mcs/mcs/iterators.cs

   1 //
   2 // iterators.cs: Support for implementing iterators
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Dual licensed under the terms of the MIT X11 or GNU GPL
   9 // Copyright 2003 Ximian, Inc.
  10 // Copyright 2003-2008 Novell, Inc.
  11 // Copyright 2011 Xamarin Inc.
  12 //
  13
  14 using System;
  15 using System.Collections.Generic;
  16 using Mono.CompilerServices.SymbolWriter;
  17
  18 #if STATIC
  19 using IKVM.Reflection.Emit;
  20 #else
  21 using System.Reflection.Emit;
  22 #endif
  23
  24 namespace Mono.CSharp
  25 {
  26         public abstract class YieldStatement<T> : ResumableStatement where T : StateMachineInitializer
  27         {
  28                 protected Expression expr;
  29                 protected bool unwind_protect;
  30                 protected T machine_initializer;
  31                 int resume_pc;
  32                 ExceptionStatement inside_try_block;
  33
  34                 protected YieldStatement (Expression expr, Location l)
  35                 {
  36                         this.expr = expr;
  37                         loc = l;
  38                 }
  39
  40                 public Expression Expr {
  41                         get { return this.expr; }
  42                 }
  43
  44                 protected override void CloneTo (CloneContext clonectx, Statement t)
  45                 {
  46                         var target = (YieldStatement<T>) t;
  47                         target.expr = expr.Clone (clonectx);
  48                 }
  49
  50                 protected override void DoEmit (EmitContext ec)
  51                 {
  52                         machine_initializer.InjectYield (ec, expr, resume_pc, unwind_protect, resume_point);
  53                 }
  54
  55                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
  56                 {
  57                         expr.FlowAnalysis (fc);
  58
  59                         RegisterResumePoint ();
  60
  61                         return false;
  62                 }
  63
  64                 public override bool Resolve (BlockContext bc)
  65                 {
  66                         expr = expr.Resolve (bc);
  67                         if (expr == null)
  68                                 return false;
  69
  70                         machine_initializer = bc.CurrentAnonymousMethod as T;
  71                         inside_try_block = bc.CurrentTryBlock;
  72                         return true;
  73                 }
  74
  75                 public void RegisterResumePoint ()
  76                 {
  77                         if (inside_try_block == null) {
  78                                 resume_pc = machine_initializer.AddResumePoint (this);
  79                         } else {
  80                                 resume_pc = inside_try_block.AddResumePoint (this, resume_pc, machine_initializer);
  81                                 unwind_protect = true;
  82                                 inside_try_block = null;
  83                         }
  84                 }
  85         }
  86
  87         public class Yield : YieldStatement<Iterator>
  88         {
  89                 public Yield (Expression expr, Location loc)
  90                         : base (expr, loc)
  91                 {
  92                 }
  93
  94                 public static bool CheckContext (BlockContext bc, Location loc)
  95                 {
  96                         if (!bc.CurrentAnonymousMethod.IsIterator) {
  97                                 bc.Report.Error (1621, loc,
  98                                         "The yield statement cannot be used inside anonymous method blocks");
  99                                 return false;
 100                         }
 101
 102                         if (bc.HasSet (ResolveContext.Options.FinallyScope)) {
 103                                 bc.Report.Error (1625, loc, "Cannot yield in the body of a finally clause");
 104                                 return false;
 105                         }
 106
 107                         return true;
 108                 }
 109
 110                 public override bool Resolve (BlockContext bc)
 111                 {
 112                         if (!CheckContext (bc, loc))
 113                                 return false;
 114
 115                         if (bc.HasAny (ResolveContext.Options.TryWithCatchScope)) {
 116                                 bc.Report.Error (1626, loc, "Cannot yield a value in the body of a try block with a catch clause");
 117                         }
 118
 119                         if (bc.HasSet (ResolveContext.Options.CatchScope)) {
 120                                 bc.Report.Error (1631, loc, "Cannot yield a value in the body of a catch clause");
 121                         }
 122
 123                         if (!base.Resolve (bc))
 124                                 return false;
 125
 126                         var otype = bc.CurrentIterator.OriginalIteratorType;
 127                         if (expr.Type != otype) {
 128                                 expr = Convert.ImplicitConversionRequired (bc, expr, otype, loc);
 129                                 if (expr == null)
 130                                         return false;
 131                         }
 132
 133                         return true;
 134                 }
 135
 136                 public override object Accept (StructuralVisitor visitor)
 137                 {
 138                         return visitor.Visit (this);
 139                 }
 140         }
 141
 142         public class YieldBreak : ExitStatement
 143         {
 144                 Iterator iterator;
 145
 146                 public YieldBreak (Location l)
 147                 {
 148                         loc = l;
 149                 }
 150
 151                 protected override bool IsLocalExit {
 152                         get {
 153                                 return false;
 154                         }
 155                 }
 156
 157                 protected override void CloneTo (CloneContext clonectx, Statement target)
 158                 {
 159                         throw new NotSupportedException ();
 160                 }
 161
 162                 protected override bool DoResolve (BlockContext bc)
 163                 {
 164                         iterator = bc.CurrentIterator;
 165                         return Yield.CheckContext (bc, loc);
 166                 }
 167
 168                 protected override void DoEmit (EmitContext ec)
 169                 {
 170                         iterator.EmitYieldBreak (ec, unwind_protect);
 171                 }
 172
 173                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 174                 {
 175                         return true;
 176                 }
 177
 178                 public override Reachability MarkReachable (Reachability rc)
 179                 {
 180                         base.MarkReachable (rc);
 181                         return Reachability.CreateUnreachable ();
 182                 }
 183
 184                 public override object Accept (StructuralVisitor visitor)
 185                 {
 186                         return visitor.Visit (this);
 187                 }
 188         }
 189
 190         public abstract class StateMachine : AnonymousMethodStorey
 191         {
 192                 public enum State
 193                 {
 194                         Running = -3, // Used only in CurrentPC, never stored into $PC
 195                         Uninitialized = -2,
 196                         After = -1,
 197                         Start = 0
 198                 }
 199
 200                 Field pc_field;
 201                 StateMachineMethod method;
 202                 int local_name_idx;
 203
 204                 protected StateMachine (ParametersBlock block, TypeDefinition parent, MemberBase host, TypeParameters tparams, string name, MemberKind kind)
 205                         : base (block, parent, host, tparams, name, kind)
 206                 {
 207                 }
 208
 209                 #region Properties
 210
 211                 public StateMachineMethod StateMachineMethod {
 212                         get {
 213                                 return method;
 214                         }
 215                 }
 216
 217                 public Field PC {
 218                         get {
 219                                 return pc_field;
 220                         }
 221                 }
 222
 223                 #endregion
 224
 225                 public void AddEntryMethod (StateMachineMethod method)
 226                 {
 227                         if (this.method != null)
 228                                 throw new InternalErrorException ();
 229
 230                         this.method = method;
 231                         Members.Add (method);
 232                 }
 233
 234                 protected override bool DoDefineMembers ()
 235                 {
 236                         pc_field = AddCompilerGeneratedField ("$PC", new TypeExpression (Compiler.BuiltinTypes.Int, Location));
 237
 238                         return base.DoDefineMembers ();
 239                 }
 240
 241                 protected override string GetVariableMangledName (LocalVariable local_info)
 242                 {
 243                         if (local_info.IsCompilerGenerated)
 244                                 return base.GetVariableMangledName (local_info);
 245
 246                         return "<" + local_info.Name + ">__" + local_name_idx++.ToString ("X");
 247                 }
 248         }
 249
 250         class IteratorStorey : StateMachine
 251         {
 252                 class GetEnumeratorMethod : StateMachineMethod
 253                 {
 254                         sealed class GetEnumeratorStatement : Statement
 255                         {
 256                                 readonly IteratorStorey host;
 257                                 readonly StateMachineMethod host_method;
 258
 259                                 Expression new_storey;
 260
 261                                 public GetEnumeratorStatement (IteratorStorey host, StateMachineMethod host_method)
 262                                 {
 263                                         this.host = host;
 264                                         this.host_method = host_method;
 265                                         loc = host_method.Location;
 266                                 }
 267
 268                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 269                                 {
 270                                         throw new NotSupportedException ();
 271                                 }
 272
 273                                 public override bool Resolve (BlockContext ec)
 274                                 {
 275                                         TypeExpression storey_type_expr = new TypeExpression (host.Definition, loc);
 276                                         List<Expression> init = null;
 277                                         if (host.hoisted_this != null) {
 278                                                 init = new List<Expression> (host.hoisted_params == null ? 1 : host.HoistedParameters.Count + 1);
 279                                                 HoistedThis ht = host.hoisted_this;
 280                                                 FieldExpr from = new FieldExpr (ht.Field, loc);
 281                                                 from.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 282                                                 init.Add (new ElementInitializer (ht.Field.Name, from, loc));
 283                                         }
 284
 285                                         if (host.hoisted_params != null) {
 286                                                 if (init == null)
 287                                                         init = new List<Expression> (host.HoistedParameters.Count);
 288
 289                                                 for (int i = 0; i < host.hoisted_params.Count; ++i) {
 290                                                         HoistedParameter hp = host.hoisted_params [i];
 291                                                         HoistedParameter hp_cp = host.hoisted_params_copy [i] ?? hp;
 292
 293                                                         FieldExpr from = new FieldExpr (hp_cp.Field, loc);
 294                                                         from.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 295
 296                                                         init.Add (new ElementInitializer (hp.Field.Name, from, loc));
 297                                                 }
 298                                         }
 299
 300                                         if (init != null) {
 301                                                 new_storey = new NewInitialize (storey_type_expr, null,
 302                                                         new CollectionOrObjectInitializers (init, loc), loc);
 303                                         } else {
 304                                                 new_storey = new New (storey_type_expr, null, loc);
 305                                         }
 306
 307                                         new_storey = new_storey.Resolve (ec);
 308                                         if (new_storey != null)
 309                                                 new_storey = Convert.ImplicitConversionRequired (ec, new_storey, host_method.MemberType, loc);
 310
 311                                         return true;
 312                                 }
 313
 314                                 protected override void DoEmit (EmitContext ec)
 315                                 {
 316                                         Label label_init = ec.DefineLabel ();
 317
 318                                         ec.EmitThis ();
 319                                         ec.Emit (OpCodes.Ldflda, host.PC.Spec);
 320                                         ec.EmitInt ((int) State.Start);
 321                                         ec.EmitInt ((int) State.Uninitialized);
 322
 323                                         var m = ec.Module.PredefinedMembers.InterlockedCompareExchange.Resolve (loc);
 324                                         if (m != null)
 325                                                 ec.Emit (OpCodes.Call, m);
 326
 327                                         ec.EmitInt ((int) State.Uninitialized);
 328                                         ec.Emit (OpCodes.Bne_Un_S, label_init);
 329
 330                                         ec.EmitThis ();
 331                                         ec.Emit (OpCodes.Ret);
 332
 333                                         ec.MarkLabel (label_init);
 334
 335                                         new_storey.Emit (ec);
 336                                         ec.Emit (OpCodes.Ret);
 337                                 }
 338
 339                                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 340                                 {
 341                                         throw new NotImplementedException ();
 342                                 }
 343
 344                                 public override Reachability MarkReachable (Reachability rc)
 345                                 {
 346                                         base.MarkReachable (rc);
 347                                         return Reachability.CreateUnreachable ();
 348                                 }
 349                         }
 350
 351                         GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 352                                 : base (host, null, returnType, Modifiers.DEBUGGER_HIDDEN, name, ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis)
 353                         {
 354                         }
 355
 356                         public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 357                         {
 358                                 return Create (host, returnType, name, null);
 359                         }
 360
 361                         public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name, Statement statement)
 362                         {
 363                                 var m = new GetEnumeratorMethod (host, returnType, name);
 364                                 var stmt = statement ?? new GetEnumeratorStatement (host, m);
 365                                 m.block.AddStatement (stmt);
 366                                 return m;
 367                         }
 368                 }
 369
 370                 class DisposeMethod : StateMachineMethod
 371                 {
 372                         sealed class DisposeMethodStatement : Statement
 373                         {
 374                                 Iterator iterator;
 375
 376                                 public DisposeMethodStatement (Iterator iterator)
 377                                 {
 378                                         this.iterator = iterator;
 379                                         this.loc = iterator.Location;
 380                                 }
 381
 382                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 383                                 {
 384                                         throw new NotSupportedException ();
 385                                 }
 386
 387                                 public override bool Resolve (BlockContext ec)
 388                                 {
 389                                         return true;
 390                                 }
 391
 392                                 protected override void DoEmit (EmitContext ec)
 393                                 {
 394                                         ec.CurrentAnonymousMethod = iterator;
 395                                         iterator.EmitDispose (ec);
 396                                 }
 397
 398                                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 399                                 {
 400                                         throw new NotImplementedException ();
 401                                 }
 402                         }
 403
 404                         public DisposeMethod (IteratorStorey host)
 405                                 : base (host, null, new TypeExpression (host.Compiler.BuiltinTypes.Void, host.Location), Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
 406                                         new MemberName ("Dispose", host.Location), ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis)
 407                         {
 408                                 host.Members.Add (this);
 409
 410                                 Block.AddStatement (new DisposeMethodStatement (host.Iterator));
 411                         }
 412                 }
 413
 414                 //
 415                 // Uses Method as method info
 416                 //
 417                 class DynamicMethodGroupExpr : MethodGroupExpr
 418                 {
 419                         readonly Method method;
 420
 421                         public DynamicMethodGroupExpr (Method method, Location loc)
 422                                 : base ((IList<MemberSpec>) null, null, loc)
 423                         {
 424                                 this.method = method;
 425                                 eclass = ExprClass.Unresolved;
 426                         }
 427
 428                         protected override Expression DoResolve (ResolveContext ec)
 429                         {
 430                                 Methods = new List<MemberSpec> (1) { method.Spec };
 431                                 type = method.Parent.Definition;
 432                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 433                                 return base.DoResolve (ec);
 434                         }
 435                 }
 436
 437                 class DynamicFieldExpr : FieldExpr
 438                 {
 439                         readonly Field field;
 440
 441                         public DynamicFieldExpr (Field field, Location loc)
 442                                 : base (loc)
 443                         {
 444                                 this.field = field;
 445                         }
 446
 447                         protected override Expression DoResolve (ResolveContext ec)
 448                         {
 449                                 spec = field.Spec;
 450                                 type = spec.MemberType;
 451                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 452                                 return base.DoResolve (ec);
 453                         }
 454                 }
 455
 456                 public readonly Iterator Iterator;
 457
 458                 List<HoistedParameter> hoisted_params_copy;
 459
 460                 TypeExpr iterator_type_expr;
 461                 Field current_field;
 462                 Field disposing_field;
 463
 464                 TypeSpec generic_enumerator_type;
 465                 TypeSpec generic_enumerable_type;
 466
 467                 public IteratorStorey (Iterator iterator)
 468                         : base (iterator.Container.ParametersBlock, iterator.Host,
 469                           iterator.OriginalMethod as MemberBase, iterator.OriginalMethod.CurrentTypeParameters, "Iterator", MemberKind.Class)
 470                 {
 471                         this.Iterator = iterator;
 472                 }
 473
 474                 public Field CurrentField {
 475                         get {
 476                                 return current_field;
 477                         }
 478                 }
 479
 480                 public Field DisposingField {
 481                         get {
 482                                 return disposing_field;
 483                         }
 484                 }
 485
 486                 public IList<HoistedParameter> HoistedParameters {
 487                         get { return hoisted_params; }
 488                 }
 489
 490                 protected override Constructor DefineDefaultConstructor (bool is_static)
 491                 {
 492                         var ctor = base.DefineDefaultConstructor (is_static);
 493                         ctor.ModFlags |= Modifiers.DEBUGGER_HIDDEN;
 494                         return ctor;
 495                 }
 496
 497                 protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
 498                 {
 499                         var mtype = Iterator.OriginalIteratorType;
 500                         if (Mutator != null)
 501                                 mtype = Mutator.Mutate (mtype);
 502
 503                         iterator_type_expr = new TypeExpression (mtype, Location);
 504
 505                         var ifaces = new List<TypeSpec> (5);
 506                         if (Iterator.IsEnumerable) {
 507                                 ifaces.Add (Compiler.BuiltinTypes.IEnumerable);
 508
 509                                 if (Module.PredefinedTypes.IEnumerableGeneric.Define ()) {
 510                                         generic_enumerable_type = Module.PredefinedTypes.IEnumerableGeneric.TypeSpec.MakeGenericType (Module, new[] { mtype });
 511                                         ifaces.Add (generic_enumerable_type);
 512                                 }
 513                         }
 514
 515                         ifaces.Add (Compiler.BuiltinTypes.IEnumerator);
 516                         ifaces.Add (Compiler.BuiltinTypes.IDisposable);
 517
 518                         var ienumerator_generic = Module.PredefinedTypes.IEnumeratorGeneric;
 519                         if (ienumerator_generic.Define ()) {
 520                                 generic_enumerator_type = ienumerator_generic.TypeSpec.MakeGenericType (Module, new [] { mtype });
 521                                 ifaces.Add (generic_enumerator_type);
 522                         }
 523
 524                         base_class = null;
 525
 526                         base_type = Compiler.BuiltinTypes.Object;
 527                         return ifaces.ToArray ();
 528                 }
 529
 530                 protected override bool DoDefineMembers ()
 531                 {
 532                         current_field = AddCompilerGeneratedField ("$current", iterator_type_expr);
 533                         disposing_field = AddCompilerGeneratedField ("$disposing", new TypeExpression (Compiler.BuiltinTypes.Bool, Location));
 534
 535                         if (Iterator.IsEnumerable && hoisted_params != null) {
 536                                 //
 537                                 // Iterators are independent, each GetEnumerator call has to
 538                                 // create same enumerator therefore we have to keep original values
 539                                 // around for re-initialization
 540                                 //
 541                                 hoisted_params_copy = new List<HoistedParameter> (hoisted_params.Count);
 542                                 foreach (HoistedParameter hp in hoisted_params) {
 543
 544                                         //
 545                                         // Don't create field copy for unmodified captured parameters
 546                                         //
 547                                         HoistedParameter hp_copy;
 548                                         if (hp.IsAssigned) {
 549                                                 hp_copy = new HoistedParameter (hp, "<$>" + hp.Field.Name);
 550                                         } else {
 551                                                 hp_copy = null;
 552                                         }
 553
 554                                         hoisted_params_copy.Add (hp_copy);
 555                                 }
 556                         }
 557
 558                         if (generic_enumerator_type != null)
 559                                 Define_Current (true);
 560
 561                         Define_Current (false);
 562                         new DisposeMethod (this);
 563                         Define_Reset ();
 564
 565                         if (Iterator.IsEnumerable) {
 566                                 FullNamedExpression explicit_iface = new TypeExpression (Compiler.BuiltinTypes.IEnumerable, Location);
 567                                 var name = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
 568
 569                                 if (generic_enumerator_type != null) {
 570                                         explicit_iface = new TypeExpression (generic_enumerable_type, Location);
 571                                         var gname = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
 572                                         Method gget_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (generic_enumerator_type, Location), gname);
 573
 574                                         //
 575                                         // Just call generic GetEnumerator implementation
 576                                         //
 577                                         var stmt = new Return (new Invocation (new DynamicMethodGroupExpr (gget_enumerator, Location), null), Location);
 578                                         Method get_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name, stmt);
 579
 580                                         Members.Add (get_enumerator);
 581                                         Members.Add (gget_enumerator);
 582                                 } else {
 583                                         Members.Add (GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name));
 584                                 }
 585                         }
 586
 587                         return base.DoDefineMembers ();
 588                 }
 589
 590                 void Define_Current (bool is_generic)
 591                 {
 592                         TypeExpr type;
 593                         FullNamedExpression explicit_iface;
 594
 595                         if (is_generic) {
 596                                 explicit_iface = new TypeExpression (generic_enumerator_type, Location);
 597                                 type = iterator_type_expr;
 598                         } else {
 599                                 explicit_iface = new TypeExpression (Module.Compiler.BuiltinTypes.IEnumerator, Location);
 600                                 type = new TypeExpression (Compiler.BuiltinTypes.Object, Location);
 601                         }
 602
 603                         var name = new MemberName ("Current", null, explicit_iface, Location);
 604
 605                         ToplevelBlock get_block = new ToplevelBlock (Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location,
 606                                 Block.Flags.CompilerGenerated | Block.Flags.NoFlowAnalysis);
 607                         get_block.AddStatement (new Return (new DynamicFieldExpr (CurrentField, Location), Location));
 608
 609                         Property current = new Property (this, type, Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED, name, null);
 610                         current.Get = new Property.GetMethod (current, Modifiers.COMPILER_GENERATED, null, Location);
 611                         current.Get.Block = get_block;
 612
 613                         Members.Add (current);
 614                 }
 615
 616                 void Define_Reset ()
 617                 {
 618                         Method reset = new Method (
 619                                 this, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
 620                                 Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED,
 621                                 new MemberName ("Reset", Location),
 622                                 ParametersCompiled.EmptyReadOnlyParameters, null);
 623                         Members.Add (reset);
 624
 625                         reset.Block = new ToplevelBlock (Compiler, reset.ParameterInfo, Location,
 626                                 Block.Flags.CompilerGenerated | Block.Flags.NoFlowAnalysis);
 627
 628                         TypeSpec ex_type = Module.PredefinedTypes.NotSupportedException.Resolve ();
 629                         if (ex_type == null)
 630                                 return;
 631
 632                         reset.Block.AddStatement (new Throw (new New (new TypeExpression (ex_type, Location), null, Location), Location));
 633                 }
 634
 635                 protected override void EmitHoistedParameters (EmitContext ec, List<HoistedParameter> hoisted)
 636                 {
 637                         base.EmitHoistedParameters (ec, hoisted);
 638                         if (hoisted_params_copy != null)
 639                                 base.EmitHoistedParameters (ec, hoisted_params_copy);
 640                 }
 641         }
 642
 643         public class StateMachineMethod : Method
 644         {
 645                 readonly StateMachineInitializer expr;
 646
 647                 public StateMachineMethod (StateMachine host, StateMachineInitializer expr, FullNamedExpression returnType,
 648                         Modifiers mod, MemberName name, ToplevelBlock.Flags blockFlags)
 649                         : base (host, returnType, mod | Modifiers.COMPILER_GENERATED,
 650                           name, ParametersCompiled.EmptyReadOnlyParameters, null)
 651                 {
 652                         this.expr = expr;
 653                         Block = new ToplevelBlock (host.Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location.Null, blockFlags);
 654                 }
 655
 656                 public override EmitContext CreateEmitContext (ILGenerator ig, SourceMethodBuilder sourceMethod)
 657                 {
 658                         EmitContext ec = new EmitContext (this, ig, MemberType, sourceMethod);
 659                         ec.CurrentAnonymousMethod = expr;
 660
 661                         if (expr is AsyncInitializer)
 662                                 ec.With (BuilderContext.Options.AsyncBody, true);
 663
 664                         return ec;
 665                 }
 666         }
 667
 668         public abstract class StateMachineInitializer : AnonymousExpression
 669         {
 670                 sealed class MoveNextBodyStatement : Statement
 671                 {
 672                         readonly StateMachineInitializer state_machine;
 673
 674                         public MoveNextBodyStatement (StateMachineInitializer stateMachine)
 675                         {
 676                                 this.state_machine = stateMachine;
 677                                 this.loc = stateMachine.Location;
 678                         }
 679
 680                         protected override void CloneTo (CloneContext clonectx, Statement target)
 681                         {
 682                                 throw new NotSupportedException ();
 683                         }
 684
 685                         public override bool Resolve (BlockContext ec)
 686                         {
 687                                 return true;
 688                         }
 689
 690                         protected override void DoEmit (EmitContext ec)
 691                         {
 692                                 state_machine.EmitMoveNext (ec);
 693                         }
 694
 695                         public override void Emit (EmitContext ec)
 696                         {
 697                                 // Don't create sequence point
 698                                 DoEmit (ec);
 699                         }
 700
 701                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 702                         {
 703                                 return state_machine.ReturnType.Kind != MemberKind.Void;
 704                         }
 705
 706                         public override Reachability MarkReachable (Reachability rc)
 707                         {
 708                                 base.MarkReachable (rc);
 709
 710                                 if (state_machine.ReturnType.Kind != MemberKind.Void)
 711                                         rc = Reachability.CreateUnreachable ();
 712
 713                                 return rc;
 714                         }
 715                 }
 716
 717                 public readonly TypeDefinition Host;
 718                 protected StateMachine storey;
 719
 720                 //
 721                 // The state as we generate the machine
 722                 //
 723                 Label move_next_ok;
 724                 Label iterator_body_end;
 725                 protected Label move_next_error;
 726                 LocalBuilder skip_finally;
 727                 protected LocalBuilder current_pc;
 728                 protected List<ResumableStatement> resume_points;
 729
 730                 protected StateMachineInitializer (ParametersBlock block, TypeDefinition host, TypeSpec returnType)
 731                         : base (block, returnType, block.StartLocation)
 732                 {
 733                         this.Host = host;
 734                 }
 735
 736                 #region Properties
 737
 738                 public Label BodyEnd {
 739                         get {
 740                                 return iterator_body_end;
 741                         }
 742                 }
 743
 744                 public LocalBuilder CurrentPC
 745                 {
 746                         get {
 747                                 return current_pc;
 748                         }
 749                 }
 750
 751                 public LocalBuilder SkipFinally {
 752                         get {
 753                                 return skip_finally;
 754                         }
 755                 }
 756
 757                 public override AnonymousMethodStorey Storey {
 758                         get {
 759                                 return storey;
 760                         }
 761                 }
 762
 763                 #endregion
 764
 765                 public int AddResumePoint (ResumableStatement stmt)
 766                 {
 767                         if (resume_points == null)
 768                                 resume_points = new List<ResumableStatement> ();
 769
 770                         resume_points.Add (stmt);
 771                         return resume_points.Count;
 772                 }
 773
 774                 public override Expression CreateExpressionTree (ResolveContext ec)
 775                 {
 776                         throw new NotSupportedException ("ET");
 777                 }
 778
 779                 protected virtual BlockContext CreateBlockContext (BlockContext bc)
 780                 {
 781                         var ctx = new BlockContext (bc, block, bc.ReturnType);
 782                         ctx.CurrentAnonymousMethod = this;
 783
 784                         ctx.AssignmentInfoOffset = bc.AssignmentInfoOffset;
 785                         ctx.EnclosingLoop = bc.EnclosingLoop;
 786                         ctx.EnclosingLoopOrSwitch = bc.EnclosingLoopOrSwitch;
 787                         ctx.Switch = bc.Switch;
 788
 789                         return ctx;
 790                 }
 791
 792                 protected override Expression DoResolve (ResolveContext rc)
 793                 {
 794                         var bc = (BlockContext) rc;
 795                         var ctx = CreateBlockContext (bc);
 796
 797                         Block.Resolve (ctx);
 798
 799                         if (!rc.IsInProbingMode) {
 800                                 var move_next = new StateMachineMethod (storey, this, new TypeExpression (ReturnType, loc), Modifiers.PUBLIC, new MemberName ("MoveNext", loc), 0);
 801                                 move_next.Block.AddStatement (new MoveNextBodyStatement (this));
 802                                 storey.AddEntryMethod (move_next);
 803                         }
 804
 805                         bc.AssignmentInfoOffset = ctx.AssignmentInfoOffset;
 806                         eclass = ExprClass.Value;
 807                         return this;
 808                 }
 809
 810                 public override void Emit (EmitContext ec)
 811                 {
 812                         //
 813                         // Load state machine instance
 814                         //
 815                         storey.Instance.Emit (ec);
 816                 }
 817
 818                 void EmitMoveNext_NoResumePoints (EmitContext ec)
 819                 {
 820                         ec.EmitThis ();
 821                         ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
 822
 823                         ec.EmitThis ();
 824                         ec.EmitInt ((int) IteratorStorey.State.After);
 825                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 826
 827                         // We only care if the PC is zero (start executing) or non-zero (don't do anything)
 828                         ec.Emit (OpCodes.Brtrue, move_next_error);
 829
 830                         iterator_body_end = ec.DefineLabel ();
 831
 832                         block.EmitEmbedded (ec);
 833
 834                         ec.MarkLabel (iterator_body_end);
 835
 836                         EmitMoveNextEpilogue (ec);
 837
 838                         ec.MarkLabel (move_next_error);
 839
 840                         if (ReturnType.Kind != MemberKind.Void) {
 841                                 ec.EmitInt (0);
 842                                 ec.Emit (OpCodes.Ret);
 843                         }
 844                 }
 845
 846                 void EmitMoveNext (EmitContext ec)
 847                 {
 848                         move_next_ok = ec.DefineLabel ();
 849                         move_next_error = ec.DefineLabel ();
 850
 851                         if (resume_points == null) {
 852                                 EmitMoveNext_NoResumePoints (ec);
 853                                 return;
 854                         }
 855
 856                         current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
 857                         ec.EmitThis ();
 858                         ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
 859                         ec.Emit (OpCodes.Stloc, current_pc);
 860
 861                         // We're actually in state 'running', but this is as good a PC value as any if there's an abnormal exit
 862                         ec.EmitThis ();
 863                         ec.EmitInt ((int) IteratorStorey.State.After);
 864                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 865
 866                         Label[] labels = new Label[1 + resume_points.Count];
 867                         labels[0] = ec.DefineLabel ();
 868
 869                         bool need_skip_finally = false;
 870                         for (int i = 0; i < resume_points.Count; ++i) {
 871                                 ResumableStatement s = resume_points[i];
 872                                 need_skip_finally |= s is ExceptionStatement;
 873                                 labels[i + 1] = s.PrepareForEmit (ec);
 874                         }
 875
 876                         if (need_skip_finally) {
 877                                 skip_finally = ec.GetTemporaryLocal (ec.BuiltinTypes.Bool);
 878                                 ec.EmitInt (0);
 879                                 ec.Emit (OpCodes.Stloc, skip_finally);
 880                         }
 881
 882                         var async_init = this as AsyncInitializer;
 883                         if (async_init != null)
 884                                 ec.BeginExceptionBlock ();
 885
 886                         ec.Emit (OpCodes.Ldloc, current_pc);
 887                         ec.Emit (OpCodes.Switch, labels);
 888
 889                         ec.Emit (async_init != null ? OpCodes.Leave : OpCodes.Br, move_next_error);
 890
 891                         ec.MarkLabel (labels[0]);
 892
 893                         iterator_body_end = ec.DefineLabel ();
 894
 895                         block.EmitEmbedded (ec);
 896
 897                         ec.MarkLabel (iterator_body_end);
 898
 899                         if (async_init != null) {
 900                                 var catch_value = LocalVariable.CreateCompilerGenerated (ec.Module.Compiler.BuiltinTypes.Exception, block, Location);
 901
 902                                 ec.BeginCatchBlock (catch_value.Type);
 903                                 catch_value.EmitAssign (ec);
 904
 905                                 ec.EmitThis ();
 906                                 ec.EmitInt ((int) IteratorStorey.State.After);
 907                                 ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 908
 909                                 ((AsyncTaskStorey) async_init.Storey).EmitSetException (ec, new LocalVariableReference (catch_value, Location));
 910
 911                                 ec.Emit (OpCodes.Leave, move_next_ok);
 912                                 ec.EndExceptionBlock ();
 913                         }
 914
 915                         ec.Mark (Block.Original.EndLocation);
 916                         ec.EmitThis ();
 917                         ec.EmitInt ((int) IteratorStorey.State.After);
 918                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 919
 920                         EmitMoveNextEpilogue (ec);
 921
 922                         ec.MarkLabel (move_next_error);
 923
 924                         if (ReturnType.Kind != MemberKind.Void) {
 925                                 ec.EmitInt (0);
 926                                 ec.Emit (OpCodes.Ret);
 927                         }
 928
 929                         ec.MarkLabel (move_next_ok);
 930
 931                         if (ReturnType.Kind != MemberKind.Void) {
 932                                 ec.EmitInt (1);
 933                                 ec.Emit (OpCodes.Ret);
 934                         }
 935                 }
 936
 937                 protected virtual void EmitMoveNextEpilogue (EmitContext ec)
 938                 {
 939                 }
 940
 941                 public void EmitLeave (EmitContext ec, bool unwind_protect)
 942                 {
 943                         // Return ok
 944                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
 945                 }
 946
 947                 //
 948                 // Called back from YieldStatement
 949                 //
 950                 public virtual void InjectYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
 951                 {
 952                         //
 953                         // Guard against being disposed meantime
 954                         //
 955                         Label disposed = ec.DefineLabel ();
 956                         var iterator = storey as IteratorStorey;
 957                         if (iterator != null) {
 958                                 ec.EmitThis ();
 959                                 ec.Emit (OpCodes.Ldfld, iterator.DisposingField.Spec);
 960                                 ec.Emit (OpCodes.Brtrue_S, disposed);
 961                         }
 962
 963                         //
 964                         // store resume program-counter
 965                         //
 966                         ec.EmitThis ();
 967                         ec.EmitInt (resume_pc);
 968                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 969
 970                         if (iterator != null) {
 971                                 ec.MarkLabel (disposed);
 972                         }
 973
 974                         // mark finally blocks as disabled
 975                         if (unwind_protect && skip_finally != null) {
 976                                 ec.EmitInt (1);
 977                                 ec.Emit (OpCodes.Stloc, skip_finally);
 978                         }
 979                 }
 980
 981                 public void SetStateMachine (StateMachine stateMachine)
 982                 {
 983                         this.storey = stateMachine;
 984                 }
 985         }
 986
 987         //
 988         // Iterators are implemented as state machine blocks
 989         //
 990         public class Iterator : StateMachineInitializer
 991         {
 992                 sealed class TryFinallyBlockProxyStatement : Statement
 993                 {
 994                         TryFinallyBlock block;
 995                         Iterator iterator;
 996
 997                         public TryFinallyBlockProxyStatement (Iterator iterator, TryFinallyBlock block)
 998                         {
 999                                 this.iterator = iterator;
1000                                 this.block = block;
1001                         }
1002
1003                         protected override void CloneTo (CloneContext clonectx, Statement target)
1004                         {
1005                                 throw new NotSupportedException ();
1006                         }
1007
1008                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1009                         {
1010                                 throw new NotSupportedException ();
1011                         }
1012
1013                         protected override void DoEmit (EmitContext ec)
1014                         {
1015                                 //
1016                                 // Restore redirection for any captured variables
1017                                 //
1018                                 ec.CurrentAnonymousMethod = iterator;
1019
1020                                 using (ec.With (BuilderContext.Options.OmitDebugInfo, !ec.HasMethodSymbolBuilder)) {
1021                                         block.EmitFinallyBody (ec);
1022                                 }
1023                         }
1024                 }
1025
1026                 public readonly IMethodData OriginalMethod;
1027                 public readonly bool IsEnumerable;
1028                 public readonly TypeSpec OriginalIteratorType;
1029                 int finally_hosts_counter;
1030
1031                 public Iterator (ParametersBlock block, IMethodData method, TypeDefinition host, TypeSpec iterator_type, bool is_enumerable)
1032                         : base (block, host, host.Compiler.BuiltinTypes.Bool)
1033                 {
1034                         this.OriginalMethod = method;
1035                         this.OriginalIteratorType = iterator_type;
1036                         this.IsEnumerable = is_enumerable;
1037                         this.type = method.ReturnType;
1038                 }
1039
1040                 #region Properties
1041
1042                 public ToplevelBlock Container {
1043                         get { return OriginalMethod.Block; }
1044                 }
1045
1046                 public override string ContainerType {
1047                         get { return "iterator"; }
1048                 }
1049
1050                 public override bool IsIterator {
1051                         get { return true; }
1052                 }
1053
1054                 #endregion
1055
1056                 public Method CreateFinallyHost (TryFinallyBlock block)
1057                 {
1058                         var method = new Method (storey, new TypeExpression (storey.Compiler.BuiltinTypes.Void, loc),
1059                                 Modifiers.COMPILER_GENERATED, new MemberName (CompilerGeneratedContainer.MakeName (null, null, "Finally", finally_hosts_counter++), loc),
1060                                 ParametersCompiled.EmptyReadOnlyParameters, null);
1061
1062                         method.Block = new ToplevelBlock (method.Compiler, method.ParameterInfo, loc,
1063                                 ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis);
1064                         method.Block.AddStatement (new TryFinallyBlockProxyStatement (this, block));
1065
1066                         // Cannot it add to storey because it'd be emitted before nested
1067                         // anonoymous methods which could capture shared variable
1068
1069                         return method;
1070                 }
1071
1072                 public void EmitYieldBreak (EmitContext ec, bool unwind_protect)
1073                 {
1074                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_error);
1075                 }
1076
1077                 public override string GetSignatureForError ()
1078                 {
1079                         return OriginalMethod.GetSignatureForError ();
1080                 }
1081
1082                 public override void Emit (EmitContext ec)
1083                 {
1084                         //
1085                         // Load Iterator storey instance
1086                         //
1087                         storey.Instance.Emit (ec);
1088
1089                         //
1090                         // Initialize iterator PC when it's unitialized
1091                         //
1092                         if (IsEnumerable) {
1093                                 ec.Emit (OpCodes.Dup);
1094                                 ec.EmitInt ((int)IteratorStorey.State.Uninitialized);
1095
1096                                 var field = storey.PC.Spec;
1097                                 if (storey.MemberName.IsGeneric) {
1098                                         field = MemberCache.GetMember (Storey.Instance.Type, field);
1099                                 }
1100
1101                                 ec.Emit (OpCodes.Stfld, field);
1102                         }
1103                 }
1104
1105                 public void EmitDispose (EmitContext ec)
1106                 {
1107                         if (resume_points == null)
1108                                 return;
1109
1110                         Label end = ec.DefineLabel ();
1111
1112                         Label[] labels = null;
1113                         for (int i = 0; i < resume_points.Count; ++i) {
1114                                 ResumableStatement s = resume_points[i];
1115                                 Label ret = s.PrepareForDispose (ec, end);
1116                                 if (ret.Equals (end) && labels == null)
1117                                         continue;
1118                                 if (labels == null) {
1119                                         labels = new Label[resume_points.Count + 1];
1120                                         for (int j = 0; j <= i; ++j)
1121                                                 labels[j] = end;
1122                                 }
1123
1124                                 labels[i + 1] = ret;
1125                         }
1126
1127                         if (labels != null) {
1128                                 current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
1129                                 ec.EmitThis ();
1130                                 ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
1131                                 ec.Emit (OpCodes.Stloc, current_pc);
1132                         }
1133
1134                         ec.EmitThis ();
1135                         ec.EmitInt (1);
1136                         ec.Emit (OpCodes.Stfld, ((IteratorStorey) storey).DisposingField.Spec);
1137
1138                         ec.EmitThis ();
1139                         ec.EmitInt ((int) IteratorStorey.State.After);
1140                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
1141
1142                         if (labels != null) {
1143                                 //SymbolWriter.StartIteratorDispatcher (ec.ig);
1144                                 ec.Emit (OpCodes.Ldloc, current_pc);
1145                                 ec.Emit (OpCodes.Switch, labels);
1146                                 //SymbolWriter.EndIteratorDispatcher (ec.ig);
1147
1148                                 foreach (ResumableStatement s in resume_points)
1149                                         s.EmitForDispose (ec, current_pc, end, true);
1150                         }
1151
1152                         ec.MarkLabel (end);
1153                 }
1154
1155                 public override void EmitStatement (EmitContext ec)
1156                 {
1157                         throw new NotImplementedException ();
1158                 }
1159
1160                 public override void InjectYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
1161                 {
1162                         // Store the new value into current
1163                         var fe = new FieldExpr (((IteratorStorey) storey).CurrentField, loc);
1164                         fe.InstanceExpression = new CompilerGeneratedThis (storey.CurrentType, loc);
1165                         fe.EmitAssign (ec, expr, false, false);
1166
1167                         base.InjectYield (ec, expr, resume_pc, unwind_protect, resume_point);
1168
1169                         EmitLeave (ec, unwind_protect);
1170
1171                         ec.MarkLabel (resume_point);
1172                 }
1173
1174                 public static void CreateIterator (IMethodData method, TypeDefinition parent, Modifiers modifiers)
1175                 {
1176                         bool is_enumerable;
1177                         TypeSpec iterator_type;
1178
1179                         TypeSpec ret = method.ReturnType;
1180                         if (ret == null)
1181                                 return;
1182
1183                         if (!CheckType (ret, parent, out iterator_type, out is_enumerable)) {
1184                                 parent.Compiler.Report.Error (1624, method.Location,
1185                                               "The body of `{0}' cannot be an iterator block " +
1186                                               "because `{1}' is not an iterator interface type",
1187                                               method.GetSignatureForError (),
1188                                               ret.GetSignatureForError ());
1189                                 return;
1190                         }
1191
1192                         ParametersCompiled parameters = method.ParameterInfo;
1193                         for (int i = 0; i < parameters.Count; i++) {
1194                                 Parameter p = parameters [i];
1195                                 Parameter.Modifier mod = p.ModFlags;
1196                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
1197                                         parent.Compiler.Report.Error (1623, p.Location,
1198                                                 "Iterators cannot have ref or out parameters");
1199                                         return;
1200                                 }
1201
1202                                 if (p is ArglistParameter) {
1203                                         parent.Compiler.Report.Error (1636, method.Location,
1204                                                 "__arglist is not allowed in parameter list of iterators");
1205                                         return;
1206                                 }
1207
1208                                 if (parameters.Types [i].IsPointer) {
1209                                         parent.Compiler.Report.Error (1637, p.Location,
1210                                                 "Iterators cannot have unsafe parameters or yield types");
1211                                         return;
1212                                 }
1213                         }
1214
1215                         if ((modifiers & Modifiers.UNSAFE) != 0) {
1216                                 parent.Compiler.Report.Error (1629, method.Location, "Unsafe code may not appear in iterators");
1217                         }
1218
1219                         method.Block = method.Block.ConvertToIterator (method, parent, iterator_type, is_enumerable);
1220                 }
1221
1222                 static bool CheckType (TypeSpec ret, TypeContainer parent, out TypeSpec original_iterator_type, out bool is_enumerable)
1223                 {
1224                         original_iterator_type = null;
1225                         is_enumerable = false;
1226
1227                         if (ret.BuiltinType == BuiltinTypeSpec.Type.IEnumerable) {
1228                                 original_iterator_type = parent.Compiler.BuiltinTypes.Object;
1229                                 is_enumerable = true;
1230                                 return true;
1231                         }
1232                         if (ret.BuiltinType == BuiltinTypeSpec.Type.IEnumerator) {
1233                                 original_iterator_type = parent.Compiler.BuiltinTypes.Object;
1234                                 is_enumerable = false;
1235                                 return true;
1236                         }
1237
1238                         InflatedTypeSpec inflated = ret as InflatedTypeSpec;
1239                         if (inflated == null)
1240                                 return false;
1241
1242                         var member_definition = inflated.MemberDefinition;
1243                         PredefinedType ptype = parent.Module.PredefinedTypes.IEnumerableGeneric;
1244
1245                         if (ptype.Define () && ptype.TypeSpec.MemberDefinition == member_definition) {
1246                                 original_iterator_type = inflated.TypeArguments[0];
1247                                 is_enumerable = true;
1248                                 return true;
1249                         }
1250
1251                         ptype = parent.Module.PredefinedTypes.IEnumeratorGeneric;
1252                         if (ptype.Define () && ptype.TypeSpec.MemberDefinition == member_definition) {
1253                                 original_iterator_type = inflated.TypeArguments[0];
1254                                 is_enumerable = false;
1255                                 return true;
1256                         }
1257
1258                         return false;
1259                 }
1260         }
1261 }
1262