Negative header ids should be valid
[mono.git] / mcs / mcs / iterators.cs
index bc9314fee130aafd82b5ba1894abd7ee970ca563..dcbf10edf722bb4a6bf635406f9e62d75466939f 100644 (file)
@@ -8,14 +8,12 @@
 // Dual licensed under the terms of the MIT X11 or GNU GPL
 // Copyright 2003 Ximian, Inc.
 // Copyright 2003-2008 Novell, Inc.
-//
-
-// TODO:
-//    Flow analysis for Yield.
+// Copyright 2011 Xamarin Inc.
 //
 
 using System;
 using System.Collections.Generic;
+using Mono.CompilerServices.SymbolWriter;
 
 #if STATIC
 using IKVM.Reflection.Emit;
@@ -28,7 +26,7 @@ namespace Mono.CSharp
        public abstract class YieldStatement<T> : ResumableStatement where T : StateMachineInitializer
        {
                protected Expression expr;
-               bool unwind_protect;
+               protected bool unwind_protect;
                protected T machine_initializer;
                int resume_pc;
 
@@ -38,6 +36,10 @@ namespace Mono.CSharp
                        loc = l;
                }
 
+               public Expression Expr {
+                       get { return this.expr; }
+               }
+               
                protected override void CloneTo (CloneContext clonectx, Statement t)
                {
                        var target = (YieldStatement<T>) t;
@@ -58,7 +60,7 @@ namespace Mono.CSharp
                        machine_initializer = bc.CurrentAnonymousMethod as T;
 
                        if (!bc.CurrentBranching.CurrentUsageVector.IsUnreachable)
-                               unwind_protect = bc.CurrentBranching.AddResumePoint (this, loc, out resume_pc);
+                               unwind_protect = bc.CurrentBranching.AddResumePoint (this, this, out resume_pc);
 
                        return true;
                }
@@ -99,6 +101,11 @@ namespace Mono.CSharp
 
                        return true;
                }
+               
+               public override object Accept (StructuralVisitor visitor)
+               {
+                       return visitor.Visit (this);
+               }
        }
 
        public class YieldBreak : ExitStatement
@@ -130,6 +137,11 @@ namespace Mono.CSharp
                {
                        iterator.EmitYieldBreak (ec, unwind_protect);
                }
+               
+               public override object Accept (StructuralVisitor visitor)
+               {
+                       return visitor.Visit (this);
+               }
        }
 
        public abstract class StateMachine : AnonymousMethodStorey
@@ -142,24 +154,17 @@ namespace Mono.CSharp
                        Start = 0
                }
 
-               Field disposing_field;
                Field pc_field;
-               int local_name_idx;
                StateMachineMethod method;
+               int local_name_idx;
 
-               protected StateMachine (Block block, TypeContainer parent, MemberBase host, TypeParameter[] tparams, string name)
-                       : base (block, parent, host, tparams, name)
+               protected StateMachine (ParametersBlock block, TypeDefinition parent, MemberBase host, TypeParameters tparams, string name, MemberKind kind)
+                       : base (block, parent, host, tparams, name, kind)
                {
                }
 
                #region Properties
 
-               public Field DisposingField {
-                       get {
-                               return disposing_field;
-                       }
-               }
-
                public StateMachineMethod StateMachineMethod {
                        get {
                                return method;
@@ -180,20 +185,22 @@ namespace Mono.CSharp
                                throw new InternalErrorException ();
 
                        this.method = method;
-                       AddMethod (method);
+                       Members.Add (method);
                }
 
                protected override bool DoDefineMembers ()
                {
                        pc_field = AddCompilerGeneratedField ("$PC", new TypeExpression (Compiler.BuiltinTypes.Int, Location));
-                       disposing_field = AddCompilerGeneratedField ("$disposing", new TypeExpression (Compiler.BuiltinTypes.Bool, Location));
 
                        return base.DoDefineMembers ();
                }
 
                protected override string GetVariableMangledName (LocalVariable local_info)
                {
-                       return "<" + local_info.Name + ">__" + local_name_idx++.ToString ();
+                       if (local_info.IsCompilerGenerated)
+                               return base.GetVariableMangledName (local_info);
+
+                       return "<" + local_info.Name + ">__" + local_name_idx++.ToString ("X");
                }
        }
 
@@ -266,7 +273,7 @@ namespace Mono.CSharp
                                {
                                        Label label_init = ec.DefineLabel ();
 
-                                       ec.Emit (OpCodes.Ldarg_0);
+                                       ec.EmitThis ();
                                        ec.Emit (OpCodes.Ldflda, host.PC.Spec);
                                        ec.EmitInt ((int) State.Start);
                                        ec.EmitInt ((int) State.Uninitialized);
@@ -278,7 +285,7 @@ namespace Mono.CSharp
                                        ec.EmitInt ((int) State.Uninitialized);
                                        ec.Emit (OpCodes.Bne_Un_S, label_init);
 
-                                       ec.Emit (OpCodes.Ldarg_0);
+                                       ec.EmitThis ();
                                        ec.Emit (OpCodes.Ret);
 
                                        ec.MarkLabel (label_init);
@@ -288,10 +295,23 @@ namespace Mono.CSharp
                                }
                        }
 
-                       public GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
+                       GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
                                : base (host, null, returnType, Modifiers.DEBUGGER_HIDDEN, name)
                        {
-                               Block.AddStatement (new GetEnumeratorStatement (host, this));
+                       }
+
+                       public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name)
+                       {
+                               return Create (host, returnType, name, null);
+                       }
+
+                       public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name, Statement statement)
+                       {
+                               var m = new GetEnumeratorMethod (host, returnType, name);
+                               var stmt = statement ?? new GetEnumeratorStatement (host, m);
+                               m.block.AddStatement (stmt);
+                               m.block.IsCompilerGenerated = true;
+                               return m;
                        }
                }
 
@@ -328,9 +348,10 @@ namespace Mono.CSharp
                                : base (host, null, new TypeExpression (host.Compiler.BuiltinTypes.Void, host.Location), Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
                                        new MemberName ("Dispose", host.Location))
                        {
-                               host.AddMethod (this);
+                               host.Members.Add (this);
 
                                Block.AddStatement (new DisposeMethodStatement (host.Iterator));
+                               Block.IsCompilerGenerated = true;
                        }
                }
 
@@ -382,22 +403,28 @@ namespace Mono.CSharp
 
                TypeExpr iterator_type_expr;
                Field current_field;
+               Field disposing_field;
 
-               TypeExpr enumerator_type;
-               TypeExpr enumerable_type;
-               TypeArguments generic_args;
-               TypeExpr generic_enumerator_type;
-               TypeExpr generic_enumerable_type;
+               TypeSpec generic_enumerator_type;
+               TypeSpec generic_enumerable_type;
 
                public IteratorStorey (Iterator iterator)
                        : base (iterator.Container.ParametersBlock, iterator.Host,
-                         iterator.OriginalMethod as MemberBase, iterator.GenericMethod == null ? null : iterator.GenericMethod.CurrentTypeParameters, "Iterator")
+                         iterator.OriginalMethod as MemberBase, iterator.OriginalMethod.CurrentTypeParameters, "Iterator", MemberKind.Class)
                {
                        this.Iterator = iterator;
                }
 
                public Field CurrentField {
-                       get { return current_field; }
+                       get {
+                               return current_field;
+                       }
+               }
+
+               public Field DisposingField {
+                       get {
+                               return disposing_field;
+                       }
                }
 
                public IList<HoistedParameter> HoistedParameters {
@@ -411,38 +438,36 @@ namespace Mono.CSharp
                                mtype = Mutator.Mutate (mtype);
 
                        iterator_type_expr = new TypeExpression (mtype, Location);
-                       generic_args = new TypeArguments (iterator_type_expr);
 
-                       var list = new List<FullNamedExpression> ();
+                       var ifaces = new List<TypeSpec> (5);
                        if (Iterator.IsEnumerable) {
-                               enumerable_type = new TypeExpression (Compiler.BuiltinTypes.IEnumerable, Location);
-                               list.Add (enumerable_type);
+                               ifaces.Add (Compiler.BuiltinTypes.IEnumerable);
 
                                if (Module.PredefinedTypes.IEnumerableGeneric.Define ()) {
-                                       generic_enumerable_type = new GenericTypeExpr (Module.PredefinedTypes.IEnumerableGeneric.TypeSpec, generic_args, Location);
-                                       list.Add (generic_enumerable_type);
+                                       generic_enumerable_type = Module.PredefinedTypes.IEnumerableGeneric.TypeSpec.MakeGenericType (Module, new[] { mtype });
+                                       ifaces.Add (generic_enumerable_type);
                                }
                        }
 
-                       enumerator_type = new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location);
-                       list.Add (enumerator_type);
-
-                       list.Add (new TypeExpression (Compiler.BuiltinTypes.IDisposable, Location));
+                       ifaces.Add (Compiler.BuiltinTypes.IEnumerator);
+                       ifaces.Add (Compiler.BuiltinTypes.IDisposable);
 
                        var ienumerator_generic = Module.PredefinedTypes.IEnumeratorGeneric;
                        if (ienumerator_generic.Define ()) {
-                               generic_enumerator_type = new GenericTypeExpr (ienumerator_generic.TypeSpec, generic_args, Location);
-                               list.Add (generic_enumerator_type);
+                               generic_enumerator_type = ienumerator_generic.TypeSpec.MakeGenericType (Module, new [] { mtype });
+                               ifaces.Add (generic_enumerator_type);
                        }
 
-                       type_bases = list;
+                       base_class = null;
 
-                       return base.ResolveBaseTypes (out base_class);
+                       base_type = Compiler.BuiltinTypes.Object;
+                       return ifaces.ToArray ();
                }
 
                protected override bool DoDefineMembers ()
                {
                        current_field = AddCompilerGeneratedField ("$current", iterator_type_expr);
+                       disposing_field = AddCompilerGeneratedField ("$disposing", new TypeExpression (Compiler.BuiltinTypes.Bool, Location));
 
                        if (hoisted_params != null) {
                                //
@@ -466,29 +491,24 @@ namespace Mono.CSharp
                        Define_Reset ();
 
                        if (Iterator.IsEnumerable) {
-                               MemberName name = new MemberName (QualifiedAliasMember.GlobalAlias, "System", null, Location);
-                               name = new MemberName (name, "Collections", Location);
-                               name = new MemberName (name, "IEnumerable", Location);
-                               name = new MemberName (name, "GetEnumerator", Location);
+                               FullNamedExpression explicit_iface = new TypeExpression (Compiler.BuiltinTypes.IEnumerable, Location);
+                               var name = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
 
                                if (generic_enumerator_type != null) {
-                                       Method get_enumerator = new StateMachineMethod (this, null, enumerator_type, 0, name);
-
-                                       name = new MemberName (name.Left.Left, "Generic", Location);
-                                       name = new MemberName (name, "IEnumerable", generic_args, Location);
-                                       name = new MemberName (name, "GetEnumerator", Location);
-                                       Method gget_enumerator = new GetEnumeratorMethod (this, generic_enumerator_type, name);
+                                       explicit_iface = new TypeExpression (generic_enumerable_type, Location);
+                                       var gname = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
+                                       Method gget_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (generic_enumerator_type, Location), gname);
 
                                        //
                                        // Just call generic GetEnumerator implementation
                                        //
-                                       get_enumerator.Block.AddStatement (
-                                               new Return (new Invocation (new DynamicMethodGroupExpr (gget_enumerator, Location), null), Location));
+                                       var stmt = new Return (new Invocation (new DynamicMethodGroupExpr (gget_enumerator, Location), null), Location);
+                                       Method get_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name, stmt);
 
-                                       AddMethod (get_enumerator);
-                                       AddMethod (gget_enumerator);
+                                       Members.Add (get_enumerator);
+                                       Members.Add (gget_enumerator);
                                } else {
-                                       AddMethod (new GetEnumeratorMethod (this, enumerator_type, name));
+                                       Members.Add (GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name));
                                }
                        }
 
@@ -498,41 +518,42 @@ namespace Mono.CSharp
                void Define_Current (bool is_generic)
                {
                        TypeExpr type;
-
-                       MemberName name = new MemberName (QualifiedAliasMember.GlobalAlias, "System", null, Location);
-                       name = new MemberName (name, "Collections", Location);
+                       FullNamedExpression explicit_iface;
 
                        if (is_generic) {
-                               name = new MemberName (name, "Generic", Location);
-                               name = new MemberName (name, "IEnumerator", generic_args, Location);
+                               explicit_iface = new TypeExpression (generic_enumerator_type, Location);
                                type = iterator_type_expr;
                        } else {
-                               name = new MemberName (name, "IEnumerator");
+                               explicit_iface = new TypeExpression (Module.Compiler.BuiltinTypes.IEnumerator, Location);
                                type = new TypeExpression (Compiler.BuiltinTypes.Object, Location);
                        }
 
-                       name = new MemberName (name, "Current", Location);
+                       var name = new MemberName ("Current", null, explicit_iface, Location);
 
-                       ToplevelBlock get_block = new ToplevelBlock (Compiler, Location);
+                       ToplevelBlock get_block = new ToplevelBlock (Compiler, Location) {
+                               IsCompilerGenerated = true
+                       };
                        get_block.AddStatement (new Return (new DynamicFieldExpr (CurrentField, Location), Location));
                                
-                       Property current = new Property (this, type, Modifiers.DEBUGGER_HIDDEN, name, null);
-                       current.Get = new Property.GetMethod (current, 0, null, Location);
+                       Property current = new Property (this, type, Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED, name, null);
+                       current.Get = new Property.GetMethod (current, Modifiers.COMPILER_GENERATED, null, Location);
                        current.Get.Block = get_block;
 
-                       AddProperty (current);
+                       Members.Add (current);
                }
 
                void Define_Reset ()
                {
                        Method reset = new Method (
-                               this, null, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
-                               Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
+                               this, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
+                               Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED,
                                new MemberName ("Reset", Location),
                                ParametersCompiled.EmptyReadOnlyParameters, null);
-                       AddMethod (reset);
+                       Members.Add (reset);
 
-                       reset.Block = new ToplevelBlock (Compiler, Location);
+                       reset.Block = new ToplevelBlock (Compiler, Location) {
+                               IsCompilerGenerated = true
+                       };
 
                        TypeSpec ex_type = Module.PredefinedTypes.NotSupportedException.Resolve ();
                        if (ex_type == null)
@@ -541,7 +562,7 @@ namespace Mono.CSharp
                        reset.Block.AddStatement (new Throw (new New (new TypeExpression (ex_type, Location), null, Location), Location));
                }
 
-               protected override void EmitHoistedParameters (EmitContext ec, IList<HoistedParameter> hoisted)
+               protected override void EmitHoistedParameters (EmitContext ec, List<HoistedParameter> hoisted)
                {
                        base.EmitHoistedParameters (ec, hoisted);
                        base.EmitHoistedParameters (ec, hoisted_params_copy);
@@ -553,17 +574,21 @@ namespace Mono.CSharp
                readonly StateMachineInitializer expr;
 
                public StateMachineMethod (StateMachine host, StateMachineInitializer expr, FullNamedExpression returnType, Modifiers mod, MemberName name)
-                       : base (host, null, returnType, mod | Modifiers.COMPILER_GENERATED,
+                       : base (host, returnType, mod | Modifiers.COMPILER_GENERATED,
                          name, ParametersCompiled.EmptyReadOnlyParameters, null)
                {
                        this.expr = expr;
-                       Block = new ToplevelBlock (host.Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location);
+                       Block = new ToplevelBlock (host.Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location.Null);
                }
 
-               public override EmitContext CreateEmitContext (ILGenerator ig)
+               public override EmitContext CreateEmitContext (ILGenerator ig, SourceMethodBuilder sourceMethod)
                {
-                       EmitContext ec = new EmitContext (this, ig, MemberType);
+                       EmitContext ec = new EmitContext (this, ig, MemberType, sourceMethod);
                        ec.CurrentAnonymousMethod = expr;
+
+                       if (expr is AsyncInitializer)
+                               ec.With (BuilderContext.Options.AsyncBody, true);
+
                        return ec;
                }
        }
@@ -594,31 +619,62 @@ namespace Mono.CSharp
                        {
                                state_machine.EmitMoveNext (ec);
                        }
+
+                       public override void Emit (EmitContext ec)
+                       {
+                               // Don't create sequence point
+                               DoEmit (ec);
+                       }
                }
 
-               public readonly TypeContainer Host;
+               public readonly TypeDefinition Host;
                protected StateMachine storey;
 
                //
                // The state as we generate the machine
                //
                Label move_next_ok;
+               Label iterator_body_end;
                protected Label move_next_error;
-               protected LocalBuilder skip_finally, current_pc;
-               List<ResumableStatement> resume_points;
+               LocalBuilder skip_finally;
+               protected LocalBuilder current_pc;
+               protected List<ResumableStatement> resume_points;
 
-               protected StateMachineInitializer (ParametersBlock block, TypeContainer host, TypeSpec returnType)
+               protected StateMachineInitializer (ParametersBlock block, TypeDefinition host, TypeSpec returnType)
                        : base (block, returnType, block.StartLocation)
                {
                        this.Host = host;
                }
 
+               #region Properties
+
+               public Label BodyEnd {
+                       get {
+                               return iterator_body_end;
+                       }
+               }
+
+               public LocalBuilder CurrentPC
+               {
+                       get {
+                               return current_pc;
+                       }
+               }
+
+               public LocalBuilder SkipFinally {
+                       get {
+                               return skip_finally;
+                       }
+               }
+
                public override AnonymousMethodStorey Storey {
                        get {
                                return storey;
                        }
                }
 
+               #endregion
+
                public int AddResumePoint (ResumableStatement stmt)
                {
                        if (resume_points == null)
@@ -633,28 +689,33 @@ namespace Mono.CSharp
                        throw new NotSupportedException ("ET");
                }
 
-               protected override Expression DoResolve (ResolveContext ec)
+               protected virtual BlockContext CreateBlockContext (ResolveContext rc)
                {
-                       storey = (StateMachine) block.Parent.ParametersBlock.AnonymousMethodStorey;
-
-                       BlockContext ctx = new BlockContext (ec, block, ReturnType);
+                       var ctx = new BlockContext (rc, block, ((BlockContext) rc).ReturnType);
                        ctx.CurrentAnonymousMethod = this;
+                       return ctx;
+               }
+
+               protected override Expression DoResolve (ResolveContext ec)
+               {
+                       var ctx = CreateBlockContext (ec);
 
-                       ctx.StartFlowBranching (this, ec.CurrentBranching);
                        Block.Resolve (ctx);
 
                        //
                        // Explicit return is required for Task<T> state machine
                        //
                        var task_storey = storey as AsyncTaskStorey;
-                       if (task_storey == null || !task_storey.ReturnType.IsGenericTask)
+                       if (task_storey == null || (task_storey.ReturnType != null && !task_storey.ReturnType.IsGenericTask))
                                ctx.CurrentBranching.CurrentUsageVector.Goto ();
 
                        ctx.EndFlowBranching ();
 
-                       var move_next = new StateMachineMethod (storey, this, new TypeExpression (ReturnType, loc), Modifiers.PUBLIC, new MemberName ("MoveNext", loc));
-                       move_next.Block.AddStatement (new MoveNextBodyStatement (this));
-                       storey.AddEntryMethod (move_next);
+                       if (!ec.IsInProbingMode) {
+                               var move_next = new StateMachineMethod (storey, this, new TypeExpression (ReturnType, loc), Modifiers.PUBLIC, new MemberName ("MoveNext", loc));
+                               move_next.Block.AddStatement (new MoveNextBodyStatement (this));
+                               storey.AddEntryMethod (move_next);
+                       }
 
                        eclass = ExprClass.Value;
                        return this;
@@ -663,74 +724,30 @@ namespace Mono.CSharp
                public override void Emit (EmitContext ec)
                {
                        //
-                       // Load Iterator storey instance
+                       // Load state machine instance
                        //
                        storey.Instance.Emit (ec);
                }
 
-               public void EmitDispose (EmitContext ec)
-               {
-                       Label end = ec.DefineLabel ();
-
-                       Label[] labels = null;
-                       int n_resume_points = resume_points == null ? 0 : resume_points.Count;
-                       for (int i = 0; i < n_resume_points; ++i) {
-                               ResumableStatement s = resume_points[i];
-                               Label ret = s.PrepareForDispose (ec, end);
-                               if (ret.Equals (end) && labels == null)
-                                       continue;
-                               if (labels == null) {
-                                       labels = new Label[resume_points.Count + 1];
-                                       for (int j = 0; j <= i; ++j)
-                                               labels[j] = end;
-                               }
-
-                               labels[i + 1] = ret;
-                       }
-
-                       if (labels != null) {
-                               current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
-                               ec.Emit (OpCodes.Ldarg_0);
-                               ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
-                               ec.Emit (OpCodes.Stloc, current_pc);
-                       }
-
-                       ec.Emit (OpCodes.Ldarg_0);
-                       ec.EmitInt (1);
-                       ec.Emit (OpCodes.Stfld, storey.DisposingField.Spec);
-
-                       ec.Emit (OpCodes.Ldarg_0);
-                       ec.EmitInt ((int) IteratorStorey.State.After);
-                       ec.Emit (OpCodes.Stfld, storey.PC.Spec);
-
-                       if (labels != null) {
-                               //SymbolWriter.StartIteratorDispatcher (ec.ig);
-                               ec.Emit (OpCodes.Ldloc, current_pc);
-                               ec.Emit (OpCodes.Switch, labels);
-                               //SymbolWriter.EndIteratorDispatcher (ec.ig);
-
-                               foreach (ResumableStatement s in resume_points)
-                                       s.EmitForDispose (ec, current_pc, end, true);
-                       }
-
-                       ec.MarkLabel (end);
-               }
-
-               void EmitMoveNext_NoResumePoints (EmitContext ec, Block original_block)
+               void EmitMoveNext_NoResumePoints (EmitContext ec)
                {
-                       ec.Emit (OpCodes.Ldarg_0);
+                       ec.EmitThis ();
                        ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
 
-                       ec.Emit (OpCodes.Ldarg_0);
+                       ec.EmitThis ();
                        ec.EmitInt ((int) IteratorStorey.State.After);
                        ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 
                        // We only care if the PC is zero (start executing) or non-zero (don't do anything)
                        ec.Emit (OpCodes.Brtrue, move_next_error);
 
-                       SymbolWriter.StartIteratorBody (ec);
-                       original_block.Emit (ec);
-                       SymbolWriter.EndIteratorBody (ec);
+                       iterator_body_end = ec.DefineLabel ();
+
+                       block.EmitEmbedded (ec);
+
+                       ec.MarkLabel (iterator_body_end);
+
+                       EmitMoveNextEpilogue (ec);
 
                        ec.MarkLabel (move_next_error);
 
@@ -746,17 +763,17 @@ namespace Mono.CSharp
                        move_next_error = ec.DefineLabel ();
 
                        if (resume_points == null) {
-                               EmitMoveNext_NoResumePoints (ec, block);
+                               EmitMoveNext_NoResumePoints (ec);
                                return;
                        }
-
+                       
                        current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
-                       ec.Emit (OpCodes.Ldarg_0);
+                       ec.EmitThis ();
                        ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
                        ec.Emit (OpCodes.Stloc, current_pc);
 
                        // We're actually in state 'running', but this is as good a PC value as any if there's an abnormal exit
-                       ec.Emit (OpCodes.Ldarg_0);
+                       ec.EmitThis ();
                        ec.EmitInt ((int) IteratorStorey.State.After);
                        ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 
@@ -772,29 +789,52 @@ namespace Mono.CSharp
 
                        if (need_skip_finally) {
                                skip_finally = ec.GetTemporaryLocal (ec.BuiltinTypes.Bool);
-                               ec.Emit (OpCodes.Ldc_I4_0);
+                               ec.EmitInt (0);
                                ec.Emit (OpCodes.Stloc, skip_finally);
                        }
 
-                       SymbolWriter.StartIteratorDispatcher (ec);
+                       var async_init = this as AsyncInitializer;
+                       if (async_init != null)
+                               ec.BeginExceptionBlock ();
+
                        ec.Emit (OpCodes.Ldloc, current_pc);
                        ec.Emit (OpCodes.Switch, labels);
 
-                       ec.Emit (OpCodes.Br, move_next_error);
-                       SymbolWriter.EndIteratorDispatcher (ec);
+                       ec.Emit (async_init != null ? OpCodes.Leave : OpCodes.Br, move_next_error);
 
                        ec.MarkLabel (labels[0]);
 
-                       SymbolWriter.StartIteratorBody (ec);
-                       block.Emit (ec);
-                       SymbolWriter.EndIteratorBody (ec);
+                       iterator_body_end = ec.DefineLabel ();
+
+                       block.EmitEmbedded (ec);
+
+                       ec.MarkLabel (iterator_body_end);
+
+                       if (async_init != null) {
+                               var catch_value = LocalVariable.CreateCompilerGenerated (ec.Module.Compiler.BuiltinTypes.Exception, block, Location);
 
-                       SymbolWriter.StartIteratorDispatcher (ec);
+                               ec.BeginCatchBlock (catch_value.Type);
+                               catch_value.EmitAssign (ec);
+
+                               ec.EmitThis ();
+                               ec.EmitInt ((int) IteratorStorey.State.After);
+                               ec.Emit (OpCodes.Stfld, storey.PC.Spec);
+
+                               ((AsyncTaskStorey) async_init.Storey).EmitSetException (ec, new LocalVariableReference (catch_value, Location));
+
+                               ec.Emit (OpCodes.Leave, move_next_ok);
+                               ec.EndExceptionBlock ();
+                       }
+
+                       ec.Mark (Block.Original.EndLocation);
+                       ec.EmitThis ();
+                       ec.EmitInt ((int) IteratorStorey.State.After);
+                       ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 
                        EmitMoveNextEpilogue (ec);
 
                        ec.MarkLabel (move_next_error);
-
+                       
                        if (ReturnType.Kind != MemberKind.Void) {
                                ec.EmitInt (0);
                                ec.Emit (OpCodes.Ret);
@@ -806,15 +846,16 @@ namespace Mono.CSharp
                                ec.EmitInt (1);
                                ec.Emit (OpCodes.Ret);
                        }
-
-                       SymbolWriter.EndIteratorDispatcher (ec);
                }
 
                protected virtual void EmitMoveNextEpilogue (EmitContext ec)
                {
-                       ec.Emit (OpCodes.Ldarg_0);
-                       ec.EmitInt ((int) IteratorStorey.State.After);
-                       ec.Emit (OpCodes.Stfld, storey.PC.Spec);
+               }
+
+               public void EmitLeave (EmitContext ec, bool unwind_protect)
+               {
+                       // Return ok
+                       ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
                }
 
                //
@@ -826,41 +867,77 @@ namespace Mono.CSharp
                        // Guard against being disposed meantime
                        //
                        Label disposed = ec.DefineLabel ();
-                       ec.Emit (OpCodes.Ldarg_0);
-                       ec.Emit (OpCodes.Ldfld, storey.DisposingField.Spec);
-                       ec.Emit (OpCodes.Brtrue_S, disposed);
+                       var iterator = storey as IteratorStorey;
+                       if (iterator != null) {
+                               ec.EmitThis ();
+                               ec.Emit (OpCodes.Ldfld, iterator.DisposingField.Spec);
+                               ec.Emit (OpCodes.Brtrue_S, disposed);
+                       }
 
                        //
                        // store resume program-counter
                        //
-                       ec.Emit (OpCodes.Ldarg_0);
+                       ec.EmitThis ();
                        ec.EmitInt (resume_pc);
                        ec.Emit (OpCodes.Stfld, storey.PC.Spec);
-                       ec.MarkLabel (disposed);
+
+                       if (iterator != null) {
+                               ec.MarkLabel (disposed);
+                       }
 
                        // mark finally blocks as disabled
                        if (unwind_protect && skip_finally != null) {
                                ec.EmitInt (1);
                                ec.Emit (OpCodes.Stloc, skip_finally);
                        }
+               }
 
-                       // Return ok
-                       ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
-
-                       ec.MarkLabel (resume_point);
+               public void SetStateMachine (StateMachine stateMachine)
+               {
+                       this.storey = stateMachine;
                }
        }
 
        //
-       // Iterators are implemented as hidden anonymous block
+       // Iterators are implemented as state machine blocks
        //
        public class Iterator : StateMachineInitializer
        {
+               sealed class TryFinallyBlockProxyStatement : Statement
+               {
+                       TryFinallyBlock block;
+                       Iterator iterator;
+
+                       public TryFinallyBlockProxyStatement (Iterator iterator, TryFinallyBlock block)
+                       {
+                               this.iterator = iterator;
+                               this.block = block;
+                       }
+
+                       protected override void CloneTo (CloneContext clonectx, Statement target)
+                       {
+                               throw new NotSupportedException ();
+                       }
+
+                       protected override void DoEmit (EmitContext ec)
+                       {
+                               //
+                               // Restore redirection for any captured variables
+                               //
+                               ec.CurrentAnonymousMethod = iterator;
+
+                               using (ec.With (BuilderContext.Options.OmitDebugInfo, !ec.HasMethodSymbolBuilder)) {
+                                       block.EmitFinallyBody (ec);
+                               }
+                       }
+               }
+
                public readonly IMethodData OriginalMethod;
                public readonly bool IsEnumerable;
                public readonly TypeSpec OriginalIteratorType;
+               int finally_hosts_counter;
 
-               public Iterator (ParametersBlock block, IMethodData method, TypeContainer host, TypeSpec iterator_type, bool is_enumerable)
+               public Iterator (ParametersBlock block, IMethodData method, TypeDefinition host, TypeSpec iterator_type, bool is_enumerable)
                        : base (block, host, host.Compiler.BuiltinTypes.Bool)
                {
                        this.OriginalMethod = method;
@@ -869,22 +946,12 @@ namespace Mono.CSharp
                        this.type = method.ReturnType;
                }
 
-               public LocalBuilder SkipFinally {
-                       get { return skip_finally; }
-               }
-
-               public LocalBuilder CurrentPC {
-                   get { return current_pc; }
-               }
+               #region Properties
 
-               public Block Container {
+               public ToplevelBlock Container {
                        get { return OriginalMethod.Block; }
                }
 
-               public GenericMethod GenericMethod {
-                       get { return OriginalMethod.GenericMethod; }
-               }
-
                public override string ContainerType {
                        get { return "iterator"; }
                }
@@ -893,6 +960,24 @@ namespace Mono.CSharp
                        get { return true; }
                }
 
+               #endregion
+
+               public Method CreateFinallyHost (TryFinallyBlock block)
+               {
+                       var method = new Method (storey, new TypeExpression (storey.Compiler.BuiltinTypes.Void, loc),
+                               Modifiers.COMPILER_GENERATED, new MemberName (CompilerGeneratedContainer.MakeName (null, null, "Finally", finally_hosts_counter++), loc),
+                               ParametersCompiled.EmptyReadOnlyParameters, null);
+
+                       method.Block = new ToplevelBlock (method.Compiler, method.ParameterInfo, loc);
+                       method.Block.IsCompilerGenerated = true;
+                       method.Block.AddStatement (new TryFinallyBlockProxyStatement (this, block));
+
+                       // Cannot it add to storey because it'd be emitted before nested
+                       // anonoymous methods which could capture shared variable
+
+                       return method;
+               }
+
                public void EmitYieldBreak (EmitContext ec, bool unwind_protect)
                {
                        ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_error);
@@ -926,6 +1011,56 @@ namespace Mono.CSharp
                        }
                }
 
+               public void EmitDispose (EmitContext ec)
+               {
+                       if (resume_points == null)
+                               return;
+
+                       Label end = ec.DefineLabel ();
+
+                       Label[] labels = null;
+                       for (int i = 0; i < resume_points.Count; ++i) {
+                               ResumableStatement s = resume_points[i];
+                               Label ret = s.PrepareForDispose (ec, end);
+                               if (ret.Equals (end) && labels == null)
+                                       continue;
+                               if (labels == null) {
+                                       labels = new Label[resume_points.Count + 1];
+                                       for (int j = 0; j <= i; ++j)
+                                               labels[j] = end;
+                               }
+
+                               labels[i + 1] = ret;
+                       }
+
+                       if (labels != null) {
+                               current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
+                               ec.EmitThis ();
+                               ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
+                               ec.Emit (OpCodes.Stloc, current_pc);
+                       }
+
+                       ec.EmitThis ();
+                       ec.EmitInt (1);
+                       ec.Emit (OpCodes.Stfld, ((IteratorStorey) storey).DisposingField.Spec);
+
+                       ec.EmitThis ();
+                       ec.EmitInt ((int) IteratorStorey.State.After);
+                       ec.Emit (OpCodes.Stfld, storey.PC.Spec);
+
+                       if (labels != null) {
+                               //SymbolWriter.StartIteratorDispatcher (ec.ig);
+                               ec.Emit (OpCodes.Ldloc, current_pc);
+                               ec.Emit (OpCodes.Switch, labels);
+                               //SymbolWriter.EndIteratorDispatcher (ec.ig);
+
+                               foreach (ResumableStatement s in resume_points)
+                                       s.EmitForDispose (ec, current_pc, end, true);
+                       }
+
+                       ec.MarkLabel (end);
+               }
+
                public override void EmitStatement (EmitContext ec)
                {
                        throw new NotImplementedException ();
@@ -939,9 +1074,20 @@ namespace Mono.CSharp
                        fe.EmitAssign (ec, expr, false, false);
 
                        base.InjectYield (ec, expr, resume_pc, unwind_protect, resume_point);
+
+                       EmitLeave (ec, unwind_protect);
+
+                       ec.MarkLabel (resume_point);
+               }
+
+               protected override BlockContext CreateBlockContext (ResolveContext rc)
+               {
+                       var bc = base.CreateBlockContext (rc);
+                       bc.StartFlowBranching (this, rc.CurrentBranching);
+                       return bc;
                }
 
-               public static void CreateIterator (IMethodData method, TypeContainer parent, Modifiers modifiers)
+               public static void CreateIterator (IMethodData method, TypeDefinition parent, Modifiers modifiers)
                {
                        bool is_enumerable;
                        TypeSpec iterator_type;
@@ -963,7 +1109,7 @@ namespace Mono.CSharp
                        for (int i = 0; i < parameters.Count; i++) {
                                Parameter p = parameters [i];
                                Parameter.Modifier mod = p.ModFlags;
-                               if ((mod & Parameter.Modifier.ISBYREF) != 0) {
+                               if ((mod & Parameter.Modifier.RefOutMask) != 0) {
                                        parent.Compiler.Report.Error (1623, p.Location,
                                                "Iterators cannot have ref or out parameters");
                                        return;
@@ -986,7 +1132,7 @@ namespace Mono.CSharp
                                parent.Compiler.Report.Error (1629, method.Location, "Unsafe code may not appear in iterators");
                        }
 
-                       method.Block.WrapIntoIterator (method, parent, iterator_type, is_enumerable);
+                       method.Block = method.Block.ConvertToIterator (method, parent, iterator_type, is_enumerable);
                }
 
                static bool CheckType (TypeSpec ret, TypeContainer parent, out TypeSpec original_iterator_type, out bool is_enumerable)