2008-10-06 Zoltan Varga <vargaz@gmail.com>

[mcs.git] / mcs / ecore.cs

//
// ecore.cs: Core of the Expression representation for the intermediate tree.
//
// Author:
//   Miguel de Icaza (miguel@ximian.com)
//   Marek Safar (marek.safar@seznam.cz)
//
// Copyright 2001, 2002, 2003 Ximian, Inc.
// Copyright 2003-2008 Novell, 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,
                TypeParameter,
                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                    = 1 << 1,

                // Returns a method group.
                MethodGroup             = 1 << 2,

                TypeParameter   = 1 << 3,

                // Mask of all the expression class flags.
                MaskExprClass = VariableOrValue | Type | MethodGroup | TypeParameter,

                // Disable control flow analysis while resolving the expression.
                // This is used when resolving the instance expression of a field expression.
                DisableFlowAnalysis     = 1 << 10,

                // Set if this is resolving the first part of a MemberAccess.
                Intermediate            = 1 << 11,

                // Disable control flow analysis _of struct_ while resolving the expression.
                // This is used when resolving the instance expression of a field expression.
                DisableStructFlowAnalysis       = 1 << 12,

        }

        //
        // 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);
        }

        //
        // An expressions resolved as a direct variable reference
        //
        public interface IVariableReference : IFixedExpression
        {
                bool IsHoisted { get; }
                string Name { get; }
                VariableInfo VariableInfo { get; }

                void SetHasAddressTaken ();
        }

        //
        // Implemented by an expression which could be or is always
        // fixed
        //
        public interface IFixedExpression
        {
                bool IsFixed { get; }
        }

        /// <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 virtual Location Location {
                        get { return loc; }
                }

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

                // Not nice but we have broken hierarchy.
                public virtual void CheckMarshalByRefAccess (EmitContext ec)
                {
                }

                public virtual bool GetAttributableValue (EmitContext ec, Type value_type, out object value)
                {
                        Attribute.Error_AttributeArgumentNotValid (loc);
                        value = null;
                        return false;
                }

                public virtual string GetSignatureForError ()
                {
                        return TypeManager.CSharpName (type);
                }

                public static bool IsAccessorAccessible (Type invocation_type, MethodInfo mi, out bool must_do_cs1540_check)
                {
                        MethodAttributes ma = mi.Attributes & MethodAttributes.MemberAccessMask;

                        must_do_cs1540_check = false; // by default we do not check for this

                        if (ma == MethodAttributes.Public)
                                return true;
                        
                        //
                        // If only accessible to the current class or children
                        //
                        if (ma == MethodAttributes.Private)
                                return TypeManager.IsPrivateAccessible (invocation_type, mi.DeclaringType) ||
                                        TypeManager.IsNestedChildOf (invocation_type, mi.DeclaringType);

                        if (TypeManager.IsThisOrFriendAssembly (mi.DeclaringType.Assembly)) {
                                if (ma == MethodAttributes.Assembly || ma == MethodAttributes.FamORAssem)
                                        return true;
                        } else {
                                if (ma == MethodAttributes.Assembly || ma == MethodAttributes.FamANDAssem)
                                        return false;
                        }

                        // Family and FamANDAssem require that we derive.
                        // FamORAssem requires that we derive if in different assemblies.
                        if (!TypeManager.IsNestedFamilyAccessible (invocation_type, mi.DeclaringType))
                                return false;

                        if (!TypeManager.IsNestedChildOf (invocation_type, mi.DeclaringType))
                                must_do_cs1540_check = true;

                        return true;
                }

                public virtual bool IsNull {
                        get {
                                return false;
                        }
                }

                /// <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 null;
                }

                //
                // This is used if the expression should be resolved as a type or namespace name.
                // the default implementation fails.   
                //
                public virtual FullNamedExpression ResolveAsTypeStep (IResolveContext rc,  bool silent)
                {
                        if (!silent) {
                                Expression e = this;
                                EmitContext ec = rc as EmitContext;
                                if (ec != null)
                                        e = e.Resolve (ec);
                                if (e != null)
                                        e.Error_UnexpectedKind (ResolveFlags.Type, loc);
                        }
                        return null;
                }

                //
                // C# 3.0 introduced contextual keywords (var) which behaves like a type if type with
                // same name exists or as a keyword when no type was found
                // 
                public virtual TypeExpr ResolveAsContextualType (IResolveContext rc, bool silent)
                {
                        return ResolveAsTypeTerminal (rc, silent);
                }               
                
                //
                // 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 virtual TypeExpr ResolveAsTypeTerminal (IResolveContext ec, bool silent)
                {
                        TypeExpr te = ResolveAsBaseTerminal (ec, silent);
                        if (te == null)
                                return null;

                        if (!silent) { // && !(te is TypeParameterExpr)) {
                                ObsoleteAttribute obsolete_attr = AttributeTester.GetObsoleteAttribute (te.Type);
                                if (obsolete_attr != null && !ec.IsInObsoleteScope) {
                                        AttributeTester.Report_ObsoleteMessage (obsolete_attr, te.GetSignatureForError (), Location);
                                }
                        }

                        ConstructedType ct = te as ConstructedType;
                        if (ct != null) {
                                // Skip constrains check for overrides and explicit implementations
                                // TODO: they should use different overload
                                GenericMethod gm = ec.GenericDeclContainer as GenericMethod;
                                if (gm != null && ((gm.ModFlags & Modifiers.OVERRIDE) != 0 || gm.MemberName.Left != null)) {
                                        te.loc = loc;
                                        return te;
                                }

                                // TODO: silent flag is ignored
                                ct.CheckConstraints (ec);
                        }

                        return te;
                }

                public TypeExpr ResolveAsBaseTerminal (IResolveContext ec, bool silent)
                {
                        int errors = Report.Errors;

                        FullNamedExpression fne = ResolveAsTypeStep (ec, silent);

                        if (fne == null)
                                return null;
                                
                        TypeExpr te = fne as TypeExpr;                          
                        if (te == null) {
                                if (!silent && errors == Report.Errors)
                                        fne.Error_UnexpectedKind (null, "type", loc);
                                return null;
                        }

                        if (!te.CheckAccessLevel (ec.GenericDeclContainer)) {
                                Report.SymbolRelatedToPreviousError (te.Type);
                                ErrorIsInaccesible (loc, TypeManager.CSharpName (te.Type));
                                return null;
                        }

                        te.loc = loc;
                        return te;
                }

                public static void ErrorIsInaccesible (Location loc, string name)
                {
                        Report.Error (122, loc, "`{0}' is inaccessible due to its protection level", name);
                }

                protected static void Error_CannotAccessProtected (Location loc, MemberInfo m, Type qualifier, Type container)
                {
                        Report.Error (1540, loc, "Cannot access protected member `{0}' via a qualifier of type `{1}'."
                                + " The qualifier must be of type `{2}' or derived from it", 
                                TypeManager.GetFullNameSignature (m),
                                TypeManager.CSharpName (qualifier),
                                TypeManager.CSharpName (container));

                }

                public static void Error_InvalidExpressionStatement (Location loc)
                {
                        Report.Error (201, loc, "Only assignment, call, increment, decrement, and new object " +
                                       "expressions can be used as a statement");
                }
                
                public void Error_InvalidExpressionStatement ()
                {
                        Error_InvalidExpressionStatement (loc);
                }

                protected void Error_CannotAssign (string to, string roContext)
                {
                        Report.Error (1656, loc, "Cannot assign to `{0}' because it is a `{1}'",
                                to, roContext);
                }

                public static void Error_VoidInvalidInTheContext (Location loc)
                {
                        Report.Error (1547, loc, "Keyword `void' cannot be used in this context");
                }

                public virtual void Error_ValueCannotBeConverted (EmitContext ec, Location loc, Type target, bool expl)
                {
                        // The error was already reported as CS1660
                        if (type == TypeManager.anonymous_method_type)
                                return;

                        if (TypeManager.IsGenericParameter (Type) && TypeManager.IsGenericParameter (target) && type.Name == target.Name) {
#if GMCS_SOURCE
                                string sig1 = type.DeclaringMethod == null ?
                                        TypeManager.CSharpName (type.DeclaringType) :
                                        TypeManager.CSharpSignature (type.DeclaringMethod);
                                string sig2 = target.DeclaringMethod == null ?
                                        TypeManager.CSharpName (target.DeclaringType) :
                                        TypeManager.CSharpSignature (target.DeclaringMethod);
                                Report.ExtraInformation (loc,
                                        String.Format (
                                                "The generic parameter `{0}' of `{1}' cannot be converted to the generic parameter `{0}' of `{2}' (in the previous ",
                                                Type.Name, sig1, sig2));
#endif
                        } else if (Type.FullName == target.FullName){
                                Report.ExtraInformation (loc,
                                        String.Format (
                                        "The type `{0}' has two conflicting definitions, one comes from `{1}' and the other from `{2}' (in the previous ",
                                        Type.FullName, Type.Assembly.FullName, target.Assembly.FullName));
                        }

                        if (expl) {
                                Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
                                        TypeManager.CSharpName (type), TypeManager.CSharpName (target));
                                return;
                        }

                        Report.DisableReporting ();
                        bool expl_exists = Convert.ExplicitConversion (ec, this, target, Location.Null) != null;
                        Report.EnableReporting ();

                        if (expl_exists) {
                                Report.Error (266, loc, "Cannot implicitly convert type `{0}' to `{1}'. " +
                                              "An explicit conversion exists (are you missing a cast?)",
                                        TypeManager.CSharpName (Type), TypeManager.CSharpName (target));
                                return;
                        }

                        Report.Error (29, loc, "Cannot implicitly convert type `{0}' to `{1}'",
                                TypeManager.CSharpName (type),
                                TypeManager.CSharpName (target));
                }

                public virtual void Error_VariableIsUsedBeforeItIsDeclared (string name)
                {
                        Report.Error (841, loc, "A local variable `{0}' cannot be used before it is declared", name);
                }

                protected virtual void Error_TypeDoesNotContainDefinition (Type type, string name)
                {
                        Error_TypeDoesNotContainDefinition (loc, type, name);
                }

                public static void Error_TypeDoesNotContainDefinition (Location loc, Type type, string name)
                {
                        Report.SymbolRelatedToPreviousError (type);
                        Report.Error (117, loc, "`{0}' does not contain a definition for `{1}'",
                                TypeManager.CSharpName (type), name);
                }

                protected static void Error_ValueAssignment (Location loc)
                {
                        Report.Error (131, loc, "The left-hand side of an assignment must be a variable, a property or an indexer");
                }

                ResolveFlags ExprClassToResolveFlags
                {
                        get {
                                switch (eclass) {
                                case ExprClass.Type:
                                case ExprClass.Namespace:
                                        return ResolveFlags.Type;
                                        
                                case ExprClass.MethodGroup:
                                        return ResolveFlags.MethodGroup;
                                        
                                case ExprClass.TypeParameter:
                                        return ResolveFlags.TypeParameter;
                                        
                                case ExprClass.Value:
                                case ExprClass.Variable:
                                case ExprClass.PropertyAccess:
                                case ExprClass.EventAccess:
                                case ExprClass.IndexerAccess:
                                        return ResolveFlags.VariableOrValue;
                                        
                                default:
                                        throw new InternalErrorException (loc.ToString () + " " +  GetType () + " ExprClass is Invalid after resolve");
                                }
                        }
                }
               
                /// <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, false);

                        bool do_flow_analysis = ec.DoFlowAnalysis;
                        bool omit_struct_analysis = ec.OmitStructFlowAnalysis;
                        if ((flags & ResolveFlags.DisableFlowAnalysis) != 0)
                                do_flow_analysis = false;
                        if ((flags & ResolveFlags.DisableStructFlowAnalysis) != 0)
                                omit_struct_analysis = true;

                        Expression e;
                        using (ec.WithFlowAnalysis (do_flow_analysis, omit_struct_analysis)) {
                                if (this is SimpleName) {
                                        bool intermediate = (flags & ResolveFlags.Intermediate) == ResolveFlags.Intermediate;
                                        e = ((SimpleName) this).DoResolve (ec, intermediate);
                                } else {
                                        e = DoResolve (ec);
                                }
                        }

                        if (e == null)
                                return null;

                        if ((flags & e.ExprClassToResolveFlags) == 0) {
                                e.Error_UnexpectedKind (flags, loc);
                                return null;
                        }

                        if (e.type == null && !(e is Namespace)) {
                                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)
                {
                        Expression e = Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);

                        if (e != null && e.eclass == ExprClass.MethodGroup && RootContext.Version == LanguageVersion.ISO_1) {
                                ((MethodGroupExpr) e).ReportUsageError ();
                                return null;
                        }
                        return e;
                }

                public Constant ResolveAsConstant (EmitContext ec, MemberCore mc)
                {
                        Expression e = Resolve (ec);
                        if (e == null)
                                return null;

                        Constant c = e as Constant;
                        if (c != null)
                                return c;

                        if (type != null && TypeManager.IsReferenceType (type))
                                Const.Error_ConstantCanBeInitializedWithNullOnly (type, loc, mc.GetSignatureForError ());
                        else
                                Const.Error_ExpressionMustBeConstant (loc, mc.GetSignatureForError ());

                        return null;
                }

                /// <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, Location loc)
                {
                        int errors = Report.Errors;
                        bool out_access = right_side == EmptyExpression.OutAccess;

                        Expression e = DoResolveLValue (ec, right_side);

                        if (e != null && out_access && !(e is IMemoryLocation)) {
                                // FIXME: There's no problem with correctness, the 'Expr = null' handles that.
                                //        Enabling this 'throw' will "only" result in deleting useless code elsewhere,

                                //throw new InternalErrorException ("ResolveLValue didn't return an IMemoryLocation: " +
                                //                                e.GetType () + " " + e.GetSignatureForError ());
                                e = null;
                        }

                        if (e == null) {
                                if (errors == Report.Errors) {
                                        if (out_access)
                                                Report.Error (1510, loc, "A ref or out argument must be an assignable variable");
                                        else
                                                Error_ValueAssignment (loc);
                                }
                                return null;
                        }

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

                        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);

                // Emit code to branch to @target if this expression is equivalent to @on_true.
                // The default implementation is to emit the value, and then emit a brtrue or brfalse.
                // Subclasses can provide more efficient implementations, but those MUST be equivalent,
                // including the use of conditional branches.  Note also that a branch MUST be emitted
                public virtual void EmitBranchable (EmitContext ec, Label target, bool on_true)
                {
                        Emit (ec);
                        ec.ig.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
                }

                // Emit this expression for its side effects, not for its value.
                // The default implementation is to emit the value, and then throw it away.
                // Subclasses can provide more efficient implementations, but those MUST be equivalent
                public virtual void EmitSideEffect (EmitContext ec)
                {
                        Emit (ec);
                        ec.ig.Emit (OpCodes.Pop);
                }

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

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

                /// <summary>
                ///   Returns a fully formed expression after a MemberLookup
                /// </summary>
                /// 
                public static Expression ExprClassFromMemberInfo (Type container_type, MemberInfo mi, Location loc)
                {
                        if (mi is EventInfo)
                                return new EventExpr ((EventInfo) mi, loc);
                        else if (mi is FieldInfo) {
                                FieldInfo fi = (FieldInfo) mi;
                                if (fi.IsLiteral || (fi.IsInitOnly && fi.FieldType == TypeManager.decimal_type))
                                        return new ConstantExpr (fi, loc);
                                return new FieldExpr (fi, loc);
                        } else if (mi is PropertyInfo)
                                return new PropertyExpr (container_type, (PropertyInfo) mi, loc);
                        else if (mi is Type) {
                                return new TypeExpression ((System.Type) mi, loc);
                        }

                        return null;
                }

                protected static ArrayList almost_matched_members = new ArrayList (4);

                //
                // 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 (Type container_type, Type queried_type, string name,
                                                       MemberTypes mt, BindingFlags bf, Location loc)
                {
                        return MemberLookup (container_type, 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 (Type container_type,
                                                       Type qualifier_type, Type queried_type,
                                                       string name, MemberTypes mt,
                                                       BindingFlags bf, Location loc)
                {
                        almost_matched_members.Clear ();

                        MemberInfo [] mi = TypeManager.MemberLookup (container_type, qualifier_type,
                                                                     queried_type, mt, bf, name, almost_matched_members);

                        if (mi == null)
                                return null;

                        if (mi.Length > 1) {
                                bool is_interface = qualifier_type != null && qualifier_type.IsInterface;
                                ArrayList methods = new ArrayList (2);
                                ArrayList non_methods = null;

                                foreach (MemberInfo m in mi) {
                                        if (m is MethodBase) {
                                                methods.Add (m);
                                                continue;
                                        }

                                        if (non_methods == null) {
                                                non_methods = new ArrayList (2);
                                                non_methods.Add (m);
                                                continue;
                                        }

                                        foreach (MemberInfo n_m in non_methods) {
                                                if (m.DeclaringType.IsInterface && TypeManager.ImplementsInterface (m.DeclaringType, n_m.DeclaringType))
                                                        continue;

                                                Report.SymbolRelatedToPreviousError (m);
                                                Report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
                                                        TypeManager.GetFullNameSignature (m), TypeManager.GetFullNameSignature (n_m));
                                                return null;
                                        }
                                }

                                if (methods.Count == 0)
                                        return ExprClassFromMemberInfo (container_type, (MemberInfo)non_methods [0], loc);

                                if (non_methods != null) {
                                        MethodBase method = (MethodBase) methods [0];
                                        MemberInfo non_method = (MemberInfo) non_methods [0];
                                        if (method.DeclaringType == non_method.DeclaringType) {
                                                // Cannot happen with C# code, but is valid in IL
                                                Report.SymbolRelatedToPreviousError (method);
                                                Report.SymbolRelatedToPreviousError (non_method);
                                                Report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
                                                              TypeManager.GetFullNameSignature (non_method),
                                                              TypeManager.CSharpSignature (method));
                                                return null;
                                        }

                                        if (is_interface) {
                                                Report.SymbolRelatedToPreviousError (method);
                                                Report.SymbolRelatedToPreviousError (non_method);
                                                Report.Warning (467, 2, loc, "Ambiguity between method `{0}' and non-method `{1}'. Using method `{0}'",
                                                                TypeManager.CSharpSignature (method), TypeManager.GetFullNameSignature (non_method));
                                        }
                                }

                                return new MethodGroupExpr (methods, queried_type, loc);
                        }

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

                        return ExprClassFromMemberInfo (container_type, 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 (Type container_type, Type queried_type,
                                                       string name, Location loc)
                {
                        return MemberLookup (container_type, null, queried_type, name,
                                             AllMemberTypes, AllBindingFlags, loc);
                }

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

                public static MethodGroupExpr MethodLookup (Type container_type, Type queried_type,
                                                       string name, Location loc)
                {
                        return (MethodGroupExpr)MemberLookup (container_type, 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>
                protected 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.ContainerType, qualifier_type, queried_type, name, mt, bf, loc);

                        if (e != null || errors != Report.Errors)
                                return e;

                        // No errors were reported by MemberLookup, but there was an error.
                        return Error_MemberLookupFailed (ec.ContainerType, qualifier_type, queried_type,
                                        name, null, mt, bf);
                }

                protected virtual Expression Error_MemberLookupFailed (Type container_type, Type qualifier_type,
                                                       Type queried_type, string name, string class_name,
                                                           MemberTypes mt, BindingFlags bf)
                {
                        if (almost_matched_members.Count != 0) {
                                for (int i = 0; i < almost_matched_members.Count; ++i) {
                                        MemberInfo m = (MemberInfo) almost_matched_members [i];
                                        for (int j = 0; j < i; ++j) {
                                                if (m == almost_matched_members [j]) {
                                                        m = null;
                                                        break;
                                                }
                                        }
                                        if (m == null)
                                                continue;
                                        
                                        Type declaring_type = m.DeclaringType;
                                        
                                        Report.SymbolRelatedToPreviousError (m);
                                        if (qualifier_type == null) {
                                                Report.Error (38, loc, "Cannot access a nonstatic member of outer type `{0}' via nested type `{1}'",
                                                              TypeManager.CSharpName (m.DeclaringType),
                                                              TypeManager.CSharpName (container_type));
                                                
                                        } else if (qualifier_type != container_type &&
                                                   TypeManager.IsNestedFamilyAccessible (container_type, declaring_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 base of the
                                                // ec.ContainerType and the lookup succeeds with the latter one,
                                                // then we are in this situation.
                                                Error_CannotAccessProtected (loc, m, qualifier_type, container_type);
                                        } else {
                                                ErrorIsInaccesible (loc, TypeManager.GetFullNameSignature (m));
                                        }
                                }
                                almost_matched_members.Clear ();
                                return null;
                        }

                        MemberInfo[] lookup = null;
                        if (queried_type == null) {
                                class_name = "global::";
                        } else {
                                lookup = TypeManager.MemberLookup (queried_type, null, queried_type,
                                        mt, (bf & ~BindingFlags.Public) | BindingFlags.NonPublic,
                                        name, null);

                                if (lookup != null) {
                                        Report.SymbolRelatedToPreviousError (lookup [0]);
                                        ErrorIsInaccesible (loc, TypeManager.GetFullNameSignature (lookup [0]));
                                        return Error_MemberLookupFailed (lookup);
                                }

                                lookup = TypeManager.MemberLookup (queried_type, null, queried_type,
                                        AllMemberTypes, AllBindingFlags | BindingFlags.NonPublic,
                                        name, null);
                        }

                        if (lookup == null) {
                                if (class_name != null) {
                                        Report.Error (103, loc, "The name `{0}' does not exist in the current context",
                                                name);
                                } else {
                                        Error_TypeDoesNotContainDefinition (queried_type, name);
                                }
                                return null;
                        }

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

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

                        return Error_MemberLookupFailed (lookup);
                }

                protected virtual Expression Error_MemberLookupFailed (MemberInfo[] members)
                {
                        for (int i = 0; i < members.Length; ++i) {
                                if (!(members [i] is MethodBase))
                                        return null;
                        }

                        // By default propagate the closest candidates upwards
                        return new MethodGroupExpr (members, type, loc);
                }

                protected virtual void Error_NegativeArrayIndex (Location loc)
                {
                        throw new NotImplementedException ();
                }

                protected void Error_PointerInsideExpressionTree ()
                {
                        Report.Error (1944, loc, "An expression tree cannot contain an unsafe pointer operation");
                }

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

                static Expression GetOperatorTrueOrFalse (EmitContext ec, Expression e, bool is_true, Location loc)
                {
                        MethodGroupExpr operator_group;
                        string mname = Operator.GetMetadataName (is_true ? Operator.OpType.True : Operator.OpType.False);
                        operator_group = MethodLookup (ec.ContainerType, e.Type, mname, loc) as MethodGroupExpr;
                        if (operator_group == null)
                                return null;

                        ArrayList arguments = new ArrayList (1);
                        arguments.Add (new Argument (e, Argument.AType.Expression));
                        operator_group = operator_group.OverloadResolve (
                                ec, ref arguments, false, loc);

                        if (operator_group == null)
                                return null;

                        return new UserOperatorCall (operator_group, arguments, null, 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;

                        if (e.Type == TypeManager.bool_type)
                                return e;

                        Expression converted = Convert.ImplicitConversion (ec, e, TypeManager.bool_type, Location.Null);

                        if (converted != null)
                                return converted;

                        //
                        // If no implicit conversion to bool exists, try using `operator true'
                        //
                        converted = Expression.GetOperatorTrue (ec, e, loc);
                        if (converted == null){
                                e.Error_ValueCannotBeConverted (ec, loc, TypeManager.bool_type, false);
                                return null;
                        }
                        return converted;
                }
                
                public virtual string ExprClassName
                {
                        get {
                                switch (eclass){
                                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";
                                case ExprClass.TypeParameter:
                                        return "type parameter";
                                }
                                throw new Exception ("Should not happen");
                        }
                }
                
                /// <summary>
                ///   Reports that we were expecting `expr' to be of class `expected'
                /// </summary>
                public void Error_UnexpectedKind (DeclSpace ds, string expected, Location loc)
                {
                        Error_UnexpectedKind (ds, expected, ExprClassName, loc);
                }

                public void Error_UnexpectedKind (DeclSpace ds, string expected, string was, Location loc)
                {
                        string name = GetSignatureForError ();
                        if (ds != null)
                                name = ds.GetSignatureForError () + '.' + name;

                        Report.Error (118, loc, "`{0}' is a `{1}' but a `{2}' was expected",
                              name, was, expected);
                }

                public void Error_UnexpectedKind (ResolveFlags flags, Location loc)
                {
                        string [] valid = new string [4];
                        int count = 0;

                        if ((flags & ResolveFlags.VariableOrValue) != 0) {
                                valid [count++] = "variable";
                                valid [count++] = "value";
                        }

                        if ((flags & ResolveFlags.Type) != 0)
                                valid [count++] = "type";

                        if ((flags & ResolveFlags.MethodGroup) != 0)
                                valid [count++] = "method group";

                        if (count == 0)
                                valid [count++] = "unknown";

                        StringBuilder sb = new StringBuilder (valid [0]);
                        for (int i = 1; i < count - 1; i++) {
                                sb.Append ("', `");
                                sb.Append (valid [i]);
                        }
                        if (count > 1) {
                                sb.Append ("' or `");
                                sb.Append (valid [count - 1]);
                        }

                        Report.Error (119, loc, 
                                "Expression denotes a `{0}', where a `{1}' was expected", ExprClassName, sb.ToString ());
                }
                
                public static void UnsafeError (Location loc)
                {
                        Report.Error (214, loc, "Pointers and fixed size buffers may only be used in an unsafe context");
                }

                //
                // 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.GetEnumUnderlyingType (t));
                        } else if (t.IsValueType || TypeManager.IsGenericParameter (t))
                                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.GetEnumUnderlyingType (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 || TypeManager.IsGenericParameter (type))
                                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;
                }

                protected void Error_CannotCallAbstractBase (string name)
                {
                        Report.Error (205, loc, "Cannot call an abstract base member `{0}'", name);
                }
                
                protected void Error_CannotModifyIntermediateExpressionValue (EmitContext ec)
                {
                        Report.SymbolRelatedToPreviousError (type);
                        if (ec.CurrentInitializerVariable != null) {
                                Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
                                        TypeManager.CSharpName (type), GetSignatureForError ());
                        } else {
                                Report.Error (1612, loc, "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
                                        GetSignatureForError ());
                        }
                }

                //
                // Converts `source' to an int, uint, long or ulong.
                //
                public Expression ConvertExpressionToArrayIndex (EmitContext ec, Expression source)
                {
                        Expression converted;
                        
                        using (ec.With (EmitContext.Flags.CheckState, true)) {
                                converted = Convert.ImplicitConversion (ec, source, TypeManager.int32_type, source.loc);
                                if (converted == null)
                                        converted = Convert.ImplicitConversion (ec, source, TypeManager.uint32_type, source.loc);
                                if (converted == null)
                                        converted = Convert.ImplicitConversion (ec, source, TypeManager.int64_type, source.loc);
                                if (converted == null)
                                        converted = Convert.ImplicitConversion (ec, source, TypeManager.uint64_type, source.loc);

                                if (converted == null) {
                                        source.Error_ValueCannotBeConverted (ec, source.loc, TypeManager.int32_type, false);
                                        return null;
                                }
                        }

                        //
                        // Only positive constants are allowed at compile time
                        //
                        Constant c = converted as Constant;
                        if (c != null) {
                                if (c.IsNegative) {
                                        Error_NegativeArrayIndex (source.loc);
                                }
                                return c;
                        }

                        return new ArrayIndexCast (converted).Resolve (ec);
                }

                //
                // Derived classes implement this method by cloning the fields that
                // could become altered during the Resolve stage
                //
                // Only expressions that are created for the parser need to implement
                // this.
                //
                protected virtual void CloneTo (CloneContext clonectx, Expression target)
                {
                        throw new NotImplementedException (
                                String.Format (
                                        "CloneTo not implemented for expression {0}", this.GetType ()));
                }

                //
                // Clones an expression created by the parser.
                //
                // We only support expressions created by the parser so far, not
                // expressions that have been resolved (many more classes would need
                // to implement CloneTo).
                //
                // This infrastructure is here merely for Lambda expressions which
                // compile the same code using different type values for the same
                // arguments to find the correct overload
                //
                public Expression Clone (CloneContext clonectx)
                {
                        Expression cloned = (Expression) MemberwiseClone ();
                        CloneTo (clonectx, cloned);

                        return cloned;
                }

                //
                // Implementation of expression to expression tree conversion
                //
                public abstract Expression CreateExpressionTree (EmitContext ec);

                protected Expression CreateExpressionFactoryCall (string name, ArrayList args)
                {
                        return CreateExpressionFactoryCall (name, null, args, loc);
                }

                protected Expression CreateExpressionFactoryCall (string name, TypeArguments typeArguments, ArrayList args)
                {
                        return CreateExpressionFactoryCall (name, typeArguments, args, loc);
                }

                public static Expression CreateExpressionFactoryCall (string name, TypeArguments typeArguments, ArrayList args, Location loc)
                {
                        return new Invocation (new MemberAccess (CreateExpressionTypeExpression (loc), name, typeArguments, loc), args);
                }

                protected static TypeExpr CreateExpressionTypeExpression (Location loc)
                {
                        TypeExpr texpr = TypeManager.expression_type_expr;
                        if (texpr == null) {
                                Type t = TypeManager.CoreLookupType ("System.Linq.Expressions", "Expression", Kind.Class, true);
                                if (t == null)
                                        return null;

                                TypeManager.expression_type_expr = texpr = new TypeExpression (t, Location.Null);
                        }

                        return texpr;
                }

                public virtual void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        // TODO: It should probably be type = storey.MutateType (type);
                }
        }

        /// <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_InvalidExpressionStatement ();

                        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);

                public override void EmitSideEffect (EmitContext ec)
                {
                        EmitStatement (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 abstract class TypeCast : Expression
        {
                protected readonly Expression child;

                protected TypeCast (Expression child, Type return_type)
                {
                        eclass = child.eclass;
                        loc = child.Location;
                        type = return_type;
                        this.child = child;
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        ArrayList args = new ArrayList (2);
                        args.Add (new Argument (child.CreateExpressionTree (ec)));
                        args.Add (new Argument (new TypeOf (new TypeExpression (type, loc), loc)));

                        if (type.IsPointer || child.Type.IsPointer)
                                Error_PointerInsideExpressionTree ();

                        return CreateExpressionFactoryCall (ec.CheckState ? "ConvertChecked" : "Convert", args);
                }

                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 bool GetAttributableValue (EmitContext ec, Type value_type, out object value)
                {
                        return child.GetAttributableValue (ec, value_type, out value);
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        type = storey.MutateType (type);
                        child.MutateHoistedGenericType (storey);
                }

                protected override void CloneTo (CloneContext clonectx, Expression t)
                {
                        // Nothing to clone
                }

                public override bool IsNull {
                        get { return child.IsNull; }
                }
        }

        public class EmptyCast : TypeCast {
                EmptyCast (Expression child, Type target_type)
                        : base (child, target_type)
                {
                }

                public static Expression Create (Expression child, Type type)
                {
                        Constant c = child as Constant;
                        if (c != null)
                                return new EmptyConstantCast (c, type);

                        EmptyCast e = child as EmptyCast;
                        if (e != null)
                                return new EmptyCast (e.child, type);

                        return new EmptyCast (child, type);
                }

                public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
                {
                        child.EmitBranchable (ec, label, on_true);
                }

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

        //
        // Used for predefined class library user casts (no obsolete check, etc.)
        //
        public class OperatorCast : TypeCast {
                MethodInfo conversion_operator;
                        
                public OperatorCast (Expression child, Type target_type) 
                        : this (child, target_type, false)
                {
                }

                public OperatorCast (Expression child, Type target_type, bool find_explicit)
                        : base (child, target_type)
                {
                        conversion_operator = GetConversionOperator (find_explicit);
                        if (conversion_operator == null)
                                throw new InternalErrorException ("Outer conversion routine is out of sync");
                }

                // Returns the implicit operator that converts from
                // 'child.Type' to our target type (type)
                MethodInfo GetConversionOperator (bool find_explicit)
                {
                        string operator_name = find_explicit ? "op_Explicit" : "op_Implicit";

                        MemberInfo [] mi;

                        mi = TypeManager.MemberLookup (child.Type, child.Type, child.Type, MemberTypes.Method,
                                BindingFlags.Static | BindingFlags.Public, operator_name, null);

                        if (mi == null){
                                mi = TypeManager.MemberLookup (type, type, type, MemberTypes.Method,
                                                               BindingFlags.Static | BindingFlags.Public, operator_name, null);
                        }
                        
                        foreach (MethodInfo oper in mi) {
                                AParametersCollection pd = TypeManager.GetParameterData (oper);

                                if (pd.Types [0] == child.Type && TypeManager.TypeToCoreType (oper.ReturnType) == type)
                                        return oper;
                        }

                        return null;
                }

                public override void Emit (EmitContext ec)
                {
                        child.Emit (ec);
                        ec.ig.Emit (OpCodes.Call, conversion_operator);
                }
        }
        
        /// <summary>
        ///     This is a numeric cast to a Decimal
        /// </summary>
        public class CastToDecimal : OperatorCast {
                public CastToDecimal (Expression child)
                        : this (child, false)
                {
                }

                public CastToDecimal (Expression child, bool find_explicit)
                        : base (child, TypeManager.decimal_type, find_explicit)
                {
                }
        }

        /// <summary>
        ///     This is an explicit numeric cast from a Decimal
        /// </summary>
        public class CastFromDecimal : TypeCast
        {
                static IDictionary operators;

                public CastFromDecimal (Expression child, Type return_type)
                        : base (child, return_type)
                {
                        if (child.Type != TypeManager.decimal_type)
                                throw new InternalErrorException (
                                        "The expected type is Decimal, instead it is " + child.Type.FullName);
                }

                // Returns the explicit operator that converts from an
                // express of type System.Decimal to 'type'.
                public Expression Resolve ()
                {
                        if (operators == null) {
                                 MemberInfo[] all_oper = TypeManager.MemberLookup (TypeManager.decimal_type,
                                        TypeManager.decimal_type, TypeManager.decimal_type, MemberTypes.Method,
                                        BindingFlags.Static | BindingFlags.Public, "op_Explicit", null);

                                operators = new System.Collections.Specialized.HybridDictionary ();
                                foreach (MethodInfo oper in all_oper) {
                                        AParametersCollection pd = TypeManager.GetParameterData (oper);
                                        if (pd.Types [0] == TypeManager.decimal_type)
                                                operators.Add (TypeManager.TypeToCoreType (oper.ReturnType), oper);
                                }
                        }

                        return operators.Contains (type) ? this : null;
                }

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

                        ig.Emit (OpCodes.Call, (MethodInfo)operators [type]);
                }
        }

        
        //
        // Constant specialization of EmptyCast.
        // We need to special case this since an empty cast of
        // a constant is still a constant. 
        //
        public class EmptyConstantCast : Constant
        {
                public readonly Constant child;

                public EmptyConstantCast(Constant child, Type type)
                        : base (child.Location)
                {
                        eclass = child.eclass;
                        this.child = child;
                        this.type = type;
                }

                public override string AsString ()
                {
                        return child.AsString ();
                }

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

                public override Constant ConvertExplicitly (bool in_checked_context, Type target_type)
                {
                        // FIXME: check that 'type' can be converted to 'target_type' first
                        return child.ConvertExplicitly (in_checked_context, target_type);
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        ArrayList args = new ArrayList (2);
                        args.Add (new Argument (child.CreateExpressionTree (ec)));
                        args.Add (new Argument (new TypeOf (new TypeExpression (type, loc), loc)));
                        if (type.IsPointer)
                                Error_PointerInsideExpressionTree ();

                        return CreateExpressionFactoryCall ("Convert", args);
                }

                public override Constant Increment ()
                {
                        return child.Increment ();
                }

                public override bool IsDefaultValue {
                        get { return child.IsDefaultValue; }
                }

                public override bool IsNegative {
                        get { return child.IsNegative; }
                }

                public override bool IsNull {
                        get { return child.IsNull; }
                }

                public override bool IsZeroInteger {
                        get { return child.IsZeroInteger; }
                }
                
                public override void Emit (EmitContext ec)
                {
                        child.Emit (ec);
                }

                public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
                {
                        child.EmitBranchable (ec, label, on_true);
                }

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

                public override Constant ConvertImplicitly (Type target_type)
                {
                        // FIXME: Do we need to check user conversions?
                        if (!Convert.ImplicitStandardConversionExists (this, target_type))
                                return null;
                        return child.ConvertImplicitly (target_type);
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        child.MutateHoistedGenericType (storey);
                }
        }


        /// <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):
                        base (child.Location)
                {
                        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 void EmitBranchable (EmitContext ec, Label label, bool on_true)
                {
                        Child.EmitBranchable (ec, label, on_true);
                }

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

                public override bool GetAttributableValue (EmitContext ec, Type value_type, out object value)
                {
                        value = GetTypedValue ();
                        return true;
                }

                public override string GetSignatureForError()
                {
                        return TypeManager.CSharpName (Type);
                }

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

                public override object GetTypedValue ()
                {
                        // FIXME: runtime is not ready to work with just emited enums
                        if (!RootContext.StdLib) {
                                return Child.GetValue ();
                        }

#if MS_COMPATIBLE
                        // Small workaround for big problem
                        // System.Enum.ToObject cannot be called on dynamic types
                        // EnumBuilder has to be used, but we cannot use EnumBuilder
                        // because it does not properly support generics
                        //
                        // This works only sometimes
                        //
                        if (type.Module == CodeGen.Module.Builder)
                                return Child.GetValue ();
#endif

                        return System.Enum.ToObject (type, Child.GetValue ());
                }
                
                public override string AsString ()
                {
                        return Child.AsString ();
                }

                public override Constant Increment()
                {
                        return new EnumConstant (Child.Increment (), type);
                }

                public override bool IsDefaultValue {
                        get {
                                return Child.IsDefaultValue;
                        }
                }

                public override bool IsZeroInteger {
                        get { return Child.IsZeroInteger; }
                }

                public override bool IsNegative {
                        get {
                                return Child.IsNegative;
                        }
                }

                public override Constant ConvertExplicitly(bool in_checked_context, Type target_type)
                {
                        if (Child.Type == target_type)
                                return Child;

                        return Child.ConvertExplicitly (in_checked_context, target_type);
                }

                public override Constant ConvertImplicitly (Type type)
                {
                        Type this_type = TypeManager.DropGenericTypeArguments (Type);
                        type = TypeManager.DropGenericTypeArguments (type);

                        if (this_type == type) {
                                // This is workaround of mono bug. It can be removed when the latest corlib spreads enough
                                if (TypeManager.IsEnumType (type.UnderlyingSystemType))
                                        return this;

                                Type child_type = TypeManager.DropGenericTypeArguments (Child.Type);
                                if (type.UnderlyingSystemType != child_type)
                                        Child = Child.ConvertImplicitly (type.UnderlyingSystemType);
                                return this;
                        }

                        if (!Convert.ImplicitStandardConversionExists (this, type)){
                                return null;
                        }

                        return Child.ConvertImplicitly(type);
                }

        }

        /// <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 : TypeCast {

                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 override void EmitSideEffect (EmitContext ec)
                {
                        // boxing is side-effectful, since it involves runtime checks, except when boxing to Object or ValueType
                        // so, we need to emit the box+pop instructions in most cases
                        if (child.Type.IsValueType &&
                            (type == TypeManager.object_type || type == TypeManager.value_type))
                                child.EmitSideEffect (ec);
                        else
                                base.EmitSideEffect (ec);
                }
        }

        public class UnboxCast : TypeCast {
                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 Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        if (right_side == EmptyExpression.LValueMemberAccess || right_side == EmptyExpression.LValueMemberOutAccess)
                                Report.Error (445, loc, "Cannot modify the result of an unboxing conversion");
                        return base.DoResolveLValue (ec, right_side);
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        base.Emit (ec);
#if GMCS_SOURCE
                        if (type.IsGenericParameter || type.IsGenericType && type.IsValueType)
                                ig.Emit (OpCodes.Unbox_Any, type);
                        else
#endif
                        {
                                ig.Emit (OpCodes.Unbox, type);

                                LoadFromPtr (ig, type);
                        }
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        type = storey.MutateType (type);
                        base.MutateHoistedGenericType (storey);                 
                }
        }
        
        /// <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 : TypeCast {
                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;
                
                public ConvCast (Expression child, Type return_type, Mode m)
                        : base (child, return_type)
                {
                        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 (ec.CheckState){
                                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 : TypeCast {
                readonly OpCode op;
                
                public OpcodeCast (Expression child, Type return_type, OpCode op)
                        : base (child, return_type)
                {
                        this.op = op;
                }

                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);
                }

                public Type UnderlyingType {
                        get { return child.Type; }
                }
        }

        /// <summary>
        ///   This kind of cast is used to encapsulate a child and cast it
        ///   to the class requested
        /// </summary>
        public sealed class ClassCast : TypeCast {
                Type child_generic_parameter;

                public ClassCast (Expression child, Type return_type)
                        : base (child, return_type)
                        
                {
                        if (TypeManager.IsGenericParameter (child.Type))
                                child_generic_parameter = child.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_generic_parameter != null)
                                ec.ig.Emit (OpCodes.Box, child_generic_parameter);

#if GMCS_SOURCE
                        if (type.IsGenericParameter)
                                ec.ig.Emit (OpCodes.Unbox_Any, type);
                        else
#endif
                                ec.ig.Emit (OpCodes.Castclass, type);
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        type = storey.MutateType (type);
                        if (child_generic_parameter != null)
                                child_generic_parameter = storey.MutateGenericArgument (child_generic_parameter);

                        base.MutateHoistedGenericType (storey);
                }
        }

        //
        // Created during resolving pahse when an expression is wrapped or constantified
        // and original expression can be used later (e.g. for expression trees)
        //
        public class ReducedExpression : Expression
        {
                sealed class ReducedConstantExpression : EmptyConstantCast
                {
                        readonly Expression orig_expr;

                        public ReducedConstantExpression (Constant expr, Expression orig_expr)
                                : base (expr, expr.Type)
                        {
                                this.orig_expr = orig_expr;
                        }

                        public override Constant ConvertImplicitly (Type target_type)
                        {
                                Constant c = base.ConvertImplicitly (target_type);
                                if (c != null)
                                        c = new ReducedConstantExpression (c, orig_expr);
                                return c;
                        }

                        public override Expression CreateExpressionTree (EmitContext ec)
                        {
                                return orig_expr.CreateExpressionTree (ec);
                        }

                        public override bool GetAttributableValue (EmitContext ec, Type value_type, out object value)
                        {
                                //
                                // Even if resolved result is a constant original expression was not
                                // and attribute accepts constants only
                                //
                                Attribute.Error_AttributeArgumentNotValid (orig_expr.Location);
                                value = null;
                                return false;
                        }

                        public override Constant ConvertExplicitly (bool in_checked_context, Type target_type)
                        {
                                Constant c = base.ConvertExplicitly (in_checked_context, target_type);
                                if (c != null)
                                        c = new ReducedConstantExpression (c, orig_expr);
                                return c;
                        }
                }

                sealed class ReducedExpressionStatement : ExpressionStatement
                {
                        readonly Expression orig_expr;
                        readonly ExpressionStatement stm;

                        public ReducedExpressionStatement (ExpressionStatement stm, Expression orig)
                        {
                                this.orig_expr = orig;
                                this.stm = stm;
                                this.loc = orig.Location;
                        }

                        public override Expression CreateExpressionTree (EmitContext ec)
                        {
                                return orig_expr.CreateExpressionTree (ec);
                        }

                        public override Expression DoResolve (EmitContext ec)
                        {
                                eclass = stm.eclass;
                                type = stm.Type;
                                return this;
                        }

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

                        public override void EmitStatement (EmitContext ec)
                        {
                                stm.EmitStatement (ec);
                        }

                        public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                        {
                                stm.MutateHoistedGenericType (storey);
                        }
                }

                readonly Expression expr, orig_expr;

                private ReducedExpression (Expression expr, Expression orig_expr)
                {
                        this.expr = expr;
                        this.orig_expr = orig_expr;
                        this.loc = orig_expr.Location;
                }

                public static Constant Create (Constant expr, Expression original_expr)
                {
                        return new ReducedConstantExpression (expr, original_expr);
                }

                public static ExpressionStatement Create (ExpressionStatement s, Expression orig)
                {
                        return new ReducedExpressionStatement (s, orig);
                }

                public static Expression Create (Expression expr, Expression original_expr)
                {
                        Constant c = expr as Constant;
                        if (c != null)
                                return Create (c, original_expr);

                        ExpressionStatement s = expr as ExpressionStatement;
                        if (s != null)
                                return Create (s, original_expr);

                        return new ReducedExpression (expr, original_expr);
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        return orig_expr.CreateExpressionTree (ec);
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        eclass = expr.eclass;
                        type = expr.Type;
                        return this;
                }

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

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

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        expr.MutateHoistedGenericType (storey);
                }
        }

        //
        // Unresolved type name expressions
        //
        public abstract class ATypeNameExpression : FullNamedExpression
        {
                public readonly string Name;
                protected TypeArguments targs;

                protected ATypeNameExpression (string name, Location l)
                {
                        Name = name;
                        loc = l;
                }

                protected ATypeNameExpression (string name, TypeArguments targs, Location l)
                {
                        Name = name;
                        this.targs = targs;
                        loc = l;
                }

                public bool HasTypeArguments {
                        get {
                                return targs != null;
                        }
                }

                public override string GetSignatureForError ()
                {
                        if (targs != null) {
                                return TypeManager.RemoveGenericArity (Name) + "<" +
                                        targs.GetSignatureForError () + ">";
                        }

                        return Name;
                }
        }
        
        /// <summary>
        ///   SimpleName expressions are formed of a single word and only happen at the beginning 
        ///   of a dotted-name.
        /// </summary>
        public class SimpleName : ATypeNameExpression {
                bool in_transit;

                public SimpleName (string name, Location l)
                        : base (name, l)
                {
                }

                public SimpleName (string name, TypeArguments args, Location l)
                        : base (name, args, l)
                {
                }

                public SimpleName (string name, TypeParameter[] type_params, Location l)
                        : base (name, l)
                {
                        targs = new TypeArguments (l);
                        foreach (TypeParameter type_param in type_params)
                                targs.Add (new TypeParameterExpr (type_param, l));
                }

                public static string RemoveGenericArity (string name)
                {
                        int start = 0;
                        StringBuilder sb = null;
                        do {
                                int pos = name.IndexOf ('`', start);
                                if (pos < 0) {
                                        if (start == 0)
                                                return name;

                                        sb.Append (name.Substring (start));
                                        break;
                                }

                                if (sb == null)
                                        sb = new StringBuilder ();
                                sb.Append (name.Substring (start, pos-start));

                                pos++;
                                while ((pos < name.Length) && Char.IsNumber (name [pos]))
                                        pos++;

                                start = pos;
                        } while (start < name.Length);

                        return sb.ToString ();
                }

                public SimpleName GetMethodGroup ()
                {
                        return new SimpleName (RemoveGenericArity (Name), targs, loc);
                }

                public static void Error_ObjectRefRequired (EmitContext ec, Location l, string name)
                {
                        if (ec.IsInFieldInitializer)
                                Report.Error (236, l,
                                        "A field initializer cannot reference the nonstatic field, method, or property `{0}'",
                                        name);
                        else
                                Report.Error (120, l,
                                        "An object reference is required to access non-static member `{0}'",
                                        name);
                }

                public bool IdenticalNameAndTypeName (EmitContext ec, Expression resolved_to, Location loc)
                {
                        return resolved_to != null && resolved_to.Type != null && 
                                resolved_to.Type.Name == Name &&
                                (ec.DeclContainer.LookupNamespaceOrType (Name, loc, /* ignore_cs0104 = */ true) != null);
                }

                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 DoResolve (EmitContext ec, bool intermediate)
                {
                        return SimpleNameResolve (ec, null, intermediate);
                }

                static bool IsNestedChild (Type t, Type parent)
                {
                        while (parent != null) {
                                if (TypeManager.IsNestedChildOf (t, TypeManager.DropGenericTypeArguments (parent)))
                                        return true;

                                parent = parent.BaseType;
                        }

                        return false;
                }

                FullNamedExpression ResolveNested (IResolveContext ec, Type t)
                {
                        if (!TypeManager.IsGenericTypeDefinition (t) && !TypeManager.IsGenericType (t))
                                return null;

                        DeclSpace ds = ec.DeclContainer;
                        while (ds != null && !IsNestedChild (t, ds.TypeBuilder))
                                ds = ds.Parent;

                        if (ds == null)
                                return null;

                        Type[] gen_params = TypeManager.GetTypeArguments (t);

                        int arg_count = targs != null ? targs.Count : 0;

                        for (; (ds != null) && ds.IsGeneric; ds = ds.Parent) {
                                if (arg_count + ds.CountTypeParameters == gen_params.Length) {
                                        TypeArguments new_args = new TypeArguments (loc);
                                        foreach (TypeParameter param in ds.TypeParameters)
                                                new_args.Add (new TypeParameterExpr (param, loc));

                                        if (targs != null)
                                                new_args.Add (targs);

                                        return new ConstructedType (t, new_args, loc);
                                }
                        }

                        return null;
                }

                public override FullNamedExpression ResolveAsTypeStep (IResolveContext ec, bool silent)
                {
                        FullNamedExpression fne = ec.GenericDeclContainer.LookupGeneric (Name, loc);
                        if (fne != null)
                                return fne.ResolveAsTypeStep (ec, silent);

                        int errors = Report.Errors;
                        fne = ec.DeclContainer.LookupNamespaceOrType (Name, loc, /*ignore_cs0104=*/ false);

                        if (fne != null) {
                                if (fne.Type == null)
                                        return fne;

                                FullNamedExpression nested = ResolveNested (ec, fne.Type);
                                if (nested != null)
                                        return nested.ResolveAsTypeStep (ec, false);

                                if (targs != null) {
                                        ConstructedType ct = new ConstructedType (fne, targs, loc);
                                        return ct.ResolveAsTypeStep (ec, false);
                                }

                                return fne;
                        }

                        if (silent || errors != Report.Errors)
                                return null;

                        Error_TypeOrNamespaceNotFound (ec);
                        return null;
                }

                protected virtual void Error_TypeOrNamespaceNotFound (IResolveContext ec)
                {
                        MemberCore mc = ec.DeclContainer.GetDefinition (Name);
                        if (mc != null) {
                                Error_UnexpectedKind (ec.DeclContainer, "type", GetMemberType (mc), loc);
                                return;
                        }

                        string ns = ec.DeclContainer.NamespaceEntry.NS.Name;
                        string fullname = (ns.Length > 0) ? ns + "." + Name : Name;
                        foreach (Assembly a in RootNamespace.Global.Assemblies) {
                                Type type = a.GetType (fullname);
                                if (type != null) {
                                        Report.SymbolRelatedToPreviousError (type);
                                        Expression.ErrorIsInaccesible (loc, TypeManager.CSharpName (type));
                                        return;
                                }
                        }

                        Type t = ec.DeclContainer.LookupAnyGeneric (Name);
                        if (t != null) {
                                Namespace.Error_InvalidNumberOfTypeArguments (t, loc);
                                return;
                        }

                        if (targs != null) {
                                FullNamedExpression retval = ec.DeclContainer.LookupNamespaceOrType (SimpleName.RemoveGenericArity (Name), loc, true);
                                if (retval != null) {
                                        Namespace.Error_TypeArgumentsCannotBeUsed (retval.Type, loc);
                                        return;
                                }
                        }
                                                
                        NamespaceEntry.Error_NamespaceNotFound (loc, Name);
                }

                // TODO: I am still not convinced about this. If someone else will need it
                // implement this as virtual property in MemberCore hierarchy
                public static string GetMemberType (MemberCore mc)
                {
                        if (mc is Property)
                                return "property";
                        if (mc is Indexer)
                                return "indexer";
                        if (mc is FieldBase)
                                return "field";
                        if (mc is MethodCore)
                                return "method";
                        if (mc is EnumMember)
                                return "enum";
                        if (mc is Event)
                                return "event";

                        return "type";
                }

                Expression SimpleNameResolve (EmitContext ec, Expression right_side, bool intermediate)
                {
                        if (in_transit)
                                return null;

                        in_transit = true;
                        Expression e = DoSimpleNameResolve (ec, right_side, intermediate);
                        in_transit = false;

                        if (e == null)
                                return null;

                        if (ec.CurrentBlock == null || ec.CurrentBlock.CheckInvariantMeaningInBlock (Name, e, Location))
                                return e;

                        return null;
                }

                /// <remarks>
                ///   7.5.2: Simple Names. 
                ///
                ///   Local Variables and Parameters are handled at
                ///   parse time, so they never occur as SimpleNames.
                ///
                ///   The `intermediate' 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 intermediate)
                {
                        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){
                                        if (targs != null) {
                                                Report.Error (307, loc,
                                                              "The variable `{0}' cannot be used with type arguments",
                                                              Name);
                                                return null;
                                        }

                                        LocalVariableReference var = new LocalVariableReference (ec.CurrentBlock, Name, loc);
                                        if (right_side != null) {
                                                return var.ResolveLValue (ec, right_side, loc);
                                        } else {
                                                ResolveFlags rf = ResolveFlags.VariableOrValue;
                                                if (intermediate)
                                                        rf |= ResolveFlags.DisableFlowAnalysis;
                                                return var.Resolve (ec, rf);
                                        }
                                }

                                ParameterReference pref = current_block.Toplevel.GetParameterReference (Name, loc);
                                if (pref != null) {
                                        if (targs != null) {
                                                Report.Error (307, loc,
                                                              "The variable `{0}' cannot be used with type arguments",
                                                              Name);
                                                return null;
                                        }

                                        if (right_side != null)
                                                return pref.ResolveLValue (ec, right_side, loc);
                                        else
                                                return pref.Resolve (ec);
                                }

                                Expression expr = current_block.Toplevel.GetTransparentIdentifier (Name);
                                if (expr != null) {
                                        if (right_side != null)
                                                return expr.ResolveLValue (ec, right_side, loc);
                                        return expr.Resolve (ec);
                                }
                        }
                        
                        //
                        // Stage 2: Lookup members 
                        //

                        Type almost_matched_type = null;
                        ArrayList almost_matched = null;
                        for (DeclSpace lookup_ds = ec.DeclContainer; lookup_ds != null; lookup_ds = lookup_ds.Parent) {
                                // either RootDeclSpace or GenericMethod
                                if (lookup_ds.TypeBuilder == null)
                                        continue;

                                e = MemberLookup (ec.ContainerType, lookup_ds.TypeBuilder, Name, loc);
                                if (e != null) {
                                        PropertyExpr pe = e as PropertyExpr;
                                        if (pe != null) {
                                                AParametersCollection param = TypeManager.GetParameterData (pe.PropertyInfo);

                                                // since TypeManager.MemberLookup doesn't know if we're doing a lvalue access or not,
                                                // it doesn't know which accessor to check permissions against
                                                if (param.IsEmpty && pe.IsAccessibleFrom (ec.ContainerType, right_side != null))
                                                        break;
                                        } else if (e is EventExpr) {
                                                if (((EventExpr) e).IsAccessibleFrom (ec.ContainerType))
                                                        break;
                                        } else {
                                                break;
                                        }
                                        e = null;
                                }

                                if (almost_matched == null && almost_matched_members.Count > 0) {
                                        almost_matched_type = lookup_ds.TypeBuilder;
                                        almost_matched = (ArrayList) almost_matched_members.Clone ();
                                }
                        }

                        if (e == null) {
                                if (almost_matched == null && almost_matched_members.Count > 0) {
                                        almost_matched_type = ec.ContainerType;
                                        almost_matched = (ArrayList) almost_matched_members.Clone ();
                                }
                                e = ResolveAsTypeStep (ec, true);
                        }

                        if (e == null) {
                                if (current_block != null) {
                                        IKnownVariable ikv = current_block.Explicit.GetKnownVariable (Name);
                                        if (ikv != null) {
                                                LocalInfo li = ikv as LocalInfo;
                                                // Supress CS0219 warning
                                                if (li != null)
                                                        li.Used = true;

                                                Error_VariableIsUsedBeforeItIsDeclared (Name);
                                                return null;
                                        }
                                }

                                if (RootContext.EvalMode){
                                        FieldInfo fi = Evaluator.LookupField (Name);
                                        if (fi != null)
                                                return new FieldExpr (fi, loc).Resolve (ec);
                                }

                                if (almost_matched != null)
                                        almost_matched_members = almost_matched;
                                if (almost_matched_type == null)
                                        almost_matched_type = ec.ContainerType;
                                Error_MemberLookupFailed (ec.ContainerType, null, almost_matched_type, Name,
                                        ec.DeclContainer.Name, AllMemberTypes, AllBindingFlags);
                                return null;
                        }

                        if (e is TypeExpr) {
                                if (targs == null)
                                        return e;

                                ConstructedType ct = new ConstructedType (
                                        e.Type, targs, loc);
                                return ct.ResolveAsTypeStep (ec, false);
                        }

                        if (e is MemberExpr) {
                                MemberExpr me = (MemberExpr) e;

                                Expression left;
                                if (me.IsInstance) {
                                        if (ec.IsStatic || ec.IsInFieldInitializer) {
                                                //
                                                // Note that an MemberExpr can be both IsInstance and IsStatic.
                                                // An unresolved MethodGroupExpr can contain both kinds of methods
                                                // and each predicate is true if the MethodGroupExpr contains
                                                // at least one of that kind of method.
                                                //

                                                if (!me.IsStatic &&
                                                    (!intermediate || !IdenticalNameAndTypeName (ec, me, loc))) {
                                                        Error_ObjectRefRequired (ec, loc, me.GetSignatureForError ());
                                                        return null;
                                                }

                                                //
                                                // Pass the buck to MemberAccess and Invocation.
                                                //
                                                left = EmptyExpression.Null;
                                        } else {
                                                left = ec.GetThis (loc);
                                        }
                                } else {
                                        left = new TypeExpression (ec.ContainerType, loc);
                                }

                                me = me.ResolveMemberAccess (ec, left, loc, null);
                                if (me == null)
                                        return null;

                                if (targs != null) {
                                        targs.Resolve (ec);
                                        me.SetTypeArguments (targs);
                                }

                                if (!me.IsStatic && (me.InstanceExpression != null) &&
                                    TypeManager.IsNestedFamilyAccessible (me.InstanceExpression.Type, me.DeclaringType) &&
                                    me.InstanceExpression.Type != me.DeclaringType &&
                                    !TypeManager.IsFamilyAccessible (me.InstanceExpression.Type, me.DeclaringType) &&
                                    (!intermediate || !IdenticalNameAndTypeName (ec, e, loc))) {
                                        Report.Error (38, loc, "Cannot access a nonstatic member of outer type `{0}' via nested type `{1}'",
                                                TypeManager.CSharpName (me.DeclaringType), TypeManager.CSharpName (me.InstanceExpression.Type));
                                        return null;
                                }

                                return (right_side != null)
                                        ? me.DoResolveLValue (ec, right_side)
                                        : me.DoResolve (ec);
                        }

                        return e;
                }
                
                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                        // CloneTo: Nothing, we do not keep any state on this expression
                }
        }

        /// <summary>
        ///   Represents a namespace or a type.  The name of the class was inspired by
        ///   section 10.8.1 (Fully Qualified Names).
        /// </summary>
        public abstract class FullNamedExpression : Expression {

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        throw new NotSupportedException ();
                }

                public override FullNamedExpression ResolveAsTypeStep (IResolveContext ec, bool silent)
                {
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        throw new InternalErrorException ("FullNamedExpression `{0}' found in resolved tree",
                                GetSignatureForError ());
                }
        }
        
        /// <summary>
        ///   Expression that evaluates to a type
        /// </summary>
        public abstract class TypeExpr : FullNamedExpression {
                public override FullNamedExpression ResolveAsTypeStep (IResolveContext ec, bool silent)
                {
                        TypeExpr t = DoResolveAsTypeStep (ec);
                        if (t == null)
                                return null;

                        eclass = ExprClass.Type;
                        return t;
                }

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

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

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

                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;
                }

                protected abstract TypeExpr DoResolveAsTypeStep (IResolveContext ec);

                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 void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        type = storey.MutateType (type);
                }
        }

        /// <summary>
        ///   Fully resolved Expression that already evaluated to a type
        /// </summary>
        public class TypeExpression : TypeExpr {
                public TypeExpression (Type t, Location l)
                {
                        Type = t;
                        eclass = ExprClass.Type;
                        loc = l;
                }

                protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
                {
                        return this;
                }

                public override TypeExpr ResolveAsTypeTerminal (IResolveContext ec, bool silent)
                {
                        return this;
                }
        }

        /// <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 sealed class TypeLookupExpression : TypeExpr {
                readonly string name;
                
                public TypeLookupExpression (string name)
                {
                        this.name = name;
                        eclass = ExprClass.Type;
                }

                public override TypeExpr ResolveAsTypeTerminal (IResolveContext ec, bool silent)
                {
                        // It's null for corlib compilation only
                        if (type == null)
                                return DoResolveAsTypeStep (ec);

                        return this;
                }

                private class UnexpectedType
                {
                }

                // This performes recursive type lookup, providing support for generic types.
                // For example, given the type:
                //
                // System.Collections.Generic.KeyValuePair`2[[System.Int32],[System.String]]
                //
                // The types will be checked in the following order:
                //                                                                             _
                // System                                                                       |
                // System.Collections                                                           |
                // System.Collections.Generic                                                   |
                //                        _                                                     |
                //     System              | recursive call 1                                   |
                //     System.Int32       _|                                                    | main method call
                //                        _                                                     |
                //     System              | recursive call 2                                   |
                //     System.String      _|                                                    |
                //                                                                              |
                // System.Collections.Generic.KeyValuePair`2[[System.Int32],[System.String]]   _|
                //
                private Type TypeLookup (IResolveContext ec, string name)
                {
                        int index = 0;
                        int dot = 0;
                        bool done = false;
                        FullNamedExpression resolved = null;
                        Type type = null;
                        Type recursive_type = null;
                        while (index < name.Length) {
                                if (name[index] == '[') {
                                        int open = index;
                                        int braces = 1;
                                        do {
                                                index++;
                                                if (name[index] == '[')
                                                        braces++;
                                                else if (name[index] == ']')
                                                        braces--;
                                        } while (braces > 0);
                                        recursive_type = TypeLookup (ec, name.Substring (open + 1, index - open - 1));
                                        if (recursive_type == null || (recursive_type == typeof(UnexpectedType)))
                                                return recursive_type;
                                }
                                else {
                                        if (name[index] == ',')
                                                done = true;
                                        else if ((name[index] == '.' && !done) || (index == name.Length && name[0] != '[')) {
                                                string substring = name.Substring(dot, index - dot);

                                                if (resolved == null)
                                                        resolved = RootNamespace.Global.Lookup (ec.DeclContainer, substring, Location.Null);
                                                else if (resolved is Namespace)
                                                    resolved = (resolved as Namespace).Lookup (ec.DeclContainer, substring, Location.Null);
                                                else if (type != null)
                                                        type = TypeManager.GetNestedType (type, substring);
                                                else
                                                        return null;

                                                if (resolved == null)
                                                        return null;
                                                else if (type == null && resolved is TypeExpr)
                                                        type = resolved.Type;

                                                dot = index + 1;
                                        }
                                }
                                index++;
                        }
                        if (name[0] != '[') {
                                string substring = name.Substring(dot, index - dot);

                                if (type != null)
                                        return TypeManager.GetNestedType (type, substring);
                                
                                if (resolved != null) {
                                        resolved = (resolved as Namespace).Lookup (ec.DeclContainer, substring, Location.Null);
                                        if (resolved is TypeExpr)
                                                return resolved.Type;
                                        
                                        if (resolved == null)
                                                return null;
                                        
                                        resolved.Error_UnexpectedKind (ec.DeclContainer, "type", loc);
                                        return typeof (UnexpectedType);
                                }
                                else
                                        return null;
                        }
                        else
                                return recursive_type;
                        }

                protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
                {
                        Type t = TypeLookup (ec, name);
                        if (t == null) {
                                NamespaceEntry.Error_NamespaceNotFound (loc, name);
                                return null;
                        }
                        if (t == typeof(UnexpectedType))
                                return null;
                        type = t;
                        return this;
                }

                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                        // CloneTo: Nothing, we do not keep any state on this expression
                }

                public override string GetSignatureForError ()
                {
                        if (type == null)
                                return TypeManager.CSharpName (name, null);

                        return base.GetSignatureForError ();
                }
        }

        /// <summary>
        ///   Represents an "unbound generic type", ie. typeof (Foo<>).
        ///   See 14.5.11.
        /// </summary>
        public class UnboundTypeExpression : TypeExpr
        {
                MemberName name;

                public UnboundTypeExpression (MemberName name, Location l)
                {
                        this.name = name;
                        loc = l;
                }

                protected override void CloneTo (CloneContext clonectx, Expression target)
                {
                        // Nothing to clone
                }

                protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
                {
                        Expression expr;
                        if (name.Left != null) {
                                Expression lexpr = name.Left.GetTypeExpression ();
                                expr = new MemberAccess (lexpr, name.Basename);
                        } else {
                                expr = new SimpleName (name.Basename, loc);
                        }

                        FullNamedExpression fne = expr.ResolveAsTypeStep (ec, false);
                        if (fne == null)
                                return null;

                        type = fne.Type;
                        return new TypeExpression (type, loc);
                }
        }

        /// <summary>
        ///   This class denotes an expression which evaluates to a member
        ///   of a struct or a class.
        /// </summary>
        public abstract class MemberExpr : Expression
        {
                protected bool is_base;

                /// <summary>
                ///   The name of this member.
                /// </summary>
                public abstract string Name {
                        get;
                }

                //
                // When base.member is used
                //
                public bool IsBase {
                        get { return is_base; }
                        set { is_base = value; }
                }

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

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

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

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

                public static void error176 (Location loc, string name)
                {
                        Report.Error (176, loc, "Static member `{0}' cannot be accessed " +
                                      "with an instance reference, qualify it with a type name instead", name);
                }

                public static void Error_BaseAccessInExpressionTree (Location loc)
                {
                        Report.Error (831, loc, "An expression tree may not contain a base access");
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        if (InstanceExpression != null)
                                InstanceExpression.MutateHoistedGenericType (storey);
                }

                // TODO: possible optimalization
                // Cache resolved constant result in FieldBuilder <-> expression map
                public virtual MemberExpr ResolveMemberAccess (EmitContext ec, Expression left, Location loc,
                                                               SimpleName original)
                {
                        //
                        // Precondition:
                        //   original == null || original.Resolve (...) ==> left
                        //

                        if (left is TypeExpr) {
                                left = left.ResolveAsBaseTerminal (ec, false);
                                if (left == null)
                                        return null;

                                // TODO: Same problem as in class.cs, TypeTerminal does not
                                // always do all necessary checks
                                ObsoleteAttribute oa = AttributeTester.GetObsoleteAttribute (left.Type);
                                if (oa != null && !ec.IsInObsoleteScope) {
                                        AttributeTester.Report_ObsoleteMessage (oa, left.GetSignatureForError (), loc);
                                }

                                ConstructedType ct = left as ConstructedType;
                                if (ct != null && !ct.CheckConstraints (ec))
                                        return null;
                                //

                                if (!IsStatic) {
                                        SimpleName.Error_ObjectRefRequired (ec, loc, GetSignatureForError ());
                                        return null;
                                }

                                return this;
                        }
                                
                        if (!IsInstance) {
                                if (original != null && original.IdenticalNameAndTypeName (ec, left, loc))
                                        return this;

                                return ResolveExtensionMemberAccess (left);
                        }

                        InstanceExpression = left;
                        return this;
                }

                protected virtual MemberExpr ResolveExtensionMemberAccess (Expression left)
                {
                        error176 (loc, GetSignatureForError ());
                        return this;
                }

                protected void EmitInstance (EmitContext ec, bool prepare_for_load)
                {
                        if (IsStatic)
                                return;

                        if (InstanceExpression == EmptyExpression.Null) {
                                SimpleName.Error_ObjectRefRequired (ec, loc, GetSignatureForError ());
                                return;
                        }

                        if (InstanceExpression.Type.IsValueType) {
                                if (InstanceExpression is IMemoryLocation) {
                                        ((IMemoryLocation) InstanceExpression).AddressOf (ec, AddressOp.LoadStore);
                                } else {
                                        LocalTemporary t = new LocalTemporary (InstanceExpression.Type);
                                        InstanceExpression.Emit (ec);
                                        t.Store (ec);
                                        t.AddressOf (ec, AddressOp.Store);
                                }
                        } else
                                InstanceExpression.Emit (ec);

                        if (prepare_for_load)
                                ec.ig.Emit (OpCodes.Dup);
                }

                public virtual void SetTypeArguments (TypeArguments ta)
                {
                        // TODO: need to get correct member type
                        Report.Error (307, loc, "The property `{0}' cannot be used with type arguments",
                                GetSignatureForError ());
                }
        }

        /// 
        /// Represents group of extension methods
        /// 
        public class ExtensionMethodGroupExpr : MethodGroupExpr
        {
                readonly NamespaceEntry namespace_entry;
                public Expression ExtensionExpression;
                Argument extension_argument;

                public ExtensionMethodGroupExpr (ArrayList list, NamespaceEntry n, Type extensionType, Location l)
                        : base (list, extensionType, l)
                {
                        this.namespace_entry = n;
                }

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

                public bool IsTopLevel {
                        get { return namespace_entry == null; }
                }

                public override void EmitArguments (EmitContext ec, ArrayList arguments)
                {
                        if (arguments == null)
                                arguments = new ArrayList (1);                  
                        arguments.Insert (0, extension_argument);
                        base.EmitArguments (ec, arguments);
                }

                public override void EmitCall (EmitContext ec, ArrayList arguments)
                {
                        if (arguments == null)
                                arguments = new ArrayList (1);
                        arguments.Insert (0, extension_argument);
                        base.EmitCall (ec, arguments);
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        extension_argument.Expr.MutateHoistedGenericType (storey);
                        base.MutateHoistedGenericType (storey);
                }

                public override MethodGroupExpr OverloadResolve (EmitContext ec, ref ArrayList arguments, bool may_fail, Location loc)
                {
                        if (arguments == null)
                                arguments = new ArrayList (1);

                        arguments.Insert (0, new Argument (ExtensionExpression));
                        MethodGroupExpr mg = ResolveOverloadExtensions (ec, arguments, namespace_entry, loc);

                        // Store resolved argument and restore original arguments
                        if (mg != null)
                                ((ExtensionMethodGroupExpr)mg).extension_argument = (Argument)arguments [0];
                        arguments.RemoveAt (0);

                        return mg;
                }

                MethodGroupExpr ResolveOverloadExtensions (EmitContext ec, ArrayList arguments, NamespaceEntry ns, Location loc)
                {
                        // Use normal resolve rules
                        MethodGroupExpr mg = base.OverloadResolve (ec, ref arguments, ns != null, loc);
                        if (mg != null)
                                return mg;

                        if (ns == null)
                                return null;

                        // Search continues
                        ExtensionMethodGroupExpr e = ns.LookupExtensionMethod (type, null, Name, loc);
                        if (e == null)
                                return base.OverloadResolve (ec, ref arguments, false, loc);

                        e.ExtensionExpression = ExtensionExpression;
                        e.SetTypeArguments (type_arguments);                    
                        return e.ResolveOverloadExtensions (ec, arguments, e.namespace_entry, loc);
                }               
        }

        /// <summary>
        ///   MethodGroupExpr represents a group of method candidates which
        ///   can be resolved to the best method overload
        /// </summary>
        public class MethodGroupExpr : MemberExpr
        {
                public interface IErrorHandler
                {
                        bool NoExactMatch (EmitContext ec, MethodBase method);
                }

                public IErrorHandler CustomErrorHandler;                
                public MethodBase [] Methods;
                MethodBase best_candidate;
                // TODO: make private
                public TypeArguments type_arguments;
                bool identical_type_name;
                Type delegate_type;
                
                public MethodGroupExpr (MemberInfo [] mi, Type type, Location l)
                        : this (type, l)
                {
                        Methods = new MethodBase [mi.Length];
                        mi.CopyTo (Methods, 0);
                }

                public MethodGroupExpr (ArrayList list, Type type, Location l)
                        : this (type, l)
                {
                        try {
                                Methods = (MethodBase[])list.ToArray (typeof (MethodBase));
                        } catch {
                                foreach (MemberInfo m in list){
                                        if (!(m is MethodBase)){
                                                Console.WriteLine ("Name " + m.Name);
                                                Console.WriteLine ("Found a: " + m.GetType ().FullName);
                                        }
                                }
                                throw;
                        }


                }

                protected MethodGroupExpr (Type type, Location loc)
                {
                        this.loc = loc;
                        eclass = ExprClass.MethodGroup;
                        this.type = type;
                }

                public override Type DeclaringType {
                        get {
                                //
                                // We assume that the top-level type is in the end
                                //
                                return Methods [Methods.Length - 1].DeclaringType;
                                //return Methods [0].DeclaringType;
                        }
                }

                public Type DelegateType {
                        set {
                                delegate_type = value;
                        }
                }

                public bool IdenticalTypeName {
                        get {
                                return identical_type_name;
                        }
                }

                public override string GetSignatureForError ()
                {
                        if (best_candidate != null)
                                return TypeManager.CSharpSignature (best_candidate);
                        
                        return TypeManager.CSharpSignature (Methods [0]);
                }

                public override string Name {
                        get {
                                return Methods [0].Name;
                        }
                }

                public override bool IsInstance {
                        get {
                                if (best_candidate != null)
                                        return !best_candidate.IsStatic;

                                foreach (MethodBase mb in Methods)
                                        if (!mb.IsStatic)
                                                return true;

                                return false;
                        }
                }

                public override bool IsStatic {
                        get {
                                if (best_candidate != null)
                                        return best_candidate.IsStatic;

                                foreach (MethodBase mb in Methods)
                                        if (mb.IsStatic)
                                                return true;

                                return false;
                        }
                }
                
                public static explicit operator ConstructorInfo (MethodGroupExpr mg)
                {
                        return (ConstructorInfo)mg.best_candidate;
                }

                public static explicit operator MethodInfo (MethodGroupExpr mg)
                {
                        return (MethodInfo)mg.best_candidate;
                }

                //
                //  7.4.3.3  Better conversion from expression
                //  Returns :   1    if a->p is better,
                //              2    if a->q is better,
                //              0 if neither is better
                //
                static int BetterExpressionConversion (EmitContext ec, Argument a, Type p, Type q)
                {
                        Type argument_type = TypeManager.TypeToCoreType (a.Type);
                        if (argument_type == TypeManager.anonymous_method_type && RootContext.Version > LanguageVersion.ISO_2) {
                                //
                                // Uwrap delegate from Expression<T>
                                //
                                if (TypeManager.DropGenericTypeArguments (p) == TypeManager.expression_type) {
                                        p = TypeManager.GetTypeArguments (p) [0];
                                }
                                if (TypeManager.DropGenericTypeArguments (q) == TypeManager.expression_type) {
                                        q = TypeManager.GetTypeArguments (q) [0];
                                }
                                
                                p = Delegate.GetInvokeMethod (null, p).ReturnType;
                                q = Delegate.GetInvokeMethod (null, q).ReturnType;
                                if (p == TypeManager.void_type && q != TypeManager.void_type)
                                        return 2;
                                if (q == TypeManager.void_type && p != TypeManager.void_type)
                                        return 1;
                        } else {
                                if (argument_type == p)
                                        return 1;

                                if (argument_type == q)
                                        return 2;
                        }

                        return BetterTypeConversion (ec, p, q);
                }

                //
                // 7.4.3.4  Better conversion from type
                //
                public static int BetterTypeConversion (EmitContext ec, Type p, Type q)
                {
                        if (p == null || q == null)
                                throw new InternalErrorException ("BetterTypeConversion got a null conversion");

                        if (p == TypeManager.int32_type) {
                                if (q == TypeManager.uint32_type || q == TypeManager.uint64_type)
                                        return 1;
                        } else if (p == TypeManager.int64_type) {
                                if (q == TypeManager.uint64_type)
                                        return 1;
                        } else if (p == TypeManager.sbyte_type) {
                                if (q == TypeManager.byte_type || q == TypeManager.ushort_type ||
                                        q == TypeManager.uint32_type || q == TypeManager.uint64_type)
                                        return 1;
                        } else if (p == TypeManager.short_type) {
                                if (q == TypeManager.ushort_type || q == TypeManager.uint32_type ||
                                        q == TypeManager.uint64_type)
                                        return 1;
                        }

                        if (q == TypeManager.int32_type) {
                                if (p == TypeManager.uint32_type || p == TypeManager.uint64_type)
                                        return 2;
                        } if (q == TypeManager.int64_type) {
                                if (p == TypeManager.uint64_type)
                                        return 2;
                        } else if (q == TypeManager.sbyte_type) {
                                if (p == TypeManager.byte_type || p == TypeManager.ushort_type ||
                                        p == TypeManager.uint32_type || p == TypeManager.uint64_type)
                                        return 2;
                        } if (q == TypeManager.short_type) {
                                if (p == TypeManager.ushort_type || p == TypeManager.uint32_type ||
                                        p == TypeManager.uint64_type)
                                        return 2;
                        }

                        // TODO: this is expensive
                        Expression p_tmp = new EmptyExpression (p);
                        Expression q_tmp = new EmptyExpression (q);

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

                        if (p_to_q && !q_to_p)
                                return 1;

                        if (q_to_p && !p_to_q)
                                return 2;

                        return 0;
                }

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

                                Type ct = candidate_pd.Types [c_idx];
                                Type bt = best_pd.Types [b_idx];

                                if (candidate_params && candidate_pd.FixedParameters [c_idx].ModFlags == Parameter.Modifier.PARAMS) 
                                {
                                        ct = TypeManager.GetElementType (ct);
                                        --c_idx;
                                }

                                if (best_params && best_pd.FixedParameters [b_idx].ModFlags == Parameter.Modifier.PARAMS) 
                                {
                                        bt = TypeManager.GetElementType (bt);
                                        --b_idx;
                                }

                                if (ct.Equals (bt))
                                        continue;

                                same = false;
                                int result = BetterExpressionConversion (ec, a, ct, bt);

                                // for each argument, the conversion to 'ct' should be no worse than 
                                // the conversion to 'bt'.
                                if (result == 2)
                                        return false;

                                // for at least one argument, the conversion to 'ct' should be better than 
                                // the conversion to 'bt'.
                                if (result != 0)
                                        better_at_least_one = true;
                        }

                        if (better_at_least_one)
                                return true;

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

                        //
                        // The two methods have equal parameter types.  Now apply tie-breaking rules
                        //
                        if (TypeManager.IsGenericMethod (best) && !TypeManager.IsGenericMethod (candidate))
                                return true;
                        if (!TypeManager.IsGenericMethod (best) && TypeManager.IsGenericMethod (candidate))
                                return false;

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

                        int candidate_param_count = candidate_pd.Count;
                        int best_param_count = best_pd.Count;

                        if (candidate_param_count != best_param_count)
                                // can only happen if (candidate_params && best_params)
                                return candidate_param_count > best_param_count;

                        //
                        // now, both methods have the same number of parameters, and the parameters have the same types
                        // Pick the "more specific" signature
                        //

                        MethodBase orig_candidate = TypeManager.DropGenericMethodArguments (candidate);
                        MethodBase orig_best = TypeManager.DropGenericMethodArguments (best);

                        AParametersCollection orig_candidate_pd = TypeManager.GetParameterData (orig_candidate);
                        AParametersCollection orig_best_pd = TypeManager.GetParameterData (orig_best);

                        bool specific_at_least_once = false;
                        for (int j = 0; j < candidate_param_count; ++j) 
                        {
                                Type ct = orig_candidate_pd.Types [j];
                                Type bt = orig_best_pd.Types [j];
                                if (ct.Equals (bt))
                                        continue;
                                Type specific = MoreSpecific (ct, bt);
                                if (specific == bt)
                                        return false;
                                if (specific == ct)
                                        specific_at_least_once = true;
                        }

                        if (specific_at_least_once)
                                return true;

                        // FIXME: handle lifted operators
                        // ...

                        return false;
                }

                protected override MemberExpr ResolveExtensionMemberAccess (Expression left)
                {
                        if (!IsStatic)
                                return base.ResolveExtensionMemberAccess (left);

                        //
                        // When left side is an expression and at least one candidate method is 
                        // static, it can be extension method
                        //
                        InstanceExpression = left;
                        return this;
                }

                public override MemberExpr ResolveMemberAccess (EmitContext ec, Expression left, Location loc,
                                                                SimpleName original)
                {
                        if (!(left is TypeExpr) &&
                            original != null && original.IdenticalNameAndTypeName (ec, left, loc))
                                identical_type_name = true;

                        return base.ResolveMemberAccess (ec, left, loc, original);
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        if (best_candidate == null) {
                                Report.Error (1953, loc, "An expression tree cannot contain an expression with method group");
                                return null;
                        }

                        if (best_candidate.IsConstructor)
                                return new TypeOfConstructorInfo (best_candidate, loc);

                        IMethodData md = TypeManager.GetMethod (best_candidate);
                        if (md != null && md.IsExcluded ())
                                Report.Error (765, loc,
                                        "Partial methods with only a defining declaration or removed conditional methods cannot be used in an expression tree");
                        
                        return new TypeOfMethodInfo (best_candidate, loc);
                }
                
                override public Expression DoResolve (EmitContext ec)
                {
                        if (InstanceExpression != null) {
                                InstanceExpression = InstanceExpression.DoResolve (ec);
                                if (InstanceExpression == 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 ();
                }
                
                public virtual void EmitArguments (EmitContext ec, ArrayList arguments)
                {
                        Invocation.EmitArguments (ec, arguments, false, null);  
                }
                
                public virtual void EmitCall (EmitContext ec, ArrayList arguments)
                {
                        Invocation.EmitCall (ec, IsBase, InstanceExpression, best_candidate, arguments, loc);                   
                }

                protected virtual void Error_InvalidArguments (EmitContext ec, Location loc, int idx, MethodBase method,
                                                                                                        Argument a, AParametersCollection expected_par, Type paramType)
                {
                        ExtensionMethodGroupExpr emg = this as ExtensionMethodGroupExpr;

                        if (a is CollectionElementInitializer.ElementInitializerArgument) {
                                Report.SymbolRelatedToPreviousError (method);
                                if ((expected_par.FixedParameters [idx].ModFlags & Parameter.Modifier.ISBYREF) != 0) {
                                        Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have 'ref', or `out' modifier",
                                                TypeManager.CSharpSignature (method));
                                        return;
                                }
                                Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
                                          TypeManager.CSharpSignature (method));
                        } else if (delegate_type == null) {
                                Report.SymbolRelatedToPreviousError (method);
                                if (emg != null) {
                                        Report.Error (1928, loc,
                                                "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' has some invalid arguments",
                                                emg.ExtensionExpression.GetSignatureForError (),
                                                emg.Name, TypeManager.CSharpSignature (method));
                                } else {
                                        Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
                                                TypeManager.CSharpSignature (method));
                                }
                        } else
                                Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
                                        TypeManager.CSharpName (delegate_type));

                        Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters [idx].ModFlags;

                        string index = (idx + 1).ToString ();
                        if (((mod & (Parameter.Modifier.REF | Parameter.Modifier.OUT)) ^
                                (a.Modifier & (Parameter.Modifier.REF | Parameter.Modifier.OUT))) != 0) {
                                if ((mod & Parameter.Modifier.ISBYREF) == 0)
                                        Report.Error (1615, loc, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
                                                index, Parameter.GetModifierSignature (a.Modifier));
                                else
                                        Report.Error (1620, loc, "Argument `#{0}' is missing `{1}' modifier",
                                                index, Parameter.GetModifierSignature (mod));
                        } else {
                                string p1 = a.GetSignatureForError ();
                                string p2 = TypeManager.CSharpName (paramType);

                                if (p1 == p2) {
                                        Report.ExtraInformation (loc, "(equally named types possibly from different assemblies in previous ");
                                        Report.SymbolRelatedToPreviousError (a.Expr.Type);
                                        Report.SymbolRelatedToPreviousError (paramType);
                                }

                                if (idx == 0 && emg != null) {
                                        Report.Error (1929, loc,
                                                "Extension method instance type `{0}' cannot be converted to `{1}'", p1, p2);
                                } else {
                                        Report.Error (1503, loc,
                                                "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
                                }
                        }
                }

                public override void Error_ValueCannotBeConverted (EmitContext ec, Location loc, Type target, bool expl)
                {
                        Report.Error (428, loc, "Cannot convert method group `{0}' to non-delegate type `{1}'. Consider using parentheses to invoke the method",
                                Name, TypeManager.CSharpName (target));
                }
                
                protected virtual int GetApplicableParametersCount (MethodBase method, AParametersCollection parameters)
                {
                        return parameters.Count;
                }               

                public static bool IsAncestralType (Type first_type, Type second_type)
                {
                        return first_type != second_type &&
                                (TypeManager.IsSubclassOf (second_type, first_type) ||
                                TypeManager.ImplementsInterface (second_type, first_type));
                }

                ///
                /// Determines if the candidate method is applicable (section 14.4.2.1)
                /// to the given set of arguments
                /// A return value rates candidate method compatibility,
                /// 0 = the best, int.MaxValue = the worst
                ///
                public int IsApplicable (EmitContext ec,
                                                 ArrayList arguments, int arg_count, ref MethodBase method, ref bool params_expanded_form)
                {
                        MethodBase candidate = method;

                        AParametersCollection pd = TypeManager.GetParameterData (candidate);
                        int param_count = GetApplicableParametersCount (candidate, pd);

                        if (arg_count != param_count) {
                                if (!pd.HasParams)
                                        return int.MaxValue - 10000 + Math.Abs (arg_count - param_count);
                                if (arg_count < param_count - 1)
                                        return int.MaxValue - 10000 + Math.Abs (arg_count - param_count);
                        }

#if GMCS_SOURCE
                        //
                        // 1. Handle generic method using type arguments when specified or type inference
                        //
                        if (TypeManager.IsGenericMethod (candidate)) {
                                if (type_arguments != null) {
                                        Type [] g_args = candidate.GetGenericArguments ();
                                        if (g_args.Length != type_arguments.Count)
                                                return int.MaxValue - 20000 + Math.Abs (type_arguments.Count - g_args.Length);

                                        // TODO: Don't create new method, create Parameters only
                                        method = ((MethodInfo) candidate).MakeGenericMethod (type_arguments.Arguments);
                                        candidate = method;
                                        pd = TypeManager.GetParameterData (candidate);
                                } else {
                                        int score = TypeManager.InferTypeArguments (ec, arguments, ref candidate);
                                        if (score != 0)
                                                return score - 20000;

                                        if (TypeManager.IsGenericMethodDefinition (candidate))
                                                throw new InternalErrorException ("A generic method `{0}' definition took part in overload resolution",
                                                        TypeManager.CSharpSignature (candidate));

                                        pd = TypeManager.GetParameterData (candidate);
                                }
                        } else {
                                if (type_arguments != null)
                                        return int.MaxValue - 15000;
                        }
#endif                  

                        //
                        // 2. Each argument has to be implicitly convertible to method parameter
                        //
                        method = candidate;
                        Parameter.Modifier p_mod = 0;
                        Type pt = null;
                        for (int i = 0; i < arg_count; i++) {
                                Argument a = (Argument) arguments [i];
                                Parameter.Modifier a_mod = a.Modifier &
                                        ~(Parameter.Modifier.OUTMASK | Parameter.Modifier.REFMASK);

                                if (p_mod != Parameter.Modifier.PARAMS) {
                                        p_mod = pd.FixedParameters [i].ModFlags & ~(Parameter.Modifier.OUTMASK | Parameter.Modifier.REFMASK);

                                        if (p_mod == Parameter.Modifier.ARGLIST) {
                                                if (a.Type == TypeManager.runtime_argument_handle_type)
                                                        continue;

                                                p_mod = 0;
                                        }

                                        pt = pd.Types [i];
                                } else {
                                        params_expanded_form = true;
                                }

                                int score = 1;
                                if (!params_expanded_form)
                                        score = IsArgumentCompatible (ec, a_mod, a, p_mod & ~Parameter.Modifier.PARAMS, pt);

                                if (score != 0 && (p_mod & Parameter.Modifier.PARAMS) != 0) {
                                        // It can be applicable in expanded form
                                        score = IsArgumentCompatible (ec, a_mod, a, 0, pt.GetElementType ());
                                        if (score == 0)
                                                params_expanded_form = true;
                                }

                                if (score != 0) {
                                        if (params_expanded_form)
                                                ++score;
                                        return (arg_count - i) * 2 + score;
                                }
                        }
                        
                        if (arg_count != param_count)
                                params_expanded_form = true;                    
                        
                        return 0;
                }

                int IsArgumentCompatible (EmitContext ec, Parameter.Modifier arg_mod, Argument argument, Parameter.Modifier param_mod, Type parameter)
                {
                        //
                        // Types have to be identical when ref or out modifer is used 
                        //
                        if (arg_mod != 0 || param_mod != 0) {
                                if (TypeManager.HasElementType (parameter))
                                        parameter = parameter.GetElementType ();

                                Type a_type = argument.Type;
                                if (TypeManager.HasElementType (a_type))
                                        a_type = a_type.GetElementType ();

                                if (a_type != parameter)
                                        return 2;
                        } else {
                                if (delegate_type != null ?
                                        !Delegate.IsTypeCovariant (argument.Expr, parameter) :
                                        !Convert.ImplicitConversionExists (ec, argument.Expr, parameter))
                                        return 2;
                        }

                        if (arg_mod != param_mod)
                                return 1;

                        return 0;
                }

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

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

                        for (int j = 0; j < cand_pd.Count; ++j) 
                        {
                                Parameter.Modifier cm = cand_pd.FixedParameters [j].ModFlags;
                                Parameter.Modifier bm = base_pd.FixedParameters [j].ModFlags;
                                Type ct = cand_pd.Types [j];
                                Type bt = base_pd.Types [j];

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

                        return true;
                }

                public static MethodGroupExpr MakeUnionSet (MethodGroupExpr mg1, MethodGroupExpr mg2, Location loc)
                {
                        if (mg1 == null) {
                                if (mg2 == null)
                                        return null;
                                return mg2;
                        }

                        if (mg2 == null)
                                return mg1;
                        
                        ArrayList all = new ArrayList (mg1.Methods);
                        foreach (MethodBase m in mg2.Methods){
                                if (!TypeManager.ArrayContainsMethod (mg1.Methods, m, false))
                                        all.Add (m);
                        }

                        return new MethodGroupExpr (all, null, loc);
                }               

                static Type MoreSpecific (Type p, Type q)
                {
                        if (TypeManager.IsGenericParameter (p) && !TypeManager.IsGenericParameter (q))
                                return q;
                        if (!TypeManager.IsGenericParameter (p) && TypeManager.IsGenericParameter (q))
                                return p;

                        if (TypeManager.HasElementType (p)) 
                        {
                                Type pe = TypeManager.GetElementType (p);
                                Type qe = TypeManager.GetElementType (q);
                                Type specific = MoreSpecific (pe, qe);
                                if (specific == pe)
                                        return p;
                                if (specific == qe)
                                        return q;
                        } 
                        else if (TypeManager.IsGenericType (p)) 
                        {
                                Type[] pargs = TypeManager.GetTypeArguments (p);
                                Type[] qargs = TypeManager.GetTypeArguments (q);

                                bool p_specific_at_least_once = false;
                                bool q_specific_at_least_once = false;

                                for (int i = 0; i < pargs.Length; i++) 
                                {
                                        Type specific = MoreSpecific (pargs [i], qargs [i]);
                                        if (specific == pargs [i])
                                                p_specific_at_least_once = true;
                                        if (specific == qargs [i])
                                                q_specific_at_least_once = true;
                                }

                                if (p_specific_at_least_once && !q_specific_at_least_once)
                                        return p;
                                if (!p_specific_at_least_once && q_specific_at_least_once)
                                        return q;
                        }

                        return null;
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        base.MutateHoistedGenericType (storey);

                        MethodInfo mi = best_candidate as MethodInfo;
                        if (mi != null) {
                                best_candidate = storey.MutateGenericMethod (mi);
                                return;
                        }

                        best_candidate = storey.MutateConstructor ((ConstructorInfo) this);
                }

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

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

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

                        if (RootContext.Version == LanguageVersion.ISO_1 && Name == "Invoke" && TypeManager.IsDelegateType (DeclaringType)) {
                                if (!may_fail)
                                        Report.Error (1533, loc, "Invoke cannot be called directly on a delegate");
                                return null;
                        }

                        int nmethods = Methods.Length;

                        if (!IsBase) {
                                //
                                // Methods marked 'override' don't take part in 'applicable_type'
                                // computation, nor in the actual overload resolution.
                                // However, they still need to be emitted instead of a base virtual method.
                                // So, we salt them away into the 'candidate_overrides' array.
                                //
                                // In case of reflected methods, we replace each overriding method with
                                // its corresponding base virtual method.  This is to improve compatibility
                                // with non-C# libraries which change the visibility of overrides (#75636)
                                //
                                int j = 0;
                                for (int i = 0; i < Methods.Length; ++i) {
                                        MethodBase m = Methods [i];
                                        if (TypeManager.IsOverride (m)) {
                                                if (candidate_overrides == null)
                                                        candidate_overrides = new ArrayList ();
                                                candidate_overrides.Add (m);
                                                m = TypeManager.TryGetBaseDefinition (m);
                                        }
                                        if (m != null)
                                                Methods [j++] = m;
                                }
                                nmethods = j;
                        }

                        //
                        // Enable message recording, it's used mainly by lambda expressions
                        //
                        Report.IMessageRecorder msg_recorder = new Report.MessageRecorder ();
                        Report.IMessageRecorder prev_recorder = Report.SetMessageRecorder (msg_recorder);

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

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

                                //
                                // Check if candidate is applicable (section 14.4.2.1)
                                //
                                bool params_expanded_form = false;
                                int candidate_rate = IsApplicable (ec, Arguments, arg_count, ref Methods [i], ref params_expanded_form);

                                if (candidate_rate < best_candidate_rate) {
                                        best_candidate_rate = candidate_rate;
                                        best_candidate = Methods [i];
                                }
                                
                                if (params_expanded_form) {
                                        if (candidate_to_form == null)
                                                candidate_to_form = new PtrHashtable ();
                                        MethodBase candidate = Methods [i];
                                        candidate_to_form [candidate] = candidate;
                                }

                                if (candidate_rate != 0) {
                                        if (msg_recorder != null)
                                                msg_recorder.EndSession ();
                                        continue;
                                }

                                msg_recorder = null;
                                candidates.Add (Methods [i]);

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

                        Report.SetMessageRecorder (prev_recorder);
                        if (msg_recorder != null && !msg_recorder.IsEmpty) {
                                if (!may_fail)
                                        msg_recorder.PrintMessages ();

                                return null;
                        }
                        
                        int candidate_top = candidates.Count;

                        if (applicable_type == null) {
                                //
                                // When we found a top level method which does not match and it's 
                                // not an extension method. We start extension methods lookup from here
                                //
                                if (InstanceExpression != null) {
                                        ExtensionMethodGroupExpr ex_method_lookup = ec.TypeContainer.LookupExtensionMethod (type, Name, loc);
                                        if (ex_method_lookup != null) {
                                                ex_method_lookup.ExtensionExpression = InstanceExpression;
                                                ex_method_lookup.SetTypeArguments (type_arguments);
                                                return ex_method_lookup.OverloadResolve (ec, ref Arguments, may_fail, loc);
                                        }
                                }
                                
                                if (may_fail)
                                        return null;

                                //
                                // Okay so we have failed to find exact match so we
                                // return error info about the closest match
                                //
                                if (best_candidate != null) {
                                        if (CustomErrorHandler != null) {
                                                if (CustomErrorHandler.NoExactMatch (ec, best_candidate))
                                                        return null;
                                        }

                                        AParametersCollection pd = TypeManager.GetParameterData (best_candidate);
                                        bool cand_params = candidate_to_form != null && candidate_to_form.Contains (best_candidate);
                                        if (arg_count == pd.Count || pd.HasParams) {
                                                if (TypeManager.IsGenericMethodDefinition (best_candidate)) {
                                                        if (type_arguments == null) {
                                                                Report.Error (411, loc,
                                                                        "The type arguments for method `{0}' cannot be inferred from " +
                                                                        "the usage. Try specifying the type arguments explicitly",
                                                                        TypeManager.CSharpSignature (best_candidate));
                                                                return null;
                                                        }
                                                                
                                                        Type [] g_args = TypeManager.GetGenericArguments (best_candidate);
                                                        if (type_arguments.Count != g_args.Length) {
                                                                Report.SymbolRelatedToPreviousError (best_candidate);
                                                                Report.Error (305, loc, "Using the generic method `{0}' requires `{1}' type argument(s)",
                                                                        TypeManager.CSharpSignature (best_candidate),
                                                                        g_args.Length.ToString ());
                                                                return null;
                                                        }
                                                } else {
                                                        if (type_arguments != null && !TypeManager.IsGenericMethod (best_candidate)) {
                                                                Namespace.Error_TypeArgumentsCannotBeUsed (best_candidate, loc);
                                                                return null;
                                                        }
                                                }
                                                
                                                if (!VerifyArgumentsCompat (ec, ref Arguments, arg_count, best_candidate, cand_params, may_fail, loc))
                                                        return null;
                                        }
                                }

                                if (almost_matched_members.Count != 0) {
                                        Error_MemberLookupFailed (ec.ContainerType, type, type, ".ctor",
                                        null, MemberTypes.Constructor, AllBindingFlags);
                                        return null;
                                }
                                
                                //
                                // We failed to find any method with correct argument count
                                //
                                if (Name == ConstructorInfo.ConstructorName) {
                                        Report.SymbolRelatedToPreviousError (type);
                                        Report.Error (1729, loc,
                                                "The type `{0}' does not contain a constructor that takes `{1}' arguments",
                                                TypeManager.CSharpName (type), arg_count);
                                } else {
                                        Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
                                                Name, arg_count.ToString ());
                                }
                                
                                return null;
                        }

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

                                int finalized = 0; // Number of finalized candidates

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

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

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

                                                if (IsAncestralType (decl_type, applicable_type))
                                                        continue;

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

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

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

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

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

                        best_candidate = (MethodBase) candidates [0];
                        if (delegate_type == null)
                                method_params = candidate_to_form != null && candidate_to_form.Contains (best_candidate);

                        for (int ix = 1; ix < candidate_top; ix++) {
                                MethodBase candidate = (MethodBase) candidates [ix];

                                if (candidate == best_candidate)
                                        continue;

                                bool cand_params = candidate_to_form != null && candidate_to_form.Contains (candidate);

                                if (BetterFunction (ec, Arguments, arg_count, 
                                        candidate, cand_params,
                                        best_candidate, method_params)) {
                                        best_candidate = candidate;
                                        method_params = cand_params;
                                }
                        }
                        //
                        // Now check that there are no ambiguities i.e the selected method
                        // should be better than all the others
                        //
                        MethodBase ambiguous = null;
                        for (int ix = 1; ix < candidate_top; ix++) {
                                MethodBase candidate = (MethodBase) candidates [ix];

                                if (candidate == best_candidate)
                                        continue;

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

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

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

                                if (candidate_overrides != null) {
                                        Type[] gen_args = null;
                                        bool gen_override = false;
                                        if (TypeManager.IsGenericMethod (best_candidate))
                                                gen_args = TypeManager.GetGenericArguments (best_candidate);

                                        foreach (MethodBase candidate in candidate_overrides) {
                                                if (TypeManager.IsGenericMethod (candidate)) {
                                                        if (gen_args == null)
                                                                continue;

                                                        if (gen_args.Length != TypeManager.GetGenericArguments (candidate).Length)
                                                                continue;
                                                } else {
                                                        if (gen_args != null)
                                                                continue;
                                                }
                                                
                                                if (IsOverride (candidate, best_candidate)) {
                                                        gen_override = true;
                                                        best_candidate = candidate;
                                                }
                                        }

                                        if (gen_override && gen_args != null) {
#if GMCS_SOURCE
                                                best_candidate = ((MethodInfo) best_candidate).MakeGenericMethod (gen_args);
#endif                                          
                                        }
                                }
                        }

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

                        if (best_candidate == null)
                                return null;

                        MethodBase the_method = TypeManager.DropGenericMethodArguments (best_candidate);
#if GMCS_SOURCE
                        if (the_method.IsGenericMethodDefinition &&
                            !ConstraintChecker.CheckConstraints (ec, the_method, best_candidate, loc))
                                return null;
#endif

                        //
                        // Check ObsoleteAttribute on the best method
                        //
                        ObsoleteAttribute oa = AttributeTester.GetMethodObsoleteAttribute (the_method);
                        if (oa != null && !ec.IsInObsoleteScope)
                                AttributeTester.Report_ObsoleteMessage (oa, GetSignatureForError (), loc);

                        IMethodData data = TypeManager.GetMethod (the_method);
                        if (data != null)
                                data.SetMemberIsUsed ();

                        return this;
                }
                
                public override void SetTypeArguments (TypeArguments ta)
                {
                        type_arguments = ta;
                }

                public bool VerifyArgumentsCompat (EmitContext ec, ref ArrayList arguments,
                                                          int arg_count, MethodBase method,
                                                          bool chose_params_expanded,
                                                          bool may_fail, Location loc)
                {
                        AParametersCollection pd = TypeManager.GetParameterData (method);

                        int errors = Report.Errors;
                        Parameter.Modifier p_mod = 0;
                        Type pt = null;
                        int a_idx = 0, a_pos = 0;
                        Argument a = null;
                        ArrayList params_initializers = null;
                        bool has_unsafe_arg = false;

                        for (; a_idx < arg_count; a_idx++, ++a_pos) {
                                a = (Argument) arguments [a_idx];
                                if (p_mod != Parameter.Modifier.PARAMS) {
                                        p_mod = pd.FixedParameters [a_idx].ModFlags;
                                        pt = pd.Types [a_idx];
                                        has_unsafe_arg |= pt.IsPointer;

                                        if (p_mod == Parameter.Modifier.ARGLIST) {
                                                if (a.Type != TypeManager.runtime_argument_handle_type)
                                                        break;
                                                continue;
                                        }

                                        if (p_mod == Parameter.Modifier.PARAMS) {
                                                if (chose_params_expanded) {
                                                        params_initializers = new ArrayList (arg_count - a_idx);
                                                        pt = TypeManager.GetElementType (pt);
                                                }
                                        }
                                }

                                //
                                // Types have to be identical when ref or out modifer is used 
                                //
                                if (a.Modifier != 0 || (p_mod & ~Parameter.Modifier.PARAMS) != 0) {
                                        if ((p_mod & ~Parameter.Modifier.PARAMS) != a.Modifier)
                                                break;

                                        if (!TypeManager.IsEqual (a.Expr.Type, pt))
                                                break;

                                        continue;
                                }

                                Expression conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
                                if (conv == null)
                                        break;

                                //
                                // Convert params arguments to an array initializer
                                //
                                if (params_initializers != null) {
                                        // we choose to use 'a.Expr' rather than 'conv' so that
                                        // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
                                        params_initializers.Add (a.Expr);
                                        arguments.RemoveAt (a_idx--);
                                        --arg_count;
                                        continue;
                                }

                                // Update the argument with the implicit conversion
                                a.Expr = conv;
                        }

                        //
                        // Fill not provided arguments required by params modifier
                        //
                        if (params_initializers == null && pd.HasParams && arg_count < pd.Count && a_idx + 1 == pd.Count) {
                                if (arguments == null)
                                        arguments = new ArrayList (1);

                                pt = pd.Types [GetApplicableParametersCount (method, pd) - 1];
                                pt = TypeManager.GetElementType (pt);
                                has_unsafe_arg |= pt.IsPointer;
                                params_initializers = new ArrayList (0);
                        }

                        if (a_idx == arg_count) {
                                //
                                // Append an array argument with all params arguments
                                //
                                if (params_initializers != null) {
                                        arguments.Add (new Argument (
                                                new ArrayCreation (new TypeExpression (pt, loc), "[]",
                                                params_initializers, loc).Resolve (ec)));
                                }

                                if (has_unsafe_arg && !ec.InUnsafe) {
                                        if (!may_fail)
                                                UnsafeError (loc);
                                        return false;
                                }

                                return true;
                        }

                        if (!may_fail && Report.Errors == errors) {
                                if (CustomErrorHandler != null)
                                        CustomErrorHandler.NoExactMatch (ec, best_candidate);
                                else
                                        Error_InvalidArguments (ec, loc, a_pos, method, a, pd, pt);
                        }
                        return false;
                }
        }

        public class ConstantExpr : MemberExpr
        {
                FieldInfo constant;

                public ConstantExpr (FieldInfo constant, Location loc)
                {
                        this.constant = constant;
                        this.loc = loc;
                }

                public override string Name {
                        get { throw new NotImplementedException (); }
                }

                public override bool IsInstance {
                        get { return !IsStatic; }
                }

                public override bool IsStatic {
                        get { return constant.IsStatic; }
                }

                public override Type DeclaringType {
                        get { return constant.DeclaringType; }
                }

                public override MemberExpr ResolveMemberAccess (EmitContext ec, Expression left, Location loc, SimpleName original)
                {
                        constant = TypeManager.GetGenericFieldDefinition (constant);

                        IConstant ic = TypeManager.GetConstant (constant);
                        if (ic == null) {
                                if (constant.IsLiteral) {
                                        ic = new ExternalConstant (constant);
                                } else {
                                        ic = ExternalConstant.CreateDecimal (constant);
                                        // HACK: decimal field was not resolved as constant
                                        if (ic == null)
                                                return new FieldExpr (constant, loc).ResolveMemberAccess (ec, left, loc, original);
                                }
                                TypeManager.RegisterConstant (constant, ic);
                        }

                        return base.ResolveMemberAccess (ec, left, loc, original);
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        IConstant ic = TypeManager.GetConstant (constant);
                        if (ic.ResolveValue ()) {
                                if (!ec.IsInObsoleteScope)
                                        ic.CheckObsoleteness (loc);
                        }

                        return ic.CreateConstantReference (loc);
                }

                public override void Emit (EmitContext ec)
                {
                        throw new NotSupportedException ();
                }

                public override string GetSignatureForError ()
                {
                        return TypeManager.GetFullNameSignature (constant);
                }
        }

        /// <summary>
        ///   Fully resolved expression that evaluates to a Field
        /// </summary>
        public class FieldExpr : MemberExpr, IAssignMethod, IMemoryLocation, IVariableReference {
                public FieldInfo FieldInfo;
                readonly Type constructed_generic_type;
                VariableInfo variable_info;
                
                LocalTemporary temp;
                bool prepared;
                
                public FieldExpr (FieldInfo fi, Location l)
                {
                        FieldInfo = fi;
                        type = TypeManager.TypeToCoreType (fi.FieldType);
                        loc = l;
                }

                public FieldExpr (FieldInfo fi, Type genericType, Location l)
                        : this (fi, l)
                {
                        this.constructed_generic_type = genericType;
                }

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

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

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

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

                public override string GetSignatureForError ()
                {
                        return TypeManager.GetFullNameSignature (FieldInfo);
                }

                public VariableInfo VariableInfo {
                        get {
                                return variable_info;
                        }
                }

                public override MemberExpr ResolveMemberAccess (EmitContext ec, Expression left, Location loc,
                                                                SimpleName original)
                {
                        FieldInfo fi = TypeManager.GetGenericFieldDefinition (FieldInfo);
                        Type t = fi.FieldType;

                        if (t.IsPointer && !ec.InUnsafe) {
                                UnsafeError (loc);
                        }

                        return base.ResolveMemberAccess (ec, left, loc, original);
                }

                public void SetHasAddressTaken ()
                {
                        IVariableReference vr = InstanceExpression as IVariableReference;
                        if (vr != null)
                                vr.SetHasAddressTaken ();
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        Expression instance;
                        if (InstanceExpression == null) {
                                instance = new NullLiteral (loc);
                        } else {
                                instance = InstanceExpression.CreateExpressionTree (ec);
                        }

                        ArrayList args = new ArrayList (2);
                        args.Add (new Argument (instance));
                        args.Add (new Argument (CreateTypeOfExpression ()));
                        return CreateExpressionFactoryCall ("Field", args);
                }

                public Expression CreateTypeOfExpression ()
                {
                        return new TypeOfField (FieldInfo, loc);
                }

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

                Expression DoResolve (EmitContext ec, bool lvalue_instance, bool out_access)
                {
                        if (!FieldInfo.IsStatic){
                                if (InstanceExpression == null){
                                        //
                                        // This can happen when referencing an instance field using
                                        // a fully qualified type expression: TypeName.InstanceField = xxx
                                        // 
                                        SimpleName.Error_ObjectRefRequired (ec, loc, GetSignatureForError ());
                                        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.

                                if (lvalue_instance) {
                                        using (ec.With (EmitContext.Flags.DoFlowAnalysis, false)) {
                                                Expression right_side =
                                                        out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
                                                InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side, loc);
                                        }
                                } else {
                                        ResolveFlags rf = ResolveFlags.VariableOrValue | ResolveFlags.DisableFlowAnalysis;
                                        InstanceExpression = InstanceExpression.Resolve (ec, rf);
                                }

                                if (InstanceExpression == null)
                                        return null;

                                using (ec.Set (EmitContext.Flags.OmitStructFlowAnalysis)) {
                                        InstanceExpression.CheckMarshalByRefAccess (ec);
                                }
                        }

                        // TODO: the code above uses some non-standard multi-resolve rules
                        if (eclass != ExprClass.Invalid)
                                return this;

                        if (!ec.IsInObsoleteScope) {
                                FieldBase f = TypeManager.GetField (FieldInfo);
                                if (f != null) {
                                        f.CheckObsoleteness (loc);
                                } else {
                                        ObsoleteAttribute oa = AttributeTester.GetMemberObsoleteAttribute (FieldInfo);
                                        if (oa != null)
                                                AttributeTester.Report_ObsoleteMessage (oa, TypeManager.GetFullNameSignature (FieldInfo), loc);
                                }
                        }

                        IFixedBuffer fb = AttributeTester.GetFixedBuffer (FieldInfo);
                        IVariableReference var = InstanceExpression as IVariableReference;
                        
                        if (fb != null) {
                                IFixedExpression fe = InstanceExpression as IFixedExpression;
                                if (!ec.InFixedInitializer && (fe == null || !fe.IsFixed)) {
                                        Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
                                }

                                if (InstanceExpression.eclass != ExprClass.Variable) {
                                        Report.SymbolRelatedToPreviousError (FieldInfo);
                                        Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
                                                TypeManager.GetFullNameSignature (FieldInfo));
                                } else if (var != null && var.IsHoisted) {
                                        AnonymousMethodExpression.Error_AddressOfCapturedVar (var, loc);
                                }
                                
                                return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
                        }

                        eclass = ExprClass.Variable;

                        // If the instance expression is a local variable or parameter.
                        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);
                        eclass = ExprClass.Variable;
                        return this;
                }

                static readonly int [] codes = {
                        191,    // instance, write access
                        192,    // instance, out access
                        198,    // static, write access
                        199,    // static, out access
                        1648,   // member of value instance, write access
                        1649,   // member of value instance, out access
                        1650,   // member of value static, write access
                        1651    // member of value static, out access
                };

                static readonly string [] msgs = {
                        /*0191*/ "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
                        /*0192*/ "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
                        /*0198*/ "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
                        /*0199*/ "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
                        /*1648*/ "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
                        /*1649*/ "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
                        /*1650*/ "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
                        /*1651*/ "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)"
                };

                // The return value is always null.  Returning a value simplifies calling code.
                Expression Report_AssignToReadonly (Expression right_side)
                {
                        int i = 0;
                        if (right_side == EmptyExpression.OutAccess || right_side == EmptyExpression.LValueMemberOutAccess)
                                i += 1;
                        if (IsStatic)
                                i += 2;
                        if (right_side == EmptyExpression.LValueMemberAccess || right_side == EmptyExpression.LValueMemberOutAccess)
                                i += 4;
                        Report.Error (codes [i], loc, msgs [i], GetSignatureForError ());

                        return null;
                }
                
                override public Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        IVariableReference var = InstanceExpression as IVariableReference;
                        if (var != null && var.VariableInfo != null)
                                var.VariableInfo.SetFieldAssigned (ec, FieldInfo.Name);

                        bool lvalue_instance = !FieldInfo.IsStatic && FieldInfo.DeclaringType.IsValueType;
                        bool out_access = right_side == EmptyExpression.OutAccess || right_side == EmptyExpression.LValueMemberOutAccess;

                        Expression e = DoResolve (ec, lvalue_instance, out_access);

                        if (e == null)
                                return null;

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

                        if (FieldInfo.IsInitOnly) {
                                // InitOnly fields can only be assigned in constructors or initializers
                                if (!ec.IsInFieldInitializer && !ec.IsConstructor)
                                        return Report_AssignToReadonly (right_side);

                                if (ec.IsConstructor) {
                                        Type ctype = ec.TypeContainer.CurrentType;
                                        if (ctype == null)
                                                ctype = ec.ContainerType;

                                        // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
                                        if (!TypeManager.IsEqual (ctype, FieldInfo.DeclaringType))
                                                return Report_AssignToReadonly (right_side);
                                        // static InitOnly fields cannot be assigned-to in an instance constructor
                                        if (IsStatic && !ec.IsStatic)
                                                return Report_AssignToReadonly (right_side);
                                        // instance constructors can't modify InitOnly fields of other instances of the same type
                                        if (!IsStatic && !(InstanceExpression is This))
                                                return Report_AssignToReadonly (right_side);
                                }
                        }

                        if (right_side == EmptyExpression.OutAccess &&
                            !IsStatic && !(InstanceExpression is This) && TypeManager.mbr_type != null && TypeManager.IsSubclassOf (DeclaringType, TypeManager.mbr_type)) {
                                Report.SymbolRelatedToPreviousError (DeclaringType);
                                Report.Warning (197, 1, loc,
                                                "Passing `{0}' as ref or out or taking its address may cause a runtime exception because it is a field of a marshal-by-reference class",
                                                GetSignatureForError ());
                        }

                        eclass = ExprClass.Variable;
                        return this;
                }

                bool is_marshal_by_ref ()
                {
                        return !IsStatic && Type.IsValueType && TypeManager.mbr_type != null && TypeManager.IsSubclassOf (DeclaringType, TypeManager.mbr_type);
                }

                public override void CheckMarshalByRefAccess (EmitContext ec)
                {
                        if (is_marshal_by_ref () && !(InstanceExpression is This)) {
                                Report.SymbolRelatedToPreviousError (DeclaringType);
                                Report.Warning (1690, 1, loc, "Cannot call methods, properties, or indexers on `{0}' because it is a value type member of a marshal-by-reference class",
                                                GetSignatureForError ());
                        }
                }

                public override int GetHashCode ()
                {
                        return FieldInfo.GetHashCode ();
                }
                
                public bool IsFixed {
                        get {
                                //
                                // A variable of the form V.I is fixed when V is a fixed variable of a struct type
                                //
                                IVariableReference variable = InstanceExpression as IVariableReference;
                                return variable != null && InstanceExpression.Type.IsValueType && variable.IsFixed;
                        }
                }

                public bool IsHoisted {
                        get {
                                IVariableReference hv = InstanceExpression as IVariableReference;
                                return hv != null && hv.IsHoisted;
                        }
                }

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

                        if (FieldInfo != fe.FieldInfo)
                                return false;

                        if (InstanceExpression == null || fe.InstanceExpression == null)
                                return true;

                        return InstanceExpression.Equals (fe.InstanceExpression);
                }
                
                public void Emit (EmitContext ec, bool leave_copy)
                {
                        ILGenerator ig = ec.ig;
                        bool is_volatile = false;

                        FieldBase f = TypeManager.GetField (FieldInfo);
                        if (f != null){
                                if ((f.ModFlags & Modifiers.VOLATILE) != 0)
                                        is_volatile = true;

                                f.SetMemberIsUsed ();
                        }
                        
                        if (FieldInfo.IsStatic){
                                if (is_volatile)
                                        ig.Emit (OpCodes.Volatile);

                                ig.Emit (OpCodes.Ldsfld, GetConstructedFieldInfo ());
                        } else {
                                if (!prepared)
                                        EmitInstance (ec, false);

                                IFixedBuffer ff = AttributeTester.GetFixedBuffer (FieldInfo);
                                if (ff != null) {
                                        ig.Emit (OpCodes.Ldflda, GetConstructedFieldInfo ());
                                        ig.Emit (OpCodes.Ldflda, ff.Element);
                                } else {
                                        if (is_volatile)
                                                ig.Emit (OpCodes.Volatile);

                                        ig.Emit (OpCodes.Ldfld, GetConstructedFieldInfo ());
                                }
                        }

                        if (leave_copy) {
                                ec.ig.Emit (OpCodes.Dup);
                                if (!FieldInfo.IsStatic) {
                                        temp = new LocalTemporary (this.Type);
                                        temp.Store (ec);
                                }
                        }
                }

                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool prepare_for_load)
                {
                        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 (source);
                                return;
                        }

                        prepared = prepare_for_load;
                        EmitInstance (ec, prepared);

                        source.Emit (ec);                       
                        if (leave_copy) {
                                ec.ig.Emit (OpCodes.Dup);
                                if (!FieldInfo.IsStatic) {
                                        temp = new LocalTemporary (this.Type);
                                        temp.Store (ec);
                                }
                        }

                        FieldBase f = TypeManager.GetField (FieldInfo);
                        if (f != null){
                                if ((f.ModFlags & Modifiers.VOLATILE) != 0)
                                        ig.Emit (OpCodes.Volatile);
                                        
                                f.SetAssigned ();
                        }

                        if (is_static)
                                ig.Emit (OpCodes.Stsfld, GetConstructedFieldInfo ());
                        else
                                ig.Emit (OpCodes.Stfld, GetConstructedFieldInfo ());
                        
                        if (temp != null) {
                                temp.Emit (ec);
                                temp.Release (ec);
                                temp = null;
                        }
                }

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

                public override void EmitSideEffect (EmitContext ec)
                {
                        FieldBase f = TypeManager.GetField (FieldInfo);
                        bool is_volatile = f != null && (f.ModFlags & Modifiers.VOLATILE) != 0;

                        if (is_volatile || is_marshal_by_ref ())
                                base.EmitSideEffect (ec);
                }

                public override void Error_VariableIsUsedBeforeItIsDeclared (string name)
                {
                        Report.Error (844, loc,
                                "A local variable `{0}' cannot be used before it is declared. Consider renaming the local variable when it hides the field `{1}'",
                                name, GetSignatureForError ());
                }

                public void AddressOf (EmitContext ec, AddressOp mode)
                {
                        ILGenerator ig = ec.ig;

                        FieldBase f = TypeManager.GetField (FieldInfo);
                        if (f != null){
                                if ((f.ModFlags & Modifiers.VOLATILE) != 0){
                                        Report.Warning (420, 1, loc, "`{0}': A volatile field references will not be treated as volatile", 
                                                        f.GetSignatureForError ());
                                }
                                        
                                if ((mode & AddressOp.Store) != 0)
                                        f.SetAssigned ();
                                if ((mode & AddressOp.Load) != 0)
                                        f.SetMemberIsUsed ();
                        }

                        //
                        // 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, GetConstructedFieldInfo ());
                        } else {
                                if (!prepared)
                                        EmitInstance (ec, false);
                                ig.Emit (OpCodes.Ldflda, GetConstructedFieldInfo ());
                        }
                }

                FieldInfo GetConstructedFieldInfo ()
                {
                        if (constructed_generic_type == null)
                                return FieldInfo;
#if GMCS_SOURCE
                        return TypeBuilder.GetField (constructed_generic_type, FieldInfo);
#else
                        throw new NotSupportedException ();
#endif                  
                }
                
                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        FieldInfo = storey.MutateField (FieldInfo);
                        base.MutateHoistedGenericType (storey);
                }               
        }

        
        /// <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 : MemberExpr, IAssignMethod {
                public readonly PropertyInfo PropertyInfo;
                MethodInfo getter, setter;
                bool is_static;

                bool resolved;
                
                LocalTemporary temp;
                bool prepared;

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

                        type = TypeManager.TypeToCoreType (pi.PropertyType);

                        ResolveAccessors (container_type);
                }

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

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

                public override bool IsStatic {
                        get {
                                return is_static;
                        }
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        ArrayList args;
                        if (IsSingleDimensionalArrayLength ()) {
                                args = new ArrayList (1);
                                args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
                                return CreateExpressionFactoryCall ("ArrayLength", args);
                        }

                        if (is_base) {
                                Error_BaseAccessInExpressionTree (loc);
                                return null;
                        }

                        args = new ArrayList (2);
                        if (InstanceExpression == null)
                                args.Add (new Argument (new NullLiteral (loc)));
                        else
                                args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
                        args.Add (new Argument (new TypeOfMethodInfo (getter, loc)));
                        return CreateExpressionFactoryCall ("Property", args);
                }

                public Expression CreateSetterTypeOfExpression ()
                {
                        return new TypeOfMethodInfo (setter, loc);
                }

                public override Type DeclaringType {
                        get {
                                return PropertyInfo.DeclaringType;
                        }
                }

                public override string GetSignatureForError ()
                {
                        return TypeManager.GetFullNameSignature (PropertyInfo);
                }

                void FindAccessors (Type invocation_type)
                {
                        const 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, null);

                                if (group == null)
                                        continue;

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

                                PropertyInfo pi = (PropertyInfo) group [0];

                                if (getter == null)
                                        getter = pi.GetGetMethod (true);

                                if (setter == null)
                                        setter = pi.GetSetMethod (true);

                                MethodInfo accessor = getter != null ? getter : setter;

                                if (!accessor.IsVirtual)
                                        return;
                        }
                }

                //
                // We also perform the permission checking here, as the PropertyInfo does not
                // hold the information for the accessibility of its setter/getter
                //
                // TODO: Refactor to use some kind of cache together with GetPropertyFromAccessor
                void ResolveAccessors (Type container_type)
                {
                        FindAccessors (container_type);

                        if (getter != null) {
                                MethodBase the_getter = TypeManager.DropGenericMethodArguments (getter);
                                IMethodData md = TypeManager.GetMethod (the_getter);
                                if (md != null)
                                        md.SetMemberIsUsed ();

                                is_static = getter.IsStatic;
                        }

                        if (setter != null) {
                                MethodBase the_setter = TypeManager.DropGenericMethodArguments (setter);
                                IMethodData md = TypeManager.GetMethod (the_setter);
                                if (md != null)
                                        md.SetMemberIsUsed ();

                                is_static = setter.IsStatic;
                        }
                }

                public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                {
                        if (InstanceExpression != null)
                                InstanceExpression.MutateHoistedGenericType (storey);

                        type = storey.MutateType (type);
                        if (getter != null)
                                getter = storey.MutateGenericMethod (getter);
                        if (setter != null)
                                setter = storey.MutateGenericMethod (setter);
                }

                bool InstanceResolve (EmitContext ec, bool lvalue_instance, bool must_do_cs1540_check)
                {
                        if (is_static) {
                                InstanceExpression = null;
                                return true;
                        }

                        if (InstanceExpression == null) {
                                SimpleName.Error_ObjectRefRequired (ec, loc, GetSignatureForError ());
                                return false;
                        }

                        InstanceExpression = InstanceExpression.DoResolve (ec);
                        if (lvalue_instance && InstanceExpression != null)
                                InstanceExpression = InstanceExpression.ResolveLValue (ec, EmptyExpression.LValueMemberAccess, loc);

                        if (InstanceExpression == null)
                                return false;

                        InstanceExpression.CheckMarshalByRefAccess (ec);

                        if (must_do_cs1540_check && (InstanceExpression != EmptyExpression.Null) &&
                            !TypeManager.IsInstantiationOfSameGenericType (InstanceExpression.Type, ec.ContainerType) &&
                            !TypeManager.IsNestedChildOf (ec.ContainerType, InstanceExpression.Type) &&
                            !TypeManager.IsSubclassOf (InstanceExpression.Type, ec.ContainerType)) {
                                Report.SymbolRelatedToPreviousError (PropertyInfo);
                                Error_CannotAccessProtected (loc, PropertyInfo, InstanceExpression.Type, ec.ContainerType);
                                return false;
                        }

                        return true;
                }

                void Error_PropertyNotFound (MethodInfo mi, bool getter)
                {
                        // TODO: correctly we should compare arguments but it will lead to bigger changes
                        if (mi is MethodBuilder) {
                                Error_TypeDoesNotContainDefinition (loc, PropertyInfo.DeclaringType, Name);
                                return;
                        }
                        
                        StringBuilder sig = new StringBuilder (TypeManager.CSharpName (mi.DeclaringType));
                        sig.Append ('.');
                        AParametersCollection iparams = TypeManager.GetParameterData (mi);
                        sig.Append (getter ? "get_" : "set_");
                        sig.Append (Name);
                        sig.Append (iparams.GetSignatureForError ());

                        Report.SymbolRelatedToPreviousError (mi);
                        Report.Error (1546, loc, "Property `{0}' is not supported by the C# language. Try to call the accessor method `{1}' directly",
                                Name, sig.ToString ());
                }

                public bool IsAccessibleFrom (Type invocation_type, bool lvalue)
                {
                        bool dummy;
                        MethodInfo accessor = lvalue ? setter : getter;
                        if (accessor == null && lvalue)
                                accessor = getter;
                        return accessor != null && IsAccessorAccessible (invocation_type, accessor, out dummy);
                }

                bool IsSingleDimensionalArrayLength ()
                {
                        if (DeclaringType != TypeManager.array_type || getter == null || Name != "Length")
                                return false;

                        string t_name = InstanceExpression.Type.Name;
                        int t_name_len = t_name.Length;
                        return t_name_len > 2 && t_name [t_name_len - 2] == '[';
                }

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

                        if (getter != null){
                                if (TypeManager.GetParameterData (getter).Count != 0){
                                        Error_PropertyNotFound (getter, true);
                                        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;

                                if (InstanceExpression != EmptyExpression.Null) {
                                        Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
                                                TypeManager.GetFullNameSignature (PropertyInfo));
                                        return null;
                                }
                        } 

                        bool must_do_cs1540_check = false;
                        if (getter != null &&
                            !IsAccessorAccessible (ec.ContainerType, getter, out must_do_cs1540_check)) {
                                PropertyBase.PropertyMethod pm = TypeManager.GetMethod (getter) as PropertyBase.PropertyMethod;
                                if (pm != null && pm.HasCustomAccessModifier) {
                                        Report.SymbolRelatedToPreviousError (pm);
                                        Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
                                                TypeManager.CSharpSignature (getter));
                                }
                                else {
                                        Report.SymbolRelatedToPreviousError (getter);
                                        ErrorIsInaccesible (loc, TypeManager.CSharpSignature (getter));
                                }
                                return null;
                        }
                        
                        if (!InstanceResolve (ec, false, must_do_cs1540_check))
                                return null;

                        //
                        // Only base will allow this invocation to happen.
                        //
                        if (IsBase && getter.IsAbstract) {
                                Error_CannotCallAbstractBase (TypeManager.GetFullNameSignature (PropertyInfo));
                        }

                        if (PropertyInfo.PropertyType.IsPointer && !ec.InUnsafe){
                                UnsafeError (loc);
                        }

                        if (!ec.IsInObsoleteScope) {
                                PropertyBase pb = TypeManager.GetProperty (PropertyInfo);
                                if (pb != null) {
                                        pb.CheckObsoleteness (loc);
                                } else {
                                        ObsoleteAttribute oa = AttributeTester.GetMemberObsoleteAttribute (PropertyInfo);
                                        if (oa != null)
                                                AttributeTester.Report_ObsoleteMessage (oa, GetSignatureForError (), loc);
                                }
                        }

                        resolved = true;

                        return this;
                }

                override public Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        if (right_side == EmptyExpression.OutAccess) {
                                if (ec.CurrentBlock.Toplevel.GetTransparentIdentifier (PropertyInfo.Name) != null) {
                                        Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
                                            PropertyInfo.Name);
                                } else {
                                        Report.Error (206, loc, "A property or indexer `{0}' may not be passed as `ref' or `out' parameter",
                                              GetSignatureForError ());
                                }
                                return null;
                        }

                        if (right_side == EmptyExpression.LValueMemberAccess || right_side == EmptyExpression.LValueMemberOutAccess) {
                                Error_CannotModifyIntermediateExpressionValue (ec);
                        }

                        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;

                                if (ec.CurrentBlock.Toplevel.GetTransparentIdentifier (PropertyInfo.Name) != null) {
                                        Report.Error (1947, loc, "A range variable `{0}' cannot be assigned to. Consider using `let' clause to store the value",
                                                PropertyInfo.Name);
                                } else {
                                        Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read only)",
                                                GetSignatureForError ());
                                }
                                return null;
                        }

                        if (TypeManager.GetParameterData (setter).Count != 1){
                                Error_PropertyNotFound (setter, false);
                                return null;
                        }

                        bool must_do_cs1540_check;
                        if (!IsAccessorAccessible (ec.ContainerType, setter, out must_do_cs1540_check)) {
                                PropertyBase.PropertyMethod pm = TypeManager.GetMethod (setter) as PropertyBase.PropertyMethod;
                                if (pm != null && pm.HasCustomAccessModifier) {
                                        Report.SymbolRelatedToPreviousError (pm);
                                        Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
                                                TypeManager.CSharpSignature (setter));
                                }
                                else {
                                        Report.SymbolRelatedToPreviousError (setter);
                                        ErrorIsInaccesible (loc, TypeManager.CSharpSignature (setter));
                                }
                                return null;
                        }
                        
                        if (!InstanceResolve (ec, PropertyInfo.DeclaringType.IsValueType, must_do_cs1540_check))
                                return null;
                        
                        //
                        // Only base will allow this invocation to happen.
                        //
                        if (IsBase && setter.IsAbstract){
                                Error_CannotCallAbstractBase (TypeManager.GetFullNameSignature (PropertyInfo));
                        }

                        if (PropertyInfo.PropertyType.IsPointer && !ec.InUnsafe) {
                                UnsafeError (loc);
                        }

                        if (!ec.IsInObsoleteScope) {
                                PropertyBase pb = TypeManager.GetProperty (PropertyInfo);
                                if (pb != null) {
                                        pb.CheckObsoleteness (loc);
                                } else {
                                        ObsoleteAttribute oa = AttributeTester.GetMemberObsoleteAttribute (PropertyInfo);
                                        if (oa != null)
                                                AttributeTester.Report_ObsoleteMessage (oa, GetSignatureForError (), loc);
                                }
                        }

                        return this;
                }
                
                public override void Emit (EmitContext ec)
                {
                        Emit (ec, false);
                }
                
                public void Emit (EmitContext ec, bool leave_copy)
                {
                        //
                        // Special case: length of single dimension array property is turned into ldlen
                        //
                        if (IsSingleDimensionalArrayLength ()) {
                                if (!prepared)
                                        EmitInstance (ec, false);
                                ec.ig.Emit (OpCodes.Ldlen);
                                ec.ig.Emit (OpCodes.Conv_I4);
                                return;
                        }

                        Invocation.EmitCall (ec, IsBase, InstanceExpression, getter, null, loc, prepared, false);
                        
                        if (leave_copy) {
                                ec.ig.Emit (OpCodes.Dup);
                                if (!is_static) {
                                        temp = new LocalTemporary (this.Type);
                                        temp.Store (ec);
                                }
                        }
                }

                //
                // Implements the IAssignMethod interface for assignments
                //
                public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool prepare_for_load)
                {
                        Expression my_source = source;

                        if (prepare_for_load) {
                                prepared = true;
                                source.Emit (ec);
                                
                                if (leave_copy) {
                                        ec.ig.Emit (OpCodes.Dup);
                                        if (!is_static) {
                                                temp = new LocalTemporary (this.Type);
                                                temp.Store (ec);
                                        }
                                }
                        } else if (leave_copy) {
                                source.Emit (ec);
                                temp = new LocalTemporary (this.Type);
                                temp.Store (ec);
                                my_source = temp;
                        }

                        ArrayList args = new ArrayList (1);
                        args.Add (new Argument (my_source, Argument.AType.Expression));
                        
                        Invocation.EmitCall (ec, IsBase, InstanceExpression, setter, args, loc, false, prepared);
                        
                        if (temp != null) {
                                temp.Emit (ec);
                                temp.Release (ec);
                        }
                }
        }

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

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

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

                public override bool IsStatic {
                        get {
                                return is_static;
                        }
                }

                public override Type DeclaringType {
                        get {
                                return EventInfo.DeclaringType;
                        }
                }
                
                void Error_AssignmentEventOnly ()
                {
                        Report.Error (79, loc, "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
                                GetSignatureForError ());
                }

                public override MemberExpr ResolveMemberAccess (EmitContext ec, Expression left, Location loc,
                                                                SimpleName original)
                {
                        //
                        // If the event is local to this class, we transform ourselves into a FieldExpr
                        //

                        if (EventInfo.DeclaringType == ec.ContainerType ||
                            TypeManager.IsNestedChildOf(ec.ContainerType, EventInfo.DeclaringType)) {
                                EventField mi = TypeManager.GetEventField (EventInfo);

                                if (mi != null) {
                                        if (!ec.IsInObsoleteScope)
                                                mi.CheckObsoleteness (loc);

                                        if ((mi.ModFlags & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0 && !ec.IsInCompoundAssignment)
                                                Error_AssignmentEventOnly ();
                                        
                                        FieldExpr ml = new FieldExpr (mi.FieldBuilder, loc);

                                        InstanceExpression = null;
                                
                                        return ml.ResolveMemberAccess (ec, left, loc, original);
                                }
                        }
                        
                        if (left is This && !ec.IsInCompoundAssignment)                 
                                Error_AssignmentEventOnly ();

                        return base.ResolveMemberAccess (ec, left, loc, original);
                }

                bool InstanceResolve (EmitContext ec, bool must_do_cs1540_check)
                {
                        if (is_static) {
                                InstanceExpression = null;
                                return true;
                        }

                        if (InstanceExpression == null) {
                                SimpleName.Error_ObjectRefRequired (ec, loc, GetSignatureForError ());
                                return false;
                        }

                        InstanceExpression = InstanceExpression.DoResolve (ec);
                        if (InstanceExpression == null)
                                return false;

                        if (IsBase && add_accessor.IsAbstract) {
                                Error_CannotCallAbstractBase(TypeManager.CSharpSignature(add_accessor));
                                return false;
                        }

                        //
                        // This is using the same mechanism as the CS1540 check in PropertyExpr.
                        // However, in the Event case, we reported a CS0122 instead.
                        //
                        // TODO: Exact copy from PropertyExpr
                        //
                        if (must_do_cs1540_check && InstanceExpression != EmptyExpression.Null &&
                            !TypeManager.IsInstantiationOfSameGenericType (InstanceExpression.Type, ec.ContainerType) &&
                            !TypeManager.IsNestedChildOf (ec.ContainerType, InstanceExpression.Type) &&
                            !TypeManager.IsSubclassOf (InstanceExpression.Type, ec.ContainerType)) {
                                Report.SymbolRelatedToPreviousError (EventInfo);
                                ErrorIsInaccesible (loc, TypeManager.CSharpSignature (EventInfo));
                                return false;
                        }

                        return true;
                }

                public bool IsAccessibleFrom (Type invocation_type)
                {
                        bool dummy;
                        return IsAccessorAccessible (invocation_type, add_accessor, out dummy) &&
                                IsAccessorAccessible (invocation_type, remove_accessor, out dummy);
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                public override Expression DoResolveLValue (EmitContext ec, Expression right_side)
                {
                        // contexts where an LValue is valid have already devolved to FieldExprs
                        Error_CannotAssign ();
                        return null;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        bool must_do_cs1540_check;
                        if (!(IsAccessorAccessible (ec.ContainerType, add_accessor, out must_do_cs1540_check) &&
                              IsAccessorAccessible (ec.ContainerType, remove_accessor, out must_do_cs1540_check))) {
                                Report.SymbolRelatedToPreviousError (EventInfo);
                                ErrorIsInaccesible (loc, TypeManager.CSharpSignature (EventInfo));
                                return null;
                        }

                        if (!InstanceResolve (ec, must_do_cs1540_check))
                                return null;

                        if (!ec.IsInCompoundAssignment) {
                                Error_CannotAssign ();
                                return null;
                        }

                        if (!ec.IsInObsoleteScope) {
                                EventField ev = TypeManager.GetEventField (EventInfo);
                                if (ev != null) {
                                        ev.CheckObsoleteness (loc);
                                } else {
                                        ObsoleteAttribute oa = AttributeTester.GetMemberObsoleteAttribute (EventInfo);
                                        if (oa != null)
                                                AttributeTester.Report_ObsoleteMessage (oa, GetSignatureForError (), loc);
                                }
                        }
                        
                        return this;
                }               

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

                public void Error_CannotAssign ()
                {
                        Report.Error (70, loc,
                                "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
                                GetSignatureForError (), TypeManager.CSharpName (EventInfo.DeclaringType));
                }

                public override string GetSignatureForError ()
                {
                        return TypeManager.CSharpSignature (EventInfo);
                }

                public void EmitAddOrRemove (EmitContext ec, bool is_add, Expression source)
                {
                        ArrayList args = new ArrayList (1);
                        args.Add (new Argument (source, Argument.AType.Expression));
                        Invocation.EmitCall (ec, IsBase, InstanceExpression, is_add ? add_accessor : remove_accessor, args, loc);
                }
        }

        public class TemporaryVariable : VariableReference
        {
                LocalInfo li;

                public TemporaryVariable (Type type, Location loc)
                {
                        this.type = type;
                        this.loc = loc;
                        eclass = ExprClass.Variable;
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        if (li != null)
                                return this;

                        TypeExpr te = new TypeExpression (type, loc);
                        li = ec.CurrentBlock.AddTemporaryVariable (te, loc);
                        if (!li.Resolve (ec))
                                return null;

                        //
                        // Don't capture temporary variables except when using
                        // iterator redirection
                        //
                        if (ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod.IsIterator && ec.IsVariableCapturingRequired) {
                                AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
                                storey.CaptureLocalVariable (ec, li);
                        }

                        return this;
                }

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

                public void EmitAssign (EmitContext ec, Expression source)
                {
                        EmitAssign (ec, source, false, false);
                }

                public override HoistedVariable HoistedVariable {
                        get { return li.HoistedVariableReference; }
                }

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

                public override bool IsRef {
                        get { return false; }
                }

                public override string Name {
                        get { throw new NotImplementedException (); }
                }

                public override void SetHasAddressTaken ()
                {
                        throw new NotImplementedException ();
                }

                protected override ILocalVariable Variable {
                        get { return li; }
                }

                public override VariableInfo VariableInfo {
                        get { throw new NotImplementedException (); }
                }
        }

        /// 
        /// Handles `var' contextual keyword; var becomes a keyword only
        /// if no type called var exists in a variable scope
        /// 
        public class VarExpr : SimpleName
        {
                // Used for error reporting only
                ArrayList initializer;

                public VarExpr (Location loc)
                        : base ("var", loc)
                {
                }

                public ArrayList VariableInitializer {
                        set {
                                this.initializer = value;
                        }
                }

                public bool InferType (EmitContext ec, Expression right_side)
                {
                        if (type != null)
                                throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
                        
                        type = right_side.Type;
                        if (type == TypeManager.null_type || type == TypeManager.void_type || type == TypeManager.anonymous_method_type) {
                                Report.Error (815, loc, "An implicitly typed local variable declaration cannot be initialized with `{0}'",
                                              right_side.GetSignatureForError ());
                                return false;
                        }

                        eclass = ExprClass.Variable;
                        return true;
                }

                protected override void Error_TypeOrNamespaceNotFound (IResolveContext ec)
                {
                        Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
                }

                public override TypeExpr ResolveAsContextualType (IResolveContext rc, bool silent)
                {
                        TypeExpr te = base.ResolveAsContextualType (rc, true);
                        if (te != null)
                                return te;

                        if (initializer == null)
                                return null;
                        
                        if (initializer.Count > 1) {
                                Location loc = ((Mono.CSharp.CSharpParser.VariableDeclaration)initializer [1]).Location;
                                Report.Error (819, loc, "An implicitly typed local variable declaration cannot include multiple declarators");
                                initializer = null;
                                return null;
                        }
                                
                        Expression variable_initializer = ((Mono.CSharp.CSharpParser.VariableDeclaration)initializer [0]).expression_or_array_initializer;
                        if (variable_initializer == null) {
                                Report.Error (818, loc, "An implicitly typed local variable declarator must include an initializer");
                                return null;
                        }
                        
                        return null;
                }
        }
}