2 // async.cs: Asynchronous functions
5 // Marek Safar (marek.safar@gmail.com)
7 // Dual licensed under the terms of the MIT X11 or GNU GPL
9 // Copyright 2011 Novell, Inc.
10 // Copyright 2011-2012 Xamarin Inc.
14 using System.Collections.Generic;
16 using System.Collections;
19 using IKVM.Reflection;
20 using IKVM.Reflection.Emit;
22 using System.Reflection;
23 using System.Reflection.Emit;
28 public class Await : ExpressionStatement
33 public Await (Expression expr, Location loc)
39 public Expression Expr {
45 public AwaitStatement Statement {
51 protected override void CloneTo (CloneContext clonectx, Expression target)
53 var t = (Await) target;
55 t.expr = expr.Clone (clonectx);
58 public override Expression CreateExpressionTree (ResolveContext ec)
60 throw new NotImplementedException ("ET");
63 public override bool ContainsEmitWithAwait ()
68 public override void FlowAnalysis (FlowAnalysisContext fc)
70 stmt.Expr.FlowAnalysis (fc);
72 stmt.RegisterResumePoint ();
75 protected override Expression DoResolve (ResolveContext rc)
77 if (rc.HasSet (ResolveContext.Options.LockScope)) {
78 rc.Report.Error (1996, loc,
79 "The `await' operator cannot be used in the body of a lock statement");
83 rc.Report.Error (4004, loc,
84 "The `await' operator cannot be used in an unsafe context");
87 var bc = (BlockContext) rc;
89 stmt = new AwaitStatement (expr, loc);
90 if (!stmt.Resolve (bc))
93 if (rc.HasSet (ResolveContext.Options.FinallyScope) && rc.CurrentAnonymousMethod != null) {
94 var ats = (AsyncTaskStorey)rc.CurrentAnonymousMethod.Storey;
95 ats.HasAwaitInsideFinally = true;
98 type = stmt.ResultType;
99 eclass = ExprClass.Variable;
103 public override void Emit (EmitContext ec)
105 stmt.EmitPrologue (ec);
107 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
112 public override Expression EmitToField (EmitContext ec)
114 stmt.EmitPrologue (ec);
115 return stmt.GetResultExpression (ec);
118 public void EmitAssign (EmitContext ec, FieldExpr field)
120 stmt.EmitPrologue (ec);
121 field.InstanceExpression.Emit (ec);
125 public override void EmitStatement (EmitContext ec)
127 stmt.EmitStatement (ec);
130 public override Reachability MarkReachable (Reachability rc)
132 return stmt.MarkReachable (rc);
135 public override object Accept (StructuralVisitor visitor)
137 return visitor.Visit (this);
141 public class AwaitStatement : YieldStatement<AsyncInitializer>
143 public sealed class AwaitableMemberAccess : MemberAccess
145 public AwaitableMemberAccess (Expression expr)
146 : base (expr, "GetAwaiter")
150 public bool ProbingMode { get; set; }
152 public override void Error_TypeDoesNotContainDefinition (ResolveContext rc, TypeSpec type, string name)
154 Error_OperatorCannotBeApplied (rc, type);
157 protected override void Error_OperatorCannotBeApplied (ResolveContext rc, TypeSpec type)
162 var invocation = LeftExpression as Invocation;
163 if (invocation != null && invocation.MethodGroup != null && (invocation.MethodGroup.BestCandidate.Modifiers & Modifiers.ASYNC) != 0) {
164 rc.Report.Error (4008, loc, "Cannot await void method `{0}'. Consider changing method return type to `Task'",
165 invocation.GetSignatureForError ());
166 } else if (type != InternalType.ErrorType) {
167 rc.Report.Error (4001, loc, "Cannot await `{0}' expression", type.GetSignatureForError ());
172 sealed class GetResultInvocation : Invocation
174 public GetResultInvocation (MethodGroupExpr mge, Arguments arguments)
175 : base (null, arguments)
178 type = mg.BestCandidateReturnType;
181 public override Expression EmitToField (EmitContext ec)
188 AwaiterDefinition awaiter_definition;
190 TypeSpec result_type;
192 public AwaitStatement (Expression expr, Location loc)
195 unwind_protect = true;
202 return awaiter_definition == null;
206 public TypeSpec ResultType {
214 protected override void DoEmit (EmitContext ec)
216 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
217 GetResultExpression (ec).Emit (ec);
221 public Expression GetResultExpression (EmitContext ec)
223 var fe_awaiter = new FieldExpr (awaiter, loc);
224 fe_awaiter.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
227 // result = awaiter.GetResult ();
230 var rc = new ResolveContext (ec.MemberContext);
231 return new Invocation (new MemberAccess (fe_awaiter, "GetResult"), new Arguments (0)).Resolve (rc);
234 var mg_result = MethodGroupExpr.CreatePredefined (awaiter_definition.GetResult, fe_awaiter.Type, loc);
235 mg_result.InstanceExpression = fe_awaiter;
237 return new GetResultInvocation (mg_result, new Arguments (0));
240 public void EmitPrologue (EmitContext ec)
242 awaiter = ((AsyncTaskStorey) machine_initializer.Storey).AddAwaiter (expr.Type);
244 var fe_awaiter = new FieldExpr (awaiter, loc);
245 fe_awaiter.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
247 Label skip_continuation = ec.DefineLabel ();
249 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
251 // awaiter = expr.GetAwaiter ();
253 fe_awaiter.EmitAssign (ec, expr, false, false);
255 Expression completed_expr;
257 var rc = new ResolveContext (ec.MemberContext);
259 Arguments dargs = new Arguments (1);
260 dargs.Add (new Argument (fe_awaiter));
261 completed_expr = new DynamicMemberBinder ("IsCompleted", dargs, loc).Resolve (rc);
263 dargs = new Arguments (1);
264 dargs.Add (new Argument (completed_expr));
265 completed_expr = new DynamicConversion (ec.Module.Compiler.BuiltinTypes.Bool, 0, dargs, loc).Resolve (rc);
267 var pe = PropertyExpr.CreatePredefined (awaiter_definition.IsCompleted, loc);
268 pe.InstanceExpression = fe_awaiter;
272 completed_expr.EmitBranchable (ec, skip_continuation, true);
278 // The stack has to be empty before calling await continuation. We handle this
279 // by lifting values which would be left on stack into class fields. The process
280 // is quite complicated and quite hard to test because any expression can possibly
281 // leave a value on the stack.
283 // Following assert fails when some of expression called before is missing EmitToField
284 // or parent expression fails to find await in children expressions
286 ec.AssertEmptyStack ();
288 var storey = (AsyncTaskStorey) machine_initializer.Storey;
290 storey.EmitAwaitOnCompletedDynamic (ec, fe_awaiter);
292 storey.EmitAwaitOnCompleted (ec, fe_awaiter);
296 machine_initializer.EmitLeave (ec, unwind_protect);
298 ec.MarkLabel (resume_point);
299 ec.MarkLabel (skip_continuation);
302 public void EmitStatement (EmitContext ec)
307 awaiter.IsAvailableForReuse = true;
309 if (ResultType.Kind != MemberKind.Void)
310 ec.Emit (OpCodes.Pop);
313 void Error_WrongAwaiterPattern (ResolveContext rc, TypeSpec awaiter)
315 rc.Report.Error (4011, loc, "The awaiter type `{0}' must have suitable IsCompleted and GetResult members",
316 awaiter.GetSignatureForError ());
319 public override bool Resolve (BlockContext bc)
321 if (bc.CurrentBlock is Linq.QueryBlock) {
322 bc.Report.Error (1995, loc,
323 "The `await' operator may only be used in a query expression within the first collection expression of the initial `from' clause or within the collection expression of a `join' clause");
327 if (!base.Resolve (bc))
331 Arguments args = new Arguments (0);
334 // The await expression is of dynamic type
336 if (type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
338 expr = new Invocation (new MemberAccess (expr, "GetAwaiter"), args).Resolve (bc);
343 // Check whether the expression is awaitable
345 Expression ama = new AwaitableMemberAccess (expr).Resolve (bc);
349 var errors_printer = new SessionReportPrinter ();
350 var old = bc.Report.SetPrinter (errors_printer);
353 // The expression await t is classified the same way as the expression (t).GetAwaiter().GetResult().
355 ama = new Invocation (new ParenthesizedExpression (ama, Location.Null), args).Resolve (bc);
356 bc.Report.SetPrinter (old);
358 if (errors_printer.ErrorsCount > 0 || !MemberAccess.IsValidDotExpression (ama.Type)) {
359 bc.Report.Error (1986, expr.Location,
360 "The `await' operand type `{0}' must have suitable GetAwaiter method",
361 expr.Type.GetSignatureForError ());
366 var awaiter_type = ama.Type;
368 awaiter_definition = bc.Module.GetAwaiter (awaiter_type);
370 if (!awaiter_definition.IsValidPattern) {
371 Error_WrongAwaiterPattern (bc, awaiter_type);
375 if (!awaiter_definition.INotifyCompletion) {
376 bc.Report.Error (4027, loc, "The awaiter type `{0}' must implement interface `{1}'",
377 awaiter_type.GetSignatureForError (), bc.Module.PredefinedTypes.INotifyCompletion.GetSignatureForError ());
382 result_type = awaiter_definition.GetResult.ReturnType;
388 class AsyncInitializerStatement : StatementExpression
390 public AsyncInitializerStatement (AsyncInitializer expr)
395 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
397 base.DoFlowAnalysis (fc);
399 var init = (AsyncInitializer) Expr;
400 var res = !init.Block.HasReachableClosingBrace;
401 var storey = (AsyncTaskStorey) init.Storey;
403 if (storey.ReturnType.IsGenericTask)
409 public override Reachability MarkReachable (Reachability rc)
411 if (!rc.IsUnreachable)
414 var init = (AsyncInitializer) Expr;
415 rc = init.Block.MarkReachable (rc);
417 var storey = (AsyncTaskStorey) init.Storey;
420 // Explicit return is required for Task<T> state machine
422 if (storey.ReturnType != null && storey.ReturnType.IsGenericTask)
425 return Reachability.CreateUnreachable ();
429 public class AsyncInitializer : StateMachineInitializer
431 TypeInferenceContext return_inference;
433 public AsyncInitializer (ParametersBlock block, TypeDefinition host, TypeSpec returnType)
434 : base (block, host, returnType)
440 public override string ContainerType {
442 return "async state machine block";
446 public TypeSpec DelegateType {
450 public StackFieldExpr HoistedReturnState {
454 public override bool IsIterator {
460 public TypeInferenceContext ReturnTypeInference {
462 return return_inference;
468 protected override BlockContext CreateBlockContext (BlockContext bc)
470 var ctx = base.CreateBlockContext (bc);
471 var am = bc.CurrentAnonymousMethod as AnonymousMethodBody;
473 return_inference = am.ReturnTypeInference;
475 ctx.Set (ResolveContext.Options.TryScope);
480 public override void Emit (EmitContext ec)
482 throw new NotImplementedException ();
485 public void EmitCatchBlock (EmitContext ec)
487 var catch_value = LocalVariable.CreateCompilerGenerated (ec.Module.Compiler.BuiltinTypes.Exception, block, Location);
489 ec.BeginCatchBlock (catch_value.Type);
490 catch_value.EmitAssign (ec);
493 ec.EmitInt ((int) IteratorStorey.State.After);
494 ec.Emit (OpCodes.Stfld, storey.PC.Spec);
496 ((AsyncTaskStorey) Storey).EmitSetException (ec, new LocalVariableReference (catch_value, Location));
498 ec.Emit (OpCodes.Leave, move_next_ok);
499 ec.EndExceptionBlock ();
503 protected override void EmitMoveNextEpilogue (EmitContext ec)
505 var storey = (AsyncTaskStorey) Storey;
506 storey.EmitSetResult (ec);
509 public override void EmitStatement (EmitContext ec)
511 var storey = (AsyncTaskStorey) Storey;
512 storey.EmitInitializer (ec);
513 ec.Emit (OpCodes.Ret);
516 public override Reachability MarkReachable (Reachability rc)
519 // Reachability has been done in AsyncInitializerStatement
525 class AsyncTaskStorey : StateMachine
529 readonly TypeSpec return_type;
530 MethodSpec set_result;
531 MethodSpec set_exception;
532 MethodSpec builder_factory;
533 MethodSpec builder_start;
536 Dictionary<TypeSpec, List<Field>> stack_fields;
537 Dictionary<TypeSpec, List<Field>> awaiter_fields;
539 public AsyncTaskStorey (ParametersBlock block, IMemberContext context, AsyncInitializer initializer, TypeSpec type)
540 : base (block, initializer.Host, context.CurrentMemberDefinition as MemberBase, context.CurrentTypeParameters, "async", MemberKind.Struct)
543 awaiter_fields = new Dictionary<TypeSpec, List<Field>> ();
548 public bool HasAwaitInsideFinally { get; set; }
550 public Expression HoistedReturnValue { get; set; }
552 public TypeSpec ReturnType {
558 public PropertySpec Task {
564 protected override TypeAttributes TypeAttr {
566 return base.TypeAttr & ~TypeAttributes.SequentialLayout;
572 public Field AddAwaiter (TypeSpec type)
575 type = mutator.Mutate (type);
577 List<Field> existing_fields;
578 if (awaiter_fields.TryGetValue (type, out existing_fields)) {
579 foreach (var f in existing_fields) {
580 if (f.IsAvailableForReuse) {
581 f.IsAvailableForReuse = false;
587 var field = AddCompilerGeneratedField ("$awaiter" + awaiters++.ToString ("X"), new TypeExpression (type, Location), true);
590 if (existing_fields == null) {
591 existing_fields = new List<Field> ();
592 awaiter_fields.Add (type, existing_fields);
595 existing_fields.Add (field);
599 public Field AddCapturedLocalVariable (TypeSpec type, bool requiresUninitialized = false)
602 type = mutator.Mutate (type);
604 List<Field> existing_fields = null;
605 if (stack_fields == null) {
606 stack_fields = new Dictionary<TypeSpec, List<Field>> ();
607 } else if (stack_fields.TryGetValue (type, out existing_fields) && !requiresUninitialized) {
608 foreach (var f in existing_fields) {
609 if (f.IsAvailableForReuse) {
610 f.IsAvailableForReuse = false;
616 var field = AddCompilerGeneratedField ("$stack" + locals_captured++.ToString ("X"), new TypeExpression (type, Location), true);
619 if (existing_fields == null) {
620 existing_fields = new List<Field> ();
621 stack_fields.Add (type, existing_fields);
624 existing_fields.Add (field);
629 protected override bool DoDefineMembers ()
631 PredefinedType builder_type;
632 PredefinedMember<MethodSpec> bf;
633 PredefinedMember<MethodSpec> bs;
634 PredefinedMember<MethodSpec> sr;
635 PredefinedMember<MethodSpec> se;
636 PredefinedMember<MethodSpec> sm;
637 bool has_task_return_type = false;
638 var pred_members = Module.PredefinedMembers;
640 if (return_type.Kind == MemberKind.Void) {
641 builder_type = Module.PredefinedTypes.AsyncVoidMethodBuilder;
642 bf = pred_members.AsyncVoidMethodBuilderCreate;
643 bs = pred_members.AsyncVoidMethodBuilderStart;
644 sr = pred_members.AsyncVoidMethodBuilderSetResult;
645 se = pred_members.AsyncVoidMethodBuilderSetException;
646 sm = pred_members.AsyncVoidMethodBuilderSetStateMachine;
647 } else if (return_type == Module.PredefinedTypes.Task.TypeSpec) {
648 builder_type = Module.PredefinedTypes.AsyncTaskMethodBuilder;
649 bf = pred_members.AsyncTaskMethodBuilderCreate;
650 bs = pred_members.AsyncTaskMethodBuilderStart;
651 sr = pred_members.AsyncTaskMethodBuilderSetResult;
652 se = pred_members.AsyncTaskMethodBuilderSetException;
653 sm = pred_members.AsyncTaskMethodBuilderSetStateMachine;
654 task = pred_members.AsyncTaskMethodBuilderTask.Get ();
656 builder_type = Module.PredefinedTypes.AsyncTaskMethodBuilderGeneric;
657 bf = pred_members.AsyncTaskMethodBuilderGenericCreate;
658 bs = pred_members.AsyncTaskMethodBuilderGenericStart;
659 sr = pred_members.AsyncTaskMethodBuilderGenericSetResult;
660 se = pred_members.AsyncTaskMethodBuilderGenericSetException;
661 sm = pred_members.AsyncTaskMethodBuilderGenericSetStateMachine;
662 task = pred_members.AsyncTaskMethodBuilderGenericTask.Get ();
663 has_task_return_type = true;
666 set_result = sr.Get ();
667 set_exception = se.Get ();
668 builder_factory = bf.Get ();
669 builder_start = bs.Get ();
671 var istate_machine = Module.PredefinedTypes.IAsyncStateMachine;
672 var set_statemachine = sm.Get ();
674 if (!builder_type.Define () || !istate_machine.Define () || set_result == null || builder_factory == null ||
675 set_exception == null || set_statemachine == null || builder_start == null ||
676 !Module.PredefinedTypes.INotifyCompletion.Define ()) {
677 Report.Error (1993, Location,
678 "Cannot find compiler required types for asynchronous functions support. Are you targeting the wrong framework version?");
679 return base.DoDefineMembers ();
682 var bt = builder_type.TypeSpec;
685 // Inflate generic Task types
687 if (has_task_return_type) {
688 var task_return_type = return_type.TypeArguments;
690 task_return_type = mutator.Mutate (task_return_type);
692 bt = bt.MakeGenericType (Module, task_return_type);
693 set_result = MemberCache.GetMember (bt, set_result);
694 set_exception = MemberCache.GetMember (bt, set_exception);
695 set_statemachine = MemberCache.GetMember (bt, set_statemachine);
698 task = MemberCache.GetMember (bt, task);
701 builder = AddCompilerGeneratedField ("$builder", new TypeExpression (bt, Location));
704 if (has_task_return_type && HasAwaitInsideFinally) {
706 // Special case async block with return value from finally clause. In such case
707 // we rewrite all return expresison stores to stfld to $return. Instead of treating
708 // returns outside of finally and inside of finally differently.
710 rfield = AddCompilerGeneratedField ("$return", new TypeExpression (bt.TypeArguments [0], Location));
715 var set_state_machine = new Method (this, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
716 Modifiers.COMPILER_GENERATED | Modifiers.DEBUGGER_HIDDEN | Modifiers.PUBLIC,
717 new MemberName ("SetStateMachine"),
718 ParametersCompiled.CreateFullyResolved (
719 new Parameter (new TypeExpression (istate_machine.TypeSpec, Location), "stateMachine", Parameter.Modifier.NONE, null, Location),
720 istate_machine.TypeSpec),
723 ToplevelBlock block = new ToplevelBlock (Compiler, set_state_machine.ParameterInfo, Location);
724 block.IsCompilerGenerated = true;
725 set_state_machine.Block = block;
727 Members.Add (set_state_machine);
729 if (!base.DoDefineMembers ())
733 // Fabricates SetStateMachine method
735 // public void SetStateMachine (IAsyncStateMachine stateMachine)
737 // $builder.SetStateMachine (stateMachine);
740 var mg = MethodGroupExpr.CreatePredefined (set_statemachine, bt, Location);
741 mg.InstanceExpression = new FieldExpr (builder, Location);
743 var param_reference = block.GetParameterReference (0, Location);
744 param_reference.Type = istate_machine.TypeSpec;
745 param_reference.eclass = ExprClass.Variable;
747 var args = new Arguments (1);
748 args.Add (new Argument (param_reference));
749 set_state_machine.Block.AddStatement (new StatementExpression (new Invocation (mg, args)));
751 if (has_task_return_type) {
752 if (rfield != null) {
753 HoistedReturnValue = new FieldExpr (rfield, Location) {
754 InstanceExpression = new CompilerGeneratedThis (CurrentType, Location.Null)
757 HoistedReturnValue = TemporaryVariableReference.Create (bt.TypeArguments [0], StateMachineMethod.Block, Location);
764 public void EmitAwaitOnCompletedDynamic (EmitContext ec, FieldExpr awaiter)
766 var critical = Module.PredefinedTypes.ICriticalNotifyCompletion;
767 if (!critical.Define ()) {
768 throw new NotImplementedException ();
771 var temp_critical = new LocalTemporary (critical.TypeSpec);
772 var label_critical = ec.DefineLabel ();
773 var label_end = ec.DefineLabel ();
776 // Special path for dynamic awaiters
778 // var awaiter = this.$awaiter as ICriticalNotifyCompletion;
779 // if (awaiter == null) {
780 // var completion = (INotifyCompletion) this.$awaiter;
781 // this.$builder.AwaitOnCompleted (ref completion, ref this);
783 // this.$builder.AwaitUnsafeOnCompleted (ref awaiter, ref this);
787 ec.Emit (OpCodes.Isinst, critical.TypeSpec);
788 temp_critical.Store (ec);
789 temp_critical.Emit (ec);
790 ec.Emit (OpCodes.Brtrue_S, label_critical);
792 var temp = new LocalTemporary (Module.PredefinedTypes.INotifyCompletion.TypeSpec);
794 ec.Emit (OpCodes.Castclass, temp.Type);
796 EmitOnCompleted (ec, temp, false);
798 ec.Emit (OpCodes.Br_S, label_end);
800 ec.MarkLabel (label_critical);
802 EmitOnCompleted (ec, temp_critical, true);
804 ec.MarkLabel (label_end);
806 temp_critical.Release (ec);
809 public void EmitAwaitOnCompleted (EmitContext ec, FieldExpr awaiter)
811 bool unsafe_version = false;
812 if (Module.PredefinedTypes.ICriticalNotifyCompletion.Define ()) {
813 unsafe_version = awaiter.Type.ImplementsInterface (Module.PredefinedTypes.ICriticalNotifyCompletion.TypeSpec, false);
816 EmitOnCompleted (ec, awaiter, unsafe_version);
819 void EmitOnCompleted (EmitContext ec, Expression awaiter, bool unsafeVersion)
821 var pm = Module.PredefinedMembers;
822 PredefinedMember<MethodSpec> predefined;
823 bool has_task_return_type = false;
824 if (return_type.Kind == MemberKind.Void) {
825 predefined = unsafeVersion ? pm.AsyncVoidMethodBuilderOnCompletedUnsafe : pm.AsyncVoidMethodBuilderOnCompleted;
826 } else if (return_type == Module.PredefinedTypes.Task.TypeSpec) {
827 predefined = unsafeVersion ? pm.AsyncTaskMethodBuilderOnCompletedUnsafe : pm.AsyncTaskMethodBuilderOnCompleted;
829 predefined = unsafeVersion ? pm.AsyncTaskMethodBuilderGenericOnCompletedUnsafe : pm.AsyncTaskMethodBuilderGenericOnCompleted;
830 has_task_return_type = true;
833 var on_completed = predefined.Resolve (Location);
834 if (on_completed == null)
837 if (has_task_return_type)
838 on_completed = MemberCache.GetMember<MethodSpec> (set_result.DeclaringType, on_completed);
840 on_completed = on_completed.MakeGenericMethod (this, awaiter.Type, ec.CurrentType);
842 var mg = MethodGroupExpr.CreatePredefined (on_completed, on_completed.DeclaringType, Location);
843 mg.InstanceExpression = new FieldExpr (builder, Location) {
844 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
847 var args = new Arguments (2);
848 args.Add (new Argument (awaiter, Argument.AType.Ref));
849 args.Add (new Argument (new CompilerGeneratedThis (CurrentType, Location), Argument.AType.Ref));
850 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
851 mg.EmitCall (ec, args, true);
855 public void EmitInitializer (EmitContext ec)
858 // Some predefined types are missing
863 var instance = (TemporaryVariableReference) Instance;
864 var builder_field = builder.Spec;
865 if (MemberName.Arity > 0) {
866 builder_field = MemberCache.GetMember (instance.Type, builder_field);
870 // Inflated factory method when task is of generic type
872 if (builder_factory.DeclaringType.IsGeneric) {
873 var task_return_type = return_type.TypeArguments;
874 var bt = builder_factory.DeclaringType.MakeGenericType (Module, task_return_type);
875 builder_factory = MemberCache.GetMember (bt, builder_factory);
876 builder_start = MemberCache.GetMember (bt, builder_start);
880 // stateMachine.$builder = AsyncTaskMethodBuilder<{task-type}>.Create();
882 instance.AddressOf (ec, AddressOp.Store);
883 ec.Emit (OpCodes.Call, builder_factory);
884 ec.Emit (OpCodes.Stfld, builder_field);
887 // stateMachine.$builder.Start<{storey-type}>(ref stateMachine);
889 instance.AddressOf (ec, AddressOp.Store);
890 ec.Emit (OpCodes.Ldflda, builder_field);
892 ec.Emit (OpCodes.Dup);
893 instance.AddressOf (ec, AddressOp.Store);
894 ec.Emit (OpCodes.Call, builder_start.MakeGenericMethod (Module, instance.Type));
897 // Emits return stateMachine.$builder.Task;
900 var task_get = Task.Get;
902 if (MemberName.Arity > 0) {
903 task_get = MemberCache.GetMember (builder_field.MemberType, task_get);
906 var pe_task = new PropertyExpr (Task, Location) {
907 InstanceExpression = EmptyExpression.Null, // Comes from the dup above
915 public void EmitSetException (EmitContext ec, LocalVariableReference exceptionVariable)
918 // $builder.SetException (Exception)
920 var mg = MethodGroupExpr.CreatePredefined (set_exception, set_exception.DeclaringType, Location);
921 mg.InstanceExpression = new FieldExpr (builder, Location) {
922 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
925 Arguments args = new Arguments (1);
926 args.Add (new Argument (exceptionVariable));
928 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
929 mg.EmitCall (ec, args, true);
933 public void EmitSetResult (EmitContext ec)
936 // $builder.SetResult ();
937 // $builder.SetResult<return-type> (value);
939 var mg = MethodGroupExpr.CreatePredefined (set_result, set_result.DeclaringType, Location);
940 mg.InstanceExpression = new FieldExpr (builder, Location) {
941 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
945 if (HoistedReturnValue == null) {
946 args = new Arguments (0);
948 args = new Arguments (1);
949 args.Add (new Argument (HoistedReturnValue));
952 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
953 mg.EmitCall (ec, args, true);
957 protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
959 base_type = Compiler.BuiltinTypes.ValueType;
962 var istate_machine = Module.PredefinedTypes.IAsyncStateMachine;
963 if (istate_machine.Define ()) {
964 return new[] { istate_machine.TypeSpec };
971 public class StackFieldExpr : FieldExpr, IExpressionCleanup
973 public StackFieldExpr (Field field)
974 : base (field, Location.Null)
976 AutomaticallyReuse = true;
979 public bool AutomaticallyReuse { get; set; }
981 public bool IsAvailableForReuse {
983 var field = (Field) spec.MemberDefinition;
984 return field.IsAvailableForReuse;
987 var field = (Field) spec.MemberDefinition;
988 field.IsAvailableForReuse = value;
992 public override void AddressOf (EmitContext ec, AddressOp mode)
994 base.AddressOf (ec, mode);
996 if (mode == AddressOp.Load && AutomaticallyReuse) {
997 IsAvailableForReuse = true;
1001 public override void Emit (EmitContext ec)
1005 if (AutomaticallyReuse)
1006 PrepareCleanup (ec);
1009 public void EmitLoad (EmitContext ec)
1014 public void PrepareCleanup (EmitContext ec)
1016 IsAvailableForReuse = true;
1019 // Release any captured reference type stack variables
1020 // to imitate real stack behavour and help GC stuff early
1022 if (TypeSpec.IsReferenceType (type)) {
1023 ec.AddStatementEpilog (this);
1027 void IExpressionCleanup.EmitCleanup (EmitContext ec)
1029 EmitAssign (ec, new NullConstant (type, loc), false, false);