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;
  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
  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 (EmitContext ec, Location loc)
  37                 {
  38                         for (Block block = ec.CurrentBlock; block != null; block = block.Parent) {
  39                                 if (!block.Unsafe)
  40                                         continue;
  41
  42                                 Report.Error (1629, loc, "Unsafe code may not appear in iterators");
  43                                 return false;
  44                         }
  45
  46                         //
  47                         // We can't use `ec.InUnsafe' here because it's allowed to have an iterator
  48                         // inside an unsafe class.  See test-martin-29.cs for an example.
  49                         //
  50                         if (!ec.CurrentAnonymousMethod.IsIterator) {
  51                                 Report.Error (1621, loc,
  52                                               "The yield statement cannot be used inside " +
  53                                               "anonymous method blocks");
  54                                 return false;
  55                         }
  56
  57                         return true;
  58                 }
  59
  60                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
  61                 {
  62                         expr.MutateHoistedGenericType (storey);
  63                 }
  64
  65                 public override bool Resolve (EmitContext ec)
  66                 {
  67                         expr = expr.Resolve (ec);
  68                         if (expr == null)
  69                                 return false;
  70
  71                         Report.Debug (64, "RESOLVE YIELD #1", this, ec, expr, expr.GetType (),
  72                                       ec.CurrentAnonymousMethod, ec.CurrentIterator);
  73
  74                         if (!CheckContext (ec, loc))
  75                                 return false;
  76
  77                         Iterator iterator = ec.CurrentIterator;
  78                         if (expr.Type != iterator.OriginalIteratorType) {
  79                                 expr = Convert.ImplicitConversionRequired (
  80                                         ec, expr, iterator.OriginalIteratorType, loc);
  81                                 if (expr == null)
  82                                         return false;
  83                         }
  84
  85                         if (!ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
  86                                 unwind_protect = ec.CurrentBranching.AddResumePoint (this, loc, out resume_pc);
  87
  88                         return true;
  89                 }
  90
  91                 protected override void DoEmit (EmitContext ec)
  92                 {
  93                         ec.CurrentIterator.MarkYield (ec, expr, resume_pc, unwind_protect, resume_point);
  94                 }
  95
  96                 protected override void CloneTo (CloneContext clonectx, Statement t)
  97                 {
  98                         Yield target = (Yield) t;
  99
 100                         target.expr = expr.Clone (clonectx);
 101                 }
 102         }
 103
 104         public class YieldBreak : ExitStatement {
 105                 public YieldBreak (Location l)
 106                 {
 107                         loc = l;
 108                 }
 109
 110                 public override void Error_FinallyClause ()
 111                 {
 112                         Report.Error (1625, loc, "Cannot yield in the body of a finally clause");
 113                 }
 114
 115                 protected override void CloneTo (CloneContext clonectx, Statement target)
 116                 {
 117                         throw new NotSupportedException ();
 118                 }
 119
 120                 protected override bool DoResolve (EmitContext ec)
 121                 {
 122                         return Yield.CheckContext (ec, loc);
 123                 }
 124
 125                 protected override void DoEmit (EmitContext ec)
 126                 {
 127                         ec.CurrentIterator.EmitYieldBreak (ec.ig, unwind_protect);
 128                 }
 129
 130                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 131                 {
 132                         // nothing to do
 133                 }
 134         }
 135
 136         //
 137         // Wraps method block into iterator wrapper block
 138         //
 139         class IteratorStatement : Statement
 140         {
 141                 Iterator iterator;
 142                 ExplicitBlock original_block;
 143
 144                 public IteratorStatement (Iterator iterator, ExplicitBlock original_block)
 145                 {
 146                         this.iterator = iterator;
 147                         this.original_block = original_block;
 148                         this.loc = iterator.Location;
 149                 }
 150
 151                 protected override void CloneTo (CloneContext clonectx, Statement target)
 152                 {
 153                         IteratorStatement t = (IteratorStatement) target;
 154                         t.original_block = (ExplicitBlock) original_block.Clone (clonectx);
 155                         t.iterator = (Iterator) iterator.Clone (clonectx);
 156                 }
 157
 158                 public override bool Resolve (EmitContext ec)
 159                 {
 160                         ec.StartFlowBranching (iterator);
 161                         bool ok = original_block.Resolve (ec);
 162                         ec.EndFlowBranching ();
 163                         return ok;
 164                 }
 165
 166                 protected override void DoEmit (EmitContext ec)
 167                 {
 168                         iterator.EmitMoveNext (ec, original_block);
 169                 }
 170
 171                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 172                 {
 173                         original_block.MutateHoistedGenericType (storey);
 174                         iterator.MutateHoistedGenericType (storey);
 175                 }
 176         }
 177
 178         public class IteratorStorey : AnonymousMethodStorey
 179         {
 180                 class IteratorMethod : Method
 181                 {
 182                         readonly IteratorStorey host;
 183
 184                         public IteratorMethod (IteratorStorey host, FullNamedExpression returnType, int mod, MemberName name)
 185                                 : base (host, null, returnType, mod | Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED,
 186                                   name, Parameters.EmptyReadOnlyParameters, null)
 187                         {
 188                                 this.host = host;
 189
 190                                 Block = new ToplevelBlock (host.Iterator.Container.Toplevel, null, Location);
 191                         }
 192
 193                         public override EmitContext CreateEmitContext (DeclSpace tc, ILGenerator ig)
 194                         {
 195                                 EmitContext ec = new EmitContext (
 196                                         this, tc, this.ds, Location, ig, MemberType, ModFlags, false);
 197
 198                                 ec.CurrentAnonymousMethod = host.Iterator;
 199                                 return ec;
 200                         }
 201                 }
 202
 203                 class GetEnumeratorMethod : IteratorMethod
 204                 {
 205                         sealed class GetEnumeratorStatement : Statement
 206                         {
 207                                 IteratorStorey host;
 208                                 Expression type;
 209
 210                                 Expression cast;
 211
 212                                 public GetEnumeratorStatement (IteratorStorey host, Expression type)
 213                                 {
 214                                         this.host = host;
 215                                         this.type = type;
 216                                         loc = host.Location;
 217                                 }
 218
 219                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 220                                 {
 221                                         throw new NotSupportedException ();
 222                                 }
 223
 224                                 public override bool Resolve (EmitContext ec)
 225                                 {
 226                                         type = type.ResolveAsTypeTerminal (ec, false);
 227                                         if ((type == null) || (type.Type == null))
 228                                                 return false;
 229
 230                                         TypeExpression storey_type_expr = new TypeExpression (host.TypeBuilder, loc);
 231                                         Expression new_storey;
 232                                         ArrayList init = null;
 233                                         if (host.hoisted_this != null) {
 234                                                 init = new ArrayList (host.hoisted_params == null ? 1 : host.HoistedParameters.Count + 1);
 235                                                 HoistedThis ht = host.hoisted_this;
 236                                                 FieldExpr from = new FieldExpr (ht.Field.FieldBuilder, loc);
 237                                                 from.InstanceExpression = CompilerGeneratedThis.Instance;
 238                                                 init.Add (new ElementInitializer (ht.Field.Name, from, loc));
 239                                         }
 240
 241                                         if (host.hoisted_params != null) {
 242                                                 if (init == null)
 243                                                         init = new ArrayList (host.HoistedParameters.Count);
 244
 245                                                 foreach (HoistedParameter hp in host.HoistedParameters) {
 246                                                         FieldExpr from = new FieldExpr (hp.Field.FieldBuilder, loc);
 247                                                         from.InstanceExpression = CompilerGeneratedThis.Instance;
 248                                                         init.Add (new ElementInitializer (hp.Field.Name, from, loc));
 249                                                 }
 250                                         }
 251
 252                                         if (init != null) {
 253                                                 new_storey = new NewInitialize (storey_type_expr, new ArrayList (0),
 254                                                         new CollectionOrObjectInitializers (init, loc), loc);
 255                                         } else {
 256                                                 new_storey = new New (storey_type_expr, new ArrayList (0), loc);
 257                                         }
 258
 259                                         new_storey = new_storey.Resolve (ec);
 260                                         if (new_storey != null)
 261                                                 cast = Convert.ImplicitConversionRequired (ec, new_storey, type.Type, loc);
 262
 263                                         if (TypeManager.int_interlocked_compare_exchange == null) {
 264                                                 Type t = TypeManager.CoreLookupType ("System.Threading", "Interlocked", Kind.Class, true);
 265                                                 if (t != null) {
 266                                                         TypeManager.int_interlocked_compare_exchange = TypeManager.GetPredefinedMethod (
 267                                                                 t, "CompareExchange", loc, TypeManager.int32_type,
 268                                                                 TypeManager.int32_type, TypeManager.int32_type);
 269                                                 }
 270                                         }
 271
 272                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 273                                         return true;
 274                                 }
 275
 276                                 protected override void DoEmit (EmitContext ec)
 277                                 {
 278                                         ILGenerator ig = ec.ig;
 279                                         Label label_init = ig.DefineLabel ();
 280
 281                                         ig.Emit (OpCodes.Ldarg_0);
 282                                         ig.Emit (OpCodes.Ldflda, host.PC.FieldBuilder);
 283                                         ig.Emit (OpCodes.Ldc_I4, (int) Iterator.State.Start);
 284                                         ig.Emit (OpCodes.Ldc_I4, (int) Iterator.State.Uninitialized);
 285                                         ig.Emit (OpCodes.Call, TypeManager.int_interlocked_compare_exchange);
 286
 287                                         ig.Emit (OpCodes.Ldc_I4, (int) Iterator.State.Uninitialized);
 288                                         ig.Emit (OpCodes.Bne_Un, label_init);
 289
 290                                         ig.Emit (OpCodes.Ldarg_0);
 291                                         ig.Emit (OpCodes.Ret);
 292
 293                                         ig.MarkLabel (label_init);
 294
 295                                         cast.Emit (ec);
 296                                         ig.Emit (OpCodes.Ret);
 297                                 }
 298
 299                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 300                                 {
 301                                         throw new NotSupportedException ();
 302                                 }
 303                         }
 304
 305                         public GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 306                                 : base (host, returnType, 0, name)
 307                         {
 308                                 Block.AddStatement (new GetEnumeratorStatement (host, type_name));
 309                         }
 310                 }
 311
 312                 class DisposeMethod : IteratorMethod
 313                 {
 314                         sealed class DisposeMethodStatement : Statement
 315                         {
 316                                 Iterator iterator;
 317
 318                                 public DisposeMethodStatement (Iterator iterator)
 319                                 {
 320                                         this.iterator = iterator;
 321                                         this.loc = iterator.Location;
 322                                 }
 323
 324                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 325                                 {
 326                                         throw new NotSupportedException ();
 327                                 }
 328
 329                                 public override bool Resolve (EmitContext ec)
 330                                 {
 331                                         return true;
 332                                 }
 333
 334                                 protected override void DoEmit (EmitContext ec)
 335                                 {
 336                                         iterator.EmitDispose (ec);
 337                                 }
 338
 339                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 340                                 {
 341                                         throw new NotSupportedException ();
 342                                 }
 343                         }
 344
 345                         public DisposeMethod (IteratorStorey host)
 346                                 : base (host, TypeManager.system_void_expr, Modifiers.PUBLIC, new MemberName ("Dispose", host.Location))
 347                         {
 348                                 host.AddMethod (this);
 349
 350                                 Block = new ToplevelBlock (host.Iterator.Container, null, Location);
 351                                 Block.AddStatement (new DisposeMethodStatement (host.Iterator));
 352                         }
 353                 }
 354
 355                 //
 356                 // Uses Method as method info
 357                 //
 358                 class DynamicMethodGroupExpr : MethodGroupExpr
 359                 {
 360                         readonly Method method;
 361
 362                         public DynamicMethodGroupExpr (Method method, Location loc)
 363                                 : base (null, loc)
 364                         {
 365                                 this.method = method;
 366                         }
 367
 368                         public override Expression DoResolve (EmitContext ec)
 369                         {
 370                                 Methods = new MethodBase [] { method.MethodBuilder };
 371                                 type = method.Parent.TypeBuilder;
 372                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 373                                 return base.DoResolve (ec);
 374                         }
 375                 }
 376
 377                 public readonly Iterator Iterator;
 378
 379                 TypeExpr iterator_type_expr;
 380                 Field pc_field;
 381                 Field current_field;
 382
 383                 TypeExpr enumerator_type;
 384                 TypeExpr enumerable_type;
 385 #if GMCS_SOURCE
 386                 TypeArguments generic_args;
 387                 TypeExpr generic_enumerator_type;
 388                 TypeExpr generic_enumerable_type;
 389 #else
 390                 const TypeArguments generic_args = null;
 391 #endif
 392
 393                 int local_name_idx;
 394
 395                 public IteratorStorey (Iterator iterator)
 396                         : base (iterator.Container.Toplevel, iterator.Host,
 397                           iterator.OriginalMethod as MemberBase, iterator.GenericMethod, "Iterator")
 398                 {
 399                         this.Iterator = iterator;
 400                         HasHoistedVariables = true;
 401                 }
 402
 403                 public Field PC {
 404                         get { return pc_field; }
 405                 }
 406
 407                 public Field CurrentField {
 408                         get { return current_field; }
 409                 }
 410
 411                 public ArrayList HoistedParameters {
 412                         get { return hoisted_params; }
 413                 }
 414
 415                 protected override TypeExpr [] ResolveBaseTypes (out TypeExpr base_class)
 416                 {
 417                         iterator_type_expr = new TypeExpression (MutateType (Iterator.OriginalIteratorType), Location);
 418
 419 #if GMCS_SOURCE
 420                         generic_args = new TypeArguments (Location);
 421                         generic_args.Add (iterator_type_expr);
 422 #endif
 423
 424                         ArrayList list = new ArrayList ();
 425                         if (Iterator.IsEnumerable) {
 426                                 enumerable_type = new TypeExpression (
 427                                         TypeManager.ienumerable_type, Location);
 428                                 list.Add (enumerable_type);
 429
 430 #if GMCS_SOURCE
 431                                 generic_enumerable_type = new ConstructedType (
 432                                         TypeManager.generic_ienumerable_type,
 433                                         generic_args, Location);
 434                                 list.Add (generic_enumerable_type);
 435 #endif
 436                         }
 437
 438                         enumerator_type = new TypeExpression (
 439                                 TypeManager.ienumerator_type, Location);
 440                         list.Add (enumerator_type);
 441
 442                         list.Add (new TypeExpression (TypeManager.idisposable_type, Location));
 443
 444 #if GMCS_SOURCE
 445                         generic_enumerator_type = new ConstructedType (
 446                                 TypeManager.generic_ienumerator_type,
 447                                 generic_args, Location);
 448                         list.Add (generic_enumerator_type);
 449 #endif
 450
 451                         type_bases = list;
 452
 453                         return base.ResolveBaseTypes (out base_class);
 454                 }
 455
 456                 protected override string GetVariableMangledName (LocalInfo local_info)
 457                 {
 458                         return "<" + local_info.Name + ">__" + local_name_idx++.ToString ();
 459                 }
 460
 461                 public void DefineIteratorMembers ()
 462                 {
 463                         pc_field = AddCompilerGeneratedField ("$PC", TypeManager.system_int32_expr);
 464                         current_field = AddCompilerGeneratedField ("$current", iterator_type_expr);
 465
 466 #if GMCS_SOURCE
 467                         Define_Current (true);
 468 #endif
 469                         Define_Current (false);
 470                         new DisposeMethod (this);
 471                         Define_Reset ();
 472
 473                         if (Iterator.IsEnumerable) {
 474                                 MemberName name = new MemberName (
 475                                         new MemberName ("System.Collections.IEnumerable", Location), "GetEnumerator", Location);
 476
 477 #if GMCS_SOURCE
 478                                 Method get_enumerator = new IteratorMethod (this, enumerator_type, 0, name);
 479
 480                                 name = new MemberName (
 481                                         new MemberName ("System.Collections.Generic.IEnumerable", generic_args, Location), "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), new ArrayList (0)), Location));
 489
 490                                 AddMethod (get_enumerator);
 491                                 AddMethod (gget_enumerator);
 492 #else
 493                                 AddMethod (new GetEnumeratorMethod (this, enumerator_type, name));
 494 #endif
 495                         }
 496                 }
 497
 498                 void Define_Current (bool is_generic)
 499                 {
 500                         MemberName left;
 501                         TypeExpr type;
 502
 503                         if (is_generic) {
 504                                 left = new MemberName (
 505                                         "System.Collections.Generic.IEnumerator",
 506                                         generic_args, Location);
 507                                 type = iterator_type_expr;
 508                         } else {
 509                                 left = new MemberName ("System.Collections.IEnumerator", Location);
 510                                 type = TypeManager.system_object_expr;
 511                         }
 512
 513                         MemberName name = new MemberName (left, "Current", null, Location);
 514
 515                         ToplevelBlock get_block = new ToplevelBlock (Location);
 516                         get_block.AddStatement (new CurrentBlock (this, is_generic));
 517
 518                         Accessor getter = new Accessor (get_block, 0, null, null, Location);
 519
 520                         Property current = new Property (
 521                                 this, type, Modifiers.DEBUGGER_HIDDEN, name, null, getter, null, false);
 522                         AddProperty (current);
 523                 }
 524
 525                 void Define_Reset ()
 526                 {
 527                         Method reset = new Method (
 528                                 this, null, TypeManager.system_void_expr,
 529                                 Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
 530                                 new MemberName ("Reset", Location),
 531                                 Parameters.EmptyReadOnlyParameters, null);
 532                         AddMethod (reset);
 533
 534                         reset.Block = new ToplevelBlock (Location);
 535                         reset.Block.AddStatement (Create_ThrowNotSupported ());
 536                 }
 537
 538                 Statement Create_ThrowNotSupported ()
 539                 {
 540                         TypeExpr ex_type = new TypeLookupExpression ("System.NotSupportedException");
 541
 542                         return new Throw (new New (ex_type, null, Location), Location);
 543                 }
 544
 545                 protected class CurrentBlock : Statement {
 546                         IteratorStorey host;
 547                         bool is_generic;
 548
 549                         public CurrentBlock (IteratorStorey host, bool is_generic)
 550                         {
 551                                 this.host = host;
 552                                 this.is_generic = is_generic;
 553                                 loc = host.Location;
 554                         }
 555
 556                         protected override void CloneTo (CloneContext clonectx, Statement target)
 557                         {
 558                                 throw new NotSupportedException ();
 559                         }
 560
 561                         public override bool Resolve (EmitContext ec)
 562                         {
 563                                 // We emit a 'ret', so prevent the enclosing TopLevelBlock from emitting one too
 564                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
 565                                 return true;
 566                         }
 567
 568                         protected override void DoEmit (EmitContext ec)
 569                         {
 570                                 ILGenerator ig = ec.ig;
 571
 572                                 ig.Emit (OpCodes.Ldarg_0);
 573                                 ig.Emit (OpCodes.Ldfld, host.CurrentField.FieldBuilder);
 574                                 if (!is_generic)
 575                                         ig.Emit (OpCodes.Box, host.CurrentField.MemberType);
 576                                 ig.Emit (OpCodes.Ret);
 577                         }
 578
 579                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 580                         {
 581                                 throw new NotSupportedException ();
 582                         }
 583                 }
 584         }
 585
 586         //
 587         // Iterators are implemented as hidden anonymous block
 588         //
 589         public class Iterator : AnonymousExpression {
 590                 public readonly IMethodData OriginalMethod;
 591                 AnonymousMethodMethod method;
 592                 public readonly TypeContainer Host;
 593                 public readonly bool IsEnumerable;
 594
 595                 //
 596                 // The state as we generate the iterator
 597                 //
 598                 Label move_next_ok, move_next_error;
 599                 LocalBuilder skip_finally, current_pc;
 600
 601                 public LocalBuilder SkipFinally {
 602                         get { return skip_finally; }
 603                 }
 604
 605                 public LocalBuilder CurrentPC {
 606                         get { return current_pc; }
 607                 }
 608
 609                 public Block Container {
 610                         get { return OriginalMethod.Block; }
 611                 }
 612
 613                 public GenericMethod GenericMethod {
 614                         get { return OriginalMethod.GenericMethod; }
 615                 }
 616
 617                 public readonly Type OriginalIteratorType;
 618
 619                 readonly IteratorStorey IteratorHost;
 620
 621                 public enum State {
 622                         Running = -3, // Used only in CurrentPC, never stored into $PC
 623                         Uninitialized = -2,
 624                         After = -1,
 625                         Start = 0
 626                 }
 627
 628                 public override void AddStoreyReference (AnonymousMethodStorey storey)
 629                 {
 630                         // do nothing
 631                 }
 632
 633                 public void EmitYieldBreak (ILGenerator ig, bool unwind_protect)
 634                 {
 635                         ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_error);
 636                 }
 637
 638                 void EmitMoveNext_NoResumePoints (EmitContext ec, Block original_block)
 639                 {
 640                         ILGenerator ig = ec.ig;
 641
 642                         ig.Emit (OpCodes.Ldarg_0);
 643                         ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 644
 645                         ig.Emit (OpCodes.Ldarg_0);
 646                         IntConstant.EmitInt (ig, (int) State.After);
 647                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 648
 649                         // We only care if the PC is zero (start executing) or non-zero (don't do anything)
 650                         ig.Emit (OpCodes.Brtrue, move_next_error);
 651
 652                         SymbolWriter.StartIteratorBody (ec.ig);
 653                         original_block.Emit (ec);
 654                         SymbolWriter.EndIteratorBody (ec.ig);
 655
 656                         ig.MarkLabel (move_next_error);
 657                         ig.Emit (OpCodes.Ldc_I4_0);
 658                         ig.Emit (OpCodes.Ret);
 659                 }
 660
 661                 internal void EmitMoveNext (EmitContext ec, Block original_block)
 662                 {
 663                         ILGenerator ig = ec.ig;
 664
 665                         move_next_ok = ig.DefineLabel ();
 666                         move_next_error = ig.DefineLabel ();
 667
 668                         if (resume_points == null) {
 669                                 EmitMoveNext_NoResumePoints (ec, original_block);
 670                                 return;
 671                         }
 672
 673                         current_pc = ec.GetTemporaryLocal (TypeManager.uint32_type);
 674                         ig.Emit (OpCodes.Ldarg_0);
 675                         ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 676                         ig.Emit (OpCodes.Stloc, current_pc);
 677
 678                         // We're actually in state 'running', but this is as good a PC value as any if there's an abnormal exit
 679                         ig.Emit (OpCodes.Ldarg_0);
 680                         IntConstant.EmitInt (ig, (int) State.After);
 681                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 682
 683                         Label [] labels = new Label [1 + resume_points.Count];
 684                         labels [0] = ig.DefineLabel ();
 685
 686                         bool need_skip_finally = false;
 687                         for (int i = 0; i < resume_points.Count; ++i) {
 688                                 ResumableStatement s = (ResumableStatement) resume_points [i];
 689                                 need_skip_finally |= s is ExceptionStatement;
 690                                 labels [i+1] = s.PrepareForEmit (ec);
 691                         }
 692
 693                         if (need_skip_finally) {
 694                                 skip_finally = ec.GetTemporaryLocal (TypeManager.bool_type);
 695                                 ig.Emit (OpCodes.Ldc_I4_0);
 696                                 ig.Emit (OpCodes.Stloc, skip_finally);
 697                         }
 698
 699                         SymbolWriter.StartIteratorDispatcher (ec.ig);
 700                         ig.Emit (OpCodes.Ldloc, current_pc);
 701                         ig.Emit (OpCodes.Switch, labels);
 702
 703                         ig.Emit (OpCodes.Br, move_next_error);
 704                         SymbolWriter.EndIteratorDispatcher (ec.ig);
 705
 706                         ig.MarkLabel (labels [0]);
 707
 708                         SymbolWriter.StartIteratorBody (ec.ig);
 709                         original_block.Emit (ec);
 710                         SymbolWriter.EndIteratorBody (ec.ig);
 711
 712                         SymbolWriter.StartIteratorDispatcher (ec.ig);
 713
 714                         ig.Emit (OpCodes.Ldarg_0);
 715                         IntConstant.EmitInt (ig, (int) State.After);
 716                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 717
 718                         ig.MarkLabel (move_next_error);
 719                         ig.Emit (OpCodes.Ldc_I4_0);
 720                         ig.Emit (OpCodes.Ret);
 721
 722                         ig.MarkLabel (move_next_ok);
 723                         ig.Emit (OpCodes.Ldc_I4_1);
 724                         ig.Emit (OpCodes.Ret);
 725
 726                         SymbolWriter.EndIteratorDispatcher (ec.ig);
 727                 }
 728
 729                 public void EmitDispose (EmitContext ec)
 730                 {
 731                         ILGenerator ig = ec.ig;
 732
 733                         Label end = ig.DefineLabel ();
 734
 735                         Label [] labels = null;
 736                         int n_resume_points = resume_points == null ? 0 : resume_points.Count;
 737                         for (int i = 0; i < n_resume_points; ++i) {
 738                                 ResumableStatement s = (ResumableStatement) resume_points [i];
 739                                 Label ret = s.PrepareForDispose (ec, end);
 740                                 if (ret.Equals (end) && labels == null)
 741                                         continue;
 742                                 if (labels == null) {
 743                                         labels = new Label [resume_points.Count + 1];
 744                                         for (int j = 0; j <= i; ++j)
 745                                                 labels [j] = end;
 746                                 }
 747                                 labels [i+1] = ret;
 748                         }
 749
 750                         if (labels != null) {
 751                                 current_pc = ec.GetTemporaryLocal (TypeManager.uint32_type);
 752                                 ig.Emit (OpCodes.Ldarg_0);
 753                                 ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 754                                 ig.Emit (OpCodes.Stloc, current_pc);
 755                         }
 756
 757                         ig.Emit (OpCodes.Ldarg_0);
 758                         IntConstant.EmitInt (ig, (int) State.After);
 759                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 760
 761                         if (labels != null) {
 762                                 //SymbolWriter.StartIteratorDispatcher (ec.ig);
 763                                 ig.Emit (OpCodes.Ldloc, current_pc);
 764                                 ig.Emit (OpCodes.Switch, labels);
 765                                 //SymbolWriter.EndIteratorDispatcher (ec.ig);
 766
 767                                 foreach (ResumableStatement s in resume_points)
 768                                         s.EmitForDispose (ec, this, end, true);
 769                         }
 770
 771                         ig.MarkLabel (end);
 772                 }
 773
 774
 775                 ArrayList resume_points;
 776                 public int AddResumePoint (ResumableStatement stmt)
 777                 {
 778                         if (resume_points == null)
 779                                 resume_points = new ArrayList ();
 780                         resume_points.Add (stmt);
 781                         return resume_points.Count;
 782                 }
 783
 784                 //
 785                 // Called back from Yield
 786                 //
 787                 public void MarkYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
 788                 {
 789                         ILGenerator ig = ec.ig;
 790
 791                         // Store the new current
 792                         ig.Emit (OpCodes.Ldarg_0);
 793                         expr.Emit (ec);
 794                         ig.Emit (OpCodes.Stfld, IteratorHost.CurrentField.FieldBuilder);
 795
 796                         // store resume program-counter
 797                         ig.Emit (OpCodes.Ldarg_0);
 798                         IntConstant.EmitInt (ig, resume_pc);
 799                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 800
 801                         // mark finally blocks as disabled
 802                         if (unwind_protect && skip_finally != null) {
 803                                 ig.Emit (OpCodes.Ldc_I4_1);
 804                                 ig.Emit (OpCodes.Stloc, skip_finally);
 805                         }
 806
 807                         // Return ok
 808                         ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
 809
 810                         ig.MarkLabel (resume_point);
 811                 }
 812
 813                 public override string ContainerType {
 814                         get { return "iterator"; }
 815                 }
 816
 817                 public override bool IsIterator {
 818                         get { return true; }
 819                 }
 820
 821                 public override AnonymousMethodStorey Storey {
 822                         get { return IteratorHost; }
 823                 }
 824
 825                 //
 826                 // Our constructor
 827                 //
 828                 private Iterator (IMethodData method, TypeContainer host, Type iterator_type, bool is_enumerable)
 829                         : base (
 830                                 new ToplevelBlock (method.Block, Parameters.EmptyReadOnlyParameters, method.Block.StartLocation),
 831                                 TypeManager.bool_type,
 832                                 method.Location)
 833                 {
 834                         this.OriginalMethod = method;
 835                         this.OriginalIteratorType = iterator_type;
 836                         this.IsEnumerable = is_enumerable;
 837                         this.Host = host;
 838
 839                         IteratorHost = Block.ChangeToIterator (this, method.Block);
 840                 }
 841
 842                 public override string GetSignatureForError ()
 843                 {
 844                         return OriginalMethod.GetSignatureForError ();
 845                 }
 846
 847                 public override Expression DoResolve (EmitContext ec)
 848                 {
 849                         method = new AnonymousMethodMethod (Storey,
 850                                 this, Storey, null, TypeManager.system_boolean_expr,
 851                                 Modifiers.PUBLIC, OriginalMethod.GetSignatureForError (),
 852                                 new MemberName ("MoveNext", Location),
 853                                 Parameters.EmptyReadOnlyParameters);
 854
 855                         if (!Compatible (ec))
 856                                 return null;
 857
 858                         IteratorHost.DefineIteratorMembers ();
 859
 860                         eclass = ExprClass.Value;
 861                         type = ec.ReturnType;
 862                         return this;
 863                 }
 864
 865                 public override void Emit (EmitContext ec)
 866                 {
 867                         //
 868                         // Load Iterator storey instance
 869                         //
 870                         method.Storey.Instance.Emit (ec);
 871
 872                         //
 873                         // Initialize iterator PC when it's unitialized
 874                         //
 875                         if (IsEnumerable) {
 876                                 ILGenerator ig = ec.ig;
 877                                 ig.Emit (OpCodes.Dup);
 878                                 IntConstant.EmitInt (ig, (int)State.Uninitialized);
 879
 880                                 FieldInfo field = IteratorHost.PC.FieldBuilder;
 881 #if GMCS_SOURCE
 882                                 if (Storey.MemberName.IsGeneric)
 883                                         field = TypeBuilder.GetField (Storey.Instance.Type, field);
 884 #endif
 885                                 ig.Emit (OpCodes.Stfld, field);
 886                         }
 887                 }
 888
 889                 public override Expression CreateExpressionTree (EmitContext ec)
 890                 {
 891                         throw new NotSupportedException ("ET");
 892                 }
 893
 894                 public static void CreateIterator (IMethodData method, TypeContainer parent, int modifiers)
 895                 {
 896                         bool is_enumerable;
 897                         Type iterator_type;
 898
 899                         Type ret = method.ReturnType;
 900                         if (ret == null)
 901                                 return;
 902
 903                         if (!CheckType (ret, out iterator_type, out is_enumerable)) {
 904                                 Report.Error (1624, method.Location,
 905                                               "The body of `{0}' cannot be an iterator block " +
 906                                               "because `{1}' is not an iterator interface type",
 907                                               method.GetSignatureForError (),
 908                                               TypeManager.CSharpName (ret));
 909                                 return;
 910                         }
 911
 912                         Parameters parameters = method.ParameterInfo;
 913                         for (int i = 0; i < parameters.Count; i++) {
 914                                 Parameter p = parameters [i];
 915                                 Parameter.Modifier mod = p.ModFlags;
 916                                 if ((mod & Parameter.Modifier.ISBYREF) != 0) {
 917                                         Report.Error (1623, p.Location,
 918                                                 "Iterators cannot have ref or out parameters");
 919                                         return;
 920                                 }
 921
 922                                 if ((mod & Parameter.Modifier.ARGLIST) != 0) {
 923                                         Report.Error (1636, method.Location,
 924                                                 "__arglist is not allowed in parameter list of iterators");
 925                                         return;
 926                                 }
 927
 928                                 if (parameters.Types [i].IsPointer) {
 929                                         Report.Error (1637, p.Location,
 930                                                           "Iterators cannot have unsafe parameters or " +
 931                                                           "yield types");
 932                                         return;
 933                                 }
 934                         }
 935
 936                         if ((modifiers & Modifiers.UNSAFE) != 0) {
 937                                 Report.Error (1629, method.Location, "Unsafe code may not appear in iterators");
 938                                 return;
 939                         }
 940
 941                         Iterator iter = new Iterator (method, parent, iterator_type, is_enumerable);
 942                         iter.Storey.DefineType ();
 943                 }
 944
 945                 static bool CheckType (Type ret, out Type original_iterator_type, out bool is_enumerable)
 946                 {
 947                         original_iterator_type = null;
 948                         is_enumerable = false;
 949
 950                         if (ret == TypeManager.ienumerable_type) {
 951                                 original_iterator_type = TypeManager.object_type;
 952                                 is_enumerable = true;
 953                                 return true;
 954                         }
 955                         if (ret == TypeManager.ienumerator_type) {
 956                                 original_iterator_type = TypeManager.object_type;
 957                                 is_enumerable = false;
 958                                 return true;
 959                         }
 960
 961                         if (!TypeManager.IsGenericType (ret))
 962                                 return false;
 963
 964                         Type[] args = TypeManager.GetTypeArguments (ret);
 965                         if (args.Length != 1)
 966                                 return false;
 967
 968                         Type gt = TypeManager.DropGenericTypeArguments (ret);
 969                         if (gt == TypeManager.generic_ienumerable_type) {
 970                                 original_iterator_type = args [0];
 971                                 is_enumerable = true;
 972                                 return true;
 973                         }
 974
 975                         if (gt == TypeManager.generic_ienumerator_type) {
 976                                 original_iterator_type = args [0];
 977                                 is_enumerable = false;
 978                                 return true;
 979                         }
 980
 981                         return false;
 982                 }
 983         }
 984 }
 985