mcs/mcs/statement.cs

   1 //
   2 // statement.cs: Statement representation for the IL tree.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Martin Baulig (martin@ximian.com)
   7 //
   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 && (RootContext.WarningLevel >= 2))
  50                                 Report.Warning (162, 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                 protected void CheckObsolete (Type type)
  60                 {
  61                         ObsoleteAttribute obsolete_attr = AttributeTester.GetObsoleteAttribute (type);
  62                         if (obsolete_attr == null)
  63                                 return;
  64
  65                         AttributeTester.Report_ObsoleteMessage (obsolete_attr, type.FullName, loc);
  66                 }
  67
  68                 /// <summary>
  69                 ///   Return value indicates whether all code paths emitted return.
  70                 /// </summary>
  71                 protected abstract void DoEmit (EmitContext ec);
  72
  73                 /// <summary>
  74                 ///   Utility wrapper routine for Error, just to beautify the code
  75                 /// </summary>
  76                 public void Error (int error, string format, params object[] args)
  77                 {
  78                         Error (error, String.Format (format, args));
  79                 }
  80
  81                 public void Error (int error, string s)
  82                 {
  83                         if (!Location.IsNull (loc))
  84                                 Report.Error (error, loc, s);
  85                         else
  86                                 Report.Error (error, s);
  87                 }
  88
  89                 /// <summary>
  90                 ///   Return value indicates whether all code paths emitted return.
  91                 /// </summary>
  92                 public virtual void Emit (EmitContext ec)
  93                 {
  94                         ec.Mark (loc, true);
  95                         DoEmit (ec);
  96                 }
  97         }
  98
  99         public sealed class EmptyStatement : Statement {
 100
 101                 private EmptyStatement () {}
 102
 103                 public static readonly EmptyStatement Value = new EmptyStatement ();
 104
 105                 public override bool Resolve (EmitContext ec)
 106                 {
 107                         return true;
 108                 }
 109
 110                 protected override void DoEmit (EmitContext ec)
 111                 {
 112                 }
 113         }
 114
 115         public class If : Statement {
 116                 Expression expr;
 117                 public Statement TrueStatement;
 118                 public Statement FalseStatement;
 119
 120                 bool is_true_ret;
 121
 122                 public If (Expression expr, Statement trueStatement, Location l)
 123                 {
 124                         this.expr = expr;
 125                         TrueStatement = trueStatement;
 126                         loc = l;
 127                 }
 128
 129                 public If (Expression expr,
 130                            Statement trueStatement,
 131                            Statement falseStatement,
 132                            Location l)
 133                 {
 134                         this.expr = expr;
 135                         TrueStatement = trueStatement;
 136                         FalseStatement = falseStatement;
 137                         loc = l;
 138                 }
 139
 140                 public override bool Resolve (EmitContext ec)
 141                 {
 142                         bool ok = true;
 143
 144                         Report.Debug (1, "START IF BLOCK", loc);
 145
 146                         expr = Expression.ResolveBoolean (ec, expr, loc);
 147                         if (expr == null){
 148                                 ok = false;
 149                                 goto skip;
 150                         }
 151
 152                         Assign ass = expr as Assign;
 153                         if (ass != null && ass.Source is Constant) {
 154                                 Report.Warning (665, 3, loc, "Assignment in conditional expression is always constant; did you mean to use == instead of = ?");
 155                         }
 156
 157                         //
 158                         // Dead code elimination
 159                         //
 160                         if (expr is BoolConstant){
 161                                 bool take = ((BoolConstant) expr).Value;
 162
 163                                 if (take){
 164                                         if (!TrueStatement.Resolve (ec))
 165                                                 return false;
 166
 167                                         if ((FalseStatement != null) &&
 168                                             !FalseStatement.ResolveUnreachable (ec, true))
 169                                                 return false;
 170                                         FalseStatement = null;
 171                                 } else {
 172                                         if (!TrueStatement.ResolveUnreachable (ec, true))
 173                                                 return false;
 174                                         TrueStatement = null;
 175
 176                                         if ((FalseStatement != null) &&
 177                                             !FalseStatement.Resolve (ec))
 178                                                 return false;
 179                                 }
 180
 181                                 return true;
 182                         }
 183                 skip:
 184                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
 185
 186                         ok &= TrueStatement.Resolve (ec);
 187
 188                         is_true_ret = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
 189
 190                         ec.CurrentBranching.CreateSibling ();
 191
 192                         if (FalseStatement != null)
 193                                 ok &= FalseStatement.Resolve (ec);
 194
 195                         ec.EndFlowBranching ();
 196
 197                         Report.Debug (1, "END IF BLOCK", loc);
 198
 199                         return ok;
 200                 }
 201
 202                 protected override void DoEmit (EmitContext ec)
 203                 {
 204                         ILGenerator ig = ec.ig;
 205                         Label false_target = ig.DefineLabel ();
 206                         Label end;
 207
 208                         //
 209                         // If we're a boolean expression, Resolve() already
 210                         // eliminated dead code for us.
 211                         //
 212                         if (expr is BoolConstant){
 213                                 bool take = ((BoolConstant) expr).Value;
 214
 215                                 if (take)
 216                                         TrueStatement.Emit (ec);
 217                                 else if (FalseStatement != null)
 218                                         FalseStatement.Emit (ec);
 219
 220                                 return;
 221                         }
 222
 223                         expr.EmitBranchable (ec, false_target, false);
 224
 225                         TrueStatement.Emit (ec);
 226
 227                         if (FalseStatement != null){
 228                                 bool branch_emitted = false;
 229
 230                                 end = ig.DefineLabel ();
 231                                 if (!is_true_ret){
 232                                         ig.Emit (OpCodes.Br, end);
 233                                         branch_emitted = true;
 234                                 }
 235
 236                                 ig.MarkLabel (false_target);
 237                                 FalseStatement.Emit (ec);
 238
 239                                 if (branch_emitted)
 240                                         ig.MarkLabel (end);
 241                         } else {
 242                                 ig.MarkLabel (false_target);
 243                         }
 244                 }
 245         }
 246
 247         public class Do : Statement {
 248                 public Expression expr;
 249                 public readonly Statement  EmbeddedStatement;
 250                 bool infinite;
 251
 252                 public Do (Statement statement, Expression boolExpr, Location l)
 253                 {
 254                         expr = boolExpr;
 255                         EmbeddedStatement = statement;
 256                         loc = l;
 257                 }
 258
 259                 public override bool Resolve (EmitContext ec)
 260                 {
 261                         bool ok = true;
 262
 263                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 264
 265                         if (!EmbeddedStatement.Resolve (ec))
 266                                 ok = false;
 267
 268                         expr = Expression.ResolveBoolean (ec, expr, loc);
 269                         if (expr == null)
 270                                 ok = false;
 271                         else if (expr is BoolConstant){
 272                                 bool res = ((BoolConstant) expr).Value;
 273
 274                                 if (res)
 275                                         infinite = true;
 276                         }
 277
 278                         ec.CurrentBranching.Infinite = infinite;
 279                         ec.EndFlowBranching ();
 280
 281                         return ok;
 282                 }
 283
 284                 protected override void DoEmit (EmitContext ec)
 285                 {
 286                         ILGenerator ig = ec.ig;
 287                         Label loop = ig.DefineLabel ();
 288                         Label old_begin = ec.LoopBegin;
 289                         Label old_end = ec.LoopEnd;
 290
 291                         ec.LoopBegin = ig.DefineLabel ();
 292                         ec.LoopEnd = ig.DefineLabel ();
 293
 294                         ig.MarkLabel (loop);
 295                         EmbeddedStatement.Emit (ec);
 296                         ig.MarkLabel (ec.LoopBegin);
 297
 298                         //
 299                         // Dead code elimination
 300                         //
 301                         if (expr is BoolConstant){
 302                                 bool res = ((BoolConstant) expr).Value;
 303
 304                                 if (res)
 305                                         ec.ig.Emit (OpCodes.Br, loop);
 306                         } else
 307                                 expr.EmitBranchable (ec, loop, true);
 308
 309                         ig.MarkLabel (ec.LoopEnd);
 310
 311                         ec.LoopBegin = old_begin;
 312                         ec.LoopEnd = old_end;
 313                 }
 314         }
 315
 316         public class While : Statement {
 317                 public Expression expr;
 318                 public readonly Statement Statement;
 319                 bool infinite, empty;
 320
 321                 public While (Expression boolExpr, Statement statement, Location l)
 322                 {
 323                         this.expr = boolExpr;
 324                         Statement = statement;
 325                         loc = l;
 326                 }
 327
 328                 public override bool Resolve (EmitContext ec)
 329                 {
 330                         bool ok = true;
 331
 332                         expr = Expression.ResolveBoolean (ec, expr, loc);
 333                         if (expr == null)
 334                                 return false;
 335
 336                         //
 337                         // Inform whether we are infinite or not
 338                         //
 339                         if (expr is BoolConstant){
 340                                 BoolConstant bc = (BoolConstant) expr;
 341
 342                                 if (bc.Value == false){
 343                                         if (!Statement.ResolveUnreachable (ec, true))
 344                                                 return false;
 345                                         empty = true;
 346                                         return true;
 347                                 } else
 348                                         infinite = true;
 349                         }
 350
 351                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 352                         if (!infinite)
 353                                 ec.CurrentBranching.CreateSibling ();
 354
 355                         if (!Statement.Resolve (ec))
 356                                 ok = false;
 357
 358                         ec.CurrentBranching.Infinite = infinite;
 359                         ec.EndFlowBranching ();
 360
 361                         return ok;
 362                 }
 363
 364                 protected override void DoEmit (EmitContext ec)
 365                 {
 366                         if (empty)
 367                                 return;
 368
 369                         ILGenerator ig = ec.ig;
 370                         Label old_begin = ec.LoopBegin;
 371                         Label old_end = ec.LoopEnd;
 372
 373                         ec.LoopBegin = ig.DefineLabel ();
 374                         ec.LoopEnd = ig.DefineLabel ();
 375
 376                         //
 377                         // Inform whether we are infinite or not
 378                         //
 379                         if (expr is BoolConstant){
 380                                 ig.MarkLabel (ec.LoopBegin);
 381                                 Statement.Emit (ec);
 382                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 383
 384                                 //
 385                                 // Inform that we are infinite (ie, `we return'), only
 386                                 // if we do not `break' inside the code.
 387                                 //
 388                                 ig.MarkLabel (ec.LoopEnd);
 389                         } else {
 390                                 Label while_loop = ig.DefineLabel ();
 391
 392                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 393                                 ig.MarkLabel (while_loop);
 394
 395                                 Statement.Emit (ec);
 396
 397                                 ig.MarkLabel (ec.LoopBegin);
 398
 399                                 expr.EmitBranchable (ec, while_loop, true);
 400
 401                                 ig.MarkLabel (ec.LoopEnd);
 402                         }
 403
 404                         ec.LoopBegin = old_begin;
 405                         ec.LoopEnd = old_end;
 406                 }
 407         }
 408
 409         public class For : Statement {
 410                 Expression Test;
 411                 readonly Statement InitStatement;
 412                 readonly Statement Increment;
 413                 readonly Statement Statement;
 414                 bool infinite, empty;
 415
 416                 public For (Statement initStatement,
 417                             Expression test,
 418                             Statement increment,
 419                             Statement statement,
 420                             Location l)
 421                 {
 422                         InitStatement = initStatement;
 423                         Test = test;
 424                         Increment = increment;
 425                         Statement = statement;
 426                         loc = l;
 427                 }
 428
 429                 public override bool Resolve (EmitContext ec)
 430                 {
 431                         bool ok = true;
 432
 433                         if (InitStatement != null){
 434                                 if (!InitStatement.Resolve (ec))
 435                                         ok = false;
 436                         }
 437
 438                         if (Test != null){
 439                                 Test = Expression.ResolveBoolean (ec, Test, loc);
 440                                 if (Test == null)
 441                                         ok = false;
 442                                 else if (Test is BoolConstant){
 443                                         BoolConstant bc = (BoolConstant) Test;
 444
 445                                         if (bc.Value == false){
 446                                                 if (!Statement.ResolveUnreachable (ec, true))
 447                                                         return false;
 448                                                 if ((Increment != null) &&
 449                                                     !Increment.ResolveUnreachable (ec, false))
 450                                                         return false;
 451                                                 empty = true;
 452                                                 return true;
 453                                         } else
 454                                                 infinite = true;
 455                                 }
 456                         } else
 457                                 infinite = true;
 458
 459                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 460                         if (!infinite)
 461                                 ec.CurrentBranching.CreateSibling ();
 462
 463                         if (!Statement.Resolve (ec))
 464                                 ok = false;
 465
 466                         if (Increment != null){
 467                                 if (!Increment.Resolve (ec))
 468                                         ok = false;
 469                         }
 470
 471                         ec.CurrentBranching.Infinite = infinite;
 472                         ec.EndFlowBranching ();
 473
 474                         return ok;
 475                 }
 476
 477                 protected override void DoEmit (EmitContext ec)
 478                 {
 479                         if (empty)
 480                                 return;
 481
 482                         ILGenerator ig = ec.ig;
 483                         Label old_begin = ec.LoopBegin;
 484                         Label old_end = ec.LoopEnd;
 485                         Label loop = ig.DefineLabel ();
 486                         Label test = ig.DefineLabel ();
 487
 488                         if (InitStatement != null && InitStatement != EmptyStatement.Value)
 489                                 InitStatement.Emit (ec);
 490
 491                         ec.LoopBegin = ig.DefineLabel ();
 492                         ec.LoopEnd = ig.DefineLabel ();
 493
 494                         ig.Emit (OpCodes.Br, test);
 495                         ig.MarkLabel (loop);
 496                         Statement.Emit (ec);
 497
 498                         ig.MarkLabel (ec.LoopBegin);
 499                         if (Increment != EmptyStatement.Value)
 500                                 Increment.Emit (ec);
 501
 502                         ig.MarkLabel (test);
 503                         //
 504                         // If test is null, there is no test, and we are just
 505                         // an infinite loop
 506                         //
 507                         if (Test != null){
 508                                 //
 509                                 // The Resolve code already catches the case for
 510                                 // Test == BoolConstant (false) so we know that
 511                                 // this is true
 512                                 //
 513                                 if (Test is BoolConstant)
 514                                         ig.Emit (OpCodes.Br, loop);
 515                                 else
 516                                         Test.EmitBranchable (ec, loop, true);
 517
 518                         } else
 519                                 ig.Emit (OpCodes.Br, loop);
 520                         ig.MarkLabel (ec.LoopEnd);
 521
 522                         ec.LoopBegin = old_begin;
 523                         ec.LoopEnd = old_end;
 524                 }
 525         }
 526
 527         public class StatementExpression : Statement {
 528                 ExpressionStatement expr;
 529
 530                 public StatementExpression (ExpressionStatement expr, Location l)
 531                 {
 532                         this.expr = expr;
 533                         loc = l;
 534                 }
 535
 536                 public override bool Resolve (EmitContext ec)
 537                 {
 538                         if (expr != null)
 539                                 expr = expr.ResolveStatement (ec);
 540                         return expr != null;
 541                 }
 542
 543                 protected override void DoEmit (EmitContext ec)
 544                 {
 545                         expr.EmitStatement (ec);
 546                 }
 547
 548                 public override string ToString ()
 549                 {
 550                         return "StatementExpression (" + expr + ")";
 551                 }
 552         }
 553
 554         /// <summary>
 555         ///   Implements the return statement
 556         /// </summary>
 557         public class Return : Statement {
 558                 public Expression Expr;
 559
 560                 public Return (Expression expr, Location l)
 561                 {
 562                         Expr = expr;
 563                         loc = l;
 564                 }
 565
 566                 bool in_exc;
 567
 568                 public override bool Resolve (EmitContext ec)
 569                 {
 570                         AnonymousContainer am = ec.CurrentAnonymousMethod;
 571                         if ((am != null) && am.IsIterator && ec.InIterator) {
 572                                 Report.Error (1622, loc, "Cannot return a value from iterators. Use the yield return " +
 573                                               "statement to return a value, or yield break to end the iteration");
 574                                 return false;
 575                         }
 576
 577                         if (ec.ReturnType == null){
 578                                 if (Expr != null){
 579                                         if (ec.CurrentAnonymousMethod != null){
 580                                                 Report.Error (1662, loc,
 581                                                         "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",
 582                                                         ec.CurrentAnonymousMethod.GetSignatureForError ());
 583                                         }
 584                                         Error (127, "A return keyword must not be followed by any expression when method returns void");
 585                                         return false;
 586                                 }
 587                         } else {
 588                                 if (Expr == null){
 589                                         Error (126, "An object of a type convertible to `{0}' is required " +
 590                                                "for the return statement",
 591                                                TypeManager.CSharpName (ec.ReturnType));
 592                                         return false;
 593                                 }
 594
 595                                 Expr = Expr.Resolve (ec);
 596                                 if (Expr == null)
 597                                         return false;
 598
 599                                 if (Expr.Type != ec.ReturnType) {
 600                                         Expr = Convert.ImplicitConversionRequired (
 601                                                 ec, Expr, ec.ReturnType, loc);
 602                                         if (Expr == null)
 603                                                 return false;
 604                                 }
 605                         }
 606
 607                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
 608
 609                         if (ec.CurrentBranching.InTryOrCatch (true)) {
 610                                 ec.CurrentBranching.AddFinallyVector (vector);
 611                                 in_exc = true;
 612                         } else if (ec.InFinally) {
 613                                 Error (157, "Control cannot leave the body of a finally clause");
 614                                 return false;
 615                         } else
 616                                 vector.CheckOutParameters (ec.CurrentBranching);
 617
 618                         if (in_exc)
 619                                 ec.NeedReturnLabel ();
 620
 621                         ec.CurrentBranching.CurrentUsageVector.Return ();
 622                         return true;
 623                 }
 624
 625                 protected override void DoEmit (EmitContext ec)
 626                 {
 627                         if (Expr != null) {
 628                                 Expr.Emit (ec);
 629
 630                                 if (in_exc)
 631                                         ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 632                         }
 633
 634                         if (in_exc)
 635                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 636                         else
 637                                 ec.ig.Emit (OpCodes.Ret);
 638                 }
 639         }
 640
 641         public class Goto : Statement {
 642                 string target;
 643                 LabeledStatement label;
 644
 645                 public override bool Resolve (EmitContext ec)
 646                 {
 647                         label = ec.CurrentBranching.LookupLabel (target, loc);
 648                         if (label == null)
 649                                 return false;
 650
 651                         // If this is a forward goto.
 652                         if (!label.IsDefined)
 653                                 label.AddUsageVector (ec.CurrentBranching.CurrentUsageVector);
 654
 655                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 656                         label.AddReference ();
 657
 658                         return true;
 659                 }
 660
 661                 public Goto (string label, Location l)
 662                 {
 663                         loc = l;
 664                         target = label;
 665                 }
 666
 667                 public string Target {
 668                         get {
 669                                 return target;
 670                         }
 671                 }
 672
 673                 protected override void DoEmit (EmitContext ec)
 674                 {
 675                         Label l = label.LabelTarget (ec);
 676                         ec.ig.Emit (OpCodes.Br, l);
 677                 }
 678         }
 679
 680         public class LabeledStatement : Statement {
 681                 bool defined;
 682                 bool referenced;
 683                 Label label;
 684                 ILGenerator ig;
 685
 686                 FlowBranching.UsageVector vectors;
 687
 688                 public LabeledStatement (string label_name, Location l)
 689                 {
 690                         this.loc = l;
 691                 }
 692
 693                 public Label LabelTarget (EmitContext ec)
 694                 {
 695                         if (defined)
 696                                 return label;
 697                         ig = ec.ig;
 698                         label = ec.ig.DefineLabel ();
 699                         defined = true;
 700
 701                         return label;
 702                 }
 703
 704                 public bool IsDefined {
 705                         get {
 706                                 return defined;
 707                         }
 708                 }
 709
 710                 public bool HasBeenReferenced {
 711                         get {
 712                                 return referenced;
 713                         }
 714                 }
 715
 716                 public void AddUsageVector (FlowBranching.UsageVector vector)
 717                 {
 718                         vector = vector.Clone ();
 719                         vector.Next = vectors;
 720                         vectors = vector;
 721                 }
 722
 723                 public override bool Resolve (EmitContext ec)
 724                 {
 725                         ec.CurrentBranching.Label (vectors);
 726
 727                         return true;
 728                 }
 729
 730                 protected override void DoEmit (EmitContext ec)
 731                 {
 732                         if (ig != null && ig != ec.ig) {
 733                                 // TODO: location is wrong
 734                                 Report.Error (1632, loc, "Control cannot leave the body of an anonymous method");
 735                                 return;
 736                         }
 737                         LabelTarget (ec);
 738                         ec.ig.MarkLabel (label);
 739                 }
 740
 741                 public void AddReference ()
 742                 {
 743                         referenced = true;
 744                 }
 745         }
 746
 747
 748         /// <summary>
 749         ///   `goto default' statement
 750         /// </summary>
 751         public class GotoDefault : Statement {
 752
 753                 public GotoDefault (Location l)
 754                 {
 755                         loc = l;
 756                 }
 757
 758                 public override bool Resolve (EmitContext ec)
 759                 {
 760                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 761                         return true;
 762                 }
 763
 764                 protected override void DoEmit (EmitContext ec)
 765                 {
 766                         if (ec.Switch == null){
 767                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
 768                                 return;
 769                         }
 770
 771                         if (!ec.Switch.GotDefault){
 772                                 Report.Error (159, loc, "No such label `default:' within the scope of the goto statement");
 773                                 return;
 774                         }
 775                         ec.ig.Emit (OpCodes.Br, ec.Switch.DefaultTarget);
 776                 }
 777         }
 778
 779         /// <summary>
 780         ///   `goto case' statement
 781         /// </summary>
 782         public class GotoCase : Statement {
 783                 Expression expr;
 784                 SwitchLabel sl;
 785
 786                 public GotoCase (Expression e, Location l)
 787                 {
 788                         expr = e;
 789                         loc = l;
 790                 }
 791
 792                 public override bool Resolve (EmitContext ec)
 793                 {
 794                         if (ec.Switch == null){
 795                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
 796                                 return false;
 797                         }
 798
 799                         expr = expr.Resolve (ec);
 800                         if (expr == null)
 801                                 return false;
 802
 803                         if (!(expr is Constant)){
 804                                 Error (150, "A constant value is expected");
 805                                 return false;
 806                         }
 807
 808                         object val = Expression.ConvertIntLiteral (
 809                                 (Constant) expr, ec.Switch.SwitchType, loc);
 810
 811                         if (val == null)
 812                                 return false;
 813
 814                         sl = (SwitchLabel) ec.Switch.Elements [val];
 815
 816                         if (sl == null){
 817                                 Report.Error (159, loc, "No such label `case {0}:' within the scope of the goto statement", val);
 818                                 return false;
 819                         }
 820
 821                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 822                         return true;
 823                 }
 824
 825                 protected override void DoEmit (EmitContext ec)
 826                 {
 827                         ec.ig.Emit (OpCodes.Br, sl.GetILLabelCode (ec));
 828                 }
 829         }
 830
 831         public class Throw : Statement {
 832                 Expression expr;
 833
 834                 public Throw (Expression expr, Location l)
 835                 {
 836                         this.expr = expr;
 837                         loc = l;
 838                 }
 839
 840                 public override bool Resolve (EmitContext ec)
 841                 {
 842                         ec.CurrentBranching.CurrentUsageVector.Throw ();
 843
 844                         if (expr != null){
 845                                 expr = expr.Resolve (ec);
 846                                 if (expr == null)
 847                                         return false;
 848
 849                                 ExprClass eclass = expr.eclass;
 850
 851                                 if (!(eclass == ExprClass.Variable || eclass == ExprClass.PropertyAccess ||
 852                                         eclass == ExprClass.Value || eclass == ExprClass.IndexerAccess)) {
 853                                         expr.Error_UnexpectedKind (ec, "value, variable, property or indexer access ", loc);
 854                                         return false;
 855                                 }
 856
 857                                 Type t = expr.Type;
 858
 859                                 if ((t != TypeManager.exception_type) &&
 860                                         !t.IsSubclassOf (TypeManager.exception_type) &&
 861                                         !(expr is NullLiteral)) {
 862                                         Error (155,
 863                                                 "The type caught or thrown must be derived " +
 864                                                 "from System.Exception");
 865                                         return false;
 866                                 }
 867                                 return true;
 868                         }
 869
 870                         if (!ec.InCatch) {
 871                                 Error (156, "A throw statement with no arguments is not allowed outside of a catch clause");
 872                                 return false;
 873                         }
 874
 875                         if (ec.InFinally) {
 876                                 Error (724, "A throw statement with no arguments is not allowed inside of a finally clause nested inside of the innermost catch clause");
 877                                 return false;
 878                         }
 879                         return true;
 880                 }
 881
 882                 protected override void DoEmit (EmitContext ec)
 883                 {
 884                         if (expr == null)
 885                                 ec.ig.Emit (OpCodes.Rethrow);
 886                         else {
 887                                 expr.Emit (ec);
 888
 889                                 ec.ig.Emit (OpCodes.Throw);
 890                         }
 891                 }
 892         }
 893
 894         public class Break : Statement {
 895
 896                 public Break (Location l)
 897                 {
 898                         loc = l;
 899                 }
 900
 901                 bool crossing_exc;
 902
 903                 public override bool Resolve (EmitContext ec)
 904                 {
 905                         if (!ec.CurrentBranching.InLoop () && !ec.CurrentBranching.InSwitch ()){
 906                                 Error (139, "No enclosing loop out of which to break or continue");
 907                                 return false;
 908                         } else if (ec.InFinally && ec.CurrentBranching.BreakCrossesTryCatchBoundary()) {
 909                                 Error (157, "Control cannot leave the body of a finally clause");
 910                                 return false;
 911                         } else if (ec.CurrentBranching.InTryOrCatch (false))
 912                                 ec.CurrentBranching.AddFinallyVector (
 913                                         ec.CurrentBranching.CurrentUsageVector);
 914                         else if (ec.CurrentBranching.InLoop () || ec.CurrentBranching.InSwitch ())
 915                                 ec.CurrentBranching.AddBreakVector (
 916                                         ec.CurrentBranching.CurrentUsageVector);
 917
 918                         crossing_exc = ec.CurrentBranching.BreakCrossesTryCatchBoundary ();
 919
 920                         if (!crossing_exc)
 921                                 ec.NeedReturnLabel ();
 922
 923                         ec.CurrentBranching.CurrentUsageVector.Break ();
 924                         return true;
 925                 }
 926
 927                 protected override void DoEmit (EmitContext ec)
 928                 {
 929                         ILGenerator ig = ec.ig;
 930
 931                         if (crossing_exc)
 932                                 ig.Emit (OpCodes.Leave, ec.LoopEnd);
 933                         else {
 934                                 ig.Emit (OpCodes.Br, ec.LoopEnd);
 935                         }
 936                 }
 937         }
 938
 939         public class Continue : Statement {
 940
 941                 public Continue (Location l)
 942                 {
 943                         loc = l;
 944                 }
 945
 946                 bool crossing_exc;
 947
 948                 public override bool Resolve (EmitContext ec)
 949                 {
 950                         if (!ec.CurrentBranching.InLoop () && !ec.CurrentBranching.InSwitch ()){
 951                                 Error (139, "No enclosing loop out of which to break or continue");
 952                                 return false;
 953                         } else if (ec.InFinally) {
 954                                 Error (157, "Control cannot leave the body of a finally clause");
 955                                 return false;
 956                         } else if (ec.CurrentBranching.InTryOrCatch (false))
 957                                 ec.CurrentBranching.AddFinallyVector (ec.CurrentBranching.CurrentUsageVector);
 958
 959                         crossing_exc = ec.CurrentBranching.BreakCrossesTryCatchBoundary ();
 960
 961                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 962                         return true;
 963                 }
 964
 965                 protected override void DoEmit (EmitContext ec)
 966                 {
 967                         Label begin = ec.LoopBegin;
 968
 969                         if (crossing_exc)
 970                                 ec.ig.Emit (OpCodes.Leave, begin);
 971                         else
 972                                 ec.ig.Emit (OpCodes.Br, begin);
 973                 }
 974         }
 975
 976         //
 977         // The information about a user-perceived local variable
 978         //
 979         public class LocalInfo {
 980                 public Expression Type;
 981
 982                 //
 983                 // Most of the time a variable will be stored in a LocalBuilder
 984                 //
 985                 // But sometimes, it will be stored in a field (variables that have been
 986                 // hoisted by iterators or by anonymous methods).  The context of the field will
 987                 // be stored in the EmitContext
 988                 //
 989                 //
 990                 public LocalBuilder LocalBuilder;
 991                 public FieldBuilder FieldBuilder;
 992
 993                 public Type VariableType;
 994                 public readonly string Name;
 995                 public readonly Location Location;
 996                 public readonly Block Block;
 997
 998                 public VariableInfo VariableInfo;
 999
1000                 enum Flags : byte {
1001                         Used = 1,
1002                         ReadOnly = 2,
1003                         Pinned = 4,
1004                         IsThis = 8,
1005                         Captured = 16,
1006                         AddressTaken = 32,
1007                         CompilerGenerated = 64
1008                 }
1009
1010                 public enum ReadOnlyContext: byte {
1011                         Using,
1012                         Foreach,
1013                         Fixed
1014                 }
1015
1016                 Flags flags;
1017                 ReadOnlyContext ro_context;
1018
1019                 public LocalInfo (Expression type, string name, Block block, Location l)
1020                 {
1021                         Type = type;
1022                         Name = name;
1023                         Block = block;
1024                         Location = l;
1025                 }
1026
1027                 public LocalInfo (TypeContainer tc, Block block, Location l)
1028                 {
1029                         VariableType = tc.TypeBuilder;
1030                         Block = block;
1031                         Location = l;
1032                 }
1033
1034                 public bool IsThisAssigned (EmitContext ec, Location loc)
1035                 {
1036                         if (VariableInfo == null)
1037                                 throw new Exception ();
1038
1039                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo))
1040                                 return true;
1041
1042                         return VariableInfo.TypeInfo.IsFullyInitialized (ec.CurrentBranching, VariableInfo, loc);
1043                 }
1044
1045                 public bool IsAssigned (EmitContext ec)
1046                 {
1047                         if (VariableInfo == null)
1048                                 throw new Exception ();
1049
1050                         return !ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo);
1051                 }
1052
1053                 public bool Resolve (EmitContext ec)
1054                 {
1055                         if (VariableType == null) {
1056                                 TypeExpr texpr = Type.ResolveAsTypeTerminal (ec, false);
1057                                 if (texpr == null)
1058                                         return false;
1059
1060                                 VariableType = texpr.ResolveType (ec);
1061                         }
1062
1063                         if (VariableType == TypeManager.void_type) {
1064                                 Report.Error (1547, Location,
1065                                               "Keyword 'void' cannot be used in this context");
1066                                 return false;
1067                         }
1068
1069                         if (VariableType.IsAbstract && VariableType.IsSealed) {
1070                                 Report.Error (723, Location, "Cannot declare variable of static type `{0}'", TypeManager.CSharpName (VariableType));
1071                                 return false;
1072                         }
1073
1074                         if (VariableType.IsPointer && !ec.InUnsafe)
1075                                 Expression.UnsafeError (Location);
1076
1077                         return true;
1078                 }
1079
1080                 public bool IsCaptured {
1081                         get {
1082                                 return (flags & Flags.Captured) != 0;
1083                         }
1084
1085                         set {
1086                                 flags |= Flags.Captured;
1087                         }
1088                 }
1089
1090                 public bool AddressTaken {
1091                         get {
1092                                 return (flags & Flags.AddressTaken) != 0;
1093                         }
1094
1095                         set {
1096                                 flags |= Flags.AddressTaken;
1097                         }
1098                 }
1099
1100                 public bool CompilerGenerated {
1101                         get {
1102                                 return (flags & Flags.CompilerGenerated) != 0;
1103                         }
1104
1105                         set {
1106                                 flags |= Flags.CompilerGenerated;
1107                         }
1108                 }
1109
1110                 public override string ToString ()
1111                 {
1112                         return String.Format ("LocalInfo ({0},{1},{2},{3})",
1113                                               Name, Type, VariableInfo, Location);
1114                 }
1115
1116                 public bool Used {
1117                         get {
1118                                 return (flags & Flags.Used) != 0;
1119                         }
1120                         set {
1121                                 flags = value ? (flags | Flags.Used) : (unchecked (flags & ~Flags.Used));
1122                         }
1123                 }
1124
1125                 public bool ReadOnly {
1126                         get {
1127                                 return (flags & Flags.ReadOnly) != 0;
1128                         }
1129                 }
1130
1131                 public void SetReadOnlyContext (ReadOnlyContext context)
1132                 {
1133                         flags |= Flags.ReadOnly;
1134                         ro_context = context;
1135                 }
1136
1137                 public string GetReadOnlyContext ()
1138                 {
1139                         if (!ReadOnly)
1140                                 throw new InternalErrorException ("Variable is not readonly");
1141
1142                         switch (ro_context) {
1143                                 case ReadOnlyContext.Fixed:
1144                                         return "fixed variable";
1145                                 case ReadOnlyContext.Foreach:
1146                                         return "foreach iteration variable";
1147                                 case ReadOnlyContext.Using:
1148                                         return "using variable";
1149                         }
1150                         throw new NotImplementedException ();
1151                 }
1152
1153                 //
1154                 // Whether the variable is pinned, if Pinned the variable has been
1155                 // allocated in a pinned slot with DeclareLocal.
1156                 //
1157                 public bool Pinned {
1158                         get {
1159                                 return (flags & Flags.Pinned) != 0;
1160                         }
1161                         set {
1162                                 flags = value ? (flags | Flags.Pinned) : (flags & ~Flags.Pinned);
1163                         }
1164                 }
1165
1166                 public bool IsThis {
1167                         get {
1168                                 return (flags & Flags.IsThis) != 0;
1169                         }
1170                         set {
1171                                 flags = value ? (flags | Flags.IsThis) : (flags & ~Flags.IsThis);
1172                         }
1173                 }
1174         }
1175
1176         /// <summary>
1177         ///   Block represents a C# block.
1178         /// </summary>
1179         ///
1180         /// <remarks>
1181         ///   This class is used in a number of places: either to represent
1182         ///   explicit blocks that the programmer places or implicit blocks.
1183         ///
1184         ///   Implicit blocks are used as labels or to introduce variable
1185         ///   declarations.
1186         ///
1187         ///   Top-level blocks derive from Block, and they are called ToplevelBlock
1188         ///   they contain extra information that is not necessary on normal blocks.
1189         /// </remarks>
1190         public class Block : Statement {
1191                 public Block    Parent;
1192                 public readonly Location  StartLocation;
1193                 public Location EndLocation = Location.Null;
1194
1195                 public readonly ToplevelBlock Toplevel;
1196
1197                 [Flags]
1198                 public enum Flags : ushort {
1199                         Implicit  = 1,
1200                         Unchecked = 2,
1201                         BlockUsed = 4,
1202                         VariablesInitialized = 8,
1203                         HasRet = 16,
1204                         IsDestructor = 32,
1205                         IsToplevel = 64,
1206                         Unsafe = 128,
1207                         HasVarargs = 256 // Used in ToplevelBlock
1208                 }
1209                 protected Flags flags;
1210
1211                 public bool Implicit {
1212                         get { return (flags & Flags.Implicit) != 0; }
1213                 }
1214
1215                 public bool Unchecked {
1216                         get { return (flags & Flags.Unchecked) != 0; }
1217                         set { flags |= Flags.Unchecked; }
1218                 }
1219
1220                 public bool Unsafe {
1221                         get { return (flags & Flags.Unsafe) != 0; }
1222                         set { flags |= Flags.Unsafe; }
1223                 }
1224
1225                 //
1226                 // The statements in this block
1227                 //
1228                 ArrayList statements;
1229                 int num_statements;
1230
1231                 //
1232                 // An array of Blocks.  We keep track of children just
1233                 // to generate the local variable declarations.
1234                 //
1235                 // Statements and child statements are handled through the
1236                 // statements.
1237                 //
1238                 ArrayList children;
1239
1240                 //
1241                 // Labels.  (label, block) pairs.
1242                 //
1243                 Hashtable labels;
1244
1245                 //
1246                 // Keeps track of (name, type) pairs
1247                 //
1248                 Hashtable variables;
1249
1250                 //
1251                 // Keeps track of constants
1252                 Hashtable constants;
1253
1254                 //
1255                 // Temporary variables.
1256                 //
1257                 ArrayList temporary_variables;
1258
1259                 //
1260                 // If this is a switch section, the enclosing switch block.
1261                 //
1262                 Block switch_block;
1263
1264                 protected static int id;
1265
1266                 int this_id;
1267
1268                 public Block (Block parent)
1269                         : this (parent, (Flags) 0, Location.Null, Location.Null)
1270                 { }
1271
1272                 public Block (Block parent, Flags flags)
1273                         : this (parent, flags, Location.Null, Location.Null)
1274                 { }
1275
1276                 public Block (Block parent, Location start, Location end)
1277                         : this (parent, (Flags) 0, start, end)
1278                 { }
1279
1280                 public Block (Block parent, Flags flags, Location start, Location end)
1281                 {
1282                         if (parent != null)
1283                                 parent.AddChild (this);
1284
1285                         this.Parent = parent;
1286                         this.flags = flags;
1287                         this.StartLocation = start;
1288                         this.EndLocation = end;
1289                         this.loc = start;
1290                         this_id = id++;
1291                         statements = new ArrayList ();
1292
1293                         if ((flags & Flags.IsToplevel) != 0)
1294                                 Toplevel = (ToplevelBlock) this;
1295                         else
1296                                 Toplevel = parent.Toplevel;
1297
1298                         if (parent != null && Implicit) {
1299                                 if (parent.known_variables == null)
1300                                         parent.known_variables = new Hashtable ();
1301                                 // share with parent
1302                                 known_variables = parent.known_variables;
1303                         }
1304
1305                 }
1306
1307                 public Block CreateSwitchBlock (Location start)
1308                 {
1309                         Block new_block = new Block (this, start, start);
1310                         new_block.switch_block = this;
1311                         return new_block;
1312                 }
1313
1314                 public int ID {
1315                         get { return this_id; }
1316                 }
1317
1318                 protected Hashtable Variables {
1319                         get {
1320                                 if (variables == null)
1321                                         variables = new Hashtable ();
1322                                 return variables;
1323                         }
1324                 }
1325
1326                 void AddChild (Block b)
1327                 {
1328                         if (children == null)
1329                                 children = new ArrayList ();
1330
1331                         children.Add (b);
1332                 }
1333
1334                 public void SetEndLocation (Location loc)
1335                 {
1336                         EndLocation = loc;
1337                 }
1338
1339                 /// <summary>
1340                 ///   Adds a label to the current block.
1341                 /// </summary>
1342                 ///
1343                 /// <returns>
1344                 ///   false if the name already exists in this block. true
1345                 ///   otherwise.
1346                 /// </returns>
1347                 ///
1348                 public bool AddLabel (string name, LabeledStatement target, Location loc)
1349                 {
1350                         if (switch_block != null)
1351                                 return switch_block.AddLabel (name, target, loc);
1352
1353                         Block cur = this;
1354                         while (cur != null) {
1355                                 if (cur.DoLookupLabel (name) != null) {
1356                                         Report.Error (
1357                                                 140, loc, "The label `{0}' is a duplicate",
1358                                                 name);
1359                                         return false;
1360                                 }
1361
1362                                 if (!Implicit)
1363                                         break;
1364
1365                                 cur = cur.Parent;
1366                         }
1367
1368                         while (cur != null) {
1369                                 if (cur.DoLookupLabel (name) != null) {
1370                                         Report.Error (
1371                                                 158, loc,
1372                                                 "The label `{0}' shadows another label " +
1373                                                 "by the same name in a contained scope.",
1374                                                 name);
1375                                         return false;
1376                                 }
1377
1378                                 if (children != null) {
1379                                         foreach (Block b in children) {
1380                                                 LabeledStatement s = b.DoLookupLabel (name);
1381                                                 if (s == null)
1382                                                         continue;
1383
1384                                                 Report.Error (
1385                                                         158, s.loc,
1386                                                         "The label `{0}' shadows another " +
1387                                                         "label by the same name in a " +
1388                                                         "contained scope.",
1389                                                         name);
1390                                                 return false;
1391                                         }
1392                                 }
1393
1394
1395                                 cur = cur.Parent;
1396                         }
1397
1398                         if (labels == null)
1399                                 labels = new Hashtable ();
1400
1401                         labels.Add (name, target);
1402                         return true;
1403                 }
1404
1405                 public LabeledStatement LookupLabel (string name)
1406                 {
1407                         LabeledStatement s = DoLookupLabel (name);
1408                         if (s != null)
1409                                 return s;
1410
1411                         if (children == null)
1412                                 return null;
1413
1414                         foreach (Block child in children) {
1415                                 if (!child.Implicit)
1416                                         continue;
1417
1418                                 s = child.LookupLabel (name);
1419                                 if (s != null)
1420                                         return s;
1421                         }
1422
1423                         return null;
1424                 }
1425
1426                 LabeledStatement DoLookupLabel (string name)
1427                 {
1428                         if (switch_block != null)
1429                                 return switch_block.LookupLabel (name);
1430
1431                         if (labels != null)
1432                                 if (labels.Contains (name))
1433                                         return ((LabeledStatement) labels [name]);
1434
1435                         return null;
1436                 }
1437
1438                 Hashtable known_variables;
1439
1440                 // <summary>
1441                 //   Marks a variable with name @name as being used in this or a child block.
1442                 //   If a variable name has been used in a child block, it's illegal to
1443                 //   declare a variable with the same name in the current block.
1444                 // </summary>
1445                 void AddKnownVariable (string name, LocalInfo info)
1446                 {
1447                         if (known_variables == null)
1448                                 known_variables = new Hashtable ();
1449
1450                         known_variables [name] = info;
1451                 }
1452
1453                 LocalInfo GetKnownVariableInfo (string name)
1454                 {
1455                         if (known_variables == null)
1456                                 return null;
1457                         return (LocalInfo) known_variables [name];
1458                 }
1459
1460                 public bool CheckInvariantMeaningInBlock (string name, Expression e, Location loc)
1461                 {
1462                         LocalInfo kvi = GetKnownVariableInfo (name);
1463                         if (kvi == null || kvi.Block == this)
1464                                 return true;
1465
1466                         if (known_variables != kvi.Block.known_variables) {
1467                                 Report.SymbolRelatedToPreviousError (kvi.Location, name);
1468                                 Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", name);
1469                                 return false;
1470                         }
1471
1472                         //
1473                         // this block and kvi.Block are the same textual block.
1474                         // However, different variables are extant.
1475                         //
1476                         // Check if the variable is in scope in both blocks.  We use
1477                         // an indirect check that depends on AddVariable doing its
1478                         // part in maintaining the invariant-meaning-in-block property.
1479                         //
1480                         if (e is LocalVariableReference || (e is Constant && GetLocalInfo (name) != null))
1481                                 return true;
1482
1483                         Report.SymbolRelatedToPreviousError (kvi.Location, name);
1484                         Error_AlreadyDeclared (loc, name, "parent or current");
1485                         return false;
1486                 }
1487
1488                 public LocalInfo AddVariable (Expression type, string name, Location l)
1489                 {
1490                         LocalInfo vi = GetLocalInfo (name);
1491                         if (vi != null) {
1492                                 Report.SymbolRelatedToPreviousError (vi.Location, name);
1493                                 if (known_variables == vi.Block.known_variables)
1494                                         Report.Error (128, l,
1495                                                 "A local variable named `{0}' is already defined in this scope", name);
1496                                 else
1497                                         Error_AlreadyDeclared (l, name, "parent");
1498                                 return null;
1499                         }
1500
1501                         vi = GetKnownVariableInfo (name);
1502                         if (vi != null) {
1503                                 Report.SymbolRelatedToPreviousError (vi.Location, name);
1504                                 Error_AlreadyDeclared (l, name, "child");
1505                                 return null;
1506                         }
1507
1508                         int idx;
1509                         Parameter p = Toplevel.Parameters.GetParameterByName (name, out idx);
1510                         if (p != null) {
1511                                 Report.SymbolRelatedToPreviousError (p.Location, name);
1512                                 Error_AlreadyDeclared (l, name, "method argument");
1513                                 return null;
1514                         }
1515
1516                         vi = new LocalInfo (type, name, this, l);
1517
1518                         Variables.Add (name, vi);
1519
1520                         for (Block b = this; b != null; b = b.Parent)
1521                                 b.AddKnownVariable (name, vi);
1522
1523                         if ((flags & Flags.VariablesInitialized) != 0)
1524                                 throw new Exception ();
1525
1526                         return vi;
1527                 }
1528
1529                 void Error_AlreadyDeclared (Location loc, string var, string reason)
1530                 {
1531                         Report.Error (136, loc, "A local variable named `{0}' cannot be declared in this scope because it would give a different meaning to `{0}', " +
1532                                 "which is already used in a `{1}' scope", var, reason);
1533                 }
1534
1535                 public bool AddConstant (Expression type, string name, Expression value, Location l)
1536                 {
1537                         if (AddVariable (type, name, l) == null)
1538                                 return false;
1539
1540                         if (constants == null)
1541                                 constants = new Hashtable ();
1542
1543                         constants.Add (name, value);
1544                         return true;
1545                 }
1546
1547                 static int next_temp_id = 0;
1548
1549                 public LocalInfo AddTemporaryVariable (TypeExpr te, Location loc)
1550                 {
1551                         if (temporary_variables == null)
1552                                 temporary_variables = new ArrayList ();
1553
1554                         int id = ++next_temp_id;
1555                         string name = "$s_" + id.ToString ();
1556
1557                         LocalInfo li = new LocalInfo (te, name, this, loc);
1558                         li.CompilerGenerated = true;
1559                         temporary_variables.Add (li);
1560                         return li;
1561                 }
1562
1563                 public LocalInfo GetLocalInfo (string name)
1564                 {
1565                         for (Block b = this; b != null; b = b.Parent) {
1566                                 if (b.variables != null) {
1567                                         LocalInfo ret = b.variables [name] as LocalInfo;
1568                                         if (ret != null)
1569                                                 return ret;
1570                                 }
1571                         }
1572                         return null;
1573                 }
1574
1575                 public Expression GetVariableType (string name)
1576                 {
1577                         LocalInfo vi = GetLocalInfo (name);
1578                         return vi == null ? null : vi.Type;
1579                 }
1580
1581                 public Expression GetConstantExpression (string name)
1582                 {
1583                         for (Block b = this; b != null; b = b.Parent) {
1584                                 if (b.constants != null) {
1585                                         Expression ret = b.constants [name] as Expression;
1586                                         if (ret != null)
1587                                                 return ret;
1588                                 }
1589                         }
1590                         return null;
1591                 }
1592
1593                 /// <summary>
1594                 ///   True if the variable named @name is a constant
1595                 ///  </summary>
1596                 public bool IsConstant (string name)
1597                 {
1598                         Expression e = GetConstantExpression (name);
1599                         return e != null;
1600                 }
1601
1602                 public void AddStatement (Statement s)
1603                 {
1604                         statements.Add (s);
1605                         flags |= Flags.BlockUsed;
1606                 }
1607
1608                 public bool Used {
1609                         get { return (flags & Flags.BlockUsed) != 0; }
1610                 }
1611
1612                 public void Use ()
1613                 {
1614                         flags |= Flags.BlockUsed;
1615                 }
1616
1617                 public bool HasRet {
1618                         get { return (flags & Flags.HasRet) != 0; }
1619                 }
1620
1621                 public bool IsDestructor {
1622                         get { return (flags & Flags.IsDestructor) != 0; }
1623                 }
1624
1625                 public void SetDestructor ()
1626                 {
1627                         flags |= Flags.IsDestructor;
1628                 }
1629
1630                 VariableMap param_map, local_map;
1631
1632                 public VariableMap ParameterMap {
1633                         get {
1634                                 if ((flags & Flags.VariablesInitialized) == 0)
1635                                         throw new Exception ("Variables have not been initialized yet");
1636
1637                                 return param_map;
1638                         }
1639                 }
1640
1641                 public VariableMap LocalMap {
1642                         get {
1643                                 if ((flags & Flags.VariablesInitialized) == 0)
1644                                         throw new Exception ("Variables have not been initialized yet");
1645
1646                                 return local_map;
1647                         }
1648                 }
1649
1650                 /// <summary>
1651                 ///   Emits the variable declarations and labels.
1652                 /// </summary>
1653                 /// <remarks>
1654                 ///   tc: is our typecontainer (to resolve type references)
1655                 ///   ig: is the code generator:
1656                 /// </remarks>
1657                 public void ResolveMeta (ToplevelBlock toplevel, EmitContext ec, InternalParameters ip)
1658                 {
1659                         bool old_unsafe = ec.InUnsafe;
1660
1661                         // If some parent block was unsafe, we remain unsafe even if this block
1662                         // isn't explicitly marked as such.
1663                         ec.InUnsafe |= Unsafe;
1664
1665                         //
1666                         // Compute the VariableMap's.
1667                         //
1668                         // Unfortunately, we don't know the type when adding variables with
1669                         // AddVariable(), so we need to compute this info here.
1670                         //
1671
1672                         LocalInfo[] locals;
1673                         if (variables != null) {
1674                                 foreach (LocalInfo li in variables.Values)
1675                                         li.Resolve (ec);
1676
1677                                 locals = new LocalInfo [variables.Count];
1678                                 variables.Values.CopyTo (locals, 0);
1679                         } else
1680                                 locals = new LocalInfo [0];
1681
1682                         if (Parent != null)
1683                                 local_map = new VariableMap (Parent.LocalMap, locals);
1684                         else
1685                                 local_map = new VariableMap (locals);
1686
1687                         param_map = new VariableMap (ip);
1688                         flags |= Flags.VariablesInitialized;
1689
1690                         bool old_check_state = ec.ConstantCheckState;
1691                         ec.ConstantCheckState = (flags & Flags.Unchecked) == 0;
1692
1693                         //
1694                         // Process this block variables
1695                         //
1696                         if (variables != null){
1697                                 foreach (DictionaryEntry de in variables){
1698                                         string name = (string) de.Key;
1699                                         LocalInfo vi = (LocalInfo) de.Value;
1700
1701                                         if (vi.VariableType == null)
1702                                                 continue;
1703
1704                                         Type variable_type = vi.VariableType;
1705
1706                                         if (variable_type.IsPointer){
1707                                                 //
1708                                                 // Am not really convinced that this test is required (Microsoft does it)
1709                                                 // but the fact is that you would not be able to use the pointer variable
1710                                                 // *anyways*
1711                                                 //
1712                                                 if (!TypeManager.VerifyUnManaged (TypeManager.GetElementType (variable_type),
1713                                                                                   vi.Location))
1714                                                         continue;
1715                                         }
1716
1717                                         if (constants == null)
1718                                                 continue;
1719
1720                                         Expression cv = (Expression) constants [name];
1721                                         if (cv == null)
1722                                                 continue;
1723
1724                                         ec.CurrentBlock = this;
1725                                         Expression e = cv.Resolve (ec);
1726
1727                                         Constant ce = e as Constant;
1728                                         if (ce == null){
1729                                                 Const.Error_ExpressionMustBeConstant (vi.Location, name);
1730                                                 continue;
1731                                         }
1732
1733                                         if (e.Type != variable_type){
1734                                                 e = Const.ChangeType (vi.Location, ce, variable_type);
1735                                                 if (e == null)
1736                                                         continue;
1737                                         }
1738
1739                                         constants.Remove (name);
1740                                         constants.Add (name, e);
1741                                 }
1742                         }
1743                         ec.ConstantCheckState = old_check_state;
1744
1745                         //
1746                         // Now, handle the children
1747                         //
1748                         if (children != null){
1749                                 foreach (Block b in children)
1750                                         b.ResolveMeta (toplevel, ec, ip);
1751                         }
1752                         ec.InUnsafe = old_unsafe;
1753                 }
1754
1755                 //
1756                 // Emits the local variable declarations for a block
1757                 //
1758                 public void EmitMeta (EmitContext ec)
1759                 {
1760                         ILGenerator ig = ec.ig;
1761
1762                         if (variables != null){
1763                                 bool have_captured_vars = ec.HaveCapturedVariables ();
1764
1765                                 foreach (DictionaryEntry de in variables){
1766                                         LocalInfo vi = (LocalInfo) de.Value;
1767
1768                                         if (have_captured_vars && ec.IsCaptured (vi))
1769                                                 continue;
1770
1771                                         if (vi.Pinned)
1772                                                 //
1773                                                 // This is needed to compile on both .NET 1.x and .NET 2.x
1774                                                 // the later introduced `DeclareLocal (Type t, bool pinned)'
1775                                                 //
1776                                                 vi.LocalBuilder = TypeManager.DeclareLocalPinned (ig, vi.VariableType);
1777                                         else if (!vi.IsThis)
1778                                                 vi.LocalBuilder = ig.DeclareLocal (vi.VariableType);
1779                                 }
1780                         }
1781
1782                         if (temporary_variables != null) {
1783                                 AnonymousContainer am = ec.CurrentAnonymousMethod;
1784                                 TypeBuilder scope = null;
1785                                 if ((am != null) && am.IsIterator) {
1786                                         scope = am.Scope.ScopeTypeBuilder;
1787                                         if (scope == null)
1788                                                 throw new InternalErrorException ();
1789                                 }
1790                                 foreach (LocalInfo vi in temporary_variables) {
1791                                         if (scope != null) {
1792                                                 if (vi.FieldBuilder == null)
1793                                                         vi.FieldBuilder = scope.DefineField (
1794                                                                 vi.Name, vi.VariableType, FieldAttributes.Assembly);
1795                                         } else
1796                                                 vi.LocalBuilder = ig.DeclareLocal (vi.VariableType);
1797                                 }
1798                         }
1799
1800                         if (children != null){
1801                                 foreach (Block b in children)
1802                                         b.EmitMeta (ec);
1803                         }
1804                 }
1805
1806                 void UsageWarning (FlowBranching.UsageVector vector)
1807                 {
1808                         string name;
1809
1810                         if ((variables != null) && (RootContext.WarningLevel >= 3)) {
1811                                 foreach (DictionaryEntry de in variables){
1812                                         LocalInfo vi = (LocalInfo) de.Value;
1813
1814                                         if (vi.Used)
1815                                                 continue;
1816
1817                                         name = (string) de.Key;
1818
1819                                         if (vector.IsAssigned (vi.VariableInfo)){
1820                                                 Report.Warning (219, vi.Location, "The variable `{0}' is assigned but its value is never used", name);
1821                                         } else {
1822                                                 Report.Warning (168, vi.Location, "The variable `{0}' is declared but never used", name);
1823                                         }
1824                                 }
1825                         }
1826                 }
1827
1828                 bool unreachable_shown;
1829                 bool unreachable;
1830
1831                 public override bool Resolve (EmitContext ec)
1832                 {
1833                         Block prev_block = ec.CurrentBlock;
1834                         bool ok = true;
1835
1836                         int errors = Report.Errors;
1837
1838                         ec.CurrentBlock = this;
1839                         ec.StartFlowBranching (this);
1840
1841                         Report.Debug (4, "RESOLVE BLOCK", StartLocation, ec.CurrentBranching);
1842
1843                         int statement_count = statements.Count;
1844                         for (int ix = 0; ix < statement_count; ix++){
1845                                 Statement s = (Statement) statements [ix];
1846
1847                                 //
1848                                 // Warn if we detect unreachable code.
1849                                 //
1850                                 if (unreachable) {
1851                                         if (s is Block)
1852                                                 ((Block) s).unreachable = true;
1853
1854                                         if (!unreachable_shown && (RootContext.WarningLevel >= 2)) {
1855                                                 Report.Warning (
1856                                                         162, loc, "Unreachable code detected");
1857                                                 unreachable_shown = true;
1858                                         }
1859                                 }
1860
1861                                 //
1862                                 // Note that we're not using ResolveUnreachable() for unreachable
1863                                 // statements here.  ResolveUnreachable() creates a temporary
1864                                 // flow branching and kills it afterwards.  This leads to problems
1865                                 // if you have two unreachable statements where the first one
1866                                 // assigns a variable and the second one tries to access it.
1867                                 //
1868
1869                                 if (!s.Resolve (ec)) {
1870                                         ok = false;
1871                                         statements [ix] = EmptyStatement.Value;
1872                                         continue;
1873                                 }
1874
1875                                 if (unreachable && !(s is LabeledStatement) && !(s is Block))
1876                                         statements [ix] = EmptyStatement.Value;
1877
1878                                 num_statements = ix + 1;
1879                                 if (s is LabeledStatement)
1880                                         unreachable = false;
1881                                 else
1882                                         unreachable = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
1883                         }
1884
1885                         Report.Debug (4, "RESOLVE BLOCK DONE", StartLocation,
1886                                       ec.CurrentBranching, statement_count, num_statements);
1887
1888                         FlowBranching.UsageVector vector = ec.DoEndFlowBranching ();
1889
1890                         ec.CurrentBlock = prev_block;
1891
1892                         // If we're a non-static `struct' constructor which doesn't have an
1893                         // initializer, then we must initialize all of the struct's fields.
1894                         if ((flags & Flags.IsToplevel) != 0 &&
1895                             !Toplevel.IsThisAssigned (ec) &&
1896                             vector.Reachability.Throws != FlowBranching.FlowReturns.Always)
1897                                 ok = false;
1898
1899                         if ((labels != null) && (RootContext.WarningLevel >= 2)) {
1900                                 foreach (LabeledStatement label in labels.Values)
1901                                         if (!label.HasBeenReferenced)
1902                                                 Report.Warning (164, label.loc,
1903                                                                 "This label has not been referenced");
1904                         }
1905
1906                         Report.Debug (4, "RESOLVE BLOCK DONE #2", StartLocation, vector);
1907
1908                         if ((vector.Reachability.Returns == FlowBranching.FlowReturns.Always) ||
1909                             (vector.Reachability.Throws == FlowBranching.FlowReturns.Always) ||
1910                             (vector.Reachability.Reachable == FlowBranching.FlowReturns.Never))
1911                                 flags |= Flags.HasRet;
1912
1913                         if (ok && (errors == Report.Errors)) {
1914                                 if (RootContext.WarningLevel >= 3)
1915                                         UsageWarning (vector);
1916                         }
1917
1918                         return ok;
1919                 }
1920
1921                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
1922                 {
1923                         unreachable_shown = true;
1924                         unreachable = true;
1925
1926                         if (warn && (RootContext.WarningLevel >= 2))
1927                                 Report.Warning (162, loc, "Unreachable code detected");
1928
1929                         ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
1930                         bool ok = Resolve (ec);
1931                         ec.KillFlowBranching ();
1932
1933                         return ok;
1934                 }
1935
1936                 protected override void DoEmit (EmitContext ec)
1937                 {
1938                         for (int ix = 0; ix < num_statements; ix++){
1939                                 Statement s = (Statement) statements [ix];
1940
1941                                 // Check whether we are the last statement in a
1942                                 // top-level block.
1943
1944                                 if (((Parent == null) || Implicit) && (ix+1 == num_statements) && !(s is Block))
1945                                         ec.IsLastStatement = true;
1946                                 else
1947                                         ec.IsLastStatement = false;
1948
1949                                 s.Emit (ec);
1950                         }
1951                 }
1952
1953                 public override void Emit (EmitContext ec)
1954                 {
1955                         Block prev_block = ec.CurrentBlock;
1956
1957                         ec.CurrentBlock = this;
1958
1959                         bool emit_debug_info = (CodeGen.SymbolWriter != null);
1960                         bool is_lexical_block = !Implicit && (Parent != null);
1961
1962                         if (emit_debug_info) {
1963                                 if (is_lexical_block)
1964                                         ec.BeginScope ();
1965
1966                                 if (variables != null) {
1967                                         foreach (DictionaryEntry de in variables) {
1968                                                 string name = (string) de.Key;
1969                                                 LocalInfo vi = (LocalInfo) de.Value;
1970
1971                                                 if (vi.LocalBuilder == null)
1972                                                         continue;
1973
1974                                                 ec.DefineLocalVariable (name, vi.LocalBuilder);
1975                                         }
1976                                 }
1977                         }
1978
1979                         ec.Mark (StartLocation, true);
1980                         DoEmit (ec);
1981                         ec.Mark (EndLocation, true);
1982
1983                         if (emit_debug_info && is_lexical_block)
1984                                 ec.EndScope ();
1985
1986                         ec.CurrentBlock = prev_block;
1987                 }
1988
1989                 //
1990                 // Returns true if we ar ea child of `b'.
1991                 //
1992                 public bool IsChildOf (Block b)
1993                 {
1994                         Block current = this;
1995
1996                         do {
1997                                 if (current.Parent == b)
1998                                         return true;
1999                                 current = current.Parent;
2000                         } while (current != null);
2001                         return false;
2002                 }
2003
2004                 public override string ToString ()
2005                 {
2006                         return String.Format ("{0} ({1}:{2})", GetType (),ID, StartLocation);
2007                 }
2008         }
2009
2010         //
2011         // A toplevel block contains extra information, the split is done
2012         // only to separate information that would otherwise bloat the more
2013         // lightweight Block.
2014         //
2015         // In particular, this was introduced when the support for Anonymous
2016         // Methods was implemented.
2017         //
2018         public class ToplevelBlock : Block {
2019                 //
2020                 // Pointer to the host of this anonymous method, or null
2021                 // if we are the topmost block
2022                 //
2023                 ToplevelBlock container;
2024                 CaptureContext capture_context;
2025                 FlowBranching top_level_branching;
2026
2027                 Hashtable capture_contexts;
2028                 ArrayList children;
2029
2030                 public bool HasVarargs {
2031                         get { return (flags & Flags.HasVarargs) != 0; }
2032                         set { flags |= Flags.HasVarargs; }
2033                 }
2034
2035                 //
2036                 // The parameters for the block.
2037                 //
2038                 public readonly Parameters Parameters;
2039
2040                 public void RegisterCaptureContext (CaptureContext cc)
2041                 {
2042                         if (capture_contexts == null)
2043                                 capture_contexts = new Hashtable ();
2044                         capture_contexts [cc] = cc;
2045                 }
2046
2047                 public void CompleteContexts ()
2048                 {
2049                         if (capture_contexts == null)
2050                                 return;
2051
2052                         foreach (CaptureContext cc in capture_contexts.Keys){
2053                                 cc.AdjustScopes ();
2054                         }
2055                 }
2056
2057                 public CaptureContext ToplevelBlockCaptureContext {
2058                         get { return capture_context; }
2059                 }
2060
2061                 public ToplevelBlock Container {
2062                         get { return container; }
2063                 }
2064
2065                 protected void AddChild (ToplevelBlock block)
2066                 {
2067                         if (children == null)
2068                                 children = new ArrayList ();
2069
2070                         children.Add (block);
2071                 }
2072
2073                 //
2074                 // Parent is only used by anonymous blocks to link back to their
2075                 // parents
2076                 //
2077                 public ToplevelBlock (ToplevelBlock container, Parameters parameters, Location start) :
2078                         this (container, (Flags) 0, parameters, start)
2079                 {
2080                 }
2081
2082                 public ToplevelBlock (Parameters parameters, Location start) :
2083                         this (null, (Flags) 0, parameters, start)
2084                 {
2085                 }
2086
2087                 public ToplevelBlock (Flags flags, Parameters parameters, Location start) :
2088                         this (null, flags, parameters, start)
2089                 {
2090                 }
2091
2092                 public ToplevelBlock (ToplevelBlock container, Flags flags, Parameters parameters, Location start) :
2093                         base (null, flags | Flags.IsToplevel, start, Location.Null)
2094                 {
2095                         Parameters = parameters == null ? Parameters.EmptyReadOnlyParameters : parameters;
2096                         this.container = container;
2097
2098                         if (container != null)
2099                                 container.AddChild (this);
2100                 }
2101
2102                 public ToplevelBlock (Location loc) : this (null, (Flags) 0, null, loc)
2103                 {
2104                 }
2105
2106                 public void SetHaveAnonymousMethods (Location loc, AnonymousContainer host)
2107                 {
2108                         if (capture_context == null)
2109                                 capture_context = new CaptureContext (this, loc, host);
2110                 }
2111
2112                 public CaptureContext CaptureContext {
2113                         get { return capture_context; }
2114                 }
2115
2116                 public FlowBranching TopLevelBranching {
2117                         get { return top_level_branching; }
2118                 }
2119
2120                 //
2121                 // This is used if anonymous methods are used inside an iterator
2122                 // (see 2test-22.cs for an example).
2123                 //
2124                 // The AnonymousMethod is created while parsing - at a time when we don't
2125                 // know yet that we're inside an iterator, so it's `Container' is initially
2126                 // null.  Later on, when resolving the iterator, we need to move the
2127                 // anonymous method into that iterator.
2128                 //
2129                 public void ReParent (ToplevelBlock new_parent, AnonymousContainer new_host)
2130                 {
2131                         foreach (ToplevelBlock block in children) {
2132                                 if (block.CaptureContext == null)
2133                                         continue;
2134
2135                                 block.container = new_parent;
2136                                 block.CaptureContext.ReParent (new_parent, new_host);
2137                         }
2138                 }
2139
2140                 //
2141                 // Returns a `ParameterReference' for the given name, or null if there
2142                 // is no such parameter
2143                 //
2144                 public ParameterReference GetParameterReference (string name, Location loc)
2145                 {
2146                         Parameter par;
2147                         int idx;
2148
2149                         for (ToplevelBlock t = this; t != null; t = t.Container) {
2150                                 Parameters pars = t.Parameters;
2151                                 par = pars.GetParameterByName (name, out idx);
2152                                 if (par != null)
2153                                         return new ParameterReference (pars, this, idx, name, loc);
2154                         }
2155                         return null;
2156                 }
2157
2158                 //
2159                 // Whether the parameter named `name' is local to this block,
2160                 // or false, if the parameter belongs to an encompassing block.
2161                 //
2162                 public bool IsLocalParameter (string name)
2163                 {
2164                         return Parameters.GetParameterByName (name) != null;
2165                 }
2166
2167                 //
2168                 // Whether the `name' is a parameter reference
2169                 //
2170                 public bool IsParameterReference (string name)
2171                 {
2172                         for (ToplevelBlock t = this; t != null; t = t.Container) {
2173                                 if (t.IsLocalParameter (name))
2174                                         return true;
2175                         }
2176                         return false;
2177                 }
2178
2179                 LocalInfo this_variable = null;
2180
2181                 // <summary>
2182                 //   Returns the "this" instance variable of this block.
2183                 //   See AddThisVariable() for more information.
2184                 // </summary>
2185                 public LocalInfo ThisVariable {
2186                         get { return this_variable; }
2187                 }
2188
2189
2190                 // <summary>
2191                 //   This is used by non-static `struct' constructors which do not have an
2192                 //   initializer - in this case, the constructor must initialize all of the
2193                 //   struct's fields.  To do this, we add a "this" variable and use the flow
2194                 //   analysis code to ensure that it's been fully initialized before control
2195                 //   leaves the constructor.
2196                 // </summary>
2197                 public LocalInfo AddThisVariable (TypeContainer tc, Location l)
2198                 {
2199                         if (this_variable == null) {
2200                                 this_variable = new LocalInfo (tc, this, l);
2201                                 this_variable.Used = true;
2202                                 this_variable.IsThis = true;
2203
2204                                 Variables.Add ("this", this_variable);
2205                         }
2206
2207                         return this_variable;
2208                 }
2209
2210                 public bool IsThisAssigned (EmitContext ec)
2211                 {
2212                         return this_variable == null || this_variable.IsThisAssigned (ec, loc);
2213                 }
2214
2215                 public bool ResolveMeta (EmitContext ec, InternalParameters ip)
2216                 {
2217                         int errors = Report.Errors;
2218
2219                         if (top_level_branching != null)
2220                                 return true;
2221
2222                         ResolveMeta (this, ec, ip);
2223
2224                         top_level_branching = ec.StartFlowBranching (this);
2225
2226                         return Report.Errors == errors;
2227                 }
2228         }
2229
2230         public class SwitchLabel {
2231                 Expression label;
2232                 object converted;
2233                 Location loc;
2234
2235                 Label il_label;
2236                 bool  il_label_set;
2237                 Label il_label_code;
2238                 bool  il_label_code_set;
2239
2240                 //
2241                 // if expr == null, then it is the default case.
2242                 //
2243                 public SwitchLabel (Expression expr, Location l)
2244                 {
2245                         label = expr;
2246                         loc = l;
2247                 }
2248
2249                 public Expression Label {
2250                         get {
2251                                 return label;
2252                         }
2253                 }
2254
2255                 public object Converted {
2256                         get {
2257                                 return converted;
2258                         }
2259                 }
2260
2261                 public Label GetILLabel (EmitContext ec)
2262                 {
2263                         if (!il_label_set){
2264                                 il_label = ec.ig.DefineLabel ();
2265                                 il_label_set = true;
2266                         }
2267                         return il_label;
2268                 }
2269
2270                 public Label GetILLabelCode (EmitContext ec)
2271                 {
2272                         if (!il_label_code_set){
2273                                 il_label_code = ec.ig.DefineLabel ();
2274                                 il_label_code_set = true;
2275                         }
2276                         return il_label_code;
2277                 }
2278
2279                 //
2280                 // Resolves the expression, reduces it to a literal if possible
2281                 // and then converts it to the requested type.
2282                 //
2283                 public bool ResolveAndReduce (EmitContext ec, Type required_type)
2284                 {
2285                         Expression e = label.Resolve (ec);
2286
2287                         if (e == null)
2288                                 return false;
2289
2290                         Constant c = e as Constant;
2291                         if (c == null){
2292                                 Report.Error (150, loc, "A constant value is expected");
2293                                 return false;
2294                         }
2295
2296                         if (required_type == TypeManager.string_type) {
2297                                 if (c.Type == TypeManager.string_type) {
2298                                         converted = c.GetValue ();
2299                                         return true;
2300                                 }
2301
2302                                 if (e is NullLiteral) {
2303                                         converted = e;
2304                                         return true;
2305                                 }
2306                         }
2307
2308                         converted = Expression.ConvertIntLiteral (c, required_type, loc);
2309                         return converted != null;
2310                 }
2311
2312                 public void Erorr_AlreadyOccurs ()
2313                 {
2314                         string label;
2315                         if (converted == null)
2316                                 label = "default";
2317                         else if (converted is NullLiteral)
2318                                 label = "null";
2319                         else
2320                                 label = converted.ToString ();
2321
2322                         Report.Error (152, loc, "The label `case {0}:' already occurs in this switch statement", label);
2323                 }
2324         }
2325
2326         public class SwitchSection {
2327                 // An array of SwitchLabels.
2328                 public readonly ArrayList Labels;
2329                 public readonly Block Block;
2330
2331                 public SwitchSection (ArrayList labels, Block block)
2332                 {
2333                         Labels = labels;
2334                         Block = block;
2335                 }
2336         }
2337
2338         public class Switch : Statement {
2339                 public readonly ArrayList Sections;
2340                 public Expression Expr;
2341
2342                 /// <summary>
2343                 ///   Maps constants whose type type SwitchType to their  SwitchLabels.
2344                 /// </summary>
2345                 public IDictionary Elements;
2346
2347                 /// <summary>
2348                 ///   The governing switch type
2349                 /// </summary>
2350                 public Type SwitchType;
2351
2352                 //
2353                 // Computed
2354                 //
2355                 Label default_target;
2356                 Expression new_expr;
2357                 bool is_constant;
2358                 SwitchSection constant_section;
2359                 SwitchSection default_section;
2360
2361                 //
2362                 // The types allowed to be implicitly cast from
2363                 // on the governing type
2364                 //
2365                 static Type [] allowed_types;
2366
2367                 public Switch (Expression e, ArrayList sects, Location l)
2368                 {
2369                         Expr = e;
2370                         Sections = sects;
2371                         loc = l;
2372                 }
2373
2374                 public bool GotDefault {
2375                         get {
2376                                 return default_section != null;
2377                         }
2378                 }
2379
2380                 public Label DefaultTarget {
2381                         get {
2382                                 return default_target;
2383                         }
2384                 }
2385
2386                 //
2387                 // Determines the governing type for a switch.  The returned
2388                 // expression might be the expression from the switch, or an
2389                 // expression that includes any potential conversions to the
2390                 // integral types or to string.
2391                 //
2392                 Expression SwitchGoverningType (EmitContext ec, Type t)
2393                 {
2394                         if (t == TypeManager.byte_type ||
2395                             t == TypeManager.sbyte_type ||
2396                             t == TypeManager.ushort_type ||
2397                             t == TypeManager.short_type ||
2398                             t == TypeManager.uint32_type ||
2399                             t == TypeManager.int32_type ||
2400                             t == TypeManager.uint64_type ||
2401                             t == TypeManager.int64_type ||
2402                             t == TypeManager.char_type ||
2403                             t == TypeManager.string_type ||
2404                             t == TypeManager.bool_type ||
2405                             t.IsSubclassOf (TypeManager.enum_type))
2406                                 return Expr;
2407
2408                         if (allowed_types == null){
2409                                 allowed_types = new Type [] {
2410                                         TypeManager.sbyte_type,
2411                                         TypeManager.byte_type,
2412                                         TypeManager.short_type,
2413                                         TypeManager.ushort_type,
2414                                         TypeManager.int32_type,
2415                                         TypeManager.uint32_type,
2416                                         TypeManager.int64_type,
2417                                         TypeManager.uint64_type,
2418                                         TypeManager.char_type,
2419                                         TypeManager.string_type,
2420                                         TypeManager.bool_type
2421                                 };
2422                         }
2423
2424                         //
2425                         // Try to find a *user* defined implicit conversion.
2426                         //
2427                         // If there is no implicit conversion, or if there are multiple
2428                         // conversions, we have to report an error
2429                         //
2430                         Expression converted = null;
2431                         foreach (Type tt in allowed_types){
2432                                 Expression e;
2433
2434                                 e = Convert.ImplicitUserConversion (ec, Expr, tt, loc);
2435                                 if (e == null)
2436                                         continue;
2437
2438                                 //
2439                                 // Ignore over-worked ImplicitUserConversions that do
2440                                 // an implicit conversion in addition to the user conversion.
2441                                 //
2442                                 if (!(e is UserCast))
2443                                         continue;
2444
2445                                 if (converted != null){
2446                                         Report.ExtraInformation (
2447                                                 loc,
2448                                                 String.Format ("reason: more than one conversion to an integral type exist for type {0}",
2449                                                                TypeManager.CSharpName (Expr.Type)));
2450                                         return null;
2451                                 }
2452
2453                                 converted = e;
2454                         }
2455                         return converted;
2456                 }
2457
2458                 //
2459                 // Performs the basic sanity checks on the switch statement
2460                 // (looks for duplicate keys and non-constant expressions).
2461                 //
2462                 // It also returns a hashtable with the keys that we will later
2463                 // use to compute the switch tables
2464                 //
2465                 bool CheckSwitch (EmitContext ec)
2466                 {
2467                         bool error = false;
2468                         Elements = Sections.Count > 10 ?
2469                                 (IDictionary)new Hashtable () :
2470                                 (IDictionary)new ListDictionary ();
2471
2472                         foreach (SwitchSection ss in Sections){
2473                                 foreach (SwitchLabel sl in ss.Labels){
2474                                         if (sl.Label == null){
2475                                                 if (default_section != null){
2476                                                         sl.Erorr_AlreadyOccurs ();
2477                                                         error = true;
2478                                                 }
2479                                                 default_section = ss;
2480                                                 continue;
2481                                         }
2482
2483                                         if (!sl.ResolveAndReduce (ec, SwitchType)){
2484                                                 error = true;
2485                                                 continue;
2486                                         }
2487
2488                                         object key = sl.Converted;
2489                                         try {
2490                                                 Elements.Add (key, sl);
2491                                         }
2492                                         catch (ArgumentException) {
2493                                                  sl.Erorr_AlreadyOccurs ();
2494                                                  error = true;
2495                                          }
2496                                 }
2497                         }
2498                         return !error;
2499                 }
2500
2501                 void EmitObjectInteger (ILGenerator ig, object k)
2502                 {
2503                         if (k is int)
2504                                 IntConstant.EmitInt (ig, (int) k);
2505                         else if (k is Constant) {
2506                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
2507                         }
2508                         else if (k is uint)
2509                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
2510                         else if (k is long)
2511                         {
2512                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
2513                                 {
2514                                         IntConstant.EmitInt (ig, (int) (long) k);
2515                                         ig.Emit (OpCodes.Conv_I8);
2516                                 }
2517                                 else
2518                                         LongConstant.EmitLong (ig, (long) k);
2519                         }
2520                         else if (k is ulong)
2521                         {
2522                                 if ((ulong) k < (1L<<32))
2523                                 {
2524                                         IntConstant.EmitInt (ig, (int) (long) k);
2525                                         ig.Emit (OpCodes.Conv_U8);
2526                                 }
2527                                 else
2528                                 {
2529                                         LongConstant.EmitLong (ig, unchecked ((long) (ulong) k));
2530                                 }
2531                         }
2532                         else if (k is char)
2533                                 IntConstant.EmitInt (ig, (int) ((char) k));
2534                         else if (k is sbyte)
2535                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
2536                         else if (k is byte)
2537                                 IntConstant.EmitInt (ig, (int) ((byte) k));
2538                         else if (k is short)
2539                                 IntConstant.EmitInt (ig, (int) ((short) k));
2540                         else if (k is ushort)
2541                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
2542                         else if (k is bool)
2543                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
2544                         else
2545                                 throw new Exception ("Unhandled case");
2546                 }
2547
2548                 // structure used to hold blocks of keys while calculating table switch
2549                 class KeyBlock : IComparable
2550                 {
2551                         public KeyBlock (long _nFirst)
2552                         {
2553                                 nFirst = nLast = _nFirst;
2554                         }
2555                         public long nFirst;
2556                         public long nLast;
2557                         public ArrayList rgKeys = null;
2558                         // how many items are in the bucket
2559                         public int Size = 1;
2560                         public int Length
2561                         {
2562                                 get { return (int) (nLast - nFirst + 1); }
2563                         }
2564                         public static long TotalLength (KeyBlock kbFirst, KeyBlock kbLast)
2565                         {
2566                                 return kbLast.nLast - kbFirst.nFirst + 1;
2567                         }
2568                         public int CompareTo (object obj)
2569                         {
2570                                 KeyBlock kb = (KeyBlock) obj;
2571                                 int nLength = Length;
2572                                 int nLengthOther = kb.Length;
2573                                 if (nLengthOther == nLength)
2574                                         return (int) (kb.nFirst - nFirst);
2575                                 return nLength - nLengthOther;
2576                         }
2577                 }
2578
2579                 /// <summary>
2580                 /// This method emits code for a lookup-based switch statement (non-string)
2581                 /// Basically it groups the cases into blocks that are at least half full,
2582                 /// and then spits out individual lookup opcodes for each block.
2583                 /// It emits the longest blocks first, and short blocks are just
2584                 /// handled with direct compares.
2585                 /// </summary>
2586                 /// <param name="ec"></param>
2587                 /// <param name="val"></param>
2588                 /// <returns></returns>
2589                 void TableSwitchEmit (EmitContext ec, LocalBuilder val)
2590                 {
2591                         int cElements = Elements.Count;
2592                         object [] rgKeys = new object [cElements];
2593                         Elements.Keys.CopyTo (rgKeys, 0);
2594                         Array.Sort (rgKeys);
2595
2596                         // initialize the block list with one element per key
2597                         ArrayList rgKeyBlocks = new ArrayList ();
2598                         foreach (object key in rgKeys)
2599                                 rgKeyBlocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));
2600
2601                         KeyBlock kbCurr;
2602                         // iteratively merge the blocks while they are at least half full
2603                         // there's probably a really cool way to do this with a tree...
2604                         while (rgKeyBlocks.Count > 1)
2605                         {
2606                                 ArrayList rgKeyBlocksNew = new ArrayList ();
2607                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
2608                                 for (int ikb = 1; ikb < rgKeyBlocks.Count; ikb++)
2609                                 {
2610                                         KeyBlock kb = (KeyBlock) rgKeyBlocks [ikb];
2611                                         if ((kbCurr.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (kbCurr, kb))
2612                                         {
2613                                                 // merge blocks
2614                                                 kbCurr.nLast = kb.nLast;
2615                                                 kbCurr.Size += kb.Size;
2616                                         }
2617                                         else
2618                                         {
2619                                                 // start a new block
2620                                                 rgKeyBlocksNew.Add (kbCurr);
2621                                                 kbCurr = kb;
2622                                         }
2623                                 }
2624                                 rgKeyBlocksNew.Add (kbCurr);
2625                                 if (rgKeyBlocks.Count == rgKeyBlocksNew.Count)
2626                                         break;
2627                                 rgKeyBlocks = rgKeyBlocksNew;
2628                         }
2629
2630                         // initialize the key lists
2631                         foreach (KeyBlock kb in rgKeyBlocks)
2632                                 kb.rgKeys = new ArrayList ();
2633
2634                         // fill the key lists
2635                         int iBlockCurr = 0;
2636                         if (rgKeyBlocks.Count > 0) {
2637                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
2638                                 foreach (object key in rgKeys)
2639                                 {
2640                                         bool fNextBlock = (key is UInt64) ? (ulong) key > (ulong) kbCurr.nLast :
2641                                                 System.Convert.ToInt64 (key) > kbCurr.nLast;
2642                                         if (fNextBlock)
2643                                                 kbCurr = (KeyBlock) rgKeyBlocks [++iBlockCurr];
2644                                         kbCurr.rgKeys.Add (key);
2645                                 }
2646                         }
2647
2648                         // sort the blocks so we can tackle the largest ones first
2649                         rgKeyBlocks.Sort ();
2650
2651                         // okay now we can start...
2652                         ILGenerator ig = ec.ig;
2653                         Label lblEnd = ig.DefineLabel ();       // at the end ;-)
2654                         Label lblDefault = ig.DefineLabel ();
2655
2656                         Type typeKeys = null;
2657                         if (rgKeys.Length > 0)
2658                                 typeKeys = rgKeys [0].GetType ();       // used for conversions
2659
2660                         Type compare_type;
2661
2662                         if (TypeManager.IsEnumType (SwitchType))
2663                                 compare_type = TypeManager.EnumToUnderlying (SwitchType);
2664                         else
2665                                 compare_type = SwitchType;
2666
2667                         for (int iBlock = rgKeyBlocks.Count - 1; iBlock >= 0; --iBlock)
2668                         {
2669                                 KeyBlock kb = ((KeyBlock) rgKeyBlocks [iBlock]);
2670                                 lblDefault = (iBlock == 0) ? DefaultTarget : ig.DefineLabel ();
2671                                 if (kb.Length <= 2)
2672                                 {
2673                                         foreach (object key in kb.rgKeys)
2674                                         {
2675                                                 ig.Emit (OpCodes.Ldloc, val);
2676                                                 EmitObjectInteger (ig, key);
2677                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
2678                                                 ig.Emit (OpCodes.Beq, sl.GetILLabel (ec));
2679                                         }
2680                                 }
2681                                 else
2682                                 {
2683                                         // TODO: if all the keys in the block are the same and there are
2684                                         //       no gaps/defaults then just use a range-check.
2685                                         if (compare_type == TypeManager.int64_type ||
2686                                                 compare_type == TypeManager.uint64_type)
2687                                         {
2688                                                 // TODO: optimize constant/I4 cases
2689
2690                                                 // check block range (could be > 2^31)
2691                                                 ig.Emit (OpCodes.Ldloc, val);
2692                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.nFirst, typeKeys));
2693                                                 ig.Emit (OpCodes.Blt, lblDefault);
2694                                                 ig.Emit (OpCodes.Ldloc, val);
2695                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.nLast, typeKeys));
2696                                                 ig.Emit (OpCodes.Bgt, lblDefault);
2697
2698                                                 // normalize range
2699                                                 ig.Emit (OpCodes.Ldloc, val);
2700                                                 if (kb.nFirst != 0)
2701                                                 {
2702                                                         EmitObjectInteger (ig, System.Convert.ChangeType (kb.nFirst, typeKeys));
2703                                                         ig.Emit (OpCodes.Sub);
2704                                                 }
2705                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
2706                                         }
2707                                         else
2708                                         {
2709                                                 // normalize range
2710                                                 ig.Emit (OpCodes.Ldloc, val);
2711                                                 int nFirst = (int) kb.nFirst;
2712                                                 if (nFirst > 0)
2713                                                 {
2714                                                         IntConstant.EmitInt (ig, nFirst);
2715                                                         ig.Emit (OpCodes.Sub);
2716                                                 }
2717                                                 else if (nFirst < 0)
2718                                                 {
2719                                                         IntConstant.EmitInt (ig, -nFirst);
2720                                                         ig.Emit (OpCodes.Add);
2721                                                 }
2722                                         }
2723
2724                                         // first, build the list of labels for the switch
2725                                         int iKey = 0;
2726                                         int cJumps = kb.Length;
2727                                         Label [] rgLabels = new Label [cJumps];
2728                                         for (int iJump = 0; iJump < cJumps; iJump++)
2729                                         {
2730                                                 object key = kb.rgKeys [iKey];
2731                                                 if (System.Convert.ToInt64 (key) == kb.nFirst + iJump)
2732                                                 {
2733                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
2734                                                         rgLabels [iJump] = sl.GetILLabel (ec);
2735                                                         iKey++;
2736                                                 }
2737                                                 else
2738                                                         rgLabels [iJump] = lblDefault;
2739                                         }
2740                                         // emit the switch opcode
2741                                         ig.Emit (OpCodes.Switch, rgLabels);
2742                                 }
2743
2744                                 // mark the default for this block
2745                                 if (iBlock != 0)
2746                                         ig.MarkLabel (lblDefault);
2747                         }
2748
2749                         // TODO: find the default case and emit it here,
2750                         //       to prevent having to do the following jump.
2751                         //       make sure to mark other labels in the default section
2752
2753                         // the last default just goes to the end
2754                         ig.Emit (OpCodes.Br, lblDefault);
2755
2756                         // now emit the code for the sections
2757                         bool fFoundDefault = false;
2758                         foreach (SwitchSection ss in Sections)
2759                         {
2760                                 foreach (SwitchLabel sl in ss.Labels)
2761                                 {
2762                                         ig.MarkLabel (sl.GetILLabel (ec));
2763                                         ig.MarkLabel (sl.GetILLabelCode (ec));
2764                                         if (sl.Label == null)
2765                                         {
2766                                                 ig.MarkLabel (lblDefault);
2767                                                 fFoundDefault = true;
2768                                         }
2769                                 }
2770                                 ss.Block.Emit (ec);
2771                                 //ig.Emit (OpCodes.Br, lblEnd);
2772                         }
2773
2774                         if (!fFoundDefault) {
2775                                 ig.MarkLabel (lblDefault);
2776                         }
2777                         ig.MarkLabel (lblEnd);
2778                 }
2779                 //
2780                 // This simple emit switch works, but does not take advantage of the
2781                 // `switch' opcode.
2782                 // TODO: remove non-string logic from here
2783                 // TODO: binary search strings?
2784                 //
2785                 void SimpleSwitchEmit (EmitContext ec, LocalBuilder val)
2786                 {
2787                         ILGenerator ig = ec.ig;
2788                         Label end_of_switch = ig.DefineLabel ();
2789                         Label next_test = ig.DefineLabel ();
2790                         Label null_target = ig.DefineLabel ();
2791                         bool first_test = true;
2792                         bool pending_goto_end = false;
2793                         bool null_marked = false;
2794                         bool null_found;
2795
2796                         ig.Emit (OpCodes.Ldloc, val);
2797
2798                         if (Elements.Contains (NullLiteral.Null)){
2799                                 ig.Emit (OpCodes.Brfalse, null_target);
2800                         } else
2801                                 ig.Emit (OpCodes.Brfalse, default_target);
2802
2803                         ig.Emit (OpCodes.Ldloc, val);
2804                         ig.Emit (OpCodes.Call, TypeManager.string_isinterneted_string);
2805                         ig.Emit (OpCodes.Stloc, val);
2806
2807                         int section_count = Sections.Count;
2808                         for (int section = 0; section < section_count; section++){
2809                                 SwitchSection ss = (SwitchSection) Sections [section];
2810
2811                                 if (ss == default_section)
2812                                         continue;
2813
2814                                 Label sec_begin = ig.DefineLabel ();
2815
2816                                 ig.Emit (OpCodes.Nop);
2817
2818                                 if (pending_goto_end)
2819                                         ig.Emit (OpCodes.Br, end_of_switch);
2820
2821                                 int label_count = ss.Labels.Count;
2822                                 null_found = false;
2823                                 for (int label = 0; label < label_count; label++){
2824                                         SwitchLabel sl = (SwitchLabel) ss.Labels [label];
2825                                         ig.MarkLabel (sl.GetILLabel (ec));
2826
2827                                         if (!first_test){
2828                                                 ig.MarkLabel (next_test);
2829                                                 next_test = ig.DefineLabel ();
2830                                         }
2831                                         //
2832                                         // If we are the default target
2833                                         //
2834                                         if (sl.Label != null){
2835                                                 object lit = sl.Converted;
2836
2837                                                 if (lit is NullLiteral){
2838                                                         null_found = true;
2839                                                         if (label_count == 1)
2840                                                                 ig.Emit (OpCodes.Br, next_test);
2841                                                         continue;
2842                                                 }
2843
2844                                                 ig.Emit (OpCodes.Ldloc, val);
2845                                                 ig.Emit (OpCodes.Ldstr, (string)lit);
2846                                                 if (label_count == 1)
2847                                                         ig.Emit (OpCodes.Bne_Un, next_test);
2848                                                 else {
2849                                                         if (label+1 == label_count)
2850                                                                 ig.Emit (OpCodes.Bne_Un, next_test);
2851                                                         else
2852                                                                 ig.Emit (OpCodes.Beq, sec_begin);
2853                                                 }
2854                                         }
2855                                 }
2856                                 if (null_found) {
2857                                         ig.MarkLabel (null_target);
2858                                         null_marked = true;
2859                                 }
2860                                 ig.MarkLabel (sec_begin);
2861                                 foreach (SwitchLabel sl in ss.Labels)
2862                                         ig.MarkLabel (sl.GetILLabelCode (ec));
2863
2864                                 ss.Block.Emit (ec);
2865                                 pending_goto_end = !ss.Block.HasRet;
2866                                 first_test = false;
2867                         }
2868                         ig.MarkLabel (next_test);
2869                         ig.MarkLabel (default_target);
2870                         if (!null_marked)
2871                                 ig.MarkLabel (null_target);
2872                         if (default_section != null)
2873                                 default_section.Block.Emit (ec);
2874                         ig.MarkLabel (end_of_switch);
2875                 }
2876
2877                 SwitchSection FindSection (SwitchLabel label)
2878                 {
2879                         foreach (SwitchSection ss in Sections){
2880                                 foreach (SwitchLabel sl in ss.Labels){
2881                                         if (label == sl)
2882                                                 return ss;
2883                                 }
2884                         }
2885
2886                         return null;
2887                 }
2888
2889                 public override bool Resolve (EmitContext ec)
2890                 {
2891                         Expr = Expr.Resolve (ec);
2892                         if (Expr == null)
2893                                 return false;
2894
2895                         new_expr = SwitchGoverningType (ec, Expr.Type);
2896                         if (new_expr == null){
2897                                 Report.Error (151, loc, "A value of an integral type or string expected for switch");
2898                                 return false;
2899                         }
2900
2901                         // Validate switch.
2902                         SwitchType = new_expr.Type;
2903
2904                         if (!CheckSwitch (ec))
2905                                 return false;
2906
2907                         Switch old_switch = ec.Switch;
2908                         ec.Switch = this;
2909                         ec.Switch.SwitchType = SwitchType;
2910
2911                         Report.Debug (1, "START OF SWITCH BLOCK", loc, ec.CurrentBranching);
2912                         ec.StartFlowBranching (FlowBranching.BranchingType.Switch, loc);
2913
2914                         is_constant = new_expr is Constant;
2915                         if (is_constant) {
2916                                 object key = ((Constant) new_expr).GetValue ();
2917                                 SwitchLabel label = (SwitchLabel) Elements [key];
2918
2919                                 constant_section = FindSection (label);
2920                                 if (constant_section == null)
2921                                         constant_section = default_section;
2922                         }
2923
2924                         bool first = true;
2925                         foreach (SwitchSection ss in Sections){
2926                                 if (!first)
2927                                         ec.CurrentBranching.CreateSibling (
2928                                                 null, FlowBranching.SiblingType.SwitchSection);
2929                                 else
2930                                         first = false;
2931
2932                                 if (is_constant && (ss != constant_section)) {
2933                                         // If we're a constant switch, we're only emitting
2934                                         // one single section - mark all the others as
2935                                         // unreachable.
2936                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
2937                                         if (!ss.Block.ResolveUnreachable (ec, true))
2938                                                 return false;
2939                                 } else {
2940                                         if (!ss.Block.Resolve (ec))
2941                                                 return false;
2942                                 }
2943                         }
2944
2945                         if (default_section == null)
2946                                 ec.CurrentBranching.CreateSibling (
2947                                         null, FlowBranching.SiblingType.SwitchSection);
2948
2949                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
2950                         ec.Switch = old_switch;
2951
2952                         Report.Debug (1, "END OF SWITCH BLOCK", loc, ec.CurrentBranching,
2953                                       reachability);
2954
2955                         return true;
2956                 }
2957
2958                 protected override void DoEmit (EmitContext ec)
2959                 {
2960                         ILGenerator ig = ec.ig;
2961
2962                         // Store variable for comparission purposes
2963                         LocalBuilder value;
2964                         if (!is_constant) {
2965                                 value = ig.DeclareLocal (SwitchType);
2966                                 new_expr.Emit (ec);
2967                                 ig.Emit (OpCodes.Stloc, value);
2968                         } else
2969                                 value = null;
2970
2971                         default_target = ig.DefineLabel ();
2972
2973                         //
2974                         // Setup the codegen context
2975                         //
2976                         Label old_end = ec.LoopEnd;
2977                         Switch old_switch = ec.Switch;
2978
2979                         ec.LoopEnd = ig.DefineLabel ();
2980                         ec.Switch = this;
2981
2982                         // Emit Code.
2983                         if (is_constant) {
2984                                 if (constant_section != null)
2985                                         constant_section.Block.Emit (ec);
2986                         } else if (SwitchType == TypeManager.string_type)
2987                                 SimpleSwitchEmit (ec, value);
2988                         else
2989                                 TableSwitchEmit (ec, value);
2990
2991                         // Restore context state.
2992                         ig.MarkLabel (ec.LoopEnd);
2993
2994                         //
2995                         // Restore the previous context
2996                         //
2997                         ec.LoopEnd = old_end;
2998                         ec.Switch = old_switch;
2999                 }
3000         }
3001
3002         public abstract class ExceptionStatement : Statement
3003         {
3004                 public abstract void EmitFinally (EmitContext ec);
3005
3006                 protected bool emit_finally = true;
3007                 ArrayList parent_vectors;
3008
3009                 protected void DoEmitFinally (EmitContext ec)
3010                 {
3011                         if (emit_finally)
3012                                 ec.ig.BeginFinallyBlock ();
3013                         else if (ec.InIterator)
3014                                 ec.CurrentIterator.MarkFinally (ec, parent_vectors);
3015                         EmitFinally (ec);
3016                 }
3017
3018                 protected void ResolveFinally (FlowBranchingException branching)
3019                 {
3020                         emit_finally = branching.EmitFinally;
3021                         if (!emit_finally)
3022                                 branching.Parent.StealFinallyClauses (ref parent_vectors);
3023                 }
3024         }
3025
3026         public class Lock : ExceptionStatement {
3027                 Expression expr;
3028                 Statement Statement;
3029                 LocalBuilder temp;
3030
3031                 public Lock (Expression expr, Statement stmt, Location l)
3032                 {
3033                         this.expr = expr;
3034                         Statement = stmt;
3035                         loc = l;
3036                 }
3037
3038                 public override bool Resolve (EmitContext ec)
3039                 {
3040                         expr = expr.Resolve (ec);
3041                         if (expr == null)
3042                                 return false;
3043
3044                         if (expr.Type.IsValueType){
3045                                 Report.Error (185, loc,
3046                                         "`{0}' is not a reference type as required by the lock statement",
3047                                TypeManager.CSharpName (expr.Type));
3048                                 return false;
3049                         }
3050
3051                         FlowBranchingException branching = ec.StartFlowBranching (this);
3052                         bool ok = Statement.Resolve (ec);
3053                         if (!ok) {
3054                                 ec.KillFlowBranching ();
3055                                 return false;
3056                         }
3057
3058                         ResolveFinally (branching);
3059
3060                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3061                         if (reachability.Returns != FlowBranching.FlowReturns.Always) {
3062                                 // Unfortunately, System.Reflection.Emit automatically emits
3063                                 // a leave to the end of the finally block.
3064                                 // This is a problem if `returns' is true since we may jump
3065                                 // to a point after the end of the method.
3066                                 // As a workaround, emit an explicit ret here.
3067                                 ec.NeedReturnLabel ();
3068                         }
3069
3070                         return true;
3071                 }
3072
3073                 protected override void DoEmit (EmitContext ec)
3074                 {
3075                         Type type = expr.Type;
3076
3077                         ILGenerator ig = ec.ig;
3078                         temp = ig.DeclareLocal (type);
3079
3080                         expr.Emit (ec);
3081                         ig.Emit (OpCodes.Dup);
3082                         ig.Emit (OpCodes.Stloc, temp);
3083                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
3084
3085                         // try
3086                         if (emit_finally)
3087                                 ig.BeginExceptionBlock ();
3088                         Statement.Emit (ec);
3089
3090                         // finally
3091                         DoEmitFinally (ec);
3092                         if (emit_finally)
3093                                 ig.EndExceptionBlock ();
3094                 }
3095
3096                 public override void EmitFinally (EmitContext ec)
3097                 {
3098                         ILGenerator ig = ec.ig;
3099                         ig.Emit (OpCodes.Ldloc, temp);
3100                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
3101                 }
3102         }
3103
3104         public class Unchecked : Statement {
3105                 public readonly Block Block;
3106
3107                 public Unchecked (Block b)
3108                 {
3109                         Block = b;
3110                         b.Unchecked = true;
3111                 }
3112
3113                 public override bool Resolve (EmitContext ec)
3114                 {
3115                         bool previous_state = ec.CheckState;
3116                         bool previous_state_const = ec.ConstantCheckState;
3117
3118                         ec.CheckState = false;
3119                         ec.ConstantCheckState = false;
3120                         bool ret = Block.Resolve (ec);
3121                         ec.CheckState = previous_state;
3122                         ec.ConstantCheckState = previous_state_const;
3123
3124                         return ret;
3125                 }
3126
3127                 protected override void DoEmit (EmitContext ec)
3128                 {
3129                         bool previous_state = ec.CheckState;
3130                         bool previous_state_const = ec.ConstantCheckState;
3131
3132                         ec.CheckState = false;
3133                         ec.ConstantCheckState = false;
3134                         Block.Emit (ec);
3135                         ec.CheckState = previous_state;
3136                         ec.ConstantCheckState = previous_state_const;
3137                 }
3138         }
3139
3140         public class Checked : Statement {
3141                 public readonly Block Block;
3142
3143                 public Checked (Block b)
3144                 {
3145                         Block = b;
3146                         b.Unchecked = false;
3147                 }
3148
3149                 public override bool Resolve (EmitContext ec)
3150                 {
3151                         bool previous_state = ec.CheckState;
3152                         bool previous_state_const = ec.ConstantCheckState;
3153
3154                         ec.CheckState = true;
3155                         ec.ConstantCheckState = true;
3156                         bool ret = Block.Resolve (ec);
3157                         ec.CheckState = previous_state;
3158                         ec.ConstantCheckState = previous_state_const;
3159
3160                         return ret;
3161                 }
3162
3163                 protected override void DoEmit (EmitContext ec)
3164                 {
3165                         bool previous_state = ec.CheckState;
3166                         bool previous_state_const = ec.ConstantCheckState;
3167
3168                         ec.CheckState = true;
3169                         ec.ConstantCheckState = true;
3170                         Block.Emit (ec);
3171                         ec.CheckState = previous_state;
3172                         ec.ConstantCheckState = previous_state_const;
3173                 }
3174         }
3175
3176         public class Unsafe : Statement {
3177                 public readonly Block Block;
3178
3179                 public Unsafe (Block b)
3180                 {
3181                         Block = b;
3182                         Block.Unsafe = true;
3183                 }
3184
3185                 public override bool Resolve (EmitContext ec)
3186                 {
3187                         bool previous_state = ec.InUnsafe;
3188                         bool val;
3189
3190                         ec.InUnsafe = true;
3191                         val = Block.Resolve (ec);
3192                         ec.InUnsafe = previous_state;
3193
3194                         return val;
3195                 }
3196
3197                 protected override void DoEmit (EmitContext ec)
3198                 {
3199                         bool previous_state = ec.InUnsafe;
3200
3201                         ec.InUnsafe = true;
3202                         Block.Emit (ec);
3203                         ec.InUnsafe = previous_state;
3204                 }
3205         }
3206
3207         //
3208         // Fixed statement
3209         //
3210         public class Fixed : Statement {
3211                 Expression type;
3212                 ArrayList declarators;
3213                 Statement statement;
3214                 Type expr_type;
3215                 Emitter[] data;
3216                 bool has_ret;
3217
3218                 abstract class Emitter
3219                 {
3220                         protected LocalInfo vi;
3221                         protected Expression converted;
3222
3223                         protected Emitter (Expression expr, LocalInfo li)
3224                         {
3225                                 converted = expr;
3226                                 vi = li;
3227                         }
3228
3229                         public abstract void Emit (EmitContext ec);
3230                         public abstract void EmitExit (ILGenerator ig);
3231                 }
3232
3233                 class ExpressionEmitter: Emitter {
3234                         public ExpressionEmitter (Expression converted, LocalInfo li) :
3235                                 base (converted, li)
3236                         {
3237                         }
3238
3239                         public override void Emit (EmitContext ec) {
3240                                 //
3241                                 // Store pointer in pinned location
3242                                 //
3243                                 converted.Emit (ec);
3244                                 ec.ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3245                         }
3246
3247                         public override void EmitExit (ILGenerator ig)
3248                         {
3249                                 ig.Emit (OpCodes.Ldc_I4_0);
3250                                 ig.Emit (OpCodes.Conv_U);
3251                                 ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3252                         }
3253                 }
3254
3255                 class StringEmitter: Emitter {
3256                         LocalBuilder pinned_string;
3257                         Location loc;
3258
3259                         public StringEmitter (Expression expr, LocalInfo li, Location loc):
3260                                 base (expr, li)
3261                         {
3262                                 this.loc = loc;
3263                         }
3264
3265                         public override void Emit (EmitContext ec)
3266                         {
3267                                 ILGenerator ig = ec.ig;
3268                                 pinned_string = TypeManager.DeclareLocalPinned (ig, TypeManager.string_type);
3269
3270                                 converted.Emit (ec);
3271                                 ig.Emit (OpCodes.Stloc, pinned_string);
3272
3273                                 Expression sptr = new StringPtr (pinned_string, loc);
3274                                 converted = Convert.ImplicitConversionRequired (
3275                                         ec, sptr, vi.VariableType, loc);
3276
3277                                 if (converted == null)
3278                                         return;
3279
3280                                 converted.Emit (ec);
3281                                 ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3282                         }
3283
3284                         public override void EmitExit(ILGenerator ig)
3285                         {
3286                                 ig.Emit (OpCodes.Ldnull);
3287                                 ig.Emit (OpCodes.Stloc, pinned_string);
3288                         }
3289                 }
3290
3291                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
3292                 {
3293                         this.type = type;
3294                         declarators = decls;
3295                         statement = stmt;
3296                         loc = l;
3297                 }
3298
3299                 public override bool Resolve (EmitContext ec)
3300                 {
3301                         if (!ec.InUnsafe){
3302                                 Expression.UnsafeError (loc);
3303                                 return false;
3304                         }
3305
3306                         TypeExpr texpr = type.ResolveAsTypeTerminal (ec, false);
3307                         if (texpr == null)
3308                                 return false;
3309
3310                         expr_type = texpr.ResolveType (ec);
3311
3312                         CheckObsolete (expr_type);
3313
3314                         data = new Emitter [declarators.Count];
3315
3316                         if (!expr_type.IsPointer){
3317                                 Report.Error (209, loc, "The type of locals declared in a fixed statement must be a pointer type");
3318                                 return false;
3319                         }
3320
3321                         int i = 0;
3322                         foreach (Pair p in declarators){
3323                                 LocalInfo vi = (LocalInfo) p.First;
3324                                 Expression e = (Expression) p.Second;
3325
3326                                 vi.VariableInfo.SetAssigned (ec);
3327                                 vi.SetReadOnlyContext (LocalInfo.ReadOnlyContext.Fixed);
3328
3329                                 //
3330                                 // The rules for the possible declarators are pretty wise,
3331                                 // but the production on the grammar is more concise.
3332                                 //
3333                                 // So we have to enforce these rules here.
3334                                 //
3335                                 // We do not resolve before doing the case 1 test,
3336                                 // because the grammar is explicit in that the token &
3337                                 // is present, so we need to test for this particular case.
3338                                 //
3339
3340                                 if (e is Cast){
3341                                         Report.Error (254, loc, "The right hand side of a fixed statement assignment may not be a cast expression");
3342                                         return false;
3343                                 }
3344
3345                                 //
3346                                 // Case 1: & object.
3347                                 //
3348                                 if (e is Unary && ((Unary) e).Oper == Unary.Operator.AddressOf){
3349                                         Expression child = ((Unary) e).Expr;
3350
3351                                         if (child is ParameterReference || child is LocalVariableReference){
3352                                                 Report.Error (
3353                                                         213, loc,
3354                                                         "No need to use fixed statement for parameters or " +
3355                                                         "local variable declarations (address is already " +
3356                                                         "fixed)");
3357                                                 return false;
3358                                         }
3359
3360                                         ec.InFixedInitializer = true;
3361                                         e = e.Resolve (ec);
3362                                         ec.InFixedInitializer = false;
3363                                         if (e == null)
3364                                                 return false;
3365
3366                                         child = ((Unary) e).Expr;
3367
3368                                         if (!TypeManager.VerifyUnManaged (child.Type, loc))
3369                                                 return false;
3370
3371                                         data [i] = new ExpressionEmitter (e, vi);
3372                                         i++;
3373
3374                                         continue;
3375                                 }
3376
3377                                 ec.InFixedInitializer = true;
3378                                 e = e.Resolve (ec);
3379                                 ec.InFixedInitializer = false;
3380                                 if (e == null)
3381                                         return false;
3382
3383                                 //
3384                                 // Case 2: Array
3385                                 //
3386                                 if (e.Type.IsArray){
3387                                         Type array_type = TypeManager.GetElementType (e.Type);
3388
3389                                         //
3390                                         // Provided that array_type is unmanaged,
3391                                         //
3392                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
3393                                                 return false;
3394
3395                                         //
3396                                         // and T* is implicitly convertible to the
3397                                         // pointer type given in the fixed statement.
3398                                         //
3399                                         ArrayPtr array_ptr = new ArrayPtr (e, array_type, loc);
3400
3401                                         Expression converted = Convert.ImplicitConversionRequired (
3402                                                 ec, array_ptr, vi.VariableType, loc);
3403                                         if (converted == null)
3404                                                 return false;
3405
3406                                         data [i] = new ExpressionEmitter (converted, vi);
3407                                         i++;
3408
3409                                         continue;
3410                                 }
3411
3412                                 //
3413                                 // Case 3: string
3414                                 //
3415                                 if (e.Type == TypeManager.string_type){
3416                                         data [i] = new StringEmitter (e, vi, loc);
3417                                         i++;
3418                                         continue;
3419                                 }
3420
3421                                 // Case 4: fixed buffer
3422                                 FieldExpr fe = e as FieldExpr;
3423                                 if (fe != null) {
3424                                         IFixedBuffer ff = AttributeTester.GetFixedBuffer (fe.FieldInfo);
3425                                         if (ff != null) {
3426                                                 Expression fixed_buffer_ptr = new FixedBufferPtr (fe, ff.ElementType, loc);
3427
3428                                                 Expression converted = Convert.ImplicitConversionRequired (
3429                                                         ec, fixed_buffer_ptr, vi.VariableType, loc);
3430                                                 if (converted == null)
3431                                                         return false;
3432
3433                                                 data [i] = new ExpressionEmitter (converted, vi);
3434                                                 i++;
3435
3436                                                 continue;
3437                                         }
3438                                 }
3439
3440                                 //
3441                                 // For other cases, flag a `this is already fixed expression'
3442                                 //
3443                                 if (e is LocalVariableReference || e is ParameterReference ||
3444                                     Convert.ImplicitConversionExists (ec, e, vi.VariableType)){
3445
3446                                         Report.Error (245, loc, "right hand expression is already fixed, no need to use fixed statement ");
3447                                         return false;
3448                                 }
3449
3450                                 Report.Error (245, loc, "Fixed statement only allowed on strings, arrays or address-of expressions");
3451                                 return false;
3452                         }
3453
3454                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
3455
3456                         if (!statement.Resolve (ec)) {
3457                                 ec.KillFlowBranching ();
3458                                 return false;
3459                         }
3460
3461                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3462                         has_ret = reachability.IsUnreachable;
3463
3464                         return true;
3465                 }
3466
3467                 protected override void DoEmit (EmitContext ec)
3468                 {
3469                         for (int i = 0; i < data.Length; i++) {
3470                                 data [i].Emit (ec);
3471                         }
3472
3473                         statement.Emit (ec);
3474
3475                         if (has_ret)
3476                                 return;
3477
3478                         ILGenerator ig = ec.ig;
3479
3480                         //
3481                         // Clear the pinned variable
3482                         //
3483                         for (int i = 0; i < data.Length; i++) {
3484                                 data [i].EmitExit (ig);
3485                         }
3486                 }
3487         }
3488
3489         public class Catch: Statement {
3490                 public readonly string Name;
3491                 public readonly Block  Block;
3492
3493                 Expression type_expr;
3494                 Type type;
3495
3496                 public Catch (Expression type, string name, Block block, Location l)
3497                 {
3498                         type_expr = type;
3499                         Name = name;
3500                         Block = block;
3501                         loc = l;
3502                 }
3503
3504                 public Type CatchType {
3505                         get {
3506                                 return type;
3507                         }
3508                 }
3509
3510                 public bool IsGeneral {
3511                         get {
3512                                 return type_expr == null;
3513                         }
3514                 }
3515
3516                 protected override void DoEmit(EmitContext ec)
3517                 {
3518                 }
3519
3520                 public override bool Resolve (EmitContext ec)
3521                 {
3522                         bool was_catch = ec.InCatch;
3523                         ec.InCatch = true;
3524                         try {
3525                                 if (type_expr != null) {
3526                                         TypeExpr te = type_expr.ResolveAsTypeTerminal (ec, false);
3527                                         if (te == null)
3528                                                 return false;
3529
3530                                         type = te.ResolveType (ec);
3531
3532                                         CheckObsolete (type);
3533
3534                                         if (type != TypeManager.exception_type && !type.IsSubclassOf (TypeManager.exception_type)){
3535                                                 Error (155, "The type caught or thrown must be derived from System.Exception");
3536                                                 return false;
3537                                         }
3538                                 } else
3539                                         type = null;
3540
3541                                 return Block.Resolve (ec);
3542                         }
3543                         finally {
3544                                 ec.InCatch = was_catch;
3545                         }
3546                 }
3547         }
3548
3549         public class Try : ExceptionStatement {
3550                 public readonly Block Fini, Block;
3551                 public readonly ArrayList Specific;
3552                 public readonly Catch General;
3553
3554                 bool need_exc_block;
3555
3556                 //
3557                 // specific, general and fini might all be null.
3558                 //
3559                 public Try (Block block, ArrayList specific, Catch general, Block fini, Location l)
3560                 {
3561                         if (specific == null && general == null){
3562                                 Console.WriteLine ("CIR.Try: Either specific or general have to be non-null");
3563                         }
3564
3565                         this.Block = block;
3566                         this.Specific = specific;
3567                         this.General = general;
3568                         this.Fini = fini;
3569                         loc = l;
3570                 }
3571
3572                 public override bool Resolve (EmitContext ec)
3573                 {
3574                         bool ok = true;
3575
3576                         FlowBranchingException branching = ec.StartFlowBranching (this);
3577
3578                         Report.Debug (1, "START OF TRY BLOCK", Block.StartLocation);
3579
3580                         if (!Block.Resolve (ec))
3581                                 ok = false;
3582
3583                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
3584
3585                         Report.Debug (1, "START OF CATCH BLOCKS", vector);
3586
3587                         Type[] prevCatches = new Type [Specific.Count];
3588                         int last_index = 0;
3589                         foreach (Catch c in Specific){
3590                                 ec.CurrentBranching.CreateSibling (
3591                                         c.Block, FlowBranching.SiblingType.Catch);
3592
3593                                 Report.Debug (1, "STARTED SIBLING FOR CATCH", ec.CurrentBranching);
3594
3595                                 if (c.Name != null) {
3596                                         LocalInfo vi = c.Block.GetLocalInfo (c.Name);
3597                                         if (vi == null)
3598                                                 throw new Exception ();
3599
3600                                         vi.VariableInfo = null;
3601                                 }
3602
3603                                 if (!c.Resolve (ec))
3604                                         return false;
3605
3606                                 Type resolvedType = c.CatchType;
3607                                 for (int ii = 0; ii < last_index; ++ii) {
3608                                         if (resolvedType == prevCatches [ii] || resolvedType.IsSubclassOf (prevCatches [ii])) {
3609                                                 Report.Error (160, c.loc, "A previous catch clause already catches all exceptions of this or a super type `{0}'", prevCatches [ii].FullName);
3610                                                 return false;
3611                                         }
3612                                 }
3613
3614                                 prevCatches [last_index++] = resolvedType;
3615                                 need_exc_block = true;
3616                         }
3617
3618                         Report.Debug (1, "END OF CATCH BLOCKS", ec.CurrentBranching);
3619
3620                         if (General != null){
3621                                 ec.CurrentBranching.CreateSibling (
3622                                         General.Block, FlowBranching.SiblingType.Catch);
3623
3624                                 Report.Debug (1, "STARTED SIBLING FOR GENERAL", ec.CurrentBranching);
3625
3626                                 if (!General.Resolve (ec))
3627                                         ok = false;
3628
3629                                 need_exc_block = true;
3630                         }
3631
3632                         Report.Debug (1, "END OF GENERAL CATCH BLOCKS", ec.CurrentBranching);
3633
3634                         if (Fini != null) {
3635                                 if (ok)
3636                                         ec.CurrentBranching.CreateSibling (
3637                                                 Fini, FlowBranching.SiblingType.Finally);
3638
3639                                 Report.Debug (1, "STARTED SIBLING FOR FINALLY", ec.CurrentBranching, vector);
3640                                 bool was_finally = ec.InFinally;
3641                                 ec.InFinally = true;
3642                                 if (!Fini.Resolve (ec))
3643                                         ok = false;
3644                                 ec.InFinally = was_finally;
3645
3646                                 if (!ec.InIterator)
3647                                         need_exc_block = true;
3648                         }
3649
3650                         if (ec.InIterator) {
3651                                 ResolveFinally (branching);
3652                                 need_exc_block |= emit_finally;
3653                         } else
3654                                 emit_finally = Fini != null;
3655
3656                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3657
3658                         FlowBranching.UsageVector f_vector = ec.CurrentBranching.CurrentUsageVector;
3659
3660                         Report.Debug (1, "END OF TRY", ec.CurrentBranching, reachability, vector, f_vector);
3661
3662                         if (reachability.Returns != FlowBranching.FlowReturns.Always) {
3663                                 // Unfortunately, System.Reflection.Emit automatically emits
3664                                 // a leave to the end of the finally block.  This is a problem
3665                                 // if `returns' is true since we may jump to a point after the
3666                                 // end of the method.
3667                                 // As a workaround, emit an explicit ret here.
3668                                 ec.NeedReturnLabel ();
3669                         }
3670
3671                         return ok;
3672                 }
3673
3674                 protected override void DoEmit (EmitContext ec)
3675                 {
3676                         ILGenerator ig = ec.ig;
3677
3678                         if (need_exc_block)
3679                                 ig.BeginExceptionBlock ();
3680                         Block.Emit (ec);
3681
3682                         foreach (Catch c in Specific){
3683                                 LocalInfo vi;
3684
3685                                 ig.BeginCatchBlock (c.CatchType);
3686
3687                                 if (c.Name != null){
3688                                         vi = c.Block.GetLocalInfo (c.Name);
3689                                         if (vi == null)
3690                                                 throw new Exception ("Variable does not exist in this block");
3691
3692                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3693                                 } else
3694                                         ig.Emit (OpCodes.Pop);
3695
3696                                 c.Block.Emit (ec);
3697                         }
3698
3699                         if (General != null){
3700                                 ig.BeginCatchBlock (TypeManager.object_type);
3701                                 ig.Emit (OpCodes.Pop);
3702                                 General.Block.Emit (ec);
3703                         }
3704
3705                         DoEmitFinally (ec);
3706                         if (need_exc_block)
3707                                 ig.EndExceptionBlock ();
3708                 }
3709
3710                 public override void EmitFinally (EmitContext ec)
3711                 {
3712                         if (Fini != null)
3713                                 Fini.Emit (ec);
3714                 }
3715
3716                 public bool HasCatch
3717                 {
3718                         get {
3719                                 return General != null || Specific.Count > 0;
3720                         }
3721                 }
3722         }
3723
3724         public class Using : ExceptionStatement {
3725                 object expression_or_block;
3726                 Statement Statement;
3727                 ArrayList var_list;
3728                 Expression expr;
3729                 Type expr_type;
3730                 Expression conv;
3731                 Expression [] resolved_vars;
3732                 Expression [] converted_vars;
3733                 ExpressionStatement [] assign;
3734                 LocalBuilder local_copy;
3735
3736                 public Using (object expression_or_block, Statement stmt, Location l)
3737                 {
3738                         this.expression_or_block = expression_or_block;
3739                         Statement = stmt;
3740                         loc = l;
3741                 }
3742
3743                 //
3744                 // Resolves for the case of using using a local variable declaration.
3745                 //
3746                 bool ResolveLocalVariableDecls (EmitContext ec)
3747                 {
3748                         int i = 0;
3749
3750                         TypeExpr texpr = expr.ResolveAsTypeTerminal (ec, false);
3751                         if (texpr == null)
3752                                 return false;
3753
3754                         expr_type = texpr.ResolveType (ec);
3755
3756                         //
3757                         // The type must be an IDisposable or an implicit conversion
3758                         // must exist.
3759                         //
3760                         converted_vars = new Expression [var_list.Count];
3761                         resolved_vars = new Expression [var_list.Count];
3762                         assign = new ExpressionStatement [var_list.Count];
3763
3764                         bool need_conv = !TypeManager.ImplementsInterface (
3765                                 expr_type, TypeManager.idisposable_type);
3766
3767                         foreach (DictionaryEntry e in var_list){
3768                                 Expression var = (Expression) e.Key;
3769
3770                                 var = var.ResolveLValue (ec, new EmptyExpression (), loc);
3771                                 if (var == null)
3772                                         return false;
3773
3774                                 resolved_vars [i] = var;
3775
3776                                 if (!need_conv) {
3777                                         i++;
3778                                         continue;
3779                                 }
3780
3781                                 converted_vars [i] = Convert.ImplicitConversionRequired (
3782                                         ec, var, TypeManager.idisposable_type, loc);
3783
3784                                 if (converted_vars [i] == null)
3785                                         return false;
3786
3787                                 i++;
3788                         }
3789
3790                         i = 0;
3791                         foreach (DictionaryEntry e in var_list){
3792                                 Expression var = resolved_vars [i];
3793                                 Expression new_expr = (Expression) e.Value;
3794                                 Expression a;
3795
3796                                 a = new Assign (var, new_expr, loc);
3797                                 a = a.Resolve (ec);
3798                                 if (a == null)
3799                                         return false;
3800
3801                                 if (!need_conv)
3802                                         converted_vars [i] = var;
3803                                 assign [i] = (ExpressionStatement) a;
3804                                 i++;
3805                         }
3806
3807                         return true;
3808                 }
3809
3810                 bool ResolveExpression (EmitContext ec)
3811                 {
3812                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)){
3813                                 if (Convert.ImplicitConversion (ec, expr, TypeManager.idisposable_type, loc) == null) {
3814                                         Report.Error (1674, loc, "`{0}': type used in a using statement must be implicitly convertible to 'System.IDisposable'",
3815                                                 TypeManager.CSharpName (expr_type));
3816                                         return false;
3817                                 }
3818                         }
3819
3820                         return true;
3821                 }
3822
3823                 //
3824                 // Emits the code for the case of using using a local variable declaration.
3825                 //
3826                 void EmitLocalVariableDecls (EmitContext ec)
3827                 {
3828                         ILGenerator ig = ec.ig;
3829                         int i = 0;
3830
3831                         for (i = 0; i < assign.Length; i++) {
3832                                 assign [i].EmitStatement (ec);
3833
3834                                 if (emit_finally)
3835                                         ig.BeginExceptionBlock ();
3836                         }
3837                         Statement.Emit (ec);
3838                         var_list.Reverse ();
3839
3840                         DoEmitFinally (ec);
3841                 }
3842
3843                 void EmitLocalVariableDeclFinally (EmitContext ec)
3844                 {
3845                         ILGenerator ig = ec.ig;
3846
3847                         int i = assign.Length;
3848                         for (int ii = 0; ii < var_list.Count; ++ii){
3849                                 Expression var = resolved_vars [--i];
3850                                 Label skip = ig.DefineLabel ();
3851
3852                                 if (!var.Type.IsValueType) {
3853                                         var.Emit (ec);
3854                                         ig.Emit (OpCodes.Brfalse, skip);
3855                                         converted_vars [i].Emit (ec);
3856                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3857                                 } else {
3858                                         Expression ml = Expression.MemberLookup(ec, TypeManager.idisposable_type, var.Type, "Dispose", Mono.CSharp.Location.Null);
3859
3860                                         if (!(ml is MethodGroupExpr)) {
3861                                                 var.Emit (ec);
3862                                                 ig.Emit (OpCodes.Box, var.Type);
3863                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3864                                         } else {
3865                                                 MethodInfo mi = null;
3866
3867                                                 foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
3868                                                         if (TypeManager.GetArgumentTypes (mk).Length == 0) {
3869                                                                 mi = mk;
3870                                                                 break;
3871                                                         }
3872                                                 }
3873
3874                                                 if (mi == null) {
3875                                                         Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
3876                                                         return;
3877                                                 }
3878
3879                                                 IMemoryLocation mloc = (IMemoryLocation) var;
3880
3881                                                 mloc.AddressOf (ec, AddressOp.Load);
3882                                                 ig.Emit (OpCodes.Call, mi);
3883                                         }
3884                                 }
3885
3886                                 ig.MarkLabel (skip);
3887
3888                                 if (emit_finally) {
3889                                         ig.EndExceptionBlock ();
3890                                         if (i > 0)
3891                                                 ig.BeginFinallyBlock ();
3892                                 }
3893                         }
3894                 }
3895
3896                 void EmitExpression (EmitContext ec)
3897                 {
3898                         //
3899                         // Make a copy of the expression and operate on that.
3900                         //
3901                         ILGenerator ig = ec.ig;
3902                         local_copy = ig.DeclareLocal (expr_type);
3903                         if (conv != null)
3904                                 conv.Emit (ec);
3905                         else
3906                                 expr.Emit (ec);
3907                         ig.Emit (OpCodes.Stloc, local_copy);
3908
3909                         if (emit_finally)
3910                                 ig.BeginExceptionBlock ();
3911
3912                         Statement.Emit (ec);
3913
3914                         DoEmitFinally (ec);
3915                         if (emit_finally)
3916                                 ig.EndExceptionBlock ();
3917                 }
3918
3919                 void EmitExpressionFinally (EmitContext ec)
3920                 {
3921                         ILGenerator ig = ec.ig;
3922                         if (!local_copy.LocalType.IsValueType) {
3923                                 Label skip = ig.DefineLabel ();
3924                                 ig.Emit (OpCodes.Ldloc, local_copy);
3925                                 ig.Emit (OpCodes.Brfalse, skip);
3926                                 ig.Emit (OpCodes.Ldloc, local_copy);
3927                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3928                                 ig.MarkLabel (skip);
3929                         } else {
3930                                 Expression ml = Expression.MemberLookup(ec, TypeManager.idisposable_type, local_copy.LocalType, "Dispose", Mono.CSharp.Location.Null);
3931
3932                                 if (!(ml is MethodGroupExpr)) {
3933                                         ig.Emit (OpCodes.Ldloc, local_copy);
3934                                         ig.Emit (OpCodes.Box, local_copy.LocalType);
3935                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3936                                 } else {
3937                                         MethodInfo mi = null;
3938
3939                                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
3940                                                 if (TypeManager.GetArgumentTypes (mk).Length == 0) {
3941                                                         mi = mk;
3942                                                         break;
3943                                                 }
3944                                         }
3945
3946                                         if (mi == null) {
3947                                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
3948                                                 return;
3949                                         }
3950
3951                                         ig.Emit (OpCodes.Ldloca, local_copy);
3952                                         ig.Emit (OpCodes.Call, mi);
3953                                 }
3954                         }
3955                 }
3956
3957                 public override bool Resolve (EmitContext ec)
3958                 {
3959                         if (expression_or_block is DictionaryEntry){
3960                                 expr = (Expression) ((DictionaryEntry) expression_or_block).Key;
3961                                 var_list = (ArrayList)((DictionaryEntry)expression_or_block).Value;
3962
3963                                 if (!ResolveLocalVariableDecls (ec))
3964                                         return false;
3965
3966                         } else if (expression_or_block is Expression){
3967                                 expr = (Expression) expression_or_block;
3968
3969                                 expr = expr.Resolve (ec);
3970                                 if (expr == null)
3971                                         return false;
3972
3973                                 expr_type = expr.Type;
3974
3975                                 if (!ResolveExpression (ec))
3976                                         return false;
3977                         }
3978
3979                         FlowBranchingException branching = ec.StartFlowBranching (this);
3980
3981                         bool ok = Statement.Resolve (ec);
3982
3983                         if (!ok) {
3984                                 ec.KillFlowBranching ();
3985                                 return false;
3986                         }
3987
3988                         ResolveFinally (branching);
3989                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3990
3991                         if (reachability.Returns != FlowBranching.FlowReturns.Always) {
3992                                 // Unfortunately, System.Reflection.Emit automatically emits a leave
3993                                 // to the end of the finally block.  This is a problem if `returns'
3994                                 // is true since we may jump to a point after the end of the method.
3995                                 // As a workaround, emit an explicit ret here.
3996                                 ec.NeedReturnLabel ();
3997                         }
3998
3999                         return true;
4000                 }
4001
4002                 protected override void DoEmit (EmitContext ec)
4003                 {
4004                         if (expression_or_block is DictionaryEntry)
4005                                 EmitLocalVariableDecls (ec);
4006                         else if (expression_or_block is Expression)
4007                                 EmitExpression (ec);
4008                 }
4009
4010                 public override void EmitFinally (EmitContext ec)
4011                 {
4012                         if (expression_or_block is DictionaryEntry)
4013                                 EmitLocalVariableDeclFinally (ec);
4014                         else if (expression_or_block is Expression)
4015                                 EmitExpressionFinally (ec);
4016                 }
4017         }
4018
4019         /// <summary>
4020         ///   Implementation of the foreach C# statement
4021         /// </summary>
4022         public class Foreach : Statement {
4023                 Expression type;
4024                 Expression variable;
4025                 Expression expr;
4026                 Statement statement;
4027                 ArrayForeach array;
4028                 CollectionForeach collection;
4029
4030                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
4031                                 Statement stmt, Location l)
4032                 {
4033                         this.type = type;
4034                         this.variable = var;
4035                         this.expr = expr;
4036                         statement = stmt;
4037                         loc = l;
4038                 }
4039
4040                 public override bool Resolve (EmitContext ec)
4041                 {
4042                         expr = expr.Resolve (ec);
4043                         if (expr == null)
4044                                 return false;
4045
4046                         if (expr is NullLiteral) {
4047                                 Report.Error (186, loc, "Use of null is not valid in this context");
4048                                 return false;
4049                         }
4050
4051                         TypeExpr texpr = type.ResolveAsTypeTerminal (ec, false);
4052                         if (texpr == null)
4053                                 return false;
4054
4055                         Type var_type = texpr.Type;
4056
4057                         //
4058                         // We need an instance variable.  Not sure this is the best
4059                         // way of doing this.
4060                         //
4061                         // FIXME: When we implement propertyaccess, will those turn
4062                         // out to return values in ExprClass?  I think they should.
4063                         //
4064                         if (!(expr.eclass == ExprClass.Variable || expr.eclass == ExprClass.Value ||
4065                               expr.eclass == ExprClass.PropertyAccess || expr.eclass == ExprClass.IndexerAccess)){
4066                                 collection.error1579 ();
4067                                 return false;
4068                         }
4069
4070                         if (expr.Type.IsArray) {
4071                                 array = new ArrayForeach (var_type, variable, expr, statement, loc);
4072                                 return array.Resolve (ec);
4073                         } else {
4074                                 collection = new CollectionForeach (
4075                                         var_type, variable, expr, statement, loc);
4076                                 return collection.Resolve (ec);
4077                         }
4078                 }
4079
4080                 protected override void DoEmit (EmitContext ec)
4081                 {
4082                         ILGenerator ig = ec.ig;
4083
4084                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
4085                         ec.LoopBegin = ig.DefineLabel ();
4086                         ec.LoopEnd = ig.DefineLabel ();
4087
4088                         if (collection != null)
4089                                 collection.Emit (ec);
4090                         else
4091                                 array.Emit (ec);
4092
4093                         ec.LoopBegin = old_begin;
4094                         ec.LoopEnd = old_end;
4095                 }
4096
4097                 protected class TemporaryVariable : Expression, IMemoryLocation
4098                 {
4099                         LocalInfo li;
4100
4101                         public TemporaryVariable (Type type, Location loc)
4102                         {
4103                                 this.type = type;
4104                                 this.loc = loc;
4105                                 eclass = ExprClass.Value;
4106                         }
4107
4108                         public override Expression DoResolve (EmitContext ec)
4109                         {
4110                                 if (li != null)
4111                                         return this;
4112
4113                                 TypeExpr te = new TypeExpression (type, loc);
4114                                 li = ec.CurrentBlock.AddTemporaryVariable (te, loc);
4115                                 if (!li.Resolve (ec))
4116                                         return null;
4117
4118                                 AnonymousContainer am = ec.CurrentAnonymousMethod;
4119                                 if ((am != null) && am.IsIterator)
4120                                         ec.CaptureVariable (li);
4121
4122                                 return this;
4123                         }
4124
4125                         public override void Emit (EmitContext ec)
4126                         {
4127                                 ILGenerator ig = ec.ig;
4128
4129                                 if (li.FieldBuilder != null) {
4130                                         ig.Emit (OpCodes.Ldarg_0);
4131                                         ig.Emit (OpCodes.Ldfld, li.FieldBuilder);
4132                                 } else {
4133                                         ig.Emit (OpCodes.Ldloc, li.LocalBuilder);
4134                                 }
4135                         }
4136
4137                         public void EmitLoadAddress (EmitContext ec)
4138                         {
4139                                 ILGenerator ig = ec.ig;
4140
4141                                 if (li.FieldBuilder != null) {
4142                                         ig.Emit (OpCodes.Ldarg_0);
4143                                         ig.Emit (OpCodes.Ldflda, li.FieldBuilder);
4144                                 } else {
4145                                         ig.Emit (OpCodes.Ldloca, li.LocalBuilder);
4146                                 }
4147                         }
4148
4149                         public void Store (EmitContext ec, Expression right_side)
4150                         {
4151                                 if (li.FieldBuilder != null)
4152                                         ec.ig.Emit (OpCodes.Ldarg_0);
4153
4154                                 right_side.Emit (ec);
4155                                 if (li.FieldBuilder != null) {
4156                                         ec.ig.Emit (OpCodes.Stfld, li.FieldBuilder);
4157                                 } else {
4158                                         ec.ig.Emit (OpCodes.Stloc, li.LocalBuilder);
4159                                 }
4160                         }
4161
4162                         public void EmitThis (EmitContext ec)
4163                         {
4164                                 if (li.FieldBuilder != null) {
4165                                         ec.ig.Emit (OpCodes.Ldarg_0);
4166                                 }
4167                         }
4168
4169                         public void EmitStore (ILGenerator ig)
4170                         {
4171                                 if (li.FieldBuilder != null)
4172                                         ig.Emit (OpCodes.Stfld, li.FieldBuilder);
4173                                 else
4174                                         ig.Emit (OpCodes.Stloc, li.LocalBuilder);
4175                         }
4176
4177                         public void AddressOf (EmitContext ec, AddressOp mode)
4178                         {
4179                                 EmitLoadAddress (ec);
4180                         }
4181                 }
4182
4183                 protected class ArrayCounter : TemporaryVariable
4184                 {
4185                         public ArrayCounter (Location loc)
4186                                 : base (TypeManager.int32_type, loc)
4187                         { }
4188
4189                         public void Initialize (EmitContext ec)
4190                         {
4191                                 EmitThis (ec);
4192                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
4193                                 EmitStore (ec.ig);
4194                         }
4195
4196                         public void Increment (EmitContext ec)
4197                         {
4198                                 EmitThis (ec);
4199                                 Emit (ec);
4200                                 ec.ig.Emit (OpCodes.Ldc_I4_1);
4201                                 ec.ig.Emit (OpCodes.Add);
4202                                 EmitStore (ec.ig);
4203                         }
4204                 }
4205
4206                 protected class ArrayForeach : Statement
4207                 {
4208                         Expression variable, expr, conv;
4209                         Statement statement;
4210                         Type array_type;
4211                         Type var_type;
4212                         TemporaryVariable[] lengths;
4213                         ArrayCounter[] counter;
4214                         int rank;
4215
4216                         TemporaryVariable copy;
4217                         Expression access;
4218
4219                         public ArrayForeach (Type var_type, Expression var,
4220                                              Expression expr, Statement stmt, Location l)
4221                         {
4222                                 this.var_type = var_type;
4223                                 this.variable = var;
4224                                 this.expr = expr;
4225                                 statement = stmt;
4226                                 loc = l;
4227                         }
4228
4229                         public override bool Resolve (EmitContext ec)
4230                         {
4231                                 array_type = expr.Type;
4232                                 rank = array_type.GetArrayRank ();
4233
4234                                 copy = new TemporaryVariable (array_type, loc);
4235                                 copy.Resolve (ec);
4236
4237                                 counter = new ArrayCounter [rank];
4238                                 lengths = new TemporaryVariable [rank];
4239
4240                                 ArrayList list = new ArrayList ();
4241                                 for (int i = 0; i < rank; i++) {
4242                                         counter [i] = new ArrayCounter (loc);
4243                                         counter [i].Resolve (ec);
4244
4245                                         lengths [i] = new TemporaryVariable (TypeManager.int32_type, loc);
4246                                         lengths [i].Resolve (ec);
4247
4248                                         list.Add (counter [i]);
4249                                 }
4250
4251                                 access = new ElementAccess (copy, list, loc).Resolve (ec);
4252                                 if (access == null)
4253                                         return false;
4254
4255                                 conv = Convert.ExplicitConversion (ec, access, var_type, loc);
4256                                 if (conv == null)
4257                                         return false;
4258
4259                                 bool ok = true;
4260
4261                                 ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
4262                                 ec.CurrentBranching.CreateSibling ();
4263
4264                                 variable = variable.ResolveLValue (ec, conv, loc);
4265                                 if (variable == null)
4266                                         ok = false;
4267
4268                                 if (!statement.Resolve (ec))
4269                                         ok = false;
4270
4271                                 ec.EndFlowBranching ();
4272
4273                                 return ok;
4274                         }
4275
4276                         protected override void DoEmit (EmitContext ec)
4277                         {
4278                                 ILGenerator ig = ec.ig;
4279
4280                                 copy.Store (ec, expr);
4281
4282                                 Label[] test = new Label [rank];
4283                                 Label[] loop = new Label [rank];
4284
4285                                 for (int i = 0; i < rank; i++) {
4286                                         test [i] = ig.DefineLabel ();
4287                                         loop [i] = ig.DefineLabel ();
4288
4289                                         lengths [i].EmitThis (ec);
4290                                         ((ArrayAccess) access).EmitGetLength (ec, i);
4291                                         lengths [i].EmitStore (ig);
4292                                 }
4293
4294                                 for (int i = 0; i < rank; i++) {
4295                                         counter [i].Initialize (ec);
4296
4297                                         ig.Emit (OpCodes.Br, test [i]);
4298                                         ig.MarkLabel (loop [i]);
4299                                 }
4300
4301                                 ((IAssignMethod) variable).EmitAssign (ec, conv, false, false);
4302
4303                                 statement.Emit (ec);
4304
4305                                 ig.MarkLabel (ec.LoopBegin);
4306
4307                                 for (int i = rank - 1; i >= 0; i--){
4308                                         counter [i].Increment (ec);
4309
4310                                         ig.MarkLabel (test [i]);
4311                                         counter [i].Emit (ec);
4312                                         lengths [i].Emit (ec);
4313                                         ig.Emit (OpCodes.Blt, loop [i]);
4314                                 }
4315
4316                                 ig.MarkLabel (ec.LoopEnd);
4317                         }
4318                 }
4319
4320                 protected class CollectionForeach : ExceptionStatement
4321                 {
4322                         Expression variable, expr;
4323                         Statement statement;
4324
4325                         TemporaryVariable enumerator;
4326                         Expression init;
4327                         Statement loop;
4328
4329                         MethodGroupExpr get_enumerator;
4330                         PropertyExpr get_current;
4331                         MethodInfo move_next;
4332                         Type var_type, enumerator_type;
4333                         bool is_disposable;
4334
4335                         public CollectionForeach (Type var_type, Expression var,
4336                                                   Expression expr, Statement stmt, Location l)
4337                         {
4338                                 this.var_type = var_type;
4339                                 this.variable = var;
4340                                 this.expr = expr;
4341                                 statement = stmt;
4342                                 loc = l;
4343                         }
4344
4345                         bool GetEnumeratorFilter (EmitContext ec, MethodInfo mi)
4346                         {
4347                                 Type [] args = TypeManager.GetArgumentTypes (mi);
4348                                 if (args != null){
4349                                         if (args.Length != 0)
4350                                                 return false;
4351                                 }
4352
4353                                 if (TypeManager.IsOverride (mi))
4354                                         return false;
4355
4356                                 // Check whether GetEnumerator is public
4357                                 if ((mi.Attributes & MethodAttributes.Public) != MethodAttributes.Public)
4358                                         return false;
4359
4360                                 if ((mi.ReturnType == TypeManager.ienumerator_type) && (mi.DeclaringType == TypeManager.string_type))
4361                                         //
4362                                         // Apply the same optimization as MS: skip the GetEnumerator
4363                                         // returning an IEnumerator, and use the one returning a
4364                                         // CharEnumerator instead. This allows us to avoid the
4365                                         // try-finally block and the boxing.
4366                                         //
4367                                         return false;
4368
4369                                 //
4370                                 // Ok, we can access it, now make sure that we can do something
4371                                 // with this `GetEnumerator'
4372                                 //
4373
4374                                 Type return_type = mi.ReturnType;
4375                                 if (mi.ReturnType == TypeManager.ienumerator_type ||
4376                                     TypeManager.ienumerator_type.IsAssignableFrom (return_type) ||
4377                                     (!RootContext.StdLib && TypeManager.ImplementsInterface (return_type, TypeManager.ienumerator_type))) {
4378                                         //
4379                                         // If it is not an interface, lets try to find the methods ourselves.
4380                                         // For example, if we have:
4381                                         // public class Foo : IEnumerator { public bool MoveNext () {} public int Current { get {}}}
4382                                         // We can avoid the iface call. This is a runtime perf boost.
4383                                         // even bigger if we have a ValueType, because we avoid the cost
4384                                         // of boxing.
4385                                         //
4386                                         // We have to make sure that both methods exist for us to take
4387                                         // this path. If one of the methods does not exist, we will just
4388                                         // use the interface. Sadly, this complex if statement is the only
4389                                         // way I could do this without a goto
4390                                         //
4391
4392                                         if (return_type.IsInterface ||
4393                                             !FetchMoveNext (ec, return_type) ||
4394                                             !FetchGetCurrent (ec, return_type)) {
4395                                                 move_next = TypeManager.bool_movenext_void;
4396                                                 get_current = new PropertyExpr (
4397                                                         ec, TypeManager.ienumerator_getcurrent, loc);
4398                                                 return true;
4399                                         }
4400                                 } else {
4401                                         //
4402                                         // Ok, so they dont return an IEnumerable, we will have to
4403                                         // find if they support the GetEnumerator pattern.
4404                                         //
4405
4406                                         if (!FetchMoveNext (ec, return_type))
4407                                                 return false;
4408
4409                                         if (!FetchGetCurrent (ec, return_type))
4410                                                 return false;
4411                                 }
4412
4413                                 enumerator_type = return_type;
4414                                 is_disposable = !enumerator_type.IsSealed ||
4415                                         TypeManager.ImplementsInterface (
4416                                                 enumerator_type, TypeManager.idisposable_type);
4417
4418                                 return true;
4419                         }
4420
4421                         //
4422                         // Retrieves a `public bool MoveNext ()' method from the Type `t'
4423                         //
4424                         bool FetchMoveNext (EmitContext ec, Type t)
4425                         {
4426                                 MemberList move_next_list;
4427
4428                                 move_next_list = TypeContainer.FindMembers (
4429                                         t, MemberTypes.Method,
4430                                         BindingFlags.Public | BindingFlags.Instance,
4431                                         Type.FilterName, "MoveNext");
4432                                 if (move_next_list.Count == 0)
4433                                         return false;
4434
4435                                 foreach (MemberInfo m in move_next_list){
4436                                         MethodInfo mi = (MethodInfo) m;
4437                                         Type [] args;
4438
4439                                         args = TypeManager.GetArgumentTypes (mi);
4440                                         if ((args != null) && (args.Length == 0) &&
4441                                             TypeManager.TypeToCoreType (mi.ReturnType) == TypeManager.bool_type) {
4442                                                 move_next = mi;
4443                                                 return true;
4444                                         }
4445                                 }
4446
4447                                 return false;
4448                         }
4449
4450                         //
4451                         // Retrieves a `public T get_Current ()' method from the Type `t'
4452                         //
4453                         bool FetchGetCurrent (EmitContext ec, Type t)
4454                         {
4455                                 PropertyExpr pe = Expression.MemberLookup (
4456                                         ec, t, "Current", MemberTypes.Property,
4457                                         Expression.AllBindingFlags, loc) as PropertyExpr;
4458                                 if (pe == null)
4459                                         return false;
4460
4461                                 get_current = pe;
4462                                 return true;
4463                         }
4464
4465                         //
4466                         // Retrieves a `public void Dispose ()' method from the Type `t'
4467                         //
4468                         static MethodInfo FetchMethodDispose (Type t)
4469                         {
4470                                 MemberList dispose_list;
4471
4472                                 dispose_list = TypeContainer.FindMembers (
4473                                         t, MemberTypes.Method,
4474                                         BindingFlags.Public | BindingFlags.Instance,
4475                                         Type.FilterName, "Dispose");
4476                                 if (dispose_list.Count == 0)
4477                                         return null;
4478
4479                                 foreach (MemberInfo m in dispose_list){
4480                                         MethodInfo mi = (MethodInfo) m;
4481                                         Type [] args;
4482
4483                                         args = TypeManager.GetArgumentTypes (mi);
4484                                         if (args != null && args.Length == 0){
4485                                                 if (mi.ReturnType == TypeManager.void_type)
4486                                                         return mi;
4487                                         }
4488                                 }
4489                                 return null;
4490                         }
4491
4492                         public void error1579 ()
4493                         {
4494                             Report.Error (1579, loc,
4495                                 "foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `GetEnumerator' or is not accessible",
4496                                 TypeManager.CSharpName (expr.Type));
4497                         }
4498
4499                         bool TryType (EmitContext ec, Type t)
4500                         {
4501                                 MethodGroupExpr mg = Expression.MemberLookup (
4502                                         ec, t, "GetEnumerator", MemberTypes.Method,
4503                                         Expression.AllBindingFlags, loc) as MethodGroupExpr;
4504                                 if (mg == null)
4505                                         return false;
4506
4507                                 foreach (MethodBase mb in mg.Methods) {
4508                                         if (!GetEnumeratorFilter (ec, (MethodInfo) mb))
4509                                                 continue;
4510
4511                                         MethodInfo[] mi = new MethodInfo[] { (MethodInfo) mb };
4512                                         get_enumerator = new MethodGroupExpr (mi, loc);
4513
4514                                         if (t != expr.Type) {
4515                                                 expr = Convert.ExplicitConversion (
4516                                                         ec, expr, t, loc);
4517                                                 if (expr == null)
4518                                                         throw new InternalErrorException ();
4519                                         }
4520
4521                                         get_enumerator.InstanceExpression = expr;
4522                                         get_enumerator.IsBase = t != expr.Type;
4523
4524                                         return true;
4525                                 }
4526
4527                                 return false;
4528                         }
4529
4530                         bool ProbeCollectionType (EmitContext ec, Type t)
4531                         {
4532                                 for (Type tt = t; tt != null && tt != TypeManager.object_type;){
4533                                         if (TryType (ec, tt))
4534                                                 return true;
4535                                         tt = tt.BaseType;
4536                                 }
4537
4538                                 //
4539                                 // Now try to find the method in the interfaces
4540                                 //
4541                                 while (t != null){
4542                                         Type [] ifaces = t.GetInterfaces ();
4543
4544                                         foreach (Type i in ifaces){
4545                                                 if (TryType (ec, i))
4546                                                         return true;
4547                                         }
4548
4549                                         //
4550                                         // Since TypeBuilder.GetInterfaces only returns the interface
4551                                         // types for this type, we have to keep looping, but once
4552                                         // we hit a non-TypeBuilder (ie, a Type), then we know we are
4553                                         // done, because it returns all the types
4554                                         //
4555                                         if ((t is TypeBuilder))
4556                                                 t = t.BaseType;
4557                                         else
4558                                                 break;
4559                                 }
4560
4561                                 return false;
4562                         }
4563
4564                         public override bool Resolve (EmitContext ec)
4565                         {
4566                                 enumerator_type = TypeManager.ienumerator_type;
4567                                 is_disposable = true;
4568
4569                                 if (!ProbeCollectionType (ec, expr.Type)) {
4570                                         error1579 ();
4571                                         return false;
4572                                 }
4573
4574                                 enumerator = new TemporaryVariable (enumerator_type, loc);
4575                                 enumerator.Resolve (ec);
4576
4577                                 init = new Invocation (get_enumerator, new ArrayList (), loc);
4578                                 init = init.Resolve (ec);
4579                                 if (init == null)
4580                                         return false;
4581
4582                                 Expression move_next_expr;
4583                                 {
4584                                         MemberInfo[] mi = new MemberInfo[] { move_next };
4585                                         MethodGroupExpr mg = new MethodGroupExpr (mi, loc);
4586                                         mg.InstanceExpression = enumerator;
4587
4588                                         move_next_expr = new Invocation (mg, new ArrayList (), loc);
4589                                 }
4590
4591                                 get_current.InstanceExpression = enumerator;
4592
4593                                 Statement block = new CollectionForeachStatement (
4594                                         var_type, variable, get_current, statement, loc);
4595
4596                                 loop = new While (move_next_expr, block, loc);
4597
4598                                 bool ok = true;
4599
4600                                 ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
4601                                 ec.CurrentBranching.CreateSibling ();
4602
4603                                 FlowBranchingException branching = null;
4604                                 if (is_disposable)
4605                                         branching = ec.StartFlowBranching (this);
4606
4607                                 if (!loop.Resolve (ec))
4608                                         ok = false;
4609
4610                                 if (is_disposable) {
4611                                         ResolveFinally (branching);
4612                                         ec.EndFlowBranching ();
4613                                 } else
4614                                         emit_finally = true;
4615
4616                                 ec.EndFlowBranching ();
4617
4618                                 return ok;
4619                         }
4620
4621                         protected override void DoEmit (EmitContext ec)
4622                         {
4623                                 ILGenerator ig = ec.ig;
4624
4625                                 enumerator.Store (ec, init);
4626
4627                                 //
4628                                 // Protect the code in a try/finalize block, so that
4629                                 // if the beast implement IDisposable, we get rid of it
4630                                 //
4631                                 if (is_disposable && emit_finally)
4632                                         ig.BeginExceptionBlock ();
4633
4634                                 loop.Emit (ec);
4635
4636                                 //
4637                                 // Now the finally block
4638                                 //
4639                                 if (is_disposable) {
4640                                         DoEmitFinally (ec);
4641                                         if (emit_finally)
4642                                                 ig.EndExceptionBlock ();
4643                                 }
4644                         }
4645
4646
4647                         public override void EmitFinally (EmitContext ec)
4648                         {
4649                                 ILGenerator ig = ec.ig;
4650
4651                                 if (enumerator_type.IsValueType) {
4652                                         enumerator.Emit (ec);
4653
4654                                         MethodInfo mi = FetchMethodDispose (enumerator_type);
4655                                         if (mi != null) {
4656                                                 enumerator.EmitLoadAddress (ec);
4657                                                 ig.Emit (OpCodes.Call, mi);
4658                                         } else {
4659                                                 enumerator.Emit (ec);
4660                                                 ig.Emit (OpCodes.Box, enumerator_type);
4661                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4662                                         }
4663                                 } else {
4664                                         Label call_dispose = ig.DefineLabel ();
4665
4666                                         enumerator.Emit (ec);
4667                                         ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
4668                                         ig.Emit (OpCodes.Dup);
4669                                         ig.Emit (OpCodes.Brtrue_S, call_dispose);
4670                                         ig.Emit (OpCodes.Pop);
4671
4672                                         Label end_finally = ig.DefineLabel ();
4673                                         ig.Emit (OpCodes.Br, end_finally);
4674
4675                                         ig.MarkLabel (call_dispose);
4676                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4677                                         ig.MarkLabel (end_finally);
4678                                 }
4679                         }
4680                 }
4681
4682                 protected class CollectionForeachStatement : Statement
4683                 {
4684                         Type type;
4685                         Expression variable, current, conv;
4686                         Statement statement;
4687                         Assign assign;
4688
4689                         public CollectionForeachStatement (Type type, Expression variable,
4690                                                            Expression current, Statement statement,
4691                                                            Location loc)
4692                         {
4693                                 this.type = type;
4694                                 this.variable = variable;
4695                                 this.current = current;
4696                                 this.statement = statement;
4697                                 this.loc = loc;
4698                         }
4699
4700                         public override bool Resolve (EmitContext ec)
4701                         {
4702                                 current = current.Resolve (ec);
4703                                 if (current == null)
4704                                         return false;
4705
4706                                 conv = Convert.ExplicitConversion (ec, current, type, loc);
4707                                 if (conv == null)
4708                                         return false;
4709
4710                                 assign = new Assign (variable, conv, loc);
4711                                 if (assign.Resolve (ec) == null)
4712                                         return false;
4713
4714                                 if (!statement.Resolve (ec))
4715                                         return false;
4716
4717                                 return true;
4718                         }
4719
4720                         protected override void DoEmit (EmitContext ec)
4721                         {
4722                                 assign.EmitStatement (ec);
4723                                 statement.Emit (ec);
4724                         }
4725                 }
4726         }
4727 }