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