mcs/mcs/statement.cs

   1 //
   2 // statement.cs: Statement representation for the IL tree.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Martin Baulig (martin@ximian.com)
   7 //   Marek Safar (marek.safar@seznam.cz)
   8 //
   9 // (C) 2001, 2002, 2003 Ximian, Inc.
  10 // (C) 2003, 2004 Novell, Inc.
  11 //
  12
  13 using System;
  14 using System.Text;
  15 using System.Reflection;
  16 using System.Reflection.Emit;
  17 using System.Diagnostics;
  18 using System.Collections;
  19 using System.Collections.Specialized;
  20
  21 namespace Mono.CSharp {
  22
  23         public abstract class Statement {
  24                 public Location loc;
  25
  26                 /// <summary>
  27                 ///   Resolves the statement, true means that all sub-statements
  28                 ///   did resolve ok.
  29                 //  </summary>
  30                 public virtual bool Resolve (EmitContext ec)
  31                 {
  32                         return true;
  33                 }
  34
  35                 /// <summary>
  36                 ///   We already know that the statement is unreachable, but we still
  37                 ///   need to resolve it to catch errors.
  38                 /// </summary>
  39                 public virtual bool ResolveUnreachable (EmitContext ec, bool warn)
  40                 {
  41                         //
  42                         // This conflicts with csc's way of doing this, but IMHO it's
  43                         // the right thing to do.
  44                         //
  45                         // If something is unreachable, we still check whether it's
  46                         // correct.  This means that you cannot use unassigned variables
  47                         // in unreachable code, for instance.
  48                         //
  49
  50                         if (warn)
  51                                 Report.Warning (162, 2, loc, "Unreachable code detected");
  52
  53                         ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
  54                         bool ok = Resolve (ec);
  55                         ec.KillFlowBranching ();
  56
  57                         return ok;
  58                 }
  59
  60                 /// <summary>
  61                 ///   Return value indicates whether all code paths emitted return.
  62                 /// </summary>
  63                 protected abstract void DoEmit (EmitContext ec);
  64
  65                 /// <summary>
  66                 ///   Utility wrapper routine for Error, just to beautify the code
  67                 /// </summary>
  68                 public void Error (int error, string format, params object[] args)
  69                 {
  70                         Error (error, String.Format (format, args));
  71                 }
  72
  73                 public void Error (int error, string s)
  74                 {
  75                         if (!loc.IsNull)
  76                                 Report.Error (error, loc, s);
  77                         else
  78                                 Report.Error (error, s);
  79                 }
  80
  81                 /// <summary>
  82                 ///   Return value indicates whether all code paths emitted return.
  83                 /// </summary>
  84                 public virtual void Emit (EmitContext ec)
  85                 {
  86                         ec.Mark (loc, true);
  87                         DoEmit (ec);
  88                 }
  89         }
  90
  91         public sealed class EmptyStatement : Statement {
  92
  93                 private EmptyStatement () {}
  94
  95                 public static readonly EmptyStatement Value = new EmptyStatement ();
  96
  97                 public override bool Resolve (EmitContext ec)
  98                 {
  99                         return true;
 100                 }
 101
 102                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
 103                 {
 104                         return true;
 105                 }
 106
 107                 protected override void DoEmit (EmitContext ec)
 108                 {
 109                 }
 110         }
 111
 112         public class If : Statement {
 113                 Expression expr;
 114                 public Statement TrueStatement;
 115                 public Statement FalseStatement;
 116
 117                 bool is_true_ret;
 118
 119                 public If (Expression expr, Statement trueStatement, Location l)
 120                 {
 121                         this.expr = expr;
 122                         TrueStatement = trueStatement;
 123                         loc = l;
 124                 }
 125
 126                 public If (Expression expr,
 127                            Statement trueStatement,
 128                            Statement falseStatement,
 129                            Location l)
 130                 {
 131                         this.expr = expr;
 132                         TrueStatement = trueStatement;
 133                         FalseStatement = falseStatement;
 134                         loc = l;
 135                 }
 136
 137                 public override bool Resolve (EmitContext ec)
 138                 {
 139                         bool ok = true;
 140
 141                         Report.Debug (1, "START IF BLOCK", loc);
 142
 143                         expr = Expression.ResolveBoolean (ec, expr, loc);
 144                         if (expr == null){
 145                                 ok = false;
 146                                 goto skip;
 147                         }
 148
 149                         Assign ass = expr as Assign;
 150                         if (ass != null && ass.Source is Constant) {
 151                                 Report.Warning (665, 3, loc, "Assignment in conditional expression is always constant; did you mean to use == instead of = ?");
 152                         }
 153
 154                         //
 155                         // Dead code elimination
 156                         //
 157                         if (expr is BoolConstant){
 158                                 bool take = ((BoolConstant) expr).Value;
 159
 160                                 if (take){
 161                                         if (!TrueStatement.Resolve (ec))
 162                                                 return false;
 163
 164                                         if ((FalseStatement != null) &&
 165                                             !FalseStatement.ResolveUnreachable (ec, true))
 166                                                 return false;
 167                                         FalseStatement = null;
 168                                 } else {
 169                                         if (!TrueStatement.ResolveUnreachable (ec, true))
 170                                                 return false;
 171                                         TrueStatement = null;
 172
 173                                         if ((FalseStatement != null) &&
 174                                             !FalseStatement.Resolve (ec))
 175                                                 return false;
 176                                 }
 177
 178                                 return true;
 179                         }
 180                 skip:
 181                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
 182
 183                         ok &= TrueStatement.Resolve (ec);
 184
 185                         is_true_ret = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
 186
 187                         ec.CurrentBranching.CreateSibling ();
 188
 189                         if (FalseStatement != null)
 190                                 ok &= FalseStatement.Resolve (ec);
 191
 192                         ec.EndFlowBranching ();
 193
 194                         Report.Debug (1, "END IF BLOCK", loc);
 195
 196                         return ok;
 197                 }
 198
 199                 protected override void DoEmit (EmitContext ec)
 200                 {
 201                         ILGenerator ig = ec.ig;
 202                         Label false_target = ig.DefineLabel ();
 203                         Label end;
 204
 205                         //
 206                         // If we're a boolean expression, Resolve() already
 207                         // eliminated dead code for us.
 208                         //
 209                         if (expr is BoolConstant){
 210                                 bool take = ((BoolConstant) expr).Value;
 211
 212                                 if (take)
 213                                         TrueStatement.Emit (ec);
 214                                 else if (FalseStatement != null)
 215                                         FalseStatement.Emit (ec);
 216
 217                                 return;
 218                         }
 219
 220                         expr.EmitBranchable (ec, false_target, false);
 221
 222                         TrueStatement.Emit (ec);
 223
 224                         if (FalseStatement != null){
 225                                 bool branch_emitted = false;
 226
 227                                 end = ig.DefineLabel ();
 228                                 if (!is_true_ret){
 229                                         ig.Emit (OpCodes.Br, end);
 230                                         branch_emitted = true;
 231                                 }
 232
 233                                 ig.MarkLabel (false_target);
 234                                 FalseStatement.Emit (ec);
 235
 236                                 if (branch_emitted)
 237                                         ig.MarkLabel (end);
 238                         } else {
 239                                 ig.MarkLabel (false_target);
 240                         }
 241                 }
 242         }
 243
 244         public class Do : Statement {
 245                 public Expression expr;
 246                 public readonly Statement  EmbeddedStatement;
 247                 bool infinite;
 248
 249                 public Do (Statement statement, Expression boolExpr, Location l)
 250                 {
 251                         expr = boolExpr;
 252                         EmbeddedStatement = statement;
 253                         loc = l;
 254                 }
 255
 256                 public override bool Resolve (EmitContext ec)
 257                 {
 258                         bool ok = true;
 259
 260                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 261
 262                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
 263
 264                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 265                         if (!EmbeddedStatement.Resolve (ec))
 266                                 ok = false;
 267                         ec.EndFlowBranching ();
 268
 269                         if (ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable && !was_unreachable)
 270                                 Report.Warning (162, 2, expr.Location, "Unreachable code detected");
 271
 272                         expr = Expression.ResolveBoolean (ec, expr, loc);
 273                         if (expr == null)
 274                                 ok = false;
 275                         else if (expr is BoolConstant){
 276                                 bool res = ((BoolConstant) expr).Value;
 277
 278                                 if (res)
 279                                         infinite = true;
 280                         }
 281                         if (infinite)
 282                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
 283
 284                         ec.EndFlowBranching ();
 285
 286                         return ok;
 287                 }
 288
 289                 protected override void DoEmit (EmitContext ec)
 290                 {
 291                         ILGenerator ig = ec.ig;
 292                         Label loop = ig.DefineLabel ();
 293                         Label old_begin = ec.LoopBegin;
 294                         Label old_end = ec.LoopEnd;
 295
 296                         ec.LoopBegin = ig.DefineLabel ();
 297                         ec.LoopEnd = ig.DefineLabel ();
 298
 299                         ig.MarkLabel (loop);
 300                         EmbeddedStatement.Emit (ec);
 301                         ig.MarkLabel (ec.LoopBegin);
 302
 303                         //
 304                         // Dead code elimination
 305                         //
 306                         if (expr is BoolConstant){
 307                                 bool res = ((BoolConstant) expr).Value;
 308
 309                                 if (res)
 310                                         ec.ig.Emit (OpCodes.Br, loop);
 311                         } else
 312                                 expr.EmitBranchable (ec, loop, true);
 313
 314                         ig.MarkLabel (ec.LoopEnd);
 315
 316                         ec.LoopBegin = old_begin;
 317                         ec.LoopEnd = old_end;
 318                 }
 319         }
 320
 321         public class While : Statement {
 322                 public Expression expr;
 323                 public readonly Statement Statement;
 324                 bool infinite, empty;
 325
 326                 public While (Expression boolExpr, Statement statement, Location l)
 327                 {
 328                         this.expr = boolExpr;
 329                         Statement = statement;
 330                         loc = l;
 331                 }
 332
 333                 public override bool Resolve (EmitContext ec)
 334                 {
 335                         bool ok = true;
 336
 337                         expr = Expression.ResolveBoolean (ec, expr, loc);
 338                         if (expr == null)
 339                                 return false;
 340
 341                         //
 342                         // Inform whether we are infinite or not
 343                         //
 344                         if (expr is BoolConstant){
 345                                 BoolConstant bc = (BoolConstant) expr;
 346
 347                                 if (bc.Value == false){
 348                                         if (!Statement.ResolveUnreachable (ec, true))
 349                                                 return false;
 350                                         empty = true;
 351                                         return true;
 352                                 } else
 353                                         infinite = true;
 354                         }
 355
 356                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 357                         if (!infinite)
 358                                 ec.CurrentBranching.CreateSibling ();
 359
 360                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 361                         if (!Statement.Resolve (ec))
 362                                 ok = false;
 363                         ec.EndFlowBranching ();
 364
 365                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 366                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 367
 368                         ec.EndFlowBranching ();
 369
 370                         return ok;
 371                 }
 372
 373                 protected override void DoEmit (EmitContext ec)
 374                 {
 375                         if (empty)
 376                                 return;
 377
 378                         ILGenerator ig = ec.ig;
 379                         Label old_begin = ec.LoopBegin;
 380                         Label old_end = ec.LoopEnd;
 381
 382                         ec.LoopBegin = ig.DefineLabel ();
 383                         ec.LoopEnd = ig.DefineLabel ();
 384
 385                         //
 386                         // Inform whether we are infinite or not
 387                         //
 388                         if (expr is BoolConstant){
 389                                 ig.MarkLabel (ec.LoopBegin);
 390                                 Statement.Emit (ec);
 391                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 392
 393                                 //
 394                                 // Inform that we are infinite (ie, `we return'), only
 395                                 // if we do not `break' inside the code.
 396                                 //
 397                                 ig.MarkLabel (ec.LoopEnd);
 398                         } else {
 399                                 Label while_loop = ig.DefineLabel ();
 400
 401                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 402                                 ig.MarkLabel (while_loop);
 403
 404                                 Statement.Emit (ec);
 405
 406                                 ig.MarkLabel (ec.LoopBegin);
 407
 408                                 expr.EmitBranchable (ec, while_loop, true);
 409
 410                                 ig.MarkLabel (ec.LoopEnd);
 411                         }
 412
 413                         ec.LoopBegin = old_begin;
 414                         ec.LoopEnd = old_end;
 415                 }
 416         }
 417
 418         public class For : Statement {
 419                 Expression Test;
 420                 readonly Statement InitStatement;
 421                 readonly Statement Increment;
 422                 public readonly Statement Statement;
 423                 bool infinite, empty;
 424
 425                 public For (Statement initStatement,
 426                             Expression test,
 427                             Statement increment,
 428                             Statement statement,
 429                             Location l)
 430                 {
 431                         InitStatement = initStatement;
 432                         Test = test;
 433                         Increment = increment;
 434                         Statement = statement;
 435                         loc = l;
 436                 }
 437
 438                 public override bool Resolve (EmitContext ec)
 439                 {
 440                         bool ok = true;
 441
 442                         if (InitStatement != null){
 443                                 if (!InitStatement.Resolve (ec))
 444                                         ok = false;
 445                         }
 446
 447                         if (Test != null){
 448                                 Test = Expression.ResolveBoolean (ec, Test, loc);
 449                                 if (Test == null)
 450                                         ok = false;
 451                                 else if (Test is BoolConstant){
 452                                         BoolConstant bc = (BoolConstant) Test;
 453
 454                                         if (bc.Value == false){
 455                                                 if (!Statement.ResolveUnreachable (ec, true))
 456                                                         return false;
 457                                                 if ((Increment != null) &&
 458                                                     !Increment.ResolveUnreachable (ec, false))
 459                                                         return false;
 460                                                 empty = true;
 461                                                 return true;
 462                                         } else
 463                                                 infinite = true;
 464                                 }
 465                         } else
 466                                 infinite = true;
 467
 468                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 469                         if (!infinite)
 470                                 ec.CurrentBranching.CreateSibling ();
 471
 472                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
 473
 474                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 475                         if (!Statement.Resolve (ec))
 476                                 ok = false;
 477                         ec.EndFlowBranching ();
 478
 479                         if (Increment != null){
 480                                 if (ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable) {
 481                                         if (!Increment.ResolveUnreachable (ec, !was_unreachable))
 482                                                 ok = false;
 483                                 } else {
 484                                         if (!Increment.Resolve (ec))
 485                                                 ok = false;
 486                                 }
 487                         }
 488
 489                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 490                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 491
 492                         ec.EndFlowBranching ();
 493
 494                         return ok;
 495                 }
 496
 497                 protected override void DoEmit (EmitContext ec)
 498                 {
 499                         if (empty)
 500                                 return;
 501
 502                         ILGenerator ig = ec.ig;
 503                         Label old_begin = ec.LoopBegin;
 504                         Label old_end = ec.LoopEnd;
 505                         Label loop = ig.DefineLabel ();
 506                         Label test = ig.DefineLabel ();
 507
 508                         if (InitStatement != null && InitStatement != EmptyStatement.Value)
 509                                 InitStatement.Emit (ec);
 510
 511                         ec.LoopBegin = ig.DefineLabel ();
 512                         ec.LoopEnd = ig.DefineLabel ();
 513
 514                         ig.Emit (OpCodes.Br, test);
 515                         ig.MarkLabel (loop);
 516                         Statement.Emit (ec);
 517
 518                         ig.MarkLabel (ec.LoopBegin);
 519                         if (Increment != EmptyStatement.Value)
 520                                 Increment.Emit (ec);
 521
 522                         ig.MarkLabel (test);
 523                         //
 524                         // If test is null, there is no test, and we are just
 525                         // an infinite loop
 526                         //
 527                         if (Test != null){
 528                                 //
 529                                 // The Resolve code already catches the case for
 530                                 // Test == BoolConstant (false) so we know that
 531                                 // this is true
 532                                 //
 533                                 if (Test is BoolConstant)
 534                                         ig.Emit (OpCodes.Br, loop);
 535                                 else
 536                                         Test.EmitBranchable (ec, loop, true);
 537
 538                         } else
 539                                 ig.Emit (OpCodes.Br, loop);
 540                         ig.MarkLabel (ec.LoopEnd);
 541
 542                         ec.LoopBegin = old_begin;
 543                         ec.LoopEnd = old_end;
 544                 }
 545         }
 546
 547         public class StatementExpression : Statement {
 548                 ExpressionStatement expr;
 549
 550                 public StatementExpression (ExpressionStatement expr)
 551                 {
 552                         this.expr = expr;
 553                         loc = expr.Location;
 554                 }
 555
 556                 public override bool Resolve (EmitContext ec)
 557                 {
 558                         if (expr != null)
 559                                 expr = expr.ResolveStatement (ec);
 560                         return expr != null;
 561                 }
 562
 563                 protected override void DoEmit (EmitContext ec)
 564                 {
 565                         expr.EmitStatement (ec);
 566                 }
 567
 568                 public override string ToString ()
 569                 {
 570                         return "StatementExpression (" + expr + ")";
 571                 }
 572         }
 573
 574         /// <summary>
 575         ///   Implements the return statement
 576         /// </summary>
 577         public class Return : Statement {
 578                 public Expression Expr;
 579
 580                 public Return (Expression expr, Location l)
 581                 {
 582                         Expr = expr;
 583                         loc = l;
 584                 }
 585
 586                 bool unwind_protect;
 587
 588                 public override bool Resolve (EmitContext ec)
 589                 {
 590                         AnonymousContainer am = ec.CurrentAnonymousMethod;
 591                         if ((am != null) && am.IsIterator && ec.InIterator) {
 592                                 Report.Error (1622, loc, "Cannot return a value from iterators. Use the yield return " +
 593                                               "statement to return a value, or yield break to end the iteration");
 594                                 return false;
 595                         }
 596
 597                         if (ec.ReturnType == null){
 598                                 if (Expr != null){
 599                                         if (ec.CurrentAnonymousMethod != null){
 600                                                 Report.Error (1662, loc,
 601                                                         "Cannot convert anonymous method block to delegate type `{0}' because some of the return types in the block are not implicitly convertible to the delegate return type",
 602                                                         ec.CurrentAnonymousMethod.GetSignatureForError ());
 603                                         }
 604                                         Error (127, "A return keyword must not be followed by any expression when method returns void");
 605                                         return false;
 606                                 }
 607                         } else {
 608                                 if (Expr == null){
 609                                         Error (126, "An object of a type convertible to `{0}' is required " +
 610                                                "for the return statement",
 611                                                TypeManager.CSharpName (ec.ReturnType));
 612                                         return false;
 613                                 }
 614
 615                                 Expr = Expr.Resolve (ec);
 616                                 if (Expr == null)
 617                                         return false;
 618
 619                                 if (Expr.Type != ec.ReturnType) {
 620                                         Expr = Convert.ImplicitConversionRequired (
 621                                                 ec, Expr, ec.ReturnType, loc);
 622                                         if (Expr == null)
 623                                                 return false;
 624                                 }
 625                         }
 626
 627                         int errors = Report.Errors;
 628                         unwind_protect = ec.CurrentBranching.AddReturnOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
 629                         if (unwind_protect)
 630                                 ec.NeedReturnLabel ();
 631                         ec.CurrentBranching.CurrentUsageVector.Return ();
 632                         return errors == Report.Errors;
 633                 }
 634
 635                 protected override void DoEmit (EmitContext ec)
 636                 {
 637                         if (Expr != null) {
 638                                 Expr.Emit (ec);
 639
 640                                 if (unwind_protect)
 641                                         ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 642                         }
 643
 644                         if (unwind_protect)
 645                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 646                         else
 647                                 ec.ig.Emit (OpCodes.Ret);
 648                 }
 649         }
 650
 651         public class Goto : Statement {
 652                 string target;
 653                 LabeledStatement label;
 654                 bool unwind_protect;
 655
 656                 public override bool Resolve (EmitContext ec)
 657                 {
 658                         int errors = Report.Errors;
 659                         unwind_protect = ec.CurrentBranching.AddGotoOrigin (ec.CurrentBranching.CurrentUsageVector, this);
 660                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 661                         return errors == Report.Errors;
 662                 }
 663
 664                 public Goto (string label, Location l)
 665                 {
 666                         loc = l;
 667                         target = label;
 668                 }
 669
 670                 public string Target {
 671                         get { return target; }
 672                 }
 673
 674                 public void SetResolvedTarget (LabeledStatement label)
 675                 {
 676                         this.label = label;
 677                         label.AddReference ();
 678                 }
 679
 680                 protected override void DoEmit (EmitContext ec)
 681                 {
 682                         if (label == null)
 683                                 throw new InternalErrorException ("goto emitted before target resolved");
 684                         Label l = label.LabelTarget (ec);
 685                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
 686                 }
 687         }
 688
 689         public class LabeledStatement : Statement {
 690                 string name;
 691                 bool defined;
 692                 bool referenced;
 693                 Label label;
 694                 ILGenerator ig;
 695
 696                 FlowBranching.UsageVector vectors;
 697
 698                 public LabeledStatement (string name, Location l)
 699                 {
 700                         this.name = name;
 701                         this.loc = l;
 702                 }
 703
 704                 public Label LabelTarget (EmitContext ec)
 705                 {
 706                         if (defined)
 707                                 return label;
 708                         ig = ec.ig;
 709                         label = ec.ig.DefineLabel ();
 710                         defined = true;
 711
 712                         return label;
 713                 }
 714
 715                 public string Name {
 716                         get { return name; }
 717                 }
 718
 719                 public bool IsDefined {
 720                         get { return defined; }
 721                 }
 722
 723                 public bool HasBeenReferenced {
 724                         get { return referenced; }
 725                 }
 726
 727                 public FlowBranching.UsageVector JumpOrigins {
 728                         get { return vectors; }
 729                 }
 730
 731                 public void AddUsageVector (FlowBranching.UsageVector vector)
 732                 {
 733                         vector = vector.Clone ();
 734                         vector.Next = vectors;
 735                         vectors = vector;
 736                 }
 737
 738                 public override bool Resolve (EmitContext ec)
 739                 {
 740                         // this flow-branching will be terminated when the surrounding block ends
 741                         ec.StartFlowBranching (this);
 742                         return true;
 743                 }
 744
 745                 protected override void DoEmit (EmitContext ec)
 746                 {
 747                         if (ig != null && ig != ec.ig)
 748                                 throw new InternalErrorException ("cannot happen");
 749                         LabelTarget (ec);
 750                         ec.ig.MarkLabel (label);
 751                 }
 752
 753                 public void AddReference ()
 754                 {
 755                         referenced = true;
 756                 }
 757         }
 758
 759
 760         /// <summary>
 761         ///   `goto default' statement
 762         /// </summary>
 763         public class GotoDefault : Statement {
 764
 765                 public GotoDefault (Location l)
 766                 {
 767                         loc = l;
 768                 }
 769
 770                 public override bool Resolve (EmitContext ec)
 771                 {
 772                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 773                         return true;
 774                 }
 775
 776                 protected override void DoEmit (EmitContext ec)
 777                 {
 778                         if (ec.Switch == null){
 779                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
 780                                 return;
 781                         }
 782
 783                         if (!ec.Switch.GotDefault){
 784                                 Report.Error (159, loc, "No such label `default:' within the scope of the goto statement");
 785                                 return;
 786                         }
 787                         ec.ig.Emit (OpCodes.Br, ec.Switch.DefaultTarget);
 788                 }
 789         }
 790
 791         /// <summary>
 792         ///   `goto case' statement
 793         /// </summary>
 794         public class GotoCase : Statement {
 795                 Expression expr;
 796                 SwitchLabel sl;
 797
 798                 public GotoCase (Expression e, Location l)
 799                 {
 800                         expr = e;
 801                         loc = l;
 802                 }
 803
 804                 public override bool Resolve (EmitContext ec)
 805                 {
 806                         if (ec.Switch == null){
 807                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
 808                                 return false;
 809                         }
 810
 811                         expr = expr.Resolve (ec);
 812                         if (expr == null)
 813                                 return false;
 814
 815                         Constant c = expr as Constant;
 816                         if (c == null) {
 817                                 Error (150, "A constant value is expected");
 818                                 return false;
 819                         }
 820
 821                         Type type = ec.Switch.SwitchType;
 822                         if (!Convert.ImplicitStandardConversionExists (c, type))
 823                                 Report.Warning (469, 2, loc, "The `goto case' value is not implicitly " +
 824                                                 "convertible to type `{0}'", TypeManager.CSharpName (type));
 825
 826                         bool fail = false;
 827                         object val = c.GetValue ();
 828                         if ((val != null) && (c.Type != type) && (c.Type != TypeManager.object_type))
 829                                 val = TypeManager.ChangeType (val, type, out fail);
 830
 831                         if (fail) {
 832                                 Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
 833                                               c.GetSignatureForError (), TypeManager.CSharpName (type));
 834                                 return false;
 835                         }
 836
 837                         if (val == null)
 838                                 val = SwitchLabel.NullStringCase;
 839
 840                         sl = (SwitchLabel) ec.Switch.Elements [val];
 841
 842                         if (sl == null){
 843                                 Report.Error (159, loc, "No such label `case {0}:' within the scope of the goto statement", c.GetValue () == null ? "null" : val.ToString ());
 844                                 return false;
 845                         }
 846
 847                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 848                         return true;
 849                 }
 850
 851                 protected override void DoEmit (EmitContext ec)
 852                 {
 853                         ec.ig.Emit (OpCodes.Br, sl.GetILLabelCode (ec));
 854                 }
 855         }
 856
 857         public class Throw : Statement {
 858                 Expression expr;
 859
 860                 public Throw (Expression expr, Location l)
 861                 {
 862                         this.expr = expr;
 863                         loc = l;
 864                 }
 865
 866                 public override bool Resolve (EmitContext ec)
 867                 {
 868                         ec.CurrentBranching.CurrentUsageVector.Throw ();
 869
 870                         if (expr != null){
 871                                 expr = expr.Resolve (ec);
 872                                 if (expr == null)
 873                                         return false;
 874
 875                                 ExprClass eclass = expr.eclass;
 876
 877                                 if (!(eclass == ExprClass.Variable || eclass == ExprClass.PropertyAccess ||
 878                                         eclass == ExprClass.Value || eclass == ExprClass.IndexerAccess)) {
 879                                         expr.Error_UnexpectedKind (ec.DeclContainer, "value, variable, property or indexer access ", loc);
 880                                         return false;
 881                                 }
 882
 883                                 Type t = expr.Type;
 884
 885                                 if ((t != TypeManager.exception_type) &&
 886                                     !TypeManager.IsSubclassOf (t, TypeManager.exception_type) &&
 887                                     !(expr is NullLiteral)) {
 888                                         Error (155,
 889                                                 "The type caught or thrown must be derived " +
 890                                                 "from System.Exception");
 891                                         return false;
 892                                 }
 893                                 return true;
 894                         }
 895
 896                         if (!ec.InCatch) {
 897                                 Error (156, "A throw statement with no arguments is not allowed outside of a catch clause");
 898                                 return false;
 899                         }
 900
 901                         if (ec.InFinally) {
 902                                 Error (724, "A throw statement with no arguments is not allowed inside of a finally clause nested inside of the innermost catch clause");
 903                                 return false;
 904                         }
 905                         return true;
 906                 }
 907
 908                 protected override void DoEmit (EmitContext ec)
 909                 {
 910                         if (expr == null)
 911                                 ec.ig.Emit (OpCodes.Rethrow);
 912                         else {
 913                                 expr.Emit (ec);
 914
 915                                 ec.ig.Emit (OpCodes.Throw);
 916                         }
 917                 }
 918         }
 919
 920         public class Break : Statement {
 921
 922                 public Break (Location l)
 923                 {
 924                         loc = l;
 925                 }
 926
 927                 bool unwind_protect;
 928
 929                 public override bool Resolve (EmitContext ec)
 930                 {
 931                         int errors = Report.Errors;
 932                         unwind_protect = ec.CurrentBranching.AddBreakOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
 933                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 934                         return errors == Report.Errors;
 935                 }
 936
 937                 protected override void DoEmit (EmitContext ec)
 938                 {
 939                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopEnd);
 940                 }
 941         }
 942
 943         public class Continue : Statement {
 944
 945                 public Continue (Location l)
 946                 {
 947                         loc = l;
 948                 }
 949
 950                 bool unwind_protect;
 951
 952                 public override bool Resolve (EmitContext ec)
 953                 {
 954                         int errors = Report.Errors;
 955                         unwind_protect = ec.CurrentBranching.AddContinueOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
 956                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 957                         return errors == Report.Errors;
 958                 }
 959
 960                 protected override void DoEmit (EmitContext ec)
 961                 {
 962                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopBegin);
 963                 }
 964         }
 965
 966         public abstract class Variable
 967         {
 968                 public abstract Type Type {
 969                         get;
 970                 }
 971
 972                 public abstract bool HasInstance {
 973                         get;
 974                 }
 975
 976                 public abstract bool NeedsTemporary {
 977                         get;
 978                 }
 979
 980                 public abstract void EmitInstance (EmitContext ec);
 981
 982                 public abstract void Emit (EmitContext ec);
 983
 984                 public abstract void EmitAssign (EmitContext ec);
 985
 986                 public abstract void EmitAddressOf (EmitContext ec);
 987         }
 988
 989         //
 990         // The information about a user-perceived local variable
 991         //
 992         public class LocalInfo {
 993                 public Expression Type;
 994
 995                 public Type VariableType;
 996                 public readonly string Name;
 997                 public readonly Location Location;
 998                 public readonly Block Block;
 999
1000                 public VariableInfo VariableInfo;
1001
1002                 Variable var;
1003                 public Variable Variable {
1004                         get { return var; }
1005                 }
1006
1007                 [Flags]
1008                 enum Flags : byte {
1009                         Used = 1,
1010                         ReadOnly = 2,
1011                         Pinned = 4,
1012                         IsThis = 8,
1013                         Captured = 16,
1014                         AddressTaken = 32,
1015                         CompilerGenerated = 64,
1016                         IsConstant = 128
1017                 }
1018
1019                 public enum ReadOnlyContext: byte {
1020                         Using,
1021                         Foreach,
1022                         Fixed
1023                 }
1024
1025                 Flags flags;
1026                 ReadOnlyContext ro_context;
1027                 LocalBuilder builder;
1028
1029                 public LocalInfo (Expression type, string name, Block block, Location l)
1030                 {
1031                         Type = type;
1032                         Name = name;
1033                         Block = block;
1034                         Location = l;
1035                 }
1036
1037                 public LocalInfo (DeclSpace ds, Block block, Location l)
1038                 {
1039                         VariableType = ds.IsGeneric ? ds.CurrentType : ds.TypeBuilder;
1040                         Block = block;
1041                         Location = l;
1042                 }
1043
1044                 public void ResolveVariable (EmitContext ec)
1045                 {
1046                         Block theblock = Block;
1047                         if (theblock.ScopeInfo != null)
1048                                 var = theblock.ScopeInfo.GetCapturedVariable (this);
1049
1050                         if (var == null) {
1051                                 if (Pinned)
1052                                         //
1053                                         // This is needed to compile on both .NET 1.x and .NET 2.x
1054                                         // the later introduced `DeclareLocal (Type t, bool pinned)'
1055                                         //
1056                                         builder = TypeManager.DeclareLocalPinned (ec.ig, VariableType);
1057                                 else
1058                                         builder = ec.ig.DeclareLocal (VariableType);
1059
1060                                 var = new LocalVariable (this, builder);
1061                         }
1062                 }
1063
1064                 public void EmitSymbolInfo (EmitContext ec, string name)
1065                 {
1066                         if (builder != null)
1067                                 ec.DefineLocalVariable (name, builder);
1068                 }
1069
1070                 public bool IsThisAssigned (EmitContext ec, Location loc)
1071                 {
1072                         if (VariableInfo == null)
1073                                 throw new Exception ();
1074
1075                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo))
1076                                 return true;
1077
1078                         return VariableInfo.TypeInfo.IsFullyInitialized (ec.CurrentBranching, VariableInfo, loc);
1079                 }
1080
1081                 public bool IsAssigned (EmitContext ec)
1082                 {
1083                         if (VariableInfo == null)
1084                                 throw new Exception ();
1085
1086                         return !ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo);
1087                 }
1088
1089                 public bool Resolve (EmitContext ec)
1090                 {
1091                         if (VariableType == null) {
1092                                 TypeExpr texpr = Type.ResolveAsTypeTerminal (ec, false);
1093                                 if (texpr == null)
1094                                         return false;
1095
1096                                 VariableType = texpr.Type;
1097                         }
1098
1099                         if (VariableType == TypeManager.void_type) {
1100                                 Expression.Error_VoidInvalidInTheContext (Location);
1101                                 return false;
1102                         }
1103
1104                         if (VariableType.IsAbstract && VariableType.IsSealed) {
1105                                 FieldMember.Error_VariableOfStaticClass (Location, Name, VariableType);
1106                                 return false;
1107                         }
1108
1109                         if (VariableType.IsPointer && !ec.InUnsafe)
1110                                 Expression.UnsafeError (Location);
1111
1112                         return true;
1113                 }
1114
1115                 public bool IsCaptured {
1116                         get {
1117                                 return (flags & Flags.Captured) != 0;
1118                         }
1119
1120                         set {
1121                                 flags |= Flags.Captured;
1122                         }
1123                 }
1124
1125                 public bool IsConstant {
1126                         get {
1127                                 return (flags & Flags.IsConstant) != 0;
1128                         }
1129                         set {
1130                                 flags |= Flags.IsConstant;
1131                         }
1132                 }
1133
1134                 public bool AddressTaken {
1135                         get {
1136                                 return (flags & Flags.AddressTaken) != 0;
1137                         }
1138
1139                         set {
1140                                 flags |= Flags.AddressTaken;
1141                         }
1142                 }
1143
1144                 public bool CompilerGenerated {
1145                         get {
1146                                 return (flags & Flags.CompilerGenerated) != 0;
1147                         }
1148
1149                         set {
1150                                 flags |= Flags.CompilerGenerated;
1151                         }
1152                 }
1153
1154                 public override string ToString ()
1155                 {
1156                         return String.Format ("LocalInfo ({0},{1},{2},{3})",
1157                                               Name, Type, VariableInfo, Location);
1158                 }
1159
1160                 public bool Used {
1161                         get {
1162                                 return (flags & Flags.Used) != 0;
1163                         }
1164                         set {
1165                                 flags = value ? (flags | Flags.Used) : (unchecked (flags & ~Flags.Used));
1166                         }
1167                 }
1168
1169                 public bool ReadOnly {
1170                         get {
1171                                 return (flags & Flags.ReadOnly) != 0;
1172                         }
1173                 }
1174
1175                 public void SetReadOnlyContext (ReadOnlyContext context)
1176                 {
1177                         flags |= Flags.ReadOnly;
1178                         ro_context = context;
1179                 }
1180
1181                 public string GetReadOnlyContext ()
1182                 {
1183                         if (!ReadOnly)
1184                                 throw new InternalErrorException ("Variable is not readonly");
1185
1186                         switch (ro_context) {
1187                                 case ReadOnlyContext.Fixed:
1188                                         return "fixed variable";
1189                                 case ReadOnlyContext.Foreach:
1190                                         return "foreach iteration variable";
1191                                 case ReadOnlyContext.Using:
1192                                         return "using variable";
1193                         }
1194                         throw new NotImplementedException ();
1195                 }
1196
1197                 //
1198                 // Whether the variable is pinned, if Pinned the variable has been
1199                 // allocated in a pinned slot with DeclareLocal.
1200                 //
1201                 public bool Pinned {
1202                         get {
1203                                 return (flags & Flags.Pinned) != 0;
1204                         }
1205                         set {
1206                                 flags = value ? (flags | Flags.Pinned) : (flags & ~Flags.Pinned);
1207                         }
1208                 }
1209
1210                 public bool IsThis {
1211                         get {
1212                                 return (flags & Flags.IsThis) != 0;
1213                         }
1214                         set {
1215                                 flags = value ? (flags | Flags.IsThis) : (flags & ~Flags.IsThis);
1216                         }
1217                 }
1218
1219                 protected class LocalVariable : Variable
1220                 {
1221                         public readonly LocalInfo LocalInfo;
1222                         LocalBuilder builder;
1223
1224                         public LocalVariable (LocalInfo local, LocalBuilder builder)
1225                         {
1226                                 this.LocalInfo = local;
1227                                 this.builder = builder;
1228                         }
1229
1230                         public override Type Type {
1231                                 get { return LocalInfo.VariableType; }
1232                         }
1233
1234                         public override bool HasInstance {
1235                                 get { return false; }
1236                         }
1237
1238                         public override bool NeedsTemporary {
1239                                 get { return false; }
1240                         }
1241
1242                         public override void EmitInstance (EmitContext ec)
1243                         {
1244                                 // Do nothing.
1245                         }
1246
1247                         public override void Emit (EmitContext ec)
1248                         {
1249                                 ec.ig.Emit (OpCodes.Ldloc, builder);
1250                         }
1251
1252                         public override void EmitAssign (EmitContext ec)
1253                         {
1254                                 ec.ig.Emit (OpCodes.Stloc, builder);
1255                         }
1256
1257                         public override void EmitAddressOf (EmitContext ec)
1258                         {
1259                                 ec.ig.Emit (OpCodes.Ldloca, builder);
1260                         }
1261                 }
1262         }
1263
1264         /// <summary>
1265         ///   Block represents a C# block.
1266         /// </summary>
1267         ///
1268         /// <remarks>
1269         ///   This class is used in a number of places: either to represent
1270         ///   explicit blocks that the programmer places or implicit blocks.
1271         ///
1272         ///   Implicit blocks are used as labels or to introduce variable
1273         ///   declarations.
1274         ///
1275         ///   Top-level blocks derive from Block, and they are called ToplevelBlock
1276         ///   they contain extra information that is not necessary on normal blocks.
1277         /// </remarks>
1278         public class Block : Statement {
1279                 public Block    Parent;
1280                 public readonly Location  StartLocation;
1281                 public Location EndLocation = Location.Null;
1282
1283                 public readonly ToplevelBlock Toplevel;
1284
1285                 [Flags]
1286                 public enum Flags : ushort {
1287                         Implicit  = 1,
1288                         Unchecked = 2,
1289                         BlockUsed = 4,
1290                         VariablesInitialized = 8,
1291                         HasRet = 16,
1292                         IsDestructor = 32,
1293                         IsToplevel = 64,
1294                         Unsafe = 128,
1295                         HasVarargs = 256, // Used in ToplevelBlock
1296                         IsIterator = 512
1297
1298                 }
1299                 protected Flags flags;
1300
1301                 public bool Implicit {
1302                         get { return (flags & Flags.Implicit) != 0; }
1303                 }
1304
1305                 public bool Unchecked {
1306                         get { return (flags & Flags.Unchecked) != 0; }
1307                         set { flags |= Flags.Unchecked; }
1308                 }
1309
1310                 public bool Unsafe {
1311                         get { return (flags & Flags.Unsafe) != 0; }
1312                         set { flags |= Flags.Unsafe; }
1313                 }
1314
1315                 //
1316                 // The statements in this block
1317                 //
1318                 protected ArrayList statements;
1319                 int num_statements;
1320
1321                 //
1322                 // An array of Blocks.  We keep track of children just
1323                 // to generate the local variable declarations.
1324                 //
1325                 // Statements and child statements are handled through the
1326                 // statements.
1327                 //
1328                 ArrayList children;
1329
1330                 //
1331                 // Labels.  (label, block) pairs.
1332                 //
1333                 Hashtable labels;
1334
1335                 //
1336                 // Keeps track of (name, type) pairs
1337                 //
1338                 IDictionary variables;
1339
1340                 //
1341                 // Keeps track of constants
1342                 Hashtable constants;
1343
1344                 //
1345                 // Temporary variables.
1346                 //
1347                 ArrayList temporary_variables;
1348
1349                 //
1350                 // If this is a switch section, the enclosing switch block.
1351                 //
1352                 Block switch_block;
1353
1354                 ExpressionStatement scope_init;
1355
1356                 ArrayList anonymous_children;
1357
1358                 protected static int id;
1359
1360                 int this_id;
1361
1362                 public Block (Block parent)
1363                         : this (parent, (Flags) 0, Location.Null, Location.Null)
1364                 { }
1365
1366                 public Block (Block parent, Flags flags)
1367                         : this (parent, flags, Location.Null, Location.Null)
1368                 { }
1369
1370                 public Block (Block parent, Location start, Location end)
1371                         : this (parent, (Flags) 0, start, end)
1372                 { }
1373
1374                 public Block (Block parent, Flags flags, Location start, Location end)
1375                 {
1376                         if (parent != null)
1377                                 parent.AddChild (this);
1378
1379                         this.Parent = parent;
1380                         this.flags = flags;
1381                         this.StartLocation = start;
1382                         this.EndLocation = end;
1383                         this.loc = start;
1384                         this_id = id++;
1385                         statements = new ArrayList ();
1386
1387                         if ((flags & Flags.IsToplevel) != 0)
1388                                 Toplevel = (ToplevelBlock) this;
1389                         else
1390                                 Toplevel = parent.Toplevel;
1391
1392                         if (parent != null && Implicit) {
1393                                 if (parent.known_variables == null)
1394                                         parent.known_variables = new Hashtable ();
1395                                 // share with parent
1396                                 known_variables = parent.known_variables;
1397                         }
1398                 }
1399
1400                 public Block CreateSwitchBlock (Location start)
1401                 {
1402                         Block new_block = new Block (this, start, start);
1403                         new_block.switch_block = this;
1404                         return new_block;
1405                 }
1406
1407                 public int ID {
1408                         get { return this_id; }
1409                 }
1410
1411                 public IDictionary Variables {
1412                         get {
1413                                 if (variables == null)
1414                                         variables = new ListDictionary ();
1415                                 return variables;
1416                         }
1417                 }
1418
1419                 void AddChild (Block b)
1420                 {
1421                         if (children == null)
1422                                 children = new ArrayList ();
1423
1424                         children.Add (b);
1425                 }
1426
1427                 public void SetEndLocation (Location loc)
1428                 {
1429                         EndLocation = loc;
1430                 }
1431
1432                 protected static void Error_158 (string name, Location loc)
1433                 {
1434                         Report.Error (158, loc, "The label `{0}' shadows another label " +
1435                                       "by the same name in a contained scope.", name);
1436                 }
1437
1438                 /// <summary>
1439                 ///   Adds a label to the current block.
1440                 /// </summary>
1441                 ///
1442                 /// <returns>
1443                 ///   false if the name already exists in this block. true
1444                 ///   otherwise.
1445                 /// </returns>
1446                 ///
1447                 public bool AddLabel (LabeledStatement target)
1448                 {
1449                         if (switch_block != null)
1450                                 return switch_block.AddLabel (target);
1451
1452                         string name = target.Name;
1453
1454                         Block cur = this;
1455                         while (cur != null) {
1456                                 if (cur.DoLookupLabel (name) != null) {
1457                                         Report.Error (140, target.loc,
1458                                                       "The label `{0}' is a duplicate", name);
1459                                         return false;
1460                                 }
1461
1462                                 if (!Implicit)
1463                                         break;
1464
1465                                 cur = cur.Parent;
1466                         }
1467
1468                         while (cur != null) {
1469                                 if (cur.DoLookupLabel (name) != null) {
1470                                         Error_158 (name, target.loc);
1471                                         return false;
1472                                 }
1473
1474                                 if (children != null) {
1475                                         foreach (Block b in children) {
1476                                                 LabeledStatement s = b.DoLookupLabel (name);
1477                                                 if (s == null)
1478                                                         continue;
1479
1480                                                 Error_158 (name, target.loc);
1481                                                 return false;
1482                                         }
1483                                 }
1484
1485                                 cur = cur.Parent;
1486                         }
1487
1488                         Toplevel.CheckError158 (name, target.loc);
1489
1490                         if (labels == null)
1491                                 labels = new Hashtable ();
1492
1493                         labels.Add (name, target);
1494                         return true;
1495                 }
1496
1497                 public LabeledStatement LookupLabel (string name)
1498                 {
1499                         LabeledStatement s = DoLookupLabel (name);
1500                         if (s != null)
1501                                 return s;
1502
1503                         if (children == null)
1504                                 return null;
1505
1506                         foreach (Block child in children) {
1507                                 if (!child.Implicit)
1508                                         continue;
1509
1510                                 s = child.LookupLabel (name);
1511                                 if (s != null)
1512                                         return s;
1513                         }
1514
1515                         return null;
1516                 }
1517
1518                 LabeledStatement DoLookupLabel (string name)
1519                 {
1520                         if (switch_block != null)
1521                                 return switch_block.LookupLabel (name);
1522
1523                         if (labels != null)
1524                                 if (labels.Contains (name))
1525                                         return ((LabeledStatement) labels [name]);
1526
1527                         return null;
1528                 }
1529
1530                 Hashtable known_variables;
1531
1532                 // <summary>
1533                 //   Marks a variable with name @name as being used in this or a child block.
1534                 //   If a variable name has been used in a child block, it's illegal to
1535                 //   declare a variable with the same name in the current block.
1536                 // </summary>
1537                 void AddKnownVariable (string name, LocalInfo info)
1538                 {
1539                         if (known_variables == null)
1540                                 known_variables = new Hashtable ();
1541
1542                         known_variables [name] = info;
1543                 }
1544
1545                 LocalInfo GetKnownVariableInfo (string name, bool recurse)
1546                 {
1547                         if (known_variables != null) {
1548                                 LocalInfo vi = (LocalInfo) known_variables [name];
1549                                 if (vi != null)
1550                                         return vi;
1551                         }
1552
1553                         if (!recurse || (children == null))
1554                                 return null;
1555
1556                         foreach (Block block in children) {
1557                                 LocalInfo vi = block.GetKnownVariableInfo (name, true);
1558                                 if (vi != null)
1559                                         return vi;
1560                         }
1561
1562                         return null;
1563                 }
1564
1565                 public bool CheckInvariantMeaningInBlock (string name, Expression e, Location loc)
1566                 {
1567                         Block b = this;
1568                         LocalInfo kvi = b.GetKnownVariableInfo (name, true);
1569                         while (kvi == null) {
1570                                 while (b.Implicit)
1571                                         b = b.Parent;
1572                                 b = b.Parent;
1573                                 if (b == null)
1574                                         return true;
1575                                 kvi = b.GetKnownVariableInfo (name, false);
1576                         }
1577
1578                         if (kvi.Block == b)
1579                                 return true;
1580
1581                         // Is kvi.Block nested inside 'b'
1582                         if (b.known_variables != kvi.Block.known_variables) {
1583                                 //
1584                                 // If a variable by the same name it defined in a nested block of this
1585                                 // block, we violate the invariant meaning in a block.
1586                                 //
1587                                 if (b == this) {
1588                                         Report.SymbolRelatedToPreviousError (kvi.Location, name);
1589                                         Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", name);
1590                                         return false;
1591                                 }
1592
1593                                 //
1594                                 // It's ok if the definition is in a nested subblock of b, but not
1595                                 // nested inside this block -- a definition in a sibling block
1596                                 // should not affect us.
1597                                 //
1598                                 return true;
1599                         }
1600
1601                         //
1602                         // Block 'b' and kvi.Block are the same textual block.
1603                         // However, different variables are extant.
1604                         //
1605                         // Check if the variable is in scope in both blocks.  We use
1606                         // an indirect check that depends on AddVariable doing its
1607                         // part in maintaining the invariant-meaning-in-block property.
1608                         //
1609                         if (e is LocalVariableReference || (e is Constant && b.GetLocalInfo (name) != null))
1610                                 return true;
1611
1612                         //
1613                         // Even though we detected the error when the name is used, we
1614                         // treat it as if the variable declaration was in error.
1615                         //
1616                         Report.SymbolRelatedToPreviousError (loc, name);
1617                         Error_AlreadyDeclared (kvi.Location, name, "parent or current");
1618                         return false;
1619                 }
1620
1621                 public bool CheckError136_InParents (string name, Location loc)
1622                 {
1623                         for (Block b = Parent; b != null; b = b.Parent) {
1624                                 if (!b.DoCheckError136 (name, "parent or current", loc))
1625                                         return false;
1626                         }
1627
1628                         for (Block b = Toplevel.ContainerBlock; b != null; b = b.Toplevel.ContainerBlock) {
1629                                 if (!b.CheckError136_InParents (name, loc))
1630                                         return false;
1631                         }
1632
1633                         return true;
1634                 }
1635
1636                 public bool CheckError136_InChildren (string name, Location loc)
1637                 {
1638                         if (!DoCheckError136_InChildren (name, loc))
1639                                 return false;
1640
1641                         Block b = this;
1642                         while (b.Implicit) {
1643                                 if (!b.Parent.DoCheckError136_InChildren (name, loc))
1644                                         return false;
1645                                 b = b.Parent;
1646                         }
1647
1648                         return true;
1649                 }
1650
1651                 protected bool DoCheckError136_InChildren (string name, Location loc)
1652                 {
1653                         if (!DoCheckError136 (name, "child", loc))
1654                                 return false;
1655
1656                         if (AnonymousChildren != null) {
1657                                 foreach (ToplevelBlock child in AnonymousChildren) {
1658                                         if (!child.DoCheckError136_InChildren (name, loc))
1659                                                 return false;
1660                                 }
1661                         }
1662
1663                         if (children != null) {
1664                                 foreach (Block child in children) {
1665                                         if (!child.DoCheckError136_InChildren (name, loc))
1666                                                 return false;
1667                                 }
1668                         }
1669
1670                         return true;
1671                 }
1672
1673                 public bool CheckError136 (string name, string scope, bool check_parents,
1674                                            bool check_children, Location loc)
1675                 {
1676                         if (!DoCheckError136 (name, scope, loc))
1677                                 return false;
1678
1679                         if (check_parents) {
1680                                 if (!CheckError136_InParents (name, loc))
1681                                         return false;
1682                         }
1683
1684                         if (check_children) {
1685                                 if (!CheckError136_InChildren (name, loc))
1686                                         return false;
1687                         }
1688
1689                         for (Block c = Toplevel.ContainerBlock; c != null; c = c.Toplevel.ContainerBlock) {
1690                                 if (!c.DoCheckError136 (name, "parent or current", loc))
1691                                         return false;
1692                         }
1693
1694                         return true;
1695                 }
1696
1697                 protected bool DoCheckError136 (string name, string scope, Location loc)
1698                 {
1699                         LocalInfo vi = GetKnownVariableInfo (name, false);
1700                         if (vi != null) {
1701                                 Report.SymbolRelatedToPreviousError (vi.Location, name);
1702                                 Error_AlreadyDeclared (loc, name, scope != null ? scope : "child");
1703                                 return false;
1704                         }
1705
1706                         int idx;
1707                         Parameter p = Toplevel.Parameters.GetParameterByName (name, out idx);
1708                         if (p != null) {
1709                                 Report.SymbolRelatedToPreviousError (p.Location, name);
1710                                 Error_AlreadyDeclared (
1711                                         loc, name, scope != null ? scope : "method argument");
1712                                 return false;
1713                         }
1714
1715                         return true;
1716                 }
1717
1718                 public LocalInfo AddVariable (Expression type, string name, Location l)
1719                 {
1720                         LocalInfo vi = GetLocalInfo (name);
1721                         if (vi != null) {
1722                                 Report.SymbolRelatedToPreviousError (vi.Location, name);
1723                                 if (known_variables == vi.Block.known_variables)
1724                                         Report.Error (128, l,
1725                                                 "A local variable named `{0}' is already defined in this scope", name);
1726                                 else
1727                                         Error_AlreadyDeclared (l, name, "parent");
1728                                 return null;
1729                         }
1730
1731                         if (!CheckError136 (name, null, true, true, l))
1732                                 return null;
1733
1734                         vi = new LocalInfo (type, name, this, l);
1735                         Variables.Add (name, vi);
1736                         AddKnownVariable (name, vi);
1737
1738                         if ((flags & Flags.VariablesInitialized) != 0)
1739                                 throw new Exception ();
1740
1741                         return vi;
1742                 }
1743
1744                 void Error_AlreadyDeclared (Location loc, string var, string reason)
1745                 {
1746                         Report.Error (136, loc, "A local variable named `{0}' cannot be declared " +
1747                                       "in this scope because it would give a different meaning " +
1748                                       "to `{0}', which is already used in a `{1}' scope " +
1749                                       "to denote something else", var, reason);
1750                 }
1751
1752                 public bool AddConstant (Expression type, string name, Expression value, Location l)
1753                 {
1754                         if (AddVariable (type, name, l) == null)
1755                                 return false;
1756
1757                         if (constants == null)
1758                                 constants = new Hashtable ();
1759
1760                         constants.Add (name, value);
1761
1762                         // A block is considered used if we perform an initialization in a local declaration, even if it is constant.
1763                         Use ();
1764                         return true;
1765                 }
1766
1767                 static int next_temp_id = 0;
1768
1769                 public LocalInfo AddTemporaryVariable (TypeExpr te, Location loc)
1770                 {
1771                         Report.Debug (64, "ADD TEMPORARY", this, Toplevel, loc);
1772
1773                         if (temporary_variables == null)
1774                                 temporary_variables = new ArrayList ();
1775
1776                         int id = ++next_temp_id;
1777                         string name = "$s_" + id.ToString ();
1778
1779                         LocalInfo li = new LocalInfo (te, name, this, loc);
1780                         li.CompilerGenerated = true;
1781                         temporary_variables.Add (li);
1782                         return li;
1783                 }
1784
1785                 public LocalInfo GetLocalInfo (string name)
1786                 {
1787                         for (Block b = this; b != null; b = b.Parent) {
1788                                 if (b.variables != null) {
1789                                         LocalInfo ret = b.variables [name] as LocalInfo;
1790                                         if (ret != null)
1791                                                 return ret;
1792                                 }
1793                         }
1794                         return null;
1795                 }
1796
1797                 public Expression GetVariableType (string name)
1798                 {
1799                         LocalInfo vi = GetLocalInfo (name);
1800                         return vi == null ? null : vi.Type;
1801                 }
1802
1803                 public Expression GetConstantExpression (string name)
1804                 {
1805                         for (Block b = this; b != null; b = b.Parent) {
1806                                 if (b.constants != null) {
1807                                         Expression ret = b.constants [name] as Expression;
1808                                         if (ret != null)
1809                                                 return ret;
1810                                 }
1811                         }
1812                         return null;
1813                 }
1814
1815                 public void AddStatement (Statement s)
1816                 {
1817                         statements.Add (s);
1818                         flags |= Flags.BlockUsed;
1819                 }
1820
1821                 public bool Used {
1822                         get { return (flags & Flags.BlockUsed) != 0; }
1823                 }
1824
1825                 public void Use ()
1826                 {
1827                         flags |= Flags.BlockUsed;
1828                 }
1829
1830                 public bool HasRet {
1831                         get { return (flags & Flags.HasRet) != 0; }
1832                 }
1833
1834                 public bool IsDestructor {
1835                         get { return (flags & Flags.IsDestructor) != 0; }
1836                 }
1837
1838                 public void SetDestructor ()
1839                 {
1840                         flags |= Flags.IsDestructor;
1841                 }
1842
1843                 VariableMap param_map, local_map;
1844
1845                 public VariableMap ParameterMap {
1846                         get {
1847                                 if ((flags & Flags.VariablesInitialized) == 0)
1848                                         throw new Exception ("Variables have not been initialized yet");
1849
1850                                 return param_map;
1851                         }
1852                 }
1853
1854                 public VariableMap LocalMap {
1855                         get {
1856                                 if ((flags & Flags.VariablesInitialized) == 0)
1857                                         throw new Exception ("Variables have not been initialized yet");
1858
1859                                 return local_map;
1860                         }
1861                 }
1862
1863                 public ScopeInfo ScopeInfo;
1864
1865                 public ScopeInfo CreateScopeInfo ()
1866                 {
1867                         if (ScopeInfo == null)
1868                                 ScopeInfo = ScopeInfo.CreateScope (this);
1869
1870                         return ScopeInfo;
1871                 }
1872
1873                 public ArrayList AnonymousChildren {
1874                         get { return anonymous_children; }
1875                 }
1876
1877                 public void AddAnonymousChild (ToplevelBlock b)
1878                 {
1879                         if (anonymous_children == null)
1880                                 anonymous_children = new ArrayList ();
1881
1882                         anonymous_children.Add (b);
1883                 }
1884
1885                 /// <summary>
1886                 ///   Emits the variable declarations and labels.
1887                 /// </summary>
1888                 /// <remarks>
1889                 ///   tc: is our typecontainer (to resolve type references)
1890                 ///   ig: is the code generator:
1891                 /// </remarks>
1892                 public void ResolveMeta (ToplevelBlock toplevel, EmitContext ec, Parameters ip)
1893                 {
1894                         Report.Debug (64, "BLOCK RESOLVE META", this, Parent, toplevel);
1895
1896                         // If some parent block was unsafe, we remain unsafe even if this block
1897                         // isn't explicitly marked as such.
1898                         using (ec.With (EmitContext.Flags.InUnsafe, ec.InUnsafe | Unsafe)) {
1899                                 //
1900                                 // Compute the VariableMap's.
1901                                 //
1902                                 // Unfortunately, we don't know the type when adding variables with
1903                                 // AddVariable(), so we need to compute this info here.
1904                                 //
1905
1906                                 LocalInfo[] locals;
1907                                 if (variables != null) {
1908                                         foreach (LocalInfo li in variables.Values)
1909                                                 li.Resolve (ec);
1910
1911                                         locals = new LocalInfo [variables.Count];
1912                                         variables.Values.CopyTo (locals, 0);
1913                                 } else
1914                                         locals = new LocalInfo [0];
1915
1916                                 if (Parent != null)
1917                                         local_map = new VariableMap (Parent.LocalMap, locals);
1918                                 else
1919                                         local_map = new VariableMap (locals);
1920
1921                                 param_map = new VariableMap (ip);
1922                                 flags |= Flags.VariablesInitialized;
1923
1924                                 //
1925                                 // Process this block variables
1926                                 //
1927                                 if (variables != null) {
1928                                         foreach (DictionaryEntry de in variables) {
1929                                                 string name = (string) de.Key;
1930                                                 LocalInfo vi = (LocalInfo) de.Value;
1931                                                 Type variable_type = vi.VariableType;
1932
1933                                                 if (variable_type == null)
1934                                                         continue;
1935
1936                                                 if (variable_type.IsPointer) {
1937                                                         //
1938                                                         // Am not really convinced that this test is required (Microsoft does it)
1939                                                         // but the fact is that you would not be able to use the pointer variable
1940                                                         // *anyways*
1941                                                         //
1942                                                         if (!TypeManager.VerifyUnManaged (TypeManager.GetElementType (variable_type),
1943                                                                                           vi.Location))
1944                                                                 continue;
1945                                                 }
1946
1947                                                 if (constants == null)
1948                                                         continue;
1949
1950                                                 Expression cv = (Expression) constants [name];
1951                                                 if (cv == null)
1952                                                         continue;
1953
1954                                                 // Don't let 'const int Foo = Foo;' succeed.
1955                                                 // Removing the name from 'constants' ensures that we get a LocalVariableReference below,
1956                                                 // which in turn causes the 'must be constant' error to be triggered.
1957                                                 constants.Remove (name);
1958
1959                                                 if (!Const.IsConstantTypeValid (variable_type)) {
1960                                                         Const.Error_InvalidConstantType (variable_type, loc);
1961                                                         continue;
1962                                                 }
1963
1964                                                 using (ec.With (EmitContext.Flags.ConstantCheckState, (flags & Flags.Unchecked) == 0)) {
1965                                                         ec.CurrentBlock = this;
1966                                                         Expression e = cv.Resolve (ec);
1967                                                         if (e == null)
1968                                                                 continue;
1969
1970                                                         Constant ce = e as Constant;
1971                                                         if (ce == null) {
1972                                                                 Const.Error_ExpressionMustBeConstant (vi.Location, name);
1973                                                                 continue;
1974                                                         }
1975
1976                                                         e = ce.ImplicitConversionRequired (variable_type, vi.Location);
1977                                                         if (e == null)
1978                                                                 continue;
1979
1980                                                         if (!variable_type.IsValueType && variable_type != TypeManager.string_type && !ce.IsDefaultValue) {
1981                                                                 Const.Error_ConstantCanBeInitializedWithNullOnly (vi.Location, vi.Name);
1982                                                                 continue;
1983                                                         }
1984
1985                                                         constants.Add (name, e);
1986                                                         vi.IsConstant = true;
1987                                                 }
1988                                         }
1989                                 }
1990
1991                                 //
1992                                 // Now, handle the children
1993                                 //
1994                                 if (children != null) {
1995                                         foreach (Block b in children)
1996                                                 b.ResolveMeta (toplevel, ec, ip);
1997                                 }
1998                         }
1999                 }
2000
2001                 //
2002                 // Emits the local variable declarations for a block
2003                 //
2004                 public virtual void EmitMeta (EmitContext ec)
2005                 {
2006                         Report.Debug (64, "BLOCK EMIT META", this, Parent, Toplevel, ScopeInfo, ec);
2007                         if (ScopeInfo != null) {
2008                                 scope_init = ScopeInfo.GetScopeInitializer (ec);
2009                                 Report.Debug (64, "BLOCK EMIT META #1", this, Toplevel, ScopeInfo,
2010                                               ec, scope_init);
2011                         }
2012
2013                         if (variables != null){
2014                                 foreach (LocalInfo vi in variables.Values)
2015                                         vi.ResolveVariable (ec);
2016                         }
2017
2018                         if (temporary_variables != null) {
2019                                 foreach (LocalInfo vi in temporary_variables)
2020                                         vi.ResolveVariable (ec);
2021                         }
2022
2023                         if (children != null){
2024                                 foreach (Block b in children)
2025                                         b.EmitMeta (ec);
2026                         }
2027                 }
2028
2029                 void UsageWarning (FlowBranching.UsageVector vector)
2030                 {
2031                         string name;
2032
2033                         if ((variables != null) && (RootContext.WarningLevel >= 3)) {
2034                                 foreach (DictionaryEntry de in variables){
2035                                         LocalInfo vi = (LocalInfo) de.Value;
2036
2037                                         if (vi.Used)
2038                                                 continue;
2039
2040                                         name = (string) de.Key;
2041
2042                                         // vi.VariableInfo can be null for 'catch' variables
2043                                         if (vi.VariableInfo != null && vector.IsAssigned (vi.VariableInfo, true)){
2044                                                 Report.Warning (219, 3, vi.Location, "The variable `{0}' is assigned but its value is never used", name);
2045                                         } else {
2046                                                 Report.Warning (168, 3, vi.Location, "The variable `{0}' is declared but never used", name);
2047                                         }
2048                                 }
2049                         }
2050                 }
2051
2052                 bool unreachable_shown;
2053                 bool unreachable;
2054
2055                 private void CheckPossibleMistakenEmptyStatement (Statement s)
2056                 {
2057                         Statement body;
2058
2059                         // Some statements are wrapped by a Block. Since
2060                         // others' internal could be changed, here I treat
2061                         // them as possibly wrapped by Block equally.
2062                         Block b = s as Block;
2063                         if (b != null && b.statements.Count == 1)
2064                                 s = (Statement) b.statements [0];
2065
2066                         if (s is Lock)
2067                                 body = ((Lock) s).Statement;
2068                         else if (s is For)
2069                                 body = ((For) s).Statement;
2070                         else if (s is Foreach)
2071                                 body = ((Foreach) s).Statement;
2072                         else if (s is While)
2073                                 body = ((While) s).Statement;
2074                         else if (s is Using)
2075                                 body = ((Using) s).Statement;
2076                         else if (s is Fixed)
2077                                 body = ((Fixed) s).Statement;
2078                         else
2079                                 return;
2080
2081                         if (body == null || body is EmptyStatement)
2082                                 Report.Warning (642, 3, s.loc, "Possible mistaken empty statement");
2083                 }
2084
2085                 public override bool Resolve (EmitContext ec)
2086                 {
2087                         Block prev_block = ec.CurrentBlock;
2088                         bool ok = true;
2089
2090                         int errors = Report.Errors;
2091
2092                         ec.CurrentBlock = this;
2093                         ec.StartFlowBranching (this);
2094
2095                         Report.Debug (4, "RESOLVE BLOCK", StartLocation, ec.CurrentBranching);
2096
2097                         //
2098                         // This flag is used to notate nested statements as unreachable from the beginning of this block.
2099                         // For the purposes of this resolution, it doesn't matter that the whole block is unreachable
2100                         // from the beginning of the function.  The outer Resolve() that detected the unreachability is
2101                         // responsible for handling the situation.
2102                         //
2103                         int statement_count = statements.Count;
2104                         for (int ix = 0; ix < statement_count; ix++){
2105                                 Statement s = (Statement) statements [ix];
2106                                 // Check possible empty statement (CS0642)
2107                                 if (RootContext.WarningLevel >= 3 &&
2108                                         ix + 1 < statement_count &&
2109                                                 statements [ix + 1] is Block)
2110                                         CheckPossibleMistakenEmptyStatement (s);
2111
2112                                 //
2113                                 // Warn if we detect unreachable code.
2114                                 //
2115                                 if (unreachable) {
2116                                         if (s is EmptyStatement)
2117                                                 continue;
2118
2119                                         if (s is Block)
2120                                                 ((Block) s).unreachable = true;
2121
2122                                         if (!unreachable_shown && !(s is LabeledStatement)) {
2123                                                 Report.Warning (162, 2, s.loc, "Unreachable code detected");
2124                                                 unreachable_shown = true;
2125                                         }
2126                                 }
2127
2128                                 //
2129                                 // Note that we're not using ResolveUnreachable() for unreachable
2130                                 // statements here.  ResolveUnreachable() creates a temporary
2131                                 // flow branching and kills it afterwards.  This leads to problems
2132                                 // if you have two unreachable statements where the first one
2133                                 // assigns a variable and the second one tries to access it.
2134                                 //
2135
2136                                 if (!s.Resolve (ec)) {
2137                                         ok = false;
2138                                         statements [ix] = EmptyStatement.Value;
2139                                         continue;
2140                                 }
2141
2142                                 if (unreachable && !(s is LabeledStatement) && !(s is Block))
2143                                         statements [ix] = EmptyStatement.Value;
2144
2145                                 num_statements = ix + 1;
2146
2147                                 unreachable = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
2148                                 if (unreachable && s is LabeledStatement)
2149                                         throw new InternalErrorException ("should not happen");
2150                         }
2151
2152                         Report.Debug (4, "RESOLVE BLOCK DONE", StartLocation,
2153                                       ec.CurrentBranching, statement_count, num_statements);
2154
2155                         while (ec.CurrentBranching is FlowBranchingLabeled)
2156                                 ec.EndFlowBranching ();
2157
2158                         FlowBranching.UsageVector vector = ec.DoEndFlowBranching ();
2159
2160                         ec.CurrentBlock = prev_block;
2161
2162                         // If we're a non-static `struct' constructor which doesn't have an
2163                         // initializer, then we must initialize all of the struct's fields.
2164                         if ((flags & Flags.IsToplevel) != 0 &&
2165                             !Toplevel.IsThisAssigned (ec) &&
2166                             !vector.Reachability.AlwaysThrows)
2167                                 ok = false;
2168
2169                         if ((labels != null) && (RootContext.WarningLevel >= 2)) {
2170                                 foreach (LabeledStatement label in labels.Values)
2171                                         if (!label.HasBeenReferenced)
2172                                                 Report.Warning (164, 2, label.loc,
2173                                                                 "This label has not been referenced");
2174                         }
2175
2176                         Report.Debug (4, "RESOLVE BLOCK DONE #2", StartLocation, vector);
2177
2178                         if (vector.Reachability.IsUnreachable)
2179                                 flags |= Flags.HasRet;
2180
2181                         if (ok && (errors == Report.Errors)) {
2182                                 if (RootContext.WarningLevel >= 3)
2183                                         UsageWarning (vector);
2184                         }
2185
2186                         return ok;
2187                 }
2188
2189                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
2190                 {
2191                         unreachable_shown = true;
2192                         unreachable = true;
2193
2194                         if (warn)
2195                                 Report.Warning (162, 2, loc, "Unreachable code detected");
2196
2197                         ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
2198                         bool ok = Resolve (ec);
2199                         ec.KillFlowBranching ();
2200
2201                         return ok;
2202                 }
2203
2204                 protected override void DoEmit (EmitContext ec)
2205                 {
2206                         for (int ix = 0; ix < num_statements; ix++){
2207                                 Statement s = (Statement) statements [ix];
2208
2209                                 // Check whether we are the last statement in a
2210                                 // top-level block.
2211
2212                                 if (((Parent == null) || Implicit) && (ix+1 == num_statements) && !(s is Block))
2213                                         ec.IsLastStatement = true;
2214                                 else
2215                                         ec.IsLastStatement = false;
2216
2217                                 s.Emit (ec);
2218                         }
2219                 }
2220
2221                 public override void Emit (EmitContext ec)
2222                 {
2223                         Block prev_block = ec.CurrentBlock;
2224
2225                         ec.CurrentBlock = this;
2226
2227                         bool emit_debug_info = (CodeGen.SymbolWriter != null);
2228                         bool is_lexical_block = !Implicit && (Parent != null);
2229
2230                         if (emit_debug_info) {
2231                                 if (is_lexical_block)
2232                                         ec.BeginScope ();
2233                         }
2234                         ec.Mark (StartLocation, true);
2235                         if (scope_init != null)
2236                                 scope_init.EmitStatement (ec);
2237                         DoEmit (ec);
2238                         ec.Mark (EndLocation, true);
2239
2240                         if (emit_debug_info) {
2241                                 if (is_lexical_block)
2242                                         ec.EndScope ();
2243
2244                                 if (variables != null) {
2245                                         foreach (DictionaryEntry de in variables) {
2246                                                 string name = (string) de.Key;
2247                                                 LocalInfo vi = (LocalInfo) de.Value;
2248
2249                                                 vi.EmitSymbolInfo (ec, name);
2250                                         }
2251                                 }
2252                         }
2253
2254                         ec.CurrentBlock = prev_block;
2255                 }
2256
2257                 //
2258                 // Returns true if we ar ea child of `b'.
2259                 //
2260                 public bool IsChildOf (Block b)
2261                 {
2262                         Block current = this;
2263
2264                         do {
2265                                 if (current.Parent == b)
2266                                         return true;
2267                                 current = current.Parent;
2268                         } while (current != null);
2269                         return false;
2270                 }
2271
2272                 public override string ToString ()
2273                 {
2274                         return String.Format ("{0} ({1}:{2})", GetType (),ID, StartLocation);
2275                 }
2276         }
2277
2278         //
2279         // A toplevel block contains extra information, the split is done
2280         // only to separate information that would otherwise bloat the more
2281         // lightweight Block.
2282         //
2283         // In particular, this was introduced when the support for Anonymous
2284         // Methods was implemented.
2285         //
2286         public class ToplevelBlock : Block {
2287                 //
2288                 // Pointer to the host of this anonymous method, or null
2289                 // if we are the topmost block
2290                 //
2291                 Block container;
2292                 ToplevelBlock child;
2293                 GenericMethod generic;
2294                 FlowBranchingToplevel top_level_branching;
2295                 AnonymousContainer anonymous_container;
2296                 RootScopeInfo root_scope;
2297
2298                 public bool HasVarargs {
2299                         get { return (flags & Flags.HasVarargs) != 0; }
2300                         set { flags |= Flags.HasVarargs; }
2301                 }
2302
2303                 public bool IsIterator {
2304                         get { return (flags & Flags.IsIterator) != 0; }
2305                 }
2306
2307                 //
2308                 // The parameters for the block.
2309                 //
2310                 Parameters parameters;
2311                 public Parameters Parameters {
2312                         get { return parameters; }
2313                 }
2314
2315                 public bool CompleteContexts (EmitContext ec)
2316                 {
2317                         Report.Debug (64, "TOPLEVEL COMPLETE CONTEXTS", this,
2318                                       container, root_scope);
2319
2320                         if (root_scope != null)
2321                                 root_scope.LinkScopes ();
2322
2323                         if ((container == null) && (root_scope != null)) {
2324                                 Report.Debug (64, "TOPLEVEL COMPLETE CONTEXTS #1", this,
2325                                               root_scope);
2326
2327                                 if (root_scope.DefineType () == null)
2328                                         return false;
2329                                 if (!root_scope.ResolveType ())
2330                                         return false;
2331                                 if (!root_scope.ResolveMembers ())
2332                                         return false;
2333                                 if (!root_scope.DefineMembers ())
2334                                         return false;
2335                         }
2336
2337                         return true;
2338                 }
2339
2340                 public GenericMethod GenericMethod {
2341                         get { return generic; }
2342                 }
2343
2344                 public ToplevelBlock Container {
2345                         get { return container != null ? container.Toplevel : null; }
2346                 }
2347
2348                 public Block ContainerBlock {
2349                         get { return container; }
2350                 }
2351
2352                 public AnonymousContainer AnonymousContainer {
2353                         get { return anonymous_container; }
2354                         set { anonymous_container = value; }
2355                 }
2356
2357                 //
2358                 // Parent is only used by anonymous blocks to link back to their
2359                 // parents
2360                 //
2361                 public ToplevelBlock (Block container, Parameters parameters, Location start) :
2362                         this (container, (Flags) 0, parameters, start)
2363                 {
2364                 }
2365
2366                 public ToplevelBlock (Block container, Parameters parameters, GenericMethod generic,
2367                                       Location start) :
2368                         this (container, parameters, start)
2369                 {
2370                         this.generic = generic;
2371                 }
2372
2373                 public ToplevelBlock (Parameters parameters, Location start) :
2374                         this (null, (Flags) 0, parameters, start)
2375                 {
2376                 }
2377
2378                 public ToplevelBlock (Flags flags, Parameters parameters, Location start) :
2379                         this (null, flags, parameters, start)
2380                 {
2381                 }
2382
2383                 public ToplevelBlock (Block container, Flags flags, Parameters parameters, Location start) :
2384                         base (null, flags | Flags.IsToplevel, start, Location.Null)
2385                 {
2386                         this.parameters = parameters == null ? Parameters.EmptyReadOnlyParameters : parameters;
2387                         this.container = container;
2388                 }
2389
2390                 public ToplevelBlock (Location loc) : this (null, (Flags) 0, null, loc)
2391                 {
2392                 }
2393
2394                 public bool CheckError158 (string name, Location loc)
2395                 {
2396                         if (AnonymousChildren != null) {
2397                                 foreach (ToplevelBlock child in AnonymousChildren) {
2398                                         if (!child.CheckError158 (name, loc))
2399                                                 return false;
2400                                 }
2401                         }
2402
2403                         for (ToplevelBlock c = Container; c != null; c = c.Container) {
2404                                 if (!c.DoCheckError158 (name, loc))
2405                                         return false;
2406                         }
2407
2408                         return true;
2409                 }
2410
2411                 bool DoCheckError158 (string name, Location loc)
2412                 {
2413                         LabeledStatement s = LookupLabel (name);
2414                         if (s != null) {
2415                                 Error_158 (name, loc);
2416                                 return false;
2417                         }
2418
2419                         return true;
2420                 }
2421
2422                 public RootScopeInfo CreateRootScope (TypeContainer host)
2423                 {
2424                         if (root_scope != null)
2425                                 return root_scope;
2426
2427                         if (Container == null)
2428                                 root_scope = new RootScopeInfo (
2429                                         this, host, generic, StartLocation);
2430
2431                         ScopeInfo = root_scope;
2432                         return root_scope;
2433                 }
2434
2435                 public void CreateIteratorHost (RootScopeInfo root)
2436                 {
2437                         Report.Debug (64, "CREATE ITERATOR HOST", this, root,
2438                                       container, root_scope);
2439
2440                         if ((container != null) || (root_scope != null))
2441                                 throw new InternalErrorException ();
2442
2443                         ScopeInfo = root_scope = root;
2444                 }
2445
2446                 public RootScopeInfo RootScope {
2447                         get {
2448                                 if (root_scope != null)
2449                                         return root_scope;
2450                                 else if (Container != null)
2451                                         return Container.RootScope;
2452                                 else
2453                                         return null;
2454                         }
2455                 }
2456
2457                 public FlowBranchingToplevel TopLevelBranching {
2458                         get { return top_level_branching; }
2459                 }
2460
2461                 //
2462                 // This is used if anonymous methods are used inside an iterator
2463                 // (see 2test-22.cs for an example).
2464                 //
2465                 // The AnonymousMethod is created while parsing - at a time when we don't
2466                 // know yet that we're inside an iterator, so it's `Container' is initially
2467                 // null.  Later on, when resolving the iterator, we need to move the
2468                 // anonymous method into that iterator.
2469                 //
2470                 public void ReParent (ToplevelBlock new_parent)
2471                 {
2472                         container = new_parent;
2473                         Parent = new_parent;
2474                         new_parent.child = this;
2475                 }
2476
2477                 //
2478                 // Returns a `ParameterReference' for the given name, or null if there
2479                 // is no such parameter
2480                 //
2481                 public ParameterReference GetParameterReference (string name, Location loc)
2482                 {
2483                         Parameter par;
2484                         int idx;
2485
2486                         for (ToplevelBlock t = this; t != null; t = t.Container) {
2487                                 Parameters pars = t.Parameters;
2488                                 par = pars.GetParameterByName (name, out idx);
2489                                 if (par != null)
2490                                         return new ParameterReference (par, this, idx, loc);
2491                         }
2492                         return null;
2493                 }
2494
2495                 //
2496                 // Whether the parameter named `name' is local to this block,
2497                 // or false, if the parameter belongs to an encompassing block.
2498                 //
2499                 public bool IsLocalParameter (string name)
2500                 {
2501                         return Parameters.GetParameterByName (name) != null;
2502                 }
2503
2504                 //
2505                 // Whether the `name' is a parameter reference
2506                 //
2507                 public bool IsParameterReference (string name)
2508                 {
2509                         for (ToplevelBlock t = this; t != null; t = t.Container) {
2510                                 if (t.IsLocalParameter (name))
2511                                         return true;
2512                         }
2513                         return false;
2514                 }
2515
2516                 LocalInfo this_variable = null;
2517
2518                 // <summary>
2519                 //   Returns the "this" instance variable of this block.
2520                 //   See AddThisVariable() for more information.
2521                 // </summary>
2522                 public LocalInfo ThisVariable {
2523                         get { return this_variable; }
2524                 }
2525
2526
2527                 // <summary>
2528                 //   This is used by non-static `struct' constructors which do not have an
2529                 //   initializer - in this case, the constructor must initialize all of the
2530                 //   struct's fields.  To do this, we add a "this" variable and use the flow
2531                 //   analysis code to ensure that it's been fully initialized before control
2532                 //   leaves the constructor.
2533                 // </summary>
2534                 public LocalInfo AddThisVariable (DeclSpace ds, Location l)
2535                 {
2536                         if (this_variable == null) {
2537                                 this_variable = new LocalInfo (ds, this, l);
2538                                 this_variable.Used = true;
2539                                 this_variable.IsThis = true;
2540
2541                                 Variables.Add ("this", this_variable);
2542                         }
2543
2544                         return this_variable;
2545                 }
2546
2547                 public bool IsThisAssigned (EmitContext ec)
2548                 {
2549                         return this_variable == null || this_variable.IsThisAssigned (ec, loc);
2550                 }
2551
2552                 public bool ResolveMeta (EmitContext ec, Parameters ip)
2553                 {
2554                         int errors = Report.Errors;
2555
2556                         if (top_level_branching != null)
2557                                 return true;
2558
2559                         if (ip != null)
2560                                 parameters = ip;
2561
2562                         if (!IsIterator && (container != null) && (parameters != null)) {
2563                                 foreach (Parameter p in parameters.FixedParameters) {
2564                                         if (!CheckError136_InParents (p.Name, loc))
2565                                                 return false;
2566                                 }
2567                         }
2568
2569                         ResolveMeta (this, ec, ip);
2570
2571                         if (child != null)
2572                                 child.ResolveMeta (this, ec, ip);
2573
2574                         top_level_branching = ec.StartFlowBranching (this);
2575
2576                         return Report.Errors == errors;
2577                 }
2578
2579                 public override void EmitMeta (EmitContext ec)
2580                 {
2581                         base.EmitMeta (ec);
2582                         parameters.ResolveVariable (this);
2583                 }
2584
2585                 public void MakeIterator (Iterator iterator)
2586                 {
2587                         flags |= Flags.IsIterator;
2588
2589                         Block block = new Block (this);
2590                         foreach (Statement stmt in statements)
2591                                 block.AddStatement (stmt);
2592                         statements = new ArrayList ();
2593                         statements.Add (new MoveNextStatement (iterator, block));
2594                 }
2595
2596                 protected class MoveNextStatement : Statement {
2597                         Iterator iterator;
2598                         Block block;
2599
2600                         public MoveNextStatement (Iterator iterator, Block block)
2601                         {
2602                                 this.iterator = iterator;
2603                                 this.block = block;
2604                                 this.loc = iterator.Location;
2605                         }
2606
2607                         public override bool Resolve (EmitContext ec)
2608                         {
2609                                 return block.Resolve (ec);
2610                         }
2611
2612                         protected override void DoEmit (EmitContext ec)
2613                         {
2614                                 iterator.EmitMoveNext (ec, block);
2615                         }
2616                 }
2617
2618                 public override string ToString ()
2619                 {
2620                         return String.Format ("{0} ({1}:{2}{3}:{4})", GetType (), ID, StartLocation,
2621                                               root_scope, anonymous_container != null ?
2622                                               anonymous_container.Scope : null);
2623                 }
2624         }
2625
2626         public class SwitchLabel {
2627                 Expression label;
2628                 object converted;
2629                 Location loc;
2630
2631                 Label il_label;
2632                 bool  il_label_set;
2633                 Label il_label_code;
2634                 bool  il_label_code_set;
2635
2636                 public static readonly object NullStringCase = new object ();
2637
2638                 //
2639                 // if expr == null, then it is the default case.
2640                 //
2641                 public SwitchLabel (Expression expr, Location l)
2642                 {
2643                         label = expr;
2644                         loc = l;
2645                 }
2646
2647                 public Expression Label {
2648                         get {
2649                                 return label;
2650                         }
2651                 }
2652
2653                 public object Converted {
2654                         get {
2655                                 return converted;
2656                         }
2657                 }
2658
2659                 public Label GetILLabel (EmitContext ec)
2660                 {
2661                         if (!il_label_set){
2662                                 il_label = ec.ig.DefineLabel ();
2663                                 il_label_set = true;
2664                         }
2665                         return il_label;
2666                 }
2667
2668                 public Label GetILLabelCode (EmitContext ec)
2669                 {
2670                         if (!il_label_code_set){
2671                                 il_label_code = ec.ig.DefineLabel ();
2672                                 il_label_code_set = true;
2673                         }
2674                         return il_label_code;
2675                 }
2676
2677                 //
2678                 // Resolves the expression, reduces it to a literal if possible
2679                 // and then converts it to the requested type.
2680                 //
2681                 public bool ResolveAndReduce (EmitContext ec, Type required_type, bool allow_nullable)
2682                 {
2683                         Expression e = label.Resolve (ec);
2684
2685                         if (e == null)
2686                                 return false;
2687
2688                         Constant c = e as Constant;
2689                         if (c == null){
2690                                 Report.Error (150, loc, "A constant value is expected");
2691                                 return false;
2692                         }
2693
2694                         if (required_type == TypeManager.string_type && c.GetValue () == null) {
2695                                 converted = NullStringCase;
2696                                 return true;
2697                         }
2698
2699                         if (allow_nullable && c.GetValue () == null) {
2700                                 converted = NullStringCase;
2701                                 return true;
2702                         }
2703
2704                         c = c.ImplicitConversionRequired (required_type, loc);
2705                         if (c == null)
2706                                 return false;
2707
2708                         converted = c.GetValue ();
2709                         return true;
2710                 }
2711
2712                 public void Erorr_AlreadyOccurs ()
2713                 {
2714                         string label;
2715                         if (converted == null)
2716                                 label = "default";
2717                         else if (converted == NullStringCase)
2718                                 label = "null";
2719                         else
2720                                 label = converted.ToString ();
2721
2722                         Report.Error (152, loc, "The label `case {0}:' already occurs in this switch statement", label);
2723                 }
2724         }
2725
2726         public class SwitchSection {
2727                 // An array of SwitchLabels.
2728                 public readonly ArrayList Labels;
2729                 public readonly Block Block;
2730
2731                 public SwitchSection (ArrayList labels, Block block)
2732                 {
2733                         Labels = labels;
2734                         Block = block;
2735                 }
2736         }
2737
2738         public class Switch : Statement {
2739                 public readonly ArrayList Sections;
2740                 public Expression Expr;
2741
2742                 /// <summary>
2743                 ///   Maps constants whose type type SwitchType to their  SwitchLabels.
2744                 /// </summary>
2745                 public IDictionary Elements;
2746
2747                 /// <summary>
2748                 ///   The governing switch type
2749                 /// </summary>
2750                 public Type SwitchType;
2751
2752                 //
2753                 // Computed
2754                 //
2755                 Label default_target;
2756                 Label null_target;
2757                 Expression new_expr;
2758                 bool is_constant;
2759                 SwitchSection constant_section;
2760                 SwitchSection default_section;
2761
2762 #if GMCS_SOURCE
2763                 //
2764                 // Nullable Types support for GMCS.
2765                 //
2766                 Nullable.Unwrap unwrap;
2767
2768                 protected bool HaveUnwrap {
2769                         get { return unwrap != null; }
2770                 }
2771 #else
2772                 protected bool HaveUnwrap {
2773                         get { return false; }
2774                 }
2775 #endif
2776
2777                 //
2778                 // The types allowed to be implicitly cast from
2779                 // on the governing type
2780                 //
2781                 static Type [] allowed_types;
2782
2783                 public Switch (Expression e, ArrayList sects, Location l)
2784                 {
2785                         Expr = e;
2786                         Sections = sects;
2787                         loc = l;
2788                 }
2789
2790                 public bool GotDefault {
2791                         get {
2792                                 return default_section != null;
2793                         }
2794                 }
2795
2796                 public Label DefaultTarget {
2797                         get {
2798                                 return default_target;
2799                         }
2800                 }
2801
2802                 //
2803                 // Determines the governing type for a switch.  The returned
2804                 // expression might be the expression from the switch, or an
2805                 // expression that includes any potential conversions to the
2806                 // integral types or to string.
2807                 //
2808                 Expression SwitchGoverningType (EmitContext ec, Expression expr)
2809                 {
2810                         Type t = expr.Type;
2811
2812                         if (t == TypeManager.byte_type ||
2813                             t == TypeManager.sbyte_type ||
2814                             t == TypeManager.ushort_type ||
2815                             t == TypeManager.short_type ||
2816                             t == TypeManager.uint32_type ||
2817                             t == TypeManager.int32_type ||
2818                             t == TypeManager.uint64_type ||
2819                             t == TypeManager.int64_type ||
2820                             t == TypeManager.char_type ||
2821                             t == TypeManager.string_type ||
2822                             t == TypeManager.bool_type ||
2823                             t.IsSubclassOf (TypeManager.enum_type))
2824                                 return expr;
2825
2826                         if (allowed_types == null){
2827                                 allowed_types = new Type [] {
2828                                         TypeManager.sbyte_type,
2829                                         TypeManager.byte_type,
2830                                         TypeManager.short_type,
2831                                         TypeManager.ushort_type,
2832                                         TypeManager.int32_type,
2833                                         TypeManager.uint32_type,
2834                                         TypeManager.int64_type,
2835                                         TypeManager.uint64_type,
2836                                         TypeManager.char_type,
2837                                         TypeManager.string_type,
2838                                         TypeManager.bool_type
2839                                 };
2840                         }
2841
2842                         //
2843                         // Try to find a *user* defined implicit conversion.
2844                         //
2845                         // If there is no implicit conversion, or if there are multiple
2846                         // conversions, we have to report an error
2847                         //
2848                         Expression converted = null;
2849                         foreach (Type tt in allowed_types){
2850                                 Expression e;
2851
2852                                 e = Convert.ImplicitUserConversion (ec, expr, tt, loc);
2853                                 if (e == null)
2854                                         continue;
2855
2856                                 //
2857                                 // Ignore over-worked ImplicitUserConversions that do
2858                                 // an implicit conversion in addition to the user conversion.
2859                                 //
2860                                 if (!(e is UserCast))
2861                                         continue;
2862
2863                                 if (converted != null){
2864                                         Report.ExtraInformation (
2865                                                 loc,
2866                                                 String.Format ("reason: more than one conversion to an integral type exist for type {0}",
2867                                                                TypeManager.CSharpName (expr.Type)));
2868                                         return null;
2869                                 }
2870
2871                                 converted = e;
2872                         }
2873                         return converted;
2874                 }
2875
2876                 //
2877                 // Performs the basic sanity checks on the switch statement
2878                 // (looks for duplicate keys and non-constant expressions).
2879                 //
2880                 // It also returns a hashtable with the keys that we will later
2881                 // use to compute the switch tables
2882                 //
2883                 bool CheckSwitch (EmitContext ec)
2884                 {
2885                         bool error = false;
2886                         Elements = Sections.Count > 10 ?
2887                                 (IDictionary)new Hashtable () :
2888                                 (IDictionary)new ListDictionary ();
2889
2890                         foreach (SwitchSection ss in Sections){
2891                                 foreach (SwitchLabel sl in ss.Labels){
2892                                         if (sl.Label == null){
2893                                                 if (default_section != null){
2894                                                         sl.Erorr_AlreadyOccurs ();
2895                                                         error = true;
2896                                                 }
2897                                                 default_section = ss;
2898                                                 continue;
2899                                         }
2900
2901                                         if (!sl.ResolveAndReduce (ec, SwitchType, HaveUnwrap)) {
2902                                                 error = true;
2903                                                 continue;
2904                                         }
2905
2906                                         object key = sl.Converted;
2907                                         try {
2908                                                 Elements.Add (key, sl);
2909                                         } catch (ArgumentException) {
2910                                                 sl.Erorr_AlreadyOccurs ();
2911                                                 error = true;
2912                                         }
2913                                 }
2914                         }
2915                         return !error;
2916                 }
2917
2918                 void EmitObjectInteger (ILGenerator ig, object k)
2919                 {
2920                         if (k is int)
2921                                 IntConstant.EmitInt (ig, (int) k);
2922                         else if (k is Constant) {
2923                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
2924                         }
2925                         else if (k is uint)
2926                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
2927                         else if (k is long)
2928                         {
2929                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
2930                                 {
2931                                         IntConstant.EmitInt (ig, (int) (long) k);
2932                                         ig.Emit (OpCodes.Conv_I8);
2933                                 }
2934                                 else
2935                                         LongConstant.EmitLong (ig, (long) k);
2936                         }
2937                         else if (k is ulong)
2938                         {
2939                                 ulong ul = (ulong) k;
2940                                 if (ul < (1L<<32))
2941                                 {
2942                                         IntConstant.EmitInt (ig, unchecked ((int) ul));
2943                                         ig.Emit (OpCodes.Conv_U8);
2944                                 }
2945                                 else
2946                                 {
2947                                         LongConstant.EmitLong (ig, unchecked ((long) ul));
2948                                 }
2949                         }
2950                         else if (k is char)
2951                                 IntConstant.EmitInt (ig, (int) ((char) k));
2952                         else if (k is sbyte)
2953                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
2954                         else if (k is byte)
2955                                 IntConstant.EmitInt (ig, (int) ((byte) k));
2956                         else if (k is short)
2957                                 IntConstant.EmitInt (ig, (int) ((short) k));
2958                         else if (k is ushort)
2959                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
2960                         else if (k is bool)
2961                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
2962                         else
2963                                 throw new Exception ("Unhandled case");
2964                 }
2965
2966                 // structure used to hold blocks of keys while calculating table switch
2967                 class KeyBlock : IComparable
2968                 {
2969                         public KeyBlock (long _nFirst)
2970                         {
2971                                 nFirst = nLast = _nFirst;
2972                         }
2973                         public long nFirst;
2974                         public long nLast;
2975                         public ArrayList rgKeys = null;
2976                         // how many items are in the bucket
2977                         public int Size = 1;
2978                         public int Length
2979                         {
2980                                 get { return (int) (nLast - nFirst + 1); }
2981                         }
2982                         public static long TotalLength (KeyBlock kbFirst, KeyBlock kbLast)
2983                         {
2984                                 return kbLast.nLast - kbFirst.nFirst + 1;
2985                         }
2986                         public int CompareTo (object obj)
2987                         {
2988                                 KeyBlock kb = (KeyBlock) obj;
2989                                 int nLength = Length;
2990                                 int nLengthOther = kb.Length;
2991                                 if (nLengthOther == nLength)
2992                                         return (int) (kb.nFirst - nFirst);
2993                                 return nLength - nLengthOther;
2994                         }
2995                 }
2996
2997                 /// <summary>
2998                 /// This method emits code for a lookup-based switch statement (non-string)
2999                 /// Basically it groups the cases into blocks that are at least half full,
3000                 /// and then spits out individual lookup opcodes for each block.
3001                 /// It emits the longest blocks first, and short blocks are just
3002                 /// handled with direct compares.
3003                 /// </summary>
3004                 /// <param name="ec"></param>
3005                 /// <param name="val"></param>
3006                 /// <returns></returns>
3007                 void TableSwitchEmit (EmitContext ec, LocalBuilder val)
3008                 {
3009                         int cElements = Elements.Count;
3010                         object [] rgKeys = new object [cElements];
3011                         Elements.Keys.CopyTo (rgKeys, 0);
3012                         Array.Sort (rgKeys);
3013
3014                         // initialize the block list with one element per key
3015                         ArrayList rgKeyBlocks = new ArrayList ();
3016                         foreach (object key in rgKeys)
3017                                 rgKeyBlocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));
3018
3019                         KeyBlock kbCurr;
3020                         // iteratively merge the blocks while they are at least half full
3021                         // there's probably a really cool way to do this with a tree...
3022                         while (rgKeyBlocks.Count > 1)
3023                         {
3024                                 ArrayList rgKeyBlocksNew = new ArrayList ();
3025                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
3026                                 for (int ikb = 1; ikb < rgKeyBlocks.Count; ikb++)
3027                                 {
3028                                         KeyBlock kb = (KeyBlock) rgKeyBlocks [ikb];
3029                                         if ((kbCurr.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (kbCurr, kb))
3030                                         {
3031                                                 // merge blocks
3032                                                 kbCurr.nLast = kb.nLast;
3033                                                 kbCurr.Size += kb.Size;
3034                                         }
3035                                         else
3036                                         {
3037                                                 // start a new block
3038                                                 rgKeyBlocksNew.Add (kbCurr);
3039                                                 kbCurr = kb;
3040                                         }
3041                                 }
3042                                 rgKeyBlocksNew.Add (kbCurr);
3043                                 if (rgKeyBlocks.Count == rgKeyBlocksNew.Count)
3044                                         break;
3045                                 rgKeyBlocks = rgKeyBlocksNew;
3046                         }
3047
3048                         // initialize the key lists
3049                         foreach (KeyBlock kb in rgKeyBlocks)
3050                                 kb.rgKeys = new ArrayList ();
3051
3052                         // fill the key lists
3053                         int iBlockCurr = 0;
3054                         if (rgKeyBlocks.Count > 0) {
3055                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
3056                                 foreach (object key in rgKeys)
3057                                 {
3058                                         bool fNextBlock = (key is UInt64) ? (ulong) key > (ulong) kbCurr.nLast :
3059                                                 System.Convert.ToInt64 (key) > kbCurr.nLast;
3060                                         if (fNextBlock)
3061                                                 kbCurr = (KeyBlock) rgKeyBlocks [++iBlockCurr];
3062                                         kbCurr.rgKeys.Add (key);
3063                                 }
3064                         }
3065
3066                         // sort the blocks so we can tackle the largest ones first
3067                         rgKeyBlocks.Sort ();
3068
3069                         // okay now we can start...
3070                         ILGenerator ig = ec.ig;
3071                         Label lblEnd = ig.DefineLabel ();       // at the end ;-)
3072                         Label lblDefault = ig.DefineLabel ();
3073
3074                         Type typeKeys = null;
3075                         if (rgKeys.Length > 0)
3076                                 typeKeys = rgKeys [0].GetType ();       // used for conversions
3077
3078                         Type compare_type;
3079
3080                         if (TypeManager.IsEnumType (SwitchType))
3081                                 compare_type = TypeManager.EnumToUnderlying (SwitchType);
3082                         else
3083                                 compare_type = SwitchType;
3084
3085                         for (int iBlock = rgKeyBlocks.Count - 1; iBlock >= 0; --iBlock)
3086                         {
3087                                 KeyBlock kb = ((KeyBlock) rgKeyBlocks [iBlock]);
3088                                 lblDefault = (iBlock == 0) ? DefaultTarget : ig.DefineLabel ();
3089                                 if (kb.Length <= 2)
3090                                 {
3091                                         foreach (object key in kb.rgKeys)
3092                                         {
3093                                                 ig.Emit (OpCodes.Ldloc, val);
3094                                                 EmitObjectInteger (ig, key);
3095                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
3096                                                 ig.Emit (OpCodes.Beq, sl.GetILLabel (ec));
3097                                         }
3098                                 }
3099                                 else
3100                                 {
3101                                         // TODO: if all the keys in the block are the same and there are
3102                                         //       no gaps/defaults then just use a range-check.
3103                                         if (compare_type == TypeManager.int64_type ||
3104                                                 compare_type == TypeManager.uint64_type)
3105                                         {
3106                                                 // TODO: optimize constant/I4 cases
3107
3108                                                 // check block range (could be > 2^31)
3109                                                 ig.Emit (OpCodes.Ldloc, val);
3110                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.nFirst, typeKeys));
3111                                                 ig.Emit (OpCodes.Blt, lblDefault);
3112                                                 ig.Emit (OpCodes.Ldloc, val);
3113                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.nLast, typeKeys));
3114                                                 ig.Emit (OpCodes.Bgt, lblDefault);
3115
3116                                                 // normalize range
3117                                                 ig.Emit (OpCodes.Ldloc, val);
3118                                                 if (kb.nFirst != 0)
3119                                                 {
3120                                                         EmitObjectInteger (ig, System.Convert.ChangeType (kb.nFirst, typeKeys));
3121                                                         ig.Emit (OpCodes.Sub);
3122                                                 }
3123                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
3124                                         }
3125                                         else
3126                                         {
3127                                                 // normalize range
3128                                                 ig.Emit (OpCodes.Ldloc, val);
3129                                                 int nFirst = (int) kb.nFirst;
3130                                                 if (nFirst > 0)
3131                                                 {
3132                                                         IntConstant.EmitInt (ig, nFirst);
3133                                                         ig.Emit (OpCodes.Sub);
3134                                                 }
3135                                                 else if (nFirst < 0)
3136                                                 {
3137                                                         IntConstant.EmitInt (ig, -nFirst);
3138                                                         ig.Emit (OpCodes.Add);
3139                                                 }
3140                                         }
3141
3142                                         // first, build the list of labels for the switch
3143                                         int iKey = 0;
3144                                         int cJumps = kb.Length;
3145                                         Label [] rgLabels = new Label [cJumps];
3146                                         for (int iJump = 0; iJump < cJumps; iJump++)
3147                                         {
3148                                                 object key = kb.rgKeys [iKey];
3149                                                 if (System.Convert.ToInt64 (key) == kb.nFirst + iJump)
3150                                                 {
3151                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
3152                                                         rgLabels [iJump] = sl.GetILLabel (ec);
3153                                                         iKey++;
3154                                                 }
3155                                                 else
3156                                                         rgLabels [iJump] = lblDefault;
3157                                         }
3158                                         // emit the switch opcode
3159                                         ig.Emit (OpCodes.Switch, rgLabels);
3160                                 }
3161
3162                                 // mark the default for this block
3163                                 if (iBlock != 0)
3164                                         ig.MarkLabel (lblDefault);
3165                         }
3166
3167                         // TODO: find the default case and emit it here,
3168                         //       to prevent having to do the following jump.
3169                         //       make sure to mark other labels in the default section
3170
3171                         // the last default just goes to the end
3172                         ig.Emit (OpCodes.Br, lblDefault);
3173
3174                         // now emit the code for the sections
3175                         bool fFoundDefault = false;
3176                         bool fFoundNull = false;
3177                         foreach (SwitchSection ss in Sections)
3178                         {
3179                                 foreach (SwitchLabel sl in ss.Labels)
3180                                         if (sl.Converted == SwitchLabel.NullStringCase)
3181                                                 fFoundNull = true;
3182                         }
3183
3184                         foreach (SwitchSection ss in Sections)
3185                         {
3186                                 foreach (SwitchLabel sl in ss.Labels)
3187                                 {
3188                                         ig.MarkLabel (sl.GetILLabel (ec));
3189                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3190                                         if (sl.Converted == SwitchLabel.NullStringCase)
3191                                                 ig.MarkLabel (null_target);
3192                                         else if (sl.Label == null) {
3193                                                 ig.MarkLabel (lblDefault);
3194                                                 fFoundDefault = true;
3195                                                 if (!fFoundNull)
3196                                                         ig.MarkLabel (null_target);
3197                                         }
3198                                 }
3199                                 ss.Block.Emit (ec);
3200                         }
3201
3202                         if (!fFoundDefault) {
3203                                 ig.MarkLabel (lblDefault);
3204                         }
3205                         ig.MarkLabel (lblEnd);
3206                 }
3207                 //
3208                 // This simple emit switch works, but does not take advantage of the
3209                 // `switch' opcode.
3210                 // TODO: remove non-string logic from here
3211                 // TODO: binary search strings?
3212                 //
3213                 void SimpleSwitchEmit (EmitContext ec, LocalBuilder val)
3214                 {
3215                         ILGenerator ig = ec.ig;
3216                         Label end_of_switch = ig.DefineLabel ();
3217                         Label next_test = ig.DefineLabel ();
3218                         bool first_test = true;
3219                         bool pending_goto_end = false;
3220                         bool null_marked = false;
3221                         bool null_found;
3222
3223                         ig.Emit (OpCodes.Ldloc, val);
3224
3225                         if (Elements.Contains (SwitchLabel.NullStringCase)){
3226                                 ig.Emit (OpCodes.Brfalse, null_target);
3227                         } else
3228                                 ig.Emit (OpCodes.Brfalse, default_target);
3229
3230                         ig.Emit (OpCodes.Ldloc, val);
3231                         ig.Emit (OpCodes.Call, TypeManager.string_isinterneted_string);
3232                         ig.Emit (OpCodes.Stloc, val);
3233
3234                         int section_count = Sections.Count;
3235                         for (int section = 0; section < section_count; section++){
3236                                 SwitchSection ss = (SwitchSection) Sections [section];
3237
3238                                 if (ss == default_section)
3239                                         continue;
3240
3241                                 Label sec_begin = ig.DefineLabel ();
3242
3243                                 ig.Emit (OpCodes.Nop);
3244
3245                                 if (pending_goto_end)
3246                                         ig.Emit (OpCodes.Br, end_of_switch);
3247
3248                                 int label_count = ss.Labels.Count;
3249                                 null_found = false;
3250                                 for (int label = 0; label < label_count; label++){
3251                                         SwitchLabel sl = (SwitchLabel) ss.Labels [label];
3252                                         ig.MarkLabel (sl.GetILLabel (ec));
3253
3254                                         if (!first_test){
3255                                                 ig.MarkLabel (next_test);
3256                                                 next_test = ig.DefineLabel ();
3257                                         }
3258                                         //
3259                                         // If we are the default target
3260                                         //
3261                                         if (sl.Label != null){
3262                                                 object lit = sl.Converted;
3263
3264                                                 if (lit == SwitchLabel.NullStringCase){
3265                                                         null_found = true;
3266                                                         if (label + 1 == label_count)
3267                                                                 ig.Emit (OpCodes.Br, next_test);
3268                                                         continue;
3269                                                 }
3270
3271                                                 ig.Emit (OpCodes.Ldloc, val);
3272                                                 ig.Emit (OpCodes.Ldstr, (string)lit);
3273                                                 if (label_count == 1)
3274                                                         ig.Emit (OpCodes.Bne_Un, next_test);
3275                                                 else {
3276                                                         if (label+1 == label_count)
3277                                                                 ig.Emit (OpCodes.Bne_Un, next_test);
3278                                                         else
3279                                                                 ig.Emit (OpCodes.Beq, sec_begin);
3280                                                 }
3281                                         }
3282                                 }
3283                                 if (null_found) {
3284                                         ig.MarkLabel (null_target);
3285                                         null_marked = true;
3286                                 }
3287                                 ig.MarkLabel (sec_begin);
3288                                 foreach (SwitchLabel sl in ss.Labels)
3289                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3290
3291                                 ss.Block.Emit (ec);
3292                                 pending_goto_end = !ss.Block.HasRet;
3293                                 first_test = false;
3294                         }
3295                         ig.MarkLabel (next_test);
3296                         ig.MarkLabel (default_target);
3297                         if (!null_marked)
3298                                 ig.MarkLabel (null_target);
3299                         if (default_section != null)
3300                                 default_section.Block.Emit (ec);
3301                         ig.MarkLabel (end_of_switch);
3302                 }
3303
3304                 SwitchSection FindSection (SwitchLabel label)
3305                 {
3306                         foreach (SwitchSection ss in Sections){
3307                                 foreach (SwitchLabel sl in ss.Labels){
3308                                         if (label == sl)
3309                                                 return ss;
3310                                 }
3311                         }
3312
3313                         return null;
3314                 }
3315
3316                 public override bool Resolve (EmitContext ec)
3317                 {
3318                         Expr = Expr.Resolve (ec);
3319                         if (Expr == null)
3320                                 return false;
3321
3322                         new_expr = SwitchGoverningType (ec, Expr);
3323
3324 #if GMCS_SOURCE
3325                         if ((new_expr == null) && TypeManager.IsNullableType (Expr.Type)) {
3326                                 unwrap = Nullable.Unwrap.Create (Expr, ec);
3327                                 if (unwrap == null)
3328                                         return false;
3329
3330                                 new_expr = SwitchGoverningType (ec, unwrap);
3331                         }
3332 #endif
3333
3334                         if (new_expr == null){
3335                                 Report.Error (151, loc, "A value of an integral type or string expected for switch");
3336                                 return false;
3337                         }
3338
3339                         // Validate switch.
3340                         SwitchType = new_expr.Type;
3341
3342                         if (!CheckSwitch (ec))
3343                                 return false;
3344
3345                         if (HaveUnwrap)
3346                                 Elements.Remove (SwitchLabel.NullStringCase);
3347
3348                         Switch old_switch = ec.Switch;
3349                         ec.Switch = this;
3350                         ec.Switch.SwitchType = SwitchType;
3351
3352                         Report.Debug (1, "START OF SWITCH BLOCK", loc, ec.CurrentBranching);
3353                         ec.StartFlowBranching (FlowBranching.BranchingType.Switch, loc);
3354
3355                         is_constant = new_expr is Constant;
3356                         if (is_constant) {
3357                                 object key = ((Constant) new_expr).GetValue ();
3358                                 SwitchLabel label = (SwitchLabel) Elements [key];
3359
3360                                 constant_section = FindSection (label);
3361                                 if (constant_section == null)
3362                                         constant_section = default_section;
3363                         }
3364
3365                         bool first = true;
3366                         foreach (SwitchSection ss in Sections){
3367                                 if (!first)
3368                                         ec.CurrentBranching.CreateSibling (
3369                                                 null, FlowBranching.SiblingType.SwitchSection);
3370                                 else
3371                                         first = false;
3372
3373                                 if (is_constant && (ss != constant_section)) {
3374                                         // If we're a constant switch, we're only emitting
3375                                         // one single section - mark all the others as
3376                                         // unreachable.
3377                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
3378                                         if (!ss.Block.ResolveUnreachable (ec, true))
3379                                                 return false;
3380                                 } else {
3381                                         if (!ss.Block.Resolve (ec))
3382                                                 return false;
3383                                 }
3384                         }
3385
3386                         if (default_section == null)
3387                                 ec.CurrentBranching.CreateSibling (
3388                                         null, FlowBranching.SiblingType.SwitchSection);
3389
3390                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3391                         ec.Switch = old_switch;
3392
3393                         Report.Debug (1, "END OF SWITCH BLOCK", loc, ec.CurrentBranching,
3394                                       reachability);
3395
3396                         return true;
3397                 }
3398
3399                 protected override void DoEmit (EmitContext ec)
3400                 {
3401                         ILGenerator ig = ec.ig;
3402
3403                         default_target = ig.DefineLabel ();
3404                         null_target = ig.DefineLabel ();
3405
3406                         // Store variable for comparission purposes
3407                         LocalBuilder value;
3408                         if (HaveUnwrap) {
3409                                 value = ig.DeclareLocal (SwitchType);
3410 #if GMCS_SOURCE
3411                                 unwrap.EmitCheck (ec);
3412                                 ig.Emit (OpCodes.Brfalse, null_target);
3413                                 new_expr.Emit (ec);
3414                                 ig.Emit (OpCodes.Stloc, value);
3415 #endif
3416                         } else if (!is_constant) {
3417                                 value = ig.DeclareLocal (SwitchType);
3418                                 new_expr.Emit (ec);
3419                                 ig.Emit (OpCodes.Stloc, value);
3420                         } else
3421                                 value = null;
3422
3423                         //
3424                         // Setup the codegen context
3425                         //
3426                         Label old_end = ec.LoopEnd;
3427                         Switch old_switch = ec.Switch;
3428
3429                         ec.LoopEnd = ig.DefineLabel ();
3430                         ec.Switch = this;
3431
3432                         // Emit Code.
3433                         if (is_constant) {
3434                                 if (constant_section != null)
3435                                         constant_section.Block.Emit (ec);
3436                         } else if (SwitchType == TypeManager.string_type)
3437                                 SimpleSwitchEmit (ec, value);
3438                         else
3439                                 TableSwitchEmit (ec, value);
3440
3441                         // Restore context state.
3442                         ig.MarkLabel (ec.LoopEnd);
3443
3444                         //
3445                         // Restore the previous context
3446                         //
3447                         ec.LoopEnd = old_end;
3448                         ec.Switch = old_switch;
3449                 }
3450         }
3451
3452         public abstract class ExceptionStatement : Statement
3453         {
3454                 public abstract void EmitFinally (EmitContext ec);
3455
3456                 protected bool emit_finally = true;
3457                 ArrayList parent_vectors;
3458
3459                 protected void DoEmitFinally (EmitContext ec)
3460                 {
3461                         if (emit_finally)
3462                                 ec.ig.BeginFinallyBlock ();
3463                         else if (ec.InIterator)
3464                                 ec.CurrentIterator.MarkFinally (ec, parent_vectors);
3465                         EmitFinally (ec);
3466                 }
3467
3468                 protected void ResolveFinally (FlowBranchingException branching)
3469                 {
3470                         emit_finally = branching.EmitFinally;
3471                         if (!emit_finally)
3472                                 branching.Parent.StealFinallyClauses (ref parent_vectors);
3473                 }
3474         }
3475
3476         public class Lock : ExceptionStatement {
3477                 Expression expr;
3478                 public Statement Statement;
3479                 TemporaryVariable temp;
3480
3481                 public Lock (Expression expr, Statement stmt, Location l)
3482                 {
3483                         this.expr = expr;
3484                         Statement = stmt;
3485                         loc = l;
3486                 }
3487
3488                 public override bool Resolve (EmitContext ec)
3489                 {
3490                         expr = expr.Resolve (ec);
3491                         if (expr == null)
3492                                 return false;
3493
3494                         if (expr.Type.IsValueType){
3495                                 Report.Error (185, loc,
3496                                               "`{0}' is not a reference type as required by the lock statement",
3497                                               TypeManager.CSharpName (expr.Type));
3498                                 return false;
3499                         }
3500
3501                         FlowBranchingException branching = ec.StartFlowBranching (this);
3502                         bool ok = Statement.Resolve (ec);
3503                         if (!ok) {
3504                                 ec.KillFlowBranching ();
3505                                 return false;
3506                         }
3507
3508                         ResolveFinally (branching);
3509
3510                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3511                         if (!reachability.AlwaysReturns) {
3512                                 // Unfortunately, System.Reflection.Emit automatically emits
3513                                 // a leave to the end of the finally block.
3514                                 // This is a problem if `returns' is true since we may jump
3515                                 // to a point after the end of the method.
3516                                 // As a workaround, emit an explicit ret here.
3517                                 ec.NeedReturnLabel ();
3518                         }
3519
3520                         // Avoid creating libraries that reference the internal
3521                         // mcs NullType:
3522                         Type t = expr.Type;
3523                         if (t == TypeManager.null_type)
3524                                 t = TypeManager.object_type;
3525
3526                         temp = new TemporaryVariable (t, loc);
3527                         temp.Resolve (ec);
3528
3529                         return true;
3530                 }
3531
3532                 protected override void DoEmit (EmitContext ec)
3533                 {
3534                         ILGenerator ig = ec.ig;
3535
3536                         temp.Store (ec, expr);
3537                         temp.Emit (ec);
3538                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
3539
3540                         // try
3541                         if (emit_finally)
3542                                 ig.BeginExceptionBlock ();
3543                         Statement.Emit (ec);
3544
3545                         // finally
3546                         DoEmitFinally (ec);
3547                         if (emit_finally)
3548                                 ig.EndExceptionBlock ();
3549                 }
3550
3551                 public override void EmitFinally (EmitContext ec)
3552                 {
3553                         temp.Emit (ec);
3554                         ec.ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
3555                 }
3556         }
3557
3558         public class Unchecked : Statement {
3559                 public readonly Block Block;
3560
3561                 public Unchecked (Block b)
3562                 {
3563                         Block = b;
3564                         b.Unchecked = true;
3565                 }
3566
3567                 public override bool Resolve (EmitContext ec)
3568                 {
3569                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
3570                                 return Block.Resolve (ec);
3571                 }
3572
3573                 protected override void DoEmit (EmitContext ec)
3574                 {
3575                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
3576                                 Block.Emit (ec);
3577                 }
3578         }
3579
3580         public class Checked : Statement {
3581                 public readonly Block Block;
3582
3583                 public Checked (Block b)
3584                 {
3585                         Block = b;
3586                         b.Unchecked = false;
3587                 }
3588
3589                 public override bool Resolve (EmitContext ec)
3590                 {
3591                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
3592                                 return Block.Resolve (ec);
3593                 }
3594
3595                 protected override void DoEmit (EmitContext ec)
3596                 {
3597                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
3598                                 Block.Emit (ec);
3599                 }
3600         }
3601
3602         public class Unsafe : Statement {
3603                 public readonly Block Block;
3604
3605                 public Unsafe (Block b)
3606                 {
3607                         Block = b;
3608                         Block.Unsafe = true;
3609                 }
3610
3611                 public override bool Resolve (EmitContext ec)
3612                 {
3613                         using (ec.With (EmitContext.Flags.InUnsafe, true))
3614                                 return Block.Resolve (ec);
3615                 }
3616
3617                 protected override void DoEmit (EmitContext ec)
3618                 {
3619                         using (ec.With (EmitContext.Flags.InUnsafe, true))
3620                                 Block.Emit (ec);
3621                 }
3622         }
3623
3624         //
3625         // Fixed statement
3626         //
3627         public class Fixed : Statement {
3628                 Expression type;
3629                 ArrayList declarators;
3630                 Statement statement;
3631                 Type expr_type;
3632                 Emitter[] data;
3633                 bool has_ret;
3634
3635                 abstract class Emitter
3636                 {
3637                         protected LocalInfo vi;
3638                         protected Expression converted;
3639
3640                         protected Emitter (Expression expr, LocalInfo li)
3641                         {
3642                                 converted = expr;
3643                                 vi = li;
3644                         }
3645
3646                         public abstract void Emit (EmitContext ec);
3647                         public abstract void EmitExit (EmitContext ec);
3648                 }
3649
3650                 class ExpressionEmitter : Emitter {
3651                         public ExpressionEmitter (Expression converted, LocalInfo li) :
3652                                 base (converted, li)
3653                         {
3654                         }
3655
3656                         public override void Emit (EmitContext ec) {
3657                                 //
3658                                 // Store pointer in pinned location
3659                                 //
3660                                 converted.Emit (ec);
3661                                 vi.Variable.EmitAssign (ec);
3662                         }
3663
3664                         public override void EmitExit (EmitContext ec)
3665                         {
3666                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
3667                                 ec.ig.Emit (OpCodes.Conv_U);
3668                                 vi.Variable.EmitAssign (ec);
3669                         }
3670                 }
3671
3672                 class StringEmitter : Emitter {
3673                         LocalBuilder pinned_string;
3674                         Location loc;
3675
3676                         public StringEmitter (Expression expr, LocalInfo li, Location loc):
3677                                 base (expr, li)
3678                         {
3679                                 this.loc = loc;
3680                         }
3681
3682                         public override void Emit (EmitContext ec)
3683                         {
3684                                 ILGenerator ig = ec.ig;
3685                                 pinned_string = TypeManager.DeclareLocalPinned (ig, TypeManager.string_type);
3686
3687                                 converted.Emit (ec);
3688                                 ig.Emit (OpCodes.Stloc, pinned_string);
3689
3690                                 Expression sptr = new StringPtr (pinned_string, loc);
3691                                 converted = Convert.ImplicitConversionRequired (
3692                                         ec, sptr, vi.VariableType, loc);
3693
3694                                 if (converted == null)
3695                                         return;
3696
3697                                 converted.Emit (ec);
3698                                 vi.Variable.EmitAssign (ec);
3699                         }
3700
3701                         public override void EmitExit (EmitContext ec)
3702                         {
3703                                 ec.ig.Emit (OpCodes.Ldnull);
3704                                 ec.ig.Emit (OpCodes.Stloc, pinned_string);
3705                         }
3706                 }
3707
3708                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
3709                 {
3710                         this.type = type;
3711                         declarators = decls;
3712                         statement = stmt;
3713                         loc = l;
3714                 }
3715
3716                 public Statement Statement {
3717                         get { return statement; }
3718                 }
3719
3720                 public override bool Resolve (EmitContext ec)
3721                 {
3722                         if (!ec.InUnsafe){
3723                                 Expression.UnsafeError (loc);
3724                                 return false;
3725                         }
3726
3727                         TypeExpr texpr = type.ResolveAsTypeTerminal (ec, false);
3728                         if (texpr == null)
3729                                 return false;
3730
3731                         expr_type = texpr.Type;
3732
3733                         data = new Emitter [declarators.Count];
3734
3735                         if (!expr_type.IsPointer){
3736                                 Report.Error (209, loc, "The type of locals declared in a fixed statement must be a pointer type");
3737                                 return false;
3738                         }
3739
3740                         int i = 0;
3741                         foreach (Pair p in declarators){
3742                                 LocalInfo vi = (LocalInfo) p.First;
3743                                 Expression e = (Expression) p.Second;
3744
3745                                 vi.VariableInfo.SetAssigned (ec);
3746                                 vi.SetReadOnlyContext (LocalInfo.ReadOnlyContext.Fixed);
3747
3748                                 //
3749                                 // The rules for the possible declarators are pretty wise,
3750                                 // but the production on the grammar is more concise.
3751                                 //
3752                                 // So we have to enforce these rules here.
3753                                 //
3754                                 // We do not resolve before doing the case 1 test,
3755                                 // because the grammar is explicit in that the token &
3756                                 // is present, so we need to test for this particular case.
3757                                 //
3758
3759                                 if (e is Cast){
3760                                         Report.Error (254, loc, "The right hand side of a fixed statement assignment may not be a cast expression");
3761                                         return false;
3762                                 }
3763
3764                                 //
3765                                 // Case 1: & object.
3766                                 //
3767                                 if (e is Unary && ((Unary) e).Oper == Unary.Operator.AddressOf){
3768                                         Expression child = ((Unary) e).Expr;
3769
3770                                         if (child is ParameterReference || child is LocalVariableReference){
3771                                                 Report.Error (
3772                                                         213, loc,
3773                                                         "No need to use fixed statement for parameters or " +
3774                                                         "local variable declarations (address is already " +
3775                                                         "fixed)");
3776                                                 return false;
3777                                         }
3778
3779                                         ec.InFixedInitializer = true;
3780                                         e = e.Resolve (ec);
3781                                         ec.InFixedInitializer = false;
3782                                         if (e == null)
3783                                                 return false;
3784
3785                                         child = ((Unary) e).Expr;
3786
3787                                         if (!TypeManager.VerifyUnManaged (child.Type, loc))
3788                                                 return false;
3789
3790                                         if (!Convert.ImplicitConversionExists (ec, e, expr_type)) {
3791                                                 e.Error_ValueCannotBeConverted (ec, e.Location, expr_type, false);
3792                                                 return false;
3793                                         }
3794
3795                                         data [i] = new ExpressionEmitter (e, vi);
3796                                         i++;
3797
3798                                         continue;
3799                                 }
3800
3801                                 ec.InFixedInitializer = true;
3802                                 e = e.Resolve (ec);
3803                                 ec.InFixedInitializer = false;
3804                                 if (e == null)
3805                                         return false;
3806
3807                                 //
3808                                 // Case 2: Array
3809                                 //
3810                                 if (e.Type.IsArray){
3811                                         Type array_type = TypeManager.GetElementType (e.Type);
3812
3813                                         //
3814                                         // Provided that array_type is unmanaged,
3815                                         //
3816                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
3817                                                 return false;
3818
3819                                         //
3820                                         // and T* is implicitly convertible to the
3821                                         // pointer type given in the fixed statement.
3822                                         //
3823                                         ArrayPtr array_ptr = new ArrayPtr (e, array_type, loc);
3824
3825                                         Expression converted = Convert.ImplicitConversionRequired (
3826                                                 ec, array_ptr, vi.VariableType, loc);
3827                                         if (converted == null)
3828                                                 return false;
3829
3830                                         data [i] = new ExpressionEmitter (converted, vi);
3831                                         i++;
3832
3833                                         continue;
3834                                 }
3835
3836                                 //
3837                                 // Case 3: string
3838                                 //
3839                                 if (e.Type == TypeManager.string_type){
3840                                         data [i] = new StringEmitter (e, vi, loc);
3841                                         i++;
3842                                         continue;
3843                                 }
3844
3845                                 // Case 4: fixed buffer
3846                                 FieldExpr fe = e as FieldExpr;
3847                                 if (fe != null) {
3848                                         IFixedBuffer ff = AttributeTester.GetFixedBuffer (fe.FieldInfo);
3849                                         if (ff != null) {
3850                                                 Expression fixed_buffer_ptr = new FixedBufferPtr (fe, ff.ElementType, loc);
3851
3852                                                 Expression converted = Convert.ImplicitConversionRequired (
3853                                                         ec, fixed_buffer_ptr, vi.VariableType, loc);
3854                                                 if (converted == null)
3855                                                         return false;
3856
3857                                                 data [i] = new ExpressionEmitter (converted, vi);
3858                                                 i++;
3859
3860                                                 continue;
3861                                         }
3862                                 }
3863
3864                                 //
3865                                 // For other cases, flag a `this is already fixed expression'
3866                                 //
3867                                 if (e is LocalVariableReference || e is ParameterReference ||
3868                                     Convert.ImplicitConversionExists (ec, e, vi.VariableType)){
3869
3870                                         Report.Error (245, loc, "right hand expression is already fixed, no need to use fixed statement ");
3871                                         return false;
3872                                 }
3873
3874                                 Report.Error (245, loc, "Fixed statement only allowed on strings, arrays or address-of expressions");
3875                                 return false;
3876                         }
3877
3878                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
3879
3880                         if (!statement.Resolve (ec)) {
3881                                 ec.KillFlowBranching ();
3882                                 return false;
3883                         }
3884
3885                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3886                         has_ret = reachability.IsUnreachable;
3887
3888                         return true;
3889                 }
3890
3891                 protected override void DoEmit (EmitContext ec)
3892                 {
3893                         for (int i = 0; i < data.Length; i++) {
3894                                 data [i].Emit (ec);
3895                         }
3896
3897                         statement.Emit (ec);
3898
3899                         if (has_ret)
3900                                 return;
3901
3902                         //
3903                         // Clear the pinned variable
3904                         //
3905                         for (int i = 0; i < data.Length; i++) {
3906                                 data [i].EmitExit (ec);
3907                         }
3908                 }
3909         }
3910
3911         public class Catch : Statement {
3912                 public readonly string Name;
3913                 public readonly Block  Block;
3914                 public readonly Block  VarBlock;
3915
3916                 Expression type_expr;
3917                 Type type;
3918
3919                 public Catch (Expression type, string name, Block block, Block var_block, Location l)
3920                 {
3921                         type_expr = type;
3922                         Name = name;
3923                         Block = block;
3924                         VarBlock = var_block;
3925                         loc = l;
3926                 }
3927
3928                 public Type CatchType {
3929                         get {
3930                                 return type;
3931                         }
3932                 }
3933
3934                 public bool IsGeneral {
3935                         get {
3936                                 return type_expr == null;
3937                         }
3938                 }
3939
3940                 protected override void DoEmit(EmitContext ec)
3941                 {
3942                         ILGenerator ig = ec.ig;
3943
3944                         if (CatchType != null)
3945                                 ig.BeginCatchBlock (CatchType);
3946                         else
3947                                 ig.BeginCatchBlock (TypeManager.object_type);
3948
3949                         if (VarBlock != null)
3950                                 VarBlock.Emit (ec);
3951
3952                         if (Name != null) {
3953                                 LocalInfo vi = Block.GetLocalInfo (Name);
3954                                 if (vi == null)
3955                                         throw new Exception ("Variable does not exist in this block");
3956
3957                                 if (vi.Variable.NeedsTemporary) {
3958                                         LocalBuilder e = ig.DeclareLocal (vi.VariableType);
3959                                         ig.Emit (OpCodes.Stloc, e);
3960
3961                                         vi.Variable.EmitInstance (ec);
3962                                         ig.Emit (OpCodes.Ldloc, e);
3963                                         vi.Variable.EmitAssign (ec);
3964                                 } else
3965                                         vi.Variable.EmitAssign (ec);
3966                         } else
3967                                 ig.Emit (OpCodes.Pop);
3968
3969                         Block.Emit (ec);
3970                 }
3971
3972                 public override bool Resolve (EmitContext ec)
3973                 {
3974                         using (ec.With (EmitContext.Flags.InCatch, true)) {
3975                                 if (type_expr != null) {
3976                                         TypeExpr te = type_expr.ResolveAsTypeTerminal (ec, false);
3977                                         if (te == null)
3978                                                 return false;
3979
3980                                         type = te.Type;
3981
3982                                         if (type != TypeManager.exception_type && !type.IsSubclassOf (TypeManager.exception_type)){
3983                                                 Error (155, "The type caught or thrown must be derived from System.Exception");
3984                                                 return false;
3985                                         }
3986                                 } else
3987                                         type = null;
3988
3989                                 if (!Block.Resolve (ec))
3990                                         return false;
3991
3992                                 // Even though VarBlock surrounds 'Block' we resolve it later, so that we can correctly
3993                                 // emit the "unused variable" warnings.
3994                                 if (VarBlock != null)
3995                                         return VarBlock.Resolve (ec);
3996
3997                                 return true;
3998                         }
3999                 }
4000         }
4001
4002         public class Try : ExceptionStatement {
4003                 public readonly Block Fini, Block;
4004                 public readonly ArrayList Specific;
4005                 public readonly Catch General;
4006
4007                 bool need_exc_block;
4008
4009                 //
4010                 // specific, general and fini might all be null.
4011                 //
4012                 public Try (Block block, ArrayList specific, Catch general, Block fini, Location l)
4013                 {
4014                         if (specific == null && general == null){
4015                                 Console.WriteLine ("CIR.Try: Either specific or general have to be non-null");
4016                         }
4017
4018                         this.Block = block;
4019                         this.Specific = specific;
4020                         this.General = general;
4021                         this.Fini = fini;
4022                         loc = l;
4023                 }
4024
4025                 public override bool Resolve (EmitContext ec)
4026                 {
4027                         bool ok = true;
4028
4029                         FlowBranchingException branching = ec.StartFlowBranching (this);
4030
4031                         Report.Debug (1, "START OF TRY BLOCK", Block.StartLocation);
4032
4033                         if (!Block.Resolve (ec))
4034                                 ok = false;
4035
4036                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
4037
4038                         Report.Debug (1, "START OF CATCH BLOCKS", vector);
4039
4040                         Type[] prevCatches = new Type [Specific.Count];
4041                         int last_index = 0;
4042                         foreach (Catch c in Specific){
4043                                 ec.CurrentBranching.CreateSibling (
4044                                         c.Block, FlowBranching.SiblingType.Catch);
4045
4046                                 Report.Debug (1, "STARTED SIBLING FOR CATCH", ec.CurrentBranching);
4047
4048                                 if (c.Name != null) {
4049                                         LocalInfo vi = c.Block.GetLocalInfo (c.Name);
4050                                         if (vi == null)
4051                                                 throw new Exception ();
4052
4053                                         vi.VariableInfo = null;
4054                                 }
4055
4056                                 if (!c.Resolve (ec))
4057                                         return false;
4058
4059                                 Type resolvedType = c.CatchType;
4060                                 for (int ii = 0; ii < last_index; ++ii) {
4061                                         if (resolvedType == prevCatches [ii] || resolvedType.IsSubclassOf (prevCatches [ii])) {
4062                                                 Report.Error (160, c.loc, "A previous catch clause already catches all exceptions of this or a super type `{0}'", prevCatches [ii].FullName);
4063                                                 return false;
4064                                         }
4065                                 }
4066
4067                                 prevCatches [last_index++] = resolvedType;
4068                                 need_exc_block = true;
4069                         }
4070
4071                         Report.Debug (1, "END OF CATCH BLOCKS", ec.CurrentBranching);
4072
4073                         if (General != null){
4074                                 if (CodeGen.Assembly.WrapNonExceptionThrows) {
4075                                         foreach (Catch c in Specific){
4076                                                 if (c.CatchType == TypeManager.exception_type) {
4077                                                         Report.Warning (1058, 1, c.loc, "A previous catch clause already catches all exceptions. All non-exceptions thrown will be wrapped in a `System.Runtime.CompilerServices.RuntimeWrappedException'");
4078                                                 }
4079                                         }
4080                                 }
4081
4082                                 ec.CurrentBranching.CreateSibling (
4083                                         General.Block, FlowBranching.SiblingType.Catch);
4084
4085                                 Report.Debug (1, "STARTED SIBLING FOR GENERAL", ec.CurrentBranching);
4086
4087                                 if (!General.Resolve (ec))
4088                                         ok = false;
4089
4090                                 need_exc_block = true;
4091                         }
4092
4093                         Report.Debug (1, "END OF GENERAL CATCH BLOCKS", ec.CurrentBranching);
4094
4095                         if (Fini != null) {
4096                                 if (ok)
4097                                         ec.CurrentBranching.CreateSibling (Fini, FlowBranching.SiblingType.Finally);
4098
4099                                 Report.Debug (1, "STARTED SIBLING FOR FINALLY", ec.CurrentBranching, vector);
4100                                 using (ec.With (EmitContext.Flags.InFinally, true)) {
4101                                         if (!Fini.Resolve (ec))
4102                                                 ok = false;
4103                                 }
4104
4105                                 if (!ec.InIterator)
4106                                         need_exc_block = true;
4107                         }
4108
4109                         if (ec.InIterator) {
4110                                 ResolveFinally (branching);
4111                                 need_exc_block |= emit_finally;
4112                         } else
4113                                 emit_finally = Fini != null;
4114
4115                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
4116
4117                         FlowBranching.UsageVector f_vector = ec.CurrentBranching.CurrentUsageVector;
4118
4119                         Report.Debug (1, "END OF TRY", ec.CurrentBranching, reachability, vector, f_vector);
4120
4121                         if (!reachability.AlwaysReturns) {
4122                                 // Unfortunately, System.Reflection.Emit automatically emits
4123                                 // a leave to the end of the finally block.  This is a problem
4124                                 // if `returns' is true since we may jump to a point after the
4125                                 // end of the method.
4126                                 // As a workaround, emit an explicit ret here.
4127                                 ec.NeedReturnLabel ();
4128                         }
4129
4130                         return ok;
4131                 }
4132
4133                 protected override void DoEmit (EmitContext ec)
4134                 {
4135                         ILGenerator ig = ec.ig;
4136
4137                         if (need_exc_block)
4138                                 ig.BeginExceptionBlock ();
4139                         Block.Emit (ec);
4140
4141                         foreach (Catch c in Specific)
4142                                 c.Emit (ec);
4143
4144                         if (General != null)
4145                                 General.Emit (ec);
4146
4147                         DoEmitFinally (ec);
4148                         if (need_exc_block)
4149                                 ig.EndExceptionBlock ();
4150                 }
4151
4152                 public override void EmitFinally (EmitContext ec)
4153                 {
4154                         if (Fini != null)
4155                                 Fini.Emit (ec);
4156                 }
4157
4158                 public bool HasCatch
4159                 {
4160                         get {
4161                                 return General != null || Specific.Count > 0;
4162                         }
4163                 }
4164         }
4165
4166         public class Using : ExceptionStatement {
4167                 object expression_or_block;
4168                 public Statement Statement;
4169                 ArrayList var_list;
4170                 Expression expr;
4171                 Type expr_type;
4172                 Expression [] resolved_vars;
4173                 Expression [] converted_vars;
4174                 ExpressionStatement [] assign;
4175                 TemporaryVariable local_copy;
4176
4177                 public Using (object expression_or_block, Statement stmt, Location l)
4178                 {
4179                         this.expression_or_block = expression_or_block;
4180                         Statement = stmt;
4181                         loc = l;
4182                 }
4183
4184                 //
4185                 // Resolves for the case of using using a local variable declaration.
4186                 //
4187                 bool ResolveLocalVariableDecls (EmitContext ec)
4188                 {
4189                         int i = 0;
4190
4191                         TypeExpr texpr = expr.ResolveAsTypeTerminal (ec, false);
4192                         if (texpr == null)
4193                                 return false;
4194
4195                         expr_type = texpr.Type;
4196
4197                         //
4198                         // The type must be an IDisposable or an implicit conversion
4199                         // must exist.
4200                         //
4201                         converted_vars = new Expression [var_list.Count];
4202                         resolved_vars = new Expression [var_list.Count];
4203                         assign = new ExpressionStatement [var_list.Count];
4204
4205                         bool need_conv = !TypeManager.ImplementsInterface (
4206                                 expr_type, TypeManager.idisposable_type);
4207
4208                         foreach (DictionaryEntry e in var_list){
4209                                 Expression var = (Expression) e.Key;
4210
4211                                 var = var.ResolveLValue (ec, new EmptyExpression (), loc);
4212                                 if (var == null)
4213                                         return false;
4214
4215                                 resolved_vars [i] = var;
4216
4217                                 if (!need_conv) {
4218                                         i++;
4219                                         continue;
4220                                 }
4221
4222                                 converted_vars [i] = Convert.ImplicitConversion (
4223                                         ec, var, TypeManager.idisposable_type, loc);
4224
4225                                 if (converted_vars [i] == null) {
4226                                         Error_IsNotConvertibleToIDisposable ();
4227                                         return false;
4228                                 }
4229
4230                                 i++;
4231                         }
4232
4233                         i = 0;
4234                         foreach (DictionaryEntry e in var_list){
4235                                 Expression var = resolved_vars [i];
4236                                 Expression new_expr = (Expression) e.Value;
4237                                 Expression a;
4238
4239                                 a = new Assign (var, new_expr, loc);
4240                                 a = a.Resolve (ec);
4241                                 if (a == null)
4242                                         return false;
4243
4244                                 if (!need_conv)
4245                                         converted_vars [i] = var;
4246                                 assign [i] = (ExpressionStatement) a;
4247                                 i++;
4248                         }
4249
4250                         return true;
4251                 }
4252
4253                 void Error_IsNotConvertibleToIDisposable ()
4254                 {
4255                         Report.Error (1674, loc, "`{0}': type used in a using statement must be implicitly convertible to `System.IDisposable'",
4256                                 TypeManager.CSharpName (expr_type));
4257                 }
4258
4259                 bool ResolveExpression (EmitContext ec)
4260                 {
4261                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)){
4262                                 if (Convert.ImplicitConversion (ec, expr, TypeManager.idisposable_type, loc) == null) {
4263                                         Error_IsNotConvertibleToIDisposable ();
4264                                         return false;
4265                                 }
4266                         }
4267
4268                         local_copy = new TemporaryVariable (expr_type, loc);
4269                         local_copy.Resolve (ec);
4270
4271                         return true;
4272                 }
4273
4274                 //
4275                 // Emits the code for the case of using using a local variable declaration.
4276                 //
4277                 void EmitLocalVariableDecls (EmitContext ec)
4278                 {
4279                         ILGenerator ig = ec.ig;
4280                         int i = 0;
4281
4282                         for (i = 0; i < assign.Length; i++) {
4283                                 assign [i].EmitStatement (ec);
4284
4285                                 if (emit_finally)
4286                                         ig.BeginExceptionBlock ();
4287                         }
4288                         Statement.Emit (ec);
4289
4290                         var_list.Reverse ();
4291
4292                         DoEmitFinally (ec);
4293                 }
4294
4295                 void EmitLocalVariableDeclFinally (EmitContext ec)
4296                 {
4297                         ILGenerator ig = ec.ig;
4298
4299                         int i = assign.Length;
4300                         for (int ii = 0; ii < var_list.Count; ++ii){
4301                                 Expression var = resolved_vars [--i];
4302                                 Label skip = ig.DefineLabel ();
4303
4304                                 if (emit_finally)
4305                                         ig.BeginFinallyBlock ();
4306
4307                                 if (!var.Type.IsValueType) {
4308                                         var.Emit (ec);
4309                                         ig.Emit (OpCodes.Brfalse, skip);
4310                                         converted_vars [i].Emit (ec);
4311                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4312                                 } else {
4313                                         Expression ml = Expression.MemberLookup(ec.ContainerType, TypeManager.idisposable_type, var.Type, "Dispose", Mono.CSharp.Location.Null);
4314
4315                                         if (!(ml is MethodGroupExpr)) {
4316                                                 var.Emit (ec);
4317                                                 ig.Emit (OpCodes.Box, var.Type);
4318                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4319                                         } else {
4320                                                 MethodInfo mi = null;
4321
4322                                                 foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4323                                                         if (TypeManager.GetParameterData (mk).Count == 0) {
4324                                                                 mi = mk;
4325                                                                 break;
4326                                                         }
4327                                                 }
4328
4329                                                 if (mi == null) {
4330                                                         Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4331                                                         return;
4332                                                 }
4333
4334                                                 IMemoryLocation mloc = (IMemoryLocation) var;
4335
4336                                                 mloc.AddressOf (ec, AddressOp.Load);
4337                                                 ig.Emit (OpCodes.Call, mi);
4338                                         }
4339                                 }
4340
4341                                 ig.MarkLabel (skip);
4342
4343                                 if (emit_finally) {
4344                                         ig.EndExceptionBlock ();
4345                                         if (i > 0)
4346                                                 ig.BeginFinallyBlock ();
4347                                 }
4348                         }
4349                 }
4350
4351                 void EmitExpression (EmitContext ec)
4352                 {
4353                         //
4354                         // Make a copy of the expression and operate on that.
4355                         //
4356                         ILGenerator ig = ec.ig;
4357
4358                         local_copy.Store (ec, expr);
4359
4360                         if (emit_finally)
4361                                 ig.BeginExceptionBlock ();
4362
4363                         Statement.Emit (ec);
4364
4365                         DoEmitFinally (ec);
4366                         if (emit_finally)
4367                                 ig.EndExceptionBlock ();
4368                 }
4369
4370                 void EmitExpressionFinally (EmitContext ec)
4371                 {
4372                         ILGenerator ig = ec.ig;
4373                         if (!expr_type.IsValueType) {
4374                                 Label skip = ig.DefineLabel ();
4375                                 local_copy.Emit (ec);
4376                                 ig.Emit (OpCodes.Brfalse, skip);
4377                                 local_copy.Emit (ec);
4378                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4379                                 ig.MarkLabel (skip);
4380                         } else {
4381                                 Expression ml = Expression.MemberLookup (
4382                                         ec.ContainerType, TypeManager.idisposable_type, expr_type,
4383                                         "Dispose", Location.Null);
4384
4385                                 if (!(ml is MethodGroupExpr)) {
4386                                         local_copy.Emit (ec);
4387                                         ig.Emit (OpCodes.Box, expr_type);
4388                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4389                                 } else {
4390                                         MethodInfo mi = null;
4391
4392                                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4393                                                 if (TypeManager.GetParameterData (mk).Count == 0) {
4394                                                         mi = mk;
4395                                                         break;
4396                                                 }
4397                                         }
4398
4399                                         if (mi == null) {
4400                                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4401                                                 return;
4402                                         }
4403
4404                                         local_copy.AddressOf (ec, AddressOp.Load);
4405                                         ig.Emit (OpCodes.Call, mi);
4406                                 }
4407                         }
4408                 }
4409
4410                 public override bool Resolve (EmitContext ec)
4411                 {
4412                         if (expression_or_block is DictionaryEntry){
4413                                 expr = (Expression) ((DictionaryEntry) expression_or_block).Key;
4414                                 var_list = (ArrayList)((DictionaryEntry)expression_or_block).Value;
4415
4416                                 if (!ResolveLocalVariableDecls (ec))
4417                                         return false;
4418
4419                         } else if (expression_or_block is Expression){
4420                                 expr = (Expression) expression_or_block;
4421
4422                                 expr = expr.Resolve (ec);
4423                                 if (expr == null)
4424                                         return false;
4425
4426                                 expr_type = expr.Type;
4427
4428                                 if (!ResolveExpression (ec))
4429                                         return false;
4430                         }
4431
4432                         FlowBranchingException branching = ec.StartFlowBranching (this);
4433
4434                         bool ok = Statement.Resolve (ec);
4435
4436                         if (!ok) {
4437                                 ec.KillFlowBranching ();
4438                                 return false;
4439                         }
4440
4441                         ResolveFinally (branching);
4442                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
4443
4444                         if (!reachability.AlwaysReturns) {
4445                                 // Unfortunately, System.Reflection.Emit automatically emits a leave
4446                                 // to the end of the finally block.  This is a problem if `returns'
4447                                 // is true since we may jump to a point after the end of the method.
4448                                 // As a workaround, emit an explicit ret here.
4449                                 ec.NeedReturnLabel ();
4450                         }
4451
4452                         return true;
4453                 }
4454
4455                 protected override void DoEmit (EmitContext ec)
4456                 {
4457                         if (expression_or_block is DictionaryEntry)
4458                                 EmitLocalVariableDecls (ec);
4459                         else if (expression_or_block is Expression)
4460                                 EmitExpression (ec);
4461                 }
4462
4463                 public override void EmitFinally (EmitContext ec)
4464                 {
4465                         if (expression_or_block is DictionaryEntry)
4466                                 EmitLocalVariableDeclFinally (ec);
4467                         else if (expression_or_block is Expression)
4468                                 EmitExpressionFinally (ec);
4469                 }
4470         }
4471
4472         /// <summary>
4473         ///   Implementation of the foreach C# statement
4474         /// </summary>
4475         public class Foreach : Statement {
4476                 Expression type;
4477                 Expression variable;
4478                 Expression expr;
4479                 Statement statement;
4480                 ArrayForeach array;
4481                 CollectionForeach collection;
4482
4483                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
4484                                 Statement stmt, Location l)
4485                 {
4486                         this.type = type;
4487                         this.variable = var;
4488                         this.expr = expr;
4489                         statement = stmt;
4490                         loc = l;
4491                 }
4492
4493                 public Statement Statement {
4494                         get { return statement; }
4495                 }
4496
4497                 public override bool Resolve (EmitContext ec)
4498                 {
4499                         expr = expr.Resolve (ec);
4500                         if (expr == null)
4501                                 return false;
4502
4503                         Constant c = expr as Constant;
4504                         if (c != null && c.GetValue () == null) {
4505                                 Report.Error (186, loc, "Use of null is not valid in this context");
4506                                 return false;
4507                         }
4508
4509                         TypeExpr texpr = type.ResolveAsTypeTerminal (ec, false);
4510                         if (texpr == null)
4511                                 return false;
4512
4513                         Type var_type = texpr.Type;
4514
4515                         if (expr.eclass == ExprClass.MethodGroup || expr is AnonymousMethodExpression) {
4516                                 Report.Error (446, expr.Location, "Foreach statement cannot operate on a `{0}'",
4517                                         expr.ExprClassName);
4518                                 return false;
4519                         }
4520
4521                         //
4522                         // We need an instance variable.  Not sure this is the best
4523                         // way of doing this.
4524                         //
4525                         // FIXME: When we implement propertyaccess, will those turn
4526                         // out to return values in ExprClass?  I think they should.
4527                         //
4528                         if (!(expr.eclass == ExprClass.Variable || expr.eclass == ExprClass.Value ||
4529                               expr.eclass == ExprClass.PropertyAccess || expr.eclass == ExprClass.IndexerAccess)){
4530                                 collection.Error_Enumerator ();
4531                                 return false;
4532                         }
4533
4534                         if (expr.Type.IsArray) {
4535                                 array = new ArrayForeach (var_type, variable, expr, statement, loc);
4536                                 return array.Resolve (ec);
4537                         } else {
4538                                 collection = new CollectionForeach (
4539                                         var_type, variable, expr, statement, loc);
4540                                 return collection.Resolve (ec);
4541                         }
4542                 }
4543
4544                 protected override void DoEmit (EmitContext ec)
4545                 {
4546                         ILGenerator ig = ec.ig;
4547
4548                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
4549                         ec.LoopBegin = ig.DefineLabel ();
4550                         ec.LoopEnd = ig.DefineLabel ();
4551
4552                         if (collection != null)
4553                                 collection.Emit (ec);
4554                         else
4555                                 array.Emit (ec);
4556
4557                         ec.LoopBegin = old_begin;
4558                         ec.LoopEnd = old_end;
4559                 }
4560
4561                 protected class ArrayCounter : TemporaryVariable
4562                 {
4563                         public ArrayCounter (Location loc)
4564                                 : base (TypeManager.int32_type, loc)
4565                         { }
4566
4567                         public void Initialize (EmitContext ec)
4568                         {
4569                                 EmitThis (ec);
4570                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
4571                                 EmitStore (ec);
4572                         }
4573
4574                         public void Increment (EmitContext ec)
4575                         {
4576                                 EmitThis (ec);
4577                                 Emit (ec);
4578                                 ec.ig.Emit (OpCodes.Ldc_I4_1);
4579                                 ec.ig.Emit (OpCodes.Add);
4580                                 EmitStore (ec);
4581                         }
4582                 }
4583
4584                 protected class ArrayForeach : Statement
4585                 {
4586                         Expression variable, expr, conv;
4587                         Statement statement;
4588                         Type array_type;
4589                         Type var_type;
4590                         TemporaryVariable[] lengths;
4591                         ArrayCounter[] counter;
4592                         int rank;
4593
4594                         TemporaryVariable copy;
4595                         Expression access;
4596
4597                         public ArrayForeach (Type var_type, Expression var,
4598                                              Expression expr, Statement stmt, Location l)
4599                         {
4600                                 this.var_type = var_type;
4601                                 this.variable = var;
4602                                 this.expr = expr;
4603                                 statement = stmt;
4604                                 loc = l;
4605                         }
4606
4607                         public override bool Resolve (EmitContext ec)
4608                         {
4609                                 array_type = expr.Type;
4610                                 rank = array_type.GetArrayRank ();
4611
4612                                 copy = new TemporaryVariable (array_type, loc);
4613                                 copy.Resolve (ec);
4614
4615                                 counter = new ArrayCounter [rank];
4616                                 lengths = new TemporaryVariable [rank];
4617
4618                                 ArrayList list = new ArrayList ();
4619                                 for (int i = 0; i < rank; i++) {
4620                                         counter [i] = new ArrayCounter (loc);
4621                                         counter [i].Resolve (ec);
4622
4623                                         lengths [i] = new TemporaryVariable (TypeManager.int32_type, loc);
4624                                         lengths [i].Resolve (ec);
4625
4626                                         list.Add (counter [i]);
4627                                 }
4628
4629                                 access = new ElementAccess (copy, list).Resolve (ec);
4630                                 if (access == null)
4631                                         return false;
4632
4633                                 conv = Convert.ExplicitConversion (ec, access, var_type, loc);
4634                                 if (conv == null)
4635                                         return false;
4636
4637                                 bool ok = true;
4638
4639                                 ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
4640                                 ec.CurrentBranching.CreateSibling ();
4641
4642                                 variable = variable.ResolveLValue (ec, conv, loc);
4643                                 if (variable == null)
4644                                         ok = false;
4645
4646                                 ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
4647                                 if (!statement.Resolve (ec))
4648                                         ok = false;
4649                                 ec.EndFlowBranching ();
4650
4651                                 // There's no direct control flow from the end of the embedded statement to the end of the loop
4652                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
4653
4654                                 ec.EndFlowBranching ();
4655
4656                                 return ok;
4657                         }
4658
4659                         protected override void DoEmit (EmitContext ec)
4660                         {
4661                                 ILGenerator ig = ec.ig;
4662
4663                                 copy.Store (ec, expr);
4664
4665                                 Label[] test = new Label [rank];
4666                                 Label[] loop = new Label [rank];
4667
4668                                 for (int i = 0; i < rank; i++) {
4669                                         test [i] = ig.DefineLabel ();
4670                                         loop [i] = ig.DefineLabel ();
4671
4672                                         lengths [i].EmitThis (ec);
4673                                         ((ArrayAccess) access).EmitGetLength (ec, i);
4674                                         lengths [i].EmitStore (ec);
4675                                 }
4676
4677                                 for (int i = 0; i < rank; i++) {
4678                                         counter [i].Initialize (ec);
4679
4680                                         ig.Emit (OpCodes.Br, test [i]);
4681                                         ig.MarkLabel (loop [i]);
4682                                 }
4683
4684                                 ((IAssignMethod) variable).EmitAssign (ec, conv, false, false);
4685
4686                                 statement.Emit (ec);
4687
4688                                 ig.MarkLabel (ec.LoopBegin);
4689
4690                                 for (int i = rank - 1; i >= 0; i--){
4691                                         counter [i].Increment (ec);
4692
4693                                         ig.MarkLabel (test [i]);
4694                                         counter [i].Emit (ec);
4695                                         lengths [i].Emit (ec);
4696                                         ig.Emit (OpCodes.Blt, loop [i]);
4697                                 }
4698
4699                                 ig.MarkLabel (ec.LoopEnd);
4700                         }
4701                 }
4702
4703                 protected class CollectionForeach : ExceptionStatement
4704                 {
4705                         Expression variable, expr;
4706                         Statement statement;
4707
4708                         TemporaryVariable enumerator;
4709                         Expression init;
4710                         Statement loop;
4711
4712                         MethodGroupExpr get_enumerator;
4713                         PropertyExpr get_current;
4714                         MethodInfo move_next;
4715                         Type var_type, enumerator_type;
4716                         bool is_disposable;
4717                         bool enumerator_found;
4718
4719                         public CollectionForeach (Type var_type, Expression var,
4720                                                   Expression expr, Statement stmt, Location l)
4721                         {
4722                                 this.var_type = var_type;
4723                                 this.variable = var;
4724                                 this.expr = expr;
4725                                 statement = stmt;
4726                                 loc = l;
4727                         }
4728
4729                         bool GetEnumeratorFilter (EmitContext ec, MethodInfo mi)
4730                         {
4731                                 Type return_type = mi.ReturnType;
4732
4733                                 if ((return_type == TypeManager.ienumerator_type) && (mi.DeclaringType == TypeManager.string_type))
4734                                         //
4735                                         // Apply the same optimization as MS: skip the GetEnumerator
4736                                         // returning an IEnumerator, and use the one returning a
4737                                         // CharEnumerator instead. This allows us to avoid the
4738                                         // try-finally block and the boxing.
4739                                         //
4740                                         return false;
4741
4742                                 //
4743                                 // Ok, we can access it, now make sure that we can do something
4744                                 // with this `GetEnumerator'
4745                                 //
4746
4747                                 if (return_type == TypeManager.ienumerator_type ||
4748                                     TypeManager.ienumerator_type.IsAssignableFrom (return_type) ||
4749                                     (!RootContext.StdLib && TypeManager.ImplementsInterface (return_type, TypeManager.ienumerator_type))) {
4750                                         //
4751                                         // If it is not an interface, lets try to find the methods ourselves.
4752                                         // For example, if we have:
4753                                         // public class Foo : IEnumerator { public bool MoveNext () {} public int Current { get {}}}
4754                                         // We can avoid the iface call. This is a runtime perf boost.
4755                                         // even bigger if we have a ValueType, because we avoid the cost
4756                                         // of boxing.
4757                                         //
4758                                         // We have to make sure that both methods exist for us to take
4759                                         // this path. If one of the methods does not exist, we will just
4760                                         // use the interface. Sadly, this complex if statement is the only
4761                                         // way I could do this without a goto
4762                                         //
4763
4764 #if GMCS_SOURCE
4765                                         //
4766                                         // Prefer a generic enumerator over a non-generic one.
4767                                         //
4768                                         if (return_type.IsInterface && return_type.IsGenericType) {
4769                                                 enumerator_type = return_type;
4770                                                 if (!FetchGetCurrent (ec, return_type))
4771                                                         get_current = new PropertyExpr (
4772                                                                 ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
4773                                                 if (!FetchMoveNext (return_type))
4774                                                         move_next = TypeManager.bool_movenext_void;
4775                                                 return true;
4776                                         }
4777 #endif
4778
4779                                         if (return_type.IsInterface ||
4780                                             !FetchMoveNext (return_type) ||
4781                                             !FetchGetCurrent (ec, return_type)) {
4782                                                 enumerator_type = return_type;
4783                                                 move_next = TypeManager.bool_movenext_void;
4784                                                 get_current = new PropertyExpr (
4785                                                         ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
4786                                                 return true;
4787                                         }
4788                                 } else {
4789                                         //
4790                                         // Ok, so they dont return an IEnumerable, we will have to
4791                                         // find if they support the GetEnumerator pattern.
4792                                         //
4793
4794                                         if (TypeManager.HasElementType (return_type) || !FetchMoveNext (return_type) || !FetchGetCurrent (ec, return_type)) {
4795                                                 Report.Error (202, loc, "foreach statement requires that the return type `{0}' of `{1}' must have a suitable public MoveNext method and public Current property",
4796                                                         TypeManager.CSharpName (return_type), TypeManager.CSharpSignature (mi));
4797                                                 return false;
4798                                         }
4799                                 }
4800
4801                                 enumerator_type = return_type;
4802                                 is_disposable = !enumerator_type.IsSealed ||
4803                                         TypeManager.ImplementsInterface (
4804                                                 enumerator_type, TypeManager.idisposable_type);
4805
4806                                 return true;
4807                         }
4808
4809                         //
4810                         // Retrieves a `public bool MoveNext ()' method from the Type `t'
4811                         //
4812                         bool FetchMoveNext (Type t)
4813                         {
4814                                 MemberList move_next_list;
4815
4816                                 move_next_list = TypeContainer.FindMembers (
4817                                         t, MemberTypes.Method,
4818                                         BindingFlags.Public | BindingFlags.Instance,
4819                                         Type.FilterName, "MoveNext");
4820                                 if (move_next_list.Count == 0)
4821                                         return false;
4822
4823                                 foreach (MemberInfo m in move_next_list){
4824                                         MethodInfo mi = (MethodInfo) m;
4825
4826                                         if ((TypeManager.GetParameterData (mi).Count == 0) &&
4827                                             TypeManager.TypeToCoreType (mi.ReturnType) == TypeManager.bool_type) {
4828                                                 move_next = mi;
4829                                                 return true;
4830                                         }
4831                                 }
4832
4833                                 return false;
4834                         }
4835
4836                         //
4837                         // Retrieves a `public T get_Current ()' method from the Type `t'
4838                         //
4839                         bool FetchGetCurrent (EmitContext ec, Type t)
4840                         {
4841                                 PropertyExpr pe = Expression.MemberLookup (
4842                                         ec.ContainerType, t, "Current", MemberTypes.Property,
4843                                         Expression.AllBindingFlags, loc) as PropertyExpr;
4844                                 if (pe == null)
4845                                         return false;
4846
4847                                 get_current = pe;
4848                                 return true;
4849                         }
4850
4851                         //
4852                         // Retrieves a `public void Dispose ()' method from the Type `t'
4853                         //
4854                         static MethodInfo FetchMethodDispose (Type t)
4855                         {
4856                                 MemberList dispose_list;
4857
4858                                 dispose_list = TypeContainer.FindMembers (
4859                                         t, MemberTypes.Method,
4860                                         BindingFlags.Public | BindingFlags.Instance,
4861                                         Type.FilterName, "Dispose");
4862                                 if (dispose_list.Count == 0)
4863                                         return null;
4864
4865                                 foreach (MemberInfo m in dispose_list){
4866                                         MethodInfo mi = (MethodInfo) m;
4867
4868                                         if (TypeManager.GetParameterData (mi).Count == 0){
4869                                                 if (mi.ReturnType == TypeManager.void_type)
4870                                                         return mi;
4871                                         }
4872                                 }
4873                                 return null;
4874                         }
4875
4876                         public void Error_Enumerator ()
4877                         {
4878                                 if (enumerator_found) {
4879                                         return;
4880                                 }
4881
4882                             Report.Error (1579, loc,
4883                                         "foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `GetEnumerator' or is not accessible",
4884                                         TypeManager.CSharpName (expr.Type));
4885                         }
4886
4887                         bool TryType (EmitContext ec, Type t)
4888                         {
4889                                 MethodGroupExpr mg = Expression.MemberLookup (
4890                                         ec.ContainerType, t, "GetEnumerator", MemberTypes.Method,
4891                                         Expression.AllBindingFlags, loc) as MethodGroupExpr;
4892                                 if (mg == null)
4893                                         return false;
4894
4895                                 MethodInfo result = null;
4896                                 MethodInfo tmp_move_next = null;
4897                                 PropertyExpr tmp_get_cur = null;
4898                                 Type tmp_enumerator_type = enumerator_type;
4899                                 foreach (MethodInfo mi in mg.Methods) {
4900                                         if (TypeManager.GetParameterData (mi).Count != 0)
4901                                                 continue;
4902
4903                                         // Check whether GetEnumerator is public
4904                                         if ((mi.Attributes & MethodAttributes.Public) != MethodAttributes.Public)
4905                                                 continue;
4906
4907                                         if (TypeManager.IsOverride (mi))
4908                                                 continue;
4909
4910                                         enumerator_found = true;
4911
4912                                         if (!GetEnumeratorFilter (ec, mi))
4913                                                 continue;
4914
4915                                         if (result != null) {
4916                                                 if (TypeManager.IsGenericType (result.ReturnType)) {
4917                                                         if (!TypeManager.IsGenericType (mi.ReturnType))
4918                                                                 continue;
4919
4920                                                         Report.SymbolRelatedToPreviousError(t);
4921                                                         Report.Error(1640, loc, "foreach statement cannot operate on variables of type `{0}' " +
4922                                                                 "because it contains multiple implementation of `{1}'. Try casting to a specific implementation",
4923                                                                 TypeManager.CSharpName (t), TypeManager.CSharpSignature (mi));
4924                                                         return false;
4925                                                 }
4926
4927                                                 // Always prefer generics enumerators
4928                                                 if (TypeManager.IsGenericType(mi.ReturnType))
4929                                                         continue;
4930
4931                                                 Report.SymbolRelatedToPreviousError (result);
4932                                                 Report.SymbolRelatedToPreviousError (mi);
4933                                                 Report.Warning (278, 2, loc, "`{0}' contains ambiguous implementation of `{1}' pattern. Method `{2}' is ambiguous with method `{3}'",
4934                                                         TypeManager.CSharpName (t), "enumerable", TypeManager.CSharpSignature (result), TypeManager.CSharpSignature (mi));
4935                                         }
4936                                         result = mi;
4937                                         tmp_move_next = move_next;
4938                                         tmp_get_cur = get_current;
4939                                         tmp_enumerator_type = enumerator_type;
4940                                         if (mi.DeclaringType == t)
4941                                                 break;
4942                                 }
4943
4944                                 if (result != null) {
4945                                         move_next = tmp_move_next;
4946                                         get_current = tmp_get_cur;
4947                                         enumerator_type = tmp_enumerator_type;
4948                                         MethodInfo[] mi = new MethodInfo[] { (MethodInfo) result };
4949                                         get_enumerator = new MethodGroupExpr (mi, loc);
4950
4951                                         if (t != expr.Type) {
4952                                                 expr = Convert.ExplicitConversion (
4953                                                         ec, expr, t, loc);
4954                                                 if (expr == null)
4955                                                         throw new InternalErrorException ();
4956                                         }
4957
4958                                         get_enumerator.InstanceExpression = expr;
4959                                         get_enumerator.IsBase = t != expr.Type;
4960
4961                                         return true;
4962                                 }
4963
4964                                 return false;
4965                         }
4966
4967                         bool ProbeCollectionType (EmitContext ec, Type t)
4968                         {
4969                                 int errors = Report.Errors;
4970                                 for (Type tt = t; tt != null && tt != TypeManager.object_type;){
4971                                         if (TryType (ec, tt))
4972                                                 return true;
4973                                         tt = tt.BaseType;
4974                                 }
4975
4976                                 if (Report.Errors > errors)
4977                                         return false;
4978
4979                                 //
4980                                 // Now try to find the method in the interfaces
4981                                 //
4982                                 while (t != null){
4983                                         Type [] ifaces = t.GetInterfaces ();
4984
4985                                         foreach (Type i in ifaces){
4986                                                 if (TryType (ec, i))
4987                                                         return true;
4988                                         }
4989
4990                                         //
4991                                         // Since TypeBuilder.GetInterfaces only returns the interface
4992                                         // types for this type, we have to keep looping, but once
4993                                         // we hit a non-TypeBuilder (ie, a Type), then we know we are
4994                                         // done, because it returns all the types
4995                                         //
4996                                         if ((t is TypeBuilder))
4997                                                 t = t.BaseType;
4998                                         else
4999                                                 break;
5000                                 }
5001
5002                                 return false;
5003                         }
5004
5005                         public override bool Resolve (EmitContext ec)
5006                         {
5007                                 enumerator_type = TypeManager.ienumerator_type;
5008                                 is_disposable = true;
5009
5010                                 if (!ProbeCollectionType (ec, expr.Type)) {
5011                                         Error_Enumerator ();
5012                                         return false;
5013                                 }
5014
5015                                 enumerator = new TemporaryVariable (enumerator_type, loc);
5016                                 enumerator.Resolve (ec);
5017
5018                                 init = new Invocation (get_enumerator, new ArrayList ());
5019                                 init = init.Resolve (ec);
5020                                 if (init == null)
5021                                         return false;
5022
5023                                 Expression move_next_expr;
5024                                 {
5025                                         MemberInfo[] mi = new MemberInfo[] { move_next };
5026                                         MethodGroupExpr mg = new MethodGroupExpr (mi, loc);
5027                                         mg.InstanceExpression = enumerator;
5028
5029                                         move_next_expr = new Invocation (mg, new ArrayList ());
5030                                 }
5031
5032                                 get_current.InstanceExpression = enumerator;
5033
5034                                 Statement block = new CollectionForeachStatement (
5035                                         var_type, variable, get_current, statement, loc);
5036
5037                                 loop = new While (move_next_expr, block, loc);
5038
5039                                 bool ok = true;
5040
5041                                 FlowBranchingException branching = null;
5042                                 if (is_disposable)
5043                                         branching = ec.StartFlowBranching (this);
5044
5045                                 if (!loop.Resolve (ec))
5046                                         ok = false;
5047
5048                                 if (is_disposable) {
5049                                         ResolveFinally (branching);
5050                                         ec.EndFlowBranching ();
5051                                 } else
5052                                         emit_finally = true;
5053
5054                                 return ok;
5055                         }
5056
5057                         protected override void DoEmit (EmitContext ec)
5058                         {
5059                                 ILGenerator ig = ec.ig;
5060
5061                                 enumerator.Store (ec, init);
5062
5063                                 //
5064                                 // Protect the code in a try/finalize block, so that
5065                                 // if the beast implement IDisposable, we get rid of it
5066                                 //
5067                                 if (is_disposable && emit_finally)
5068                                         ig.BeginExceptionBlock ();
5069
5070                                 loop.Emit (ec);
5071
5072                                 //
5073                                 // Now the finally block
5074                                 //
5075                                 if (is_disposable) {
5076                                         DoEmitFinally (ec);
5077                                         if (emit_finally)
5078                                                 ig.EndExceptionBlock ();
5079                                 }
5080                         }
5081
5082
5083                         public override void EmitFinally (EmitContext ec)
5084                         {
5085                                 ILGenerator ig = ec.ig;
5086
5087                                 if (enumerator_type.IsValueType) {
5088                                         MethodInfo mi = FetchMethodDispose (enumerator_type);
5089                                         if (mi != null) {
5090                                                 enumerator.EmitLoadAddress (ec);
5091                                                 ig.Emit (OpCodes.Call, mi);
5092                                         } else {
5093                                                 enumerator.Emit (ec);
5094                                                 ig.Emit (OpCodes.Box, enumerator_type);
5095                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
5096                                         }
5097                                 } else {
5098                                         Label call_dispose = ig.DefineLabel ();
5099
5100                                         enumerator.Emit (ec);
5101                                         ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
5102                                         ig.Emit (OpCodes.Dup);
5103                                         ig.Emit (OpCodes.Brtrue_S, call_dispose);
5104                                         ig.Emit (OpCodes.Pop);
5105
5106                                         Label end_finally = ig.DefineLabel ();
5107                                         ig.Emit (OpCodes.Br, end_finally);
5108
5109                                         ig.MarkLabel (call_dispose);
5110                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
5111                                         ig.MarkLabel (end_finally);
5112                                 }
5113                         }
5114                 }
5115
5116                 protected class CollectionForeachStatement : Statement
5117                 {
5118                         Type type;
5119                         Expression variable, current, conv;
5120                         Statement statement;
5121                         Assign assign;
5122
5123                         public CollectionForeachStatement (Type type, Expression variable,
5124                                                            Expression current, Statement statement,
5125                                                            Location loc)
5126                         {
5127                                 this.type = type;
5128                                 this.variable = variable;
5129                                 this.current = current;
5130                                 this.statement = statement;
5131                                 this.loc = loc;
5132                         }
5133
5134                         public override bool Resolve (EmitContext ec)
5135                         {
5136                                 current = current.Resolve (ec);
5137                                 if (current == null)
5138                                         return false;
5139
5140                                 conv = Convert.ExplicitConversion (ec, current, type, loc);
5141                                 if (conv == null)
5142                                         return false;
5143
5144                                 assign = new Assign (variable, conv, loc);
5145                                 if (assign.Resolve (ec) == null)
5146                                         return false;
5147
5148                                 if (!statement.Resolve (ec))
5149                                         return false;
5150
5151                                 return true;
5152                         }
5153
5154                         protected override void DoEmit (EmitContext ec)
5155                         {
5156                                 assign.EmitStatement (ec);
5157                                 statement.Emit (ec);
5158                         }
5159                 }
5160         }
5161 }