mcs/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, bool isYieldBreak)
  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
  55                         AnonymousContainer am = ec.CurrentAnonymousMethod;
  56                         if ((am != null) && !am.IsIterator){
  57                                 Report.Error (1621, loc, "The yield statement cannot be used inside anonymous method blocks");
  58                                 return false;
  59                         }
  60
  61                         if (ec.CurrentBranching.InTryWithCatch () && (!isYieldBreak || !ec.InCatch)) {
  62                                 if (!ec.InCatch)
  63                                         Report.Error (1626, loc, "Cannot yield a value in the body of a " +
  64                                         "try block with a catch clause");
  65                                 else
  66                                         Report.Error (1631, loc, "Cannot yield a value in the body of a catch clause");
  67                                 return false;
  68                         }
  69                         return true;
  70                 }
  71
  72                 public override bool Resolve (EmitContext ec)
  73                 {
  74                         expr = expr.Resolve (ec);
  75                         if (expr == null)
  76                                 return false;
  77
  78                         if (!CheckContext (ec, loc, false))
  79                                 return false;
  80
  81                         Iterator iterator = ec.CurrentIterator;
  82
  83                         if (expr.Type != iterator.IteratorType){
  84                                 expr = Convert.ImplicitConversionRequired (
  85                                         ec, expr, iterator.IteratorType, loc);
  86                                 if (expr == null)
  87                                         return false;
  88                         }
  89
  90                         ec.CurrentBranching.StealFinallyClauses (ref finally_blocks);
  91                         return true;
  92                 }
  93
  94                 protected override void DoEmit (EmitContext ec)
  95                 {
  96                         ec.CurrentIterator.MarkYield (ec, expr, finally_blocks);
  97                 }
  98         }
  99
 100         public class YieldBreak : Statement {
 101
 102                 public YieldBreak (Location l)
 103                 {
 104                         loc = l;
 105                 }
 106
 107                 public override bool Resolve (EmitContext ec)
 108                 {
 109                         if (!Yield.CheckContext (ec, loc, true))
 110                                 return false;
 111
 112                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 113                         return true;
 114                 }
 115
 116                 protected override void DoEmit (EmitContext ec)
 117                 {
 118                         ec.CurrentIterator.EmitYieldBreak (ec.ig);
 119                 }
 120         }
 121
 122         public class Iterator : Class {
 123                 protected ToplevelBlock original_block;
 124                 protected ToplevelBlock block;
 125
 126                 Type iterator_type;
 127                 TypeExpr iterator_type_expr;
 128                 bool is_enumerable;
 129                 public readonly bool IsStatic;
 130
 131                 //
 132                 // The state as we generate the iterator
 133                 //
 134                 Label move_next_ok, move_next_error;
 135                 ArrayList resume_points = new ArrayList ();
 136                 int pc;
 137
 138                 //
 139                 // Context from the original method
 140                 //
 141                 TypeContainer container;
 142                 Type this_type;
 143                 Parameters parameters;
 144                 IMethodData orig_method;
 145
 146                 MoveNextMethod move_next_method;
 147                 Constructor ctor;
 148                 CaptureContext cc;
 149                 EmitContext ec;
 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, DeclSpace parent,
 342                                  int modifiers)
 343                         : base (parent.NamespaceEntry, parent, 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 = ((TypeContainer) parent).PartialContainer;
 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, 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
 640                         //
 641                         // We call append instead of add, as we need to make sure that
 642                         // this method is resolved after the MoveNext method, as that one
 643                         // triggers the computation of the AnonymousMethod Scope, which is
 644                         // required during the code generation of the enumerator
 645                         //
 646                         AppendMethod (get_enumerator);
 647
 648                         get_enumerator.Block = new ToplevelBlock (
 649                                 block, parameters, Location);
 650
 651                         get_enumerator.Block.SetHaveAnonymousMethods (Location, move_next_method);
 652
 653                         Expression ce = new MemberAccess (
 654                                 new SimpleName ("System.Threading.Interlocked", Location),
 655                                 "CompareExchange");
 656
 657                         Expression pc = new FieldExpression (this, pc_field);
 658                         Expression before = new IntLiteral ((int) State.Running, Location);
 659                         Expression uninitialized = new IntLiteral ((int) State.Uninitialized, Location);
 660
 661                         ArrayList args = new ArrayList ();
 662                         args.Add (new Argument (pc, Argument.AType.Ref));
 663                         args.Add (new Argument (before, Argument.AType.Expression));
 664                         args.Add (new Argument (uninitialized, Argument.AType.Expression));
 665
 666                         get_enumerator.Block.AddStatement (new If (
 667                                 new Binary (
 668                                         Binary.Operator.Equality,
 669                                         new Invocation (ce, args),
 670                                         uninitialized),
 671                                 new Return (new ThisParameterReference (
 672                                                     TypeManager.ienumerator_type, Location),
 673                                             Location),
 674                                 Location));
 675
 676                         args = new ArrayList ();
 677                         if (!IsStatic) {
 678                                 args.Add (new Argument (new CapturedThisReference (this, Location)));
 679                         }
 680
 681                         args.Add (new Argument (new BoolLiteral (true, Location)));
 682
 683                         for (int i = 0; i < parameters.Count; i++) {
 684                                 Expression cp = new CapturedParameterReference (
 685                                         this, parameters.ParameterType (i),
 686                                         parameters.ParameterName (i), Location);
 687                                 args.Add (new Argument (cp));
 688                         }
 689
 690                         Expression new_expr = new New (
 691                                 new TypeExpression (TypeBuilder, Location), args, Location);
 692                         get_enumerator.Block.AddStatement (new Return (new_expr, Location));
 693                 }
 694
 695                 protected class SimpleParameterReference : Expression
 696                 {
 697                         int idx;
 698
 699                         public SimpleParameterReference (Type type, int idx, Location loc)
 700                         {
 701                                 this.idx = idx;
 702                                 this.loc = loc;
 703                                 this.type = type;
 704                                 eclass = ExprClass.Variable;
 705                         }
 706
 707                         public override Expression DoResolve (EmitContext ec)
 708                         {
 709                                 return this;
 710                         }
 711
 712                         public override void Emit (EmitContext ec)
 713                         {
 714                                 DoEmit (ec);
 715                         }
 716
 717                         protected virtual void DoEmit (EmitContext ec)
 718                         {
 719                                 ParameterReference.EmitLdArg (ec.ig, idx);
 720                         }
 721                 }
 722
 723                 protected class ThisParameterReference : SimpleParameterReference, IMemoryLocation
 724                 {
 725                         public ThisParameterReference (Type type, Location loc)
 726                                 : base (type, 0, loc)
 727                         { }
 728
 729                         protected override void DoEmit (EmitContext ec)
 730                         {
 731                                 base.DoEmit (ec);
 732                                 if (ec.TypeContainer is Struct)
 733                                         ec.ig.Emit (OpCodes.Ldobj, type);
 734                         }
 735
 736                         public void AddressOf (EmitContext ec, AddressOp mode)
 737                         {
 738                                 if (ec.TypeContainer is Struct)
 739                                         ec.ig.Emit (OpCodes.Ldarga, 0);
 740                                 else
 741                                         ec.ig.Emit (OpCodes.Ldarg, 0);
 742                         }
 743                 }
 744
 745                 protected class CapturedParameterReference : Expression
 746                 {
 747                         Iterator iterator;
 748                         string name;
 749
 750                         public CapturedParameterReference (Iterator iterator, Type type,
 751                                                            string name, Location loc)
 752                         {
 753                                 this.iterator = iterator;
 754                                 this.loc = loc;
 755                                 this.type = type;
 756                                 this.name = name;
 757                                 eclass = ExprClass.Variable;
 758                         }
 759
 760                         public override Expression DoResolve (EmitContext ec)
 761                         {
 762                                 return this;
 763                         }
 764
 765                         public override void Emit (EmitContext ec)
 766                         {
 767                                 ec.CurrentAnonymousMethod = iterator.move_next_method;
 768
 769                                 LocalTemporary dummy = null;
 770
 771                                 iterator.cc.EmitParameter (ec, name, false, false, ref dummy);
 772                         }
 773                 }
 774
 775                 protected class CapturedThisReference : Expression
 776                 {
 777                         public CapturedThisReference (Iterator iterator, Location loc)
 778                         {
 779                                 this.loc = loc;
 780                                 this.type = iterator.this_type;
 781                                 eclass = ExprClass.Variable;
 782                         }
 783
 784                         public override Expression DoResolve (EmitContext ec)
 785                         {
 786                                 return this;
 787                         }
 788
 789                         public override void Emit (EmitContext ec)
 790                         {
 791                                 ec.EmitThis (false);
 792                         }
 793                 }
 794
 795                 protected class FieldExpression : Expression
 796                 {
 797                         Iterator iterator;
 798                         Field field;
 799
 800                         public FieldExpression (Iterator iterator, Field field)
 801                         {
 802                                 this.iterator = iterator;
 803                                 this.field = field;
 804                                 this.loc = iterator.Location;
 805                         }
 806
 807                         public override Expression DoResolveLValue (EmitContext ec, Expression right_side)
 808                         {
 809                                 FieldExpr fexpr = new FieldExpr (field.FieldBuilder, loc);
 810                                 fexpr.InstanceExpression = new ThisParameterReference (
 811                                         iterator.this_type, loc);
 812                                 return fexpr.ResolveLValue (ec, right_side, loc);
 813                         }
 814
 815                         public override Expression DoResolve (EmitContext ec)
 816                         {
 817                                 FieldExpr fexpr = new FieldExpr (field.FieldBuilder, loc);
 818                                 fexpr.InstanceExpression = new ThisParameterReference (
 819                                         iterator.this_type, loc);
 820                                 return fexpr.Resolve (ec);
 821                         }
 822
 823                         public override void Emit (EmitContext ec)
 824                         {
 825                                 throw new InvalidOperationException ();
 826                         }
 827                 }
 828
 829                 protected class MoveNextMethod : AnonymousContainer
 830                 {
 831                         Iterator iterator;
 832
 833                         public MoveNextMethod (Iterator iterator, Location loc)
 834                                 : base (iterator.parameters, iterator.original_block, loc)
 835                         {
 836                                 this.iterator = iterator;
 837                         }
 838
 839                         protected override bool CreateMethodHost (EmitContext ec)
 840                         {
 841                                 method = new Method (
 842                                         iterator, TypeManager.system_boolean_expr,
 843                                         Modifiers.PUBLIC, false, new MemberName ("MoveNext", loc),
 844                                         Parameters.EmptyReadOnlyParameters, null);
 845
 846                                 method.Block = Block;
 847
 848                                 MoveNextStatement inline = new MoveNextStatement (iterator, loc);
 849                                 Block.AddStatement (inline);
 850
 851                                 return true;
 852                         }
 853
 854                         public bool CreateMethod (EmitContext ec)
 855                         {
 856                                 return CreateMethodHost (ec);
 857                         }
 858
 859                         public void ComputeHost ()
 860                         {
 861                                 ComputeMethodHost ();
 862                         }
 863
 864                         public override bool IsIterator {
 865                                 get { return true; }
 866                         }
 867
 868                         public override void CreateScopeType (EmitContext ec, ScopeInfo scope)
 869                         {
 870                                 scope.ScopeTypeBuilder = iterator.TypeBuilder;
 871                                 scope.ScopeConstructor = iterator.ctor.ConstructorBuilder;
 872                         }
 873
 874                         public override void Emit (EmitContext ec)
 875                         {
 876                                 throw new InternalErrorException ();
 877                         }
 878                 }
 879
 880                 protected class MoveNextStatement : Statement {
 881                         Iterator iterator;
 882
 883                         public MoveNextStatement (Iterator iterator, Location loc)
 884                         {
 885                                 this.loc = loc;
 886                                 this.iterator = iterator;
 887                         }
 888
 889                         protected override void DoEmit (EmitContext ec)
 890                         {
 891                                 iterator.move_next_method.ComputeHost ();
 892
 893                                 ec.CurrentIterator = iterator;
 894                                 ec.CurrentAnonymousMethod = iterator.move_next_method;
 895                                 ec.InIterator = true;
 896
 897                                 iterator.EmitMoveNext (ec);
 898                         }
 899                 }
 900
 901                 protected class DisposeMethod : Statement {
 902                         Iterator iterator;
 903
 904                         public DisposeMethod (Iterator iterator, Location loc)
 905                         {
 906                                 this.loc = loc;
 907                                 this.iterator = iterator;
 908                         }
 909
 910                         public override bool Resolve (EmitContext ec)
 911                         {
 912                                 return true;
 913                         }
 914
 915                         protected override void DoEmit (EmitContext ec)
 916                         {
 917                                 iterator.EmitDispose (ec);
 918                         }
 919                 }
 920
 921                 protected class StatementList : Statement {
 922                         ArrayList statements;
 923
 924                         public StatementList (Location loc)
 925                         {
 926                                 this.loc = loc;
 927                                 statements = new ArrayList ();
 928                         }
 929
 930                         public void Add (Statement statement)
 931                         {
 932                                 statements.Add (statement);
 933                         }
 934
 935                         public override bool Resolve (EmitContext ec)
 936                         {
 937                                 foreach (Statement stmt in statements) {
 938                                         if (!stmt.Resolve (ec))
 939                                                 return false;
 940                                 }
 941
 942                                 return true;
 943                         }
 944
 945                         protected override void DoEmit (EmitContext ec)
 946                         {
 947                                 foreach (Statement stmt in statements)
 948                                         stmt.Emit (ec);
 949                         }
 950                 }
 951
 952                 protected class SetState : Statement
 953                 {
 954                         Iterator iterator;
 955                         State state;
 956
 957                         public SetState (Iterator iterator, State state, Location loc)
 958                         {
 959                                 this.iterator = iterator;
 960                                 this.state = state;
 961                                 this.loc = loc;
 962                         }
 963
 964                         public override bool Resolve (EmitContext ec)
 965                         {
 966                                 return true;
 967                         }
 968
 969                         protected override void DoEmit (EmitContext ec)
 970                         {
 971                                 ec.ig.Emit (OpCodes.Ldarg_0);
 972                                 IntConstant.EmitInt (ec.ig, (int) state);
 973                                 ec.ig.Emit (OpCodes.Stfld, iterator.pc_field.FieldBuilder);
 974                         }
 975                 }
 976
 977                 protected class InitScope : Statement
 978                 {
 979                         Iterator iterator;
 980
 981                         public InitScope (Iterator iterator, Location loc)
 982                         {
 983                                 this.iterator = iterator;
 984                                 this.loc = loc;
 985                         }
 986
 987                         public override bool Resolve (EmitContext ec)
 988                         {
 989                                 return true;
 990                         }
 991
 992                         protected override void DoEmit (EmitContext ec)
 993                         {
 994                                 iterator.cc.EmitInitScope (ec);
 995                         }
 996                 }
 997
 998                 void Define_Reset ()
 999                 {
1000                         Method reset = new Method (
1001                                 this, TypeManager.system_void_expr, Modifiers.PUBLIC,
1002                                 false, new MemberName ("Reset", Location),
1003                                 Parameters.EmptyReadOnlyParameters, null);
1004                         AddMethod (reset);
1005
1006                         reset.Block = new ToplevelBlock (Location);
1007                         reset.Block = new ToplevelBlock (block, parameters, Location);
1008                         reset.Block.SetHaveAnonymousMethods (Location, move_next_method);
1009
1010                         reset.Block.AddStatement (Create_ThrowNotSupported ());
1011                 }
1012
1013                 void Define_Dispose ()
1014                 {
1015                         dispose = new Method (
1016                                 this, TypeManager.system_void_expr, Modifiers.PUBLIC,
1017                                 false, new MemberName ("Dispose", Location),
1018                                 Parameters.EmptyReadOnlyParameters, null);
1019                         AddMethod (dispose);
1020
1021                         dispose.Block = new ToplevelBlock (block, parameters, Location);
1022                         dispose.Block.SetHaveAnonymousMethods (Location, move_next_method);
1023
1024                         dispose.Block.AddStatement (new DisposeMethod (this, Location));
1025                 }
1026
1027                 public Type IteratorType {
1028                         get { return iterator_type; }
1029                 }
1030
1031                 //
1032                 // This return statement tricks return into not flagging an error for being
1033                 // used in a Yields method
1034                 //
1035                 class NoCheckReturn : Statement {
1036                         public Expression Expr;
1037
1038                         public NoCheckReturn (Expression expr, Location l)
1039                         {
1040                                 Expr = expr;
1041                                 loc = l;
1042                         }
1043
1044                         public override bool Resolve (EmitContext ec)
1045                         {
1046                                 Expr = Expr.Resolve (ec);
1047                                 if (Expr == null)
1048                                         return false;
1049
1050                                 ec.CurrentBranching.CurrentUsageVector.Return ();
1051
1052                                 return true;
1053                         }
1054
1055                         protected override void DoEmit (EmitContext ec)
1056                         {
1057                                 Expr.Emit (ec);
1058                                 ec.ig.Emit (OpCodes.Ret);
1059                         }
1060                 }
1061
1062                 bool CheckType ()
1063                 {
1064                         Type ret = orig_method.ReturnType;
1065
1066                         if (ret == TypeManager.ienumerable_type) {
1067                                 iterator_type = TypeManager.object_type;
1068                                 is_enumerable = true;
1069                                 return true;
1070                         }
1071                         if (ret == TypeManager.ienumerator_type) {
1072                                 iterator_type = TypeManager.object_type;
1073                                 is_enumerable = false;
1074                                 return true;
1075                         }
1076
1077                         return false;
1078                 }
1079         }
1080 }
1081