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 Xamarin Inc.
14 using System.Collections.Generic;
16 using System.Collections;
19 using IKVM.Reflection.Emit;
21 using System.Reflection.Emit;
26 public class Await : ExpressionStatement
31 public Await (Expression expr, Location loc)
37 public Expression Expr {
43 public AwaitStatement Statement {
49 protected override void CloneTo (CloneContext clonectx, Expression target)
51 var t = (Await) target;
53 t.expr = expr.Clone (clonectx);
56 public override Expression CreateExpressionTree (ResolveContext ec)
58 throw new NotImplementedException ("ET");
61 public override bool ContainsEmitWithAwait ()
66 protected override Expression DoResolve (ResolveContext rc)
68 if (rc.HasSet (ResolveContext.Options.LockScope)) {
69 rc.Report.Error (1996, loc,
70 "The `await' operator cannot be used in the body of a lock statement");
74 rc.Report.Error (4004, loc,
75 "The `await' operator cannot be used in an unsafe context");
78 var bc = (BlockContext) rc;
80 stmt = new AwaitStatement (expr, loc);
81 if (!stmt.Resolve (bc))
84 type = stmt.ResultType;
85 eclass = ExprClass.Variable;
89 public override void Emit (EmitContext ec)
91 stmt.EmitPrologue (ec);
93 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
98 public override Expression EmitToField (EmitContext ec)
100 stmt.EmitPrologue (ec);
101 return stmt.GetResultExpression (ec);
104 public void EmitAssign (EmitContext ec, FieldExpr field)
106 stmt.EmitPrologue (ec);
107 field.InstanceExpression.Emit (ec);
111 public override void EmitStatement (EmitContext ec)
113 stmt.EmitStatement (ec);
116 public override object Accept (StructuralVisitor visitor)
118 return visitor.Visit (this);
122 public class AwaitStatement : YieldStatement<AsyncInitializer>
124 sealed class AwaitableMemberAccess : MemberAccess
126 public AwaitableMemberAccess (Expression expr)
127 : base (expr, "GetAwaiter")
131 protected override void Error_TypeDoesNotContainDefinition (ResolveContext rc, TypeSpec type, string name)
133 Error_OperatorCannotBeApplied (rc, type);
136 protected override void Error_OperatorCannotBeApplied (ResolveContext rc, TypeSpec type)
138 var invocation = LeftExpression as Invocation;
139 if (invocation != null && invocation.MethodGroup != null && (invocation.MethodGroup.BestCandidate.Modifiers & Modifiers.ASYNC) != 0) {
140 rc.Report.Error (4008, loc, "Cannot await void method `{0}'. Consider changing method return type to `Task'",
141 invocation.GetSignatureForError ());
143 rc.Report.Error (4001, loc, "Cannot await `{0}' expression", type.GetSignatureForError ());
148 sealed class GetResultInvocation : Invocation
150 public GetResultInvocation (MethodGroupExpr mge, Arguments arguments)
151 : base (null, arguments)
154 type = mg.BestCandidateReturnType;
157 public override Expression EmitToField (EmitContext ec)
164 PropertySpec is_completed;
165 MethodSpec get_result;
167 TypeSpec result_type;
169 public AwaitStatement (Expression expr, Location loc)
178 return is_completed == null;
182 public TypeSpec ResultType {
190 protected override void DoEmit (EmitContext ec)
192 GetResultExpression (ec).Emit (ec);
195 public Expression GetResultExpression (EmitContext ec)
197 var fe_awaiter = new FieldExpr (awaiter, loc);
198 fe_awaiter.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
201 // result = awaiter.GetResult ();
204 var rc = new ResolveContext (ec.MemberContext);
205 return new Invocation (new MemberAccess (fe_awaiter, "GetResult"), new Arguments (0)).Resolve (rc);
207 var mg_result = MethodGroupExpr.CreatePredefined (get_result, fe_awaiter.Type, loc);
208 mg_result.InstanceExpression = fe_awaiter;
210 return new GetResultInvocation (mg_result, new Arguments (0));
214 public void EmitPrologue (EmitContext ec)
216 awaiter = ((AsyncTaskStorey) machine_initializer.Storey).AddAwaiter (expr.Type, loc);
218 var fe_awaiter = new FieldExpr (awaiter, loc);
219 fe_awaiter.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
222 // awaiter = expr.GetAwaiter ();
224 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
225 fe_awaiter.EmitAssign (ec, expr, false, false);
228 Label skip_continuation = ec.DefineLabel ();
230 Expression completed_expr;
232 var rc = new ResolveContext (ec.MemberContext);
234 Arguments dargs = new Arguments (1);
235 dargs.Add (new Argument (fe_awaiter));
236 completed_expr = new DynamicMemberBinder ("IsCompleted", dargs, loc).Resolve (rc);
238 dargs = new Arguments (1);
239 dargs.Add (new Argument (completed_expr));
240 completed_expr = new DynamicConversion (ec.Module.Compiler.BuiltinTypes.Bool, 0, dargs, loc).Resolve (rc);
242 var pe = PropertyExpr.CreatePredefined (is_completed, loc);
243 pe.InstanceExpression = fe_awaiter;
247 completed_expr.EmitBranchable (ec, skip_continuation, true);
252 // The stack has to be empty before calling await continuation. We handle this
253 // by lifting values which would be left on stack into class fields. The process
254 // is quite complicated and quite hard to test because any expression can possibly
255 // leave a value on the stack.
257 // Following assert fails when some of expression called before is missing EmitToField
258 // or parent expression fails to find await in children expressions
260 ec.AssertEmptyStack ();
262 var storey = (AsyncTaskStorey) machine_initializer.Storey;
264 storey.EmitAwaitOnCompletedDynamic (ec, fe_awaiter);
266 storey.EmitAwaitOnCompleted (ec, fe_awaiter);
270 machine_initializer.EmitLeave (ec, unwind_protect);
272 ec.MarkLabel (resume_point);
273 ec.MarkLabel (skip_continuation);
276 public void EmitStatement (EmitContext ec)
281 awaiter.IsAvailableForReuse = true;
283 if (ResultType.Kind != MemberKind.Void)
284 ec.Emit (OpCodes.Pop);
287 void Error_WrongAwaiterPattern (ResolveContext rc, TypeSpec awaiter)
289 rc.Report.Error (4011, loc, "The awaiter type `{0}' must have suitable IsCompleted and GetResult members",
290 awaiter.GetSignatureForError ());
293 public override bool Resolve (BlockContext bc)
295 if (bc.CurrentBlock is Linq.QueryBlock) {
296 bc.Report.Error (1995, loc,
297 "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");
301 if (!base.Resolve (bc))
304 Arguments args = new Arguments (0);
309 // The await expression is of dynamic type
311 if (type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
313 expr = new Invocation (new MemberAccess (expr, "GetAwaiter"), args).Resolve (bc);
318 // Check whether the expression is awaitable
320 Expression ama = new AwaitableMemberAccess (expr).Resolve (bc);
324 var errors_printer = new SessionReportPrinter ();
325 var old = bc.Report.SetPrinter (errors_printer);
326 ama = new Invocation (ama, args).Resolve (bc);
327 bc.Report.SetPrinter (old);
329 if (errors_printer.ErrorsCount > 0 || !MemberAccess.IsValidDotExpression (ama.Type)) {
330 bc.Report.Error (1986, expr.Location,
331 "The `await' operand type `{0}' must have suitable GetAwaiter method",
332 expr.Type.GetSignatureForError ());
337 var awaiter_type = ama.Type;
341 // Predefined: bool IsCompleted { get; }
343 is_completed = MemberCache.FindMember (awaiter_type, MemberFilter.Property ("IsCompleted", bc.Module.Compiler.BuiltinTypes.Bool),
344 BindingRestriction.InstanceOnly) as PropertySpec;
346 if (is_completed == null || !is_completed.HasGet) {
347 Error_WrongAwaiterPattern (bc, awaiter_type);
352 // Predefined: GetResult ()
354 // The method return type is also result type of await expression
356 get_result = MemberCache.FindMember (awaiter_type, MemberFilter.Method ("GetResult", 0,
357 ParametersCompiled.EmptyReadOnlyParameters, null),
358 BindingRestriction.InstanceOnly) as MethodSpec;
360 if (get_result == null) {
361 Error_WrongAwaiterPattern (bc, awaiter_type);
366 // Predefined: INotifyCompletion.OnCompleted (System.Action)
368 var nc = bc.Module.PredefinedTypes.INotifyCompletion;
369 if (nc.Define () && !awaiter_type.ImplementsInterface (nc.TypeSpec, false)) {
370 bc.Report.Error (4027, loc, "The awaiter type `{0}' must implement interface `{1}'",
371 awaiter_type.GetSignatureForError (), nc.GetSignatureForError ());
375 result_type = get_result.ReturnType;
381 public class AsyncInitializer : StateMachineInitializer
383 TypeInferenceContext return_inference;
385 public AsyncInitializer (ParametersBlock block, TypeDefinition host, TypeSpec returnType)
386 : base (block, host, returnType)
392 public override string ContainerType {
394 return "async state machine block";
398 public override bool IsIterator {
404 public TypeInferenceContext ReturnTypeInference {
406 return return_inference;
412 protected override BlockContext CreateBlockContext (ResolveContext rc)
414 var ctx = base.CreateBlockContext (rc);
415 var lambda = rc.CurrentAnonymousMethod as LambdaMethod;
417 return_inference = lambda.ReturnTypeInference;
419 ctx.StartFlowBranching (this, rc.CurrentBranching);
423 public override Expression CreateExpressionTree (ResolveContext ec)
425 return base.CreateExpressionTree (ec);
428 public override void Emit (EmitContext ec)
430 throw new NotImplementedException ();
433 protected override void EmitMoveNextEpilogue (EmitContext ec)
435 var storey = (AsyncTaskStorey) Storey;
436 storey.EmitSetResult (ec);
439 public override void EmitStatement (EmitContext ec)
441 var storey = (AsyncTaskStorey) Storey;
442 storey.EmitInitializer (ec);
443 ec.Emit (OpCodes.Ret);
447 class AsyncTaskStorey : StateMachine
451 readonly TypeSpec return_type;
452 MethodSpec set_result;
453 MethodSpec set_exception;
454 MethodSpec builder_factory;
455 MethodSpec builder_start;
457 LocalVariable hoisted_return;
459 Dictionary<TypeSpec, List<Field>> stack_fields;
460 Dictionary<TypeSpec, List<Field>> awaiter_fields;
462 public AsyncTaskStorey (ParametersBlock block, IMemberContext context, AsyncInitializer initializer, TypeSpec type)
463 : base (block, initializer.Host, context.CurrentMemberDefinition as MemberBase, context.CurrentTypeParameters, "async", MemberKind.Struct)
466 awaiter_fields = new Dictionary<TypeSpec, List<Field>> ();
471 public LocalVariable HoistedReturn {
473 return hoisted_return;
477 public TypeSpec ReturnType {
483 public PropertySpec Task {
491 public Field AddAwaiter (TypeSpec type, Location loc)
494 type = mutator.Mutate (type);
496 List<Field> existing_fields = null;
497 if (awaiter_fields.TryGetValue (type, out existing_fields)) {
498 foreach (var f in existing_fields) {
499 if (f.IsAvailableForReuse) {
500 f.IsAvailableForReuse = false;
506 var field = AddCompilerGeneratedField ("$awaiter" + awaiters++.ToString ("X"), new TypeExpression (type, Location), true);
509 if (existing_fields == null) {
510 existing_fields = new List<Field> ();
511 awaiter_fields.Add (type, existing_fields);
514 existing_fields.Add (field);
518 public Field AddCapturedLocalVariable (TypeSpec type)
521 type = mutator.Mutate (type);
523 List<Field> existing_fields = null;
524 if (stack_fields == null) {
525 stack_fields = new Dictionary<TypeSpec, List<Field>> ();
526 } else if (stack_fields.TryGetValue (type, out existing_fields)) {
527 foreach (var f in existing_fields) {
528 if (f.IsAvailableForReuse) {
529 f.IsAvailableForReuse = false;
535 var field = AddCompilerGeneratedField ("$stack" + locals_captured++.ToString ("X"), new TypeExpression (type, Location), true);
538 if (existing_fields == null) {
539 existing_fields = new List<Field> ();
540 stack_fields.Add (type, existing_fields);
543 existing_fields.Add (field);
548 protected override bool DoDefineMembers ()
550 PredefinedType builder_type;
551 PredefinedMember<MethodSpec> bf;
552 PredefinedMember<MethodSpec> bs;
553 PredefinedMember<MethodSpec> sr;
554 PredefinedMember<MethodSpec> se;
555 PredefinedMember<MethodSpec> sm;
556 bool has_task_return_type = false;
557 var pred_members = Module.PredefinedMembers;
559 if (return_type.Kind == MemberKind.Void) {
560 builder_type = Module.PredefinedTypes.AsyncVoidMethodBuilder;
561 bf = pred_members.AsyncVoidMethodBuilderCreate;
562 bs = pred_members.AsyncVoidMethodBuilderStart;
563 sr = pred_members.AsyncVoidMethodBuilderSetResult;
564 se = pred_members.AsyncVoidMethodBuilderSetException;
565 sm = pred_members.AsyncVoidMethodBuilderSetStateMachine;
566 } else if (return_type == Module.PredefinedTypes.Task.TypeSpec) {
567 builder_type = Module.PredefinedTypes.AsyncTaskMethodBuilder;
568 bf = pred_members.AsyncTaskMethodBuilderCreate;
569 bs = pred_members.AsyncTaskMethodBuilderStart;
570 sr = pred_members.AsyncTaskMethodBuilderSetResult;
571 se = pred_members.AsyncTaskMethodBuilderSetException;
572 sm = pred_members.AsyncTaskMethodBuilderSetStateMachine;
573 task = pred_members.AsyncTaskMethodBuilderTask.Get ();
575 builder_type = Module.PredefinedTypes.AsyncTaskMethodBuilderGeneric;
576 bf = pred_members.AsyncTaskMethodBuilderGenericCreate;
577 bs = pred_members.AsyncTaskMethodBuilderGenericStart;
578 sr = pred_members.AsyncTaskMethodBuilderGenericSetResult;
579 se = pred_members.AsyncTaskMethodBuilderGenericSetException;
580 sm = pred_members.AsyncTaskMethodBuilderGenericSetStateMachine;
581 task = pred_members.AsyncTaskMethodBuilderGenericTask.Get ();
582 has_task_return_type = true;
585 set_result = sr.Get ();
586 set_exception = se.Get ();
587 builder_factory = bf.Get ();
588 builder_start = bs.Get ();
590 var istate_machine = Module.PredefinedTypes.IAsyncStateMachine;
591 var set_statemachine = sm.Get ();
593 if (!builder_type.Define () || !istate_machine.Define () || set_result == null || builder_factory == null ||
594 set_exception == null || set_statemachine == null || builder_start == null ||
595 !Module.PredefinedTypes.INotifyCompletion.Define ()) {
596 Report.Error (1993, Location,
597 "Cannot find compiler required types for asynchronous functions support. Are you targeting the wrong framework version?");
598 return base.DoDefineMembers ();
601 var bt = builder_type.TypeSpec;
604 // Inflate generic Task types
606 if (has_task_return_type) {
607 var task_return_type = return_type.TypeArguments;
609 task_return_type = mutator.Mutate (task_return_type);
611 bt = bt.MakeGenericType (Module, task_return_type);
612 set_result = MemberCache.GetMember (bt, set_result);
613 set_exception = MemberCache.GetMember (bt, set_exception);
614 set_statemachine = MemberCache.GetMember (bt, set_statemachine);
617 task = MemberCache.GetMember (bt, task);
620 builder = AddCompilerGeneratedField ("$builder", new TypeExpression (bt, Location));
622 var set_state_machine = new Method (this, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
623 Modifiers.COMPILER_GENERATED | Modifiers.DEBUGGER_HIDDEN | Modifiers.PUBLIC,
624 new MemberName ("SetStateMachine"),
625 ParametersCompiled.CreateFullyResolved (
626 new Parameter (new TypeExpression (istate_machine.TypeSpec, Location), "stateMachine", Parameter.Modifier.NONE, null, Location),
627 istate_machine.TypeSpec),
630 ToplevelBlock block = new ToplevelBlock (Compiler, set_state_machine.ParameterInfo, Location);
631 block.IsCompilerGenerated = true;
632 set_state_machine.Block = block;
634 Members.Add (set_state_machine);
636 if (!base.DoDefineMembers ())
640 // Fabricates SetStateMachine method
642 // public void SetStateMachine (IAsyncStateMachine stateMachine)
644 // $builder.SetStateMachine (stateMachine);
647 var mg = MethodGroupExpr.CreatePredefined (set_statemachine, bt, Location);
648 mg.InstanceExpression = new FieldExpr (builder, Location);
650 var param_reference = block.GetParameterReference (0, Location);
651 param_reference.Type = istate_machine.TypeSpec;
652 param_reference.eclass = ExprClass.Variable;
654 var args = new Arguments (1);
655 args.Add (new Argument (param_reference));
656 set_state_machine.Block.AddStatement (new StatementExpression (new Invocation (mg, args)));
658 if (has_task_return_type) {
659 hoisted_return = LocalVariable.CreateCompilerGenerated (bt.TypeArguments[0], StateMachineMethod.Block, Location);
665 public void EmitAwaitOnCompletedDynamic (EmitContext ec, FieldExpr awaiter)
667 var critical = Module.PredefinedTypes.ICriticalNotifyCompletion;
668 if (!critical.Define ()) {
669 throw new NotImplementedException ();
672 var temp_critical = new LocalTemporary (critical.TypeSpec);
673 var label_critical = ec.DefineLabel ();
674 var label_end = ec.DefineLabel ();
677 // Special path for dynamic awaiters
679 // var awaiter = this.$awaiter as ICriticalNotifyCompletion;
680 // if (awaiter == null) {
681 // var completion = (INotifyCompletion) this.$awaiter;
682 // this.$builder.AwaitOnCompleted (ref completion, ref this);
684 // this.$builder.AwaitUnsafeOnCompleted (ref awaiter, ref this);
688 ec.Emit (OpCodes.Isinst, critical.TypeSpec);
689 temp_critical.Store (ec);
690 temp_critical.Emit (ec);
691 ec.Emit (OpCodes.Brtrue_S, label_critical);
693 var temp = new LocalTemporary (Module.PredefinedTypes.INotifyCompletion.TypeSpec);
695 ec.Emit (OpCodes.Castclass, temp.Type);
697 EmitOnCompleted (ec, temp, false);
699 ec.Emit (OpCodes.Br_S, label_end);
701 ec.MarkLabel (label_critical);
703 EmitOnCompleted (ec, temp_critical, true);
705 ec.MarkLabel (label_end);
707 temp_critical.Release (ec);
710 public void EmitAwaitOnCompleted (EmitContext ec, FieldExpr awaiter)
712 bool unsafe_version = false;
713 if (Module.PredefinedTypes.ICriticalNotifyCompletion.Define ()) {
714 unsafe_version = awaiter.Type.ImplementsInterface (Module.PredefinedTypes.ICriticalNotifyCompletion.TypeSpec, false);
717 EmitOnCompleted (ec, awaiter, unsafe_version);
720 void EmitOnCompleted (EmitContext ec, Expression awaiter, bool unsafeVersion)
722 var pm = Module.PredefinedMembers;
723 PredefinedMember<MethodSpec> predefined;
724 bool has_task_return_type = false;
725 if (return_type.Kind == MemberKind.Void) {
726 predefined = unsafeVersion ? pm.AsyncVoidMethodBuilderOnCompletedUnsafe : pm.AsyncVoidMethodBuilderOnCompleted;
727 } else if (return_type == Module.PredefinedTypes.Task.TypeSpec) {
728 predefined = unsafeVersion ? pm.AsyncTaskMethodBuilderOnCompletedUnsafe : pm.AsyncTaskMethodBuilderOnCompleted;
730 predefined = unsafeVersion ? pm.AsyncTaskMethodBuilderGenericOnCompletedUnsafe : pm.AsyncTaskMethodBuilderGenericOnCompleted;
731 has_task_return_type = true;
734 var on_completed = predefined.Resolve (Location);
735 if (on_completed == null)
738 if (has_task_return_type)
739 on_completed = MemberCache.GetMember<MethodSpec> (set_result.DeclaringType, on_completed);
741 on_completed = on_completed.MakeGenericMethod (this, awaiter.Type, ec.CurrentType);
743 var mg = MethodGroupExpr.CreatePredefined (on_completed, on_completed.DeclaringType, Location);
744 mg.InstanceExpression = new FieldExpr (builder, Location) {
745 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
748 var args = new Arguments (2);
749 args.Add (new Argument (awaiter, Argument.AType.Ref));
750 args.Add (new Argument (new CompilerGeneratedThis (CurrentType, Location), Argument.AType.Ref));
751 mg.EmitCall (ec, args);
754 public void EmitInitializer (EmitContext ec)
757 // Some predefined types are missing
762 var instance = (TemporaryVariableReference) Instance;
763 var builder_field = builder.Spec;
764 if (MemberName.Arity > 0) {
765 builder_field = MemberCache.GetMember (instance.Type, builder_field);
769 // Inflated factory method when task is of generic type
771 if (builder_factory.DeclaringType.IsGeneric) {
772 var task_return_type = return_type.TypeArguments;
773 var bt = builder_factory.DeclaringType.MakeGenericType (Module, task_return_type);
774 builder_factory = MemberCache.GetMember (bt, builder_factory);
775 builder_start = MemberCache.GetMember (bt, builder_start);
779 // stateMachine.$builder = AsyncTaskMethodBuilder<{task-type}>.Create();
781 instance.AddressOf (ec, AddressOp.Store);
782 ec.Emit (OpCodes.Call, builder_factory);
783 ec.Emit (OpCodes.Stfld, builder_field);
786 // stateMachine.$builder.Start<{storey-type}>(ref stateMachine);
788 instance.AddressOf (ec, AddressOp.Store);
789 ec.Emit (OpCodes.Ldflda, builder_field);
791 ec.Emit (OpCodes.Dup);
792 instance.AddressOf (ec, AddressOp.Store);
793 ec.Emit (OpCodes.Call, builder_start.MakeGenericMethod (Module, instance.Type));
796 // Emits return stateMachine.$builder.Task;
799 var task_get = Task.Get;
801 if (MemberName.Arity > 0) {
802 task_get = MemberCache.GetMember (builder_field.MemberType, task_get);
805 var pe_task = new PropertyExpr (Task, Location) {
806 InstanceExpression = EmptyExpression.Null, // Comes from the dup above
814 public void EmitSetException (EmitContext ec, LocalVariableReference exceptionVariable)
817 // $builder.SetException (Exception)
819 var mg = MethodGroupExpr.CreatePredefined (set_exception, set_exception.DeclaringType, Location);
820 mg.InstanceExpression = new FieldExpr (builder, Location) {
821 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
824 Arguments args = new Arguments (1);
825 args.Add (new Argument (exceptionVariable));
827 mg.EmitCall (ec, args);
830 public void EmitSetResult (EmitContext ec)
833 // $builder.SetResult ();
834 // $builder.SetResult<return-type> (value);
836 var mg = MethodGroupExpr.CreatePredefined (set_result, set_result.DeclaringType, Location);
837 mg.InstanceExpression = new FieldExpr (builder, Location) {
838 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
842 if (hoisted_return == null) {
843 args = new Arguments (0);
845 args = new Arguments (1);
846 args.Add (new Argument (new LocalVariableReference (hoisted_return, Location)));
849 mg.EmitCall (ec, args);
852 protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
854 base_type = Compiler.BuiltinTypes.ValueType;
857 var istate_machine = Module.PredefinedTypes.IAsyncStateMachine;
858 if (istate_machine.Define ()) {
859 return new[] { istate_machine.TypeSpec };
866 class StackFieldExpr : FieldExpr, IExpressionCleanup
868 public StackFieldExpr (Field field)
869 : base (field, Location.Null)
873 public override void AddressOf (EmitContext ec, AddressOp mode)
875 base.AddressOf (ec, mode);
877 if (mode == AddressOp.Load) {
878 var field = (Field) spec.MemberDefinition;
879 field.IsAvailableForReuse = true;
883 public override void Emit (EmitContext ec)
887 var field = (Field) spec.MemberDefinition;
888 field.IsAvailableForReuse = true;
891 // Release any captured reference type stack variables
892 // to imitate real stack behavour and help GC stuff early
894 if (TypeSpec.IsReferenceType (type)) {
895 ec.AddStatementEpilog (this);
899 void IExpressionCleanup.EmitCleanup (EmitContext ec)
901 EmitAssign (ec, new NullConstant (type, loc), false, false);