**** Merged from MCS ****

[mono.git] / mcs / gmcs / ecore.cs

//
// ecore.cs: Core of the Expression representation for the intermediate tree.
//
// Author:
//   Miguel de Icaza (miguel@ximian.com)
//
// (C) 2001, 2002, 2003 Ximian, Inc.
//
//

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

        /// <remarks>
        ///   The ExprClass class contains the is used to pass the 
        ///   classification of an expression (value, variable, namespace,
        ///   type, method group, property access, event access, indexer access,
        ///   nothing).
        /// </remarks>
        public enum ExprClass : byte {
                Invalid,
                
                Value,
                Variable,
                Namespace,
                Type,
                MethodGroup,
                PropertyAccess,
                EventAccess,
                IndexerAccess,
                Nothing, 
        }

        /// <remarks>
        ///   This is used to tell Resolve in which types of expressions we're
        ///   interested.
        /// </remarks>
        [Flags]
        public enum ResolveFlags {
                // Returns Value, Variable, PropertyAccess, EventAccess or IndexerAccess.
                VariableOrValue         = 1,

                // Returns a type expression.
                Type                    = 2,

                // Returns a method group.
                MethodGroup             = 4,

                // Allows SimpleNames to be returned.
                // This is used by MemberAccess to construct long names that can not be
                // partially resolved (namespace-qualified names for example).
                SimpleName              = 8,

                // Mask of all the expression class flags.
                MaskExprClass           = 15,

                // Disable control flow analysis while resolving the expression.
                // This is used when resolving the instance expression of a field expression.
                DisableFlowAnalysis     = 16
        }

        //
        // This is just as a hint to AddressOf of what will be done with the
        // address.
        [Flags]
        public enum AddressOp {
                Store = 1,
                Load  = 2,
                LoadStore = 3
        };
        
        /// <summary>
        ///   This interface is implemented by variables
        /// </summary>
        public interface IMemoryLocation {
                /// <summary>
                ///   The AddressOf method should generate code that loads
                ///   the address of the object and leaves it on the stack.
                ///
                ///   The `mode' argument is used to notify the expression
                ///   of whether this will be used to read from the address or
                ///   write to the address.
                ///
                ///   This is just a hint that can be used to provide good error
                ///   reporting, and should have no other side effects. 
                /// </summary>
                void AddressOf (EmitContext ec, AddressOp mode);
        }

        /// <summary>
        ///   We are either a namespace or a type.
        ///   If we're a type, `IsType' is true and we may use `Type' to get
        ///   a TypeExpr representing that type.
        /// </summary>
        public interface IAlias {
                bool IsType {
                        get;
                }

                string Name {
                        get;
                }

                TypeExpr Type {
                        get;
                }
        }

        /// <summary>
        ///   This interface is implemented by variables
        /// </summary>
        public interface IVariable {
                VariableInfo VariableInfo {
                        get;
                }

                bool VerifyFixed (bool is_expression);
        }

        /// <summary>
        ///   This interface denotes an expression which evaluates to a member
        ///   of a struct or a class.
        /// </summary>
        public interface IMemberExpr
        {
                /// <summary>
                ///   The name of this member.
                /// </summary>
                string Name {
                        get;
                }

                /// <summary>
                ///   Whether this is an instance member.
                /// </summary>
                bool IsInstance {
                        get;
                }

                /// <summary>
                ///   Whether this is a static member.
                /// </summary>
                bool IsStatic {
                        get;
                }

                /// <summary>
                ///   The type which declares this member.
                /// </summary>
                Type DeclaringType {
                        get;
                }

                /// <summary>
                ///   The instance expression associated with this member, if it's a
                ///   non-static member.
                /// </summary>
                Expression InstanceExpression {
                        get; set;
                }
        }

        /// <remarks>
        ///   Base class for expressions
        /// </remarks>
        public abstract class Expression {
                public ExprClass eclass;
                protected Type type;
                protected Location loc;
                
                public Type Type {
                        get {
                                return type;
                        }

                        set {
                                type = value;
                        }
                }

                public Location Location {
                        get {
                                return loc;
                        }
                }

                /// <summary>
                ///   Utility wrapper routine for Error, just to beautify the code
                /// </summary>
                public void Error (int error, string s)
                {
                        if (!Location.IsNull (loc))
                                Report.Error (error, loc, s);
                        else
                                Report.Error (error, s);
                }

                /// <summary>
                ///   Utility wrapper routine for Warning, just to beautify the code
                /// </summary>
                public void Warning (int warning, string s)
                {
                        if (!Location.IsNull (loc))
                                Report.Warning (warning, loc, s);
                        else
                                Report.Warning (warning, s);
                }

                /// <summary>
                ///   Utility wrapper routine for Warning, only prints the warning if
                ///   warnings of level `level' are enabled.
                /// </summary>
                public void Warning (int warning, int level, string s)
                {
                        if (level <= RootContext.WarningLevel)
                                Warning (warning, s);
                }

                /// <summary>
                ///   Performs semantic analysis on the Expression
                /// </summary>
                ///
                /// <remarks>
                ///   The Resolve method is invoked to perform the semantic analysis
                ///   on the node.
                ///
                ///   The return value is an expression (it can be the
                ///   same expression in some cases) or a new
                ///   expression that better represents this node.
                ///   
                ///   For example, optimizations of Unary (LiteralInt)
                ///   would return a new LiteralInt with a negated
                ///   value.
                ///   
                ///   If there is an error during semantic analysis,
                ///   then an error should be reported (using Report)
                ///   and a null value should be returned.
                ///   
                ///   There are two side effects expected from calling
                ///   Resolve(): the the field variable "eclass" should
                ///   be set to any value of the enumeration
                ///   `ExprClass' and the type variable should be set
                ///   to a valid type (this is the type of the
                ///   expression).
                /// </remarks>
                public abstract Expression DoResolve (EmitContext ec);

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

                //
                // This is used if the expression should be resolved as a type.
                // the default implementation fails.   Use this method in
                // those participants in the SimpleName chain system.
                //
                public virtual Expression ResolveAsTypeStep (EmitContext ec)
                {
                        return null;
                }

                //
                // This is used to resolve the expression as a type, a null
                // value will be returned if the expression is not a type
                // reference
                //
                public TypeExpr ResolveAsTypeTerminal (EmitContext ec)
                {
                        return ResolveAsTypeStep (ec) as TypeExpr;
                }
               
                /// <summary>
                ///   Resolves an expression and performs semantic analysis on it.
                /// </summary>
                ///
                /// <remarks>
                ///   Currently Resolve wraps DoResolve to perform sanity
                ///   checking and assertion checking on what we expect from Resolve.
                /// </remarks>
                public Expression Resolve (EmitContext ec, ResolveFlags flags)
                {
                        if ((flags & ResolveFlags.MaskExprClass) == ResolveFlags.Type) 
                                return ResolveAsTypeStep (ec);

                        bool old_do_flow_analysis = ec.DoFlowAnalysis;
                        if ((flags & ResolveFlags.DisableFlowAnalysis) != 0)
                                ec.DoFlowAnalysis = false;

                        Expression e;
                        if (this is SimpleName)
                                e = ((SimpleName) this).DoResolveAllowStatic (ec);
                        else 
                                e = DoResolve (ec);

                        ec.DoFlowAnalysis = old_do_flow_analysis;

                        if (e == null)
                                return null;

                        if (e is SimpleName){
                                SimpleName s = (SimpleName) e;

                                if ((flags & ResolveFlags.SimpleName) == 0) {
                                        MemberLookupFailed (ec, null, ec.ContainerType, s.Name,
                                                            ec.DeclSpace.Name, loc);
                                        return null;
                                }

                                return s;
                        }

                        if ((e is TypeExpr) || (e is ComposedCast)) {
                                if ((flags & ResolveFlags.Type) == 0) {
                                        e.Error_UnexpectedKind (flags);
                                        return null;
                                }

                                return e;
                        }

                        switch (e.eclass) {
                        case ExprClass.Type:
                                if ((flags & ResolveFlags.VariableOrValue) == 0) {
                                        e.Error_UnexpectedKind (flags);
                                        return null;
                                }
                                break;

                        case ExprClass.MethodGroup:
                                if (!RootContext.V2){
                                if ((flags & ResolveFlags.MethodGroup) == 0) {
                                        ((MethodGroupExpr) e).ReportUsageError ();
                                        return null;
                                }
                                }
                                break;

                        case ExprClass.Value:
                        case ExprClass.Variable:
                        case ExprClass.PropertyAccess:
                        case ExprClass.EventAccess:
                        case ExprClass.IndexerAccess:
                                if ((flags & ResolveFlags.VariableOrValue) == 0) {
                                        Console.WriteLine ("I got: {0} and {1}", e.GetType (), e);
                                        Console.WriteLine ("I am {0} and {1}", this.GetType (), this);
                                        FieldInfo fi = ((FieldExpr) e).FieldInfo;
                                        
                                        Console.WriteLine ("{0} and {1}", fi.DeclaringType, fi.Name);
                                        e.Error_UnexpectedKind (flags);
                                        return null;
                                }
                                break;

                        default:
                                throw new Exception ("Expression " + e.GetType () +
                                                     " ExprClass is Invalid after resolve");
                        }

                        if (e.type == null)
                                throw new Exception (
                                        "Expression " + e.GetType () +
                                        " did not set its type after Resolve\n" +
                                        "called from: " + this.GetType ());

                        return e;
                }

                /// <summary>
                ///   Resolves an expression and performs semantic analysis on it.
                /// </summary>
                public Expression Resolve (EmitContext ec)
                {
                        return Resolve (ec, ResolveFlags.VariableOrValue);
                }

                /// <summary>
                ///   Resolves an expression for LValue assignment
                /// </summary>
                ///
                /// <remarks>
                ///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
                ///   checking and assertion checking on what we expect from Resolve
                /// </remarks>
                public Expression ResolveLValue (EmitContext ec, Expression right_side)
                {
                        Expression e = DoResolveLValue (ec, right_side);

                        if (e != null){
                                if (e is SimpleName){
                                        SimpleName s = (SimpleName) e;
                                        MemberLookupFailed (ec, null, ec.ContainerType, s.Name,
                                                            ec.DeclSpace.Name, loc);
                                        return null;
                                }

                                if (e.eclass == ExprClass.Invalid)
                                        throw new Exception ("Expression " + e +
                                                             " ExprClass is Invalid after resolve");

                                if (e.eclass == ExprClass.MethodGroup) {
                                        ((MethodGroupExpr) e).ReportUsageError ();
                                        return null;
                                }

                                if ((e.type == null) && !(e is ConstructedType))
                                        throw new Exception ("Expression " + e +
                                                             " did not set its type after Resolve");
                        }

                        return e;
                }
                
                /// <summary>
                ///   Emits the code for the expression
                /// </summary>
                ///
                /// <remarks>
                ///   The Emit method is invoked to generate the code
                ///   for the expression.  
                /// </remarks>
                public abstract void Emit (EmitContext ec);

                public virtual void EmitBranchable (EmitContext ec, Label target, bool onTrue)
                {
                        Emit (ec);
                        ec.ig.Emit (onTrue ? OpCodes.Brtrue : OpCodes.Brfalse, target);
                }

                /// <summary>
                ///   Protected constructor.  Only derivate types should
                ///   be able to be created
                /// </summary>

                protected Expression ()
                {
                        eclass = ExprClass.Invalid;
                        type = null;
                }

                /// <summary>
                ///   Returns a literalized version of a literal FieldInfo
                /// </summary>
                ///
                /// <remarks>
                ///   The possible return values are:
                ///      IntConstant, UIntConstant
                ///      LongLiteral, ULongConstant
                ///      FloatConstant, DoubleConstant
                ///      StringConstant
                ///
                ///   The value returned is already resolved.
                /// </remarks>
                public static Constant Constantify (object v, Type t)
                {
                        if (t == TypeManager.int32_type)
                                return new IntConstant ((int) v);
                        else if (t == TypeManager.uint32_type)
                                return new UIntConstant ((uint) v);
                        else if (t == TypeManager.int64_type)
                                return new LongConstant ((long) v);
                        else if (t == TypeManager.uint64_type)
                                return new ULongConstant ((ulong) v);
                        else if (t == TypeManager.float_type)
                                return new FloatConstant ((float) v);
                        else if (t == TypeManager.double_type)
                                return new DoubleConstant ((double) v);
                        else if (t == TypeManager.string_type)
                                return new StringConstant ((string) v);
                        else if (t == TypeManager.short_type)
                                return new ShortConstant ((short)v);
                        else if (t == TypeManager.ushort_type)
                                return new UShortConstant ((ushort)v);
                        else if (t == TypeManager.sbyte_type)
                                return new SByteConstant (((sbyte)v));
                        else if (t == TypeManager.byte_type)
                                return new ByteConstant ((byte)v);
                        else if (t == TypeManager.char_type)
                                return new CharConstant ((char)v);
                        else if (t == TypeManager.bool_type)
                                return new BoolConstant ((bool) v);
                        else if (TypeManager.IsEnumType (t)){
                                Type real_type = TypeManager.TypeToCoreType (v.GetType ());
                                if (real_type == t)
                                        real_type = real_type.UnderlyingSystemType;

                                Constant e = Constantify (v, real_type);

                                return new EnumConstant (e, t);
                        } else
                                throw new Exception ("Unknown type for constant (" + t +
                                                     "), details: " + v);
                }

                /// <summary>
                ///   Returns a fully formed expression after a MemberLookup
                /// </summary>
                public static Expression ExprClassFromMemberInfo (EmitContext ec, MemberInfo mi, Location loc)
                {
                        if (mi is EventInfo)
                                return new EventExpr ((EventInfo) mi, loc);
                        else if (mi is FieldInfo)
                                return new FieldExpr ((FieldInfo) mi, loc);
                        else if (mi is PropertyInfo)
                                return new PropertyExpr (ec, (PropertyInfo) mi, loc);
                        else if (mi is Type){
                                return new TypeExpression ((System.Type) mi, loc);
                        }

                        return null;
                }

                //
                // FIXME: Probably implement a cache for (t,name,current_access_set)?
                //
                // This code could use some optimizations, but we need to do some
                // measurements.  For example, we could use a delegate to `flag' when
                // something can not any longer be a method-group (because it is something
                // else).
                //
                // Return values:
                //     If the return value is an Array, then it is an array of
                //     MethodBases
                //   
                //     If the return value is an MemberInfo, it is anything, but a Method
                //
                //     null on error.
                //
                // FIXME: When calling MemberLookup inside an `Invocation', we should pass
                // the arguments here and have MemberLookup return only the methods that
                // match the argument count/type, unlike we are doing now (we delay this
                // decision).
                //
                // This is so we can catch correctly attempts to invoke instance methods
                // from a static body (scan for error 120 in ResolveSimpleName).
                //
                //
                // FIXME: Potential optimization, have a static ArrayList
                //

                public static Expression MemberLookup (EmitContext ec, Type queried_type, string name,
                                                       MemberTypes mt, BindingFlags bf, Location loc)
                {
                        return MemberLookup (ec, ec.ContainerType, null, queried_type, name, mt, bf, loc);
                }

                //
                // Lookup type `queried_type' for code in class `container_type' with a qualifier of
                // `qualifier_type' or null to lookup members in the current class.
                //

                public static Expression MemberLookup (EmitContext ec, Type container_type,
                                                       Type qualifier_type, Type queried_type,
                                                       string name, MemberTypes mt,
                                                       BindingFlags bf, Location loc)
                {
                        MemberInfo [] mi = TypeManager.MemberLookup (
                                container_type, qualifier_type,queried_type, mt, bf, name);

                        if (mi == null)
                                return null;

                        int count = mi.Length;

                        if (mi [0] is MethodBase)
                                return new MethodGroupExpr (mi, loc);

                        if (count > 1)
                                return null;

                        return ExprClassFromMemberInfo (ec, mi [0], loc);
                }

                public const MemberTypes AllMemberTypes =
                        MemberTypes.Constructor |
                        MemberTypes.Event       |
                        MemberTypes.Field       |
                        MemberTypes.Method      |
                        MemberTypes.NestedType  |
                        MemberTypes.Property;
                
                public const BindingFlags AllBindingFlags =
                        BindingFlags.Public |
                        BindingFlags.Static |
                        BindingFlags.Instance;

                public static Expression MemberLookup (EmitContext ec, Type queried_type,
                                                       string name, Location loc)
                {
                        return MemberLookup (ec, ec.ContainerType, null, queried_type, name,
                                             AllMemberTypes, AllBindingFlags, loc);
                }

                public static Expression MemberLookup (EmitContext ec, Type qualifier_type,
                                                       Type queried_type, string name, Location loc)
                {
                        return MemberLookup (ec, ec.ContainerType, qualifier_type, queried_type,
                                             name, AllMemberTypes, AllBindingFlags, loc);
                }

                public static Expression MethodLookup (EmitContext ec, Type queried_type,
                                                       string name, Location loc)
                {
                        return MemberLookup (ec, ec.ContainerType, null, queried_type, name,
                                             MemberTypes.Method, AllBindingFlags, loc);
                }

                /// <summary>
                ///   This is a wrapper for MemberLookup that is not used to "probe", but
                ///   to find a final definition.  If the final definition is not found, we
                ///   look for private members and display a useful debugging message if we
                ///   find it.
                /// </summary>
                public static Expression MemberLookupFinal (EmitContext ec, Type qualifier_type,
                                                            Type queried_type, string name,
                                                            Location loc)
                {
                        return MemberLookupFinal (ec, qualifier_type, queried_type, name,
                                                  AllMemberTypes, AllBindingFlags, loc);
                }

                public static Expression MemberLookupFinal (EmitContext ec, Type qualifier_type,
                                                            Type queried_type, string name,
                                                            MemberTypes mt, BindingFlags bf,
                                                            Location loc)
                {
                        Expression e;

                        int errors = Report.Errors;

                        e = MemberLookup (ec, ec.ContainerType, qualifier_type, queried_type,
                                          name, mt, bf, loc);

                        if (e != null)
                                return e;

                        // Error has already been reported.
                        if (errors < Report.Errors)
                                return null;

                        MemberLookupFailed (ec, qualifier_type, queried_type, name,
                                            null, loc);
                        return null;
                }

                public static void MemberLookupFailed (EmitContext ec, Type qualifier_type,
                                                       Type queried_type, string name,
                                                       string class_name, Location loc)
                {
                        MemberInfo[] mi = TypeManager.MemberLookup (queried_type, null, queried_type,
                                                                    AllMemberTypes, AllBindingFlags |
                                                                    BindingFlags.NonPublic, name);

                        if (mi == null) {
                                if (class_name != null)
                                        Report.Error (103, loc, "The name `" + name + "' could not be " +
                                                      "found in `" + class_name + "'");
                                else
                                        Report.Error (
                                                117, loc, "`" + queried_type + "' does not contain a " +
                                                "definition for `" + name + "'");
                                return;
                        }

                        if (TypeManager.MemberLookup (queried_type, null, queried_type,
                                                      AllMemberTypes, AllBindingFlags |
                                                      BindingFlags.NonPublic, name) == null) {
                                if ((mi.Length == 1) && (mi [0] is Type)) {
                                        Type t = (Type) mi [0];

                                        Report.Error (305, loc,
                                                      "Using the generic type `{0}' " +
                                                      "requires {1} type arguments",
                                                      TypeManager.GetFullName (t),
                                                      TypeManager.GetNumberOfTypeArguments (t));
                                        return;
                                }
                        }

                        if ((qualifier_type != null) && (qualifier_type != ec.ContainerType) &&
                            ec.ContainerType.IsSubclassOf (qualifier_type)) {
                                // Although a derived class can access protected members of
                                // its base class it cannot do so through an instance of the
                                // base class (CS1540).  If the qualifier_type is a parent of the
                                // ec.ContainerType and the lookup succeeds with the latter one,
                                // then we are in this situation.

                                mi = TypeManager.MemberLookup (
                                        ec.ContainerType, ec.ContainerType, ec.ContainerType,
                                        AllMemberTypes, AllBindingFlags, name);

                                if (mi != null) {
                                        Report.Error (
                                                1540, loc, "Cannot access protected member `" +
                                                TypeManager.CSharpName (qualifier_type) + "." +
                                                name + "' " + "via a qualifier of type `" +
                                                TypeManager.CSharpName (qualifier_type) + "'; the " +
                                                "qualifier must be of type `" +
                                                TypeManager.CSharpName (ec.ContainerType) + "' " +
                                                "(or derived from it)");
                                        return;
                                }
                        }

                        if (qualifier_type != null)
                                Report.Error_T (122, loc, TypeManager.CSharpName (qualifier_type) + "." + name);
                        else if (name == ".ctor") {
                                Report.Error (143, loc, String.Format ("The type {0} has no constructors defined",
                                                                       TypeManager.CSharpName (queried_type)));
                        } else {
                                Report.Error_T (122, loc, name);
                }
                }

                static public MemberInfo GetFieldFromEvent (EventExpr event_expr)
                {
                        EventInfo ei = event_expr.EventInfo;

                        return TypeManager.GetPrivateFieldOfEvent (ei);
                }
                
                /// <summary>
                ///   Returns an expression that can be used to invoke operator true
                ///   on the expression if it exists.
                /// </summary>
                static public StaticCallExpr GetOperatorTrue (EmitContext ec, Expression e, Location loc)
                {
                        return GetOperatorTrueOrFalse (ec, e, true, loc);
                }

                /// <summary>
                ///   Returns an expression that can be used to invoke operator false
                ///   on the expression if it exists.
                /// </summary>
                static public StaticCallExpr GetOperatorFalse (EmitContext ec, Expression e, Location loc)
                {
                        return GetOperatorTrueOrFalse (ec, e, false, loc);
                }

                static StaticCallExpr GetOperatorTrueOrFalse (EmitContext ec, Expression e, bool is_true, Location loc)
                {
                        MethodBase method;
                        Expression operator_group;

                        operator_group = MethodLookup (ec, e.Type, is_true ? "op_True" : "op_False", loc);
                        if (operator_group == null)
                                return null;

                        ArrayList arguments = new ArrayList ();
                        arguments.Add (new Argument (e, Argument.AType.Expression));
                        method = Invocation.OverloadResolve (
                                ec, (MethodGroupExpr) operator_group, arguments, false, loc);

                        if (method == null)
                                return null;

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

                /// <summary>
                ///   Resolves the expression `e' into a boolean expression: either through
                ///   an implicit conversion, or through an `operator true' invocation
                /// </summary>
                public static Expression ResolveBoolean (EmitContext ec, Expression e, Location loc)
                {
                        e = e.Resolve (ec);
                        if (e == null)
                                return null;

                        Expression converted = e;
                        if (e.Type != TypeManager.bool_type)
                                converted = Convert.ImplicitConversion (ec, e, TypeManager.bool_type, new Location (-1));

                        //
                        // If no implicit conversion to bool exists, try using `operator true'
                        //
                        if (converted == null){
                                Expression operator_true = Expression.GetOperatorTrue (ec, e, loc);
                                if (operator_true == null){
                                        Report.Error (
                                                31, loc, "Can not convert the expression to a boolean");
                                        return null;
                                }
                                e = operator_true;
                        } else
                                e = converted;

                        return e;
                }
                
                static string ExprClassName (ExprClass c)
                {
                        switch (c){
                        case ExprClass.Invalid:
                                return "Invalid";
                        case ExprClass.Value:
                                return "value";
                        case ExprClass.Variable:
                                return "variable";
                        case ExprClass.Namespace:
                                return "namespace";
                        case ExprClass.Type:
                                return "type";
                        case ExprClass.MethodGroup:
                                return "method group";
                        case ExprClass.PropertyAccess:
                                return "property access";
                        case ExprClass.EventAccess:
                                return "event access";
                        case ExprClass.IndexerAccess:
                                return "indexer access";
                        case ExprClass.Nothing:
                                return "null";
                        }
                        throw new Exception ("Should not happen");
                }
                
                /// <summary>
                ///   Reports that we were expecting `expr' to be of class `expected'
                /// </summary>
                public void Error_UnexpectedKind (string expected)
                {
                        string kind = "Unknown";
                        
                        kind = ExprClassName (eclass);

                        Error (118, "Expression denotes a `" + kind +
                               "' where a `" + expected + "' was expected");
                }

                public void Error_UnexpectedKind (ResolveFlags flags)
                {
                        ArrayList valid = new ArrayList (10);

                        if ((flags & ResolveFlags.VariableOrValue) != 0) {
                                valid.Add ("variable");
                                valid.Add ("value");
                        }

                        if ((flags & ResolveFlags.Type) != 0)
                                valid.Add ("type");

                        if ((flags & ResolveFlags.MethodGroup) != 0)
                                valid.Add ("method group");

                        if ((flags & ResolveFlags.SimpleName) != 0)
                                valid.Add ("simple name");

                        if (valid.Count == 0)
                                valid.Add ("unknown");

                        StringBuilder sb = new StringBuilder ();
                        for (int i = 0; i < valid.Count; i++) {
                                if (i > 0)
                                        sb.Append (", ");
                                else if (i == valid.Count)
                                        sb.Append (" or ");
                                sb.Append (valid [i]);
                        }

                        string kind = ExprClassName (eclass);

                        Error (119, "Expression denotes a `" + kind + "' where " +
                               "a `" + sb.ToString () + "' was expected");
                }
                
                static public void Error_ConstantValueCannotBeConverted (Location l, string val, Type t)
                {
                        Report.Error (31, l, "Constant value `" + val + "' cannot be converted to " +
                                      TypeManager.CSharpName (t));
                }

                public static void UnsafeError (Location loc)
                {
                        Report.Error (214, loc, "Pointers may only be used in an unsafe context");
                }
                
                /// <summary>
                ///   Converts the IntConstant, UIntConstant, LongConstant or
                ///   ULongConstant into the integral target_type.   Notice
                ///   that we do not return an `Expression' we do return
                ///   a boxed integral type.
                ///
                ///   FIXME: Since I added the new constants, we need to
                ///   also support conversions from CharConstant, ByteConstant,
                ///   SByteConstant, UShortConstant, ShortConstant
                ///
                ///   This is used by the switch statement, so the domain
                ///   of work is restricted to the literals above, and the
                ///   targets are int32, uint32, char, byte, sbyte, ushort,
                ///   short, uint64 and int64
                /// </summary>
                public static object ConvertIntLiteral (Constant c, Type target_type, Location loc)
                {
                        if (!Convert.ImplicitStandardConversionExists (c, target_type)){
                                Convert.Error_CannotImplicitConversion (loc, c.Type, target_type);
                                return null;
                        }
                        
                        string s = "";

                        if (c.Type == target_type)
                                return ((Constant) c).GetValue ();

                        //
                        // Make into one of the literals we handle, we dont really care
                        // about this value as we will just return a few limited types
                        // 
                        if (c is EnumConstant)
                                c = ((EnumConstant)c).WidenToCompilerConstant ();

                        if (c is IntConstant){
                                int v = ((IntConstant) c).Value;
                                
                                if (target_type == TypeManager.uint32_type){
                                        if (v >= 0)
                                                return (uint) v;
                                } else if (target_type == TypeManager.char_type){
                                        if (v >= Char.MinValue && v <= Char.MaxValue)
                                                return (char) v;
                                } else if (target_type == TypeManager.byte_type){
                                        if (v >= Byte.MinValue && v <= Byte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.sbyte_type){
                                        if (v >= SByte.MinValue && v <= SByte.MaxValue)
                                                return (sbyte) v;
                                } else if (target_type == TypeManager.short_type){
                                        if (v >= Int16.MinValue && v <= UInt16.MaxValue)
                                                return (short) v;
                                } else if (target_type == TypeManager.ushort_type){
                                        if (v >= UInt16.MinValue && v <= UInt16.MaxValue)
                                                return (ushort) v;
                                } else if (target_type == TypeManager.int64_type)
                                        return (long) v;
                                else if (target_type == TypeManager.uint64_type){
                                        if (v > 0)
                                                return (ulong) v;
                                }

                                s = v.ToString ();
                        } else if (c is UIntConstant){
                                uint v = ((UIntConstant) c).Value;

                                if (target_type == TypeManager.int32_type){
                                        if (v <= Int32.MaxValue)
                                                return (int) v;
                                } else if (target_type == TypeManager.char_type){
                                        if (v >= Char.MinValue && v <= Char.MaxValue)
                                                return (char) v;
                                } else if (target_type == TypeManager.byte_type){
                                        if (v <= Byte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.sbyte_type){
                                        if (v <= SByte.MaxValue)
                                                return (sbyte) v;
                                } else if (target_type == TypeManager.short_type){
                                        if (v <= UInt16.MaxValue)
                                                return (short) v;
                                } else if (target_type == TypeManager.ushort_type){
                                        if (v <= UInt16.MaxValue)
                                                return (ushort) v;
                                } else if (target_type == TypeManager.int64_type)
                                        return (long) v;
                                else if (target_type == TypeManager.uint64_type)
                                        return (ulong) v;
                                s = v.ToString ();
                        } else if (c is LongConstant){ 
                                long v = ((LongConstant) c).Value;

                                if (target_type == TypeManager.int32_type){
                                        if (v >= UInt32.MinValue && v <= UInt32.MaxValue)
                                                return (int) v;
                                } else if (target_type == TypeManager.uint32_type){
                                        if (v >= 0 && v <= UInt32.MaxValue)
                                                return (uint) v;
                                } else if (target_type == TypeManager.char_type){
                                        if (v >= Char.MinValue && v <= Char.MaxValue)
                                                return (char) v;
                                } else if (target_type == TypeManager.byte_type){
                                        if (v >= Byte.MinValue && v <= Byte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.sbyte_type){
                                        if (v >= SByte.MinValue && v <= SByte.MaxValue)
                                                return (sbyte) v;
                                } else if (target_type == TypeManager.short_type){
                                        if (v >= Int16.MinValue && v <= UInt16.MaxValue)
                                                return (short) v;
                                } else if (target_type == TypeManager.ushort_type){
                                        if (v >= UInt16.MinValue && v <= UInt16.MaxValue)
                                                return (ushort) v;
                                } else if (target_type == TypeManager.uint64_type){
                                        if (v > 0)
                                                return (ulong) v;
                                }
                                s = v.ToString ();
                        } else if (c is ULongConstant){
                                ulong v = ((ULongConstant) c).Value;

                                if (target_type == TypeManager.int32_type){
                                        if (v <= Int32.MaxValue)
                                                return (int) v;
                                } else if (target_type == TypeManager.uint32_type){
                                        if (v <= UInt32.MaxValue)
                                                return (uint) v;
                                } else if (target_type == TypeManager.char_type){
                                        if (v >= Char.MinValue && v <= Char.MaxValue)
                                                return (char) v;
                                } else if (target_type == TypeManager.byte_type){
                                        if (v >= Byte.MinValue && v <= Byte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.sbyte_type){
                                        if (v <= (int) SByte.MaxValue)
                                                return (sbyte) v;
                                } else if (target_type == TypeManager.short_type){
                                        if (v <= UInt16.MaxValue)
                                                return (short) v;
                                } else if (target_type == TypeManager.ushort_type){
                                        if (v <= UInt16.MaxValue)
                                                return (ushort) v;
                                } else if (target_type == TypeManager.int64_type){
                                        if (v <= Int64.MaxValue)
                                                return (long) v;
                                }
                                s = v.ToString ();
                        } else if (c is ByteConstant){
                                byte v = ((ByteConstant) c).Value;
                                
                                if (target_type == TypeManager.int32_type)
                                        return (int) v;
                                else if (target_type == TypeManager.uint32_type)
                                        return (uint) v;
                                else if (target_type == TypeManager.char_type)
                                        return (char) v;
                                else if (target_type == TypeManager.sbyte_type){
                                        if (v <= SByte.MaxValue)
                                                return (sbyte) v;
                                } else if (target_type == TypeManager.short_type)
                                        return (short) v;
                                else if (target_type == TypeManager.ushort_type)
                                        return (ushort) v;
                                else if (target_type == TypeManager.int64_type)
                                        return (long) v;
                                else if (target_type == TypeManager.uint64_type)
                                        return (ulong) v;
                                s = v.ToString ();
                        } else if (c is SByteConstant){
                                sbyte v = ((SByteConstant) c).Value;
                                
                                if (target_type == TypeManager.int32_type)
                                        return (int) v;
                                else if (target_type == TypeManager.uint32_type){
                                        if (v >= 0)
                                                return (uint) v;
                                } else if (target_type == TypeManager.char_type){
                                        if (v >= 0)
                                                return (char) v;
                                } else if (target_type == TypeManager.byte_type){
                                        if (v >= 0)
                                                return (byte) v;
                                } else if (target_type == TypeManager.short_type)
                                        return (short) v;
                                else if (target_type == TypeManager.ushort_type){
                                        if (v >= 0)
                                                return (ushort) v;
                                } else if (target_type == TypeManager.int64_type)
                                        return (long) v;
                                else if (target_type == TypeManager.uint64_type){
                                        if (v >= 0)
                                                return (ulong) v;
                                }
                                s = v.ToString ();
                        } else if (c is ShortConstant){
                                short v = ((ShortConstant) c).Value;
                                
                                if (target_type == TypeManager.int32_type){
                                        return (int) v;
                                } else if (target_type == TypeManager.uint32_type){
                                        if (v >= 0)
                                                return (uint) v;
                                } else if (target_type == TypeManager.char_type){
                                        if (v >= 0)
                                                return (char) v;
                                } else if (target_type == TypeManager.byte_type){
                                        if (v >= Byte.MinValue && v <= Byte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.sbyte_type){
                                        if (v >= SByte.MinValue && v <= SByte.MaxValue)
                                                return (sbyte) v;
                                } else if (target_type == TypeManager.ushort_type){
                                        if (v >= 0)
                                                return (ushort) v;
                                } else if (target_type == TypeManager.int64_type)
                                        return (long) v;
                                else if (target_type == TypeManager.uint64_type)
                                        return (ulong) v;

                                s = v.ToString ();
                        } else if (c is UShortConstant){
                                ushort v = ((UShortConstant) c).Value;
                                
                                if (target_type == TypeManager.int32_type)
                                        return (int) v;
                                else if (target_type == TypeManager.uint32_type)
                                        return (uint) v;
                                else if (target_type == TypeManager.char_type){
                                        if (v >= Char.MinValue && v <= Char.MaxValue)
                                                return (char) v;
                                } else if (target_type == TypeManager.byte_type){
                                        if (v >= Byte.MinValue && v <= Byte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.sbyte_type){
                                        if (v <= SByte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.short_type){
                                        if (v <= Int16.MaxValue)
                                                return (short) v;
                                } else if (target_type == TypeManager.int64_type)
                                        return (long) v;
                                else if (target_type == TypeManager.uint64_type)
                                        return (ulong) v;

                                s = v.ToString ();
                        } else if (c is CharConstant){
                                char v = ((CharConstant) c).Value;
                                
                                if (target_type == TypeManager.int32_type)
                                        return (int) v;
                                else if (target_type == TypeManager.uint32_type)
                                        return (uint) v;
                                else if (target_type == TypeManager.byte_type){
                                        if (v >= Byte.MinValue && v <= Byte.MaxValue)
                                                return (byte) v;
                                } else if (target_type == TypeManager.sbyte_type){
                                        if (v <= SByte.MaxValue)
                                                return (sbyte) v;
                                } else if (target_type == TypeManager.short_type){
                                        if (v <= Int16.MaxValue)
                                                return (short) v;
                                } else if (target_type == TypeManager.ushort_type)
                                        return (short) v;
                                else if (target_type == TypeManager.int64_type)
                                        return (long) v;
                                else if (target_type == TypeManager.uint64_type)
                                        return (ulong) v;

                                s = v.ToString ();
                        }
                        Error_ConstantValueCannotBeConverted (loc, s, target_type);
                        return null;
                }

                //
                // Load the object from the pointer.  
                //
                public static void LoadFromPtr (ILGenerator ig, Type t)
                {
                        if (t == TypeManager.int32_type)
                                ig.Emit (OpCodes.Ldind_I4);
                        else if (t == TypeManager.uint32_type)
                                ig.Emit (OpCodes.Ldind_U4);
                        else if (t == TypeManager.short_type)
                                ig.Emit (OpCodes.Ldind_I2);
                        else if (t == TypeManager.ushort_type)
                                ig.Emit (OpCodes.Ldind_U2);
                        else if (t == TypeManager.char_type)
                                ig.Emit (OpCodes.Ldind_U2);
                        else if (t == TypeManager.byte_type)
                                ig.Emit (OpCodes.Ldind_U1);
                        else if (t == TypeManager.sbyte_type)
                                ig.Emit (OpCodes.Ldind_I1);
                        else if (t == TypeManager.uint64_type)
                                ig.Emit (OpCodes.Ldind_I8);
                        else if (t == TypeManager.int64_type)
                                ig.Emit (OpCodes.Ldind_I8);
                        else if (t == TypeManager.float_type)
                                ig.Emit (OpCodes.Ldind_R4);
                        else if (t == TypeManager.double_type)
                                ig.Emit (OpCodes.Ldind_R8);
                        else if (t == TypeManager.bool_type)
                                ig.Emit (OpCodes.Ldind_I1);
                        else if (t == TypeManager.intptr_type)
                                ig.Emit (OpCodes.Ldind_I);
                        else if (TypeManager.IsEnumType (t)) {
                                if (t == TypeManager.enum_type)
                                        ig.Emit (OpCodes.Ldind_Ref);
                                else
                                        LoadFromPtr (ig, TypeManager.EnumToUnderlying (t));
                        } else if (t.IsValueType)
                                ig.Emit (OpCodes.Ldobj, t);
                        else if (t.IsPointer)
                                ig.Emit (OpCodes.Ldind_I);
                        else 
                                ig.Emit (OpCodes.Ldind_Ref);
                }

                //
                // The stack contains the pointer and the value of type `type'
                //
                public static void StoreFromPtr (ILGenerator ig, Type type)
                {
                        if (TypeManager.IsEnumType (type))
                                type = TypeManager.EnumToUnderlying (type);
                        if (type == TypeManager.int32_type || type == TypeManager.uint32_type)
                                ig.Emit (OpCodes.Stind_I4);
                        else if (type == TypeManager.int64_type || type == TypeManager.uint64_type)
                                ig.Emit (OpCodes.Stind_I8);
                        else if (type == TypeManager.char_type || type == TypeManager.short_type ||
                                 type == TypeManager.ushort_type)
                                ig.Emit (OpCodes.Stind_I2);
                        else if (type == TypeManager.float_type)
                                ig.Emit (OpCodes.Stind_R4);
                        else if (type == TypeManager.double_type)
                                ig.Emit (OpCodes.Stind_R8);
                        else if (type == TypeManager.byte_type || type == TypeManager.sbyte_type ||
                                 type == TypeManager.bool_type)
                                ig.Emit (OpCodes.Stind_I1);
                        else if (type == TypeManager.intptr_type)
                                ig.Emit (OpCodes.Stind_I);
                        else if (type.IsValueType)
                                ig.Emit (OpCodes.Stobj, type);
                        else
                                ig.Emit (OpCodes.Stind_Ref);
                }
                
                //
                // Returns the size of type `t' if known, otherwise, 0
                //
                public static int GetTypeSize (Type t)
                {
                        t = TypeManager.TypeToCoreType (t);
                        if (t == TypeManager.int32_type ||
                            t == TypeManager.uint32_type ||
                            t == TypeManager.float_type)
                                return 4;
                        else if (t == TypeManager.int64_type ||
                                 t == TypeManager.uint64_type ||
                                 t == TypeManager.double_type)
                                return 8;
                        else if (t == TypeManager.byte_type ||
                                 t == TypeManager.sbyte_type ||
                                 t == TypeManager.bool_type)    
                                return 1;
                        else if (t == TypeManager.short_type ||
                                 t == TypeManager.char_type ||
                                 t == TypeManager.ushort_type)
                                return 2;
                        else if (t == TypeManager.decimal_type)
                                return 16;
                        else
                                return 0;
                }

                //
                // Default implementation of IAssignMethod.CacheTemporaries
                //
                public virtual void CacheTemporaries (EmitContext ec)
                {
                }

                static void Error_NegativeArrayIndex (Location loc)
                {
                        Report.Error (284, loc, "Can not create array with a negative size");
                }
                
                //
                // Converts `source' to an int, uint, long or ulong.
                //
                public Expression ExpressionToArrayArgument (EmitContext ec, Expression source, Location loc)
                {
                        Expression target;
                        
                        bool old_checked = ec.CheckState;
                        ec.CheckState = true;
                        
                        target = Convert.ImplicitConversion (ec, source, TypeManager.int32_type, loc);
                        if (target == null){
                                target = Convert.ImplicitConversion (ec, source, TypeManager.uint32_type, loc);
                                if (target == null){
                                        target = Convert.ImplicitConversion (ec, source, TypeManager.int64_type, loc);
                                        if (target == null){
                                                target = Convert.ImplicitConversion (ec, source, TypeManager.uint64_type, loc);
                                                if (target == null)
                                                        Convert.Error_CannotImplicitConversion (loc, source.Type, TypeManager.int32_type);
                                        }
                                }
                        } 
                        ec.CheckState = old_checked;

                        //
                        // Only positive constants are allowed at compile time
                        //
                        if (target is Constant){
                                if (target is IntConstant){
                                        if (((IntConstant) target).Value < 0){
                                                Error_NegativeArrayIndex (loc);
                                                return null;
                                        }
                                }

                                if (target is LongConstant){
                                        if (((LongConstant) target).Value < 0){
                                                Error_NegativeArrayIndex (loc);
                                                return null;
                                        }
                                }
                                
                        }

                        return target;
                }
                
        }

        /// <summary>
        ///   This is just a base class for expressions that can
        ///   appear on statements (invocations, object creation,
        ///   assignments, post/pre increment and decrement).  The idea
        ///   being that they would support an extra Emition interface that
        ///   does not leave a result on the stack.
        /// </summary>
        public abstract class ExpressionStatement : Expression {

                public virtual ExpressionStatement ResolveStatement (EmitContext ec)
                {
                        Expression e = Resolve (ec);
                        if (e == null)
                                return null;

                        ExpressionStatement es = e as ExpressionStatement;
                        if (es == null)
                                Error (201, "Only assignment, call, increment, decrement and new object " +
                                       "expressions can be used as a statement");

                        return es;
                }

                /// <summary>
                ///   Requests the expression to be emitted in a `statement'
                ///   context.  This means that no new value is left on the
                ///   stack after invoking this method (constrasted with
                ///   Emit that will always leave a value on the stack).
                /// </summary>
                public abstract void EmitStatement (EmitContext ec);
        }

        /// <summary>
        ///   This kind of cast is used to encapsulate the child
        ///   whose type is child.Type into an expression that is
        ///   reported to return "return_type".  This is used to encapsulate
        ///   expressions which have compatible types, but need to be dealt
        ///   at higher levels with.
        ///
        ///   For example, a "byte" expression could be encapsulated in one
        ///   of these as an "unsigned int".  The type for the expression
        ///   would be "unsigned int".
        ///
        /// </summary>
        public class EmptyCast : Expression {
                protected Expression child;
                
                public Expression Child {
                        get {
                                return child;
                        }
                }               

                public EmptyCast (Expression child, Type return_type)
                {
                        eclass = child.eclass;
                        type = return_type;
                        this.child = child;
                }

                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)
                {
                        child.Emit (ec);
                }
        }

        //
        // We need to special case this since an empty cast of
        // a NullLiteral is still a Constant
        //
        public class NullCast : Constant {
                protected Expression child;
                                
                public NullCast (Expression child, Type return_type)
                {
                        eclass = child.eclass;
                        type = return_type;
                        this.child = child;
                }

                override public string AsString ()
                {
                        return "null";
                }

                public override object GetValue ()
                {
                        return null;
                }

                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)
                {
                        child.Emit (ec);
                }
        }


        /// <summary>
        ///  This class is used to wrap literals which belong inside Enums
        /// </summary>
        public class EnumConstant : Constant {
                public Constant Child;

                public EnumConstant (Constant child, Type enum_type)
                {
                        eclass = child.eclass;
                        this.Child = child;
                        type = enum_type;
                }
                
                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)
                {
                        Child.Emit (ec);
                }

                public override object GetValue ()
                {
                        return Child.GetValue ();
                }

                //
                // Converts from one of the valid underlying types for an enumeration
                // (int32, uint32, int64, uint64, short, ushort, byte, sbyte) to
                // one of the internal compiler literals: Int/UInt/Long/ULong Literals.
                //
                public Constant WidenToCompilerConstant ()
                {
                        Type t = TypeManager.EnumToUnderlying (Child.Type);
                        object v = ((Constant) Child).GetValue ();;
                        
                        if (t == TypeManager.int32_type)
                                return new IntConstant ((int) v);
                        if (t == TypeManager.uint32_type)
                                return new UIntConstant ((uint) v);
                        if (t == TypeManager.int64_type)
                                return new LongConstant ((long) v);
                        if (t == TypeManager.uint64_type)
                                return new ULongConstant ((ulong) v);
                        if (t == TypeManager.short_type)
                                return new ShortConstant ((short) v);
                        if (t == TypeManager.ushort_type)
                                return new UShortConstant ((ushort) v);
                        if (t == TypeManager.byte_type)
                                return new ByteConstant ((byte) v);
                        if (t == TypeManager.sbyte_type)
                                return new SByteConstant ((sbyte) v);

                        throw new Exception ("Invalid enumeration underlying type: " + t);
                }

                //
                // Extracts the value in the enumeration on its native representation
                //
                public object GetPlainValue ()
                {
                        Type t = TypeManager.EnumToUnderlying (Child.Type);
                        object v = ((Constant) Child).GetValue ();;
                        
                        if (t == TypeManager.int32_type)
                                return (int) v;
                        if (t == TypeManager.uint32_type)
                                return (uint) v;
                        if (t == TypeManager.int64_type)
                                return (long) v;
                        if (t == TypeManager.uint64_type)
                                return (ulong) v;
                        if (t == TypeManager.short_type)
                                return (short) v;
                        if (t == TypeManager.ushort_type)
                                return (ushort) v;
                        if (t == TypeManager.byte_type)
                                return (byte) v;
                        if (t == TypeManager.sbyte_type)
                                return (sbyte) v;

                        return null;
                }
                
                public override string AsString ()
                {
                        return Child.AsString ();
                }

                public override DoubleConstant ConvertToDouble ()
                {
                        return Child.ConvertToDouble ();
                }

                public override FloatConstant ConvertToFloat ()
                {
                        return Child.ConvertToFloat ();
                }

                public override ULongConstant ConvertToULong ()
                {
                        return Child.ConvertToULong ();
                }

                public override LongConstant ConvertToLong ()
                {
                        return Child.ConvertToLong ();
                }

                public override UIntConstant ConvertToUInt ()
                {
                        return Child.ConvertToUInt ();
                }

                public override IntConstant ConvertToInt ()
                {
                        return Child.ConvertToInt ();
                }
                
                public override bool IsZeroInteger {
                        get { return Child.IsZeroInteger; }
                }
        }

        /// <summary>
        ///   This kind of cast is used to encapsulate Value Types in objects.
        ///
        ///   The effect of it is to box the value type emitted by the previous
        ///   operation.
        /// </summary>
        public class BoxedCast : EmptyCast {

                public BoxedCast (Expression expr)
                        : base (expr, TypeManager.object_type) 
                {
                        eclass = ExprClass.Value;
                }

                public BoxedCast (Expression expr, Type target_type)
                        : base (expr, target_type)
                {
                        eclass = ExprClass.Value;
                }
                
                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)
                {
                        base.Emit (ec);
                        
                        ec.ig.Emit (OpCodes.Box, child.Type);
                }
        }

        public class UnboxCast : EmptyCast {
                public UnboxCast (Expression expr, Type return_type)
                        : base (expr, return_type)
                {
                }

                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)
                {
                        Type t = type;
                        ILGenerator ig = ec.ig;
                        
                        base.Emit (ec);
                        if (t.IsGenericParameter)
                                ig.Emit (OpCodes.Unbox_Any, t);
                        else {
                                ig.Emit (OpCodes.Unbox, t);

                                LoadFromPtr (ig, t);
                        }
                }
        }
        
        /// <summary>
        ///   This is used to perform explicit numeric conversions.
        ///
        ///   Explicit numeric conversions might trigger exceptions in a checked
        ///   context, so they should generate the conv.ovf opcodes instead of
        ///   conv opcodes.
        /// </summary>
        public class ConvCast : EmptyCast {
                public enum Mode : byte {
                        I1_U1, I1_U2, I1_U4, I1_U8, I1_CH,
                        U1_I1, U1_CH,
                        I2_I1, I2_U1, I2_U2, I2_U4, I2_U8, I2_CH,
                        U2_I1, U2_U1, U2_I2, U2_CH,
                        I4_I1, I4_U1, I4_I2, I4_U2, I4_U4, I4_U8, I4_CH,
                        U4_I1, U4_U1, U4_I2, U4_U2, U4_I4, U4_CH,
                        I8_I1, I8_U1, I8_I2, I8_U2, I8_I4, I8_U4, I8_U8, I8_CH,
                        U8_I1, U8_U1, U8_I2, U8_U2, U8_I4, U8_U4, U8_I8, U8_CH,
                        CH_I1, CH_U1, CH_I2,
                        R4_I1, R4_U1, R4_I2, R4_U2, R4_I4, R4_U4, R4_I8, R4_U8, R4_CH,
                        R8_I1, R8_U1, R8_I2, R8_U2, R8_I4, R8_U4, R8_I8, R8_U8, R8_CH, R8_R4
                }

                Mode mode;
                bool checked_state;
                
                public ConvCast (EmitContext ec, Expression child, Type return_type, Mode m)
                        : base (child, return_type)
                {
                        checked_state = ec.CheckState;
                        mode = m;
                }

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

                        return this;
                }

                public override string ToString ()
                {
                        return String.Format ("ConvCast ({0}, {1})", mode, child);
                }
                
                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        base.Emit (ec);

                        if (checked_state){
                                switch (mode){
                                case Mode.I1_U1: ig.Emit (OpCodes.Conv_Ovf_U1); break;
                                case Mode.I1_U2: ig.Emit (OpCodes.Conv_Ovf_U2); break;
                                case Mode.I1_U4: ig.Emit (OpCodes.Conv_Ovf_U4); break;
                                case Mode.I1_U8: ig.Emit (OpCodes.Conv_Ovf_U8); break;
                                case Mode.I1_CH: ig.Emit (OpCodes.Conv_Ovf_U2); break;

                                case Mode.U1_I1: ig.Emit (OpCodes.Conv_Ovf_I1_Un); break;
                                case Mode.U1_CH: /* nothing */ break;

                                case Mode.I2_I1: ig.Emit (OpCodes.Conv_Ovf_I1); break;
                                case Mode.I2_U1: ig.Emit (OpCodes.Conv_Ovf_U1); break;
                                case Mode.I2_U2: ig.Emit (OpCodes.Conv_Ovf_U2); break;
                                case Mode.I2_U4: ig.Emit (OpCodes.Conv_Ovf_U4); break;
                                case Mode.I2_U8: ig.Emit (OpCodes.Conv_Ovf_U8); break;
                                case Mode.I2_CH: ig.Emit (OpCodes.Conv_Ovf_U2); break;

                                case Mode.U2_I1: ig.Emit (OpCodes.Conv_Ovf_I1_Un); break;
                                case Mode.U2_U1: ig.Emit (OpCodes.Conv_Ovf_U1_Un); break;
                                case Mode.U2_I2: ig.Emit (OpCodes.Conv_Ovf_I2_Un); break;
                                case Mode.U2_CH: /* nothing */ break;

                                case Mode.I4_I1: ig.Emit (OpCodes.Conv_Ovf_I1); break;
                                case Mode.I4_U1: ig.Emit (OpCodes.Conv_Ovf_U1); break;
                                case Mode.I4_I2: ig.Emit (OpCodes.Conv_Ovf_I2); break;
                                case Mode.I4_U4: ig.Emit (OpCodes.Conv_Ovf_U4); break;
                                case Mode.I4_U2: ig.Emit (OpCodes.Conv_Ovf_U2); break;
                                case Mode.I4_U8: ig.Emit (OpCodes.Conv_Ovf_U8); break;
                                case Mode.I4_CH: ig.Emit (OpCodes.Conv_Ovf_U2); break;

                                case Mode.U4_I1: ig.Emit (OpCodes.Conv_Ovf_I1_Un); break;
                                case Mode.U4_U1: ig.Emit (OpCodes.Conv_Ovf_U1_Un); break;
                                case Mode.U4_I2: ig.Emit (OpCodes.Conv_Ovf_I2_Un); break;
                                case Mode.U4_U2: ig.Emit (OpCodes.Conv_Ovf_U2_Un); break;
                                case Mode.U4_I4: ig.Emit (OpCodes.Conv_Ovf_I4_Un); break;
                                case Mode.U4_CH: ig.Emit (OpCodes.Conv_Ovf_U2_Un); break;

                                case Mode.I8_I1: ig.Emit (OpCodes.Conv_Ovf_I1); break;
                                case Mode.I8_U1: ig.Emit (OpCodes.Conv_Ovf_U1); break;
                                case Mode.I8_I2: ig.Emit (OpCodes.Conv_Ovf_I2); break;
                                case Mode.I8_U2: ig.Emit (OpCodes.Conv_Ovf_U2); break;
                                case Mode.I8_I4: ig.Emit (OpCodes.Conv_Ovf_I4); break;
                                case Mode.I8_U4: ig.Emit (OpCodes.Conv_Ovf_U4); break;
                                case Mode.I8_U8: ig.Emit (OpCodes.Conv_Ovf_U8); break;
                                case Mode.I8_CH: ig.Emit (OpCodes.Conv_Ovf_U2); break;

                                case Mode.U8_I1: ig.Emit (OpCodes.Conv_Ovf_I1_Un); break;
                                case Mode.U8_U1: ig.Emit (OpCodes.Conv_Ovf_U1_Un); break;
                                case Mode.U8_I2: ig.Emit (OpCodes.Conv_Ovf_I2_Un); break;
                                case Mode.U8_U2: ig.Emit (OpCodes.Conv_Ovf_U2_Un); break;
                                case Mode.U8_I4: ig.Emit (OpCodes.Conv_Ovf_I4_Un); break;
                                case Mode.U8_U4: ig.Emit (OpCodes.Conv_Ovf_U4_Un); break;
                                case Mode.U8_I8: ig.Emit (OpCodes.Conv_Ovf_I8_Un); break;
                                case Mode.U8_CH: ig.Emit (OpCodes.Conv_Ovf_U2_Un); break;

                                case Mode.CH_I1: ig.Emit (OpCodes.Conv_Ovf_I1_Un); break;
                                case Mode.CH_U1: ig.Emit (OpCodes.Conv_Ovf_U1_Un); break;
                                case Mode.CH_I2: ig.Emit (OpCodes.Conv_Ovf_I2_Un); break;

                                case Mode.R4_I1: ig.Emit (OpCodes.Conv_Ovf_I1); break;
                                case Mode.R4_U1: ig.Emit (OpCodes.Conv_Ovf_U1); break;
                                case Mode.R4_I2: ig.Emit (OpCodes.Conv_Ovf_I2); break;
                                case Mode.R4_U2: ig.Emit (OpCodes.Conv_Ovf_U2); break;
                                case Mode.R4_I4: ig.Emit (OpCodes.Conv_Ovf_I4); break;
                                case Mode.R4_U4: ig.Emit (OpCodes.Conv_Ovf_U4); break;
                                case Mode.R4_I8: ig.Emit (OpCodes.Conv_Ovf_I8); break;
                                case Mode.R4_U8: ig.Emit (OpCodes.Conv_Ovf_U8); break;
                                case Mode.R4_CH: ig.Emit (OpCodes.Conv_Ovf_U2); break;

                                case Mode.R8_I1: ig.Emit (OpCodes.Conv_Ovf_I1); break;
                                case Mode.R8_U1: ig.Emit (OpCodes.Conv_Ovf_U1); break;
                                case Mode.R8_I2: ig.Emit (OpCodes.Conv_Ovf_I2); break;
                                case Mode.R8_U2: ig.Emit (OpCodes.Conv_Ovf_U2); break;
                                case Mode.R8_I4: ig.Emit (OpCodes.Conv_Ovf_I4); break;
                                case Mode.R8_U4: ig.Emit (OpCodes.Conv_Ovf_U4); break;
                                case Mode.R8_I8: ig.Emit (OpCodes.Conv_Ovf_I8); break;
                                case Mode.R8_U8: ig.Emit (OpCodes.Conv_Ovf_U8); break;
                                case Mode.R8_CH: ig.Emit (OpCodes.Conv_Ovf_U2); break;
                                case Mode.R8_R4: ig.Emit (OpCodes.Conv_R4); break;
                                }
                        } else {
                                switch (mode){
                                case Mode.I1_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.I1_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.I1_U4: ig.Emit (OpCodes.Conv_U4); break;
                                case Mode.I1_U8: ig.Emit (OpCodes.Conv_I8); break;
                                case Mode.I1_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.U1_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.U1_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.I2_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.I2_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.I2_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.I2_U4: ig.Emit (OpCodes.Conv_U4); break;
                                case Mode.I2_U8: ig.Emit (OpCodes.Conv_I8); break;
                                case Mode.I2_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.U2_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.U2_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.U2_I2: ig.Emit (OpCodes.Conv_I2); break;
                                case Mode.U2_CH: /* nothing */ break;

                                case Mode.I4_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.I4_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.I4_I2: ig.Emit (OpCodes.Conv_I2); break;
                                case Mode.I4_U4: /* nothing */ break;
                                case Mode.I4_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.I4_U8: ig.Emit (OpCodes.Conv_I8); break;
                                case Mode.I4_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.U4_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.U4_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.U4_I2: ig.Emit (OpCodes.Conv_I2); break;
                                case Mode.U4_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.U4_I4: /* nothing */ break;
                                case Mode.U4_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.I8_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.I8_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.I8_I2: ig.Emit (OpCodes.Conv_I2); break;
                                case Mode.I8_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.I8_I4: ig.Emit (OpCodes.Conv_I4); break;
                                case Mode.I8_U4: ig.Emit (OpCodes.Conv_U4); break;
                                case Mode.I8_U8: /* nothing */ break;
                                case Mode.I8_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.U8_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.U8_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.U8_I2: ig.Emit (OpCodes.Conv_I2); break;
                                case Mode.U8_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.U8_I4: ig.Emit (OpCodes.Conv_I4); break;
                                case Mode.U8_U4: ig.Emit (OpCodes.Conv_U4); break;
                                case Mode.U8_I8: /* nothing */ break;
                                case Mode.U8_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.CH_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.CH_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.CH_I2: ig.Emit (OpCodes.Conv_I2); break;

                                case Mode.R4_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.R4_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.R4_I2: ig.Emit (OpCodes.Conv_I2); break;
                                case Mode.R4_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.R4_I4: ig.Emit (OpCodes.Conv_I4); break;
                                case Mode.R4_U4: ig.Emit (OpCodes.Conv_U4); break;
                                case Mode.R4_I8: ig.Emit (OpCodes.Conv_I8); break;
                                case Mode.R4_U8: ig.Emit (OpCodes.Conv_U8); break;
                                case Mode.R4_CH: ig.Emit (OpCodes.Conv_U2); break;

                                case Mode.R8_I1: ig.Emit (OpCodes.Conv_I1); break;
                                case Mode.R8_U1: ig.Emit (OpCodes.Conv_U1); break;
                                case Mode.R8_I2: ig.Emit (OpCodes.Conv_I2); break;
                                case Mode.R8_U2: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.R8_I4: ig.Emit (OpCodes.Conv_I4); break;
                                case Mode.R8_U4: ig.Emit (OpCodes.Conv_U4); break;
                                case Mode.R8_I8: ig.Emit (OpCodes.Conv_I8); break;
                                case Mode.R8_U8: ig.Emit (OpCodes.Conv_U8); break;
                                case Mode.R8_CH: ig.Emit (OpCodes.Conv_U2); break;
                                case Mode.R8_R4: ig.Emit (OpCodes.Conv_R4); break;
                                }
                        }
                }
        }
        
        public class OpcodeCast : EmptyCast {
                OpCode op, op2;
                bool second_valid;
                
                public OpcodeCast (Expression child, Type return_type, OpCode op)
                        : base (child, return_type)
                        
                {
                        this.op = op;
                        second_valid = false;
                }

                public OpcodeCast (Expression child, Type return_type, OpCode op, OpCode op2)
                        : base (child, return_type)
                        
                {
                        this.op = op;
                        this.op2 = op2;
                        second_valid = true;
                }

                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)
                {
                        base.Emit (ec);
                        ec.ig.Emit (op);

                        if (second_valid)
                                ec.ig.Emit (op2);
                }                       
        }

        /// <summary>
        ///   This kind of cast is used to encapsulate a child and cast it
        ///   to the class requested
        /// </summary>
        public class ClassCast : EmptyCast {
                public ClassCast (Expression child, Type return_type)
                        : base (child, return_type)
                        
                {
                }

                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)
                {
                        base.Emit (ec);

                        if (child.Type.IsGenericParameter)
                                ec.ig.Emit (OpCodes.Box, child.Type);

                        if (type.IsGenericParameter)
                                ec.ig.Emit (OpCodes.Unbox_Any, type);
                        else
                                ec.ig.Emit (OpCodes.Castclass, type);
                }
        }
        
        /// <summary>
        ///   SimpleName expressions are initially formed of a single
        ///   word and it only happens at the beginning of the expression.
        /// </summary>
        ///
        /// <remarks>
        ///   The expression will try to be bound to a Field, a Method
        ///   group or a Property.  If those fail we pass the name to our
        ///   caller and the SimpleName is compounded to perform a type
        ///   lookup.  The idea behind this process is that we want to avoid
        ///   creating a namespace map from the assemblies, as that requires
        ///   the GetExportedTypes function to be called and a hashtable to
        ///   be constructed which reduces startup time.  If later we find
        ///   that this is slower, we should create a `NamespaceExpr' expression
        ///   that fully participates in the resolution process. 
        ///   
        ///   For example `System.Console.WriteLine' is decomposed into
        ///   MemberAccess (MemberAccess (SimpleName ("System"), "Console"), "WriteLine")
        ///   
        ///   The first SimpleName wont produce a match on its own, so it will
        ///   be turned into:
        ///   MemberAccess (SimpleName ("System.Console"), "WriteLine").
        ///   
        ///   System.Console will produce a TypeExpr match.
        ///   
        ///   The downside of this is that we might be hitting `LookupType' too many
        ///   times with this scheme.
        /// </remarks>
        public class SimpleName : Expression {
                public string Name;

                //
                // If true, then we are a simple name, not composed with a ".
                //
                bool is_base;

                public SimpleName (string a, string b, Location l)
                {
                        Name = String.Concat (a, ".", b);
                        loc = l;
                        is_base = false;
                }
                
                public SimpleName (string name, Location l)
                {
                        Name = name;
                        loc = l;
                        is_base = true;
                }

                public static void Error_ObjectRefRequired (EmitContext ec, Location l, string name)
                {
                        if (ec.IsFieldInitializer)
                                Report.Error (
                                        236, l,
                                        "A field initializer cannot reference the non-static field, " +
                                        "method or property `"+name+"'");
                        else
                                Report.Error (
                                        120, l,
                                        "An object reference is required " +
                                        "for the non-static field `"+name+"'");
                }
                
                //
                // Checks whether we are trying to access an instance
                // property, method or field from a static body.
                //
                Expression MemberStaticCheck (EmitContext ec, Expression e)
                {
                        if (e is IMemberExpr){
                                IMemberExpr member = (IMemberExpr) e;
                                
                                if (!member.IsStatic){
                                        Error_ObjectRefRequired (ec, loc, Name);
                                        return null;
                                }
                        }

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

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

                public Expression DoResolveAllowStatic (EmitContext ec)
                {
                        return SimpleNameResolve (ec, null, true);
                }

                public override Expression ResolveAsTypeStep (EmitContext ec)
                {
                        DeclSpace ds = ec.DeclSpace;
                        NamespaceEntry ns = ds.NamespaceEntry;
                        TypeExpr t;
                        IAlias alias_value;

                        //
                        // Since we are cheating: we only do the Alias lookup for
                        // namespaces if the name does not include any dots in it
                        //
                        if (ns != null && is_base)
                                alias_value = ns.LookupAlias (Name);
                        else
                                alias_value = null;

                        TypeParameterExpr generic_type = ds.LookupGeneric (Name, loc);
                        if (generic_type != null)
                                return generic_type.ResolveAsTypeTerminal (ec);

                        if (ec.ResolvingTypeTree){
                                int errors = Report.Errors;
                                Type dt = ds.FindType (loc, Name);
                                
                                if (Report.Errors != errors)
                                        return null;
                                
                                if (dt != null)
                                        return new TypeExpression (dt, loc);

                                if (alias_value != null){
                                        if (alias_value.IsType)
                                                return alias_value.Type;
                                        if ((t = RootContext.LookupType (ds, alias_value.Name, true, loc)) != null)
                                                return t;
                                }
                        }

                        //
                        // First, the using aliases
                        //
                        if (alias_value != null){
                                if (alias_value.IsType)
                                        return alias_value.Type;
                                if ((t = RootContext.LookupType (ds, alias_value.Name, true, loc)) != null)
                                        return t;
                                
                                // we have alias value, but it isn't Type, so try if it's namespace
                                return new SimpleName (alias_value.Name, loc);
                        }

                        //
                        // Stage 2: Lookup up if we are an alias to a type
                        // or a namespace.
                        //

                        if ((t = RootContext.LookupType (ds, Name, true, loc)) != null)
                                return t;
                                
                        // No match, maybe our parent can compose us
                        // into something meaningful.
                        return this;
                }

                Expression SimpleNameResolve (EmitContext ec, Expression right_side,
                                              bool allow_static)
                {
                        Expression e = DoSimpleNameResolve (ec, right_side, allow_static);
                        if (e == null)
                                return null;

                        Block current_block = ec.CurrentBlock;
                        if (current_block != null){
                                LocalInfo vi = current_block.GetLocalInfo (Name);
                                if (is_base &&
                                    current_block.IsVariableNameUsedInChildBlock(Name)) {
                                        Report.Error (135, Location,
                                                      "'{0}' has a different meaning in a " +
                                                      "child block", Name);
                                        return null;
                                }
                        }

                        return e;
                }

                /// <remarks>
                ///   7.5.2: Simple Names. 
                ///
                ///   Local Variables and Parameters are handled at
                ///   parse time, so they never occur as SimpleNames.
                ///
                ///   The `allow_static' flag is used by MemberAccess only
                ///   and it is used to inform us that it is ok for us to 
                ///   avoid the static check, because MemberAccess might end
                ///   up resolving the Name as a Type name and the access as
                ///   a static type access.
                ///
                ///   ie: Type Type; .... { Type.GetType (""); }
                ///
                ///   Type is both an instance variable and a Type;  Type.GetType
                ///   is the static method not an instance method of type.
                /// </remarks>
                Expression DoSimpleNameResolve (EmitContext ec, Expression right_side, bool allow_static)
                {
                        Expression e = null;

                        //
                        // Stage 1: Performed by the parser (binding to locals or parameters).
                        //
                        Block current_block = ec.CurrentBlock;
                        if (current_block != null){
                                LocalInfo vi = current_block.GetLocalInfo (Name);
                                if (vi != null){
                                        Expression var;
                                        
                                        var = new LocalVariableReference (ec.CurrentBlock, Name, loc);
                                        
                                        if (right_side != null)
                                                return var.ResolveLValue (ec, right_side);
                                        else
                                                return var.Resolve (ec);
                                }

                                int idx = -1;
                                Parameter par = null;
                                Parameters pars = current_block.Parameters;
                                if (pars != null)
                                        par = pars.GetParameterByName (Name, out idx);

                                if (par != null) {
                                        ParameterReference param;
                                        
                                        param = new ParameterReference (pars, current_block, idx, Name, loc);

                                        if (right_side != null)
                                                return param.ResolveLValue (ec, right_side);
                                        else
                                                return param.Resolve (ec);
                                }
                        }
                        
                        //
                        // Stage 2: Lookup members 
                        //

                        DeclSpace lookup_ds = ec.DeclSpace;
                        do {
                                if (lookup_ds.TypeBuilder == null)
                                        break;

                                e = MemberLookup (ec, lookup_ds.TypeBuilder, Name, loc);
                                if (e != null)
                                        break;

                                lookup_ds =lookup_ds.Parent;
                        } while (lookup_ds != null);

                        if (e == null && ec.ContainerType != null)
                                e = MemberLookup (ec, ec.ContainerType, Name, loc);

                        if (e == null) {
                                //
                                // Since we are cheating (is_base is our hint
                                // that we are the beginning of the name): we
                                // only do the Alias lookup for namespaces if
                                // the name does not include any dots in it
                                //
                                NamespaceEntry ns = ec.DeclSpace.NamespaceEntry;
                                if (is_base && ns != null){
                                        IAlias alias_value = ns.LookupAlias (Name);
                                        if (alias_value != null){
                                                if (alias_value.IsType)
                                                        return alias_value.Type;

                                                Name = alias_value.Name;
                                                Type t;

                                                if ((t = TypeManager.LookupType (Name)) != null)
                                                        return new TypeExpression (t, loc);
                                        
                                                // No match, maybe our parent can compose us
                                                // into something meaningful.
                                                return this;
                                        }
                                }

                                return ResolveAsTypeStep (ec);
                        }

                        if (e is TypeExpr)
                                return e;

                        if (e is IMemberExpr) {
                                e = MemberAccess.ResolveMemberAccess (ec, e, null, loc, this);
                                if (e == null)
                                        return null;

                                IMemberExpr me = e as IMemberExpr;
                                if (me == null)
                                        return e;

                                // This fails if ResolveMemberAccess() was unable to decide whether
                                // it's a field or a type of the same name.
                                if (!me.IsStatic && (me.InstanceExpression == null))
                                        return e;

                                if (!me.IsStatic &&
                                    TypeManager.IsNestedChildOf (me.InstanceExpression.Type, me.DeclaringType) &&
                                    !me.InstanceExpression.Type.IsSubclassOf (me.DeclaringType)) {
                                        Error (38, "Cannot access nonstatic member `" + me.Name + "' of " +
                                               "outer type `" + me.DeclaringType + "' via nested type `" +
                                               me.InstanceExpression.Type + "'");
                                        return null;
                                }

                                if (right_side != null)
                                        e = e.DoResolveLValue (ec, right_side);
                                else
                                        e = e.DoResolve (ec);

                                return e;                               
                        }

                        if (ec.IsStatic || ec.IsFieldInitializer){
                                if (allow_static)
                                        return e;

                                return MemberStaticCheck (ec, e);
                        } else
                                return e;
                }
                
                public override void Emit (EmitContext ec)
                {
                        //
                        // If this is ever reached, then we failed to
                        // find the name as a namespace
                        //

                        Error (103, "The name `" + Name +
                               "' does not exist in the class `" +
                               ec.DeclSpace.Name + "'");
                }

                public override string ToString ()
                {
                        return Name;
                }
        }
        
        /// <summary>
        ///   Fully resolved expression that evaluates to a type
        /// </summary>
        public abstract class TypeExpr : Expression, IAlias {
                override public Expression ResolveAsTypeStep (EmitContext ec)
                {
                        TypeExpr t = DoResolveAsTypeStep (ec);
                        if (t == null)
                                return null;

                        eclass = ExprClass.Type;
                        return t;
                }

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

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

                public virtual bool CheckAccessLevel (DeclSpace ds)
                {
                        return ds.CheckAccessLevel (Type);
                }

                public virtual bool AsAccessible (DeclSpace ds, int flags)
                {
                        return ds.AsAccessible (Type, flags);
                }

                public virtual bool IsClass {
                        get { return Type.IsClass; }
                }

                public virtual bool IsValueType {
                        get { return Type.IsValueType; }
                }

                public virtual bool IsInterface {
                        get { return Type.IsInterface; }
                }

                public virtual bool IsSealed {
                        get { return Type.IsSealed; }
                }

                public virtual bool CanInheritFrom ()
                {
                        if (Type == TypeManager.enum_type ||
                            (Type == TypeManager.value_type && RootContext.StdLib) ||
                            Type == TypeManager.multicast_delegate_type ||
                            Type == TypeManager.delegate_type ||
                            Type == TypeManager.array_type)
                                return false;

                        return true;
                }

                public virtual bool IsAttribute {
                        get {
                                return Type == TypeManager.attribute_type ||
                                        Type.IsSubclassOf (TypeManager.attribute_type);
                        }
                }

                public virtual TypeExpr[] GetInterfaces ()
                {
                        return TypeManager.GetInterfaces (Type);
                }

                public abstract TypeExpr DoResolveAsTypeStep (EmitContext ec);

                public virtual Type ResolveType (EmitContext ec)
                {
                        TypeExpr t = ResolveAsTypeTerminal (ec);
                        if (t == null)
                                return null;

                        return t.Type;
                }

                public abstract string Name {
                        get;
                }

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

                        return Type == tobj.Type;
                }

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

                bool IAlias.IsType {
                        get { return true; }
                }

                TypeExpr IAlias.Type {
                        get {
                                return this;
                        }
                }
        }

        public class TypeExpression : TypeExpr, IAlias {
                public TypeExpression (Type t, Location l)
                {
                        Type = t;
                        eclass = ExprClass.Type;
                        loc = l;
                }

                public override TypeExpr DoResolveAsTypeStep (EmitContext ec)
                {
                        return this;
                }

                public override string Name {
                        get {
                                return Type.ToString ();
                        }
                }

                string IAlias.Name {
                        get {
                                return Type.FullName != null ? Type.FullName : Type.Name;
                        }
                }
        }

        /// <summary>
        ///   Used to create types from a fully qualified name.  These are just used
        ///   by the parser to setup the core types.  A TypeLookupExpression is always
        ///   classified as a type.
        /// </summary>
        public class TypeLookupExpression : TypeExpr {
                string name;
                
                public TypeLookupExpression (string name)
                {
                        this.name = name;
                }

                public override TypeExpr DoResolveAsTypeStep (EmitContext ec)
                {
                        if (type == null) {
                                TypeExpr texpr = RootContext.LookupType (
                                        ec.DeclSpace, name, false, Location.Null);
                                if (texpr == null)
                                        return null;

                                type = texpr.ResolveType (ec);
                                if (type == null)
                                        return null;
                        }

                        return this;
                }

                public override string Name {
                        get {
                                return name;
                        }
                }
        }

        public class TypeAliasExpression : TypeExpr, IAlias {
                TypeExpr texpr;
                TypeArguments args;
                string name;

                public TypeAliasExpression (TypeExpr texpr, TypeArguments args, Location l)
                {
                        this.texpr = texpr;
                        this.args = args;
                        loc = texpr.Location;

                        eclass = ExprClass.Type;
                        if (args != null)
                                name = texpr.Name + "<" + args.ToString () + ">";
                        else
                                name = texpr.Name;
                }

                public override string Name {
                        get { return name; }
                }

                public override TypeExpr DoResolveAsTypeStep (EmitContext ec)
                {
                        Type type = texpr.ResolveType (ec);
                        if (type == null)
                                return null;

                        int num_args = TypeManager.GetNumberOfTypeArguments (type);

                        if (args != null) {
                                if (num_args == 0) {
                                        Report.Error (308, loc,
                                                      "The non-generic type `{0}' cannot " +
                                                      "be used with type arguments.",
                                                      TypeManager.CSharpName (type));
                                        return null;
                                }

                                ConstructedType ctype = new ConstructedType (type, args, loc);
                                return ctype.ResolveAsTypeTerminal (ec);
                        } else if (num_args > 0) {
                                Report.Error (305, loc,
                                              "Using the generic type `{0}' " +
                                              "requires {1} type arguments",
                                              TypeManager.GetFullName (type), num_args);
                                return null;
                        }

                        return new TypeExpression (type, loc);
                }

                public override Type ResolveType (EmitContext ec)
                {
                        TypeExpr t = ResolveAsTypeTerminal (ec);
                        if (t == null)
                                return null;

                        type = t.ResolveType (ec);
                        return type;
                }

                public override bool CheckAccessLevel (DeclSpace ds)
                {
                        return texpr.CheckAccessLevel (ds);
                }

                public override bool AsAccessible (DeclSpace ds, int flags)
                {
                        return texpr.AsAccessible (ds, flags);
                }

                public override bool IsClass {
                        get { return texpr.IsClass; }
                }

                public override bool IsValueType {
                        get { return texpr.IsValueType; }
                }

                public override bool IsInterface {
                        get { return texpr.IsInterface; }
                }

                public override bool IsSealed {
                        get { return texpr.IsSealed; }
                }

                public override bool IsAttribute {
                        get { return texpr.IsAttribute; }
                }
        }

        /// <summary>
        ///   MethodGroup Expression.
        ///  
        ///   This is a fully resolved expression that evaluates to a type
        /// </summary>
        public class MethodGroupExpr : Expression, IMemberExpr {
                public MethodBase [] Methods;
                Expression instance_expression = null;
                bool is_explicit_impl = false;
                bool has_type_arguments = false;
                bool identical_type_name = false;
                
                public MethodGroupExpr (MemberInfo [] mi, Location l)
                {
                        Methods = new MethodBase [mi.Length];
                        mi.CopyTo (Methods, 0);
                        eclass = ExprClass.MethodGroup;
                        type = TypeManager.object_type;
                        loc = l;
                }

                public MethodGroupExpr (ArrayList list, Location l)
                {
                        Methods = new MethodBase [list.Count];

                        try {
                                list.CopyTo (Methods, 0);
                        } catch {
                                foreach (MemberInfo m in list){
                                        if (!(m is MethodBase)){
                                                Console.WriteLine ("Name " + m.Name);
                                                Console.WriteLine ("Found a: " + m.GetType ().FullName);
                                        }
                                }
                                throw;
                        }

                        loc = l;
                        eclass = ExprClass.MethodGroup;
                        type = TypeManager.object_type;
                }

                public Type DeclaringType {
                        get {
                                //
                                // We assume that the top-level type is in the end
                                //
                                return Methods [Methods.Length - 1].DeclaringType;
                                //return Methods [0].DeclaringType;
                        }
                }
                
                //
                // `A method group may have associated an instance expression' 
                // 
                public Expression InstanceExpression {
                        get {
                                return instance_expression;
                        }

                        set {
                                instance_expression = value;
                        }
                }

                public bool IsExplicitImpl {
                        get {
                                return is_explicit_impl;
                        }

                        set {
                                is_explicit_impl = value;
                        }
                }

                public bool HasTypeArguments {
                        get {
                                return has_type_arguments;
                        }

                        set {
                                has_type_arguments = value;
                        }
                }

                public bool IdenticalTypeName {
                        get {
                                return identical_type_name;
                        }

                        set {
                                identical_type_name = value;
                        }
                }

                public string Name {
                        get {
                                return TypeManager.CSharpSignature (
                                        Methods [Methods.Length - 1]);
                        }
                }

                public bool IsInstance {
                        get {
                                foreach (MethodBase mb in Methods)
                                        if (!mb.IsStatic)
                                                return true;

                                return false;
                        }
                }

                public bool IsStatic {
                        get {
                                foreach (MethodBase mb in Methods)
                                        if (mb.IsStatic)
                                                return true;

                                return false;
                        }
                }
                
                override public Expression DoResolve (EmitContext ec)
                {
                        if (!IsInstance)
                                instance_expression = null;

                        if (instance_expression != null) {
                                instance_expression = instance_expression.DoResolve (ec);
                                if (instance_expression == null)
                                        return null;
                        }

                        return this;
                }

                public void ReportUsageError ()
                {
                        Report.Error (654, loc, "Method `" + DeclaringType + "." +
                                      Name + "()' is referenced without parentheses");
                }

                override public void Emit (EmitContext ec)
                {
                        ReportUsageError ();
                }

                bool RemoveMethods (bool keep_static)
                {
                        ArrayList smethods = new ArrayList ();

                        foreach (MethodBase mb in Methods){
                                if (mb.IsStatic == keep_static)
                                        smethods.Add (mb);
                        }

                        if (smethods.Count == 0)
                                return false;

                        Methods = new MethodBase [smethods.Count];
                        smethods.CopyTo (Methods, 0);

                        return true;
                }
                
                /// <summary>
                ///   Removes any instance methods from the MethodGroup, returns
                ///   false if the resulting set is empty.
                /// </summary>
                public bool RemoveInstanceMethods ()
                {
                        return RemoveMethods (true);
                }

                /// <summary>
                ///   Removes any static methods from the MethodGroup, returns
                ///   false if the resulting set is empty.
                /// </summary>
                public bool RemoveStaticMethods ()
                {
                        return RemoveMethods (false);
                }
        }

        /// <summary>
        ///   Fully resolved expression that evaluates to a Field
        /// </summary>
        public class FieldExpr : Expression, IAssignMethod, IMemoryLocation, IMemberExpr, IVariable {
                public readonly FieldInfo FieldInfo;
                Expression instance_expr;
                VariableInfo variable_info;
                
                LocalTemporary temporary;
                IMemoryLocation instance_ml;
                bool have_temporary;
                
                public FieldExpr (FieldInfo fi, Location l)
                {
                        FieldInfo = fi;
                        eclass = ExprClass.Variable;
                        type = TypeManager.TypeToCoreType (fi.FieldType);
                        loc = l;
                }

                public string Name {
                        get {
                                return FieldInfo.Name;
                        }
                }

                public bool IsInstance {
                        get {
                                return !FieldInfo.IsStatic;
                        }
                }

                public bool IsStatic {
                        get {
                                return FieldInfo.IsStatic;
                        }
                }

                public Type DeclaringType {
                        get {
                                return FieldInfo.DeclaringType;
                        }
                }

                public Expression InstanceExpression {
                        get {
                                return instance_expr;
                        }

                        set {
                                instance_expr = value;
                        }
                }

                public VariableInfo VariableInfo {
                        get {
                                return variable_info;
                        }
                }

                override public Expression DoResolve (EmitContext ec)
                {
                        if (!FieldInfo.IsStatic){
                                if (instance_expr == null){
                                        //
                                        // This can happen when referencing an instance field using
                                        // a fully qualified type expression: TypeName.InstanceField = xxx
                                        // 
                                        SimpleName.Error_ObjectRefRequired (ec, loc, FieldInfo.Name);
                                        return null;
                                }

                                // Resolve the field's instance expression while flow analysis is turned
                                // off: when accessing a field "a.b", we must check whether the field
                                // "a.b" is initialized, not whether the whole struct "a" is initialized.
                                instance_expr = instance_expr.Resolve (ec, ResolveFlags.VariableOrValue |
                                                                       ResolveFlags.DisableFlowAnalysis);
                                if (instance_expr == null)
                                        return null;
                        }

                        // If the instance expression is a local variable or parameter.
                        IVariable var = instance_expr as IVariable;
                        if ((var == null) || (var.VariableInfo == null))
                                return this;

                        VariableInfo vi = var.VariableInfo;
                        if (!vi.IsFieldAssigned (ec, FieldInfo.Name, loc))
                                return null;

                        variable_info = vi.GetSubStruct (FieldInfo.Name);
                        return this;
                }

                void Report_AssignToReadonly (bool is_instance)
                {
                        string msg;
                        
                        if (is_instance)
                                msg = "Readonly field can not be assigned outside " +
                                "of constructor or variable initializer";
                        else
                                msg = "A static readonly field can only be assigned in " +
                                "a static constructor";

                        Report.Error (is_instance ? 191 : 198, loc, msg);
                }
                
                override public Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        IVariable var = instance_expr as IVariable;
                        if ((var != null) && (var.VariableInfo != null))
                                var.VariableInfo.SetFieldAssigned (ec, FieldInfo.Name);

                        Expression e = DoResolve (ec);

                        if (e == null)
                                return null;

                        if (!FieldInfo.IsStatic && (instance_expr.Type.IsValueType && !(instance_expr is IMemoryLocation))) {
                                // FIXME: Provide better error reporting.
                                Error (1612, "Cannot modify expression because it is not a variable.");
                                return null;
                        }

                        if (!FieldInfo.IsInitOnly)
                                return this;

                        FieldBase fb = TypeManager.GetField (FieldInfo);
                        if (fb != null)
                                fb.SetAssigned ();

                        //
                        // InitOnly fields can only be assigned in constructors
                        //

                        if (ec.IsConstructor){
                                if (IsStatic && !ec.IsStatic)
                                        Report_AssignToReadonly (false);

                                Type ctype;
                                if (ec.TypeContainer.CurrentType != null)
                                        ctype = ec.TypeContainer.CurrentType.ResolveType (ec);
                                else
                                        ctype = ec.ContainerType;

                                if (TypeManager.IsEqual (ctype, FieldInfo.DeclaringType))
                                        return this;
                        }

                        Report_AssignToReadonly (true);
                        
                        return null;
                }

                public bool VerifyFixed (bool is_expression)
                {
                        IVariable variable = instance_expr as IVariable;
                        if ((variable == null) || !variable.VerifyFixed (true))
                                return false;

                        return true;
                }

                public override void CacheTemporaries (EmitContext ec)
                {
                        if (!FieldInfo.IsStatic && (temporary == null))
                                temporary = new LocalTemporary (ec, instance_expr.Type);
                }

                void EmitInstance (EmitContext ec)
                {
                        if (instance_expr.Type.IsValueType)
                                CacheTemporaries (ec);

                        if ((temporary == null) || have_temporary)
                                return;

                        if (instance_expr.Type.IsValueType) {
                                instance_ml = instance_expr as IMemoryLocation;
                                if (instance_ml == null) {
                                        instance_expr.Emit (ec);
                                        temporary.Store (ec);
                                        instance_ml = temporary;
                                }
                        } else {
                                instance_expr.Emit (ec);
                                temporary.Store (ec);
                        }

                        have_temporary = true;
                }

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

                        if (FieldInfo is FieldBuilder){
                                FieldBase f = TypeManager.GetField (FieldInfo);
                                if (f != null){
                                        if ((f.ModFlags & Modifiers.VOLATILE) != 0)
                                                is_volatile = true;
                                        
                                        f.status |= Field.Status.USED;
                                }
                        } 
                        
                        if (FieldInfo.IsStatic){
                                if (is_volatile)
                                        ig.Emit (OpCodes.Volatile);
                                
                                ig.Emit (OpCodes.Ldsfld, FieldInfo);
                                return;
                        }
                        
                        EmitInstance (ec);
                        if (instance_ml != null)
                                instance_ml.AddressOf (ec, AddressOp.Load);
                        else if (temporary != null)
                                temporary.Emit (ec);
                        else
                                instance_expr.Emit (ec);

                        if (is_volatile)
                                ig.Emit (OpCodes.Volatile);
                        
                        ig.Emit (OpCodes.Ldfld, FieldInfo);
                }

                public void EmitAssign (EmitContext ec, Expression source)
                {
                        FieldAttributes fa = FieldInfo.Attributes;
                        bool is_static = (fa & FieldAttributes.Static) != 0;
                        bool is_readonly = (fa & FieldAttributes.InitOnly) != 0;
                        ILGenerator ig = ec.ig;

                        if (is_readonly && !ec.IsConstructor){
                                Report_AssignToReadonly (!is_static);
                                return;
                        }

                        if (!is_static){
                                EmitInstance (ec);
                                if (instance_ml != null)
                                        instance_ml.AddressOf (ec, AddressOp.Store);
                                else if (temporary != null)
                                        temporary.Emit (ec);
                                else
                                        instance_expr.Emit (ec);
                        }

                        source.Emit (ec);

                        if (FieldInfo is FieldBuilder){
                                FieldBase f = TypeManager.GetField (FieldInfo);
                                if (f != null){
                                        if ((f.ModFlags & Modifiers.VOLATILE) != 0)
                                                ig.Emit (OpCodes.Volatile);
                                        
                                        f.status |= Field.Status.ASSIGNED;
                                }
                        } 

                        if (is_static)
                                ig.Emit (OpCodes.Stsfld, FieldInfo);
                        else 
                                ig.Emit (OpCodes.Stfld, FieldInfo);
                }
                
                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        ILGenerator ig = ec.ig;
                        
                        if (FieldInfo is FieldBuilder){
                                FieldBase f = TypeManager.GetField (FieldInfo);
                                if (f != null){
                                        if ((f.ModFlags & Modifiers.VOLATILE) != 0){
                                                Error (676, "volatile variable: can not take its address, or pass as ref/out parameter");
                                                return;
                                        }
                                        
                                        if ((mode & AddressOp.Store) != 0)
                                                f.status |= Field.Status.ASSIGNED;
                                        if ((mode & AddressOp.Load) != 0)
                                                f.status |= Field.Status.USED;
                                }
                        } 

                        //
                        // Handle initonly fields specially: make a copy and then
                        // get the address of the copy.
                        //
                        bool need_copy;
                        if (FieldInfo.IsInitOnly){
                                need_copy = true;
                                if (ec.IsConstructor){
                                        if (FieldInfo.IsStatic){
                                                if (ec.IsStatic)
                                                        need_copy = false;
                                        } else
                                                need_copy = false;
                                }
                        } else
                                need_copy = false;
                        
                        if (need_copy){
                                LocalBuilder local;
                                Emit (ec);
                                local = ig.DeclareLocal (type);
                                ig.Emit (OpCodes.Stloc, local);
                                ig.Emit (OpCodes.Ldloca, local);
                                return;
                        }


                        if (FieldInfo.IsStatic){
                                ig.Emit (OpCodes.Ldsflda, FieldInfo);
                        } else {
                                //
                                // In the case of `This', we call the AddressOf method, which will
                                // only load the pointer, and not perform an Ldobj immediately after
                                // the value has been loaded into the stack.
                                //
                                EmitInstance (ec);
                                if (instance_ml != null)
                                        instance_ml.AddressOf (ec, AddressOp.LoadStore);
                                else if (temporary != null)
                                        temporary.Emit (ec);
                                else if (instance_expr is This)
                                        ((This)instance_expr).AddressOf (ec, AddressOp.LoadStore);
                                else
                                        instance_expr.Emit (ec);
                                ig.Emit (OpCodes.Ldflda, FieldInfo);
                        }
                }
        }

        //
        // A FieldExpr whose address can not be taken
        //
        public class FieldExprNoAddress : FieldExpr, IMemoryLocation {
                public FieldExprNoAddress (FieldInfo fi, Location loc) : base (fi, loc)
                {
                }
                
                public new void AddressOf (EmitContext ec, AddressOp mode)
                {
                        Report.Error (-215, "Report this: Taking the address of a remapped parameter not supported");
                }
        }
        
        /// <summary>
        ///   Expression that evaluates to a Property.  The Assign class
        ///   might set the `Value' expression if we are in an assignment.
        ///
        ///   This is not an LValue because we need to re-write the expression, we
        ///   can not take data from the stack and store it.  
        /// </summary>
        public class PropertyExpr : ExpressionStatement, IAssignMethod, IMemberExpr {
                public readonly PropertyInfo PropertyInfo;

                //
                // This is set externally by the  `BaseAccess' class
                //
                public bool IsBase;
                MethodInfo getter, setter;
                bool is_static;
                bool must_do_cs1540_check;
                
                Expression instance_expr;
                LocalTemporary temporary;
                bool have_temporary;

                public PropertyExpr (EmitContext ec, PropertyInfo pi, Location l)
                {
                        PropertyInfo = pi;
                        eclass = ExprClass.PropertyAccess;
                        is_static = false;
                        loc = l;

                        type = TypeManager.TypeToCoreType (pi.PropertyType);

                        ResolveAccessors (ec);
                }

                public string Name {
                        get {
                                return PropertyInfo.Name;
                        }
                }

                public bool IsInstance {
                        get {
                                return !is_static;
                        }
                }

                public bool IsStatic {
                        get {
                                return is_static;
                        }
                }
                
                public Type DeclaringType {
                        get {
                                return PropertyInfo.DeclaringType;
                        }
                }

                //
                // The instance expression associated with this expression
                //
                public Expression InstanceExpression {
                        set {
                                instance_expr = value;
                        }

                        get {
                                return instance_expr;
                        }
                }

                public bool VerifyAssignable ()
                {
                        if (setter == null) {
                                Report.Error (200, loc, 
                                              "The property `" + PropertyInfo.Name +
                                              "' can not be assigned to, as it has not set accessor");
                                return false;
                        }

                        return true;
                }

                MethodInfo FindAccessor (Type invocation_type, bool is_set)
                {
                        BindingFlags flags = BindingFlags.Public | BindingFlags.NonPublic |
                                BindingFlags.Static | BindingFlags.Instance |
                                BindingFlags.DeclaredOnly;

                        Type current = PropertyInfo.DeclaringType;
                        for (; current != null; current = current.BaseType) {
                                MemberInfo[] group = TypeManager.MemberLookup (
                                        invocation_type, invocation_type, current,
                                        MemberTypes.Property, flags, PropertyInfo.Name);

                                if (group == null)
                                        continue;

                                if (group.Length != 1)
                                        // Oooops, can this ever happen ?
                                        return null;

                                PropertyInfo pi = (PropertyInfo) group [0];

                                MethodInfo get = pi.GetGetMethod (true);
                                MethodInfo set = pi.GetSetMethod (true);

                                if (is_set) {
                                        if (set != null)
                                                return set;
                                } else {
                                        if (get != null)
                                                return get;
                                }

                                MethodInfo accessor = get != null ? get : set;
                                if (accessor == null)
                                        continue;
                                if ((accessor.Attributes & MethodAttributes.NewSlot) != 0)
                                        break;
                        }

                        return null;
                }

                MethodInfo GetAccessor (Type invocation_type, bool is_set)
                {
                        MethodInfo mi = FindAccessor (invocation_type, is_set);
                        if (mi == null)
                                return null;

                        MethodAttributes ma = mi.Attributes & MethodAttributes.MemberAccessMask;

                        //
                        // If only accessible to the current class or children
                        //
                        if (ma == MethodAttributes.Private) {
                                Type declaring_type = mi.DeclaringType;
                                        
                                if (invocation_type != declaring_type){
                                        if (TypeManager.IsSubclassOrNestedChildOf (invocation_type, mi.DeclaringType))
                                                return mi;
                                        else
                                                return null;
                                } else
                                        return mi;
                        }
                        //
                        // FamAndAssem requires that we not only derivate, but we are on the
                        // same assembly.  
                        //
                        if (ma == MethodAttributes.FamANDAssem){
                                if (mi.DeclaringType.Assembly != invocation_type.Assembly)
                                        return null;
                                else
                                        return mi;
                        }

                        // Assembly and FamORAssem succeed if we're in the same assembly.
                        if ((ma == MethodAttributes.Assembly) || (ma == MethodAttributes.FamORAssem)){
                                if (mi.DeclaringType.Assembly == invocation_type.Assembly)
                                        return mi;
                        }

                        // We already know that we aren't in the same assembly.
                        if (ma == MethodAttributes.Assembly)
                                return null;

                        // Family and FamANDAssem require that we derive.
                        if ((ma == MethodAttributes.Family) || (ma == MethodAttributes.FamANDAssem) || (ma == MethodAttributes.FamORAssem)){
                                if (!TypeManager.IsSubclassOrNestedChildOf (invocation_type, mi.DeclaringType))
                                        return null;
                                else {
                                        if (!TypeManager.IsNestedChildOf (invocation_type, mi.DeclaringType))
                                                must_do_cs1540_check = true;

                                        return mi;
                                }
                        }

                        return mi;
                }

                //
                // We also perform the permission checking here, as the PropertyInfo does not
                // hold the information for the accessibility of its setter/getter
                //
                void ResolveAccessors (EmitContext ec)
                {
                        getter = GetAccessor (ec.ContainerType, false);
                        if ((getter != null) && getter.IsStatic)
                                is_static = true;

                        setter = GetAccessor (ec.ContainerType, true);
                        if ((setter != null) && setter.IsStatic)
                                is_static = true;

                        if (setter == null && getter == null){
                                Report.Error_T (122, loc, PropertyInfo.Name);
                        }
                }

                bool InstanceResolve (EmitContext ec)
                {
                        if ((instance_expr == null) && ec.IsStatic && !is_static) {
                                SimpleName.Error_ObjectRefRequired (ec, loc, PropertyInfo.Name);
                                return false;
                        }

                        if (instance_expr != null) {
                                instance_expr = instance_expr.DoResolve (ec);
                                if (instance_expr == null)
                                        return false;
                        }

                        if (must_do_cs1540_check && (instance_expr != null)) {
                                if ((instance_expr.Type != ec.ContainerType) &&
                                    ec.ContainerType.IsSubclassOf (instance_expr.Type)) {
                                        Report.Error (1540, loc, "Cannot access protected member `" +
                                                      PropertyInfo.DeclaringType + "." + PropertyInfo.Name + 
                                                      "' via a qualifier of type `" +
                                                      TypeManager.CSharpName (instance_expr.Type) +
                                                      "'; the qualifier must be of type `" +
                                                      TypeManager.CSharpName (ec.ContainerType) +
                                                      "' (or derived from it)");
                                        return false;
                                }
                        }

                        return true;
                }
                
                override public Expression DoResolve (EmitContext ec)
                {
                        if (getter != null){
                                if (TypeManager.GetArgumentTypes (getter).Length != 0){
                                        Report.Error (
                                                117, loc, "`{0}' does not contain a " +
                                                "definition for `{1}'.", getter.DeclaringType,
                                                Name);
                                        return null;
                                }
                        }

                        if (getter == null){
                                //
                                // The following condition happens if the PropertyExpr was
                                // created, but is invalid (ie, the property is inaccessible),
                                // and we did not want to embed the knowledge about this in
                                // the caller routine.  This only avoids double error reporting.
                                //
                                if (setter == null)
                                        return null;
                                
                                Report.Error (154, loc, 
                                              "The property `" + PropertyInfo.Name +
                                              "' can not be used in " +
                                              "this context because it lacks a get accessor");
                                return null;
                        } 

                        if (!InstanceResolve (ec))
                                return null;

                        //
                        // Only base will allow this invocation to happen.
                        //
                        if (IsBase && getter.IsAbstract){
                                Report.Error (205, loc, "Cannot call an abstract base property: " +
                                              PropertyInfo.DeclaringType + "." +PropertyInfo.Name);
                                return null;
                        }

                        return this;
                }

                override public Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        if (setter == null){
                                //
                                // The following condition happens if the PropertyExpr was
                                // created, but is invalid (ie, the property is inaccessible),
                                // and we did not want to embed the knowledge about this in
                                // the caller routine.  This only avoids double error reporting.
                                //
                                if (getter == null)
                                        return null;
                                
                                Report.Error (154, loc, 
                                              "The property `" + PropertyInfo.Name +
                                              "' can not be used in " +
                                              "this context because it lacks a set accessor");
                                return null;
                        }

                        if (TypeManager.GetArgumentTypes (setter).Length != 1){
                                Report.Error (
                                        117, loc, "`{0}' does not contain a " +
                                        "definition for `{1}'.", getter.DeclaringType,
                                        Name);
                                return null;
                        }

                        if (!InstanceResolve (ec))
                                return null;
                        
                        //
                        // Only base will allow this invocation to happen.
                        //
                        if (IsBase && setter.IsAbstract){
                                Report.Error (205, loc, "Cannot call an abstract base property: " +
                                              PropertyInfo.DeclaringType + "." +PropertyInfo.Name);
                                return null;
                        }
                        return this;
                }

                public override void CacheTemporaries (EmitContext ec)
                {
                        if (!is_static)
                                temporary = new LocalTemporary (ec, instance_expr.Type);
                }

                Expression EmitInstance (EmitContext ec)
                {
                        if (temporary != null){
                                if (!have_temporary){
                                        instance_expr.Emit (ec);
                                        temporary.Store (ec);
                                        have_temporary = true;
                                }
                                return temporary;
                        } else
                                return instance_expr;
                }

                override public void Emit (EmitContext ec)
                {
                        Expression expr = EmitInstance (ec);

                        //
                        // Special case: length of single dimension array property is turned into ldlen
                        //
                        if ((getter == TypeManager.system_int_array_get_length) ||
                            (getter == TypeManager.int_array_get_length)){
                                Type iet = instance_expr.Type;

                                //
                                // System.Array.Length can be called, but the Type does not
                                // support invoking GetArrayRank, so test for that case first
                                //
                                if (iet != TypeManager.array_type && (iet.GetArrayRank () == 1)){
                                        expr.Emit (ec);
                                        ec.ig.Emit (OpCodes.Ldlen);
                                        ec.ig.Emit (OpCodes.Conv_I4);
                                        return;
                                }
                        }

                        Invocation.EmitCall (ec, IsBase, IsStatic, expr, getter, null, loc);
                        
                }

                //
                // Implements the IAssignMethod interface for assignments
                //
                public void EmitAssign (EmitContext ec, Expression source)
                {
                        Expression expr = EmitInstance (ec);

                        Argument arg = new Argument (source, Argument.AType.Expression);
                        ArrayList args = new ArrayList ();

                        args.Add (arg);
                        Invocation.EmitCall (ec, IsBase, IsStatic, expr, setter, args, loc);
                }

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

        /// <summary>
        ///   Fully resolved expression that evaluates to an Event
        /// </summary>
        public class EventExpr : Expression, IMemberExpr {
                public readonly EventInfo EventInfo;
                Expression instance_expr;

                bool is_static;
                MethodInfo add_accessor, remove_accessor;
                
                public EventExpr (EventInfo ei, Location loc)
                {
                        EventInfo = ei;
                        this.loc = loc;
                        eclass = ExprClass.EventAccess;

                        add_accessor = TypeManager.GetAddMethod (ei);
                        remove_accessor = TypeManager.GetRemoveMethod (ei);
                        
                        if (add_accessor.IsStatic || remove_accessor.IsStatic)
                                is_static = true;

                        if (EventInfo is MyEventBuilder){
                                MyEventBuilder eb = (MyEventBuilder) EventInfo;
                                type = eb.EventType;
                                eb.SetUsed ();
                        } else
                                type = EventInfo.EventHandlerType;
                }

                public string Name {
                        get {
                                return EventInfo.Name;
                        }
                }

                public bool IsInstance {
                        get {
                                return !is_static;
                        }
                }

                public bool IsStatic {
                        get {
                                return is_static;
                        }
                }

                public Type DeclaringType {
                        get {
                                return EventInfo.DeclaringType;
                        }
                }

                public Expression InstanceExpression {
                        get {
                                return instance_expr;
                        }

                        set {
                                instance_expr = value;
                        }
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        if (instance_expr != null) {
                                instance_expr = instance_expr.DoResolve (ec);
                                if (instance_expr == null)
                                        return null;
                        }

                        
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        Report.Error (70, loc, "The event `" + Name + "' can only appear on the left hand side of += or -= (except on the defining type)");
                }

                public void EmitAddOrRemove (EmitContext ec, Expression source)
                {
                        BinaryDelegate source_del = (BinaryDelegate) source;
                        Expression handler = source_del.Right;
                        
                        Argument arg = new Argument (handler, Argument.AType.Expression);
                        ArrayList args = new ArrayList ();
                                
                        args.Add (arg);
                        
                        if (source_del.IsAddition)
                                Invocation.EmitCall (
                                        ec, false, IsStatic, instance_expr, add_accessor, args, loc);
                        else
                                Invocation.EmitCall (
                                        ec, false, IsStatic, instance_expr, remove_accessor, args, loc);
                }
        }
}