mcs/gmcs/statement.cs

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