mcs/mcs/async.cs

   1 //
   2 // async.cs: Asynchronous functions
   3 //
   4 // Author:
   5 //   Marek Safar (marek.safar@gmail.com)
   6 //
   7 // Dual licensed under the terms of the MIT X11 or GNU GPL
   8 //
   9 // Copyright 2011 Novell, Inc.
  10 // Copyright 2011-2012 Xamarin Inc.
  11 //
  12
  13 using System;
  14 using System.Collections.Generic;
  15 using System.Linq;
  16 using System.Collections;
  17
  18 #if STATIC
  19 using IKVM.Reflection;
  20 using IKVM.Reflection.Emit;
  21 #else
  22 using System.Reflection;
  23 using System.Reflection.Emit;
  24 #endif
  25
  26 namespace Mono.CSharp
  27 {
  28         public class Await : ExpressionStatement
  29         {
  30                 Expression expr;
  31                 AwaitStatement stmt;
  32
  33                 public Await (Expression expr, Location loc)
  34                 {
  35                         this.expr = expr;
  36                         this.loc = loc;
  37                 }
  38
  39                 public Expression Expr {
  40                         get {
  41                                 return expr;
  42                         }
  43                 }
  44
  45                 public AwaitStatement Statement {
  46                         get {
  47                                 return stmt;
  48                         }
  49                 }
  50
  51                 protected override void CloneTo (CloneContext clonectx, Expression target)
  52                 {
  53                         var t = (Await) target;
  54
  55                         t.expr = expr.Clone (clonectx);
  56                 }
  57
  58                 public override Expression CreateExpressionTree (ResolveContext ec)
  59                 {
  60                         throw new NotImplementedException ("ET");
  61                 }
  62
  63                 public override bool ContainsEmitWithAwait ()
  64                 {
  65                         return true;
  66                 }
  67
  68                 public override void FlowAnalysis (FlowAnalysisContext fc)
  69                 {
  70                         stmt.Expr.FlowAnalysis (fc);
  71
  72                         stmt.RegisterResumePoint ();
  73                 }
  74
  75                 protected override Expression DoResolve (ResolveContext rc)
  76                 {
  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");
  80                         }
  81
  82                         if (rc.IsUnsafe) {
  83                                 rc.Report.Error (4004, loc,
  84                                         "The `await' operator cannot be used in an unsafe context");
  85                         }
  86
  87                         var bc = (BlockContext) rc;
  88
  89                         stmt = new AwaitStatement (expr, loc);
  90                         if (!stmt.Resolve (bc))
  91                                 return null;
  92
  93                         if (rc.HasSet (ResolveContext.Options.FinallyScope) && rc.CurrentAnonymousMethod != null) {
  94                                 var ats = (AsyncTaskStorey)rc.CurrentAnonymousMethod.Storey;
  95                                 ats.HasAwaitInsideFinally = true;
  96                         }
  97
  98                         type = stmt.ResultType;
  99                         eclass = ExprClass.Variable;
 100                         return this;
 101                 }
 102
 103                 public override void Emit (EmitContext ec)
 104                 {
 105                         stmt.EmitPrologue (ec);
 106
 107                         using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
 108                                 stmt.Emit (ec);
 109                         }
 110                 }
 111
 112                 public override Expression EmitToField (EmitContext ec)
 113                 {
 114                         stmt.EmitPrologue (ec);
 115                         return stmt.GetResultExpression (ec);
 116                 }
 117
 118                 public void EmitAssign (EmitContext ec, FieldExpr field)
 119                 {
 120                         stmt.EmitPrologue (ec);
 121                         field.InstanceExpression.Emit (ec);
 122                         stmt.Emit (ec);
 123                 }
 124
 125                 public override void EmitStatement (EmitContext ec)
 126                 {
 127                         stmt.EmitStatement (ec);
 128                 }
 129
 130                 public override void MarkReachable (Reachability rc)
 131                 {
 132                         base.MarkReachable (rc);
 133                         stmt.MarkReachable (rc);
 134                 }
 135
 136                 public override object Accept (StructuralVisitor visitor)
 137                 {
 138                         return visitor.Visit (this);
 139                 }
 140         }
 141
 142         public class AwaitStatement : YieldStatement<AsyncInitializer>
 143         {
 144                 public sealed class AwaitableMemberAccess : MemberAccess
 145                 {
 146                         public AwaitableMemberAccess (Expression expr)
 147                                 : base (expr, "GetAwaiter")
 148                         {
 149                         }
 150
 151                         public bool ProbingMode { get; set; }
 152
 153                         public override void Error_TypeDoesNotContainDefinition (ResolveContext rc, TypeSpec type, string name)
 154                         {
 155                                 Error_OperatorCannotBeApplied (rc, type);
 156                         }
 157
 158                         protected override void Error_OperatorCannotBeApplied (ResolveContext rc, TypeSpec type)
 159                         {
 160                                 if (ProbingMode)
 161                                         return;
 162
 163                                 var invocation = LeftExpression as Invocation;
 164                                 if (invocation != null && invocation.MethodGroup != null && (invocation.MethodGroup.BestCandidate.Modifiers & Modifiers.ASYNC) != 0) {
 165                                         rc.Report.Error (4008, loc, "Cannot await void method `{0}'. Consider changing method return type to `Task'",
 166                                                 invocation.GetSignatureForError ());
 167                                 } else if (type != InternalType.ErrorType) {
 168                                         rc.Report.Error (4001, loc, "Cannot await `{0}' expression", type.GetSignatureForError ());
 169                                 }
 170                         }
 171                 }
 172
 173                 sealed class GetResultInvocation : Invocation
 174                 {
 175                         public GetResultInvocation (MethodGroupExpr mge, Arguments arguments)
 176                                 : base (null, arguments)
 177                         {
 178                                 mg = mge;
 179                                 type = mg.BestCandidateReturnType;
 180                         }
 181
 182                         public override Expression EmitToField (EmitContext ec)
 183                         {
 184                                 return this;
 185                         }
 186                 }
 187
 188                 Field awaiter;
 189                 AwaiterDefinition awaiter_definition;
 190                 TypeSpec type;
 191                 TypeSpec result_type;
 192
 193                 public AwaitStatement (Expression expr, Location loc)
 194                         : base (expr, loc)
 195                 {
 196                         unwind_protect = true;
 197                 }
 198
 199                 #region Properties
 200
 201                 bool IsDynamic {
 202                         get {
 203                                 return awaiter_definition == null;
 204                         }
 205                 }
 206
 207                 public TypeSpec ResultType {
 208                         get {
 209                                 return result_type;
 210                         }
 211                 }
 212
 213                 #endregion
 214
 215                 protected override void DoEmit (EmitContext ec)
 216                 {
 217                         using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
 218                                 GetResultExpression (ec).Emit (ec);
 219                         }
 220                 }
 221
 222                 public Expression GetResultExpression (EmitContext ec)
 223                 {
 224                         var fe_awaiter = new FieldExpr (awaiter, loc);
 225                         fe_awaiter.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 226
 227                         //
 228                         // result = awaiter.GetResult ();
 229                         //
 230                         if (IsDynamic) {
 231                                 var rc = new ResolveContext (ec.MemberContext);
 232                                 return new Invocation (new MemberAccess (fe_awaiter, "GetResult"), new Arguments (0)).Resolve (rc);
 233                         }
 234
 235                         var mg_result = MethodGroupExpr.CreatePredefined (awaiter_definition.GetResult, fe_awaiter.Type, loc);
 236                         mg_result.InstanceExpression = fe_awaiter;
 237
 238                         return new GetResultInvocation (mg_result, new Arguments (0));
 239                 }
 240
 241                 public void EmitPrologue (EmitContext ec)
 242                 {
 243                         awaiter = ((AsyncTaskStorey) machine_initializer.Storey).AddAwaiter (expr.Type);
 244
 245                         var fe_awaiter = new FieldExpr (awaiter, loc);
 246                         fe_awaiter.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 247
 248                         Label skip_continuation = ec.DefineLabel ();
 249
 250                         using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
 251                                 //
 252                                 // awaiter = expr.GetAwaiter ();
 253                                 //
 254                                 fe_awaiter.EmitAssign (ec, expr, false, false);
 255
 256                                 Expression completed_expr;
 257                                 if (IsDynamic) {
 258                                         var rc = new ResolveContext (ec.MemberContext);
 259
 260                                         Arguments dargs = new Arguments (1);
 261                                         dargs.Add (new Argument (fe_awaiter));
 262                                         completed_expr = new DynamicMemberBinder ("IsCompleted", dargs, loc).Resolve (rc);
 263
 264                                         dargs = new Arguments (1);
 265                                         dargs.Add (new Argument (completed_expr));
 266                                         completed_expr = new DynamicConversion (ec.Module.Compiler.BuiltinTypes.Bool, 0, dargs, loc).Resolve (rc);
 267                                 } else {
 268                                         var pe = PropertyExpr.CreatePredefined (awaiter_definition.IsCompleted, loc);
 269                                         pe.InstanceExpression = fe_awaiter;
 270                                         completed_expr = pe;
 271                                 }
 272
 273                                 completed_expr.EmitBranchable (ec, skip_continuation, true);
 274                         }
 275
 276                         base.DoEmit (ec);
 277
 278                         //
 279                         // The stack has to be empty before calling await continuation. We handle this
 280                         // by lifting values which would be left on stack into class fields. The process
 281                         // is quite complicated and quite hard to test because any expression can possibly
 282                         // leave a value on the stack.
 283                         //
 284                         // Following assert fails when some of expression called before is missing EmitToField
 285                         // or parent expression fails to find await in children expressions
 286                         //
 287                         ec.AssertEmptyStack ();
 288
 289                         var storey = (AsyncTaskStorey) machine_initializer.Storey;
 290                         if (IsDynamic) {
 291                                 storey.EmitAwaitOnCompletedDynamic (ec, fe_awaiter);
 292                         } else {
 293                                 storey.EmitAwaitOnCompleted (ec, fe_awaiter);
 294                         }
 295
 296                         // Return ok
 297                         machine_initializer.EmitLeave (ec, unwind_protect);
 298
 299                         ec.MarkLabel (resume_point);
 300                         ec.MarkLabel (skip_continuation);
 301                 }
 302
 303                 public void EmitStatement (EmitContext ec)
 304                 {
 305                         EmitPrologue (ec);
 306                         DoEmit (ec);
 307
 308                         awaiter.IsAvailableForReuse = true;
 309
 310                         if (ResultType.Kind != MemberKind.Void)
 311                                 ec.Emit (OpCodes.Pop);
 312                 }
 313
 314                 void Error_WrongAwaiterPattern (ResolveContext rc, TypeSpec awaiter)
 315                 {
 316                         rc.Report.Error (4011, loc, "The awaiter type `{0}' must have suitable IsCompleted and GetResult members",
 317                                 awaiter.GetSignatureForError ());
 318                 }
 319
 320                 public override bool Resolve (BlockContext bc)
 321                 {
 322                         if (bc.CurrentBlock is Linq.QueryBlock) {
 323                                 bc.Report.Error (1995, loc,
 324                                         "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");
 325                                 return false;
 326                         }
 327
 328                         if (!base.Resolve (bc))
 329                                 return false;
 330
 331                         type = expr.Type;
 332                         Arguments args = new Arguments (0);
 333
 334                         //
 335                         // The await expression is of dynamic type
 336                         //
 337                         if (type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
 338                                 result_type = type;
 339                                 expr = new Invocation (new MemberAccess (expr, "GetAwaiter"), args).Resolve (bc);
 340                                 return true;
 341                         }
 342
 343                         //
 344                         // Check whether the expression is awaitable
 345                         //
 346                         Expression ama = new AwaitableMemberAccess (expr).Resolve (bc);
 347                         if (ama == null)
 348                                 return false;
 349
 350                         var errors_printer = new SessionReportPrinter ();
 351                         var old = bc.Report.SetPrinter (errors_printer);
 352                         ama = new Invocation (ama, args).Resolve (bc);
 353                         bc.Report.SetPrinter (old);
 354
 355                         if (errors_printer.ErrorsCount > 0 || !MemberAccess.IsValidDotExpression (ama.Type)) {
 356                                 bc.Report.Error (1986, expr.Location,
 357                                         "The `await' operand type `{0}' must have suitable GetAwaiter method",
 358                                         expr.Type.GetSignatureForError ());
 359
 360                                 return false;
 361                         }
 362
 363                         var awaiter_type = ama.Type;
 364
 365                         awaiter_definition = bc.Module.GetAwaiter (awaiter_type);
 366
 367                         if (!awaiter_definition.IsValidPattern) {
 368                                 Error_WrongAwaiterPattern (bc, awaiter_type);
 369                                 return false;
 370                         }
 371
 372                         if (!awaiter_definition.INotifyCompletion) {
 373                                 bc.Report.Error (4027, loc, "The awaiter type `{0}' must implement interface `{1}'",
 374                                         awaiter_type.GetSignatureForError (), bc.Module.PredefinedTypes.INotifyCompletion.GetSignatureForError ());
 375                                 return false;
 376                         }
 377
 378                         expr = ama;
 379                         result_type = awaiter_definition.GetResult.ReturnType;
 380
 381                         return true;
 382                 }
 383         }
 384
 385         class AsyncInitializerStatement : StatementExpression
 386         {
 387                 public AsyncInitializerStatement (AsyncInitializer expr)
 388                         : base (expr)
 389                 {
 390                 }
 391
 392                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 393                 {
 394                         base.DoFlowAnalysis (fc);
 395
 396                         var init = (AsyncInitializer) Expr;
 397                         var res = !init.Block.HasReachableClosingBrace;
 398                         var storey = (AsyncTaskStorey) init.Storey;
 399
 400                         if (storey.ReturnType.IsGenericTask)
 401                                 return res;
 402
 403                         return true;
 404                 }
 405
 406                 public override Reachability MarkReachable (Reachability rc)
 407                 {
 408                         if (!rc.IsUnreachable)
 409                                 reachable = true;
 410
 411                         var init = (AsyncInitializer) Expr;
 412                         rc = init.Block.MarkReachable (rc);
 413
 414                         var storey = (AsyncTaskStorey) init.Storey;
 415
 416                         //
 417                         // Explicit return is required for Task<T> state machine
 418                         //
 419                         if (storey.ReturnType != null && storey.ReturnType.IsGenericTask)
 420                                 return rc;
 421
 422                     return Reachability.CreateUnreachable ();
 423                 }
 424         }
 425
 426         public class AsyncInitializer : StateMachineInitializer
 427         {
 428                 TypeInferenceContext return_inference;
 429
 430                 public AsyncInitializer (ParametersBlock block, TypeDefinition host, TypeSpec returnType)
 431                         : base (block, host, returnType)
 432                 {
 433                 }
 434
 435                 #region Properties
 436
 437                 public override string ContainerType {
 438                         get {
 439                                 return "async state machine block";
 440                         }
 441                 }
 442
 443                 public TypeSpec DelegateType {
 444                         get; set;
 445                 }
 446
 447                 public StackFieldExpr HoistedReturnState {
 448                         get; set;
 449                 }
 450
 451                 public override bool IsIterator {
 452                         get {
 453                                 return false;
 454                         }
 455                 }
 456
 457                 public TypeInferenceContext ReturnTypeInference {
 458                         get {
 459                                 return return_inference;
 460                         }
 461                 }
 462
 463                 #endregion
 464
 465                 protected override BlockContext CreateBlockContext (BlockContext bc)
 466                 {
 467                         var ctx = base.CreateBlockContext (bc);
 468                         var am = bc.CurrentAnonymousMethod as AnonymousMethodBody;
 469                         if (am != null)
 470                                 return_inference = am.ReturnTypeInference;
 471
 472                         ctx.Set (ResolveContext.Options.TryScope);
 473
 474                         return ctx;
 475                 }
 476
 477                 public override void Emit (EmitContext ec)
 478                 {
 479                         throw new NotImplementedException ();
 480                 }
 481
 482                 public void EmitCatchBlock (EmitContext ec)
 483                 {
 484                         var catch_value = LocalVariable.CreateCompilerGenerated (ec.Module.Compiler.BuiltinTypes.Exception, block, Location);
 485
 486                         ec.BeginCatchBlock (catch_value.Type);
 487                         catch_value.EmitAssign (ec);
 488
 489                         ec.EmitThis ();
 490                         ec.EmitInt ((int) IteratorStorey.State.After);
 491                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 492
 493                         ((AsyncTaskStorey) Storey).EmitSetException (ec, new LocalVariableReference (catch_value, Location));
 494
 495                         ec.Emit (OpCodes.Leave, move_next_ok);
 496                         ec.EndExceptionBlock ();
 497
 498                 }
 499
 500                 protected override void EmitMoveNextEpilogue (EmitContext ec)
 501                 {
 502                         var storey = (AsyncTaskStorey) Storey;
 503                         storey.EmitSetResult (ec);
 504                 }
 505
 506                 public override void EmitStatement (EmitContext ec)
 507                 {
 508                         var storey = (AsyncTaskStorey) Storey;
 509                         storey.EmitInitializer (ec);
 510                         ec.Emit (OpCodes.Ret);
 511                 }
 512
 513                 public override void MarkReachable (Reachability rc)
 514                 {
 515                         //
 516                         // Reachability has been done in AsyncInitializerStatement
 517                         //
 518                 }
 519         }
 520
 521         class AsyncTaskStorey : StateMachine
 522         {
 523                 int awaiters;
 524                 Field builder;
 525                 readonly TypeSpec return_type;
 526                 MethodSpec set_result;
 527                 MethodSpec set_exception;
 528                 MethodSpec builder_factory;
 529                 MethodSpec builder_start;
 530                 PropertySpec task;
 531                 int locals_captured;
 532                 Dictionary<TypeSpec, List<Field>> stack_fields;
 533                 Dictionary<TypeSpec, List<Field>> awaiter_fields;
 534
 535                 public AsyncTaskStorey (ParametersBlock block, IMemberContext context, AsyncInitializer initializer, TypeSpec type)
 536                         : base (block, initializer.Host, context.CurrentMemberDefinition as MemberBase, context.CurrentTypeParameters, "async", MemberKind.Struct)
 537                 {
 538                         return_type = type;
 539                         awaiter_fields = new Dictionary<TypeSpec, List<Field>> ();
 540                 }
 541
 542                 #region Properties
 543
 544                 public bool HasAwaitInsideFinally { get; set; }
 545
 546                 public Expression HoistedReturnValue { get; set; }
 547
 548                 public TypeSpec ReturnType {
 549                         get {
 550                                 return return_type;
 551                         }
 552                 }
 553
 554                 public PropertySpec Task {
 555                         get {
 556                                 return task;
 557                         }
 558                 }
 559
 560                 protected override TypeAttributes TypeAttr {
 561                         get {
 562                                 return base.TypeAttr & ~TypeAttributes.SequentialLayout;
 563                         }
 564                 }
 565
 566                 #endregion
 567
 568                 public Field AddAwaiter (TypeSpec type)
 569                 {
 570                         if (mutator != null)
 571                                 type = mutator.Mutate (type);
 572
 573                         List<Field> existing_fields;
 574                         if (awaiter_fields.TryGetValue (type, out existing_fields)) {
 575                                 foreach (var f in existing_fields) {
 576                                         if (f.IsAvailableForReuse) {
 577                                                 f.IsAvailableForReuse = false;
 578                                                 return f;
 579                                         }
 580                                 }
 581                         }
 582
 583                         var field = AddCompilerGeneratedField ("$awaiter" + awaiters++.ToString ("X"), new TypeExpression (type, Location), true);
 584                         field.Define ();
 585
 586                         if (existing_fields == null) {
 587                                 existing_fields = new List<Field> ();
 588                                 awaiter_fields.Add (type, existing_fields);
 589                         }
 590
 591                         existing_fields.Add (field);
 592                         return field;
 593                 }
 594
 595                 public Field AddCapturedLocalVariable (TypeSpec type, bool requiresUninitialized = false)
 596                 {
 597                         if (mutator != null)
 598                                 type = mutator.Mutate (type);
 599
 600                         List<Field> existing_fields = null;
 601                         if (stack_fields == null) {
 602                                 stack_fields = new Dictionary<TypeSpec, List<Field>> ();
 603                         } else if (stack_fields.TryGetValue (type, out existing_fields) && !requiresUninitialized) {
 604                                 foreach (var f in existing_fields) {
 605                                         if (f.IsAvailableForReuse) {
 606                                                 f.IsAvailableForReuse = false;
 607                                                 return f;
 608                                         }
 609                                 }
 610                         }
 611
 612                         var field = AddCompilerGeneratedField ("$stack" + locals_captured++.ToString ("X"), new TypeExpression (type, Location), true);
 613                         field.Define ();
 614
 615                         if (existing_fields == null) {
 616                                 existing_fields = new List<Field> ();
 617                                 stack_fields.Add (type, existing_fields);
 618                         }
 619
 620                         existing_fields.Add (field);
 621
 622                         return field;
 623                 }
 624
 625                 protected override bool DoDefineMembers ()
 626                 {
 627                         PredefinedType builder_type;
 628                         PredefinedMember<MethodSpec> bf;
 629                         PredefinedMember<MethodSpec> bs;
 630                         PredefinedMember<MethodSpec> sr;
 631                         PredefinedMember<MethodSpec> se;
 632                         PredefinedMember<MethodSpec> sm;
 633                         bool has_task_return_type = false;
 634                         var pred_members = Module.PredefinedMembers;
 635
 636                         if (return_type.Kind == MemberKind.Void) {
 637                                 builder_type = Module.PredefinedTypes.AsyncVoidMethodBuilder;
 638                                 bf = pred_members.AsyncVoidMethodBuilderCreate;
 639                                 bs = pred_members.AsyncVoidMethodBuilderStart;
 640                                 sr = pred_members.AsyncVoidMethodBuilderSetResult;
 641                                 se = pred_members.AsyncVoidMethodBuilderSetException;
 642                                 sm = pred_members.AsyncVoidMethodBuilderSetStateMachine;
 643                         } else if (return_type == Module.PredefinedTypes.Task.TypeSpec) {
 644                                 builder_type = Module.PredefinedTypes.AsyncTaskMethodBuilder;
 645                                 bf = pred_members.AsyncTaskMethodBuilderCreate;
 646                                 bs = pred_members.AsyncTaskMethodBuilderStart;
 647                                 sr = pred_members.AsyncTaskMethodBuilderSetResult;
 648                                 se = pred_members.AsyncTaskMethodBuilderSetException;
 649                                 sm = pred_members.AsyncTaskMethodBuilderSetStateMachine;
 650                                 task = pred_members.AsyncTaskMethodBuilderTask.Get ();
 651                         } else {
 652                                 builder_type = Module.PredefinedTypes.AsyncTaskMethodBuilderGeneric;
 653                                 bf = pred_members.AsyncTaskMethodBuilderGenericCreate;
 654                                 bs = pred_members.AsyncTaskMethodBuilderGenericStart;
 655                                 sr = pred_members.AsyncTaskMethodBuilderGenericSetResult;
 656                                 se = pred_members.AsyncTaskMethodBuilderGenericSetException;
 657                                 sm = pred_members.AsyncTaskMethodBuilderGenericSetStateMachine;
 658                                 task = pred_members.AsyncTaskMethodBuilderGenericTask.Get ();
 659                                 has_task_return_type = true;
 660                         }
 661
 662                         set_result = sr.Get ();
 663                         set_exception = se.Get ();
 664                         builder_factory = bf.Get ();
 665                         builder_start = bs.Get ();
 666
 667                         var istate_machine = Module.PredefinedTypes.IAsyncStateMachine;
 668                         var set_statemachine = sm.Get ();
 669
 670                         if (!builder_type.Define () || !istate_machine.Define () || set_result == null || builder_factory == null ||
 671                                 set_exception == null || set_statemachine == null || builder_start == null ||
 672                                 !Module.PredefinedTypes.INotifyCompletion.Define ()) {
 673                                 Report.Error (1993, Location,
 674                                         "Cannot find compiler required types for asynchronous functions support. Are you targeting the wrong framework version?");
 675                                 return base.DoDefineMembers ();
 676                         }
 677
 678                         var bt = builder_type.TypeSpec;
 679
 680                         //
 681                         // Inflate generic Task types
 682                         //
 683                         if (has_task_return_type) {
 684                                 var task_return_type = return_type.TypeArguments;
 685                                 if (mutator != null)
 686                                         task_return_type = mutator.Mutate (task_return_type);
 687
 688                                 bt = bt.MakeGenericType (Module, task_return_type);
 689                                 set_result = MemberCache.GetMember (bt, set_result);
 690                                 set_exception = MemberCache.GetMember (bt, set_exception);
 691                                 set_statemachine = MemberCache.GetMember (bt, set_statemachine);
 692
 693                                 if (task != null)
 694                                         task = MemberCache.GetMember (bt, task);
 695                         }
 696
 697                         builder = AddCompilerGeneratedField ("$builder", new TypeExpression (bt, Location));
 698
 699                         Field rfield;
 700                         if (has_task_return_type && HasAwaitInsideFinally) {
 701                                 //
 702                                 // Special case async block with return value from finally clause. In such case
 703                                 // we rewrite all return expresison stores to stfld to $return. Instead of treating
 704                                 // returns outside of finally and inside of finally differently.
 705                                 //
 706                                 rfield = AddCompilerGeneratedField ("$return", new TypeExpression (bt.TypeArguments [0], Location));
 707                         } else {
 708                                 rfield = null;
 709                         }
 710
 711                         var set_state_machine = new Method (this, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
 712                                 Modifiers.COMPILER_GENERATED | Modifiers.DEBUGGER_HIDDEN | Modifiers.PUBLIC,
 713                                 new MemberName ("SetStateMachine"),
 714                                 ParametersCompiled.CreateFullyResolved (
 715                                         new Parameter (new TypeExpression (istate_machine.TypeSpec, Location), "stateMachine", Parameter.Modifier.NONE, null, Location),
 716                                         istate_machine.TypeSpec),
 717                                 null);
 718
 719                         ToplevelBlock block = new ToplevelBlock (Compiler, set_state_machine.ParameterInfo, Location);
 720                         block.IsCompilerGenerated = true;
 721                         set_state_machine.Block = block;
 722
 723                         Members.Add (set_state_machine);
 724
 725                         if (!base.DoDefineMembers ())
 726                                 return false;
 727
 728                         //
 729                         // Fabricates SetStateMachine method
 730                         //
 731                         // public void SetStateMachine (IAsyncStateMachine stateMachine)
 732                         // {
 733                         //    $builder.SetStateMachine (stateMachine);
 734                         // }
 735                         //
 736                         var mg = MethodGroupExpr.CreatePredefined (set_statemachine, bt, Location);
 737                         mg.InstanceExpression = new FieldExpr (builder, Location);
 738
 739                         var param_reference = block.GetParameterReference (0, Location);
 740                         param_reference.Type = istate_machine.TypeSpec;
 741                         param_reference.eclass = ExprClass.Variable;
 742
 743                         var args = new Arguments (1);
 744                         args.Add (new Argument (param_reference));
 745                         set_state_machine.Block.AddStatement (new StatementExpression (new Invocation (mg, args)));
 746
 747                         if (has_task_return_type) {
 748                                 if (rfield != null) {
 749                                         HoistedReturnValue = new FieldExpr (rfield, Location) {
 750                                                 InstanceExpression = new CompilerGeneratedThis (CurrentType, Location.Null)
 751                                         };
 752                                 } else {
 753                                         HoistedReturnValue = TemporaryVariableReference.Create (bt.TypeArguments [0], StateMachineMethod.Block, Location);
 754                                 }
 755                         }
 756
 757                         return true;
 758                 }
 759
 760                 public void EmitAwaitOnCompletedDynamic (EmitContext ec, FieldExpr awaiter)
 761                 {
 762                         var critical = Module.PredefinedTypes.ICriticalNotifyCompletion;
 763                         if (!critical.Define ()) {
 764                                 throw new NotImplementedException ();
 765                         }
 766
 767                         var temp_critical = new LocalTemporary (critical.TypeSpec);
 768                         var label_critical = ec.DefineLabel ();
 769                         var label_end = ec.DefineLabel ();
 770
 771                         //
 772                         // Special path for dynamic awaiters
 773                         //
 774                         // var awaiter = this.$awaiter as ICriticalNotifyCompletion;
 775                         // if (awaiter == null) {
 776                         //    var completion = (INotifyCompletion) this.$awaiter;
 777                         //    this.$builder.AwaitOnCompleted (ref completion, ref this);
 778                         // } else {
 779                         //    this.$builder.AwaitUnsafeOnCompleted (ref awaiter, ref this);
 780                         // }
 781                         //
 782                         awaiter.Emit (ec);
 783                         ec.Emit (OpCodes.Isinst, critical.TypeSpec);
 784                         temp_critical.Store (ec);
 785                         temp_critical.Emit (ec);
 786                         ec.Emit (OpCodes.Brtrue_S, label_critical);
 787
 788                         var temp = new LocalTemporary (Module.PredefinedTypes.INotifyCompletion.TypeSpec);
 789                         awaiter.Emit (ec);
 790                         ec.Emit (OpCodes.Castclass, temp.Type);
 791                         temp.Store (ec);
 792                         EmitOnCompleted (ec, temp, false);
 793                         temp.Release (ec);
 794                         ec.Emit (OpCodes.Br_S, label_end);
 795
 796                         ec.MarkLabel (label_critical);
 797
 798                         EmitOnCompleted (ec, temp_critical, true);
 799
 800                         ec.MarkLabel (label_end);
 801
 802                         temp_critical.Release (ec);
 803                 }
 804
 805                 public void EmitAwaitOnCompleted (EmitContext ec, FieldExpr awaiter)
 806                 {
 807                         bool unsafe_version = false;
 808                         if (Module.PredefinedTypes.ICriticalNotifyCompletion.Define ()) {
 809                                 unsafe_version = awaiter.Type.ImplementsInterface (Module.PredefinedTypes.ICriticalNotifyCompletion.TypeSpec, false);
 810                         }
 811
 812                         EmitOnCompleted (ec, awaiter, unsafe_version);
 813                 }
 814
 815                 void EmitOnCompleted (EmitContext ec, Expression awaiter, bool unsafeVersion)
 816                 {
 817                         var pm = Module.PredefinedMembers;
 818                         PredefinedMember<MethodSpec> predefined;
 819                         bool has_task_return_type = false;
 820                         if (return_type.Kind == MemberKind.Void) {
 821                                 predefined = unsafeVersion ? pm.AsyncVoidMethodBuilderOnCompletedUnsafe : pm.AsyncVoidMethodBuilderOnCompleted;
 822                         } else if (return_type == Module.PredefinedTypes.Task.TypeSpec) {
 823                                 predefined = unsafeVersion ? pm.AsyncTaskMethodBuilderOnCompletedUnsafe : pm.AsyncTaskMethodBuilderOnCompleted;
 824                         } else {
 825                                 predefined = unsafeVersion ? pm.AsyncTaskMethodBuilderGenericOnCompletedUnsafe : pm.AsyncTaskMethodBuilderGenericOnCompleted;
 826                                 has_task_return_type = true;
 827                         }
 828
 829                         var on_completed = predefined.Resolve (Location);
 830                         if (on_completed == null)
 831                                 return;
 832
 833                         if (has_task_return_type)
 834                                 on_completed = MemberCache.GetMember<MethodSpec> (set_result.DeclaringType, on_completed);
 835
 836                         on_completed = on_completed.MakeGenericMethod (this, awaiter.Type, ec.CurrentType);
 837
 838                         var mg = MethodGroupExpr.CreatePredefined (on_completed, on_completed.DeclaringType, Location);
 839                         mg.InstanceExpression = new FieldExpr (builder, Location) {
 840                                 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
 841                         };
 842
 843                         var args = new Arguments (2);
 844                         args.Add (new Argument (awaiter, Argument.AType.Ref));
 845                         args.Add (new Argument (new CompilerGeneratedThis (CurrentType, Location), Argument.AType.Ref));
 846                         using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
 847                                 mg.EmitCall (ec, args, true);
 848                         }
 849                 }
 850
 851                 public void EmitInitializer (EmitContext ec)
 852                 {
 853                         //
 854                         // Some predefined types are missing
 855                         //
 856                         if (builder == null)
 857                                 return;
 858
 859                         var instance = (TemporaryVariableReference) Instance;
 860                         var builder_field = builder.Spec;
 861                         if (MemberName.Arity > 0) {
 862                                 builder_field = MemberCache.GetMember (instance.Type, builder_field);
 863                         }
 864
 865                         //
 866                         // Inflated factory method when task is of generic type
 867                         //
 868                         if (builder_factory.DeclaringType.IsGeneric) {
 869                                 var task_return_type = return_type.TypeArguments;
 870                                 var bt = builder_factory.DeclaringType.MakeGenericType (Module, task_return_type);
 871                                 builder_factory = MemberCache.GetMember (bt, builder_factory);
 872                                 builder_start = MemberCache.GetMember (bt, builder_start);
 873                         }
 874
 875                         //
 876                         // stateMachine.$builder = AsyncTaskMethodBuilder<{task-type}>.Create();
 877                         //
 878                         instance.AddressOf (ec, AddressOp.Store);
 879                         ec.Emit (OpCodes.Call, builder_factory);
 880                         ec.Emit (OpCodes.Stfld, builder_field);
 881
 882                         //
 883                         // stateMachine.$builder.Start<{storey-type}>(ref stateMachine);
 884                         //
 885                         instance.AddressOf (ec, AddressOp.Store);
 886                         ec.Emit (OpCodes.Ldflda, builder_field);
 887                         if (Task != null)
 888                                 ec.Emit (OpCodes.Dup);
 889                         instance.AddressOf (ec, AddressOp.Store);
 890                         ec.Emit (OpCodes.Call, builder_start.MakeGenericMethod (Module, instance.Type));
 891
 892                         //
 893                         // Emits return stateMachine.$builder.Task;
 894                         //
 895                         if (Task != null) {
 896                                 var task_get = Task.Get;
 897
 898                                 if (MemberName.Arity > 0) {
 899                                         task_get = MemberCache.GetMember (builder_field.MemberType, task_get);
 900                                 }
 901
 902                                 var pe_task = new PropertyExpr (Task, Location) {
 903                                         InstanceExpression = EmptyExpression.Null,      // Comes from the dup above
 904                                         Getter = task_get
 905                                 };
 906
 907                                 pe_task.Emit (ec);
 908                         }
 909                 }
 910
 911                 public void EmitSetException (EmitContext ec, LocalVariableReference exceptionVariable)
 912                 {
 913                         //
 914                         // $builder.SetException (Exception)
 915                         //
 916                         var mg = MethodGroupExpr.CreatePredefined (set_exception, set_exception.DeclaringType, Location);
 917                         mg.InstanceExpression = new FieldExpr (builder, Location) {
 918                                 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
 919                         };
 920
 921                         Arguments args = new Arguments (1);
 922                         args.Add (new Argument (exceptionVariable));
 923
 924                         using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
 925                                 mg.EmitCall (ec, args, true);
 926                         }
 927                 }
 928
 929                 public void EmitSetResult (EmitContext ec)
 930                 {
 931                         //
 932                         // $builder.SetResult ();
 933                         // $builder.SetResult<return-type> (value);
 934                         //
 935                         var mg = MethodGroupExpr.CreatePredefined (set_result, set_result.DeclaringType, Location);
 936                         mg.InstanceExpression = new FieldExpr (builder, Location) {
 937                                 InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, Location)
 938                         };
 939
 940                         Arguments args;
 941                         if (HoistedReturnValue == null) {
 942                                 args = new Arguments (0);
 943                         } else {
 944                                 args = new Arguments (1);
 945                                 args.Add (new Argument (HoistedReturnValue));
 946                         }
 947
 948                         using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
 949                                 mg.EmitCall (ec, args, true);
 950                         }
 951                 }
 952
 953                 protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
 954                 {
 955                         base_type = Compiler.BuiltinTypes.ValueType;
 956                         base_class = null;
 957
 958                         var istate_machine = Module.PredefinedTypes.IAsyncStateMachine;
 959                         if (istate_machine.Define ()) {
 960                                 return new[] { istate_machine.TypeSpec };
 961                         }
 962
 963                         return null;
 964                 }
 965         }
 966
 967         public class StackFieldExpr : FieldExpr, IExpressionCleanup
 968         {
 969                 public StackFieldExpr (Field field)
 970                         : base (field, Location.Null)
 971                 {
 972                 }
 973
 974                 public bool IsAvailableForReuse {
 975                         get {
 976                                 var field = (Field) spec.MemberDefinition;
 977                                 return field.IsAvailableForReuse;
 978                         }
 979                         set {
 980                                 var field = (Field) spec.MemberDefinition;
 981                                 field.IsAvailableForReuse = value;
 982                         }
 983                 }
 984
 985                 public override void AddressOf (EmitContext ec, AddressOp mode)
 986                 {
 987                         base.AddressOf (ec, mode);
 988
 989                         if (mode == AddressOp.Load) {
 990                                 IsAvailableForReuse = true;
 991                         }
 992                 }
 993
 994                 public override void Emit (EmitContext ec)
 995                 {
 996                         base.Emit (ec);
 997
 998                         PrepareCleanup (ec);
 999                 }
1000
1001                 public void EmitLoad (EmitContext ec)
1002                 {
1003                         base.Emit (ec);
1004                 }
1005
1006                 public void PrepareCleanup (EmitContext ec)
1007                 {
1008                         IsAvailableForReuse = true;
1009
1010                         //
1011                         // Release any captured reference type stack variables
1012                         // to imitate real stack behavour and help GC stuff early
1013                         //
1014                         if (TypeSpec.IsReferenceType (type)) {
1015                                 ec.AddStatementEpilog (this);
1016                         }
1017                 }
1018
1019                 void IExpressionCleanup.EmitCleanup (EmitContext ec)
1020                 {
1021                         EmitAssign (ec, new NullConstant (type, loc), false, false);
1022                 }
1023         }
1024 }