mcs/mcs/statement.cs

   1 //
   2 // statement.cs: Statement representation for the IL tree.
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Martin Baulig (martin@ximian.com)
   7 //   Marek Safar (marek.safar@gmail.com)
   8 //
   9 // Copyright 2001, 2002, 2003 Ximian, Inc.
  10 // Copyright 2003, 2004 Novell, Inc.
  11 // Copyright 2011 Xamarin Inc.
  12 //
  13
  14 using System;
  15 using System.Collections.Generic;
  16
  17 #if STATIC
  18 using IKVM.Reflection.Emit;
  19 #else
  20 using System.Reflection.Emit;
  21 #endif
  22
  23 namespace Mono.CSharp {
  24
  25         public abstract class Statement {
  26                 public Location loc;
  27                 protected bool reachable;
  28
  29                 public bool IsUnreachable {
  30                         get {
  31                                 return !reachable;
  32                         }
  33                 }
  34
  35                 /// <summary>
  36                 ///   Resolves the statement, true means that all sub-statements
  37                 ///   did resolve ok.
  38                 ///  </summary>
  39                 public virtual bool Resolve (BlockContext bc)
  40                 {
  41                         return true;
  42                 }
  43
  44                 /// <summary>
  45                 ///   Return value indicates whether all code paths emitted return.
  46                 /// </summary>
  47                 protected abstract void DoEmit (EmitContext ec);
  48
  49                 public virtual void Emit (EmitContext ec)
  50                 {
  51                         ec.Mark (loc);
  52                         DoEmit (ec);
  53
  54                         if (ec.StatementEpilogue != null) {
  55                                 ec.EmitEpilogue ();
  56                         }
  57                 }
  58
  59                 //
  60                 // This routine must be overrided in derived classes and make copies
  61                 // of all the data that might be modified if resolved
  62                 //
  63                 protected abstract void CloneTo (CloneContext clonectx, Statement target);
  64
  65                 public Statement Clone (CloneContext clonectx)
  66                 {
  67                         Statement s = (Statement) this.MemberwiseClone ();
  68                         CloneTo (clonectx, s);
  69                         return s;
  70                 }
  71
  72                 public virtual Expression CreateExpressionTree (ResolveContext ec)
  73                 {
  74                         ec.Report.Error (834, loc, "A lambda expression with statement body cannot be converted to an expresion tree");
  75                         return null;
  76                 }
  77
  78                 public virtual object Accept (StructuralVisitor visitor)
  79                 {
  80                         return visitor.Visit (this);
  81                 }
  82
  83                 //
  84                 // Return value indicates whether statement has unreachable end
  85                 //
  86                 protected abstract bool DoFlowAnalysis (FlowAnalysisContext fc);
  87
  88                 public bool FlowAnalysis (FlowAnalysisContext fc)
  89                 {
  90                         if (reachable) {
  91                                 fc.UnreachableReported = false;
  92                                 var res = DoFlowAnalysis (fc);
  93                                 return res;
  94                         }
  95
  96                         //
  97                         // Special handling cases
  98                         //
  99                         if (this is Block) {
 100                                 return DoFlowAnalysis (fc);
 101                         }
 102
 103                         if (this is EmptyStatement || loc.IsNull)
 104                                 return true;
 105
 106                         if (fc.UnreachableReported)
 107                                 return true;
 108
 109                         fc.Report.Warning (162, 2, loc, "Unreachable code detected");
 110                         fc.UnreachableReported = true;
 111                         return true;
 112                 }
 113
 114                 public virtual Reachability MarkReachable (Reachability rc)
 115                 {
 116                         if (!rc.IsUnreachable)
 117                                 reachable = true;
 118
 119                         return rc;
 120                 }
 121
 122                 protected void CheckExitBoundaries (BlockContext bc, Block scope)
 123                 {
 124                         if (bc.CurrentBlock.ParametersBlock.Original != scope.ParametersBlock.Original) {
 125                                 bc.Report.Error (1632, loc, "Control cannot leave the body of an anonymous method");
 126                                 return;
 127                         }
 128
 129                         for (var b = bc.CurrentBlock; b != null && b != scope; b = b.Parent) {
 130                                 if (b.IsFinallyBlock) {
 131                                         Error_FinallyClauseExit (bc);
 132                                         break;
 133                                 }
 134                         }
 135                 }
 136
 137                 protected void Error_FinallyClauseExit (BlockContext bc)
 138                 {
 139                         bc.Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 140                 }
 141         }
 142
 143         public sealed class EmptyStatement : Statement
 144         {
 145                 public EmptyStatement (Location loc)
 146                 {
 147                         this.loc = loc;
 148                 }
 149
 150                 public override bool Resolve (BlockContext ec)
 151                 {
 152                         return true;
 153                 }
 154
 155                 public override void Emit (EmitContext ec)
 156                 {
 157                 }
 158
 159                 protected override void DoEmit (EmitContext ec)
 160                 {
 161                         throw new NotSupportedException ();
 162                 }
 163
 164                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 165                 {
 166                         return false;
 167                 }
 168
 169                 protected override void CloneTo (CloneContext clonectx, Statement target)
 170                 {
 171                         // nothing needed.
 172                 }
 173
 174                 public override object Accept (StructuralVisitor visitor)
 175                 {
 176                         return visitor.Visit (this);
 177                 }
 178         }
 179
 180         public class If : Statement {
 181                 Expression expr;
 182                 public Statement TrueStatement;
 183                 public Statement FalseStatement;
 184
 185                 bool true_returns, false_returns;
 186
 187                 public If (Expression bool_expr, Statement true_statement, Location l)
 188                         : this (bool_expr, true_statement, null, l)
 189                 {
 190                 }
 191
 192                 public If (Expression bool_expr,
 193                            Statement true_statement,
 194                            Statement false_statement,
 195                            Location l)
 196                 {
 197                         this.expr = bool_expr;
 198                         TrueStatement = true_statement;
 199                         FalseStatement = false_statement;
 200                         loc = l;
 201                 }
 202
 203                 public Expression Expr {
 204                         get {
 205                                 return this.expr;
 206                         }
 207                 }
 208
 209                 public override bool Resolve (BlockContext ec)
 210                 {
 211                         expr = expr.Resolve (ec);
 212
 213                         var ok = TrueStatement.Resolve (ec);
 214
 215                         if (FalseStatement != null) {
 216                                 ok &= FalseStatement.Resolve (ec);
 217                         }
 218
 219                         return ok;
 220                 }
 221
 222                 protected override void DoEmit (EmitContext ec)
 223                 {
 224                         Label false_target = ec.DefineLabel ();
 225                         Label end;
 226
 227                         //
 228                         // If we're a boolean constant, Resolve() already
 229                         // eliminated dead code for us.
 230                         //
 231                         Constant c = expr as Constant;
 232                         if (c != null){
 233                                 c.EmitSideEffect (ec);
 234
 235                                 if (!c.IsDefaultValue)
 236                                         TrueStatement.Emit (ec);
 237                                 else if (FalseStatement != null)
 238                                         FalseStatement.Emit (ec);
 239
 240                                 return;
 241                         }
 242
 243                         expr.EmitBranchable (ec, false_target, false);
 244
 245                         TrueStatement.Emit (ec);
 246
 247                         if (FalseStatement != null){
 248                                 bool branch_emitted = false;
 249
 250                                 end = ec.DefineLabel ();
 251                                 if (!true_returns){
 252                                         ec.Emit (OpCodes.Br, end);
 253                                         branch_emitted = true;
 254                                 }
 255
 256                                 ec.MarkLabel (false_target);
 257                                 FalseStatement.Emit (ec);
 258
 259                                 if (branch_emitted)
 260                                         ec.MarkLabel (end);
 261                         } else {
 262                                 ec.MarkLabel (false_target);
 263                         }
 264                 }
 265
 266                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 267                 {
 268                         expr.FlowAnalysisConditional (fc);
 269
 270                         var da_false = new DefiniteAssignmentBitSet (fc.DefiniteAssignmentOnFalse);
 271
 272                         fc.DefiniteAssignment = fc.DefiniteAssignmentOnTrue;
 273
 274                         var res = TrueStatement.FlowAnalysis (fc);
 275
 276                         if (FalseStatement == null) {
 277                                 var c = expr as Constant;
 278                                 if (c != null && !c.IsDefaultValue)
 279                                         return true_returns;
 280
 281                                 if (true_returns)
 282                                         fc.DefiniteAssignment = da_false;
 283                                 else
 284                                         fc.DefiniteAssignment &= da_false;
 285
 286                                 return false;
 287                         }
 288
 289                         if (true_returns) {
 290                                 fc.DefiniteAssignment = da_false;
 291                                 return FalseStatement.FlowAnalysis (fc);
 292                         }
 293
 294                         var da_true = fc.DefiniteAssignment;
 295
 296                         fc.DefiniteAssignment = da_false;
 297                         res &= FalseStatement.FlowAnalysis (fc);
 298
 299                         if (!TrueStatement.IsUnreachable) {
 300                                 if (false_returns || FalseStatement.IsUnreachable)
 301                                         fc.DefiniteAssignment = da_true;
 302                                 else
 303                                         fc.DefiniteAssignment &= da_true;
 304                         }
 305
 306                         return res;
 307                 }
 308
 309                 public override Reachability MarkReachable (Reachability rc)
 310                 {
 311                         if (rc.IsUnreachable)
 312                                 return rc;
 313
 314                         base.MarkReachable (rc);
 315
 316                         var c = expr as Constant;
 317                         if (c != null) {
 318                                 bool take = !c.IsDefaultValue;
 319                                 if (take) {
 320                                         rc = TrueStatement.MarkReachable (rc);
 321                                 } else {
 322                                         if (FalseStatement != null)
 323                                                 rc = FalseStatement.MarkReachable (rc);
 324                                 }
 325
 326                                 return rc;
 327                         }
 328
 329                         var true_rc = TrueStatement.MarkReachable (rc);
 330                         true_returns = true_rc.IsUnreachable;
 331
 332                         if (FalseStatement == null)
 333                                 return rc;
 334
 335                         var false_rc = FalseStatement.MarkReachable (rc);
 336                         false_returns = false_rc.IsUnreachable;
 337
 338                         return true_rc & false_rc;
 339                 }
 340
 341                 protected override void CloneTo (CloneContext clonectx, Statement t)
 342                 {
 343                         If target = (If) t;
 344
 345                         target.expr = expr.Clone (clonectx);
 346                         target.TrueStatement = TrueStatement.Clone (clonectx);
 347                         if (FalseStatement != null)
 348                                 target.FalseStatement = FalseStatement.Clone (clonectx);
 349                 }
 350
 351                 public override object Accept (StructuralVisitor visitor)
 352                 {
 353                         return visitor.Visit (this);
 354                 }
 355         }
 356
 357         public class Do : LoopStatement
 358         {
 359                 public Expression expr;
 360                 bool iterator_reachable, end_reachable;
 361
 362                 public Do (Statement statement, BooleanExpression bool_expr, Location doLocation, Location whileLocation)
 363                         : base (statement)
 364                 {
 365                         expr = bool_expr;
 366                         loc = doLocation;
 367                         WhileLocation = whileLocation;
 368                 }
 369
 370                 public Location WhileLocation {
 371                         get; private set;
 372                 }
 373
 374                 public override bool Resolve (BlockContext bc)
 375                 {
 376                         var ok = base.Resolve (bc);
 377
 378                         expr = expr.Resolve (bc);
 379
 380                         return ok;
 381                 }
 382
 383                 protected override void DoEmit (EmitContext ec)
 384                 {
 385                         Label loop = ec.DefineLabel ();
 386                         Label old_begin = ec.LoopBegin;
 387                         Label old_end = ec.LoopEnd;
 388
 389                         ec.LoopBegin = ec.DefineLabel ();
 390                         ec.LoopEnd = ec.DefineLabel ();
 391
 392                         ec.MarkLabel (loop);
 393                         Statement.Emit (ec);
 394                         ec.MarkLabel (ec.LoopBegin);
 395
 396                         // Mark start of while condition
 397                         ec.Mark (WhileLocation);
 398
 399                         //
 400                         // Dead code elimination
 401                         //
 402                         if (expr is Constant) {
 403                                 bool res = !((Constant) expr).IsDefaultValue;
 404
 405                                 expr.EmitSideEffect (ec);
 406                                 if (res)
 407                                         ec.Emit (OpCodes.Br, loop);
 408                         } else {
 409                                 expr.EmitBranchable (ec, loop, true);
 410                         }
 411
 412                         ec.MarkLabel (ec.LoopEnd);
 413
 414                         ec.LoopBegin = old_begin;
 415                         ec.LoopEnd = old_end;
 416                 }
 417
 418                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 419                 {
 420                         var res = Statement.FlowAnalysis (fc);
 421
 422                         expr.FlowAnalysisConditional (fc);
 423
 424                         fc.DefiniteAssignment = fc.DefiniteAssignmentOnFalse;
 425
 426                         if (res && !iterator_reachable)
 427                                 return !end_reachable;
 428
 429                         if (!end_reachable) {
 430                                 var c = expr as Constant;
 431                                 if (c != null && !c.IsDefaultValue)
 432                                         return true;
 433                         }
 434
 435                         return false;
 436                 }
 437
 438                 public override Reachability MarkReachable (Reachability rc)
 439                 {
 440                         base.MarkReachable (rc);
 441
 442                         var body_rc = Statement.MarkReachable (rc);
 443
 444                         if (body_rc.IsUnreachable && !iterator_reachable) {
 445                                 expr = new UnreachableExpression (expr);
 446                                 return end_reachable ? rc : Reachability.CreateUnreachable ();
 447                         }
 448
 449                         if (!end_reachable) {
 450                                 var c = expr as Constant;
 451                                 if (c != null && !c.IsDefaultValue)
 452                                         return Reachability.CreateUnreachable ();
 453                         }
 454
 455                         return rc;
 456                 }
 457
 458                 protected override void CloneTo (CloneContext clonectx, Statement t)
 459                 {
 460                         Do target = (Do) t;
 461
 462                         target.Statement = Statement.Clone (clonectx);
 463                         target.expr = expr.Clone (clonectx);
 464                 }
 465
 466                 public override object Accept (StructuralVisitor visitor)
 467                 {
 468                         return visitor.Visit (this);
 469                 }
 470
 471                 public override void SetEndReachable ()
 472                 {
 473                         end_reachable = true;
 474                 }
 475
 476                 public override void SetIteratorReachable ()
 477                 {
 478                         iterator_reachable = true;
 479                 }
 480         }
 481
 482         public class While : LoopStatement
 483         {
 484                 public Expression expr;
 485                 bool empty, infinite, end_reachable;
 486                 List<DefiniteAssignmentBitSet> end_reachable_das;
 487
 488                 public While (BooleanExpression bool_expr, Statement statement, Location l)
 489                         : base (statement)
 490                 {
 491                         this.expr = bool_expr;
 492                         loc = l;
 493                 }
 494
 495                 public override bool Resolve (BlockContext bc)
 496                 {
 497                         bool ok = true;
 498
 499                         expr = expr.Resolve (bc);
 500                         if (expr == null)
 501                                 ok = false;
 502
 503                         var c = expr as Constant;
 504                         if (c != null) {
 505                                 empty = c.IsDefaultValue;
 506                                 infinite = !empty;
 507                         }
 508
 509                         ok &= base.Resolve (bc);
 510                         return ok;
 511                 }
 512
 513                 protected override void DoEmit (EmitContext ec)
 514                 {
 515                         if (empty) {
 516                                 expr.EmitSideEffect (ec);
 517                                 return;
 518                         }
 519
 520                         Label old_begin = ec.LoopBegin;
 521                         Label old_end = ec.LoopEnd;
 522
 523                         ec.LoopBegin = ec.DefineLabel ();
 524                         ec.LoopEnd = ec.DefineLabel ();
 525
 526                         //
 527                         // Inform whether we are infinite or not
 528                         //
 529                         if (expr is Constant) {
 530                                 // expr is 'true', since the 'empty' case above handles the 'false' case
 531                                 ec.MarkLabel (ec.LoopBegin);
 532
 533                                 if (ec.EmitAccurateDebugInfo)
 534                                         ec.Emit (OpCodes.Nop);
 535
 536                                 expr.EmitSideEffect (ec);
 537                                 Statement.Emit (ec);
 538                                 ec.Emit (OpCodes.Br, ec.LoopBegin);
 539
 540                                 //
 541                                 // Inform that we are infinite (ie, `we return'), only
 542                                 // if we do not `break' inside the code.
 543                                 //
 544                                 ec.MarkLabel (ec.LoopEnd);
 545                         } else {
 546                                 Label while_loop = ec.DefineLabel ();
 547
 548                                 ec.Emit (OpCodes.Br, ec.LoopBegin);
 549                                 ec.MarkLabel (while_loop);
 550
 551                                 Statement.Emit (ec);
 552
 553                                 ec.MarkLabel (ec.LoopBegin);
 554
 555                                 ec.Mark (loc);
 556                                 expr.EmitBranchable (ec, while_loop, true);
 557
 558                                 ec.MarkLabel (ec.LoopEnd);
 559                         }
 560
 561                         ec.LoopBegin = old_begin;
 562                         ec.LoopEnd = old_end;
 563                 }
 564
 565                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 566                 {
 567                         expr.FlowAnalysisConditional (fc);
 568
 569                         fc.DefiniteAssignment = fc.DefiniteAssignmentOnTrue;
 570                         var da_false = new DefiniteAssignmentBitSet (fc.DefiniteAssignmentOnFalse);
 571
 572                         Statement.FlowAnalysis (fc);
 573
 574                         //
 575                         // Special case infinite while with breaks
 576                         //
 577                         if (end_reachable_das != null) {
 578                                 da_false = DefiniteAssignmentBitSet.And (end_reachable_das);
 579                                 end_reachable_das = null;
 580                         }
 581
 582                         fc.DefiniteAssignment = da_false;
 583
 584                         if (infinite && !end_reachable)
 585                                 return true;
 586
 587                         return false;
 588                 }
 589
 590                 public override Reachability MarkReachable (Reachability rc)
 591                 {
 592                         if (rc.IsUnreachable)
 593                                 return rc;
 594
 595                         base.MarkReachable (rc);
 596
 597                         //
 598                         // Special case unreachable while body
 599                         //
 600                         if (empty) {
 601                                 Statement.MarkReachable (Reachability.CreateUnreachable ());
 602                                 return rc;
 603                         }
 604
 605                         Statement.MarkReachable (rc);
 606
 607                         //
 608                         // When infinite while end is unreachable via break anything what follows is unreachable too
 609                         //
 610                         if (infinite && !end_reachable)
 611                                 return Reachability.CreateUnreachable ();
 612
 613                         return rc;
 614                 }
 615
 616                 protected override void CloneTo (CloneContext clonectx, Statement t)
 617                 {
 618                         While target = (While) t;
 619
 620                         target.expr = expr.Clone (clonectx);
 621                         target.Statement = Statement.Clone (clonectx);
 622                 }
 623
 624                 public override object Accept (StructuralVisitor visitor)
 625                 {
 626                         return visitor.Visit (this);
 627                 }
 628
 629                 public override void AddEndDefiniteAssignment (FlowAnalysisContext fc)
 630                 {
 631                         if (!infinite)
 632                                 return;
 633
 634                         if (end_reachable_das == null)
 635                                 end_reachable_das = new List<DefiniteAssignmentBitSet> ();
 636
 637                         end_reachable_das.Add (fc.DefiniteAssignment);
 638                 }
 639
 640                 public override void SetEndReachable ()
 641                 {
 642                         end_reachable = true;
 643                 }
 644         }
 645
 646         public class For : LoopStatement
 647         {
 648                 bool infinite, empty, iterator_reachable, end_reachable;
 649                 List<DefiniteAssignmentBitSet> end_reachable_das;
 650
 651                 public For (Location l)
 652                         : base (null)
 653                 {
 654                         loc = l;
 655                 }
 656
 657                 public Statement Initializer {
 658                         get; set;
 659                 }
 660
 661                 public Expression Condition {
 662                         get; set;
 663                 }
 664
 665                 public Statement Iterator {
 666                         get; set;
 667                 }
 668
 669                 public override bool Resolve (BlockContext bc)
 670                 {
 671                         Initializer.Resolve (bc);
 672
 673                         if (Condition != null) {
 674                                 Condition = Condition.Resolve (bc);
 675                                 var condition_constant = Condition as Constant;
 676                                 if (condition_constant != null) {
 677                                         if (condition_constant.IsDefaultValue) {
 678                                                 empty = true;
 679                                         } else {
 680                                                 infinite = true;
 681                                         }
 682                                 }
 683                         } else {
 684                                 infinite = true;
 685                         }
 686
 687                         return base.Resolve (bc) && Iterator.Resolve (bc);
 688                 }
 689
 690                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 691                 {
 692                         Initializer.FlowAnalysis (fc);
 693
 694                         DefiniteAssignmentBitSet da_false;
 695                         if (Condition != null) {
 696                                 Condition.FlowAnalysisConditional (fc);
 697                                 fc.DefiniteAssignment = fc.DefiniteAssignmentOnTrue;
 698                                 da_false = new DefiniteAssignmentBitSet (fc.DefiniteAssignmentOnFalse);
 699                         } else {
 700                                 da_false = fc.BranchDefiniteAssignment ();
 701                         }
 702
 703                         Statement.FlowAnalysis (fc);
 704
 705                         Iterator.FlowAnalysis (fc);
 706
 707                         //
 708                         // Special case infinite for with breaks
 709                         //
 710                         if (end_reachable_das != null) {
 711                                 da_false = DefiniteAssignmentBitSet.And (end_reachable_das);
 712                                 end_reachable_das = null;
 713                         }
 714
 715                         fc.DefiniteAssignment = da_false;
 716
 717                         if (infinite && !end_reachable)
 718                                 return true;
 719
 720                         return false;
 721                 }
 722
 723                 public override Reachability MarkReachable (Reachability rc)
 724                 {
 725                         base.MarkReachable (rc);
 726
 727                         Initializer.MarkReachable (rc);
 728
 729                         var body_rc = Statement.MarkReachable (rc);
 730                         if (!body_rc.IsUnreachable || iterator_reachable) {
 731                                 Iterator.MarkReachable (rc);
 732                         }
 733
 734                         //
 735                         // When infinite for end is unreachable via break anything what follows is unreachable too
 736                         //
 737                         if (infinite && !end_reachable) {
 738                                 return Reachability.CreateUnreachable ();
 739                         }
 740
 741                         return rc;
 742                 }
 743
 744                 protected override void DoEmit (EmitContext ec)
 745                 {
 746                         if (Initializer != null)
 747                                 Initializer.Emit (ec);
 748
 749                         if (empty) {
 750                                 Condition.EmitSideEffect (ec);
 751                                 return;
 752                         }
 753
 754                         Label old_begin = ec.LoopBegin;
 755                         Label old_end = ec.LoopEnd;
 756                         Label loop = ec.DefineLabel ();
 757                         Label test = ec.DefineLabel ();
 758
 759                         ec.LoopBegin = ec.DefineLabel ();
 760                         ec.LoopEnd = ec.DefineLabel ();
 761
 762                         ec.Emit (OpCodes.Br, test);
 763                         ec.MarkLabel (loop);
 764                         Statement.Emit (ec);
 765
 766                         ec.MarkLabel (ec.LoopBegin);
 767                         Iterator.Emit (ec);
 768
 769                         ec.MarkLabel (test);
 770                         //
 771                         // If test is null, there is no test, and we are just
 772                         // an infinite loop
 773                         //
 774                         if (Condition != null) {
 775                                 ec.Mark (Condition.Location);
 776
 777                                 //
 778                                 // The Resolve code already catches the case for
 779                                 // Test == Constant (false) so we know that
 780                                 // this is true
 781                                 //
 782                                 if (Condition is Constant) {
 783                                         Condition.EmitSideEffect (ec);
 784                                         ec.Emit (OpCodes.Br, loop);
 785                                 } else {
 786                                         Condition.EmitBranchable (ec, loop, true);
 787                                 }
 788
 789                         } else
 790                                 ec.Emit (OpCodes.Br, loop);
 791                         ec.MarkLabel (ec.LoopEnd);
 792
 793                         ec.LoopBegin = old_begin;
 794                         ec.LoopEnd = old_end;
 795                 }
 796
 797                 protected override void CloneTo (CloneContext clonectx, Statement t)
 798                 {
 799                         For target = (For) t;
 800
 801                         if (Initializer != null)
 802                                 target.Initializer = Initializer.Clone (clonectx);
 803                         if (Condition != null)
 804                                 target.Condition = Condition.Clone (clonectx);
 805                         if (Iterator != null)
 806                                 target.Iterator = Iterator.Clone (clonectx);
 807                         target.Statement = Statement.Clone (clonectx);
 808                 }
 809
 810                 public override object Accept (StructuralVisitor visitor)
 811                 {
 812                         return visitor.Visit (this);
 813                 }
 814
 815                 public override void AddEndDefiniteAssignment (FlowAnalysisContext fc)
 816                 {
 817                         if (!infinite)
 818                                 return;
 819
 820                         if (end_reachable_das == null)
 821                                 end_reachable_das = new List<DefiniteAssignmentBitSet> ();
 822
 823                         end_reachable_das.Add (fc.DefiniteAssignment);
 824                 }
 825
 826                 public override void SetEndReachable ()
 827                 {
 828                         end_reachable = true;
 829                 }
 830
 831                 public override void SetIteratorReachable ()
 832                 {
 833                         iterator_reachable = true;
 834                 }
 835         }
 836
 837         public abstract class LoopStatement : Statement
 838         {
 839                 protected LoopStatement (Statement statement)
 840                 {
 841                         Statement = statement;
 842                 }
 843
 844                 public Statement Statement { get; set; }
 845
 846                 public override bool Resolve (BlockContext bc)
 847                 {
 848                         var prev_loop = bc.EnclosingLoop;
 849                         var prev_los = bc.EnclosingLoopOrSwitch;
 850                         bc.EnclosingLoopOrSwitch = bc.EnclosingLoop = this;
 851                         var ok = Statement.Resolve (bc);
 852                         bc.EnclosingLoopOrSwitch = prev_los;
 853                         bc.EnclosingLoop = prev_loop;
 854
 855                         return ok;
 856                 }
 857
 858                 //
 859                 // Needed by possibly infinite loops statements (for, while) and switch statment
 860                 //
 861                 public virtual void AddEndDefiniteAssignment (FlowAnalysisContext fc)
 862                 {
 863                 }
 864
 865                 public virtual void SetEndReachable ()
 866                 {
 867                 }
 868
 869                 public virtual void SetIteratorReachable ()
 870                 {
 871                 }
 872         }
 873
 874         public class StatementExpression : Statement
 875         {
 876                 ExpressionStatement expr;
 877
 878                 public StatementExpression (ExpressionStatement expr)
 879                 {
 880                         this.expr = expr;
 881                         loc = expr.StartLocation;
 882                 }
 883
 884                 public StatementExpression (ExpressionStatement expr, Location loc)
 885                 {
 886                         this.expr = expr;
 887                         this.loc = loc;
 888                 }
 889
 890                 public ExpressionStatement Expr {
 891                         get {
 892                                 return this.expr;
 893                         }
 894                 }
 895
 896                 protected override void CloneTo (CloneContext clonectx, Statement t)
 897                 {
 898                         StatementExpression target = (StatementExpression) t;
 899                         target.expr = (ExpressionStatement) expr.Clone (clonectx);
 900                 }
 901
 902                 protected override void DoEmit (EmitContext ec)
 903                 {
 904                         expr.EmitStatement (ec);
 905                 }
 906
 907                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 908                 {
 909                         expr.FlowAnalysis (fc);
 910                         return false;
 911                 }
 912
 913                 public override Reachability MarkReachable (Reachability rc)
 914                 {
 915                         base.MarkReachable (rc);
 916                         expr.MarkReachable (rc);
 917                         return rc;
 918                 }
 919
 920                 public override bool Resolve (BlockContext ec)
 921                 {
 922                         expr = expr.ResolveStatement (ec);
 923                         return expr != null;
 924                 }
 925
 926                 public override object Accept (StructuralVisitor visitor)
 927                 {
 928                         return visitor.Visit (this);
 929                 }
 930         }
 931
 932         public class StatementErrorExpression : Statement
 933         {
 934                 Expression expr;
 935
 936                 public StatementErrorExpression (Expression expr)
 937                 {
 938                         this.expr = expr;
 939                         this.loc = expr.StartLocation;
 940                 }
 941
 942                 public Expression Expr {
 943                         get {
 944                                 return expr;
 945                         }
 946                 }
 947
 948                 public override bool Resolve (BlockContext bc)
 949                 {
 950                         expr.Error_InvalidExpressionStatement (bc);
 951                         return true;
 952                 }
 953
 954                 protected override void DoEmit (EmitContext ec)
 955                 {
 956                         throw new NotSupportedException ();
 957                 }
 958
 959                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 960                 {
 961                         return false;
 962                 }
 963
 964                 protected override void CloneTo (CloneContext clonectx, Statement target)
 965                 {
 966                         var t = (StatementErrorExpression) target;
 967
 968                         t.expr = expr.Clone (clonectx);
 969                 }
 970
 971                 public override object Accept (StructuralVisitor visitor)
 972                 {
 973                         return visitor.Visit (this);
 974                 }
 975         }
 976
 977         //
 978         // Simple version of statement list not requiring a block
 979         //
 980         public class StatementList : Statement
 981         {
 982                 List<Statement> statements;
 983
 984                 public StatementList (Statement first, Statement second)
 985                 {
 986                         statements = new List<Statement> { first, second };
 987                 }
 988
 989                 #region Properties
 990                 public IList<Statement> Statements {
 991                         get {
 992                                 return statements;
 993                         }
 994                 }
 995                 #endregion
 996
 997                 public void Add (Statement statement)
 998                 {
 999                         statements.Add (statement);
1000                 }
1001
1002                 public override bool Resolve (BlockContext ec)
1003                 {
1004                         foreach (var s in statements)
1005                                 s.Resolve (ec);
1006
1007                         return true;
1008                 }
1009
1010                 protected override void DoEmit (EmitContext ec)
1011                 {
1012                         foreach (var s in statements)
1013                                 s.Emit (ec);
1014                 }
1015
1016                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1017                 {
1018                         foreach (var s in statements)
1019                                 s.FlowAnalysis (fc);
1020
1021                         return false;
1022                 }
1023
1024                 public override Reachability MarkReachable (Reachability rc)
1025                 {
1026                         base.MarkReachable (rc);
1027
1028                         Reachability res = rc;
1029                         foreach (var s in statements)
1030                                 res = s.MarkReachable (rc);
1031
1032                         return res;
1033                 }
1034
1035                 protected override void CloneTo (CloneContext clonectx, Statement target)
1036                 {
1037                         StatementList t = (StatementList) target;
1038
1039                         t.statements = new List<Statement> (statements.Count);
1040                         foreach (Statement s in statements)
1041                                 t.statements.Add (s.Clone (clonectx));
1042                 }
1043
1044                 public override object Accept (StructuralVisitor visitor)
1045                 {
1046                         return visitor.Visit (this);
1047                 }
1048         }
1049
1050         //
1051         // For statements which require special handling when inside try or catch block
1052         //
1053         public abstract class ExitStatement : Statement
1054         {
1055                 protected bool unwind_protect;
1056
1057                 protected abstract bool DoResolve (BlockContext bc);
1058                 protected abstract bool IsLocalExit { get; }
1059
1060                 public override bool Resolve (BlockContext bc)
1061                 {
1062                         var res = DoResolve (bc);
1063
1064                         if (!IsLocalExit) {
1065                                 //
1066                                 // We are inside finally scope but is it the scope we are exiting
1067                                 //
1068                                 if (bc.HasSet (ResolveContext.Options.FinallyScope)) {
1069
1070                                         for (var b = bc.CurrentBlock; b != null; b = b.Parent) {
1071                                                 if (b.IsFinallyBlock) {
1072                                                         Error_FinallyClauseExit (bc);
1073                                                         break;
1074                                                 }
1075
1076                                                 if (b is ParametersBlock)
1077                                                         break;
1078                                         }
1079                                 }
1080                         }
1081
1082                         unwind_protect = bc.HasAny (ResolveContext.Options.TryScope | ResolveContext.Options.CatchScope);
1083                         return res;
1084                 }
1085
1086                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1087                 {
1088                         if (IsLocalExit)
1089                                 return true;
1090
1091                         if (fc.TryFinally != null) {
1092                             fc.TryFinally.RegisterForControlExitCheck (new DefiniteAssignmentBitSet (fc.DefiniteAssignment));
1093                         } else {
1094                             fc.ParametersBlock.CheckControlExit (fc);
1095                         }
1096
1097                         return true;
1098                 }
1099         }
1100
1101         /// <summary>
1102         ///   Implements the return statement
1103         /// </summary>
1104         public class Return : ExitStatement
1105         {
1106                 Expression expr;
1107
1108                 public Return (Expression expr, Location l)
1109                 {
1110                         this.expr = expr;
1111                         loc = l;
1112                 }
1113
1114                 #region Properties
1115
1116                 public Expression Expr {
1117                         get {
1118                                 return expr;
1119                         }
1120                         protected set {
1121                                 expr = value;
1122                         }
1123                 }
1124
1125                 protected override bool IsLocalExit {
1126                         get {
1127                                 return false;
1128                         }
1129                 }
1130
1131                 #endregion
1132
1133                 protected override bool DoResolve (BlockContext ec)
1134                 {
1135                         var block_return_type = ec.ReturnType;
1136
1137                         if (expr == null) {
1138                                 if (block_return_type.Kind == MemberKind.Void || block_return_type == InternalType.ErrorType)
1139                                         return true;
1140
1141                                 //
1142                                 // Return must not be followed by an expression when
1143                                 // the method return type is Task
1144                                 //
1145                                 if (ec.CurrentAnonymousMethod is AsyncInitializer) {
1146                                         var storey = (AsyncTaskStorey) ec.CurrentAnonymousMethod.Storey;
1147                                         if (storey.ReturnType == ec.Module.PredefinedTypes.Task.TypeSpec) {
1148                                                 //
1149                                                 // Extra trick not to emit ret/leave inside awaiter body
1150                                                 //
1151                                                 expr = EmptyExpression.Null;
1152                                                 return true;
1153                                         }
1154
1155                                         if (storey.ReturnType.IsGenericTask)
1156                                                 block_return_type = storey.ReturnType.TypeArguments[0];
1157                                 }
1158
1159                                 if (ec.CurrentIterator != null) {
1160                                         Error_ReturnFromIterator (ec);
1161                                 } else if (block_return_type != InternalType.ErrorType) {
1162                                         ec.Report.Error (126, loc,
1163                                                 "An object of a type convertible to `{0}' is required for the return statement",
1164                                                 block_return_type.GetSignatureForError ());
1165                                 }
1166
1167                                 return false;
1168                         }
1169
1170                         expr = expr.Resolve (ec);
1171
1172                         AnonymousExpression am = ec.CurrentAnonymousMethod;
1173                         if (am == null) {
1174                                 if (block_return_type.Kind == MemberKind.Void) {
1175                                         ec.Report.Error (127, loc,
1176                                                 "`{0}': A return keyword must not be followed by any expression when method returns void",
1177                                                 ec.GetSignatureForError ());
1178
1179                                         return false;
1180                                 }
1181                         } else {
1182                                 if (am.IsIterator) {
1183                                         Error_ReturnFromIterator (ec);
1184                                         return false;
1185                                 }
1186
1187                                 var async_block = am as AsyncInitializer;
1188                                 if (async_block != null) {
1189                                         if (expr != null) {
1190                                                 var storey = (AsyncTaskStorey) am.Storey;
1191                                                 var async_type = storey.ReturnType;
1192
1193                                                 if (async_type == null && async_block.ReturnTypeInference != null) {
1194                                                         if (expr.Type.Kind == MemberKind.Void && !(this is ContextualReturn))
1195                                                                 ec.Report.Error (4029, loc, "Cannot return an expression of type `void'");
1196                                                         else
1197                                                                 async_block.ReturnTypeInference.AddCommonTypeBoundAsync (expr.Type);
1198                                                         return true;
1199                                                 }
1200
1201                                                 if (async_type.Kind == MemberKind.Void) {
1202                                                         ec.Report.Error (8030, loc,
1203                                                                 "Anonymous function or lambda expression converted to a void returning delegate cannot return a value");
1204                                                         return false;
1205                                                 }
1206
1207                                                 if (!async_type.IsGenericTask) {
1208                                                         if (this is ContextualReturn)
1209                                                                 return true;
1210
1211                                                         if (async_block.DelegateType != null) {
1212                                                                 ec.Report.Error (8031, loc,
1213                                                                         "Async lambda expression or anonymous method converted to a `Task' cannot return a value. Consider returning `Task<T>'");
1214                                                         } else {
1215                                                                 ec.Report.Error (1997, loc,
1216                                                                         "`{0}': A return keyword must not be followed by an expression when async method returns `Task'. Consider using `Task<T>' return type",
1217                                                                         ec.GetSignatureForError ());
1218                                                         }
1219                                                         return false;
1220                                                 }
1221
1222                                                 //
1223                                                 // The return type is actually Task<T> type argument
1224                                                 //
1225                                                 if (expr.Type == async_type && async_type.TypeArguments [0] != ec.Module.PredefinedTypes.Task.TypeSpec) {
1226                                                         ec.Report.Error (4016, loc,
1227                                                                 "`{0}': The return expression type of async method must be `{1}' rather than `Task<{1}>'",
1228                                                                 ec.GetSignatureForError (), async_type.TypeArguments[0].GetSignatureForError ());
1229                                                 } else {
1230                                                         block_return_type = async_type.TypeArguments[0];
1231                                                 }
1232                                         }
1233                                 } else {
1234                                         if (block_return_type.Kind == MemberKind.Void) {
1235                                                 ec.Report.Error (8030, loc,
1236                                                         "Anonymous function or lambda expression converted to a void returning delegate cannot return a value");
1237                                                 return false;
1238                                         }
1239
1240                                         var l = am as AnonymousMethodBody;
1241                                         if (l != null && expr != null) {
1242                                                 if (l.ReturnTypeInference != null) {
1243                                                         l.ReturnTypeInference.AddCommonTypeBound (expr.Type);
1244                                                         return true;
1245                                                 }
1246
1247                                                 //
1248                                                 // Try to optimize simple lambda. Only when optimizations are enabled not to cause
1249                                                 // unexpected debugging experience
1250                                                 //
1251                                                 if (this is ContextualReturn && !ec.IsInProbingMode && ec.Module.Compiler.Settings.Optimize) {
1252                                                         l.DirectMethodGroupConversion = expr.CanReduceLambda (l);
1253                                                 }
1254                                         }
1255                                 }
1256                         }
1257
1258                         if (expr == null)
1259                                 return false;
1260
1261                         if (expr.Type != block_return_type && expr.Type != InternalType.ErrorType) {
1262                                 expr = Convert.ImplicitConversionRequired (ec, expr, block_return_type, loc);
1263
1264                                 if (expr == null) {
1265                                         if (am != null && block_return_type == ec.ReturnType) {
1266                                                 ec.Report.Error (1662, loc,
1267                                                         "Cannot convert `{0}' to delegate type `{1}' because some of the return types in the block are not implicitly convertible to the delegate return type",
1268                                                         am.ContainerType, am.GetSignatureForError ());
1269                                         }
1270                                         return false;
1271                                 }
1272                         }
1273
1274                         return true;
1275                 }
1276
1277                 protected override void DoEmit (EmitContext ec)
1278                 {
1279                         if (expr != null) {
1280
1281                                 var async_body = ec.CurrentAnonymousMethod as AsyncInitializer;
1282                                 if (async_body != null) {
1283                                         var storey = (AsyncTaskStorey)async_body.Storey;
1284                                         Label exit_label = async_body.BodyEnd;
1285
1286                                         //
1287                                         // It's null for await without async
1288                                         //
1289                                         if (storey.HoistedReturnValue != null) {
1290                                                 //
1291                                                 // Special case hoisted return value (happens in try/finally scenario)
1292                                                 //
1293                                                 if (ec.TryFinallyUnwind != null) {
1294                                                         exit_label = TryFinally.EmitRedirectedReturn (ec, async_body);
1295                                                 }
1296
1297                                                 var async_return = (IAssignMethod)storey.HoistedReturnValue;
1298                                                 async_return.EmitAssign (ec, expr, false, false);
1299                                                 ec.EmitEpilogue ();
1300                                         } else {
1301                                                 expr.Emit (ec);
1302
1303                                                 if (ec.TryFinallyUnwind != null)
1304                                                         exit_label = TryFinally.EmitRedirectedReturn (ec, async_body);
1305                                         }
1306
1307                                         ec.Emit (OpCodes.Leave, exit_label);
1308                                         return;
1309                                 }
1310
1311                                 expr.Emit (ec);
1312                                 ec.EmitEpilogue ();
1313
1314                                 if (unwind_protect || ec.EmitAccurateDebugInfo)
1315                                         ec.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
1316                         }
1317
1318                         if (unwind_protect) {
1319                                 ec.Emit (OpCodes.Leave, ec.CreateReturnLabel ());
1320                         } else if (ec.EmitAccurateDebugInfo) {
1321                                 ec.Emit (OpCodes.Br, ec.CreateReturnLabel ());
1322                         } else {
1323                                 ec.Emit (OpCodes.Ret);
1324                         }
1325                 }
1326
1327                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1328                 {
1329                         if (expr != null)
1330                                 expr.FlowAnalysis (fc);
1331
1332                         base.DoFlowAnalysis (fc);
1333                         return true;
1334                 }
1335
1336                 void Error_ReturnFromIterator (ResolveContext rc)
1337                 {
1338                         rc.Report.Error (1622, loc,
1339                                 "Cannot return a value from iterators. Use the yield return statement to return a value, or yield break to end the iteration");
1340                 }
1341
1342                 public override Reachability MarkReachable (Reachability rc)
1343                 {
1344                         base.MarkReachable (rc);
1345                         return Reachability.CreateUnreachable ();
1346                 }
1347
1348                 protected override void CloneTo (CloneContext clonectx, Statement t)
1349                 {
1350                         Return target = (Return) t;
1351                         // It's null for simple return;
1352                         if (expr != null)
1353                                 target.expr = expr.Clone (clonectx);
1354                 }
1355
1356                 public override object Accept (StructuralVisitor visitor)
1357                 {
1358                         return visitor.Visit (this);
1359                 }
1360         }
1361
1362         public class Goto : ExitStatement
1363         {
1364                 string target;
1365                 LabeledStatement label;
1366                 TryFinally try_finally;
1367
1368                 public Goto (string label, Location l)
1369                 {
1370                         loc = l;
1371                         target = label;
1372                 }
1373
1374                 public string Target {
1375                         get { return target; }
1376                 }
1377
1378                 protected override bool IsLocalExit {
1379                         get {
1380                                 return true;
1381                         }
1382                 }
1383
1384                 protected override bool DoResolve (BlockContext bc)
1385                 {
1386                         label = bc.CurrentBlock.LookupLabel (target);
1387                         if (label == null) {
1388                                 Error_UnknownLabel (bc, target, loc);
1389                                 return false;
1390                         }
1391
1392                         try_finally = bc.CurrentTryBlock as TryFinally;
1393
1394                         CheckExitBoundaries (bc, label.Block);
1395
1396                         return true;
1397                 }
1398
1399                 public static void Error_UnknownLabel (BlockContext bc, string label, Location loc)
1400                 {
1401                         bc.Report.Error (159, loc, "The label `{0}:' could not be found within the scope of the goto statement",
1402                                 label);
1403                 }
1404
1405                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1406                 {
1407                         // Goto to unreachable label
1408                         if (label == null)
1409                                 return true;
1410
1411                         if (fc.AddReachedLabel (label))
1412                                 return true;
1413
1414                         label.Block.ScanGotoJump (label, fc);
1415                         return true;
1416                 }
1417
1418                 public override Reachability MarkReachable (Reachability rc)
1419                 {
1420                         if (rc.IsUnreachable)
1421                                 return rc;
1422
1423                         base.MarkReachable (rc);
1424
1425                         if (try_finally != null) {
1426                                 if (try_finally.FinallyBlock.HasReachableClosingBrace) {
1427                                         label.AddGotoReference (rc);
1428                                 } else {
1429                                         label = null;
1430                                 }
1431                         } else {
1432                                 label.AddGotoReference (rc);
1433                         }
1434
1435                         return Reachability.CreateUnreachable ();
1436                 }
1437
1438                 protected override void CloneTo (CloneContext clonectx, Statement target)
1439                 {
1440                         // Nothing to clone
1441                 }
1442
1443                 protected override void DoEmit (EmitContext ec)
1444                 {
1445                         // This should only happen for goto from try block to unrechable label
1446                         if (label == null)
1447                                 return;
1448
1449                         Label l = label.LabelTarget (ec);
1450
1451                         if (ec.TryFinallyUnwind != null && IsLeavingFinally (label.Block)) {
1452                                 var async_body = (AsyncInitializer) ec.CurrentAnonymousMethod;
1453                                 l = TryFinally.EmitRedirectedJump (ec, async_body, l, label.Block);
1454                         }
1455
1456                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
1457                 }
1458
1459                 bool IsLeavingFinally (Block labelBlock)
1460                 {
1461                         var b = try_finally.Statement as Block;
1462                         while (b != null) {
1463                                 if (b == labelBlock)
1464                                         return true;
1465
1466                                 b = b.Parent;
1467                         }
1468
1469                         return false;
1470                 }
1471
1472                 public override object Accept (StructuralVisitor visitor)
1473                 {
1474                         return visitor.Visit (this);
1475                 }
1476         }
1477
1478         public class LabeledStatement : Statement {
1479                 string name;
1480                 bool defined;
1481                 bool referenced;
1482                 Label label;
1483                 Block block;
1484
1485                 public LabeledStatement (string name, Block block, Location l)
1486                 {
1487                         this.name = name;
1488                         this.block = block;
1489                         this.loc = l;
1490                 }
1491
1492                 public Label LabelTarget (EmitContext ec)
1493                 {
1494                         if (defined)
1495                                 return label;
1496
1497                         label = ec.DefineLabel ();
1498                         defined = true;
1499                         return label;
1500                 }
1501
1502                 public Block Block {
1503                         get {
1504                                 return block;
1505                         }
1506                 }
1507
1508                 public string Name {
1509                         get { return name; }
1510                 }
1511
1512                 protected override void CloneTo (CloneContext clonectx, Statement target)
1513                 {
1514                         var t = (LabeledStatement) target;
1515
1516                         t.block = clonectx.RemapBlockCopy (block);
1517                 }
1518
1519                 public override bool Resolve (BlockContext bc)
1520                 {
1521                         return true;
1522                 }
1523
1524                 protected override void DoEmit (EmitContext ec)
1525                 {
1526                         LabelTarget (ec);
1527                         ec.MarkLabel (label);
1528                 }
1529
1530                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1531                 {
1532                         if (!referenced) {
1533                                 fc.Report.Warning (164, 2, loc, "This label has not been referenced");
1534                         }
1535
1536                         return false;
1537                 }
1538
1539                 public override Reachability MarkReachable (Reachability rc)
1540                 {
1541                         base.MarkReachable (rc);
1542
1543                         if (referenced)
1544                                 rc = new Reachability ();
1545
1546                         return rc;
1547                 }
1548
1549                 public void AddGotoReference (Reachability rc)
1550                 {
1551                         if (referenced)
1552                                 return;
1553
1554                         referenced = true;
1555                         MarkReachable (rc);
1556
1557                         block.ScanGotoJump (this);
1558                 }
1559
1560                 public override object Accept (StructuralVisitor visitor)
1561                 {
1562                         return visitor.Visit (this);
1563                 }
1564         }
1565
1566
1567         /// <summary>
1568         ///   `goto default' statement
1569         /// </summary>
1570         public class GotoDefault : SwitchGoto
1571         {
1572                 public GotoDefault (Location l)
1573                         : base (l)
1574                 {
1575                 }
1576
1577                 public override bool Resolve (BlockContext bc)
1578                 {
1579                         if (bc.Switch == null) {
1580                                 Error_GotoCaseRequiresSwitchBlock (bc);
1581                                 return false;
1582                         }
1583
1584                         bc.Switch.RegisterGotoCase (null, null);
1585                         base.Resolve (bc);
1586
1587                         return true;
1588                 }
1589
1590                 protected override void DoEmit (EmitContext ec)
1591                 {
1592                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.Switch.DefaultLabel.GetILLabel (ec));
1593                 }
1594
1595                 public override Reachability MarkReachable (Reachability rc)
1596                 {
1597                         if (!rc.IsUnreachable) {
1598                                 var label = switch_statement.DefaultLabel;
1599                                 if (label.IsUnreachable) {
1600                                         label.MarkReachable (rc);
1601                                         switch_statement.Block.ScanGotoJump (label);
1602                                 }
1603                         }
1604
1605                         return base.MarkReachable (rc);
1606                 }
1607
1608                 public override object Accept (StructuralVisitor visitor)
1609                 {
1610                         return visitor.Visit (this);
1611                 }
1612         }
1613
1614         /// <summary>
1615         ///   `goto case' statement
1616         /// </summary>
1617         public class GotoCase : SwitchGoto
1618         {
1619                 Expression expr;
1620
1621                 public GotoCase (Expression e, Location l)
1622                         : base (l)
1623                 {
1624                         expr = e;
1625                 }
1626
1627                 public Expression Expr {
1628                         get {
1629                                 return expr;
1630                         }
1631                 }
1632
1633                 public SwitchLabel Label { get; set; }
1634
1635                 public override bool Resolve (BlockContext ec)
1636                 {
1637                         if (ec.Switch == null) {
1638                                 Error_GotoCaseRequiresSwitchBlock (ec);
1639                                 return false;
1640                         }
1641
1642                         Constant c = expr.ResolveLabelConstant (ec);
1643                         if (c == null) {
1644                                 return false;
1645                         }
1646
1647                         Constant res;
1648                         if (ec.Switch.IsNullable && c is NullLiteral) {
1649                                 res = c;
1650                         } else {
1651                                 TypeSpec type = ec.Switch.SwitchType;
1652                                 res = c.Reduce (ec, type);
1653                                 if (res == null) {
1654                                         c.Error_ValueCannotBeConverted (ec, type, true);
1655                                         return false;
1656                                 }
1657
1658                                 if (!Convert.ImplicitStandardConversionExists (c, type))
1659                                         ec.Report.Warning (469, 2, loc,
1660                                                 "The `goto case' value is not implicitly convertible to type `{0}'",
1661                                                 type.GetSignatureForError ());
1662
1663                         }
1664
1665                         ec.Switch.RegisterGotoCase (this, res);
1666                         base.Resolve (ec);
1667                         expr = res;
1668
1669                         return true;
1670                 }
1671
1672                 protected override void DoEmit (EmitContext ec)
1673                 {
1674                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, Label.GetILLabel (ec));
1675                 }
1676
1677                 protected override void CloneTo (CloneContext clonectx, Statement t)
1678                 {
1679                         GotoCase target = (GotoCase) t;
1680
1681                         target.expr = expr.Clone (clonectx);
1682                 }
1683
1684                 public override Reachability MarkReachable (Reachability rc)
1685                 {
1686                         if (!rc.IsUnreachable) {
1687                                 var label = switch_statement.FindLabel ((Constant) expr);
1688                                 if (label.IsUnreachable) {
1689                                         label.MarkReachable (rc);
1690                                         switch_statement.Block.ScanGotoJump (label);
1691                                 }
1692                         }
1693
1694                         return base.MarkReachable (rc);
1695                 }
1696
1697                 public override object Accept (StructuralVisitor visitor)
1698                 {
1699                         return visitor.Visit (this);
1700                 }
1701         }
1702
1703         public abstract class SwitchGoto : Statement
1704         {
1705                 protected bool unwind_protect;
1706                 protected Switch switch_statement;
1707
1708                 protected SwitchGoto (Location loc)
1709                 {
1710                         this.loc = loc;
1711                 }
1712
1713                 protected override void CloneTo (CloneContext clonectx, Statement target)
1714                 {
1715                         // Nothing to clone
1716                 }
1717
1718                 public override bool Resolve (BlockContext bc)
1719                 {
1720                         CheckExitBoundaries (bc, bc.Switch.Block);
1721
1722                         unwind_protect = bc.HasAny (ResolveContext.Options.TryScope | ResolveContext.Options.CatchScope);
1723                         switch_statement = bc.Switch;
1724
1725                         return true;
1726                 }
1727
1728                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1729                 {
1730                         return true;
1731                 }
1732
1733                 public override Reachability MarkReachable (Reachability rc)
1734                 {
1735                         base.MarkReachable (rc);
1736                         return Reachability.CreateUnreachable ();
1737                 }
1738
1739                 protected void Error_GotoCaseRequiresSwitchBlock (BlockContext bc)
1740                 {
1741                         bc.Report.Error (153, loc, "A goto case is only valid inside a switch statement");
1742                 }
1743         }
1744
1745         public class Throw : Statement {
1746                 Expression expr;
1747
1748                 public Throw (Expression expr, Location l)
1749                 {
1750                         this.expr = expr;
1751                         loc = l;
1752                 }
1753
1754                 public Expression Expr {
1755                         get {
1756                                 return this.expr;
1757                         }
1758                 }
1759
1760                 public override bool Resolve (BlockContext ec)
1761                 {
1762                         if (expr == null) {
1763                                 if (!ec.HasSet (ResolveContext.Options.CatchScope)) {
1764                                         ec.Report.Error (156, loc, "A throw statement with no arguments is not allowed outside of a catch clause");
1765                                 } else if (ec.HasSet (ResolveContext.Options.FinallyScope)) {
1766                                         for (var b = ec.CurrentBlock; b != null && !b.IsCatchBlock; b = b.Parent) {
1767                                                 if (b.IsFinallyBlock) {
1768                                                         ec.Report.Error (724, loc,
1769                                                                 "A throw statement with no arguments is not allowed inside of a finally clause nested inside of the innermost catch clause");
1770                                                         break;
1771                                                 }
1772                                         }
1773                                 }
1774
1775                                 return true;
1776                         }
1777
1778                         expr = expr.Resolve (ec, ResolveFlags.Type | ResolveFlags.VariableOrValue);
1779
1780                         if (expr == null)
1781                                 return false;
1782
1783                         var et = ec.BuiltinTypes.Exception;
1784                         if (Convert.ImplicitConversionExists (ec, expr, et))
1785                                 expr = Convert.ImplicitConversion (ec, expr, et, loc);
1786                         else
1787                                 ec.Report.Error (155, expr.Location, "The type caught or thrown must be derived from System.Exception");
1788
1789                         return true;
1790                 }
1791
1792                 protected override void DoEmit (EmitContext ec)
1793                 {
1794                         if (expr == null) {
1795                                 var atv = ec.AsyncThrowVariable;
1796                                 if (atv != null) {
1797                                         if (atv.HoistedVariant != null) {
1798                                                 atv.HoistedVariant.Emit (ec);
1799                                         } else {
1800                                                 atv.Emit (ec);
1801                                         }
1802
1803                                         ec.Emit (OpCodes.Throw);
1804                                 } else {
1805                                         ec.Emit (OpCodes.Rethrow);
1806                                 }
1807                         } else {
1808                                 expr.Emit (ec);
1809
1810                                 ec.Emit (OpCodes.Throw);
1811                         }
1812                 }
1813
1814                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1815                 {
1816                         if (expr != null)
1817                                 expr.FlowAnalysis (fc);
1818
1819                         return true;
1820                 }
1821
1822                 public override Reachability MarkReachable (Reachability rc)
1823                 {
1824                         base.MarkReachable (rc);
1825                         return Reachability.CreateUnreachable ();
1826                 }
1827
1828                 protected override void CloneTo (CloneContext clonectx, Statement t)
1829                 {
1830                         Throw target = (Throw) t;
1831
1832                         if (expr != null)
1833                                 target.expr = expr.Clone (clonectx);
1834                 }
1835
1836                 public override object Accept (StructuralVisitor visitor)
1837                 {
1838                         return visitor.Visit (this);
1839                 }
1840         }
1841
1842         public class Break : LocalExitStatement
1843         {
1844                 public Break (Location l)
1845                         : base (l)
1846                 {
1847                 }
1848
1849                 public override object Accept (StructuralVisitor visitor)
1850                 {
1851                         return visitor.Visit (this);
1852                 }
1853
1854                 protected override void DoEmit (EmitContext ec)
1855                 {
1856                         var l = ec.LoopEnd;
1857
1858                         if (ec.TryFinallyUnwind != null) {
1859                                 var async_body = (AsyncInitializer) ec.CurrentAnonymousMethod;
1860                                 l = TryFinally.EmitRedirectedJump (ec, async_body, l, enclosing_loop.Statement as Block);
1861                         }
1862
1863                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
1864                 }
1865
1866                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1867                 {
1868                         enclosing_loop.AddEndDefiniteAssignment (fc);
1869                         return true;
1870                 }
1871
1872                 protected override bool DoResolve (BlockContext bc)
1873                 {
1874                         enclosing_loop = bc.EnclosingLoopOrSwitch;
1875                         return base.DoResolve (bc);
1876                 }
1877
1878                 public override Reachability MarkReachable (Reachability rc)
1879                 {
1880                         base.MarkReachable (rc);
1881
1882                         if (!rc.IsUnreachable)
1883                                 enclosing_loop.SetEndReachable ();
1884
1885                         return Reachability.CreateUnreachable ();
1886                 }
1887         }
1888
1889         public class Continue : LocalExitStatement
1890         {
1891                 public Continue (Location l)
1892                         : base (l)
1893                 {
1894                 }
1895
1896                 public override object Accept (StructuralVisitor visitor)
1897                 {
1898                         return visitor.Visit (this);
1899                 }
1900
1901
1902                 protected override void DoEmit (EmitContext ec)
1903                 {
1904                         var l = ec.LoopBegin;
1905
1906                         if (ec.TryFinallyUnwind != null) {
1907                                 var async_body = (AsyncInitializer) ec.CurrentAnonymousMethod;
1908                                 l = TryFinally.EmitRedirectedJump (ec, async_body, l, enclosing_loop.Statement as Block);
1909                         }
1910
1911                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
1912                 }
1913
1914                 protected override bool DoResolve (BlockContext bc)
1915                 {
1916                         enclosing_loop = bc.EnclosingLoop;
1917                         return base.DoResolve (bc);
1918                 }
1919
1920                 public override Reachability MarkReachable (Reachability rc)
1921                 {
1922                         base.MarkReachable (rc);
1923
1924                         if (!rc.IsUnreachable)
1925                                 enclosing_loop.SetIteratorReachable ();
1926
1927                         return Reachability.CreateUnreachable ();
1928                 }
1929         }
1930
1931         public abstract class LocalExitStatement : ExitStatement
1932         {
1933                 protected LoopStatement enclosing_loop;
1934
1935                 protected LocalExitStatement (Location loc)
1936                 {
1937                         this.loc = loc;
1938                 }
1939
1940                 protected override bool IsLocalExit {
1941                         get {
1942                                 return true;
1943                         }
1944                 }
1945
1946                 protected override void CloneTo (CloneContext clonectx, Statement t)
1947                 {
1948                         // nothing needed.
1949                 }
1950
1951                 protected override bool DoResolve (BlockContext bc)
1952                 {
1953                         if (enclosing_loop == null) {
1954                                 bc.Report.Error (139, loc, "No enclosing loop out of which to break or continue");
1955                                 return false;
1956                         }
1957
1958                         var block = enclosing_loop.Statement as Block;
1959
1960                         // Don't need to do extra checks for simple statements loops
1961                         if (block != null) {
1962                                 CheckExitBoundaries (bc, block);
1963                         }
1964
1965                         return true;
1966                 }
1967         }
1968
1969         public interface ILocalVariable
1970         {
1971                 void Emit (EmitContext ec);
1972                 void EmitAssign (EmitContext ec);
1973                 void EmitAddressOf (EmitContext ec);
1974         }
1975
1976         public interface INamedBlockVariable
1977         {
1978                 Block Block { get; }
1979                 Expression CreateReferenceExpression (ResolveContext rc, Location loc);
1980                 bool IsDeclared { get; }
1981                 bool IsParameter { get; }
1982                 Location Location { get; }
1983         }
1984
1985         public class BlockVariableDeclarator
1986         {
1987                 LocalVariable li;
1988                 Expression initializer;
1989
1990                 public BlockVariableDeclarator (LocalVariable li, Expression initializer)
1991                 {
1992                         if (li.Type != null)
1993                                 throw new ArgumentException ("Expected null variable type");
1994
1995                         this.li = li;
1996                         this.initializer = initializer;
1997                 }
1998
1999                 #region Properties
2000
2001                 public LocalVariable Variable {
2002                         get {
2003                                 return li;
2004                         }
2005                 }
2006
2007                 public Expression Initializer {
2008                         get {
2009                                 return initializer;
2010                         }
2011                         set {
2012                                 initializer = value;
2013                         }
2014                 }
2015
2016                 #endregion
2017
2018                 public virtual BlockVariableDeclarator Clone (CloneContext cloneCtx)
2019                 {
2020                         var t = (BlockVariableDeclarator) MemberwiseClone ();
2021                         if (initializer != null)
2022                                 t.initializer = initializer.Clone (cloneCtx);
2023
2024                         return t;
2025                 }
2026         }
2027
2028         public class BlockVariable : Statement
2029         {
2030                 Expression initializer;
2031                 protected FullNamedExpression type_expr;
2032                 protected LocalVariable li;
2033                 protected List<BlockVariableDeclarator> declarators;
2034                 TypeSpec type;
2035
2036                 public BlockVariable (FullNamedExpression type, LocalVariable li)
2037                 {
2038                         this.type_expr = type;
2039                         this.li = li;
2040                         this.loc = type_expr.Location;
2041                 }
2042
2043                 protected BlockVariable (LocalVariable li)
2044                 {
2045                         this.li = li;
2046                 }
2047
2048                 #region Properties
2049
2050                 public List<BlockVariableDeclarator> Declarators {
2051                         get {
2052                                 return declarators;
2053                         }
2054                 }
2055
2056                 public Expression Initializer {
2057                         get {
2058                                 return initializer;
2059                         }
2060                         set {
2061                                 initializer = value;
2062                         }
2063                 }
2064
2065                 public FullNamedExpression TypeExpression {
2066                         get {
2067                                 return type_expr;
2068                         }
2069                 }
2070
2071                 public LocalVariable Variable {
2072                         get {
2073                                 return li;
2074                         }
2075                 }
2076
2077                 #endregion
2078
2079                 public void AddDeclarator (BlockVariableDeclarator decl)
2080                 {
2081                         if (declarators == null)
2082                                 declarators = new List<BlockVariableDeclarator> ();
2083
2084                         declarators.Add (decl);
2085                 }
2086
2087                 static void CreateEvaluatorVariable (BlockContext bc, LocalVariable li)
2088                 {
2089                         if (bc.Report.Errors != 0)
2090                                 return;
2091
2092                         var container = bc.CurrentMemberDefinition.Parent.PartialContainer;
2093
2094                         Field f = new Field (container, new TypeExpression (li.Type, li.Location), Modifiers.PUBLIC | Modifiers.STATIC,
2095                                 new MemberName (li.Name, li.Location), null);
2096
2097                         container.AddField (f);
2098                         f.Define ();
2099
2100                         li.HoistedVariant = new HoistedEvaluatorVariable (f);
2101                         li.SetIsUsed ();
2102                 }
2103
2104                 public override bool Resolve (BlockContext bc)
2105                 {
2106                         return Resolve (bc, true);
2107                 }
2108
2109                 public bool Resolve (BlockContext bc, bool resolveDeclaratorInitializers)
2110                 {
2111                         if (type == null && !li.IsCompilerGenerated) {
2112                                 var vexpr = type_expr as VarExpr;
2113
2114                                 //
2115                                 // C# 3.0 introduced contextual keywords (var) which behaves like a type if type with
2116                                 // same name exists or as a keyword when no type was found
2117                                 //
2118                                 if (vexpr != null && !vexpr.IsPossibleType (bc)) {
2119                                         if (bc.Module.Compiler.Settings.Version < LanguageVersion.V_3)
2120                                                 bc.Report.FeatureIsNotAvailable (bc.Module.Compiler, loc, "implicitly typed local variable");
2121
2122                                         if (li.IsFixed) {
2123                                                 bc.Report.Error (821, loc, "A fixed statement cannot use an implicitly typed local variable");
2124                                                 return false;
2125                                         }
2126
2127                                         if (li.IsConstant) {
2128                                                 bc.Report.Error (822, loc, "An implicitly typed local variable cannot be a constant");
2129                                                 return false;
2130                                         }
2131
2132                                         if (Initializer == null) {
2133                                                 bc.Report.Error (818, loc, "An implicitly typed local variable declarator must include an initializer");
2134                                                 return false;
2135                                         }
2136
2137                                         if (declarators != null) {
2138                                                 bc.Report.Error (819, loc, "An implicitly typed local variable declaration cannot include multiple declarators");
2139                                                 declarators = null;
2140                                         }
2141
2142                                         Initializer = Initializer.Resolve (bc);
2143                                         if (Initializer != null) {
2144                                                 ((VarExpr) type_expr).InferType (bc, Initializer);
2145                                                 type = type_expr.Type;
2146                                         } else {
2147                                                 // Set error type to indicate the var was placed correctly but could
2148                                                 // not be infered
2149                                                 //
2150                                                 // var a = missing ();
2151                                                 //
2152                                                 type = InternalType.ErrorType;
2153                                         }
2154                                 }
2155
2156                                 if (type == null) {
2157                                         type = type_expr.ResolveAsType (bc);
2158                                         if (type == null)
2159                                                 return false;
2160
2161                                         if (li.IsConstant && !type.IsConstantCompatible) {
2162                                                 Const.Error_InvalidConstantType (type, loc, bc.Report);
2163                                         }
2164                                 }
2165
2166                                 if (type.IsStatic)
2167                                         FieldBase.Error_VariableOfStaticClass (loc, li.Name, type, bc.Report);
2168
2169                                 li.Type = type;
2170                         }
2171
2172                         bool eval_global = bc.Module.Compiler.Settings.StatementMode && bc.CurrentBlock is ToplevelBlock;
2173                         if (eval_global) {
2174                                 CreateEvaluatorVariable (bc, li);
2175                         } else if (type != InternalType.ErrorType) {
2176                                 li.PrepareAssignmentAnalysis (bc);
2177                         }
2178
2179                         if (initializer != null) {
2180                                 initializer = ResolveInitializer (bc, li, initializer);
2181                                 // li.Variable.DefinitelyAssigned
2182                         }
2183
2184                         if (declarators != null) {
2185                                 foreach (var d in declarators) {
2186                                         d.Variable.Type = li.Type;
2187                                         if (eval_global) {
2188                                                 CreateEvaluatorVariable (bc, d.Variable);
2189                                         } else if (type != InternalType.ErrorType) {
2190                                                 d.Variable.PrepareAssignmentAnalysis (bc);
2191                                         }
2192
2193                                         if (d.Initializer != null && resolveDeclaratorInitializers) {
2194                                                 d.Initializer = ResolveInitializer (bc, d.Variable, d.Initializer);
2195                                                 // d.Variable.DefinitelyAssigned
2196                                         }
2197                                 }
2198                         }
2199
2200                         return true;
2201                 }
2202
2203                 protected virtual Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
2204                 {
2205                         var a = new SimpleAssign (li.CreateReferenceExpression (bc, li.Location), initializer, li.Location);
2206                         return a.ResolveStatement (bc);
2207                 }
2208
2209                 protected override void DoEmit (EmitContext ec)
2210                 {
2211                         li.CreateBuilder (ec);
2212
2213                         if (Initializer != null && !IsUnreachable)
2214                                 ((ExpressionStatement) Initializer).EmitStatement (ec);
2215
2216                         if (declarators != null) {
2217                                 foreach (var d in declarators) {
2218                                         d.Variable.CreateBuilder (ec);
2219                                         if (d.Initializer != null && !IsUnreachable) {
2220                                                 ec.Mark (d.Variable.Location);
2221                                                 ((ExpressionStatement) d.Initializer).EmitStatement (ec);
2222                                         }
2223                                 }
2224                         }
2225                 }
2226
2227                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
2228                 {
2229                         if (Initializer != null)
2230                                 Initializer.FlowAnalysis (fc);
2231
2232                         if (declarators != null) {
2233                                 foreach (var d in declarators) {
2234                                         if (d.Initializer != null)
2235                                                 d.Initializer.FlowAnalysis (fc);
2236                                 }
2237                         }
2238
2239                         return false;
2240                 }
2241
2242                 public override Reachability MarkReachable (Reachability rc)
2243                 {
2244                         var init = initializer as ExpressionStatement;
2245                         if (init != null)
2246                                 init.MarkReachable (rc);
2247
2248                         return base.MarkReachable (rc);
2249                 }
2250
2251                 protected override void CloneTo (CloneContext clonectx, Statement target)
2252                 {
2253                         BlockVariable t = (BlockVariable) target;
2254
2255                         if (type_expr != null)
2256                                 t.type_expr = (FullNamedExpression) type_expr.Clone (clonectx);
2257
2258                         if (initializer != null)
2259                                 t.initializer = initializer.Clone (clonectx);
2260
2261                         if (declarators != null) {
2262                                 t.declarators = null;
2263                                 foreach (var d in declarators)
2264                                         t.AddDeclarator (d.Clone (clonectx));
2265                         }
2266                 }
2267
2268                 public override object Accept (StructuralVisitor visitor)
2269                 {
2270                         return visitor.Visit (this);
2271                 }
2272         }
2273
2274         public class BlockConstant : BlockVariable
2275         {
2276                 public BlockConstant (FullNamedExpression type, LocalVariable li)
2277                         : base (type, li)
2278                 {
2279                 }
2280
2281                 public override void Emit (EmitContext ec)
2282                 {
2283                         // Nothing to emit, not even sequence point
2284                 }
2285
2286                 protected override Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
2287                 {
2288                         initializer = initializer.Resolve (bc);
2289                         if (initializer == null)
2290                                 return null;
2291
2292                         var c = initializer as Constant;
2293                         if (c == null) {
2294                                 initializer.Error_ExpressionMustBeConstant (bc, initializer.Location, li.Name);
2295                                 return null;
2296                         }
2297
2298                         c = c.ConvertImplicitly (li.Type);
2299                         if (c == null) {
2300                                 if (TypeSpec.IsReferenceType (li.Type))
2301                                         initializer.Error_ConstantCanBeInitializedWithNullOnly (bc, li.Type, initializer.Location, li.Name);
2302                                 else
2303                                         initializer.Error_ValueCannotBeConverted (bc, li.Type, false);
2304
2305                                 return null;
2306                         }
2307
2308                         li.ConstantValue = c;
2309                         return initializer;
2310                 }
2311
2312                 public override object Accept (StructuralVisitor visitor)
2313                 {
2314                         return visitor.Visit (this);
2315                 }
2316         }
2317
2318         //
2319         // The information about a user-perceived local variable
2320         //
2321         public sealed class LocalVariable : INamedBlockVariable, ILocalVariable
2322         {
2323                 [Flags]
2324                 public enum Flags
2325                 {
2326                         Used = 1,
2327                         IsThis = 1 << 1,
2328                         AddressTaken = 1 << 2,
2329                         CompilerGenerated = 1 << 3,
2330                         Constant = 1 << 4,
2331                         ForeachVariable = 1 << 5,
2332                         FixedVariable = 1 << 6,
2333                         UsingVariable = 1 << 7,
2334                         IsLocked = 1 << 8,
2335                         SymbolFileHidden = 1 << 9,
2336
2337                         ReadonlyMask = ForeachVariable | FixedVariable | UsingVariable
2338                 }
2339
2340                 TypeSpec type;
2341                 readonly string name;
2342                 readonly Location loc;
2343                 readonly Block block;
2344                 Flags flags;
2345                 Constant const_value;
2346
2347                 public VariableInfo VariableInfo;
2348                 HoistedVariable hoisted_variant;
2349
2350                 LocalBuilder builder;
2351
2352                 public LocalVariable (Block block, string name, Location loc)
2353                 {
2354                         this.block = block;
2355                         this.name = name;
2356                         this.loc = loc;
2357                 }
2358
2359                 public LocalVariable (Block block, string name, Flags flags, Location loc)
2360                         : this (block, name, loc)
2361                 {
2362                         this.flags = flags;
2363                 }
2364
2365                 //
2366                 // Used by variable declarators
2367                 //
2368                 public LocalVariable (LocalVariable li, string name, Location loc)
2369                         : this (li.block, name, li.flags, loc)
2370                 {
2371                 }
2372
2373                 #region Properties
2374
2375                 public bool AddressTaken {
2376                         get {
2377                                 return (flags & Flags.AddressTaken) != 0;
2378                         }
2379                 }
2380
2381                 public Block Block {
2382                         get {
2383                                 return block;
2384                         }
2385                 }
2386
2387                 public Constant ConstantValue {
2388                         get {
2389                                 return const_value;
2390                         }
2391                         set {
2392                                 const_value = value;
2393                         }
2394                 }
2395
2396                 //
2397                 // Hoisted local variable variant
2398                 //
2399                 public HoistedVariable HoistedVariant {
2400                         get {
2401                                 return hoisted_variant;
2402                         }
2403                         set {
2404                                 hoisted_variant = value;
2405                         }
2406                 }
2407
2408                 public bool IsDeclared {
2409                         get {
2410                                 return type != null;
2411                         }
2412                 }
2413
2414                 public bool IsCompilerGenerated {
2415                         get {
2416                                 return (flags & Flags.CompilerGenerated) != 0;
2417                         }
2418                 }
2419
2420                 public bool IsConstant {
2421                         get {
2422                                 return (flags & Flags.Constant) != 0;
2423                         }
2424                 }
2425
2426                 public bool IsLocked {
2427                         get {
2428                                 return (flags & Flags.IsLocked) != 0;
2429                         }
2430                         set {
2431                                 flags = value ? flags | Flags.IsLocked : flags & ~Flags.IsLocked;
2432                         }
2433                 }
2434
2435                 public bool IsThis {
2436                         get {
2437                                 return (flags & Flags.IsThis) != 0;
2438                         }
2439                 }
2440
2441                 public bool IsFixed {
2442                         get {
2443                                 return (flags & Flags.FixedVariable) != 0;
2444                         }
2445                         set {
2446                                 flags = value ? flags | Flags.FixedVariable : flags & ~Flags.FixedVariable;
2447                         }
2448                 }
2449
2450                 bool INamedBlockVariable.IsParameter {
2451                         get {
2452                                 return false;
2453                         }
2454                 }
2455
2456                 public bool IsReadonly {
2457                         get {
2458                                 return (flags & Flags.ReadonlyMask) != 0;
2459                         }
2460                 }
2461
2462                 public Location Location {
2463                         get {
2464                                 return loc;
2465                         }
2466                 }
2467
2468                 public string Name {
2469                         get {
2470                                 return name;
2471                         }
2472                 }
2473
2474                 public TypeSpec Type {
2475                     get {
2476                                 return type;
2477                         }
2478                     set {
2479                                 type = value;
2480                         }
2481                 }
2482
2483                 #endregion
2484
2485                 public void CreateBuilder (EmitContext ec)
2486                 {
2487                         if ((flags & Flags.Used) == 0) {
2488                                 if (VariableInfo == null) {
2489                                         // Missing flow analysis or wrong variable flags
2490                                         throw new InternalErrorException ("VariableInfo is null and the variable `{0}' is not used", name);
2491                                 }
2492
2493                                 if (VariableInfo.IsEverAssigned)
2494                                         ec.Report.Warning (219, 3, Location, "The variable `{0}' is assigned but its value is never used", Name);
2495                                 else
2496                                         ec.Report.Warning (168, 3, Location, "The variable `{0}' is declared but never used", Name);
2497                         }
2498
2499                         if (HoistedVariant != null)
2500                                 return;
2501
2502                         if (builder != null) {
2503                                 if ((flags & Flags.CompilerGenerated) != 0)
2504                                         return;
2505
2506                                 // To avoid Used warning duplicates
2507                                 throw new InternalErrorException ("Already created variable `{0}'", name);
2508                         }
2509
2510                         //
2511                         // All fixed variabled are pinned, a slot has to be alocated
2512                         //
2513                         builder = ec.DeclareLocal (Type, IsFixed);
2514                         if ((flags & Flags.SymbolFileHidden) == 0)
2515                                 ec.DefineLocalVariable (name, builder);
2516                 }
2517
2518                 public static LocalVariable CreateCompilerGenerated (TypeSpec type, Block block, Location loc, bool writeToSymbolFile = false)
2519                 {
2520                         LocalVariable li = new LocalVariable (block, GetCompilerGeneratedName (block), Flags.CompilerGenerated | Flags.Used, loc);
2521                         if (!writeToSymbolFile)
2522                                 li.flags |= Flags.SymbolFileHidden;
2523
2524                         li.Type = type;
2525                         return li;
2526                 }
2527
2528                 public Expression CreateReferenceExpression (ResolveContext rc, Location loc)
2529                 {
2530                         if (IsConstant && const_value != null)
2531                                 return Constant.CreateConstantFromValue (Type, const_value.GetValue (), loc);
2532
2533                         return new LocalVariableReference (this, loc);
2534                 }
2535
2536                 public void Emit (EmitContext ec)
2537                 {
2538                         // TODO: Need something better for temporary variables
2539                         if ((flags & Flags.CompilerGenerated) != 0)
2540                                 CreateBuilder (ec);
2541
2542                         ec.Emit (OpCodes.Ldloc, builder);
2543                 }
2544
2545                 public void EmitAssign (EmitContext ec)
2546                 {
2547                         // TODO: Need something better for temporary variables
2548                         if ((flags & Flags.CompilerGenerated) != 0)
2549                                 CreateBuilder (ec);
2550
2551                         ec.Emit (OpCodes.Stloc, builder);
2552                 }
2553
2554                 public void EmitAddressOf (EmitContext ec)
2555                 {
2556                         // TODO: Need something better for temporary variables
2557                         if ((flags & Flags.CompilerGenerated) != 0)
2558                                 CreateBuilder (ec);
2559
2560                         ec.Emit (OpCodes.Ldloca, builder);
2561                 }
2562
2563                 public static string GetCompilerGeneratedName (Block block)
2564                 {
2565                         // HACK: Debugger depends on the name semantics
2566                         return "$locvar" + block.ParametersBlock.TemporaryLocalsCount++.ToString ("X");
2567                 }
2568
2569                 public string GetReadOnlyContext ()
2570                 {
2571                         switch (flags & Flags.ReadonlyMask) {
2572                         case Flags.FixedVariable:
2573                                 return "fixed variable";
2574                         case Flags.ForeachVariable:
2575                                 return "foreach iteration variable";
2576                         case Flags.UsingVariable:
2577                                 return "using variable";
2578                         }
2579
2580                         throw new InternalErrorException ("Variable is not readonly");
2581                 }
2582
2583                 public bool IsThisAssigned (FlowAnalysisContext fc, Block block)
2584                 {
2585                         if (VariableInfo == null)
2586                                 throw new Exception ();
2587
2588                         if (IsAssigned (fc))
2589                                 return true;
2590
2591                         return VariableInfo.IsFullyInitialized (fc, block.StartLocation);
2592                 }
2593
2594                 public bool IsAssigned (FlowAnalysisContext fc)
2595                 {
2596                         return fc.IsDefinitelyAssigned (VariableInfo);
2597                 }
2598
2599                 public void PrepareAssignmentAnalysis (BlockContext bc)
2600                 {
2601                         //
2602                         // No need to run assignment analysis for these guys
2603                         //
2604                         if ((flags & (Flags.Constant | Flags.ReadonlyMask | Flags.CompilerGenerated)) != 0)
2605                                 return;
2606
2607                         VariableInfo = VariableInfo.Create (bc, this);
2608                 }
2609
2610                 //
2611                 // Mark the variables as referenced in the user code
2612                 //
2613                 public void SetIsUsed ()
2614                 {
2615                         flags |= Flags.Used;
2616                 }
2617
2618                 public void SetHasAddressTaken ()
2619                 {
2620                         flags |= (Flags.AddressTaken | Flags.Used);
2621                 }
2622
2623                 public override string ToString ()
2624                 {
2625                         return string.Format ("LocalInfo ({0},{1},{2},{3})", name, type, VariableInfo, Location);
2626                 }
2627         }
2628
2629         /// <summary>
2630         ///   Block represents a C# block.
2631         /// </summary>
2632         ///
2633         /// <remarks>
2634         ///   This class is used in a number of places: either to represent
2635         ///   explicit blocks that the programmer places or implicit blocks.
2636         ///
2637         ///   Implicit blocks are used as labels or to introduce variable
2638         ///   declarations.
2639         ///
2640         ///   Top-level blocks derive from Block, and they are called ToplevelBlock
2641         ///   they contain extra information that is not necessary on normal blocks.
2642         /// </remarks>
2643         public class Block : Statement {
2644                 [Flags]
2645                 public enum Flags
2646                 {
2647                         Unchecked = 1,
2648                         ReachableEnd = 8,
2649                         Unsafe = 16,
2650                         HasCapturedVariable = 64,
2651                         HasCapturedThis = 1 << 7,
2652                         IsExpressionTree = 1 << 8,
2653                         CompilerGenerated = 1 << 9,
2654                         HasAsyncModifier = 1 << 10,
2655                         Resolved = 1 << 11,
2656                         YieldBlock = 1 << 12,
2657                         AwaitBlock = 1 << 13,
2658                         FinallyBlock = 1 << 14,
2659                         CatchBlock = 1 << 15,
2660                         HasReferenceToStoreyForInstanceLambdas = 1 << 16,
2661                         Iterator = 1 << 20,
2662                         NoFlowAnalysis = 1 << 21,
2663                         InitializationEmitted = 1 << 22
2664                 }
2665
2666                 public Block Parent;
2667                 public Location StartLocation;
2668                 public Location EndLocation;
2669
2670                 public ExplicitBlock Explicit;
2671                 public ParametersBlock ParametersBlock;
2672
2673                 protected Flags flags;
2674
2675                 //
2676                 // The statements in this block
2677                 //
2678                 protected List<Statement> statements;
2679
2680                 protected List<Statement> scope_initializers;
2681
2682                 int? resolving_init_idx;
2683
2684                 Block original;
2685
2686 #if DEBUG
2687                 static int id;
2688                 public int ID = id++;
2689
2690                 static int clone_id_counter;
2691                 int clone_id;
2692 #endif
2693
2694 //              int assignable_slots;
2695
2696                 public Block (Block parent, Location start, Location end)
2697                         : this (parent, 0, start, end)
2698                 {
2699                 }
2700
2701                 public Block (Block parent, Flags flags, Location start, Location end)
2702                 {
2703                         if (parent != null) {
2704                                 // the appropriate constructors will fixup these fields
2705                                 ParametersBlock = parent.ParametersBlock;
2706                                 Explicit = parent.Explicit;
2707                         }
2708
2709                         this.Parent = parent;
2710                         this.flags = flags;
2711                         this.StartLocation = start;
2712                         this.EndLocation = end;
2713                         this.loc = start;
2714                         statements = new List<Statement> (4);
2715
2716                         this.original = this;
2717                 }
2718
2719                 #region Properties
2720
2721                 public Block Original {
2722                         get {
2723                                 return original;
2724                         }
2725                         protected set {
2726                                 original = value;
2727                         }
2728                 }
2729
2730                 public bool IsCompilerGenerated {
2731                         get { return (flags & Flags.CompilerGenerated) != 0; }
2732                         set { flags = value ? flags | Flags.CompilerGenerated : flags & ~Flags.CompilerGenerated; }
2733                 }
2734
2735
2736                 public bool IsCatchBlock {
2737                         get {
2738                                 return (flags & Flags.CatchBlock) != 0;
2739                         }
2740                 }
2741
2742                 public bool IsFinallyBlock {
2743                         get {
2744                                 return (flags & Flags.FinallyBlock) != 0;
2745                         }
2746                 }
2747
2748                 public bool Unchecked {
2749                         get { return (flags & Flags.Unchecked) != 0; }
2750                         set { flags = value ? flags | Flags.Unchecked : flags & ~Flags.Unchecked; }
2751                 }
2752
2753                 public bool Unsafe {
2754                         get { return (flags & Flags.Unsafe) != 0; }
2755                         set { flags |= Flags.Unsafe; }
2756                 }
2757
2758                 public List<Statement> Statements {
2759                         get { return statements; }
2760                 }
2761
2762                 #endregion
2763
2764                 public void SetEndLocation (Location loc)
2765                 {
2766                         EndLocation = loc;
2767                 }
2768
2769                 public void AddLabel (LabeledStatement target)
2770                 {
2771                         ParametersBlock.TopBlock.AddLabel (target.Name, target);
2772                 }
2773
2774                 public void AddLocalName (LocalVariable li)
2775                 {
2776                         AddLocalName (li.Name, li);
2777                 }
2778
2779                 public void AddLocalName (string name, INamedBlockVariable li)
2780                 {
2781                         ParametersBlock.TopBlock.AddLocalName (name, li, false);
2782                 }
2783
2784                 public virtual void Error_AlreadyDeclared (string name, INamedBlockVariable variable, string reason)
2785                 {
2786                         if (reason == null) {
2787                                 Error_AlreadyDeclared (name, variable);
2788                                 return;
2789                         }
2790
2791                         ParametersBlock.TopBlock.Report.Error (136, variable.Location,
2792                                 "A local variable named `{0}' cannot be declared in this scope because it would give a different meaning " +
2793                                 "to `{0}', which is already used in a `{1}' scope to denote something else",
2794                                 name, reason);
2795                 }
2796
2797                 public virtual void Error_AlreadyDeclared (string name, INamedBlockVariable variable)
2798                 {
2799                         var pi = variable as ParametersBlock.ParameterInfo;
2800                         if (pi != null) {
2801                                 pi.Parameter.Error_DuplicateName (ParametersBlock.TopBlock.Report);
2802                         } else {
2803                                 ParametersBlock.TopBlock.Report.Error (128, variable.Location,
2804                                         "A local variable named `{0}' is already defined in this scope", name);
2805                         }
2806                 }
2807
2808                 public virtual void Error_AlreadyDeclaredTypeParameter (string name, Location loc)
2809                 {
2810                         ParametersBlock.TopBlock.Report.Error (412, loc,
2811                                 "The type parameter name `{0}' is the same as local variable or parameter name",
2812                                 name);
2813                 }
2814
2815                 //
2816                 // It should be used by expressions which require to
2817                 // register a statement during resolve process.
2818                 //
2819                 public void AddScopeStatement (Statement s)
2820                 {
2821                         if (scope_initializers == null)
2822                                 scope_initializers = new List<Statement> ();
2823
2824                         //
2825                         // Simple recursive helper, when resolve scope initializer another
2826                         // new scope initializer can be added, this ensures it's initialized
2827                         // before existing one. For now this can happen with expression trees
2828                         // in base ctor initializer only
2829                         //
2830                         if (resolving_init_idx.HasValue) {
2831                                 scope_initializers.Insert (resolving_init_idx.Value, s);
2832                                 ++resolving_init_idx;
2833                         } else {
2834                                 scope_initializers.Add (s);
2835                         }
2836                 }
2837
2838                 public void InsertStatement (int index, Statement s)
2839                 {
2840                         statements.Insert (index, s);
2841                 }
2842
2843                 public void AddStatement (Statement s)
2844                 {
2845                         statements.Add (s);
2846                 }
2847
2848                 public LabeledStatement LookupLabel (string name)
2849                 {
2850                         return ParametersBlock.GetLabel (name, this);
2851                 }
2852
2853                 public override Reachability MarkReachable (Reachability rc)
2854                 {
2855                         if (rc.IsUnreachable)
2856                                 return rc;
2857
2858                         MarkReachableScope (rc);
2859
2860                         foreach (var s in statements) {
2861                                 rc = s.MarkReachable (rc);
2862                                 if (rc.IsUnreachable) {
2863                                         if ((flags & Flags.ReachableEnd) != 0)
2864                                                 return new Reachability ();
2865
2866                                         return rc;
2867                                 }
2868                         }
2869
2870                         flags |= Flags.ReachableEnd;
2871
2872                         return rc;
2873                 }
2874
2875                 public void MarkReachableScope (Reachability rc)
2876                 {
2877                         base.MarkReachable (rc);
2878
2879                         if (scope_initializers != null) {
2880                                 foreach (var si in scope_initializers)
2881                                         si.MarkReachable (rc);
2882                         }
2883                 }
2884
2885                 public override bool Resolve (BlockContext bc)
2886                 {
2887                         if ((flags & Flags.Resolved) != 0)
2888                                 return true;
2889
2890                         Block prev_block = bc.CurrentBlock;
2891                         bc.CurrentBlock = this;
2892
2893                         //
2894                         // Compiler generated scope statements
2895                         //
2896                         if (scope_initializers != null) {
2897                                 for (resolving_init_idx = 0; resolving_init_idx < scope_initializers.Count; ++resolving_init_idx) {
2898                                         scope_initializers[resolving_init_idx.Value].Resolve (bc);
2899                                 }
2900
2901                                 resolving_init_idx = null;
2902                         }
2903
2904                         bool ok = true;
2905                         int statement_count = statements.Count;
2906                         for (int ix = 0; ix < statement_count; ix++){
2907                                 Statement s = statements [ix];
2908
2909                                 if (!s.Resolve (bc)) {
2910                                         ok = false;
2911                                         statements [ix] = new EmptyStatement (s.loc);
2912                                         continue;
2913                                 }
2914                         }
2915
2916                         bc.CurrentBlock = prev_block;
2917
2918                         flags |= Flags.Resolved;
2919                         return ok;
2920                 }
2921
2922                 protected override void DoEmit (EmitContext ec)
2923                 {
2924                         for (int ix = 0; ix < statements.Count; ix++){
2925                                 statements [ix].Emit (ec);
2926                         }
2927                 }
2928
2929                 public override void Emit (EmitContext ec)
2930                 {
2931                         if (scope_initializers != null)
2932                                 EmitScopeInitializers (ec);
2933
2934                         DoEmit (ec);
2935                 }
2936
2937                 protected void EmitScopeInitializers (EmitContext ec)
2938                 {
2939                         foreach (Statement s in scope_initializers)
2940                                 s.Emit (ec);
2941                 }
2942
2943                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
2944                 {
2945                         if (scope_initializers != null) {
2946                                 foreach (var si in scope_initializers)
2947                                         si.FlowAnalysis (fc);
2948                         }
2949
2950                         return DoFlowAnalysis (fc, 0);
2951                 }
2952
2953                 bool DoFlowAnalysis (FlowAnalysisContext fc, int startIndex)
2954                 {
2955                         bool end_unreachable = !reachable;
2956                         bool goto_flow_analysis = startIndex != 0;
2957                         for (; startIndex < statements.Count; ++startIndex) {
2958                                 var s = statements[startIndex];
2959
2960                                 end_unreachable = s.FlowAnalysis (fc);
2961                                 if (s.IsUnreachable) {
2962                                         statements [startIndex] = RewriteUnreachableStatement (s);
2963                                         continue;
2964                                 }
2965
2966                                 //
2967                                 // Statement end reachability is needed mostly due to goto support. Consider
2968                                 //
2969                                 // if (cond) {
2970                                 //    goto X;
2971                                 // } else {
2972                                 //    goto Y;
2973                                 // }
2974                                 // X:
2975                                 //
2976                                 // X label is reachable only via goto not as another statement after if. We need
2977                                 // this for flow-analysis only to carry variable info correctly.
2978                                 //
2979                                 if (end_unreachable) {
2980                                         bool after_goto_case = goto_flow_analysis && s is GotoCase;
2981
2982                                         var f = s as TryFinally;
2983                                         if (f != null && !f.FinallyBlock.HasReachableClosingBrace) {
2984                                                 //
2985                                                 // Special case for try-finally with unreachable code after
2986                                                 // finally block. Try block has to include leave opcode but there is
2987                                                 // no label to leave to after unreachable finally block closing
2988                                                 // brace. This sentinel ensures there is always IL instruction to
2989                                                 // leave to even if we know it'll never be reached.
2990                                                 //
2991                                                 statements.Insert (startIndex + 1, new SentinelStatement ());
2992                                         } else {
2993                                                 for (++startIndex; startIndex < statements.Count; ++startIndex) {
2994                                                         s = statements [startIndex];
2995                                                         if (s is SwitchLabel) {
2996                                                                 if (!after_goto_case)
2997                                                                         s.FlowAnalysis (fc);
2998
2999                                                                 break;
3000                                                         }
3001
3002                                                         if (s.IsUnreachable) {
3003                                                                 s.FlowAnalysis (fc);
3004                                                                 statements [startIndex] = RewriteUnreachableStatement (s);
3005                                                         }
3006                                                 }
3007                                         }
3008
3009                                         //
3010                                         // Idea is to stop after goto case because goto case will always have at least same
3011                                         // variable assigned as switch case label. This saves a lot for complex goto case tests
3012                                         //
3013                                         if (after_goto_case)
3014                                                 break;
3015
3016                                         continue;
3017                                 }
3018
3019                                 var lb = s as LabeledStatement;
3020                                 if (lb != null && fc.AddReachedLabel (lb))
3021                                         break;
3022                         }
3023
3024                         //
3025                         // The condition should be true unless there is forward jumping goto
3026                         //
3027                         // if (this is ExplicitBlock && end_unreachable != Explicit.HasReachableClosingBrace)
3028                         //      Debug.Fail ();
3029
3030                         return !Explicit.HasReachableClosingBrace;
3031                 }
3032
3033                 static Statement RewriteUnreachableStatement (Statement s)
3034                 {
3035                         // LAMESPEC: It's not clear whether declararion statement should be part of reachability
3036                         // analysis. Even csc report unreachable warning for it but it's actually used hence
3037                         // we try to emulate this behaviour
3038                         //
3039                         // Consider:
3040                         //      goto L;
3041                         //      int v;
3042                         // L:
3043                         //      v = 1;
3044
3045                         if (s is BlockVariable || s is EmptyStatement || s is SentinelStatement)
3046                                 return s;
3047
3048                         return new EmptyStatement (s.loc);
3049                 }
3050
3051                 public void ScanGotoJump (Statement label)
3052                 {
3053                         int i;
3054                         for (i = 0; i < statements.Count; ++i) {
3055                                 if (statements[i] == label)
3056                                         break;
3057                         }
3058
3059                         var rc = new Reachability ();
3060                         for (++i; i < statements.Count; ++i) {
3061                                 var s = statements[i];
3062                                 rc = s.MarkReachable (rc);
3063                                 if (rc.IsUnreachable)
3064                                         return;
3065                         }
3066
3067                         flags |= Flags.ReachableEnd;
3068                 }
3069
3070                 public void ScanGotoJump (Statement label, FlowAnalysisContext fc)
3071                 {
3072                         int i;
3073                         for (i = 0; i < statements.Count; ++i) {
3074                                 if (statements[i] == label)
3075                                         break;
3076                         }
3077
3078                         DoFlowAnalysis (fc, ++i);
3079                 }
3080
3081 #if DEBUG
3082                 public override string ToString ()
3083                 {
3084                         return String.Format ("{0}: ID={1} Clone={2} Location={3}", GetType (), ID, clone_id != 0, StartLocation);
3085                 }
3086 #endif
3087
3088                 protected override void CloneTo (CloneContext clonectx, Statement t)
3089                 {
3090                         Block target = (Block) t;
3091 #if DEBUG
3092                         target.clone_id = ++clone_id_counter;
3093 #endif
3094
3095                         clonectx.AddBlockMap (this, target);
3096                         if (original != this)
3097                                 clonectx.AddBlockMap (original, target);
3098
3099                         target.ParametersBlock = (ParametersBlock) (ParametersBlock == this ? target : clonectx.RemapBlockCopy (ParametersBlock));
3100                         target.Explicit = (ExplicitBlock) (Explicit == this ? target : clonectx.LookupBlock (Explicit));
3101
3102                         if (Parent != null)
3103                                 target.Parent = clonectx.RemapBlockCopy (Parent);
3104
3105                         target.statements = new List<Statement> (statements.Count);
3106                         foreach (Statement s in statements)
3107                                 target.statements.Add (s.Clone (clonectx));
3108                 }
3109
3110                 public override object Accept (StructuralVisitor visitor)
3111                 {
3112                         return visitor.Visit (this);
3113                 }
3114         }
3115
3116         public class ExplicitBlock : Block
3117         {
3118                 protected AnonymousMethodStorey am_storey;
3119                 int debug_scope_index;
3120
3121                 public ExplicitBlock (Block parent, Location start, Location end)
3122                         : this (parent, (Flags) 0, start, end)
3123                 {
3124                 }
3125
3126                 public ExplicitBlock (Block parent, Flags flags, Location start, Location end)
3127                         : base (parent, flags, start, end)
3128                 {
3129                         this.Explicit = this;
3130                 }
3131
3132                 #region Properties
3133
3134                 public AnonymousMethodStorey AnonymousMethodStorey {
3135                         get {
3136                                 return am_storey;
3137                         }
3138                 }
3139
3140                 public bool HasAwait {
3141                         get {
3142                                 return (flags & Flags.AwaitBlock) != 0;
3143                         }
3144                 }
3145
3146                 public bool HasCapturedThis {
3147                         set {
3148                                 flags = value ? flags | Flags.HasCapturedThis : flags & ~Flags.HasCapturedThis;
3149                         }
3150                         get {
3151                                 return (flags & Flags.HasCapturedThis) != 0;
3152                         }
3153                 }
3154
3155                 //
3156                 // Used to indicate that the block has reference to parent
3157                 // block and cannot be made static when defining anonymous method
3158                 //
3159                 public bool HasCapturedVariable {
3160                         set {
3161                                 flags = value ? flags | Flags.HasCapturedVariable : flags & ~Flags.HasCapturedVariable;
3162                         }
3163                         get {
3164                                 return (flags & Flags.HasCapturedVariable) != 0;
3165                         }
3166                 }
3167
3168                 public bool HasReachableClosingBrace {
3169                     get {
3170                         return (flags & Flags.ReachableEnd) != 0;
3171                     }
3172                         set {
3173                                 flags = value ? flags | Flags.ReachableEnd : flags & ~Flags.ReachableEnd;
3174                         }
3175                 }
3176
3177                 public bool HasYield {
3178                         get {
3179                                 return (flags & Flags.YieldBlock) != 0;
3180                         }
3181                 }
3182
3183                 #endregion
3184
3185                 //
3186                 // Creates anonymous method storey in current block
3187                 //
3188                 public AnonymousMethodStorey CreateAnonymousMethodStorey (ResolveContext ec)
3189                 {
3190                         //
3191                         // Return same story for iterator and async blocks unless we are
3192                         // in nested anonymous method
3193                         //
3194                         if (ec.CurrentAnonymousMethod is StateMachineInitializer && ParametersBlock.Original == ec.CurrentAnonymousMethod.Block.Original)
3195                                 return ec.CurrentAnonymousMethod.Storey;
3196
3197                         if (am_storey == null) {
3198                                 MemberBase mc = ec.MemberContext as MemberBase;
3199
3200                                 //
3201                                 // Creates anonymous method storey for this block
3202                                 //
3203                                 am_storey = new AnonymousMethodStorey (this, ec.CurrentMemberDefinition.Parent.PartialContainer, mc, ec.CurrentTypeParameters, "AnonStorey", MemberKind.Class);
3204                         }
3205
3206                         return am_storey;
3207                 }
3208
3209                 public void EmitScopeInitialization (EmitContext ec)
3210                 {
3211                         if ((flags & Flags.InitializationEmitted) != 0)
3212                                 return;
3213
3214                         if (am_storey != null) {
3215                                 DefineStoreyContainer (ec, am_storey);
3216                                 am_storey.EmitStoreyInstantiation (ec, this);
3217                         }
3218
3219                         if (scope_initializers != null)
3220                                 EmitScopeInitializers (ec);
3221
3222                         flags |= Flags.InitializationEmitted;
3223                 }
3224
3225                 public override void Emit (EmitContext ec)
3226                 {
3227                         if (Parent != null) {
3228                                 // TODO: It's needed only when scope has variable (normal or lifted)
3229                                 ec.BeginScope (GetDebugSymbolScopeIndex ());
3230                         }
3231
3232                         EmitScopeInitialization (ec);
3233
3234                         if (ec.EmitAccurateDebugInfo && !IsCompilerGenerated && ec.Mark (StartLocation)) {
3235                                 ec.Emit (OpCodes.Nop);
3236                         }
3237
3238                         DoEmit (ec);
3239
3240                         if (Parent != null)
3241                                 ec.EndScope ();
3242
3243                         if (ec.EmitAccurateDebugInfo && HasReachableClosingBrace && !(this is ParametersBlock) &&
3244                                 !IsCompilerGenerated && ec.Mark (EndLocation)) {
3245                                 ec.Emit (OpCodes.Nop);
3246                         }
3247                 }
3248
3249                 protected void DefineStoreyContainer (EmitContext ec, AnonymousMethodStorey storey)
3250                 {
3251                         if (ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod.Storey != null) {
3252                                 storey.SetNestedStoryParent (ec.CurrentAnonymousMethod.Storey);
3253                                 storey.Mutator = ec.CurrentAnonymousMethod.Storey.Mutator;
3254                         }
3255
3256                         //
3257                         // Creates anonymous method storey
3258                         //
3259                         storey.CreateContainer ();
3260                         storey.DefineContainer ();
3261                         storey.ExpandBaseInterfaces ();
3262
3263                         if (Original.Explicit.HasCapturedThis && Original.ParametersBlock.TopBlock.ThisReferencesFromChildrenBlock != null) {
3264
3265                                 //
3266                                 // Only first storey in path will hold this reference. All children blocks will
3267                                 // reference it indirectly using $ref field
3268                                 //
3269                                 for (Block b = Original.Explicit; b != null; b = b.Parent) {
3270                                         if (b.Parent != null) {
3271                                                 var s = b.Parent.Explicit.AnonymousMethodStorey;
3272                                                 if (s != null) {
3273                                                         storey.HoistedThis = s.HoistedThis;
3274                                                         break;
3275                                                 }
3276                                         }
3277
3278                                         if (b.Explicit == b.Explicit.ParametersBlock && b.Explicit.ParametersBlock.StateMachine != null) {
3279                                                 if (storey.HoistedThis == null)
3280                                                         storey.HoistedThis = b.Explicit.ParametersBlock.StateMachine.HoistedThis;
3281
3282                                                 if (storey.HoistedThis != null)
3283                                                         break;
3284                                         }
3285                                 }
3286
3287                                 //
3288                                 // We are the first storey on path and 'this' has to be hoisted
3289                                 //
3290                                 if (storey.HoistedThis == null || !(storey.Parent is HoistedStoreyClass)) {
3291                                         foreach (ExplicitBlock ref_block in Original.ParametersBlock.TopBlock.ThisReferencesFromChildrenBlock) {
3292                                                 //
3293                                                 // ThisReferencesFromChildrenBlock holds all reference even if they
3294                                                 // are not on this path. It saves some memory otherwise it'd have to
3295                                                 // be in every explicit block. We run this check to see if the reference
3296                                                 // is valid for this storey
3297                                                 //
3298                                                 Block block_on_path = ref_block;
3299                                                 for (; block_on_path != null && block_on_path != Original; block_on_path = block_on_path.Parent);
3300
3301                                                 if (block_on_path == null)
3302                                                         continue;
3303
3304                                                 if (storey.HoistedThis == null) {
3305                                                         storey.AddCapturedThisField (ec, null);
3306                                                 }
3307
3308                                                 for (ExplicitBlock b = ref_block; b.AnonymousMethodStorey != storey; b = b.Parent.Explicit) {
3309                                                         ParametersBlock pb;
3310                                                         AnonymousMethodStorey b_storey = b.AnonymousMethodStorey;
3311
3312                                                         if (b_storey != null) {
3313                                                                 //
3314                                                                 // Don't add storey cross reference for `this' when the storey ends up not
3315                                                                 // beeing attached to any parent
3316                                                                 //
3317                                                                 if (b.ParametersBlock.StateMachine == null) {
3318                                                                         AnonymousMethodStorey s = null;
3319                                                                         for (Block ab = b.AnonymousMethodStorey.OriginalSourceBlock.Parent; ab != null; ab = ab.Parent) {
3320                                                                                 s = ab.Explicit.AnonymousMethodStorey;
3321                                                                                 if (s != null)
3322                                                                                         break;
3323                                                                         }
3324
3325                                                                         // Needs to be in sync with AnonymousMethodBody::DoCreateMethodHost
3326                                                                         if (s == null) {
3327                                                                                 var parent = storey == null || storey.Kind == MemberKind.Struct ? null : storey;
3328                                                                                 b.AnonymousMethodStorey.AddCapturedThisField (ec, parent);
3329                                                                                 break;
3330                                                                         }
3331
3332                                                                 }
3333
3334                                                                 //
3335                                                                 // Stop propagation inside same top block
3336                                                                 //
3337                                                                 if (b.ParametersBlock == ParametersBlock.Original) {
3338                                                                         b_storey.AddParentStoreyReference (ec, storey);
3339 //                                                                      b_storey.HoistedThis = storey.HoistedThis;
3340                                                                         break;
3341                                                                 }
3342
3343                                                                 b = pb = b.ParametersBlock;
3344                                                         } else {
3345                                                                 pb = b as ParametersBlock;
3346                                                         }
3347
3348                                                         if (pb != null && pb.StateMachine != null) {
3349                                                                 if (pb.StateMachine == storey)
3350                                                                         break;
3351
3352                                                                 //
3353                                                                 // If we are state machine with no parent. We can hook into parent without additional
3354                                                                 // reference and capture this directly
3355                                                                 //
3356                                                                 ExplicitBlock parent_storey_block = pb;
3357                                                                 while (parent_storey_block.Parent != null) {
3358                                                                         parent_storey_block = parent_storey_block.Parent.Explicit;
3359                                                                         if (parent_storey_block.AnonymousMethodStorey != null) {
3360                                                                                 break;
3361                                                                         }
3362                                                                 }
3363
3364                                                                 if (parent_storey_block.AnonymousMethodStorey == null) {
3365                                                                         if (pb.StateMachine.HoistedThis == null) {
3366                                                                                 pb.StateMachine.AddCapturedThisField (ec, null);
3367                                                                                 b.HasCapturedThis = true;
3368                                                                         }
3369
3370                                                                         continue;
3371                                                                 }
3372
3373                                                                 var parent_this_block = pb;
3374                                                                 while (parent_this_block.Parent != null) {
3375                                                                         parent_this_block = parent_this_block.Parent.ParametersBlock;
3376                                                                         if (parent_this_block.StateMachine != null && parent_this_block.StateMachine.HoistedThis != null) {
3377                                                                                 break;
3378                                                                         }
3379                                                                 }
3380
3381                                                                 //
3382                                                                 // Add reference to closest storey which holds captured this
3383                                                                 //
3384                                                                 pb.StateMachine.AddParentStoreyReference (ec, parent_this_block.StateMachine ?? storey);
3385                                                         }
3386
3387                                                         //
3388                                                         // Add parent storey reference only when this is not captured directly
3389                                                         //
3390                                                         if (b_storey != null) {
3391                                                                 b_storey.AddParentStoreyReference (ec, storey);
3392                                                                 b_storey.HoistedThis = storey.HoistedThis;
3393                                                         }
3394                                                 }
3395                                         }
3396                                 }
3397                         }
3398
3399                         var ref_blocks = storey.ReferencesFromChildrenBlock;
3400                         if (ref_blocks != null) {
3401                                 foreach (ExplicitBlock ref_block in ref_blocks) {
3402                                         for (ExplicitBlock b = ref_block; b.AnonymousMethodStorey != storey; b = b.Parent.Explicit) {
3403                                                 if (b.AnonymousMethodStorey != null) {
3404                                                         b.AnonymousMethodStorey.AddParentStoreyReference (ec, storey);
3405
3406                                                         //
3407                                                         // Stop propagation inside same top block
3408                                                         //
3409                                                         if (b.ParametersBlock == ParametersBlock.Original)
3410                                                                 break;
3411
3412                                                         b = b.ParametersBlock;
3413                                                 }
3414
3415                                                 var pb = b as ParametersBlock;
3416                                                 if (pb != null && pb.StateMachine != null) {
3417                                                         if (pb.StateMachine == storey)
3418                                                                 break;
3419
3420                                                         pb.StateMachine.AddParentStoreyReference (ec, storey);
3421                                                 }
3422
3423                                                 b.HasCapturedVariable = true;
3424                                         }
3425                                 }
3426                         }
3427
3428                         storey.Define ();
3429                         storey.PrepareEmit ();
3430                         storey.Parent.PartialContainer.AddCompilerGeneratedClass (storey);
3431                 }
3432
3433                 public int GetDebugSymbolScopeIndex ()
3434                 {
3435                         if (debug_scope_index == 0)
3436                                 debug_scope_index = ++ParametersBlock.debug_scope_index;
3437
3438                         return debug_scope_index;
3439                 }
3440
3441                 public void RegisterAsyncAwait ()
3442                 {
3443                         var block = this;
3444                         while ((block.flags & Flags.AwaitBlock) == 0) {
3445                                 block.flags |= Flags.AwaitBlock;
3446
3447                                 if (block is ParametersBlock)
3448                                         return;
3449
3450                                 block = block.Parent.Explicit;
3451                         }
3452                 }
3453
3454                 public void RegisterIteratorYield ()
3455                 {
3456                         ParametersBlock.TopBlock.IsIterator = true;
3457
3458                         var block = this;
3459                         while ((block.flags & Flags.YieldBlock) == 0) {
3460                                 block.flags |= Flags.YieldBlock;
3461
3462                                 if (block.Parent == null)
3463                                         return;
3464
3465                                 block = block.Parent.Explicit;
3466                         }
3467                 }
3468
3469                 public void SetCatchBlock ()
3470                 {
3471                         flags |= Flags.CatchBlock;
3472                 }
3473
3474                 public void SetFinallyBlock ()
3475                 {
3476                         flags |= Flags.FinallyBlock;
3477                 }
3478
3479                 public void WrapIntoDestructor (TryFinally tf, ExplicitBlock tryBlock)
3480                 {
3481                         tryBlock.statements = statements;
3482                         statements = new List<Statement> (1);
3483                         statements.Add (tf);
3484                 }
3485         }
3486
3487         //
3488         // ParametersBlock was introduced to support anonymous methods
3489         // and lambda expressions
3490         //
3491         public class ParametersBlock : ExplicitBlock
3492         {
3493                 public class ParameterInfo : INamedBlockVariable
3494                 {
3495                         readonly ParametersBlock block;
3496                         readonly int index;
3497                         public VariableInfo VariableInfo;
3498                         bool is_locked;
3499
3500                         public ParameterInfo (ParametersBlock block, int index)
3501                         {
3502                                 this.block = block;
3503                                 this.index = index;
3504                         }
3505
3506                         #region Properties
3507
3508                         public ParametersBlock Block {
3509                                 get {
3510                                         return block;
3511                                 }
3512                         }
3513
3514                         Block INamedBlockVariable.Block {
3515                                 get {
3516                                         return block;
3517                                 }
3518                         }
3519
3520                         public bool IsDeclared {
3521                                 get {
3522                                         return true;
3523                                 }
3524                         }
3525
3526                         public bool IsParameter {
3527                                 get {
3528                                         return true;
3529                                 }
3530                         }
3531
3532                         public bool IsLocked {
3533                                 get {
3534                                         return is_locked;
3535                                 }
3536                                 set {
3537                                         is_locked = value;
3538                                 }
3539                         }
3540
3541                         public Location Location {
3542                                 get {
3543                                         return Parameter.Location;
3544                                 }
3545                         }
3546
3547                         public Parameter Parameter {
3548                                 get {
3549                                         return block.Parameters [index];
3550                                 }
3551                         }
3552
3553                         public TypeSpec ParameterType {
3554                                 get {
3555                                         return Parameter.Type;
3556                                 }
3557                         }
3558
3559                         #endregion
3560
3561                         public Expression CreateReferenceExpression (ResolveContext rc, Location loc)
3562                         {
3563                                 return new ParameterReference (this, loc);
3564                         }
3565                 }
3566
3567                 //
3568                 // Block is converted into an expression
3569                 //
3570                 sealed class BlockScopeExpression : Expression
3571                 {
3572                         Expression child;
3573                         readonly ParametersBlock block;
3574
3575                         public BlockScopeExpression (Expression child, ParametersBlock block)
3576                         {
3577                                 this.child = child;
3578                                 this.block = block;
3579                         }
3580
3581                         public override bool ContainsEmitWithAwait ()
3582                         {
3583                                 return child.ContainsEmitWithAwait ();
3584                         }
3585
3586                         public override Expression CreateExpressionTree (ResolveContext ec)
3587                         {
3588                                 throw new NotSupportedException ();
3589                         }
3590
3591                         protected override Expression DoResolve (ResolveContext ec)
3592                         {
3593                                 if (child == null)
3594                                         return null;
3595
3596                                 child = child.Resolve (ec);
3597                                 if (child == null)
3598                                         return null;
3599
3600                                 eclass = child.eclass;
3601                                 type = child.Type;
3602                                 return this;
3603                         }
3604
3605                         public override void Emit (EmitContext ec)
3606                         {
3607                                 block.EmitScopeInitializers (ec);
3608                                 child.Emit (ec);
3609                         }
3610                 }
3611
3612                 protected ParametersCompiled parameters;
3613                 protected ParameterInfo[] parameter_info;
3614                 protected bool resolved;
3615                 protected ToplevelBlock top_block;
3616                 protected StateMachine state_machine;
3617                 protected Dictionary<string, object> labels;
3618
3619                 public ParametersBlock (Block parent, ParametersCompiled parameters, Location start, Flags flags = 0)
3620                         : base (parent, 0, start, start)
3621                 {
3622                         if (parameters == null)
3623                                 throw new ArgumentNullException ("parameters");
3624
3625                         this.parameters = parameters;
3626                         ParametersBlock = this;
3627
3628                         this.flags |= flags | (parent.ParametersBlock.flags & (Flags.YieldBlock | Flags.AwaitBlock));
3629
3630                         this.top_block = parent.ParametersBlock.top_block;
3631                         ProcessParameters ();
3632                 }
3633
3634                 protected ParametersBlock (ParametersCompiled parameters, Location start)
3635                         : base (null, 0, start, start)
3636                 {
3637                         if (parameters == null)
3638                                 throw new ArgumentNullException ("parameters");
3639
3640                         this.parameters = parameters;
3641                         ParametersBlock = this;
3642                 }
3643
3644                 //
3645                 // It's supposed to be used by method body implementation of anonymous methods
3646                 //
3647                 protected ParametersBlock (ParametersBlock source, ParametersCompiled parameters)
3648                         : base (null, 0, source.StartLocation, source.EndLocation)
3649                 {
3650                         this.parameters = parameters;
3651                         this.statements = source.statements;
3652                         this.scope_initializers = source.scope_initializers;
3653
3654                         this.resolved = true;
3655                         this.reachable = source.reachable;
3656                         this.am_storey = source.am_storey;
3657                         this.state_machine = source.state_machine;
3658                         this.flags = source.flags & Flags.ReachableEnd;
3659
3660                         ParametersBlock = this;
3661
3662                         //
3663                         // Overwrite original for comparison purposes when linking cross references
3664                         // between anonymous methods
3665                         //
3666                         Original = source.Original;
3667                 }
3668
3669                 #region Properties
3670
3671                 public bool HasReferenceToStoreyForInstanceLambdas {
3672                         get {
3673                                 return (flags & Flags.HasReferenceToStoreyForInstanceLambdas) != 0;
3674                         }
3675                         set {
3676                                 flags = value ? flags | Flags.HasReferenceToStoreyForInstanceLambdas : flags & ~Flags.HasReferenceToStoreyForInstanceLambdas;
3677                         }
3678                 }
3679
3680                 public bool IsAsync {
3681                         get {
3682                                 return (flags & Flags.HasAsyncModifier) != 0;
3683                         }
3684                         set {
3685                                 flags = value ? flags | Flags.HasAsyncModifier : flags & ~Flags.HasAsyncModifier;
3686                         }
3687                 }
3688
3689                 //
3690                 // Block has been converted to expression tree
3691                 //
3692                 public bool IsExpressionTree {
3693                         get {
3694                                 return (flags & Flags.IsExpressionTree) != 0;
3695                         }
3696                 }
3697
3698                 //
3699                 // The parameters for the block.
3700                 //
3701                 public ParametersCompiled Parameters {
3702                         get {
3703                                 return parameters;
3704                         }
3705                 }
3706
3707                 public StateMachine StateMachine {
3708                         get {
3709                                 return state_machine;
3710                         }
3711                 }
3712
3713                 public ToplevelBlock TopBlock {
3714                         get {
3715                                 return top_block;
3716                         }
3717                         set {
3718                                 top_block = value;
3719                         }
3720                 }
3721
3722                 public bool Resolved {
3723                         get {
3724                                 return (flags & Flags.Resolved) != 0;
3725                         }
3726                 }
3727
3728                 public int TemporaryLocalsCount { get; set; }
3729
3730                 #endregion
3731
3732                 //
3733                 // Checks whether all `out' parameters have been assigned.
3734                 //
3735                 public void CheckControlExit (FlowAnalysisContext fc)
3736                 {
3737                         CheckControlExit (fc, fc.DefiniteAssignment);
3738                 }
3739
3740                 public virtual void CheckControlExit (FlowAnalysisContext fc, DefiniteAssignmentBitSet dat)
3741                 {
3742                         if (parameter_info == null)
3743                                 return;
3744
3745                         foreach (var p in parameter_info) {
3746                                 if (p.VariableInfo == null)
3747                                         continue;
3748
3749                                 if (p.VariableInfo.IsAssigned (dat))
3750                                         continue;
3751
3752                                 fc.Report.Error (177, p.Location,
3753                                         "The out parameter `{0}' must be assigned to before control leaves the current method",
3754                                         p.Parameter.Name);
3755                         }
3756                 }
3757
3758                 protected override void CloneTo (CloneContext clonectx, Statement t)
3759                 {
3760                         base.CloneTo (clonectx, t);
3761
3762                         var target = (ParametersBlock) t;
3763
3764                         //
3765                         // Clone label statements as well as they contain block reference
3766                         //
3767                         var pb = this;
3768                         while (true) {
3769                                 if (pb.labels != null) {
3770                                         target.labels = new Dictionary<string, object> ();
3771
3772                                         foreach (var entry in pb.labels) {
3773                                                 var list = entry.Value as List<LabeledStatement>;
3774
3775                                                 if (list != null) {
3776                                                         var list_clone = new List<LabeledStatement> ();
3777                                                         foreach (var lentry in list) {
3778                                                                 list_clone.Add (RemapLabeledStatement (lentry, clonectx.RemapBlockCopy (lentry.Block)));
3779                                                         }
3780
3781                                                         target.labels.Add (entry.Key, list_clone);
3782                                                 } else {
3783                                                         var labeled = (LabeledStatement) entry.Value;
3784                                                         target.labels.Add (entry.Key, RemapLabeledStatement (labeled, clonectx.RemapBlockCopy (labeled.Block)));
3785                                                 }
3786                                         }
3787
3788                                         break;
3789                                 }
3790
3791                                 if (pb.Parent == null)
3792                                         break;
3793
3794                                 pb = pb.Parent.ParametersBlock;
3795                         }
3796                 }
3797
3798                 public override Expression CreateExpressionTree (ResolveContext ec)
3799                 {
3800                         if (statements.Count == 1) {
3801                                 Expression expr = statements[0].CreateExpressionTree (ec);
3802                                 if (scope_initializers != null)
3803                                         expr = new BlockScopeExpression (expr, this);
3804
3805                                 return expr;
3806                         }
3807
3808                         return base.CreateExpressionTree (ec);
3809                 }
3810
3811                 public override void Emit (EmitContext ec)
3812                 {
3813                         if (state_machine != null && state_machine.OriginalSourceBlock != this) {
3814                                 DefineStoreyContainer (ec, state_machine);
3815                                 state_machine.EmitStoreyInstantiation (ec, this);
3816                         }
3817
3818                         base.Emit (ec);
3819                 }
3820
3821                 public void EmitEmbedded (EmitContext ec)
3822                 {
3823                         if (state_machine != null && state_machine.OriginalSourceBlock != this) {
3824                                 DefineStoreyContainer (ec, state_machine);
3825                                 state_machine.EmitStoreyInstantiation (ec, this);
3826                         }
3827
3828                         base.Emit (ec);
3829                 }
3830
3831                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
3832                 {
3833                         var res = base.DoFlowAnalysis (fc);
3834
3835                         if (HasReachableClosingBrace)
3836                                 CheckControlExit (fc);
3837
3838                         return res;
3839                 }
3840
3841                 public LabeledStatement GetLabel (string name, Block block)
3842                 {
3843                         //
3844                         // Cloned parameters blocks can have their own cloned version of top-level labels
3845                         //
3846                         if (labels == null) {
3847                                 if (Parent != null)
3848                                         return Parent.ParametersBlock.GetLabel (name, block);
3849
3850                                 return null;
3851                         }
3852
3853                         object value;
3854                         if (!labels.TryGetValue (name, out value)) {
3855                                 return null;
3856                         }
3857
3858                         var label = value as LabeledStatement;
3859                         Block b = block;
3860                         if (label != null) {
3861                                 if (IsLabelVisible (label, b))
3862                                         return label;
3863
3864                         } else {
3865                                 List<LabeledStatement> list = (List<LabeledStatement>) value;
3866                                 for (int i = 0; i < list.Count; ++i) {
3867                                         label = list[i];
3868                                         if (IsLabelVisible (label, b))
3869                                                 return label;
3870                                 }
3871                         }
3872
3873                         return null;
3874                 }
3875
3876                 static bool IsLabelVisible (LabeledStatement label, Block b)
3877                 {
3878                         do {
3879                                 if (label.Block == b)
3880                                         return true;
3881                                 b = b.Parent;
3882                         } while (b != null);
3883
3884                         return false;
3885                 }
3886
3887                 public ParameterInfo GetParameterInfo (Parameter p)
3888                 {
3889                         for (int i = 0; i < parameters.Count; ++i) {
3890                                 if (parameters[i] == p)
3891                                         return parameter_info[i];
3892                         }
3893
3894                         throw new ArgumentException ("Invalid parameter");
3895                 }
3896
3897                 public ParameterReference GetParameterReference (int index, Location loc)
3898                 {
3899                         return new ParameterReference (parameter_info[index], loc);
3900                 }
3901
3902                 public Statement PerformClone (ref HashSet<LocalVariable> undeclaredVariables)
3903                 {
3904                         undeclaredVariables = TopBlock.GetUndeclaredVariables ();
3905
3906                         CloneContext clonectx = new CloneContext ();
3907                         return Clone (clonectx);
3908                 }
3909
3910                 protected void ProcessParameters ()
3911                 {
3912                         if (parameters.Count == 0)
3913                                 return;
3914
3915                         parameter_info = new ParameterInfo[parameters.Count];
3916                         for (int i = 0; i < parameter_info.Length; ++i) {
3917                                 var p = parameters.FixedParameters[i];
3918                                 if (p == null)
3919                                         continue;
3920
3921                                 // TODO: Should use Parameter only and more block there
3922                                 parameter_info[i] = new ParameterInfo (this, i);
3923                                 if (p.Name != null)
3924                                         AddLocalName (p.Name, parameter_info[i]);
3925                         }
3926                 }
3927
3928                 LabeledStatement RemapLabeledStatement (LabeledStatement stmt, Block dst)
3929                 {
3930                         var src = stmt.Block;
3931
3932                         //
3933                         // Cannot remap label block if the label was not yet cloned which
3934                         // can happen in case of anonymous method inside anoynymous method
3935                         // with a label. But in this case we don't care because goto cannot
3936                         // jump of out anonymous method
3937                         //
3938                         if (src.ParametersBlock != this)
3939                                 return stmt;
3940
3941                         var src_stmts = src.Statements;
3942                         for (int i = 0; i < src_stmts.Count; ++i) {
3943                                 if (src_stmts[i] == stmt)
3944                                         return (LabeledStatement) dst.Statements[i];
3945                         }
3946
3947                         throw new InternalErrorException ("Should never be reached");
3948                 }
3949
3950                 public override bool Resolve (BlockContext bc)
3951                 {
3952                         // TODO: if ((flags & Flags.Resolved) != 0)
3953
3954                         if (resolved)
3955                                 return true;
3956
3957                         resolved = true;
3958
3959                         if (bc.HasSet (ResolveContext.Options.ExpressionTreeConversion))
3960                                 flags |= Flags.IsExpressionTree;
3961
3962                         try {
3963                                 PrepareAssignmentAnalysis (bc);
3964
3965                                 if (!base.Resolve (bc))
3966                                         return false;
3967
3968                         } catch (Exception e) {
3969                                 if (e is CompletionResult || bc.Report.IsDisabled || e is FatalException || bc.Report.Printer is NullReportPrinter || bc.Module.Compiler.Settings.BreakOnInternalError)
3970                                         throw;
3971
3972                                 if (bc.CurrentBlock != null) {
3973                                         bc.Report.Error (584, bc.CurrentBlock.StartLocation, "Internal compiler error: {0}", e.Message);
3974                                 } else {
3975                                         bc.Report.Error (587, "Internal compiler error: {0}", e.Message);
3976                                 }
3977                         }
3978
3979                         //
3980                         // If an asynchronous body of F is either an expression classified as nothing, or a
3981                         // statement block where no return statements have expressions, the inferred return type is Task
3982                         //
3983                         if (IsAsync) {
3984                                 var am = bc.CurrentAnonymousMethod as AnonymousMethodBody;
3985                                 if (am != null && am.ReturnTypeInference != null && !am.ReturnTypeInference.HasBounds (0)) {
3986                                         am.ReturnTypeInference = null;
3987                                         am.ReturnType = bc.Module.PredefinedTypes.Task.TypeSpec;
3988                                         return true;
3989                                 }
3990                         }
3991
3992                         return true;
3993                 }
3994
3995                 void PrepareAssignmentAnalysis (BlockContext bc)
3996                 {
3997                         for (int i = 0; i < parameters.Count; ++i) {
3998                                 var par = parameters.FixedParameters[i];
3999
4000                                 if ((par.ModFlags & Parameter.Modifier.OUT) == 0)
4001                                         continue;
4002
4003                                 parameter_info [i].VariableInfo = VariableInfo.Create (bc, (Parameter) par);
4004                         }
4005                 }
4006
4007                 public ToplevelBlock ConvertToIterator (IMethodData method, TypeDefinition host, TypeSpec iterator_type, bool is_enumerable)
4008                 {
4009                         var iterator = new Iterator (this, method, host, iterator_type, is_enumerable);
4010                         var stateMachine = new IteratorStorey (iterator);
4011
4012                         state_machine = stateMachine;
4013                         iterator.SetStateMachine (stateMachine);
4014
4015                         var tlb = new ToplevelBlock (host.Compiler, Parameters, Location.Null, Flags.CompilerGenerated);
4016                         tlb.Original = this;
4017                         tlb.state_machine = stateMachine;
4018                         tlb.AddStatement (new Return (iterator, iterator.Location));
4019                         return tlb;
4020                 }
4021
4022                 public ParametersBlock ConvertToAsyncTask (IMemberContext context, TypeDefinition host, ParametersCompiled parameters, TypeSpec returnType, TypeSpec delegateType, Location loc)
4023                 {
4024                         for (int i = 0; i < parameters.Count; i++) {
4025                                 Parameter p = parameters[i];
4026                                 Parameter.Modifier mod = p.ModFlags;
4027                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
4028                                         host.Compiler.Report.Error (1988, p.Location,
4029                                                 "Async methods cannot have ref or out parameters");
4030                                         return this;
4031                                 }
4032
4033                                 if (p is ArglistParameter) {
4034                                         host.Compiler.Report.Error (4006, p.Location,
4035                                                 "__arglist is not allowed in parameter list of async methods");
4036                                         return this;
4037                                 }
4038
4039                                 if (parameters.Types[i].IsPointer) {
4040                                         host.Compiler.Report.Error (4005, p.Location,
4041                                                 "Async methods cannot have unsafe parameters");
4042                                         return this;
4043                                 }
4044                         }
4045
4046                         if (!HasAwait) {
4047                                 host.Compiler.Report.Warning (1998, 1, loc,
4048                                         "Async block lacks `await' operator and will run synchronously");
4049                         }
4050
4051                         var block_type = host.Module.Compiler.BuiltinTypes.Void;
4052                         var initializer = new AsyncInitializer (this, host, block_type);
4053                         initializer.Type = block_type;
4054                         initializer.DelegateType = delegateType;
4055
4056                         var stateMachine = new AsyncTaskStorey (this, context, initializer, returnType);
4057
4058                         state_machine = stateMachine;
4059                         initializer.SetStateMachine (stateMachine);
4060
4061                         const Flags flags = Flags.CompilerGenerated;
4062
4063                         var b = this is ToplevelBlock ?
4064                                 new ToplevelBlock (host.Compiler, Parameters, Location.Null, flags) :
4065                                 new ParametersBlock (Parent, parameters, Location.Null, flags | Flags.HasAsyncModifier);
4066
4067                         b.Original = this;
4068                         b.state_machine = stateMachine;
4069                         b.AddStatement (new AsyncInitializerStatement (initializer));
4070                         return b;
4071                 }
4072         }
4073
4074         //
4075         //
4076         //
4077         public class ToplevelBlock : ParametersBlock
4078         {
4079                 LocalVariable this_variable;
4080                 CompilerContext compiler;
4081                 Dictionary<string, object> names;
4082
4083                 List<ExplicitBlock> this_references;
4084
4085                 public ToplevelBlock (CompilerContext ctx, Location loc)
4086                         : this (ctx, ParametersCompiled.EmptyReadOnlyParameters, loc)
4087                 {
4088                 }
4089
4090                 public ToplevelBlock (CompilerContext ctx, ParametersCompiled parameters, Location start, Flags flags = 0)
4091                         : base (parameters, start)
4092                 {
4093                         this.compiler = ctx;
4094                         this.flags = flags;
4095                         top_block = this;
4096
4097                         ProcessParameters ();
4098                 }
4099
4100                 //
4101                 // Recreates a top level block from parameters block. Used for
4102                 // compiler generated methods where the original block comes from
4103                 // explicit child block. This works for already resolved blocks
4104                 // only to ensure we resolve them in the correct flow order
4105                 //
4106                 public ToplevelBlock (ParametersBlock source, ParametersCompiled parameters)
4107                         : base (source, parameters)
4108                 {
4109                         this.compiler = source.TopBlock.compiler;
4110                         top_block = this;
4111                 }
4112
4113                 public bool IsIterator {
4114                         get {
4115                                 return (flags & Flags.Iterator) != 0;
4116                         }
4117                         set {
4118                                 flags = value ? flags | Flags.Iterator : flags & ~Flags.Iterator;
4119                         }
4120                 }
4121
4122                 public Report Report {
4123                         get {
4124                                 return compiler.Report;
4125                         }
4126                 }
4127
4128                 //
4129                 // Used by anonymous blocks to track references of `this' variable
4130                 //
4131                 public List<ExplicitBlock> ThisReferencesFromChildrenBlock {
4132                         get {
4133                                 return this_references;
4134                         }
4135                 }
4136
4137                 //
4138                 // Returns the "this" instance variable of this block.
4139                 // See AddThisVariable() for more information.
4140                 //
4141                 public LocalVariable ThisVariable {
4142                         get {
4143                                 return this_variable;
4144                         }
4145                 }
4146
4147                 public void AddLocalName (string name, INamedBlockVariable li, bool ignoreChildrenBlocks)
4148                 {
4149                         if (names == null)
4150                                 names = new Dictionary<string, object> ();
4151
4152                         object value;
4153                         if (!names.TryGetValue (name, out value)) {
4154                                 names.Add (name, li);
4155                                 return;
4156                         }
4157
4158                         INamedBlockVariable existing = value as INamedBlockVariable;
4159                         List<INamedBlockVariable> existing_list;
4160                         if (existing != null) {
4161                                 existing_list = new List<INamedBlockVariable> ();
4162                                 existing_list.Add (existing);
4163                                 names[name] = existing_list;
4164                         } else {
4165                                 existing_list = (List<INamedBlockVariable>) value;
4166                         }
4167
4168                         //
4169                         // A collision checking between local names
4170                         //
4171                         var variable_block = li.Block.Explicit;
4172                         for (int i = 0; i < existing_list.Count; ++i) {
4173                                 existing = existing_list[i];
4174                                 Block b = existing.Block.Explicit;
4175
4176                                 // Collision at same level
4177                                 if (variable_block == b) {
4178                                         li.Block.Error_AlreadyDeclared (name, li);
4179                                         break;
4180                                 }
4181
4182                                 // Collision with parent
4183                                 Block parent = variable_block;
4184                                 while ((parent = parent.Parent) != null) {
4185                                         if (parent == b) {
4186                                                 li.Block.Error_AlreadyDeclared (name, li, "parent or current");
4187                                                 i = existing_list.Count;
4188                                                 break;
4189                                         }
4190                                 }
4191
4192                                 if (!ignoreChildrenBlocks && variable_block.Parent != b.Parent) {
4193                                         // Collision with children
4194                                         while ((b = b.Parent) != null) {
4195                                                 if (variable_block == b) {
4196                                                         li.Block.Error_AlreadyDeclared (name, li, "child");
4197                                                         i = existing_list.Count;
4198                                                         break;
4199                                                 }
4200                                         }
4201                                 }
4202                         }
4203
4204                         existing_list.Add (li);
4205                 }
4206
4207                 public void AddLabel (string name, LabeledStatement label)
4208                 {
4209                         if (labels == null)
4210                                 labels = new Dictionary<string, object> ();
4211
4212                         object value;
4213                         if (!labels.TryGetValue (name, out value)) {
4214                                 labels.Add (name, label);
4215                                 return;
4216                         }
4217
4218                         LabeledStatement existing = value as LabeledStatement;
4219                         List<LabeledStatement> existing_list;
4220                         if (existing != null) {
4221                                 existing_list = new List<LabeledStatement> ();
4222                                 existing_list.Add (existing);
4223                                 labels[name] = existing_list;
4224                         } else {
4225                                 existing_list = (List<LabeledStatement>) value;
4226                         }
4227
4228                         //
4229                         // A collision checking between labels
4230                         //
4231                         for (int i = 0; i < existing_list.Count; ++i) {
4232                                 existing = existing_list[i];
4233                                 Block b = existing.Block;
4234
4235                                 // Collision at same level
4236                                 if (label.Block == b) {
4237                                         Report.SymbolRelatedToPreviousError (existing.loc, name);
4238                                         Report.Error (140, label.loc, "The label `{0}' is a duplicate", name);
4239                                         break;
4240                                 }
4241
4242                                 // Collision with parent
4243                                 b = label.Block;
4244                                 while ((b = b.Parent) != null) {
4245                                         if (existing.Block == b) {
4246                                                 Report.Error (158, label.loc,
4247                                                         "The label `{0}' shadows another label by the same name in a contained scope", name);
4248                                                 i = existing_list.Count;
4249                                                 break;
4250                                         }
4251                                 }
4252
4253                                 // Collision with with children
4254                                 b = existing.Block;
4255                                 while ((b = b.Parent) != null) {
4256                                         if (label.Block == b) {
4257                                                 Report.Error (158, label.loc,
4258                                                         "The label `{0}' shadows another label by the same name in a contained scope", name);
4259                                                 i = existing_list.Count;
4260                                                 break;
4261                                         }
4262                                 }
4263                         }
4264
4265                         existing_list.Add (label);
4266                 }
4267
4268                 public void AddThisReferenceFromChildrenBlock (ExplicitBlock block)
4269                 {
4270                         if (this_references == null)
4271                                 this_references = new List<ExplicitBlock> ();
4272
4273                         if (!this_references.Contains (block))
4274                                 this_references.Add (block);
4275                 }
4276
4277                 public void RemoveThisReferenceFromChildrenBlock (ExplicitBlock block)
4278                 {
4279                         this_references.Remove (block);
4280                 }
4281
4282                 //
4283                 // Creates an arguments set from all parameters, useful for method proxy calls
4284                 //
4285                 public Arguments GetAllParametersArguments ()
4286                 {
4287                         int count = parameters.Count;
4288                         Arguments args = new Arguments (count);
4289                         for (int i = 0; i < count; ++i) {
4290                                 var pi = parameter_info[i];
4291                                 var arg_expr = GetParameterReference (i, pi.Location);
4292
4293                                 Argument.AType atype_modifier;
4294                                 switch (pi.Parameter.ParameterModifier & Parameter.Modifier.RefOutMask) {
4295                                 case Parameter.Modifier.REF:
4296                                         atype_modifier = Argument.AType.Ref;
4297                                         break;
4298                                 case Parameter.Modifier.OUT:
4299                                         atype_modifier = Argument.AType.Out;
4300                                         break;
4301                                 default:
4302                                         atype_modifier = 0;
4303                                         break;
4304                                 }
4305
4306                                 args.Add (new Argument (arg_expr, atype_modifier));
4307                         }
4308
4309                         return args;
4310                 }
4311
4312                 //
4313                 // Lookup inside a block, the returned value can represent 3 states
4314                 //
4315                 // true+variable: A local name was found and it's valid
4316                 // false+variable: A local name was found in a child block only
4317                 // false+null: No local name was found
4318                 //
4319                 public bool GetLocalName (string name, Block block, ref INamedBlockVariable variable)
4320                 {
4321                         if (names == null)
4322                                 return false;
4323
4324                         object value;
4325                         if (!names.TryGetValue (name, out value))
4326                                 return false;
4327
4328                         variable = value as INamedBlockVariable;
4329                         Block b = block;
4330                         if (variable != null) {
4331                                 do {
4332                                         if (variable.Block == b.Original)
4333                                                 return true;
4334
4335                                         b = b.Parent;
4336                                 } while (b != null);
4337
4338                                 b = variable.Block;
4339                                 do {
4340                                         if (block == b)
4341                                                 return false;
4342
4343                                         b = b.Parent;
4344                                 } while (b != null);
4345                         } else {
4346                                 List<INamedBlockVariable> list = (List<INamedBlockVariable>) value;
4347                                 for (int i = 0; i < list.Count; ++i) {
4348                                         variable = list[i];
4349                                         do {
4350                                                 if (variable.Block == b.Original)
4351                                                         return true;
4352
4353                                                 b = b.Parent;
4354                                         } while (b != null);
4355
4356                                         b = variable.Block;
4357                                         do {
4358                                                 if (block == b)
4359                                                         return false;
4360
4361                                                 b = b.Parent;
4362                                         } while (b != null);
4363
4364                                         b = block;
4365                                 }
4366                         }
4367
4368                         variable = null;
4369                         return false;
4370                 }
4371
4372                 public void IncludeBlock (ParametersBlock pb, ToplevelBlock block)
4373                 {
4374                         if (block.names != null) {
4375                                 foreach (var n in block.names) {
4376                                         var variable = n.Value as INamedBlockVariable;
4377                                         if (variable != null) {
4378                                                 if (variable.Block.ParametersBlock == pb)
4379                                                         AddLocalName (n.Key, variable, false);
4380                                                 continue;
4381                                         }
4382
4383                                         foreach (var v in (List<INamedBlockVariable>) n.Value)
4384                                                 if (v.Block.ParametersBlock == pb)
4385                                                         AddLocalName (n.Key, v, false);
4386                                 }
4387                         }
4388                 }
4389
4390                 // <summary>
4391                 //   This is used by non-static `struct' constructors which do not have an
4392                 //   initializer - in this case, the constructor must initialize all of the
4393                 //   struct's fields.  To do this, we add a "this" variable and use the flow
4394                 //   analysis code to ensure that it's been fully initialized before control
4395                 //   leaves the constructor.
4396                 // </summary>
4397                 public void AddThisVariable (BlockContext bc)
4398                 {
4399                         if (this_variable != null)
4400                                 throw new InternalErrorException (StartLocation.ToString ());
4401
4402                         this_variable = new LocalVariable (this, "this", LocalVariable.Flags.IsThis | LocalVariable.Flags.Used, StartLocation);
4403                         this_variable.Type = bc.CurrentType;
4404                         this_variable.PrepareAssignmentAnalysis (bc);
4405                 }
4406
4407                 public override void CheckControlExit (FlowAnalysisContext fc, DefiniteAssignmentBitSet dat)
4408                 {
4409                         //
4410                         // If we're a non-static struct constructor which doesn't have an
4411                         // initializer, then we must initialize all of the struct's fields.
4412                         //
4413                         if (this_variable != null)
4414                                 this_variable.IsThisAssigned (fc, this);
4415
4416                         base.CheckControlExit (fc, dat);
4417                 }
4418
4419                 public HashSet<LocalVariable> GetUndeclaredVariables ()
4420                 {
4421                         if (names == null)
4422                                 return null;
4423
4424                         HashSet<LocalVariable> variables = null;
4425
4426                         foreach (var entry in names) {
4427                                 var complex = entry.Value as List<INamedBlockVariable>;
4428                                 if (complex != null) {
4429                                         foreach (var centry in complex) {
4430                                                 if (IsUndeclaredVariable (centry)) {
4431                                                         if (variables == null)
4432                                                                 variables = new HashSet<LocalVariable> ();
4433
4434                                                         variables.Add ((LocalVariable) centry);
4435                                                 }
4436                                         }
4437                                 } else if (IsUndeclaredVariable ((INamedBlockVariable)entry.Value)) {
4438                                         if (variables == null)
4439                                                 variables = new HashSet<LocalVariable> ();
4440
4441                                         variables.Add ((LocalVariable)entry.Value);
4442                                 }
4443                         }
4444
4445                         return variables;
4446                 }
4447
4448                 static bool IsUndeclaredVariable (INamedBlockVariable namedBlockVariable)
4449                 {
4450                         var lv = namedBlockVariable as LocalVariable;
4451                         return lv != null && !lv.IsDeclared;
4452                 }
4453
4454                 public void SetUndeclaredVariables (HashSet<LocalVariable> undeclaredVariables)
4455                 {
4456                         if (names == null)
4457                                 return;
4458
4459                         foreach (var entry in names) {
4460                                 var complex = entry.Value as List<INamedBlockVariable>;
4461                                 if (complex != null) {
4462                                         foreach (var centry in complex) {
4463                                                 var lv = centry as LocalVariable;
4464                                                 if (lv != null && undeclaredVariables.Contains (lv)) {
4465                                                         lv.Type = null;
4466                                                 }
4467                                         }
4468                                 } else {
4469                                         var lv = entry.Value as LocalVariable;
4470                                         if (lv != null && undeclaredVariables.Contains (lv))
4471                                                 lv.Type = null;
4472                                 }
4473                         }
4474                 }
4475
4476                 public override void Emit (EmitContext ec)
4477                 {
4478                         if (Report.Errors > 0)
4479                                 return;
4480
4481                         try {
4482                         if (IsCompilerGenerated) {
4483                                 using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
4484                                         base.Emit (ec);
4485                                 }
4486                         } else {
4487                                 base.Emit (ec);
4488                         }
4489
4490                         //
4491                         // If `HasReturnLabel' is set, then we already emitted a
4492                         // jump to the end of the method, so we must emit a `ret'
4493                         // there.
4494                         //
4495                         // Unfortunately, System.Reflection.Emit automatically emits
4496                         // a leave to the end of a finally block.  This is a problem
4497                         // if no code is following the try/finally block since we may
4498                         // jump to a point after the end of the method.
4499                         // As a workaround, we're always creating a return label in
4500                         // this case.
4501                         //
4502                         if (ec.HasReturnLabel || HasReachableClosingBrace) {
4503                                 if (ec.HasReturnLabel)
4504                                         ec.MarkLabel (ec.ReturnLabel);
4505
4506                                 if (ec.EmitAccurateDebugInfo && !IsCompilerGenerated)
4507                                         ec.Mark (EndLocation);
4508
4509                                 if (ec.ReturnType.Kind != MemberKind.Void)
4510                                         ec.Emit (OpCodes.Ldloc, ec.TemporaryReturn ());
4511
4512                                 ec.Emit (OpCodes.Ret);
4513                         }
4514
4515                         } catch (Exception e) {
4516                                 throw new InternalErrorException (e, StartLocation);
4517                         }
4518                 }
4519
4520                 public bool Resolve (BlockContext bc, IMethodData md)
4521                 {
4522                         if (resolved)
4523                                 return true;
4524
4525                         var errors = bc.Report.Errors;
4526
4527                         base.Resolve (bc);
4528
4529                         if (bc.Report.Errors > errors)
4530                                 return false;
4531
4532                         MarkReachable (new Reachability ());
4533
4534                         if (HasReachableClosingBrace && bc.ReturnType.Kind != MemberKind.Void) {
4535                                 // TODO: var md = bc.CurrentMemberDefinition;
4536                                 bc.Report.Error (161, md.Location, "`{0}': not all code paths return a value", md.GetSignatureForError ());
4537                         }
4538
4539                         if ((flags & Flags.NoFlowAnalysis) != 0)
4540                                 return true;
4541
4542                         var fc = new FlowAnalysisContext (bc.Module.Compiler, this, bc.AssignmentInfoOffset);
4543                         try {
4544                                 FlowAnalysis (fc);
4545                         } catch (Exception e) {
4546                                 throw new InternalErrorException (e, StartLocation);
4547                         }
4548
4549                         return true;
4550                 }
4551         }
4552
4553         public class SwitchLabel : Statement
4554         {
4555                 Constant converted;
4556                 Expression label;
4557
4558                 Label? il_label;
4559
4560                 //
4561                 // if expr == null, then it is the default case.
4562                 //
4563                 public SwitchLabel (Expression expr, Location l)
4564                 {
4565                         label = expr;
4566                         loc = l;
4567                 }
4568
4569                 public bool IsDefault {
4570                         get {
4571                                 return label == null;
4572                         }
4573                 }
4574
4575                 public Expression Label {
4576                         get {
4577                                 return label;
4578                         }
4579                 }
4580
4581                 public Location Location {
4582                         get {
4583                                 return loc;
4584                         }
4585                 }
4586
4587                 public Constant Converted {
4588                         get {
4589                                 return converted;
4590                         }
4591                         set {
4592                                 converted = value;
4593                         }
4594                 }
4595
4596                 public bool PatternMatching { get; set; }
4597
4598                 public bool SectionStart { get; set; }
4599
4600                 public Label GetILLabel (EmitContext ec)
4601                 {
4602                         if (il_label == null){
4603                                 il_label = ec.DefineLabel ();
4604                         }
4605
4606                         return il_label.Value;
4607                 }
4608
4609                 protected override void DoEmit (EmitContext ec)
4610                 {
4611                         ec.MarkLabel (GetILLabel (ec));
4612                 }
4613
4614                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
4615                 {
4616                         if (!SectionStart)
4617                                 return false;
4618
4619                         fc.BranchDefiniteAssignment (fc.SwitchInitialDefinitiveAssignment);
4620                         return false;
4621                 }
4622
4623                 public override bool Resolve (BlockContext bc)
4624                 {
4625                         if (ResolveAndReduce (bc))
4626                                 bc.Switch.RegisterLabel (bc, this);
4627
4628                         return true;
4629                 }
4630
4631                 //
4632                 // Resolves the expression, reduces it to a literal if possible
4633                 // and then converts it to the requested type.
4634                 //
4635                 bool ResolveAndReduce (BlockContext bc)
4636                 {
4637                         if (IsDefault)
4638                                 return true;
4639
4640                         var switch_statement = bc.Switch;
4641
4642                         if (PatternMatching) {
4643                                 label = new Is (switch_statement.ExpressionValue, label, loc).Resolve (bc);
4644                                 return label != null;
4645                         }
4646
4647                         var c = label.ResolveLabelConstant (bc);
4648                         if (c == null)
4649                                 return false;
4650
4651                         if (switch_statement.IsNullable && c is NullLiteral) {
4652                                 converted = c;
4653                                 return true;
4654                         }
4655
4656                         if (switch_statement.IsPatternMatching) {
4657                                 label = new Is (switch_statement.ExpressionValue, label, loc).Resolve (bc);
4658                                 return true;
4659                         }
4660
4661                         converted = c.ImplicitConversionRequired (bc, switch_statement.SwitchType);
4662                         return converted != null;
4663                 }
4664
4665                 public void Error_AlreadyOccurs (ResolveContext ec, SwitchLabel collision_with)
4666                 {
4667                         ec.Report.SymbolRelatedToPreviousError (collision_with.loc, null);
4668                         ec.Report.Error (152, loc, "The label `{0}' already occurs in this switch statement", GetSignatureForError ());
4669                 }
4670
4671                 protected override void CloneTo (CloneContext clonectx, Statement target)
4672                 {
4673                         var t = (SwitchLabel) target;
4674                         if (label != null)
4675                                 t.label = label.Clone (clonectx);
4676                 }
4677
4678                 public override object Accept (StructuralVisitor visitor)
4679                 {
4680                         return visitor.Visit (this);
4681                 }
4682
4683                 public string GetSignatureForError ()
4684                 {
4685                         string label;
4686                         if (converted == null)
4687                                 label = "default";
4688                         else
4689                                 label = converted.GetValueAsLiteral ();
4690
4691                         return string.Format ("case {0}:", label);
4692                 }
4693         }
4694
4695         public class Switch : LoopStatement
4696         {
4697                 // structure used to hold blocks of keys while calculating table switch
4698                 sealed class LabelsRange : IComparable<LabelsRange>
4699                 {
4700                         public readonly long min;
4701                         public long max;
4702                         public readonly List<long> label_values;
4703
4704                         public LabelsRange (long value)
4705                         {
4706                                 min = max = value;
4707                                 label_values = new List<long> ();
4708                                 label_values.Add (value);
4709                         }
4710
4711                         public LabelsRange (long min, long max, ICollection<long> values)
4712                         {
4713                                 this.min = min;
4714                                 this.max = max;
4715                                 this.label_values = new List<long> (values);
4716                         }
4717
4718                         public long Range {
4719                                 get {
4720                                         return max - min + 1;
4721                                 }
4722                         }
4723
4724                         public bool AddValue (long value)
4725                         {
4726                                 var gap = value - min + 1;
4727                                 // Ensure the range has > 50% occupancy
4728                                 if (gap > 2 * (label_values.Count + 1) || gap <= 0)
4729                                         return false;
4730
4731                                 max = value;
4732                                 label_values.Add (value);
4733                                 return true;
4734                         }
4735
4736                         public int CompareTo (LabelsRange other)
4737                         {
4738                                 int nLength = label_values.Count;
4739                                 int nLengthOther = other.label_values.Count;
4740                                 if (nLengthOther == nLength)
4741                                         return (int) (other.min - min);
4742
4743                                 return nLength - nLengthOther;
4744                         }
4745                 }
4746
4747                 sealed class DispatchStatement : Statement
4748                 {
4749                         readonly Switch body;
4750
4751                         public DispatchStatement (Switch body)
4752                         {
4753                                 this.body = body;
4754                         }
4755
4756                         protected override void CloneTo (CloneContext clonectx, Statement target)
4757                         {
4758                                 throw new NotImplementedException ();
4759                         }
4760
4761                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
4762                         {
4763                                 return false;
4764                         }
4765
4766                         protected override void DoEmit (EmitContext ec)
4767                         {
4768                                 body.EmitDispatch (ec);
4769                         }
4770                 }
4771
4772                 class MissingBreak : Statement
4773                 {
4774                         readonly SwitchLabel label;
4775
4776                         public MissingBreak (SwitchLabel sl)
4777                         {
4778                                 this.label = sl;
4779                                 this.loc = sl.loc;
4780                         }
4781
4782                         public bool FallOut { get; set; }
4783
4784                         protected override void DoEmit (EmitContext ec)
4785                         {
4786                         }
4787
4788                         protected override void CloneTo (CloneContext clonectx, Statement target)
4789                         {
4790                         }
4791
4792                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
4793                         {
4794                                 if (FallOut) {
4795                                         fc.Report.Error (8070, loc, "Control cannot fall out of switch statement through final case label `{0}'",
4796                                                 label.GetSignatureForError ());
4797                                 } else {
4798                                         fc.Report.Error (163, loc, "Control cannot fall through from one case label `{0}' to another",
4799                                                 label.GetSignatureForError ());
4800                                 }
4801                                 return true;
4802                         }
4803                 }
4804
4805                 public Expression Expr;
4806
4807                 //
4808                 // Mapping of all labels to their SwitchLabels
4809                 //
4810                 Dictionary<long, SwitchLabel> labels;
4811                 Dictionary<string, SwitchLabel> string_labels;
4812                 List<SwitchLabel> case_labels;
4813
4814                 List<Tuple<GotoCase, Constant>> goto_cases;
4815                 List<DefiniteAssignmentBitSet> end_reachable_das;
4816
4817                 /// <summary>
4818                 ///   The governing switch type
4819                 /// </summary>
4820                 public TypeSpec SwitchType;
4821
4822                 Expression new_expr;
4823
4824                 SwitchLabel case_null;
4825                 SwitchLabel case_default;
4826
4827                 Label defaultLabel, nullLabel;
4828                 VariableReference value;
4829                 ExpressionStatement string_dictionary;
4830                 FieldExpr switch_cache_field;
4831                 ExplicitBlock block;
4832                 bool end_reachable;
4833
4834                 //
4835                 // Nullable Types support
4836                 //
4837                 Nullable.Unwrap unwrap;
4838
4839                 public Switch (Expression e, ExplicitBlock block, Location l)
4840                         : base (block)
4841                 {
4842                         Expr = e;
4843                         this.block = block;
4844                         loc = l;
4845                 }
4846
4847                 public SwitchLabel ActiveLabel { get; set; }
4848
4849                 public ExplicitBlock Block {
4850                         get {
4851                                 return block;
4852                         }
4853                 }
4854
4855                 public SwitchLabel DefaultLabel {
4856                         get {
4857                                 return case_default;
4858                         }
4859                 }
4860
4861                 public bool IsNullable {
4862                         get {
4863                                 return unwrap != null;
4864                         }
4865                 }
4866
4867                 public bool IsPatternMatching {
4868                         get {
4869                                 return new_expr == null && SwitchType != null;
4870                         }
4871                 }
4872
4873                 public List<SwitchLabel> RegisteredLabels {
4874                         get {
4875                                 return case_labels;
4876                         }
4877                 }
4878
4879                 public VariableReference ExpressionValue {
4880                         get {
4881                                 return value;
4882                         }
4883                 }
4884
4885                 //
4886                 // Determines the governing type for a switch.  The returned
4887                 // expression might be the expression from the switch, or an
4888                 // expression that includes any potential conversions to
4889                 //
4890                 static Expression SwitchGoverningType (ResolveContext rc, Expression expr, bool unwrapExpr)
4891                 {
4892                         switch (expr.Type.BuiltinType) {
4893                         case BuiltinTypeSpec.Type.Byte:
4894                         case BuiltinTypeSpec.Type.SByte:
4895                         case BuiltinTypeSpec.Type.UShort:
4896                         case BuiltinTypeSpec.Type.Short:
4897                         case BuiltinTypeSpec.Type.UInt:
4898                         case BuiltinTypeSpec.Type.Int:
4899                         case BuiltinTypeSpec.Type.ULong:
4900                         case BuiltinTypeSpec.Type.Long:
4901                         case BuiltinTypeSpec.Type.Char:
4902                         case BuiltinTypeSpec.Type.String:
4903                         case BuiltinTypeSpec.Type.Bool:
4904                                 return expr;
4905                         }
4906
4907                         if (expr.Type.IsEnum)
4908                                 return expr;
4909
4910                         //
4911                         // Try to find a *user* defined implicit conversion.
4912                         //
4913                         // If there is no implicit conversion, or if there are multiple
4914                         // conversions, we have to report an error
4915                         //
4916                         Expression converted = null;
4917                         foreach (TypeSpec tt in rc.Module.PredefinedTypes.SwitchUserTypes) {
4918
4919                                 if (!unwrapExpr && tt.IsNullableType && expr.Type.IsNullableType)
4920                                         break;
4921
4922                                 var restr = Convert.UserConversionRestriction.ImplicitOnly |
4923                                         Convert.UserConversionRestriction.ProbingOnly;
4924
4925                                 if (unwrapExpr)
4926                                         restr |= Convert.UserConversionRestriction.NullableSourceOnly;
4927
4928                                 var e = Convert.UserDefinedConversion (rc, expr, tt, restr, Location.Null);
4929                                 if (e == null)
4930                                         continue;
4931
4932                                 //
4933                                 // Ignore over-worked ImplicitUserConversions that do
4934                                 // an implicit conversion in addition to the user conversion.
4935                                 //
4936                                 var uc = e as UserCast;
4937                                 if (uc == null)
4938                                         continue;
4939
4940                                 if (converted != null){
4941 //                                      rc.Report.ExtraInformation (loc, "(Ambiguous implicit user defined conversion in previous ");
4942                                         return null;
4943                                 }
4944
4945                                 converted = e;
4946                         }
4947                         return converted;
4948                 }
4949
4950                 public static TypeSpec[] CreateSwitchUserTypes (ModuleContainer module, TypeSpec nullable)
4951                 {
4952                         var types = module.Compiler.BuiltinTypes;
4953
4954                         // LAMESPEC: For some reason it does not contain bool which looks like csc bug
4955                         TypeSpec[] stypes = new[] {
4956                                 types.SByte,
4957                                 types.Byte,
4958                                 types.Short,
4959                                 types.UShort,
4960                                 types.Int,
4961                                 types.UInt,
4962                                 types.Long,
4963                                 types.ULong,
4964                                 types.Char,
4965                                 types.String
4966                         };
4967
4968                         if (nullable != null) {
4969
4970                                 Array.Resize (ref stypes, stypes.Length + 9);
4971
4972                                 for (int i = 0; i < 9; ++i) {
4973                                         stypes [10 + i] = nullable.MakeGenericType (module, new [] { stypes [i] });
4974                                 }
4975                         }
4976
4977                         return stypes;
4978                 }
4979
4980                 public void RegisterLabel (BlockContext rc, SwitchLabel sl)
4981                 {
4982                         case_labels.Add (sl);
4983
4984                         if (sl.IsDefault) {
4985                                 if (case_default != null) {
4986                                         sl.Error_AlreadyOccurs (rc, case_default);
4987                                 } else {
4988                                         case_default = sl;
4989                                 }
4990
4991                                 return;
4992                         }
4993
4994                         if (sl.Converted == null)
4995                                 return;
4996
4997                         try {
4998                                 if (string_labels != null) {
4999                                         string string_value = sl.Converted.GetValue () as string;
5000                                         if (string_value == null)
5001                                                 case_null = sl;
5002                                         else
5003                                                 string_labels.Add (string_value, sl);
5004                                 } else {
5005                                         if (sl.Converted.IsNull) {
5006                                                 case_null = sl;
5007                                         } else {
5008                                                 labels.Add (sl.Converted.GetValueAsLong (), sl);
5009                                         }
5010                                 }
5011                         } catch (ArgumentException) {
5012                                 if (string_labels != null)
5013                                         sl.Error_AlreadyOccurs (rc, string_labels[(string) sl.Converted.GetValue ()]);
5014                                 else
5015                                         sl.Error_AlreadyOccurs (rc, labels[sl.Converted.GetValueAsLong ()]);
5016                         }
5017                 }
5018
5019                 //
5020                 // This method emits code for a lookup-based switch statement (non-string)
5021                 // Basically it groups the cases into blocks that are at least half full,
5022                 // and then spits out individual lookup opcodes for each block.
5023                 // It emits the longest blocks first, and short blocks are just
5024                 // handled with direct compares.
5025                 //
5026                 void EmitTableSwitch (EmitContext ec, Expression val)
5027                 {
5028                         if (labels != null && labels.Count > 0) {
5029                                 List<LabelsRange> ranges;
5030                                 if (string_labels != null) {
5031                                         // We have done all hard work for string already
5032                                         // setup single range only
5033                                         ranges = new List<LabelsRange> (1);
5034                                         ranges.Add (new LabelsRange (0, labels.Count - 1, labels.Keys));
5035                                 } else {
5036                                         var element_keys = new long[labels.Count];
5037                                         labels.Keys.CopyTo (element_keys, 0);
5038                                         Array.Sort (element_keys);
5039
5040                                         //
5041                                         // Build possible ranges of switch labes to reduce number
5042                                         // of comparisons
5043                                         //
5044                                         ranges = new List<LabelsRange> (element_keys.Length);
5045                                         var range = new LabelsRange (element_keys[0]);
5046                                         ranges.Add (range);
5047                                         for (int i = 1; i < element_keys.Length; ++i) {
5048                                                 var l = element_keys[i];
5049                                                 if (range.AddValue (l))
5050                                                         continue;
5051
5052                                                 range = new LabelsRange (l);
5053                                                 ranges.Add (range);
5054                                         }
5055
5056                                         // sort the blocks so we can tackle the largest ones first
5057                                         ranges.Sort ();
5058                                 }
5059
5060                                 Label lbl_default = defaultLabel;
5061                                 TypeSpec compare_type = SwitchType.IsEnum ? EnumSpec.GetUnderlyingType (SwitchType) : SwitchType;
5062
5063                                 for (int range_index = ranges.Count - 1; range_index >= 0; --range_index) {
5064                                         LabelsRange kb = ranges[range_index];
5065                                         lbl_default = (range_index == 0) ? defaultLabel : ec.DefineLabel ();
5066
5067                                         // Optimize small ranges using simple equality check
5068                                         if (kb.Range <= 2) {
5069                                                 foreach (var key in kb.label_values) {
5070                                                         SwitchLabel sl = labels[key];
5071                                                         if (sl == case_default || sl == case_null)
5072                                                                 continue;
5073
5074                                                         if (sl.Converted.IsZeroInteger) {
5075                                                                 val.EmitBranchable (ec, sl.GetILLabel (ec), false);
5076                                                         } else {
5077                                                                 val.Emit (ec);
5078                                                                 sl.Converted.Emit (ec);
5079                                                                 ec.Emit (OpCodes.Beq, sl.GetILLabel (ec));
5080                                                         }
5081                                                 }
5082                                         } else {
5083                                                 // TODO: if all the keys in the block are the same and there are
5084                                                 //       no gaps/defaults then just use a range-check.
5085                                                 if (compare_type.BuiltinType == BuiltinTypeSpec.Type.Long || compare_type.BuiltinType == BuiltinTypeSpec.Type.ULong) {
5086                                                         // TODO: optimize constant/I4 cases
5087
5088                                                         // check block range (could be > 2^31)
5089                                                         val.Emit (ec);
5090                                                         ec.EmitLong (kb.min);
5091                                                         ec.Emit (OpCodes.Blt, lbl_default);
5092
5093                                                         val.Emit (ec);
5094                                                         ec.EmitLong (kb.max);
5095                                                         ec.Emit (OpCodes.Bgt, lbl_default);
5096
5097                                                         // normalize range
5098                                                         val.Emit (ec);
5099                                                         if (kb.min != 0) {
5100                                                                 ec.EmitLong (kb.min);
5101                                                                 ec.Emit (OpCodes.Sub);
5102                                                         }
5103
5104                                                         ec.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
5105                                                 } else {
5106                                                         // normalize range
5107                                                         val.Emit (ec);
5108                                                         int first = (int) kb.min;
5109                                                         if (first > 0) {
5110                                                                 ec.EmitInt (first);
5111                                                                 ec.Emit (OpCodes.Sub);
5112                                                         } else if (first < 0) {
5113                                                                 ec.EmitInt (-first);
5114                                                                 ec.Emit (OpCodes.Add);
5115                                                         }
5116                                                 }
5117
5118                                                 // first, build the list of labels for the switch
5119                                                 int iKey = 0;
5120                                                 long cJumps = kb.Range;
5121                                                 Label[] switch_labels = new Label[cJumps];
5122                                                 for (int iJump = 0; iJump < cJumps; iJump++) {
5123                                                         var key = kb.label_values[iKey];
5124                                                         if (key == kb.min + iJump) {
5125                                                                 switch_labels[iJump] = labels[key].GetILLabel (ec);
5126                                                                 iKey++;
5127                                                         } else {
5128                                                                 switch_labels[iJump] = lbl_default;
5129                                                         }
5130                                                 }
5131
5132                                                 // emit the switch opcode
5133                                                 ec.Emit (OpCodes.Switch, switch_labels);
5134                                         }
5135
5136                                         // mark the default for this block
5137                                         if (range_index != 0)
5138                                                 ec.MarkLabel (lbl_default);
5139                                 }
5140
5141                                 // the last default just goes to the end
5142                                 if (ranges.Count > 0)
5143                                         ec.Emit (OpCodes.Br, lbl_default);
5144                         }
5145                 }
5146
5147                 public SwitchLabel FindLabel (Constant value)
5148                 {
5149                         SwitchLabel sl = null;
5150
5151                         if (string_labels != null) {
5152                                 string s = value.GetValue () as string;
5153                                 if (s == null) {
5154                                         if (case_null != null)
5155                                                 sl = case_null;
5156                                         else if (case_default != null)
5157                                                 sl = case_default;
5158                                 } else {
5159                                         string_labels.TryGetValue (s, out sl);
5160                                 }
5161                         } else {
5162                                 if (value is NullLiteral) {
5163                                         sl = case_null;
5164                                 } else {
5165                                         labels.TryGetValue (value.GetValueAsLong (), out sl);
5166                                 }
5167                         }
5168
5169                         if (sl == null || sl.SectionStart)
5170                                 return sl;
5171
5172                         //
5173                         // Always return section start, it simplifies handling of switch labels
5174                         //
5175                         for (int idx = case_labels.IndexOf (sl); ; --idx) {
5176                                 var cs = case_labels [idx];
5177                                 if (cs.SectionStart)
5178                                         return cs;
5179                         }
5180                 }
5181
5182                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
5183                 {
5184                         Expr.FlowAnalysis (fc);
5185
5186                         var prev_switch = fc.SwitchInitialDefinitiveAssignment;
5187                         var InitialDefinitiveAssignment = fc.DefiniteAssignment;
5188                         fc.SwitchInitialDefinitiveAssignment = InitialDefinitiveAssignment;
5189
5190                         block.FlowAnalysis (fc);
5191
5192                         fc.SwitchInitialDefinitiveAssignment = prev_switch;
5193
5194                         if (end_reachable_das != null) {
5195                                 var sections_das = DefiniteAssignmentBitSet.And (end_reachable_das);
5196                                 InitialDefinitiveAssignment |= sections_das;
5197                                 end_reachable_das = null;
5198                         }
5199
5200                         fc.DefiniteAssignment = InitialDefinitiveAssignment;
5201
5202                         return case_default != null && !end_reachable;
5203                 }
5204
5205                 public override bool Resolve (BlockContext ec)
5206                 {
5207                         Expr = Expr.Resolve (ec);
5208                         if (Expr == null)
5209                                 return false;
5210
5211                         //
5212                         // LAMESPEC: User conversion from non-nullable governing type has a priority
5213                         //
5214                         new_expr = SwitchGoverningType (ec, Expr, false);
5215
5216                         if (new_expr == null) {
5217                                 if (Expr.Type.IsNullableType) {
5218                                         unwrap = Nullable.Unwrap.Create (Expr, false);
5219                                         if (unwrap == null)
5220                                                 return false;
5221
5222                                         //
5223                                         // Unwrap + user conversion using non-nullable type is not allowed but user operator
5224                                         // involving nullable Expr and nullable governing type is
5225                                         //
5226                                         new_expr = SwitchGoverningType (ec, unwrap, true);
5227                                 }
5228                         }
5229
5230                         Expression switch_expr;
5231                         if (new_expr == null) {
5232                                 if (ec.Module.Compiler.Settings.Version != LanguageVersion.Experimental) {
5233                                         if (Expr.Type != InternalType.ErrorType) {
5234                                                 ec.Report.Error (151, loc,
5235                                                         "A switch expression of type `{0}' cannot be converted to an integral type, bool, char, string, enum or nullable type",
5236                                                         Expr.Type.GetSignatureForError ());
5237                                         }
5238
5239                                         return false;
5240                                 }
5241
5242                                 switch_expr = Expr;
5243                                 SwitchType = Expr.Type;
5244                         } else {
5245                                 switch_expr = new_expr;
5246                                 SwitchType = new_expr.Type;
5247                                 if (SwitchType.IsNullableType) {
5248                                         new_expr = unwrap = Nullable.Unwrap.Create (new_expr, true);
5249                                         SwitchType = Nullable.NullableInfo.GetUnderlyingType (SwitchType);
5250                                 }
5251
5252                                 if (SwitchType.BuiltinType == BuiltinTypeSpec.Type.Bool && ec.Module.Compiler.Settings.Version == LanguageVersion.ISO_1) {
5253                                         ec.Report.FeatureIsNotAvailable (ec.Module.Compiler, loc, "switch expression of boolean type");
5254                                         return false;
5255                                 }
5256
5257                                 if (block.Statements.Count == 0)
5258                                         return true;
5259
5260                                 if (SwitchType.BuiltinType == BuiltinTypeSpec.Type.String) {
5261                                         string_labels = new Dictionary<string, SwitchLabel> ();
5262                                 } else {
5263                                         labels = new Dictionary<long, SwitchLabel> ();
5264                                 }
5265                         }
5266
5267                         var constant = switch_expr as Constant;
5268
5269                         //
5270                         // Don't need extra variable for constant switch or switch with
5271                         // only default case
5272                         //
5273                         if (constant == null) {
5274                                 //
5275                                 // Store switch expression for comparison purposes
5276                                 //
5277                                 value = switch_expr as VariableReference;
5278                                 if (value == null && !HasOnlyDefaultSection ()) {
5279                                         var current_block = ec.CurrentBlock;
5280                                         ec.CurrentBlock = Block;
5281                                         // Create temporary variable inside switch scope
5282                                         value = TemporaryVariableReference.Create (SwitchType, ec.CurrentBlock, loc);
5283                                         value.Resolve (ec);
5284                                         ec.CurrentBlock = current_block;
5285                                 }
5286                         }
5287
5288                         case_labels = new List<SwitchLabel> ();
5289
5290                         Switch old_switch = ec.Switch;
5291                         ec.Switch = this;
5292                         var parent_los = ec.EnclosingLoopOrSwitch;
5293                         ec.EnclosingLoopOrSwitch = this;
5294
5295                         var ok = Statement.Resolve (ec);
5296
5297                         ec.EnclosingLoopOrSwitch = parent_los;
5298                         ec.Switch = old_switch;
5299
5300                         //
5301                         // Check if all goto cases are valid. Needs to be done after switch
5302                         // is resolved because goto can jump forward in the scope.
5303                         //
5304                         if (goto_cases != null) {
5305                                 foreach (var gc in goto_cases) {
5306                                         if (gc.Item1 == null) {
5307                                                 if (DefaultLabel == null) {
5308                                                         Goto.Error_UnknownLabel (ec, "default", loc);
5309                                                 }
5310
5311                                                 continue;
5312                                         }
5313
5314                                         var sl = FindLabel (gc.Item2);
5315                                         if (sl == null) {
5316                                                 Goto.Error_UnknownLabel (ec, "case " + gc.Item2.GetValueAsLiteral (), loc);
5317                                         } else {
5318                                                 gc.Item1.Label = sl;
5319                                         }
5320                                 }
5321                         }
5322
5323                         if (!ok)
5324                                 return false;
5325
5326                         if (constant == null && SwitchType.BuiltinType == BuiltinTypeSpec.Type.String && string_labels.Count > 6) {
5327                                 ResolveStringSwitchMap (ec);
5328                         }
5329
5330                         //
5331                         // Anonymous storey initialization has to happen before
5332                         // any generated switch dispatch
5333                         //
5334                         block.InsertStatement (0, new DispatchStatement (this));
5335
5336                         return true;
5337                 }
5338
5339                 bool HasOnlyDefaultSection ()
5340                 {
5341                         for (int i = 0; i < block.Statements.Count; ++i) {
5342                                 var s = block.Statements[i] as SwitchLabel;
5343
5344                                 if (s == null || s.IsDefault)
5345                                         continue;
5346
5347                                 return false;
5348                         }
5349
5350                         return true;
5351                 }
5352
5353                 public override Reachability MarkReachable (Reachability rc)
5354                 {
5355                         if (rc.IsUnreachable)
5356                                 return rc;
5357
5358                         base.MarkReachable (rc);
5359
5360                         block.MarkReachableScope (rc);
5361
5362                         if (block.Statements.Count == 0)
5363                                 return rc;
5364
5365                         SwitchLabel constant_label = null;
5366                         var constant = new_expr as Constant;
5367
5368                         if (constant != null) {
5369                                 constant_label = FindLabel (constant) ?? case_default;
5370                                 if (constant_label == null) {
5371                                         block.Statements.RemoveAt (0);
5372                                         return rc;
5373                                 }
5374                         }
5375
5376                         var section_rc = new Reachability ();
5377                         SwitchLabel prev_label = null;
5378
5379                         for (int i = 0; i < block.Statements.Count; ++i) {
5380                                 var s = block.Statements[i];
5381                                 var sl = s as SwitchLabel;
5382
5383                                 if (sl != null && sl.SectionStart) {
5384                                         //
5385                                         // Section is marked already via goto case
5386                                         //
5387                                         if (!sl.IsUnreachable) {
5388                                                 section_rc = new Reachability ();
5389                                                 continue;
5390                                         }
5391
5392                                         if (section_rc.IsUnreachable) {
5393                                                 //
5394                                                 // Common case. Previous label section end is unreachable as
5395                                                 // it ends with break, return, etc. For next section revert
5396                                                 // to reachable again unless we have constant switch block
5397                                                 //
5398                                                 section_rc = constant_label != null && constant_label != sl ?
5399                                                         Reachability.CreateUnreachable () :
5400                                                         new Reachability ();
5401                                         } else if (prev_label != null) {
5402                                                 //
5403                                                 // Error case as control cannot fall through from one case label
5404                                                 //
5405                                                 sl.SectionStart = false;
5406                                                 s = new MissingBreak (prev_label);
5407                                                 s.MarkReachable (rc);
5408                                                 block.Statements.Insert (i - 1, s);
5409                                                 ++i;
5410                                         } else if (constant_label != null && constant_label != sl) {
5411                                                 //
5412                                                 // Special case for the first unreachable label in constant
5413                                                 // switch block
5414                                                 //
5415                                                 section_rc = Reachability.CreateUnreachable ();
5416                                         }
5417
5418                                         prev_label = sl;
5419                                 }
5420
5421                                 section_rc = s.MarkReachable (section_rc);
5422                         }
5423
5424                         if (!section_rc.IsUnreachable && prev_label != null) {
5425                                 prev_label.SectionStart = false;
5426                                 var s = new MissingBreak (prev_label) {
5427                                         FallOut = true
5428                                 };
5429
5430                                 s.MarkReachable (rc);
5431                                 block.Statements.Add (s);
5432                         }
5433
5434                         //
5435                         // Reachability can affect parent only when all possible paths are handled but
5436                         // we still need to run reachability check on switch body to check for fall-through
5437                         //
5438                         if (case_default == null && constant_label == null)
5439                                 return rc;
5440
5441                         //
5442                         // We have at least one local exit from the switch
5443                         //
5444                         if (end_reachable)
5445                                 return rc;
5446
5447                         return Reachability.CreateUnreachable ();
5448                 }
5449
5450                 public void RegisterGotoCase (GotoCase gotoCase, Constant value)
5451                 {
5452                         if (goto_cases == null)
5453                                 goto_cases = new List<Tuple<GotoCase, Constant>> ();
5454
5455                         goto_cases.Add (Tuple.Create (gotoCase, value));
5456                 }
5457
5458                 //
5459                 // Converts string switch into string hashtable
5460                 //
5461                 void ResolveStringSwitchMap (ResolveContext ec)
5462                 {
5463                         FullNamedExpression string_dictionary_type;
5464                         if (ec.Module.PredefinedTypes.Dictionary.Define ()) {
5465                                 string_dictionary_type = new TypeExpression (
5466                                         ec.Module.PredefinedTypes.Dictionary.TypeSpec.MakeGenericType (ec,
5467                                                 new [] { ec.BuiltinTypes.String, ec.BuiltinTypes.Int }),
5468                                         loc);
5469                         } else if (ec.Module.PredefinedTypes.Hashtable.Define ()) {
5470                                 string_dictionary_type = new TypeExpression (ec.Module.PredefinedTypes.Hashtable.TypeSpec, loc);
5471                         } else {
5472                                 ec.Module.PredefinedTypes.Dictionary.Resolve ();
5473                                 return;
5474                         }
5475
5476                         var ctype = ec.CurrentMemberDefinition.Parent.PartialContainer;
5477                         Field field = new Field (ctype, string_dictionary_type,
5478                                 Modifiers.STATIC | Modifiers.PRIVATE | Modifiers.COMPILER_GENERATED,
5479                                 new MemberName (CompilerGeneratedContainer.MakeName (null, "f", "switch$map", ec.Module.CounterSwitchTypes++), loc), null);
5480                         if (!field.Define ())
5481                                 return;
5482                         ctype.AddField (field);
5483
5484                         var init = new List<Expression> ();
5485                         int counter = -1;
5486                         labels = new Dictionary<long, SwitchLabel> (string_labels.Count);
5487                         string value = null;
5488
5489                         foreach (SwitchLabel sl in case_labels) {
5490
5491                                 if (sl.SectionStart)
5492                                         labels.Add (++counter, sl);
5493
5494                                 if (sl == case_default || sl == case_null)
5495                                         continue;
5496
5497                                 value = (string) sl.Converted.GetValue ();
5498                                 var init_args = new List<Expression> (2);
5499                                 init_args.Add (new StringLiteral (ec.BuiltinTypes, value, sl.Location));
5500
5501                                 sl.Converted = new IntConstant (ec.BuiltinTypes, counter, loc);
5502                                 init_args.Add (sl.Converted);
5503
5504                                 init.Add (new CollectionElementInitializer (init_args, loc));
5505                         }
5506
5507                         Arguments args = new Arguments (1);
5508                         args.Add (new Argument (new IntConstant (ec.BuiltinTypes, init.Count, loc)));
5509                         Expression initializer = new NewInitialize (string_dictionary_type, args,
5510                                 new CollectionOrObjectInitializers (init, loc), loc);
5511
5512                         switch_cache_field = new FieldExpr (field, loc);
5513                         string_dictionary = new SimpleAssign (switch_cache_field, initializer.Resolve (ec));
5514                 }
5515
5516                 void DoEmitStringSwitch (EmitContext ec)
5517                 {
5518                         Label l_initialized = ec.DefineLabel ();
5519
5520                         //
5521                         // Skip initialization when value is null
5522                         //
5523                         value.EmitBranchable (ec, nullLabel, false);
5524
5525                         //
5526                         // Check if string dictionary is initialized and initialize
5527                         //
5528                         switch_cache_field.EmitBranchable (ec, l_initialized, true);
5529                         using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
5530                                 string_dictionary.EmitStatement (ec);
5531                         }
5532                         ec.MarkLabel (l_initialized);
5533
5534                         LocalTemporary string_switch_variable = new LocalTemporary (ec.BuiltinTypes.Int);
5535
5536                         ResolveContext rc = new ResolveContext (ec.MemberContext);
5537
5538                         if (switch_cache_field.Type.IsGeneric) {
5539                                 Arguments get_value_args = new Arguments (2);
5540                                 get_value_args.Add (new Argument (value));
5541                                 get_value_args.Add (new Argument (string_switch_variable, Argument.AType.Out));
5542                                 Expression get_item = new Invocation (new MemberAccess (switch_cache_field, "TryGetValue", loc), get_value_args).Resolve (rc);
5543                                 if (get_item == null)
5544                                         return;
5545
5546                                 //
5547                                 // A value was not found, go to default case
5548                                 //
5549                                 get_item.EmitBranchable (ec, defaultLabel, false);
5550                         } else {
5551                                 Arguments get_value_args = new Arguments (1);
5552                                 get_value_args.Add (new Argument (value));
5553
5554                                 Expression get_item = new ElementAccess (switch_cache_field, get_value_args, loc).Resolve (rc);
5555                                 if (get_item == null)
5556                                         return;
5557
5558                                 LocalTemporary get_item_object = new LocalTemporary (ec.BuiltinTypes.Object);
5559                                 get_item_object.EmitAssign (ec, get_item, true, false);
5560                                 ec.Emit (OpCodes.Brfalse, defaultLabel);
5561
5562                                 ExpressionStatement get_item_int = (ExpressionStatement) new SimpleAssign (string_switch_variable,
5563                                         new Cast (new TypeExpression (ec.BuiltinTypes.Int, loc), get_item_object, loc)).Resolve (rc);
5564
5565                                 get_item_int.EmitStatement (ec);
5566                                 get_item_object.Release (ec);
5567                         }
5568
5569                         EmitTableSwitch (ec, string_switch_variable);
5570                         string_switch_variable.Release (ec);
5571                 }
5572
5573                 //
5574                 // Emits switch using simple if/else comparison for small label count (4 + optional default)
5575                 //
5576                 void EmitShortSwitch (EmitContext ec)
5577                 {
5578                         MethodSpec equal_method = null;
5579                         if (SwitchType.BuiltinType == BuiltinTypeSpec.Type.String) {
5580                                 equal_method = ec.Module.PredefinedMembers.StringEqual.Resolve (loc);
5581                         }
5582
5583                         if (equal_method != null) {
5584                                 value.EmitBranchable (ec, nullLabel, false);
5585                         }
5586
5587                         for (int i = 0; i < case_labels.Count; ++i) {
5588                                 var label = case_labels [i];
5589                                 if (label == case_default || label == case_null)
5590                                         continue;
5591
5592                                 var constant = label.Converted;
5593
5594                                 if (constant == null) {
5595                                         label.Label.EmitBranchable (ec, label.GetILLabel (ec), true);
5596                                         continue;
5597                                 }
5598
5599                                 if (equal_method != null) {
5600                                         value.Emit (ec);
5601                                         constant.Emit (ec);
5602
5603                                         var call = new CallEmitter ();
5604                                         call.EmitPredefined (ec, equal_method, new Arguments (0));
5605                                         ec.Emit (OpCodes.Brtrue, label.GetILLabel (ec));
5606                                         continue;
5607                                 }
5608
5609                                 if (constant.IsZeroInteger && constant.Type.BuiltinType != BuiltinTypeSpec.Type.Long && constant.Type.BuiltinType != BuiltinTypeSpec.Type.ULong) {
5610                                         value.EmitBranchable (ec, label.GetILLabel (ec), false);
5611                                         continue;
5612                                 }
5613
5614                                 value.Emit (ec);
5615                                 constant.Emit (ec);
5616                                 ec.Emit (OpCodes.Beq, label.GetILLabel (ec));
5617                         }
5618
5619                         ec.Emit (OpCodes.Br, defaultLabel);
5620                 }
5621
5622                 void EmitDispatch (EmitContext ec)
5623                 {
5624                         if (IsPatternMatching) {
5625                                 EmitShortSwitch (ec);
5626                                 return;
5627                         }
5628
5629                         if (value == null) {
5630                                 //
5631                                 // Constant switch, we've already done the work if there is only 1 label
5632                                 // referenced
5633                                 //
5634                                 int reachable = 0;
5635                                 foreach (var sl in case_labels) {
5636                                         if (sl.IsUnreachable)
5637                                                 continue;
5638
5639                                         if (reachable++ > 0) {
5640                                                 var constant = (Constant) new_expr;
5641                                                 var constant_label = FindLabel (constant) ?? case_default;
5642
5643                                                 ec.Emit (OpCodes.Br, constant_label.GetILLabel (ec));
5644                                                 break;
5645                                         }
5646                                 }
5647
5648                                 return;
5649                         }
5650
5651                         if (string_dictionary != null) {
5652                                 DoEmitStringSwitch (ec);
5653                         } else if (case_labels.Count < 4 || string_labels != null) {
5654                                 EmitShortSwitch (ec);
5655                         } else {
5656                                 EmitTableSwitch (ec, value);
5657                         }
5658                 }
5659
5660                 protected override void DoEmit (EmitContext ec)
5661                 {
5662                         //
5663                         // Setup the codegen context
5664                         //
5665                         Label old_end = ec.LoopEnd;
5666                         Switch old_switch = ec.Switch;
5667
5668                         ec.LoopEnd = ec.DefineLabel ();
5669                         ec.Switch = this;
5670
5671                         defaultLabel = case_default == null ? ec.LoopEnd : case_default.GetILLabel (ec);
5672                         nullLabel = case_null == null ? defaultLabel : case_null.GetILLabel (ec);
5673
5674                         if (value != null) {
5675                                 ec.Mark (loc);
5676
5677                                 var switch_expr = new_expr ?? Expr;
5678                                 if (IsNullable) {
5679                                         unwrap.EmitCheck (ec);
5680                                         ec.Emit (OpCodes.Brfalse, nullLabel);
5681                                         value.EmitAssign (ec, switch_expr, false, false);
5682                                 } else if (switch_expr != value) {
5683                                         value.EmitAssign (ec, switch_expr, false, false);
5684                                 }
5685
5686
5687                                 //
5688                                 // Next statement is compiler generated we don't need extra
5689                                 // nop when we can use the statement for sequence point
5690                                 //
5691                                 ec.Mark (block.StartLocation);
5692                                 block.IsCompilerGenerated = true;
5693                         } else {
5694                                 new_expr.EmitSideEffect (ec);
5695                         }
5696
5697                         block.Emit (ec);
5698
5699                         // Restore context state.
5700                         ec.MarkLabel (ec.LoopEnd);
5701
5702                         //
5703                         // Restore the previous context
5704                         //
5705                         ec.LoopEnd = old_end;
5706                         ec.Switch = old_switch;
5707                 }
5708
5709                 protected override void CloneTo (CloneContext clonectx, Statement t)
5710                 {
5711                         Switch target = (Switch) t;
5712
5713                         target.Expr = Expr.Clone (clonectx);
5714                         target.Statement = target.block = (ExplicitBlock) block.Clone (clonectx);
5715                 }
5716
5717                 public override object Accept (StructuralVisitor visitor)
5718                 {
5719                         return visitor.Visit (this);
5720                 }
5721
5722                 public override void AddEndDefiniteAssignment (FlowAnalysisContext fc)
5723                 {
5724                         if (case_default == null && !(new_expr is Constant))
5725                                 return;
5726
5727                         if (end_reachable_das == null)
5728                                 end_reachable_das = new List<DefiniteAssignmentBitSet> ();
5729
5730                         end_reachable_das.Add (fc.DefiniteAssignment);
5731                 }
5732
5733                 public override void SetEndReachable ()
5734                 {
5735                         end_reachable = true;
5736                 }
5737         }
5738
5739         // A place where execution can restart in a state machine
5740         public abstract class ResumableStatement : Statement
5741         {
5742                 bool prepared;
5743                 protected Label resume_point;
5744
5745                 public Label PrepareForEmit (EmitContext ec)
5746                 {
5747                         if (!prepared) {
5748                                 prepared = true;
5749                                 resume_point = ec.DefineLabel ();
5750                         }
5751                         return resume_point;
5752                 }
5753
5754                 public virtual Label PrepareForDispose (EmitContext ec, Label end)
5755                 {
5756                         return end;
5757                 }
5758
5759                 public virtual void EmitForDispose (EmitContext ec, LocalBuilder pc, Label end, bool have_dispatcher)
5760                 {
5761                 }
5762         }
5763
5764         public abstract class TryFinallyBlock : ExceptionStatement
5765         {
5766                 protected Statement stmt;
5767                 Label dispose_try_block;
5768                 bool prepared_for_dispose, emitted_dispose;
5769                 Method finally_host;
5770
5771                 protected TryFinallyBlock (Statement stmt, Location loc)
5772                         : base (loc)
5773                 {
5774                         this.stmt = stmt;
5775                 }
5776
5777                 #region Properties
5778
5779                 public Statement Statement {
5780                         get {
5781                                 return stmt;
5782                         }
5783                 }
5784
5785                 #endregion
5786
5787                 protected abstract void EmitTryBody (EmitContext ec);
5788                 public abstract void EmitFinallyBody (EmitContext ec);
5789
5790                 public override Label PrepareForDispose (EmitContext ec, Label end)
5791                 {
5792                         if (!prepared_for_dispose) {
5793                                 prepared_for_dispose = true;
5794                                 dispose_try_block = ec.DefineLabel ();
5795                         }
5796                         return dispose_try_block;
5797                 }
5798
5799                 protected sealed override void DoEmit (EmitContext ec)
5800                 {
5801                         EmitTryBodyPrepare (ec);
5802                         EmitTryBody (ec);
5803
5804                         bool beginFinally = EmitBeginFinallyBlock (ec);
5805
5806                         Label start_finally = ec.DefineLabel ();
5807                         if (resume_points != null && beginFinally) {
5808                                 var state_machine = (StateMachineInitializer) ec.CurrentAnonymousMethod;
5809
5810                                 ec.Emit (OpCodes.Ldloc, state_machine.SkipFinally);
5811                                 ec.Emit (OpCodes.Brfalse_S, start_finally);
5812                                 ec.Emit (OpCodes.Endfinally);
5813                         }
5814
5815                         ec.MarkLabel (start_finally);
5816
5817                         if (finally_host != null) {
5818                                 finally_host.Define ();
5819                                 finally_host.PrepareEmit ();
5820                                 finally_host.Emit ();
5821
5822                                 // Now it's safe to add, to close it properly and emit sequence points
5823                                 finally_host.Parent.AddMember (finally_host);
5824
5825                                 var ce = new CallEmitter ();
5826                                 ce.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
5827                                 ce.EmitPredefined (ec, finally_host.Spec, new Arguments (0), true);
5828                         } else {
5829                                 EmitFinallyBody (ec);
5830                         }
5831
5832                         if (beginFinally)
5833                                 ec.EndExceptionBlock ();
5834                 }
5835
5836                 public override void EmitForDispose (EmitContext ec, LocalBuilder pc, Label end, bool have_dispatcher)
5837                 {
5838                         if (emitted_dispose)
5839                                 return;
5840
5841                         emitted_dispose = true;
5842
5843                         Label end_of_try = ec.DefineLabel ();
5844
5845                         // Ensure that the only way we can get into this code is through a dispatcher
5846                         if (have_dispatcher)
5847                                 ec.Emit (OpCodes.Br, end);
5848
5849                         ec.BeginExceptionBlock ();
5850
5851                         ec.MarkLabel (dispose_try_block);
5852
5853                         Label[] labels = null;
5854                         for (int i = 0; i < resume_points.Count; ++i) {
5855                                 ResumableStatement s = resume_points[i];
5856                                 Label ret = s.PrepareForDispose (ec, end_of_try);
5857                                 if (ret.Equals (end_of_try) && labels == null)
5858                                         continue;
5859                                 if (labels == null) {
5860                                         labels = new Label[resume_points.Count];
5861                                         for (int j = 0; j < i; ++j)
5862                                                 labels[j] = end_of_try;
5863                                 }
5864                                 labels[i] = ret;
5865                         }
5866
5867                         if (labels != null) {
5868                                 int j;
5869                                 for (j = 1; j < labels.Length; ++j)
5870                                         if (!labels[0].Equals (labels[j]))
5871                                                 break;
5872                                 bool emit_dispatcher = j < labels.Length;
5873
5874                                 if (emit_dispatcher) {
5875                                         ec.Emit (OpCodes.Ldloc, pc);
5876                                         ec.EmitInt (first_resume_pc);
5877                                         ec.Emit (OpCodes.Sub);
5878                                         ec.Emit (OpCodes.Switch, labels);
5879                                 }
5880
5881                                 foreach (ResumableStatement s in resume_points)
5882                                         s.EmitForDispose (ec, pc, end_of_try, emit_dispatcher);
5883                         }
5884
5885                         ec.MarkLabel (end_of_try);
5886
5887                         ec.BeginFinallyBlock ();
5888
5889                         if (finally_host != null) {
5890                                 var ce = new CallEmitter ();
5891                                 ce.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
5892                                 ce.EmitPredefined (ec, finally_host.Spec, new Arguments (0), true);
5893                         } else {
5894                                 EmitFinallyBody (ec);
5895                         }
5896
5897                         ec.EndExceptionBlock ();
5898                 }
5899
5900                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
5901                 {
5902                         var res = stmt.FlowAnalysis (fc);
5903                         parent_try_block = null;
5904                         return res;
5905                 }
5906
5907                 protected virtual bool EmitBeginFinallyBlock (EmitContext ec)
5908                 {
5909                         ec.BeginFinallyBlock ();
5910                         return true;
5911                 }
5912
5913                 public override Reachability MarkReachable (Reachability rc)
5914                 {
5915                         base.MarkReachable (rc);
5916                         return Statement.MarkReachable (rc);
5917                 }
5918
5919                 public override bool Resolve (BlockContext bc)
5920                 {
5921                         bool ok;
5922
5923                         parent_try_block = bc.CurrentTryBlock;
5924                         bc.CurrentTryBlock = this;
5925
5926                         if (stmt is TryCatch) {
5927                                 ok = stmt.Resolve (bc);
5928                         } else {
5929                                 using (bc.Set (ResolveContext.Options.TryScope)) {
5930                                         ok = stmt.Resolve (bc);
5931                                 }
5932                         }
5933
5934                         bc.CurrentTryBlock = parent_try_block;
5935
5936                         //
5937                         // Finally block inside iterator is called from MoveNext and
5938                         // Dispose methods that means we need to lift the block into
5939                         // newly created host method to emit the body only once. The
5940                         // original block then simply calls the newly generated method.
5941                         //
5942                         if (bc.CurrentIterator != null && !bc.IsInProbingMode) {
5943                                 var b = stmt as Block;
5944                                 if (b != null && b.Explicit.HasYield) {
5945                                         finally_host = bc.CurrentIterator.CreateFinallyHost (this);
5946                                 }
5947                         }
5948
5949                         return base.Resolve (bc) && ok;
5950                 }
5951         }
5952
5953         //
5954         // Base class for blocks using exception handling
5955         //
5956         public abstract class ExceptionStatement : ResumableStatement
5957         {
5958                 protected List<ResumableStatement> resume_points;
5959                 protected int first_resume_pc;
5960                 protected ExceptionStatement parent_try_block;
5961                 protected int first_catch_resume_pc = -1;
5962
5963                 protected ExceptionStatement (Location loc)
5964                 {
5965                         this.loc = loc;
5966                 }
5967
5968                 protected virtual void EmitTryBodyPrepare (EmitContext ec)
5969                 {
5970                         StateMachineInitializer state_machine = null;
5971                         if (resume_points != null) {
5972                                 state_machine = (StateMachineInitializer) ec.CurrentAnonymousMethod;
5973
5974                                 ec.EmitInt ((int) IteratorStorey.State.Running);
5975                                 ec.Emit (OpCodes.Stloc, state_machine.CurrentPC);
5976                         }
5977
5978                         //
5979                         // The resume points in catch section when this is try-catch-finally
5980                         //
5981                         if (IsRewrittenTryCatchFinally ()) {
5982                                 ec.BeginExceptionBlock ();
5983
5984                                 if (first_catch_resume_pc >= 0) {
5985
5986                                         ec.MarkLabel (resume_point);
5987
5988                                         // For normal control flow, we want to fall-through the Switch
5989                                         // So, we use CurrentPC rather than the $PC field, and initialize it to an outside value above
5990                                         ec.Emit (OpCodes.Ldloc, state_machine.CurrentPC);
5991                                         ec.EmitInt (first_resume_pc + first_catch_resume_pc);
5992                                         ec.Emit (OpCodes.Sub);
5993
5994                                         var labels = new Label [resume_points.Count - first_catch_resume_pc];
5995                                         for (int i = 0; i < labels.Length; ++i)
5996                                                 labels [i] = resume_points [i + first_catch_resume_pc].PrepareForEmit (ec);
5997                                         ec.Emit (OpCodes.Switch, labels);
5998                                 }
5999                         }
6000
6001                         ec.BeginExceptionBlock ();
6002
6003                         //
6004                         // The resume points for try section
6005                         //
6006                         if (resume_points != null && first_catch_resume_pc != 0) {
6007                                 if (first_catch_resume_pc < 0)
6008                                         ec.MarkLabel (resume_point);
6009
6010                                 // For normal control flow, we want to fall-through the Switch
6011                                 // So, we use CurrentPC rather than the $PC field, and initialize it to an outside value above
6012                                 ec.Emit (OpCodes.Ldloc, state_machine.CurrentPC);
6013                                 ec.EmitInt (first_resume_pc);
6014                                 ec.Emit (OpCodes.Sub);
6015
6016                                 var labels = new Label [first_catch_resume_pc > 0 ? first_catch_resume_pc : resume_points.Count];
6017                                 for (int i = 0; i < labels.Length; ++i)
6018                                         labels[i] = resume_points[i].PrepareForEmit (ec);
6019                                 ec.Emit (OpCodes.Switch, labels);
6020                         }
6021                 }
6022
6023                 bool IsRewrittenTryCatchFinally ()
6024                 {
6025                         var tf = this as TryFinally;
6026                         if (tf == null)
6027                                 return false;
6028
6029                         var tc = tf.Statement as TryCatch;
6030                         if (tc == null)
6031                                 return false;
6032
6033                         return tf.FinallyBlock.HasAwait || tc.HasClauseWithAwait;
6034                 }
6035
6036                 public int AddResumePoint (ResumableStatement stmt, int pc, StateMachineInitializer stateMachine, TryCatch catchBlock)
6037                 {
6038                         if (parent_try_block != null) {
6039                                 pc = parent_try_block.AddResumePoint (this, pc, stateMachine, catchBlock);
6040                         } else {
6041                                 pc = stateMachine.AddResumePoint (this);
6042                         }
6043
6044                         if (resume_points == null) {
6045                                 resume_points = new List<ResumableStatement> ();
6046                                 first_resume_pc = pc;
6047                         }
6048
6049                         if (pc != first_resume_pc + resume_points.Count)
6050                                 throw new InternalErrorException ("missed an intervening AddResumePoint?");
6051
6052                         var tf = this as TryFinally;
6053                         if (tf != null && tf.Statement == catchBlock && first_catch_resume_pc < 0) {
6054                                 first_catch_resume_pc = resume_points.Count;
6055                         }
6056
6057                         resume_points.Add (stmt);
6058                         return pc;
6059                 }
6060         }
6061
6062         public class Lock : TryFinallyBlock
6063         {
6064                 Expression expr;
6065                 TemporaryVariableReference expr_copy;
6066                 TemporaryVariableReference lock_taken;
6067
6068                 public Lock (Expression expr, Statement stmt, Location loc)
6069                         : base (stmt, loc)
6070                 {
6071                         this.expr = expr;
6072                 }
6073
6074                 public Expression Expr {
6075                         get {
6076                                 return this.expr;
6077                         }
6078                 }
6079
6080                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6081                 {
6082                         expr.FlowAnalysis (fc);
6083                         return base.DoFlowAnalysis (fc);
6084                 }
6085
6086                 public override bool Resolve (BlockContext ec)
6087                 {
6088                         expr = expr.Resolve (ec);
6089                         if (expr == null)
6090                                 return false;
6091
6092                         if (!TypeSpec.IsReferenceType (expr.Type) && expr.Type != InternalType.ErrorType) {
6093                                 ec.Report.Error (185, loc,
6094                                         "`{0}' is not a reference type as required by the lock statement",
6095                                         expr.Type.GetSignatureForError ());
6096                         }
6097
6098                         if (expr.Type.IsGenericParameter) {
6099                                 expr = Convert.ImplicitTypeParameterConversion (expr, (TypeParameterSpec)expr.Type, ec.BuiltinTypes.Object);
6100                         }
6101
6102                         VariableReference lv = expr as VariableReference;
6103                         bool locked;
6104                         if (lv != null) {
6105                                 locked = lv.IsLockedByStatement;
6106                                 lv.IsLockedByStatement = true;
6107                         } else {
6108                                 lv = null;
6109                                 locked = false;
6110                         }
6111
6112                         //
6113                         // Have to keep original lock value around to unlock same location
6114                         // in the case of original value has changed or is null
6115                         //
6116                         expr_copy = TemporaryVariableReference.Create (ec.BuiltinTypes.Object, ec.CurrentBlock, loc);
6117                         expr_copy.Resolve (ec);
6118
6119                         //
6120                         // Ensure Monitor methods are available
6121                         //
6122                         if (ResolvePredefinedMethods (ec) > 1) {
6123                                 lock_taken = TemporaryVariableReference.Create (ec.BuiltinTypes.Bool, ec.CurrentBlock, loc);
6124                                 lock_taken.Resolve (ec);
6125                         }
6126
6127                         using (ec.Set (ResolveContext.Options.LockScope)) {
6128                                 base.Resolve (ec);
6129                         }
6130
6131                         if (lv != null) {
6132                                 lv.IsLockedByStatement = locked;
6133                         }
6134
6135                         return true;
6136                 }
6137
6138                 protected override void EmitTryBodyPrepare (EmitContext ec)
6139                 {
6140                         expr_copy.EmitAssign (ec, expr);
6141
6142                         if (lock_taken != null) {
6143                                 //
6144                                 // Initialize ref variable
6145                                 //
6146                                 lock_taken.EmitAssign (ec, new BoolLiteral (ec.BuiltinTypes, false, loc));
6147                         } else {
6148                                 //
6149                                 // Monitor.Enter (expr_copy)
6150                                 //
6151                                 expr_copy.Emit (ec);
6152                                 ec.Emit (OpCodes.Call, ec.Module.PredefinedMembers.MonitorEnter.Get ());
6153                         }
6154
6155                         base.EmitTryBodyPrepare (ec);
6156                 }
6157
6158                 protected override void EmitTryBody (EmitContext ec)
6159                 {
6160                         //
6161                         // Monitor.Enter (expr_copy, ref lock_taken)
6162                         //
6163                         if (lock_taken != null) {
6164                                 expr_copy.Emit (ec);
6165                                 lock_taken.LocalInfo.CreateBuilder (ec);
6166                                 lock_taken.AddressOf (ec, AddressOp.Load);
6167                                 ec.Emit (OpCodes.Call, ec.Module.PredefinedMembers.MonitorEnter_v4.Get ());
6168                         }
6169
6170                         Statement.Emit (ec);
6171                 }
6172
6173                 public override void EmitFinallyBody (EmitContext ec)
6174                 {
6175                         //
6176                         // if (lock_taken) Monitor.Exit (expr_copy)
6177                         //
6178                         Label skip = ec.DefineLabel ();
6179
6180                         if (lock_taken != null) {
6181                                 lock_taken.Emit (ec);
6182                                 ec.Emit (OpCodes.Brfalse_S, skip);
6183                         }
6184
6185                         expr_copy.Emit (ec);
6186                         var m = ec.Module.PredefinedMembers.MonitorExit.Resolve (loc);
6187                         if (m != null)
6188                                 ec.Emit (OpCodes.Call, m);
6189
6190                         ec.MarkLabel (skip);
6191                 }
6192
6193                 int ResolvePredefinedMethods (ResolveContext rc)
6194                 {
6195                         // Try 4.0 Monitor.Enter (object, ref bool) overload first
6196                         var m = rc.Module.PredefinedMembers.MonitorEnter_v4.Get ();
6197                         if (m != null)
6198                                 return 4;
6199
6200                         m = rc.Module.PredefinedMembers.MonitorEnter.Get ();
6201                         if (m != null)
6202                                 return 1;
6203
6204                         rc.Module.PredefinedMembers.MonitorEnter_v4.Resolve (loc);
6205                         return 0;
6206                 }
6207
6208                 protected override void CloneTo (CloneContext clonectx, Statement t)
6209                 {
6210                         Lock target = (Lock) t;
6211
6212                         target.expr = expr.Clone (clonectx);
6213                         target.stmt = Statement.Clone (clonectx);
6214                 }
6215
6216                 public override object Accept (StructuralVisitor visitor)
6217                 {
6218                         return visitor.Visit (this);
6219                 }
6220
6221         }
6222
6223         public class Unchecked : Statement {
6224                 public Block Block;
6225
6226                 public Unchecked (Block b, Location loc)
6227                 {
6228                         Block = b;
6229                         b.Unchecked = true;
6230                         this.loc = loc;
6231                 }
6232
6233                 public override bool Resolve (BlockContext ec)
6234                 {
6235                         using (ec.With (ResolveContext.Options.AllCheckStateFlags, false))
6236                                 return Block.Resolve (ec);
6237                 }
6238
6239                 protected override void DoEmit (EmitContext ec)
6240                 {
6241                         using (ec.With (EmitContext.Options.CheckedScope, false))
6242                                 Block.Emit (ec);
6243                 }
6244
6245                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6246                 {
6247                         return Block.FlowAnalysis (fc);
6248                 }
6249
6250                 public override Reachability MarkReachable (Reachability rc)
6251                 {
6252                         base.MarkReachable (rc);
6253                         return Block.MarkReachable (rc);
6254                 }
6255
6256                 protected override void CloneTo (CloneContext clonectx, Statement t)
6257                 {
6258                         Unchecked target = (Unchecked) t;
6259
6260                         target.Block = clonectx.LookupBlock (Block);
6261                 }
6262
6263                 public override object Accept (StructuralVisitor visitor)
6264                 {
6265                         return visitor.Visit (this);
6266                 }
6267         }
6268
6269         public class Checked : Statement {
6270                 public Block Block;
6271
6272                 public Checked (Block b, Location loc)
6273                 {
6274                         Block = b;
6275                         b.Unchecked = false;
6276                         this.loc = loc;
6277                 }
6278
6279                 public override bool Resolve (BlockContext ec)
6280                 {
6281                         using (ec.With (ResolveContext.Options.AllCheckStateFlags, true))
6282                                 return Block.Resolve (ec);
6283                 }
6284
6285                 protected override void DoEmit (EmitContext ec)
6286                 {
6287                         using (ec.With (EmitContext.Options.CheckedScope, true))
6288                                 Block.Emit (ec);
6289                 }
6290
6291                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6292                 {
6293                         return Block.FlowAnalysis (fc);
6294                 }
6295
6296                 public override Reachability MarkReachable (Reachability rc)
6297                 {
6298                         base.MarkReachable (rc);
6299                         return Block.MarkReachable (rc);
6300                 }
6301
6302                 protected override void CloneTo (CloneContext clonectx, Statement t)
6303                 {
6304                         Checked target = (Checked) t;
6305
6306                         target.Block = clonectx.LookupBlock (Block);
6307                 }
6308
6309                 public override object Accept (StructuralVisitor visitor)
6310                 {
6311                         return visitor.Visit (this);
6312                 }
6313         }
6314
6315         public class Unsafe : Statement {
6316                 public Block Block;
6317
6318                 public Unsafe (Block b, Location loc)
6319                 {
6320                         Block = b;
6321                         Block.Unsafe = true;
6322                         this.loc = loc;
6323                 }
6324
6325                 public override bool Resolve (BlockContext ec)
6326                 {
6327                         if (ec.CurrentIterator != null)
6328                                 ec.Report.Error (1629, loc, "Unsafe code may not appear in iterators");
6329
6330                         using (ec.Set (ResolveContext.Options.UnsafeScope))
6331                                 return Block.Resolve (ec);
6332                 }
6333
6334                 protected override void DoEmit (EmitContext ec)
6335                 {
6336                         Block.Emit (ec);
6337                 }
6338
6339                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6340                 {
6341                         return Block.FlowAnalysis (fc);
6342                 }
6343
6344                 public override Reachability MarkReachable (Reachability rc)
6345                 {
6346                         base.MarkReachable (rc);
6347                         return Block.MarkReachable (rc);
6348                 }
6349
6350                 protected override void CloneTo (CloneContext clonectx, Statement t)
6351                 {
6352                         Unsafe target = (Unsafe) t;
6353
6354                         target.Block = clonectx.LookupBlock (Block);
6355                 }
6356
6357                 public override object Accept (StructuralVisitor visitor)
6358                 {
6359                         return visitor.Visit (this);
6360                 }
6361         }
6362
6363         //
6364         // Fixed statement
6365         //
6366         public class Fixed : Statement
6367         {
6368                 abstract class Emitter : ShimExpression
6369                 {
6370                         protected LocalVariable vi;
6371
6372                         protected Emitter (Expression expr, LocalVariable li)
6373                                 : base (expr)
6374                         {
6375                                 vi = li;
6376                         }
6377
6378                         public abstract void EmitExit (EmitContext ec);
6379
6380                         public override void FlowAnalysis (FlowAnalysisContext fc)
6381                         {
6382                                 expr.FlowAnalysis (fc);
6383                         }
6384                 }
6385
6386                 sealed class ExpressionEmitter : Emitter {
6387                         public ExpressionEmitter (Expression converted, LocalVariable li)
6388                                 : base (converted, li)
6389                         {
6390                         }
6391
6392                         protected override Expression DoResolve (ResolveContext rc)
6393                         {
6394                                 throw new NotImplementedException ();
6395                         }
6396
6397                         public override void Emit (EmitContext ec) {
6398                                 //
6399                                 // Store pointer in pinned location
6400                                 //
6401                                 expr.Emit (ec);
6402                                 vi.EmitAssign (ec);
6403                         }
6404
6405                         public override void EmitExit (EmitContext ec)
6406                         {
6407                                 ec.EmitInt (0);
6408                                 ec.Emit (OpCodes.Conv_U);
6409                                 vi.EmitAssign (ec);
6410                         }
6411                 }
6412
6413                 class StringEmitter : Emitter
6414                 {
6415                         LocalVariable pinned_string;
6416
6417                         public StringEmitter (Expression expr, LocalVariable li)
6418                                 : base (expr, li)
6419                         {
6420                         }
6421
6422                         protected override Expression DoResolve (ResolveContext rc)
6423                         {
6424                                 pinned_string = new LocalVariable (vi.Block, "$pinned",
6425                                         LocalVariable.Flags.FixedVariable | LocalVariable.Flags.CompilerGenerated | LocalVariable.Flags.Used,
6426                                         vi.Location);
6427                                 pinned_string.Type = rc.BuiltinTypes.String;
6428                                 vi.IsFixed = false;
6429
6430                                 eclass = ExprClass.Variable;
6431                                 type = rc.BuiltinTypes.Int;
6432                                 return this;
6433                         }
6434
6435                         public override void Emit (EmitContext ec)
6436                         {
6437                                 pinned_string.CreateBuilder (ec);
6438
6439                                 expr.Emit (ec);
6440                                 pinned_string.EmitAssign (ec);
6441
6442                                 // TODO: Should use Binary::Add
6443                                 pinned_string.Emit (ec);
6444                                 ec.Emit (OpCodes.Conv_I);
6445
6446                                 var m = ec.Module.PredefinedMembers.RuntimeHelpersOffsetToStringData.Resolve (loc);
6447                                 if (m == null)
6448                                         return;
6449
6450                                 PropertyExpr pe = new PropertyExpr (m, pinned_string.Location);
6451                                 //pe.InstanceExpression = pinned_string;
6452                                 pe.Resolve (new ResolveContext (ec.MemberContext)).Emit (ec);
6453
6454                                 ec.Emit (OpCodes.Add);
6455                                 vi.EmitAssign (ec);
6456                         }
6457
6458                         public override void EmitExit (EmitContext ec)
6459                         {
6460                                 ec.EmitNull ();
6461                                 pinned_string.EmitAssign (ec);
6462                         }
6463                 }
6464
6465                 public class VariableDeclaration : BlockVariable
6466                 {
6467                         public VariableDeclaration (FullNamedExpression type, LocalVariable li)
6468                                 : base (type, li)
6469                         {
6470                         }
6471
6472                         protected override Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
6473                         {
6474                                 if (!Variable.Type.IsPointer && li == Variable) {
6475                                         bc.Report.Error (209, TypeExpression.Location,
6476                                                 "The type of locals declared in a fixed statement must be a pointer type");
6477                                         return null;
6478                                 }
6479
6480                                 var res = initializer.Resolve (bc);
6481                                 if (res == null)
6482                                         return null;
6483
6484                                 //
6485                                 // Case 1: Array
6486                                 //
6487                                 var ac = res.Type as ArrayContainer;
6488                                 if (ac != null) {
6489                                         TypeSpec array_type = ac.Element;
6490
6491                                         //
6492                                         // Provided that array_type is unmanaged,
6493                                         //
6494                                         if (!TypeManager.VerifyUnmanaged (bc.Module, array_type, loc))
6495                                                 return null;
6496
6497                                         Expression res_init;
6498                                         if (ExpressionAnalyzer.IsInexpensiveLoad (res)) {
6499                                                 res_init = res;
6500                                         } else {
6501                                                 var expr_variable = LocalVariable.CreateCompilerGenerated (ac, bc.CurrentBlock, loc);
6502                                                 res_init = new CompilerAssign (expr_variable.CreateReferenceExpression (bc, loc), res, loc);
6503                                                 res = expr_variable.CreateReferenceExpression (bc, loc);
6504                                         }
6505
6506                                         //
6507                                         // and T* is implicitly convertible to the
6508                                         // pointer type given in the fixed statement.
6509                                         //
6510                                         ArrayPtr array_ptr = new ArrayPtr (res, array_type, loc);
6511
6512                                         Expression converted = Convert.ImplicitConversionRequired (bc, array_ptr.Resolve (bc), li.Type, loc);
6513                                         if (converted == null)
6514                                                 return null;
6515
6516                                         //
6517                                         // fixed (T* e_ptr = (e == null || e.Length == 0) ? null : converted [0])
6518                                         //
6519                                         converted = new Conditional (new BooleanExpression (new Binary (Binary.Operator.LogicalOr,
6520                                                 new Binary (Binary.Operator.Equality, res_init, new NullLiteral (loc)),
6521                                                 new Binary (Binary.Operator.Equality, new MemberAccess (res, "Length"), new IntConstant (bc.BuiltinTypes, 0, loc)))),
6522                                                         new NullLiteral (loc),
6523                                                         converted, loc);
6524
6525                                         converted = converted.Resolve (bc);
6526
6527                                         return new ExpressionEmitter (converted, li);
6528                                 }
6529
6530                                 //
6531                                 // Case 2: string
6532                                 //
6533                                 if (res.Type.BuiltinType == BuiltinTypeSpec.Type.String) {
6534                                         return new StringEmitter (res, li).Resolve (bc);
6535                                 }
6536
6537                                 // Case 3: fixed buffer
6538                                 if (res is FixedBufferPtr) {
6539                                         return new ExpressionEmitter (res, li);
6540                                 }
6541
6542                                 bool already_fixed = true;
6543
6544                                 //
6545                                 // Case 4: & object.
6546                                 //
6547                                 Unary u = res as Unary;
6548                                 if (u != null) {
6549                                         if (u.Oper == Unary.Operator.AddressOf) {
6550                                                 IVariableReference vr = u.Expr as IVariableReference;
6551                                                 if (vr == null || !vr.IsFixed) {
6552                                                         already_fixed = false;
6553                                                 }
6554                                         }
6555                                 } else if (initializer is Cast) {
6556                                         bc.Report.Error (254, initializer.Location, "The right hand side of a fixed statement assignment may not be a cast expression");
6557                                         return null;
6558                                 }
6559
6560                                 if (already_fixed) {
6561                                         bc.Report.Error (213, loc, "You cannot use the fixed statement to take the address of an already fixed expression");
6562                                 }
6563
6564                                 res = Convert.ImplicitConversionRequired (bc, res, li.Type, loc);
6565                                 return new ExpressionEmitter (res, li);
6566                         }
6567                 }
6568
6569
6570                 VariableDeclaration decl;
6571                 Statement statement;
6572                 bool has_ret;
6573
6574                 public Fixed (VariableDeclaration decl, Statement stmt, Location l)
6575                 {
6576                         this.decl = decl;
6577                         statement = stmt;
6578                         loc = l;
6579                 }
6580
6581                 #region Properties
6582
6583                 public Statement Statement {
6584                         get {
6585                                 return statement;
6586                         }
6587                 }
6588
6589                 public BlockVariable Variables {
6590                         get {
6591                                 return decl;
6592                         }
6593                 }
6594
6595                 #endregion
6596
6597                 public override bool Resolve (BlockContext bc)
6598                 {
6599                         using (bc.Set (ResolveContext.Options.FixedInitializerScope)) {
6600                                 if (!decl.Resolve (bc))
6601                                         return false;
6602                         }
6603
6604                         return statement.Resolve (bc);
6605                 }
6606
6607                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6608                 {
6609                         decl.FlowAnalysis (fc);
6610                         return statement.FlowAnalysis (fc);
6611                 }
6612
6613                 protected override void DoEmit (EmitContext ec)
6614                 {
6615                         decl.Variable.CreateBuilder (ec);
6616                         decl.Initializer.Emit (ec);
6617                         if (decl.Declarators != null) {
6618                                 foreach (var d in decl.Declarators) {
6619                                         d.Variable.CreateBuilder (ec);
6620                                         d.Initializer.Emit (ec);
6621                                 }
6622                         }
6623
6624                         statement.Emit (ec);
6625
6626                         if (has_ret)
6627                                 return;
6628
6629                         //
6630                         // Clear the pinned variable
6631                         //
6632                         ((Emitter) decl.Initializer).EmitExit (ec);
6633                         if (decl.Declarators != null) {
6634                                 foreach (var d in decl.Declarators) {
6635                                         ((Emitter)d.Initializer).EmitExit (ec);
6636                                 }
6637                         }
6638                 }
6639
6640                 public override Reachability MarkReachable (Reachability rc)
6641                 {
6642                         base.MarkReachable (rc);
6643
6644                         decl.MarkReachable (rc);
6645
6646                         rc = statement.MarkReachable (rc);
6647
6648                         // TODO: What if there is local exit?
6649                         has_ret = rc.IsUnreachable;
6650                         return rc;
6651                 }
6652
6653                 protected override void CloneTo (CloneContext clonectx, Statement t)
6654                 {
6655                         Fixed target = (Fixed) t;
6656
6657                         target.decl = (VariableDeclaration) decl.Clone (clonectx);
6658                         target.statement = statement.Clone (clonectx);
6659                 }
6660
6661                 public override object Accept (StructuralVisitor visitor)
6662                 {
6663                         return visitor.Visit (this);
6664                 }
6665         }
6666
6667         public class Catch : Statement
6668         {
6669                 class CatchVariableStore : Statement
6670                 {
6671                         readonly Catch ctch;
6672
6673                         public CatchVariableStore (Catch ctch)
6674                         {
6675                                 this.ctch = ctch;
6676                         }
6677
6678                         protected override void CloneTo (CloneContext clonectx, Statement target)
6679                         {
6680                         }
6681
6682                         protected override void DoEmit (EmitContext ec)
6683                         {
6684                                 // Emits catch variable debug information inside correct block
6685                                 ctch.EmitCatchVariableStore (ec);
6686                         }
6687
6688                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6689                         {
6690                                 return true;
6691                         }
6692                 }
6693
6694                 class FilterStatement : Statement
6695                 {
6696                         readonly Catch ctch;
6697
6698                         public FilterStatement (Catch ctch)
6699                         {
6700                                 this.ctch = ctch;
6701                         }
6702
6703                         protected override void CloneTo (CloneContext clonectx, Statement target)
6704                         {
6705                         }
6706
6707                         protected override void DoEmit (EmitContext ec)
6708                         {
6709                                 if (ctch.li != null) {
6710                                         if (ctch.hoisted_temp != null)
6711                                                 ctch.hoisted_temp.Emit (ec);
6712                                         else
6713                                                 ctch.li.Emit (ec);
6714
6715                                         if (!ctch.IsGeneral && ctch.type.Kind == MemberKind.TypeParameter)
6716                                                 ec.Emit (OpCodes.Box, ctch.type);
6717                                 }
6718
6719                                 var expr_start = ec.DefineLabel ();
6720                                 var end = ec.DefineLabel ();
6721
6722                                 ec.Emit (OpCodes.Brtrue_S, expr_start);
6723                                 ec.EmitInt (0);
6724                                 ec.Emit (OpCodes.Br, end);
6725                                 ec.MarkLabel (expr_start);
6726
6727                                 ctch.Filter.Emit (ec);
6728
6729                                 ec.MarkLabel (end);
6730                                 ec.Emit (OpCodes.Endfilter);
6731                                 ec.BeginFilterHandler ();
6732                                 ec.Emit (OpCodes.Pop);
6733                         }
6734
6735                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6736                         {
6737                                 ctch.Filter.FlowAnalysis (fc);
6738                                 return true;
6739                         }
6740
6741                         public override bool Resolve (BlockContext bc)
6742                         {
6743                                 ctch.Filter = ctch.Filter.Resolve (bc);
6744
6745                                 if (ctch.Filter != null) {
6746                                         if (ctch.Filter.ContainsEmitWithAwait ()) {
6747                                                 bc.Report.Error (7094, ctch.Filter.Location, "The `await' operator cannot be used in the filter expression of a catch clause");
6748                                         }
6749
6750                                         var c = ctch.Filter as Constant;
6751                                         if (c != null && !c.IsDefaultValue) {
6752                                                 bc.Report.Warning (7095, 1, ctch.Filter.Location, "Exception filter expression is a constant");
6753                                         }
6754                                 }
6755
6756                                 return true;
6757                         }
6758                 }
6759
6760                 ExplicitBlock block;
6761                 LocalVariable li;
6762                 FullNamedExpression type_expr;
6763                 CompilerAssign assign;
6764                 TypeSpec type;
6765                 LocalTemporary hoisted_temp;
6766
6767                 public Catch (ExplicitBlock block, Location loc)
6768                 {
6769                         this.block = block;
6770                         this.loc = loc;
6771                 }
6772
6773                 #region Properties
6774
6775                 public ExplicitBlock Block {
6776                         get {
6777                                 return block;
6778                         }
6779                 }
6780
6781                 public TypeSpec CatchType {
6782                         get {
6783                                 return type;
6784                         }
6785                 }
6786
6787                 public Expression Filter {
6788                         get; set;
6789                 }
6790
6791                 public bool IsGeneral {
6792                         get {
6793                                 return type_expr == null;
6794                         }
6795                 }
6796
6797                 public FullNamedExpression TypeExpression {
6798                         get {
6799                                 return type_expr;
6800                         }
6801                         set {
6802                                 type_expr = value;
6803                         }
6804                 }
6805
6806                 public LocalVariable Variable {
6807                         get {
6808                                 return li;
6809                         }
6810                         set {
6811                                 li = value;
6812                         }
6813                 }
6814
6815                 #endregion
6816
6817                 protected override void DoEmit (EmitContext ec)
6818                 {
6819                         if (Filter != null) {
6820                                 ec.BeginExceptionFilterBlock ();
6821                                 ec.Emit (OpCodes.Isinst, IsGeneral ? ec.BuiltinTypes.Object : CatchType);
6822
6823                                 if (Block.HasAwait) {
6824                                         Block.EmitScopeInitialization (ec);
6825                                 } else {
6826                                         Block.Emit (ec);
6827                                 }
6828
6829                                 return;
6830                         }
6831
6832                         if (IsGeneral)
6833                                 ec.BeginCatchBlock (ec.BuiltinTypes.Object);
6834                         else
6835                                 ec.BeginCatchBlock (CatchType);
6836
6837                         if (li == null)
6838                                 ec.Emit (OpCodes.Pop);
6839
6840                         if (Block.HasAwait) {
6841                                 if (li != null)
6842                                         EmitCatchVariableStore (ec);
6843                         } else {
6844                                 Block.Emit (ec);
6845                         }
6846                 }
6847
6848                 void EmitCatchVariableStore (EmitContext ec)
6849                 {
6850                         li.CreateBuilder (ec);
6851
6852                         //
6853                         // For hoisted catch variable we have to use a temporary local variable
6854                         // for captured variable initialization during storey setup because variable
6855                         // needs to be on the stack after storey instance for stfld operation
6856                         //
6857                         if (li.HoistedVariant != null) {
6858                                 hoisted_temp = new LocalTemporary (li.Type);
6859                                 hoisted_temp.Store (ec);
6860
6861                                 // switch to assignment from temporary variable and not from top of the stack
6862                                 assign.UpdateSource (hoisted_temp);
6863                         }
6864                 }
6865
6866                 public override bool Resolve (BlockContext bc)
6867                 {
6868                         using (bc.Set (ResolveContext.Options.CatchScope)) {
6869                                 if (type_expr == null) {
6870                                         if (CreateExceptionVariable (bc.Module.Compiler.BuiltinTypes.Object)) {
6871                                                 if (!block.HasAwait || Filter != null)
6872                                                         block.AddScopeStatement (new CatchVariableStore (this));
6873
6874                                                 Expression source = new EmptyExpression (li.Type);
6875                                                 assign = new CompilerAssign (new LocalVariableReference (li, Location.Null), source, Location.Null);
6876                                                 Block.AddScopeStatement (new StatementExpression (assign, Location.Null));
6877                                         }
6878                                 } else {
6879                                         type = type_expr.ResolveAsType (bc);
6880                                         if (type == null)
6881                                                 return false;
6882
6883                                         if (li == null)
6884                                                 CreateExceptionVariable (type);
6885
6886                                         if (type.BuiltinType != BuiltinTypeSpec.Type.Exception && !TypeSpec.IsBaseClass (type, bc.BuiltinTypes.Exception, false)) {
6887                                                 bc.Report.Error (155, loc, "The type caught or thrown must be derived from System.Exception");
6888                                         } else if (li != null) {
6889                                                 li.Type = type;
6890                                                 li.PrepareAssignmentAnalysis (bc);
6891
6892                                                 // source variable is at the top of the stack
6893                                                 Expression source = new EmptyExpression (li.Type);
6894                                                 if (li.Type.IsGenericParameter)
6895                                                         source = new UnboxCast (source, li.Type);
6896
6897                                                 if (!block.HasAwait || Filter != null)
6898                                                         block.AddScopeStatement (new CatchVariableStore (this));
6899
6900                                                 //
6901                                                 // Uses Location.Null to hide from symbol file
6902                                                 //
6903                                                 assign = new CompilerAssign (new LocalVariableReference (li, Location.Null), source, Location.Null);
6904                                                 Block.AddScopeStatement (new StatementExpression (assign, Location.Null));
6905                                         }
6906                                 }
6907
6908                                 if (Filter != null) {
6909                                         Block.AddScopeStatement (new FilterStatement (this));
6910                                 }
6911
6912                                 Block.SetCatchBlock ();
6913                                 return Block.Resolve (bc);
6914                         }
6915                 }
6916
6917                 bool CreateExceptionVariable (TypeSpec type)
6918                 {
6919                         if (!Block.HasAwait)
6920                                 return false;
6921
6922                         // TODO: Scan the block for rethrow expression
6923                         //if (!Block.HasRethrow)
6924                         //      return;
6925
6926                         li = LocalVariable.CreateCompilerGenerated (type, block, Location.Null);
6927                         return true;
6928                 }
6929
6930                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6931                 {
6932                         if (li != null && !li.IsCompilerGenerated) {
6933                                 fc.SetVariableAssigned (li.VariableInfo, true);
6934                         }
6935
6936                         return block.FlowAnalysis (fc);
6937                 }
6938
6939                 public override Reachability MarkReachable (Reachability rc)
6940                 {
6941                         base.MarkReachable (rc);
6942
6943                         var c = Filter as Constant;
6944                         if (c != null && c.IsDefaultValue)
6945                                 return Reachability.CreateUnreachable ();
6946
6947                         return block.MarkReachable (rc);
6948                 }
6949
6950                 protected override void CloneTo (CloneContext clonectx, Statement t)
6951                 {
6952                         Catch target = (Catch) t;
6953
6954                         if (type_expr != null)
6955                                 target.type_expr = (FullNamedExpression) type_expr.Clone (clonectx);
6956
6957                         if (Filter != null)
6958                                 target.Filter = Filter.Clone (clonectx);
6959
6960                         target.block = (ExplicitBlock) clonectx.LookupBlock (block);
6961                 }
6962         }
6963
6964         public class TryFinally : TryFinallyBlock
6965         {
6966                 ExplicitBlock fini;
6967                 List<DefiniteAssignmentBitSet> try_exit_dat;
6968                 List<Label> redirected_jumps;
6969                 Label? start_fin_label;
6970
6971                 public TryFinally (Statement stmt, ExplicitBlock fini, Location loc)
6972                          : base (stmt, loc)
6973                 {
6974                         this.fini = fini;
6975                 }
6976
6977                 public ExplicitBlock FinallyBlock {
6978                         get {
6979                                 return fini;
6980                         }
6981                 }
6982
6983                 public void RegisterForControlExitCheck (DefiniteAssignmentBitSet vector)
6984                 {
6985                         if (try_exit_dat == null)
6986                                 try_exit_dat = new List<DefiniteAssignmentBitSet> ();
6987
6988                         try_exit_dat.Add (vector);
6989                 }
6990
6991                 public override bool Resolve (BlockContext bc)
6992                 {
6993                         bool ok = base.Resolve (bc);
6994
6995                         fini.SetFinallyBlock ();
6996                         using (bc.Set (ResolveContext.Options.FinallyScope)) {
6997                                 ok &= fini.Resolve (bc);
6998                         }
6999
7000                         return ok;
7001                 }
7002
7003                 protected override void EmitTryBody (EmitContext ec)
7004                 {
7005                         if (fini.HasAwait) {
7006                                 if (ec.TryFinallyUnwind == null)
7007                                         ec.TryFinallyUnwind = new List<TryFinally> ();
7008
7009                                 ec.TryFinallyUnwind.Add (this);
7010                                 stmt.Emit (ec);
7011
7012                                 if (first_catch_resume_pc < 0 && stmt is TryCatch)
7013                                         ec.EndExceptionBlock ();
7014
7015                                 ec.TryFinallyUnwind.Remove (this);
7016
7017                                 if (start_fin_label != null)
7018                                         ec.MarkLabel (start_fin_label.Value);
7019
7020                                 return;
7021                         }
7022
7023                         stmt.Emit (ec);
7024                 }
7025
7026                 protected override bool EmitBeginFinallyBlock (EmitContext ec)
7027                 {
7028                         if (fini.HasAwait)
7029                                 return false;
7030
7031                         return base.EmitBeginFinallyBlock (ec);
7032                 }
7033
7034                 public override void EmitFinallyBody (EmitContext ec)
7035                 {
7036                         if (!fini.HasAwait) {
7037                                 fini.Emit (ec);
7038                                 return;
7039                         }
7040
7041                         //
7042                         // Emits catch block like
7043                         //
7044                         // catch (object temp) {
7045                         //      this.exception_field = temp;
7046                         // }
7047                         //
7048                         var type = ec.BuiltinTypes.Object;
7049                         ec.BeginCatchBlock (type);
7050
7051                         var temp = ec.GetTemporaryLocal (type);
7052                         ec.Emit (OpCodes.Stloc, temp);
7053
7054                         var exception_field = ec.GetTemporaryField (type);
7055                         exception_field.AutomaticallyReuse = false;
7056                         ec.EmitThis ();
7057                         ec.Emit (OpCodes.Ldloc, temp);
7058                         exception_field.EmitAssignFromStack (ec);
7059
7060                         ec.EndExceptionBlock ();
7061
7062                         ec.FreeTemporaryLocal (temp, type);
7063
7064                         fini.Emit (ec);
7065
7066                         //
7067                         // Emits exception rethrow
7068                         //
7069                         // if (this.exception_field != null)
7070                         //      throw this.exception_field;
7071                         //
7072                         exception_field.Emit (ec);
7073                         var skip_throw = ec.DefineLabel ();
7074                         ec.Emit (OpCodes.Brfalse_S, skip_throw);
7075                         exception_field.Emit (ec);
7076                         ec.Emit (OpCodes.Throw);
7077                         ec.MarkLabel (skip_throw);
7078
7079                         exception_field.PrepareCleanup (ec);
7080
7081                         EmitUnwindFinallyTable (ec);
7082                 }
7083
7084                 bool IsParentBlock (Block block)
7085                 {
7086                         for (Block b = fini; b != null; b = b.Parent) {
7087                                 if (b == block)
7088                                         return true;
7089                         }
7090
7091                         return false;
7092                 }
7093
7094                 public static Label EmitRedirectedJump (EmitContext ec, AsyncInitializer initializer, Label label, Block labelBlock)
7095                 {
7096                         int idx;
7097                         if (labelBlock != null) {
7098                                 for (idx = ec.TryFinallyUnwind.Count; idx != 0; --idx) {
7099                                         var fin = ec.TryFinallyUnwind [idx - 1];
7100                                         if (!fin.IsParentBlock (labelBlock))
7101                                                 break;
7102                                 }
7103                         } else {
7104                                 idx = 0;
7105                         }
7106
7107                         bool set_return_state = true;
7108
7109                         for (; idx < ec.TryFinallyUnwind.Count; ++idx) {
7110                                 var fin = ec.TryFinallyUnwind [idx];
7111                                 if (labelBlock != null && !fin.IsParentBlock (labelBlock))
7112                                         break;
7113
7114                                 fin.EmitRedirectedExit (ec, label, initializer, set_return_state);
7115                                 set_return_state = false;
7116
7117                                 if (fin.start_fin_label == null) {
7118                                         fin.start_fin_label = ec.DefineLabel ();
7119                                 }
7120
7121                                 label = fin.start_fin_label.Value;
7122                         }
7123
7124                         return label;
7125                 }
7126
7127                 public static Label EmitRedirectedReturn (EmitContext ec, AsyncInitializer initializer)
7128                 {
7129                         return EmitRedirectedJump (ec, initializer, initializer.BodyEnd, null);
7130                 }
7131
7132                 void EmitRedirectedExit (EmitContext ec, Label label, AsyncInitializer initializer, bool setReturnState)
7133                 {
7134                         if (redirected_jumps == null) {
7135                                 redirected_jumps = new List<Label> ();
7136
7137                                 // Add fallthrough label
7138                                 redirected_jumps.Add (ec.DefineLabel ());
7139
7140                                 if (setReturnState)
7141                                         initializer.HoistedReturnState = ec.GetTemporaryField (ec.Module.Compiler.BuiltinTypes.Int, true);
7142                         }
7143
7144                         int index = redirected_jumps.IndexOf (label);
7145                         if (index < 0) {
7146                                 redirected_jumps.Add (label);
7147                                 index = redirected_jumps.Count - 1;
7148                         }
7149
7150                         //
7151                         // Indicates we have captured exit jump
7152                         //
7153                         if (setReturnState) {
7154                                 var value = new IntConstant (initializer.HoistedReturnState.Type, index, Location.Null);
7155                                 initializer.HoistedReturnState.EmitAssign (ec, value, false, false);
7156                         }
7157                 }
7158
7159                 //
7160                 // Emits state table of jumps outside of try block and reload of return
7161                 // value when try block returns value
7162                 //
7163                 void EmitUnwindFinallyTable (EmitContext ec)
7164                 {
7165                         if (redirected_jumps == null)
7166                                 return;
7167
7168                         var initializer = (AsyncInitializer)ec.CurrentAnonymousMethod;
7169                         initializer.HoistedReturnState.EmitLoad (ec);
7170                         ec.Emit (OpCodes.Switch, redirected_jumps.ToArray ());
7171
7172                         // Mark fallthrough label
7173                         ec.MarkLabel (redirected_jumps [0]);
7174                 }
7175
7176                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
7177                 {
7178                         var da = fc.BranchDefiniteAssignment ();
7179
7180                         var tf = fc.TryFinally;
7181                         fc.TryFinally = this;
7182
7183                         var res_stmt = Statement.FlowAnalysis (fc);
7184
7185                         fc.TryFinally = tf;
7186
7187                         var try_da = fc.DefiniteAssignment;
7188                         fc.DefiniteAssignment = da;
7189
7190                         var res_fin = fini.FlowAnalysis (fc);
7191
7192                         if (try_exit_dat != null) {
7193                                 //
7194                                 // try block has global exit but we need to run definite assignment check
7195                                 // for parameter block out parameter after finally block because it's always
7196                                 // executed before exit
7197                                 //
7198                                 foreach (var try_da_part in try_exit_dat)
7199                                         fc.ParametersBlock.CheckControlExit (fc, fc.DefiniteAssignment | try_da_part);
7200
7201                                 try_exit_dat = null;
7202                         }
7203
7204                         fc.DefiniteAssignment |= try_da;
7205                         return res_stmt | res_fin;
7206                 }
7207
7208                 public override Reachability MarkReachable (Reachability rc)
7209                 {
7210                         //
7211                         // Mark finally block first for any exit statement in try block
7212                         // to know whether the code which follows finally is reachable
7213                         //
7214                         return fini.MarkReachable (rc) | base.MarkReachable (rc);
7215                 }
7216
7217                 protected override void CloneTo (CloneContext clonectx, Statement t)
7218                 {
7219                         TryFinally target = (TryFinally) t;
7220
7221                         target.stmt = stmt.Clone (clonectx);
7222                         if (fini != null)
7223                                 target.fini = (ExplicitBlock) clonectx.LookupBlock (fini);
7224                 }
7225
7226                 public override object Accept (StructuralVisitor visitor)
7227                 {
7228                         return visitor.Visit (this);
7229                 }
7230         }
7231
7232         public class TryCatch : ExceptionStatement
7233         {
7234                 public Block Block;
7235                 List<Catch> clauses;
7236                 readonly bool inside_try_finally;
7237                 List<Catch> catch_sm;
7238
7239                 public TryCatch (Block block, List<Catch> catch_clauses, Location l, bool inside_try_finally)
7240                         : base (l)
7241                 {
7242                         this.Block = block;
7243                         this.clauses = catch_clauses;
7244                         this.inside_try_finally = inside_try_finally;
7245                 }
7246
7247                 public List<Catch> Clauses {
7248                         get {
7249                                 return clauses;
7250                         }
7251                 }
7252
7253                 public bool HasClauseWithAwait {
7254                         get {
7255                                 return catch_sm != null;
7256                         }
7257                 }
7258
7259                 public bool IsTryCatchFinally {
7260                         get {
7261                                 return inside_try_finally;
7262                         }
7263                 }
7264
7265                 public override bool Resolve (BlockContext bc)
7266                 {
7267                         bool ok;
7268
7269                         using (bc.Set (ResolveContext.Options.TryScope)) {
7270
7271                                 parent_try_block = bc.CurrentTryBlock;
7272
7273                                 if (IsTryCatchFinally) {
7274                                         ok = Block.Resolve (bc);
7275                                 } else {
7276                                         using (bc.Set (ResolveContext.Options.TryWithCatchScope)) {
7277                                                 bc.CurrentTryBlock = this;
7278                                                 ok = Block.Resolve (bc);
7279                                                 bc.CurrentTryBlock = parent_try_block;
7280                                         }
7281                                 }
7282                         }
7283
7284                         var prev_catch = bc.CurrentTryCatch;
7285                         bc.CurrentTryCatch = this;
7286
7287                         for (int i = 0; i < clauses.Count; ++i) {
7288                                 var c = clauses[i];
7289
7290                                 ok &= c.Resolve (bc);
7291
7292                                 if (c.Block.HasAwait) {
7293                                         if (catch_sm == null)
7294                                                 catch_sm = new List<Catch> ();
7295
7296                                         catch_sm.Add (c);
7297                                 }
7298
7299                                 if (c.Filter != null)
7300                                         continue;
7301
7302                                 TypeSpec resolved_type = c.CatchType;
7303                                 if (resolved_type == null)
7304                                         continue;
7305
7306                                 for (int ii = 0; ii < clauses.Count; ++ii) {
7307                                         if (ii == i)
7308                                                 continue;
7309
7310                                         if (clauses[ii].Filter != null)
7311                                                 continue;
7312
7313                                         if (clauses[ii].IsGeneral) {
7314                                                 if (resolved_type.BuiltinType != BuiltinTypeSpec.Type.Exception)
7315                                                         continue;
7316
7317                                                 if (!bc.Module.DeclaringAssembly.WrapNonExceptionThrows)
7318                                                         continue;
7319
7320                                                 if (!bc.Module.PredefinedAttributes.RuntimeCompatibility.IsDefined)
7321                                                         continue;
7322
7323                                                 bc.Report.Warning (1058, 1, c.loc,
7324                                                         "A previous catch clause already catches all exceptions. All non-exceptions thrown will be wrapped in a `System.Runtime.CompilerServices.RuntimeWrappedException'");
7325
7326                                                 continue;
7327                                         }
7328
7329                                         if (ii >= i)
7330                                                 continue;
7331
7332                                         var ct = clauses[ii].CatchType;
7333                                         if (ct == null)
7334                                                 continue;
7335
7336                                         if (resolved_type == ct || TypeSpec.IsBaseClass (resolved_type, ct, true)) {
7337                                                 bc.Report.Error (160, c.loc,
7338                                                         "A previous catch clause already catches all exceptions of this or a super type `{0}'",
7339                                                         ct.GetSignatureForError ());
7340                                                 ok = false;
7341                                         }
7342                                 }
7343                         }
7344
7345                         bc.CurrentTryCatch = prev_catch;
7346
7347                         return base.Resolve (bc) && ok;
7348                 }
7349
7350                 protected sealed override void DoEmit (EmitContext ec)
7351                 {
7352                         if (!inside_try_finally)
7353                                 EmitTryBodyPrepare (ec);
7354
7355                         Block.Emit (ec);
7356
7357                         LocalBuilder state_variable = null;
7358                         foreach (Catch c in clauses) {
7359                                 c.Emit (ec);
7360
7361                                 if (catch_sm != null) {
7362                                         if (state_variable == null) {
7363                                                 //
7364                                                 // Cannot reuse temp variable because non-catch path assumes the value is 0
7365                                                 // which may not be true for reused local variable
7366                                                 //
7367                                                 state_variable = ec.DeclareLocal (ec.Module.Compiler.BuiltinTypes.Int, false);
7368                                         }
7369
7370                                         var index = catch_sm.IndexOf (c);
7371                                         if (index < 0)
7372                                                 continue;
7373
7374                                         ec.EmitInt (index + 1);
7375                                         ec.Emit (OpCodes.Stloc, state_variable);
7376                                 }
7377                         }
7378
7379                         if (state_variable == null) {
7380                                 if (!inside_try_finally)
7381                                         ec.EndExceptionBlock ();
7382                         } else {
7383                                 ec.EndExceptionBlock ();
7384
7385                                 ec.Emit (OpCodes.Ldloc, state_variable);
7386
7387                                 var labels = new Label [catch_sm.Count + 1];
7388                                 for (int i = 0; i < labels.Length; ++i) {
7389                                         labels [i] = ec.DefineLabel ();
7390                                 }
7391
7392                                 var end = ec.DefineLabel ();
7393                                 ec.Emit (OpCodes.Switch, labels);
7394
7395                                 // 0 value is default label
7396                                 ec.MarkLabel (labels [0]);
7397                                 ec.Emit (OpCodes.Br, end);
7398
7399                                 var atv = ec.AsyncThrowVariable;
7400                                 Catch c = null;
7401                                 for (int i = 0; i < catch_sm.Count; ++i) {
7402                                         if (c != null && c.Block.HasReachableClosingBrace)
7403                                                 ec.Emit (OpCodes.Br, end);
7404
7405                                         ec.MarkLabel (labels [i + 1]);
7406                                         c = catch_sm [i];
7407                                         ec.AsyncThrowVariable = c.Variable;
7408                                         c.Block.Emit (ec);
7409                                 }
7410                                 ec.AsyncThrowVariable = atv;
7411
7412                                 ec.MarkLabel (end);
7413                         }
7414                 }
7415
7416                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
7417                 {
7418                         var start_fc = fc.BranchDefiniteAssignment ();
7419                         var res = Block.FlowAnalysis (fc);
7420
7421                         DefiniteAssignmentBitSet try_fc = res ? null : fc.DefiniteAssignment;
7422
7423                         foreach (var c in clauses) {
7424                                 fc.BranchDefiniteAssignment (start_fc);
7425                                 if (!c.FlowAnalysis (fc)) {
7426                                         if (try_fc == null)
7427                                                 try_fc = fc.DefiniteAssignment;
7428                                         else
7429                                                 try_fc &= fc.DefiniteAssignment;
7430
7431                                         res = false;
7432                                 }
7433                         }
7434
7435                         fc.DefiniteAssignment = try_fc ?? start_fc;
7436                         parent_try_block = null;
7437                         return res;
7438                 }
7439
7440                 public override Reachability MarkReachable (Reachability rc)
7441                 {
7442                         if (rc.IsUnreachable)
7443                                 return rc;
7444
7445                         base.MarkReachable (rc);
7446
7447                         var tc_rc = Block.MarkReachable (rc);
7448
7449                         foreach (var c in clauses)
7450                                 tc_rc &= c.MarkReachable (rc);
7451
7452                         return tc_rc;
7453                 }
7454
7455                 protected override void CloneTo (CloneContext clonectx, Statement t)
7456                 {
7457                         TryCatch target = (TryCatch) t;
7458
7459                         target.Block = clonectx.LookupBlock (Block);
7460                         if (clauses != null){
7461                                 target.clauses = new List<Catch> ();
7462                                 foreach (Catch c in clauses)
7463                                         target.clauses.Add ((Catch) c.Clone (clonectx));
7464                         }
7465                 }
7466
7467                 public override object Accept (StructuralVisitor visitor)
7468                 {
7469                         return visitor.Visit (this);
7470                 }
7471         }
7472
7473         public class Using : TryFinallyBlock
7474         {
7475                 public class VariableDeclaration : BlockVariable
7476                 {
7477                         Statement dispose_call;
7478
7479                         public VariableDeclaration (FullNamedExpression type, LocalVariable li)
7480                                 : base (type, li)
7481                         {
7482                         }
7483
7484                         public VariableDeclaration (LocalVariable li, Location loc)
7485                                 : base (li)
7486                         {
7487                                 reachable = true;
7488                                 this.loc = loc;
7489                         }
7490
7491                         public VariableDeclaration (Expression expr)
7492                                 : base (null)
7493                         {
7494                                 loc = expr.Location;
7495                                 Initializer = expr;
7496                         }
7497
7498                         #region Properties
7499
7500                         public bool IsNested { get; private set; }
7501
7502                         #endregion
7503
7504                         public void EmitDispose (EmitContext ec)
7505                         {
7506                                 dispose_call.Emit (ec);
7507                         }
7508
7509                         public override bool Resolve (BlockContext bc)
7510                         {
7511                                 if (IsNested)
7512                                         return true;
7513
7514                                 return base.Resolve (bc, false);
7515                         }
7516
7517                         public Expression ResolveExpression (BlockContext bc)
7518                         {
7519                                 var e = Initializer.Resolve (bc);
7520                                 if (e == null)
7521                                         return null;
7522
7523                                 li = LocalVariable.CreateCompilerGenerated (e.Type, bc.CurrentBlock, loc);
7524                                 Initializer = ResolveInitializer (bc, Variable, e);
7525                                 return e;
7526                         }
7527
7528                         protected override Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
7529                         {
7530                                 if (li.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
7531                                         initializer = initializer.Resolve (bc);
7532                                         if (initializer == null)
7533                                                 return null;
7534
7535                                         // Once there is dynamic used defer conversion to runtime even if we know it will never succeed
7536                                         Arguments args = new Arguments (1);
7537                                         args.Add (new Argument (initializer));
7538                                         initializer = new DynamicConversion (bc.BuiltinTypes.IDisposable, 0, args, initializer.Location).Resolve (bc);
7539                                         if (initializer == null)
7540                                                 return null;
7541
7542                                         var var = LocalVariable.CreateCompilerGenerated (initializer.Type, bc.CurrentBlock, loc);
7543                                         dispose_call = CreateDisposeCall (bc, var);
7544                                         dispose_call.Resolve (bc);
7545
7546                                         return base.ResolveInitializer (bc, li, new SimpleAssign (var.CreateReferenceExpression (bc, loc), initializer, loc));
7547                                 }
7548
7549                                 if (li == Variable) {
7550                                         CheckIDiposableConversion (bc, li, initializer);
7551                                         dispose_call = CreateDisposeCall (bc, li);
7552                                         dispose_call.Resolve (bc);
7553                                 }
7554
7555                                 return base.ResolveInitializer (bc, li, initializer);
7556                         }
7557
7558                         protected virtual void CheckIDiposableConversion (BlockContext bc, LocalVariable li, Expression initializer)
7559                         {
7560                                 var type = li.Type;
7561
7562                                 if (type.BuiltinType != BuiltinTypeSpec.Type.IDisposable && !CanConvertToIDisposable (bc, type)) {
7563                                         if (type.IsNullableType) {
7564                                                 // it's handled in CreateDisposeCall
7565                                                 return;
7566                                         }
7567
7568                                         if (type != InternalType.ErrorType) {
7569                                                 bc.Report.SymbolRelatedToPreviousError (type);
7570                                                 var loc = type_expr == null ? initializer.Location : type_expr.Location;
7571                                                 bc.Report.Error (1674, loc, "`{0}': type used in a using statement must be implicitly convertible to `System.IDisposable'",
7572                                                         type.GetSignatureForError ());
7573                                         }
7574
7575                                         return;
7576                                 }
7577                         }
7578
7579                         static bool CanConvertToIDisposable (BlockContext bc, TypeSpec type)
7580                         {
7581                                 var target = bc.BuiltinTypes.IDisposable;
7582                                 var tp = type as TypeParameterSpec;
7583                                 if (tp != null)
7584                                         return Convert.ImplicitTypeParameterConversion (null, tp, target) != null;
7585
7586                                 return type.ImplementsInterface (target, false);
7587                         }
7588
7589                         protected virtual Statement CreateDisposeCall (BlockContext bc, LocalVariable lv)
7590                         {
7591                                 var lvr = lv.CreateReferenceExpression (bc, lv.Location);
7592                                 var type = lv.Type;
7593                                 var loc = lv.Location;
7594
7595                                 var idt = bc.BuiltinTypes.IDisposable;
7596                                 var m = bc.Module.PredefinedMembers.IDisposableDispose.Resolve (loc);
7597
7598                                 var dispose_mg = MethodGroupExpr.CreatePredefined (m, idt, loc);
7599                                 dispose_mg.InstanceExpression = type.IsNullableType ?
7600                                         new Cast (new TypeExpression (idt, loc), lvr, loc).Resolve (bc) :
7601                                         lvr;
7602
7603                                 //
7604                                 // Hide it from symbol file via null location
7605                                 //
7606                                 Statement dispose = new StatementExpression (new Invocation (dispose_mg, null), Location.Null);
7607
7608                                 // Add conditional call when disposing possible null variable
7609                                 if (!TypeSpec.IsValueType (type) || type.IsNullableType)
7610                                         dispose = new If (new Binary (Binary.Operator.Inequality, lvr, new NullLiteral (loc)), dispose, dispose.loc);
7611
7612                                 return dispose;
7613                         }
7614
7615                         public void ResolveDeclaratorInitializer (BlockContext bc)
7616                         {
7617                                 Initializer = base.ResolveInitializer (bc, Variable, Initializer);
7618                         }
7619
7620                         public Statement RewriteUsingDeclarators (BlockContext bc, Statement stmt)
7621                         {
7622                                 for (int i = declarators.Count - 1; i >= 0; --i) {
7623                                         var d = declarators [i];
7624                                         var vd = new VariableDeclaration (d.Variable, d.Variable.Location);
7625                                         vd.Initializer = d.Initializer;
7626                                         vd.IsNested = true;
7627                                         vd.dispose_call = CreateDisposeCall (bc, d.Variable);
7628                                         vd.dispose_call.Resolve (bc);
7629
7630                                         stmt = new Using (vd, stmt, d.Variable.Location);
7631                                 }
7632
7633                                 declarators = null;
7634                                 return stmt;
7635                         }
7636
7637                         public override object Accept (StructuralVisitor visitor)
7638                         {
7639                                 return visitor.Visit (this);
7640                         }
7641                 }
7642
7643                 VariableDeclaration decl;
7644
7645                 public Using (VariableDeclaration decl, Statement stmt, Location loc)
7646                         : base (stmt, loc)
7647                 {
7648                         this.decl = decl;
7649                 }
7650
7651                 public Using (Expression expr, Statement stmt, Location loc)
7652                         : base (stmt, loc)
7653                 {
7654                         this.decl = new VariableDeclaration (expr);
7655                 }
7656
7657                 #region Properties
7658
7659                 public Expression Expr {
7660                         get {
7661                                 return decl.Variable == null ? decl.Initializer : null;
7662                         }
7663                 }
7664
7665                 public BlockVariable Variables {
7666                         get {
7667                                 return decl;
7668                         }
7669                 }
7670
7671                 #endregion
7672
7673                 public override void Emit (EmitContext ec)
7674                 {
7675                         //
7676                         // Don't emit sequence point it will be set on variable declaration
7677                         //
7678                         DoEmit (ec);
7679                 }
7680
7681                 protected override void EmitTryBodyPrepare (EmitContext ec)
7682                 {
7683                         decl.Emit (ec);
7684                         base.EmitTryBodyPrepare (ec);
7685                 }
7686
7687                 protected override void EmitTryBody (EmitContext ec)
7688                 {
7689                         stmt.Emit (ec);
7690                 }
7691
7692                 public override void EmitFinallyBody (EmitContext ec)
7693                 {
7694                         decl.EmitDispose (ec);
7695                 }
7696
7697                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
7698                 {
7699                         decl.FlowAnalysis (fc);
7700                         return stmt.FlowAnalysis (fc);
7701                 }
7702
7703                 public override Reachability MarkReachable (Reachability rc)
7704                 {
7705                         decl.MarkReachable (rc);
7706                         return base.MarkReachable (rc);
7707                 }
7708
7709                 public override bool Resolve (BlockContext ec)
7710                 {
7711                         VariableReference vr;
7712                         bool vr_locked = false;
7713
7714                         using (ec.Set (ResolveContext.Options.UsingInitializerScope)) {
7715                                 if (decl.Variable == null) {
7716                                         vr = decl.ResolveExpression (ec) as VariableReference;
7717                                         if (vr != null) {
7718                                                 vr_locked = vr.IsLockedByStatement;
7719                                                 vr.IsLockedByStatement = true;
7720                                         }
7721                                 } else {
7722                                         if (decl.IsNested) {
7723                                                 decl.ResolveDeclaratorInitializer (ec);
7724                                         } else {
7725                                                 if (!decl.Resolve (ec))
7726                                                         return false;
7727
7728                                                 if (decl.Declarators != null) {
7729                                                         stmt = decl.RewriteUsingDeclarators (ec, stmt);
7730                                                 }
7731                                         }
7732
7733                                         vr = null;
7734                                 }
7735                         }
7736
7737                         var ok = base.Resolve (ec);
7738
7739                         if (vr != null)
7740                                 vr.IsLockedByStatement = vr_locked;
7741
7742                         return ok;
7743                 }
7744
7745                 protected override void CloneTo (CloneContext clonectx, Statement t)
7746                 {
7747                         Using target = (Using) t;
7748
7749                         target.decl = (VariableDeclaration) decl.Clone (clonectx);
7750                         target.stmt = stmt.Clone (clonectx);
7751                 }
7752
7753                 public override object Accept (StructuralVisitor visitor)
7754                 {
7755                         return visitor.Visit (this);
7756                 }
7757         }
7758
7759         /// <summary>
7760         ///   Implementation of the foreach C# statement
7761         /// </summary>
7762         public class Foreach : LoopStatement
7763         {
7764                 abstract class IteratorStatement : Statement
7765                 {
7766                         protected readonly Foreach for_each;
7767
7768                         protected IteratorStatement (Foreach @foreach)
7769                         {
7770                                 this.for_each = @foreach;
7771                                 this.loc = @foreach.expr.Location;
7772                         }
7773
7774                         protected override void CloneTo (CloneContext clonectx, Statement target)
7775                         {
7776                                 throw new NotImplementedException ();
7777                         }
7778
7779                         public override void Emit (EmitContext ec)
7780                         {
7781                                 if (ec.EmitAccurateDebugInfo) {
7782                                         ec.Emit (OpCodes.Nop);
7783                                 }
7784
7785                                 base.Emit (ec);
7786                         }
7787
7788                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
7789                         {
7790                                 throw new NotImplementedException ();
7791                         }
7792                 }
7793
7794                 sealed class ArrayForeach : IteratorStatement
7795                 {
7796                         TemporaryVariableReference[] lengths;
7797                         Expression [] length_exprs;
7798                         StatementExpression[] counter;
7799                         TemporaryVariableReference[] variables;
7800
7801                         TemporaryVariableReference copy;
7802
7803                         public ArrayForeach (Foreach @foreach, int rank)
7804                                 : base (@foreach)
7805                         {
7806                                 counter = new StatementExpression[rank];
7807                                 variables = new TemporaryVariableReference[rank];
7808                                 length_exprs = new Expression [rank];
7809
7810                                 //
7811                                 // Only use temporary length variables when dealing with
7812                                 // multi-dimensional arrays
7813                                 //
7814                                 if (rank > 1)
7815                                         lengths = new TemporaryVariableReference [rank];
7816                         }
7817
7818                         public override bool Resolve (BlockContext ec)
7819                         {
7820                                 Block variables_block = for_each.variable.Block;
7821                                 copy = TemporaryVariableReference.Create (for_each.expr.Type, variables_block, loc);
7822                                 copy.Resolve (ec);
7823
7824                                 int rank = length_exprs.Length;
7825                                 Arguments list = new Arguments (rank);
7826                                 for (int i = 0; i < rank; i++) {
7827                                         var v = TemporaryVariableReference.Create (ec.BuiltinTypes.Int, variables_block, loc);
7828                                         variables[i] = v;
7829                                         counter[i] = new StatementExpression (new UnaryMutator (UnaryMutator.Mode.PostIncrement, v, Location.Null));
7830                                         counter[i].Resolve (ec);
7831
7832                                         if (rank == 1) {
7833                                                 length_exprs [i] = new MemberAccess (copy, "Length").Resolve (ec);
7834                                         } else {
7835                                                 lengths[i] = TemporaryVariableReference.Create (ec.BuiltinTypes.Int, variables_block, loc);
7836                                                 lengths[i].Resolve (ec);
7837
7838                                                 Arguments args = new Arguments (1);
7839                                                 args.Add (new Argument (new IntConstant (ec.BuiltinTypes, i, loc)));
7840                                                 length_exprs [i] = new Invocation (new MemberAccess (copy, "GetLength"), args).Resolve (ec);
7841                                         }
7842
7843                                         list.Add (new Argument (v));
7844                                 }
7845
7846                                 var access = new ElementAccess (copy, list, loc).Resolve (ec);
7847                                 if (access == null)
7848                                         return false;
7849
7850                                 TypeSpec var_type;
7851                                 if (for_each.type is VarExpr) {
7852                                         // Infer implicitly typed local variable from foreach array type
7853                                         var_type = access.Type;
7854                                 } else {
7855                                         var_type = for_each.type.ResolveAsType (ec);
7856
7857                                         if (var_type == null)
7858                                                 return false;
7859
7860                                         access = Convert.ExplicitConversion (ec, access, var_type, loc);
7861                                         if (access == null)
7862                                                 return false;
7863                                 }
7864
7865                                 for_each.variable.Type = var_type;
7866
7867                                 var prev_block = ec.CurrentBlock;
7868                                 ec.CurrentBlock = variables_block;
7869                                 var variable_ref = new LocalVariableReference (for_each.variable, loc).Resolve (ec);
7870                                 ec.CurrentBlock = prev_block;
7871
7872                                 if (variable_ref == null)
7873                                         return false;
7874
7875                                 for_each.body.AddScopeStatement (new StatementExpression (new CompilerAssign (variable_ref, access, Location.Null), for_each.type.Location));
7876
7877                                 return for_each.body.Resolve (ec);
7878                         }
7879
7880                         protected override void DoEmit (EmitContext ec)
7881                         {
7882                                 copy.EmitAssign (ec, for_each.expr);
7883
7884                                 int rank = length_exprs.Length;
7885                                 Label[] test = new Label [rank];
7886                                 Label[] loop = new Label [rank];
7887
7888                                 for (int i = 0; i < rank; i++) {
7889                                         test [i] = ec.DefineLabel ();
7890                                         loop [i] = ec.DefineLabel ();
7891
7892                                         if (lengths != null)
7893                                                 lengths [i].EmitAssign (ec, length_exprs [i]);
7894                                 }
7895
7896                                 IntConstant zero = new IntConstant (ec.BuiltinTypes, 0, loc);
7897                                 for (int i = 0; i < rank; i++) {
7898                                         variables [i].EmitAssign (ec, zero);
7899
7900                                         ec.Emit (OpCodes.Br, test [i]);
7901                                         ec.MarkLabel (loop [i]);
7902                                 }
7903
7904                                 for_each.body.Emit (ec);
7905
7906                                 ec.MarkLabel (ec.LoopBegin);
7907                                 ec.Mark (for_each.expr.Location);
7908
7909                                 for (int i = rank - 1; i >= 0; i--){
7910                                         counter [i].Emit (ec);
7911
7912                                         ec.MarkLabel (test [i]);
7913                                         variables [i].Emit (ec);
7914
7915                                         if (lengths != null)
7916                                                 lengths [i].Emit (ec);
7917                                         else
7918                                                 length_exprs [i].Emit (ec);
7919
7920                                         ec.Emit (OpCodes.Blt, loop [i]);
7921                                 }
7922
7923                                 ec.MarkLabel (ec.LoopEnd);
7924                         }
7925                 }
7926
7927                 sealed class CollectionForeach : IteratorStatement, OverloadResolver.IErrorHandler
7928                 {
7929                         class RuntimeDispose : Using.VariableDeclaration
7930                         {
7931                                 public RuntimeDispose (LocalVariable lv, Location loc)
7932                                         : base (lv, loc)
7933                                 {
7934                                         reachable = true;
7935                                 }
7936
7937                                 protected override void CheckIDiposableConversion (BlockContext bc, LocalVariable li, Expression initializer)
7938                                 {
7939                                         // Defered to runtime check
7940                                 }
7941
7942                                 protected override Statement CreateDisposeCall (BlockContext bc, LocalVariable lv)
7943                                 {
7944                                         var idt = bc.BuiltinTypes.IDisposable;
7945
7946                                         //
7947                                         // Fabricates code like
7948                                         //
7949                                         // if ((temp = vr as IDisposable) != null) temp.Dispose ();
7950                                         //
7951
7952                                         var dispose_variable = LocalVariable.CreateCompilerGenerated (idt, bc.CurrentBlock, loc);
7953
7954                                         var idisaposable_test = new Binary (Binary.Operator.Inequality, new CompilerAssign (
7955                                                 dispose_variable.CreateReferenceExpression (bc, loc),
7956                                                 new As (lv.CreateReferenceExpression (bc, loc), new TypeExpression (dispose_variable.Type, loc), loc),
7957                                                 loc), new NullLiteral (loc));
7958
7959                                         var m = bc.Module.PredefinedMembers.IDisposableDispose.Resolve (loc);
7960
7961                                         var dispose_mg = MethodGroupExpr.CreatePredefined (m, idt, loc);
7962                                         dispose_mg.InstanceExpression = dispose_variable.CreateReferenceExpression (bc, loc);
7963
7964                                         Statement dispose = new StatementExpression (new Invocation (dispose_mg, null));
7965                                         return new If (idisaposable_test, dispose, loc);
7966                                 }
7967                         }
7968
7969                         LocalVariable variable;
7970                         Expression expr;
7971                         Statement statement;
7972                         ExpressionStatement init;
7973                         TemporaryVariableReference enumerator_variable;
7974                         bool ambiguous_getenumerator_name;
7975
7976                         public CollectionForeach (Foreach @foreach, LocalVariable var, Expression expr)
7977                                 : base (@foreach)
7978                         {
7979                                 this.variable = var;
7980                                 this.expr = expr;
7981                         }
7982
7983                         void Error_WrongEnumerator (ResolveContext rc, MethodSpec enumerator)
7984                         {
7985                                 rc.Report.SymbolRelatedToPreviousError (enumerator);
7986                                 rc.Report.Error (202, loc,
7987                                         "foreach statement requires that the return type `{0}' of `{1}' must have a suitable public MoveNext method and public Current property",
7988                                                 enumerator.ReturnType.GetSignatureForError (), enumerator.GetSignatureForError ());
7989                         }
7990
7991                         MethodGroupExpr ResolveGetEnumerator (ResolveContext rc)
7992                         {
7993                                 //
7994                                 // Option 1: Try to match by name GetEnumerator first
7995                                 //
7996                                 var mexpr = Expression.MemberLookup (rc, false, expr.Type,
7997                                         "GetEnumerator", 0, Expression.MemberLookupRestrictions.ExactArity, loc);               // TODO: What if CS0229 ?
7998
7999                                 var mg = mexpr as MethodGroupExpr;
8000                                 if (mg != null) {
8001                                         mg.InstanceExpression = expr;
8002                                         Arguments args = new Arguments (0);
8003                                         mg = mg.OverloadResolve (rc, ref args, this, OverloadResolver.Restrictions.ProbingOnly | OverloadResolver.Restrictions.GetEnumeratorLookup);
8004
8005                                         // For ambiguous GetEnumerator name warning CS0278 was reported, but Option 2 could still apply
8006                                         if (ambiguous_getenumerator_name)
8007                                                 mg = null;
8008
8009                                         if (mg != null && !mg.BestCandidate.IsStatic && mg.BestCandidate.IsPublic) {
8010                                                 return mg;
8011                                         }
8012                                 }
8013
8014                                 //
8015                                 // Option 2: Try to match using IEnumerable interfaces with preference of generic version
8016                                 //
8017                                 var t = expr.Type;
8018                                 PredefinedMember<MethodSpec> iface_candidate = null;
8019                                 var ptypes = rc.Module.PredefinedTypes;
8020                                 var gen_ienumerable = ptypes.IEnumerableGeneric;
8021                                 if (!gen_ienumerable.Define ())
8022                                         gen_ienumerable = null;
8023
8024                                 var ifaces = t.Interfaces;
8025                                 if (ifaces != null) {
8026                                         foreach (var iface in ifaces) {
8027                                                 if (gen_ienumerable != null && iface.MemberDefinition == gen_ienumerable.TypeSpec.MemberDefinition) {
8028                                                         if (iface_candidate != null && iface_candidate != rc.Module.PredefinedMembers.IEnumerableGetEnumerator) {
8029                                                                 rc.Report.SymbolRelatedToPreviousError (expr.Type);
8030                                                                 rc.Report.Error (1640, loc,
8031                                                                         "foreach statement cannot operate on variables of type `{0}' because it contains multiple implementation of `{1}'. Try casting to a specific implementation",
8032                                                                         expr.Type.GetSignatureForError (), gen_ienumerable.TypeSpec.GetSignatureForError ());
8033
8034                                                                 return null;
8035                                                         }
8036
8037                                                         // TODO: Cache this somehow
8038                                                         iface_candidate = new PredefinedMember<MethodSpec> (rc.Module, iface,
8039                                                                 MemberFilter.Method ("GetEnumerator", 0, ParametersCompiled.EmptyReadOnlyParameters, null));
8040
8041                                                         continue;
8042                                                 }
8043
8044                                                 if (iface.BuiltinType == BuiltinTypeSpec.Type.IEnumerable && iface_candidate == null) {
8045                                                         iface_candidate = rc.Module.PredefinedMembers.IEnumerableGetEnumerator;
8046                                                 }
8047                                         }
8048                                 }
8049
8050                                 if (iface_candidate == null) {
8051                                         if (expr.Type != InternalType.ErrorType) {
8052                                                 rc.Report.Error (1579, loc,
8053                                                         "foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `{1}' or is inaccessible",
8054                                                         expr.Type.GetSignatureForError (), "GetEnumerator");
8055                                         }
8056
8057                                         return null;
8058                                 }
8059
8060                                 var method = iface_candidate.Resolve (loc);
8061                                 if (method == null)
8062                                         return null;
8063
8064                                 mg = MethodGroupExpr.CreatePredefined (method, expr.Type, loc);
8065                                 mg.InstanceExpression = expr;
8066                                 return mg;
8067                         }
8068
8069                         MethodGroupExpr ResolveMoveNext (ResolveContext rc, MethodSpec enumerator)
8070                         {
8071                                 var ms = MemberCache.FindMember (enumerator.ReturnType,
8072                                         MemberFilter.Method ("MoveNext", 0, ParametersCompiled.EmptyReadOnlyParameters, rc.BuiltinTypes.Bool),
8073                                         BindingRestriction.InstanceOnly) as MethodSpec;
8074
8075                                 if (ms == null || !ms.IsPublic) {
8076                                         Error_WrongEnumerator (rc, enumerator);
8077                                         return null;
8078                                 }
8079
8080                                 return MethodGroupExpr.CreatePredefined (ms, enumerator.ReturnType, expr.Location);
8081                         }
8082
8083                         PropertySpec ResolveCurrent (ResolveContext rc, MethodSpec enumerator)
8084                         {
8085                                 var ps = MemberCache.FindMember (enumerator.ReturnType,
8086                                         MemberFilter.Property ("Current", null),
8087                                         BindingRestriction.InstanceOnly) as PropertySpec;
8088
8089                                 if (ps == null || !ps.IsPublic) {
8090                                         Error_WrongEnumerator (rc, enumerator);
8091                                         return null;
8092                                 }
8093
8094                                 return ps;
8095                         }
8096
8097                         public override bool Resolve (BlockContext ec)
8098                         {
8099                                 bool is_dynamic = expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic;
8100
8101                                 if (is_dynamic) {
8102                                         expr = Convert.ImplicitConversionRequired (ec, expr, ec.BuiltinTypes.IEnumerable, loc);
8103                                 } else if (expr.Type.IsNullableType) {
8104                                         expr = new Nullable.UnwrapCall (expr).Resolve (ec);
8105                                 }
8106
8107                                 var get_enumerator_mg = ResolveGetEnumerator (ec);
8108                                 if (get_enumerator_mg == null) {
8109                                         return false;
8110                                 }
8111
8112                                 var get_enumerator = get_enumerator_mg.BestCandidate;
8113                                 enumerator_variable = TemporaryVariableReference.Create (get_enumerator.ReturnType, variable.Block, loc);
8114                                 enumerator_variable.Resolve (ec);
8115
8116                                 // Prepare bool MoveNext ()
8117                                 var move_next_mg = ResolveMoveNext (ec, get_enumerator);
8118                                 if (move_next_mg == null) {
8119                                         return false;
8120                                 }
8121
8122                                 move_next_mg.InstanceExpression = enumerator_variable;
8123
8124                                 // Prepare ~T~ Current { get; }
8125                                 var current_prop = ResolveCurrent (ec, get_enumerator);
8126                                 if (current_prop == null) {
8127                                         return false;
8128                                 }
8129
8130                                 var current_pe = new PropertyExpr (current_prop, loc) { InstanceExpression = enumerator_variable }.Resolve (ec);
8131                                 if (current_pe == null)
8132                                         return false;
8133
8134                                 VarExpr ve = for_each.type as VarExpr;
8135
8136                                 if (ve != null) {
8137                                         if (is_dynamic) {
8138                                                 // Source type is dynamic, set element type to dynamic too
8139                                                 variable.Type = ec.BuiltinTypes.Dynamic;
8140                                         } else {
8141                                                 // Infer implicitly typed local variable from foreach enumerable type
8142                                                 variable.Type = current_pe.Type;
8143                                         }
8144                                 } else {
8145                                         if (is_dynamic) {
8146                                                 // Explicit cast of dynamic collection elements has to be done at runtime
8147                                                 current_pe = EmptyCast.Create (current_pe, ec.BuiltinTypes.Dynamic);
8148                                         }
8149
8150                                         variable.Type = for_each.type.ResolveAsType (ec);
8151
8152                                         if (variable.Type == null)
8153                                                 return false;
8154
8155                                         current_pe = Convert.ExplicitConversion (ec, current_pe, variable.Type, loc);
8156                                         if (current_pe == null)
8157                                                 return false;
8158                                 }
8159
8160                                 var prev_block = ec.CurrentBlock;
8161                                 ec.CurrentBlock = for_each.variable.Block;
8162                                 var variable_ref = new LocalVariableReference (variable, loc).Resolve (ec);
8163                                 ec.CurrentBlock = prev_block;
8164                                 if (variable_ref == null)
8165                                         return false;
8166
8167                                 for_each.body.AddScopeStatement (new StatementExpression (new CompilerAssign (variable_ref, current_pe, Location.Null), for_each.type.Location));
8168
8169                                 var init = new Invocation.Predefined (get_enumerator_mg, null);
8170
8171                                 statement = new While (new BooleanExpression (new Invocation (move_next_mg, null)),
8172                                          for_each.body, Location.Null);
8173
8174                                 var enum_type = enumerator_variable.Type;
8175
8176                                 //
8177                                 // Add Dispose method call when enumerator can be IDisposable
8178                                 //
8179                                 if (!enum_type.ImplementsInterface (ec.BuiltinTypes.IDisposable, false)) {
8180                                         if (!enum_type.IsSealed && !TypeSpec.IsValueType (enum_type)) {
8181                                                 //
8182                                                 // Runtime Dispose check
8183                                                 //
8184                                                 var vd = new RuntimeDispose (enumerator_variable.LocalInfo, Location.Null);
8185                                                 vd.Initializer = init;
8186                                                 statement = new Using (vd, statement, Location.Null);
8187                                         } else {
8188                                                 //
8189                                                 // No Dispose call needed
8190                                                 //
8191                                                 this.init = new SimpleAssign (enumerator_variable, init, Location.Null);
8192                                                 this.init.Resolve (ec);
8193                                         }
8194                                 } else {
8195                                         //
8196                                         // Static Dispose check
8197                                         //
8198                                         var vd = new Using.VariableDeclaration (enumerator_variable.LocalInfo, Location.Null);
8199                                         vd.Initializer = init;
8200                                         statement = new Using (vd, statement, Location.Null);
8201                                 }
8202
8203                                 return statement.Resolve (ec);
8204                         }
8205
8206                         protected override void DoEmit (EmitContext ec)
8207                         {
8208                                 enumerator_variable.LocalInfo.CreateBuilder (ec);
8209
8210                                 if (init != null)
8211                                         init.EmitStatement (ec);
8212
8213                                 statement.Emit (ec);
8214                         }
8215
8216                         #region IErrorHandler Members
8217
8218                         bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext ec, MemberSpec best, MemberSpec ambiguous)
8219                         {
8220                                 ec.Report.SymbolRelatedToPreviousError (best);
8221                                 ec.Report.Warning (278, 2, expr.Location,
8222                                         "`{0}' contains ambiguous implementation of `{1}' pattern. Method `{2}' is ambiguous with method `{3}'",
8223                                         expr.Type.GetSignatureForError (), "enumerable",
8224                                         best.GetSignatureForError (), ambiguous.GetSignatureForError ());
8225
8226                                 ambiguous_getenumerator_name = true;
8227                                 return true;
8228                         }
8229
8230                         bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
8231                         {
8232                                 return false;
8233                         }
8234
8235                         bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
8236                         {
8237                                 return false;
8238                         }
8239
8240                         bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
8241                         {
8242                                 return false;
8243                         }
8244
8245                         #endregion
8246                 }
8247
8248                 Expression type;
8249                 LocalVariable variable;
8250                 Expression expr;
8251                 Block body;
8252
8253                 public Foreach (Expression type, LocalVariable var, Expression expr, Statement stmt, Block body, Location l)
8254                         : base (stmt)
8255                 {
8256                         this.type = type;
8257                         this.variable = var;
8258                         this.expr = expr;
8259                         this.body = body;
8260                         loc = l;
8261                 }
8262
8263                 public Expression Expr {
8264                         get { return expr; }
8265                 }
8266
8267                 public Expression TypeExpression {
8268                         get { return type; }
8269                 }
8270
8271                 public LocalVariable Variable {
8272                         get { return variable; }
8273                 }
8274
8275                 public override Reachability MarkReachable (Reachability rc)
8276                 {
8277                         base.MarkReachable (rc);
8278
8279                         body.MarkReachable (rc);
8280
8281                         return rc;
8282                 }
8283
8284                 public override bool Resolve (BlockContext ec)
8285                 {
8286                         expr = expr.Resolve (ec);
8287                         if (expr == null)
8288                                 return false;
8289
8290                         if (expr.IsNull) {
8291                                 ec.Report.Error (186, loc, "Use of null is not valid in this context");
8292                                 return false;
8293                         }
8294
8295                         body.AddStatement (Statement);
8296
8297                         if (expr.Type.BuiltinType == BuiltinTypeSpec.Type.String) {
8298                                 Statement = new ArrayForeach (this, 1);
8299                         } else if (expr.Type is ArrayContainer) {
8300                                 Statement = new ArrayForeach (this, ((ArrayContainer) expr.Type).Rank);
8301                         } else {
8302                                 if (expr.eclass == ExprClass.MethodGroup || expr is AnonymousMethodExpression) {
8303                                         ec.Report.Error (446, expr.Location, "Foreach statement cannot operate on a `{0}'",
8304                                                 expr.ExprClassName);
8305                                         return false;
8306                                 }
8307
8308                                 Statement = new CollectionForeach (this, variable, expr);
8309                         }
8310
8311                         return base.Resolve (ec);
8312                 }
8313
8314                 protected override void DoEmit (EmitContext ec)
8315                 {
8316                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
8317                         ec.LoopBegin = ec.DefineLabel ();
8318                         ec.LoopEnd = ec.DefineLabel ();
8319
8320                         if (!(Statement is Block))
8321                                 ec.BeginCompilerScope (variable.Block.Explicit.GetDebugSymbolScopeIndex ());
8322
8323                         variable.CreateBuilder (ec);
8324
8325                         Statement.Emit (ec);
8326
8327                         if (!(Statement is Block))
8328                                 ec.EndScope ();
8329
8330                         ec.LoopBegin = old_begin;
8331                         ec.LoopEnd = old_end;
8332                 }
8333
8334                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
8335                 {
8336                         expr.FlowAnalysis (fc);
8337
8338                         var da = fc.BranchDefiniteAssignment ();
8339                         body.FlowAnalysis (fc);
8340                         fc.DefiniteAssignment = da;
8341                         return false;
8342                 }
8343
8344                 protected override void CloneTo (CloneContext clonectx, Statement t)
8345                 {
8346                         Foreach target = (Foreach) t;
8347
8348                         target.type = type.Clone (clonectx);
8349                         target.expr = expr.Clone (clonectx);
8350                         target.body = (Block) body.Clone (clonectx);
8351                         target.Statement = Statement.Clone (clonectx);
8352                 }
8353
8354                 public override object Accept (StructuralVisitor visitor)
8355                 {
8356                         return visitor.Visit (this);
8357                 }
8358         }
8359
8360         class SentinelStatement: Statement
8361         {
8362                 protected override void CloneTo (CloneContext clonectx, Statement target)
8363                 {
8364                 }
8365
8366                 protected override void DoEmit (EmitContext ec)
8367                 {
8368                         var l = ec.DefineLabel ();
8369                         ec.MarkLabel (l);
8370                         ec.Emit (OpCodes.Br_S, l);
8371                 }
8372
8373                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
8374                 {
8375                         throw new NotImplementedException ();
8376                 }
8377         }
8378 }