mcs/mcs/iterators.cs

   1 //
   2 // iterators.cs: Support for implementing iterators
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Dual licensed under the terms of the MIT X11 or GNU GPL
   9 // Copyright 2003 Ximian, Inc.
  10 // Copyright 2003-2008 Novell, Inc.
  11 // Copyright 2011 Xamarin Inc.
  12 //
  13
  14 using System;
  15 using System.Collections.Generic;
  16 using Mono.CompilerServices.SymbolWriter;
  17
  18 #if STATIC
  19 using IKVM.Reflection.Emit;
  20 #else
  21 using System.Reflection.Emit;
  22 #endif
  23
  24 namespace Mono.CSharp
  25 {
  26         public abstract class YieldStatement<T> : ResumableStatement where T : StateMachineInitializer
  27         {
  28                 protected Expression expr;
  29                 protected bool unwind_protect;
  30                 protected T machine_initializer;
  31                 int resume_pc;
  32                 ExceptionStatement inside_try_block;
  33
  34                 protected YieldStatement (Expression expr, Location l)
  35                 {
  36                         this.expr = expr;
  37                         loc = l;
  38                 }
  39
  40                 public Expression Expr {
  41                         get { return this.expr; }
  42                 }
  43
  44                 protected override void CloneTo (CloneContext clonectx, Statement t)
  45                 {
  46                         var target = (YieldStatement<T>) t;
  47                         target.expr = expr.Clone (clonectx);
  48                 }
  49
  50                 protected override void DoEmit (EmitContext ec)
  51                 {
  52                         machine_initializer.InjectYield (ec, expr, resume_pc, unwind_protect, resume_point);
  53                 }
  54
  55                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
  56                 {
  57                         expr.FlowAnalysis (fc);
  58
  59                         RegisterResumePoint ();
  60
  61                         return false;
  62                 }
  63
  64                 public override bool Resolve (BlockContext bc)
  65                 {
  66                         expr = expr.Resolve (bc);
  67                         if (expr == null)
  68                                 return false;
  69
  70                         machine_initializer = bc.CurrentAnonymousMethod as T;
  71                         inside_try_block = bc.CurrentTryBlock;
  72                         return true;
  73                 }
  74
  75                 public void RegisterResumePoint ()
  76                 {
  77                         if (inside_try_block == null) {
  78                                 resume_pc = machine_initializer.AddResumePoint (this);
  79                         } else {
  80                                 resume_pc = inside_try_block.AddResumePoint (this, resume_pc, machine_initializer);
  81                                 unwind_protect = true;
  82                                 inside_try_block = null;
  83                         }
  84                 }
  85         }
  86
  87         public class Yield : YieldStatement<Iterator>
  88         {
  89                 public Yield (Expression expr, Location loc)
  90                         : base (expr, loc)
  91                 {
  92                 }
  93
  94                 public static bool CheckContext (BlockContext bc, Location loc)
  95                 {
  96                         if (!bc.CurrentAnonymousMethod.IsIterator) {
  97                                 bc.Report.Error (1621, loc,
  98                                         "The yield statement cannot be used inside anonymous method blocks");
  99                                 return false;
 100                         }
 101
 102                         if (bc.HasSet (ResolveContext.Options.FinallyScope)) {
 103                                 bc.Report.Error (1625, loc, "Cannot yield in the body of a finally clause");
 104                                 return false;
 105                         }
 106
 107                         return true;
 108                 }
 109
 110                 public override bool Resolve (BlockContext bc)
 111                 {
 112                         if (!CheckContext (bc, loc))
 113                                 return false;
 114
 115                         if (bc.HasAny (ResolveContext.Options.TryWithCatchScope)) {
 116                                 bc.Report.Error (1626, loc, "Cannot yield a value in the body of a try block with a catch clause");
 117                         }
 118
 119                         if (bc.HasSet (ResolveContext.Options.CatchScope)) {
 120                                 bc.Report.Error (1631, loc, "Cannot yield a value in the body of a catch clause");
 121                         }
 122
 123                         if (!base.Resolve (bc))
 124                                 return false;
 125
 126                         var otype = bc.CurrentIterator.OriginalIteratorType;
 127                         if (expr.Type != otype) {
 128                                 expr = Convert.ImplicitConversionRequired (bc, expr, otype, loc);
 129                                 if (expr == null)
 130                                         return false;
 131                         }
 132
 133                         return true;
 134                 }
 135
 136                 public override object Accept (StructuralVisitor visitor)
 137                 {
 138                         return visitor.Visit (this);
 139                 }
 140         }
 141
 142         public class YieldBreak : ExitStatement
 143         {
 144                 Iterator iterator;
 145
 146                 public YieldBreak (Location l)
 147                 {
 148                         loc = l;
 149                 }
 150
 151                 protected override bool IsLocalExit {
 152                         get {
 153                                 return false;
 154                         }
 155                 }
 156
 157                 protected override void CloneTo (CloneContext clonectx, Statement target)
 158                 {
 159                         throw new NotSupportedException ();
 160                 }
 161
 162                 protected override bool DoResolve (BlockContext bc)
 163                 {
 164                         iterator = bc.CurrentIterator;
 165                         return Yield.CheckContext (bc, loc);
 166                 }
 167
 168                 protected override void DoEmit (EmitContext ec)
 169                 {
 170                         iterator.EmitYieldBreak (ec, unwind_protect);
 171                 }
 172
 173                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 174                 {
 175                         return true;
 176                 }
 177
 178                 public override Reachability MarkReachable (Reachability rc)
 179                 {
 180                         base.MarkReachable (rc);
 181                         return Reachability.CreateUnreachable ();
 182                 }
 183
 184                 public override object Accept (StructuralVisitor visitor)
 185                 {
 186                         return visitor.Visit (this);
 187                 }
 188         }
 189
 190         public abstract class StateMachine : AnonymousMethodStorey
 191         {
 192                 public enum State
 193                 {
 194                         Running = -3, // Used only in CurrentPC, never stored into $PC
 195                         Uninitialized = -2,
 196                         After = -1,
 197                         Start = 0
 198                 }
 199
 200                 Field pc_field;
 201                 StateMachineMethod method;
 202                 int local_name_idx;
 203
 204                 protected StateMachine (ParametersBlock block, TypeDefinition parent, MemberBase host, TypeParameters tparams, string name, MemberKind kind)
 205                         : base (block, parent, host, tparams, name, kind)
 206                 {
 207                         OriginalTypeParameters = tparams;
 208                 }
 209
 210                 #region Properties
 211
 212                 public TypeParameters OriginalTypeParameters { get; private set; }
 213
 214                 public StateMachineMethod StateMachineMethod {
 215                         get {
 216                                 return method;
 217                         }
 218                 }
 219
 220                 public Field PC {
 221                         get {
 222                                 return pc_field;
 223                         }
 224                 }
 225
 226                 #endregion
 227
 228                 public void AddEntryMethod (StateMachineMethod method)
 229                 {
 230                         if (this.method != null)
 231                                 throw new InternalErrorException ();
 232
 233                         this.method = method;
 234                         Members.Add (method);
 235                 }
 236
 237                 protected override bool DoDefineMembers ()
 238                 {
 239                         pc_field = AddCompilerGeneratedField ("$PC", new TypeExpression (Compiler.BuiltinTypes.Int, Location));
 240
 241                         return base.DoDefineMembers ();
 242                 }
 243
 244                 protected override string GetVariableMangledName (LocalVariable local_info)
 245                 {
 246                         if (local_info.IsCompilerGenerated)
 247                                 return base.GetVariableMangledName (local_info);
 248
 249                         return "<" + local_info.Name + ">__" + local_name_idx++.ToString ("X");
 250                 }
 251         }
 252
 253         class IteratorStorey : StateMachine
 254         {
 255                 class GetEnumeratorMethod : StateMachineMethod
 256                 {
 257                         sealed class GetEnumeratorStatement : Statement
 258                         {
 259                                 readonly IteratorStorey host;
 260                                 readonly StateMachineMethod host_method;
 261
 262                                 Expression new_storey;
 263
 264                                 public GetEnumeratorStatement (IteratorStorey host, StateMachineMethod host_method)
 265                                 {
 266                                         this.host = host;
 267                                         this.host_method = host_method;
 268                                         loc = host_method.Location;
 269                                 }
 270
 271                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 272                                 {
 273                                         throw new NotSupportedException ();
 274                                 }
 275
 276                                 public override bool Resolve (BlockContext ec)
 277                                 {
 278                                         TypeExpression storey_type_expr = new TypeExpression (host.Definition, loc);
 279                                         List<Expression> init = null;
 280                                         if (host.hoisted_this != null) {
 281                                                 init = new List<Expression> (host.hoisted_params == null ? 1 : host.HoistedParameters.Count + 1);
 282                                                 HoistedThis ht = host.hoisted_this;
 283                                                 FieldExpr from = new FieldExpr (ht.Field, loc);
 284                                                 from.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 285                                                 init.Add (new ElementInitializer (ht.Field.Name, from, loc));
 286                                         }
 287
 288                                         if (host.hoisted_params != null) {
 289                                                 if (init == null)
 290                                                         init = new List<Expression> (host.HoistedParameters.Count);
 291
 292                                                 for (int i = 0; i < host.hoisted_params.Count; ++i) {
 293                                                         HoistedParameter hp = host.hoisted_params [i];
 294                                                         HoistedParameter hp_cp = host.hoisted_params_copy [i] ?? hp;
 295
 296                                                         FieldExpr from = new FieldExpr (hp_cp.Field, loc);
 297                                                         from.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 298
 299                                                         init.Add (new ElementInitializer (hp.Field.Name, from, loc));
 300                                                 }
 301                                         }
 302
 303                                         if (init != null) {
 304                                                 new_storey = new NewInitialize (storey_type_expr, null,
 305                                                         new CollectionOrObjectInitializers (init, loc), loc);
 306                                         } else {
 307                                                 new_storey = new New (storey_type_expr, null, loc);
 308                                         }
 309
 310                                         new_storey = new_storey.Resolve (ec);
 311                                         if (new_storey != null)
 312                                                 new_storey = Convert.ImplicitConversionRequired (ec, new_storey, host_method.MemberType, loc);
 313
 314                                         return true;
 315                                 }
 316
 317                                 protected override void DoEmit (EmitContext ec)
 318                                 {
 319                                         Label label_init = ec.DefineLabel ();
 320
 321                                         ec.EmitThis ();
 322                                         ec.Emit (OpCodes.Ldflda, host.PC.Spec);
 323                                         ec.EmitInt ((int) State.Start);
 324                                         ec.EmitInt ((int) State.Uninitialized);
 325
 326                                         var m = ec.Module.PredefinedMembers.InterlockedCompareExchange.Resolve (loc);
 327                                         if (m != null)
 328                                                 ec.Emit (OpCodes.Call, m);
 329
 330                                         ec.EmitInt ((int) State.Uninitialized);
 331                                         ec.Emit (OpCodes.Bne_Un_S, label_init);
 332
 333                                         ec.EmitThis ();
 334                                         ec.Emit (OpCodes.Ret);
 335
 336                                         ec.MarkLabel (label_init);
 337
 338                                         new_storey.Emit (ec);
 339                                         ec.Emit (OpCodes.Ret);
 340                                 }
 341
 342                                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 343                                 {
 344                                         throw new NotImplementedException ();
 345                                 }
 346
 347                                 public override Reachability MarkReachable (Reachability rc)
 348                                 {
 349                                         base.MarkReachable (rc);
 350                                         return Reachability.CreateUnreachable ();
 351                                 }
 352                         }
 353
 354                         GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 355                                 : base (host, null, returnType, Modifiers.DEBUGGER_HIDDEN, name, ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis)
 356                         {
 357                         }
 358
 359                         public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 360                         {
 361                                 return Create (host, returnType, name, null);
 362                         }
 363
 364                         public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name, Statement statement)
 365                         {
 366                                 var m = new GetEnumeratorMethod (host, returnType, name);
 367                                 var stmt = statement ?? new GetEnumeratorStatement (host, m);
 368                                 m.block.AddStatement (stmt);
 369                                 return m;
 370                         }
 371                 }
 372
 373                 class DisposeMethod : StateMachineMethod
 374                 {
 375                         sealed class DisposeMethodStatement : Statement
 376                         {
 377                                 Iterator iterator;
 378
 379                                 public DisposeMethodStatement (Iterator iterator)
 380                                 {
 381                                         this.iterator = iterator;
 382                                         this.loc = iterator.Location;
 383                                 }
 384
 385                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 386                                 {
 387                                         throw new NotSupportedException ();
 388                                 }
 389
 390                                 public override bool Resolve (BlockContext ec)
 391                                 {
 392                                         return true;
 393                                 }
 394
 395                                 protected override void DoEmit (EmitContext ec)
 396                                 {
 397                                         ec.CurrentAnonymousMethod = iterator;
 398                                         iterator.EmitDispose (ec);
 399                                 }
 400
 401                                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 402                                 {
 403                                         throw new NotImplementedException ();
 404                                 }
 405                         }
 406
 407                         public DisposeMethod (IteratorStorey host)
 408                                 : base (host, null, new TypeExpression (host.Compiler.BuiltinTypes.Void, host.Location), Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
 409                                         new MemberName ("Dispose", host.Location), ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis)
 410                         {
 411                                 host.Members.Add (this);
 412
 413                                 Block.AddStatement (new DisposeMethodStatement (host.Iterator));
 414                         }
 415                 }
 416
 417                 //
 418                 // Uses Method as method info
 419                 //
 420                 class DynamicMethodGroupExpr : MethodGroupExpr
 421                 {
 422                         readonly Method method;
 423
 424                         public DynamicMethodGroupExpr (Method method, Location loc)
 425                                 : base ((IList<MemberSpec>) null, null, loc)
 426                         {
 427                                 this.method = method;
 428                                 eclass = ExprClass.Unresolved;
 429                         }
 430
 431                         protected override Expression DoResolve (ResolveContext ec)
 432                         {
 433                                 Methods = new List<MemberSpec> (1) { method.Spec };
 434                                 type = method.Parent.Definition;
 435                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 436                                 return base.DoResolve (ec);
 437                         }
 438                 }
 439
 440                 class DynamicFieldExpr : FieldExpr
 441                 {
 442                         readonly Field field;
 443
 444                         public DynamicFieldExpr (Field field, Location loc)
 445                                 : base (loc)
 446                         {
 447                                 this.field = field;
 448                         }
 449
 450                         protected override Expression DoResolve (ResolveContext ec)
 451                         {
 452                                 spec = field.Spec;
 453                                 type = spec.MemberType;
 454                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 455                                 return base.DoResolve (ec);
 456                         }
 457                 }
 458
 459                 public readonly Iterator Iterator;
 460
 461                 List<HoistedParameter> hoisted_params_copy;
 462
 463                 TypeExpr iterator_type_expr;
 464                 Field current_field;
 465                 Field disposing_field;
 466
 467                 TypeSpec generic_enumerator_type;
 468                 TypeSpec generic_enumerable_type;
 469
 470                 public IteratorStorey (Iterator iterator)
 471                         : base (iterator.Container.ParametersBlock, iterator.Host,
 472                           iterator.OriginalMethod as MemberBase, iterator.OriginalMethod.CurrentTypeParameters, "Iterator", MemberKind.Class)
 473                 {
 474                         this.Iterator = iterator;
 475                 }
 476
 477                 public Field CurrentField {
 478                         get {
 479                                 return current_field;
 480                         }
 481                 }
 482
 483                 public Field DisposingField {
 484                         get {
 485                                 return disposing_field;
 486                         }
 487                 }
 488
 489                 public IList<HoistedParameter> HoistedParameters {
 490                         get { return hoisted_params; }
 491                 }
 492
 493                 protected override Constructor DefineDefaultConstructor (bool is_static)
 494                 {
 495                         var ctor = base.DefineDefaultConstructor (is_static);
 496                         ctor.ModFlags |= Modifiers.DEBUGGER_HIDDEN;
 497                         return ctor;
 498                 }
 499
 500                 protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
 501                 {
 502                         var mtype = Iterator.OriginalIteratorType;
 503                         if (Mutator != null)
 504                                 mtype = Mutator.Mutate (mtype);
 505
 506                         iterator_type_expr = new TypeExpression (mtype, Location);
 507
 508                         var ifaces = new List<TypeSpec> (5);
 509                         if (Iterator.IsEnumerable) {
 510                                 ifaces.Add (Compiler.BuiltinTypes.IEnumerable);
 511
 512                                 if (Module.PredefinedTypes.IEnumerableGeneric.Define ()) {
 513                                         generic_enumerable_type = Module.PredefinedTypes.IEnumerableGeneric.TypeSpec.MakeGenericType (Module, new[] { mtype });
 514                                         ifaces.Add (generic_enumerable_type);
 515                                 }
 516                         }
 517
 518                         ifaces.Add (Compiler.BuiltinTypes.IEnumerator);
 519                         ifaces.Add (Compiler.BuiltinTypes.IDisposable);
 520
 521                         var ienumerator_generic = Module.PredefinedTypes.IEnumeratorGeneric;
 522                         if (ienumerator_generic.Define ()) {
 523                                 generic_enumerator_type = ienumerator_generic.TypeSpec.MakeGenericType (Module, new [] { mtype });
 524                                 ifaces.Add (generic_enumerator_type);
 525                         }
 526
 527                         base_class = null;
 528
 529                         base_type = Compiler.BuiltinTypes.Object;
 530                         return ifaces.ToArray ();
 531                 }
 532
 533                 protected override bool DoDefineMembers ()
 534                 {
 535                         current_field = AddCompilerGeneratedField ("$current", iterator_type_expr);
 536                         disposing_field = AddCompilerGeneratedField ("$disposing", new TypeExpression (Compiler.BuiltinTypes.Bool, Location));
 537
 538                         if (Iterator.IsEnumerable && hoisted_params != null) {
 539                                 //
 540                                 // Iterators are independent, each GetEnumerator call has to
 541                                 // create same enumerator therefore we have to keep original values
 542                                 // around for re-initialization
 543                                 //
 544                                 hoisted_params_copy = new List<HoistedParameter> (hoisted_params.Count);
 545                                 foreach (HoistedParameter hp in hoisted_params) {
 546
 547                                         //
 548                                         // Don't create field copy for unmodified captured parameters
 549                                         //
 550                                         HoistedParameter hp_copy;
 551                                         if (hp.IsAssigned) {
 552                                                 hp_copy = new HoistedParameter (hp, "<$>" + hp.Field.Name);
 553                                         } else {
 554                                                 hp_copy = null;
 555                                         }
 556
 557                                         hoisted_params_copy.Add (hp_copy);
 558                                 }
 559                         }
 560
 561                         if (generic_enumerator_type != null)
 562                                 Define_Current (true);
 563
 564                         Define_Current (false);
 565                         new DisposeMethod (this);
 566                         Define_Reset ();
 567
 568                         if (Iterator.IsEnumerable) {
 569                                 FullNamedExpression explicit_iface = new TypeExpression (Compiler.BuiltinTypes.IEnumerable, Location);
 570                                 var name = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
 571
 572                                 if (generic_enumerator_type != null) {
 573                                         explicit_iface = new TypeExpression (generic_enumerable_type, Location);
 574                                         var gname = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
 575                                         Method gget_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (generic_enumerator_type, Location), gname);
 576
 577                                         //
 578                                         // Just call generic GetEnumerator implementation
 579                                         //
 580                                         var stmt = new Return (new Invocation (new DynamicMethodGroupExpr (gget_enumerator, Location), null), Location);
 581                                         Method get_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name, stmt);
 582
 583                                         Members.Add (get_enumerator);
 584                                         Members.Add (gget_enumerator);
 585                                 } else {
 586                                         Members.Add (GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name));
 587                                 }
 588                         }
 589
 590                         return base.DoDefineMembers ();
 591                 }
 592
 593                 void Define_Current (bool is_generic)
 594                 {
 595                         TypeExpr type;
 596                         FullNamedExpression explicit_iface;
 597
 598                         if (is_generic) {
 599                                 explicit_iface = new TypeExpression (generic_enumerator_type, Location);
 600                                 type = iterator_type_expr;
 601                         } else {
 602                                 explicit_iface = new TypeExpression (Module.Compiler.BuiltinTypes.IEnumerator, Location);
 603                                 type = new TypeExpression (Compiler.BuiltinTypes.Object, Location);
 604                         }
 605
 606                         var name = new MemberName ("Current", null, explicit_iface, Location);
 607
 608                         ToplevelBlock get_block = new ToplevelBlock (Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location,
 609                                 Block.Flags.CompilerGenerated | Block.Flags.NoFlowAnalysis);
 610                         get_block.AddStatement (new Return (new DynamicFieldExpr (CurrentField, Location), Location));
 611
 612                         Property current = new Property (this, type, Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED, name, null);
 613                         current.Get = new Property.GetMethod (current, Modifiers.COMPILER_GENERATED, null, Location);
 614                         current.Get.Block = get_block;
 615
 616                         Members.Add (current);
 617                 }
 618
 619                 void Define_Reset ()
 620                 {
 621                         Method reset = new Method (
 622                                 this, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
 623                                 Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED,
 624                                 new MemberName ("Reset", Location),
 625                                 ParametersCompiled.EmptyReadOnlyParameters, null);
 626                         Members.Add (reset);
 627
 628                         reset.Block = new ToplevelBlock (Compiler, reset.ParameterInfo, Location,
 629                                 Block.Flags.CompilerGenerated | Block.Flags.NoFlowAnalysis);
 630
 631                         TypeSpec ex_type = Module.PredefinedTypes.NotSupportedException.Resolve ();
 632                         if (ex_type == null)
 633                                 return;
 634
 635                         reset.Block.AddStatement (new Throw (new New (new TypeExpression (ex_type, Location), null, Location), Location));
 636                 }
 637
 638                 protected override void EmitHoistedParameters (EmitContext ec, List<HoistedParameter> hoisted)
 639                 {
 640                         base.EmitHoistedParameters (ec, hoisted);
 641                         if (hoisted_params_copy != null)
 642                                 base.EmitHoistedParameters (ec, hoisted_params_copy);
 643                 }
 644         }
 645
 646         public class StateMachineMethod : Method
 647         {
 648                 readonly StateMachineInitializer expr;
 649
 650                 public StateMachineMethod (StateMachine host, StateMachineInitializer expr, FullNamedExpression returnType,
 651                         Modifiers mod, MemberName name, ToplevelBlock.Flags blockFlags)
 652                         : base (host, returnType, mod | Modifiers.COMPILER_GENERATED,
 653                           name, ParametersCompiled.EmptyReadOnlyParameters, null)
 654                 {
 655                         this.expr = expr;
 656                         Block = new ToplevelBlock (host.Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location.Null, blockFlags);
 657                 }
 658
 659                 public override EmitContext CreateEmitContext (ILGenerator ig, SourceMethodBuilder sourceMethod)
 660                 {
 661                         EmitContext ec = new EmitContext (this, ig, MemberType, sourceMethod);
 662                         ec.CurrentAnonymousMethod = expr;
 663
 664                         if (expr is AsyncInitializer)
 665                                 ec.With (BuilderContext.Options.AsyncBody, true);
 666
 667                         return ec;
 668                 }
 669         }
 670
 671         public abstract class StateMachineInitializer : AnonymousExpression
 672         {
 673                 sealed class MoveNextBodyStatement : Statement
 674                 {
 675                         readonly StateMachineInitializer state_machine;
 676
 677                         public MoveNextBodyStatement (StateMachineInitializer stateMachine)
 678                         {
 679                                 this.state_machine = stateMachine;
 680                                 this.loc = stateMachine.Location;
 681                         }
 682
 683                         protected override void CloneTo (CloneContext clonectx, Statement target)
 684                         {
 685                                 throw new NotSupportedException ();
 686                         }
 687
 688                         public override bool Resolve (BlockContext ec)
 689                         {
 690                                 return true;
 691                         }
 692
 693                         protected override void DoEmit (EmitContext ec)
 694                         {
 695                                 state_machine.EmitMoveNext (ec);
 696                         }
 697
 698                         public override void Emit (EmitContext ec)
 699                         {
 700                                 // Don't create sequence point
 701                                 DoEmit (ec);
 702                         }
 703
 704                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 705                         {
 706                                 return state_machine.ReturnType.Kind != MemberKind.Void;
 707                         }
 708
 709                         public override Reachability MarkReachable (Reachability rc)
 710                         {
 711                                 base.MarkReachable (rc);
 712
 713                                 if (state_machine.ReturnType.Kind != MemberKind.Void)
 714                                         rc = Reachability.CreateUnreachable ();
 715
 716                                 return rc;
 717                         }
 718                 }
 719
 720                 public readonly TypeDefinition Host;
 721                 protected StateMachine storey;
 722
 723                 //
 724                 // The state as we generate the machine
 725                 //
 726                 Label move_next_ok;
 727                 protected Label move_next_error;
 728                 LocalBuilder skip_finally;
 729                 protected LocalBuilder current_pc;
 730                 protected List<ResumableStatement> resume_points;
 731
 732                 protected StateMachineInitializer (ParametersBlock block, TypeDefinition host, TypeSpec returnType)
 733                         : base (block, returnType, block.StartLocation)
 734                 {
 735                         this.Host = host;
 736                 }
 737
 738                 #region Properties
 739
 740                 public Label BodyEnd { get; set; }
 741
 742                 public LocalBuilder CurrentPC
 743                 {
 744                         get {
 745                                 return current_pc;
 746                         }
 747                 }
 748
 749                 public LocalBuilder SkipFinally {
 750                         get {
 751                                 return skip_finally;
 752                         }
 753                 }
 754
 755                 public override AnonymousMethodStorey Storey {
 756                         get {
 757                                 return storey;
 758                         }
 759                 }
 760
 761                 #endregion
 762
 763                 public int AddResumePoint (ResumableStatement stmt)
 764                 {
 765                         if (resume_points == null)
 766                                 resume_points = new List<ResumableStatement> ();
 767
 768                         resume_points.Add (stmt);
 769                         return resume_points.Count;
 770                 }
 771
 772                 public override Expression CreateExpressionTree (ResolveContext ec)
 773                 {
 774                         throw new NotSupportedException ("ET");
 775                 }
 776
 777                 protected virtual BlockContext CreateBlockContext (BlockContext bc)
 778                 {
 779                         var ctx = new BlockContext (bc, block, bc.ReturnType);
 780                         ctx.CurrentAnonymousMethod = this;
 781
 782                         ctx.AssignmentInfoOffset = bc.AssignmentInfoOffset;
 783                         ctx.EnclosingLoop = bc.EnclosingLoop;
 784                         ctx.EnclosingLoopOrSwitch = bc.EnclosingLoopOrSwitch;
 785                         ctx.Switch = bc.Switch;
 786
 787                         return ctx;
 788                 }
 789
 790                 protected override Expression DoResolve (ResolveContext rc)
 791                 {
 792                         var bc = (BlockContext) rc;
 793                         var ctx = CreateBlockContext (bc);
 794
 795                         Block.Resolve (ctx);
 796
 797                         if (!rc.IsInProbingMode) {
 798                                 var move_next = new StateMachineMethod (storey, this, new TypeExpression (ReturnType, loc), Modifiers.PUBLIC, new MemberName ("MoveNext", loc), 0);
 799                                 move_next.Block.AddStatement (new MoveNextBodyStatement (this));
 800                                 storey.AddEntryMethod (move_next);
 801                         }
 802
 803                         bc.AssignmentInfoOffset = ctx.AssignmentInfoOffset;
 804                         eclass = ExprClass.Value;
 805                         return this;
 806                 }
 807
 808                 public override void Emit (EmitContext ec)
 809                 {
 810                         //
 811                         // Load state machine instance
 812                         //
 813                         storey.Instance.Emit (ec);
 814                 }
 815
 816                 void EmitMoveNext_NoResumePoints (EmitContext ec)
 817                 {
 818                         ec.EmitThis ();
 819                         ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
 820
 821                         ec.EmitThis ();
 822                         ec.EmitInt ((int) IteratorStorey.State.After);
 823                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 824
 825                         // We only care if the PC is zero (start executing) or non-zero (don't do anything)
 826                         ec.Emit (OpCodes.Brtrue, move_next_error);
 827
 828                         BodyEnd = ec.DefineLabel ();
 829
 830                         block.EmitEmbedded (ec);
 831
 832                         ec.MarkLabel (BodyEnd);
 833
 834                         EmitMoveNextEpilogue (ec);
 835
 836                         ec.MarkLabel (move_next_error);
 837
 838                         if (ReturnType.Kind != MemberKind.Void) {
 839                                 ec.EmitInt (0);
 840                                 ec.Emit (OpCodes.Ret);
 841                         }
 842                 }
 843
 844                 void EmitMoveNext (EmitContext ec)
 845                 {
 846                         move_next_ok = ec.DefineLabel ();
 847                         move_next_error = ec.DefineLabel ();
 848
 849                         if (resume_points == null) {
 850                                 EmitMoveNext_NoResumePoints (ec);
 851                                 return;
 852                         }
 853
 854                         current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
 855                         ec.EmitThis ();
 856                         ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
 857                         ec.Emit (OpCodes.Stloc, current_pc);
 858
 859                         // We're actually in state 'running', but this is as good a PC value as any if there's an abnormal exit
 860                         ec.EmitThis ();
 861                         ec.EmitInt ((int) IteratorStorey.State.After);
 862                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 863
 864                         Label[] labels = new Label[1 + resume_points.Count];
 865                         labels[0] = ec.DefineLabel ();
 866
 867                         bool need_skip_finally = false;
 868                         for (int i = 0; i < resume_points.Count; ++i) {
 869                                 ResumableStatement s = resume_points[i];
 870                                 need_skip_finally |= s is ExceptionStatement;
 871                                 labels[i + 1] = s.PrepareForEmit (ec);
 872                         }
 873
 874                         if (need_skip_finally) {
 875                                 skip_finally = ec.GetTemporaryLocal (ec.BuiltinTypes.Bool);
 876                                 ec.EmitInt (0);
 877                                 ec.Emit (OpCodes.Stloc, skip_finally);
 878                         }
 879
 880                         var async_init = this as AsyncInitializer;
 881                         if (async_init != null)
 882                                 ec.BeginExceptionBlock ();
 883
 884                         ec.Emit (OpCodes.Ldloc, current_pc);
 885                         ec.Emit (OpCodes.Switch, labels);
 886
 887                         ec.Emit (async_init != null ? OpCodes.Leave : OpCodes.Br, move_next_error);
 888
 889                         ec.MarkLabel (labels[0]);
 890
 891                         BodyEnd = ec.DefineLabel ();
 892
 893                         block.EmitEmbedded (ec);
 894
 895                         ec.MarkLabel (BodyEnd);
 896
 897                         if (async_init != null) {
 898                                 var catch_value = LocalVariable.CreateCompilerGenerated (ec.Module.Compiler.BuiltinTypes.Exception, block, Location);
 899
 900                                 ec.BeginCatchBlock (catch_value.Type);
 901                                 catch_value.EmitAssign (ec);
 902
 903                                 ec.EmitThis ();
 904                                 ec.EmitInt ((int) IteratorStorey.State.After);
 905                                 ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 906
 907                                 ((AsyncTaskStorey) async_init.Storey).EmitSetException (ec, new LocalVariableReference (catch_value, Location));
 908
 909                                 ec.Emit (OpCodes.Leave, move_next_ok);
 910                                 ec.EndExceptionBlock ();
 911                         }
 912
 913                         ec.Mark (Block.Original.EndLocation);
 914                         ec.EmitThis ();
 915                         ec.EmitInt ((int) IteratorStorey.State.After);
 916                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 917
 918                         EmitMoveNextEpilogue (ec);
 919
 920                         ec.MarkLabel (move_next_error);
 921
 922                         if (ReturnType.Kind != MemberKind.Void) {
 923                                 ec.EmitInt (0);
 924                                 ec.Emit (OpCodes.Ret);
 925                         }
 926
 927                         ec.MarkLabel (move_next_ok);
 928
 929                         if (ReturnType.Kind != MemberKind.Void) {
 930                                 ec.EmitInt (1);
 931                                 ec.Emit (OpCodes.Ret);
 932                         }
 933                 }
 934
 935                 protected virtual void EmitMoveNextEpilogue (EmitContext ec)
 936                 {
 937                 }
 938
 939                 public void EmitLeave (EmitContext ec, bool unwind_protect)
 940                 {
 941                         // Return ok
 942                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
 943                 }
 944
 945                 //
 946                 // Called back from YieldStatement
 947                 //
 948                 public virtual void InjectYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
 949                 {
 950                         //
 951                         // Guard against being disposed meantime
 952                         //
 953                         Label disposed = ec.DefineLabel ();
 954                         var iterator = storey as IteratorStorey;
 955                         if (iterator != null) {
 956                                 ec.EmitThis ();
 957                                 ec.Emit (OpCodes.Ldfld, iterator.DisposingField.Spec);
 958                                 ec.Emit (OpCodes.Brtrue_S, disposed);
 959                         }
 960
 961                         //
 962                         // store resume program-counter
 963                         //
 964                         ec.EmitThis ();
 965                         ec.EmitInt (resume_pc);
 966                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 967
 968                         if (iterator != null) {
 969                                 ec.MarkLabel (disposed);
 970                         }
 971
 972                         // mark finally blocks as disabled
 973                         if (unwind_protect && skip_finally != null) {
 974                                 ec.EmitInt (1);
 975                                 ec.Emit (OpCodes.Stloc, skip_finally);
 976                         }
 977                 }
 978
 979                 public void SetStateMachine (StateMachine stateMachine)
 980                 {
 981                         this.storey = stateMachine;
 982                 }
 983         }
 984
 985         //
 986         // Iterators are implemented as state machine blocks
 987         //
 988         public class Iterator : StateMachineInitializer
 989         {
 990                 sealed class TryFinallyBlockProxyStatement : Statement
 991                 {
 992                         TryFinallyBlock block;
 993                         Iterator iterator;
 994
 995                         public TryFinallyBlockProxyStatement (Iterator iterator, TryFinallyBlock block)
 996                         {
 997                                 this.iterator = iterator;
 998                                 this.block = block;
 999                         }
1000
1001                         protected override void CloneTo (CloneContext clonectx, Statement target)
1002                         {
1003                                 throw new NotSupportedException ();
1004                         }
1005
1006                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1007                         {
1008                                 throw new NotSupportedException ();
1009                         }
1010
1011                         protected override void DoEmit (EmitContext ec)
1012                         {
1013                                 //
1014                                 // Restore redirection for any captured variables
1015                                 //
1016                                 ec.CurrentAnonymousMethod = iterator;
1017
1018                                 using (ec.With (BuilderContext.Options.OmitDebugInfo, !ec.HasMethodSymbolBuilder)) {
1019                                         block.EmitFinallyBody (ec);
1020                                 }
1021                         }
1022                 }
1023
1024                 public readonly IMethodData OriginalMethod;
1025                 public readonly bool IsEnumerable;
1026                 public readonly TypeSpec OriginalIteratorType;
1027                 int finally_hosts_counter;
1028
1029                 public Iterator (ParametersBlock block, IMethodData method, TypeDefinition host, TypeSpec iterator_type, bool is_enumerable)
1030                         : base (block, host, host.Compiler.BuiltinTypes.Bool)
1031                 {
1032                         this.OriginalMethod = method;
1033                         this.OriginalIteratorType = iterator_type;
1034                         this.IsEnumerable = is_enumerable;
1035                         this.type = method.ReturnType;
1036                 }
1037
1038                 #region Properties
1039
1040                 public ToplevelBlock Container {
1041                         get { return OriginalMethod.Block; }
1042                 }
1043
1044                 public override string ContainerType {
1045                         get { return "iterator"; }
1046                 }
1047
1048                 public override bool IsIterator {
1049                         get { return true; }
1050                 }
1051
1052                 #endregion
1053
1054                 public Method CreateFinallyHost (TryFinallyBlock block)
1055                 {
1056                         var method = new Method (storey, new TypeExpression (storey.Compiler.BuiltinTypes.Void, loc),
1057                                 Modifiers.COMPILER_GENERATED, new MemberName (CompilerGeneratedContainer.MakeName (null, null, "Finally", finally_hosts_counter++), loc),
1058                                 ParametersCompiled.EmptyReadOnlyParameters, null);
1059
1060                         method.Block = new ToplevelBlock (method.Compiler, method.ParameterInfo, loc,
1061                                 ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis);
1062                         method.Block.AddStatement (new TryFinallyBlockProxyStatement (this, block));
1063
1064                         // Cannot it add to storey because it'd be emitted before nested
1065                         // anonoymous methods which could capture shared variable
1066
1067                         return method;
1068                 }
1069
1070                 public void EmitYieldBreak (EmitContext ec, bool unwind_protect)
1071                 {
1072                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_error);
1073                 }
1074
1075                 public override string GetSignatureForError ()
1076                 {
1077                         return OriginalMethod.GetSignatureForError ();
1078                 }
1079
1080                 public override void Emit (EmitContext ec)
1081                 {
1082                         //
1083                         // Load Iterator storey instance
1084                         //
1085                         storey.Instance.Emit (ec);
1086
1087                         //
1088                         // Initialize iterator PC when it's unitialized
1089                         //
1090                         if (IsEnumerable) {
1091                                 ec.Emit (OpCodes.Dup);
1092                                 ec.EmitInt ((int)IteratorStorey.State.Uninitialized);
1093
1094                                 var field = storey.PC.Spec;
1095                                 if (storey.MemberName.IsGeneric) {
1096                                         field = MemberCache.GetMember (Storey.Instance.Type, field);
1097                                 }
1098
1099                                 ec.Emit (OpCodes.Stfld, field);
1100                         }
1101                 }
1102
1103                 public void EmitDispose (EmitContext ec)
1104                 {
1105                         if (resume_points == null)
1106                                 return;
1107
1108                         Label end = ec.DefineLabel ();
1109
1110                         Label[] labels = null;
1111                         for (int i = 0; i < resume_points.Count; ++i) {
1112                                 ResumableStatement s = resume_points[i];
1113                                 Label ret = s.PrepareForDispose (ec, end);
1114                                 if (ret.Equals (end) && labels == null)
1115                                         continue;
1116                                 if (labels == null) {
1117                                         labels = new Label[resume_points.Count + 1];
1118                                         for (int j = 0; j <= i; ++j)
1119                                                 labels[j] = end;
1120                                 }
1121
1122                                 labels[i + 1] = ret;
1123                         }
1124
1125                         if (labels != null) {
1126                                 current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
1127                                 ec.EmitThis ();
1128                                 ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
1129                                 ec.Emit (OpCodes.Stloc, current_pc);
1130                         }
1131
1132                         ec.EmitThis ();
1133                         ec.EmitInt (1);
1134                         ec.Emit (OpCodes.Stfld, ((IteratorStorey) storey).DisposingField.Spec);
1135
1136                         ec.EmitThis ();
1137                         ec.EmitInt ((int) IteratorStorey.State.After);
1138                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
1139
1140                         if (labels != null) {
1141                                 //SymbolWriter.StartIteratorDispatcher (ec.ig);
1142                                 ec.Emit (OpCodes.Ldloc, current_pc);
1143                                 ec.Emit (OpCodes.Switch, labels);
1144                                 //SymbolWriter.EndIteratorDispatcher (ec.ig);
1145
1146                                 foreach (ResumableStatement s in resume_points)
1147                                         s.EmitForDispose (ec, current_pc, end, true);
1148                         }
1149
1150                         ec.MarkLabel (end);
1151                 }
1152
1153                 public override void EmitStatement (EmitContext ec)
1154                 {
1155                         throw new NotImplementedException ();
1156                 }
1157
1158                 public override void InjectYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
1159                 {
1160                         // Store the new value into current
1161                         var fe = new FieldExpr (((IteratorStorey) storey).CurrentField, loc);
1162                         fe.InstanceExpression = new CompilerGeneratedThis (storey.CurrentType, loc);
1163                         fe.EmitAssign (ec, expr, false, false);
1164
1165                         base.InjectYield (ec, expr, resume_pc, unwind_protect, resume_point);
1166
1167                         EmitLeave (ec, unwind_protect);
1168
1169                         ec.MarkLabel (resume_point);
1170                 }
1171
1172                 public static void CreateIterator (IMethodData method, TypeDefinition parent, Modifiers modifiers)
1173                 {
1174                         bool is_enumerable;
1175                         TypeSpec iterator_type;
1176
1177                         TypeSpec ret = method.ReturnType;
1178                         if (ret == null)
1179                                 return;
1180
1181                         if (!CheckType (ret, parent, out iterator_type, out is_enumerable)) {
1182                                 parent.Compiler.Report.Error (1624, method.Location,
1183                                               "The body of `{0}' cannot be an iterator block " +
1184                                               "because `{1}' is not an iterator interface type",
1185                                               method.GetSignatureForError (),
1186                                               ret.GetSignatureForError ());
1187                                 return;
1188                         }
1189
1190                         ParametersCompiled parameters = method.ParameterInfo;
1191                         for (int i = 0; i < parameters.Count; i++) {
1192                                 Parameter p = parameters [i];
1193                                 Parameter.Modifier mod = p.ModFlags;
1194                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
1195                                         parent.Compiler.Report.Error (1623, p.Location,
1196                                                 "Iterators cannot have ref or out parameters");
1197                                         return;
1198                                 }
1199
1200                                 if (p is ArglistParameter) {
1201                                         parent.Compiler.Report.Error (1636, method.Location,
1202                                                 "__arglist is not allowed in parameter list of iterators");
1203                                         return;
1204                                 }
1205
1206                                 if (parameters.Types [i].IsPointer) {
1207                                         parent.Compiler.Report.Error (1637, p.Location,
1208                                                 "Iterators cannot have unsafe parameters or yield types");
1209                                         return;
1210                                 }
1211                         }
1212
1213                         if ((modifiers & Modifiers.UNSAFE) != 0) {
1214                                 parent.Compiler.Report.Error (1629, method.Location, "Unsafe code may not appear in iterators");
1215                         }
1216
1217                         method.Block = method.Block.ConvertToIterator (method, parent, iterator_type, is_enumerable);
1218                 }
1219
1220                 static bool CheckType (TypeSpec ret, TypeContainer parent, out TypeSpec original_iterator_type, out bool is_enumerable)
1221                 {
1222                         original_iterator_type = null;
1223                         is_enumerable = false;
1224
1225                         if (ret.BuiltinType == BuiltinTypeSpec.Type.IEnumerable) {
1226                                 original_iterator_type = parent.Compiler.BuiltinTypes.Object;
1227                                 is_enumerable = true;
1228                                 return true;
1229                         }
1230                         if (ret.BuiltinType == BuiltinTypeSpec.Type.IEnumerator) {
1231                                 original_iterator_type = parent.Compiler.BuiltinTypes.Object;
1232                                 is_enumerable = false;
1233                                 return true;
1234                         }
1235
1236                         InflatedTypeSpec inflated = ret as InflatedTypeSpec;
1237                         if (inflated == null)
1238                                 return false;
1239
1240                         var member_definition = inflated.MemberDefinition;
1241                         PredefinedType ptype = parent.Module.PredefinedTypes.IEnumerableGeneric;
1242
1243                         if (ptype.Define () && ptype.TypeSpec.MemberDefinition == member_definition) {
1244                                 original_iterator_type = inflated.TypeArguments[0];
1245                                 is_enumerable = true;
1246                                 return true;
1247                         }
1248
1249                         ptype = parent.Module.PredefinedTypes.IEnumeratorGeneric;
1250                         if (ptype.Define () && ptype.TypeSpec.MemberDefinition == member_definition) {
1251                                 original_iterator_type = inflated.TypeArguments[0];
1252                                 is_enumerable = false;
1253                                 return true;
1254                         }
1255
1256                         return false;
1257                 }
1258         }
1259 }
1260