Change async host type to struct to run on .net (broken for reference types)

[mono.git] / mcs / 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 2003-2011 Novell, Inc.
// Copyright 2011 Xamarin Inc
//

using System;
using System.Collections.Generic;
using Mono.CompilerServices.SymbolWriter;
using System.Diagnostics;

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

namespace Mono.CSharp {

        public abstract class CompilerGeneratedContainer : ClassOrStruct
        {
                protected CompilerGeneratedContainer (TypeContainer parent, MemberName name, Modifiers mod)
                        : this (parent, name, mod, MemberKind.Class)
                {
                }

                protected CompilerGeneratedContainer (TypeContainer parent, MemberName name, Modifiers mod, MemberKind kind)
                        : base (parent, name, null, kind)
                {
                        Debug.Assert ((mod & Modifiers.AccessibilityMask) != 0);

                        ModFlags = mod | Modifiers.COMPILER_GENERATED | Modifiers.SEALED;
                        spec = new TypeSpec (Kind, null, this, null, ModFlags);
                }

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

                protected override bool DoDefineMembers ()
                {
                        if (Kind == MemberKind.Class && !IsStatic && !PartialContainer.HasInstanceConstructor) {
                                DefineDefaultConstructor (false);
                        }

                        return base.DoDefineMembers ();
                }

                protected static MemberName MakeMemberName (MemberBase host, string name, int unique_id, TypeParameters tparams, Location loc)
                {
                        string host_name = host == null ? null : host is InterfaceMemberBase ? ((InterfaceMemberBase)host).GetFullName (host.MemberName) : host.MemberName.Name;
                        string tname = MakeName (host_name, "c", name, unique_id);
                        TypeParameters args = null;
                        if (tparams != null) {
                                args = new TypeParameters (tparams.Count);

                                // Type parameters will be filled later when we have TypeContainer
                                // instance, for now we need only correct arity to create valid name
                                for (int i = 0; i < tparams.Count; ++i)
                                        args.Add ((TypeParameter) null);
                        }

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

                public static string MakeName (string host, string typePrefix, string name, int id)
                {
                        return "<" + host + ">" + typePrefix + "__" + name + id.ToString ("X");
                }

                protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
                {
                        base_type = Compiler.BuiltinTypes.Object;

                        base_class = null;
                        return null;
                }
        }

        public class HoistedStoreyClass : CompilerGeneratedContainer
        {
                public sealed class HoistedField : Field
                {
                        public HoistedField (HoistedStoreyClass parent, FullNamedExpression type, Modifiers 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;

                                HoistedStoreyClass parent = ((HoistedStoreyClass) Parent).GetGenericStorey ();
                                if (parent != null && parent.Mutator != null)
                                        member_type = parent.Mutator.Mutate (MemberType);

                                return true;
                        }
                }

                protected TypeParameterMutator mutator;

                public HoistedStoreyClass (TypeDefinition parent, MemberName name, TypeParameters tparams, Modifiers mods, MemberKind kind)
                        : base (parent, name, mods | Modifiers.PRIVATE, kind)
                {

                        if (tparams != null) {
                                var type_params = name.TypeParameters;
                                var src = new TypeParameterSpec[tparams.Count];
                                var dst = new TypeParameterSpec[tparams.Count];

                                for (int i = 0; i < tparams.Count; ++i) {
                                        type_params[i] = tparams[i].CreateHoistedCopy (spec);

                                        src[i] = tparams[i].Type;
                                        dst[i] = type_params[i].Type;
                                }

                                // A copy is not enough, inflate any type parameter constraints
                                // using a new type parameters
                                var inflator = new TypeParameterInflator (this, null, src, dst);
                                for (int i = 0; i < tparams.Count; ++i) {
                                        src[i].InflateConstraints (inflator, dst[i]);
                                }

                                mutator = new TypeParameterMutator (tparams, type_params);
                        }
                }

                #region Properties

                public TypeParameterMutator Mutator {
                        get {
                                return mutator;
                        }
                        set {
                                mutator = value;
                        }
                }

                #endregion

                public HoistedStoreyClass GetGenericStorey ()
                {
                        TypeContainer storey = this;
                        while (storey != null && storey.CurrentTypeParameters == null)
                                storey = storey.Parent;

                        return storey as HoistedStoreyClass;
                }
        }


        //
        // 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 : HoistedStoreyClass
        {
                struct StoreyFieldPair
                {
                        public readonly AnonymousMethodStorey Storey;
                        public readonly Field Field;

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

                //
                // 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.EmitAssign (ec, new CompilerGeneratedThis (ec.CurrentType, loc), false, false);
                        }

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

                // Unique storey ID
                public readonly int ID;

                public readonly ExplicitBlock OriginalSourceBlock;

                // A list of StoreyFieldPair with local field keeping parent storey instance
                List<StoreyFieldPair> used_parent_storeys;
                List<ExplicitBlock> children_references;

                // A list of hoisted parameters
                protected List<HoistedParameter> hoisted_params;
                protected List<HoistedVariable> hoisted_locals;

                // Hoisted this
                protected HoistedThis hoisted_this;

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

                bool initialize_hoisted_this;

                public AnonymousMethodStorey (ExplicitBlock block, TypeDefinition parent, MemberBase host, TypeParameters tparams, string name, MemberKind kind)
                        : base (parent, MakeMemberName (host, name, parent.Module.CounterAnonymousContainers, tparams, block.StartLocation),
                                tparams, 0, kind)
                {
                        OriginalSourceBlock = block;
                        ID = parent.Module.CounterAnonymousContainers++;
                }

                public void AddCapturedThisField (EmitContext ec)
                {
                        TypeExpr type_expr = new TypeExpression (ec.CurrentType, Location);
                        Field f = AddCompilerGeneratedField ("$this", type_expr);
                        hoisted_this = new HoistedThis (this, f);

                        initialize_hoisted_this = true;
                }

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

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

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

                protected Field AddCompilerGeneratedField (string name, FullNamedExpression type)
                {
                        return AddCompilerGeneratedField (name, type, false);
                }

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

                //
                // Creates a link between hoisted variable 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 List<ExplicitBlock> ();

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

                public void AddParentStoreyReference (EmitContext ec, AnonymousMethodStorey storey)
                {
                        CheckMembersDefined ();

                        if (used_parent_storeys == null)
                                used_parent_storeys = new List<StoreyFieldPair> ();
                        else if (used_parent_storeys.Exists (i => i.Storey == storey))
                                return;

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

                public void CaptureLocalVariable (ResolveContext ec, LocalVariable localVariable)
                {
                        if (this is StateMachine) {
                                if (ec.CurrentBlock.ParametersBlock != localVariable.Block.ParametersBlock)
                                        ec.CurrentBlock.Explicit.HasCapturedVariable = true;
                        } else {
                                ec.CurrentBlock.Explicit.HasCapturedVariable = true;
                        }

                        var hoisted = localVariable.HoistedVariant;
                        if (hoisted != null && hoisted.Storey != this && hoisted.Storey.Kind == MemberKind.Struct) {
                                // TODO: It's too late the field is defined in HoistedLocalVariable ctor
                                hoisted.Storey.hoisted_locals.Remove (hoisted);
                                hoisted = null;
                        }

                        if (hoisted == null) {
                                hoisted = new HoistedLocalVariable (this, localVariable, GetVariableMangledName (localVariable));
                                localVariable.HoistedVariant = hoisted;

                                if (hoisted_locals == null)
                                        hoisted_locals = new List<HoistedVariable> ();

                                hoisted_locals.Add (hoisted);
                        }

                        if (ec.CurrentBlock.Explicit != localVariable.Block.Explicit)
                                hoisted.Storey.AddReferenceFromChildrenBlock (ec.CurrentBlock.Explicit);
                }

                public void CaptureParameter (ResolveContext ec, ParametersBlock.ParameterInfo parameterInfo, ParameterReference parameterReference)
                {
                        if (!(this is StateMachine)) {
                                ec.CurrentBlock.Explicit.HasCapturedVariable = true;
                        }

                        var hoisted = parameterInfo.Parameter.HoistedVariant;
                        if (hoisted == null) {
                                var storey = parameterInfo.Block.StateMachine ?? this;
                                var hp = new HoistedParameter (storey, parameterReference);
                                hoisted = hp;
                                parameterInfo.Parameter.HoistedVariant = hoisted;

                                if (storey.hoisted_params == null)
                                        storey.hoisted_params = new List<HoistedParameter> (2);

                                storey.hoisted_params.Add (hp);
                        }

                        //
                        // Register link between current block and parameter storey. It will
                        // be used when setting up storey definition to deploy storey reference
                        // when parameters are used from multiple blocks
                        //
                        if (ec.CurrentBlock.Explicit != parameterInfo.Block) {
                                hoisted.Storey.AddReferenceFromChildrenBlock (ec.CurrentBlock.Explicit);
                        }
                }

                TypeExpr CreateStoreyTypeExpression (EmitContext ec)
                {
                        //
                        // Create an instance of storey type
                        //
                        TypeExpr storey_type_expr;
                        if (CurrentTypeParameters != null) {
                                //
                                // Use current method type parameter (MVAR) for top level storey only. All
                                // nested storeys use class type parameter (VAR)
                                //
                                var tparams = ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod.Storey != null ?
                                        ec.CurrentAnonymousMethod.Storey.CurrentTypeParameters :
                                        ec.CurrentTypeParameters;

                                TypeArguments targs = new TypeArguments ();

                                //
                                // Use type parameter name instead of resolved type parameter
                                // specification to resolve to correctly nested type parameters
                                //
                                for (int i = 0; i < tparams.Count; ++i)
                                        targs.Add (new SimpleName (tparams [i].Name, Location)); //  new TypeParameterExpr (tparams[i], Location));

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

                        return storey_type_expr;
                }

                public void SetNestedStoryParent (AnonymousMethodStorey parentStorey)
                {
                        Parent = parentStorey;
                        spec.IsGeneric = false;
                        spec.DeclaringType = parentStorey.CurrentType;
                        MemberName.TypeParameters = null;
                }

                protected override bool DoResolveTypeParameters ()
                {
                        // Although any storey can have type parameters they are all clones of method type
                        // parameters therefore have to mutate MVAR references in any of cloned constraints
                        if (CurrentTypeParameters != null) {
                                for (int i = 0; i < CurrentTypeParameters.Count; ++i) {
                                        var spec = CurrentTypeParameters[i].Type;
                                        spec.BaseType = mutator.Mutate (spec.BaseType);
                                        if (spec.InterfacesDefined != null) {
                                                var mutated = new TypeSpec[spec.InterfacesDefined.Length];
                                                for (int ii = 0; ii < mutated.Length; ++ii) {
                                                        mutated[ii] = mutator.Mutate (spec.InterfacesDefined[ii]);
                                                }

                                                spec.InterfacesDefined = mutated;
                                        }

                                        if (spec.TypeArguments != null) {
                                                spec.TypeArguments = mutator.Mutate (spec.TypeArguments);
                                        }
                                }
                        }

                        //
                        // Update parent cache as we most likely passed the point
                        // where the cache was constructed
                        //
                        Parent.CurrentType.MemberCache.AddMember (this.spec);

                        return true;
                }

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

                        //
                        // Create an instance of this storey
                        //
                        ResolveContext rc = new ResolveContext (ec.MemberContext);
                        rc.CurrentBlock = block;

                        var storey_type_expr = CreateStoreyTypeExpression (ec);
                        var source = new New (storey_type_expr, null, Location).Resolve (rc);

                        //
                        // When the current context is async (or iterator) lift local storey
                        // instantiation to the currect storey
                        //
                        if (ec.CurrentAnonymousMethod is StateMachineInitializer) {
                                //
                                // Unfortunately, normal capture mechanism could not be used because we are
                                // too late in the pipeline and standart assign cannot be used either due to
                                // recursive nature of GetStoreyInstanceExpression
                                //
                                var field = ec.CurrentAnonymousMethod.Storey.AddCompilerGeneratedField (
                                        LocalVariable.GetCompilerGeneratedName (block), storey_type_expr, true);

                                field.Define ();
                                field.Emit ();

                                var fexpr = new FieldExpr (field, Location);
                                fexpr.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location);
                                fexpr.EmitAssign (ec, source, false, false);
                                Instance = fexpr;
                        } else {
                                var local = TemporaryVariableReference.Create (source.Type, block, Location);
                                if (source.Type.IsStruct) {
                                        local.LocalInfo.CreateBuilder (ec);
                                } else {
                                        local.EmitAssign (ec, source);
                                }

                                Instance = local;
                        }

                        EmitHoistedFieldsInitialization (rc, ec);

                        // TODO: Implement properly
                        //SymbolWriter.DefineScopeVariable (ID, Instance.Builder);
                }

                void EmitHoistedFieldsInitialization (ResolveContext rc, 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) {
                                        //
                                        // Get instance expression of storey field
                                        //
                                        Expression instace_expr = GetStoreyInstanceExpression (ec);
                                        var fs = sf.Field.Spec;
                                        if (TypeManager.IsGenericType (instace_expr.Type))
                                                fs = MemberCache.GetMember (instace_expr.Type, fs);

                                        FieldExpr f_set_expr = new FieldExpr (fs, Location);
                                        f_set_expr.InstanceExpression = instace_expr;

                                        // TODO: CompilerAssign expression
                                        SimpleAssign a = new SimpleAssign (f_set_expr, sf.Storey.GetStoreyInstanceExpression (ec));
                                        if (a.Resolve (rc) != null)
                                                a.EmitStatement (ec);
                                }
                        }

                        //
                        // Initialize hoisted `this' only once, everywhere else will be
                        // referenced indirectly
                        //
                        if (initialize_hoisted_this) {
                                rc.CurrentBlock.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, IList<HoistedParameter> hoisted)
                {
                        foreach (HoistedParameter hp in hoisted) {
                                hp.EmitHoistingAssignment (ec);
                        }
                }

                //
                // 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 from inside of same storey (S -> S)
                                        //
                                        return new CompilerGeneratedThis (CurrentType, Location);
                                }

                                //
                                // External field access
                                //
                                return Instance;
                        }

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

                protected virtual string GetVariableMangledName (LocalVariable 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;
                        }
                        set {
                                hoisted_this = value;
                        }
                }

                public IList<ExplicitBlock> ReferencesFromChildrenBlock {
                        get { return children_references; }
                }
        }

        public abstract class HoistedVariable
        {
                //
                // Hoisted version of variable references used in expression
                // tree has to be delayed until we know its location. The variable
                // doesn't know its location until all stories are calculated
                //
                class ExpressionTreeVariableReference : Expression
                {
                        readonly HoistedVariable hv;

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

                        public override bool ContainsEmitWithAwait ()
                        {
                                return false;
                        }

                        public override Expression CreateExpressionTree (ResolveContext ec)
                        {
                                return hv.CreateExpressionTree ();
                        }

                        protected override Expression DoResolve (ResolveContext ec)
                        {
                                eclass = ExprClass.Value;
                                type = ec.Module.PredefinedTypes.Expression.Resolve ();
                                return this;
                        }

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

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

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

                public AnonymousMethodStorey Storey {
                        get {
                                return storey;
                        }
                }

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

                public Expression CreateExpressionTree ()
                {
                        return new ExpressionTreeVariableReference (this);
                }

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

                public Expression EmitToField (EmitContext ec)
                {
                        return GetFieldExpression (ec);
                }

                //
                // Creates field access expression for hoisted variable
                //
                protected virtual 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)
                                //
                                if (storey.Instance.Type.IsGenericOrParentIsGeneric) {
                                        var fs = MemberCache.GetMember (storey.Instance.Type, field.Spec);
                                        cached_outer_access = new FieldExpr (fs, field.Location);
                                } else {
                                        cached_outer_access = new FieldExpr (field, field.Location);
                                }

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

                        FieldExpr inner_access;
                        if (cached_inner_access != null) {
                                if (!cached_inner_access.TryGetValue (ec.CurrentAnonymousMethod, out inner_access))
                                        inner_access = null;
                        } else {
                                inner_access = null;
                                cached_inner_access = new Dictionary<AnonymousExpression, FieldExpr> (4);
                        }

                        if (inner_access == null) {
                                if (field.Parent.IsGenericOrParentIsGeneric) {
                                        var fs = MemberCache.GetMember (field.Parent.CurrentType, field.Spec);
                                        inner_access = new FieldExpr (fs, field.Location);
                                } else {
                                        inner_access = new FieldExpr (field, field.Location);
                                }

                                inner_access.InstanceExpression = storey.GetStoreyInstanceExpression (ec);
                                cached_inner_access.Add (ec.CurrentAnonymousMethod, inner_access);
                        }

                        return inner_access;
                }

                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 isCompound)
                {
                        GetFieldExpression (ec).EmitAssign (ec, source, leave_copy, false);
                }
        }

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

                        protected override Expression ResolveConversions (ResolveContext 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 Field Field {
                        get {
                                return field;
                        }
                }

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

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

                        parameter.Parameter.HoistedVariant = temp;
                }
        }

        class HoistedLocalVariable : HoistedVariable
        {
                public HoistedLocalVariable (AnonymousMethodStorey storey, LocalVariable local, string name)
                        : base (storey, name, local.Type)
                {
                }
        }

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

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

        //
        // Anonymous method expression as created by parser
        //
        public class AnonymousMethodExpression : Expression
        {
                //
                // Special conversion for nested expression tree lambdas
                //
                class Quote : ShimExpression
                {
                        public Quote (Expression expr)
                                : base (expr)
                        {
                        }

                        public override Expression CreateExpressionTree (ResolveContext ec)
                        {
                                var args = new Arguments (1);
                                args.Add (new Argument (expr.CreateExpressionTree (ec)));
                                return CreateExpressionFactoryCall (ec, "Quote", args);
                        }

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

                                eclass = expr.eclass;
                                type = expr.Type;
                                return this;
                        }
                }

                readonly Dictionary<TypeSpec, Expression> compatibles;

                public ParametersBlock Block;

                public AnonymousMethodExpression (Location loc)
                {
                        this.loc = loc;
                        this.compatibles = new Dictionary<TypeSpec, Expression> ();
                }

                #region Properties

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

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

                public ParametersCompiled Parameters {
                        get {
                                return Block.Parameters;
                        }
                }

                #endregion

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

                TypeSpec CompatibleChecks (ResolveContext ec, TypeSpec delegate_type)
                {
                        if (delegate_type.IsDelegate)
                                return delegate_type;

                        if (delegate_type.IsExpressionTreeType) {
                                delegate_type = delegate_type.TypeArguments [0];
                                if (delegate_type.IsDelegate)
                                        return delegate_type;

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

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

                protected bool VerifyExplicitParameters (ResolveContext ec, TypeSpec delegate_type, AParametersCollection parameters)
                {
                        if (VerifyParameterCompatibility (ec, delegate_type, parameters, ec.IsInProbingMode))
                                return true;

                        if (!ec.IsInProbingMode)
                                ec.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 (ResolveContext ec, TypeSpec delegate_type, AParametersCollection invoke_pd, bool ignore_errors)
                {
                        if (Parameters.Count != invoke_pd.Count) {
                                if (ignore_errors)
                                        return false;
                                
                                ec.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)
                                                ec.Report.Error (1677, loc, "Parameter `{0}' should not be declared with the `{1}' keyword",
                                                              (i + 1).ToString (), Parameter.GetModifierSignature (Parameters.FixedParameters [i].ModFlags));
                                        else
                                                ec.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;

                                TypeSpec 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 (!TypeSpecComparer.IsEqual (invoke_pd.Types [i], Parameters.Types [i])) {
                                        if (ignore_errors)
                                                return false;
                                        
                                        ec.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 (ResolveContext ec, TypeInferenceContext type_inference, TypeSpec delegate_type)
                {
                        if (!HasExplicitParameters)
                                return false;

                        if (!delegate_type.IsDelegate) {
                                if (!delegate_type.IsExpressionTreeType)
                                        return false;

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

                        for (int i = 0; i < Parameters.Count; ++i) {
                                if (type_inference.ExactInference (Parameters.Types[i], d_params.Types[i]) == 0)
                                        return false;
                        }

                        return true;
                }

                public TypeSpec InferReturnType (ResolveContext ec, TypeInferenceContext tic, TypeSpec delegate_type)
                {
                        Expression expr;
                        AnonymousExpression am;

                        if (compatibles.TryGetValue (delegate_type, out expr)) {
                                am = expr as AnonymousExpression;
                                return am == null ? null : am.ReturnType;
                        }

                        using (ec.Set (ResolveContext.Options.ProbingMode | ResolveContext.Options.InferReturnType)) {
                                var body = CompatibleMethodBody (ec, tic, null, delegate_type);
                                if (body != null) {
                                        am = body.Compatible (ec, body);
                                } else {
                                        am = null;
                                }
                        }

                        if (am == null)
                                return null;

//                      compatibles.Add (delegate_type, am);
                        return am.ReturnType;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                //
                // Returns AnonymousMethod container if this anonymous method
                // expression can be implicitly converted to the delegate type `delegate_type'
                //
                public Expression Compatible (ResolveContext ec, TypeSpec type)
                {
                        Expression am;
                        if (compatibles.TryGetValue (type, out am))
                                return am;

                        TypeSpec 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.
                        //

                        var invoke_mb = Delegate.GetInvokeMethod (delegate_type);
                        TypeSpec return_type = invoke_mb.ReturnType;

                        //
                        // 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.
                        //

                        var body = CompatibleMethodBody (ec, null, return_type, delegate_type);
                        if (body == null)
                                return null;

                        bool etree_conversion = delegate_type != type;

                        try {
                                if (etree_conversion) {
                                        if (ec.HasSet (ResolveContext.Options.ExpressionTreeConversion)) {
                                                //
                                                // Nested expression tree lambda use same scope as parent
                                                // lambda, this also means no variable capturing between this
                                                // and parent scope
                                                //
                                                am = body.Compatible (ec, ec.CurrentAnonymousMethod);

                                                //
                                                // Quote nested expression tree
                                                //
                                                if (am != null)
                                                        am = new Quote (am);
                                        } else {
                                                int errors = ec.Report.Errors;

                                                if (Block.IsAsync) {
                                                        ec.Report.Error (1989, loc, "Async lambda expressions cannot be converted to expression trees");
                                                }

                                                using (ec.Set (ResolveContext.Options.ExpressionTreeConversion)) {
                                                        am = body.Compatible (ec);
                                                }

                                                //
                                                // Rewrite expressions into expression tree when targeting Expression<T>
                                                //
                                                if (am != null && errors == ec.Report.Errors)
                                                        am = CreateExpressionTree (ec, delegate_type);
                                        }
                                } else {
                                        am = body.Compatible (ec);
                                }
                        } catch (CompletionResult) {
                                throw;
                        } catch (FatalException) {
                                throw;
                        } catch (Exception e) {
                                throw new InternalErrorException (e, loc);
                        }

                        if (!ec.IsInProbingMode) {
                                compatibles.Add (type, am ?? EmptyExpression.Null);
                        }

                        return am;
                }

                protected virtual Expression CreateExpressionTree (ResolveContext ec, TypeSpec delegate_type)
                {
                        return CreateExpressionTree (ec);
                }

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

                protected virtual ParametersCompiled ResolveParameters (ResolveContext ec, TypeInferenceContext tic, TypeSpec delegate_type)
                {
                        var delegate_parameters = Delegate.GetParameters (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) != 0) {
                                                if (!ec.IsInProbingMode) {
                                                        ec.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",
                                                                delegate_type.GetSignatureForError ());
                                                }

                                                return null;
                                        }
                                        fixedpars[i] = new Parameter (
                                                new TypeExpression (delegate_parameters.Types [i], loc), null,
                                                delegate_parameters.FixedParameters [i].ModFlags, null, loc);
                                }

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

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

                        return Parameters;
                }

                protected override Expression DoResolve (ResolveContext ec)
                {
                        if (ec.HasSet (ResolveContext.Options.ConstantScope)) {
                                ec.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 (!DoResolveParameters (ec))
                                return null;

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

                protected virtual bool DoResolveParameters (ResolveContext rc)
                {
                        return Parameters.Resolve (rc);
                }

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

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

                public override string GetSignatureForError ()
                {
                        return ExprClassName;
                }

                AnonymousMethodBody CompatibleMethodBody (ResolveContext ec, TypeInferenceContext tic, TypeSpec return_type, TypeSpec delegate_type)
                {
                        ParametersCompiled p = ResolveParameters (ec, tic, delegate_type);
                        if (p == null)
                                return null;

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

                        if (b.IsAsync) {
                                var rt = return_type;
                                if (rt != null && rt.Kind != MemberKind.Void && rt != ec.Module.PredefinedTypes.Task.TypeSpec && !rt.IsGenericTask) {
                                        ec.Report.Error (4010, loc, "Cannot convert async {0} to delegate type `{1}'",
                                                GetSignatureForError (), delegate_type.GetSignatureForError ());

                                        return null;
                                }

                                b = b.ConvertToAsyncTask (ec, ec.CurrentMemberDefinition.Parent.PartialContainer, p, return_type, loc);
                        }

                        return CompatibleMethodFactory (return_type ?? InternalType.Arglist, delegate_type, p, b);
                }

                protected virtual AnonymousMethodBody CompatibleMethodFactory (TypeSpec return_type, TypeSpec delegate_type, ParametersCompiled p, ParametersBlock 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 = (ParametersBlock) clonectx.LookupBlock (Block);
                }
                
                public override object Accept (StructuralVisitor visitor)
                {
                        return visitor.Visit (this);
                }
        }

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

                        public AnonymousMethodMethod (TypeDefinition parent, AnonymousExpression am, AnonymousMethodStorey storey,
                                                          TypeExpr return_type,
                                                          Modifiers mod, MemberName name,
                                                          ParametersCompiled parameters)
                                : base (parent, return_type, mod | Modifiers.COMPILER_GENERATED,
                                                name, parameters, null)
                        {
                                this.AnonymousMethod = am;
                                this.Storey = storey;

                                Parent.PartialContainer.Members.Add (this);
                                Block = new ToplevelBlock (am.block, parameters);
                        }

                        public override EmitContext CreateEmitContext (ILGenerator ig, SourceMethodBuilder sourceMethod)
                        {
                                EmitContext ec = new EmitContext (this, ig, ReturnType, sourceMethod);
                                ec.CurrentAnonymousMethod = AnonymousMethod;
                                return ec;
                        }

                        protected override void DefineTypeParameters ()
                        {
                                // Type parameters were cloned
                        }

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

                                if (Storey != null && Storey.Mutator != null) {
                                        if (!parameters.IsEmpty) {
                                                var mutated = Storey.Mutator.Mutate (parameters.Types);
                                                if (mutated != parameters.Types)
                                                        parameters = ParametersCompiled.CreateFullyResolved ((Parameter[]) parameters.FixedParameters, mutated);
                                        }

                                        member_type = Storey.Mutator.Mutate (member_type);
                                }

                                return true;
                        }

                        public override void Emit ()
                        {
                                if (MethodBuilder == null) {
                                        Define ();
                                }

                                base.Emit ();
                        }
                }

                protected ParametersBlock block;

                public TypeSpec ReturnType;

                protected AnonymousExpression (ParametersBlock block, TypeSpec 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; }

                //
                // The block that makes up the body for the anonymous method
                //
                public ParametersBlock Block {
                        get {
                                return block;
                        }
                }

                public AnonymousExpression Compatible (ResolveContext ec)
                {
                        return Compatible (ec, this);
                }

                public AnonymousExpression Compatible (ResolveContext ec, AnonymousExpression ae)
                {
                        if (block.Resolved)
                                return this;

                        // TODO: Implement clone
                        BlockContext aec = new BlockContext (ec, block, ReturnType);
                        aec.CurrentAnonymousMethod = ae;

                        ResolveContext.Options flags = 0;

                        var am = this as AnonymousMethodBody;

                        if (ec.HasSet (ResolveContext.Options.InferReturnType) && am != null) {
                                am.ReturnTypeInference = new TypeInferenceContext ();
                        }

                        if (ec.IsInProbingMode)
                                flags |= ResolveContext.Options.ProbingMode;

                        if (ec.HasSet (ResolveContext.Options.FieldInitializerScope))
                                flags |= ResolveContext.Options.FieldInitializerScope;

                        if (ec.HasSet (ResolveContext.Options.ExpressionTreeConversion))
                                flags |= ResolveContext.Options.ExpressionTreeConversion;

                        aec.Set (flags);

                        var errors = ec.Report.Errors;

                        bool res = Block.Resolve (ec.CurrentBranching, aec, null);

                        if (am != null && am.ReturnTypeInference != null) {
                                am.ReturnTypeInference.FixAllTypes (ec);
                                ReturnType = am.ReturnTypeInference.InferredTypeArguments [0];
                                am.ReturnTypeInference = null;

                                //
                                // If e is synchronous the inferred return type is T
                                // If e is asynchronous the inferred return type is Task<T>
                                //
                                if (block.IsAsync && ReturnType != null) {
                                        ReturnType = ec.Module.PredefinedTypes.TaskGeneric.TypeSpec.MakeGenericType (ec, new [] { ReturnType });
                                }
                        }

                        if (res && errors != ec.Report.Errors)
                                return null;

                        return res ? this : null;
                }

                public override bool ContainsEmitWithAwait ()
                {
                        return false;
                }

                public void SetHasThisAccess ()
                {
                        ExplicitBlock b = block;
                        do {
                                if (b.HasCapturedThis)
                                        return;

                                b.HasCapturedThis = true;
                                b = b.Parent == null ? null : b.Parent.Explicit;
                        } while (b != null);
                }
        }

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

                AnonymousMethodMethod method;
                Field am_cache;
                string block_name;
                TypeInferenceContext return_inference;

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

                #region Properties

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

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

                public ParametersCompiled Parameters {
                        get {
                                return parameters;
                        }
                }

                public TypeInferenceContext ReturnTypeInference {
                        get {
                                return return_inference;
                        }
                        set {
                                return_inference = value;
                        }
                }

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

                #endregion

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

                bool Define (ResolveContext ec)
                {
                        if (!Block.Resolved && Compatible (ec) == null)
                                return false;

                        if (block_name == null) {
                                MemberCore mc = (MemberCore) ec.MemberContext;
                                block_name = mc.MemberName.Basename;
                        }

                        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
                        //

                        Modifiers modifiers;
                        TypeDefinition parent = null;

                        var src_block = Block.Original.Explicit;
                        if (src_block.HasCapturedVariable || src_block.HasCapturedThis) {
                                parent = storey = FindBestMethodStorey ();

                                if (storey == null) {
                                        var sm = src_block.ParametersBlock.TopBlock.StateMachine;

                                        //
                                        // Remove hoisted this demand when simple instance method is enough
                                        //
                                        if (src_block.HasCapturedThis) {
                                                src_block.ParametersBlock.TopBlock.RemoveThisReferenceFromChildrenBlock (src_block);

                                                //
                                                // Special case where parent class is used to emit instance method
                                                // because currect storey is of value type (async host) and we don't
                                                // want to create another childer storey to host this reference only
                                                //
                                                if (sm != null && sm.Kind == MemberKind.Struct)
                                                        parent = sm.Parent.PartialContainer;
                                        }

                                        //
                                        // For iterators we can host everything in one class
                                        //
                                        if (sm is IteratorStorey)
                                                parent = storey = sm;
                                }

                                modifiers = storey != null ? Modifiers.INTERNAL : Modifiers.PRIVATE;
                        } else {
                                if (ec.CurrentAnonymousMethod != null)
                                        parent = storey = ec.CurrentAnonymousMethod.Storey;

                                modifiers = Modifiers.STATIC | Modifiers.PRIVATE;
                        }

                        if (parent == null)
                                parent = ec.CurrentTypeDefinition.Parent.PartialContainer;

                        string name = CompilerGeneratedContainer.MakeName (parent != storey ? block_name : null,
                                "m", null, ec.Module.CounterAnonymousMethods++);

                        MemberName member_name;
                        if (storey == null && ec.CurrentTypeParameters != null) {

                                var hoisted_tparams = ec.CurrentTypeParameters;
                                var type_params = new TypeParameters (hoisted_tparams.Count);
                                for (int i = 0; i < hoisted_tparams.Count; ++i) {
                                    type_params.Add (hoisted_tparams[i].CreateHoistedCopy (null));
                                }

                                member_name = new MemberName (name, type_params, Location);
                        } else {
                                member_name = new MemberName (name, Location);
                        }

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

                protected override Expression DoResolve (ResolveContext ec)
                {
                        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) {
                                        var parent = method.Parent.PartialContainer;
                                        int id = parent.AnonymousMethodsCounter++;
                                        var cache_type = storey != null && storey.Mutator != null ? storey.Mutator.Mutate (type) : type;

                                        am_cache = new Field (parent, new TypeExpression (cache_type, loc),
                                                Modifiers.STATIC | Modifiers.PRIVATE | Modifiers.COMPILER_GENERATED,
                                                new MemberName (CompilerGeneratedContainer.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;"
                                        //
                                }
                        }

                        Label l_initialized = ec.DefineLabel ();

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

                        //
                        // Load method delegate implementation
                        //

                        if (is_static) {
                                ec.EmitNull ();
                        } else if (storey != null) {
                                Expression e = storey.GetStoreyInstanceExpression (ec).Resolve (new ResolveContext (ec.MemberContext));
                                if (e != null) {
                                        e.Emit (ec);
                                }
                        } else {
                                ec.EmitThis ();

                                //
                                // Special case for value type storey where this is not lifted but
                                // droped off to parent class
                                //
                                for (var b = Block.Parent; b != null; b = b.Parent) {
                                        if (b.ParametersBlock.StateMachine != null) {
                                                ec.Emit (OpCodes.Ldfld, b.ParametersBlock.StateMachine.HoistedThis.Field.Spec);
                                                break;
                                        }
                                }
                        }

                        var delegate_method = method.Spec;
                        if (storey != null && storey.MemberName.IsGeneric) {
                                TypeSpec t = storey.Instance.Type;

                                //
                                // Mutate anonymous method instance type if we are in nested
                                // hoisted generic anonymous method storey
                                //
                                if (ec.IsAnonymousStoreyMutateRequired) {
                                        t = storey.Mutator.Mutate (t);
                                }

                                ec.Emit (OpCodes.Ldftn, TypeBuilder.GetMethod (t.GetMetaInfo (), (MethodInfo) delegate_method.GetMetaInfo ()));
                        } else {
                                if (delegate_method.IsGeneric)
                                        delegate_method = delegate_method.MakeGenericMethod (ec.MemberContext, method.TypeParameters);

                                ec.Emit (OpCodes.Ldftn, delegate_method);
                        }

                        var constructor_method = Delegate.GetConstructor (type);
                        ec.Emit (OpCodes.Newobj, constructor_method);

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

                public override void EmitStatement (EmitContext ec)
                {
                        throw new NotImplementedException ();
                }

                //
                // 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);
                }
        }

        //
        // Anonymous type container
        //
        public class AnonymousTypeClass : CompilerGeneratedContainer
        {
                public const string ClassNamePrefix = "<>__AnonType";
                public const string SignatureForError = "anonymous type";
                
                readonly IList<AnonymousTypeParameter> parameters;

                private AnonymousTypeClass (ModuleContainer parent, MemberName name, IList<AnonymousTypeParameter> parameters, Location loc)
                        : base (parent, name, parent.Evaluator != null ? Modifiers.PUBLIC : Modifiers.INTERNAL)
                {
                        this.parameters = parameters;
                }

                public static AnonymousTypeClass Create (TypeContainer parent, IList<AnonymousTypeParameter> parameters, Location loc)
                {
                        string name = ClassNamePrefix + parent.Module.CounterAnonymousTypes++;

                        ParametersCompiled all_parameters;
                        TypeParameters tparams = null;
                        SimpleName[] t_args;

                        if (parameters.Count == 0) {
                                all_parameters = ParametersCompiled.EmptyReadOnlyParameters;
                                t_args = null;
                        } else {
                                t_args = new SimpleName[parameters.Count];
                                tparams = new TypeParameters ();
                                Parameter[] ctor_params = new Parameter[parameters.Count];
                                for (int i = 0; i < parameters.Count; ++i) {
                                        AnonymousTypeParameter p = parameters[i];
                                        for (int ii = 0; ii < i; ++ii) {
                                                if (parameters[ii].Name == p.Name) {
                                                        parent.Compiler.Report.Error (833, parameters[ii].Location,
                                                                "`{0}': An anonymous type cannot have multiple properties with the same name",
                                                                        p.Name);

                                                        p = new AnonymousTypeParameter (null, "$" + i.ToString (), p.Location);
                                                        parameters[i] = p;
                                                        break;
                                                }
                                        }

                                        t_args[i] = new SimpleName ("<" + p.Name + ">__T", p.Location);
                                        tparams.Add (new TypeParameter (i, new MemberName (t_args[i].Name, p.Location), null, null, Variance.None));
                                        ctor_params[i] = new Parameter (t_args[i], p.Name, Parameter.Modifier.NONE, null, p.Location);
                                }

                                all_parameters = new ParametersCompiled (ctor_params);
                        }

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

                        Constructor c = new Constructor (a_type, name, Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
                                null, all_parameters, loc);
                        c.Block = new ToplevelBlock (parent.Module.Compiler, c.ParameterInfo, loc);

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

                                Field f = new Field (a_type, t_args [i], Modifiers.PRIVATE | Modifiers.READONLY | Modifiers.DEBUGGER_HIDDEN,
                                        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 (i, p.Location))));

                                ToplevelBlock get_block = new ToplevelBlock (parent.Module.Compiler, p.Location);
                                get_block.AddStatement (new Return (
                                        new MemberAccess (new This (p.Location), f.Name), p.Location));

                                Property prop = new Property (a_type, t_args [i], Modifiers.PUBLIC,
                                        new MemberName (p.Name, p.Location), null);
                                prop.Get = new Property.GetMethod (prop, 0, null, p.Location);
                                prop.Get.Block = get_block;
                                a_type.AddMember (prop);
                        }

                        if (error)
                                return null;

                        a_type.AddConstructor (c);
                        return a_type;
                }
                
                protected override bool DoDefineMembers ()
                {
                        if (!base.DoDefineMembers ())
                                return false;

                        Location loc = Location;

                        var equals_parameters = ParametersCompiled.CreateFullyResolved (
                                new Parameter (new TypeExpression (Compiler.BuiltinTypes.Object, loc), "obj", 0, null, loc), Compiler.BuiltinTypes.Object);

                        Method equals = new Method (this, new TypeExpression (Compiler.BuiltinTypes.Bool, loc),
                                Modifiers.PUBLIC | Modifiers.OVERRIDE | Modifiers.DEBUGGER_HIDDEN, new MemberName ("Equals", loc),
                                equals_parameters, null);

                        equals_parameters[0].Resolve (equals, 0);

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

                        ToplevelBlock equals_block = new ToplevelBlock (Compiler, equals.ParameterInfo, loc);

                        TypeExpr current_type;
                        if (CurrentTypeParameters != null) {
                                var targs = new TypeArguments ();
                                for (int i = 0; i < CurrentTypeParameters.Count; ++i) {
                                        targs.Add (new TypeParameterExpr (CurrentTypeParameters[i], Location));
                                }

                                current_type = new GenericTypeExpr (Definition, targs, loc);
                        } else {
                                current_type = new TypeExpression (Definition, loc);
                        }

                        var li_other = LocalVariable.CreateCompilerGenerated (CurrentType, equals_block, loc);
                        equals_block.AddStatement (new BlockVariableDeclaration (new TypeExpression (li_other.Type, loc), li_other));
                        var other_variable = new LocalVariableReference (li_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 (Compiler.BuiltinTypes, "{", loc);
                        Expression rs_hashcode = new IntConstant (Compiler.BuiltinTypes, -2128831035, loc);
                        for (int i = 0; i < parameters.Count; ++i) {
                                var p = parameters [i];
                                var f = (Field) Members [i * 2];

                                MemberAccess equality_comparer = new MemberAccess (new MemberAccess (
                                        system_collections_generic, "EqualityComparer",
                                                new TypeArguments (new SimpleName (CurrentTypeParameters [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 (Compiler.BuiltinTypes, 16777619, loc);                         
                                rs_hashcode = new Binary (Binary.Operator.Multiply,
                                        new Binary (Binary.Operator.ExclusiveOr, rs_hashcode, field_hashcode, loc),
                                        FNV_prime, loc);

                                Expression field_to_string = new Conditional (new BooleanExpression (new Binary (Binary.Operator.Inequality,
                                        new MemberAccess (new This (f.Location), f.Name), new NullLiteral (loc), loc)),
                                        new Invocation (new MemberAccess (
                                                new MemberAccess (new This (f.Location), f.Name), "ToString"), null),
                                        new StringConstant (Compiler.BuiltinTypes, string.Empty, loc), 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 (Compiler.BuiltinTypes, " " + p.Name + " = ", loc),
                                                        field_to_string,
                                                        loc),
                                                loc);
                                        continue;
                                }

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

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

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

                        //
                        // Equals (object obj) override
                        //              
                        var other_variable_assign = new TemporaryVariableReference (li_other, loc);
                        equals_block.AddStatement (new StatementExpression (
                                new SimpleAssign (other_variable_assign,
                                        new As (equals_block.GetParameterReference (0, loc),
                                                current_type, loc), loc)));

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

                        equals.Block = equals_block;
                        equals.Define ();
                        Members.Add (equals);

                        //
                        // GetHashCode () override
                        //
                        Method hashcode = new Method (this, new TypeExpression (Compiler.BuiltinTypes.Int, loc),
                                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 (Compiler, loc);
                        Block hashcode_block = new Block (hashcode_top, loc, loc);
                        hashcode_top.AddStatement (new Unchecked (hashcode_block, loc));

                        var li_hash = LocalVariable.CreateCompilerGenerated (Compiler.BuiltinTypes.Int, hashcode_top, loc);
                        hashcode_block.AddStatement (new BlockVariableDeclaration (new TypeExpression (li_hash.Type, loc), li_hash));
                        LocalVariableReference hash_variable_assign = new LocalVariableReference (li_hash, loc);
                        hashcode_block.AddStatement (new StatementExpression (
                                new SimpleAssign (hash_variable_assign, rs_hashcode)));

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

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

                        //
                        // ToString () override
                        //

                        ToplevelBlock tostring_block = new ToplevelBlock (Compiler, loc);
                        tostring_block.AddStatement (new Return (string_concat, loc));
                        tostring.Block = tostring_block;
                        tostring.Define ();
                        Members.Add (tostring);

                        return true;
                }

                public override string GetSignatureForError ()
                {
                        return SignatureForError;
                }

                public override CompilationSourceFile GetCompilationSourceFile ()
                {
                        return null;
                }

                public IList<AnonymousTypeParameter> Parameters {
                        get {
                                return parameters;
                        }
                }
        }
}