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