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
  18 namespace Mono.CSharp {
  19
  20         using System.Collections;
  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                         Report.Debug (1, "START IF BLOCK", loc);
 143
 144                         expr = Expression.ResolveBoolean (ec, expr, loc);
 145                         if (expr == null){
 146                                 return false;
 147                         }
 148
 149                         Assign ass = expr as Assign;
 150                         if (ass != null && ass.Source is Constant) {
 151                                 Report.Warning (665, 3, loc, "Assignment in conditional expression is always constant; did you mean to use == instead of = ?");
 152                         }
 153
 154                         //
 155                         // Dead code elimination
 156                         //
 157                         if (expr is BoolConstant){
 158                                 bool take = ((BoolConstant) expr).Value;
 159
 160                                 if (take){
 161                                         if (!TrueStatement.Resolve (ec))
 162                                                 return false;
 163
 164                                         if ((FalseStatement != null) &&
 165                                             !FalseStatement.ResolveUnreachable (ec, true))
 166                                                 return false;
 167                                         FalseStatement = null;
 168                                 } else {
 169                                         if (!TrueStatement.ResolveUnreachable (ec, true))
 170                                                 return false;
 171                                         TrueStatement = null;
 172
 173                                         if ((FalseStatement != null) &&
 174                                             !FalseStatement.Resolve (ec))
 175                                                 return false;
 176                                 }
 177
 178                                 return true;
 179                         }
 180
 181                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
 182
 183                         bool ok = TrueStatement.Resolve (ec);
 184
 185                         is_true_ret = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
 186
 187                         ec.CurrentBranching.CreateSibling ();
 188
 189                         if ((FalseStatement != null) && !FalseStatement.Resolve (ec))
 190                                 ok = false;
 191
 192                         ec.EndFlowBranching ();
 193
 194                         Report.Debug (1, "END IF BLOCK", loc);
 195
 196                         return ok;
 197                 }
 198
 199                 protected override void DoEmit (EmitContext ec)
 200                 {
 201                         ILGenerator ig = ec.ig;
 202                         Label false_target = ig.DefineLabel ();
 203                         Label end;
 204
 205                         //
 206                         // If we're a boolean expression, Resolve() already
 207                         // eliminated dead code for us.
 208                         //
 209                         if (expr is BoolConstant){
 210                                 bool take = ((BoolConstant) expr).Value;
 211
 212                                 if (take)
 213                                         TrueStatement.Emit (ec);
 214                                 else if (FalseStatement != null)
 215                                         FalseStatement.Emit (ec);
 216
 217                                 return;
 218                         }
 219
 220                         expr.EmitBranchable (ec, false_target, false);
 221
 222                         TrueStatement.Emit (ec);
 223
 224                         if (FalseStatement != null){
 225                                 bool branch_emitted = false;
 226
 227                                 end = ig.DefineLabel ();
 228                                 if (!is_true_ret){
 229                                         ig.Emit (OpCodes.Br, end);
 230                                         branch_emitted = true;
 231                                 }
 232
 233                                 ig.MarkLabel (false_target);
 234                                 FalseStatement.Emit (ec);
 235
 236                                 if (branch_emitted)
 237                                         ig.MarkLabel (end);
 238                         } else {
 239                                 ig.MarkLabel (false_target);
 240                         }
 241                 }
 242         }
 243
 244         public class Do : Statement {
 245                 public Expression expr;
 246                 public readonly Statement  EmbeddedStatement;
 247                 bool infinite;
 248
 249                 public Do (Statement statement, Expression boolExpr, Location l)
 250                 {
 251                         expr = boolExpr;
 252                         EmbeddedStatement = statement;
 253                         loc = l;
 254                 }
 255
 256                 public override bool Resolve (EmitContext ec)
 257                 {
 258                         bool ok = true;
 259
 260                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 261
 262                         if (!EmbeddedStatement.Resolve (ec))
 263                                 ok = false;
 264
 265                         expr = Expression.ResolveBoolean (ec, expr, loc);
 266                         if (expr == null)
 267                                 ok = false;
 268                         else if (expr is BoolConstant){
 269                                 bool res = ((BoolConstant) expr).Value;
 270
 271                                 if (res)
 272                                         infinite = true;
 273                         }
 274
 275                         ec.CurrentBranching.Infinite = infinite;
 276                         ec.EndFlowBranching ();
 277
 278                         return ok;
 279                 }
 280
 281                 protected override void DoEmit (EmitContext ec)
 282                 {
 283                         ILGenerator ig = ec.ig;
 284                         Label loop = ig.DefineLabel ();
 285                         Label old_begin = ec.LoopBegin;
 286                         Label old_end = ec.LoopEnd;
 287
 288                         ec.LoopBegin = ig.DefineLabel ();
 289                         ec.LoopEnd = ig.DefineLabel ();
 290
 291                         ig.MarkLabel (loop);
 292                         EmbeddedStatement.Emit (ec);
 293                         ig.MarkLabel (ec.LoopBegin);
 294
 295                         //
 296                         // Dead code elimination
 297                         //
 298                         if (expr is BoolConstant){
 299                                 bool res = ((BoolConstant) expr).Value;
 300
 301                                 if (res)
 302                                         ec.ig.Emit (OpCodes.Br, loop);
 303                         } else
 304                                 expr.EmitBranchable (ec, loop, true);
 305
 306                         ig.MarkLabel (ec.LoopEnd);
 307
 308                         ec.LoopBegin = old_begin;
 309                         ec.LoopEnd = old_end;
 310                 }
 311         }
 312
 313         public class While : Statement {
 314                 public Expression expr;
 315                 public readonly Statement Statement;
 316                 bool infinite, empty;
 317
 318                 public While (Expression boolExpr, Statement statement, Location l)
 319                 {
 320                         this.expr = boolExpr;
 321                         Statement = statement;
 322                         loc = l;
 323                 }
 324
 325                 public override bool Resolve (EmitContext ec)
 326                 {
 327                         bool ok = true;
 328
 329                         expr = Expression.ResolveBoolean (ec, expr, loc);
 330                         if (expr == null)
 331                                 return false;
 332
 333                         //
 334                         // Inform whether we are infinite or not
 335                         //
 336                         if (expr is BoolConstant){
 337                                 BoolConstant bc = (BoolConstant) expr;
 338
 339                                 if (bc.Value == false){
 340                                         if (!Statement.ResolveUnreachable (ec, true))
 341                                                 return false;
 342                                         empty = true;
 343                                         return true;
 344                                 } else
 345                                         infinite = true;
 346                         }
 347
 348                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 349
 350                         if (!Statement.Resolve (ec))
 351                                 ok = false;
 352
 353                         ec.CurrentBranching.Infinite = infinite;
 354                         ec.EndFlowBranching ();
 355
 356                         return ok;
 357                 }
 358
 359                 protected override void DoEmit (EmitContext ec)
 360                 {
 361                         if (empty)
 362                                 return;
 363
 364                         ILGenerator ig = ec.ig;
 365                         Label old_begin = ec.LoopBegin;
 366                         Label old_end = ec.LoopEnd;
 367
 368                         ec.LoopBegin = ig.DefineLabel ();
 369                         ec.LoopEnd = ig.DefineLabel ();
 370
 371                         //
 372                         // Inform whether we are infinite or not
 373                         //
 374                         if (expr is BoolConstant){
 375                                 ig.MarkLabel (ec.LoopBegin);
 376                                 Statement.Emit (ec);
 377                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 378
 379                                 //
 380                                 // Inform that we are infinite (ie, `we return'), only
 381                                 // if we do not `break' inside the code.
 382                                 //
 383                                 ig.MarkLabel (ec.LoopEnd);
 384                         } else {
 385                                 Label while_loop = ig.DefineLabel ();
 386
 387                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 388                                 ig.MarkLabel (while_loop);
 389
 390                                 Statement.Emit (ec);
 391
 392                                 ig.MarkLabel (ec.LoopBegin);
 393
 394                                 expr.EmitBranchable (ec, while_loop, true);
 395
 396                                 ig.MarkLabel (ec.LoopEnd);
 397                         }
 398
 399                         ec.LoopBegin = old_begin;
 400                         ec.LoopEnd = old_end;
 401                 }
 402         }
 403
 404         public class For : Statement {
 405                 Expression Test;
 406                 readonly Statement InitStatement;
 407                 readonly Statement Increment;
 408                 readonly Statement Statement;
 409                 bool infinite, empty;
 410
 411                 public For (Statement initStatement,
 412                             Expression test,
 413                             Statement increment,
 414                             Statement statement,
 415                             Location l)
 416                 {
 417                         InitStatement = initStatement;
 418                         Test = test;
 419                         Increment = increment;
 420                         Statement = statement;
 421                         loc = l;
 422                 }
 423
 424                 public override bool Resolve (EmitContext ec)
 425                 {
 426                         bool ok = true;
 427
 428                         if (InitStatement != null){
 429                                 if (!InitStatement.Resolve (ec))
 430                                         ok = false;
 431                         }
 432
 433                         if (Test != null){
 434                                 Test = Expression.ResolveBoolean (ec, Test, loc);
 435                                 if (Test == null)
 436                                         ok = false;
 437                                 else if (Test is BoolConstant){
 438                                         BoolConstant bc = (BoolConstant) Test;
 439
 440                                         if (bc.Value == false){
 441                                                 if (!Statement.ResolveUnreachable (ec, true))
 442                                                         return false;
 443                                                 if ((Increment != null) &&
 444                                                     !Increment.ResolveUnreachable (ec, false))
 445                                                         return false;
 446                                                 empty = true;
 447                                                 return true;
 448                                         } else
 449                                                 infinite = true;
 450                                 }
 451                         } else
 452                                 infinite = true;
 453
 454                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 455                         if (!infinite)
 456                                 ec.CurrentBranching.CreateSibling ();
 457
 458                         if (!Statement.Resolve (ec))
 459                                 ok = false;
 460
 461                         if (Increment != null){
 462                                 if (!Increment.Resolve (ec))
 463                                         ok = false;
 464                         }
 465
 466                         ec.CurrentBranching.Infinite = infinite;
 467                         ec.EndFlowBranching ();
 468
 469                         return ok;
 470                 }
 471
 472                 protected override void DoEmit (EmitContext ec)
 473                 {
 474                         if (empty)
 475                                 return;
 476
 477                         ILGenerator ig = ec.ig;
 478                         Label old_begin = ec.LoopBegin;
 479                         Label old_end = ec.LoopEnd;
 480                         Label loop = ig.DefineLabel ();
 481                         Label test = ig.DefineLabel ();
 482
 483                         if (InitStatement != null && InitStatement != EmptyStatement.Value)
 484                                 InitStatement.Emit (ec);
 485
 486                         ec.LoopBegin = ig.DefineLabel ();
 487                         ec.LoopEnd = ig.DefineLabel ();
 488
 489                         ig.Emit (OpCodes.Br, test);
 490                         ig.MarkLabel (loop);
 491                         Statement.Emit (ec);
 492
 493                         ig.MarkLabel (ec.LoopBegin);
 494                         if (Increment != EmptyStatement.Value)
 495                                 Increment.Emit (ec);
 496
 497                         ig.MarkLabel (test);
 498                         //
 499                         // If test is null, there is no test, and we are just
 500                         // an infinite loop
 501                         //
 502                         if (Test != null){
 503                                 //
 504                                 // The Resolve code already catches the case for
 505                                 // Test == BoolConstant (false) so we know that
 506                                 // this is true
 507                                 //
 508                                 if (Test is BoolConstant)
 509                                         ig.Emit (OpCodes.Br, loop);
 510                                 else
 511                                         Test.EmitBranchable (ec, loop, true);
 512
 513                         } else
 514                                 ig.Emit (OpCodes.Br, loop);
 515                         ig.MarkLabel (ec.LoopEnd);
 516
 517                         ec.LoopBegin = old_begin;
 518                         ec.LoopEnd = old_end;
 519                 }
 520         }
 521
 522         public class StatementExpression : Statement {
 523                 ExpressionStatement expr;
 524
 525                 public StatementExpression (ExpressionStatement expr, Location l)
 526                 {
 527                         this.expr = expr;
 528                         loc = l;
 529                 }
 530
 531                 public override bool Resolve (EmitContext ec)
 532                 {
 533                         expr = expr.ResolveStatement (ec);
 534                         return expr != null;
 535                 }
 536
 537                 protected override void DoEmit (EmitContext ec)
 538                 {
 539                         expr.EmitStatement (ec);
 540                 }
 541
 542                 public override string ToString ()
 543                 {
 544                         return "StatementExpression (" + expr + ")";
 545                 }
 546         }
 547
 548         /// <summary>
 549         ///   Implements the return statement
 550         /// </summary>
 551         public class Return : Statement {
 552                 public Expression Expr;
 553
 554                 public Return (Expression expr, Location l)
 555                 {
 556                         Expr = expr;
 557                         loc = l;
 558                 }
 559
 560                 bool in_exc;
 561
 562                 public override bool Resolve (EmitContext ec)
 563                 {
 564                         if (ec.ReturnType == null){
 565                                 if (Expr != null){
 566                                         if (ec.CurrentAnonymousMethod != null){
 567                                                 Report.Error (1662, loc, String.Format (
 568                                                         "Anonymous method could not be converted to delegate " +
 569                                                         "since the return value does not match the delegate value"));
 570                                         }
 571                                         Error (127, "Return with a value not allowed here");
 572                                         return false;
 573                                 }
 574                         } else {
 575                                 if (Expr == null){
 576                                         Error (126, "An object of type `{0}' is expected " +
 577                                                "for the return statement",
 578                                                TypeManager.CSharpName (ec.ReturnType));
 579                                         return false;
 580                                 }
 581
 582                                 Expr = Expr.Resolve (ec);
 583                                 if (Expr == null)
 584                                         return false;
 585
 586                                 if (Expr.Type != ec.ReturnType) {
 587                                         Expr = Convert.ImplicitConversionRequired (
 588                                                 ec, Expr, ec.ReturnType, loc);
 589                                         if (Expr == null)
 590                                                 return false;
 591                                 }
 592                         }
 593
 594                         if (ec.InIterator){
 595                                 Error (-206, "Return statement not allowed inside iterators");
 596                                 return false;
 597                         }
 598
 599                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
 600
 601                         if (ec.CurrentBranching.InTryOrCatch (true)) {
 602                                 ec.CurrentBranching.AddFinallyVector (vector);
 603                                 in_exc = true;
 604                         } else if (ec.CurrentBranching.InFinally (true)) {
 605                                 Error (157, "Control can not leave the body of the finally block");
 606                                 return false;
 607                         } else
 608                                 vector.CheckOutParameters (ec.CurrentBranching);
 609
 610                         if (in_exc)
 611                                 ec.NeedReturnLabel ();
 612
 613                         ec.CurrentBranching.CurrentUsageVector.Return ();
 614                         return true;
 615                 }
 616
 617                 protected override void DoEmit (EmitContext ec)
 618                 {
 619                         if (Expr != null) {
 620                                 Expr.Emit (ec);
 621
 622                                 if (in_exc)
 623                                         ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 624                         }
 625
 626                         if (in_exc)
 627                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 628                         else
 629                                 ec.ig.Emit (OpCodes.Ret);
 630                 }
 631         }
 632
 633         public class Goto : Statement {
 634                 string target;
 635                 Block block;
 636                 LabeledStatement label;
 637
 638                 public override bool Resolve (EmitContext ec)
 639                 {
 640                         label = ec.CurrentBranching.LookupLabel (target, loc);
 641                         if (label == null)
 642                                 return false;
 643
 644                         // If this is a forward goto.
 645                         if (!label.IsDefined)
 646                                 label.AddUsageVector (ec.CurrentBranching.CurrentUsageVector);
 647
 648                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 649
 650                         return true;
 651                 }
 652
 653                 public Goto (Block parent_block, string label, Location l)
 654                 {
 655                         block = parent_block;
 656                         loc = l;
 657                         target = label;
 658                 }
 659
 660                 public string Target {
 661                         get {
 662                                 return target;
 663                         }
 664                 }
 665
 666                 protected override void DoEmit (EmitContext ec)
 667                 {
 668                         Label l = label.LabelTarget (ec);
 669                         ec.ig.Emit (OpCodes.Br, l);
 670                 }
 671         }
 672
 673         public class LabeledStatement : Statement {
 674                 public readonly Location Location;
 675                 bool defined;
 676                 bool referenced;
 677                 Label label;
 678                 ILGenerator ig;
 679
 680                 FlowBranching.UsageVector vectors;
 681
 682                 public LabeledStatement (string label_name, Location l)
 683                 {
 684                         this.Location = l;
 685                 }
 686
 687                 public Label LabelTarget (EmitContext ec)
 688                 {
 689                         if (defined)
 690                                 return label;
 691                         ig = ec.ig;
 692                         label = ec.ig.DefineLabel ();
 693                         defined = true;
 694
 695                         return label;
 696                 }
 697
 698                 public bool IsDefined {
 699                         get {
 700                                 return defined;
 701                         }
 702                 }
 703
 704                 public bool HasBeenReferenced {
 705                         get {
 706                                 return referenced;
 707                         }
 708                 }
 709
 710                 public void AddUsageVector (FlowBranching.UsageVector vector)
 711                 {
 712                         vector = vector.Clone ();
 713                         vector.Next = vectors;
 714                         vectors = vector;
 715                 }
 716
 717                 public override bool Resolve (EmitContext ec)
 718                 {
 719                         ec.CurrentBranching.Label (vectors);
 720
 721                         referenced = true;
 722
 723                         return true;
 724                 }
 725
 726                 protected override void DoEmit (EmitContext ec)
 727                 {
 728                         if (ig != null && ig != ec.ig) {
 729                                 Report.Error (1632, "Control cannot leave body of anonymous method");
 730                                 return;
 731                         }
 732                         LabelTarget (ec);
 733                         ec.ig.MarkLabel (label);
 734                 }
 735         }
 736
 737
 738         /// <summary>
 739         ///   `goto default' statement
 740         /// </summary>
 741         public class GotoDefault : Statement {
 742
 743                 public GotoDefault (Location l)
 744                 {
 745                         loc = l;
 746                 }
 747
 748                 public override bool Resolve (EmitContext ec)
 749                 {
 750                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 751                         return true;
 752                 }
 753
 754                 protected override void DoEmit (EmitContext ec)
 755                 {
 756                         if (ec.Switch == null){
 757                                 Report.Error (153, loc, "goto default is only valid in a switch statement");
 758                                 return;
 759                         }
 760
 761                         if (!ec.Switch.GotDefault){
 762                                 Report.Error (159, loc, "No default target on switch statement");
 763                                 return;
 764                         }
 765                         ec.ig.Emit (OpCodes.Br, ec.Switch.DefaultTarget);
 766                 }
 767         }
 768
 769         /// <summary>
 770         ///   `goto case' statement
 771         /// </summary>
 772         public class GotoCase : Statement {
 773                 Expression expr;
 774                 SwitchLabel sl;
 775
 776                 public GotoCase (Expression e, Location l)
 777                 {
 778                         expr = e;
 779                         loc = l;
 780                 }
 781
 782                 public override bool Resolve (EmitContext ec)
 783                 {
 784                         if (ec.Switch == null){
 785                                 Report.Error (153, loc, "goto case is only valid in a switch statement");
 786                                 return false;
 787                         }
 788
 789                         expr = expr.Resolve (ec);
 790                         if (expr == null)
 791                                 return false;
 792
 793                         if (!(expr is Constant)){
 794                                 Report.Error (159, loc, "Target expression for goto case is not constant");
 795                                 return false;
 796                         }
 797
 798                         object val = Expression.ConvertIntLiteral (
 799                                 (Constant) expr, ec.Switch.SwitchType, loc);
 800
 801                         if (val == null)
 802                                 return false;
 803
 804                         sl = (SwitchLabel) ec.Switch.Elements [val];
 805
 806                         if (sl == null){
 807                                 Report.Error (
 808                                         159, loc,
 809                                         "No such label 'case " + val + "': for the goto case");
 810                                 return false;
 811                         }
 812
 813                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 814                         return true;
 815                 }
 816
 817                 protected override void DoEmit (EmitContext ec)
 818                 {
 819                         ec.ig.Emit (OpCodes.Br, sl.GetILLabelCode (ec));
 820                 }
 821         }
 822
 823         public class Throw : Statement {
 824                 Expression expr;
 825
 826                 public Throw (Expression expr, Location l)
 827                 {
 828                         this.expr = expr;
 829                         loc = l;
 830                 }
 831
 832                 public override bool Resolve (EmitContext ec)
 833                 {
 834                         ec.CurrentBranching.CurrentUsageVector.Throw ();
 835
 836                         if (expr != null){
 837                                 expr = expr.Resolve (ec);
 838                                 if (expr == null)
 839                                         return false;
 840
 841                                 ExprClass eclass = expr.eclass;
 842
 843                                 if (!(eclass == ExprClass.Variable || eclass == ExprClass.PropertyAccess ||
 844                                         eclass == ExprClass.Value || eclass == ExprClass.IndexerAccess)) {
 845                                         expr.Error_UnexpectedKind ("value, variable, property or indexer access ", loc);
 846                                         return false;
 847                                 }
 848
 849                                 Type t = expr.Type;
 850
 851                                 if ((t != TypeManager.exception_type) &&
 852                                         !t.IsSubclassOf (TypeManager.exception_type) &&
 853                                         !(expr is NullLiteral)) {
 854                                         Error (155,
 855                                                 "The type caught or thrown must be derived " +
 856                                                 "from System.Exception");
 857                                         return false;
 858                                 }
 859                                 return true;
 860                         }
 861
 862                         if (ec.CurrentBranching.InFinally (true)) {
 863                                 Error (724, "A throw statement with no argument is only allowed in a catch clause nested inside of the innermost catch clause");
 864                                 return false;
 865                         }
 866
 867                         if (!ec.CurrentBranching.InCatch ()) {
 868                                 Error (156, "A throw statement with no argument is only allowed in a catch clause");
 869                                 return false;
 870                         }
 871                         return true;
 872                 }
 873
 874                 protected override void DoEmit (EmitContext ec)
 875                 {
 876                         if (expr == null)
 877                                 ec.ig.Emit (OpCodes.Rethrow);
 878                         else {
 879                                 expr.Emit (ec);
 880
 881                                 ec.ig.Emit (OpCodes.Throw);
 882                         }
 883                 }
 884         }
 885
 886         public class Break : Statement {
 887
 888                 public Break (Location l)
 889                 {
 890                         loc = l;
 891                 }
 892
 893                 bool crossing_exc;
 894
 895                 public override bool Resolve (EmitContext ec)
 896                 {
 897                         if (!ec.CurrentBranching.InLoop () && !ec.CurrentBranching.InSwitch ()){
 898                                 Error (139, "No enclosing loop or switch to continue to");
 899                                 return false;
 900                         } else if (ec.CurrentBranching.InFinally (false)) {
 901                                 Error (157, "Control can not leave the body of the finally block");
 902                                 return false;
 903                         } else if (ec.CurrentBranching.InTryOrCatch (false))
 904                                 ec.CurrentBranching.AddFinallyVector (
 905                                         ec.CurrentBranching.CurrentUsageVector);
 906                         else if (ec.CurrentBranching.InLoop ())
 907                                 ec.CurrentBranching.AddBreakVector (
 908                                         ec.CurrentBranching.CurrentUsageVector);
 909
 910                         crossing_exc = ec.CurrentBranching.BreakCrossesTryCatchBoundary ();
 911
 912                         if (!crossing_exc)
 913                                 ec.NeedReturnLabel ();
 914
 915                         ec.CurrentBranching.CurrentUsageVector.Break ();
 916                         return true;
 917                 }
 918
 919                 protected override void DoEmit (EmitContext ec)
 920                 {
 921                         ILGenerator ig = ec.ig;
 922
 923                         if (crossing_exc)
 924                                 ig.Emit (OpCodes.Leave, ec.LoopEnd);
 925                         else {
 926                                 ig.Emit (OpCodes.Br, ec.LoopEnd);
 927                         }
 928                 }
 929         }
 930
 931         public class Continue : Statement {
 932
 933                 public Continue (Location l)
 934                 {
 935                         loc = l;
 936                 }
 937
 938                 bool crossing_exc;
 939
 940                 public override bool Resolve (EmitContext ec)
 941                 {
 942                         if (!ec.CurrentBranching.InLoop () && !ec.CurrentBranching.InSwitch ()){
 943                                 Error (139, "No enclosing loop to continue to");
 944                                 return false;
 945                         } else if (ec.CurrentBranching.InFinally (false)) {
 946                                 Error (157, "Control can not leave the body of the finally block");
 947                                 return false;
 948                         } else if (ec.CurrentBranching.InTryOrCatch (false))
 949                                 ec.CurrentBranching.AddFinallyVector (ec.CurrentBranching.CurrentUsageVector);
 950
 951                         crossing_exc = ec.CurrentBranching.BreakCrossesTryCatchBoundary ();
 952
 953                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 954                         return true;
 955                 }
 956
 957                 protected override void DoEmit (EmitContext ec)
 958                 {
 959                         Label begin = ec.LoopBegin;
 960
 961                         if (crossing_exc)
 962                                 ec.ig.Emit (OpCodes.Leave, begin);
 963                         else
 964                                 ec.ig.Emit (OpCodes.Br, begin);
 965                 }
 966         }
 967
 968         //
 969         // The information about a user-perceived local variable
 970         //
 971         public class LocalInfo {
 972                 public Expression Type;
 973
 974                 //
 975                 // Most of the time a variable will be stored in a LocalBuilder
 976                 //
 977                 // But sometimes, it will be stored in a field (variables that have been
 978                 // hoisted by iterators or by anonymous methods).  The context of the field will
 979                 // be stored in the EmitContext
 980                 //
 981                 //
 982                 public LocalBuilder LocalBuilder;
 983                 public FieldBuilder FieldBuilder;
 984
 985                 public Type VariableType;
 986                 public readonly string Name;
 987                 public readonly Location Location;
 988                 public readonly Block Block;
 989
 990                 public VariableInfo VariableInfo;
 991
 992                 enum Flags : byte {
 993                         Used = 1,
 994                         ReadOnly = 2,
 995                         Pinned = 4,
 996                         IsThis = 8,
 997                         Captured = 16,
 998                         AddressTaken = 32
 999                 }
1000
1001                 Flags flags;
1002
1003                 public LocalInfo (Expression type, string name, Block block, Location l)
1004                 {
1005                         Type = type;
1006                         Name = name;
1007                         Block = block;
1008                         Location = l;
1009                 }
1010
1011                 public LocalInfo (TypeContainer tc, Block block, Location l)
1012                 {
1013                         VariableType = tc.TypeBuilder;
1014                         Block = block;
1015                         Location = l;
1016                 }
1017
1018                 public bool IsThisAssigned (EmitContext ec, Location loc)
1019                 {
1020                         if (VariableInfo == null)
1021                                 throw new Exception ();
1022
1023                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo))
1024                                 return true;
1025
1026                         return VariableInfo.TypeInfo.IsFullyInitialized (ec.CurrentBranching, VariableInfo, loc);
1027                 }
1028
1029                 public bool IsAssigned (EmitContext ec)
1030                 {
1031                         if (VariableInfo == null)
1032                                 throw new Exception ();
1033
1034                         return !ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo);
1035                 }
1036
1037                 public bool Resolve (EmitContext ec)
1038                 {
1039                         if (VariableType == null) {
1040                                 TypeExpr texpr = Type.ResolveAsTypeTerminal (ec, false);
1041                                 if (texpr == null)
1042                                         return false;
1043
1044                                 VariableType = texpr.ResolveType (ec);
1045                         }
1046
1047                         if (VariableType == TypeManager.void_type) {
1048                                 Report.Error (1547, Location,
1049                                               "Keyword 'void' cannot be used in this context");
1050                                 return false;
1051                         }
1052
1053                         if (VariableType.IsAbstract && VariableType.IsSealed) {
1054                                 Report.Error (723, Location, "Cannot declare variable of static type '{0}'", TypeManager.CSharpName (VariableType));
1055                                 return false;
1056                         }
1057 // TODO: breaks the build
1058 //                      if (VariableType.IsPointer && !ec.InUnsafe)
1059 //                              Expression.UnsafeError (Location);
1060
1061                         return true;
1062                 }
1063
1064                 //
1065                 // Whether the variable is Fixed (because its Pinned or its a value type)
1066                 //
1067                 public bool IsFixed {
1068                         get {
1069                                 if (((flags & Flags.Pinned) != 0) || TypeManager.IsValueType (VariableType))
1070                                         return true;
1071
1072                                 return false;
1073                         }
1074                 }
1075
1076                 public bool IsCaptured {
1077                         get {
1078                                 return (flags & Flags.Captured) != 0;
1079                         }
1080
1081                         set {
1082                                 flags |= Flags.Captured;
1083                         }
1084                 }
1085
1086                 public bool AddressTaken {
1087                         get {
1088                                 return (flags & Flags.AddressTaken) != 0;
1089                         }
1090
1091                         set {
1092                                 flags |= Flags.AddressTaken;
1093                         }
1094                 }
1095
1096                 public override string ToString ()
1097                 {
1098                         return String.Format ("LocalInfo ({0},{1},{2},{3})",
1099                                               Name, Type, VariableInfo, Location);
1100                 }
1101
1102                 public bool Used {
1103                         get {
1104                                 return (flags & Flags.Used) != 0;
1105                         }
1106                         set {
1107                                 flags = value ? (flags | Flags.Used) : (unchecked (flags & ~Flags.Used));
1108                         }
1109                 }
1110
1111                 public bool ReadOnly {
1112                         get {
1113                                 return (flags & Flags.ReadOnly) != 0;
1114                         }
1115                         set {
1116                                 flags = value ? (flags | Flags.ReadOnly) : (unchecked (flags & ~Flags.ReadOnly));
1117                         }
1118                 }
1119
1120                 //
1121                 // Whether the variable is pinned, if Pinned the variable has been
1122                 // allocated in a pinned slot with DeclareLocal.
1123                 //
1124                 public bool Pinned {
1125                         get {
1126                                 return (flags & Flags.Pinned) != 0;
1127                         }
1128                         set {
1129                                 flags = value ? (flags | Flags.Pinned) : (flags & ~Flags.Pinned);
1130                         }
1131                 }
1132
1133                 public bool IsThis {
1134                         get {
1135                                 return (flags & Flags.IsThis) != 0;
1136                         }
1137                         set {
1138                                 flags = value ? (flags | Flags.IsThis) : (flags & ~Flags.IsThis);
1139                         }
1140                 }
1141         }
1142
1143         /// <summary>
1144         ///   Block represents a C# block.
1145         /// </summary>
1146         ///
1147         /// <remarks>
1148         ///   This class is used in a number of places: either to represent
1149         ///   explicit blocks that the programmer places or implicit blocks.
1150         ///
1151         ///   Implicit blocks are used as labels or to introduce variable
1152         ///   declarations.
1153         ///
1154         ///   Top-level blocks derive from Block, and they are called ToplevelBlock
1155         ///   they contain extra information that is not necessary on normal blocks.
1156         /// </remarks>
1157         public class Block : Statement {
1158                 public Block    Parent;
1159                 public readonly Location  StartLocation;
1160                 public Location EndLocation = Location.Null;
1161
1162                 [Flags]
1163                 public enum Flags {
1164                         Implicit  = 1,
1165                         Unchecked = 2,
1166                         BlockUsed = 4,
1167                         VariablesInitialized = 8,
1168                         HasRet = 16,
1169                         IsDestructor = 32,
1170                         HasVarargs = 64,
1171                         IsToplevel = 128,
1172                         Unsafe = 256
1173                 }
1174                 Flags flags;
1175
1176                 public bool Implicit {
1177                         get {
1178                                 return (flags & Flags.Implicit) != 0;
1179                         }
1180                 }
1181
1182                 public bool Unchecked {
1183                         get {
1184                                 return (flags & Flags.Unchecked) != 0;
1185                         }
1186                         set {
1187                                 flags |= Flags.Unchecked;
1188                         }
1189                 }
1190
1191                 public bool Unsafe {
1192                         get {
1193                                 return (flags & Flags.Unsafe) != 0;
1194                         }
1195                         set {
1196                                 flags |= Flags.Unsafe;
1197                         }
1198                 }
1199
1200                 public bool HasVarargs {
1201                         get {
1202                                 if (Parent != null)
1203                                         return Parent.HasVarargs;
1204                                 else
1205                                         return (flags & Flags.HasVarargs) != 0;
1206                         }
1207                         set {
1208                                 flags |= Flags.HasVarargs;
1209                         }
1210                 }
1211
1212                 //
1213                 // The statements in this block
1214                 //
1215                 ArrayList statements;
1216                 int num_statements;
1217
1218                 //
1219                 // An array of Blocks.  We keep track of children just
1220                 // to generate the local variable declarations.
1221                 //
1222                 // Statements and child statements are handled through the
1223                 // statements.
1224                 //
1225                 ArrayList children;
1226
1227                 //
1228                 // Labels.  (label, block) pairs.
1229                 //
1230                 Hashtable labels;
1231
1232                 //
1233                 // Keeps track of (name, type) pairs
1234                 //
1235                 Hashtable variables;
1236
1237                 //
1238                 // Keeps track of constants
1239                 Hashtable constants;
1240
1241                 //
1242                 // The parameters for the block, this is only needed on the toplevel block really
1243                 // TODO: move `parameters' into ToplevelBlock
1244                 Parameters parameters;
1245
1246                 //
1247                 // If this is a switch section, the enclosing switch block.
1248                 //
1249                 Block switch_block;
1250
1251                 protected static int id;
1252
1253                 int this_id;
1254
1255                 public Block (Block parent)
1256                         : this (parent, (Flags) 0, Location.Null, Location.Null)
1257                 { }
1258
1259                 public Block (Block parent, Flags flags)
1260                         : this (parent, flags, Location.Null, Location.Null)
1261                 { }
1262
1263                 public Block (Block parent, Flags flags, Parameters parameters)
1264                         : this (parent, flags, parameters, Location.Null, Location.Null)
1265                 { }
1266
1267                 public Block (Block parent, Location start, Location end)
1268                         : this (parent, (Flags) 0, start, end)
1269                 { }
1270
1271                 public Block (Block parent, Parameters parameters, Location start, Location end)
1272                         : this (parent, (Flags) 0, parameters, start, end)
1273                 { }
1274
1275                 public Block (Block parent, Flags flags, Location start, Location end)
1276                         : this (parent, flags, Parameters.EmptyReadOnlyParameters, start, end)
1277                 { }
1278
1279                 public Block (Block parent, Flags flags, Parameters parameters,
1280                               Location start, Location end)
1281                 {
1282                         if (parent != null)
1283                                 parent.AddChild (this);
1284
1285                         this.Parent = parent;
1286                         this.flags = flags;
1287                         this.parameters = parameters;
1288                         this.StartLocation = start;
1289                         this.EndLocation = end;
1290                         this.loc = start;
1291                         this_id = id++;
1292                         statements = new ArrayList ();
1293
1294                         if (parent != null && Implicit) {
1295                                 if (parent.child_variable_names == null)
1296                                         parent.child_variable_names = new Hashtable();
1297                                 // share with parent
1298                                 child_variable_names = parent.child_variable_names;
1299                         }
1300
1301                 }
1302
1303                 public Block CreateSwitchBlock (Location start)
1304                 {
1305                         Block new_block = new Block (this, start, start);
1306                         new_block.switch_block = this;
1307                         return new_block;
1308                 }
1309
1310                 public int ID {
1311                         get {
1312                                 return this_id;
1313                         }
1314                 }
1315
1316                 void AddChild (Block b)
1317                 {
1318                         if (children == null)
1319                                 children = new ArrayList ();
1320
1321                         children.Add (b);
1322                 }
1323
1324                 public void SetEndLocation (Location loc)
1325                 {
1326                         EndLocation = loc;
1327                 }
1328
1329                 /// <summary>
1330                 ///   Adds a label to the current block.
1331                 /// </summary>
1332                 ///
1333                 /// <returns>
1334                 ///   false if the name already exists in this block. true
1335                 ///   otherwise.
1336                 /// </returns>
1337                 ///
1338                 public bool AddLabel (string name, LabeledStatement target, Location loc)
1339                 {
1340                         if (switch_block != null)
1341                                 return switch_block.AddLabel (name, target, loc);
1342
1343                         Block cur = this;
1344                         while (cur != null) {
1345                                 if (cur.DoLookupLabel (name) != null) {
1346                                         Report.Error (
1347                                                 140, loc, "The label '{0}' is a duplicate",
1348                                                 name);
1349                                         return false;
1350                                 }
1351
1352                                 if (!Implicit)
1353                                         break;
1354
1355                                 cur = cur.Parent;
1356                         }
1357
1358                         while (cur != null) {
1359                                 if (cur.DoLookupLabel (name) != null) {
1360                                         Report.Error (
1361                                                 158, loc,
1362                                                 "The label '{0}' shadows another label " +
1363                                                 "by the same name in a containing scope.",
1364                                                 name);
1365                                         return false;
1366                                 }
1367
1368                                 if (children != null) {
1369                                         foreach (Block b in children) {
1370                                                 LabeledStatement s = b.DoLookupLabel (name);
1371                                                 if (s == null)
1372                                                         continue;
1373
1374                                                 Report.Error (
1375                                                         158, s.Location,
1376                                                         "The label '{0}' shadows another " +
1377                                                         "label by the same name in a " +
1378                                                         "containing scope.",
1379                                                         name);
1380                                                 return false;
1381                                         }
1382                                 }
1383
1384
1385                                 cur = cur.Parent;
1386                         }
1387
1388                         if (labels == null)
1389                                 labels = new Hashtable ();
1390
1391                         labels.Add (name, target);
1392                         return true;
1393                 }
1394
1395                 public LabeledStatement LookupLabel (string name)
1396                 {
1397                         LabeledStatement s = DoLookupLabel (name);
1398                         if (s != null)
1399                                 return s;
1400
1401                         if (children == null)
1402                                 return null;
1403
1404                         foreach (Block child in children) {
1405                                 if (!child.Implicit)
1406                                         continue;
1407
1408                                 s = child.LookupLabel (name);
1409                                 if (s != null)
1410                                         return s;
1411                         }
1412
1413                         return null;
1414                 }
1415
1416                 LabeledStatement DoLookupLabel (string name)
1417                 {
1418                         if (switch_block != null)
1419                                 return switch_block.LookupLabel (name);
1420
1421                         if (labels != null)
1422                                 if (labels.Contains (name))
1423                                         return ((LabeledStatement) labels [name]);
1424
1425                         return null;
1426                 }
1427
1428                 LocalInfo this_variable = null;
1429
1430                 // <summary>
1431                 //   Returns the "this" instance variable of this block.
1432                 //   See AddThisVariable() for more information.
1433                 // </summary>
1434                 public LocalInfo ThisVariable {
1435                         get {
1436                                 for (Block b = this; b != null; b = b.Parent) {
1437                                         if (b.this_variable != null)
1438                                                 return b.this_variable;
1439                                 }
1440
1441                                 return null;
1442                         }
1443                 }
1444
1445                 Hashtable child_variable_names;
1446
1447                 // <summary>
1448                 //   Marks a variable with name @name as being used in a child block.
1449                 //   If a variable name has been used in a child block, it's illegal to
1450                 //   declare a variable with the same name in the current block.
1451                 // </summary>
1452                 public void AddChildVariableName (string name)
1453                 {
1454                         if (child_variable_names == null)
1455                                 child_variable_names = new Hashtable ();
1456
1457                         child_variable_names [name] = null;
1458                 }
1459
1460                 // <summary>
1461                 //   Checks whether a variable name has already been used in a child block.
1462                 // </summary>
1463                 public bool IsVariableNameUsedInChildBlock (string name)
1464                 {
1465                         if (child_variable_names == null)
1466                                 return false;
1467
1468                         return child_variable_names.Contains (name);
1469                 }
1470
1471                 // <summary>
1472                 //   This is used by non-static `struct' constructors which do not have an
1473                 //   initializer - in this case, the constructor must initialize all of the
1474                 //   struct's fields.  To do this, we add a "this" variable and use the flow
1475                 //   analysis code to ensure that it's been fully initialized before control
1476                 //   leaves the constructor.
1477                 // </summary>
1478                 public LocalInfo AddThisVariable (TypeContainer tc, Location l)
1479                 {
1480                         if (this_variable != null)
1481                                 return this_variable;
1482
1483                         if (variables == null)
1484                                 variables = new Hashtable ();
1485
1486                         this_variable = new LocalInfo (tc, this, l);
1487                         this_variable.Used = true;
1488                         this_variable.IsThis = true;
1489
1490                         variables.Add ("this", this_variable);
1491
1492                         return this_variable;
1493                 }
1494
1495                 public LocalInfo AddVariable (Expression type, string name, Parameters pars, Location l)
1496                 {
1497                         if (variables == null)
1498                                 variables = new Hashtable ();
1499
1500                         LocalInfo vi = GetLocalInfo (name);
1501                         if (vi != null) {
1502                                 if (vi.Block != this)
1503                                         Report.Error (136, l, "A local variable named `" + name + "' " +
1504                                                       "cannot be declared in this scope since it would " +
1505                                                       "give a different meaning to `" + name + "', which " +
1506                                                       "is already used in a `parent or current' scope to " +
1507                                                       "denote something else");
1508                                 else
1509                                         Report.Error (128, l, "A local variable `" + name + "' is already " +
1510                                                       "defined in this scope");
1511                                 return null;
1512                         }
1513
1514                         if (IsVariableNameUsedInChildBlock (name)) {
1515                                 Report.Error (136, l, "A local variable named `" + name + "' " +
1516                                               "cannot be declared in this scope since it would " +
1517                                               "give a different meaning to `" + name + "', which " +
1518                                               "is already used in a `child' scope to denote something " +
1519                                               "else");
1520                                 return null;
1521                         }
1522
1523                         if (pars != null) {
1524                                 int idx;
1525                                 Parameter p = pars.GetParameterByName (name, out idx);
1526                                 if (p != null) {
1527                                         Report.Error (136, l, "A local variable named `" + name + "' " +
1528                                                       "cannot be declared in this scope since it would " +
1529                                                       "give a different meaning to `" + name + "', which " +
1530                                                       "is already used in a `parent or current' scope to " +
1531                                                       "denote something else");
1532                                         return null;
1533                                 }
1534                         }
1535
1536                         vi = new LocalInfo (type, name, this, l);
1537
1538                         variables.Add (name, vi);
1539
1540                         // Mark 'name' as "used by a child block" in every surrounding block
1541                         Block cur = this;
1542                         while (cur != null && cur.Implicit)
1543                                 cur = cur.Parent;
1544                         if (cur != null)
1545                                 for (Block par = cur.Parent; par != null; par = par.Parent)
1546                                         par.AddChildVariableName (name);
1547
1548                         if ((flags & Flags.VariablesInitialized) != 0)
1549                                 throw new Exception ();
1550
1551                         // Console.WriteLine ("Adding {0} to {1}", name, ID);
1552                         return vi;
1553                 }
1554
1555                 public bool AddConstant (Expression type, string name, Expression value, Parameters pars, Location l)
1556                 {
1557                         if (AddVariable (type, name, pars, l) == null)
1558                                 return false;
1559
1560                         if (constants == null)
1561                                 constants = new Hashtable ();
1562
1563                         constants.Add (name, value);
1564                         return true;
1565                 }
1566
1567                 public Hashtable Variables {
1568                         get {
1569                                 return variables;
1570                         }
1571                 }
1572
1573                 public LocalInfo GetLocalInfo (string name)
1574                 {
1575                         for (Block b = this; b != null; b = b.Parent) {
1576                                 if (b.variables != null) {
1577                                         LocalInfo ret = b.variables [name] as LocalInfo;
1578                                         if (ret != null)
1579                                                 return ret;
1580                                 }
1581                         }
1582                         return null;
1583                 }
1584
1585                 public Expression GetVariableType (string name)
1586                 {
1587                         LocalInfo vi = GetLocalInfo (name);
1588
1589                         if (vi != null)
1590                                 return vi.Type;
1591
1592                         return null;
1593                 }
1594
1595                 public Expression GetConstantExpression (string name)
1596                 {
1597                         for (Block b = this; b != null; b = b.Parent) {
1598                                 if (b.constants != null) {
1599                                         Expression ret = b.constants [name] as Expression;
1600                                         if (ret != null)
1601                                                 return ret;
1602                                 }
1603                         }
1604                         return null;
1605                 }
1606
1607                 /// <summary>
1608                 ///   True if the variable named @name is a constant
1609                 ///  </summary>
1610                 public bool IsConstant (string name)
1611                 {
1612                         Expression e = null;
1613
1614                         e = GetConstantExpression (name);
1615
1616                         return e != null;
1617                 }
1618
1619                 //
1620                 // Returns a `ParameterReference' for the given name, or null if there
1621                 // is no such parameter
1622                 //
1623                 public ParameterReference GetParameterReference (string name, Location loc)
1624                 {
1625                         Block b = this;
1626
1627                         do {
1628                                 Parameters pars = b.parameters;
1629
1630                                 if (pars != null){
1631                                         Parameter par;
1632                                         int idx;
1633
1634                                         par = pars.GetParameterByName (name, out idx);
1635                                         if (par != null){
1636                                                 ParameterReference pr;
1637
1638                                                 pr = new ParameterReference (pars, this, idx, name, loc);
1639                                                 return pr;
1640                                         }
1641                                 }
1642                                 b = b.Parent;
1643                         } while (b != null);
1644                         return null;
1645                 }
1646
1647                 //
1648                 // Whether the parameter named `name' is local to this block,
1649                 // or false, if the parameter belongs to an encompassing block.
1650                 //
1651                 public bool IsLocalParameter (string name)
1652                 {
1653                         Block b = this;
1654                         int toplevel_count = 0;
1655
1656                         do {
1657                                 if (this is ToplevelBlock)
1658                                         toplevel_count++;
1659
1660                                 Parameters pars = b.parameters;
1661                                 if (pars != null){
1662                                         if (pars.GetParameterByName (name) != null)
1663                                                 return true;
1664                                         return false;
1665                                 }
1666                                 if (toplevel_count > 0)
1667                                         return false;
1668                                 b = b.Parent;
1669                         } while (b != null);
1670                         return false;
1671                 }
1672
1673                 //
1674                 // Whether the `name' is a parameter reference
1675                 //
1676                 public bool IsParameterReference (string name)
1677                 {
1678                         Block b = this;
1679
1680                         do {
1681                                 Parameters pars = b.parameters;
1682
1683                                 if (pars != null)
1684                                         if (pars.GetParameterByName (name) != null)
1685                                                 return true;
1686                                 b = b.Parent;
1687                         } while (b != null);
1688                         return false;
1689                 }
1690
1691                 /// <returns>
1692                 ///   A list of labels that were not used within this block
1693                 /// </returns>
1694                 public string [] GetUnreferenced ()
1695                 {
1696                         // FIXME: Implement me
1697                         return null;
1698                 }
1699
1700                 public void AddStatement (Statement s)
1701                 {
1702                         statements.Add (s);
1703                         flags |= Flags.BlockUsed;
1704                 }
1705
1706                 public bool Used {
1707                         get {
1708                                 return (flags & Flags.BlockUsed) != 0;
1709                         }
1710                 }
1711
1712                 public void Use ()
1713                 {
1714                         flags |= Flags.BlockUsed;
1715                 }
1716
1717                 public bool HasRet {
1718                         get {
1719                                 return (flags & Flags.HasRet) != 0;
1720                         }
1721                 }
1722
1723                 public bool IsDestructor {
1724                         get {
1725                                 return (flags & Flags.IsDestructor) != 0;
1726                         }
1727                 }
1728
1729                 public void SetDestructor ()
1730                 {
1731                         flags |= Flags.IsDestructor;
1732                 }
1733
1734                 VariableMap param_map, local_map;
1735
1736                 public VariableMap ParameterMap {
1737                         get {
1738                                 if ((flags & Flags.VariablesInitialized) == 0)
1739                                         throw new Exception ("Variables have not been initialized yet");
1740
1741                                 return param_map;
1742                         }
1743                 }
1744
1745                 public VariableMap LocalMap {
1746                         get {
1747                                 if ((flags & Flags.VariablesInitialized) == 0)
1748                                         throw new Exception ("Variables have not been initialized yet");
1749
1750                                 return local_map;
1751                         }
1752                 }
1753
1754                 /// <summary>
1755                 ///   Emits the variable declarations and labels.
1756                 /// </summary>
1757                 /// <remarks>
1758                 ///   tc: is our typecontainer (to resolve type references)
1759                 ///   ig: is the code generator:
1760                 /// </remarks>
1761                 public void ResolveMeta (ToplevelBlock toplevel, EmitContext ec, InternalParameters ip)
1762                 {
1763                         bool old_unsafe = ec.InUnsafe;
1764
1765                         // If some parent block was unsafe, we remain unsafe even if this block
1766                         // isn't explicitly marked as such.
1767                         ec.InUnsafe |= Unsafe;
1768
1769                         //
1770                         // Compute the VariableMap's.
1771                         //
1772                         // Unfortunately, we don't know the type when adding variables with
1773                         // AddVariable(), so we need to compute this info here.
1774                         //
1775
1776                         LocalInfo[] locals;
1777                         if (variables != null) {
1778                                 foreach (LocalInfo li in variables.Values)
1779                                         li.Resolve (ec);
1780
1781                                 locals = new LocalInfo [variables.Count];
1782                                 variables.Values.CopyTo (locals, 0);
1783                         } else
1784                                 locals = new LocalInfo [0];
1785
1786                         if (Parent != null)
1787                                 local_map = new VariableMap (Parent.LocalMap, locals);
1788                         else
1789                                 local_map = new VariableMap (locals);
1790
1791                         param_map = new VariableMap (ip);
1792                         flags |= Flags.VariablesInitialized;
1793
1794                         bool old_check_state = ec.ConstantCheckState;
1795                         ec.ConstantCheckState = (flags & Flags.Unchecked) == 0;
1796
1797                         //
1798                         // Process this block variables
1799                         //
1800                         if (variables != null){
1801                                 foreach (DictionaryEntry de in variables){
1802                                         string name = (string) de.Key;
1803                                         LocalInfo vi = (LocalInfo) de.Value;
1804
1805                                         if (vi.VariableType == null)
1806                                                 continue;
1807
1808                                         Type variable_type = vi.VariableType;
1809
1810                                         if (variable_type.IsPointer){
1811                                                 //
1812                                                 // Am not really convinced that this test is required (Microsoft does it)
1813                                                 // but the fact is that you would not be able to use the pointer variable
1814                                                 // *anyways*
1815                                                 //
1816                                                 if (!TypeManager.VerifyUnManaged (TypeManager.GetElementType (variable_type),
1817                                                                                   vi.Location))
1818                                                         continue;
1819                                         }
1820
1821 #if false
1822                                         if (remap_locals)
1823                                                 vi.FieldBuilder = ec.MapVariable (name, vi.VariableType);
1824                                         else if (vi.Pinned)
1825                                                 //
1826                                                 // This is needed to compile on both .NET 1.x and .NET 2.x
1827                                                 // the later introduced `DeclareLocal (Type t, bool pinned)'
1828                                                 //
1829                                                 vi.LocalBuilder = TypeManager.DeclareLocalPinned (ig, vi.VariableType);
1830                                         else if (!vi.IsThis)
1831                                                 vi.LocalBuilder = ig.DeclareLocal (vi.VariableType);
1832 #endif
1833
1834                                         if (constants == null)
1835                                                 continue;
1836
1837                                         Expression cv = (Expression) constants [name];
1838                                         if (cv == null)
1839                                                 continue;
1840
1841                                         ec.CurrentBlock = this;
1842                                         Expression e = cv.Resolve (ec);
1843                                         if (e == null)
1844                                                 continue;
1845
1846                                         Constant ce = e as Constant;
1847                                         if (ce == null){
1848                                                 Report.Error (133, vi.Location,
1849                                                               "The expression being assigned to `" +
1850                                                               name + "' must be constant (" + e + ")");
1851                                                 continue;
1852                                         }
1853
1854                                         if (e.Type != variable_type){
1855                                                 e = Const.ChangeType (vi.Location, ce, variable_type);
1856                                                 if (e == null)
1857                                                         continue;
1858                                         }
1859
1860                                         constants.Remove (name);
1861                                         constants.Add (name, e);
1862                                 }
1863                         }
1864                         ec.ConstantCheckState = old_check_state;
1865
1866                         //
1867                         // Now, handle the children
1868                         //
1869                         if (children != null){
1870                                 foreach (Block b in children)
1871                                         b.ResolveMeta (toplevel, ec, ip);
1872                         }
1873                         ec.InUnsafe = old_unsafe;
1874                 }
1875
1876                 //
1877                 // Emits the local variable declarations for a block
1878                 //
1879                 public void EmitMeta (EmitContext ec)
1880                 {
1881                         ILGenerator ig = ec.ig;
1882
1883                         if (variables != null){
1884                                 bool have_captured_vars = ec.HaveCapturedVariables ();
1885                                 bool remap_locals = ec.RemapToProxy;
1886
1887                                 foreach (DictionaryEntry de in variables){
1888                                         LocalInfo vi = (LocalInfo) de.Value;
1889
1890                                         if (have_captured_vars && ec.IsCaptured (vi))
1891                                                 continue;
1892
1893                                         if (remap_locals){
1894                                                 vi.FieldBuilder = ec.MapVariable (vi.Name, vi.VariableType);
1895                                         } else {
1896                                                 if (vi.Pinned)
1897                                                         //
1898                                                         // This is needed to compile on both .NET 1.x and .NET 2.x
1899                                                         // the later introduced `DeclareLocal (Type t, bool pinned)'
1900                                                         //
1901                                                         vi.LocalBuilder = TypeManager.DeclareLocalPinned (ig, vi.VariableType);
1902                                                 else if (!vi.IsThis)
1903                                                         vi.LocalBuilder = ig.DeclareLocal (vi.VariableType);
1904                                         }
1905                                 }
1906                         }
1907
1908                         if (children != null){
1909                                 foreach (Block b in children)
1910                                         b.EmitMeta (ec);
1911                         }
1912                 }
1913
1914                 void UsageWarning (FlowBranching.UsageVector vector)
1915                 {
1916                         string name;
1917
1918                         if ((variables != null) && (RootContext.WarningLevel >= 3)) {
1919                                 foreach (DictionaryEntry de in variables){
1920                                         LocalInfo vi = (LocalInfo) de.Value;
1921
1922                                         if (vi.Used)
1923                                                 continue;
1924
1925                                         name = (string) de.Key;
1926
1927                                         if (vector.IsAssigned (vi.VariableInfo)){
1928                                                 Report.Warning (219, vi.Location, "The variable '{0}' is assigned but its value is never used", name);
1929                                         } else {
1930                                                 Report.Warning (168, vi.Location, "The variable '{0}' is declared but never used", name);
1931                                         }
1932                                 }
1933                         }
1934                 }
1935
1936                 bool unreachable_shown;
1937
1938                 public override bool Resolve (EmitContext ec)
1939                 {
1940                         Block prev_block = ec.CurrentBlock;
1941                         bool ok = true;
1942
1943                         int errors = Report.Errors;
1944
1945                         ec.CurrentBlock = this;
1946                         ec.StartFlowBranching (this);
1947
1948                         Report.Debug (4, "RESOLVE BLOCK", StartLocation, ec.CurrentBranching);
1949
1950                         bool unreachable = false;
1951
1952                         int statement_count = statements.Count;
1953                         for (int ix = 0; ix < statement_count; ix++){
1954                                 Statement s = (Statement) statements [ix];
1955
1956                                 if (unreachable && !(s is LabeledStatement)) {
1957                                         if (s == EmptyStatement.Value)
1958                                                 s.loc = EndLocation;
1959
1960                                         if (!s.ResolveUnreachable (ec, !unreachable_shown))
1961                                                 ok = false;
1962
1963                                         if (s != EmptyStatement.Value)
1964                                                 unreachable_shown = true;
1965                                         else
1966                                                 s.loc = Location.Null;
1967
1968                                         statements [ix] = EmptyStatement.Value;
1969                                         continue;
1970                                 }
1971
1972                                 if (s.Resolve (ec) == false) {
1973                                         ok = false;
1974                                         statements [ix] = EmptyStatement.Value;
1975                                         continue;
1976                                 }
1977
1978                                 num_statements = ix + 1;
1979
1980                                 if (s is LabeledStatement)
1981                                         unreachable = false;
1982                                 else
1983                                         unreachable = ec.CurrentBranching.CurrentUsageVector.Reachability.IsUnreachable;
1984                         }
1985
1986                         Report.Debug (4, "RESOLVE BLOCK DONE", StartLocation,
1987                                       ec.CurrentBranching, statement_count, num_statements);
1988
1989
1990                         FlowBranching.UsageVector vector = ec.DoEndFlowBranching ();
1991
1992                         ec.CurrentBlock = prev_block;
1993
1994                         // If we're a non-static `struct' constructor which doesn't have an
1995                         // initializer, then we must initialize all of the struct's fields.
1996                         if ((this_variable != null) &&
1997                             (vector.Reachability.Throws != FlowBranching.FlowReturns.Always) &&
1998                             !this_variable.IsThisAssigned (ec, loc))
1999                                 ok = false;
2000
2001                         if ((labels != null) && (RootContext.WarningLevel >= 2)) {
2002                                 foreach (LabeledStatement label in labels.Values)
2003                                         if (!label.HasBeenReferenced)
2004                                                 Report.Warning (164, label.Location,
2005                                                                 "This label has not been referenced");
2006                         }
2007
2008                         Report.Debug (4, "RESOLVE BLOCK DONE #2", StartLocation, vector);
2009
2010                         if ((vector.Reachability.Returns == FlowBranching.FlowReturns.Always) ||
2011                             (vector.Reachability.Throws == FlowBranching.FlowReturns.Always) ||
2012                             (vector.Reachability.Reachable == FlowBranching.FlowReturns.Never))
2013                                 flags |= Flags.HasRet;
2014
2015                         if (ok && (errors == Report.Errors)) {
2016                                 if (RootContext.WarningLevel >= 3)
2017                                         UsageWarning (vector);
2018                         }
2019
2020                         return ok;
2021                 }
2022
2023                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
2024                 {
2025                         unreachable_shown = true;
2026                         return base.ResolveUnreachable (ec, warn);
2027                 }
2028
2029                 protected override void DoEmit (EmitContext ec)
2030                 {
2031                         for (int ix = 0; ix < num_statements; ix++){
2032                                 Statement s = (Statement) statements [ix];
2033
2034                                 // Check whether we are the last statement in a
2035                                 // top-level block.
2036
2037                                 if ((Parent == null) && (ix+1 == num_statements))
2038                                         ec.IsLastStatement = true;
2039                                 else
2040                                         ec.IsLastStatement = false;
2041
2042                                 s.Emit (ec);
2043                         }
2044                 }
2045
2046                 public override void Emit (EmitContext ec)
2047                 {
2048                         Block prev_block = ec.CurrentBlock;
2049
2050                         ec.CurrentBlock = this;
2051
2052                         bool emit_debug_info = (CodeGen.SymbolWriter != null);
2053                         bool is_lexical_block = !Implicit && (Parent != null);
2054
2055                         if (emit_debug_info) {
2056                                 if (is_lexical_block)
2057                                         ec.ig.BeginScope ();
2058
2059                                 if (variables != null) {
2060                                         foreach (DictionaryEntry de in variables) {
2061                                                 string name = (string) de.Key;
2062                                                 LocalInfo vi = (LocalInfo) de.Value;
2063
2064                                                 if (vi.LocalBuilder == null)
2065                                                         continue;
2066
2067                                                 ec.DefineLocalVariable (name, vi.LocalBuilder);
2068                                         }
2069                                 }
2070                         }
2071
2072                         ec.Mark (StartLocation, true);
2073                         DoEmit (ec);
2074                         ec.Mark (EndLocation, true);
2075
2076                         if (emit_debug_info && is_lexical_block)
2077                                 ec.ig.EndScope ();
2078
2079                         ec.CurrentBlock = prev_block;
2080                 }
2081
2082                 public ToplevelBlock Toplevel {
2083                         get {
2084                                 Block b = this;
2085                                 while (b.Parent != null){
2086                                         if ((b.flags & Flags.IsToplevel) != 0)
2087                                                 break;
2088                                         b = b.Parent;
2089                                 }
2090
2091                                 return (ToplevelBlock) b;
2092                         }
2093                 }
2094
2095                 //
2096                 // Returns true if we ar ea child of `b'.
2097                 //
2098                 public bool IsChildOf (Block b)
2099                 {
2100                         Block current = this;
2101
2102                         do {
2103                                 if (current.Parent == b)
2104                                         return true;
2105                                 current = current.Parent;
2106                         } while (current != null);
2107                         return false;
2108                 }
2109         }
2110
2111         //
2112         // A toplevel block contains extra information, the split is done
2113         // only to separate information that would otherwise bloat the more
2114         // lightweight Block.
2115         //
2116         // In particular, this was introduced when the support for Anonymous
2117         // Methods was implemented.
2118         //
2119         public class ToplevelBlock : Block {
2120                 //
2121                 // Pointer to the host of this anonymous method, or null
2122                 // if we are the topmost block
2123                 //
2124                 public ToplevelBlock Container;
2125                 CaptureContext capture_context;
2126
2127                 Hashtable capture_contexts;
2128
2129                 static int did = 0;
2130
2131
2132                 public void RegisterCaptureContext (CaptureContext cc)
2133                 {
2134                         if (capture_contexts == null)
2135                                 capture_contexts = new Hashtable ();
2136                         capture_contexts [cc] = cc;
2137                 }
2138
2139                 public void CompleteContexts ()
2140                 {
2141                         if (capture_contexts == null)
2142                                 return;
2143
2144                         foreach (CaptureContext cc in capture_contexts.Keys){
2145                                 cc.AdjustScopes ();
2146                         }
2147                 }
2148
2149                 public CaptureContext ToplevelBlockCaptureContext {
2150                         get {
2151                                 return capture_context;
2152                         }
2153                 }
2154
2155                 //
2156                 // Parent is only used by anonymous blocks to link back to their
2157                 // parents
2158                 //
2159                 public ToplevelBlock (ToplevelBlock container, Parameters parameters, Location start) :
2160                         base (null, Flags.IsToplevel, parameters, start, Location.Null)
2161                 {
2162                         Container = container;
2163                 }
2164
2165                 public ToplevelBlock (Parameters parameters, Location start) :
2166                         base (null, Flags.IsToplevel, parameters, start, Location.Null)
2167                 {
2168                 }
2169
2170                 public ToplevelBlock (Flags flags, Parameters parameters, Location start) :
2171                         base (null, flags | Flags.IsToplevel, parameters, start, Location.Null)
2172                 {
2173                 }
2174
2175                 public ToplevelBlock (Location loc) : base (null, Flags.IsToplevel, loc, loc)
2176                 {
2177                 }
2178
2179                 public void SetHaveAnonymousMethods (Location loc, AnonymousMethod host)
2180                 {
2181                         if (capture_context == null)
2182                                 capture_context = new CaptureContext (this, loc, host);
2183                 }
2184
2185                 public CaptureContext CaptureContext {
2186                         get {
2187                                 return capture_context;
2188                         }
2189                 }
2190         }
2191
2192         public class SwitchLabel {
2193                 Expression label;
2194                 object converted;
2195                 public Location loc;
2196
2197                 Label il_label;
2198                 bool  il_label_set;
2199                 Label il_label_code;
2200                 bool  il_label_code_set;
2201
2202                 //
2203                 // if expr == null, then it is the default case.
2204                 //
2205                 public SwitchLabel (Expression expr, Location l)
2206                 {
2207                         label = expr;
2208                         loc = l;
2209                 }
2210
2211                 public Expression Label {
2212                         get {
2213                                 return label;
2214                         }
2215                 }
2216
2217                 public object Converted {
2218                         get {
2219                                 return converted;
2220                         }
2221                 }
2222
2223                 public Label GetILLabel (EmitContext ec)
2224                 {
2225                         if (!il_label_set){
2226                                 il_label = ec.ig.DefineLabel ();
2227                                 il_label_set = true;
2228                         }
2229                         return il_label;
2230                 }
2231
2232                 public Label GetILLabelCode (EmitContext ec)
2233                 {
2234                         if (!il_label_code_set){
2235                                 il_label_code = ec.ig.DefineLabel ();
2236                                 il_label_code_set = true;
2237                         }
2238                         return il_label_code;
2239                 }
2240
2241                 //
2242                 // Resolves the expression, reduces it to a literal if possible
2243                 // and then converts it to the requested type.
2244                 //
2245                 public bool ResolveAndReduce (EmitContext ec, Type required_type)
2246                 {
2247                         if (label == null)
2248                                 return true;
2249
2250                         Expression e = label.Resolve (ec);
2251
2252                         if (e == null)
2253                                 return false;
2254
2255                         if (!(e is Constant)){
2256                                 Report.Error (150, loc, "A constant value is expected, got: " + e);
2257                                 return false;
2258                         }
2259
2260                         if (e is StringConstant || e is NullLiteral){
2261                                 if (required_type == TypeManager.string_type){
2262                                         converted = e;
2263                                         return true;
2264                                 }
2265                         }
2266
2267                         converted = Expression.ConvertIntLiteral ((Constant) e, required_type, loc);
2268                         if (converted == null)
2269                                 return false;
2270
2271                         return true;
2272                 }
2273         }
2274
2275         public class SwitchSection {
2276                 // An array of SwitchLabels.
2277                 public readonly ArrayList Labels;
2278                 public readonly Block Block;
2279
2280                 public SwitchSection (ArrayList labels, Block block)
2281                 {
2282                         Labels = labels;
2283                         Block = block;
2284                 }
2285         }
2286
2287         public class Switch : Statement {
2288                 public readonly ArrayList Sections;
2289                 public Expression Expr;
2290
2291                 /// <summary>
2292                 ///   Maps constants whose type type SwitchType to their  SwitchLabels.
2293                 /// </summary>
2294                 public Hashtable Elements;
2295
2296                 /// <summary>
2297                 ///   The governing switch type
2298                 /// </summary>
2299                 public Type SwitchType;
2300
2301                 //
2302                 // Computed
2303                 //
2304                 bool got_default;
2305                 Label default_target;
2306                 Expression new_expr;
2307                 bool is_constant;
2308                 SwitchSection constant_section;
2309
2310                 //
2311                 // The types allowed to be implicitly cast from
2312                 // on the governing type
2313                 //
2314                 static Type [] allowed_types;
2315
2316                 public Switch (Expression e, ArrayList sects, Location l)
2317                 {
2318                         Expr = e;
2319                         Sections = sects;
2320                         loc = l;
2321                 }
2322
2323                 public bool GotDefault {
2324                         get {
2325                                 return got_default;
2326                         }
2327                 }
2328
2329                 public Label DefaultTarget {
2330                         get {
2331                                 return default_target;
2332                         }
2333                 }
2334
2335                 //
2336                 // Determines the governing type for a switch.  The returned
2337                 // expression might be the expression from the switch, or an
2338                 // expression that includes any potential conversions to the
2339                 // integral types or to string.
2340                 //
2341                 Expression SwitchGoverningType (EmitContext ec, Type t)
2342                 {
2343                         if (t == TypeManager.int32_type ||
2344                             t == TypeManager.uint32_type ||
2345                             t == TypeManager.char_type ||
2346                             t == TypeManager.byte_type ||
2347                             t == TypeManager.sbyte_type ||
2348                             t == TypeManager.ushort_type ||
2349                             t == TypeManager.short_type ||
2350                             t == TypeManager.uint64_type ||
2351                             t == TypeManager.int64_type ||
2352                             t == TypeManager.string_type ||
2353                                 t == TypeManager.bool_type ||
2354                                 t.IsSubclassOf (TypeManager.enum_type))
2355                                 return Expr;
2356
2357                         if (allowed_types == null){
2358                                 allowed_types = new Type [] {
2359                                         TypeManager.int32_type,
2360                                         TypeManager.uint32_type,
2361                                         TypeManager.sbyte_type,
2362                                         TypeManager.byte_type,
2363                                         TypeManager.short_type,
2364                                         TypeManager.ushort_type,
2365                                         TypeManager.int64_type,
2366                                         TypeManager.uint64_type,
2367                                         TypeManager.char_type,
2368                                         TypeManager.bool_type,
2369                                         TypeManager.string_type
2370                                 };
2371                         }
2372
2373                         //
2374                         // Try to find a *user* defined implicit conversion.
2375                         //
2376                         // If there is no implicit conversion, or if there are multiple
2377                         // conversions, we have to report an error
2378                         //
2379                         Expression converted = null;
2380                         foreach (Type tt in allowed_types){
2381                                 Expression e;
2382
2383                                 e = Convert.ImplicitUserConversion (ec, Expr, tt, loc);
2384                                 if (e == null)
2385                                         continue;
2386
2387                                 //
2388                                 // Ignore over-worked ImplicitUserConversions that do
2389                                 // an implicit conversion in addition to the user conversion.
2390                                 //
2391                                 if (e is UserCast){
2392                                         UserCast ue = e as UserCast;
2393
2394                                         if (ue.Source != Expr)
2395                                                 e = null;
2396                                 }
2397
2398                                 if (converted != null){
2399                                         Report.ExtraInformation (
2400                                                 loc,
2401                                                 String.Format ("reason: more than one conversion to an integral type exist for type {0}",
2402                                                                TypeManager.CSharpName (Expr.Type)));
2403                                         return null;
2404                                 } else {
2405                                         converted = e;
2406                                 }
2407                         }
2408                         return converted;
2409                 }
2410
2411                 static string Error152 {
2412                         get {
2413                                 return "The label '{0}:' already occurs in this switch statement";
2414                         }
2415                 }
2416
2417                 //
2418                 // Performs the basic sanity checks on the switch statement
2419                 // (looks for duplicate keys and non-constant expressions).
2420                 //
2421                 // It also returns a hashtable with the keys that we will later
2422                 // use to compute the switch tables
2423                 //
2424                 bool CheckSwitch (EmitContext ec)
2425                 {
2426                         Type compare_type;
2427                         bool error = false;
2428                         Elements = new Hashtable ();
2429
2430                         got_default = false;
2431
2432                         if (TypeManager.IsEnumType (SwitchType)){
2433                                 compare_type = TypeManager.EnumToUnderlying (SwitchType);
2434                         } else
2435                                 compare_type = SwitchType;
2436
2437                         foreach (SwitchSection ss in Sections){
2438                                 foreach (SwitchLabel sl in ss.Labels){
2439                                         if (!sl.ResolveAndReduce (ec, SwitchType)){
2440                                                 error = true;
2441                                                 continue;
2442                                         }
2443
2444                                         if (sl.Label == null){
2445                                                 if (got_default){
2446                                                         Report.Error (152, sl.loc, Error152, "default");
2447                                                         error = true;
2448                                                 }
2449                                                 got_default = true;
2450                                                 continue;
2451                                         }
2452
2453                                         object key = sl.Converted;
2454
2455                                         if (key is Constant)
2456                                                 key = ((Constant) key).GetValue ();
2457
2458                                         if (key == null)
2459                                                 key = NullLiteral.Null;
2460
2461                                         string lname = null;
2462                                         if (compare_type == TypeManager.uint64_type){
2463                                                 ulong v = (ulong) key;
2464
2465                                                 if (Elements.Contains (v))
2466                                                         lname = v.ToString ();
2467                                                 else
2468                                                         Elements.Add (v, sl);
2469                                         } else if (compare_type == TypeManager.int64_type){
2470                                                 long v = (long) key;
2471
2472                                                 if (Elements.Contains (v))
2473                                                         lname = v.ToString ();
2474                                                 else
2475                                                         Elements.Add (v, sl);
2476                                         } else if (compare_type == TypeManager.uint32_type){
2477                                                 uint v = (uint) key;
2478
2479                                                 if (Elements.Contains (v))
2480                                                         lname = v.ToString ();
2481                                                 else
2482                                                         Elements.Add (v, sl);
2483                                         } else if (compare_type == TypeManager.char_type){
2484                                                 char v = (char) key;
2485
2486                                                 if (Elements.Contains (v))
2487                                                         lname = v.ToString ();
2488                                                 else
2489                                                         Elements.Add (v, sl);
2490                                         } else if (compare_type == TypeManager.byte_type){
2491                                                 byte v = (byte) key;
2492
2493                                                 if (Elements.Contains (v))
2494                                                         lname = v.ToString ();
2495                                                 else
2496                                                         Elements.Add (v, sl);
2497                                         } else if (compare_type == TypeManager.sbyte_type){
2498                                                 sbyte v = (sbyte) key;
2499
2500                                                 if (Elements.Contains (v))
2501                                                         lname = v.ToString ();
2502                                                 else
2503                                                         Elements.Add (v, sl);
2504                                         } else if (compare_type == TypeManager.short_type){
2505                                                 short v = (short) key;
2506
2507                                                 if (Elements.Contains (v))
2508                                                         lname = v.ToString ();
2509                                                 else
2510                                                         Elements.Add (v, sl);
2511                                         } else if (compare_type == TypeManager.ushort_type){
2512                                                 ushort v = (ushort) key;
2513
2514                                                 if (Elements.Contains (v))
2515                                                         lname = v.ToString ();
2516                                                 else
2517                                                         Elements.Add (v, sl);
2518                                         } else if (compare_type == TypeManager.string_type){
2519                                                 if (key is NullLiteral){
2520                                                         if (Elements.Contains (NullLiteral.Null))
2521                                                                 lname = "null";
2522                                                         else
2523                                                                 Elements.Add (NullLiteral.Null, null);
2524                                                 } else {
2525                                                         string s = (string) key;
2526
2527                                                         if (Elements.Contains (s))
2528                                                                 lname = s;
2529                                                         else
2530                                                                 Elements.Add (s, sl);
2531                                                 }
2532                                         } else if (compare_type == TypeManager.int32_type) {
2533                                                 int v = (int) key;
2534
2535                                                 if (Elements.Contains (v))
2536                                                         lname = v.ToString ();
2537                                                 else
2538                                                         Elements.Add (v, sl);
2539                                         } else if (compare_type == TypeManager.bool_type) {
2540                                                 bool v = (bool) key;
2541
2542                                                 if (Elements.Contains (v))
2543                                                         lname = v.ToString ();
2544                                                 else
2545                                                         Elements.Add (v, sl);
2546                                         }
2547                                         else
2548                                         {
2549                                                 throw new Exception ("Unknown switch type!" +
2550                                                                      SwitchType + " " + compare_type);
2551                                         }
2552
2553                                         if (lname != null) {
2554                                                 Report.Error (152, sl.loc, Error152, "case " + lname);
2555                                                 error = true;
2556                                         }
2557                                 }
2558                         }
2559                         if (error)
2560                                 return false;
2561
2562                         return true;
2563                 }
2564
2565                 void EmitObjectInteger (ILGenerator ig, object k)
2566                 {
2567                         if (k is int)
2568                                 IntConstant.EmitInt (ig, (int) k);
2569                         else if (k is Constant) {
2570                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
2571                         }
2572                         else if (k is uint)
2573                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
2574                         else if (k is long)
2575                         {
2576                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
2577                                 {
2578                                         IntConstant.EmitInt (ig, (int) (long) k);
2579                                         ig.Emit (OpCodes.Conv_I8);
2580                                 }
2581                                 else
2582                                         LongConstant.EmitLong (ig, (long) k);
2583                         }
2584                         else if (k is ulong)
2585                         {
2586                                 if ((ulong) k < (1L<<32))
2587                                 {
2588                                         IntConstant.EmitInt (ig, (int) (long) k);
2589                                         ig.Emit (OpCodes.Conv_U8);
2590                                 }
2591                                 else
2592                                 {
2593                                         LongConstant.EmitLong (ig, unchecked ((long) (ulong) k));
2594                                 }
2595                         }
2596                         else if (k is char)
2597                                 IntConstant.EmitInt (ig, (int) ((char) k));
2598                         else if (k is sbyte)
2599                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
2600                         else if (k is byte)
2601                                 IntConstant.EmitInt (ig, (int) ((byte) k));
2602                         else if (k is short)
2603                                 IntConstant.EmitInt (ig, (int) ((short) k));
2604                         else if (k is ushort)
2605                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
2606                         else if (k is bool)
2607                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
2608                         else
2609                                 throw new Exception ("Unhandled case");
2610                 }
2611
2612                 // structure used to hold blocks of keys while calculating table switch
2613                 class KeyBlock : IComparable
2614                 {
2615                         public KeyBlock (long _nFirst)
2616                         {
2617                                 nFirst = nLast = _nFirst;
2618                         }
2619                         public long nFirst;
2620                         public long nLast;
2621                         public ArrayList rgKeys = null;
2622                         // how many items are in the bucket
2623                         public int Size = 1;
2624                         public int Length
2625                         {
2626                                 get { return (int) (nLast - nFirst + 1); }
2627                         }
2628                         public static long TotalLength (KeyBlock kbFirst, KeyBlock kbLast)
2629                         {
2630                                 return kbLast.nLast - kbFirst.nFirst + 1;
2631                         }
2632                         public int CompareTo (object obj)
2633                         {
2634                                 KeyBlock kb = (KeyBlock) obj;
2635                                 int nLength = Length;
2636                                 int nLengthOther = kb.Length;
2637                                 if (nLengthOther == nLength)
2638                                         return (int) (kb.nFirst - nFirst);
2639                                 return nLength - nLengthOther;
2640                         }
2641                 }
2642
2643                 /// <summary>
2644                 /// This method emits code for a lookup-based switch statement (non-string)
2645                 /// Basically it groups the cases into blocks that are at least half full,
2646                 /// and then spits out individual lookup opcodes for each block.
2647                 /// It emits the longest blocks first, and short blocks are just
2648                 /// handled with direct compares.
2649                 /// </summary>
2650                 /// <param name="ec"></param>
2651                 /// <param name="val"></param>
2652                 /// <returns></returns>
2653                 void TableSwitchEmit (EmitContext ec, LocalBuilder val)
2654                 {
2655                         int cElements = Elements.Count;
2656                         object [] rgKeys = new object [cElements];
2657                         Elements.Keys.CopyTo (rgKeys, 0);
2658                         Array.Sort (rgKeys);
2659
2660                         // initialize the block list with one element per key
2661                         ArrayList rgKeyBlocks = new ArrayList ();
2662                         foreach (object key in rgKeys)
2663                                 rgKeyBlocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));
2664
2665                         KeyBlock kbCurr;
2666                         // iteratively merge the blocks while they are at least half full
2667                         // there's probably a really cool way to do this with a tree...
2668                         while (rgKeyBlocks.Count > 1)
2669                         {
2670                                 ArrayList rgKeyBlocksNew = new ArrayList ();
2671                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
2672                                 for (int ikb = 1; ikb < rgKeyBlocks.Count; ikb++)
2673                                 {
2674                                         KeyBlock kb = (KeyBlock) rgKeyBlocks [ikb];
2675                                         if ((kbCurr.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (kbCurr, kb))
2676                                         {
2677                                                 // merge blocks
2678                                                 kbCurr.nLast = kb.nLast;
2679                                                 kbCurr.Size += kb.Size;
2680                                         }
2681                                         else
2682                                         {
2683                                                 // start a new block
2684                                                 rgKeyBlocksNew.Add (kbCurr);
2685                                                 kbCurr = kb;
2686                                         }
2687                                 }
2688                                 rgKeyBlocksNew.Add (kbCurr);
2689                                 if (rgKeyBlocks.Count == rgKeyBlocksNew.Count)
2690                                         break;
2691                                 rgKeyBlocks = rgKeyBlocksNew;
2692                         }
2693
2694                         // initialize the key lists
2695                         foreach (KeyBlock kb in rgKeyBlocks)
2696                                 kb.rgKeys = new ArrayList ();
2697
2698                         // fill the key lists
2699                         int iBlockCurr = 0;
2700                         if (rgKeyBlocks.Count > 0) {
2701                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
2702                                 foreach (object key in rgKeys)
2703                                 {
2704                                         bool fNextBlock = (key is UInt64) ? (ulong) key > (ulong) kbCurr.nLast :
2705                                                 System.Convert.ToInt64 (key) > kbCurr.nLast;
2706                                         if (fNextBlock)
2707                                                 kbCurr = (KeyBlock) rgKeyBlocks [++iBlockCurr];
2708                                         kbCurr.rgKeys.Add (key);
2709                                 }
2710                         }
2711
2712                         // sort the blocks so we can tackle the largest ones first
2713                         rgKeyBlocks.Sort ();
2714
2715                         // okay now we can start...
2716                         ILGenerator ig = ec.ig;
2717                         Label lblEnd = ig.DefineLabel ();       // at the end ;-)
2718                         Label lblDefault = ig.DefineLabel ();
2719
2720                         Type typeKeys = null;
2721                         if (rgKeys.Length > 0)
2722                                 typeKeys = rgKeys [0].GetType ();       // used for conversions
2723
2724                         Type compare_type;
2725
2726                         if (TypeManager.IsEnumType (SwitchType))
2727                                 compare_type = TypeManager.EnumToUnderlying (SwitchType);
2728                         else
2729                                 compare_type = SwitchType;
2730
2731                         for (int iBlock = rgKeyBlocks.Count - 1; iBlock >= 0; --iBlock)
2732                         {
2733                                 KeyBlock kb = ((KeyBlock) rgKeyBlocks [iBlock]);
2734                                 lblDefault = (iBlock == 0) ? DefaultTarget : ig.DefineLabel ();
2735                                 if (kb.Length <= 2)
2736                                 {
2737                                         foreach (object key in kb.rgKeys)
2738                                         {
2739                                                 ig.Emit (OpCodes.Ldloc, val);
2740                                                 EmitObjectInteger (ig, key);
2741                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
2742                                                 ig.Emit (OpCodes.Beq, sl.GetILLabel (ec));
2743                                         }
2744                                 }
2745                                 else
2746                                 {
2747                                         // TODO: if all the keys in the block are the same and there are
2748                                         //       no gaps/defaults then just use a range-check.
2749                                         if (compare_type == TypeManager.int64_type ||
2750                                                 compare_type == TypeManager.uint64_type)
2751                                         {
2752                                                 // TODO: optimize constant/I4 cases
2753
2754                                                 // check block range (could be > 2^31)
2755                                                 ig.Emit (OpCodes.Ldloc, val);
2756                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.nFirst, typeKeys));
2757                                                 ig.Emit (OpCodes.Blt, lblDefault);
2758                                                 ig.Emit (OpCodes.Ldloc, val);
2759                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.nLast, typeKeys));
2760                                                 ig.Emit (OpCodes.Bgt, lblDefault);
2761
2762                                                 // normalize range
2763                                                 ig.Emit (OpCodes.Ldloc, val);
2764                                                 if (kb.nFirst != 0)
2765                                                 {
2766                                                         EmitObjectInteger (ig, System.Convert.ChangeType (kb.nFirst, typeKeys));
2767                                                         ig.Emit (OpCodes.Sub);
2768                                                 }
2769                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
2770                                         }
2771                                         else
2772                                         {
2773                                                 // normalize range
2774                                                 ig.Emit (OpCodes.Ldloc, val);
2775                                                 int nFirst = (int) kb.nFirst;
2776                                                 if (nFirst > 0)
2777                                                 {
2778                                                         IntConstant.EmitInt (ig, nFirst);
2779                                                         ig.Emit (OpCodes.Sub);
2780                                                 }
2781                                                 else if (nFirst < 0)
2782                                                 {
2783                                                         IntConstant.EmitInt (ig, -nFirst);
2784                                                         ig.Emit (OpCodes.Add);
2785                                                 }
2786                                         }
2787
2788                                         // first, build the list of labels for the switch
2789                                         int iKey = 0;
2790                                         int cJumps = kb.Length;
2791                                         Label [] rgLabels = new Label [cJumps];
2792                                         for (int iJump = 0; iJump < cJumps; iJump++)
2793                                         {
2794                                                 object key = kb.rgKeys [iKey];
2795                                                 if (System.Convert.ToInt64 (key) == kb.nFirst + iJump)
2796                                                 {
2797                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
2798                                                         rgLabels [iJump] = sl.GetILLabel (ec);
2799                                                         iKey++;
2800                                                 }
2801                                                 else
2802                                                         rgLabels [iJump] = lblDefault;
2803                                         }
2804                                         // emit the switch opcode
2805                                         ig.Emit (OpCodes.Switch, rgLabels);
2806                                 }
2807
2808                                 // mark the default for this block
2809                                 if (iBlock != 0)
2810                                         ig.MarkLabel (lblDefault);
2811                         }
2812
2813                         // TODO: find the default case and emit it here,
2814                         //       to prevent having to do the following jump.
2815                         //       make sure to mark other labels in the default section
2816
2817                         // the last default just goes to the end
2818                         ig.Emit (OpCodes.Br, lblDefault);
2819
2820                         // now emit the code for the sections
2821                         bool fFoundDefault = false;
2822                         foreach (SwitchSection ss in Sections)
2823                         {
2824                                 foreach (SwitchLabel sl in ss.Labels)
2825                                 {
2826                                         ig.MarkLabel (sl.GetILLabel (ec));
2827                                         ig.MarkLabel (sl.GetILLabelCode (ec));
2828                                         if (sl.Label == null)
2829                                         {
2830                                                 ig.MarkLabel (lblDefault);
2831                                                 fFoundDefault = true;
2832                                         }
2833                                 }
2834                                 ss.Block.Emit (ec);
2835                                 //ig.Emit (OpCodes.Br, lblEnd);
2836                         }
2837
2838                         if (!fFoundDefault) {
2839                                 ig.MarkLabel (lblDefault);
2840                         }
2841                         ig.MarkLabel (lblEnd);
2842                 }
2843                 //
2844                 // This simple emit switch works, but does not take advantage of the
2845                 // `switch' opcode.
2846                 // TODO: remove non-string logic from here
2847                 // TODO: binary search strings?
2848                 //
2849                 void SimpleSwitchEmit (EmitContext ec, LocalBuilder val)
2850                 {
2851                         ILGenerator ig = ec.ig;
2852                         Label end_of_switch = ig.DefineLabel ();
2853                         Label next_test = ig.DefineLabel ();
2854                         Label null_target = ig.DefineLabel ();
2855                         bool default_found = false;
2856                         bool first_test = true;
2857                         bool pending_goto_end = false;
2858                         bool null_found;
2859                         bool default_at_end = false;
2860
2861                         ig.Emit (OpCodes.Ldloc, val);
2862
2863                         if (Elements.Contains (NullLiteral.Null)){
2864                                 ig.Emit (OpCodes.Brfalse, null_target);
2865                         } else
2866                                 ig.Emit (OpCodes.Brfalse, default_target);
2867
2868                         ig.Emit (OpCodes.Ldloc, val);
2869                         ig.Emit (OpCodes.Call, TypeManager.string_isinterneted_string);
2870                         ig.Emit (OpCodes.Stloc, val);
2871
2872                         int section_count = Sections.Count;
2873                         for (int section = 0; section < section_count; section++){
2874                                 SwitchSection ss = (SwitchSection) Sections [section];
2875                                 Label sec_begin = ig.DefineLabel ();
2876
2877                                 if (pending_goto_end)
2878                                         ig.Emit (OpCodes.Br, end_of_switch);
2879
2880                                 int label_count = ss.Labels.Count;
2881                                 bool mark_default = false;
2882                                 null_found = false;
2883                                 for (int label = 0; label < label_count; label++){
2884                                         SwitchLabel sl = (SwitchLabel) ss.Labels [label];
2885                                         ig.MarkLabel (sl.GetILLabel (ec));
2886
2887                                         if (!first_test){
2888                                                 ig.MarkLabel (next_test);
2889                                                 next_test = ig.DefineLabel ();
2890                                         }
2891                                         //
2892                                         // If we are the default target
2893                                         //
2894                                         if (sl.Label == null){
2895                                                 if (label+1 == label_count)
2896                                                         default_at_end = true;
2897                                                 mark_default = true;
2898                                                 default_found = true;
2899                                         } else {
2900                                                 object lit = sl.Converted;
2901
2902                                                 if (lit is NullLiteral){
2903                                                         null_found = true;
2904                                                         if (label_count == 1)
2905                                                                 ig.Emit (OpCodes.Br, next_test);
2906                                                         continue;
2907
2908                                                 }
2909                                                 StringConstant str = (StringConstant) lit;
2910
2911                                                 ig.Emit (OpCodes.Ldloc, val);
2912                                                 ig.Emit (OpCodes.Ldstr, str.Value);
2913                                                 if (label_count == 1)
2914                                                         ig.Emit (OpCodes.Bne_Un, next_test);
2915                                                 else {
2916                                                         if (label+1 == label_count)
2917                                                                 ig.Emit (OpCodes.Bne_Un, next_test);
2918                                                         else
2919                                                                 ig.Emit (OpCodes.Beq, sec_begin);
2920                                                 }
2921                                         }
2922                                 }
2923                                 if (null_found)
2924                                         ig.MarkLabel (null_target);
2925                                 ig.MarkLabel (sec_begin);
2926                                 foreach (SwitchLabel sl in ss.Labels)
2927                                         ig.MarkLabel (sl.GetILLabelCode (ec));
2928
2929                                 if (mark_default)
2930                                         ig.MarkLabel (default_target);
2931                                 ss.Block.Emit (ec);
2932                                 pending_goto_end = !ss.Block.HasRet;
2933                                 first_test = false;
2934                         }
2935                         ig.MarkLabel (next_test);
2936                         if (default_found){
2937                                 if (!default_at_end)
2938                                         ig.Emit (OpCodes.Br, default_target);
2939                         } else
2940                                 ig.MarkLabel (default_target);
2941                         ig.MarkLabel (end_of_switch);
2942                 }
2943
2944                 SwitchSection FindSection (SwitchLabel label)
2945                 {
2946                         foreach (SwitchSection ss in Sections){
2947                                 foreach (SwitchLabel sl in ss.Labels){
2948                                         if (label == sl)
2949                                                 return ss;
2950                                 }
2951                         }
2952
2953                         return null;
2954                 }
2955
2956                 bool ResolveConstantSwitch (EmitContext ec)
2957                 {
2958                         object key = ((Constant) new_expr).GetValue ();
2959                         SwitchLabel label = (SwitchLabel) Elements [key];
2960
2961                         if (label == null)
2962                                 return true;
2963
2964                         constant_section = FindSection (label);
2965                         if (constant_section == null)
2966                                 return true;
2967
2968                         if (constant_section.Block.Resolve (ec) != true)
2969                                 return false;
2970
2971                         return true;
2972                 }
2973
2974                 public override bool Resolve (EmitContext ec)
2975                 {
2976                         Expr = Expr.Resolve (ec);
2977                         if (Expr == null)
2978                                 return false;
2979
2980                         new_expr = SwitchGoverningType (ec, Expr.Type);
2981                         if (new_expr == null){
2982                                 Report.Error (151, loc, "An integer type or string was expected for switch");
2983                                 return false;
2984                         }
2985
2986                         // Validate switch.
2987                         SwitchType = new_expr.Type;
2988
2989                         if (!CheckSwitch (ec))
2990                                 return false;
2991
2992                         Switch old_switch = ec.Switch;
2993                         ec.Switch = this;
2994                         ec.Switch.SwitchType = SwitchType;
2995
2996                         Report.Debug (1, "START OF SWITCH BLOCK", loc, ec.CurrentBranching);
2997                         ec.StartFlowBranching (FlowBranching.BranchingType.Switch, loc);
2998
2999                         is_constant = new_expr is Constant;
3000                         if (is_constant) {
3001                                 object key = ((Constant) new_expr).GetValue ();
3002                                 SwitchLabel label = (SwitchLabel) Elements [key];
3003
3004                                 constant_section = FindSection (label);
3005                         }
3006
3007                         bool first = true;
3008                         foreach (SwitchSection ss in Sections){
3009                                 if (!first)
3010                                         ec.CurrentBranching.CreateSibling (
3011                                                 null, FlowBranching.SiblingType.SwitchSection);
3012                                 else
3013                                         first = false;
3014
3015                                 if (is_constant && (ss != constant_section)) {
3016                                         // If we're a constant switch, we're only emitting
3017                                         // one single section - mark all the others as
3018                                         // unreachable.
3019                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
3020                                         if (!ss.Block.ResolveUnreachable (ec, true))
3021                                                 return false;
3022                                 } else {
3023                                         if (!ss.Block.Resolve (ec))
3024                                                 return false;
3025                                 }
3026                         }
3027
3028                         if (!got_default)
3029                                 ec.CurrentBranching.CreateSibling (
3030                                         null, FlowBranching.SiblingType.SwitchSection);
3031
3032                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3033                         ec.Switch = old_switch;
3034
3035                         Report.Debug (1, "END OF SWITCH BLOCK", loc, ec.CurrentBranching,
3036                                       reachability);
3037
3038                         return true;
3039                 }
3040
3041                 protected override void DoEmit (EmitContext ec)
3042                 {
3043                         ILGenerator ig = ec.ig;
3044
3045                         // Store variable for comparission purposes
3046                         LocalBuilder value;
3047                         if (!is_constant) {
3048                                 value = ig.DeclareLocal (SwitchType);
3049                                 new_expr.Emit (ec);
3050                                 ig.Emit (OpCodes.Stloc, value);
3051                         } else
3052                                 value = null;
3053
3054                         default_target = ig.DefineLabel ();
3055
3056                         //
3057                         // Setup the codegen context
3058                         //
3059                         Label old_end = ec.LoopEnd;
3060                         Switch old_switch = ec.Switch;
3061
3062                         ec.LoopEnd = ig.DefineLabel ();
3063                         ec.Switch = this;
3064
3065                         // Emit Code.
3066                         if (is_constant) {
3067                                 if (constant_section != null)
3068                                         constant_section.Block.Emit (ec);
3069                         } else if (SwitchType == TypeManager.string_type)
3070                                 SimpleSwitchEmit (ec, value);
3071                         else
3072                                 TableSwitchEmit (ec, value);
3073
3074                         // Restore context state.
3075                         ig.MarkLabel (ec.LoopEnd);
3076
3077                         //
3078                         // Restore the previous context
3079                         //
3080                         ec.LoopEnd = old_end;
3081                         ec.Switch = old_switch;
3082                 }
3083         }
3084
3085         public abstract class ExceptionStatement : Statement
3086         {
3087                 public abstract void EmitFinally (EmitContext ec);
3088
3089                 protected bool emit_finally = true;
3090                 ArrayList parent_vectors;
3091
3092                 protected void DoEmitFinally (EmitContext ec)
3093                 {
3094                         if (emit_finally)
3095                                 ec.ig.BeginFinallyBlock ();
3096                         else
3097                                 ec.CurrentIterator.MarkFinally (ec, parent_vectors);
3098                         EmitFinally (ec);
3099                 }
3100
3101                 protected void ResolveFinally (FlowBranchingException branching)
3102                 {
3103                         emit_finally = branching.EmitFinally;
3104                         if (!emit_finally)
3105                                 branching.Parent.StealFinallyClauses (ref parent_vectors);
3106                 }
3107         }
3108
3109         public class Lock : ExceptionStatement {
3110                 Expression expr;
3111                 Statement Statement;
3112                 LocalBuilder temp;
3113
3114                 public Lock (Expression expr, Statement stmt, Location l)
3115                 {
3116                         this.expr = expr;
3117                         Statement = stmt;
3118                         loc = l;
3119                 }
3120
3121                 public override bool Resolve (EmitContext ec)
3122                 {
3123                         expr = expr.Resolve (ec);
3124                         if (expr == null)
3125                                 return false;
3126
3127                         if (expr.Type.IsValueType){
3128                                 Error (185, "lock statement requires the expression to be " +
3129                                        " a reference type (type is: `{0}'",
3130                                        TypeManager.CSharpName (expr.Type));
3131                                 return false;
3132                         }
3133
3134                         FlowBranchingException branching = ec.StartFlowBranching (this);
3135                         bool ok = Statement.Resolve (ec);
3136                         if (!ok) {
3137                                 ec.KillFlowBranching ();
3138                                 return false;
3139                         }
3140
3141                         ResolveFinally (branching);
3142
3143                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3144                         if (reachability.Returns != FlowBranching.FlowReturns.Always) {
3145                                 // Unfortunately, System.Reflection.Emit automatically emits
3146                                 // a leave to the end of the finally block.
3147                                 // This is a problem if `returns' is true since we may jump
3148                                 // to a point after the end of the method.
3149                                 // As a workaround, emit an explicit ret here.
3150                                 ec.NeedReturnLabel ();
3151                         }
3152
3153                         return true;
3154                 }
3155
3156                 protected override void DoEmit (EmitContext ec)
3157                 {
3158                         Type type = expr.Type;
3159
3160                         ILGenerator ig = ec.ig;
3161                         temp = ig.DeclareLocal (type);
3162
3163                         expr.Emit (ec);
3164                         ig.Emit (OpCodes.Dup);
3165                         ig.Emit (OpCodes.Stloc, temp);
3166                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
3167
3168                         // try
3169                         if (emit_finally)
3170                                 ig.BeginExceptionBlock ();
3171                         Statement.Emit (ec);
3172
3173                         // finally
3174                         DoEmitFinally (ec);
3175                         if (emit_finally)
3176                                 ig.EndExceptionBlock ();
3177                 }
3178
3179                 public override void EmitFinally (EmitContext ec)
3180                 {
3181                         ILGenerator ig = ec.ig;
3182                         ig.Emit (OpCodes.Ldloc, temp);
3183                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
3184                 }
3185         }
3186
3187         public class Unchecked : Statement {
3188                 public readonly Block Block;
3189
3190                 public Unchecked (Block b)
3191                 {
3192                         Block = b;
3193                         b.Unchecked = true;
3194                 }
3195
3196                 public override bool Resolve (EmitContext ec)
3197                 {
3198                         bool previous_state = ec.CheckState;
3199                         bool previous_state_const = ec.ConstantCheckState;
3200
3201                         ec.CheckState = false;
3202                         ec.ConstantCheckState = false;
3203                         bool ret = Block.Resolve (ec);
3204                         ec.CheckState = previous_state;
3205                         ec.ConstantCheckState = previous_state_const;
3206
3207                         return ret;
3208                 }
3209
3210                 protected override void DoEmit (EmitContext ec)
3211                 {
3212                         bool previous_state = ec.CheckState;
3213                         bool previous_state_const = ec.ConstantCheckState;
3214
3215                         ec.CheckState = false;
3216                         ec.ConstantCheckState = false;
3217                         Block.Emit (ec);
3218                         ec.CheckState = previous_state;
3219                         ec.ConstantCheckState = previous_state_const;
3220                 }
3221         }
3222
3223         public class Checked : Statement {
3224                 public readonly Block Block;
3225
3226                 public Checked (Block b)
3227                 {
3228                         Block = b;
3229                         b.Unchecked = false;
3230                 }
3231
3232                 public override bool Resolve (EmitContext ec)
3233                 {
3234                         bool previous_state = ec.CheckState;
3235                         bool previous_state_const = ec.ConstantCheckState;
3236
3237                         ec.CheckState = true;
3238                         ec.ConstantCheckState = true;
3239                         bool ret = Block.Resolve (ec);
3240                         ec.CheckState = previous_state;
3241                         ec.ConstantCheckState = previous_state_const;
3242
3243                         return ret;
3244                 }
3245
3246                 protected override void DoEmit (EmitContext ec)
3247                 {
3248                         bool previous_state = ec.CheckState;
3249                         bool previous_state_const = ec.ConstantCheckState;
3250
3251                         ec.CheckState = true;
3252                         ec.ConstantCheckState = true;
3253                         Block.Emit (ec);
3254                         ec.CheckState = previous_state;
3255                         ec.ConstantCheckState = previous_state_const;
3256                 }
3257         }
3258
3259         public class Unsafe : Statement {
3260                 public readonly Block Block;
3261
3262                 public Unsafe (Block b)
3263                 {
3264                         Block = b;
3265                         Block.Unsafe = true;
3266                 }
3267
3268                 public override bool Resolve (EmitContext ec)
3269                 {
3270                         bool previous_state = ec.InUnsafe;
3271                         bool val;
3272
3273                         ec.InUnsafe = true;
3274                         val = Block.Resolve (ec);
3275                         ec.InUnsafe = previous_state;
3276
3277                         return val;
3278                 }
3279
3280                 protected override void DoEmit (EmitContext ec)
3281                 {
3282                         bool previous_state = ec.InUnsafe;
3283
3284                         ec.InUnsafe = true;
3285                         Block.Emit (ec);
3286                         ec.InUnsafe = previous_state;
3287                 }
3288         }
3289
3290         //
3291         // Fixed statement
3292         //
3293         public class Fixed : Statement {
3294                 Expression type;
3295                 ArrayList declarators;
3296                 Statement statement;
3297                 Type expr_type;
3298                 FixedData[] data;
3299                 bool has_ret;
3300
3301                 struct FixedData {
3302                         public bool is_object;
3303                         public LocalInfo vi;
3304                         public Expression expr;
3305                         public Expression converted;
3306                 }
3307
3308                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
3309                 {
3310                         this.type = type;
3311                         declarators = decls;
3312                         statement = stmt;
3313                         loc = l;
3314                 }
3315
3316                 public override bool Resolve (EmitContext ec)
3317                 {
3318                         if (!ec.InUnsafe){
3319                                 Expression.UnsafeError (loc);
3320                                 return false;
3321                         }
3322
3323                         TypeExpr texpr = type.ResolveAsTypeTerminal (ec, false);
3324                         if (texpr == null)
3325                                 return false;
3326
3327                         expr_type = texpr.ResolveType (ec);
3328
3329                         CheckObsolete (expr_type);
3330
3331                         if (ec.RemapToProxy){
3332                                 Report.Error (-210, loc, "Fixed statement not allowed in iterators");
3333                                 return false;
3334                         }
3335
3336                         data = new FixedData [declarators.Count];
3337
3338                         if (!expr_type.IsPointer){
3339                                 Report.Error (209, loc, "Variables in a fixed statement must be pointers");
3340                                 return false;
3341                         }
3342
3343                         int i = 0;
3344                         foreach (Pair p in declarators){
3345                                 LocalInfo vi = (LocalInfo) p.First;
3346                                 Expression e = (Expression) p.Second;
3347
3348                                 vi.VariableInfo.SetAssigned (ec);
3349                                 vi.ReadOnly = true;
3350
3351                                 //
3352                                 // The rules for the possible declarators are pretty wise,
3353                                 // but the production on the grammar is more concise.
3354                                 //
3355                                 // So we have to enforce these rules here.
3356                                 //
3357                                 // We do not resolve before doing the case 1 test,
3358                                 // because the grammar is explicit in that the token &
3359                                 // is present, so we need to test for this particular case.
3360                                 //
3361
3362                                 if (e is Cast){
3363                                         Report.Error (254, loc, "Cast expression not allowed as right hand expression in fixed statement");
3364                                         return false;
3365                                 }
3366
3367                                 //
3368                                 // Case 1: & object.
3369                                 //
3370                                 if (e is Unary && ((Unary) e).Oper == Unary.Operator.AddressOf){
3371                                         Expression child = ((Unary) e).Expr;
3372
3373                                         if (child is ParameterReference || child is LocalVariableReference){
3374                                                 Report.Error (
3375                                                         213, loc,
3376                                                         "No need to use fixed statement for parameters or " +
3377                                                         "local variable declarations (address is already " +
3378                                                         "fixed)");
3379                                                 return false;
3380                                         }
3381
3382                                         ec.InFixedInitializer = true;
3383                                         e = e.Resolve (ec);
3384                                         ec.InFixedInitializer = false;
3385                                         if (e == null)
3386                                                 return false;
3387
3388                                         child = ((Unary) e).Expr;
3389
3390                                         if (!TypeManager.VerifyUnManaged (child.Type, loc))
3391                                                 return false;
3392
3393                                         data [i].is_object = true;
3394                                         data [i].expr = e;
3395                                         data [i].converted = null;
3396                                         data [i].vi = vi;
3397                                         i++;
3398
3399                                         continue;
3400                                 }
3401
3402                                 ec.InFixedInitializer = true;
3403                                 e = e.Resolve (ec);
3404                                 ec.InFixedInitializer = false;
3405                                 if (e == null)
3406                                         return false;
3407
3408                                 //
3409                                 // Case 2: Array
3410                                 //
3411                                 if (e.Type.IsArray){
3412                                         Type array_type = TypeManager.GetElementType (e.Type);
3413
3414                                         //
3415                                         // Provided that array_type is unmanaged,
3416                                         //
3417                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
3418                                                 return false;
3419
3420                                         //
3421                                         // and T* is implicitly convertible to the
3422                                         // pointer type given in the fixed statement.
3423                                         //
3424                                         ArrayPtr array_ptr = new ArrayPtr (e, loc);
3425
3426                                         Expression converted = Convert.ImplicitConversionRequired (
3427                                                 ec, array_ptr, vi.VariableType, loc);
3428                                         if (converted == null)
3429                                                 return false;
3430
3431                                         data [i].is_object = false;
3432                                         data [i].expr = e;
3433                                         data [i].converted = converted;
3434                                         data [i].vi = vi;
3435                                         i++;
3436
3437                                         continue;
3438                                 }
3439
3440                                 //
3441                                 // Case 3: string
3442                                 //
3443                                 if (e.Type == TypeManager.string_type){
3444                                         data [i].is_object = false;
3445                                         data [i].expr = e;
3446                                         data [i].converted = null;
3447                                         data [i].vi = vi;
3448                                         i++;
3449                                         continue;
3450                                 }
3451
3452                                 //
3453                                 // For other cases, flag a `this is already fixed expression'
3454                                 //
3455                                 if (e is LocalVariableReference || e is ParameterReference ||
3456                                     Convert.ImplicitConversionExists (ec, e, vi.VariableType)){
3457
3458                                         Report.Error (245, loc, "right hand expression is already fixed, no need to use fixed statement ");
3459                                         return false;
3460                                 }
3461
3462                                 Report.Error (245, loc, "Fixed statement only allowed on strings, arrays or address-of expressions");
3463                                 return false;
3464                         }
3465
3466                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
3467
3468                         if (!statement.Resolve (ec)) {
3469                                 ec.KillFlowBranching ();
3470                                 return false;
3471                         }
3472
3473                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3474                         has_ret = reachability.IsUnreachable;
3475
3476                         return true;
3477                 }
3478
3479                 protected override void DoEmit (EmitContext ec)
3480                 {
3481                         ILGenerator ig = ec.ig;
3482
3483                         LocalBuilder [] clear_list = new LocalBuilder [data.Length];
3484
3485                         for (int i = 0; i < data.Length; i++) {
3486                                 LocalInfo vi = data [i].vi;
3487
3488                                 //
3489                                 // Case 1: & object.
3490                                 //
3491                                 if (data [i].is_object) {
3492                                         //
3493                                         // Store pointer in pinned location
3494                                         //
3495                                         data [i].expr.Emit (ec);
3496                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3497                                         clear_list [i] = vi.LocalBuilder;
3498                                         continue;
3499                                 }
3500
3501                                 //
3502                                 // Case 2: Array
3503                                 //
3504                                 if (data [i].expr.Type.IsArray){
3505                                         //
3506                                         // Store pointer in pinned location
3507                                         //
3508                                         data [i].converted.Emit (ec);
3509
3510                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3511                                         clear_list [i] = vi.LocalBuilder;
3512                                         continue;
3513                                 }
3514
3515                                 //
3516                                 // Case 3: string
3517                                 //
3518                                 if (data [i].expr.Type == TypeManager.string_type){
3519                                         LocalBuilder pinned_string = TypeManager.DeclareLocalPinned (ig, TypeManager.string_type);
3520                                         clear_list [i] = pinned_string;
3521
3522                                         data [i].expr.Emit (ec);
3523                                         ig.Emit (OpCodes.Stloc, pinned_string);
3524
3525                                         Expression sptr = new StringPtr (pinned_string, loc);
3526                                         Expression converted = Convert.ImplicitConversionRequired (
3527                                                 ec, sptr, vi.VariableType, loc);
3528
3529                                         if (converted == null)
3530                                                 continue;
3531
3532                                         converted.Emit (ec);
3533                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3534                                 }
3535                         }
3536
3537                         statement.Emit (ec);
3538
3539                         if (has_ret)
3540                                 return;
3541
3542                         //
3543                         // Clear the pinned variable
3544                         //
3545                         for (int i = 0; i < data.Length; i++) {
3546                                 if (data [i].is_object || data [i].expr.Type.IsArray) {
3547                                         ig.Emit (OpCodes.Ldc_I4_0);
3548                                         ig.Emit (OpCodes.Conv_U);
3549                                         ig.Emit (OpCodes.Stloc, clear_list [i]);
3550                                 } else if (data [i].expr.Type == TypeManager.string_type){
3551                                         ig.Emit (OpCodes.Ldnull);
3552                                         ig.Emit (OpCodes.Stloc, clear_list [i]);
3553                                 }
3554                         }
3555                 }
3556         }
3557
3558         public class Catch: Statement {
3559                 public readonly string Name;
3560                 public readonly Block  Block;
3561
3562                 Expression type_expr;
3563                 Type type;
3564
3565                 public Catch (Expression type, string name, Block block, Location l)
3566                 {
3567                         type_expr = type;
3568                         Name = name;
3569                         Block = block;
3570                         loc = l;
3571                 }
3572
3573                 public Type CatchType {
3574                         get {
3575                                 return type;
3576                         }
3577                 }
3578
3579                 public bool IsGeneral {
3580                         get {
3581                                 return type_expr == null;
3582                         }
3583                 }
3584
3585                 protected override void DoEmit(EmitContext ec)
3586                 {
3587                 }
3588
3589                 public override bool Resolve (EmitContext ec)
3590                 {
3591                         if (type_expr != null) {
3592                                 TypeExpr te = type_expr.ResolveAsTypeTerminal (ec, false);
3593                                 if (te == null)
3594                                         return false;
3595
3596                                 type = te.ResolveType (ec);
3597
3598                                 CheckObsolete (type);
3599
3600                                 if (type != TypeManager.exception_type && !type.IsSubclassOf (TypeManager.exception_type)){
3601                                         Error (155, "The type caught or thrown must be derived from System.Exception");
3602                                         return false;
3603                                 }
3604                         } else
3605                                 type = null;
3606
3607                         return Block.Resolve (ec);
3608                 }
3609         }
3610
3611         public class Try : ExceptionStatement {
3612                 public readonly Block Fini, Block;
3613                 public readonly ArrayList Specific;
3614                 public readonly Catch General;
3615
3616                 bool need_exc_block;
3617
3618                 //
3619                 // specific, general and fini might all be null.
3620                 //
3621                 public Try (Block block, ArrayList specific, Catch general, Block fini, Location l)
3622                 {
3623                         if (specific == null && general == null){
3624                                 Console.WriteLine ("CIR.Try: Either specific or general have to be non-null");
3625                         }
3626
3627                         this.Block = block;
3628                         this.Specific = specific;
3629                         this.General = general;
3630                         this.Fini = fini;
3631                         loc = l;
3632                 }
3633
3634                 public override bool Resolve (EmitContext ec)
3635                 {
3636                         bool ok = true;
3637
3638                         FlowBranchingException branching = ec.StartFlowBranching (this);
3639
3640                         Report.Debug (1, "START OF TRY BLOCK", Block.StartLocation);
3641
3642                         if (!Block.Resolve (ec))
3643                                 ok = false;
3644
3645                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
3646
3647                         Report.Debug (1, "START OF CATCH BLOCKS", vector);
3648
3649                         Type[] prevCatches = new Type [Specific.Count];
3650                         int last_index = 0;
3651                         foreach (Catch c in Specific){
3652                                 ec.CurrentBranching.CreateSibling (
3653                                         c.Block, FlowBranching.SiblingType.Catch);
3654
3655                                 Report.Debug (1, "STARTED SIBLING FOR CATCH", ec.CurrentBranching);
3656
3657                                 if (c.Name != null) {
3658                                         LocalInfo vi = c.Block.GetLocalInfo (c.Name);
3659                                         if (vi == null)
3660                                                 throw new Exception ();
3661
3662                                         vi.VariableInfo = null;
3663                                 }
3664
3665                                 if (!c.Resolve (ec))
3666                                         return false;
3667
3668                                 Type resolvedType = c.CatchType;
3669                                 for (int ii = 0; ii < last_index; ++ii) {
3670                                         if (resolvedType == prevCatches [ii] || resolvedType.IsSubclassOf (prevCatches [ii])) {
3671                                                 Report.Error (160, c.loc, "A previous catch clause already catches all exceptions of this or a super type '{0}'", prevCatches [ii].FullName);
3672                                                 return false;
3673                                         }
3674                                 }
3675
3676                                 prevCatches [last_index++] = resolvedType;
3677                                 need_exc_block = true;
3678                         }
3679
3680                         Report.Debug (1, "END OF CATCH BLOCKS", ec.CurrentBranching);
3681
3682                         if (General != null){
3683                                 ec.CurrentBranching.CreateSibling (
3684                                         General.Block, FlowBranching.SiblingType.Catch);
3685
3686                                 Report.Debug (1, "STARTED SIBLING FOR GENERAL", ec.CurrentBranching);
3687
3688                                 if (!General.Resolve (ec))
3689                                         ok = false;
3690
3691                                 need_exc_block = true;
3692                         }
3693
3694                         Report.Debug (1, "END OF GENERAL CATCH BLOCKS", ec.CurrentBranching);
3695
3696                         if (Fini != null) {
3697                                 if (ok)
3698                                         ec.CurrentBranching.CreateSibling (
3699                                                 Fini, FlowBranching.SiblingType.Finally);
3700
3701                                 Report.Debug (1, "STARTED SIBLING FOR FINALLY", ec.CurrentBranching, vector);
3702
3703                                 if (!Fini.Resolve (ec))
3704                                         ok = false;
3705                         }
3706
3707                         ResolveFinally (branching);
3708                         need_exc_block |= emit_finally;
3709
3710                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
3711
3712                         FlowBranching.UsageVector f_vector = ec.CurrentBranching.CurrentUsageVector;
3713
3714                         Report.Debug (1, "END OF TRY", ec.CurrentBranching, reachability, vector, f_vector);
3715
3716                         if (reachability.Returns != FlowBranching.FlowReturns.Always) {
3717                                 // Unfortunately, System.Reflection.Emit automatically emits
3718                                 // a leave to the end of the finally block.  This is a problem
3719                                 // if `returns' is true since we may jump to a point after the
3720                                 // end of the method.
3721                                 // As a workaround, emit an explicit ret here.
3722                                 ec.NeedReturnLabel ();
3723                         }
3724
3725                         return ok;
3726                 }
3727
3728                 protected override void DoEmit (EmitContext ec)
3729                 {
3730                         ILGenerator ig = ec.ig;
3731
3732                         if (need_exc_block)
3733                                 ig.BeginExceptionBlock ();
3734                         Block.Emit (ec);
3735
3736                         foreach (Catch c in Specific){
3737                                 LocalInfo vi;
3738
3739                                 ig.BeginCatchBlock (c.CatchType);
3740
3741                                 if (c.Name != null){
3742                                         vi = c.Block.GetLocalInfo (c.Name);
3743                                         if (vi == null)
3744                                                 throw new Exception ("Variable does not exist in this block");
3745
3746                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
3747                                 } else
3748                                         ig.Emit (OpCodes.Pop);
3749
3750                                 c.Block.Emit (ec);
3751                         }
3752
3753                         if (General != null){
3754                                 ig.BeginCatchBlock (TypeManager.object_type);
3755                                 ig.Emit (OpCodes.Pop);
3756                                 General.Block.Emit (ec);
3757                         }
3758
3759                         DoEmitFinally (ec);
3760                         if (need_exc_block)
3761                                 ig.EndExceptionBlock ();
3762                 }
3763
3764                 public override void EmitFinally (EmitContext ec)
3765                 {
3766                         if (Fini != null){
3767                                 Fini.Emit (ec);
3768                         }
3769                 }
3770         }
3771
3772         public class Using : ExceptionStatement {
3773                 object expression_or_block;
3774                 Statement Statement;
3775                 ArrayList var_list;
3776                 Expression expr;
3777                 Type expr_type;
3778                 Expression conv;
3779                 Expression [] resolved_vars;
3780                 Expression [] converted_vars;
3781                 ExpressionStatement [] assign;
3782                 LocalBuilder local_copy;
3783
3784                 public Using (object expression_or_block, Statement stmt, Location l)
3785                 {
3786                         this.expression_or_block = expression_or_block;
3787                         Statement = stmt;
3788                         loc = l;
3789                 }
3790
3791                 //
3792                 // Resolves for the case of using using a local variable declaration.
3793                 //
3794                 bool ResolveLocalVariableDecls (EmitContext ec)
3795                 {
3796                         int i = 0;
3797
3798                         TypeExpr texpr = expr.ResolveAsTypeTerminal (ec, false);
3799                         if (texpr == null)
3800                                 return false;
3801
3802                         expr_type = texpr.ResolveType (ec);
3803
3804                         //
3805                         // The type must be an IDisposable or an implicit conversion
3806                         // must exist.
3807                         //
3808                         converted_vars = new Expression [var_list.Count];
3809                         resolved_vars = new Expression [var_list.Count];
3810                         assign = new ExpressionStatement [var_list.Count];
3811
3812                         bool need_conv = !TypeManager.ImplementsInterface (
3813                                 expr_type, TypeManager.idisposable_type);
3814
3815                         foreach (DictionaryEntry e in var_list){
3816                                 Expression var = (Expression) e.Key;
3817
3818                                 var = var.ResolveLValue (ec, new EmptyExpression ());
3819                                 if (var == null)
3820                                         return false;
3821
3822                                 resolved_vars [i] = var;
3823
3824                                 if (!need_conv) {
3825                                         i++;
3826                                         continue;
3827                                 }
3828
3829                                 converted_vars [i] = Convert.ImplicitConversionRequired (
3830                                         ec, var, TypeManager.idisposable_type, loc);
3831
3832                                 if (converted_vars [i] == null)
3833                                         return false;
3834
3835                                 i++;
3836                         }
3837
3838                         i = 0;
3839                         foreach (DictionaryEntry e in var_list){
3840                                 Expression var = resolved_vars [i];
3841                                 Expression new_expr = (Expression) e.Value;
3842                                 Expression a;
3843
3844                                 a = new Assign (var, new_expr, loc);
3845                                 a = a.Resolve (ec);
3846                                 if (a == null)
3847                                         return false;
3848
3849                                 if (!need_conv)
3850                                         converted_vars [i] = var;
3851                                 assign [i] = (ExpressionStatement) a;
3852                                 i++;
3853                         }
3854
3855                         return true;
3856                 }
3857
3858                 bool ResolveExpression (EmitContext ec)
3859                 {
3860                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)){
3861                                 conv = Convert.ImplicitConversionRequired (
3862                                         ec, expr, TypeManager.idisposable_type, loc);
3863
3864                                 if (conv == null)
3865                                         return false;
3866                         }
3867
3868                         return true;
3869                 }
3870
3871                 //
3872                 // Emits the code for the case of using using a local variable declaration.
3873                 //
3874                 void EmitLocalVariableDecls (EmitContext ec)
3875                 {
3876                         ILGenerator ig = ec.ig;
3877                         int i = 0;
3878
3879                         for (i = 0; i < assign.Length; i++) {
3880                                 assign [i].EmitStatement (ec);
3881
3882                                 if (emit_finally)
3883                                         ig.BeginExceptionBlock ();
3884                         }
3885                         Statement.Emit (ec);
3886                         var_list.Reverse ();
3887
3888                         DoEmitFinally (ec);
3889                 }
3890
3891                 void EmitLocalVariableDeclFinally (EmitContext ec)
3892                 {
3893                         ILGenerator ig = ec.ig;
3894
3895                         int i = assign.Length;
3896                         for (int ii = 0; ii < var_list.Count; ++ii){
3897                                 Expression var = resolved_vars [--i];
3898                                 Label skip = ig.DefineLabel ();
3899
3900                                 if (!var.Type.IsValueType) {
3901                                         var.Emit (ec);
3902                                         ig.Emit (OpCodes.Brfalse, skip);
3903                                         converted_vars [i].Emit (ec);
3904                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3905                                 } else {
3906                                         Expression ml = Expression.MemberLookup(ec, TypeManager.idisposable_type, var.Type, "Dispose", Mono.CSharp.Location.Null);
3907
3908                                         if (!(ml is MethodGroupExpr)) {
3909                                                 var.Emit (ec);
3910                                                 ig.Emit (OpCodes.Box, var.Type);
3911                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3912                                         } else {
3913                                                 MethodInfo mi = null;
3914
3915                                                 foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
3916                                                         if (TypeManager.GetArgumentTypes (mk).Length == 0) {
3917                                                                 mi = mk;
3918                                                                 break;
3919                                                         }
3920                                                 }
3921
3922                                                 if (mi == null) {
3923                                                         Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
3924                                                         return;
3925                                                 }
3926
3927                                                 IMemoryLocation mloc = (IMemoryLocation) var;
3928
3929                                                 mloc.AddressOf (ec, AddressOp.Load);
3930                                                 ig.Emit (OpCodes.Call, mi);
3931                                         }
3932                                 }
3933
3934                                 ig.MarkLabel (skip);
3935
3936                                 if (emit_finally) {
3937                                         ig.EndExceptionBlock ();
3938                                         if (i > 0)
3939                                                 ig.BeginFinallyBlock ();
3940                                 }
3941                         }
3942                 }
3943
3944                 void EmitExpression (EmitContext ec)
3945                 {
3946                         //
3947                         // Make a copy of the expression and operate on that.
3948                         //
3949                         ILGenerator ig = ec.ig;
3950                         local_copy = ig.DeclareLocal (expr_type);
3951                         if (conv != null)
3952                                 conv.Emit (ec);
3953                         else
3954                                 expr.Emit (ec);
3955                         ig.Emit (OpCodes.Stloc, local_copy);
3956
3957                         if (emit_finally)
3958                                 ig.BeginExceptionBlock ();
3959
3960                         Statement.Emit (ec);
3961
3962                         DoEmitFinally (ec);
3963                         if (emit_finally)
3964                                 ig.EndExceptionBlock ();
3965                 }
3966
3967                 void EmitExpressionFinally (EmitContext ec)
3968                 {
3969                         ILGenerator ig = ec.ig;
3970                         if (!local_copy.LocalType.IsValueType) {
3971                                 Label skip = ig.DefineLabel ();
3972                                 ig.Emit (OpCodes.Ldloc, local_copy);
3973                                 ig.Emit (OpCodes.Brfalse, skip);
3974                                 ig.Emit (OpCodes.Ldloc, local_copy);
3975                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3976                                 ig.MarkLabel (skip);
3977                         } else {
3978                                 Expression ml = Expression.MemberLookup(ec, TypeManager.idisposable_type, local_copy.LocalType, "Dispose", Mono.CSharp.Location.Null);
3979
3980                                 if (!(ml is MethodGroupExpr)) {
3981                                         ig.Emit (OpCodes.Ldloc, local_copy);
3982                                         ig.Emit (OpCodes.Box, local_copy.LocalType);
3983                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
3984                                 } else {
3985                                         MethodInfo mi = null;
3986
3987                                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
3988                                                 if (TypeManager.GetArgumentTypes (mk).Length == 0) {
3989                                                         mi = mk;
3990                                                         break;
3991                                                 }
3992                                         }
3993
3994                                         if (mi == null) {
3995                                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
3996                                                 return;
3997                                         }
3998
3999                                         ig.Emit (OpCodes.Ldloca, local_copy);
4000                                         ig.Emit (OpCodes.Call, mi);
4001                                 }
4002                         }
4003                 }
4004
4005                 public override bool Resolve (EmitContext ec)
4006                 {
4007                         if (expression_or_block is DictionaryEntry){
4008                                 expr = (Expression) ((DictionaryEntry) expression_or_block).Key;
4009                                 var_list = (ArrayList)((DictionaryEntry)expression_or_block).Value;
4010
4011                                 if (!ResolveLocalVariableDecls (ec))
4012                                         return false;
4013
4014                         } else if (expression_or_block is Expression){
4015                                 expr = (Expression) expression_or_block;
4016
4017                                 expr = expr.Resolve (ec);
4018                                 if (expr == null)
4019                                         return false;
4020
4021                                 expr_type = expr.Type;
4022
4023                                 if (!ResolveExpression (ec))
4024                                         return false;
4025                         }
4026
4027                         FlowBranchingException branching = ec.StartFlowBranching (this);
4028
4029                         bool ok = Statement.Resolve (ec);
4030
4031                         if (!ok) {
4032                                 ec.KillFlowBranching ();
4033                                 return false;
4034                         }
4035
4036                         ResolveFinally (branching);
4037                         FlowBranching.Reachability reachability = ec.EndFlowBranching ();
4038
4039                         if (reachability.Returns != FlowBranching.FlowReturns.Always) {
4040                                 // Unfortunately, System.Reflection.Emit automatically emits a leave
4041                                 // to the end of the finally block.  This is a problem if `returns'
4042                                 // is true since we may jump to a point after the end of the method.
4043                                 // As a workaround, emit an explicit ret here.
4044                                 ec.NeedReturnLabel ();
4045                         }
4046
4047                         return true;
4048                 }
4049
4050                 protected override void DoEmit (EmitContext ec)
4051                 {
4052                         if (expression_or_block is DictionaryEntry)
4053                                 EmitLocalVariableDecls (ec);
4054                         else if (expression_or_block is Expression)
4055                                 EmitExpression (ec);
4056                 }
4057
4058                 public override void EmitFinally (EmitContext ec)
4059                 {
4060                         if (expression_or_block is DictionaryEntry)
4061                                 EmitLocalVariableDeclFinally (ec);
4062                         else if (expression_or_block is Expression)
4063                                 EmitExpressionFinally (ec);
4064                 }
4065         }
4066
4067         /// <summary>
4068         ///   Implementation of the foreach C# statement
4069         /// </summary>
4070         public class Foreach : ExceptionStatement {
4071                 Expression type;
4072                 Expression variable;
4073                 Expression expr;
4074                 Statement statement;
4075                 ForeachHelperMethods hm;
4076                 Expression empty, conv;
4077                 Type array_type, element_type;
4078                 Type var_type;
4079                 VariableStorage enumerator;
4080
4081                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
4082                                 Statement stmt, Location l)
4083                 {
4084                         this.type = type;
4085                         this.variable = var;
4086                         this.expr = expr;
4087                         statement = stmt;
4088                         loc = l;
4089                 }
4090
4091                 public override bool Resolve (EmitContext ec)
4092                 {
4093                         expr = expr.Resolve (ec);
4094                         if (expr == null)
4095                                 return false;
4096
4097                         if (expr is NullLiteral) {
4098                                 Report.Error (186, expr.Location, "Use of null is not valid in this context");
4099                                 return false;
4100                         }
4101
4102                         TypeExpr texpr = type.ResolveAsTypeTerminal (ec, false);
4103                         if (texpr == null)
4104                                 return false;
4105
4106                         var_type = texpr.ResolveType (ec);
4107
4108                         //
4109                         // We need an instance variable.  Not sure this is the best
4110                         // way of doing this.
4111                         //
4112                         // FIXME: When we implement propertyaccess, will those turn
4113                         // out to return values in ExprClass?  I think they should.
4114                         //
4115                         if (!(expr.eclass == ExprClass.Variable || expr.eclass == ExprClass.Value ||
4116                               expr.eclass == ExprClass.PropertyAccess || expr.eclass == ExprClass.IndexerAccess)){
4117                                 error1579 (expr.Type);
4118                                 return false;
4119                         }
4120
4121                         if (expr.Type.IsArray) {
4122                                 array_type = expr.Type;
4123                                 element_type = TypeManager.GetElementType (array_type);
4124
4125                                 empty = new EmptyExpression (element_type);
4126                         } else {
4127                                 hm = ProbeCollectionType (ec, expr.Type);
4128                                 if (hm == null){
4129                                         error1579 (expr.Type);
4130                                         return false;
4131                                 }
4132
4133                                 // When ProbeCollection reported error
4134                                 if (hm.move_next == null)
4135                                         return false;
4136
4137                                 array_type = expr.Type;
4138                                 element_type = hm.element_type;
4139
4140                                 empty = new EmptyExpression (hm.element_type);
4141                         }
4142
4143                         bool ok = true;
4144
4145                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
4146                         ec.CurrentBranching.CreateSibling ();
4147
4148                         //
4149                         //
4150                         // FIXME: maybe we can apply the same trick we do in the
4151                         // array handling to avoid creating empty and conv in some cases.
4152                         //
4153                         // Although it is not as important in this case, as the type
4154                         // will not likely be object (what the enumerator will return).
4155                         //
4156                         conv = Convert.ExplicitConversion (ec, empty, var_type, loc);
4157                         if (conv == null)
4158                                 ok = false;
4159
4160                         variable = variable.ResolveLValue (ec, empty);
4161                         if (variable == null)
4162                                 ok = false;
4163
4164                         bool disposable = (hm != null) && hm.is_disposable;
4165                         FlowBranchingException branching = null;
4166                         if (disposable)
4167                                 branching = ec.StartFlowBranching (this);
4168
4169                         if (!statement.Resolve (ec))
4170                                 ok = false;
4171
4172                         if (disposable) {
4173                                 ResolveFinally (branching);
4174                                 ec.EndFlowBranching ();
4175                         } else
4176                                 emit_finally = true;
4177
4178                         ec.EndFlowBranching ();
4179
4180                         return ok;
4181                 }
4182
4183                 //
4184                 // Retrieves a `public bool MoveNext ()' method from the Type `t'
4185                 //
4186                 static MethodInfo FetchMethodMoveNext (Type t)
4187                 {
4188                         MemberList move_next_list;
4189
4190                         move_next_list = TypeContainer.FindMembers (
4191                                 t, MemberTypes.Method,
4192                                 BindingFlags.Public | BindingFlags.Instance,
4193                                 Type.FilterName, "MoveNext");
4194                         if (move_next_list.Count == 0)
4195                                 return null;
4196
4197                         foreach (MemberInfo m in move_next_list){
4198                                 MethodInfo mi = (MethodInfo) m;
4199                                 Type [] args;
4200
4201                                 args = TypeManager.GetArgumentTypes (mi);
4202                                 if (args != null && args.Length == 0){
4203                                         if (mi.ReturnType == TypeManager.bool_type)
4204                                                 return mi;
4205                                 }
4206                         }
4207                         return null;
4208                 }
4209
4210                 //
4211                 // Retrieves a `public T get_Current ()' method from the Type `t'
4212                 //
4213                 static MethodInfo FetchMethodGetCurrent (Type t)
4214                 {
4215                         MemberList get_current_list;
4216
4217                         get_current_list = TypeContainer.FindMembers (
4218                                 t, MemberTypes.Method,
4219                                 BindingFlags.Public | BindingFlags.Instance,
4220                                 Type.FilterName, "get_Current");
4221                         if (get_current_list.Count == 0)
4222                                 return null;
4223
4224                         foreach (MemberInfo m in get_current_list){
4225                                 MethodInfo mi = (MethodInfo) m;
4226                                 Type [] args;
4227
4228                                 args = TypeManager.GetArgumentTypes (mi);
4229                                 if (args != null && args.Length == 0)
4230                                         return mi;
4231                         }
4232                         return null;
4233                 }
4234
4235                 //
4236                 // Retrieves a `public void Dispose ()' method from the Type `t'
4237                 //
4238                 static MethodInfo FetchMethodDispose (Type t)
4239                 {
4240                         MemberList dispose_list;
4241
4242                         dispose_list = TypeContainer.FindMembers (
4243                                 t, MemberTypes.Method,
4244                                 BindingFlags.Public | BindingFlags.Instance,
4245                                 Type.FilterName, "Dispose");
4246                         if (dispose_list.Count == 0)
4247                                 return null;
4248
4249                         foreach (MemberInfo m in dispose_list){
4250                                 MethodInfo mi = (MethodInfo) m;
4251                                 Type [] args;
4252
4253                                 args = TypeManager.GetArgumentTypes (mi);
4254                                 if (args != null && args.Length == 0){
4255                                         if (mi.ReturnType == TypeManager.void_type)
4256                                                 return mi;
4257                                 }
4258                         }
4259                         return null;
4260                 }
4261
4262                 //
4263                 // This struct records the helper methods used by the Foreach construct
4264                 //
4265                 class ForeachHelperMethods {
4266                         public EmitContext ec;
4267                         public MethodInfo get_enumerator;
4268                         public MethodInfo move_next;
4269                         public MethodInfo get_current;
4270                         public Type element_type;
4271                         public Type enumerator_type;
4272                         public bool is_disposable;
4273                         public readonly Location Location;
4274
4275                         public ForeachHelperMethods (EmitContext ec, Location loc)
4276                         {
4277                                 this.ec = ec;
4278                                 this.Location = loc;
4279                                 this.element_type = TypeManager.object_type;
4280                                 this.enumerator_type = TypeManager.ienumerator_type;
4281                                 this.is_disposable = true;
4282                         }
4283                 }
4284
4285                 static bool GetEnumeratorFilter (MemberInfo m, object criteria)
4286                 {
4287                         if (m == null)
4288                                 return false;
4289
4290                         if (!(m is MethodInfo))
4291                                 return false;
4292
4293                         if (m.Name != "GetEnumerator")
4294                                 return false;
4295
4296                         MethodInfo mi = (MethodInfo) m;
4297                         Type [] args = TypeManager.GetArgumentTypes (mi);
4298                         if (args != null){
4299                                 if (args.Length != 0)
4300                                         return false;
4301                         }
4302                         ForeachHelperMethods hm = (ForeachHelperMethods) criteria;
4303
4304                         // Check whether GetEnumerator is public
4305                         if ((mi.Attributes & MethodAttributes.Public) != MethodAttributes.Public)
4306                                 return false;
4307
4308                         if ((mi.ReturnType == TypeManager.ienumerator_type) && (mi.DeclaringType == TypeManager.string_type))
4309                                 //
4310                                 // Apply the same optimization as MS: skip the GetEnumerator
4311                                 // returning an IEnumerator, and use the one returning a
4312                                 // CharEnumerator instead. This allows us to avoid the
4313                                 // try-finally block and the boxing.
4314                                 //
4315                                 return false;
4316
4317                         //
4318                         // Ok, we can access it, now make sure that we can do something
4319                         // with this `GetEnumerator'
4320                         //
4321
4322                         Type return_type = mi.ReturnType;
4323                         if (mi.ReturnType == TypeManager.ienumerator_type ||
4324                             TypeManager.ienumerator_type.IsAssignableFrom (return_type) ||
4325                             (!RootContext.StdLib && TypeManager.ImplementsInterface (return_type, TypeManager.ienumerator_type))) {
4326
4327                                 //
4328                                 // If it is not an interface, lets try to find the methods ourselves.
4329                                 // For example, if we have:
4330                                 // public class Foo : IEnumerator { public bool MoveNext () {} public int Current { get {}}}
4331                                 // We can avoid the iface call. This is a runtime perf boost.
4332                                 // even bigger if we have a ValueType, because we avoid the cost
4333                                 // of boxing.
4334                                 //
4335                                 // We have to make sure that both methods exist for us to take
4336                                 // this path. If one of the methods does not exist, we will just
4337                                 // use the interface. Sadly, this complex if statement is the only
4338                                 // way I could do this without a goto
4339                                 //
4340
4341                                 if (return_type.IsInterface ||
4342                                     (hm.move_next = FetchMethodMoveNext (return_type)) == null ||
4343                                     (hm.get_current = FetchMethodGetCurrent (return_type)) == null) {
4344
4345                                         hm.move_next = TypeManager.bool_movenext_void;
4346                                         hm.get_current = TypeManager.object_getcurrent_void;
4347                                         return true;
4348                                 }
4349
4350                         } else {
4351
4352                                 if (return_type.IsPointer || return_type.IsArray) {
4353                                         Report.SymbolRelatedToPreviousError (mi);
4354                                         Type t = return_type.GetElementType ();
4355                                         Report.SymbolRelatedToPreviousError (t);
4356                                         Report.Error (202, hm.Location, "foreach requires that the return type '{0}' of '{1}' must have a suitable public MoveNext method and public Current property",
4357                                                 TypeManager.CSharpName (return_type), TypeManager.GetFullNameSignature (m));
4358                                         hm.get_enumerator = mi;
4359                                         return false;
4360                                 }
4361
4362                                 //
4363                                 // Ok, so they dont return an IEnumerable, we will have to
4364                                 // find if they support the GetEnumerator pattern.
4365                                 //
4366
4367                                 hm.move_next = FetchMethodMoveNext (return_type);
4368                                 if (hm.move_next == null)
4369                                         return false;
4370
4371                                 hm.get_current = FetchMethodGetCurrent (return_type);
4372                                 if (hm.get_current == null)
4373                                         return false;
4374                         }
4375
4376                         hm.element_type = hm.get_current.ReturnType;
4377                         hm.enumerator_type = return_type;
4378                         hm.is_disposable = !hm.enumerator_type.IsSealed ||
4379                                 TypeManager.ImplementsInterface (
4380                                         hm.enumerator_type, TypeManager.idisposable_type);
4381
4382                         return true;
4383                 }
4384
4385                 /// <summary>
4386                 ///   This filter is used to find the GetEnumerator method
4387                 ///   on which IEnumerator operates
4388                 /// </summary>
4389                 static MemberFilter FilterEnumerator;
4390
4391                 static Foreach ()
4392                 {
4393                         FilterEnumerator = new MemberFilter (GetEnumeratorFilter);
4394                 }
4395
4396                 void error1579 (Type t)
4397                 {
4398                         Report.Error (1579, loc,
4399                                       "foreach statement cannot operate on variables of type `" +
4400                                       t.FullName + "' because that class does not provide a " +
4401                                       " GetEnumerator method or it is inaccessible");
4402                 }
4403
4404                 static bool TryType (Type t, ForeachHelperMethods hm)
4405                 {
4406                         MemberList mi;
4407
4408                         mi = TypeContainer.FindMembers (t, MemberTypes.Method,
4409                                                         BindingFlags.Public | BindingFlags.NonPublic |
4410                                                         BindingFlags.Instance | BindingFlags.DeclaredOnly,
4411                                                         FilterEnumerator, hm);
4412
4413                         if (mi.Count == 0)
4414                                 return false;
4415
4416                         hm.get_enumerator = (MethodInfo) mi [0];
4417                         return true;
4418                 }
4419
4420                 //
4421                 // Looks for a usable GetEnumerator in the Type, and if found returns
4422                 // the three methods that participate: GetEnumerator, MoveNext and get_Current
4423                 //
4424                 ForeachHelperMethods ProbeCollectionType (EmitContext ec, Type t)
4425                 {
4426                         ForeachHelperMethods hm = new ForeachHelperMethods (ec, loc);
4427
4428                         for (Type tt = t; tt != null && tt != TypeManager.object_type;){
4429                                 if (TryType (tt, hm))
4430                                         return hm;
4431                                 tt = tt.BaseType;
4432                         }
4433
4434                         //
4435                         // Now try to find the method in the interfaces
4436                         //
4437                         while (t != null){
4438                                 Type [] ifaces = t.GetInterfaces ();
4439
4440                                 foreach (Type i in ifaces){
4441                                         if (TryType (i, hm))
4442                                                 return hm;
4443                                 }
4444
4445                                 //
4446                                 // Since TypeBuilder.GetInterfaces only returns the interface
4447                                 // types for this type, we have to keep looping, but once
4448                                 // we hit a non-TypeBuilder (ie, a Type), then we know we are
4449                                 // done, because it returns all the types
4450                                 //
4451                                 if ((t is TypeBuilder))
4452                                         t = t.BaseType;
4453                                 else
4454                                         break;
4455                         }
4456
4457                         return null;
4458                 }
4459
4460                 //
4461                 // FIXME: possible optimization.
4462                 // We might be able to avoid creating `empty' if the type is the sam
4463                 //
4464                 bool EmitCollectionForeach (EmitContext ec)
4465                 {
4466                         ILGenerator ig = ec.ig;
4467
4468                         enumerator = new VariableStorage (ec, hm.enumerator_type);
4469                         enumerator.EmitThis (ig);
4470                         //
4471                         // Instantiate the enumerator
4472                         //
4473                         if (expr.Type.IsValueType) {
4474                                 IMemoryLocation ml = expr as IMemoryLocation;
4475                                 // Load the address of the value type.
4476                                 if (ml == null) {
4477                                         // This happens if, for example, you have a property
4478                                         // returning a struct which is IEnumerable
4479                                         LocalBuilder t = ec.GetTemporaryLocal (expr.Type);
4480                                         expr.Emit (ec);
4481                                         ig.Emit (OpCodes.Stloc, t);
4482                                         ig.Emit (OpCodes.Ldloca, t);
4483                                         ec.FreeTemporaryLocal (t, expr.Type);
4484                                 } else {
4485                                         ml.AddressOf (ec, AddressOp.Load);
4486                                 }
4487
4488                                 // Emit the call.
4489                                 if (hm.get_enumerator.DeclaringType.IsValueType) {
4490                                         // the method is declared on the value type
4491                                         ig.Emit (OpCodes.Call, hm.get_enumerator);
4492                                 } else {
4493                                         // it is an interface method, so we must box
4494                                         ig.Emit (OpCodes.Box, expr.Type);
4495                                         ig.Emit (OpCodes.Callvirt, hm.get_enumerator);
4496                                 }
4497                         } else {
4498                                 expr.Emit (ec);
4499                                 ig.Emit (OpCodes.Callvirt, hm.get_enumerator);
4500                         }
4501                         enumerator.EmitStore (ig);
4502
4503                         //
4504                         // Protect the code in a try/finalize block, so that
4505                         // if the beast implement IDisposable, we get rid of it
4506                         //
4507                         if (hm.is_disposable && emit_finally)
4508                                 ig.BeginExceptionBlock ();
4509
4510                         Label end_try = ig.DefineLabel ();
4511
4512                         ig.MarkLabel (ec.LoopBegin);
4513
4514                         enumerator.EmitCall (ig, hm.move_next);
4515
4516                         ig.Emit (OpCodes.Brfalse, end_try);
4517
4518                         if (ec.InIterator)
4519                                 ig.Emit (OpCodes.Ldarg_0);
4520
4521                         enumerator.EmitCall (ig, hm.get_current);
4522
4523                         if (ec.InIterator){
4524                                 conv.Emit (ec);
4525                                 ig.Emit (OpCodes.Stfld, ((LocalVariableReference) variable).local_info.FieldBuilder);
4526                         } else
4527                                 ((IAssignMethod)variable).EmitAssign (ec, conv, false, false);
4528
4529                         statement.Emit (ec);
4530                         ig.Emit (OpCodes.Br, ec.LoopBegin);
4531                         ig.MarkLabel (end_try);
4532
4533                         //
4534                         // Now the finally block
4535                         //
4536                         if (hm.is_disposable) {
4537                                 DoEmitFinally (ec);
4538                                 if (emit_finally)
4539                                         ig.EndExceptionBlock ();
4540                         }
4541
4542                         ig.MarkLabel (ec.LoopEnd);
4543                         return false;
4544                 }
4545
4546                 public override void EmitFinally (EmitContext ec)
4547                 {
4548                         ILGenerator ig = ec.ig;
4549
4550                         if (hm.enumerator_type.IsValueType) {
4551                                 enumerator.EmitThis (ig);
4552
4553                                 MethodInfo mi = FetchMethodDispose (hm.enumerator_type);
4554                                 if (mi != null) {
4555                                         enumerator.EmitLoadAddress (ig);
4556                                         ig.Emit (OpCodes.Call, mi);
4557                                 } else {
4558                                         enumerator.EmitLoad (ig);
4559                                         ig.Emit (OpCodes.Box, hm.enumerator_type);
4560                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4561                                 }
4562                         } else {
4563                                 Label call_dispose = ig.DefineLabel ();
4564
4565                                 enumerator.EmitThis (ig);
4566                                 enumerator.EmitLoad (ig);
4567                                 ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
4568                                 ig.Emit (OpCodes.Dup);
4569                                 ig.Emit (OpCodes.Brtrue_S, call_dispose);
4570                                 ig.Emit (OpCodes.Pop);
4571
4572                                 Label end_finally = ig.DefineLabel ();
4573                                 ig.Emit (OpCodes.Br, end_finally);
4574
4575                                 ig.MarkLabel (call_dispose);
4576                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4577                                 ig.MarkLabel (end_finally);
4578
4579                                 if (emit_finally)
4580                                         ig.Emit (OpCodes.Endfinally);
4581                         }
4582                 }
4583
4584                 //
4585                 // FIXME: possible optimization.
4586                 // We might be able to avoid creating `empty' if the type is the sam
4587                 //
4588                 bool EmitArrayForeach (EmitContext ec)
4589                 {
4590                         int rank = array_type.GetArrayRank ();
4591                         ILGenerator ig = ec.ig;
4592
4593                         VariableStorage copy = new VariableStorage (ec, array_type);
4594
4595                         //
4596                         // Make our copy of the array
4597                         //
4598                         copy.EmitThis (ig);
4599                         expr.Emit (ec);
4600                         copy.EmitStore (ig);
4601
4602                         if (rank == 1){
4603                                 VariableStorage counter = new VariableStorage (ec,TypeManager.int32_type);
4604
4605                                 Label loop, test;
4606
4607                                 counter.EmitThis (ig);
4608                                 ig.Emit (OpCodes.Ldc_I4_0);
4609                                 counter.EmitStore (ig);
4610                                 test = ig.DefineLabel ();
4611                                 ig.Emit (OpCodes.Br, test);
4612
4613                                 loop = ig.DefineLabel ();
4614                                 ig.MarkLabel (loop);
4615
4616                                 if (ec.InIterator)
4617                                         ig.Emit (OpCodes.Ldarg_0);
4618
4619                                 copy.EmitThis (ig);
4620                                 copy.EmitLoad (ig);
4621                                 counter.EmitThis (ig);
4622                                 counter.EmitLoad (ig);
4623
4624                                 //
4625                                 // Load the value, we load the value using the underlying type,
4626                                 // then we use the variable.EmitAssign to load using the proper cast.
4627                                 //
4628                                 ArrayAccess.EmitLoadOpcode (ig, element_type);
4629                                 if (ec.InIterator){
4630                                         conv.Emit (ec);
4631                                         ig.Emit (OpCodes.Stfld, ((LocalVariableReference) variable).local_info.FieldBuilder);
4632                                 } else
4633                                         ((IAssignMethod)variable).EmitAssign (ec, conv, false, false);
4634
4635                                 statement.Emit (ec);
4636
4637                                 ig.MarkLabel (ec.LoopBegin);
4638                                 counter.EmitThis (ig);
4639                                 counter.EmitThis (ig);
4640                                 counter.EmitLoad (ig);
4641                                 ig.Emit (OpCodes.Ldc_I4_1);
4642                                 ig.Emit (OpCodes.Add);
4643                                 counter.EmitStore (ig);
4644
4645                                 ig.MarkLabel (test);
4646                                 counter.EmitThis (ig);
4647                                 counter.EmitLoad (ig);
4648                                 copy.EmitThis (ig);
4649                                 copy.EmitLoad (ig);
4650                                 ig.Emit (OpCodes.Ldlen);
4651                                 ig.Emit (OpCodes.Conv_I4);
4652                                 ig.Emit (OpCodes.Blt, loop);
4653                         } else {
4654                                 VariableStorage [] dim_len   = new VariableStorage [rank];
4655                                 VariableStorage [] dim_count = new VariableStorage [rank];
4656                                 Label [] loop = new Label [rank];
4657                                 Label [] test = new Label [rank];
4658                                 int dim;
4659
4660                                 for (dim = 0; dim < rank; dim++){
4661                                         dim_len [dim] = new VariableStorage (ec, TypeManager.int32_type);
4662                                         dim_count [dim] = new VariableStorage (ec, TypeManager.int32_type);
4663                                         test [dim] = ig.DefineLabel ();
4664                                         loop [dim] = ig.DefineLabel ();
4665                                 }
4666
4667                                 for (dim = 0; dim < rank; dim++){
4668                                         dim_len [dim].EmitThis (ig);
4669                                         copy.EmitThis (ig);
4670                                         copy.EmitLoad (ig);
4671                                         IntLiteral.EmitInt (ig, dim);
4672                                         ig.Emit (OpCodes.Callvirt, TypeManager.int_getlength_int);
4673                                         dim_len [dim].EmitStore (ig);
4674
4675                                 }
4676
4677                                 for (dim = 0; dim < rank; dim++){
4678                                         dim_count [dim].EmitThis (ig);
4679                                         ig.Emit (OpCodes.Ldc_I4_0);
4680                                         dim_count [dim].EmitStore (ig);
4681                                         ig.Emit (OpCodes.Br, test [dim]);
4682                                         ig.MarkLabel (loop [dim]);
4683                                 }
4684
4685                                 if (ec.InIterator)
4686                                         ig.Emit (OpCodes.Ldarg_0);
4687
4688                                 copy.EmitThis (ig);
4689                                 copy.EmitLoad (ig);
4690                                 for (dim = 0; dim < rank; dim++){
4691                                         dim_count [dim].EmitThis (ig);
4692                                         dim_count [dim].EmitLoad (ig);
4693                                 }
4694
4695                                 //
4696                                 // FIXME: Maybe we can cache the computation of `get'?
4697                                 //
4698                                 Type [] args = new Type [rank];
4699                                 MethodInfo get;
4700
4701                                 for (int i = 0; i < rank; i++)
4702                                         args [i] = TypeManager.int32_type;
4703
4704                                 ModuleBuilder mb = CodeGen.Module.Builder;
4705                                 get = mb.GetArrayMethod (
4706                                         array_type, "Get",
4707                                         CallingConventions.HasThis| CallingConventions.Standard,
4708                                         var_type, args);
4709                                 ig.Emit (OpCodes.Call, get);
4710                                 if (ec.InIterator){
4711                                         conv.Emit (ec);
4712                                         ig.Emit (OpCodes.Stfld, ((LocalVariableReference) variable).local_info.FieldBuilder);
4713                                 } else
4714                                         ((IAssignMethod)variable).EmitAssign (ec, conv, false, false);
4715                                 statement.Emit (ec);
4716                                 ig.MarkLabel (ec.LoopBegin);
4717                                 for (dim = rank - 1; dim >= 0; dim--){
4718                                         dim_count [dim].EmitThis (ig);
4719                                         dim_count [dim].EmitThis (ig);
4720                                         dim_count [dim].EmitLoad (ig);
4721                                         ig.Emit (OpCodes.Ldc_I4_1);
4722                                         ig.Emit (OpCodes.Add);
4723                                         dim_count [dim].EmitStore (ig);
4724
4725                                         ig.MarkLabel (test [dim]);
4726                                         dim_count [dim].EmitThis (ig);
4727                                         dim_count [dim].EmitLoad (ig);
4728                                         dim_len [dim].EmitThis (ig);
4729                                         dim_len [dim].EmitLoad (ig);
4730                                         ig.Emit (OpCodes.Blt, loop [dim]);
4731                                 }
4732                         }
4733                         ig.MarkLabel (ec.LoopEnd);
4734
4735                         return false;
4736                 }
4737
4738                 protected override void DoEmit (EmitContext ec)
4739                 {
4740                         ILGenerator ig = ec.ig;
4741
4742                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
4743                         ec.LoopBegin = ig.DefineLabel ();
4744                         ec.LoopEnd = ig.DefineLabel ();
4745
4746                         if (hm != null)
4747                                 EmitCollectionForeach (ec);
4748                         else
4749                                 EmitArrayForeach (ec);
4750
4751                         ec.LoopBegin = old_begin;
4752                         ec.LoopEnd = old_end;
4753                 }
4754         }
4755 }