2 // iterators.cs: Support for implementing iterators
5 // Miguel de Icaza (miguel@ximian.com)
7 // (C) 2003 Ximian, Inc.
10 // Flow analysis for Yield.
11 // Emit calls to base object constructor.
14 // Current should be defined to return T, and IEnumerator.Current returns object
18 using System.Collections;
19 using System.Reflection;
20 using System.Reflection.Emit;
22 namespace Mono.CSharp {
24 public class Yield : Statement {
26 ArrayList finally_blocks;
28 public Yield (Expression expr, Location l)
34 public static bool CheckContext (EmitContext ec, Location loc, bool isYieldBreak)
37 Report.Error (1625, loc, "Cannot yield in the body of a " +
42 for (Block block = ec.CurrentBlock; block != null; block = block.Parent) {
46 Report.Error (1629, loc, "Unsafe code may not appear in iterators");
51 // We can't use `ec.InUnsafe' here because it's allowed to have an iterator
52 // inside an unsafe class. See test-martin-29.cs for an example.
54 if (!ec.CurrentAnonymousMethod.IsIterator) {
55 Report.Error (1621, loc,
56 "The yield statement cannot be used inside " +
57 "anonymous method blocks");
61 if (ec.CurrentBranching.InTryWithCatch () && (!isYieldBreak || !ec.InCatch)) {
63 Report.Error (1626, loc, "Cannot yield a value in the body " +
64 "of a try block with a catch clause");
66 Report.Error (1631, loc, "Cannot yield a value in the body " +
74 public override bool Resolve (EmitContext ec)
76 Report.Debug (64, "RESOLVE YIELD", this, ec, expr, expr.GetType ());
77 expr = expr.Resolve (ec);
81 Report.Debug (64, "RESOLVE YIELD #1", this, ec, expr, expr.GetType (),
82 ec.CurrentAnonymousMethod, ec.CurrentIterator);
84 if (!CheckContext (ec, loc, false))
87 Iterator iterator = ec.CurrentIterator;
88 if (expr.Type != iterator.IteratorType) {
89 expr = Convert.ImplicitConversionRequired (
90 ec, expr, iterator.IteratorType, loc);
95 ec.CurrentBranching.StealFinallyClauses (ref finally_blocks);
99 protected override void DoEmit (EmitContext ec)
101 ec.CurrentIterator.MarkYield (ec, expr, finally_blocks);
104 protected override void CloneTo (CloneContext clonectx, Statement t)
106 Yield target = (Yield) t;
108 target.expr = expr.Clone (clonectx);
112 public class YieldBreak : Statement {
114 public YieldBreak (Location l)
119 public override bool Resolve (EmitContext ec)
121 if (!Yield.CheckContext (ec, loc, true))
124 ec.CurrentBranching.CurrentUsageVector.Goto ();
128 protected override void DoEmit (EmitContext ec)
130 ec.CurrentIterator.EmitYieldBreak (ec.ig);
134 public class IteratorHost : RootScopeInfo
136 public readonly Iterator Iterator;
138 TypeExpr iterator_type_expr;
141 MethodInfo dispose_method;
143 TypeExpr enumerator_type;
144 TypeExpr enumerable_type;
145 TypeArguments generic_args;
146 TypeExpr generic_enumerator_type;
148 TypeExpr generic_enumerable_type;
151 public IteratorHost (Iterator iterator)
152 : base (iterator.Container.Toplevel, iterator.Host, iterator.GenericMethod,
155 this.Iterator = iterator;
158 public override bool IsIterator {
162 public MethodInfo Dispose {
163 get { return dispose_method; }
167 get { return pc_field; }
170 public Field CurrentField {
171 get { return current_field; }
174 public Type IteratorType {
175 get { return iterator_type_expr.Type; }
178 public override TypeExpr [] GetClassBases (out TypeExpr base_class)
180 iterator_type_expr = InflateType (Iterator.OriginalIteratorType);
183 generic_args = new TypeArguments (Location);
184 generic_args.Add (iterator_type_expr);
187 ArrayList list = new ArrayList ();
188 if (Iterator.IsEnumerable) {
189 enumerable_type = new TypeExpression (
190 TypeManager.ienumerable_type, Location);
191 list.Add (enumerable_type);
194 generic_enumerable_type = new ConstructedType (
195 TypeManager.generic_ienumerable_type,
196 generic_args, Location);
197 list.Add (generic_enumerable_type);
201 enumerator_type = new TypeExpression (
202 TypeManager.ienumerator_type, Location);
203 list.Add (enumerator_type);
205 list.Add (new TypeExpression (TypeManager.idisposable_type, Location));
208 generic_enumerator_type = new ConstructedType (
209 TypeManager.generic_ienumerator_type,
210 generic_args, Location);
211 list.Add (generic_enumerator_type);
216 return base.GetClassBases (out base_class);
219 protected override bool DoResolveMembers ()
221 pc_field = CaptureVariable ("$PC", TypeManager.system_int32_expr);
222 current_field = CaptureVariable ("$current", iterator_type_expr);
225 Define_Current (true);
227 Define_Current (false);
228 new DisposeMethod (this);
231 if (Iterator.IsEnumerable) {
232 new GetEnumeratorMethod (this, false);
234 new GetEnumeratorMethod (this, true);
238 return base.DoResolveMembers ();
241 public void CaptureScopes ()
243 Report.Debug (128, "DEFINE ITERATOR HOST", this, scopes);
245 foreach (ScopeInfo si in scopes)
248 foreach (ScopeInfo si in scopes) {
250 throw new InternalErrorException ();
251 if (si.DefineType () == null)
252 throw new InternalErrorException ();
253 if (!si.ResolveType ())
254 throw new InternalErrorException ();
255 if (!si.ResolveMembers ())
256 throw new InternalErrorException ();
257 if (!si.DefineMembers ())
258 throw new InternalErrorException ();
262 protected override bool DoDefineMembers ()
264 if (!base.DoDefineMembers ())
267 FetchMethodDispose ();
272 protected override void EmitScopeConstructor (EmitContext ec)
274 ec.ig.Emit (OpCodes.Ldarg_0);
275 ec.ig.Emit (OpCodes.Ldarg_1);
276 ec.ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);
277 base.EmitScopeConstructor (ec);
280 void FetchMethodDispose ()
282 MemberList dispose_list;
284 dispose_list = FindMembers (
285 CurrentType != null ? CurrentType : TypeBuilder,
286 MemberTypes.Method, BindingFlags.Public | BindingFlags.Instance,
287 Type.FilterName, "Dispose");
289 if (dispose_list.Count != 1)
290 throw new InternalErrorException ("Cannot find Dipose() method.");
292 dispose_method = (MethodInfo) dispose_list [0];
295 void Define_Current (bool is_generic)
301 left = new MemberName (
302 "System.Collections.Generic.IEnumerator",
303 generic_args, Location);
304 type = iterator_type_expr;
306 left = new MemberName ("System.Collections.IEnumerator", Location);
307 type = TypeManager.system_object_expr;
310 MemberName name = new MemberName (left, "Current", null, Location);
312 ToplevelBlock get_block = new ToplevelBlock (Location);
313 get_block.AddStatement (new CurrentBlock (this, is_generic));
315 Accessor getter = new Accessor (get_block, 0, null, Location);
317 Property current = new Property (
318 this, type, 0, false, name, null, getter, null, false);
319 AddProperty (current);
324 Method reset = new Method (
325 this, null, TypeManager.system_void_expr, Modifiers.PUBLIC,
326 false, new MemberName ("Reset", Location),
327 Parameters.EmptyReadOnlyParameters, null);
330 reset.Block = new ToplevelBlock (Location);
331 reset.Block.AddStatement (Create_ThrowNotSupported ());
334 Statement Create_ThrowNotSupported ()
336 TypeExpr ex_type = new TypeExpression (
337 TypeManager.not_supported_exception_type, Location);
339 return new Throw (new New (ex_type, null, Location), Location);
342 ConstructorInfo GetInvalidOperationException ()
344 return TypeManager.GetConstructor (
345 TypeManager.invalid_operation_exception_type, Type.EmptyTypes);
348 protected override ScopeInitializer CreateScopeInitializer ()
350 return new IteratorHostInitializer (this);
353 protected class IteratorHostInitializer : RootScopeInitializer
355 new public readonly IteratorHost Host;
356 protected Iterator.State state;
358 public IteratorHostInitializer (IteratorHost host)
364 protected override bool DoResolveInternal (EmitContext ec)
366 if (this is EnumeratorScopeInitializer)
367 state = Iterator.State.Running;
368 else if (Host.Iterator.IsEnumerable)
369 state = Iterator.State.Uninitialized;
371 state = Iterator.State.Running;
373 return base.DoResolveInternal (ec);
376 protected override void EmitScopeConstructor (EmitContext ec)
378 ec.ig.Emit (OpCodes.Ldc_I4, (int) state);
379 base.EmitScopeConstructor (ec);
383 protected class GetEnumeratorMethod : Method
385 public IteratorHost Host;
387 static MemberName GetMemberName (IteratorHost host, bool is_generic)
391 left = new MemberName (
392 "System.Collections.Generic.IEnumerable",
393 host.generic_args, host.Location);
395 left = new MemberName (
396 "System.Collections.IEnumerable", host.Location);
399 return new MemberName (left, "GetEnumerator", host.Location);
402 public GetEnumeratorMethod (IteratorHost host, bool is_generic)
403 : base (host, null, is_generic ?
404 host.generic_enumerator_type : host.enumerator_type,
405 0, false, GetMemberName (host, is_generic),
406 Parameters.EmptyReadOnlyParameters, null)
410 host.AddMethod (this);
412 Block = new ToplevelBlock (host.Iterator.Container.Toplevel, null, Location);
413 Block.AddStatement (new GetEnumeratorStatement (host, Type));
416 public override EmitContext CreateEmitContext (DeclSpace tc, ILGenerator ig)
418 EmitContext ec = new EmitContext (
419 this, tc, this.ds, Location, ig, MemberType, ModFlags, false);
421 ec.CurrentAnonymousMethod = Host.Iterator;
425 protected class GetEnumeratorStatement : Statement
430 ExpressionStatement initializer;
434 public GetEnumeratorStatement (IteratorHost host, Expression type)
441 public override bool Resolve (EmitContext ec)
443 type = type.ResolveAsTypeTerminal (ec, false);
444 if ((type == null) || (type.Type == null))
447 initializer = host.GetEnumeratorInitializer (ec);
448 if (initializer == null)
451 cast = new ClassCast (initializer, type.Type);
453 ce = TypeManager.int_interlocked_compare_exchange;
455 ec.CurrentBranching.CurrentUsageVector.Goto ();
459 protected override void DoEmit (EmitContext ec)
461 ILGenerator ig = ec.ig;
462 Label label_init = ig.DefineLabel ();
464 ig.Emit (OpCodes.Ldarg_0);
465 ig.Emit (OpCodes.Ldflda, host.PC.FieldBuilder);
466 ig.Emit (OpCodes.Ldc_I4, (int) Iterator.State.Running);
467 ig.Emit (OpCodes.Ldc_I4, (int) Iterator.State.Uninitialized);
468 ig.Emit (OpCodes.Call, ce);
470 ig.Emit (OpCodes.Ldc_I4, (int) Iterator.State.Uninitialized);
471 ig.Emit (OpCodes.Bne_Un, label_init);
473 ig.Emit (OpCodes.Ldarg_0);
474 ig.Emit (OpCodes.Ret);
476 ig.MarkLabel (label_init);
478 initializer.EmitStatement (ec);
480 ig.Emit (OpCodes.Ret);
485 protected class DisposeMethod : Method
487 public IteratorHost Host;
489 public DisposeMethod (IteratorHost host)
490 : base (host, null, TypeManager.system_void_expr, Modifiers.PUBLIC,
491 false, new MemberName ("Dispose", host.Location),
492 Parameters.EmptyReadOnlyParameters, null)
496 host.AddMethod (this);
498 Block = new ToplevelBlock (host.Iterator.Block, null, Location);
499 Block.AddStatement (new DisposeMethodStatement (Host.Iterator));
501 Report.Debug (64, "DISPOSE METHOD", host, Block);
504 public override EmitContext CreateEmitContext (DeclSpace tc, ILGenerator ig)
506 EmitContext ec = new EmitContext (
507 this, tc, this.ds, Location, ig, MemberType, ModFlags, false);
509 ec.CurrentAnonymousMethod = Host.Iterator;
513 protected class DisposeMethodStatement : Statement
517 public DisposeMethodStatement (Iterator iterator)
519 this.iterator = iterator;
520 this.loc = iterator.Location;
523 public override bool Resolve (EmitContext ec)
528 protected override void DoEmit (EmitContext ec)
530 iterator.EmitDispose (ec);
535 protected ScopeInitializer GetEnumeratorInitializer (EmitContext ec)
537 ScopeInitializer init = new EnumeratorScopeInitializer (this);
538 if (init.Resolve (ec) == null)
539 throw new InternalErrorException ();
543 protected class EnumeratorScopeInitializer : IteratorHostInitializer
547 public EnumeratorScopeInitializer (IteratorHost host)
553 protected override bool DoResolveInternal (EmitContext ec)
555 type = host.IsGeneric ? host.CurrentType : host.TypeBuilder;
556 return base.DoResolveInternal (ec);
559 protected override void DoEmit (EmitContext ec)
564 protected override bool IsGetEnumerator {
568 protected override void EmitParameterReference (EmitContext ec,
569 CapturedParameter cp)
571 ec.ig.Emit (OpCodes.Ldarg_0);
572 ec.ig.Emit (OpCodes.Ldfld, cp.Field.FieldBuilder);
576 protected class CurrentBlock : Statement {
580 public CurrentBlock (IteratorHost host, bool is_generic)
583 this.is_generic = is_generic;
587 public override bool Resolve (EmitContext ec)
589 ec.CurrentBranching.CurrentUsageVector.Goto ();
593 protected override void DoEmit (EmitContext ec)
595 ILGenerator ig = ec.ig;
596 Label label_ok = ig.DefineLabel ();
598 ig.Emit (OpCodes.Ldarg_0);
599 ig.Emit (OpCodes.Ldfld, host.PC.FieldBuilder);
600 ig.Emit (OpCodes.Ldc_I4, (int) Iterator.State.Running);
601 ig.Emit (OpCodes.Bgt, label_ok);
603 ig.Emit (OpCodes.Newobj, host.GetInvalidOperationException ());
604 ig.Emit (OpCodes.Throw);
606 ig.MarkLabel (label_ok);
607 ig.Emit (OpCodes.Ldarg_0);
608 ig.Emit (OpCodes.Ldfld, host.CurrentField.FieldBuilder);
610 ig.Emit (OpCodes.Box, host.CurrentField.MemberType);
611 ig.Emit (OpCodes.Ret);
616 public class Iterator : AnonymousContainer {
617 protected readonly ToplevelBlock OriginalBlock;
618 protected readonly IMethodData OriginalMethod;
619 protected ToplevelBlock block;
621 public readonly bool IsEnumerable;
622 public readonly bool IsStatic;
625 // The state as we generate the iterator
627 Label move_next_ok, move_next_error;
628 ArrayList resume_points = new ArrayList ();
631 public readonly Type OriginalIteratorType;
632 public readonly IteratorHost IteratorHost;
640 public void EmitYieldBreak (ILGenerator ig)
642 ig.Emit (OpCodes.Ldarg_0);
643 IntConstant.EmitInt (ig, (int) State.After);
644 ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
645 ig.Emit (OpCodes.Br, move_next_error);
648 internal void EmitMoveNext (EmitContext ec, Block original_block)
650 ILGenerator ig = ec.ig;
652 move_next_ok = ig.DefineLabel ();
653 move_next_error = ig.DefineLabel ();
655 LocalBuilder retval = ec.GetTemporaryLocal (TypeManager.int32_type);
657 ig.BeginExceptionBlock ();
659 Label dispatcher = ig.DefineLabel ();
660 ig.Emit (OpCodes.Br, dispatcher);
662 ResumePoint entry_point = new ResumePoint (null);
663 resume_points.Add (entry_point);
664 entry_point.Define (ig);
666 original_block.Emit (ec);
670 ig.MarkLabel (dispatcher);
672 Label [] labels = new Label [resume_points.Count];
673 for (int i = 0; i < labels.Length; i++)
674 labels [i] = ((ResumePoint) resume_points [i]).Label;
676 ig.Emit (OpCodes.Ldarg_0);
677 ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
678 ig.Emit (OpCodes.Switch, labels);
680 Label end = ig.DefineLabel ();
682 ig.MarkLabel (move_next_error);
683 ig.Emit (OpCodes.Ldc_I4_0);
684 ig.Emit (OpCodes.Stloc, retval);
685 ig.Emit (OpCodes.Leave, end);
687 ig.MarkLabel (move_next_ok);
688 ig.Emit (OpCodes.Ldc_I4_1);
689 ig.Emit (OpCodes.Stloc, retval);
690 ig.Emit (OpCodes.Leave, end);
692 ig.BeginFaultBlock ();
694 ig.Emit (OpCodes.Ldarg_0);
695 ig.Emit (OpCodes.Callvirt, IteratorHost.Dispose);
697 ig.EndExceptionBlock ();
700 ig.Emit (OpCodes.Ldloc, retval);
701 ig.Emit (OpCodes.Ret);
704 public void EmitDispose (EmitContext ec)
706 ILGenerator ig = ec.ig;
708 Label end = ig.DefineLabel ();
709 Label dispatcher = ig.DefineLabel ();
710 ig.Emit (OpCodes.Br, dispatcher);
712 Label [] labels = new Label [resume_points.Count];
713 for (int i = 0; i < labels.Length; i++) {
714 ResumePoint point = (ResumePoint) resume_points [i];
716 if (point.FinallyBlocks == null) {
721 labels [i] = ig.DefineLabel ();
722 ig.MarkLabel (labels [i]);
724 ig.BeginExceptionBlock ();
725 ig.BeginFinallyBlock ();
727 foreach (ExceptionStatement stmt in point.FinallyBlocks) {
729 stmt.EmitFinally (ec);
732 ig.EndExceptionBlock ();
733 ig.Emit (OpCodes.Br, end);
736 ig.MarkLabel (dispatcher);
737 ig.Emit (OpCodes.Ldarg_0);
738 ig.Emit (OpCodes.Ldfld, IteratorHost.PC.FieldBuilder);
739 ig.Emit (OpCodes.Switch, labels);
741 ig.Emit (OpCodes.Ldarg_0);
742 IntConstant.EmitInt (ig, (int) State.After);
743 ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
748 protected class ResumePoint
751 public readonly ExceptionStatement[] FinallyBlocks;
753 public ResumePoint (ArrayList list)
756 FinallyBlocks = new ExceptionStatement [list.Count];
757 list.CopyTo (FinallyBlocks, 0);
761 public void Define (ILGenerator ig)
763 Label = ig.DefineLabel ();
764 ig.MarkLabel (Label);
769 // Called back from Yield
771 public void MarkYield (EmitContext ec, Expression expr,
772 ArrayList finally_blocks)
774 ILGenerator ig = ec.ig;
776 // Store the new current
777 ig.Emit (OpCodes.Ldarg_0);
779 ig.Emit (OpCodes.Stfld, IteratorHost.CurrentField.FieldBuilder);
783 ig.Emit (OpCodes.Ldarg_0);
784 IntConstant.EmitInt (ig, pc);
785 ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
788 ig.Emit (OpCodes.Br, move_next_ok);
790 ResumePoint point = new ResumePoint (finally_blocks);
791 resume_points.Add (point);
795 public void MarkFinally (EmitContext ec, ArrayList finally_blocks)
797 ILGenerator ig = ec.ig;
801 ig.Emit (OpCodes.Ldarg_0);
802 IntConstant.EmitInt (ig, pc);
803 ig.Emit (OpCodes.Stfld, IteratorHost.PC.FieldBuilder);
805 ResumePoint point = new ResumePoint (finally_blocks);
806 resume_points.Add (point);
810 public override string ContainerType {
811 get { return "iterator"; }
814 public override bool IsIterator {
818 public override RootScopeInfo RootScope {
819 get { return IteratorHost; }
822 public override ScopeInfo Scope {
823 get { return IteratorHost; }
829 private Iterator (IMethodData m_container, DeclSpace host, GenericMethod generic,
830 int modifiers, Type iterator_type, bool is_enumerable)
831 : base (null, host, generic, m_container.ParameterInfo,
832 new ToplevelBlock (m_container.ParameterInfo, m_container.Location),
833 m_container.Block, TypeManager.bool_type, modifiers,
834 m_container.Location)
836 this.OriginalBlock = m_container.Block;
837 this.OriginalMethod = m_container;
838 this.OriginalIteratorType = iterator_type;
839 this.IsEnumerable = is_enumerable;
841 Report.Debug (64, "NEW ITERATOR", host, generic, OriginalBlock,
844 IteratorHost = new IteratorHost (this);
845 Block.CreateIteratorHost (IteratorHost);
847 OriginalBlock.ReParent (Container.Toplevel);
849 m_container.Block = Container.Toplevel;
851 OriginalBlock.MakeIterator (this);
854 protected class TestStatement : Statement
856 public override bool Resolve (EmitContext ec)
861 protected override void DoEmit (EmitContext ec)
863 ec.ig.Emit (OpCodes.Nop);
864 ec.ig.Emit (OpCodes.Neg);
865 ec.ig.Emit (OpCodes.Pop);
866 ec.ig.Emit (OpCodes.Ret);
870 public override string GetSignatureForError ()
872 return OriginalMethod.GetSignatureForError ();
875 public override bool Resolve (EmitContext ec)
877 Report.Debug (64, "RESOLVE ITERATOR", this, Container, Block);
879 Parameters parameters = OriginalMethod.ParameterInfo;
880 for (int i = 0; i < parameters.Count; i++){
881 Parameter.Modifier mod = parameters.ParameterModifier (i);
882 if ((mod & (Parameter.Modifier.REF | Parameter.Modifier.OUT)) != 0){
883 Report.Error (1623, Location,
884 "Iterators cannot have ref or out parameters");
888 if ((mod & Parameter.Modifier.ARGLIST) != 0) {
889 Report.Error (1636, Location,
890 "__arglist is not allowed in parameter list " +
895 if (parameters.ParameterType (i).IsPointer) {
896 Report.Error (1637, Location,
897 "Iterators cannot have unsafe parameters or " +
903 if ((ModFlags & Modifiers.UNSAFE) != 0) {
904 Report.Error (1629, Location, "Unsafe code may not appear in iterators");
908 if (!base.Resolve (ec))
911 Report.Debug (64, "RESOLVE ITERATOR #1", this, method, method.Parent,
914 if (!RootScope.ResolveType ())
916 if (!RootScope.ResolveMembers ())
918 if (!RootScope.DefineMembers ())
921 ExpressionStatement scope_init = RootScope.GetScopeInitializer (ec);
922 Container.AddStatement (new StatementExpression (scope_init));
923 Expression cast = new ClassCast (scope_init, OriginalMethod.ReturnType);
924 Container.AddStatement (new NoCheckReturn (cast));
929 protected override Method DoCreateMethodHost (EmitContext ec)
931 Report.Debug (128, "CREATE METHOD HOST", this, IteratorHost);
933 IteratorHost.CaptureScopes ();
935 return new AnonymousMethodMethod (
936 this, RootScope, null, TypeManager.system_boolean_expr,
937 Modifiers.PUBLIC, new MemberName ("MoveNext", Location),
938 Parameters.EmptyReadOnlyParameters);
941 protected class MoveNextStatement : Statement {
944 public MoveNextStatement (Iterator iterator, Location loc)
947 this.iterator = iterator;
950 public override bool Resolve (EmitContext ec)
952 return iterator.OriginalBlock.Resolve (ec);
955 protected override void DoEmit (EmitContext ec)
957 iterator.EmitMoveNext (ec, iterator.Block);
961 public Type IteratorType {
962 get { return IteratorHost.IteratorType; }
966 // This return statement tricks return into not flagging an error for being
967 // used in a Yields method
969 class NoCheckReturn : Statement {
970 public Expression Expr;
972 public NoCheckReturn (Expression expr)
978 public override bool Resolve (EmitContext ec)
980 Expr = Expr.Resolve (ec);
984 ec.CurrentBranching.CurrentUsageVector.Goto ();
989 protected override void DoEmit (EmitContext ec)
992 ec.ig.Emit (OpCodes.Ret);
996 public static Iterator CreateIterator (IMethodData method, DeclSpace parent,
997 GenericMethod generic, int modifiers)
1002 Type ret = method.ReturnType;
1006 if (!CheckType (ret, out iterator_type, out is_enumerable)) {
1007 Report.Error (1624, method.Location,
1008 "The body of `{0}' cannot be an iterator block " +
1009 "because `{1}' is not an iterator interface type",
1010 method.GetSignatureForError (),
1011 TypeManager.CSharpName (ret));
1015 return new Iterator (method, parent, generic, modifiers,
1016 iterator_type, is_enumerable);
1019 static bool CheckType (Type ret, out Type original_iterator_type, out bool is_enumerable)
1021 original_iterator_type = null;
1022 is_enumerable = false;
1024 if (ret == TypeManager.ienumerable_type) {
1025 original_iterator_type = TypeManager.object_type;
1026 is_enumerable = true;
1029 if (ret == TypeManager.ienumerator_type) {
1030 original_iterator_type = TypeManager.object_type;
1031 is_enumerable = false;
1036 if (!ret.IsGenericType)
1039 Type[] args = TypeManager.GetTypeArguments (ret);
1040 if (args.Length != 1)
1043 Type gt = ret.GetGenericTypeDefinition ();
1044 if (gt == TypeManager.generic_ienumerable_type) {
1045 original_iterator_type = args [0];
1046 is_enumerable = true;
1048 } else if (gt == TypeManager.generic_ienumerator_type) {
1049 original_iterator_type = args [0];
1050 is_enumerable = false;