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