mcs/iterators.cs

   1 //
   2 // iterators.cs: Support for implementing iterators
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //
   7 // (C) 2003 Ximian, Inc.
   8 //
   9 // TODO:
  10 //    Flow analysis for Yield.
  11 //    Emit calls to base object constructor.
  12 //
  13 // Generics note:
  14 //    Current should be defined to return T, and IEnumerator.Current returns object
  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 interface IIteratorContainer {
  25
  26                 //
  27                 // Invoked if a yield statement is found in the body
  28                 //
  29                 void SetYields ();
  30         }
  31
  32         public class Yield : Statement {
  33                 Expression expr;
  34                 ArrayList finally_blocks;
  35
  36                 public Yield (Expression expr, Location l)
  37                 {
  38                         this.expr = expr;
  39                         loc = l;
  40                 }
  41
  42                 public static bool CheckContext (EmitContext ec, Location loc)
  43                 {
  44                         if (ec.InFinally) {
  45                                 Report.Error (1625, loc, "Cannot yield in the body of a " +
  46                                               "finally clause");
  47                                 return false;
  48                         }
  49
  50                         if (ec.InUnsafe) {
  51                                 Report.Error (1629, loc, "Unsafe code may not appear in iterators");
  52                                 return false;
  53                         }
  54                         if (ec.InCatch){
  55                                 Report.Error (1631, loc, "Cannot yield a value in the body of a catch clause");
  56                                 return false;
  57                         }
  58
  59                         AnonymousContainer am = ec.CurrentAnonymousMethod;
  60                         if ((am != null) && !am.IsIterator){
  61                                 Report.Error (1621, loc, "The yield statement cannot be used inside anonymous method blocks");
  62                                 return false;
  63                         }
  64
  65                         if (ec.CurrentBranching.InTryWithCatch ()) {
  66                                 Report.Error (1626, loc, "Cannot yield a value in the body of a " +
  67                                         "try block with a catch clause");
  68                                 return false;
  69                         }
  70                         return true;
  71                 }
  72
  73                 public override bool Resolve (EmitContext ec)
  74                 {
  75                         expr = expr.Resolve (ec);
  76                         if (expr == null)
  77                                 return false;
  78
  79                         if (!CheckContext (ec, loc))
  80                                 return false;
  81
  82                         Iterator iterator = ec.CurrentIterator;
  83
  84                         if (expr.Type != iterator.IteratorType){
  85                                 expr = Convert.ImplicitConversionRequired (
  86                                         ec, expr, iterator.IteratorType, loc);
  87                                 if (expr == null)
  88                                         return false;
  89                         }
  90
  91                         ec.CurrentBranching.StealFinallyClauses (ref finally_blocks);
  92                         return true;
  93                 }
  94
  95                 protected override void DoEmit (EmitContext ec)
  96                 {
  97                         ec.CurrentIterator.MarkYield (ec, expr, finally_blocks);
  98                 }
  99         }
 100
 101         public class YieldBreak : Statement {
 102
 103                 public YieldBreak (Location l)
 104                 {
 105                         loc = l;
 106                 }
 107
 108                 public override bool Resolve (EmitContext ec)
 109                 {
 110                         if (!Yield.CheckContext (ec, loc))
 111                                 return false;
 112
 113                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 114                         return true;
 115                 }
 116
 117                 protected override void DoEmit (EmitContext ec)
 118                 {
 119                         ec.CurrentIterator.EmitYieldBreak (ec.ig);
 120                 }
 121         }
 122
 123         public class Iterator : Class {
 124                 protected ToplevelBlock original_block;
 125                 protected ToplevelBlock block;
 126
 127                 Type iterator_type;
 128                 TypeExpr iterator_type_expr;
 129                 bool is_enumerable;
 130                 public readonly bool IsStatic;
 131
 132                 //
 133                 // The state as we generate the iterator
 134                 //
 135                 Label move_next_ok, move_next_error;
 136                 ArrayList resume_points = new ArrayList ();
 137                 int pc;
 138
 139                 //
 140                 // Context from the original method
 141                 //
 142                 TypeContainer container;
 143                 Type this_type;
 144                 Parameters parameters;
 145                 IMethodData orig_method;
 146
 147                 MoveNextMethod move_next_method;
 148                 Constructor ctor;
 149                 CaptureContext cc;
 150
 151                 protected enum State {
 152                         Uninitialized   = -2,
 153                         After,
 154                         Running
 155                 }
 156
 157                 static int proxy_count;
 158
 159                 public void EmitYieldBreak (ILGenerator ig)
 160                 {
 161                         ig.Emit (OpCodes.Ldarg_0);
 162                         IntConstant.EmitInt (ig, (int) State.After);
 163                         ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);
 164                         ig.Emit (OpCodes.Br, move_next_error);
 165                 }
 166
 167                 public void EmitMoveNext (EmitContext ec)
 168                 {
 169                         ILGenerator ig = ec.ig;
 170
 171                         move_next_ok = ig.DefineLabel ();
 172                         move_next_error = ig.DefineLabel ();
 173
 174                         LocalBuilder retval = ec.GetTemporaryLocal (TypeManager.int32_type);
 175
 176                         ig.BeginExceptionBlock ();
 177
 178                         Label dispatcher = ig.DefineLabel ();
 179                         ig.Emit (OpCodes.Br, dispatcher);
 180
 181                         ResumePoint entry_point = new ResumePoint (null);
 182                         resume_points.Add (entry_point);
 183                         entry_point.Define (ig);
 184
 185                         ec.EmitTopBlock (orig_method, original_block);
 186
 187                         EmitYieldBreak (ig);
 188
 189                         ig.MarkLabel (dispatcher);
 190
 191                         Label [] labels = new Label [resume_points.Count];
 192                         for (int i = 0; i < labels.Length; i++)
 193                                 labels [i] = ((ResumePoint) resume_points [i]).Label;
 194
 195                         ig.Emit (OpCodes.Ldarg_0);
 196                         ig.Emit (OpCodes.Ldfld, pc_field.FieldBuilder);
 197                         ig.Emit (OpCodes.Switch, labels);
 198
 199                         Label end = ig.DefineLabel ();
 200
 201                         ig.MarkLabel (move_next_error);
 202                         ig.Emit (OpCodes.Ldc_I4_0);
 203                         ig.Emit (OpCodes.Stloc, retval);
 204                         ig.Emit (OpCodes.Leave, end);
 205
 206                         ig.MarkLabel (move_next_ok);
 207                         ig.Emit (OpCodes.Ldc_I4_1);
 208                         ig.Emit (OpCodes.Stloc, retval);
 209                         ig.Emit (OpCodes.Leave, end);
 210
 211                         ig.BeginFaultBlock ();
 212
 213                         ig.Emit (OpCodes.Ldarg_0);
 214                         ig.Emit (OpCodes.Callvirt, dispose.MethodBuilder);
 215
 216                         ig.EndExceptionBlock ();
 217
 218                         ig.MarkLabel (end);
 219                         ig.Emit (OpCodes.Ldloc, retval);
 220                         ig.Emit (OpCodes.Ret);
 221                 }
 222
 223                 public void EmitDispose (EmitContext ec)
 224                 {
 225                         ILGenerator ig = ec.ig;
 226
 227                         Label end = ig.DefineLabel ();
 228                         Label dispatcher = ig.DefineLabel ();
 229                         ig.Emit (OpCodes.Br, dispatcher);
 230
 231                         Label [] labels = new Label [resume_points.Count];
 232                         for (int i = 0; i < labels.Length; i++) {
 233                                 ResumePoint point = (ResumePoint) resume_points [i];
 234
 235                                 if (point.FinallyBlocks == null) {
 236                                         labels [i] = end;
 237                                         continue;
 238                                 }
 239
 240                                 labels [i] = ig.DefineLabel ();
 241                                 ig.MarkLabel (labels [i]);
 242
 243                                 ig.BeginExceptionBlock ();
 244                                 ig.BeginFinallyBlock ();
 245
 246                                 foreach (ExceptionStatement stmt in point.FinallyBlocks) {
 247                                         if (stmt != null)
 248                                                 stmt.EmitFinally (ec);
 249                                 }
 250
 251                                 ig.EndExceptionBlock ();
 252                                 ig.Emit (OpCodes.Br, end);
 253                         }
 254
 255                         ig.MarkLabel (dispatcher);
 256                         ig.Emit (OpCodes.Ldarg_0);
 257                         ig.Emit (OpCodes.Ldfld, pc_field.FieldBuilder);
 258                         ig.Emit (OpCodes.Switch, labels);
 259
 260                         ig.Emit (OpCodes.Ldarg_0);
 261                         IntConstant.EmitInt (ig, (int) State.After);
 262                         ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);
 263
 264                         ig.MarkLabel (end);
 265                 }
 266
 267                 protected class ResumePoint
 268                 {
 269                         public Label Label;
 270                         public readonly ExceptionStatement[] FinallyBlocks;
 271
 272                         public ResumePoint (ArrayList list)
 273                         {
 274                                 if (list != null) {
 275                                         FinallyBlocks = new ExceptionStatement [list.Count];
 276                                         list.CopyTo (FinallyBlocks, 0);
 277                                 }
 278                         }
 279
 280                         public void Define (ILGenerator ig)
 281                         {
 282                                 Label = ig.DefineLabel ();
 283                                 ig.MarkLabel (Label);
 284                         }
 285                 }
 286
 287                 //
 288                 // Called back from Yield
 289                 //
 290                 public void MarkYield (EmitContext ec, Expression expr,
 291                                        ArrayList finally_blocks)
 292                 {
 293                         ILGenerator ig = ec.ig;
 294
 295                         // Store the new current
 296                         ig.Emit (OpCodes.Ldarg_0);
 297                         expr.Emit (ec);
 298                         ig.Emit (OpCodes.Stfld, current_field.FieldBuilder);
 299
 300                         // increment pc
 301                         pc++;
 302                         ig.Emit (OpCodes.Ldarg_0);
 303                         IntConstant.EmitInt (ig, pc);
 304                         ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);
 305
 306                         // Return ok
 307                         ig.Emit (OpCodes.Br, move_next_ok);
 308
 309                         ResumePoint point = new ResumePoint (finally_blocks);
 310                         resume_points.Add (point);
 311                         point.Define (ig);
 312                 }
 313
 314                 public void MarkFinally (EmitContext ec, ArrayList finally_blocks)
 315                 {
 316                         ILGenerator ig = ec.ig;
 317
 318                         // increment pc
 319                         pc++;
 320                         ig.Emit (OpCodes.Ldarg_0);
 321                         IntConstant.EmitInt (ig, pc);
 322                         ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);
 323
 324                         ResumePoint point = new ResumePoint (finally_blocks);
 325                         resume_points.Add (point);
 326                         point.Define (ig);
 327                 }
 328
 329                 private static MemberName MakeProxyName (string name, Location loc)
 330                 {
 331                         int pos = name.LastIndexOf ('.');
 332                         if (pos > 0)
 333                                 name = name.Substring (pos + 1);
 334
 335                         return new MemberName ("<" + name + ">__" + (proxy_count++), loc);
 336                 }
 337
 338                 //
 339                 // Our constructor
 340                 //
 341                 public Iterator (IMethodData m_container, TypeContainer container,
 342                                  int modifiers)
 343                         : base (container.NamespaceEntry, container, MakeProxyName (m_container.MethodName.Name, m_container.Location),
 344                                 (modifiers & Modifiers.UNSAFE) | Modifiers.PRIVATE, null)
 345                 {
 346                         this.orig_method = m_container;
 347
 348                         this.container = container;
 349                         this.parameters = m_container.ParameterInfo;
 350                         this.original_block = orig_method.Block;
 351                         this.block = new ToplevelBlock (orig_method.Block, parameters, orig_method.Location);
 352
 353                         IsStatic = (modifiers & Modifiers.STATIC) != 0;
 354                 }
 355
 356                 public AnonymousContainer Host {
 357                         get { return move_next_method; }
 358                 }
 359
 360                 public bool DefineIterator ()
 361                 {
 362                         ec = new EmitContext (this, Mono.CSharp.Location.Null, null, null, ModFlags);
 363                         ec.CurrentAnonymousMethod = move_next_method;
 364                         ec.CurrentIterator = this;
 365                         ec.InIterator = true;
 366
 367                         if (!CheckType ()) {
 368                                 Report.Error (1624, Location,
 369                                         "The body of `{0}' cannot be an iterator block because `{1}' is not an iterator interface type",
 370                                         orig_method.GetSignatureForError (), TypeManager.CSharpName (orig_method.ReturnType));
 371                                 return false;
 372                         }
 373
 374                         for (int i = 0; i < parameters.Count; i++){
 375                                 Parameter.Modifier mod = parameters.ParameterModifier (i);
 376                                 if ((mod & (Parameter.Modifier.REF | Parameter.Modifier.OUT)) != 0){
 377                                         Report.Error (
 378                                                 1623, Location,
 379                                                 "Iterators cannot have ref or out parameters");
 380                                         return false;
 381                                 }
 382
 383                                 if ((mod & Parameter.Modifier.ARGLIST) != 0) {
 384                                         Report.Error (1636, Location, "__arglist is not allowed in parameter list of iterators");
 385                                         return false;
 386                                 }
 387
 388                                 if (parameters.ParameterType (i).IsPointer) {
 389                                         Report.Error (1637, Location, "Iterators cannot have unsafe parameters or yield types");
 390                                         return false;
 391                                 }
 392                         }
 393
 394                         this_type = container.TypeBuilder;
 395
 396                         ArrayList list = new ArrayList ();
 397                         if (is_enumerable)
 398                                 list.Add (new TypeExpression (
 399                                                   TypeManager.ienumerable_type, Location));
 400                         list.Add (new TypeExpression (TypeManager.ienumerator_type, Location));
 401                         list.Add (new TypeExpression (TypeManager.idisposable_type, Location));
 402
 403                         iterator_type_expr = new TypeExpression (iterator_type, Location);
 404
 405                         container.AddIterator (this);
 406
 407                         Bases = list;
 408                         orig_method.Block = block;
 409                         return true;
 410                 }
 411
 412                 protected override bool DoDefineMembers ()
 413                 {
 414                         ec.InIterator = true;
 415                         ec.CurrentIterator = this;
 416                         ec.CurrentAnonymousMethod = move_next_method;
 417                         ec.capture_context = cc;
 418
 419                         if (!base.DoDefineMembers ())
 420                                 return false;
 421
 422                         return true;
 423                 }
 424
 425                 public override bool Define ()
 426                 {
 427                         if (!base.Define ())
 428                                 return false;
 429
 430                         ec.InIterator = true;
 431                         ec.CurrentIterator = this;
 432                         ec.CurrentAnonymousMethod = move_next_method;
 433                         ec.capture_context = cc;
 434                         ec.TypeContainer = ec.TypeContainer.Parent;
 435
 436                         ec.ContainerType = ec.TypeContainer.TypeBuilder;
 437
 438                         ec.ig = move_next_method.method.MethodBuilder.GetILGenerator ();
 439
 440                         if (!ctor.Define ())
 441                                 return false;
 442
 443                         bool unreachable;
 444
 445                         if (!ec.ResolveTopBlock (null, original_block, parameters, orig_method, out unreachable))
 446                                 return false;
 447
 448                         if (!ec.ResolveTopBlock (null, block, parameters, orig_method, out unreachable))
 449                                 return false;
 450
 451                         original_block.CompleteContexts ();
 452
 453                         cc.EmitAnonymousHelperClasses (ec);
 454
 455                         return true;
 456                 }
 457
 458                 //
 459                 // Returns the new block for the method, or null on failure
 460                 //
 461                 protected override bool DefineNestedTypes ()
 462                 {
 463                         Define_Fields ();
 464                         Define_Current ();
 465                         Define_MoveNext ();
 466                         Define_Reset ();
 467                         Define_Dispose ();
 468
 469                         Create_Block ();
 470
 471                         Define_Constructor ();
 472
 473                         if (is_enumerable)
 474                                 Define_GetEnumerator ();
 475
 476                         return base.DefineNestedTypes ();
 477                 }
 478
 479                 Field pc_field;
 480                 Field current_field;
 481                 Method dispose;
 482
 483                 void Create_Block ()
 484                 {
 485                         original_block.SetHaveAnonymousMethods (Location, move_next_method);
 486                         block.SetHaveAnonymousMethods (Location, move_next_method);
 487
 488                         cc = original_block.CaptureContext;
 489
 490                         int first = IsStatic ? 0 : 1;
 491
 492                         ArrayList args = new ArrayList ();
 493                         if (!IsStatic) {
 494                                 Type t = container.TypeBuilder;
 495                                 args.Add (new Argument (
 496                                         new ThisParameterReference (t, Location)));
 497                                 cc.CaptureThis (move_next_method);
 498                         }
 499
 500                         args.Add (new Argument (new BoolLiteral (false, Location)));
 501
 502                         for (int i = 0; i < parameters.Count; i++) {
 503                                 Type t = parameters.ParameterType (i);
 504                                 string name = parameters.ParameterName (i);
 505
 506                                 args.Add (new Argument (
 507                                         new SimpleParameterReference (t, first + i, Location)));
 508
 509                                 cc.AddParameterToContext (move_next_method, name, t, first + i);
 510                         }
 511
 512                         Expression new_expr = new New (
 513                                 new TypeExpression (TypeBuilder, Location), args, Location);
 514
 515                         block.AddStatement (new NoCheckReturn (new_expr, Location));
 516                 }
 517
 518                 void Define_Fields ()
 519                 {
 520                         pc_field = new Field (
 521                                 this, TypeManager.system_int32_expr, Modifiers.PRIVATE, "$PC",
 522                                 null, Location);
 523                         AddField (pc_field);
 524
 525                         current_field = new Field (
 526                                 this, iterator_type_expr, Modifiers.PRIVATE, "$current",
 527                                 null, Location);
 528                         AddField (current_field);
 529                 }
 530
 531                 void Define_Constructor ()
 532                 {
 533                         Parameters ctor_params;
 534
 535                         ArrayList list = new ArrayList ();
 536
 537                         if (!IsStatic)
 538                                 list.Add (new Parameter (
 539                                         new TypeExpression (container.TypeBuilder, Location),
 540                                         "this", Parameter.Modifier.NONE,
 541                                         null, Location));
 542                         list.Add (new Parameter (
 543                                 TypeManager.bool_type, "initialized",
 544                                 Parameter.Modifier.NONE, null, Location));
 545
 546                         Parameter[] old_fixed = parameters.FixedParameters;
 547                         list.AddRange (old_fixed);
 548
 549                         Parameter[] fixed_params = new Parameter [list.Count];
 550                         list.CopyTo (fixed_params);
 551
 552                         ctor_params = new Parameters (fixed_params);
 553
 554                         ctor = new Constructor (
 555                                 this, Name, Modifiers.PUBLIC, ctor_params,
 556                                 new GeneratedBaseInitializer (Location),
 557                                 Location);
 558                         AddConstructor (ctor);
 559
 560                         ctor.Block = new ToplevelBlock (block, parameters, Location);
 561
 562                         int first = IsStatic ? 2 : 3;
 563
 564                         State initial = is_enumerable ? State.Uninitialized : State.Running;
 565                         ctor.Block.AddStatement (new SetState (this, initial, Location));
 566
 567                         ctor.Block.AddStatement (new If (
 568                                 new SimpleParameterReference (
 569                                         TypeManager.bool_type, first - 1, Location),
 570                                 new SetState (this, State.Running, Location),
 571                                 Location));
 572
 573                         ctor.Block.AddStatement (new InitScope (this, Location));
 574                 }
 575
 576                 Statement Create_ThrowInvalidOperation ()
 577                 {
 578                         TypeExpr ex_type = new TypeExpression (
 579                                 TypeManager.invalid_operation_exception_type, Location);
 580
 581                         return new Throw (new New (ex_type, null, Location), Location);
 582                 }
 583
 584                 Statement Create_ThrowNotSupported ()
 585                 {
 586                         TypeExpr ex_type = new TypeExpression (
 587                                 TypeManager.not_supported_exception_type, Location);
 588
 589                         return new Throw (new New (ex_type, null, Location), Location);
 590                 }
 591
 592                 void Define_Current ()
 593                 {
 594                         ToplevelBlock get_block = new ToplevelBlock (
 595                                 block, parameters, Location);
 596                         MemberName left = new MemberName ("System.Collections.IEnumerator");
 597                         MemberName name = new MemberName (left, "Current", Location);
 598
 599                         get_block.AddStatement (new If (
 600                                 new Binary (
 601                                         Binary.Operator.LessThanOrEqual,
 602                                         new FieldExpression (this, pc_field),
 603                                         new IntLiteral ((int) State.Running, pc_field.Location)),
 604                                 Create_ThrowInvalidOperation (),
 605                                 new Return (
 606                                         new FieldExpression (this, current_field), Location),
 607                                 Location));
 608
 609                         Accessor getter = new Accessor (get_block, 0, null, Location);
 610
 611                         Property current = new Property (
 612                                 this, iterator_type_expr, 0,
 613                                 false, name, null, getter, null);
 614                         AddProperty (current);
 615                 }
 616
 617                 void Define_MoveNext ()
 618                 {
 619                         move_next_method = new MoveNextMethod (this, Location);
 620
 621                         original_block.ReParent (block, move_next_method);
 622
 623                         move_next_method.CreateMethod (ec);
 624
 625                         AddMethod (move_next_method.method);
 626                 }
 627
 628                 void Define_GetEnumerator ()
 629                 {
 630                         MemberName left = new MemberName ("System.Collections.IEnumerable");
 631
 632                         MemberName name = new MemberName (left, "GetEnumerator", Location);
 633
 634                         Method get_enumerator = new Method (
 635                                 this,
 636                                 new TypeExpression (TypeManager.ienumerator_type, Location),
 637                                 0, false, name,
 638                                 Parameters.EmptyReadOnlyParameters, null);
 639                         AddMethod (get_enumerator);
 640
 641                         get_enumerator.Block = new ToplevelBlock (
 642                                 block, parameters, Location);
 643
 644                         get_enumerator.Block.SetHaveAnonymousMethods (Location, move_next_method);
 645
 646                         Expression ce = new MemberAccess (
 647                                 new SimpleName ("System.Threading.Interlocked", Location),
 648                                 "CompareExchange", Location);
 649
 650                         Expression pc = new FieldExpression (this, pc_field);
 651                         Expression before = new IntLiteral ((int) State.Running, Location);
 652                         Expression uninitialized = new IntLiteral ((int) State.Uninitialized, Location);
 653
 654                         ArrayList args = new ArrayList ();
 655                         args.Add (new Argument (pc, Argument.AType.Ref));
 656                         args.Add (new Argument (before, Argument.AType.Expression));
 657                         args.Add (new Argument (uninitialized, Argument.AType.Expression));
 658
 659                         get_enumerator.Block.AddStatement (new If (
 660                                 new Binary (
 661                                         Binary.Operator.Equality,
 662                                         new Invocation (ce, args),
 663                                         uninitialized),
 664                                 new Return (new ThisParameterReference (
 665                                                     TypeManager.ienumerator_type, Location),
 666                                             Location),
 667                                 Location));
 668
 669                         args = new ArrayList ();
 670                         if (!IsStatic) {
 671                                 args.Add (new Argument (new CapturedThisReference (this, Location)));
 672                         }
 673
 674                         args.Add (new Argument (new BoolLiteral (true, Location)));
 675
 676                         for (int i = 0; i < parameters.Count; i++) {
 677                                 Expression cp = new CapturedParameterReference (
 678                                         this, parameters.ParameterType (i),
 679                                         parameters.ParameterName (i), Location);
 680                                 args.Add (new Argument (cp));
 681                         }
 682
 683                         Expression new_expr = new New (
 684                                 new TypeExpression (TypeBuilder, Location), args, Location);
 685                         get_enumerator.Block.AddStatement (new Return (new_expr, Location));
 686                 }
 687
 688                 protected class SimpleParameterReference : Expression
 689                 {
 690                         int idx;
 691
 692                         public SimpleParameterReference (Type type, int idx, Location loc)
 693                         {
 694                                 this.idx = idx;
 695                                 this.loc = loc;
 696                                 this.type = type;
 697                                 eclass = ExprClass.Variable;
 698                         }
 699
 700                         public override Expression DoResolve (EmitContext ec)
 701                         {
 702                                 return this;
 703                         }
 704
 705                         public override void Emit (EmitContext ec)
 706                         {
 707                                 DoEmit (ec);
 708                         }
 709
 710                         protected virtual void DoEmit (EmitContext ec)
 711                         {
 712                                 ParameterReference.EmitLdArg (ec.ig, idx);
 713                         }
 714                 }
 715
 716                 protected class ThisParameterReference : SimpleParameterReference, IMemoryLocation
 717                 {
 718                         public ThisParameterReference (Type type, Location loc)
 719                                 : base (type, 0, loc)
 720                         { }
 721
 722                         protected override void DoEmit (EmitContext ec)
 723                         {
 724                                 base.DoEmit (ec);
 725                                 if (ec.TypeContainer is Struct)
 726                                         ec.ig.Emit (OpCodes.Ldobj, type);
 727                         }
 728
 729                         public void AddressOf (EmitContext ec, AddressOp mode)
 730                         {
 731                                 if (ec.TypeContainer is Struct)
 732                                         ec.ig.Emit (OpCodes.Ldarga, 0);
 733                                 else
 734                                         ec.ig.Emit (OpCodes.Ldarg, 0);
 735                         }
 736                 }
 737
 738                 protected class CapturedParameterReference : Expression
 739                 {
 740                         Iterator iterator;
 741                         string name;
 742
 743                         public CapturedParameterReference (Iterator iterator, Type type,
 744                                                            string name, Location loc)
 745                         {
 746                                 this.iterator = iterator;
 747                                 this.loc = loc;
 748                                 this.type = type;
 749                                 this.name = name;
 750                                 eclass = ExprClass.Variable;
 751                         }
 752
 753                         public override Expression DoResolve (EmitContext ec)
 754                         {
 755                                 return this;
 756                         }
 757
 758                         public override void Emit (EmitContext ec)
 759                         {
 760                                 ec.CurrentAnonymousMethod = iterator.move_next_method;
 761
 762                                 LocalTemporary dummy = null;
 763
 764                                 iterator.cc.EmitParameter (ec, name, false, false, ref dummy);
 765                         }
 766                 }
 767
 768                 protected class CapturedThisReference : Expression
 769                 {
 770                         public CapturedThisReference (Iterator iterator, Location loc)
 771                         {
 772                                 this.loc = loc;
 773                                 this.type = iterator.this_type;
 774                                 eclass = ExprClass.Variable;
 775                         }
 776
 777                         public override Expression DoResolve (EmitContext ec)
 778                         {
 779                                 return this;
 780                         }
 781
 782                         public override void Emit (EmitContext ec)
 783                         {
 784                                 ec.EmitThis ();
 785                         }
 786                 }
 787
 788                 protected class FieldExpression : Expression
 789                 {
 790                         Iterator iterator;
 791                         Field field;
 792
 793                         public FieldExpression (Iterator iterator, Field field)
 794                         {
 795                                 this.iterator = iterator;
 796                                 this.field = field;
 797                                 this.loc = iterator.Location;
 798                         }
 799
 800                         public override Expression DoResolveLValue (EmitContext ec, Expression right_side)
 801                         {
 802                                 FieldExpr fexpr = new FieldExpr (field.FieldBuilder, loc);
 803                                 fexpr.InstanceExpression = new ThisParameterReference (
 804                                         iterator.this_type, loc);
 805                                 return fexpr.ResolveLValue (ec, right_side, loc);
 806                         }
 807
 808                         public override Expression DoResolve (EmitContext ec)
 809                         {
 810                                 FieldExpr fexpr = new FieldExpr (field.FieldBuilder, loc);
 811                                 fexpr.InstanceExpression = new ThisParameterReference (
 812                                         iterator.this_type, loc);
 813                                 return fexpr.Resolve (ec);
 814                         }
 815
 816                         public override void Emit (EmitContext ec)
 817                         {
 818                                 throw new InvalidOperationException ();
 819                         }
 820                 }
 821
 822                 protected class MoveNextMethod : AnonymousContainer
 823                 {
 824                         Iterator iterator;
 825
 826                         public MoveNextMethod (Iterator iterator, Location loc)
 827                                 : base (iterator.parameters, iterator.original_block, loc)
 828                         {
 829                                 this.iterator = iterator;
 830                         }
 831
 832                         protected override bool CreateMethodHost (EmitContext ec)
 833                         {
 834                                 method = new Method (
 835                                         iterator, TypeManager.system_boolean_expr,
 836                                         Modifiers.PUBLIC, false, new MemberName ("MoveNext", loc),
 837                                         Parameters.EmptyReadOnlyParameters, null);
 838
 839                                 method.Block = Block;
 840
 841                                 MoveNextStatement inline = new MoveNextStatement (iterator, loc);
 842                                 Block.AddStatement (inline);
 843
 844                                 return true;
 845                         }
 846
 847                         public bool CreateMethod (EmitContext ec)
 848                         {
 849                                 return CreateMethodHost (ec);
 850                         }
 851
 852                         public override bool IsIterator {
 853                                 get { return true; }
 854                         }
 855
 856                         public override void CreateScopeType (EmitContext ec, ScopeInfo scope)
 857                         {
 858                                 scope.ScopeTypeBuilder = iterator.TypeBuilder;
 859                                 scope.ScopeConstructor = iterator.ctor.ConstructorBuilder;
 860                         }
 861
 862                         public override void Emit (EmitContext ec)
 863                         {
 864                                 throw new InternalErrorException ();
 865                         }
 866                 }
 867
 868                 protected class MoveNextStatement : Statement {
 869                         Iterator iterator;
 870
 871                         public MoveNextStatement (Iterator iterator, Location loc)
 872                         {
 873                                 this.loc = loc;
 874                                 this.iterator = iterator;
 875                         }
 876
 877                         public override bool Resolve (EmitContext ec)
 878                         {
 879                                 return true;
 880                         }
 881
 882                         protected override void DoEmit (EmitContext ec)
 883                         {
 884                                 ec.CurrentIterator = iterator;
 885                                 ec.CurrentAnonymousMethod = iterator.move_next_method;
 886                                 ec.InIterator = true;
 887
 888                                 iterator.EmitMoveNext (ec);
 889                         }
 890                 }
 891
 892                 protected class DisposeMethod : Statement {
 893                         Iterator iterator;
 894
 895                         public DisposeMethod (Iterator iterator, Location loc)
 896                         {
 897                                 this.loc = loc;
 898                                 this.iterator = iterator;
 899                         }
 900
 901                         public override bool Resolve (EmitContext ec)
 902                         {
 903                                 return true;
 904                         }
 905
 906                         protected override void DoEmit (EmitContext ec)
 907                         {
 908                                 iterator.EmitDispose (ec);
 909                         }
 910                 }
 911
 912                 protected class StatementList : Statement {
 913                         ArrayList statements;
 914
 915                         public StatementList (Location loc)
 916                         {
 917                                 this.loc = loc;
 918                                 statements = new ArrayList ();
 919                         }
 920
 921                         public void Add (Statement statement)
 922                         {
 923                                 statements.Add (statement);
 924                         }
 925
 926                         public override bool Resolve (EmitContext ec)
 927                         {
 928                                 foreach (Statement stmt in statements) {
 929                                         if (!stmt.Resolve (ec))
 930                                                 return false;
 931                                 }
 932
 933                                 return true;
 934                         }
 935
 936                         protected override void DoEmit (EmitContext ec)
 937                         {
 938                                 foreach (Statement stmt in statements)
 939                                         stmt.Emit (ec);
 940                         }
 941                 }
 942
 943                 protected class SetState : Statement
 944                 {
 945                         Iterator iterator;
 946                         State state;
 947
 948                         public SetState (Iterator iterator, State state, Location loc)
 949                         {
 950                                 this.iterator = iterator;
 951                                 this.state = state;
 952                                 this.loc = loc;
 953                         }
 954
 955                         public override bool Resolve (EmitContext ec)
 956                         {
 957                                 return true;
 958                         }
 959
 960                         protected override void DoEmit (EmitContext ec)
 961                         {
 962                                 ec.ig.Emit (OpCodes.Ldarg_0);
 963                                 IntConstant.EmitInt (ec.ig, (int) state);
 964                                 ec.ig.Emit (OpCodes.Stfld, iterator.pc_field.FieldBuilder);
 965                         }
 966                 }
 967
 968                 protected class InitScope : Statement
 969                 {
 970                         Iterator iterator;
 971
 972                         public InitScope (Iterator iterator, Location loc)
 973                         {
 974                                 this.iterator = iterator;
 975                                 this.loc = loc;
 976                         }
 977
 978                         public override bool Resolve (EmitContext ec)
 979                         {
 980                                 return true;
 981                         }
 982
 983                         protected override void DoEmit (EmitContext ec)
 984                         {
 985                                 iterator.cc.EmitInitScope (ec);
 986                         }
 987                 }
 988
 989                 void Define_Reset ()
 990                 {
 991                         Method reset = new Method (
 992                                 this, TypeManager.system_void_expr, Modifiers.PUBLIC,
 993                                 false, new MemberName ("Reset", Location),
 994                                 Parameters.EmptyReadOnlyParameters, null);
 995                         AddMethod (reset);
 996
 997                         reset.Block = new ToplevelBlock (Location);
 998                         reset.Block = new ToplevelBlock (block, parameters, Location);
 999                         reset.Block.SetHaveAnonymousMethods (Location, move_next_method);
1000
1001                         reset.Block.AddStatement (Create_ThrowNotSupported ());
1002                 }
1003
1004                 void Define_Dispose ()
1005                 {
1006                         dispose = new Method (
1007                                 this, TypeManager.system_void_expr, Modifiers.PUBLIC,
1008                                 false, new MemberName ("Dispose", Location),
1009                                 Parameters.EmptyReadOnlyParameters, null);
1010                         AddMethod (dispose);
1011
1012                         dispose.Block = new ToplevelBlock (block, parameters, Location);
1013                         dispose.Block.SetHaveAnonymousMethods (Location, move_next_method);
1014
1015                         dispose.Block.AddStatement (new DisposeMethod (this, Location));
1016                 }
1017
1018                 public Type IteratorType {
1019                         get { return iterator_type; }
1020                 }
1021
1022                 //
1023                 // This return statement tricks return into not flagging an error for being
1024                 // used in a Yields method
1025                 //
1026                 class NoCheckReturn : Statement {
1027                         public Expression Expr;
1028
1029                         public NoCheckReturn (Expression expr, Location l)
1030                         {
1031                                 Expr = expr;
1032                                 loc = l;
1033                         }
1034
1035                         public override bool Resolve (EmitContext ec)
1036                         {
1037                                 Expr = Expr.Resolve (ec);
1038                                 if (Expr == null)
1039                                         return false;
1040
1041                                 ec.CurrentBranching.CurrentUsageVector.Return ();
1042
1043                                 return true;
1044                         }
1045
1046                         protected override void DoEmit (EmitContext ec)
1047                         {
1048                                 Expr.Emit (ec);
1049                                 ec.ig.Emit (OpCodes.Ret);
1050                         }
1051                 }
1052
1053                 bool CheckType ()
1054                 {
1055                         Type ret = orig_method.ReturnType;
1056
1057                         if (ret == TypeManager.ienumerable_type) {
1058                                 iterator_type = TypeManager.object_type;
1059                                 is_enumerable = true;
1060                                 return true;
1061                         }
1062                         if (ret == TypeManager.ienumerator_type) {
1063                                 iterator_type = TypeManager.object_type;
1064                                 is_enumerable = false;
1065                                 return true;
1066                         }
1067
1068                         return false;
1069                 }
1070         }
1071 }
1072