2009-07-20 Jb Evain <jbevain@novell.com>

[mcs.git] / mcs / anonymous.cs

//
// anonymous.cs: Support for anonymous methods and types
//
// Author:
//   Miguel de Icaza (miguel@ximain.com)
//   Marek Safar (marek.safar@gmail.com)
//
// Dual licensed under the terms of the MIT X11 or GNU GPL
// Copyright 2003-2008 Novell, Inc.
//

using System;
using System.Text;
using System.Collections;
using System.Collections.Specialized;
using System.Reflection;
using System.Reflection.Emit;

namespace Mono.CSharp {

        public abstract class CompilerGeneratedClass : Class
        {
                public static string MakeName (string host, string typePrefix, string name, int id)
                {
                        return "<" + host + ">" + typePrefix + "__" + name + id.ToString ("X");
                }
                
                protected CompilerGeneratedClass (DeclSpace parent, MemberName name, int mod)
                        : base (parent.NamespaceEntry, parent, name, mod | Modifiers.COMPILER_GENERATED | Modifiers.SEALED, null)
                {
                }

                protected CompilerGeneratedClass (DeclSpace parent, GenericMethod generic, MemberName name, int mod)
                        : this (parent, name, mod)
                {
                        if (generic != null) {
                                ArrayList list = new ArrayList ();
                                foreach (TypeParameter tparam in generic.TypeParameters) {
                                        if (tparam.Constraints != null)
                                                list.Add (tparam.Constraints.Clone ());
                                }
                                SetParameterInfo (list);
                        }
                }

                protected void CheckMembersDefined ()
                {
                        if (members_defined)
                                throw new InternalErrorException ("Helper class already defined!");
                }
        }

        //
        // Anonymous method storey is created when an anonymous method uses
        // variable or parameter from outer scope. They are then hoisted to
        // anonymous method storey (captured)
        //
        public class AnonymousMethodStorey : CompilerGeneratedClass
        {
                class StoreyFieldPair {
                        public readonly AnonymousMethodStorey Storey;
                        public readonly Field Field;

                        public StoreyFieldPair (AnonymousMethodStorey storey, Field field)
                        {
                                this.Storey = storey;
                                this.Field = field;
                        }

                        public override int GetHashCode ()
                        {
                                return Storey.ID.GetHashCode ();
                        }

                        public override bool Equals (object obj)
                        {
                                return (AnonymousMethodStorey)obj == Storey;
                        }
                }

                sealed class HoistedGenericField : Field
                {
                        public HoistedGenericField (DeclSpace parent, FullNamedExpression type, int mod, string name,
                                  Attributes attrs, Location loc)
                                : base (parent, type, mod, new MemberName (name, loc), attrs)
                        {
                        }

                        protected override bool ResolveMemberType ()
                        {
                                if (!base.ResolveMemberType ())
                                        return false;

                                AnonymousMethodStorey parent = ((AnonymousMethodStorey) Parent).GetGenericStorey ();
                                if (parent != null)
                                        member_type = parent.MutateType (member_type);

                                return true;
                        }
                }

                //
                // Needed to delay hoisted _this_ initialization. When an anonymous
                // method is used inside ctor and _this_ is hoisted, base ctor has to
                // be called first, otherwise _this_ will be initialized with 
                // uninitialized value.
                //
                sealed class ThisInitializer : Statement
                {
                        readonly HoistedThis hoisted_this;

                        public ThisInitializer (HoistedThis hoisted_this)
                        {
                                this.hoisted_this = hoisted_this;
                        }

                        protected override void DoEmit (EmitContext ec)
                        {
                                hoisted_this.EmitHoistingAssignment (ec);
                        }

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

                        public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
                        {
                                // Nothing to mutate
                        }
                }

                // Unique storey ID
                public readonly int ID;
                static int unique_id;

                public readonly Block OriginalSourceBlock;

                // A list of StoreyFieldPair with local field keeping parent storey instance
                ArrayList used_parent_storeys;
                ArrayList children_references;

                // A list of hoisted parameters
                protected ArrayList hoisted_params;
                protected ArrayList hoisted_locals;

                // Hoisted this
                protected HoistedThis hoisted_this;

                // Local variable which holds this storey instance
                public LocalTemporary Instance;

                public AnonymousMethodStorey (Block block, DeclSpace parent, MemberBase host, GenericMethod generic, string name)
                        : base (parent, generic, MakeMemberName (host, name, generic, block.StartLocation), Modifiers.PRIVATE)
                {
                        Parent = parent;
                        OriginalSourceBlock = block;
                        ID = unique_id++;
                }

                static MemberName MakeMemberName (MemberBase host, string name, GenericMethod generic, Location loc)
                {
                        string host_name = host == null ? null : host.Name;
                        string tname = MakeName (host_name, "c", name, unique_id);
                        TypeArguments args = null;
                        if (generic != null) {
                                args = new TypeArguments ();
                                foreach (TypeParameter tparam in generic.CurrentTypeParameters)
                                        args.Add (new TypeParameterName (tparam.Name, null, loc));
                        }

                        return new MemberName (tname, args, loc);
                }

                public void AddCapturedThisField (EmitContext ec)
                {
                        TypeExpr type_expr = new TypeExpression (ec.ContainerType, Location);
                        Field f = AddCompilerGeneratedField ("<>f__this", type_expr);
                        f.Define ();
                        hoisted_this = new HoistedThis (this, f);
                }

                public Field AddCapturedVariable (string name, Type type)
                {
                        CheckMembersDefined ();

                        FullNamedExpression field_type = new TypeExpression (type, Location);
                        if (!IsGeneric)
                                return AddCompilerGeneratedField (name, field_type);

                        const int mod = Modifiers.INTERNAL | Modifiers.COMPILER_GENERATED;
                        Field f = new HoistedGenericField (this, field_type, mod, name, null, Location);
                        AddField (f);
                        return f;
                }

                protected Field AddCompilerGeneratedField (string name, FullNamedExpression type)
                {
                        const int mod = Modifiers.INTERNAL | Modifiers.COMPILER_GENERATED;
                        Field f = new Field (this, type, mod, new MemberName (name, Location), null);
                        AddField (f);
                        return f;
                }

                //
                // Creates a link between block and the anonymous method storey
                //
                // An anonymous method can reference variables from any outer block, but they are
                // hoisted in their own ExplicitBlock. When more than one block is referenced we
                // need to create another link between those variable storeys
                //
                public void AddReferenceFromChildrenBlock (ExplicitBlock block)
                {
                        if (children_references == null)
                                children_references = new ArrayList ();

                        if (!children_references.Contains (block))
                                children_references.Add (block);
                }

                public void AddParentStoreyReference (AnonymousMethodStorey storey)
                {
                        CheckMembersDefined ();

                        if (used_parent_storeys == null)
                                used_parent_storeys = new ArrayList ();
                        else if (used_parent_storeys.IndexOf (storey) != -1)
                                return;

                        TypeExpr type_expr = new TypeExpression (storey.TypeBuilder, Location);
                        Field f = AddCompilerGeneratedField ("<>f__ref$" + storey.ID, type_expr);
                        used_parent_storeys.Add (new StoreyFieldPair (storey, f));
                }

                public void CaptureLocalVariable (EmitContext ec, LocalInfo local_info)
                {
                        ec.CurrentBlock.Explicit.HasCapturedVariable = true;
                        if (ec.CurrentBlock.Explicit != local_info.Block.Explicit)
                                AddReferenceFromChildrenBlock (ec.CurrentBlock.Explicit);

                        if (local_info.HoistedVariableReference != null)
                                return;

                        HoistedVariable var = new HoistedLocalVariable (this, local_info, GetVariableMangledName (local_info));
                        local_info.HoistedVariableReference = var;

                        if (hoisted_locals == null)
                                hoisted_locals = new ArrayList ();

                        hoisted_locals.Add (var);
                }

                public void CaptureParameter (EmitContext ec, ParameterReference param_ref)
                {
                        ec.CurrentBlock.Explicit.HasCapturedVariable = true;
                        AddReferenceFromChildrenBlock (ec.CurrentBlock.Explicit);

                        if (param_ref.GetHoistedVariable (ec) != null)
                                return;

                        if (hoisted_params == null)
                                hoisted_params = new ArrayList (2);

                        HoistedVariable expr = new HoistedParameter (this, param_ref);
                        param_ref.Parameter.HoistedVariableReference = expr;
                        hoisted_params.Add (expr);
                }

                public void ChangeParentStorey (AnonymousMethodStorey parentStorey)
                {
                        Parent = parentStorey;
                        type_params = null;
                }

                //
                // Initializes all hoisted variables
                //
                public void EmitStoreyInstantiation (EmitContext ec)
                {
                        // There can be only one instance variable for each storey type
                        if (Instance != null)
                                throw new InternalErrorException ();

                        SymbolWriter.OpenCompilerGeneratedBlock (ec.ig);

                        //
                        // Create an instance of storey type
                        //
                        Expression storey_type_expr;
                        if (is_generic) {
                                //
                                // Use current method type parameter (MVAR) for top level storey only. All
                                // nested storeys use class type parameter (VAR)
                                //
                                TypeParameter[] tparams = ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod.Storey != null ?
                                        ec.CurrentAnonymousMethod.Storey.TypeParameters :
                                        ec.GenericDeclContainer.TypeParameters;

                                TypeArguments targs = new TypeArguments ();

                                if (tparams.Length < CountTypeParameters) {
                                        TypeParameter[] parent_tparams = ec.DeclContainer.Parent.PartialContainer.TypeParameters;
                                        for (int i = 0; i < parent_tparams.Length; ++i)
                                                targs.Add (new TypeParameterExpr (parent_tparams[i], Location));
                                }
                                
                                for (int i = 0; i < tparams.Length; ++i)
                                        targs.Add (new TypeParameterExpr (tparams[i], Location));

                                storey_type_expr = new GenericTypeExpr (TypeBuilder, targs, Location);
                        } else {
                                storey_type_expr = new TypeExpression (TypeBuilder, Location);
                        }

                        Expression e = new New (storey_type_expr, null, Location).Resolve (ec);
                        e.Emit (ec);

                        Instance = new LocalTemporary (storey_type_expr.Type);
                        Instance.Store (ec);

                        EmitHoistedFieldsInitialization (ec);

                        SymbolWriter.DefineScopeVariable (ID, Instance.Builder);
                        SymbolWriter.CloseCompilerGeneratedBlock (ec.ig);
                }

                void EmitHoistedFieldsInitialization (EmitContext ec)
                {
                        //
                        // Initialize all storey reference fields by using local or hoisted variables
                        //
                        if (used_parent_storeys != null) {
                                foreach (StoreyFieldPair sf in used_parent_storeys) {
                                        //
                                        // Setting local field
                                        //
                                        Expression instace_expr = GetStoreyInstanceExpression (ec);
                                        FieldExpr f_set_expr = TypeManager.IsGenericType (instace_expr.Type) ?
                                                new FieldExpr (sf.Field.FieldBuilder, instace_expr.Type, Location) :
                                                new FieldExpr (sf.Field.FieldBuilder, Location);
                                        f_set_expr.InstanceExpression = instace_expr;

                                        SimpleAssign a = new SimpleAssign (f_set_expr, sf.Storey.GetStoreyInstanceExpression (ec));
                                        if (a.Resolve (ec) != null)
                                                a.EmitStatement (ec);
                                }
                        }

                        //
                        // Define hoisted `this' in top-level storey only 
                        //
                        if (OriginalSourceBlock.Explicit.HasCapturedThis && !(Parent is AnonymousMethodStorey)) {
                                AddCapturedThisField (ec);
                                OriginalSourceBlock.AddScopeStatement (new ThisInitializer (hoisted_this));
                        }

                        //
                        // Setting currect anonymous method to null blocks any further variable hoisting
                        //
                        AnonymousExpression ae = ec.CurrentAnonymousMethod;
                        ec.CurrentAnonymousMethod = null;

                        if (hoisted_params != null) {
                                EmitHoistedParameters (ec, hoisted_params);
                        }

                        ec.CurrentAnonymousMethod = ae;
                }

                protected virtual void EmitHoistedParameters (EmitContext ec, ArrayList hoisted)
                {
                        foreach (HoistedParameter hp in hoisted) {
                                hp.EmitHoistingAssignment (ec);
                        }
                }

                public override void EmitType ()
                {
                        SymbolWriter.DefineAnonymousScope (ID);

                        if (hoisted_this != null)
                                hoisted_this.EmitSymbolInfo ();

                        if (hoisted_locals != null) {
                                foreach (HoistedVariable local in hoisted_locals)
                                        local.EmitSymbolInfo ();
                        }

                        if (hoisted_params != null) {
                                foreach (HoistedParameter param in hoisted_params)
                                        param.EmitSymbolInfo ();
                        }

                        if (used_parent_storeys != null) {
                                foreach (StoreyFieldPair sf in used_parent_storeys) {
                                        SymbolWriter.DefineCapturedScope (ID, sf.Storey.ID, sf.Field.Name);
                                }
                        }

                        base.EmitType ();
                }

                public AnonymousMethodStorey GetGenericStorey ()
                {
                        DeclSpace storey = this;
                        while (storey != null && storey.CurrentTypeParameters.Length == 0)
                                storey = storey.Parent;

                        return storey as AnonymousMethodStorey;
                }

                //
                // Returns a field which holds referenced storey instance
                //
                Field GetReferencedStoreyField (AnonymousMethodStorey storey)
                {
                        if (used_parent_storeys == null)
                                return null;

                        foreach (StoreyFieldPair sf in used_parent_storeys) {
                                if (sf.Storey == storey)
                                        return sf.Field;
                        }

                        return null;
                }

                //
                // Creates storey instance expression regardless of currect IP
                //
                public Expression GetStoreyInstanceExpression (EmitContext ec)
                {
                        AnonymousExpression am = ec.CurrentAnonymousMethod;

                        //
                        // Access from original block -> storey
                        //
                        if (am == null)
                                return Instance;

                        //
                        // Access from anonymous method implemented as a static -> storey
                        //
                        if (am.Storey == null)
                                return Instance;

                        Field f = am.Storey.GetReferencedStoreyField (this);
                        if (f == null) {
                                if (am.Storey == this) {
                                        //
                                        // Access inside of same storey (S -> S)
                                        //
                                        return new CompilerGeneratedThis (TypeBuilder, Location);
                                }
                                //
                                // External field access
                                //
                                return Instance;
                        }

                        //
                        // Storey was cached to local field
                        //
                        FieldExpr f_ind = new FieldExpr (f.FieldBuilder, Location);
                        f_ind.InstanceExpression = new CompilerGeneratedThis (TypeBuilder, Location);
                        return f_ind;
                }

                protected virtual string GetVariableMangledName (LocalInfo local_info)
                {
                        //
                        // No need to mangle anonymous method hoisted variables cause they
                        // are hoisted in their own scopes
                        //
                        return local_info.Name;
                }

                public HoistedThis HoistedThis {
                        get { return hoisted_this; }
                }

                //
                // Mutate type dispatcher
                //
                public Type MutateType (Type type)
                {
#if GMCS_SOURCE
                        if (TypeManager.IsGenericType (type))
                                return MutateGenericType (type);

                        if (TypeManager.IsGenericParameter (type))
                                return MutateGenericArgument (type);

                        if (type.IsArray)
                                return MutateArrayType (type);
#endif
                        return type;
                }

                //
                // Changes method type arguments (MVAR) to storey (VAR) type arguments
                //
                public MethodInfo MutateGenericMethod (MethodInfo method)
                {
#if GMCS_SOURCE
                        Type [] t_args = TypeManager.GetGenericArguments (method);
                        if (TypeManager.IsGenericType (method.DeclaringType)) {
                                Type t = MutateGenericType (method.DeclaringType);
                                if (t != method.DeclaringType) {
                                        method = (MethodInfo) TypeManager.DropGenericMethodArguments (method);
                                        if (method.Module == Module.Builder)
                                                method = TypeBuilder.GetMethod (t, method);
                                        else
                                                method = (MethodInfo) MethodInfo.GetMethodFromHandle (method.MethodHandle, t.TypeHandle);
                                }                               
                        }

                        if (t_args == null || t_args.Length == 0)
                                return method;

                        for (int i = 0; i < t_args.Length; ++i)
                                t_args [i] = MutateType (t_args [i]);

                        return method.GetGenericMethodDefinition ().MakeGenericMethod (t_args);
#else
                        throw new NotSupportedException ();
#endif
                }

                public ConstructorInfo MutateConstructor (ConstructorInfo ctor)
                {
#if GMCS_SOURCE         
                        if (TypeManager.IsGenericType (ctor.DeclaringType)) {
                                Type t = MutateGenericType (ctor.DeclaringType);
                                if (t != ctor.DeclaringType) {
                                        ctor = (ConstructorInfo) TypeManager.DropGenericMethodArguments (ctor);
                                        if (ctor.Module == Module.Builder)
                                                return TypeBuilder.GetConstructor (t, ctor);
                                                
                                        return (ConstructorInfo) ConstructorInfo.GetMethodFromHandle (ctor.MethodHandle, t.TypeHandle);
                                }
                        }
#endif
                        return ctor;
                }
                
                public FieldInfo MutateField (FieldInfo field)
                {
#if GMCS_SOURCE
                        if (TypeManager.IsGenericType (field.DeclaringType)) {
                                Type t = MutateGenericType (field.DeclaringType);
                                if (t != field.DeclaringType) {
                                        // TODO: It should throw on imported types
                                        return TypeBuilder.GetField (t, field);
                                }
                        }
#endif
                        return field;
                }               

#if GMCS_SOURCE
                protected Type MutateArrayType (Type array)
                {
                        int rank = array.GetArrayRank ();
                        Type element = TypeManager.GetElementType (array);
                        if (element.IsArray) {
                                element = MutateArrayType (element);
                        } else if (TypeManager.IsGenericParameter (element)) {
                                element = MutateGenericArgument (element);
                        } else if (TypeManager.IsGenericType (element)) {
                                element = MutateGenericType (element);
                        } else {
                                return array;
                        }

                        return element.MakeArrayType (rank);
                }

                protected Type MutateGenericType (Type type)
                {
                        Type [] t_args = TypeManager.GetTypeArguments (type);
                        if (t_args == null || t_args.Length == 0)
                                return type;

                        for (int i = 0; i < t_args.Length; ++i)
                                t_args [i] = MutateType (t_args [i]);

                        return TypeManager.DropGenericTypeArguments (type).MakeGenericType (t_args);
                }
#endif

                //
                // Changes method generic argument (MVAR) to type generic argument (VAR)
                //
                public Type MutateGenericArgument (Type type)
                {
                        foreach (TypeParameter tp in CurrentTypeParameters) {
                                if (tp.Name == type.Name) {
                                        return tp.Type;
                                }
                        }

                        return type;
                }

                public ArrayList ReferencesFromChildrenBlock {
                        get { return children_references; }
                }

                public static void Reset ()
                {
                        unique_id = 0;
                }               
        }

        public abstract class HoistedVariable
        {
                class ExpressionTreeProxy : Expression
                {
                        readonly HoistedVariable hv;

                        public ExpressionTreeProxy (HoistedVariable hv)
                        {
                                this.hv = hv;
                        }

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

                        public override Expression DoResolve (EmitContext ec)
                        {
                                eclass = ExprClass.Value;
                                type = TypeManager.expression_type_expr.Type;
                                return this;
                        }

                        public override void Emit (EmitContext ec)
                        {
                                Expression e = hv.GetFieldExpression (ec).CreateExpressionTree (ec);
                                // This should never fail
                                e = e.Resolve (ec);
                                if (e != null)
                                        e.Emit (ec);
                        }
                }
        
                protected readonly AnonymousMethodStorey storey;
                protected Field field;
                Hashtable cached_inner_access; // TODO: Hashtable is too heavyweight
                FieldExpr cached_outer_access;

                protected HoistedVariable (AnonymousMethodStorey storey, string name, Type type)
                        : this (storey, storey.AddCapturedVariable (name, type))
                {
                }

                protected HoistedVariable (AnonymousMethodStorey storey, Field field)
                {
                        this.storey = storey;
                        this.field = field;
                }

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

                public Expression CreateExpressionTree (EmitContext ec)
                {
                        return new ExpressionTreeProxy (this);
                }

                public void Emit (EmitContext ec)
                {
                        GetFieldExpression (ec).Emit (ec);
                }

                //
                // Creates field access expression for hoisted variable
                //
                protected FieldExpr GetFieldExpression (EmitContext ec)
                {
                        if (ec.CurrentAnonymousMethod == null || ec.CurrentAnonymousMethod.Storey == null) {
                                if (cached_outer_access != null)
                                        return cached_outer_access;

                                //
                                // When setting top-level hoisted variable in generic storey
                                // change storey generic types to method generic types (VAR -> MVAR)
                                //
                                cached_outer_access = storey.MemberName.IsGeneric ?
                                        new FieldExpr (field.FieldBuilder, storey.Instance.Type, field.Location) :
                                        new FieldExpr (field.FieldBuilder, field.Location);

                                cached_outer_access.InstanceExpression = storey.GetStoreyInstanceExpression (ec);
                                cached_outer_access.Resolve (ec);
                                return cached_outer_access;
                        }

                        FieldExpr inner_access;
                        if (cached_inner_access != null) {
                                inner_access = (FieldExpr) cached_inner_access [ec.CurrentAnonymousMethod];
                        } else {
                                inner_access = null;
                                cached_inner_access = new Hashtable (4);
                        }

                        if (inner_access == null) {
                                inner_access = new FieldExpr (field.FieldBuilder, field.Location);
                                inner_access.InstanceExpression = storey.GetStoreyInstanceExpression (ec);
                                inner_access.Resolve (ec);
                                cached_inner_access.Add (ec.CurrentAnonymousMethod, inner_access);
                        }

                        return inner_access;
                }

                public abstract void EmitSymbolInfo ();

                public void Emit (EmitContext ec, bool leave_copy)
                {
                        GetFieldExpression (ec).Emit (ec, leave_copy);
                }

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

        class HoistedParameter : HoistedVariable
        {
                sealed class HoistedFieldAssign : Assign
                {
                        public HoistedFieldAssign (Expression target, Expression source)
                                : base (target, source, source.Location)
                        {
                        }

                        protected override Expression ResolveConversions (EmitContext ec)
                        {
                                //
                                // Implicit conversion check fails for hoisted type arguments
                                // as they are of different types (!!0 x !0)
                                //
                                return this;
                        }
                }

                readonly ParameterReference parameter;

                public HoistedParameter (AnonymousMethodStorey scope, ParameterReference par)
                        : base (scope, par.Name, par.Type)
                {
                        this.parameter = par;
                }

                public HoistedParameter (HoistedParameter hp, string name)
                        : base (hp.storey, name, hp.parameter.Type)
                {
                        this.parameter = hp.parameter;
                }

                public void EmitHoistingAssignment (EmitContext ec)
                {
                        //
                        // Remove hoisted redirection to emit assignment from original parameter
                        //
                        HoistedVariable temp = parameter.Parameter.HoistedVariableReference;
                        parameter.Parameter.HoistedVariableReference = null;

                        Assign a = new HoistedFieldAssign (GetFieldExpression (ec), parameter);
                        if (a.Resolve (ec) != null)
                                a.EmitStatement (ec);

                        parameter.Parameter.HoistedVariableReference = temp;
                }

                public override void EmitSymbolInfo ()
                {
                        SymbolWriter.DefineCapturedParameter (storey.ID, field.Name, field.Name);
                }

                public Field Field {
                        get { return field; }
                }
        }

        class HoistedLocalVariable : HoistedVariable
        {
                readonly string name;

                public HoistedLocalVariable (AnonymousMethodStorey scope, LocalInfo local, string name)
                        : base (scope, name, local.VariableType)
                {
                        this.name = local.Name;
                }

                public override void EmitSymbolInfo ()
                {
                        SymbolWriter.DefineCapturedLocal (storey.ID, name, field.Name);
                }
        }

        public class HoistedThis : HoistedVariable
        {
                public HoistedThis (AnonymousMethodStorey storey, Field field)
                        : base (storey, field)
                {
                }

                public void EmitHoistingAssignment (EmitContext ec)
                {
                        SimpleAssign a = new SimpleAssign (GetFieldExpression (ec), ec.GetThis (field.Location));
                        if (a.Resolve (ec) != null)
                                a.EmitStatement (ec);
                }

                public override void EmitSymbolInfo ()
                {
                        SymbolWriter.DefineCapturedThis (storey.ID, field.Name);
                }

                public Field Field {
                        get { return field; }
                }
        }

        //
        // Anonymous method expression as created by parser
        //
        public class AnonymousMethodExpression : Expression
        {
                ListDictionary compatibles;
                public ToplevelBlock Block;

                public AnonymousMethodExpression (Location loc)
                {
                        this.loc = loc;
                        this.compatibles = new ListDictionary ();
                }

                public override string ExprClassName {
                        get {
                                return "anonymous method";
                        }
                }

                public virtual bool HasExplicitParameters {
                        get {
                                return Parameters != ParametersCompiled.Undefined;
                        }
                }
                
                public ParametersCompiled Parameters {
                        get { return Block.Parameters; }
                }

                //
                // Returns true if the body of lambda expression can be implicitly
                // converted to the delegate of type `delegate_type'
                //
                public bool ImplicitStandardConversionExists (EmitContext ec, Type delegate_type)
                {
                        using (ec.With (EmitContext.Flags.InferReturnType, false)) {
                                using (ec.Set (EmitContext.Flags.ProbingMode)) {
                                        return Compatible (ec, delegate_type) != null;
                                }
                        }
                }

                protected Type CompatibleChecks (EmitContext ec, Type delegate_type)
                {
                        if (TypeManager.IsDelegateType (delegate_type))
                                return delegate_type;

                        if (TypeManager.DropGenericTypeArguments (delegate_type) == TypeManager.expression_type) {
                                delegate_type = TypeManager.GetTypeArguments (delegate_type) [0];
                                if (TypeManager.IsDelegateType (delegate_type))
                                        return delegate_type;

                                Report.Error (835, loc, "Cannot convert `{0}' to an expression tree of non-delegate type `{1}'",
                                        GetSignatureForError (), TypeManager.CSharpName (delegate_type));
                                return null;
                        }

                        Report.Error (1660, loc, "Cannot convert `{0}' to non-delegate type `{1}'",
                                      GetSignatureForError (), TypeManager.CSharpName (delegate_type));
                        return null;
                }

                protected bool VerifyExplicitParameters (Type delegate_type, AParametersCollection parameters, bool ignore_error)
                {
                        if (VerifyParameterCompatibility (delegate_type, parameters, ignore_error))
                                return true;

                        if (!ignore_error)
                                Report.Error (1661, loc,
                                        "Cannot convert `{0}' to delegate type `{1}' since there is a parameter mismatch",
                                        GetSignatureForError (), TypeManager.CSharpName (delegate_type));

                        return false;
                }

                protected bool VerifyParameterCompatibility (Type delegate_type, AParametersCollection invoke_pd, bool ignore_errors)
                {
                        if (Parameters.Count != invoke_pd.Count) {
                                if (ignore_errors)
                                        return false;
                                
                                Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
                                              TypeManager.CSharpName (delegate_type), Parameters.Count.ToString ());
                                return false;
                        }

                        bool has_implicit_parameters = !HasExplicitParameters;
                        bool error = false;

                        for (int i = 0; i < Parameters.Count; ++i) {
                                Parameter.Modifier p_mod = invoke_pd.FixedParameters [i].ModFlags;
                                if (Parameters.FixedParameters [i].ModFlags != p_mod && p_mod != Parameter.Modifier.PARAMS) {
                                        if (ignore_errors)
                                                return false;
                                        
                                        if (p_mod == Parameter.Modifier.NONE)
                                                Report.Error (1677, loc, "Parameter `{0}' should not be declared with the `{1}' keyword",
                                                              (i + 1).ToString (), Parameter.GetModifierSignature (Parameters.FixedParameters [i].ModFlags));
                                        else
                                                Report.Error (1676, loc, "Parameter `{0}' must be declared with the `{1}' keyword",
                                                              (i+1).ToString (), Parameter.GetModifierSignature (p_mod));
                                        error = true;
                                }

                                if (has_implicit_parameters)
                                        continue;

                                Type type = invoke_pd.Types [i];
                                
                                // We assume that generic parameters are always inflated
                                if (TypeManager.IsGenericParameter (type))
                                        continue;
                                
                                if (TypeManager.HasElementType (type) && TypeManager.IsGenericParameter (TypeManager.GetElementType (type)))
                                        continue;
                                
                                if (invoke_pd.Types [i] != Parameters.Types [i]) {
                                        if (ignore_errors)
                                                return false;
                                        
                                        Report.Error (1678, loc, "Parameter `{0}' is declared as type `{1}' but should be `{2}'",
                                                      (i+1).ToString (),
                                                      TypeManager.CSharpName (Parameters.Types [i]),
                                                      TypeManager.CSharpName (invoke_pd.Types [i]));
                                        error = true;
                                }
                        }

                        return !error;
                }

                //
                // Infers type arguments based on explicit arguments
                //
                public bool ExplicitTypeInference (TypeInferenceContext type_inference, Type delegate_type)
                {
                        if (!HasExplicitParameters)
                                return false;

                        if (!TypeManager.IsDelegateType (delegate_type)) {
                                if (TypeManager.DropGenericTypeArguments (delegate_type) != TypeManager.expression_type)
                                        return false;

                                delegate_type = TypeManager.GetTypeArguments (delegate_type) [0];
                                if (!TypeManager.IsDelegateType (delegate_type))
                                        return false;
                        }
                        
                        AParametersCollection d_params = TypeManager.GetDelegateParameters (delegate_type);
                        if (d_params.Count != Parameters.Count)
                                return false;

                        for (int i = 0; i < Parameters.Count; ++i) {
                                Type itype = d_params.Types [i];
                                if (!TypeManager.IsGenericParameter (itype)) {
                                        if (!TypeManager.HasElementType (itype))
                                                continue;
                                        
                                        if (!TypeManager.IsGenericParameter (TypeManager.GetElementType (itype)))
                                            continue;
                                }
                                type_inference.ExactInference (Parameters.Types [i], itype);
                        }
                        return true;
                }

                public Type InferReturnType (EmitContext ec, TypeInferenceContext tic, Type delegate_type)
                {
                        AnonymousMethodBody am;
                        using (ec.Set (EmitContext.Flags.ProbingMode | EmitContext.Flags.InferReturnType)) {
                                am = CompatibleMethod (ec, tic, TypeManager.null_type, delegate_type);
                        }
                        
                        if (am == null)
                                return null;

                        // Stop referencing gmcs NullLiteral type
                        if (am.ReturnType == TypeManager.null_type)
                                am.ReturnType = null;

                        return am.ReturnType;
                }

                //
                // Returns AnonymousMethod container if this anonymous method
                // expression can be implicitly converted to the delegate type `delegate_type'
                //
                public Expression Compatible (EmitContext ec, Type type)
                {
                        Expression am = (Expression) compatibles [type];
                        if (am != null)
                                return am;

                        Type delegate_type = CompatibleChecks (ec, type);
                        if (delegate_type == null)
                                return null;

                        //
                        // At this point its the first time we know the return type that is 
                        // needed for the anonymous method.  We create the method here.
                        //

                        MethodInfo invoke_mb = Delegate.GetInvokeMethod (
                                ec.ContainerType, delegate_type);
                        Type return_type = TypeManager.TypeToCoreType (invoke_mb.ReturnType);

#if MS_COMPATIBLE
                        Type[] g_args = delegate_type.GetGenericArguments ();
                        if (return_type.IsGenericParameter)
                                return_type = g_args [return_type.GenericParameterPosition];
#endif

                        //
                        // Second: the return type of the delegate must be compatible with 
                        // the anonymous type.   Instead of doing a pass to examine the block
                        // we satisfy the rule by setting the return type on the EmitContext
                        // to be the delegate type return type.
                        //

                        try {
                                int errors = Report.Errors;
                                am = CompatibleMethod (ec, null, return_type, delegate_type);
                                if (am != null && delegate_type != type && errors == Report.Errors)
                                        am = CreateExpressionTree (ec, delegate_type);

                                if (!ec.IsInProbingMode)
                                        compatibles.Add (type, am == null ? EmptyExpression.Null : am);

                                return am;
                        } catch (CompletionResult){
                                throw;
                        } catch (Exception e) {
                                throw new InternalErrorException (e, loc);
                        }
                }

                protected virtual Expression CreateExpressionTree (EmitContext ec, Type delegate_type)
                {
                        return CreateExpressionTree (ec);
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        Report.Error (1946, loc, "An anonymous method cannot be converted to an expression tree");
                        return null;
                }

                protected virtual ParametersCompiled ResolveParameters (EmitContext ec, TypeInferenceContext tic, Type delegate_type)
                {
                        AParametersCollection delegate_parameters = TypeManager.GetDelegateParameters (delegate_type);

                        if (Parameters == ParametersCompiled.Undefined) {
                                //
                                // We provide a set of inaccessible parameters
                                //
                                Parameter[] fixedpars = new Parameter[delegate_parameters.Count];

                                for (int i = 0; i < delegate_parameters.Count; i++) {
                                        Parameter.Modifier i_mod = delegate_parameters.FixedParameters [i].ModFlags;
                                        if (i_mod == Parameter.Modifier.OUT) {
                                                Report.Error (1688, loc, "Cannot convert anonymous " +
                                                                  "method block without a parameter list " +
                                                                  "to delegate type `{0}' because it has " +
                                                                  "one or more `out' parameters.",
                                                                  TypeManager.CSharpName (delegate_type));
                                                return null;
                                        }
                                        fixedpars[i] = new Parameter (
                                                null, null,
                                                delegate_parameters.FixedParameters [i].ModFlags, null, loc);
                                }

                                return ParametersCompiled.CreateFullyResolved (fixedpars, delegate_parameters.Types);
                        }

                        if (!VerifyExplicitParameters (delegate_type, delegate_parameters, ec.IsInProbingMode)) {
                                return null;
                        }

                        return Parameters;
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        if (!ec.IsAnonymousMethodAllowed) {
                                Report.Error (1706, loc, "Anonymous methods and lambda expressions cannot be used in the current context");
                                return null;
                        }

                        //
                        // Set class type, set type
                        //

                        eclass = ExprClass.Value;

                        //
                        // This hack means `The type is not accessible
                        // anywhere', we depend on special conversion
                        // rules.
                        // 
                        type = InternalType.AnonymousMethod;

                        if ((Parameters != null) && !Parameters.Resolve (ec))
                                return null;

                        // FIXME: The emitted code isn't very careful about reachability
                        // so, ensure we have a 'ret' at the end
                        if (ec.CurrentBranching != null &&
                            ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
                                ec.NeedReturnLabel ();

                        return this;
                }

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

                public static void Error_AddressOfCapturedVar (IVariableReference var, Location loc)
                {
                        Report.Error (1686, loc,
                                "Local variable or parameter `{0}' cannot have their address taken and be used inside an anonymous method or lambda expression",
                                var.Name);
                }

                public override string GetSignatureForError ()
                {
                        return ExprClassName;
                }

                protected AnonymousMethodBody CompatibleMethod (EmitContext ec, TypeInferenceContext tic, Type return_type, Type delegate_type)
                {
                        ParametersCompiled p = ResolveParameters (ec, tic, delegate_type);
                        if (p == null)
                                return null;

                        ToplevelBlock b = ec.IsInProbingMode ? (ToplevelBlock) Block.PerformClone () : Block;

                        AnonymousMethodBody anonymous = CompatibleMethodFactory (return_type, delegate_type, p, b);
                        if (!anonymous.Compatible (ec))
                                return null;

                        return anonymous;
                }

                protected virtual AnonymousMethodBody CompatibleMethodFactory (Type return_type, Type delegate_type, ParametersCompiled p, ToplevelBlock b)
                {
                        return new AnonymousMethodBody (p, b, return_type, delegate_type, loc);
                }

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

                        target.Block = (ToplevelBlock) clonectx.LookupBlock (Block);
                }
        }

        //
        // Abstract expression for any block which requires variables hoisting
        //
        public abstract class AnonymousExpression : Expression
        {
                protected class AnonymousMethodMethod : Method
                {
                        public readonly AnonymousExpression AnonymousMethod;
                        public readonly AnonymousMethodStorey Storey;
                        readonly string RealName;

                        public AnonymousMethodMethod (DeclSpace parent, AnonymousExpression am, AnonymousMethodStorey storey,
                                                          GenericMethod generic, TypeExpr return_type,
                                                          int mod, string real_name, MemberName name,
                                                          ParametersCompiled parameters)
                                : base (parent, generic, return_type, mod | Modifiers.COMPILER_GENERATED,
                                                name, parameters, null)
                        {
                                this.AnonymousMethod = am;
                                this.Storey = storey;
                                this.RealName = real_name;

                                Parent.PartialContainer.AddMethod (this);
                                Block = am.Block;
                        }

                        public override EmitContext CreateEmitContext (DeclSpace tc, ILGenerator ig)
                        {
                                EmitContext aec = AnonymousMethod.aec;
                                aec.ig = ig;
                                aec.IsStatic = (ModFlags & Modifiers.STATIC) != 0;
                                return aec;
                        }

                        protected override bool ResolveMemberType ()
                        {
                                if (!base.ResolveMemberType ())
                                        return false;

                                if (Storey != null && Storey.IsGeneric) {
                                        AnonymousMethodStorey gstorey = Storey.GetGenericStorey ();
                                        if (gstorey != null) {
                                                if (!Parameters.IsEmpty) {
                                                        Type [] ptypes = Parameters.Types;
                                                        for (int i = 0; i < ptypes.Length; ++i)
                                                                ptypes [i] = gstorey.MutateType (ptypes [i]);
                                                }

                                                member_type = gstorey.MutateType (member_type);
                                        }
                                }

                                return true;
                        }

                        public override void Emit ()
                        {
                                //
                                // Before emitting any code we have to change all MVAR references to VAR
                                // when the method is of generic type and has hoisted variables
                                //
                                if (Storey == Parent && Storey.IsGeneric) {
                                        AnonymousMethodStorey gstorey = Storey.GetGenericStorey ();
                                        if (gstorey != null) {
                                                AnonymousMethod.aec.ReturnType = gstorey.MutateType (ReturnType);
                                                block.MutateHoistedGenericType (gstorey);
                                        }
                                }

                                if (MethodBuilder == null) {
                                        Define ();
                                }

                                base.Emit ();
                        }

                        public override void EmitExtraSymbolInfo (SourceMethod source)
                        {
                                source.SetRealMethodName (RealName);
                        }
                }

                //
                // The block that makes up the body for the anonymous method
                //
                protected readonly ToplevelBlock Block;

                public Type ReturnType;
                protected EmitContext aec;

                protected AnonymousExpression (ToplevelBlock block, Type return_type, Location loc)
                {
                        this.ReturnType = return_type;
                        this.Block = block;
                        this.loc = loc;
                }

                public abstract string ContainerType { get; }
                public abstract bool IsIterator { get; }
                public abstract AnonymousMethodStorey Storey { get; }

                public bool Compatible (EmitContext ec)
                {
                        // TODO: Implement clone
                        aec = new EmitContext (
                                ec.ResolveContext, ec.TypeContainer, ec.DeclContainer,
                                Location, null, ReturnType,
                                (ec.InUnsafe ? Modifiers.UNSAFE : 0), /* No constructor */ false);

                        aec.CurrentAnonymousMethod = this;
                        aec.IsStatic = ec.IsStatic;

                        IDisposable aec_dispose = null;
                        EmitContext.Flags flags = 0;
                        if (ec.InferReturnType)
                                flags |= EmitContext.Flags.InferReturnType;

                        if (ec.IsInProbingMode)
                                flags |= EmitContext.Flags.ProbingMode;

                        if (ec.IsInFieldInitializer)
                                flags |= EmitContext.Flags.InFieldInitializer;

                        if (ec.IsInUnsafeScope)
                                flags |= EmitContext.Flags.InUnsafe;

                        // HACK: Flag with 0 cannot be set 
                        if (flags != 0)
                                aec_dispose = aec.Set (flags);

                        bool unreachable;
                        bool res = aec.ResolveTopBlock (ec, Block, Block.Parameters, null, out unreachable);

                        if (ec.InferReturnType)
                                ReturnType = aec.ReturnType;

                        if (aec_dispose != null) {
                                aec_dispose.Dispose ();
                        }

                        return res;
                }

                public void SetHasThisAccess ()
                {
                        Block.HasCapturedThis = true;
                        ExplicitBlock b = Block.Parent.Explicit;

                        while (b != null) {
                                if (b.HasCapturedThis)
                                        return;

                                b.HasCapturedThis = true;
                                b = b.Parent == null ? null : b.Parent.Explicit;
                        }
                }
        }

        public class AnonymousMethodBody : AnonymousExpression
        {
                protected readonly ParametersCompiled parameters;
                AnonymousMethodStorey storey;

                AnonymousMethodMethod method;
                Field am_cache;

                static int unique_id;

                public AnonymousMethodBody (ParametersCompiled parameters,
                                        ToplevelBlock block, Type return_type, Type delegate_type,
                                        Location loc)
                        : base (block, return_type, loc)
                {
                        this.type = delegate_type;
                        this.parameters = parameters;
                }

                public override string ContainerType {
                        get { return "anonymous method"; }
                }

                public override AnonymousMethodStorey Storey {
                        get { return storey; }
                }

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

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        Report.Error (1945, loc, "An expression tree cannot contain an anonymous method expression");
                        return null;
                }

                bool Define (EmitContext ec)
                {
                        if (aec == null && !Compatible (ec))
                                return false;

                        return true;
                }

                //
                // Creates a host for the anonymous method
                //
                AnonymousMethodMethod DoCreateMethodHost (EmitContext ec)
                {
                        //
                        // Anonymous method body can be converted to
                        //
                        // 1, an instance method in current scope when only `this' is hoisted
                        // 2, a static method in current scope when neither `this' nor any variable is hoisted
                        // 3, an instance method in compiler generated storey when any hoisted variable exists
                        //

                        int modifiers;
                        if (Block.HasCapturedVariable || Block.HasCapturedThis) {
                                storey = FindBestMethodStorey ();
                                modifiers = storey != null ? Modifiers.INTERNAL : Modifiers.PRIVATE;
                        } else {
                                if (ec.CurrentAnonymousMethod != null)
                                        storey = ec.CurrentAnonymousMethod.Storey;

                                modifiers = Modifiers.STATIC | Modifiers.PRIVATE;
                        }

                        DeclSpace parent = storey != null ? storey : ec.TypeContainer;

                        MemberCore mc = ec.ResolveContext as MemberCore;
                        string name = CompilerGeneratedClass.MakeName (parent != storey ? mc.Name : null,
                                "m", null, unique_id++);

                        MemberName member_name;
                        GenericMethod generic_method;
                        if (storey == null && mc.MemberName.IsGeneric) {
                                member_name = new MemberName (name, mc.MemberName.TypeArguments.Clone (), Location);

                                generic_method = new GenericMethod (parent.NamespaceEntry, parent, member_name,
                                        new TypeExpression (ReturnType, Location), parameters);

                                ArrayList list = new ArrayList ();
                                foreach (TypeParameter tparam in ((IMethodData)mc).GenericMethod.CurrentTypeParameters) {
                                        if (tparam.Constraints != null)
                                                list.Add (tparam.Constraints.Clone ());
                                }
                                generic_method.SetParameterInfo (list);
                        } else {
                                member_name = new MemberName (name, Location);
                                generic_method = null;
                        }

                        string real_name = String.Format (
                                "{0}~{1}{2}", mc.GetSignatureForError (), GetSignatureForError (),
                                parameters.GetSignatureForError ());

                        return new AnonymousMethodMethod (parent,
                                this, storey, generic_method, new TypeExpression (ReturnType, Location), modifiers,
                                real_name, member_name, parameters);
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        if (eclass == ExprClass.Invalid) {
                                if (!Define (ec))
                                        return null;
                        }

                        eclass = ExprClass.Value;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        //
                        // Use same anonymous method implementation for scenarios where same
                        // code is used from multiple blocks, e.g. field initializers
                        //
                        if (method == null) {
                                //
                                // Delay an anonymous method definition to avoid emitting unused code
                                // for unreachable blocks or expression trees
                                //
                                method = DoCreateMethodHost (ec);
                                method.Define ();
                        }

                        bool is_static = (method.ModFlags & Modifiers.STATIC) != 0;
                        if (is_static && am_cache == null) {
                                //
                                // Creates a field cache to store delegate instance if it's not generic
                                //
                                if (!method.MemberName.IsGeneric) {
                                        TypeContainer parent = method.Parent.PartialContainer;
                                        int id = parent.Fields == null ? 0 : parent.Fields.Count;
                                        am_cache = new Field (parent, new TypeExpression (type, loc),
                                                Modifiers.STATIC | Modifiers.PRIVATE | Modifiers.COMPILER_GENERATED,
                                                new MemberName (CompilerGeneratedClass.MakeName (null, "f", "am$cache", id), loc), null);
                                        am_cache.Define ();
                                        parent.AddField (am_cache);
                                } else {
                                        // TODO: Implement caching of generated generic static methods
                                        //
                                        // Idea:
                                        //
                                        // Some extra class is needed to capture variable generic type
                                        // arguments. Maybe we could re-use anonymous types, with a unique
                                        // anonymous method id, but they are quite heavy.
                                        //
                                        // Consider : "() => typeof(T);"
                                        //
                                        // We need something like
                                        // static class Wrap<Tn, Tm, DelegateType> {
                                        //              public static DelegateType cache;
                                        // }
                                        //
                                        // We then specialize local variable to capture all generic parameters
                                        // and delegate type, e.g. "Wrap<Ta, Tb, DelegateTypeInst> cache;"
                                        //
                                }
                        }

                        ILGenerator ig = ec.ig;
                        Label l_initialized = ig.DefineLabel ();

                        if (am_cache != null) {
                                ig.Emit (OpCodes.Ldsfld, am_cache.FieldBuilder);
                                ig.Emit (OpCodes.Brtrue_S, l_initialized);
                        }

                        //
                        // Load method delegate implementation
                        //

                        if (is_static) {
                                ig.Emit (OpCodes.Ldnull);
                        } else if (storey != null) {
                                Expression e = storey.GetStoreyInstanceExpression (ec).Resolve (ec);
                                if (e != null)
                                        e.Emit (ec);
                        } else {
                                ig.Emit (OpCodes.Ldarg_0);
                        }

                        MethodInfo delegate_method = method.MethodBuilder;
                        if (storey != null && storey.MemberName.IsGeneric) {
                                Type t = storey.Instance.Type;
                                
                                //
                                // Mutate anonymous method instance type if we are in nested
                                // hoisted generic anonymous method storey
                                //
                                if (ec.CurrentAnonymousMethod != null &&
                                        ec.CurrentAnonymousMethod.Storey != null &&
                                        ec.CurrentAnonymousMethod.Storey.IsGeneric) {
                                        t = storey.GetGenericStorey ().MutateType (t);
                                }

#if GMCS_SOURCE
                                delegate_method = TypeBuilder.GetMethod (t, delegate_method);
#else
                                throw new NotSupportedException ();
#endif
                        }

                        ig.Emit (OpCodes.Ldftn, delegate_method);

                        ConstructorInfo constructor_method = Delegate.GetConstructor (ec.ContainerType, type);
#if MS_COMPATIBLE
            if (type.IsGenericType && type is TypeBuilder)
                constructor_method = TypeBuilder.GetConstructor (type, constructor_method);
#endif
                        ig.Emit (OpCodes.Newobj, constructor_method);

                        if (am_cache != null) {
                                ig.Emit (OpCodes.Stsfld, am_cache.FieldBuilder);
                                ig.MarkLabel (l_initialized);
                                ig.Emit (OpCodes.Ldsfld, am_cache.FieldBuilder);
                        }
                }

                //
                // Look for the best storey for this anonymous method
                //
                AnonymousMethodStorey FindBestMethodStorey ()
                {
                        //
                        // Use the nearest parent block which has a storey
                        //
                        for (Block b = Block.Parent; b != null; b = b.Parent) {
                                AnonymousMethodStorey s = b.Explicit.AnonymousMethodStorey;
                                if (s != null)
                                        return s;
                        }
                                        
                        return null;
                }

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

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

                public static void Reset ()
                {
                        unique_id = 0;
                }
        }

        //
        // Anonymous type container
        //
        public class AnonymousTypeClass : CompilerGeneratedClass
        {
                sealed class AnonymousParameters : ParametersCompiled
                {
                        public AnonymousParameters (params Parameter[] parameters)
                                : base (parameters)
                        {
                        }

                        protected override void ErrorDuplicateName (Parameter p)
                        {
                                Report.Error (833, p.Location, "`{0}': An anonymous type cannot have multiple properties with the same name",
                                        p.Name);
                        }
                }

                static int types_counter;
                public const string ClassNamePrefix = "<>__AnonType";
                public const string SignatureForError = "anonymous type";
                
                readonly ArrayList parameters;

                private AnonymousTypeClass (DeclSpace parent, MemberName name, ArrayList parameters, Location loc)
                        : base (parent, name, (RootContext.EvalMode ? Modifiers.PUBLIC : 0) | Modifiers.SEALED)
                {
                        this.parameters = parameters;
                }

                public static AnonymousTypeClass Create (TypeContainer parent, ArrayList parameters, Location loc)
                {
                        if (RootContext.MetadataCompatibilityVersion < MetadataVersion.v2)
                                Report.FeatureIsNotSupported (loc, "anonymous types");

                        string name = ClassNamePrefix + types_counter++;

                        SimpleName [] t_args = new SimpleName [parameters.Count];
                        TypeParameterName [] t_params = new TypeParameterName [parameters.Count];
                        Parameter [] ctor_params = new Parameter [parameters.Count];
                        for (int i = 0; i < parameters.Count; ++i) {
                                AnonymousTypeParameter p = (AnonymousTypeParameter) parameters [i];

                                t_args [i] = new SimpleName ("<" + p.Name + ">__T", p.Location);
                                t_params [i] = new TypeParameterName (t_args [i].Name, null, p.Location);
                                ctor_params [i] = new Parameter (t_args [i], p.Name, 0, null, p.Location);
                        }

                        //
                        // Create generic anonymous type host with generic arguments
                        // named upon properties names
                        //
                        AnonymousTypeClass a_type = new AnonymousTypeClass (parent.NamespaceEntry.SlaveDeclSpace,
                                new MemberName (name, new TypeArguments (t_params), loc), parameters, loc);

                        if (parameters.Count > 0)
                                a_type.SetParameterInfo (null);

                        Constructor c = new Constructor (a_type, name, Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
                                null, new AnonymousParameters (ctor_params), null, loc);
                        c.Block = new ToplevelBlock (c.Parameters, loc);

                        // 
                        // Create fields and contructor body with field initialization
                        //
                        bool error = false;
                        for (int i = 0; i < parameters.Count; ++i) {
                                AnonymousTypeParameter p = (AnonymousTypeParameter) parameters [i];

                                Field f = new Field (a_type, t_args [i], Modifiers.PRIVATE | Modifiers.READONLY,
                                        new MemberName ("<" + p.Name + ">", p.Location), null);

                                if (!a_type.AddField (f)) {
                                        error = true;
                                        continue;
                                }

                                c.Block.AddStatement (new StatementExpression (
                                        new SimpleAssign (new MemberAccess (new This (p.Location), f.Name),
                                                c.Block.GetParameterReference (p.Name, p.Location))));

                                ToplevelBlock get_block = new ToplevelBlock (p.Location);
                                get_block.AddStatement (new Return (
                                        new MemberAccess (new This (p.Location), f.Name), p.Location));
                                Accessor get_accessor = new Accessor (get_block, 0, null, null, p.Location);
                                Property prop = new Property (a_type, t_args [i], Modifiers.PUBLIC,
                                        new MemberName (p.Name, p.Location), null, get_accessor, null, false);
                                a_type.AddProperty (prop);
                        }

                        if (error)
                                return null;

                        a_type.AddConstructor (c);
                        return a_type;
                }
                
                public static void Reset ()
                {
                        types_counter = 0;
                }

                protected override bool AddToContainer (MemberCore symbol, string name)
                {
                        MemberCore mc = (MemberCore) defined_names [name];

                        if (mc == null) {
                                defined_names.Add (name, symbol);
                                return true;
                        }

                        Report.SymbolRelatedToPreviousError (mc);
                        return false;
                }

                void DefineOverrides ()
                {
                        Location loc = Location;

                        Method equals = new Method (this, null, TypeManager.system_boolean_expr,
                                Modifiers.PUBLIC | Modifiers.OVERRIDE | Modifiers.DEBUGGER_HIDDEN, new MemberName ("Equals", loc),
                                Mono.CSharp.ParametersCompiled.CreateFullyResolved (new Parameter (null, "obj", 0, null, loc), TypeManager.object_type), null);

                        Method tostring = new Method (this, null, TypeManager.system_string_expr,
                                Modifiers.PUBLIC | Modifiers.OVERRIDE | Modifiers.DEBUGGER_HIDDEN, new MemberName ("ToString", loc),
                                Mono.CSharp.ParametersCompiled.EmptyReadOnlyParameters, null);

                        ToplevelBlock equals_block = new ToplevelBlock (equals.Parameters, loc);
                        TypeExpr current_type;
                        if (IsGeneric)
                                current_type = new GenericTypeExpr (this, loc);
                        else
                                current_type = new TypeExpression (TypeBuilder, loc);

                        equals_block.AddVariable (current_type, "other", loc);
                        LocalVariableReference other_variable = new LocalVariableReference (equals_block, "other", loc);

                        MemberAccess system_collections_generic = new MemberAccess (new MemberAccess (
                                new QualifiedAliasMember ("global", "System", loc), "Collections", loc), "Generic", loc);

                        Expression rs_equals = null;
                        Expression string_concat = new StringConstant ("{", loc);
                        Expression rs_hashcode = new IntConstant (-2128831035, loc);
                        for (int i = 0; i < parameters.Count; ++i) {
                                AnonymousTypeParameter p = (AnonymousTypeParameter) parameters [i];
                                Field f = (Field) Fields [i];

                                MemberAccess equality_comparer = new MemberAccess (new MemberAccess (
                                        system_collections_generic, "EqualityComparer",
                                                new TypeArguments (new SimpleName (TypeParameters [i].Name, loc)), loc),
                                                "Default", loc);

                                Arguments arguments_equal = new Arguments (2);
                                arguments_equal.Add (new Argument (new MemberAccess (new This (f.Location), f.Name)));
                                arguments_equal.Add (new Argument (new MemberAccess (other_variable, f.Name)));

                                Expression field_equal = new Invocation (new MemberAccess (equality_comparer,
                                        "Equals", loc), arguments_equal);

                                Arguments arguments_hashcode = new Arguments (1);
                                arguments_hashcode.Add (new Argument (new MemberAccess (new This (f.Location), f.Name)));
                                Expression field_hashcode = new Invocation (new MemberAccess (equality_comparer,
                                        "GetHashCode", loc), arguments_hashcode);

                                IntConstant FNV_prime = new IntConstant (16777619, loc);                                
                                rs_hashcode = new Binary (Binary.Operator.Multiply,
                                        new Binary (Binary.Operator.ExclusiveOr, rs_hashcode, field_hashcode),
                                        FNV_prime);

                                Expression field_to_string = new Conditional (new Binary (Binary.Operator.Inequality,
                                        new MemberAccess (new This (f.Location), f.Name), new NullLiteral (loc)),
                                        new Invocation (new MemberAccess (
                                                new MemberAccess (new This (f.Location), f.Name), "ToString"), null),
                                        new StringConstant (string.Empty, loc));

                                if (rs_equals == null) {
                                        rs_equals = field_equal;
                                        string_concat = new Binary (Binary.Operator.Addition,
                                                string_concat,
                                                new Binary (Binary.Operator.Addition,
                                                        new StringConstant (" " + p.Name + " = ", loc),
                                                        field_to_string));
                                        continue;
                                }

                                //
                                // Implementation of ToString () body using string concatenation
                                //                              
                                string_concat = new Binary (Binary.Operator.Addition,
                                        new Binary (Binary.Operator.Addition,
                                                string_concat,
                                                new StringConstant (", " + p.Name + " = ", loc)),
                                        field_to_string);

                                rs_equals = new Binary (Binary.Operator.LogicalAnd, rs_equals, field_equal);
                        }

                        string_concat = new Binary (Binary.Operator.Addition,
                                string_concat,
                                new StringConstant (" }", loc));

                        //
                        // Equals (object obj) override
                        //              
                        LocalVariableReference other_variable_assign = new LocalVariableReference (equals_block, "other", loc);
                        equals_block.AddStatement (new StatementExpression (
                                new SimpleAssign (other_variable_assign,
                                        new As (equals_block.GetParameterReference ("obj", loc),
                                                current_type, loc), loc)));

                        Expression equals_test = new Binary (Binary.Operator.Inequality, other_variable, new NullLiteral (loc));
                        if (rs_equals != null)
                                equals_test = new Binary (Binary.Operator.LogicalAnd, equals_test, rs_equals);
                        equals_block.AddStatement (new Return (equals_test, loc));

                        equals.Block = equals_block;
                        equals.Define ();
                        AddMethod (equals);

                        //
                        // GetHashCode () override
                        //
                        Method hashcode = new Method (this, null, TypeManager.system_int32_expr,
                                Modifiers.PUBLIC | Modifiers.OVERRIDE | Modifiers.DEBUGGER_HIDDEN,
                                new MemberName ("GetHashCode", loc),
                                Mono.CSharp.ParametersCompiled.EmptyReadOnlyParameters, null);

                        //
                        // Modified FNV with good avalanche behavior and uniform
                        // distribution with larger hash sizes.
                        //
                        // const int FNV_prime = 16777619;
                        // int hash = (int) 2166136261;
                        // foreach (int d in data)
                        //     hash = (hash ^ d) * FNV_prime;
                        // hash += hash << 13;
                        // hash ^= hash >> 7;
                        // hash += hash << 3;
                        // hash ^= hash >> 17;
                        // hash += hash << 5;

                        ToplevelBlock hashcode_top = new ToplevelBlock (loc);
                        Block hashcode_block = new Block (hashcode_top);
                        hashcode_top.AddStatement (new Unchecked (hashcode_block));

                        hashcode_block.AddVariable (TypeManager.system_int32_expr, "hash", loc);
                        LocalVariableReference hash_variable = new LocalVariableReference (hashcode_block, "hash", loc);
                        LocalVariableReference hash_variable_assign = new LocalVariableReference (hashcode_block, "hash", loc);
                        hashcode_block.AddStatement (new StatementExpression (
                                new SimpleAssign (hash_variable_assign, rs_hashcode)));

                        hashcode_block.AddStatement (new StatementExpression (
                                new CompoundAssign (Binary.Operator.Addition, hash_variable,
                                        new Binary (Binary.Operator.LeftShift, hash_variable, new IntConstant (13, loc)))));
                        hashcode_block.AddStatement (new StatementExpression (
                                new CompoundAssign (Binary.Operator.ExclusiveOr, hash_variable,
                                        new Binary (Binary.Operator.RightShift, hash_variable, new IntConstant (7, loc)))));
                        hashcode_block.AddStatement (new StatementExpression (
                                new CompoundAssign (Binary.Operator.Addition, hash_variable,
                                        new Binary (Binary.Operator.LeftShift, hash_variable, new IntConstant (3, loc)))));
                        hashcode_block.AddStatement (new StatementExpression (
                                new CompoundAssign (Binary.Operator.ExclusiveOr, hash_variable,
                                        new Binary (Binary.Operator.RightShift, hash_variable, new IntConstant (17, loc)))));
                        hashcode_block.AddStatement (new StatementExpression (
                                new CompoundAssign (Binary.Operator.Addition, hash_variable,
                                        new Binary (Binary.Operator.LeftShift, hash_variable, new IntConstant (5, loc)))));

                        hashcode_block.AddStatement (new Return (hash_variable, loc));
                        hashcode.Block = hashcode_top;
                        hashcode.Define ();
                        AddMethod (hashcode);

                        //
                        // ToString () override
                        //

                        ToplevelBlock tostring_block = new ToplevelBlock (loc);
                        tostring_block.AddStatement (new Return (string_concat, loc));
                        tostring.Block = tostring_block;
                        tostring.Define ();
                        AddMethod (tostring);
                }

                public override bool Define ()
                {
                        if (!base.Define ())
                                return false;

                        DefineOverrides ();
                        return true;
                }

                public override string GetSignatureForError ()
                {
                        return SignatureForError;
                }

                public ArrayList Parameters {
                        get {
                                return parameters;
                        }
                }
        }
}