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