mcs/mcs/statement.cs

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