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;
  19 using System.Reflection;
  20 using System.Reflection.Emit;
  21
  22 namespace Mono.CSharp {
  23
  24         public class Yield : ResumableStatement {
  25                 Expression expr;
  26                 bool unwind_protect;
  27                 Iterator iterator;
  28                 int resume_pc;
  29
  30                 public Yield (Expression expr, Location l)
  31                 {
  32                         this.expr = expr;
  33                         loc = l;
  34                 }
  35
  36                 public static bool CheckContext (ResolveContext ec, Location loc)
  37                 {
  38                         //
  39                         // We can't use `ec.InUnsafe' here because it's allowed to have an iterator
  40                         // inside an unsafe class.  See test-martin-29.cs for an example.
  41                         //
  42                         if (!ec.CurrentAnonymousMethod.IsIterator) {
  43                                 Report.Error (1621, loc,
  44                                               "The yield statement cannot be used inside " +
  45                                               "anonymous method blocks");
  46                                 return false;
  47                         }
  48
  49                         return true;
  50                 }
  51
  52                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
  53                 {
  54                         expr.MutateHoistedGenericType (storey);
  55                 }
  56
  57                 public override bool Resolve (BlockContext ec)
  58                 {
  59                         expr = expr.Resolve (ec);
  60                         if (expr == null)
  61                                 return false;
  62
  63                         Report.Debug (64, "RESOLVE YIELD #1", this, ec, expr, expr.GetType (),
  64                                       ec.CurrentAnonymousMethod, ec.CurrentIterator);
  65
  66                         if (!CheckContext (ec, loc))
  67                                 return false;
  68
  69                         iterator = ec.CurrentIterator;
  70                         if (expr.Type != iterator.OriginalIteratorType) {
  71                                 expr = Convert.ImplicitConversionRequired (
  72                                         ec, expr, iterator.OriginalIteratorType, loc);
  73                                 if (expr == null)
  74                                         return false;
  75                         }
  76
  77                         if (!ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
  78                                 unwind_protect = ec.CurrentBranching.AddResumePoint (this, loc, out resume_pc);
  79
  80                         return true;
  81                 }
  82
  83                 protected override void DoEmit (EmitContext ec)
  84                 {
  85                         iterator.MarkYield (ec, expr, resume_pc, unwind_protect, resume_point);
  86                 }
  87
  88                 protected override void CloneTo (CloneContext clonectx, Statement t)
  89                 {
  90                         Yield target = (Yield) t;
  91
  92                         target.expr = expr.Clone (clonectx);
  93                 }
  94         }
  95
  96         public class YieldBreak : ExitStatement
  97         {
  98                 Iterator iterator;
  99
 100                 public YieldBreak (Location l)
 101                 {
 102                         loc = l;
 103                 }
 104
 105                 public override void Error_FinallyClause ()
 106                 {
 107                         Report.Error (1625, loc, "Cannot yield in the body of a finally clause");
 108                 }
 109
 110                 protected override void CloneTo (CloneContext clonectx, Statement target)
 111                 {
 112                         throw new NotSupportedException ();
 113                 }
 114
 115                 protected override bool DoResolve (BlockContext ec)
 116                 {
 117                         iterator = ec.CurrentIterator;
 118                         return Yield.CheckContext (ec, loc);
 119                 }
 120
 121                 protected override void DoEmit (EmitContext ec)
 122                 {
 123                         iterator.EmitYieldBreak (ec.ig, unwind_protect);
 124                 }
 125
 126                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 127                 {
 128                         // nothing to do
 129                 }
 130         }
 131
 132         //
 133         // Wraps method block into iterator wrapper block
 134         //
 135         class IteratorStatement : Statement
 136         {
 137                 Iterator iterator;
 138                 Block original_block;
 139
 140                 public IteratorStatement (Iterator iterator, Block original_block)
 141                 {
 142                         this.iterator = iterator;
 143                         this.original_block = original_block;
 144                         this.loc = iterator.Location;
 145                 }
 146
 147                 protected override void CloneTo (CloneContext clonectx, Statement target)
 148                 {
 149                         IteratorStatement t = (IteratorStatement) target;
 150                         t.original_block = (ExplicitBlock) original_block.Clone (clonectx);
 151                         t.iterator = (Iterator) iterator.Clone (clonectx);
 152                 }
 153
 154                 public override bool Resolve (BlockContext ec)
 155                 {
 156                         ec.StartFlowBranching (iterator);
 157                         bool ok = original_block.Resolve (ec);
 158                         ec.EndFlowBranching ();
 159                         return ok;
 160                 }
 161
 162                 protected override void DoEmit (EmitContext ec)
 163                 {
 164                         iterator.EmitMoveNext (ec, original_block);
 165                 }
 166
 167                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 168                 {
 169                         original_block.MutateHoistedGenericType (storey);
 170                         iterator.MutateHoistedGenericType (storey);
 171                 }
 172         }
 173
 174         public class IteratorStorey : AnonymousMethodStorey
 175         {
 176                 class IteratorMethod : Method
 177                 {
 178                         readonly IteratorStorey host;
 179
 180                         public IteratorMethod (IteratorStorey host, FullNamedExpression returnType, int mod, MemberName name)
 181                                 : base (host, null, returnType, mod | Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED,
 182                                   name, ParametersCompiled.EmptyReadOnlyParameters, null)
 183                         {
 184                                 this.host = host;
 185
 186                                 Block = new ToplevelBlock (host.Iterator.Container.Toplevel, ParametersCompiled.EmptyReadOnlyParameters, Location);
 187                         }
 188
 189                         public override EmitContext CreateEmitContext (ILGenerator ig)
 190                         {
 191                                 EmitContext ec = new EmitContext (
 192                                         this, ig, MemberType);
 193
 194                                 ec.CurrentAnonymousMethod = host.Iterator;
 195                                 return ec;
 196                         }
 197                 }
 198
 199                 class GetEnumeratorMethod : IteratorMethod
 200                 {
 201                         sealed class GetEnumeratorStatement : Statement
 202                         {
 203                                 IteratorStorey host;
 204                                 IteratorMethod host_method;
 205
 206                                 Expression new_storey;
 207
 208                                 public GetEnumeratorStatement (IteratorStorey host, IteratorMethod host_method)
 209                                 {
 210                                         this.host = host;
 211                                         this.host_method = host_method;
 212                                         loc = host_method.Location;
 213                                 }
 214
 215                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 216                                 {
 217                                         throw new NotSupportedException ();
 218                                 }
 219
 220                                 public override bool Resolve (BlockContext ec)
 221                                 {
 222                                         TypeExpression storey_type_expr = new TypeExpression (host.TypeBuilder, loc);
 223                                         ArrayList init = null;
 224                                         if (host.hoisted_this != null) {
 225                                                 init = new ArrayList (host.hoisted_params == null ? 1 : host.HoistedParameters.Count + 1);
 226                                                 HoistedThis ht = host.hoisted_this;
 227                                                 FieldExpr from = new FieldExpr (ht.Field.FieldBuilder, loc);
 228                                                 from.InstanceExpression = CompilerGeneratedThis.Instance;
 229                                                 init.Add (new ElementInitializer (ht.Field.Name, from, loc));
 230                                         }
 231
 232                                         if (host.hoisted_params != null) {
 233                                                 if (init == null)
 234                                                         init = new ArrayList (host.HoistedParameters.Count);
 235
 236                                                 for (int i = 0; i < host.hoisted_params.Count; ++i) {
 237                                                         HoistedParameter hp = (HoistedParameter) host.hoisted_params [i];
 238                                                         HoistedParameter hp_cp = (HoistedParameter) host.hoisted_params_copy [i];
 239
 240                                                         FieldExpr from = new FieldExpr (hp_cp.Field.FieldBuilder, loc);
 241                                                         from.InstanceExpression = CompilerGeneratedThis.Instance;
 242
 243                                                         init.Add (new ElementInitializer (hp.Field.Name, from, loc));
 244                                                 }
 245                                         }
 246
 247                                         if (init != null) {
 248                                                 new_storey = new NewInitialize (storey_type_expr, null,
 249                                                         new CollectionOrObjectInitializers (init, loc), loc);
 250                                         } else {
 251                                                 new_storey = new New (storey_type_expr, null, loc);
 252                                         }
 253
 254                                         new_storey = new_storey.Resolve (ec);
 255                                         if (new_storey != null)
 256                                                 new_storey = Convert.ImplicitConversionRequired (ec, new_storey, host_method.MemberType, loc);
 257
 258                                         if (TypeManager.int_interlocked_compare_exchange == null) {
 259                                                 Type t = TypeManager.CoreLookupType ("System.Threading", "Interlocked", Kind.Class, true);
 260                                                 if (t != null) {
 261                                                         TypeManager.int_interlocked_compare_exchange = TypeManager.GetPredefinedMethod (
 262                                                                 t, "CompareExchange", loc, TypeManager.int32_type,
 263                                                                 TypeManager.int32_type, TypeManager.int32_type);
 264                                                 }
 265                                         }
 266
 267                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 268                                         return true;
 269                                 }
 270
 271                                 protected override void DoEmit (EmitContext ec)
 272                                 {
 273                                         ILGenerator ig = ec.ig;
 274                                         Label label_init = ig.DefineLabel ();
 275
 276                                         ig.Emit (OpCodes.Ldarg_0);
 277                                         ig.Emit (OpCodes.Ldflda, host.PC.FieldBuilder);
 278                                         IntConstant.EmitInt (ig, (int) Iterator.State.Start);
 279                                         IntConstant.EmitInt (ig, (int) Iterator.State.Uninitialized);
 280                                         ig.Emit (OpCodes.Call, TypeManager.int_interlocked_compare_exchange);
 281
 282                                         IntConstant.EmitInt (ig, (int) Iterator.State.Uninitialized);
 283                                         ig.Emit (OpCodes.Bne_Un_S, label_init);
 284
 285                                         ig.Emit (OpCodes.Ldarg_0);
 286                                         ig.Emit (OpCodes.Ret);
 287
 288                                         ig.MarkLabel (label_init);
 289
 290                                         new_storey.Emit (ec);
 291                                         ig.Emit (OpCodes.Ret);
 292                                 }
 293
 294                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 295                                 {
 296                                         throw new NotSupportedException ();
 297                                 }
 298                         }
 299
 300                         public GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 301                                 : base (host, returnType, 0, name)
 302                         {
 303                                 Block.AddStatement (new GetEnumeratorStatement (host, this));
 304                         }
 305                 }
 306
 307                 class DisposeMethod : IteratorMethod
 308                 {
 309                         sealed class DisposeMethodStatement : Statement
 310                         {
 311                                 Iterator iterator;
 312
 313                                 public DisposeMethodStatement (Iterator iterator)
 314                                 {
 315                                         this.iterator = iterator;
 316                                         this.loc = iterator.Location;
 317                                 }
 318
 319                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 320                                 {
 321                                         throw new NotSupportedException ();
 322                                 }
 323
 324                                 public override bool Resolve (BlockContext ec)
 325                                 {
 326                                         return true;
 327                                 }
 328
 329                                 protected override void DoEmit (EmitContext ec)
 330                                 {
 331                                         iterator.EmitDispose (ec);
 332                                 }
 333
 334                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 335                                 {
 336                                         throw new NotSupportedException ();
 337                                 }
 338                         }
 339
 340                         public DisposeMethod (IteratorStorey host)
 341                                 : base (host, TypeManager.system_void_expr, Modifiers.PUBLIC, new MemberName ("Dispose", host.Location))
 342                         {
 343                                 host.AddMethod (this);
 344
 345                                 Block = new ToplevelBlock (host.Iterator.Container, ParametersCompiled.EmptyReadOnlyParameters, Location);
 346                                 Block.AddStatement (new DisposeMethodStatement (host.Iterator));
 347                         }
 348                 }
 349
 350                 //
 351                 // Uses Method as method info
 352                 //
 353                 class DynamicMethodGroupExpr : MethodGroupExpr
 354                 {
 355                         readonly Method method;
 356
 357                         public DynamicMethodGroupExpr (Method method, Location loc)
 358                                 : base (null, loc)
 359                         {
 360                                 this.method = method;
 361                         }
 362
 363                         public override Expression DoResolve (ResolveContext ec)
 364                         {
 365                                 Methods = new MethodBase [] { method.MethodBuilder };
 366                                 type = method.Parent.TypeBuilder;
 367                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 368                                 return base.DoResolve (ec);
 369                         }
 370                 }
 371
 372                 class DynamicFieldExpr : FieldExpr
 373                 {
 374                         readonly Field field;
 375
 376                         public DynamicFieldExpr (Field field, Location loc)
 377                                 : base (loc)
 378                         {
 379                                 this.field = field;
 380                         }
 381
 382                         public override Expression DoResolve (ResolveContext ec)
 383                         {
 384                                 FieldInfo = field.FieldBuilder;
 385                                 type = TypeManager.TypeToCoreType (FieldInfo.FieldType);
 386                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 387                                 return base.DoResolve (ec);
 388                         }
 389                 }
 390
 391                 public readonly Iterator Iterator;
 392
 393                 TypeExpr iterator_type_expr;
 394                 Field pc_field;
 395                 Field current_field;
 396
 397                 TypeExpr enumerator_type;
 398                 TypeExpr enumerable_type;
 399                 TypeArguments generic_args;
 400                 TypeExpr generic_enumerator_type;
 401                 TypeExpr generic_enumerable_type;
 402
 403                 ArrayList hoisted_params_copy;
 404                 int local_name_idx;
 405
 406                 public IteratorStorey (Iterator iterator)
 407                         : base (iterator.Container.Toplevel, iterator.Host,
 408                           iterator.OriginalMethod as MemberBase, iterator.GenericMethod, "Iterator")
 409                 {
 410                         this.Iterator = iterator;
 411                 }
 412
 413                 public Field PC {
 414                         get { return pc_field; }
 415                 }
 416
 417                 public Field CurrentField {
 418                         get { return current_field; }
 419                 }
 420
 421                 public ArrayList HoistedParameters {
 422                         get { return hoisted_params; }
 423                 }
 424
 425                 protected override TypeExpr [] ResolveBaseTypes (out TypeExpr base_class)
 426                 {
 427                         iterator_type_expr = new TypeExpression (MutateType (Iterator.OriginalIteratorType), Location);
 428                         generic_args = new TypeArguments (iterator_type_expr);
 429
 430                         ArrayList list = new ArrayList ();
 431                         if (Iterator.IsEnumerable) {
 432                                 enumerable_type = new TypeExpression (
 433                                         TypeManager.ienumerable_type, Location);
 434                                 list.Add (enumerable_type);
 435
 436                                 if (TypeManager.generic_ienumerable_type != null) {
 437                                         generic_enumerable_type = new GenericTypeExpr (
 438                                                 TypeManager.generic_ienumerable_type,
 439                                                 generic_args, Location);
 440                                         list.Add (generic_enumerable_type);
 441                                 }
 442                         }
 443
 444                         enumerator_type = new TypeExpression (
 445                                 TypeManager.ienumerator_type, Location);
 446                         list.Add (enumerator_type);
 447
 448                         list.Add (new TypeExpression (TypeManager.idisposable_type, Location));
 449
 450                         if (TypeManager.generic_ienumerator_type != null) {
 451                                 generic_enumerator_type = new GenericTypeExpr (
 452                                         TypeManager.generic_ienumerator_type,
 453                                         generic_args, Location);
 454                                 list.Add (generic_enumerator_type);
 455                         }
 456
 457                         type_bases = list;
 458
 459                         return base.ResolveBaseTypes (out base_class);
 460                 }
 461
 462                 protected override string GetVariableMangledName (LocalInfo local_info)
 463                 {
 464                         return "<" + local_info.Name + ">__" + local_name_idx++.ToString ();
 465                 }
 466
 467                 public void DefineIteratorMembers ()
 468                 {
 469                         pc_field = AddCompilerGeneratedField ("$PC", TypeManager.system_int32_expr);
 470                         current_field = AddCompilerGeneratedField ("$current", iterator_type_expr);
 471
 472                         if (hoisted_params != null) {
 473                                 //
 474                                 // Iterators are independent, each GetEnumerator call has to
 475                                 // create same enumerator therefore we have to keep original values
 476                                 // around for re-initialization
 477                                 //
 478                                 // TODO: Do it for assigned/modified parameters only
 479                                 //
 480                                 hoisted_params_copy = new ArrayList (hoisted_params.Count);
 481                                 foreach (HoistedParameter hp in hoisted_params) {
 482                                         hoisted_params_copy.Add (new HoistedParameter (hp, "<$>" + hp.Field.Name));
 483                                 }
 484                         }
 485
 486                         if (generic_enumerator_type != null)
 487                                 Define_Current (true);
 488
 489                         Define_Current (false);
 490                         new DisposeMethod (this);
 491                         Define_Reset ();
 492
 493                         if (Iterator.IsEnumerable) {
 494                                 MemberName name = new MemberName (QualifiedAliasMember.GlobalAlias, "System", null, Location);
 495                                 name = new MemberName (name, "Collections", Location);
 496                                 name = new MemberName (name, "IEnumerable", Location);
 497                                 name = new MemberName (name, "GetEnumerator", Location);
 498
 499                                 if (generic_enumerator_type != null) {
 500                                         Method get_enumerator = new IteratorMethod (this, enumerator_type, 0, name);
 501
 502                                         name = new MemberName (name.Left.Left, "Generic", Location);
 503                                         name = new MemberName (name, "IEnumerable", generic_args, Location);
 504                                         name = new MemberName (name, "GetEnumerator", Location);
 505                                         Method gget_enumerator = new GetEnumeratorMethod (this, generic_enumerator_type, name);
 506
 507                                         //
 508                                         // Just call generic GetEnumerator implementation
 509                                         //
 510                                         get_enumerator.Block.AddStatement (
 511                                                 new Return (new Invocation (new DynamicMethodGroupExpr (gget_enumerator, Location), null), Location));
 512
 513                                         AddMethod (get_enumerator);
 514                                         AddMethod (gget_enumerator);
 515                                 } else {
 516                                         AddMethod (new GetEnumeratorMethod (this, enumerator_type, name));
 517                                 }
 518                         }
 519                 }
 520
 521                 protected override void EmitHoistedParameters (EmitContext ec, ArrayList hoisted)
 522                 {
 523                         base.EmitHoistedParameters (ec, hoisted);
 524                         base.EmitHoistedParameters (ec, hoisted_params_copy);
 525                 }
 526
 527                 void Define_Current (bool is_generic)
 528                 {
 529                         TypeExpr type;
 530
 531                         MemberName name = new MemberName (QualifiedAliasMember.GlobalAlias, "System", null, Location);
 532                         name = new MemberName (name, "Collections", Location);
 533
 534                         if (is_generic) {
 535                                 name = new MemberName (name, "Generic", Location);
 536                                 name = new MemberName (name, "IEnumerator", generic_args, Location);
 537                                 type = iterator_type_expr;
 538                         } else {
 539                                 name = new MemberName (name, "IEnumerator");
 540                                 type = TypeManager.system_object_expr;
 541                         }
 542
 543                         name = new MemberName (name, "Current", Location);
 544
 545                         ToplevelBlock get_block = new ToplevelBlock (Location);
 546                         get_block.AddStatement (new Return (new DynamicFieldExpr (CurrentField, Location), Location));
 547
 548                         Accessor getter = new Accessor (get_block, 0, null, null, Location);
 549
 550                         Property current = new Property (
 551                                 this, type, Modifiers.DEBUGGER_HIDDEN, name, null, getter, null, false);
 552                         AddProperty (current);
 553                 }
 554
 555                 void Define_Reset ()
 556                 {
 557                         Method reset = new Method (
 558                                 this, null, TypeManager.system_void_expr,
 559                                 Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
 560                                 new MemberName ("Reset", Location),
 561                                 ParametersCompiled.EmptyReadOnlyParameters, null);
 562                         AddMethod (reset);
 563
 564                         reset.Block = new ToplevelBlock (Location);
 565
 566                         Type ex_type = TypeManager.CoreLookupType ("System", "NotSupportedException", Kind.Class, true);
 567                         if (ex_type == null)
 568                                 return;
 569
 570                         reset.Block.AddStatement (new Throw (new New (new TypeExpression (ex_type, Location), null, Location), Location));
 571                 }
 572         }
 573
 574         //
 575         // Iterators are implemented as hidden anonymous block
 576         //
 577         public class Iterator : AnonymousExpression {
 578                 public readonly IMethodData OriginalMethod;
 579                 AnonymousMethodMethod method;
 580                 public readonly TypeContainer Host;
 581                 public readonly bool IsEnumerable;
 582
 583                 //
 584                 // The state as we generate the iterator
 585                 //
 586                 Label move_next_ok, move_next_error;
 587                 LocalBuilder skip_finally, current_pc;
 588
 589                 public LocalBuilder SkipFinally {
 590                         get { return skip_finally; }
 591                 }
 592
 593                 public LocalBuilder CurrentPC {
 594                         get { return current_pc; }
 595                 }
 596
 597                 public Block Container {
 598                         get { return OriginalMethod.Block; }
 599                 }
 600
 601                 public GenericMethod GenericMethod {
 602                         get { return OriginalMethod.GenericMethod; }
 603                 }
 604
 605                 public readonly Type OriginalIteratorType;
 606
 607                 readonly IteratorStorey IteratorHost;
 608
 609                 public enum State {
 610                         Running = -3, // Used only in CurrentPC, never stored into $PC
 611                         Uninitialized = -2,
 612                         After = -1,
 613                         Start = 0
 614                 }
 615
 616                 public void EmitYieldBreak (ILGenerator ig, bool unwind_protect)
 617                 {
 618                         ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_error);
 619                 }
 620
 621                 void EmitMoveNext_NoResumePoints (EmitContext ec, Block original_block)
 622                 {
 623                         ILGenerator ig = ec.ig;
 624
 625                         ig.Emit (OpCodes.Ldarg_0);
 626                         ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 627
 628                         ig.Emit (OpCodes.Ldarg_0);
 629                         IntConstant.EmitInt (ig, (int) State.After);
 630                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 631
 632                         // We only care if the PC is zero (start executing) or non-zero (don't do anything)
 633                         ig.Emit (OpCodes.Brtrue, move_next_error);
 634
 635                         SymbolWriter.StartIteratorBody (ec.ig);
 636                         original_block.Emit (ec);
 637                         SymbolWriter.EndIteratorBody (ec.ig);
 638
 639                         ig.MarkLabel (move_next_error);
 640                         ig.Emit (OpCodes.Ldc_I4_0);
 641                         ig.Emit (OpCodes.Ret);
 642                 }
 643
 644                 internal void EmitMoveNext (EmitContext ec, Block original_block)
 645                 {
 646                         ILGenerator ig = ec.ig;
 647
 648                         move_next_ok = ig.DefineLabel ();
 649                         move_next_error = ig.DefineLabel ();
 650
 651                         if (resume_points == null) {
 652                                 EmitMoveNext_NoResumePoints (ec, original_block);
 653                                 return;
 654                         }
 655
 656                         current_pc = ec.GetTemporaryLocal (TypeManager.uint32_type);
 657                         ig.Emit (OpCodes.Ldarg_0);
 658                         ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 659                         ig.Emit (OpCodes.Stloc, current_pc);
 660
 661                         // We're actually in state 'running', but this is as good a PC value as any if there's an abnormal exit
 662                         ig.Emit (OpCodes.Ldarg_0);
 663                         IntConstant.EmitInt (ig, (int) State.After);
 664                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 665
 666                         Label [] labels = new Label [1 + resume_points.Count];
 667                         labels [0] = ig.DefineLabel ();
 668
 669                         bool need_skip_finally = false;
 670                         for (int i = 0; i < resume_points.Count; ++i) {
 671                                 ResumableStatement s = (ResumableStatement) resume_points [i];
 672                                 need_skip_finally |= s is ExceptionStatement;
 673                                 labels [i+1] = s.PrepareForEmit (ec);
 674                         }
 675
 676                         if (need_skip_finally) {
 677                                 skip_finally = ec.GetTemporaryLocal (TypeManager.bool_type);
 678                                 ig.Emit (OpCodes.Ldc_I4_0);
 679                                 ig.Emit (OpCodes.Stloc, skip_finally);
 680                         }
 681
 682                         SymbolWriter.StartIteratorDispatcher (ec.ig);
 683                         ig.Emit (OpCodes.Ldloc, current_pc);
 684                         ig.Emit (OpCodes.Switch, labels);
 685
 686                         ig.Emit (OpCodes.Br, move_next_error);
 687                         SymbolWriter.EndIteratorDispatcher (ec.ig);
 688
 689                         ig.MarkLabel (labels [0]);
 690
 691                         SymbolWriter.StartIteratorBody (ec.ig);
 692                         original_block.Emit (ec);
 693                         SymbolWriter.EndIteratorBody (ec.ig);
 694
 695                         SymbolWriter.StartIteratorDispatcher (ec.ig);
 696
 697                         ig.Emit (OpCodes.Ldarg_0);
 698                         IntConstant.EmitInt (ig, (int) State.After);
 699                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 700
 701                         ig.MarkLabel (move_next_error);
 702                         ig.Emit (OpCodes.Ldc_I4_0);
 703                         ig.Emit (OpCodes.Ret);
 704
 705                         ig.MarkLabel (move_next_ok);
 706                         ig.Emit (OpCodes.Ldc_I4_1);
 707                         ig.Emit (OpCodes.Ret);
 708
 709                         SymbolWriter.EndIteratorDispatcher (ec.ig);
 710                 }
 711
 712                 public void EmitDispose (EmitContext ec)
 713                 {
 714                         ILGenerator ig = ec.ig;
 715
 716                         Label end = ig.DefineLabel ();
 717
 718                         Label [] labels = null;
 719                         int n_resume_points = resume_points == null ? 0 : resume_points.Count;
 720                         for (int i = 0; i < n_resume_points; ++i) {
 721                                 ResumableStatement s = (ResumableStatement) resume_points [i];
 722                                 Label ret = s.PrepareForDispose (ec, end);
 723                                 if (ret.Equals (end) && labels == null)
 724                                         continue;
 725                                 if (labels == null) {
 726                                         labels = new Label [resume_points.Count + 1];
 727                                         for (int j = 0; j <= i; ++j)
 728                                                 labels [j] = end;
 729                                 }
 730                                 labels [i+1] = ret;
 731                         }
 732
 733                         if (labels != null) {
 734                                 current_pc = ec.GetTemporaryLocal (TypeManager.uint32_type);
 735                                 ig.Emit (OpCodes.Ldarg_0);
 736                                 ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 737                                 ig.Emit (OpCodes.Stloc, current_pc);
 738                         }
 739
 740                         ig.Emit (OpCodes.Ldarg_0);
 741                         IntConstant.EmitInt (ig, (int) State.After);
 742                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 743
 744                         if (labels != null) {
 745                                 //SymbolWriter.StartIteratorDispatcher (ec.ig);
 746                                 ig.Emit (OpCodes.Ldloc, current_pc);
 747                                 ig.Emit (OpCodes.Switch, labels);
 748                                 //SymbolWriter.EndIteratorDispatcher (ec.ig);
 749
 750                                 foreach (ResumableStatement s in resume_points)
 751                                         s.EmitForDispose (ec, this, end, true);
 752                         }
 753
 754                         ig.MarkLabel (end);
 755                 }
 756
 757
 758                 ArrayList resume_points;
 759                 public int AddResumePoint (ResumableStatement stmt)
 760                 {
 761                         if (resume_points == null)
 762                                 resume_points = new ArrayList ();
 763                         resume_points.Add (stmt);
 764                         return resume_points.Count;
 765                 }
 766
 767                 //
 768                 // Called back from Yield
 769                 //
 770                 public void MarkYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
 771                 {
 772                         ILGenerator ig = ec.ig;
 773
 774                         // Store the new current
 775                         ig.Emit (OpCodes.Ldarg_0);
 776                         expr.Emit (ec);
 777                         ig.Emit (OpCodes.Stfld, IteratorHost.CurrentField.FieldBuilder);
 778
 779                         // store resume program-counter
 780                         ig.Emit (OpCodes.Ldarg_0);
 781                         IntConstant.EmitInt (ig, resume_pc);
 782                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 783
 784                         // mark finally blocks as disabled
 785                         if (unwind_protect && skip_finally != null) {
 786                                 ig.Emit (OpCodes.Ldc_I4_1);
 787                                 ig.Emit (OpCodes.Stloc, skip_finally);
 788                         }
 789
 790                         // Return ok
 791                         ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
 792
 793                         ig.MarkLabel (resume_point);
 794                 }
 795
 796                 public override string ContainerType {
 797                         get { return "iterator"; }
 798                 }
 799
 800                 public override bool IsIterator {
 801                         get { return true; }
 802                 }
 803
 804                 public override AnonymousMethodStorey Storey {
 805                         get { return IteratorHost; }
 806                 }
 807
 808                 //
 809                 // Our constructor
 810                 //
 811                 private Iterator (IMethodData method, TypeContainer host, Type iterator_type, bool is_enumerable)
 812                         : base (
 813                                 new ToplevelBlock (method.Block, ParametersCompiled.EmptyReadOnlyParameters, method.Block.StartLocation),
 814                                 TypeManager.bool_type,
 815                                 method.Location)
 816                 {
 817                         this.OriginalMethod = method;
 818                         this.OriginalIteratorType = iterator_type;
 819                         this.IsEnumerable = is_enumerable;
 820                         this.Host = host;
 821                         this.type = method.ReturnType;
 822
 823                         IteratorHost = Block.ChangeToIterator (this, method.Block);
 824                 }
 825
 826                 public override string GetSignatureForError ()
 827                 {
 828                         return OriginalMethod.GetSignatureForError ();
 829                 }
 830
 831                 public override Expression DoResolve (ResolveContext ec)
 832                 {
 833                         method = new AnonymousMethodMethod (Storey,
 834                                 this, Storey, null, TypeManager.system_boolean_expr,
 835                                 Modifiers.PUBLIC, OriginalMethod.GetSignatureForError (),
 836                                 new MemberName ("MoveNext", Location),
 837                                 ParametersCompiled.EmptyReadOnlyParameters);
 838
 839                         if (!Compatible (ec))
 840                                 return null;
 841
 842                         IteratorHost.DefineIteratorMembers ();
 843
 844                         eclass = ExprClass.Value;
 845                         return this;
 846                 }
 847
 848                 public override void Emit (EmitContext ec)
 849                 {
 850                         //
 851                         // Load Iterator storey instance
 852                         //
 853                         method.Storey.Instance.Emit (ec);
 854
 855                         //
 856                         // Initialize iterator PC when it's unitialized
 857                         //
 858                         if (IsEnumerable) {
 859                                 ILGenerator ig = ec.ig;
 860                                 ig.Emit (OpCodes.Dup);
 861                                 IntConstant.EmitInt (ig, (int)State.Uninitialized);
 862
 863                                 FieldInfo field = IteratorHost.PC.FieldBuilder;
 864 #if GMCS_SOURCE
 865                                 if (Storey.MemberName.IsGeneric)
 866                                         field = TypeBuilder.GetField (Storey.Instance.Type, field);
 867 #endif
 868                                 ig.Emit (OpCodes.Stfld, field);
 869                         }
 870                 }
 871
 872                 public override Expression CreateExpressionTree (ResolveContext ec)
 873                 {
 874                         throw new NotSupportedException ("ET");
 875                 }
 876
 877                 public static void CreateIterator (IMethodData method, TypeContainer parent, int modifiers)
 878                 {
 879                         bool is_enumerable;
 880                         Type iterator_type;
 881
 882                         Type ret = method.ReturnType;
 883                         if (ret == null)
 884                                 return;
 885
 886                         if (!CheckType (ret, out iterator_type, out is_enumerable)) {
 887                                 Report.Error (1624, method.Location,
 888                                               "The body of `{0}' cannot be an iterator block " +
 889                                               "because `{1}' is not an iterator interface type",
 890                                               method.GetSignatureForError (),
 891                                               TypeManager.CSharpName (ret));
 892                                 return;
 893                         }
 894
 895                         ParametersCompiled parameters = method.ParameterInfo;
 896                         for (int i = 0; i < parameters.Count; i++) {
 897                                 Parameter p = parameters [i];
 898                                 Parameter.Modifier mod = p.ModFlags;
 899                                 if ((mod & Parameter.Modifier.ISBYREF) != 0) {
 900                                         Report.Error (1623, p.Location,
 901                                                 "Iterators cannot have ref or out parameters");
 902                                         return;
 903                                 }
 904
 905                                 if (p is ArglistParameter) {
 906                                         Report.Error (1636, method.Location,
 907                                                 "__arglist is not allowed in parameter list of iterators");
 908                                         return;
 909                                 }
 910
 911                                 if (parameters.Types [i].IsPointer) {
 912                                         Report.Error (1637, p.Location,
 913                                                           "Iterators cannot have unsafe parameters or " +
 914                                                           "yield types");
 915                                         return;
 916                                 }
 917                         }
 918
 919                         if ((modifiers & Modifiers.UNSAFE) != 0) {
 920                                 Report.Error (1629, method.Location, "Unsafe code may not appear in iterators");
 921                                 return;
 922                         }
 923
 924                         Iterator iter = new Iterator (method, parent, iterator_type, is_enumerable);
 925                         iter.Storey.DefineType ();
 926                 }
 927
 928                 static bool CheckType (Type ret, out Type original_iterator_type, out bool is_enumerable)
 929                 {
 930                         original_iterator_type = null;
 931                         is_enumerable = false;
 932
 933                         if (ret == TypeManager.ienumerable_type) {
 934                                 original_iterator_type = TypeManager.object_type;
 935                                 is_enumerable = true;
 936                                 return true;
 937                         }
 938                         if (ret == TypeManager.ienumerator_type) {
 939                                 original_iterator_type = TypeManager.object_type;
 940                                 is_enumerable = false;
 941                                 return true;
 942                         }
 943
 944                         if (!TypeManager.IsGenericType (ret))
 945                                 return false;
 946
 947                         Type[] args = TypeManager.GetTypeArguments (ret);
 948                         if (args.Length != 1)
 949                                 return false;
 950
 951                         Type gt = TypeManager.DropGenericTypeArguments (ret);
 952                         if (gt == TypeManager.generic_ienumerable_type) {
 953                                 original_iterator_type = TypeManager.TypeToCoreType (args [0]);
 954                                 is_enumerable = true;
 955                                 return true;
 956                         }
 957
 958                         if (gt == TypeManager.generic_ienumerator_type) {
 959                                 original_iterator_type = TypeManager.TypeToCoreType (args [0]);
 960                                 is_enumerable = false;
 961                                 return true;
 962                         }
 963
 964                         return false;
 965                 }
 966         }
 967 }
 968