mcs/mcs/statement.cs

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