_strings_only ? 
                                        TypeManager.string_concat_string_dot_dot_dot :
                                        TypeManager.string_concat_object_dot_dot_dot ;
                                break;
                        }
                        
                        Invocation.EmitArguments (ec, concat_method, operands, false, null);
                        ec.ig.Emit (OpCodes.Call, concat_method);
                }
        }

        //
        // Object created with +/= on delegates
        //
        public class BinaryDelegate : Expression {
                MethodInfo method;
                ArrayList  args;

                public BinaryDelegate (Type t, MethodInfo mi, ArrayList args)
                {
                        method = mi;
                        this.args = args;
                        type = t;
                        eclass = ExprClass.Value;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        Invocation.EmitArguments (ec, method, args, false, null);
                        
                        ig.Emit (OpCodes.Call, (MethodInfo) method);
                        ig.Emit (OpCodes.Castclass, type);
                }

                public Expression Right {
                        get {
                                Argument arg = (Argument) args [1];
                                return arg.Expr;
                        }
                }

                public bool IsAddition {
                        get {
                                return method == TypeManager.delegate_combine_delegate_delegate;
                        }
                }
        }
        
        //
        // User-defined conditional logical operator
        public class ConditionalLogicalOperator : Expression {
                Expression left, right;
                bool is_and;

                public ConditionalLogicalOperator (bool is_and, Expression left, Expression right, Type t, Location loc)
                {
                        type = t;
                        eclass = ExprClass.Value;
                        this.loc = loc;
                        this.left = left;
                        this.right = right;
                        this.is_and = is_and;
                }

                protected void Error19 ()
                {
                        Binary.Error_OperatorCannotBeApplied (loc, is_and ? "&&" : "||", left.GetSignatureForError (), right.GetSignatureForError ());
                }

                protected void Error218 ()
                {
                        Error (218, "The type ('" + TypeManager.CSharpName (type) + "') must contain " +
                               "declarations of operator true and operator false");
                }

                Expression op_true, op_false, op;
                LocalTemporary left_temp;

                public override Expression DoResolve (EmitContext ec)
                {
                        MethodInfo method;
                        Expression operator_group;

                        operator_group = MethodLookup (ec, type, is_and ? "op_BitwiseAnd" : "op_BitwiseOr", loc);
                        if (operator_group == null) {
                                Error19 ();
                                return null;
                        }

                        left_temp = new LocalTemporary (ec, type);

                        ArrayList arguments = new ArrayList ();
                        arguments.Add (new Argument (left_temp, Argument.AType.Expression));
                        arguments.Add (new Argument (right, Argument.AType.Expression));
                        method = Invocation.OverloadResolve (
                                ec, (MethodGroupExpr) operator_group, arguments, false, loc)
                                as MethodInfo;
                        if (method == null) {
                                Error19 ();
                                return null;
                        }

                        if (method.ReturnType != type) {
                                Report.Error (217, loc, "In order to be applicable as a short circuit operator a user-defined logical operator `{0}' " +
                                                "must have the same return type as the type of its 2 parameters", TypeManager.CSharpSignature (method));
                                return null;
                        }

                        op = new StaticCallExpr (method, arguments, loc);

                        op_true = GetOperatorTrue (ec, left_temp, loc);
                        op_false = GetOperatorFalse (ec, left_temp, loc);
                        if ((op_true == null) || (op_false == null)) {
                                Error218 ();
                                return null;
                        }

                        return this;
                }

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

                        left.Emit (ec);
                        left_temp.Store (ec);

                        (is_and ? op_false : op_true).EmitBranchable (ec, false_target, false);
                        left_temp.Emit (ec);
                        ig.Emit (OpCodes.Br, end_target);
                        ig.MarkLabel (false_target);
                        op.Emit (ec);
                        ig.MarkLabel (end_target);
                }
        }

        public class PointerArithmetic : Expression {
                Expression left, right;
                bool is_add;

                //
                // We assume that `l' is always a pointer
                //
                public PointerArithmetic (bool is_addition, Expression l, Expression r, Type t, Location loc)
                {
                        type = t;
                        this.loc = loc;
                        left = l;
                        right = r;
                        is_add = is_addition;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        eclass = ExprClass.Variable;
                        
                        if (left.Type == TypeManager.void_ptr_type) {
                                Error (242, "The operation in question is undefined on void pointers");
                                return null;
                        }
                        
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        Type op_type = left.Type;
                        ILGenerator ig = ec.ig;
                        
                        // It must be either array or fixed buffer
                        Type element = TypeManager.HasElementType (op_type) ?
                                element = TypeManager.GetElementType (op_type) :
                                element = AttributeTester.GetFixedBuffer (((FieldExpr)left).FieldInfo).ElementType;

                        int size = GetTypeSize (element);
                        Type rtype = right.Type;
                        
                        if (rtype.IsPointer){
                                //
                                // handle (pointer - pointer)
                                //
                                left.Emit (ec);
                                right.Emit (ec);
                                ig.Emit (OpCodes.Sub);

                                if (size != 1){
                                        if (size == 0)
                                                ig.Emit (OpCodes.Sizeof, element);
                                        else 
                                                IntLiteral.EmitInt (ig, size);
                                        ig.Emit (OpCodes.Div);
                                }
                                ig.Emit (OpCodes.Conv_I8);
                        } else {
                                //
                                // handle + and - on (pointer op int)
                                //
                                left.Emit (ec);
                                ig.Emit (OpCodes.Conv_I);

                                Constant right_const = right as Constant;
                                if (right_const != null && size != 0) {
                                        Expression ex = ConstantFold.BinaryFold (ec, Binary.Operator.Multiply, new IntConstant (size, right.Location), right_const, loc);
                                        if (ex == null)
                                                return;
                                        ex.Emit (ec);
                                } else {
                                        right.Emit (ec);
                                        if (size != 1){
                                                if (size == 0)
                                                        ig.Emit (OpCodes.Sizeof, element);
                                                else 
                                                        IntLiteral.EmitInt (ig, size);
                                                if (rtype == TypeManager.int64_type)
                                                        ig.Emit (OpCodes.Conv_I8);
                                                else if (rtype == TypeManager.uint64_type)
                                                        ig.Emit (OpCodes.Conv_U8);
                                                ig.Emit (OpCodes.Mul);
                                        }
                                }
                                
                                if (rtype == TypeManager.int64_type || rtype == TypeManager.uint64_type)
                                        ig.Emit (OpCodes.Conv_I);
                                
                                if (is_add)
                                        ig.Emit (OpCodes.Add);
                                else
                                        ig.Emit (OpCodes.Sub);
                        }
                }
        }
        
        /// <summary>
        ///   Implements the ternary conditional operator (?:)
        /// </summary>
        public class Conditional : Expression {
                Expression expr, trueExpr, falseExpr;
                
                public Conditional (Expression expr, Expression trueExpr, Expression falseExpr)
                {
                        this.expr = expr;
                        this.trueExpr = trueExpr;
                        this.falseExpr = falseExpr;
                        this.loc = expr.Location;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public Expression TrueExpr {
                        get {
                                return trueExpr;
                        }
                }

                public Expression FalseExpr {
                        get {
                                return falseExpr;
                        }
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        expr = expr.Resolve (ec);

                        if (expr == null)
                                return null;
                        
                        if (expr.Type != TypeManager.bool_type){
                                expr = Expression.ResolveBoolean (
                                        ec, expr, loc);
                                
                                if (expr == null)
                                        return null;
                        }
                        
                        Assign ass = expr as Assign;
                        if (ass != null && ass.Source is Constant) {
                                Report.Warning (665, 3, loc, "Assignment in conditional expression is always constant; did you mean to use == instead of = ?");
                        }

                        trueExpr = trueExpr.Resolve (ec);
                        falseExpr = falseExpr.Resolve (ec);

                        if (trueExpr == null || falseExpr == null)
                                return null;

                        eclass = ExprClass.Value;
                        if (trueExpr.Type == falseExpr.Type)
                                type = trueExpr.Type;
                        else {
                                Expression conv;
                                Type true_type = trueExpr.Type;
                                Type false_type = falseExpr.Type;

                                //
                                // First, if an implicit conversion exists from trueExpr
                                // to falseExpr, then the result type is of type falseExpr.Type
                                //
                                conv = Convert.ImplicitConversion (ec, trueExpr, false_type, loc);
                                if (conv != null){
                                        //
                                        // Check if both can convert implicitl to each other's type
                                        //
                                        if (Convert.ImplicitConversion (ec, falseExpr, true_type, loc) != null){
                                                Error (172,
                                                       "Can not compute type of conditional expression " +
                                                       "as `" + TypeManager.CSharpName (trueExpr.Type) +
                                                       "' and `" + TypeManager.CSharpName (falseExpr.Type) +
                                                       "' convert implicitly to each other");
                                                return null;
                                        }
                                        type = false_type;
                                        trueExpr = conv;
                                } else if ((conv = Convert.ImplicitConversion(ec, falseExpr, true_type,loc))!= null){
                                        type = true_type;
                                        falseExpr = conv;
                                } else {
                                        Report.Error (173, loc, "Type of conditional expression cannot be determined because there is no implicit conversion between `{0}' and `{1}'",
                                                trueExpr.GetSignatureForError (), falseExpr.GetSignatureForError ());
                                        return null;
                                }
                        }

                        // Dead code optimalization
                        if (expr is BoolConstant){
                                BoolConstant bc = (BoolConstant) expr;

                                Report.Warning (429, 4, bc.Value ? falseExpr.Location : trueExpr.Location, "Unreachable expression code detected");
                                return bc.Value ? trueExpr : falseExpr;
                        }

                        return this;
                }

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

                        expr.EmitBranchable (ec, false_target, false);
                        trueExpr.Emit (ec);
                        ig.Emit (OpCodes.Br, end_target);
                        ig.MarkLabel (false_target);
                        falseExpr.Emit (ec);
                        ig.MarkLabel (end_target);
                }

        }

        /// <summary>
        ///   Local variables
        /// </summary>
        public class LocalVariableReference : Expression, IAssignMethod, IMemoryLocation, IVariable {
                public readonly string Name;
                public readonly Block Block;
                public LocalInfo local_info;
                bool is_readonly;
                bool prepared;
                LocalTemporary temp;
                
                public LocalVariableReference (Block block, string name, Location l)
                {
                        Block = block;
                        Name = name;
                        loc = l;
                        eclass = ExprClass.Variable;
                }

                //
                // Setting `is_readonly' to false will allow you to create a writable
                // reference to a read-only variable.  This is used by foreach and using.
                //
                public LocalVariableReference (Block block, string name, Location l,
                                               LocalInfo local_info, bool is_readonly)
                        : this (block, name, l)
                {
                        this.local_info = local_info;
                        this.is_readonly = is_readonly;
                }

                public VariableInfo VariableInfo {
                        get {
                                return local_info.VariableInfo;
                        }
                }

                public bool IsReadOnly {
                        get {
                                return is_readonly;
                        }
                }

                public bool VerifyAssigned (EmitContext ec)
                {
                        VariableInfo variable_info = local_info.VariableInfo;
                        return variable_info == null || variable_info.IsAssigned (ec, loc);
                }

                protected Expression DoResolveBase (EmitContext ec, Expression lvalue_right_side)
                {
                        if (local_info == null) {
                                local_info = Block.GetLocalInfo (Name);

                                // is out param
                                if (lvalue_right_side == EmptyExpression.Null)
                                        local_info.Used = true;

                                is_readonly = local_info.ReadOnly;
                        }

                        type = local_info.VariableType;

                        VariableInfo variable_info = local_info.VariableInfo;
                        if (lvalue_right_side != null){
                                if (is_readonly){
                                        if (lvalue_right_side is LocalVariableReference || lvalue_right_side == EmptyExpression.Null)
                                                Report.Error (1657, loc, "Cannot pass `{0}' as a ref or out argument because it is a `{1}'",
                                                        Name, local_info.GetReadOnlyContext ());
                                        else
                                                Report.Error (1656, loc, "Cannot assign to `{0}' because it is a `{1}'",
                                                        Name, local_info.GetReadOnlyContext ());
                                        return null;
                                }
                                
                                if (variable_info != null)
                                        variable_info.SetAssigned (ec);
                        }
                        
                        Expression e = Block.GetConstantExpression (Name);
                        if (e != null) {
                                local_info.Used = true;
                                eclass = ExprClass.Value;
                                return e.Resolve (ec);
                        }

                        if (!VerifyAssigned (ec))
                                return null;

                        if (lvalue_right_side == null)
                                local_info.Used = true;

                        if (ec.CurrentAnonymousMethod != null){
                                //
                                // If we are referencing a variable from the external block
                                // flag it for capturing
                                //
                                if ((local_info.Block.Toplevel != ec.CurrentBlock.Toplevel) ||
                                    ec.CurrentAnonymousMethod.IsIterator)
                                {
                                        if (local_info.AddressTaken){
                                                AnonymousMethod.Error_AddressOfCapturedVar (local_info.Name, loc);
                                                return null;
                                        }
                                        ec.CaptureVariable (local_info);
                                }
                        }

                        return this;
                }
                
                public override Expression DoResolve (EmitContext ec)
                {
                        return DoResolveBase (ec, null);
                }

                override public Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        return DoResolveBase (ec, right_side);
                }

                public bool VerifyFixed ()
                {
                        // A local Variable is always fixed.
                        return true;
                }

                public override int GetHashCode()
                {
                        return Name.GetHashCode ();
                }

                public override bool Equals (object obj)
                {
                        LocalVariableReference lvr = obj as LocalVariableReference;
                        if (lvr == null)
                                return false;

                        return Name == lvr.Name && Block == lvr.Block;
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;

                        if (local_info.FieldBuilder == null){
                                //
                                // A local variable on the local CLR stack
                                //
                                ig.Emit (OpCodes.Ldloc, local_info.LocalBuilder);
                        } else {
                                //
                                // A local variable captured by anonymous methods.
                                //
                                if (!prepared)
                                        ec.EmitCapturedVariableInstance (local_info);
                                
                                ig.Emit (OpCodes.Ldfld, local_info.FieldBuilder);
                        }
                }
                
                public void Emit (EmitContext ec, bool leave_copy)
                {
                        Emit (ec);
                        if (leave_copy){
                                ec.ig.Emit (OpCodes.Dup);
                                if (local_info.FieldBuilder != null){
                                        temp = new LocalTemporary (ec, Type);
                                        temp.Store (ec);
                                }
                        }
                }
                
                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool prepare_for_load)
                {
                        ILGenerator ig = ec.ig;
                        prepared = prepare_for_load;

                        if (local_info.FieldBuilder == null){
                                //
                                // A local variable on the local CLR stack
                                //
                                if (local_info.LocalBuilder == null)
                                        throw new Exception ("This should not happen: both Field and Local are null");

                                source.Emit (ec);
                                if (leave_copy)
                                        ec.ig.Emit (OpCodes.Dup);
                                ig.Emit (OpCodes.Stloc, local_info.LocalBuilder);
                        } else {
                                //
                                // A local variable captured by anonymous methods or itereators.
                                //
                                ec.EmitCapturedVariableInstance (local_info);

                                if (prepare_for_load)
                                        ig.Emit (OpCodes.Dup);
                                source.Emit (ec);
                                if (leave_copy){
                                        ig.Emit (OpCodes.Dup);
                                        temp = new LocalTemporary (ec, Type);
                                        temp.Store (ec);
                                }
                                ig.Emit (OpCodes.Stfld, local_info.FieldBuilder);
                                if (temp != null)
                                        temp.Emit (ec);
                        }
                }
                
                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        ILGenerator ig = ec.ig;

                        if (local_info.FieldBuilder == null){
                                //
                                // A local variable on the local CLR stack
                                //
                                ig.Emit (OpCodes.Ldloca, local_info.LocalBuilder);
                        } else {
                                //
                                // A local variable captured by anonymous methods or iterators
                                //
                                ec.EmitCapturedVariableInstance (local_info);
                                ig.Emit (OpCodes.Ldflda, local_info.FieldBuilder);
                        }
                }

                public override string ToString ()
                {
                        return String.Format ("{0} ({1}:{2})", GetType (), Name, loc);
                }
        }

        /// <summary>
        ///   This represents a reference to a parameter in the intermediate
        ///   representation.
        /// </summary>
        public class ParameterReference : Expression, IAssignMethod, IMemoryLocation, IVariable {
                Parameter par;
                string name;
                int idx;
                Block block;
                VariableInfo vi;
                public bool is_ref, is_out, prepared;

                public bool IsOut {
                        get {
                                return is_out;
                        }
                }

                public bool IsRef {
                        get {
                                return is_ref;
                        }
                }

                LocalTemporary temp;
                
                public ParameterReference (Parameter par, Block block, int idx, Location loc)
                {
                        this.par = par;
                        this.name = par.Name;
                        this.block = block;
                        this.idx  = idx;
                        this.loc = loc;
                        eclass = ExprClass.Variable;
                }

                public VariableInfo VariableInfo {
                        get { return vi; }
                }

                public bool VerifyFixed ()
                {
                        // A parameter is fixed if it's a value parameter (i.e., no modifier like out, ref, param).
                        return par.ModFlags == Parameter.Modifier.NONE;
                }

                public bool IsAssigned (EmitContext ec, Location loc)
                {
                        if (!ec.DoFlowAnalysis || !is_out || ec.CurrentBranching.IsAssigned (vi))
                                return true;

                        Report.Error (269, loc,
                                      "Use of unassigned out parameter `{0}'", par.Name);
                        return false;
                }

                public bool IsFieldAssigned (EmitContext ec, string field_name, Location loc)
                {
                        if (!ec.DoFlowAnalysis || !is_out || ec.CurrentBranching.IsFieldAssigned (vi, field_name))
                                return true;

                        Report.Error (170, loc,
                                      "Use of possibly unassigned field `" + field_name + "'");
                        return false;
                }

                public void SetAssigned (EmitContext ec)
                {
                        if (is_out && ec.DoFlowAnalysis)
                                ec.CurrentBranching.SetAssigned (vi);
                }

                public void SetFieldAssigned (EmitContext ec, string field_name)        
                {
                        if (is_out && ec.DoFlowAnalysis)
                                ec.CurrentBranching.SetFieldAssigned (vi, field_name);
                }

                protected void DoResolveBase (EmitContext ec)
                {
                        if (!par.Resolve (ec)) {
                                //TODO:
                        }

                        type = par.ParameterType;
                        Parameter.Modifier mod = par.ModFlags;
                        is_ref = (mod & Parameter.Modifier.ISBYREF) != 0;
                        is_out = (mod & Parameter.Modifier.OUT) == Parameter.Modifier.OUT;
                        eclass = ExprClass.Variable;

                        if (is_out)
                                vi = block.ParameterMap [idx];

                        if (ec.CurrentAnonymousMethod != null){
                                if (is_ref){
                                        Report.Error (1628, Location, "Cannot use ref or out parameter `{0}' inside an anonymous method block",
                                                par.Name);
                                        return;
                                }

                                //
                                // If we are referencing the parameter from the external block
                                // flag it for capturing
                                //
                                //Console.WriteLine ("Is parameter `{0}' local? {1}", name, block.IsLocalParameter (name));
                                if (!block.Toplevel.IsLocalParameter (name)){
                                        ec.CaptureParameter (name, type, idx);
                                }
                        }
                }

                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 && block == pr.block;
                }

                //
                // Notice that for ref/out parameters, the type exposed is not the
                // same type exposed externally.
                //
                // for "ref int a":
                //   externally we expose "int&"
                //   here we expose       "int".
                //
                // We record this in "is_ref".  This means that the type system can treat
                // the type as it is expected, but when we generate the code, we generate
                // the alternate kind of code.
                //
                public override Expression DoResolve (EmitContext ec)
                {
                        DoResolveBase (ec);

                        if (is_out && ec.DoFlowAnalysis && (!ec.OmitStructFlowAnalysis || !vi.TypeInfo.IsStruct) && !IsAssigned (ec, loc))
                                return null;

                        return this;
                }

                override public Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        DoResolveBase (ec);

                        SetAssigned (ec);

                        return this;
                }

                static public void EmitLdArg (ILGenerator ig, int x)
                {
                        if (x <= 255){
                                switch (x){
                                case 0: ig.Emit (OpCodes.Ldarg_0); break;
                                case 1: ig.Emit (OpCodes.Ldarg_1); break;
                                case 2: ig.Emit (OpCodes.Ldarg_2); break;
                                case 3: ig.Emit (OpCodes.Ldarg_3); break;
                                default: ig.Emit (OpCodes.Ldarg_S, (byte) x); break;
                                }
                        } else
                                ig.Emit (OpCodes.Ldarg, x);
                }
                
                //
                // 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)
                {
                        ILGenerator ig = ec.ig;
                        int arg_idx = idx;

                        if (!ec.MethodIsStatic)
                                arg_idx++;
                        
                        EmitLdArg (ig, arg_idx);

                        //
                        // FIXME: Review for anonymous methods
                        //
                }
                
                public override void Emit (EmitContext ec)
                {
                        Emit (ec, false);
                }
                
                public void Emit (EmitContext ec, bool leave_copy)
                {
                        ILGenerator ig = ec.ig;
                        int arg_idx = idx;

                        if (ec.HaveCaptureInfo && ec.IsParameterCaptured (name)){
                                if (leave_copy)
                                        throw new InternalErrorException ();
                                
                                ec.EmitParameter (name);
                                return;
                        }

                        if (!ec.MethodIsStatic)
                                arg_idx++;

                        EmitLdArg (ig, arg_idx);

                        if (is_ref) {
                                if (prepared)
                                        ec.ig.Emit (OpCodes.Dup);
        
                                //
                                // If we are a reference, we loaded on the stack a pointer
                                // Now lets load the real value
                                //
                                LoadFromPtr (ig, type);
                        }
                        
                        if (leave_copy) {
                                ec.ig.Emit (OpCodes.Dup);
                                
                                if (is_ref) {
                                        temp = new LocalTemporary (ec, type);
                                        temp.Store (ec);
                                }
                        }
                }
                
                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool prepare_for_load)
                {
                        if (ec.HaveCaptureInfo && ec.IsParameterCaptured (name)){
                                ec.EmitAssignParameter (name, source, leave_copy, prepare_for_load);
                                return;
                        }

                        ILGenerator ig = ec.ig;
                        int arg_idx = idx;
                        
                        prepared = prepare_for_load;
                        
                        if (!ec.MethodIsStatic)
                                arg_idx++;

                        if (is_ref && !prepared)
                                EmitLdArg (ig, arg_idx);
                        
                        source.Emit (ec);

                        if (leave_copy)
                                ec.ig.Emit (OpCodes.Dup);
                        
                        if (is_ref) {
                                if (leave_copy) {
                                        temp = new LocalTemporary (ec, type);
                                        temp.Store (ec);
                                }
                                
                                StoreFromPtr (ig, type);
                                
                                if (temp != null)
                                        temp.Emit (ec);
                        } else {
                                if (arg_idx <= 255)
                                        ig.Emit (OpCodes.Starg_S, (byte) arg_idx);
                                else
                                        ig.Emit (OpCodes.Starg, arg_idx);
                        }
                }

                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        if (ec.HaveCaptureInfo && ec.IsParameterCaptured (name)){
                                ec.EmitAddressOfParameter (name);
                                return;
                        }
                        
                        int arg_idx = idx;

                        if (!ec.MethodIsStatic)
                                arg_idx++;

                        if (is_ref){
                                if (arg_idx <= 255)
                                        ec.ig.Emit (OpCodes.Ldarg_S, (byte) arg_idx);
                                else
                                        ec.ig.Emit (OpCodes.Ldarg, arg_idx);
                        } else {
                                if (arg_idx <= 255)
                                        ec.ig.Emit (OpCodes.Ldarga_S, (byte) arg_idx);
                                else
                                        ec.ig.Emit (OpCodes.Ldarga, arg_idx);
                        }
                }

                public override string ToString ()
                {
                        return "ParameterReference[" + name + "]";
                }
        }
        
        /// <summary>
        ///   Used for arguments to New(), Invocation()
        /// </summary>
        public class Argument {
                public enum AType : byte {
                        Expression,
                        Ref,
                        Out,
                        ArgList
                };

                public readonly AType ArgType;
                public Expression Expr;
                
                public Argument (Expression expr, AType type)
                {
                        this.Expr = expr;
                        this.ArgType = type;
                }

                public Argument (Expression expr)
                {
                        this.Expr = expr;
                        this.ArgType = AType.Expression;
                }

                public Type Type {
                        get {
                                if (ArgType == AType.Ref || ArgType == AType.Out)
                                        return TypeManager.GetReferenceType (Expr.Type);
                                else
                                        return Expr.Type;
                        }
                }

                public Parameter.Modifier Modifier
                {
                        get {
                                switch (ArgType) {
                                        case AType.Out:
                                                return Parameter.Modifier.OUT;

                                        case AType.Ref:
                                                return Parameter.Modifier.REF;

                                        default:
                                                return Parameter.Modifier.NONE;
                                }
                        }
                }

                public static string FullDesc (Argument a)
                {
                        if (a.ArgType == AType.ArgList)
                                return "__arglist";

                        return (a.ArgType == AType.Ref ? "ref " :
                                (a.ArgType == AType.Out ? "out " : "")) +
                                TypeManager.CSharpName (a.Expr.Type);
                }

                public bool ResolveMethodGroup (EmitContext ec, Location loc)
                {
                        // FIXME: csc doesn't report any error if you try to use `ref' or
                        //        `out' in a delegate creation expression.
                        Expr = Expr.Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
                        if (Expr == null)
                                return false;

                        return true;
                }
                
                void Error_LValueRequired (Location loc)
                {
                        Report.Error (1510, loc, "A ref or out argument must be an assignable variable");
                }

                public bool Resolve (EmitContext ec, Location loc)
                {
                        bool old_do_flow_analysis = ec.DoFlowAnalysis;
                        ec.DoFlowAnalysis = true;

                        if (ArgType == AType.Ref) {
                                ec.InRefOutArgumentResolving = true;
                                Expr = Expr.Resolve (ec);
                                ec.InRefOutArgumentResolving = false;
                                if (Expr == null) {
                                        ec.DoFlowAnalysis = old_do_flow_analysis;
                                        return false;
                                }

                                Expr = Expr.DoResolveLValue (ec, Expr);
                                if (Expr == null)
                                        Error_LValueRequired (loc);
                        } else if (ArgType == AType.Out) {
                                ec.InRefOutArgumentResolving = true;
                                Expr = Expr.DoResolveLValue (ec, EmptyExpression.Null);
                                ec.InRefOutArgumentResolving = false;

                                if (Expr == null)
                                        Error_LValueRequired (loc);
                        }
                        else
                                Expr = Expr.Resolve (ec);

                        ec.DoFlowAnalysis = old_do_flow_analysis;

                        if (Expr == null)
                                return false;

                        if (ArgType == AType.Expression)
                                return true;
                        else {
                                //
                                // Catch errors where fields of a MarshalByRefObject are passed as ref or out
                                // This is only allowed for `this'
                                //
                                FieldExpr fe = Expr as FieldExpr;
                                if (fe != null && !fe.IsStatic){
                                        Expression instance = fe.InstanceExpression;

                                        if (instance.GetType () != typeof (This)){
                                                if (fe.InstanceExpression.Type.IsSubclassOf (TypeManager.mbr_type)){
                                                        Report.SymbolRelatedToPreviousError (fe.InstanceExpression.Type);
                                                        Report.Warning (197, 1, loc,
                                                                "Passing `{0}' as ref or out or taking its address may cause a runtime exception because it is a field of a marshal-by-reference class",
                                                                fe.GetSignatureForError ());
                                                        return false;
                                                }
                                        }
                                }
                        }

                        if (Expr.eclass != ExprClass.Variable){
                                //
                                // We just probe to match the CSC output
                                //
                                if (Expr.eclass == ExprClass.PropertyAccess ||
                                    Expr.eclass == ExprClass.IndexerAccess){
                                        Report.Error (206, loc, "A property or indexer `{0}' may not be passed as an out or ref parameter",
                                                Expr.GetSignatureForError ());
                                } else {
                                        Error_LValueRequired (loc);
                                }
                                return false;
                        }
                                
                        return true;
                }

                public void Emit (EmitContext ec)
                {
                        //
                        // Ref and Out parameters need to have their addresses taken.
                        //
                        // ParameterReferences might already be references, so we want
                        // to pass just the value
                        //
                        if (ArgType == AType.Ref || ArgType == AType.Out){
                                AddressOp mode = AddressOp.Store;

                                if (ArgType == AType.Ref)
                                        mode |= AddressOp.Load;
                                
                                if (Expr is ParameterReference){
                                        ParameterReference pr = (ParameterReference) Expr;

                                        if (pr.IsRef)
                                                pr.EmitLoad (ec);
                                        else {
                                                
                                                pr.AddressOf (ec, mode);
                                        }
                                } else {
                                        if (Expr is IMemoryLocation)
                                               ((IMemoryLocation) Expr).AddressOf (ec, mode);
                                        else {
                                                Error_LValueRequired (Expr.Location);
                                                return;
                                        }
                                }
                        } else
                                Expr.Emit (ec);
                }
        }

        /// <summary>
        ///   Invocation of methods or delegates.
        /// </summary>
        public class Invocation : ExpressionStatement {
                public readonly ArrayList Arguments;

                Expression expr;
                MethodBase method = null;
                
                //
                // arguments is an ArrayList, but we do not want to typecast,
                // as it might be null.
                //
                // FIXME: only allow expr to be a method invocation or a
                // delegate invocation (7.5.5)
                //
                public Invocation (Expression expr, ArrayList arguments)
                {
                        this.expr = expr;
                        Arguments = arguments;
                        loc = expr.Location;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                /// <summary>
                ///   Determines "better conversion" as specified in 14.4.2.3
                ///
                ///    Returns : p    if a->p is better,
                ///              q    if a->q is better,
                ///              null if neither is better
                /// </summary>
                static Type BetterConversion (EmitContext ec, Argument a, Type p, Type q, Location loc)
                {
                        Type argument_type = a.Type;
                        Expression argument_expr = a.Expr;

                        if (argument_type == null)
                                throw new Exception ("Expression of type " + a.Expr +
                                                     " does not resolve its type");

                        if (p == null || q == null)
                                throw new InternalErrorException ("BetterConversion Got a null conversion");

                        if (p == q)
                                return null;

                        if (argument_expr is NullLiteral) {
                                //
                                // If the argument is null and one of the types to compare is 'object' and
                                // the other is a reference type, we prefer the other.
                                //
                                // This follows from the usual rules:
                                //   * There is an implicit conversion from 'null' to type 'object'
                                //   * There is an implicit conversion from 'null' to any reference type
                                //   * There is an implicit conversion from any reference type to type 'object'
                                //   * There is no implicit conversion from type 'object' to other reference types
                                //  => Conversion of 'null' to a reference type is better than conversion to 'object'
                                //
                                //  FIXME: This probably isn't necessary, since the type of a NullLiteral is the 
                                //         null type. I think it used to be 'object' and thus needed a special 
                                //         case to avoid the immediately following two checks.
                                //
                                if (!p.IsValueType && q == TypeManager.object_type)
                                        return p;
                                if (!q.IsValueType && p == TypeManager.object_type)
                                        return q;
                        }
                                
                        if (argument_type == p)
                                return p;

                        if (argument_type == q)
                                return q;

                        Expression p_tmp = new EmptyExpression (p);
                        Expression q_tmp = new EmptyExpression (q);

                        bool p_to_q = Convert.ImplicitConversionExists (ec, p_tmp, q);
                        bool q_to_p = Convert.ImplicitConversionExists (ec, q_tmp, p);

                        if (p_to_q && !q_to_p)
                                return p;

                        if (q_to_p && !p_to_q)
                                return q;

                        if (p == TypeManager.sbyte_type)
                                if (q == TypeManager.byte_type || q == TypeManager.ushort_type ||
                                    q == TypeManager.uint32_type || q == TypeManager.uint64_type)
                                        return p;
                        if (q == TypeManager.sbyte_type)
                                if (p == TypeManager.byte_type || p == TypeManager.ushort_type ||
                                    p == TypeManager.uint32_type || p == TypeManager.uint64_type)
                                        return q;

                        if (p == TypeManager.short_type)
                                if (q == TypeManager.ushort_type || q == TypeManager.uint32_type ||
                                    q == TypeManager.uint64_type)
                                        return p;
                        if (q == TypeManager.short_type)
                                if (p == TypeManager.ushort_type || p == TypeManager.uint32_type ||
                                    p == TypeManager.uint64_type)
                                        return q;

                        if (p == TypeManager.int32_type)
                                if (q == TypeManager.uint32_type || q == TypeManager.uint64_type)
                                        return p;
                        if (q == TypeManager.int32_type)
                                if (p == TypeManager.uint32_type || p == TypeManager.uint64_type)
                                        return q;

                        if (p == TypeManager.int64_type)
                                if (q == TypeManager.uint64_type)
                                        return p;
                        if (q == TypeManager.int64_type)
                                if (p == TypeManager.uint64_type)
                                        return q;

                        return null;
                }
                
                /// <summary>
                ///   Determines "Better function" between candidate
                ///   and the current best match
                /// </summary>
                /// <remarks>
                ///    Returns an integer indicating :
                ///     false if candidate ain't better
                ///     true if candidate is better than the current best match
                /// </remarks>
                static bool BetterFunction (EmitContext ec, ArrayList args, int argument_count,
                                            MethodBase candidate, bool candidate_params,
                                            MethodBase best, bool best_params, Location loc)
                {
                        ParameterData candidate_pd = TypeManager.GetParameterData (candidate);
                        ParameterData best_pd = TypeManager.GetParameterData (best);
                
                        bool better_at_least_one = false;
                        bool same = true;
                        for (int j = 0; j < argument_count; ++j) {
                                Argument a = (Argument) args [j];

                                Type ct = TypeManager.TypeToCoreType (candidate_pd.ParameterType (j));
                                Type bt = TypeManager.TypeToCoreType (best_pd.ParameterType (j));

                                if (candidate_pd.ParameterModifier (j) == Parameter.Modifier.PARAMS)
                                        if (candidate_params)
                                                ct = TypeManager.GetElementType (ct);

                                if (best_pd.ParameterModifier (j) == Parameter.Modifier.PARAMS)
                                        if (best_params)
                                                bt = TypeManager.GetElementType (bt);

                                if (ct == bt)
                                        continue;

                                same = false;
                                Type better = BetterConversion (ec, a, ct, bt, loc);

                                // for each argument, the conversion to 'ct' should be no worse than 
                                // the conversion to 'bt'.
                                if (better == bt)
                                        return false;

                                // for at least one argument, the conversion to 'ct' should be better than 
                                // the conversion to 'bt'.
                                if (better == ct)
                                        better_at_least_one = true;
                        }

                        if (better_at_least_one)
                                return true;

                        //
                        // This handles the case
                        //
                        //   Add (float f1, float f2, float f3);
                        //   Add (params decimal [] foo);
                        //
                        // The call Add (3, 4, 5) should be ambiguous.  Without this check, the
                        // first candidate would've chosen as better.
                        //
                        if (!same)
                                return false;

                        //
                        // This handles the following cases:
                        //
                        //   Trim () is better than Trim (params char[] chars)
                        //   Concat (string s1, string s2, string s3) is better than
                        //     Concat (string s1, params string [] srest)
                        //
                        return !candidate_params && best_params;
                }

                internal static bool IsOverride (MethodBase cand_method, MethodBase base_method)
                {
                        if (!IsAncestralType (base_method.DeclaringType, cand_method.DeclaringType))
                                return false;

                        ParameterData cand_pd = TypeManager.GetParameterData (cand_method);
                        ParameterData base_pd = TypeManager.GetParameterData (base_method);
                
                        if (cand_pd.Count != base_pd.Count)
                                return false;

                        for (int j = 0; j < cand_pd.Count; ++j) {
                                Parameter.Modifier cm = cand_pd.ParameterModifier (j);
                                Parameter.Modifier bm = base_pd.ParameterModifier (j);
                                Type ct = TypeManager.TypeToCoreType (cand_pd.ParameterType (j));
                                Type bt = TypeManager.TypeToCoreType (base_pd.ParameterType (j));

                                if (cm != bm || ct != bt)
                                        return false;
                        }

                        return true;
                }

                public static string FullMethodDesc (MethodBase mb)
                {
                        if (mb == null)
                                return "";

                        StringBuilder sb;
                        if (mb is MethodInfo) {
                                sb = new StringBuilder (TypeManager.CSharpName (((MethodInfo) mb).ReturnType));
                                sb.Append (" ");
                        }
                        else
                                sb = new StringBuilder ();

                        sb.Append (TypeManager.CSharpSignature (mb));
                        return sb.ToString ();
                }

                public static MethodGroupExpr MakeUnionSet (Expression mg1, Expression mg2, Location loc)
                {
                        MemberInfo [] miset;
                        MethodGroupExpr union;

                        if (mg1 == null) {
                                if (mg2 == null)
                                        return null;
                                return (MethodGroupExpr) mg2;
                        } else {
                                if (mg2 == null)
                                        return (MethodGroupExpr) mg1;
                        }
                        
                        MethodGroupExpr left_set = null, right_set = null;
                        int length1 = 0, length2 = 0;
                        
                        left_set = (MethodGroupExpr) mg1;
                        length1 = left_set.Methods.Length;
                        
                        right_set = (MethodGroupExpr) mg2;
                        length2 = right_set.Methods.Length;
                        
                        ArrayList common = new ArrayList ();

                        foreach (MethodBase r in right_set.Methods){
                                if (TypeManager.ArrayContainsMethod (left_set.Methods, r))
                                        common.Add (r);
                        }

                        miset = new MemberInfo [length1 + length2 - common.Count];
                        left_set.Methods.CopyTo (miset, 0);
                        
                        int k = length1;

                        foreach (MethodBase r in right_set.Methods) {
                                if (!common.Contains (r))
                                        miset [k++] = r;
                        }

                        union = new MethodGroupExpr (miset, loc);
                        
                        return union;
                }

                public static bool IsParamsMethodApplicable (EmitContext ec,
                                                             ArrayList arguments, int arg_count,
                                                             MethodBase candidate)
                {
                        return IsParamsMethodApplicable (
                                ec, arguments, arg_count, candidate, false) ||
                                IsParamsMethodApplicable (
                                        ec, arguments, arg_count, candidate, true);


                }

                /// <summary>
                ///   Determines if the candidate method, if a params method, is applicable
                ///   in its expanded form to the given set of arguments
                /// </summary>
                static bool IsParamsMethodApplicable (EmitContext ec, ArrayList arguments,
                                                      int arg_count, MethodBase candidate,
                                                      bool do_varargs)
                {
                        ParameterData pd = TypeManager.GetParameterData (candidate);

                        int pd_count = pd.Count;
                        if (pd_count == 0)
                                return false;

                        int count = pd_count - 1;
                        if (do_varargs) {
                                if (pd.ParameterModifier (count) != Parameter.Modifier.ARGLIST)
                                        return false;
                                if (pd_count != arg_count)
                                        return false;
                        } else {
                                if (!pd.HasParams)
                                        return false;
                        }
                        
                        if (count > arg_count)
                                return false;
                        
                        if (pd_count == 1 && arg_count == 0)
                                return true;

                        //
                        // If we have come this far, the case which
                        // remains is when the number of parameters is
                        // less than or equal to the argument count.
                        //
                        for (int i = 0; i < count; ++i) {

                                Argument a = (Argument) arguments [i];

                                Parameter.Modifier a_mod = a.Modifier & 
                                        (unchecked (~(Parameter.Modifier.OUTMASK | Parameter.Modifier.REFMASK)));
                                Parameter.Modifier p_mod = pd.ParameterModifier (i) &
                                        (unchecked (~(Parameter.Modifier.OUTMASK | Parameter.Modifier.REFMASK)));

                                if (a_mod == p_mod) {

                                        if (a_mod == Parameter.Modifier.NONE)
                                                if (!Convert.ImplicitConversionExists (ec,
                                                                                       a.Expr,
                                                                                       pd.ParameterType (i)))
                                return false;

                                        if ((a_mod & Parameter.Modifier.ISBYREF) != 0) {
                                                Type pt = pd.ParameterType (i);

                                                if (!pt.IsByRef)
                                                        pt = TypeManager.GetReferenceType (pt);
                                                
                                                if (pt != a.Type)
                                                        return false;
                                        }
                                } else
                                        return false;
                                
                        }

                        if (do_varargs) {
                                Argument a = (Argument) arguments [count];
                                if (!(a.Expr is Arglist))
                                        return false;

                                return true;
                        }

                        Type element_type = TypeManager.GetElementType (pd.ParameterType (pd_count - 1));

                        for (int i = pd_count - 1; i < arg_count; i++) {
                                Argument a = (Argument) arguments [i];

                                if (!Convert.ImplicitConversionExists (ec, a.Expr, element_type))
                                        return false;
                        }
                        
                        return true;
                }

                /// <summary>
                ///   Determines if the candidate method is applicable (section 14.4.2.1)
                ///   to the given set of arguments
                /// </summary>
                public static bool IsApplicable (EmitContext ec, ArrayList arguments, int arg_count,
                        MethodBase candidate)
                {
                        ParameterData pd = TypeManager.GetParameterData (candidate);

                        if (arg_count != pd.Count)
                                return false;

                        for (int i = arg_count; i > 0; ) {
                                i--;

                                Argument a = (Argument) arguments [i];

                                Parameter.Modifier a_mod = a.Modifier &
                                        ~(Parameter.Modifier.OUTMASK | Parameter.Modifier.REFMASK);

                                Parameter.Modifier p_mod = pd.ParameterModifier (i) &
                                        ~(Parameter.Modifier.OUTMASK | Parameter.Modifier.REFMASK | Parameter.Modifier.PARAMS);

                                if (a_mod == p_mod) {
                                        Type pt = pd.ParameterType (i);

                                        if (a_mod == Parameter.Modifier.NONE) {
                                                if (!Convert.ImplicitConversionExists (ec, a.Expr, pt))
                                                        return false;
                                                continue;
                                        }
                                        
                                        if (pt != a.Type)
                                                return false;
                                } else
                                        return false;
                        }

                        return true;
                }

                static internal bool IsAncestralType (Type first_type, Type second_type)
                {
                        return first_type != second_type &&
                                (second_type.IsSubclassOf (first_type) ||
                                 TypeManager.ImplementsInterface (second_type, first_type));
                }
                
                /// <summary>
                ///   Find the Applicable Function Members (7.4.2.1)
                ///
                ///   me: Method Group expression with the members to select.
                ///       it might contain constructors or methods (or anything
                ///       that maps to a method).
                ///
                ///   Arguments: ArrayList containing resolved Argument objects.
                ///
                ///   loc: The location if we want an error to be reported, or a Null
                ///        location for "probing" purposes.
                ///
                ///   Returns: The MethodBase (either a ConstructorInfo or a MethodInfo)
                ///            that is the best match of me on Arguments.
                ///
                /// </summary>
                public static MethodBase OverloadResolve (EmitContext ec, MethodGroupExpr me,
                                                          ArrayList Arguments, bool may_fail, 
                                                          Location loc)
                {
                        MethodBase method = null;
                        bool method_params = false;
                        Type applicable_type = null;
                        int arg_count = 0;
                        ArrayList candidates = new ArrayList (2);
                        ArrayList candidate_overrides = null;

                        //
                        // Used to keep a map between the candidate
                        // and whether it is being considered in its
                        // normal or expanded form
                        //
                        // false is normal form, true is expanded form
                        //
                        Hashtable candidate_to_form = null;

                        if (Arguments != null)
                                arg_count = Arguments.Count;

                        if ((me.Name == "Invoke") &&
                                TypeManager.IsDelegateType (me.DeclaringType)) {
                                Error_InvokeOnDelegate (loc);
                                return null;
                        }

                        MethodBase[] methods = me.Methods;

                        //
                        // First we construct the set of applicable methods
                        //
                        bool is_sorted = true;
                        for (int i = 0; i < methods.Length; i++){
                                Type decl_type = methods [i].DeclaringType;

                                //
                                // If we have already found an applicable method
                                // we eliminate all base types (Section 14.5.5.1)
                                //
                                if ((applicable_type != null) &&
                                        IsAncestralType (decl_type, applicable_type))
                                        continue;

                                //
                                // Methods marked 'override' don't take part in 'applicable_type'
                                // computation, nor in the actual overload resolution.
                                // However, they still need to be emitted instead of a base virtual method.
                                // We avoid doing the 'applicable' test here, since it'll anyway be applied
                                // to the base virtual function, and IsOverride is much faster than IsApplicable.
                                //
                                if (!me.IsBase && TypeManager.IsOverride (methods [i])) {
                                        if (candidate_overrides == null)
                                                candidate_overrides = new ArrayList ();
                                        candidate_overrides.Add (methods [i]);
                                        continue;
                                }

                                //
                                // Check if candidate is applicable (section 14.4.2.1)
                                //   Is candidate applicable in normal form?
                                //
                                bool is_applicable = IsApplicable (
                                        ec, Arguments, arg_count, methods [i]);

                                if (!is_applicable &&
                                        (IsParamsMethodApplicable (
                                        ec, Arguments, arg_count, methods [i]))) {
                                        MethodBase candidate = methods [i];
                                        if (candidate_to_form == null)
                                                candidate_to_form = new PtrHashtable ();
                                        candidate_to_form [candidate] = candidate;
                                        // Candidate is applicable in expanded form
                                        is_applicable = true;
                                }

                                if (!is_applicable)
                                        continue;

                                candidates.Add (methods [i]);

                                if (applicable_type == null)
                                        applicable_type = decl_type;
                                else if (applicable_type != decl_type) {
                                        is_sorted = false;
                                        if (IsAncestralType (applicable_type, decl_type))
                                                applicable_type = decl_type;
                                }
                        }

                        int candidate_top = candidates.Count;

                        if (applicable_type == null) {
                                //
                                // Okay so we have failed to find anything so we
                                // return by providing info about the closest match
                                //
                                int errors = Report.Errors;
                                for (int i = 0; i < methods.Length; ++i) {
                                        MethodBase c = (MethodBase) methods [i];
                                        ParameterData pd = TypeManager.GetParameterData (c);

                                        if (pd.Count != arg_count)
                                                continue;

                                        VerifyArgumentsCompat (ec, Arguments, arg_count,
                                                c, false, null, may_fail, loc);

                                        if (!may_fail && errors == Report.Errors)
                                                throw new InternalErrorException (
                                                        "VerifyArgumentsCompat and IsApplicable do not agree; " +
                                                        "likely reason: ImplicitConversion and ImplicitConversionExists have gone out of sync");

                                        break;
                                }

                                if (!may_fail && errors == Report.Errors) {
                                        string report_name = me.Name;
                                        if (report_name == ".ctor")
                                                report_name = me.DeclaringType.ToString ();
                                        Error_WrongNumArguments (loc, report_name, arg_count);
                                }
                                
                                return null;
                        }

                        if (!is_sorted) {
                                //
                                // At this point, applicable_type is _one_ of the most derived types
                                // in the set of types containing the methods in this MethodGroup.
                                // Filter the candidates so that they only contain methods from the
                                // most derived types.
                                //

                                int finalized = 0; // Number of finalized candidates

                                do {
                                        // Invariant: applicable_type is a most derived type

                                        // We'll try to complete Section 14.5.5.1 for 'applicable_type' by 
                                        // eliminating all it's base types.  At the same time, we'll also move
                                        // every unrelated type to the end of the array, and pick the next
                                        // 'applicable_type'.

                                        Type next_applicable_type = null;
                                        int j = finalized; // where to put the next finalized candidate
                                        int k = finalized; // where to put the next undiscarded candidate
                                        for (int i = finalized; i < candidate_top; ++i) {
                                                MethodBase candidate = (MethodBase) candidates [i];
                                                Type decl_type = candidate.DeclaringType;

                                                if (decl_type == applicable_type) {
                                                        candidates [k++] = candidates [j];
                                                        candidates [j++] = candidates [i];
                                                        continue;
                                                }

                                                if (IsAncestralType (decl_type, applicable_type))
                                                        continue;

                                                if (next_applicable_type != null &&
                                                    IsAncestralType (decl_type, next_applicable_type))
                                                        continue;

                                                candidates [k++] = candidates [i];

                                                if (next_applicable_type == null ||
                                                    IsAncestralType (next_applicable_type, decl_type))
                                                        next_applicable_type = decl_type;
                                        }

                                        applicable_type = next_applicable_type;
                                        finalized = j;
                                        candidate_top = k;
                                } while (applicable_type != null);
                        }

                        //
                        // Now we actually find the best method
                        //

                        method = (MethodBase) candidates [0];
                        method_params = candidate_to_form != null && candidate_to_form.Contains (method);
                        for (int ix = 1; ix < candidate_top; ix++){
                                MethodBase candidate = (MethodBase) candidates [ix];

                                if (candidate == method)
                                        continue;

                                bool cand_params = candidate_to_form != null && candidate_to_form.Contains (candidate);
                                
                                if (BetterFunction (ec, Arguments, arg_count, 
                                                    candidate, cand_params,
                                                    method, method_params, loc)) {
                                        method = candidate;
                                        method_params = cand_params;
                                }
                        }
                        //
                        // Now check that there are no ambiguities i.e the selected method
                        // should be better than all the others
                        //
                        MethodBase ambiguous = null;
                        for (int ix = 0; ix < candidate_top; ix++){
                                MethodBase candidate = (MethodBase) candidates [ix];

                                if (candidate == method)
                                        continue;

                                bool cand_params = candidate_to_form != null && candidate_to_form.Contains (candidate);
                                if (!BetterFunction (ec, Arguments, arg_count,
                                                     method, method_params,
                                                     candidate, cand_params,
                                                     loc)) {
                                        Report.SymbolRelatedToPreviousError (candidate);
                                        ambiguous = candidate;
                                }
                        }

                        if (ambiguous != null) {
                                Report.SymbolRelatedToPreviousError (method);
                                Report.Error (121, loc, "The call is ambiguous between the following methods or properties: `{0}' and `{1}'",
                                        TypeManager.CSharpSignature (ambiguous), TypeManager.CSharpSignature (method));
                                return null;
                        }

                        //
                        // If the method is a virtual function, pick an override closer to the LHS type.
                        //
                        if (!me.IsBase && method.IsVirtual) {
                                if (TypeManager.IsOverride (method))
                                        throw new InternalErrorException (
                                                "Should not happen.  An 'override' method took part in overload resolution: " + method);

                                if (candidate_overrides != null)
                                        foreach (MethodBase candidate in candidate_overrides) {
                                                if (IsOverride (candidate, method))
                                                        method = candidate;
                                        }
                        }

                        //
                        // And now check if the arguments are all
                        // compatible, perform conversions if
                        // necessary etc. and return if everything is
                        // all right
                        //
                        if (!VerifyArgumentsCompat (ec, Arguments, arg_count, method,
                                                    method_params, null, may_fail, loc))
                                return null;

                        if (method != null) {
                                IMethodData data = TypeManager.GetMethod (method);
                                if (data != null)
                                        data.SetMemberIsUsed ();
                        }
                        return method;
                }

                public static void Error_WrongNumArguments (Location loc, String name, int arg_count)
                {
                        Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
                                name, arg_count.ToString ());
                }

                static void Error_InvokeOnDelegate (Location loc)
                {
                        Report.Error (1533, loc,
                                      "Invoke cannot be called directly on a delegate");
                }
                        
                static void Error_InvalidArguments (Location loc, int idx, MethodBase method,
                                                    Type delegate_type, Argument a, ParameterData expected_par)
                {
                        if (delegate_type == null) 
                                Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
                                              TypeManager.CSharpSignature (method));
                        else
                                Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
                                        TypeManager.CSharpName (delegate_type));

                        Parameter.Modifier mod = expected_par.ParameterModifier (idx);

                        string index = (idx + 1).ToString ();
                        if (mod != Parameter.Modifier.ARGLIST && mod != a.Modifier) {
                                if ((mod & (Parameter.Modifier.REF | Parameter.Modifier.OUT)) == 0)
                                        Report.Error (1615, loc, "Argument `{0}' should not be passed with the `{1}' keyword",
                                                index, Parameter.GetModifierSignature (a.Modifier));
                                else
                                        Report.Error (1620, loc, "Argument `{0}' must be passed with the `{1}' keyword",
                                                index, Parameter.GetModifierSignature (mod));
                        } else {
                                Report.Error (1503, loc, "Argument {0}: Cannot convert from `{1}' to `{2}'",
                                        index, Argument.FullDesc (a), expected_par.ParameterDesc (idx));
                        }
                }
                
                public static bool VerifyArgumentsCompat (EmitContext ec, ArrayList Arguments,
                                                          int arg_count, MethodBase method, 
                                                          bool chose_params_expanded,
                                                          Type delegate_type, bool may_fail,
                                                          Location loc)
                {
                        ParameterData pd = TypeManager.GetParameterData (method);
                        int pd_count = pd.Count;

                        for (int j = 0; j < arg_count; j++) {
                                Argument a = (Argument) Arguments [j];
                                Expression a_expr = a.Expr;
                                Type parameter_type = pd.ParameterType (j);
                                Parameter.Modifier pm = pd.ParameterModifier (j);
                                
                                if (pm == Parameter.Modifier.PARAMS){
                                        if ((pm & ~Parameter.Modifier.PARAMS) != a.Modifier) {
                                                if (!may_fail)
                                                        Error_InvalidArguments (loc, j, method, delegate_type, a, pd);
                                                return false;
                                        }

                                        if (chose_params_expanded)
                                                parameter_type = TypeManager.GetElementType (parameter_type);
                                } else if (pm == Parameter.Modifier.ARGLIST) {
                                        if (!(a.Expr is Arglist)) {
                                                if (!may_fail)
                                                        Error_InvalidArguments (loc, j, method, delegate_type, a, pd);
                                                return false;
                                        }
                                        continue;
                                } else {
                                        //
                                        // Check modifiers
                                        //
                                        if (pd.ParameterModifier (j) != a.Modifier){
                                                if (!may_fail)
                                                        Error_InvalidArguments (loc, j, method, delegate_type, a, pd);
                                                return false;
                                        }
                                }

                                //
                                // Check Type
                                //
                                if (!a.Type.Equals (parameter_type)){
                                        Expression conv;
                                        
                                        conv = Convert.ImplicitConversion (ec, a_expr, parameter_type, loc);

                                        if (conv == null) {
                                                if (!may_fail)
                                                        Error_InvalidArguments (loc, j, method, delegate_type, a, pd);
                                                return false;
                                        }
                                        
                                        //
                                        // Update the argument with the implicit conversion
                                        //
                                        if (a_expr != conv)
                                                a.Expr = conv;
                                }

                                if (parameter_type.IsPointer){
                                        if (!ec.InUnsafe){
                                                UnsafeError (loc);
                                                return false;
                                        }
                                }
                                
                                Parameter.Modifier a_mod = a.Modifier &
                                        unchecked (~(Parameter.Modifier.OUT | Parameter.Modifier.REF));
                                Parameter.Modifier p_mod = pd.ParameterModifier (j) &
                                        unchecked (~(Parameter.Modifier.OUT | Parameter.Modifier.REF));
                                
                                if (a_mod != p_mod &&
                                    pd.ParameterModifier (pd_count - 1) != Parameter.Modifier.PARAMS) {
                                        if (!may_fail) {
                                                Invocation.Error_InvalidArguments (loc, j, method, null, a, pd);
                                        }
                                        
                                        return false;
                                }
                        }

                        return true;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        //
                        // First, resolve the expression that is used to
                        // trigger the invocation
                        //
                        expr = expr.Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
                        if (expr == null)
                                return null;

                        if (!(expr is MethodGroupExpr)) {
                                Type expr_type = expr.Type;

                                if (expr_type != null){
                                        bool IsDelegate = TypeManager.IsDelegateType (expr_type);
                                        if (IsDelegate)
                                                return (new DelegateInvocation (
                                                        this.expr, Arguments, loc)).Resolve (ec);
                                }
                        }

                        if (!(expr is MethodGroupExpr)){
                                expr.Error_UnexpectedKind (ResolveFlags.MethodGroup, loc);
                                return null;
                        }

                        //
                        // Next, evaluate all the expressions in the argument list
                        //
                        if (Arguments != null){
                                foreach (Argument a in Arguments){
                                        if (!a.Resolve (ec, loc))
                                                return null;
                                }
                        }

                        MethodGroupExpr mg = (MethodGroupExpr) expr;
                        method = OverloadResolve (ec, mg, Arguments, false, loc);

                        if (method == null)
                                return null;

                        MethodInfo mi = method as MethodInfo;
                        if (mi != null) {
                                type = TypeManager.TypeToCoreType (mi.ReturnType);
                                Expression iexpr = mg.InstanceExpression;
                                if (mi.IsStatic) {
                                        if (iexpr == null || 
                                            iexpr is This || iexpr is EmptyExpression ||
                                            mg.IdenticalTypeName) {
                                                mg.InstanceExpression = null;
                                        } else {
                                                MemberExpr.error176 (loc, TypeManager.CSharpSignature (mi));
                                                return null;
                                        }
                                } else {
                                        if (iexpr == null || iexpr is EmptyExpression) {
                                                SimpleName.Error_ObjectRefRequired (ec, loc, TypeManager.CSharpSignature (mi));
                                                return null;
                                        }
                                }
                        }

                        if (type.IsPointer){
                                if (!ec.InUnsafe){
                                        UnsafeError (loc);
                                        return null;
                                }
                        }
                        
                        //
                        // Only base will allow this invocation to happen.
                        //
                        if (mg.IsBase && method.IsAbstract){
                                Error_CannotCallAbstractBase (TypeManager.CSharpSignature (method));
                                return null;
                        }

                        if (Arguments == null && method.Name == "Finalize") {
                                if (mg.IsBase)
                                        Report.Error (250, loc, "Do not directly call your base class Finalize method. It is called automatically from your destructor");
                                else
                                        Report.Error (245, loc, "Destructors and object.Finalize cannot be called directly. Consider calling IDisposable.Dispose if available");
                                return null;
                        }

                        if ((method.Attributes & MethodAttributes.SpecialName) != 0 && IsSpecialMethodInvocation (method)) {
                                return null;
                        }

                        if (mg.InstanceExpression != null)
                                mg.InstanceExpression.CheckMarshallByRefAccess (ec.ContainerType);

                        eclass = ExprClass.Value;
                        return this;
                }

                bool IsSpecialMethodInvocation (MethodBase method)
                {
                        IMethodData md = TypeManager.GetMethod (method);
                        if (md != null) {
                                if (!(md is AbstractPropertyEventMethod) && !(md is Operator))
                                        return false;
                        } else {
                                if (!TypeManager.IsSpecialMethod (method))
                                        return false;

                                int args = TypeManager.GetParameterData (method).Count;
                                if (method.Name.StartsWith ("get_") && args > 0)
                                        return false;
                                else if (method.Name.StartsWith ("set_") && args > 2)
                                        return false;

                                // TODO: check operators and events as well ?
                        }

                        Report.SymbolRelatedToPreviousError (method);
                        Report.Error (571, loc, "`{0}': cannot explicitly call operator or accessor",
                                TypeManager.CSharpSignature (method, true));
        
                        return true;
                }

                // <summary>
                //   Emits the list of arguments as an array
                // </summary>
                static void EmitParams (EmitContext ec, int idx, ArrayList arguments)
                {
                        ILGenerator ig = ec.ig;
                        int count = arguments.Count - idx;
                        Argument a = (Argument) arguments [idx];
                        Type t = a.Expr.Type;
                        
                        IntConstant.EmitInt (ig, count);
                        ig.Emit (OpCodes.Newarr, TypeManager.TypeToCoreType (t));

                        int top = arguments.Count;
                        for (int j = idx; j < top; j++){
                                a = (Argument) arguments [j];
                                
                                ig.Emit (OpCodes.Dup);
                                IntConstant.EmitInt (ig, j - idx);

                                bool is_stobj;
                                OpCode op = ArrayAccess.GetStoreOpcode (t, out is_stobj);
                                if (is_stobj)
                                        ig.Emit (OpCodes.Ldelema, t);

                                a.Emit (ec);

                                if (is_stobj)
                                        ig.Emit (OpCodes.Stobj, t);
                                else
                                        ig.Emit (op);
                        }
                }
                
                /// <summary>
                ///   Emits a list of resolved Arguments that are in the arguments
                ///   ArrayList.
                /// 
                ///   The MethodBase argument might be null if the
                ///   emission of the arguments is known not to contain
                ///   a `params' field (for example in constructors or other routines
                ///   that keep their arguments in this structure)
                ///   
                ///   if `dup_args' is true, a copy of the arguments will be left
                ///   on the stack. If `dup_args' is true, you can specify `this_arg'
                ///   which will be duplicated before any other args. Only EmitCall
                ///   should be using this interface.
                /// </summary>
                public static void EmitArguments (EmitContext ec, MethodBase mb, ArrayList arguments, bool dup_args, LocalTemporary this_arg)
                {
                        ParameterData pd = mb == null ? null : TypeManager.GetParameterData (mb);
                        int top = arguments == null ? 0 : arguments.Count;
                        LocalTemporary [] temps = null;
                        
                        if (dup_args && top != 0)
                                temps = new LocalTemporary [top];

                        for (int i = 0; i < top; i++){
                                Argument a = (Argument) arguments [i];

                                if (pd != null){
                                        if (pd.ParameterModifier (i) == Parameter.Modifier.PARAMS){
                                                //
                                                // Special case if we are passing the same data as the
                                                // params argument, do not put it in an array.
                                                //
                                                if (pd.ParameterType (i) == a.Type)
                                                        a.Emit (ec);
                                                else
                                                        EmitParams (ec, i, arguments);
                                                return;
                                        }
                                }
                                            
                                a.Emit (ec);
                                if (dup_args) {
                                        ec.ig.Emit (OpCodes.Dup);
                                        (temps [i] = new LocalTemporary (ec, a.Type)).Store (ec);
                                }
                        }
                        
                        if (dup_args) {
                                if (this_arg != null)
                                        this_arg.Emit (ec);
                                
                                for (int i = 0; i < top; i ++)
                                        temps [i].Emit (ec);
                        }

                        if (pd != null && pd.Count > top &&
                            pd.ParameterModifier (top) == Parameter.Modifier.PARAMS){
                                ILGenerator ig = ec.ig;

                                IntConstant.EmitInt (ig, 0);
                                ig.Emit (OpCodes.Newarr, TypeManager.GetElementType (pd.ParameterType (top)));
                        }
                }

                static Type[] GetVarargsTypes (EmitContext ec, MethodBase mb,
                                               ArrayList arguments)
                {
                        ParameterData pd = TypeManager.GetParameterData (mb);

                        if (arguments == null)
                                return new Type [0];

                        Argument a = (Argument) arguments [pd.Count - 1];
                        Arglist list = (Arglist) a.Expr;

                        return list.ArgumentTypes;
                }

                /// <summary>
                /// This checks the ConditionalAttribute on the method 
                /// </summary>
                static bool IsMethodExcluded (MethodBase method, EmitContext ec)
                {
                        if (method.IsConstructor)
                                return false;

                        IMethodData md = TypeManager.GetMethod (method);
                        if (md != null)
                                return md.IsExcluded (ec);

                        // For some methods (generated by delegate class) GetMethod returns null
                        // because they are not included in builder_to_method table
                        if (method.DeclaringType is TypeBuilder)
                                return false;

                        return AttributeTester.IsConditionalMethodExcluded (method);
                }

                /// <remarks>
                ///   is_base tells whether we want to force the use of the `call'
                ///   opcode instead of using callvirt.  Call is required to call
                ///   a specific method, while callvirt will always use the most
                ///   recent method in the vtable.
                ///
                ///   is_static tells whether this is an invocation on a static method
                ///
                ///   instance_expr is an expression that represents the instance
                ///   it must be non-null if is_static is false.
                ///
                ///   method is the method to invoke.
                ///
                ///   Arguments is the list of arguments to pass to the method or constructor.
                /// </remarks>
                public static void EmitCall (EmitContext ec, bool is_base,
                                             bool is_static, Expression instance_expr,
                                             MethodBase method, ArrayList Arguments, Location loc)
                {
                        EmitCall (ec, is_base, is_static, instance_expr, method, Arguments, loc, false, false);
                }
                
                // `dup_args' leaves an extra copy of the arguments on the stack
                // `omit_args' does not leave any arguments at all.
                // So, basically, you could make one call with `dup_args' set to true,
                // and then another with `omit_args' set to true, and the two calls
                // would have the same set of arguments. However, each argument would
                // only have been evaluated once.
                public static void EmitCall (EmitContext ec, bool is_base,
                                             bool is_static, Expression instance_expr,
                                             MethodBase method, ArrayList Arguments, Location loc,
                                             bool dup_args, bool omit_args)
                {
                        ILGenerator ig = ec.ig;
                        bool struct_call = false;
                        bool this_call = false;
                        LocalTemporary this_arg = null;

                        Type decl_type = method.DeclaringType;

                        if (!RootContext.StdLib) {
                                // Replace any calls to the system's System.Array type with calls to
                                // the newly created one.
                                if (method == TypeManager.system_int_array_get_length)
                                        method = TypeManager.int_array_get_length;
                                else if (method == TypeManager.system_int_array_get_rank)
                                        method = TypeManager.int_array_get_rank;
                                else if (method == TypeManager.system_object_array_clone)
                                        method = TypeManager.object_array_clone;
                                else if (method == TypeManager.system_int_array_get_length_int)
                                        method = TypeManager.int_array_get_length_int;
                                else if (method == TypeManager.system_int_array_get_lower_bound_int)
                                        method = TypeManager.int_array_get_lower_bound_int;
                                else if (method == TypeManager.system_int_array_get_upper_bound_int)
                                        method = TypeManager.int_array_get_upper_bound_int;
                                else if (method == TypeManager.system_void_array_copyto_array_int)
                                        method = TypeManager.void_array_copyto_array_int;
                        }

                        if (ec.TestObsoleteMethodUsage) {
                                //
                                // This checks ObsoleteAttribute on the method and on the declaring type
                                //
                                ObsoleteAttribute oa = AttributeTester.GetMethodObsoleteAttribute (method);
                                if (oa != null)
                                        AttributeTester.Report_ObsoleteMessage (oa, TypeManager.CSharpSignature (method), loc);


                                oa = AttributeTester.GetObsoleteAttribute (method.DeclaringType);
                                if (oa != null) {
                                        AttributeTester.Report_ObsoleteMessage (oa, method.DeclaringType.FullName, loc);
                                }
                        }

                        if (IsMethodExcluded (method, ec))
                                return; 
                        
                        if (!is_static){
                                if (instance_expr == EmptyExpression.Null) {
                                        SimpleName.Error_ObjectRefRequired (ec, loc, TypeManager.CSharpSignature (method));
                                        return;
                                }

                                this_call = instance_expr is This;
                                if (decl_type.IsValueType || (!this_call && instance_expr.Type.IsValueType))
                                        struct_call = true;
                                
                                if (!omit_args) {
                                        Type t = null;
                                        //
                                        // Push the instance expression
                                        //
                                        if (instance_expr.Type.IsValueType) {
                                                //
                                                // Special case: calls to a function declared in a 
                                                // reference-type with a value-type argument need
                                                // to have their value boxed.
                                                if (decl_type.IsValueType) {
                                                        //
                                                        // If the expression implements IMemoryLocation, then
                                                        // we can optimize and use AddressOf on the
                                                        // return.
                                                        //
                                                        // If not we have to use some temporary storage for
                                                        // it.
                                                        if (instance_expr is IMemoryLocation) {
                                                                ((IMemoryLocation)instance_expr).
                                                                        AddressOf (ec, AddressOp.LoadStore);
                                                        } else {
                                                                LocalTemporary temp = new LocalTemporary (ec, instance_expr.Type);
                                                                instance_expr.Emit (ec);
                                                                temp.Store (ec);
                                                                temp.AddressOf (ec, AddressOp.Load);
                                                        }
                                                        
                                                        // avoid the overhead of doing this all the time.
                                                        if (dup_args)
                                                                t = TypeManager.GetReferenceType (instance_expr.Type);
                                                } else {
                                                        instance_expr.Emit (ec);
                                                        ig.Emit (OpCodes.Box, instance_expr.Type);
                                                        t = TypeManager.object_type;
                                                } 
                                        } else {
                                                instance_expr.Emit (ec);
                                                t = instance_expr.Type;
                                        }

                                        if (dup_args) {
                                                ig.Emit (OpCodes.Dup);
                                                if (Arguments != null && Arguments.Count != 0) {
                                                        this_arg = new LocalTemporary (ec, t);
                                                        this_arg.Store (ec);
                                                }
                                        }
                                }
                        }

                        if (!omit_args)
                                EmitArguments (ec, method, Arguments, dup_args, this_arg);

                        OpCode call_op;
                        if (is_static || struct_call || is_base || (this_call && !method.IsVirtual))
                                call_op = OpCodes.Call;
                        else
                                call_op = OpCodes.Callvirt;

                        if ((method.CallingConvention & CallingConventions.VarArgs) != 0) {
                                Type[] varargs_types = GetVarargsTypes (ec, method, Arguments);
                                ig.EmitCall (call_op, (MethodInfo) method, varargs_types);
                                return;
                        }

                        //
                        // If you have:
                        // this.DoFoo ();
                        // and DoFoo is not virtual, you can omit the callvirt,
                        // because you don't need the null checking behavior.
                        //
                        if (method is MethodInfo)
                                ig.Emit (call_op, (MethodInfo) method);
                        else
                                ig.Emit (call_op, (ConstructorInfo) method);
                }
                
                public override void Emit (EmitContext ec)
                {
                        MethodGroupExpr mg = (MethodGroupExpr) this.expr;

                        EmitCall (ec, mg.IsBase, method.IsStatic, mg.InstanceExpression, method, Arguments, loc);
                }
                
                public override void EmitStatement (EmitContext ec)
                {
                        Emit (ec);

                        // 
                        // Pop the return value if there is one
                        //
                        if (method is MethodInfo){
                                Type ret = ((MethodInfo)method).ReturnType;
                                if (TypeManager.TypeToCoreType (ret) != TypeManager.void_type)
                                        ec.ig.Emit (OpCodes.Pop);
                        }
                }
        }

        public class InvocationOrCast : ExpressionStatement
        {
                Expression expr;
                Expression argument;

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

                public override Expression DoResolve (EmitContext ec)
                {
                        //
                        // First try to resolve it as a cast.
                        //
                        TypeExpr te = expr.ResolveAsTypeTerminal (ec, true);
                        if (te != null) {
                                Cast cast = new Cast (te, argument, loc);
                                return cast.Resolve (ec);
                        }

                        //
                        // This can either be a type or a delegate invocation.
                        // Let's just resolve it and see what we'll get.
                        //
                        expr = expr.Resolve (ec, ResolveFlags.Type | ResolveFlags.VariableOrValue);
                        if (expr == null)
                                return null;

                        //
                        // Ok, so it's a Cast.
                        //
                        if (expr.eclass == ExprClass.Type) {
                                Cast cast = new Cast (new TypeExpression (expr.Type, loc), argument, loc);
                                return cast.Resolve (ec);
                        }

                        //
                        // It's a delegate invocation.
                        //
                        if (!TypeManager.IsDelegateType (expr.Type)) {
                                Error (149, "Method name expected");
                                return null;
                        }

                        ArrayList args = new ArrayList ();
                        args.Add (new Argument (argument, Argument.AType.Expression));
                        DelegateInvocation invocation = new DelegateInvocation (expr, args, loc);
                        return invocation.Resolve (ec);
                }

                void error201 ()
                {
                        Error (201, "Only assignment, call, increment, decrement and new object " +
                               "expressions can be used as a statement");
                }

                public override ExpressionStatement ResolveStatement (EmitContext ec)
                {
                        //
                        // First try to resolve it as a cast.
                        //
                        TypeExpr te = expr.ResolveAsTypeTerminal (ec, true);
                        if (te != null) {
                                error201 ();
                                return null;
                        }

                        //
                        // This can either be a type or a delegate invocation.
                        // Let's just resolve it and see what we'll get.
                        //
                        expr = expr.Resolve (ec, ResolveFlags.Type | ResolveFlags.VariableOrValue);
                        if ((expr == null) || (expr.eclass == ExprClass.Type)) {
                                error201 ();
                                return null;
                        }

                        //
                        // It's a delegate invocation.
                        //
                        if (!TypeManager.IsDelegateType (expr.Type)) {
                                Error (149, "Method name expected");
                                return null;
                        }

                        ArrayList args = new ArrayList ();
                        args.Add (new Argument (argument, Argument.AType.Expression));
                        DelegateInvocation invocation = new DelegateInvocation (expr, args, loc);
                        return invocation.ResolveStatement (ec);
                }

                public override void Emit (EmitContext ec)
                {
                        throw new Exception ("Cannot happen");
                }

                public override void EmitStatement (EmitContext ec)
                {
                        throw new Exception ("Cannot happen");
                }
        }

        //
        // This class is used to "disable" the code generation for the
        // temporary variable when initializing value types.
        //
        class EmptyAddressOf : EmptyExpression, IMemoryLocation {
                public void AddressOf (EmitContext ec, AddressOp Mode)
                {
                        // nothing
                }
        }
        
        /// <summary>
        ///    Implements the new expression 
        /// </summary>
        public class New : ExpressionStatement, IMemoryLocation {
                public readonly ArrayList Arguments;

                //
                // During bootstrap, it contains the RequestedType,
                // but if `type' is not null, it *might* contain a NewDelegate
                // (because of field multi-initialization)
                //
                public Expression RequestedType;

                MethodBase method = null;

                //
                // If set, the new expression is for a value_target, and
                // we will not leave anything on the stack.
                //
                Expression value_target;
                bool value_target_set = false;
                
                public New (Expression requested_type, ArrayList arguments, Location l)
                {
                        RequestedType = requested_type;
                        Arguments = arguments;
                        loc = l;
                }

                public bool SetValueTypeVariable (Expression value)
                {
                        value_target = value;
                        value_target_set = true;
                        if (!(value_target is IMemoryLocation)){
                                Error_UnexpectedKind (null, "variable", loc);
                                return false;
                        }
                        return true;
                }

                //
                // This function is used to disable the following code sequence for
                // value type initialization:
                //
                // AddressOf (temporary)
                // Construct/Init
                // LoadTemporary
                //
                // Instead the provide will have provided us with the address on the
                // stack to store the results.
                //
                static Expression MyEmptyExpression;
                
                public void DisableTemporaryValueType ()
                {
                        if (MyEmptyExpression == null)
                                MyEmptyExpression = new EmptyAddressOf ();

                        //
                        // To enable this, look into:
                        // test-34 and test-89 and self bootstrapping.
                        //
                        // For instance, we can avoid a copy by using `newobj'
                        // instead of Call + Push-temp on value types.
//                      value_target = MyEmptyExpression;
                }


                /// <summary>
                /// Converts complex core type syntax like 'new int ()' to simple constant
                /// </summary>
                public static Constant Constantify (Type t)
                {
                        if (t == TypeManager.int32_type)
                                return new IntConstant (0, Location.Null);
                        if (t == TypeManager.uint32_type)
                                return new UIntConstant (0, Location.Null);
                        if (t == TypeManager.int64_type)
                                return new LongConstant (0, Location.Null);
                        if (t == TypeManager.uint64_type)
                                return new ULongConstant (0, Location.Null);
                        if (t == TypeManager.float_type)
                                return new FloatConstant (0, Location.Null);
                        if (t == TypeManager.double_type)
                                return new DoubleConstant (0, Location.Null);
                        if (t == TypeManager.short_type)
                                return new ShortConstant (0, Location.Null);
                        if (t == TypeManager.ushort_type)
                                return new UShortConstant (0, Location.Null);
                        if (t == TypeManager.sbyte_type)
                                return new SByteConstant (0, Location.Null);
                        if (t == TypeManager.byte_type)
                                return new ByteConstant (0, Location.Null);
                        if (t == TypeManager.char_type)
                                return new CharConstant ('\0', Location.Null);
                        if (t == TypeManager.bool_type)
                                return new BoolConstant (false, Location.Null);
                        if (t == TypeManager.decimal_type)
                                return new DecimalConstant (0, Location.Null);

                        return null;
                }

                //
                // Checks whether the type is an interface that has the
                // [ComImport, CoClass] attributes and must be treated
                // specially
                //
                public Expression CheckComImport (EmitContext ec)
                {
                        if (!type.IsInterface)
                                return null;

                        //
                        // Turn the call into:
                        // (the-interface-stated) (new class-referenced-in-coclassattribute ())
                        //
                        Type real_class = AttributeTester.GetCoClassAttribute (type);
                        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 DoResolve (EmitContext ec)
                {
                        //
                        // The New DoResolve might be called twice when initializing field
                        // expressions (see EmitFieldInitializers, the call to
                        // GetInitializerExpression will perform a resolve on the expression,
                        // and later the assign will trigger another resolution
                        //
                        // This leads to bugs (#37014)
                        //
                        if (type != null){
                                if (RequestedType is NewDelegate)
                                        return RequestedType;
                                return this;
                        }

                        TypeExpr texpr = RequestedType.ResolveAsTypeTerminal (ec, false);
                        if (texpr == null)
                                return null;

                        type = texpr.ResolveType (ec);

                        if (Arguments == null) {
                                Expression c = Constantify (type);
                                if (c != null)
                                        return c;
                        }

                        if (TypeManager.IsDelegateType (type)) {
                                RequestedType = (new NewDelegate (type, Arguments, loc)).Resolve (ec);
                                if (RequestedType != null)
                                        if (!(RequestedType is DelegateCreation))
                                                throw new Exception ("NewDelegate.Resolve returned a non NewDelegate: " + RequestedType.GetType ());
                                return RequestedType;
                        }

                        if (type.IsAbstract && type.IsSealed) {
                                Report.SymbolRelatedToPreviousError (type);
                                Report.Error (712, loc, "Cannot create an instance of the static class `{0}'", TypeManager.CSharpName (type));
                                return null;
                        }

                        if (type.IsInterface || type.IsAbstract){
                                RequestedType = CheckComImport (ec);
                                if (RequestedType != null)
                                        return RequestedType;
                                
                                Report.SymbolRelatedToPreviousError (type);
                                Report.Error (144, loc, "Cannot create an instance of the abstract class or interface `{0}'", TypeManager.CSharpName (type));
                                return null;
                        }

                        bool is_struct = type.IsValueType;
                        eclass = ExprClass.Value;

                        //
                        // SRE returns a match for .ctor () on structs (the object constructor), 
                        // so we have to manually ignore it.
                        //
                        if (is_struct && Arguments == null)
                                return this;

                        // For member-lookup, treat 'new Foo (bar)' as call to 'foo.ctor (bar)', where 'foo' is of type 'Foo'.
                        Expression ml = MemberLookupFinal (ec, type, type, ".ctor",
                                MemberTypes.Constructor, AllBindingFlags | BindingFlags.DeclaredOnly, loc);

                        if (ml == null)
                                return null;

                        MethodGroupExpr mg = ml as MethodGroupExpr;

                        if (mg == null) {
                                ml.Error_UnexpectedKind (ec, "method group", loc);
                                return null;
                        }

                        if (Arguments != null){
                                foreach (Argument a in Arguments){
                                        if (!a.Resolve (ec, loc))
                                                return null;
                                }
                        }

                        method = Invocation.OverloadResolve (ec, mg, Arguments, false, loc);
                        if (method == null) {
                                if (almostMatchedMembers.Count != 0)
                                        MemberLookupFailed (ec, type, type, ".ctor", null, true, loc);
                                return null;
                        }

                        return this;
                }

                //
                // This DoEmit 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)
                //
                // You can control whether a value is required on the stack by passing
                // need_value_on_stack.  The code *might* leave a value on the stack
                // so it must be popped manually
                //
                // 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
                //
                bool DoEmit (EmitContext ec, bool need_value_on_stack)
                {
                        bool is_value_type = type.IsValueType;
                        ILGenerator ig = ec.ig;

                        if (is_value_type){
                                IMemoryLocation ml;

                                // Allow DoEmit() to be called multiple times.
                                // We need to create a new LocalTemporary each time since
                                // you can't share LocalBuilders among ILGeneators.
                                if (!value_target_set)
                                        value_target = new LocalTemporary (ec, type);

                                ml = (IMemoryLocation) value_target;
                                ml.AddressOf (ec, AddressOp.Store);
                        }

                        if (method != null)
                                Invocation.EmitArguments (ec, method, Arguments, false, null);

                        if (is_value_type){
                                if (method == null)
                                        ig.Emit (OpCodes.Initobj, type);
                                else 
                                        ig.Emit (OpCodes.Call, (ConstructorInfo) method);
                                if (need_value_on_stack){
                                        value_target.Emit (ec);
                                        return true;
                                }
                                return false;
                        } else {
                                ig.Emit (OpCodes.Newobj, (ConstructorInfo) method);
                                return true;
                        }
                }

                public override void Emit (EmitContext ec)
                {
                        DoEmit (ec, true);
                }
                
                public override void EmitStatement (EmitContext ec)
                {
                        if (DoEmit (ec, false))
                                ec.ig.Emit (OpCodes.Pop);
                }

                public void AddressOf (EmitContext ec, AddressOp Mode)
                {
                        if (!type.IsValueType){
                                //
                                // We throw an exception.  So far, I believe we only need to support
                                // value types:
                                // foreach (int j in new StructType ())
                                // see bug 42390
                                //
                                throw new Exception ("AddressOf should not be used for classes");
                        }

                        if (!value_target_set)
                                value_target = new LocalTemporary (ec, type);
                                        
                        IMemoryLocation ml = (IMemoryLocation) value_target;
                        ml.AddressOf (ec, AddressOp.Store);
                        if (method != null)
                                Invocation.EmitArguments (ec, method, Arguments, false, null);

                        if (method == null)
                                ec.ig.Emit (OpCodes.Initobj, type);
                        else 
                                ec.ig.Emit (OpCodes.Call, (ConstructorInfo) method);
                        
                        ((IMemoryLocation) value_target).AddressOf (ec, Mode);
                }
        }

        /// <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 {
                Expression requested_base_type;
                ArrayList initializers;

                //
                // The list of Argument types.
                // This is used to construct the `newarray' or constructor signature
                //
                ArrayList arguments;

                //
                // Method used to create the array object.
                //
                MethodBase new_method = null;
                
                Type array_element_type;
                Type underlying_type;
                bool is_one_dimensional = false;
                bool is_builtin_type = false;
                bool expect_initializers = false;
                int num_arguments = 0;
                int dimensions = 0;
                string rank;

                ArrayList array_data;

                Hashtable bounds;

                //
                // The number of array initializers that we can handle
                // via the InitializeArray method - through EmitStaticInitializers
                //
                int num_automatic_initializers;

                const int max_automatic_initializers = 6;
                
                public ArrayCreation (Expression requested_base_type, ArrayList exprs, string rank, ArrayList initializers, Location l)
                {
                        this.requested_base_type = requested_base_type;
                        this.initializers = initializers;
                        this.rank = rank;
                        loc = l;

                        arguments = new ArrayList ();

                        foreach (Expression e in exprs) {
                                arguments.Add (new Argument (e, Argument.AType.Expression));
                                num_arguments++;
                        }
                }

                public ArrayCreation (Expression requested_base_type, string rank, ArrayList initializers, Location l)
                {
                        this.requested_base_type = requested_base_type;
                        this.initializers = initializers;
                        this.rank = rank;
                        loc = l;

                        //this.rank = rank.Substring (0, rank.LastIndexOf ('['));
                        //
                        //string tmp = rank.Substring (rank.LastIndexOf ('['));
                        //
                        //dimensions = tmp.Length - 1;
                        expect_initializers = true;
                }

                public Expression FormArrayType (Expression base_type, int idx_count, string rank)
                {
                        StringBuilder sb = new StringBuilder (rank);
                        
                        sb.Append ("[");
                        for (int i = 1; i < idx_count; i++)
                                sb.Append (",");
                        
                        sb.Append ("]");

                        return new ComposedCast (base_type, sb.ToString (), loc);
                }

                void Error_IncorrectArrayInitializer ()
                {
                        Error (178, "Invalid rank specifier: expected `,' or `]'");
                }
                
                public bool CheckIndices (EmitContext ec, ArrayList probe, int idx, bool specified_dims)
                {
                        if (specified_dims) { 
                                Argument a = (Argument) arguments [idx];

                                if (!a.Resolve (ec, loc))
                                        return false;

                                Constant c = a.Expr as Constant;
                                if (c != null) {
                                        c = c.ToType (TypeManager.int32_type, a.Expr.Location);
                                }

                                if (c == null) {
                                        Report.Error (150, a.Expr.Location, "A constant value is expected");
                                        return false;
                                }

                                int value = (int) c.GetValue ();
                                
                                if (value != probe.Count) {
                                        Error_IncorrectArrayInitializer ();
                                        return false;
                                }
                                
                                bounds [idx] = value;
                        }

                        int child_bounds = -1;
                        for (int i = 0; i < probe.Count; ++i) {
                                object o = probe [i];
                                if (o is ArrayList) {
                                        ArrayList sub_probe = o as ArrayList;
                                        int current_bounds = sub_probe.Count;
                                        
                                        if (child_bounds == -1) 
                                                child_bounds = current_bounds;

                                        else if (child_bounds != current_bounds){
                                                Error_IncorrectArrayInitializer ();
                                                return false;
                                        }
                                        if (specified_dims && (idx + 1 >= arguments.Count)){
                                                Error (623, "Array initializers can only be used in a variable or field initializer. Try using a new expression instead");
                                                return false;
                                        }
                                        
                                        bool ret = CheckIndices (ec, sub_probe, idx + 1, specified_dims);
                                        if (!ret)
                                                return false;
                                } else {
                                        if (child_bounds != -1){
                                                Error_IncorrectArrayInitializer ();
                                                return false;
                                        }
                                        
                                        Expression tmp = (Expression) o;
                                        tmp = tmp.Resolve (ec);
                                        probe [i] = tmp;
                                        if (tmp == null)
                                                return false;

                                        // Console.WriteLine ("I got: " + tmp);
                                        // Handle initialization from vars, fields etc.

                                        Expression conv = Convert.ImplicitConversionRequired (
                                                ec, tmp, underlying_type, loc);
                                        
                                        if (conv == null) 
                                                return false;
                                        
                                        if (conv is StringConstant || conv is DecimalConstant || conv is NullCast) {
                                                // These are subclasses of Constant that can appear as elements of an
                                                // array that cannot be statically initialized (with num_automatic_initializers
                                                // > max_automatic_initializers), so num_automatic_initializers should be left as zero.
                                                array_data.Add (conv);
                                        } else if (conv is Constant) {
                                                // These are the types of Constant that can appear in arrays that can be
                                                // statically allocated.
                                                array_data.Add (conv);
                                                num_automatic_initializers++;
                                        } else
                                                array_data.Add (conv);
                                }
                        }

                        return true;
                }
                
                public void UpdateIndices (EmitContext ec)
                {
                        int i = 0;
                        for (ArrayList probe = initializers; probe != null;) {
                                if (probe.Count > 0 && probe [0] is ArrayList) {
                                        Expression e = new IntConstant (probe.Count, Location.Null);
                                        arguments.Add (new Argument (e, Argument.AType.Expression));

                                        bounds [i++] =  probe.Count;
                                        
                                        probe = (ArrayList) probe [0];
                                        
                                } else {
                                        Expression e = new IntConstant (probe.Count, Location.Null);
                                        arguments.Add (new Argument (e, Argument.AType.Expression));

                                        bounds [i++] = probe.Count;
                                        probe = null;
                                }
                        }

                }
                
                public bool ValidateInitializers (EmitContext ec, Type array_type)
                {
                        if (initializers == null) {
                                if (expect_initializers)
                                        return false;
                                else
                                        return true;
                        }
                        
                        if (underlying_type == null)
                                return false;
                        
                        //
                        // We use this to store all the date values in the order in which we
                        // will need to store them in the byte blob later
                        //
                        array_data = new ArrayList ();
                        bounds = new Hashtable ();
                        
                        bool ret;

                        if (arguments != null) {
                                ret = CheckIndices (ec, initializers, 0, true);
                                return ret;
                        } else {
                                arguments = new ArrayList ();

                                ret = CheckIndices (ec, initializers, 0, false);
                                
                                if (!ret)
                                        return false;
                                
                                UpdateIndices (ec);
                                
                                if (arguments.Count != dimensions) {
                                        Error_IncorrectArrayInitializer ();
                                        return false;
                                }

                                return ret;
                        }
                }

                //
                // Creates the type of the array
                //
                bool LookupType (EmitContext ec)
                {
                        StringBuilder array_qualifier = new StringBuilder (rank);

                        //
                        // `In the first form allocates an array instace of the type that results
                        // from deleting each of the individual expression from the expression list'
                        //
                        if (num_arguments > 0) {
                                array_qualifier.Append ("[");
                                for (int i = num_arguments-1; i > 0; i--)
                                        array_qualifier.Append (",");
                                array_qualifier.Append ("]");                           
                        }

                        //
                        // Lookup the type
                        //
                        TypeExpr array_type_expr;
                        array_type_expr = new ComposedCast (requested_base_type, array_qualifier.ToString (), loc);
                        array_type_expr = array_type_expr.ResolveAsTypeTerminal (ec, false);
                        if (array_type_expr == null)
                                return false;

                        type = array_type_expr.ResolveType (ec);
                        
                        if (!type.IsArray) {
                                Error (622, "Can only use array initializer expressions to assign to array types. Try using a new expression instead.");
                                return false;
                        }
                        underlying_type = TypeManager.GetElementType (type);
                        dimensions = type.GetArrayRank ();

                        return true;
                }
                
                public override Expression DoResolve (EmitContext ec)
                {
                        int arg_count;

                        if (!LookupType (ec))
                                return null;
                        
                        //
                        // First step is to validate the initializers and fill
                        // in any missing bits
                        //
                        if (!ValidateInitializers (ec, type))
                                return null;

                        if (arguments == null)
                                arg_count = 0;
                        else {
                                arg_count = arguments.Count;
                                foreach (Argument a in arguments){
                                        if (!a.Resolve (ec, loc))
                                                return null;

                                        Expression real_arg = ExpressionToArrayArgument (ec, a.Expr, loc);
                                        if (real_arg == null)
                                                return null;

                                        a.Expr = real_arg;
                                }
                        }
                        
                        array_element_type = TypeManager.GetElementType (type);

                        if (array_element_type.IsAbstract && array_element_type.IsSealed) {
                                Report.Error (719, loc, "`{0}': array elements cannot be of static type", TypeManager.CSharpName (array_element_type));
                                return null;
                        }

                        if (arg_count == 1) {
                                is_one_dimensional = true;
                                eclass = ExprClass.Value;
                                return this;
                        }

                        is_builtin_type = TypeManager.IsBuiltinType (type);

                        if (is_builtin_type) {
                                Expression ml;
                                
                                ml = MemberLookup (ec, type, ".ctor", MemberTypes.Constructor,
                                                   AllBindingFlags, loc);
                                
                                if (!(ml is MethodGroupExpr)) {
                                        ml.Error_UnexpectedKind (ec, "method group", loc);
                                        return null;
                                }
                                
                                if (ml == null) {
                                        Error (-6, "New invocation: Can not find a constructor for " +
                                                      "this argument list");
                                        return null;
                                }
                                
                                new_method = Invocation.OverloadResolve (
                                        ec, (MethodGroupExpr) ml, arguments, false, loc);

                                if (new_method == null) {
                                        Error (-6, "New invocation: Can not find a constructor for " +
                                                      "this argument list");
                                        return null;
                                }
                                
                                eclass = ExprClass.Value;
                                return this;
                        } else {
                                ModuleBuilder mb = CodeGen.Module.Builder;
                                ArrayList args = new ArrayList ();
                                
                                if (arguments != null) {
                                        for (int i = 0; i < arg_count; i++)
                                                args.Add (TypeManager.int32_type);
                                }
                                
                                Type [] arg_types = null;

                                if (args.Count > 0)
                                        arg_types = new Type [args.Count];
                                
                                args.CopyTo (arg_types, 0);
                                
                                new_method = mb.GetArrayMethod (type, ".ctor", CallingConventions.HasThis, null,
                                                            arg_types);

                                if (new_method == null) {
                                        Error (-6, "New invocation: Can not find a constructor for " +
                                                      "this argument list");
                                        return null;
                                }
                                
                                eclass = ExprClass.Value;
                                return this;
                        }
                }

                public static byte [] MakeByteBlob (ArrayList array_data, Type underlying_type, Location loc)
                {
                        int factor;
                        byte [] data;
                        byte [] element;
                        int count = array_data.Count;

                        if (underlying_type.IsEnum)
                                underlying_type = TypeManager.EnumToUnderlying (underlying_type);
                        
                        factor = GetTypeSize (underlying_type);
                        if (factor == 0)
                                throw new Exception ("unrecognized type in MakeByteBlob: " + underlying_type);

                        data = new byte [(count * factor + 4) & ~3];
                        int idx = 0;
                        
                        for (int i = 0; i < count; ++i) {
                                object v = array_data [i];

                                if (v is EnumConstant)
                                        v = ((EnumConstant) v).Child;
                                
                                if (v is Constant && !(v is StringConstant))
                                        v = ((Constant) v).GetValue ();
                                else {
                                        idx += factor;
                                        continue;
                                }
                                
                                if (underlying_type == TypeManager.int64_type){
                                        if (!(v is Expression)){
                                                long val = (long) v;
                                                
                                                for (int j = 0; j < factor; ++j) {
                                                        data [idx + j] = (byte) (val & 0xFF);
                                                        val = (val >> 8);
                                                }
                                        }
                                } else if (underlying_type == TypeManager.uint64_type){
                                        if (!(v is Expression)){
                                                ulong val = (ulong) v;

                                                for (int j = 0; j < factor; ++j) {
                                                        data [idx + j] = (byte) (val & 0xFF);
                                                        val = (val >> 8);
                                                }
                                        }
                                } else if (underlying_type == TypeManager.float_type) {
                                        if (!(v is Expression)){
                                                element = BitConverter.GetBytes ((float) v);
                                                        
                                                for (int j = 0; j < factor; ++j)
                                                        data [idx + j] = element [j];
                                        }
                                } else if (underlying_type == TypeManager.double_type) {
                                        if (!(v is Expression)){
                                                element = BitConverter.GetBytes ((double) v);

                                                for (int j = 0; j < factor; ++j)
                                                        data [idx + j] = element [j];
                                        }
                                } else if (underlying_type == TypeManager.char_type){
                                        if (!(v is Expression)){
                                                int val = (int) ((char) v);
                                                
                                                data [idx] = (byte) (val & 0xff);
                                                data [idx+1] = (byte) (val >> 8);
                                        }
                                } else if (underlying_type == TypeManager.short_type){
                                        if (!(v is Expression)){
                                                int val = (int) ((short) v);
                                        
                                                data [idx] = (byte) (val & 0xff);
                                                data [idx+1] = (byte) (val >> 8);
                                        }
                                } else if (underlying_type == TypeManager.ushort_type){
                                        if (!(v is Expression)){
                                                int val = (int) ((ushort) v);
                                        
                                                data [idx] = (byte) (val & 0xff);
                                                data [idx+1] = (byte) (val >> 8);
                                        }
                                } else if (underlying_type == TypeManager.int32_type) {
                                        if (!(v is Expression)){
                                                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);
                                        }
                                } else if (underlying_type == TypeManager.uint32_type) {
                                        if (!(v is Expression)){
                                                uint val = (uint) 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);
                                        }
                                } else if (underlying_type == TypeManager.sbyte_type) {
                                        if (!(v is Expression)){
                                                sbyte val = (sbyte) v;
                                                data [idx] = (byte) val;
                                        }
                                } else if (underlying_type == TypeManager.byte_type) {
                                        if (!(v is Expression)){
                                                byte val = (byte) v;
                                                data [idx] = (byte) val;
                                        }
                                } else if (underlying_type == TypeManager.bool_type) {
                                        if (!(v is Expression)){
                                                bool val = (bool) v;
                                                data [idx] = (byte) (val ? 1 : 0);
                                        }
                                } else if (underlying_type == TypeManager.decimal_type){
                                        if (!(v is Expression)){
                                                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);
                                                }
                                        }
                                } else
                                        throw new Exception ("Unrecognized type in MakeByteBlob: " + underlying_type);

                                idx += factor;
                        }

                        return data;
                }

                //
                // Emits the initializers for the array
                //
                void EmitStaticInitializers (EmitContext ec)
                {
                        //
                        // First, the static data
                        //
                        FieldBuilder fb;
                        ILGenerator ig = ec.ig;
                        
                        byte [] data = MakeByteBlob (array_data, underlying_type, loc);

                        fb = RootContext.MakeStaticData (data);

                        ig.Emit (OpCodes.Dup);
                        ig.Emit (OpCodes.Ldtoken, fb);
                        ig.Emit (OpCodes.Call,
                                 TypeManager.void_initializearray_array_fieldhandle);
                }

                //
                // 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)
                {
                        ILGenerator ig = ec.ig;
                        int dims = bounds.Count;
                        int [] current_pos = new int [dims];
                        int top = array_data.Count;

                        MethodInfo set = null;

                        if (dims != 1){
                                Type [] args;
                                ModuleBuilder mb = null;
                                mb = CodeGen.Module.Builder;
                                args = new Type [dims + 1];

                                int j;
                                for (j = 0; j < dims; j++)
                                        args [j] = TypeManager.int32_type;

                                args [j] = array_element_type;
                                
                                set = mb.GetArrayMethod (
                                        type, "Set",
                                        CallingConventions.HasThis | CallingConventions.Standard,
                                        TypeManager.void_type, args);
                        }
                        
                        for (int i = 0; i < top; i++){

                                Expression e = null;

                                if (array_data [i] is Expression)
                                        e = (Expression) array_data [i];

                                if (e != null) {
                                        //
                                        // Basically we do this for string literals and
                                        // other non-literal expressions
                                        //
                                        if (e is EnumConstant){
                                                e = ((EnumConstant) e).Child;
                                        }
                                        
                                        if (e is StringConstant || e is DecimalConstant || !(e is Constant) ||
                                            num_automatic_initializers <= max_automatic_initializers) {
                                                Type etype = e.Type;

                                                ig.Emit (OpCodes.Dup);

                                                for (int idx = 0; idx < dims; idx++) 
                                                        IntConstant.EmitInt (ig, current_pos [idx]);

                                                //
                                                // If we are dealing with a struct, get the
                                                // address of it, so we can store it.
                                                //
                                                if ((dims == 1) && 
                                                    TypeManager.IsValueType (etype) &&
                                                    (!TypeManager.IsBuiltinOrEnum (etype) ||
                                                     etype == TypeManager.decimal_type)) {
                                                        if (e is New){
                                                                New n = (New) e;

                                                                //
                                                                // Let new know that we are providing
                                                                // the address where to store the results
                                                                //
                                                                n.DisableTemporaryValueType ();
                                                        }

                                                        ig.Emit (OpCodes.Ldelema, etype);
                                                }

                                                e.Emit (ec);

                                                if (dims == 1) {
                                                        bool is_stobj;
                                                        OpCode op = ArrayAccess.GetStoreOpcode (etype, out is_stobj);
                                                        if (is_stobj)
                                                                ig.Emit (OpCodes.Stobj, etype);
                                                        else
                                                                ig.Emit (op);
                                                } else 
                                                        ig.Emit (OpCodes.Call, set);

                                        }
                                }
                                
                                //
                                // Advance counter
                                //
                                for (int j = dims - 1; j >= 0; j--){
                                        current_pos [j]++;
                                        if (current_pos [j] < (int) bounds [j])
                                                break;
                                        current_pos [j] = 0;
                                }
                        }
                }

                void EmitArrayArguments (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        foreach (Argument a in arguments) {
                                Type atype = a.Type;
                                a.Emit (ec);

                                if (atype == TypeManager.uint64_type)
                                        ig.Emit (OpCodes.Conv_Ovf_U4);
                                else if (atype == TypeManager.int64_type)
                                        ig.Emit (OpCodes.Conv_Ovf_I4);
                        }
                }
                
                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        EmitArrayArguments (ec);
                        if (is_one_dimensional)
                                ig.Emit (OpCodes.Newarr, array_element_type);
                        else {
                                if (is_builtin_type) 
                                        ig.Emit (OpCodes.Newobj, (ConstructorInfo) new_method);
                                else 
                                        ig.Emit (OpCodes.Newobj, (MethodInfo) new_method);
                        }
                        
                        if (initializers != null){
                                //
                                // FIXME: Set this variable correctly.
                                // 
                                bool dynamic_initializers = true;

                                // This will never be true for array types that cannot be statically
                                // initialized. num_automatic_initializers will always be zero.  See
                                // CheckIndices.
                                if (num_automatic_initializers > max_automatic_initializers)
                                        EmitStaticInitializers (ec);
                                
                                if (dynamic_initializers)
                                        EmitDynamicInitializers (ec);
                        }
                }

                public object EncodeAsAttribute ()
                {
                        if (!is_one_dimensional){
                                Report.Error (-211, Location, "attribute can not encode multi-dimensional arrays");
                                return null;
                        }

                        if (array_data == null){
                                Report.Error (-212, Location, "array should be initialized when passing it to an attribute");
                                return null;
                        }
                        
                        object [] ret = new object [array_data.Count];
                        int i = 0;
                        foreach (Expression e in array_data){
                                object v;
                                
                                if (e is NullLiteral)
                                        v = null;
                                else {
                                        if (!Attribute.GetAttributeArgumentExpression (e, Location, array_element_type, out v))
                                                return null;
                                }
                                ret [i++] = v;
                        }
                        return ret;
                }
        }
        
        /// <summary>
        ///   Represents the `this' construct
        /// </summary>
        public class This : Expression, IAssignMethod, IMemoryLocation, IVariable {

                Block block;
                VariableInfo variable_info;
                
                public This (Block block, Location loc)
                {
                        this.loc = loc;
                        this.block = block;
                }

                public This (Location loc)
                {
                        this.loc = loc;
                }

                public VariableInfo VariableInfo {
                        get { return variable_info; }
                }

                public bool VerifyFixed ()
                {
                        return !TypeManager.IsValueType (Type);
                }

                public bool ResolveBase (EmitContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = ec.ContainerType;

                        if (ec.IsStatic) {
                                Error (26, "Keyword `this' is not valid in a static property, static method, or static field initializer");
                                return false;
                        }

                        if (block != null && block.Toplevel.ThisVariable != null)
                                variable_info = block.Toplevel.ThisVariable.VariableInfo;

                        if (ec.CurrentAnonymousMethod != null)
                                ec.CaptureThis ();
                        
                        return true;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        if (!ResolveBase (ec))
                                return null;

                        if ((variable_info != null) && !(type.IsValueType && ec.OmitStructFlowAnalysis) && !variable_info.IsAssigned (ec)) {
                                Error (188, "The `this' object cannot be used before all of its fields are assigned to");
                                variable_info.SetAssigned (ec);
                                return this;
                        }

                        if (ec.IsFieldInitializer) {
                                Error (27, "Keyword `this' is not available in the current context");
                                return null;
                        }

                        return this;
                }

                override public Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        if (!ResolveBase (ec))
                                return null;

                        if (variable_info != null)
                                variable_info.SetAssigned (ec);
                        
                        if (ec.TypeContainer is Class){
                                Error (1604, "Cannot assign to 'this' because it is read-only");
                                return null;
                        }

                        return this;
                }

                public void Emit (EmitContext ec, bool leave_copy)
                {
                        Emit (ec);
                        if (leave_copy)
                                ec.ig.Emit (OpCodes.Dup);
                }
                
                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool prepare_for_load)
                {
                        ILGenerator ig = ec.ig;
                        
                        if (ec.TypeContainer is Struct){
                                ec.EmitThis ();
                                source.Emit (ec);
                                if (leave_copy)
                                        ec.ig.Emit (OpCodes.Dup);
                                ig.Emit (OpCodes.Stobj, type);
                        } else {
                                throw new Exception ("how did you get here");
                        }
                }
                
                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;

                        ec.EmitThis ();
                        if (ec.TypeContainer is Struct)
                                ig.Emit (OpCodes.Ldobj, type);
                }

                public override int GetHashCode()
                {
                        return block.GetHashCode ();
                }

                public override bool Equals (object obj)
                {
                        This t = obj as This;
                        if (t == null)
                                return false;

                        return block == t.block;
                }

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

                        // FIMXE
                        // FIGURE OUT WHY LDARG_S does not work
                        //
                        // consider: struct X { int val; int P { set { val = value; }}}
                        //
                        // Yes, this looks very bad. Look at `NOTAS' for
                        // an explanation.
                        // ec.ig.Emit (OpCodes.Ldarga_S, (byte) 0);
                }
        }

        /// <summary>
        ///   Represents the `__arglist' construct
        /// </summary>
        public class ArglistAccess : Expression
        {
                public ArglistAccess (Location loc)
                {
                        this.loc = loc;
                }

                public bool ResolveBase (EmitContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = TypeManager.runtime_argument_handle_type;
                        return true;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        if (!ResolveBase (ec))
                                return null;

                        if (ec.IsFieldInitializer || !ec.CurrentBlock.Toplevel.HasVarargs) {
                                Error (190, "The __arglist construct is valid only within " +
                                       "a variable argument method.");
                                return null;
                        }

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ec.ig.Emit (OpCodes.Arglist);
                }
        }

        /// <summary>
        ///   Represents the `__arglist (....)' construct
        /// </summary>
        public class Arglist : Expression
        {
                public readonly Argument[] Arguments;

                public Arglist (Argument[] args, Location l)
                {
                        Arguments = args;
                        loc = l;
                }

                public Type[] ArgumentTypes {
                        get {
                                Type[] retval = new Type [Arguments.Length];
                                for (int i = 0; i < Arguments.Length; i++)
                                        retval [i] = Arguments [i].Type;
                                return retval;
                        }
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = TypeManager.runtime_argument_handle_type;

                        foreach (Argument arg in Arguments) {
                                if (!arg.Resolve (ec, loc))
                                        return null;
                        }

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        foreach (Argument arg in Arguments)
                                arg.Emit (ec);
                }
        }

        //
        // This produces the value that renders an instance, used by the iterators code
        //
        public class ProxyInstance : Expression, IMemoryLocation  {
                public override Expression DoResolve (EmitContext ec)
                {
                        eclass = ExprClass.Variable;
                        type = ec.ContainerType;
                        return this;
                }
                
                public override void Emit (EmitContext ec)
                {
                        ec.ig.Emit (OpCodes.Ldarg_0);

                }
                
                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        ec.ig.Emit (OpCodes.Ldarg_0);
                }
        }

        /// <summary>
        ///   Implements the typeof operator
        /// </summary>
        public class TypeOf : Expression {
                public Expression QueriedType;
                protected Type typearg;
                
                public TypeOf (Expression queried_type, Location l)
                {
                        QueriedType = queried_type;
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        TypeExpr texpr = QueriedType.ResolveAsTypeTerminal (ec, false);
                        if (texpr == null)
                                return null;

                        typearg = texpr.ResolveType (ec);

                        if (typearg == TypeManager.void_type) {
                                Error (673, "System.Void cannot be used from C#. Use typeof (void) to get the void type object");
                                return null;
                        }

                        if (typearg.IsPointer && !ec.InUnsafe){
                                UnsafeError (loc);
                                return null;
                        }

                        type = TypeManager.type_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;
                }

                public override void Emit (EmitContext ec)
                {
                        ec.ig.Emit (OpCodes.Ldtoken, typearg);
                        ec.ig.Emit (OpCodes.Call, TypeManager.system_type_get_type_from_handle);
                }

                public Type TypeArg { 
                        get { return typearg; }
                }
        }

        /// <summary>
        ///   Implements the `typeof (void)' operator
        /// </summary>
        public class TypeOfVoid : TypeOf {
                public TypeOfVoid (Location l) : base (null, l)
                {
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        type = TypeManager.type_type;
                        typearg = TypeManager.void_type;
                        // See description in TypeOf.
                        eclass = ExprClass.Value;
                        return this;
                }
        }

        /// <summary>
        ///   Implements the sizeof expression
        /// </summary>
        public class SizeOf : Expression {
                public Expression QueriedType;
                Type type_queried;
                
                public SizeOf (Expression queried_type, Location l)
                {
                        this.QueriedType = queried_type;
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        TypeExpr texpr = QueriedType.ResolveAsTypeTerminal (ec, false);
                        if (texpr == null)
                                return null;

                        type_queried = texpr.ResolveType (ec);

                        int size_of = GetTypeSize (type_queried);
                        if (size_of > 0) {
                                return new IntConstant (size_of, loc);
                        }

                        if (!ec.InUnsafe) {
                                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)",
                                         TypeManager.CSharpName (type_queried));
                                return null;
                        }

                        if (!TypeManager.VerifyUnManaged (type_queried, loc)){
                                return null;
                        }
                        
                        type = TypeManager.int32_type;
                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        int size = GetTypeSize (type_queried);

                        if (size == 0)
                                ec.ig.Emit (OpCodes.Sizeof, type_queried);
                        else
                                IntConstant.EmitInt (ec.ig, size);
                }
        }

        /// <summary>
        ///   Implements the qualified-alias-member (::) expression.
        /// </summary>
        public class QualifiedAliasMember : Expression
        {
                string alias, identifier;

                public QualifiedAliasMember (string alias, string identifier, Location l)
                {
                        this.alias = alias;
                        this.identifier = identifier;
                        loc = l;
                }

                public override FullNamedExpression ResolveAsTypeStep (EmitContext ec, bool silent)
                {
                        if (alias == "global")
                                return new MemberAccess (RootNamespace.Global, identifier, loc).ResolveAsTypeStep (ec, silent);

                        int errors = Report.Errors;
                        FullNamedExpression fne = ec.DeclSpace.NamespaceEntry.LookupAlias (alias);
                        if (fne == null) {
                                if (errors == Report.Errors)
                                        Report.Error (432, loc, "Alias `{0}' not found", alias);
                                return null;
                        }
                        if (fne.eclass != ExprClass.Namespace) {
                                if (!silent)
                                        Report.Error (431, loc, "`{0}' cannot be used with '::' since it denotes a type", alias);
                                return null;
                        }
                        return new MemberAccess (fne, identifier, loc).ResolveAsTypeStep (ec, silent);
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        FullNamedExpression fne;
                        if (alias == "global") {
                                fne = RootNamespace.Global;
                        } else {
                                int errors = Report.Errors;
                                fne = ec.DeclSpace.NamespaceEntry.LookupAlias (alias);
                                if (fne == null) {
                                        if (errors == Report.Errors)
                                                Report.Error (432, loc, "Alias `{0}' not found", alias);
                                        return null;
                                }
                        }

                        Expression retval = new MemberAccess (fne, identifier, loc).DoResolve (ec);
                        if (retval == null)
                                return null;

                        if (!(retval is FullNamedExpression)) {
                                Report.Error (687, loc, "The expression `{0}::{1}' did not resolve to a namespace or a type", alias, identifier);
                                return null;
                        }

                        // We defer this check till the end to match the behaviour of CSC
                        if (fne.eclass != ExprClass.Namespace) {
                                Report.Error (431, loc, "`{0}' cannot be used with '::' since it denotes a type", alias);
                                return null;
                        }
                        return retval;
                }

                public override void Emit (EmitContext ec)
                {
                        throw new InternalErrorException ("QualifiedAliasMember found in resolved tree");
                }


                public override string ToString ()
                {
                        return alias + "::" + identifier;
                }

                public override string GetSignatureForError ()
                {
                        return ToString ();
                }
        }

        /// <summary>
        ///   Implements the member access expression
        /// </summary>
        public class MemberAccess : Expression {
                public readonly string Identifier;
                Expression expr;
                
                // TODO: Location can be removed
                public MemberAccess (Expression expr, string id, Location l)
                {
                        this.expr = expr;
                        Identifier = id;
                        loc = expr.Location;
                }

                public Expression Expr {
                        get { return expr; }
                }

                // TODO: this method has very poor performace for Enum fields and
                // probably for other constants as well
                Expression DoResolve (EmitContext ec, Expression right_side)
                {
                        if (type != null)
                                throw new Exception ();

                        //
                        // Resolve the expression with flow analysis turned off, we'll do the definite
                        // assignment checks later.  This is because we don't know yet what the expression
                        // will resolve to - it may resolve to a FieldExpr and in this case we must do the
                        // definite assignment check on the actual field and not on the whole struct.
                        //

                        SimpleName original = expr as SimpleName;
                        Expression new_expr = expr.Resolve (ec,
                                ResolveFlags.VariableOrValue | ResolveFlags.Type |
                                ResolveFlags.Intermediate | ResolveFlags.DisableStructFlowAnalysis);

                        if (new_expr == null)
                                return null;

                        if (new_expr is Namespace) {
                                Namespace ns = (Namespace) new_expr;
                                FullNamedExpression retval = ns.Lookup (ec.DeclSpace, Identifier, loc);
                                if (retval == null)
                                        Report.Error (234, loc, "The type or namespace name `{0}' does not exist in the namespace `{1}'. Are you missing an assembly reference?",
                                                Identifier, ns.FullName);
                                return retval;
                        }

                        Type expr_type = new_expr.Type;
                        if (expr_type.IsPointer){
                                Error (23, "The `.' operator can not be applied to pointer operands (" +
                                       TypeManager.CSharpName (expr_type) + ")");
                                return null;
                        }

                        Expression member_lookup;
                        member_lookup = MemberLookupFinal (ec, expr_type, expr_type, Identifier, loc);
                        if (member_lookup == null)
                                return null;

                        if (member_lookup is TypeExpr) {
                                if (!(new_expr is TypeExpr) && 
                                    (original == null || !original.IdenticalNameAndTypeName (ec, new_expr, loc))) {
                                        Report.Error (572, loc, "`{0}': cannot reference a type through an expression; try `{1}' instead",
                                                Identifier, member_lookup.GetSignatureForError ());
                                        return null;
                                }

                                return member_lookup;
                        }

                        MemberExpr me = (MemberExpr) member_lookup;
                        member_lookup = me.ResolveMemberAccess (ec, new_expr, loc, original);
                        if (member_lookup == null)
                                return null;

                        if (original != null && !TypeManager.IsValueType (expr_type)) {
                                me = member_lookup as MemberExpr;
                                if (me != null && me.IsInstance) {
                                        LocalVariableReference var = new_expr as LocalVariableReference;
                                        if (var != null && !var.VerifyAssigned (ec))
                                                return null;
                                }
                        }

                        // The following DoResolve/DoResolveLValue will do the definite assignment
                        // check.

                        if (right_side != null)
                                return member_lookup.DoResolveLValue (ec, right_side);
                        else
                                return member_lookup.DoResolve (ec);
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        return DoResolve (ec, null);
                }

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

                public override FullNamedExpression ResolveAsTypeStep (EmitContext ec, bool silent)
                {
                        return ResolveNamespaceOrType (ec, silent);
                }

                public FullNamedExpression ResolveNamespaceOrType (EmitContext ec, bool silent)
                {
                        FullNamedExpression new_expr = expr.ResolveAsTypeStep (ec, silent);

                        if (new_expr == null)
                                return null;

                        if (new_expr is Namespace) {
                                Namespace ns = (Namespace) new_expr;
                                FullNamedExpression retval = ns.Lookup (ec.DeclSpace, Identifier, loc);
                                if (!silent && retval == null)
                                        Report.Error (234, loc, "The type or namespace name `{0}' does not exist in the namespace `{1}'. Are you missing an assembly reference?",
                                                Identifier, ns.FullName);
                                return retval;
                        }

                        Type expr_type = new_expr.Type;
                      
                        if (expr_type.IsPointer){
                                Error (23, "The `.' operator can not be applied to pointer operands (" +
                                       TypeManager.CSharpName (expr_type) + ")");
                                return null;
                        }
                        
                        Expression member_lookup = MemberLookup (ec, expr_type, expr_type, Identifier, loc);
                        if (member_lookup == null) {
                                int errors = Report.Errors;
                                MemberLookupFailed (ec, expr_type, expr_type, Identifier, null, false, loc);

                                if (!silent && errors == Report.Errors) {
                                        Report.Error (426, loc, "The nested type `{0}' does not exist in the type `{1}'",
                                                Identifier, new_expr.GetSignatureForError ());
                                }
                                return null;
                        }

                        if (!(member_lookup is TypeExpr)) {
                                new_expr.Error_UnexpectedKind (ec, "type", loc);
                                return null;
                        } 

                        member_lookup = member_lookup.Resolve (ec, ResolveFlags.Type);
                        return (member_lookup as TypeExpr);
                }

                public override void Emit (EmitContext ec)
                {
                        throw new Exception ("Should not happen");
                }

                public override string ToString ()
                {
                        return expr + "." + Identifier;
                }

                public override string GetSignatureForError ()
                {
                        return expr.GetSignatureForError () + "." + Identifier;
                }
        }

        /// <summary>
        ///   Implements checked expressions
        /// </summary>
        public class CheckedExpr : Expression {

                public Expression Expr;

                public CheckedExpr (Expression e, Location l)
                {
                        Expr = e;
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        bool last_check = ec.CheckState;
                        bool last_const_check = ec.ConstantCheckState;

                        ec.CheckState = true;
                        ec.ConstantCheckState = true;
                        Expr = Expr.Resolve (ec);
                        ec.CheckState = last_check;
                        ec.ConstantCheckState = last_const_check;
                        
                        if (Expr == null)
                                return null;

                        if (Expr is Constant)
                                return Expr;
                        
                        eclass = Expr.eclass;
                        type = Expr.Type;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        bool last_check = ec.CheckState;
                        bool last_const_check = ec.ConstantCheckState;
                        
                        ec.CheckState = true;
                        ec.ConstantCheckState = true;
                        Expr.Emit (ec);
                        ec.CheckState = last_check;
                        ec.ConstantCheckState = last_const_check;
                }
                
        }

        /// <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 Expression DoResolve (EmitContext ec)
                {
                        bool last_check = ec.CheckState;
                        bool last_const_check = ec.ConstantCheckState;

                        ec.CheckState = false;
                        ec.ConstantCheckState = false;
                        Expr = Expr.Resolve (ec);
                        ec.CheckState = last_check;
                        ec.ConstantCheckState = last_const_check;

                        if (Expr == null)
                                return null;

                        if (Expr is Constant)
                                return Expr;
                        
                        eclass = Expr.eclass;
                        type = Expr.Type;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        bool last_check = ec.CheckState;
                        bool last_const_check = ec.ConstantCheckState;
                        
                        ec.CheckState = false;
                        ec.ConstantCheckState = false;
                        Expr.Emit (ec);
                        ec.CheckState = last_check;
                        ec.ConstantCheckState = last_const_check;
                }
                
        }

        /// <summary>
        ///   An Element Access expression.
        ///
        ///   During semantic analysis these are transformed into 
        ///   IndexerAccess, ArrayAccess or a PointerArithmetic.
        /// </summary>
        public class ElementAccess : Expression {
                public ArrayList  Arguments;
                public Expression Expr;
                
                public ElementAccess (Expression e, ArrayList e_list)
                {
                        Expr = e;

                        loc  = e.Location;
                        
                        if (e_list == null)
                                return;
                        
                        Arguments = new ArrayList ();
                        foreach (Expression tmp in e_list)
                                Arguments.Add (new Argument (tmp, Argument.AType.Expression));
                        
                }

                bool CommonResolve (EmitContext ec)
                {
                        Expr = Expr.Resolve (ec);

                        if (Expr == null) 
                                return false;

                        if (Arguments == null)
                                return false;

                        foreach (Argument a in Arguments){
                                if (!a.Resolve (ec, loc))
                                        return false;
                        }

                        return true;
                }

                Expression MakePointerAccess (EmitContext ec, Type t)
                {
                        if (t == TypeManager.void_ptr_type){
                                Error (242, "The array index operation is not valid on void pointers");
                                return null;
                        }
                        if (Arguments.Count != 1){
                                Error (196, "A pointer must be indexed by only one value");
                                return null;
                        }
                        Expression p;

                        p = new PointerArithmetic (true, Expr, ((Argument)Arguments [0]).Expr, t, loc).Resolve (ec);
                        if (p == null)
                                return null;
                        return new Indirection (p, loc).Resolve (ec);
                }
                
                public override Expression DoResolve (EmitContext ec)
                {
                        if (!CommonResolve (ec))
                                return null;

                        //
                        // 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.
                        //
                        // I am experimenting with this pattern.
                        //
                        Type t = Expr.Type;

                        if (t == TypeManager.array_type){
                                Report.Error (21, loc, "Cannot apply indexing with [] to an expression of type `System.Array'");
                                return null;
                        }
                        
                        if (t.IsArray)
                                return (new ArrayAccess (this, loc)).Resolve (ec);
                        if (t.IsPointer)
                                return MakePointerAccess (ec, Expr.Type);

                        FieldExpr fe = Expr as FieldExpr;
                        if (fe != null) {
                                IFixedBuffer ff = AttributeTester.GetFixedBuffer (fe.FieldInfo);
                                if (ff != null) {
                                        return MakePointerAccess (ec, ff.ElementType);
                                }
                        }
                        return (new IndexerAccess (this, loc)).Resolve (ec);
                }

                public override Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        if (!CommonResolve (ec))
                                return null;

                        Type t = Expr.Type;
                        if (t.IsArray)
                                return (new ArrayAccess (this, loc)).DoResolveLValue (ec, right_side);

                        if (t.IsPointer)
                                return MakePointerAccess (ec, Expr.Type);

                        FieldExpr fe = Expr as FieldExpr;
                        if (fe != null) {
                                IFixedBuffer ff = AttributeTester.GetFixedBuffer (fe.FieldInfo);
                                if (ff != null) {
                                        if (!(fe.InstanceExpression is LocalVariableReference) && 
                                                !(fe.InstanceExpression is This)) {
                                                Report.Error (1708, loc, "Fixed size buffers can only be accessed through locals or fields");
                                                return null;
                                        }
                                        if (!ec.InFixedInitializer && ec.ContainerType.IsValueType) {
                                                Error (1666, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
                                                return null;
                                        }
                                        return MakePointerAccess (ec, ff.ElementType);
                                }
                        }
                        return (new IndexerAccess (this, loc)).DoResolveLValue (ec, right_side);
                }
                
                public override void Emit (EmitContext ec)
                {
                        throw new Exception ("Should never be reached");
                }
        }

        /// <summary>
        ///   Implements array access 
        /// </summary>
        public class ArrayAccess : Expression, IAssignMethod, IMemoryLocation {
                //
                // Points to our "data" repository
                //
                ElementAccess ea;

                LocalTemporary temp;
                bool prepared;
                
                public ArrayAccess (ElementAccess ea_data, Location l)
                {
                        ea = ea_data;
                        eclass = ExprClass.Variable;
                        loc = l;
                }

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

                public override Expression DoResolve (EmitContext ec)
                {
#if false
                        ExprClass eclass = ea.Expr.eclass;

                        // As long as the type is valid
                        if (!(eclass == ExprClass.Variable || eclass == ExprClass.PropertyAccess ||
                              eclass == ExprClass.Value)) {
                                ea.Expr.Error_UnexpectedKind ("variable or value");
                                return null;
                        }
#endif

                        Type t = ea.Expr.Type;
                        if (t.GetArrayRank () != ea.Arguments.Count){
                                Report.Error (22, ea.Location, "Wrong number of indexes `{0}' inside [], expected `{1}'",
                                          ea.Arguments.Count.ToString (), t.GetArrayRank ().ToString ());
                                return null;
                        }

                        type = TypeManager.GetElementType (t);
                        if (type.IsPointer && !ec.InUnsafe){
                                UnsafeError (ea.Location);
                                return null;
                        }

                        foreach (Argument a in ea.Arguments){
                                Type argtype = a.Type;

                                if (argtype == TypeManager.int32_type ||
                                    argtype == TypeManager.uint32_type ||
                                    argtype == TypeManager.int64_type ||
                                    argtype == TypeManager.uint64_type) {
                                        Constant c = a.Expr as Constant;
                                        if (c != null && c.IsNegative) {
                                                Report.Warning (251, 2, ea.Location, "Indexing an array with a negative index (array indices always start at zero)");
                                        }
                                        continue;
                                }

                                //
                                // Mhm.  This is strage, because the Argument.Type is not the same as
                                // Argument.Expr.Type: the value changes depending on the ref/out setting.
                                //
                                // Wonder if I will run into trouble for this.
                                //
                                a.Expr = ExpressionToArrayArgument (ec, a.Expr, ea.Location);
                                if (a.Expr == null)
                                        return null;
                        }
                        
                        eclass = ExprClass.Variable;

                        return this;
                }

                /// <summary>
                ///    Emits the right opcode to load an object of Type `t'
                ///    from an array of T
                /// </summary>
                static public void EmitLoadOpcode (ILGenerator ig, Type type)
                {
                        if (type == TypeManager.byte_type || type == TypeManager.bool_type)
                                ig.Emit (OpCodes.Ldelem_U1);
                        else if (type == TypeManager.sbyte_type)
                                ig.Emit (OpCodes.Ldelem_I1);
                        else if (type == TypeManager.short_type)
                                ig.Emit (OpCodes.Ldelem_I2);
                        else if (type == TypeManager.ushort_type || type == TypeManager.char_type)
                                ig.Emit (OpCodes.Ldelem_U2);
                        else if (type == TypeManager.int32_type)
                                ig.Emit (OpCodes.Ldelem_I4);
                        else if (type == TypeManager.uint32_type)
                                ig.Emit (OpCodes.Ldelem_U4);
                        else if (type == TypeManager.uint64_type)
                                ig.Emit (OpCodes.Ldelem_I8);
                        else if (type == TypeManager.int64_type)
                                ig.Emit (OpCodes.Ldelem_I8);
                        else if (type == TypeManager.float_type)
                                ig.Emit (OpCodes.Ldelem_R4);
                        else if (type == TypeManager.double_type)
                                ig.Emit (OpCodes.Ldelem_R8);
                        else if (type == TypeManager.intptr_type)
                                ig.Emit (OpCodes.Ldelem_I);
                        else if (TypeManager.IsEnumType (type)){
                                EmitLoadOpcode (ig, TypeManager.EnumToUnderlying (type));
                        } else if (type.IsValueType){
                                ig.Emit (OpCodes.Ldelema, type);
                                ig.Emit (OpCodes.Ldobj, type);
                        } else if (type.IsPointer)
                                ig.Emit (OpCodes.Ldelem_I);
                        else
                                ig.Emit (OpCodes.Ldelem_Ref);
                }

                /// <summary>
                ///    Returns the right opcode to store an object of Type `t'
                ///    from an array of T.  
                /// </summary>
                static public OpCode GetStoreOpcode (Type t, out bool is_stobj)
                {
                        //Console.WriteLine (new System.Diagnostics.StackTrace ());
                        is_stobj = false;
                        t = TypeManager.TypeToCoreType (t);
                        if (TypeManager.IsEnumType (t))
                                t = TypeManager.EnumToUnderlying (t);
                        if (t == TypeManager.byte_type || t == TypeManager.sbyte_type ||
                            t == TypeManager.bool_type)
                                return OpCodes.Stelem_I1;
                        else if (t == TypeManager.short_type || t == TypeManager.ushort_type ||
                                 t == TypeManager.char_type)
                                return OpCodes.Stelem_I2;
                        else if (t == TypeManager.int32_type || t == TypeManager.uint32_type)
                                return OpCodes.Stelem_I4;
                        else if (t == TypeManager.int64_type || t == TypeManager.uint64_type)
                                return OpCodes.Stelem_I8;
                        else if (t == TypeManager.float_type)
                                return OpCodes.Stelem_R4;
                        else if (t == TypeManager.double_type)
                                return OpCodes.Stelem_R8;
                        else if (t == TypeManager.intptr_type) {
                                is_stobj = true;
                                return OpCodes.Stobj;
                        } else if (t.IsValueType) {
                                is_stobj = true;
                                return OpCodes.Stobj;
                        } else if (t.IsPointer)
                                return OpCodes.Stelem_I;
                        else
                                return OpCodes.Stelem_Ref;
                }

                MethodInfo FetchGetMethod ()
                {
                        ModuleBuilder mb = CodeGen.Module.Builder;
                        int arg_count = ea.Arguments.Count;
                        Type [] args = new Type [arg_count];
                        MethodInfo get;
                        
                        for (int i = 0; i < arg_count; i++){
                                //args [i++] = a.Type;
                                args [i] = TypeManager.int32_type;
                        }
                        
                        get = mb.GetArrayMethod (
                                ea.Expr.Type, "Get",
                                CallingConventions.HasThis |
                                CallingConventions.Standard,
                                type, args);
                        return get;
                }
                                

                MethodInfo FetchAddressMethod ()
                {
                        ModuleBuilder mb = CodeGen.Module.Builder;
                        int arg_count = ea.Arguments.Count;
                        Type [] args = new Type [arg_count];
                        MethodInfo address;
                        Type ret_type;
                        
                        ret_type = TypeManager.GetReferenceType (type);
                        
                        for (int i = 0; i < arg_count; i++){
                                //args [i++] = a.Type;
                                args [i] = TypeManager.int32_type;
                        }
                        
                        address = mb.GetArrayMethod (
                                ea.Expr.Type, "Address",
                                CallingConventions.HasThis |
                                CallingConventions.Standard,
                                ret_type, args);

                        return address;
                }

                //
                // Load the array arguments into the stack.
                //
                // If we have been requested to cache the values (cached_locations array
                // initialized), then load the arguments the first time and store them
                // in locals.  otherwise load from local variables.
                //
                void LoadArrayAndArguments (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        ea.Expr.Emit (ec);
                        foreach (Argument a in ea.Arguments){
                                Type argtype = a.Expr.Type;
                                
                                a.Expr.Emit (ec);
                                
                                if (argtype == TypeManager.int64_type)
                                        ig.Emit (OpCodes.Conv_Ovf_I);
                                else if (argtype == TypeManager.uint64_type)
                                        ig.Emit (OpCodes.Conv_Ovf_I_Un);
                        }
                }

                public void Emit (EmitContext ec, bool leave_copy)
                {
                        int rank = ea.Expr.Type.GetArrayRank ();
                        ILGenerator ig = ec.ig;

                        if (!prepared) {
                                LoadArrayAndArguments (ec);
                                
                                if (rank == 1)
                                        EmitLoadOpcode (ig, type);
                                else {
                                        MethodInfo method;
                                        
                                        method = FetchGetMethod ();
                                        ig.Emit (OpCodes.Call, method);
                                }
                        } else
                                LoadFromPtr (ec.ig, this.type);
                        
                        if (leave_copy) {
                                ec.ig.Emit (OpCodes.Dup);
                                temp = new LocalTemporary (ec, 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 prepare_for_load)
                {
                        int rank = ea.Expr.Type.GetArrayRank ();
                        ILGenerator ig = ec.ig;
                        Type t = source.Type;
                        prepared = prepare_for_load;

                        if (prepare_for_load) {
                                AddressOf (ec, AddressOp.LoadStore);
                                ec.ig.Emit (OpCodes.Dup);
                                source.Emit (ec);
                                if (leave_copy) {
                                        ec.ig.Emit (OpCodes.Dup);
                                        temp = new LocalTemporary (ec, this.type);
                                        temp.Store (ec);
                                }
                                StoreFromPtr (ec.ig, t);
                                
                                if (temp != null)
                                        temp.Emit (ec);
                                
                                return;
                        }
                        
                        LoadArrayAndArguments (ec);

                        if (rank == 1) {
                                bool is_stobj;
                                OpCode op = GetStoreOpcode (t, out is_stobj);
                                //
                                // The stobj opcode used by value types will need
                                // an address on the stack, not really an array/array
                                // pair
                                //
                                if (is_stobj)
                                        ig.Emit (OpCodes.Ldelema, t);
                                
                                source.Emit (ec);
                                if (leave_copy) {
                                        ec.ig.Emit (OpCodes.Dup);
                                        temp = new LocalTemporary (ec, this.type);
                                        temp.Store (ec);
                                }
                                
                                if (is_stobj)
                                        ig.Emit (OpCodes.Stobj, t);
                                else
                                        ig.Emit (op);
                        } else {
                                ModuleBuilder mb = CodeGen.Module.Builder;
                                int arg_count = ea.Arguments.Count;
                                Type [] args = new Type [arg_count + 1];
                                MethodInfo set;
                                
                                source.Emit (ec);
                                if (leave_copy) {
                                        ec.ig.Emit (OpCodes.Dup);
                                        temp = new LocalTemporary (ec, this.type);
                                        temp.Store (ec);
                                }
                                
                                for (int i = 0; i < arg_count; i++){
                                        //args [i++] = a.Type;
                                        args [i] = TypeManager.int32_type;
                                }

                                args [arg_count] = type;
                                
                                set = mb.GetArrayMethod (
                                        ea.Expr.Type, "Set",
                                        CallingConventions.HasThis |
                                        CallingConventions.Standard,
                                        TypeManager.void_type, args);
                                
                                ig.Emit (OpCodes.Call, set);
                        }
                        
                        if (temp != null)
                                temp.Emit (ec);
                }

                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        int rank = ea.Expr.Type.GetArrayRank ();
                        ILGenerator ig = ec.ig;

                        LoadArrayAndArguments (ec);

                        if (rank == 1){
                                ig.Emit (OpCodes.Ldelema, type);
                        } else {
                                MethodInfo address = FetchAddressMethod ();
                                ig.Emit (OpCodes.Call, address);
                        }
                }

                public void EmitGetLength (EmitContext ec, int dim)
                {
                        int rank = ea.Expr.Type.GetArrayRank ();
                        ILGenerator ig = ec.ig;

                        ea.Expr.Emit (ec);
                        if (rank == 1) {
                                ig.Emit (OpCodes.Ldlen);
                                ig.Emit (OpCodes.Conv_I4);
                        } else {
                                IntLiteral.EmitInt (ig, dim);
                                ig.Emit (OpCodes.Callvirt, TypeManager.int_getlength_int);
                        }
                }
        }
        
        class Indexers {
                // note that the ArrayList itself in mutable.  We just can't assign to 'Properties' again.
                public readonly ArrayList Properties;
                static Indexers empty;

                public struct Indexer {
                        public readonly PropertyInfo PropertyInfo;
                        public readonly MethodInfo Getter, Setter;

                        public Indexer (PropertyInfo property_info, MethodInfo get, MethodInfo set)
                        {
                                this.PropertyInfo = property_info;
                                this.Getter = get;
                                this.Setter = set;
                        }
                }

                static Indexers ()
                {
                        empty = new Indexers (null);
                }

                Indexers (ArrayList array)
                {
                        Properties = array;
                }

                static void Append (ref Indexers ix, Type caller_type, MemberInfo [] mi)
                {
                        bool dummy;
                        if (mi == null)
                                return;
                        foreach (PropertyInfo property in mi){
                                MethodInfo get, set;
                                
                                get = property.GetGetMethod (true);
                                set = property.GetSetMethod (true);
                                if (get != null && !Expression.IsAccessorAccessible (caller_type, get, out dummy))
                                        get = null;
                                if (set != null && !Expression.IsAccessorAccessible (caller_type, set, out dummy))
                                        set = null;
                                if (get != null || set != null) {
                                        if (ix == empty)
                                                ix = new Indexers (new ArrayList ());
                                        ix.Properties.Add (new Indexer (property, get, set));
                                }
                        }
                }

                static private MemberInfo [] GetIndexersForTypeOrInterface (Type caller_type, Type lookup_type)
                {
                        string p_name = TypeManager.IndexerPropertyName (lookup_type);

                        return TypeManager.MemberLookup (
                                caller_type, caller_type, lookup_type, MemberTypes.Property,
                                BindingFlags.Public | BindingFlags.Instance |
                                BindingFlags.DeclaredOnly, p_name, null);
                }
                
                static public Indexers GetIndexersForType (Type caller_type, Type lookup_type, Location loc) 
                {
                        Indexers ix = empty;

                        Type copy = lookup_type;
                        while (copy != TypeManager.object_type && copy != null){
                                Append (ref ix, caller_type, GetIndexersForTypeOrInterface (caller_type, copy));
                                copy = copy.BaseType;
                        }

                        if (lookup_type.IsInterface) {
                                Type [] ifaces = TypeManager.GetInterfaces (lookup_type);
                                if (ifaces != null) {
                                        foreach (Type itype in ifaces)
                                                Append (ref ix, caller_type, GetIndexersForTypeOrInterface (caller_type, itype));
                                }
                        }

                        return ix;
                }
        }

        /// <summary>
        ///   Expressions that represent an indexer call.
        /// </summary>
        public class IndexerAccess : Expression, IAssignMethod {
                //
                // Points to our "data" repository
                //
                MethodInfo get, set;
                ArrayList set_arguments;
                bool is_base_indexer;

                protected Type indexer_type;
                protected Type current_type;
                protected Expression instance_expr;
                protected ArrayList arguments;
                
                public IndexerAccess (ElementAccess ea, Location loc)
                        : this (ea.Expr, false, loc)
                {
                        this.arguments = ea.Arguments;
                }

                protected IndexerAccess (Expression instance_expr, bool is_base_indexer,
                                         Location loc)
                {
                        this.instance_expr = instance_expr;
                        this.is_base_indexer = is_base_indexer;
                        this.eclass = ExprClass.Value;
                        this.loc = loc;
                }

                protected virtual bool CommonResolve (EmitContext ec)
                {
                        indexer_type = instance_expr.Type;
                        current_type = ec.ContainerType;

                        return true;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        ArrayList AllGetters = new ArrayList();
                        if (!CommonResolve (ec))
                                return null;

                        //
                        // Step 1: Query for all `Item' *properties*.  Notice
                        // that the actual methods are pointed from here.
                        //
                        // This is a group of properties, piles of them.  

                        bool found_any = false, found_any_getters = false;
                        Type lookup_type = indexer_type;

                        Indexers ilist = Indexers.GetIndexersForType (current_type, lookup_type, loc);
                        if (ilist.Properties != null) {
                                found_any = true;
                                foreach (Indexers.Indexer ix in ilist.Properties) {
                                        if (ix.Getter != null)
                                                AllGetters.Add (ix.Getter);
                                }
                        }

                        if (AllGetters.Count > 0) {
                                found_any_getters = true;
                                get = (MethodInfo) Invocation.OverloadResolve (
                                        ec, new MethodGroupExpr (AllGetters, loc),
                                        arguments, false, loc);
                        }

                        if (!found_any) {
                                Report.Error (21, loc, "Cannot apply indexing with [] to an expression of type `{0}'",
                                              TypeManager.CSharpName (indexer_type));
                                return null;
                        }

                        if (!found_any_getters) {
                                Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
                                       "XXXXXXXX");
                                return null;
                        }

                        if (get == null) {
                                Invocation.Error_WrongNumArguments (loc, "this", arguments.Count);
                                return null;
                        }

                        //
                        // Only base will allow this invocation to happen.
                        //
                        if (get.IsAbstract && this is BaseIndexerAccess){
                                Error_CannotCallAbstractBase (TypeManager.CSharpSignature (get));
                                return null;
                        }

                        type = get.ReturnType;
                        if (type.IsPointer && !ec.InUnsafe){
                                UnsafeError (loc);
                                return null;
                        }

                        instance_expr.CheckMarshallByRefAccess (ec.ContainerType);
                        
                        eclass = ExprClass.IndexerAccess;
                        return this;
                }

                public override Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        ArrayList AllSetters = new ArrayList();
                        if (!CommonResolve (ec))
                                return null;

                        bool found_any = false, found_any_setters = false;

                        Indexers ilist = Indexers.GetIndexersForType (current_type, indexer_type, loc);
                        if (ilist.Properties != null) {
                                found_any = true;
                                foreach (Indexers.Indexer ix in ilist.Properties) {
                                        if (ix.Setter != null)
                                                AllSetters.Add (ix.Setter);
                                }
                        }
                        if (AllSetters.Count > 0) {
                                found_any_setters = true;
                                set_arguments = (ArrayList) arguments.Clone ();
                                set_arguments.Add (new Argument (right_side, Argument.AType.Expression));
                                set = (MethodInfo) Invocation.OverloadResolve (
                                        ec, new MethodGroupExpr (AllSetters, loc),
                                        set_arguments, false, loc);
                        }

                        if (!found_any) {
                                Report.Error (21, loc, "Cannot apply indexing with [] to an expression of type `{0}'",
                                              TypeManager.CSharpName (indexer_type));
                                return null;
                        }

                        if (!found_any_setters) {
                                Error (154, "indexer can not be used in this context, because " +
                                       "it lacks a `set' accessor");
                                return null;
                        }

                        if (set == null) {
                                Invocation.Error_WrongNumArguments (loc, "this", arguments.Count);
                                return null;
                        }

                        //
                        // Only base will allow this invocation to happen.
                        //
                        if (set.IsAbstract && this is BaseIndexerAccess){
                                Error_CannotCallAbstractBase (TypeManager.CSharpSignature (set));
                                return null;
                        }

                        //
                        // Now look for the actual match in the list of indexers to set our "return" type
                        //
                        type = TypeManager.void_type;   // default value
                        foreach (Indexers.Indexer ix in ilist.Properties){
                                if (ix.Setter == set){
                                        type = ix.PropertyInfo.PropertyType;
                                        break;
                                }
                        }

                        instance_expr.CheckMarshallByRefAccess (ec.ContainerType);

                        eclass = ExprClass.IndexerAccess;
                        return this;
                }
                
                bool prepared = false;
                LocalTemporary temp;
                
                public void Emit (EmitContext ec, bool leave_copy)
                {
                        Invocation.EmitCall (ec, is_base_indexer, false, instance_expr, get, arguments, loc, prepared, false);
                        if (leave_copy) {
                                ec.ig.Emit (OpCodes.Dup);
                                temp = new LocalTemporary (ec, Type);
                                temp.Store (ec);
                        }
                }
                
                //
                // source is ignored, because we already have a copy of it from the
                // LValue resolution and we have already constructed a pre-cached
                // version of the arguments (ea.set_arguments);
                //
                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool prepare_for_load)
                {
                        prepared = prepare_for_load;
                        Argument a = (Argument) set_arguments [set_arguments.Count - 1];
                        
                        if (prepared) {
                                source.Emit (ec);
                                if (leave_copy) {
                                        ec.ig.Emit (OpCodes.Dup);
                                        temp = new LocalTemporary (ec, Type);
                                        temp.Store (ec);
                                }
                        } else if (leave_copy) {
                                temp = new LocalTemporary (ec, Type);
                                source.Emit (ec);
                                temp.Store (ec);
                                a.Expr = temp;
                        }
                        
                        Invocation.EmitCall (ec, is_base_indexer, false, instance_expr, set, set_arguments, loc, false, prepared);
                        
                        if (temp != null)
                                temp.Emit (ec);
                }
                
                
                public override void Emit (EmitContext ec)
                {
                        Emit (ec, false);
                }
        }

        /// <summary>
        ///   The base operator for method names
        /// </summary>
        public class BaseAccess : Expression {
                string member;
                
                public BaseAccess (string member, Location l)
                {
                        this.member = member;
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        Expression c = CommonResolve (ec);

                        if (c == null)
                                return null;

                        //
                        // MethodGroups use this opportunity to flag an error on lacking ()
                        //
                        if (!(c is MethodGroupExpr))
                                return c.Resolve (ec);
                        return c;
                }

                public override Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        Expression c = CommonResolve (ec);

                        if (c == null)
                                return null;

                        //
                        // MethodGroups use this opportunity to flag an error on lacking ()
                        //
                        if (! (c is MethodGroupExpr))
                                return c.DoResolveLValue (ec, right_side);

                        return c;
                }

                Expression CommonResolve (EmitContext ec)
                {
                        Expression member_lookup;
                        Type current_type = ec.ContainerType;
                        Type base_type = current_type.BaseType;

                        if (ec.IsStatic){
                                Error (1511, "Keyword `base' is not available in a static method");
                                return null;
                        }

                        if (ec.IsFieldInitializer){
                                Error (1512, "Keyword `base' is not available in the current context");
                                return null;
                        }
                        
                        member_lookup = MemberLookup (ec, ec.ContainerType, null, base_type, member,
                                                      AllMemberTypes, AllBindingFlags, loc);
                        if (member_lookup == null) {
                                MemberLookupFailed (ec, base_type, base_type, member, null, true, loc);
                                return null;
                        }

                        Expression left;
                        
                        if (ec.IsStatic)
                                left = new TypeExpression (base_type, loc);
                        else
                                left = ec.GetThis (loc);

                        MemberExpr me = (MemberExpr) member_lookup;
                        
                        Expression e = me.ResolveMemberAccess (ec, left, loc, null);

                        if (e is PropertyExpr) {
                                PropertyExpr pe = (PropertyExpr) e;

                                pe.IsBase = true;
                        }
                        
                        if (e is MethodGroupExpr)
                                ((MethodGroupExpr) e).IsBase = true;

                        return e;
                }

                public override void Emit (EmitContext ec)
                {
                        throw new Exception ("Should never be called"); 
                }
        }

        /// <summary>
        ///   The base indexer operator
        /// </summary>
        public class BaseIndexerAccess : IndexerAccess {
                public BaseIndexerAccess (ArrayList args, Location loc)
                        : base (null, true, loc)
                {
                        arguments = new ArrayList ();
                        foreach (Expression tmp in args)
                                arguments.Add (new Argument (tmp, Argument.AType.Expression));
                }

                protected override bool CommonResolve (EmitContext ec)
                {
                        instance_expr = ec.GetThis (loc);

                        current_type = ec.ContainerType.BaseType;
                        indexer_type = current_type;

                        foreach (Argument a in arguments){
                                if (!a.Resolve (ec, loc))
                                        return false;
                        }

                        return true;
                }
        }
        
        /// <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 {
                public static readonly EmptyExpression Null = new EmptyExpression ();

                static EmptyExpression temp = new EmptyExpression ();
                public static EmptyExpression Grab ()
                {
                        if (temp == null)
                                throw new InternalErrorException ("Nested Grab");
                        EmptyExpression retval = temp;
                        temp = null;
                        return retval;
                }

                public static void Release (EmptyExpression e)
                {
                        if (temp != null)
                                throw new InternalErrorException ("Already released");
                        temp = e;
                }

                // TODO: should be protected
                public EmptyExpression ()
                {
                        type = TypeManager.object_type;
                        eclass = ExprClass.Value;
                        loc = Location.Null;
                }

                public EmptyExpression (Type t)
                {
                        type = t;
                        eclass = ExprClass.Value;
                        loc = Location.Null;
                }
                
                public override Expression DoResolve (EmitContext ec)
                {
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        // nothing, as we only exist to not do anything.
                }

                //
                // This is just because we might want to reuse this bad boy
                // instead of creating gazillions of EmptyExpressions.
                // (CanImplicitConversion uses it)
                //
                public void SetType (Type t)
                {
                        type = t;
                }
        }

        public class UserCast : Expression {
                MethodBase method;
                Expression source;
                
                public UserCast (MethodInfo method, Expression source, Location l)
                {
                        this.method = method;
                        this.source = source;
                        type = method.ReturnType;
                        eclass = ExprClass.Value;
                        loc = l;
                }

                public Expression Source {
                        get {
                                return source;
                        }
                }
                        
                public override Expression DoResolve (EmitContext ec)
                {
                        //
                        // We are born fully resolved
                        //
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;

                        source.Emit (ec);
                        
                        if (method is MethodInfo)
                                ig.Emit (OpCodes.Call, (MethodInfo) method);
                        else
                                ig.Emit (OpCodes.Call, (ConstructorInfo) method);

                }
        }

        // <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 {
                Expression left;
                string dim;
                
                public ComposedCast (Expression left, string dim)
                        : this (left, dim, left.Location)
                {
                }

                public ComposedCast (Expression left, string dim, Location l)
                {
                        this.left = left;
                        this.dim = dim;
                        loc = l;
                }

                public override TypeExpr DoResolveAsTypeStep (EmitContext ec)
                {
                        TypeExpr lexpr = left.ResolveAsTypeTerminal (ec, false);
                        if (lexpr == null)
                                return null;

                        bool old = ec.TestObsoleteMethodUsage;
                        ec.TestObsoleteMethodUsage = false;
                        Type ltype = lexpr.ResolveType (ec);
                        ec.TestObsoleteMethodUsage = old;

                        if ((ltype == TypeManager.void_type) && (dim != "*")) {
                                Report.Error (1547, Location,
                                              "Keyword 'void' cannot be used in this context");
                                return null;
                        }

                        if (dim == "*" && !TypeManager.VerifyUnManaged (ltype, loc)) {
                                return null;
                        }

                        type = TypeManager.GetConstructedType (ltype, dim);
                        if (type == null) {
                                throw new InternalErrorException ("Couldn't create computed type " + ltype + dim);
                        }

                        if (!ec.InUnsafe && type.IsPointer){
                                UnsafeError (loc);
                                return null;
                        }

                        if (type.IsArray && (type.GetElementType () == TypeManager.arg_iterator_type ||
                                type.GetElementType () == TypeManager.typed_reference_type)) {
                                Report.Error (611, loc, "Array elements cannot be of type `{0}'", TypeManager.CSharpName (type.GetElementType ()));
                                return null;
                        }
                        
                        eclass = ExprClass.Type;
                        return this;
                }

                public override string Name {
                        get {
                                return left + dim;
                        }
                }

                public override string FullName {
                        get {
                                return type.FullName;
                        }
                }
        }

        public class FixedBufferPtr : Expression {
                Expression array;

                public FixedBufferPtr (Expression array, Type array_type, Location l)
                {
                        this.array = array;
                        this.loc = l;

                        type = TypeManager.GetPointerType (array_type);
                        eclass = ExprClass.Value;
                }

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

                public override Expression DoResolve (EmitContext ec)
                {
                        //
                        // We are born fully resolved
                        //
                        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)
        //
        public class ArrayPtr : FixedBufferPtr {
                Type array_type;
                
                public ArrayPtr (Expression array, Type array_type, Location l):
                        base (array, array_type, l)
                {
                        this.array_type = array_type;
                }

                public override void Emit (EmitContext ec)
                {
                        base.Emit (ec);
                        
                        ILGenerator ig = ec.ig;
                        IntLiteral.EmitInt (ig, 0);
                        ig.Emit (OpCodes.Ldelema, array_type);
                }
        }

        //
        // Used by the fixed statement
        //
        public class StringPtr : Expression {
                LocalBuilder b;
                
                public StringPtr (LocalBuilder b, Location l)
                {
                        this.b = b;
                        eclass = ExprClass.Value;
                        type = TypeManager.char_ptr_type;
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        // This should never be invoked, we are born in fully
                        // initialized state.

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;

                        ig.Emit (OpCodes.Ldloc, b);
                        ig.Emit (OpCodes.Conv_I);
                        ig.Emit (OpCodes.Call, TypeManager.int_get_offset_to_string_data);
                        ig.Emit (OpCodes.Add);
                }
        }
        
        //
        // Implements the `stackalloc' keyword
        //
        public class StackAlloc : Expression {
                Type otype;
                Expression t;
                Expression count;
                
                public StackAlloc (Expression type, Expression count, Location l)
                {
                        t = type;
                        this.count = count;
                        loc = l;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        count = count.Resolve (ec);
                        if (count == null)
                                return null;
                        
                        if (count.Type != TypeManager.int32_type){
                                count = Convert.ImplicitConversionRequired (ec, count, TypeManager.int32_type, loc);
                                if (count == null)
                                        return null;
                        }

                        Constant c = count as Constant;
                        if (c != null && c.IsNegative) {
                                Report.Error (247, loc, "Cannot use a negative size with stackalloc");
                                return null;
                        }

                        if (ec.InCatch || ec.InFinally) {
                                Error (255, "Cannot use stackalloc in finally or catch");
                                return null;
                        }

                        TypeExpr texpr = t.ResolveAsTypeTerminal (ec, false);
                        if (texpr == null)
                                return null;

                        otype = texpr.ResolveType (ec);

                        if (!TypeManager.VerifyUnManaged (otype, loc))
                                return null;

                        type = TypeManager.GetPointerType (otype);
                        eclass = ExprClass.Value;

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        int size = GetTypeSize (otype);
                        ILGenerator ig = ec.ig;
                                
                        if (size == 0)
                                ig.Emit (OpCodes.Sizeof, otype);
                        else
                                IntConstant.EmitInt (ig, size);
                        count.Emit (ec);
                        ig.Emit (OpCodes.Mul);
                        ig.Emit (OpCodes.Localloc);
                }
        }
}