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 new_storey;
 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                                         ArrayList init = null;
 232                                         if (host.hoisted_this != null) {
 233                                                 init = new ArrayList (host.hoisted_params == null ? 1 : host.HoistedParameters.Count + 1);
 234                                                 HoistedThis ht = host.hoisted_this;
 235                                                 FieldExpr from = new FieldExpr (ht.Field.FieldBuilder, loc);
 236                                                 from.InstanceExpression = CompilerGeneratedThis.Instance;
 237                                                 init.Add (new ElementInitializer (ht.Field.Name, from, loc));
 238                                         }
 239
 240                                         if (host.hoisted_params != null) {
 241                                                 if (init == null)
 242                                                         init = new ArrayList (host.HoistedParameters.Count);
 243
 244                                                 for (int i = 0; i < host.hoisted_params.Count; ++i) {
 245                                                         HoistedParameter hp = (HoistedParameter) host.hoisted_params [i];
 246                                                         HoistedParameter hp_cp = (HoistedParameter) host.hoisted_params_copy [i];
 247
 248                                                         FieldExpr from = new FieldExpr (hp_cp.Field.FieldBuilder, loc);
 249                                                         from.InstanceExpression = CompilerGeneratedThis.Instance;
 250
 251                                                         init.Add (new ElementInitializer (hp.Field.Name, from, loc));
 252                                                 }
 253                                         }
 254
 255                                         if (init != null) {
 256                                                 new_storey = new NewInitialize (storey_type_expr, new ArrayList (0),
 257                                                         new CollectionOrObjectInitializers (init, loc), loc);
 258                                         } else {
 259                                                 new_storey = new New (storey_type_expr, new ArrayList (0), loc);
 260                                         }
 261
 262                                         new_storey = new_storey.Resolve (ec);
 263                                         if (new_storey != null)
 264                                                 new_storey = Convert.ImplicitConversionRequired (ec, new_storey, type.Type, loc);
 265
 266                                         if (TypeManager.int_interlocked_compare_exchange == null) {
 267                                                 Type t = TypeManager.CoreLookupType ("System.Threading", "Interlocked", Kind.Class, true);
 268                                                 if (t != null) {
 269                                                         TypeManager.int_interlocked_compare_exchange = TypeManager.GetPredefinedMethod (
 270                                                                 t, "CompareExchange", loc, TypeManager.int32_type,
 271                                                                 TypeManager.int32_type, TypeManager.int32_type);
 272                                                 }
 273                                         }
 274
 275                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 276                                         return true;
 277                                 }
 278
 279                                 protected override void DoEmit (EmitContext ec)
 280                                 {
 281                                         ILGenerator ig = ec.ig;
 282                                         Label label_init = ig.DefineLabel ();
 283
 284                                         ig.Emit (OpCodes.Ldarg_0);
 285                                         ig.Emit (OpCodes.Ldflda, host.PC.FieldBuilder);
 286                                         IntConstant.EmitInt (ig, (int) Iterator.State.Start);
 287                                         IntConstant.EmitInt (ig, (int) Iterator.State.Uninitialized);
 288                                         ig.Emit (OpCodes.Call, TypeManager.int_interlocked_compare_exchange);
 289
 290                                         IntConstant.EmitInt (ig, (int) Iterator.State.Uninitialized);
 291                                         ig.Emit (OpCodes.Bne_Un_S, label_init);
 292
 293                                         ig.Emit (OpCodes.Ldarg_0);
 294                                         ig.Emit (OpCodes.Ret);
 295
 296                                         ig.MarkLabel (label_init);
 297
 298                                         new_storey.Emit (ec);
 299                                         ig.Emit (OpCodes.Ret);
 300                                 }
 301
 302                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 303                                 {
 304                                         throw new NotSupportedException ();
 305                                 }
 306                         }
 307
 308                         public GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 309                                 : base (host, returnType, 0, name)
 310                         {
 311                                 Block.AddStatement (new GetEnumeratorStatement (host, type_name));
 312                         }
 313                 }
 314
 315                 class DisposeMethod : IteratorMethod
 316                 {
 317                         sealed class DisposeMethodStatement : Statement
 318                         {
 319                                 Iterator iterator;
 320
 321                                 public DisposeMethodStatement (Iterator iterator)
 322                                 {
 323                                         this.iterator = iterator;
 324                                         this.loc = iterator.Location;
 325                                 }
 326
 327                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 328                                 {
 329                                         throw new NotSupportedException ();
 330                                 }
 331
 332                                 public override bool Resolve (EmitContext ec)
 333                                 {
 334                                         return true;
 335                                 }
 336
 337                                 protected override void DoEmit (EmitContext ec)
 338                                 {
 339                                         iterator.EmitDispose (ec);
 340                                 }
 341
 342                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 343                                 {
 344                                         throw new NotSupportedException ();
 345                                 }
 346                         }
 347
 348                         public DisposeMethod (IteratorStorey host)
 349                                 : base (host, TypeManager.system_void_expr, Modifiers.PUBLIC, new MemberName ("Dispose", host.Location))
 350                         {
 351                                 host.AddMethod (this);
 352
 353                                 Block = new ToplevelBlock (host.Iterator.Container, null, Location);
 354                                 Block.AddStatement (new DisposeMethodStatement (host.Iterator));
 355                         }
 356                 }
 357
 358                 //
 359                 // Uses Method as method info
 360                 //
 361                 class DynamicMethodGroupExpr : MethodGroupExpr
 362                 {
 363                         readonly Method method;
 364
 365                         public DynamicMethodGroupExpr (Method method, Location loc)
 366                                 : base (null, loc)
 367                         {
 368                                 this.method = method;
 369                         }
 370
 371                         public override Expression DoResolve (EmitContext ec)
 372                         {
 373                                 Methods = new MethodBase [] { method.MethodBuilder };
 374                                 type = method.Parent.TypeBuilder;
 375                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 376                                 return base.DoResolve (ec);
 377                         }
 378                 }
 379
 380                 public readonly Iterator Iterator;
 381
 382                 TypeExpr iterator_type_expr;
 383                 Field pc_field;
 384                 Field current_field;
 385
 386                 TypeExpr enumerator_type;
 387                 TypeExpr enumerable_type;
 388 #if GMCS_SOURCE
 389                 TypeArguments generic_args;
 390                 TypeExpr generic_enumerator_type;
 391                 TypeExpr generic_enumerable_type;
 392 #else
 393                 const TypeArguments generic_args = null;
 394 #endif
 395
 396                 ArrayList hoisted_params_copy;
 397                 int local_name_idx;
 398
 399                 public IteratorStorey (Iterator iterator)
 400                         : base (iterator.Container.Toplevel, iterator.Host,
 401                           iterator.OriginalMethod as MemberBase, iterator.GenericMethod, "Iterator")
 402                 {
 403                         this.Iterator = iterator;
 404                         HasHoistedVariables = true;
 405                 }
 406
 407                 public Field PC {
 408                         get { return pc_field; }
 409                 }
 410
 411                 public Field CurrentField {
 412                         get { return current_field; }
 413                 }
 414
 415                 public ArrayList HoistedParameters {
 416                         get { return hoisted_params; }
 417                 }
 418
 419                 protected override TypeExpr [] ResolveBaseTypes (out TypeExpr base_class)
 420                 {
 421                         iterator_type_expr = new TypeExpression (MutateType (Iterator.OriginalIteratorType), Location);
 422
 423 #if GMCS_SOURCE
 424                         generic_args = new TypeArguments (Location);
 425                         generic_args.Add (iterator_type_expr);
 426 #endif
 427
 428                         ArrayList list = new ArrayList ();
 429                         if (Iterator.IsEnumerable) {
 430                                 enumerable_type = new TypeExpression (
 431                                         TypeManager.ienumerable_type, Location);
 432                                 list.Add (enumerable_type);
 433
 434 #if GMCS_SOURCE
 435                                 generic_enumerable_type = new ConstructedType (
 436                                         TypeManager.generic_ienumerable_type,
 437                                         generic_args, Location);
 438                                 list.Add (generic_enumerable_type);
 439 #endif
 440                         }
 441
 442                         enumerator_type = new TypeExpression (
 443                                 TypeManager.ienumerator_type, Location);
 444                         list.Add (enumerator_type);
 445
 446                         list.Add (new TypeExpression (TypeManager.idisposable_type, Location));
 447
 448 #if GMCS_SOURCE
 449                         generic_enumerator_type = new ConstructedType (
 450                                 TypeManager.generic_ienumerator_type,
 451                                 generic_args, Location);
 452                         list.Add (generic_enumerator_type);
 453 #endif
 454
 455                         type_bases = list;
 456
 457                         return base.ResolveBaseTypes (out base_class);
 458                 }
 459
 460                 protected override string GetVariableMangledName (LocalInfo local_info)
 461                 {
 462                         return "<" + local_info.Name + ">__" + local_name_idx++.ToString ();
 463                 }
 464
 465                 public void DefineIteratorMembers ()
 466                 {
 467                         pc_field = AddCompilerGeneratedField ("$PC", TypeManager.system_int32_expr);
 468                         current_field = AddCompilerGeneratedField ("$current", iterator_type_expr);
 469
 470                         if (hoisted_params != null) {
 471                                 //
 472                                 // Iterators are independent, each GetEnumerator call has to
 473                                 // create same enumerator therefore we have to keep original values
 474                                 // around for re-initialization
 475                                 //
 476                                 // TODO: Do it for assigned/modified parameters only
 477                                 //
 478                                 hoisted_params_copy = new ArrayList (hoisted_params.Count);
 479                                 foreach (HoistedParameter hp in hoisted_params) {
 480                                         hoisted_params_copy.Add (new HoistedParameter (hp, "<$>" + hp.Field.Name));
 481                                 }
 482                         }
 483
 484 #if GMCS_SOURCE
 485                         Define_Current (true);
 486 #endif
 487                         Define_Current (false);
 488                         new DisposeMethod (this);
 489                         Define_Reset ();
 490
 491                         if (Iterator.IsEnumerable) {
 492                                 MemberName name = new MemberName (
 493                                         new MemberName ("System.Collections.IEnumerable", Location), "GetEnumerator", Location);
 494
 495 #if GMCS_SOURCE
 496                                 Method get_enumerator = new IteratorMethod (this, enumerator_type, 0, name);
 497
 498                                 name = new MemberName (
 499                                         new MemberName ("System.Collections.Generic.IEnumerable", generic_args, Location), "GetEnumerator", Location);
 500                                 Method gget_enumerator = new GetEnumeratorMethod (this, generic_enumerator_type, name);
 501
 502                                 //
 503                                 // Just call generic GetEnumerator implementation
 504                                 //
 505                                 get_enumerator.Block.AddStatement (
 506                                         new Return (new Invocation (new DynamicMethodGroupExpr (gget_enumerator, Location), new ArrayList (0)), Location));
 507
 508                                 AddMethod (get_enumerator);
 509                                 AddMethod (gget_enumerator);
 510 #else
 511                                 AddMethod (new GetEnumeratorMethod (this, enumerator_type, name));
 512 #endif
 513                         }
 514                 }
 515
 516                 protected override void EmitHoistedParameters (EmitContext ec, ArrayList hoisted)
 517                 {
 518                         base.EmitHoistedParameters (ec, hoisted);
 519                         base.EmitHoistedParameters (ec, hoisted_params_copy);
 520                 }
 521
 522                 void Define_Current (bool is_generic)
 523                 {
 524                         MemberName left;
 525                         TypeExpr type;
 526
 527                         if (is_generic) {
 528                                 left = new MemberName (
 529                                         "System.Collections.Generic.IEnumerator",
 530                                         generic_args, Location);
 531                                 type = iterator_type_expr;
 532                         } else {
 533                                 left = new MemberName ("System.Collections.IEnumerator", Location);
 534                                 type = TypeManager.system_object_expr;
 535                         }
 536
 537                         MemberName name = new MemberName (left, "Current", null, Location);
 538
 539                         ToplevelBlock get_block = new ToplevelBlock (Location);
 540                         get_block.AddStatement (new CurrentBlock (this, is_generic));
 541
 542                         Accessor getter = new Accessor (get_block, 0, null, null, Location);
 543
 544                         Property current = new Property (
 545                                 this, type, Modifiers.DEBUGGER_HIDDEN, name, null, getter, null, false);
 546                         AddProperty (current);
 547                 }
 548
 549                 void Define_Reset ()
 550                 {
 551                         Method reset = new Method (
 552                                 this, null, TypeManager.system_void_expr,
 553                                 Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
 554                                 new MemberName ("Reset", Location),
 555                                 Parameters.EmptyReadOnlyParameters, null);
 556                         AddMethod (reset);
 557
 558                         reset.Block = new ToplevelBlock (Location);
 559                         reset.Block.AddStatement (Create_ThrowNotSupported ());
 560                 }
 561
 562                 Statement Create_ThrowNotSupported ()
 563                 {
 564                         TypeExpr ex_type = new TypeLookupExpression ("System.NotSupportedException");
 565
 566                         return new Throw (new New (ex_type, null, Location), Location);
 567                 }
 568
 569                 protected class CurrentBlock : Statement {
 570                         IteratorStorey host;
 571                         bool is_generic;
 572
 573                         public CurrentBlock (IteratorStorey host, bool is_generic)
 574                         {
 575                                 this.host = host;
 576                                 this.is_generic = is_generic;
 577                                 loc = host.Location;
 578                         }
 579
 580                         protected override void CloneTo (CloneContext clonectx, Statement target)
 581                         {
 582                                 throw new NotSupportedException ();
 583                         }
 584
 585                         public override bool Resolve (EmitContext ec)
 586                         {
 587                                 // We emit a 'ret', so prevent the enclosing TopLevelBlock from emitting one too
 588                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
 589                                 return true;
 590                         }
 591
 592                         protected override void DoEmit (EmitContext ec)
 593                         {
 594                                 ILGenerator ig = ec.ig;
 595
 596                                 ig.Emit (OpCodes.Ldarg_0);
 597                                 ig.Emit (OpCodes.Ldfld, host.CurrentField.FieldBuilder);
 598                                 if (!is_generic)
 599                                         ig.Emit (OpCodes.Box, host.CurrentField.MemberType);
 600                                 ig.Emit (OpCodes.Ret);
 601                         }
 602
 603                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 604                         {
 605                                 throw new NotSupportedException ();
 606                         }
 607                 }
 608         }
 609
 610         //
 611         // Iterators are implemented as hidden anonymous block
 612         //
 613         public class Iterator : AnonymousExpression {
 614                 public readonly IMethodData OriginalMethod;
 615                 AnonymousMethodMethod method;
 616                 public readonly TypeContainer Host;
 617                 public readonly bool IsEnumerable;
 618
 619                 //
 620                 // The state as we generate the iterator
 621                 //
 622                 Label move_next_ok, move_next_error;
 623                 LocalBuilder skip_finally, current_pc;
 624
 625                 public LocalBuilder SkipFinally {
 626                         get { return skip_finally; }
 627                 }
 628
 629                 public LocalBuilder CurrentPC {
 630                         get { return current_pc; }
 631                 }
 632
 633                 public Block Container {
 634                         get { return OriginalMethod.Block; }
 635                 }
 636
 637                 public GenericMethod GenericMethod {
 638                         get { return OriginalMethod.GenericMethod; }
 639                 }
 640
 641                 public readonly Type OriginalIteratorType;
 642
 643                 readonly IteratorStorey IteratorHost;
 644
 645                 public enum State {
 646                         Running = -3, // Used only in CurrentPC, never stored into $PC
 647                         Uninitialized = -2,
 648                         After = -1,
 649                         Start = 0
 650                 }
 651
 652                 public override void AddStoreyReference (AnonymousMethodStorey storey)
 653                 {
 654                         // do nothing
 655                 }
 656
 657                 public void EmitYieldBreak (ILGenerator ig, bool unwind_protect)
 658                 {
 659                         ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_error);
 660                 }
 661
 662                 void EmitMoveNext_NoResumePoints (EmitContext ec, Block original_block)
 663                 {
 664                         ILGenerator ig = ec.ig;
 665
 666                         ig.Emit (OpCodes.Ldarg_0);
 667                         ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 668
 669                         ig.Emit (OpCodes.Ldarg_0);
 670                         IntConstant.EmitInt (ig, (int) State.After);
 671                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 672
 673                         // We only care if the PC is zero (start executing) or non-zero (don't do anything)
 674                         ig.Emit (OpCodes.Brtrue, move_next_error);
 675
 676                         SymbolWriter.StartIteratorBody (ec.ig);
 677                         original_block.Emit (ec);
 678                         SymbolWriter.EndIteratorBody (ec.ig);
 679
 680                         ig.MarkLabel (move_next_error);
 681                         ig.Emit (OpCodes.Ldc_I4_0);
 682                         ig.Emit (OpCodes.Ret);
 683                 }
 684
 685                 internal void EmitMoveNext (EmitContext ec, Block original_block)
 686                 {
 687                         ILGenerator ig = ec.ig;
 688
 689                         move_next_ok = ig.DefineLabel ();
 690                         move_next_error = ig.DefineLabel ();
 691
 692                         if (resume_points == null) {
 693                                 EmitMoveNext_NoResumePoints (ec, original_block);
 694                                 return;
 695                         }
 696
 697                         current_pc = ec.GetTemporaryLocal (TypeManager.uint32_type);
 698                         ig.Emit (OpCodes.Ldarg_0);
 699                         ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 700                         ig.Emit (OpCodes.Stloc, current_pc);
 701
 702                         // We're actually in state 'running', but this is as good a PC value as any if there's an abnormal exit
 703                         ig.Emit (OpCodes.Ldarg_0);
 704                         IntConstant.EmitInt (ig, (int) State.After);
 705                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 706
 707                         Label [] labels = new Label [1 + resume_points.Count];
 708                         labels [0] = ig.DefineLabel ();
 709
 710                         bool need_skip_finally = false;
 711                         for (int i = 0; i < resume_points.Count; ++i) {
 712                                 ResumableStatement s = (ResumableStatement) resume_points [i];
 713                                 need_skip_finally |= s is ExceptionStatement;
 714                                 labels [i+1] = s.PrepareForEmit (ec);
 715                         }
 716
 717                         if (need_skip_finally) {
 718                                 skip_finally = ec.GetTemporaryLocal (TypeManager.bool_type);
 719                                 ig.Emit (OpCodes.Ldc_I4_0);
 720                                 ig.Emit (OpCodes.Stloc, skip_finally);
 721                         }
 722
 723                         SymbolWriter.StartIteratorDispatcher (ec.ig);
 724                         ig.Emit (OpCodes.Ldloc, current_pc);
 725                         ig.Emit (OpCodes.Switch, labels);
 726
 727                         ig.Emit (OpCodes.Br, move_next_error);
 728                         SymbolWriter.EndIteratorDispatcher (ec.ig);
 729
 730                         ig.MarkLabel (labels [0]);
 731
 732                         SymbolWriter.StartIteratorBody (ec.ig);
 733                         original_block.Emit (ec);
 734                         SymbolWriter.EndIteratorBody (ec.ig);
 735
 736                         SymbolWriter.StartIteratorDispatcher (ec.ig);
 737
 738                         ig.Emit (OpCodes.Ldarg_0);
 739                         IntConstant.EmitInt (ig, (int) State.After);
 740                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 741
 742                         ig.MarkLabel (move_next_error);
 743                         ig.Emit (OpCodes.Ldc_I4_0);
 744                         ig.Emit (OpCodes.Ret);
 745
 746                         ig.MarkLabel (move_next_ok);
 747                         ig.Emit (OpCodes.Ldc_I4_1);
 748                         ig.Emit (OpCodes.Ret);
 749
 750                         SymbolWriter.EndIteratorDispatcher (ec.ig);
 751                 }
 752
 753                 public void EmitDispose (EmitContext ec)
 754                 {
 755                         ILGenerator ig = ec.ig;
 756
 757                         Label end = ig.DefineLabel ();
 758
 759                         Label [] labels = null;
 760                         int n_resume_points = resume_points == null ? 0 : resume_points.Count;
 761                         for (int i = 0; i < n_resume_points; ++i) {
 762                                 ResumableStatement s = (ResumableStatement) resume_points [i];
 763                                 Label ret = s.PrepareForDispose (ec, end);
 764                                 if (ret.Equals (end) && labels == null)
 765                                         continue;
 766                                 if (labels == null) {
 767                                         labels = new Label [resume_points.Count + 1];
 768                                         for (int j = 0; j <= i; ++j)
 769                                                 labels [j] = end;
 770                                 }
 771                                 labels [i+1] = ret;
 772                         }
 773
 774                         if (labels != null) {
 775                                 current_pc = ec.GetTemporaryLocal (TypeManager.uint32_type);
 776                                 ig.Emit (OpCodes.Ldarg_0);
 777                                 ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
 778                                 ig.Emit (OpCodes.Stloc, current_pc);
 779                         }
 780
 781                         ig.Emit (OpCodes.Ldarg_0);
 782                         IntConstant.EmitInt (ig, (int) State.After);
 783                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 784
 785                         if (labels != null) {
 786                                 //SymbolWriter.StartIteratorDispatcher (ec.ig);
 787                                 ig.Emit (OpCodes.Ldloc, current_pc);
 788                                 ig.Emit (OpCodes.Switch, labels);
 789                                 //SymbolWriter.EndIteratorDispatcher (ec.ig);
 790
 791                                 foreach (ResumableStatement s in resume_points)
 792                                         s.EmitForDispose (ec, this, end, true);
 793                         }
 794
 795                         ig.MarkLabel (end);
 796                 }
 797
 798
 799                 ArrayList resume_points;
 800                 public int AddResumePoint (ResumableStatement stmt)
 801                 {
 802                         if (resume_points == null)
 803                                 resume_points = new ArrayList ();
 804                         resume_points.Add (stmt);
 805                         return resume_points.Count;
 806                 }
 807
 808                 //
 809                 // Called back from Yield
 810                 //
 811                 public void MarkYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
 812                 {
 813                         ILGenerator ig = ec.ig;
 814
 815                         // Store the new current
 816                         ig.Emit (OpCodes.Ldarg_0);
 817                         expr.Emit (ec);
 818                         ig.Emit (OpCodes.Stfld, IteratorHost.CurrentField.FieldBuilder);
 819
 820                         // store resume program-counter
 821                         ig.Emit (OpCodes.Ldarg_0);
 822                         IntConstant.EmitInt (ig, resume_pc);
 823                         ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
 824
 825                         // mark finally blocks as disabled
 826                         if (unwind_protect && skip_finally != null) {
 827                                 ig.Emit (OpCodes.Ldc_I4_1);
 828                                 ig.Emit (OpCodes.Stloc, skip_finally);
 829                         }
 830
 831                         // Return ok
 832                         ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
 833
 834                         ig.MarkLabel (resume_point);
 835                 }
 836
 837                 public override string ContainerType {
 838                         get { return "iterator"; }
 839                 }
 840
 841                 public override bool IsIterator {
 842                         get { return true; }
 843                 }
 844
 845                 public override AnonymousMethodStorey Storey {
 846                         get { return IteratorHost; }
 847                 }
 848
 849                 //
 850                 // Our constructor
 851                 //
 852                 private Iterator (IMethodData method, TypeContainer host, Type iterator_type, bool is_enumerable)
 853                         : base (
 854                                 new ToplevelBlock (method.Block, Parameters.EmptyReadOnlyParameters, method.Block.StartLocation),
 855                                 TypeManager.bool_type,
 856                                 method.Location)
 857                 {
 858                         this.OriginalMethod = method;
 859                         this.OriginalIteratorType = iterator_type;
 860                         this.IsEnumerable = is_enumerable;
 861                         this.Host = host;
 862
 863                         IteratorHost = Block.ChangeToIterator (this, method.Block);
 864                 }
 865
 866                 public override string GetSignatureForError ()
 867                 {
 868                         return OriginalMethod.GetSignatureForError ();
 869                 }
 870
 871                 public override Expression DoResolve (EmitContext ec)
 872                 {
 873                         method = new AnonymousMethodMethod (Storey,
 874                                 this, Storey, null, TypeManager.system_boolean_expr,
 875                                 Modifiers.PUBLIC, OriginalMethod.GetSignatureForError (),
 876                                 new MemberName ("MoveNext", Location),
 877                                 Parameters.EmptyReadOnlyParameters);
 878
 879                         if (!Compatible (ec))
 880                                 return null;
 881
 882                         IteratorHost.DefineIteratorMembers ();
 883
 884                         eclass = ExprClass.Value;
 885                         type = ec.ReturnType;
 886                         return this;
 887                 }
 888
 889                 public override void Emit (EmitContext ec)
 890                 {
 891                         //
 892                         // Load Iterator storey instance
 893                         //
 894                         method.Storey.Instance.Emit (ec);
 895
 896                         //
 897                         // Initialize iterator PC when it's unitialized
 898                         //
 899                         if (IsEnumerable) {
 900                                 ILGenerator ig = ec.ig;
 901                                 ig.Emit (OpCodes.Dup);
 902                                 IntConstant.EmitInt (ig, (int)State.Uninitialized);
 903
 904                                 FieldInfo field = IteratorHost.PC.FieldBuilder;
 905 #if GMCS_SOURCE
 906                                 if (Storey.MemberName.IsGeneric)
 907                                         field = TypeBuilder.GetField (Storey.Instance.Type, field);
 908 #endif
 909                                 ig.Emit (OpCodes.Stfld, field);
 910                         }
 911                 }
 912
 913                 public override Expression CreateExpressionTree (EmitContext ec)
 914                 {
 915                         throw new NotSupportedException ("ET");
 916                 }
 917
 918                 public static void CreateIterator (IMethodData method, TypeContainer parent, int modifiers)
 919                 {
 920                         bool is_enumerable;
 921                         Type iterator_type;
 922
 923                         Type ret = method.ReturnType;
 924                         if (ret == null)
 925                                 return;
 926
 927                         if (!CheckType (ret, out iterator_type, out is_enumerable)) {
 928                                 Report.Error (1624, method.Location,
 929                                               "The body of `{0}' cannot be an iterator block " +
 930                                               "because `{1}' is not an iterator interface type",
 931                                               method.GetSignatureForError (),
 932                                               TypeManager.CSharpName (ret));
 933                                 return;
 934                         }
 935
 936                         Parameters parameters = method.ParameterInfo;
 937                         for (int i = 0; i < parameters.Count; i++) {
 938                                 Parameter p = parameters [i];
 939                                 Parameter.Modifier mod = p.ModFlags;
 940                                 if ((mod & Parameter.Modifier.ISBYREF) != 0) {
 941                                         Report.Error (1623, p.Location,
 942                                                 "Iterators cannot have ref or out parameters");
 943                                         return;
 944                                 }
 945
 946                                 if ((mod & Parameter.Modifier.ARGLIST) != 0) {
 947                                         Report.Error (1636, method.Location,
 948                                                 "__arglist is not allowed in parameter list of iterators");
 949                                         return;
 950                                 }
 951
 952                                 if (parameters.Types [i].IsPointer) {
 953                                         Report.Error (1637, p.Location,
 954                                                           "Iterators cannot have unsafe parameters or " +
 955                                                           "yield types");
 956                                         return;
 957                                 }
 958                         }
 959
 960                         if ((modifiers & Modifiers.UNSAFE) != 0) {
 961                                 Report.Error (1629, method.Location, "Unsafe code may not appear in iterators");
 962                                 return;
 963                         }
 964
 965                         Iterator iter = new Iterator (method, parent, iterator_type, is_enumerable);
 966                         iter.Storey.DefineType ();
 967                 }
 968
 969                 static bool CheckType (Type ret, out Type original_iterator_type, out bool is_enumerable)
 970                 {
 971                         original_iterator_type = null;
 972                         is_enumerable = false;
 973
 974                         if (ret == TypeManager.ienumerable_type) {
 975                                 original_iterator_type = TypeManager.object_type;
 976                                 is_enumerable = true;
 977                                 return true;
 978                         }
 979                         if (ret == TypeManager.ienumerator_type) {
 980                                 original_iterator_type = TypeManager.object_type;
 981                                 is_enumerable = false;
 982                                 return true;
 983                         }
 984
 985                         if (!TypeManager.IsGenericType (ret))
 986                                 return false;
 987
 988                         Type[] args = TypeManager.GetTypeArguments (ret);
 989                         if (args.Length != 1)
 990                                 return false;
 991
 992                         Type gt = TypeManager.DropGenericTypeArguments (ret);
 993                         if (gt == TypeManager.generic_ienumerable_type) {
 994                                 original_iterator_type = args [0];
 995                                 is_enumerable = true;
 996                                 return true;
 997                         }
 998
 999                         if (gt == TypeManager.generic_ienumerator_type) {
1000                                 original_iterator_type = args [0];
1001                                 is_enumerable = false;
1002                                 return true;
1003                         }
1004
1005                         return false;
1006                 }
1007         }
1008 }
1009