mcs/mcs/statement.cs

   1 //
   2 // statement.cs: Statement representation for the IL tree.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Martin Baulig (martin@gnome.org)
   7 //
   8 // (C) 2001, 2002 Ximian, Inc.
   9 //
  10
  11 using System;
  12 using System.Text;
  13 using System.Reflection;
  14 using System.Reflection.Emit;
  15 using System.Diagnostics;
  16
  17 namespace Mono.CSharp {
  18
  19         using System.Collections;
  20
  21         public abstract class Statement {
  22                 public Location loc;
  23
  24                 ///
  25                 /// Resolves the statement, true means that all sub-statements
  26                 /// did resolve ok.
  27                 //
  28                 public virtual bool Resolve (EmitContext ec)
  29                 {
  30                         return true;
  31                 }
  32
  33                 /// <summary>
  34                 ///   Return value indicates whether all code paths emitted return.
  35                 /// </summary>
  36                 public abstract bool Emit (EmitContext ec);
  37
  38                 public static Expression ResolveBoolean (EmitContext ec, Expression e, Location loc)
  39                 {
  40                         e = e.Resolve (ec);
  41                         if (e == null)
  42                                 return null;
  43
  44                         if (e.Type != TypeManager.bool_type){
  45                                 e = Expression.ConvertImplicit (ec, e, TypeManager.bool_type,
  46                                                                 new Location (-1));
  47                         }
  48
  49                         if (e == null){
  50                                 Report.Error (
  51                                         31, loc, "Can not convert the expression to a boolean");
  52                         }
  53
  54                         if (CodeGen.SymbolWriter != null)
  55                                 ec.Mark (loc);
  56
  57                         return e;
  58                 }
  59
  60                 /// <remarks>
  61                 ///    Encapsulates the emission of a boolean test and jumping to a
  62                 ///    destination.
  63                 ///
  64                 ///    This will emit the bool expression in `bool_expr' and if
  65                 ///    `target_is_for_true' is true, then the code will generate a
  66                 ///    brtrue to the target.   Otherwise a brfalse.
  67                 /// </remarks>
  68                 public static void EmitBoolExpression (EmitContext ec, Expression bool_expr,
  69                                                        Label target, bool target_is_for_true)
  70                 {
  71                         ILGenerator ig = ec.ig;
  72
  73                         bool invert = false;
  74                         if (bool_expr is Unary){
  75                                 Unary u = (Unary) bool_expr;
  76
  77                                 if (u.Oper == Unary.Operator.LogicalNot){
  78                                         invert = true;
  79
  80                                         u.EmitLogicalNot (ec);
  81                                 }
  82                         } else if (bool_expr is Binary){
  83                                 Binary b = (Binary) bool_expr;
  84
  85                                 if (b.EmitBranchable (ec, target, target_is_for_true))
  86                                         return;
  87                         }
  88
  89                         if (!invert)
  90                                 bool_expr.Emit (ec);
  91
  92                         if (target_is_for_true){
  93                                 if (invert)
  94                                         ig.Emit (OpCodes.Brfalse, target);
  95                                 else
  96                                         ig.Emit (OpCodes.Brtrue, target);
  97                         } else {
  98                                 if (invert)
  99                                         ig.Emit (OpCodes.Brtrue, target);
 100                                 else
 101                                         ig.Emit (OpCodes.Brfalse, target);
 102                         }
 103                 }
 104
 105                 public static void Warning_DeadCodeFound (Location loc)
 106                 {
 107                         Report.Warning (162, loc, "Unreachable code detected");
 108                 }
 109         }
 110
 111         public class EmptyStatement : Statement {
 112                 public override bool Resolve (EmitContext ec)
 113                 {
 114                         return true;
 115                 }
 116
 117                 public override bool Emit (EmitContext ec)
 118                 {
 119                         return false;
 120                 }
 121         }
 122
 123         public class If : Statement {
 124                 Expression expr;
 125                 public Statement TrueStatement;
 126                 public Statement FalseStatement;
 127
 128                 public If (Expression expr, Statement trueStatement, Location l)
 129                 {
 130                         this.expr = expr;
 131                         TrueStatement = trueStatement;
 132                         loc = l;
 133                 }
 134
 135                 public If (Expression expr,
 136                            Statement trueStatement,
 137                            Statement falseStatement,
 138                            Location l)
 139                 {
 140                         this.expr = expr;
 141                         TrueStatement = trueStatement;
 142                         FalseStatement = falseStatement;
 143                         loc = l;
 144                 }
 145
 146                 public override bool Resolve (EmitContext ec)
 147                 {
 148                         Report.Debug (1, "START IF BLOCK", loc);
 149
 150                         expr = ResolveBoolean (ec, expr, loc);
 151                         if (expr == null){
 152                                 return false;
 153                         }
 154
 155                         ec.StartFlowBranching (FlowBranchingType.BLOCK, loc);
 156
 157                         if (!TrueStatement.Resolve (ec)) {
 158                                 ec.KillFlowBranching ();
 159                                 return false;
 160                         }
 161
 162                         ec.CurrentBranching.CreateSibling ();
 163
 164                         if ((FalseStatement != null) && !FalseStatement.Resolve (ec)) {
 165                                 ec.KillFlowBranching ();
 166                                 return false;
 167                         }
 168
 169                         ec.EndFlowBranching ();
 170
 171                         Report.Debug (1, "END IF BLOCK", loc);
 172
 173                         return true;
 174                 }
 175
 176                 public override bool Emit (EmitContext ec)
 177                 {
 178                         ILGenerator ig = ec.ig;
 179                         Label false_target = ig.DefineLabel ();
 180                         Label end;
 181                         bool is_true_ret, is_false_ret;
 182
 183                         //
 184                         // Dead code elimination
 185                         //
 186                         if (expr is BoolConstant){
 187                                 bool take = ((BoolConstant) expr).Value;
 188
 189                                 if (take){
 190                                         if (FalseStatement != null){
 191                                                 Warning_DeadCodeFound (FalseStatement.loc);
 192                                         }
 193                                         return TrueStatement.Emit (ec);
 194                                 } else {
 195                                         Warning_DeadCodeFound (TrueStatement.loc);
 196                                         if (FalseStatement != null)
 197                                                 return FalseStatement.Emit (ec);
 198                                 }
 199                         }
 200
 201                         EmitBoolExpression (ec, expr, false_target, false);
 202
 203                         is_true_ret = TrueStatement.Emit (ec);
 204                         is_false_ret = is_true_ret;
 205
 206                         if (FalseStatement != null){
 207                                 bool branch_emitted = false;
 208
 209                                 end = ig.DefineLabel ();
 210                                 if (!is_true_ret){
 211                                         ig.Emit (OpCodes.Br, end);
 212                                         branch_emitted = true;
 213                                 }
 214
 215                                 ig.MarkLabel (false_target);
 216                                 is_false_ret = FalseStatement.Emit (ec);
 217
 218                                 if (branch_emitted)
 219                                         ig.MarkLabel (end);
 220                         } else {
 221                                 ig.MarkLabel (false_target);
 222                                 is_false_ret = false;
 223                         }
 224
 225                         return is_true_ret && is_false_ret;
 226                 }
 227         }
 228
 229         public class Do : Statement {
 230                 public Expression expr;
 231                 public readonly Statement  EmbeddedStatement;
 232
 233                 public Do (Statement statement, Expression boolExpr, Location l)
 234                 {
 235                         expr = boolExpr;
 236                         EmbeddedStatement = statement;
 237                         loc = l;
 238                 }
 239
 240                 public override bool Resolve (EmitContext ec)
 241                 {
 242                         bool ok = true;
 243
 244                         ec.StartFlowBranching (FlowBranchingType.LOOP_BLOCK, loc);
 245
 246                         if (!EmbeddedStatement.Resolve (ec))
 247                                 ok = false;
 248
 249                         ec.EndFlowBranching ();
 250
 251                         expr = ResolveBoolean (ec, expr, loc);
 252                         if (expr == null)
 253                                 ok = false;
 254
 255                         return ok;
 256                 }
 257
 258                 public override bool Emit (EmitContext ec)
 259                 {
 260                         ILGenerator ig = ec.ig;
 261                         Label loop = ig.DefineLabel ();
 262                         Label old_begin = ec.LoopBegin;
 263                         Label old_end = ec.LoopEnd;
 264                         bool  old_inloop = ec.InLoop;
 265                         bool old_breaks = ec.Breaks;
 266                         int old_loop_begin_try_catch_level = ec.LoopBeginTryCatchLevel;
 267
 268                         ec.LoopBegin = ig.DefineLabel ();
 269                         ec.LoopEnd = ig.DefineLabel ();
 270                         ec.InLoop = true;
 271                         ec.LoopBeginTryCatchLevel = ec.TryCatchLevel;
 272
 273                         ig.MarkLabel (loop);
 274                         ec.Breaks = false;
 275                         EmbeddedStatement.Emit (ec);
 276                         bool breaks = ec.Breaks;
 277                         ig.MarkLabel (ec.LoopBegin);
 278
 279                         //
 280                         // Dead code elimination
 281                         //
 282                         if (expr is BoolConstant){
 283                                 bool res = ((BoolConstant) expr).Value;
 284
 285                                 if (res)
 286                                         ec.ig.Emit (OpCodes.Br, loop);
 287                         } else
 288                                 EmitBoolExpression (ec, expr, loop, true);
 289
 290                         ig.MarkLabel (ec.LoopEnd);
 291
 292                         ec.LoopBeginTryCatchLevel = old_loop_begin_try_catch_level;
 293                         ec.LoopBegin = old_begin;
 294                         ec.LoopEnd = old_end;
 295                         ec.InLoop = old_inloop;
 296                         ec.Breaks = old_breaks;
 297
 298                         //
 299                         // Inform whether we are infinite or not
 300                         //
 301                         if (expr is BoolConstant){
 302                                 BoolConstant bc = (BoolConstant) expr;
 303
 304                                 if (bc.Value == true)
 305                                         return breaks == false;
 306                         }
 307
 308                         return false;
 309                 }
 310         }
 311
 312         public class While : Statement {
 313                 public Expression expr;
 314                 public readonly Statement Statement;
 315
 316                 public While (Expression boolExpr, Statement statement, Location l)
 317                 {
 318                         this.expr = boolExpr;
 319                         Statement = statement;
 320                         loc = l;
 321                 }
 322
 323                 public override bool Resolve (EmitContext ec)
 324                 {
 325                         bool ok = true;
 326
 327                         expr = ResolveBoolean (ec, expr, loc);
 328                         if (expr == null)
 329                                 return false;
 330
 331                         ec.StartFlowBranching (FlowBranchingType.LOOP_BLOCK, loc);
 332
 333                         if (!Statement.Resolve (ec))
 334                                 ok = false;
 335
 336                         ec.EndFlowBranching ();
 337
 338                         return ok;
 339                 }
 340
 341                 public override bool Emit (EmitContext ec)
 342                 {
 343                         ILGenerator ig = ec.ig;
 344                         Label old_begin = ec.LoopBegin;
 345                         Label old_end = ec.LoopEnd;
 346                         bool old_inloop = ec.InLoop;
 347                         bool old_breaks = ec.Breaks;
 348                         Label while_loop = ig.DefineLabel ();
 349                         int old_loop_begin_try_catch_level = ec.LoopBeginTryCatchLevel;
 350                         bool ret;
 351
 352                         ec.LoopBegin = ig.DefineLabel ();
 353                         ec.LoopEnd = ig.DefineLabel ();
 354                         ec.InLoop = true;
 355                         ec.LoopBeginTryCatchLevel = ec.TryCatchLevel;
 356
 357                         ig.Emit (OpCodes.Br, ec.LoopBegin);
 358                         ig.MarkLabel (while_loop);
 359
 360                         //
 361                         // Inform whether we are infinite or not
 362                         //
 363                         if (expr is BoolConstant){
 364                                 BoolConstant bc = (BoolConstant) expr;
 365
 366                                 ig.MarkLabel (ec.LoopBegin);
 367                                 if (bc.Value == false){
 368                                         Warning_DeadCodeFound (Statement.loc);
 369                                         ret = false;
 370                                 } else {
 371                                         bool breaks;
 372
 373                                         ec.Breaks = false;
 374                                         Statement.Emit (ec);
 375                                         breaks = ec.Breaks;
 376                                         ig.Emit (OpCodes.Br, ec.LoopBegin);
 377
 378                                         //
 379                                         // Inform that we are infinite (ie, `we return'), only
 380                                         // if we do not `break' inside the code.
 381                                         //
 382                                         ret = breaks == false;
 383                                 }
 384                                 ig.MarkLabel (ec.LoopEnd);
 385                         } else {
 386                                 Statement.Emit (ec);
 387
 388                                 ig.MarkLabel (ec.LoopBegin);
 389
 390                                 EmitBoolExpression (ec, expr, while_loop, true);
 391                                 ig.MarkLabel (ec.LoopEnd);
 392
 393                                 ret = false;
 394                         }
 395
 396                         ec.LoopBegin = old_begin;
 397                         ec.LoopEnd = old_end;
 398                         ec.InLoop = old_inloop;
 399                         ec.Breaks = old_breaks;
 400                         ec.LoopBeginTryCatchLevel = old_loop_begin_try_catch_level;
 401
 402                         return ret;
 403                 }
 404         }
 405
 406         public class For : Statement {
 407                 Expression Test;
 408                 readonly Statement InitStatement;
 409                 readonly Statement Increment;
 410                 readonly Statement Statement;
 411
 412                 public For (Statement initStatement,
 413                             Expression test,
 414                             Statement increment,
 415                             Statement statement,
 416                             Location l)
 417                 {
 418                         InitStatement = initStatement;
 419                         Test = test;
 420                         Increment = increment;
 421                         Statement = statement;
 422                         loc = l;
 423                 }
 424
 425                 public override bool Resolve (EmitContext ec)
 426                 {
 427                         bool ok = true;
 428
 429                         if (InitStatement != null){
 430                                 if (!InitStatement.Resolve (ec))
 431                                         ok = false;
 432                         }
 433
 434                         if (Test != null){
 435                                 Test = ResolveBoolean (ec, Test, loc);
 436                                 if (Test == null)
 437                                         ok = false;
 438                         }
 439
 440                         if (Increment != null){
 441                                 if (!Increment.Resolve (ec))
 442                                         ok = false;
 443                         }
 444
 445                         ec.StartFlowBranching (FlowBranchingType.LOOP_BLOCK, loc);
 446
 447                         if (!Statement.Resolve (ec))
 448                                 ok = false;
 449
 450                         ec.EndFlowBranching ();
 451
 452                         return ok;
 453                 }
 454
 455                 public override bool Emit (EmitContext ec)
 456                 {
 457                         ILGenerator ig = ec.ig;
 458                         Label old_begin = ec.LoopBegin;
 459                         Label old_end = ec.LoopEnd;
 460                         bool old_inloop = ec.InLoop;
 461                         bool old_breaks = ec.Breaks;
 462                         int old_loop_begin_try_catch_level = ec.LoopBeginTryCatchLevel;
 463                         Label loop = ig.DefineLabel ();
 464                         Label test = ig.DefineLabel ();
 465
 466                         if (InitStatement != null)
 467                                 if (! (InitStatement is EmptyStatement))
 468                                         InitStatement.Emit (ec);
 469
 470                         ec.LoopBegin = ig.DefineLabel ();
 471                         ec.LoopEnd = ig.DefineLabel ();
 472                         ec.InLoop = true;
 473                         ec.LoopBeginTryCatchLevel = ec.TryCatchLevel;
 474
 475                         ig.Emit (OpCodes.Br, test);
 476                         ig.MarkLabel (loop);
 477                         ec.Breaks = false;
 478                         Statement.Emit (ec);
 479                         bool breaks = ec.Breaks;
 480
 481                         ig.MarkLabel (ec.LoopBegin);
 482                         if (!(Increment is EmptyStatement))
 483                                 Increment.Emit (ec);
 484
 485                         ig.MarkLabel (test);
 486                         //
 487                         // If test is null, there is no test, and we are just
 488                         // an infinite loop
 489                         //
 490                         if (Test != null)
 491                                 EmitBoolExpression (ec, Test, loop, true);
 492                         else
 493                                 ig.Emit (OpCodes.Br, loop);
 494                         ig.MarkLabel (ec.LoopEnd);
 495
 496                         ec.LoopBegin = old_begin;
 497                         ec.LoopEnd = old_end;
 498                         ec.InLoop = old_inloop;
 499                         ec.Breaks = old_breaks;
 500                         ec.LoopBeginTryCatchLevel = old_loop_begin_try_catch_level;
 501
 502                         //
 503                         // Inform whether we are infinite or not
 504                         //
 505                         if (Test != null){
 506                                 if (Test is BoolConstant){
 507                                         BoolConstant bc = (BoolConstant) Test;
 508
 509                                         if (bc.Value)
 510                                                 return breaks == false;
 511                                 }
 512                                 return false;
 513                         } else
 514                                 return true;
 515                 }
 516         }
 517
 518         public class StatementExpression : Statement {
 519                 Expression expr;
 520
 521                 public StatementExpression (ExpressionStatement expr, Location l)
 522                 {
 523                         this.expr = expr;
 524                         loc = l;
 525                 }
 526
 527                 public override bool Resolve (EmitContext ec)
 528                 {
 529                         expr = (Expression) expr.Resolve (ec);
 530                         return expr != null;
 531                 }
 532
 533                 public override bool Emit (EmitContext ec)
 534                 {
 535                         ILGenerator ig = ec.ig;
 536
 537                         if (expr is ExpressionStatement)
 538                                 ((ExpressionStatement) expr).EmitStatement (ec);
 539                         else {
 540                                 expr.Emit (ec);
 541                                 ig.Emit (OpCodes.Pop);
 542                         }
 543
 544                         return false;
 545                 }
 546
 547                 public override string ToString ()
 548                 {
 549                         return "StatementExpression (" + expr + ")";
 550                 }
 551         }
 552
 553         /// <summary>
 554         ///   Implements the return statement
 555         /// </summary>
 556         public class Return : Statement {
 557                 public Expression Expr;
 558
 559                 public Return (Expression expr, Location l)
 560                 {
 561                         Expr = expr;
 562                         loc = l;
 563                 }
 564
 565                 public override bool Resolve (EmitContext ec)
 566                 {
 567                         if (Expr != null){
 568                                 Expr = Expr.Resolve (ec);
 569                                 if (Expr == null)
 570                                         return false;
 571                         }
 572
 573                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
 574
 575                         if (ec.CurrentBranching.InTryBlock ())
 576                                 ec.CurrentBranching.AddFinallyVector (vector);
 577
 578                         vector.Returns = FlowReturns.ALWAYS;
 579                         return true;
 580                 }
 581
 582                 public override bool Emit (EmitContext ec)
 583                 {
 584                         if (ec.InFinally){
 585                                 Report.Error (157,loc,"Control can not leave the body of the finally block");
 586                                 return false;
 587                         }
 588
 589                         if (ec.ReturnType == null){
 590                                 if (Expr != null){
 591                                         Report.Error (127, loc, "Return with a value not allowed here");
 592                                         return true;
 593                                 }
 594                         } else {
 595                                 if (Expr == null){
 596                                         Report.Error (126, loc, "An object of type `" +
 597                                                       TypeManager.CSharpName (ec.ReturnType) + "' is " +
 598                                                       "expected for the return statement");
 599                                         return true;
 600                                 }
 601
 602                                 if (Expr.Type != ec.ReturnType)
 603                                         Expr = Expression.ConvertImplicitRequired (
 604                                                 ec, Expr, ec.ReturnType, loc);
 605
 606                                 if (Expr == null)
 607                                         return true;
 608
 609                                 Expr.Emit (ec);
 610
 611                                 if (ec.InTry || ec.InCatch)
 612                                         ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 613                         }
 614
 615                         if (ec.InTry || ec.InCatch) {
 616                                 if (!ec.HasReturnLabel) {
 617                                         ec.ReturnLabel = ec.ig.DefineLabel ();
 618                                         ec.HasReturnLabel = true;
 619                                 }
 620                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 621                         } else
 622                                 ec.ig.Emit (OpCodes.Ret);
 623
 624                         return true;
 625                 }
 626         }
 627
 628         public class Goto : Statement {
 629                 string target;
 630                 Block block;
 631                 LabeledStatement label;
 632
 633                 public override bool Resolve (EmitContext ec)
 634                 {
 635                         label = block.LookupLabel (target);
 636                         if (label == null){
 637                                 Report.Error (
 638                                         159, loc,
 639                                         "No such label `" + target + "' in this scope");
 640                                 return false;
 641                         }
 642
 643                         // If this is a forward goto.
 644                         if (!label.IsDefined)
 645                                 label.AddUsageVector (ec.CurrentBranching.CurrentUsageVector);
 646
 647                         ec.CurrentBranching.CurrentUsageVector.Breaks = FlowReturns.ALWAYS;
 648
 649                         return true;
 650                 }
 651
 652                 public Goto (Block parent_block, string label, Location l)
 653                 {
 654                         block = parent_block;
 655                         loc = l;
 656                         target = label;
 657                 }
 658
 659                 public string Target {
 660                         get {
 661                                 return target;
 662                         }
 663                 }
 664
 665                 public override bool Emit (EmitContext ec)
 666                 {
 667                         Label l = label.LabelTarget (ec);
 668                         ec.ig.Emit (OpCodes.Br, l);
 669
 670                         return false;
 671                 }
 672         }
 673
 674         public class LabeledStatement : Statement {
 675                 public readonly Location Location;
 676                 string label_name;
 677                 bool defined;
 678                 bool referenced;
 679                 Label label;
 680
 681                 ArrayList vectors;
 682
 683                 public LabeledStatement (string label_name, Location l)
 684                 {
 685                         this.label_name = label_name;
 686                         this.Location = l;
 687                 }
 688
 689                 public Label LabelTarget (EmitContext ec)
 690                 {
 691                         if (defined)
 692                                 return label;
 693                         label = ec.ig.DefineLabel ();
 694                         defined = true;
 695
 696                         return label;
 697                 }
 698
 699                 public bool IsDefined {
 700                         get {
 701                                 return defined;
 702                         }
 703                 }
 704
 705                 public bool HasBeenReferenced {
 706                         get {
 707                                 return referenced;
 708                         }
 709                 }
 710
 711                 public void AddUsageVector (FlowBranching.UsageVector vector)
 712                 {
 713                         if (vectors == null)
 714                                 vectors = new ArrayList ();
 715
 716                         vectors.Add (vector.Clone ());
 717                 }
 718
 719                 public override bool Resolve (EmitContext ec)
 720                 {
 721                         if (vectors != null)
 722                                 ec.CurrentBranching.CurrentUsageVector.MergeJumpOrigins (vectors);
 723
 724                         referenced = true;
 725
 726                         return true;
 727                 }
 728
 729                 public override bool Emit (EmitContext ec)
 730                 {
 731                         LabelTarget (ec);
 732                         ec.ig.MarkLabel (label);
 733
 734                         return false;
 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.Returns = FlowReturns.UNREACHABLE;
 752                         ec.CurrentBranching.CurrentUsageVector.Breaks = FlowReturns.ALWAYS;
 753                         return true;
 754                 }
 755
 756                 public override bool Emit (EmitContext ec)
 757                 {
 758                         if (ec.Switch == null){
 759                                 Report.Error (153, loc, "goto default is only valid in a switch statement");
 760                                 return false;
 761                         }
 762
 763                         if (!ec.Switch.GotDefault){
 764                                 Report.Error (159, loc, "No default target on switch statement");
 765                                 return false;
 766                         }
 767                         ec.ig.Emit (OpCodes.Br, ec.Switch.DefaultTarget);
 768                         return false;
 769                 }
 770         }
 771
 772         /// <summary>
 773         ///   `goto case' statement
 774         /// </summary>
 775         public class GotoCase : Statement {
 776                 Expression expr;
 777                 Label label;
 778
 779                 public GotoCase (Expression e, Location l)
 780                 {
 781                         expr = e;
 782                         loc = l;
 783                 }
 784
 785                 public override bool Resolve (EmitContext ec)
 786                 {
 787                         if (ec.Switch == null){
 788                                 Report.Error (153, loc, "goto case is only valid in a switch statement");
 789                                 return false;
 790                         }
 791
 792                         expr = expr.Resolve (ec);
 793                         if (expr == null)
 794                                 return false;
 795
 796                         if (!(expr is Constant)){
 797                                 Report.Error (159, loc, "Target expression for goto case is not constant");
 798                                 return false;
 799                         }
 800
 801                         object val = Expression.ConvertIntLiteral (
 802                                 (Constant) expr, ec.Switch.SwitchType, loc);
 803
 804                         if (val == null)
 805                                 return false;
 806
 807                         SwitchLabel sl = (SwitchLabel) ec.Switch.Elements [val];
 808
 809                         if (sl == null){
 810                                 Report.Error (
 811                                         159, loc,
 812                                         "No such label 'case " + val + "': for the goto case");
 813                         }
 814
 815                         label = sl.ILLabelCode;
 816
 817                         ec.CurrentBranching.CurrentUsageVector.Returns = FlowReturns.UNREACHABLE;
 818                         ec.CurrentBranching.CurrentUsageVector.Breaks = FlowReturns.ALWAYS;
 819                         return true;
 820                 }
 821
 822                 public override bool Emit (EmitContext ec)
 823                 {
 824                         ec.ig.Emit (OpCodes.Br, label);
 825                         return true;
 826                 }
 827         }
 828
 829         public class Throw : Statement {
 830                 Expression expr;
 831
 832                 public Throw (Expression expr, Location l)
 833                 {
 834                         this.expr = expr;
 835                         loc = l;
 836                 }
 837
 838                 public override bool Resolve (EmitContext ec)
 839                 {
 840                         if (expr != null){
 841                                 expr = expr.Resolve (ec);
 842                                 if (expr == null)
 843                                         return false;
 844
 845                                 ExprClass eclass = expr.eclass;
 846
 847                                 if (!(eclass == ExprClass.Variable || eclass == ExprClass.PropertyAccess ||
 848                                       eclass == ExprClass.Value || eclass == ExprClass.IndexerAccess)) {
 849                                         expr.Error118 ("value, variable, property or indexer access ");
 850                                         return false;
 851                                 }
 852
 853                                 Type t = expr.Type;
 854
 855                                 if (t != TypeManager.exception_type && !t.IsSubclassOf (TypeManager.exception_type)) {
 856                                         Report.Error (155, loc,
 857                                                       "The type caught or thrown must be derived " +
 858                                                       "from System.Exception");
 859                                         return false;
 860                                 }
 861                         }
 862
 863                         ec.CurrentBranching.CurrentUsageVector.Returns = FlowReturns.EXCEPTION;
 864                         return true;
 865                 }
 866
 867                 public override bool Emit (EmitContext ec)
 868                 {
 869                         if (expr == null){
 870                                 if (ec.InCatch)
 871                                         ec.ig.Emit (OpCodes.Rethrow);
 872                                 else {
 873                                         Report.Error (
 874                                                 156, loc,
 875                                                 "A throw statement with no argument is only " +
 876                                                 "allowed in a catch clause");
 877                                 }
 878                                 return false;
 879                         }
 880
 881                         expr.Emit (ec);
 882
 883                         ec.ig.Emit (OpCodes.Throw);
 884
 885                         return true;
 886                 }
 887         }
 888
 889         public class Break : Statement {
 890
 891                 public Break (Location l)
 892                 {
 893                         loc = l;
 894                 }
 895
 896                 public override bool Resolve (EmitContext ec)
 897                 {
 898                         ec.CurrentBranching.CurrentUsageVector.Breaks = FlowReturns.ALWAYS;
 899                         return true;
 900                 }
 901
 902                 public override bool Emit (EmitContext ec)
 903                 {
 904                         ILGenerator ig = ec.ig;
 905
 906                         if (ec.InLoop == false && ec.Switch == null){
 907                                 Report.Error (139, loc, "No enclosing loop or switch to continue to");
 908                                 return false;
 909                         }
 910
 911                         ec.Breaks = true;
 912                         if (ec.InTry || ec.InCatch)
 913                                 ig.Emit (OpCodes.Leave, ec.LoopEnd);
 914                         else
 915                                 ig.Emit (OpCodes.Br, ec.LoopEnd);
 916
 917                         return false;
 918                 }
 919         }
 920
 921         public class Continue : Statement {
 922
 923                 public Continue (Location l)
 924                 {
 925                         loc = l;
 926                 }
 927
 928                 public override bool Resolve (EmitContext ec)
 929                 {
 930                         ec.CurrentBranching.CurrentUsageVector.Breaks = FlowReturns.ALWAYS;
 931                         return true;
 932                 }
 933
 934                 public override bool Emit (EmitContext ec)
 935                 {
 936                         Label begin = ec.LoopBegin;
 937
 938                         if (!ec.InLoop){
 939                                 Report.Error (139, loc, "No enclosing loop to continue to");
 940                                 return false;
 941                         }
 942
 943                         //
 944                         // UGH: Non trivial.  This Br might cross a try/catch boundary
 945                         // How can we tell?
 946                         //
 947                         // while () {
 948                         //   try { ... } catch { continue; }
 949                         // }
 950                         //
 951                         // From:
 952                         // try {} catch { while () { continue; }}
 953                         //
 954                         if (ec.TryCatchLevel > ec.LoopBeginTryCatchLevel)
 955                                 ec.ig.Emit (OpCodes.Leave, begin);
 956                         else if (ec.TryCatchLevel < ec.LoopBeginTryCatchLevel)
 957                                 throw new Exception ("Should never happen");
 958                         else
 959                                 ec.ig.Emit (OpCodes.Br, begin);
 960                         return false;
 961                 }
 962         }
 963
 964         // <summary>
 965         //   This is used in the control flow analysis code to specify whether the
 966         //   current code block may return to its enclosing block before reaching
 967         //   its end.
 968         // </summary>
 969         public enum FlowReturns {
 970                 // It can never return.
 971                 NEVER,
 972
 973                 // This means that the block contains a conditional return statement
 974                 // somewhere.
 975                 SOMETIMES,
 976
 977                 // The code always returns, ie. there's an unconditional return / break
 978                 // statement in it.
 979                 ALWAYS,
 980
 981                 // The code always throws an exception.
 982                 EXCEPTION,
 983
 984                 // The current code block is unreachable.  This happens if it's immediately
 985                 // following a FlowReturns.ALWAYS block.
 986                 UNREACHABLE
 987         }
 988
 989         // <summary>
 990         //   This is a special bit vector which can inherit from another bit vector doing a
 991         //   copy-on-write strategy.  The inherited vector may have a smaller size than the
 992         //   current one.
 993         // </summary>
 994         public class MyBitVector {
 995                 public readonly int Count;
 996                 public readonly MyBitVector InheritsFrom;
 997
 998                 bool is_dirty;
 999                 BitArray vector;
1000
1001                 public MyBitVector (int Count)
1002                         : this (null, Count)
1003                 { }
1004
1005                 public MyBitVector (MyBitVector InheritsFrom, int Count)
1006                 {
1007                         this.InheritsFrom = InheritsFrom;
1008                         this.Count = Count;
1009                 }
1010
1011                 // <summary>
1012                 //   Checks whether this bit vector has been modified.  After setting this to true,
1013                 //   we won't use the inherited vector anymore, but our own copy of it.
1014                 // </summary>
1015                 public bool IsDirty {
1016                         get {
1017                                 return is_dirty;
1018                         }
1019
1020                         set {
1021                                 if (!is_dirty)
1022                                         initialize_vector ();
1023                         }
1024                 }
1025
1026                 // <summary>
1027                 //   Get/set bit `index' in the bit vector.
1028                 // </summary>
1029                 public bool this [int index]
1030                 {
1031                         get {
1032                                 if (index > Count)
1033                                         throw new ArgumentOutOfRangeException ();
1034
1035                                 // We're doing a "copy-on-write" strategy here; as long
1036                                 // as nobody writes to the array, we can use our parent's
1037                                 // copy instead of duplicating the vector.
1038
1039                                 if (vector != null)
1040                                         return vector [index];
1041                                 else if (InheritsFrom != null) {
1042                                         BitArray inherited = InheritsFrom.Vector;
1043
1044                                         if (index < inherited.Count)
1045                                                 return inherited [index];
1046                                         else
1047                                                 return false;
1048                                 } else
1049                                         return false;
1050                         }
1051
1052                         set {
1053                                 if (index > Count)
1054                                         throw new ArgumentOutOfRangeException ();
1055
1056                                 // Only copy the vector if we're actually modifying it.
1057
1058                                 if (this [index] != value) {
1059                                         initialize_vector ();
1060
1061                                         vector [index] = value;
1062                                 }
1063                         }
1064                 }
1065
1066                 // <summary>
1067                 //   If you explicitly convert the MyBitVector to a BitArray, you will get a deep
1068                 //   copy of the bit vector.
1069                 // </summary>
1070                 public static explicit operator BitArray (MyBitVector vector)
1071                 {
1072                         vector.initialize_vector ();
1073                         return vector.Vector;
1074                 }
1075
1076                 // <summary>
1077                 //   Performs an `or' operation on the bit vector.  The `new_vector' may have a
1078                 //   different size than the current one.
1079                 // </summary>
1080                 public void Or (MyBitVector new_vector)
1081                 {
1082                         BitArray new_array = new_vector.Vector;
1083
1084                         initialize_vector ();
1085
1086                         int upper;
1087                         if (vector.Count < new_array.Count)
1088                                 upper = vector.Count;
1089                         else
1090                                 upper = new_array.Count;
1091
1092                         for (int i = 0; i < upper; i++)
1093                                 vector [i] = vector [i] | new_array [i];
1094                 }
1095
1096                 // <summary>
1097                 //   Perfonrms an `and' operation on the bit vector.  The `new_vector' may have
1098                 //   a different size than the current one.
1099                 // </summary>
1100                 public void And (MyBitVector new_vector)
1101                 {
1102                         BitArray new_array = new_vector.Vector;
1103
1104                         initialize_vector ();
1105
1106                         int lower, upper;
1107                         if (vector.Count < new_array.Count)
1108                                 lower = upper = vector.Count;
1109                         else {
1110                                 lower = new_array.Count;
1111                                 upper = vector.Count;
1112                         }
1113
1114                         for (int i = 0; i < lower; i++)
1115                                 vector [i] = vector [i] & new_array [i];
1116
1117                         for (int i = lower; i < upper; i++)
1118                                 vector [i] = false;
1119                 }
1120
1121                 // <summary>
1122                 //   This does a deep copy of the bit vector.
1123                 // </summary>
1124                 public MyBitVector Clone ()
1125                 {
1126                         MyBitVector retval = new MyBitVector (Count);
1127
1128                         retval.Vector = Vector;
1129
1130                         return retval;
1131                 }
1132
1133                 BitArray Vector {
1134                         get {
1135                                 if (vector != null)
1136                                         return vector;
1137                                 else if (!is_dirty && (InheritsFrom != null))
1138                                         return InheritsFrom.Vector;
1139
1140                                 initialize_vector ();
1141
1142                                 return vector;
1143                         }
1144
1145                         set {
1146                                 initialize_vector ();
1147
1148                                 for (int i = 0; i < Math.Min (vector.Count, value.Count); i++)
1149                                         vector [i] = value [i];
1150                         }
1151                 }
1152
1153                 void initialize_vector ()
1154                 {
1155                         if (vector != null)
1156                                 return;
1157
1158                         vector = new BitArray (Count, false);
1159                         if (InheritsFrom != null)
1160                                 Vector = InheritsFrom.Vector;
1161
1162                         is_dirty = true;
1163                 }
1164
1165                 public override string ToString ()
1166                 {
1167                         StringBuilder sb = new StringBuilder ("MyBitVector (");
1168
1169                         BitArray vector = Vector;
1170                         sb.Append (Count);
1171                         sb.Append (",");
1172                         if (!IsDirty)
1173                                 sb.Append ("INHERITED - ");
1174                         for (int i = 0; i < vector.Count; i++) {
1175                                 if (i > 0)
1176                                         sb.Append (",");
1177                                 sb.Append (vector [i]);
1178                         }
1179
1180                         sb.Append (")");
1181                         return sb.ToString ();
1182                 }
1183         }
1184
1185         // <summary>
1186         //   The type of a FlowBranching.
1187         // </summary>
1188         public enum FlowBranchingType {
1189                 // Normal (conditional or toplevel) block.
1190                 BLOCK,
1191
1192                 // A loop block.
1193                 LOOP_BLOCK,
1194
1195                 // Try/Catch block.
1196                 EXCEPTION,
1197
1198                 // Switch block.
1199                 SWITCH,
1200
1201                 // Switch section.
1202                 SWITCH_SECTION
1203         }
1204
1205         // <summary>
1206         //   A new instance of this class is created every time a new block is resolved
1207         //   and if there's branching in the block's control flow.
1208         // </summary>
1209         public class FlowBranching {
1210                 // <summary>
1211                 //   The type of this flow branching.
1212                 // </summary>
1213                 public readonly FlowBranchingType Type;
1214
1215                 // <summary>
1216                 //   The block this branching is contained in.  This may be null if it's not
1217                 //   a top-level block and it doesn't declare any local variables.
1218                 // </summary>
1219                 public readonly Block Block;
1220
1221                 // <summary>
1222                 //   The parent of this branching or null if this is the top-block.
1223                 // </summary>
1224                 public readonly FlowBranching Parent;
1225
1226                 // <summary>
1227                 //   Start-Location of this flow branching.
1228                 // </summary>
1229                 public readonly Location Location;
1230
1231                 // <summary>
1232                 //   A list of UsageVectors.  A new vector is added each time control flow may
1233                 //   take a different path.
1234                 // </summary>
1235                 public ArrayList Siblings;
1236
1237                 //
1238                 // Private
1239                 //
1240                 InternalParameters param_info;
1241                 int[] param_map;
1242                 MyStructInfo[] struct_params;
1243                 int num_params;
1244                 ArrayList finally_vectors;
1245
1246                 static int next_id = 0;
1247                 int id;
1248
1249                 // <summary>
1250                 //   Performs an `And' operation on the FlowReturns status
1251                 //   (for instance, a block only returns ALWAYS if all its siblings
1252                 //   always return).
1253                 // </summary>
1254                 public static FlowReturns AndFlowReturns (FlowReturns a, FlowReturns b)
1255                 {
1256                         if (b == FlowReturns.UNREACHABLE)
1257                                 return a;
1258
1259                         switch (a) {
1260                         case FlowReturns.NEVER:
1261                                 if (b == FlowReturns.NEVER)
1262                                         return FlowReturns.NEVER;
1263                                 else
1264                                         return FlowReturns.SOMETIMES;
1265
1266                         case FlowReturns.SOMETIMES:
1267                                 return FlowReturns.SOMETIMES;
1268
1269                         case FlowReturns.ALWAYS:
1270                                 if ((b == FlowReturns.ALWAYS) || (b == FlowReturns.EXCEPTION))
1271                                         return FlowReturns.ALWAYS;
1272                                 else
1273                                         return FlowReturns.SOMETIMES;
1274
1275                         case FlowReturns.EXCEPTION:
1276                                 if (b == FlowReturns.EXCEPTION)
1277                                         return FlowReturns.EXCEPTION;
1278                                 else if (b == FlowReturns.ALWAYS)
1279                                         return FlowReturns.ALWAYS;
1280                                 else
1281                                         return FlowReturns.SOMETIMES;
1282                         }
1283
1284                         return b;
1285                 }
1286
1287                 // <summary>
1288                 //   The vector contains a BitArray with information about which local variables
1289                 //   and parameters are already initialized at the current code position.
1290                 // </summary>
1291                 public class UsageVector {
1292                         // <summary>
1293                         //   If this is true, then the usage vector has been modified and must be
1294                         //   merged when we're done with this branching.
1295                         // </summary>
1296                         public bool IsDirty;
1297
1298                         // <summary>
1299                         //   The number of parameters in this block.
1300                         // </summary>
1301                         public readonly int CountParameters;
1302
1303                         // <summary>
1304                         //   The number of locals in this block.
1305                         // </summary>
1306                         public readonly int CountLocals;
1307
1308                         // <summary>
1309                         //   If not null, then we inherit our state from this vector and do a
1310                         //   copy-on-write.  If null, then we're the first sibling in a top-level
1311                         //   block and inherit from the empty vector.
1312                         // </summary>
1313                         public readonly UsageVector InheritsFrom;
1314
1315                         //
1316                         // Private.
1317                         //
1318                         MyBitVector locals, parameters;
1319                         FlowReturns real_returns, real_breaks;
1320                         bool returns_set, breaks_set, is_finally;
1321
1322                         static int next_id = 0;
1323                         int id;
1324
1325                         //
1326                         // Normally, you should not use any of these constructors.
1327                         //
1328                         public UsageVector (UsageVector parent, int num_params, int num_locals)
1329                         {
1330                                 this.InheritsFrom = parent;
1331                                 this.CountParameters = num_params;
1332                                 this.CountLocals = num_locals;
1333                                 this.real_returns = FlowReturns.NEVER;
1334                                 this.real_breaks = FlowReturns.NEVER;
1335
1336                                 if (parent != null) {
1337                                         locals = new MyBitVector (parent.locals, CountLocals);
1338                                         if (num_params > 0)
1339                                                 parameters = new MyBitVector (parent.parameters, num_params);
1340                                 } else {
1341                                         locals = new MyBitVector (null, CountLocals);
1342                                         if (num_params > 0)
1343                                                 parameters = new MyBitVector (null, num_params);
1344                                 }
1345
1346                                 id = ++next_id;
1347                         }
1348
1349                         public UsageVector (UsageVector parent)
1350                                 : this (parent, parent.CountParameters, parent.CountLocals)
1351                         { }
1352
1353                         // <summary>
1354                         //   This does a deep copy of the usage vector.
1355                         // </summary>
1356                         public UsageVector Clone ()
1357                         {
1358                                 UsageVector retval = new UsageVector (null, CountParameters, CountLocals);
1359
1360                                 retval.locals = locals.Clone ();
1361                                 if (parameters != null)
1362                                         retval.parameters = parameters.Clone ();
1363                                 retval.real_returns = real_returns;
1364                                 retval.real_breaks = real_breaks;
1365
1366                                 return retval;
1367                         }
1368
1369                         //
1370                         // State of parameter `number'.
1371                         //
1372                         public bool this [int number]
1373                         {
1374                                 get {
1375                                         if (number == -1)
1376                                                 return true;
1377                                         else if (number == 0)
1378                                                 throw new ArgumentException ();
1379
1380                                         return parameters [number - 1];
1381                                 }
1382
1383                                 set {
1384                                         if (number == -1)
1385                                                 return;
1386                                         else if (number == 0)
1387                                                 throw new ArgumentException ();
1388
1389                                         parameters [number - 1] = value;
1390                                 }
1391                         }
1392
1393                         //
1394                         // State of the local variable `vi'.
1395                         // If the local variable is a struct, use a non-zero `field_idx'
1396                         // to check an individual field in it.
1397                         //
1398                         public bool this [VariableInfo vi, int field_idx]
1399                         {
1400                                 get {
1401                                         if (vi.Number == -1)
1402                                                 return true;
1403                                         else if (vi.Number == 0)
1404                                                 throw new ArgumentException ();
1405
1406                                         return locals [vi.Number + field_idx - 1];
1407                                 }
1408
1409                                 set {
1410                                         if (vi.Number == -1)
1411                                                 return;
1412                                         else if (vi.Number == 0)
1413                                                 throw new ArgumentException ();
1414
1415                                         locals [vi.Number + field_idx - 1] = value;
1416                                 }
1417                         }
1418
1419                         // <summary>
1420                         //   Specifies when the current block returns.
1421                         // </summary>
1422                         public FlowReturns Returns {
1423                                 get {
1424                                         return real_returns;
1425                                 }
1426
1427                                 set {
1428                                         real_returns = value;
1429                                         returns_set = true;
1430                                 }
1431                         }
1432
1433                         // <summary>
1434                         //   Specifies whether control may return to our containing block
1435                         //   before reaching the end of this block.  This happens if there
1436                         //   is a break/continue/goto/return in it.
1437                         // </summary>
1438                         public FlowReturns Breaks {
1439                                 get {
1440                                         return real_breaks;
1441                                 }
1442
1443                                 set {
1444                                         real_breaks = value;
1445                                         breaks_set = true;
1446                                 }
1447                         }
1448
1449                         // <summary>
1450                         //   Merge a child branching.
1451                         // </summary>
1452                         public FlowReturns MergeChildren (FlowBranching branching, ICollection children)
1453                         {
1454                                 MyBitVector new_locals = null;
1455                                 MyBitVector new_params = null;
1456
1457                                 FlowReturns new_returns = FlowReturns.NEVER;
1458                                 FlowReturns new_breaks = FlowReturns.NEVER;
1459                                 bool new_returns_set = false, new_breaks_set = false;
1460                                 bool breaks;
1461
1462                                 Report.Debug (1, "MERGING CHILDREN", branching, this);
1463
1464                                 foreach (UsageVector child in children) {
1465                                         Report.Debug (1, "  MERGING CHILD", child);
1466
1467                                         // If Returns is already set, perform an `And' operation on it,
1468                                         // otherwise just set just.
1469                                         if (!new_returns_set) {
1470                                                 new_returns = child.Returns;
1471                                                 new_returns_set = true;
1472                                         } else
1473                                                 new_returns = AndFlowReturns (new_returns, child.Returns);
1474
1475                                         // If Breaks is already set, perform an `And' operation on it,
1476                                         // otherwise just set just.
1477                                         if (!new_breaks_set) {
1478                                                 new_breaks = child.Breaks;
1479                                                 new_breaks_set = true;
1480                                         } else
1481                                                 new_breaks = AndFlowReturns (new_breaks, child.Breaks);
1482
1483                                         // Ignore unreachable children.
1484                                         if (child.Returns == FlowReturns.UNREACHABLE)
1485                                                 continue;
1486
1487                                         // Check whether control may reach the end of this sibling.
1488                                         // This happens unless we either always return or always break.
1489                                         if ((child.Returns == FlowReturns.EXCEPTION) ||
1490                                             (child.Returns == FlowReturns.ALWAYS) ||
1491                                             ((branching.Type != FlowBranchingType.SWITCH_SECTION) &&
1492                                              (branching.Type != FlowBranchingType.LOOP_BLOCK) &&
1493                                              (child.Breaks == FlowReturns.ALWAYS)))
1494                                                 breaks = true;
1495                                         else
1496                                                 breaks = false;
1497
1498                                         // A local variable is initialized after a flow branching if it
1499                                         // has been initialized in all its branches which do neither
1500                                         // always return or always throw an exception.
1501                                         //
1502                                         // If a branch may return, but does not always return, then we
1503                                         // can treat it like a never-returning branch here: control will
1504                                         // only reach the code position after the branching if we did not
1505                                         // return here.
1506                                         //
1507                                         // It's important to distinguish between always and sometimes
1508                                         // returning branches here:
1509                                         //
1510                                         //    1   int a;
1511                                         //    2   if (something) {
1512                                         //    3      return;
1513                                         //    4      a = 5;
1514                                         //    5   }
1515                                         //    6   Console.WriteLine (a);
1516                                         //
1517                                         // The if block in lines 3-4 always returns, so we must not look
1518                                         // at the initialization of `a' in line 4 - thus it'll still be
1519                                         // uninitialized in line 6.
1520                                         //
1521                                         // On the other hand, the following is allowed:
1522                                         //
1523                                         //    1   int a;
1524                                         //    2   if (something)
1525                                         //    3      a = 5;
1526                                         //    4   else
1527                                         //    5      return;
1528                                         //    6   Console.WriteLine (a);
1529                                         //
1530                                         // Here, `a' is initialized in line 3 and we must not look at
1531                                         // line 5 since it always returns.
1532                                         //
1533                                         if (!breaks) {
1534                                                 if (new_locals != null)
1535                                                         new_locals.And (child.locals);
1536                                                 else {
1537                                                         new_locals = locals.Clone ();
1538                                                         new_locals.Or (child.locals);
1539                                                 }
1540                                         }
1541
1542                                         // An `out' parameter must be assigned in all branches which do
1543                                         // not always throw an exception.
1544                                         if (!child.is_finally && (child.Returns != FlowReturns.EXCEPTION)) {
1545                                                 if (parameters != null) {
1546                                                         if (new_params != null)
1547                                                                 new_params.And (child.parameters);
1548                                                         else {
1549                                                                 new_params = parameters.Clone ();
1550                                                                 new_params.Or (child.parameters);
1551                                                         }
1552                                                 }
1553                                         }
1554
1555                                         // If we always return, check whether all `out' parameters have
1556                                         // been assigned.
1557                                         if ((child.Returns == FlowReturns.ALWAYS) && (child.parameters != null)) {
1558                                                 branching.CheckOutParameters (
1559                                                         child.parameters, branching.Location);
1560                                         }
1561                                 }
1562
1563                                 // Set new `Returns' status.
1564                                 if (!returns_set) {
1565                                         Returns = new_returns;
1566                                         returns_set = true;
1567                                 } else
1568                                         Returns = AndFlowReturns (Returns, new_returns);
1569
1570                                 //
1571                                 // We've now either reached the point after the branching or we will
1572                                 // never get there since we always return or always throw an exception.
1573                                 //
1574                                 // If we can reach the point after the branching, mark all locals and
1575                                 // parameters as initialized which have been initialized in all branches
1576                                 // we need to look at (see above).
1577                                 //
1578
1579                                 bool or_locals = (Returns == FlowReturns.NEVER) ||
1580                                         (Returns == FlowReturns.SOMETIMES);
1581                                 if ((branching.Type != FlowBranchingType.SWITCH_SECTION) &&
1582                                     (branching.Type != FlowBranchingType.LOOP_BLOCK))
1583                                         or_locals &= ((Breaks == FlowReturns.NEVER) ||
1584                                                       (Breaks == FlowReturns.SOMETIMES));
1585
1586                                 if ((new_locals != null) && or_locals) {
1587                                         locals.Or (new_locals);
1588                                 }
1589
1590                                 if ((new_params != null) && (Breaks == FlowReturns.NEVER))
1591                                         parameters.Or (new_params);
1592
1593                                 //
1594                                 // If we may have returned (this only happens if there was a reachable
1595                                 // `return' statement in one of the branches), then we may return to our
1596                                 // parent block before reaching the end of the block, so set `Breaks'.
1597                                 //
1598                                 if ((Returns != FlowReturns.NEVER) && (Returns != FlowReturns.SOMETIMES)) {
1599                                         // real_breaks = Returns;
1600                                         // breaks_set = true;
1601                                 } else if (branching.Type == FlowBranchingType.BLOCK) {
1602                                         //
1603                                         // If this is not a loop or switch block, `break' actually breaks.
1604                                         //
1605
1606                                         if (!breaks_set) {
1607                                                 Breaks = new_breaks;
1608                                                 breaks_set = true;
1609                                         } else
1610                                                 Breaks = AndFlowReturns (Breaks, new_breaks);
1611                                 }
1612
1613                                 Report.Debug (1, "MERGING CHILDREN DONE", new_params, new_locals,
1614                                               new_returns, new_breaks, this);
1615
1616                                 return new_returns;
1617                         }
1618
1619                         // <summary>
1620                         //   Tells control flow analysis that the current code position may be reached with
1621                         //   a forward jump from any of the origins listed in `origin_vectors' which is a
1622                         //   list of UsageVectors.
1623                         //
1624                         //   This is used when resolving forward gotos - in the following example, the
1625                         //   variable `a' is uninitialized in line 8 becase this line may be reached via
1626                         //   the goto in line 4:
1627                         //
1628                         //      1     int a;
1629                         //
1630                         //      3     if (something)
1631                         //      4        goto World;
1632                         //
1633                         //      6     a = 5;
1634                         //
1635                         //      7  World:
1636                         //      8     Console.WriteLine (a);
1637                         //
1638                         // </summary>
1639                         public void MergeJumpOrigins (ICollection origin_vectors)
1640                         {
1641                                 Report.Debug (1, "MERGING JUMP ORIGIN", this);
1642
1643                                 real_breaks = FlowReturns.NEVER;
1644                                 breaks_set = false;
1645
1646                                 foreach (UsageVector vector in origin_vectors) {
1647                                         Report.Debug (1, "  MERGING JUMP ORIGIN", vector);
1648
1649                                         locals.And (vector.locals);
1650                                         if (parameters != null)
1651                                                 parameters.And (vector.parameters);
1652                                         Breaks = AndFlowReturns (Breaks, vector.Breaks);
1653                                 }
1654
1655                                 Report.Debug (1, "MERGING JUMP ORIGIN DONE", this);
1656                         }
1657
1658                         // <summary>
1659                         //   This is used at the beginning of a finally block if there were
1660                         //   any return statements in the try block or one of the catch blocks.
1661                         // </summary>
1662                         public void MergeFinallyOrigins (ICollection finally_vectors)
1663                         {
1664                                 Report.Debug (1, "MERGING FINALLY ORIGIN", this);
1665
1666                                 real_breaks = FlowReturns.NEVER;
1667                                 breaks_set = false;
1668
1669                                 foreach (UsageVector vector in finally_vectors) {
1670                                         Report.Debug (1, "  MERGING FINALLY ORIGIN", vector);
1671
1672                                         if (parameters != null)
1673                                                 parameters.And (vector.parameters);
1674                                         Breaks = AndFlowReturns (Breaks, vector.Breaks);
1675                                 }
1676
1677                                 is_finally = true;
1678
1679                                 Report.Debug (1, "MERGING FINALLY ORIGIN DONE", this);
1680                         }
1681
1682                         // <summary>
1683                         //   Performs an `or' operation on the locals and the parameters.
1684                         // </summary>
1685                         public void Or (UsageVector new_vector)
1686                         {
1687                                 locals.Or (new_vector.locals);
1688                                 if (parameters != null)
1689                                         parameters.Or (new_vector.parameters);
1690                         }
1691
1692                         // <summary>
1693                         //   Performs an `and' operation on the locals.
1694                         // </summary>
1695                         public void AndLocals (UsageVector new_vector)
1696                         {
1697                                 locals.And (new_vector.locals);
1698                         }
1699
1700                         // <summary>
1701                         //   Returns a deep copy of the parameters.
1702                         // </summary>
1703                         public MyBitVector Parameters {
1704                                 get {
1705                                         if (parameters != null)
1706                                                 return parameters.Clone ();
1707                                         else
1708                                                 return null;
1709                                 }
1710                         }
1711
1712                         // <summary>
1713                         //   Returns a deep copy of the locals.
1714                         // </summary>
1715                         public MyBitVector Locals {
1716                                 get {
1717                                         return locals.Clone ();
1718                                 }
1719                         }
1720
1721                         //
1722                         // Debugging stuff.
1723                         //
1724
1725                         public override string ToString ()
1726                         {
1727                                 StringBuilder sb = new StringBuilder ();
1728
1729                                 sb.Append ("Vector (");
1730                                 sb.Append (id);
1731                                 sb.Append (",");
1732                                 sb.Append (Returns);
1733                                 sb.Append (",");
1734                                 sb.Append (Breaks);
1735                                 if (parameters != null) {
1736                                         sb.Append (" - ");
1737                                         sb.Append (parameters);
1738                                 }
1739                                 sb.Append (" - ");
1740                                 sb.Append (locals);
1741                                 sb.Append (")");
1742
1743                                 return sb.ToString ();
1744                         }
1745                 }
1746
1747                 FlowBranching (FlowBranchingType type, Location loc)
1748                 {
1749                         this.Siblings = new ArrayList ();
1750                         this.Block = null;
1751                         this.Location = loc;
1752                         this.Type = type;
1753                         id = ++next_id;
1754                 }
1755
1756                 // <summary>
1757                 //   Creates a new flow branching for `block'.
1758                 //   This is used from Block.Resolve to create the top-level branching of
1759                 //   the block.
1760                 // </summary>
1761                 public FlowBranching (Block block, InternalParameters ip, Location loc)
1762                         : this (FlowBranchingType.BLOCK, loc)
1763                 {
1764                         Block = block;
1765                         Parent = null;
1766
1767                         int count = (ip != null) ? ip.Count : 0;
1768
1769                         param_info = ip;
1770                         param_map = new int [count];
1771                         struct_params = new MyStructInfo [count];
1772                         num_params = 0;
1773
1774                         for (int i = 0; i < count; i++) {
1775                                 Parameter.Modifier mod = param_info.ParameterModifier (i);
1776
1777                                 if ((mod & Parameter.Modifier.OUT) == 0)
1778                                         continue;
1779
1780                                 param_map [i] = ++num_params;
1781
1782                                 Type param_type = param_info.ParameterType (i);
1783
1784                                 struct_params [i] = MyStructInfo.GetStructInfo (param_type);
1785                                 if (struct_params [i] != null)
1786                                         num_params += struct_params [i].Count;
1787                         }
1788
1789                         Siblings = new ArrayList ();
1790                         Siblings.Add (new UsageVector (null, num_params, block.CountVariables));
1791                 }
1792
1793                 // <summary>
1794                 //   Creates a new flow branching which is contained in `parent'.
1795                 //   You should only pass non-null for the `block' argument if this block
1796                 //   introduces any new variables - in this case, we need to create a new
1797                 //   usage vector with a different size than our parent's one.
1798                 // </summary>
1799                 public FlowBranching (FlowBranching parent, FlowBranchingType type,
1800                                       Block block, Location loc)
1801                         : this (type, loc)
1802                 {
1803                         Parent = parent;
1804                         Block = block;
1805
1806                         if (parent != null) {
1807                                 param_info = parent.param_info;
1808                                 param_map = parent.param_map;
1809                                 struct_params = parent.struct_params;
1810                                 num_params = parent.num_params;
1811                         }
1812
1813                         UsageVector vector;
1814                         if (Block != null)
1815                                 vector = new UsageVector (parent.CurrentUsageVector, num_params,
1816                                                           Block.CountVariables);
1817                         else
1818                                 vector = new UsageVector (Parent.CurrentUsageVector);
1819
1820                         Siblings.Add (vector);
1821
1822                         switch (Type) {
1823                         case FlowBranchingType.EXCEPTION:
1824                                 finally_vectors = new ArrayList ();
1825                                 break;
1826
1827                         default:
1828                                 break;
1829                         }
1830                 }
1831
1832                 // <summary>
1833                 //   Returns the branching's current usage vector.
1834                 // </summary>
1835                 public UsageVector CurrentUsageVector
1836                 {
1837                         get {
1838                                 return (UsageVector) Siblings [Siblings.Count - 1];
1839                         }
1840                 }
1841
1842                 // <summary>
1843                 //   Creates a sibling of the current usage vector.
1844                 // </summary>
1845                 public void CreateSibling ()
1846                 {
1847                         Siblings.Add (new UsageVector (Parent.CurrentUsageVector));
1848
1849                         Report.Debug (1, "CREATED SIBLING", CurrentUsageVector);
1850                 }
1851
1852                 // <summary>
1853                 //   Creates a sibling for a `finally' block.
1854                 // </summary>
1855                 public void CreateSiblingForFinally ()
1856                 {
1857                         if (Type != FlowBranchingType.EXCEPTION)
1858                                 throw new NotSupportedException ();
1859
1860                         CreateSibling ();
1861
1862                         CurrentUsageVector.MergeFinallyOrigins (finally_vectors);
1863                 }
1864
1865                 // <summary>
1866                 //   Check whether all `out' parameters have been assigned.
1867                 // </summary>
1868                 public void CheckOutParameters (MyBitVector parameters, Location loc)
1869                 {
1870                         if (InTryBlock ())
1871                                 return;
1872
1873                         for (int i = 0; i < param_map.Length; i++) {
1874                                 int index = param_map [i];
1875
1876                                 if (index == 0)
1877                                         continue;
1878
1879                                 if (parameters [index - 1])
1880                                         continue;
1881
1882                                 // If it's a struct, we must ensure that all its fields have
1883                                 // been assigned.  If the struct has any non-public fields, this
1884                                 // can only be done by assigning the whole struct.
1885
1886                                 MyStructInfo struct_info = struct_params [index - 1];
1887                                 if ((struct_info == null) || struct_info.HasNonPublicFields) {
1888                                         Report.Error (
1889                                                 177, loc, "The out parameter `" +
1890                                                 param_info.ParameterName (i) + "' must be " +
1891                                                 "assigned before control leave the current method.");
1892                                         param_map [i] = 0;
1893                                         continue;
1894                                 }
1895
1896
1897                                 for (int j = 0; j < struct_info.Count; j++) {
1898                                         if (!parameters [index + j]) {
1899                                                 Report.Error (
1900                                                         177, loc, "The out parameter `" +
1901                                                         param_info.ParameterName (i) + "' must be " +
1902                                                         "assigned before control leave the current method.");
1903                                                 param_map [i] = 0;
1904                                                 break;
1905                                         }
1906                                 }
1907                         }
1908                 }
1909
1910                 // <summary>
1911                 //   Merge a child branching.
1912                 // </summary>
1913                 public FlowReturns MergeChild (FlowBranching child)
1914                 {
1915                         return CurrentUsageVector.MergeChildren (child, child.Siblings);
1916                 }
1917
1918                 // <summary>
1919                 //   Does the toplevel merging.
1920                 // </summary>
1921                 public FlowReturns MergeTopBlock ()
1922                 {
1923                         if ((Type != FlowBranchingType.BLOCK) || (Block == null))
1924                                 throw new NotSupportedException ();
1925
1926                         UsageVector vector = new UsageVector (null, num_params, Block.CountVariables);
1927
1928                         vector.MergeChildren (this, Siblings);
1929
1930                         Siblings.Clear ();
1931                         Siblings.Add (vector);
1932
1933                         Report.Debug (1, "MERGING TOP BLOCK", vector);
1934
1935                         if (vector.Returns != FlowReturns.EXCEPTION)
1936                                 CheckOutParameters (CurrentUsageVector.Parameters, Location);
1937
1938                         return vector.Returns;
1939                 }
1940
1941                 public bool InTryBlock ()
1942                 {
1943                         if (finally_vectors != null)
1944                                 return true;
1945                         else if (Parent != null)
1946                                 return Parent.InTryBlock ();
1947                         else
1948                                 return false;
1949                 }
1950
1951                 public void AddFinallyVector (UsageVector vector)
1952                 {
1953                         if (finally_vectors != null) {
1954                                 finally_vectors.Add (vector.Clone ());
1955                                 return;
1956                         }
1957
1958                         if (Parent != null)
1959                                 Parent.AddFinallyVector (vector);
1960                         else
1961                                 throw new NotSupportedException ();
1962                 }
1963
1964                 public bool IsVariableAssigned (VariableInfo vi)
1965                 {
1966                         if (CurrentUsageVector.Breaks == FlowReturns.UNREACHABLE)
1967                                 return true;
1968                         else
1969                                 return CurrentUsageVector [vi, 0];
1970                 }
1971
1972                 public bool IsVariableAssigned (VariableInfo vi, int field_idx)
1973                 {
1974                         if (CurrentUsageVector.Breaks == FlowReturns.UNREACHABLE)
1975                                 return true;
1976                         else
1977                                 return CurrentUsageVector [vi, field_idx];
1978                 }
1979
1980                 public void SetVariableAssigned (VariableInfo vi)
1981                 {
1982                         if (CurrentUsageVector.Breaks == FlowReturns.UNREACHABLE)
1983                                 return;
1984
1985                         CurrentUsageVector [vi, 0] = true;
1986                 }
1987
1988                 public void SetVariableAssigned (VariableInfo vi, int field_idx)
1989                 {
1990                         if (CurrentUsageVector.Breaks == FlowReturns.UNREACHABLE)
1991                                 return;
1992
1993                         CurrentUsageVector [vi, field_idx] = true;
1994                 }
1995
1996                 public bool IsParameterAssigned (int number)
1997                 {
1998                         int index = param_map [number];
1999
2000                         if (index == 0)
2001                                 return true;
2002
2003                         if (CurrentUsageVector [index])
2004                                 return true;
2005
2006                         // Parameter is not assigned, so check whether it's a struct.
2007                         // If it's either not a struct or a struct which non-public
2008                         // fields, return false.
2009                         MyStructInfo struct_info = struct_params [number];
2010                         if ((struct_info == null) || struct_info.HasNonPublicFields)
2011                                 return false;
2012
2013                         // Ok, so each field must be assigned.
2014                         for (int i = 0; i < struct_info.Count; i++)
2015                                 if (!CurrentUsageVector [index + i])
2016                                         return false;
2017
2018                         return true;
2019                 }
2020
2021                 public bool IsParameterAssigned (int number, string field_name)
2022                 {
2023                         int index = param_map [number];
2024
2025                         if (index == 0)
2026                                 return true;
2027
2028                         int field_idx = struct_params [number] [field_name];
2029
2030                         return CurrentUsageVector [index + field_idx];
2031                 }
2032
2033                 public void SetParameterAssigned (int number)
2034                 {
2035                         if (param_map [number] == 0)
2036                                 return;
2037
2038                         if (CurrentUsageVector.Breaks == FlowReturns.NEVER)
2039                                 CurrentUsageVector [param_map [number]] = true;
2040                 }
2041
2042                 public void SetParameterAssigned (int number, string field_name)
2043                 {
2044                         int index = param_map [number];
2045
2046                         if (index == 0)
2047                                 return;
2048
2049                         int field_idx = struct_params [number] [field_name];
2050
2051                         if (CurrentUsageVector.Breaks == FlowReturns.NEVER)
2052                                 CurrentUsageVector [index + field_idx] = true;
2053                 }
2054
2055                 public override string ToString ()
2056                 {
2057                         StringBuilder sb = new StringBuilder ("FlowBranching (");
2058
2059                         sb.Append (id);
2060                         sb.Append (",");
2061                         sb.Append (Type);
2062                         if (Block != null) {
2063                                 sb.Append (" - ");
2064                                 sb.Append (Block.ID);
2065                                 sb.Append (" - ");
2066                                 sb.Append (Block.StartLocation);
2067                         }
2068                         sb.Append (" - ");
2069                         sb.Append (Siblings.Count);
2070                         sb.Append (" - ");
2071                         sb.Append (CurrentUsageVector);
2072                         sb.Append (")");
2073                         return sb.ToString ();
2074                 }
2075         }
2076
2077         public class MyStructInfo {
2078                 public readonly Type Type;
2079                 public readonly FieldInfo[] Fields;
2080                 public readonly FieldInfo[] NonPublicFields;
2081                 public readonly int Count;
2082                 public readonly int CountNonPublic;
2083                 public readonly bool HasNonPublicFields;
2084
2085                 private static Hashtable field_type_hash = new Hashtable ();
2086                 private Hashtable field_hash;
2087
2088                 // Private constructor.  To save memory usage, we only need to create one instance
2089                 // of this class per struct type.
2090                 private MyStructInfo (Type type)
2091                 {
2092                         this.Type = type;
2093
2094                         if (type is TypeBuilder) {
2095                                 TypeContainer tc = TypeManager.LookupTypeContainer (type);
2096
2097                                 ArrayList fields = tc.Fields;
2098                                 foreach (Field field in fields) {
2099                                         if ((field.ModFlags & Modifiers.STATIC) != 0)
2100                                                 continue;
2101                                         if ((field.ModFlags & Modifiers.PUBLIC) != 0)
2102                                                 ++Count;
2103                                         else
2104                                                 ++CountNonPublic;
2105                                 }
2106
2107                                 Fields = new FieldInfo [Count];
2108                                 NonPublicFields = new FieldInfo [CountNonPublic];
2109
2110                                 Count = CountNonPublic = 0;
2111                                 foreach (Field field in fields) {
2112                                         if ((field.ModFlags & Modifiers.STATIC) != 0)
2113                                                 continue;
2114                                         if ((field.ModFlags & Modifiers.PUBLIC) != 0)
2115                                                 Fields [Count++] = field.FieldBuilder;
2116                                         else
2117                                                 NonPublicFields [CountNonPublic++] = field.FieldBuilder;
2118                                 }
2119                         } else {
2120                                 Fields = type.GetFields (BindingFlags.Instance|BindingFlags.Public);
2121                                 Count = Fields.Length;
2122
2123                                 NonPublicFields = type.GetFields (BindingFlags.Instance|BindingFlags.NonPublic);
2124                                 CountNonPublic = NonPublicFields.Length;
2125                         }
2126
2127                         Count += NonPublicFields.Length;
2128
2129                         int number = 0;
2130                         field_hash = new Hashtable ();
2131                         foreach (FieldInfo field in Fields)
2132                                 field_hash.Add (field.Name, ++number);
2133
2134                         if (NonPublicFields.Length != 0)
2135                                 HasNonPublicFields = true;
2136
2137                         foreach (FieldInfo field in NonPublicFields)
2138                                 field_hash.Add (field.Name, ++number);
2139                 }
2140
2141                 public int this [string name] {
2142                         get {
2143                                 if (field_hash.Contains (name))
2144                                         return (int) field_hash [name];
2145                                 else
2146                                         return 0;
2147                         }
2148                 }
2149
2150                 public FieldInfo this [int index] {
2151                         get {
2152                                 if (index >= Fields.Length)
2153                                         return NonPublicFields [index - Fields.Length];
2154                                 else
2155                                         return Fields [index];
2156                         }
2157                 }
2158
2159                 public static MyStructInfo GetStructInfo (Type type)
2160                 {
2161                         if (!TypeManager.IsValueType (type) || TypeManager.IsEnumType (type))
2162                                 return null;
2163
2164                         if (!(type is TypeBuilder) && TypeManager.IsBuiltinType (type))
2165                                 return null;
2166
2167                         MyStructInfo info = (MyStructInfo) field_type_hash [type];
2168                         if (info != null)
2169                                 return info;
2170
2171                         info = new MyStructInfo (type);
2172                         field_type_hash.Add (type, info);
2173                         return info;
2174                 }
2175
2176                 public static MyStructInfo GetStructInfo (TypeContainer tc)
2177                 {
2178                         MyStructInfo info = (MyStructInfo) field_type_hash [tc.TypeBuilder];
2179                         if (info != null)
2180                                 return info;
2181
2182                         info = new MyStructInfo (tc.TypeBuilder);
2183                         field_type_hash.Add (tc.TypeBuilder, info);
2184                         return info;
2185                 }
2186         }
2187
2188         public class VariableInfo : IVariable {
2189                 public Expression Type;
2190                 public LocalBuilder LocalBuilder;
2191                 public Type VariableType;
2192                 public readonly string Name;
2193                 public readonly Location Location;
2194                 public readonly int Block;
2195
2196                 public int Number;
2197
2198                 public bool Used;
2199                 public bool Assigned;
2200                 public bool ReadOnly;
2201
2202                 public VariableInfo (Expression type, string name, int block, Location l)
2203                 {
2204                         Type = type;
2205                         Name = name;
2206                         Block = block;
2207                         LocalBuilder = null;
2208                         Location = l;
2209                 }
2210
2211                 public VariableInfo (TypeContainer tc, int block, Location l)
2212                 {
2213                         VariableType = tc.TypeBuilder;
2214                         struct_info = MyStructInfo.GetStructInfo (tc);
2215                         Block = block;
2216                         LocalBuilder = null;
2217                         Location = l;
2218                 }
2219
2220                 MyStructInfo struct_info;
2221                 public MyStructInfo StructInfo {
2222                         get {
2223                                 return struct_info;
2224                         }
2225                 }
2226
2227                 public bool IsAssigned (EmitContext ec, Location loc)
2228                 {
2229                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsVariableAssigned (this))
2230                                 return true;
2231
2232                         MyStructInfo struct_info = StructInfo;
2233                         if ((struct_info == null) || (struct_info.HasNonPublicFields && (Name != null))) {
2234                                 Report.Error (165, loc, "Use of unassigned local variable `" + Name + "'");
2235                                 ec.CurrentBranching.SetVariableAssigned (this);
2236                                 return false;
2237                         }
2238
2239                         int count = struct_info.Count;
2240
2241                         for (int i = 0; i < count; i++) {
2242                                 if (!ec.CurrentBranching.IsVariableAssigned (this, i+1)) {
2243                                         if (Name != null) {
2244                                                 Report.Error (165, loc,
2245                                                               "Use of unassigned local variable `" +
2246                                                               Name + "'");
2247                                                 ec.CurrentBranching.SetVariableAssigned (this);
2248                                                 return false;
2249                                         }
2250
2251                                         FieldInfo field = struct_info [i];
2252                                         Report.Error (171, loc,
2253                                                       "Field `" + TypeManager.CSharpName (VariableType) +
2254                                                       "." + field.Name + "' must be fully initialized " +
2255                                                       "before control leaves the constructor");
2256                                         return false;
2257                                 }
2258                         }
2259
2260                         return true;
2261                 }
2262
2263                 public bool IsFieldAssigned (EmitContext ec, string name, Location loc)
2264                 {
2265                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsVariableAssigned (this) ||
2266                             (struct_info == null))
2267                                 return true;
2268
2269                         int field_idx = StructInfo [name];
2270                         if (field_idx == 0)
2271                                 return true;
2272
2273                         if (!ec.CurrentBranching.IsVariableAssigned (this, field_idx)) {
2274                                 Report.Error (170, loc,
2275                                               "Use of possibly unassigned field `" + name + "'");
2276                                 ec.CurrentBranching.SetVariableAssigned (this, field_idx);
2277                                 return false;
2278                         }
2279
2280                         return true;
2281                 }
2282
2283                 public void SetAssigned (EmitContext ec)
2284                 {
2285                         if (ec.DoFlowAnalysis)
2286                                 ec.CurrentBranching.SetVariableAssigned (this);
2287                 }
2288
2289                 public void SetFieldAssigned (EmitContext ec, string name)
2290                 {
2291                         if (ec.DoFlowAnalysis && (struct_info != null))
2292                                 ec.CurrentBranching.SetVariableAssigned (this, StructInfo [name]);
2293                 }
2294
2295                 public bool Resolve (DeclSpace decl)
2296                 {
2297                         if (struct_info != null)
2298                                 return true;
2299
2300                         if (VariableType == null)
2301                                 VariableType = decl.ResolveType (Type, false, Location);
2302
2303                         if (VariableType == null)
2304                                 return false;
2305
2306                         struct_info = MyStructInfo.GetStructInfo (VariableType);
2307
2308                         return true;
2309                 }
2310
2311                 public void MakePinned ()
2312                 {
2313                         TypeManager.MakePinned (LocalBuilder);
2314                 }
2315
2316                 public override string ToString ()
2317                 {
2318                         return "VariableInfo (" + Number + "," + Type + "," + Location + ")";
2319                 }
2320         }
2321
2322         /// <summary>
2323         ///   Block represents a C# block.
2324         /// </summary>
2325         ///
2326         /// <remarks>
2327         ///   This class is used in a number of places: either to represent
2328         ///   explicit blocks that the programmer places or implicit blocks.
2329         ///
2330         ///   Implicit blocks are used as labels or to introduce variable
2331         ///   declarations.
2332         /// </remarks>
2333         public class Block : Statement {
2334                 public readonly Block     Parent;
2335                 public readonly bool      Implicit;
2336                 public readonly Location  StartLocation;
2337                 public Location           EndLocation;
2338
2339                 //
2340                 // The statements in this block
2341                 //
2342                 ArrayList statements;
2343
2344                 //
2345                 // An array of Blocks.  We keep track of children just
2346                 // to generate the local variable declarations.
2347                 //
2348                 // Statements and child statements are handled through the
2349                 // statements.
2350                 //
2351                 ArrayList children;
2352
2353                 //
2354                 // Labels.  (label, block) pairs.
2355                 //
2356                 Hashtable labels;
2357
2358                 //
2359                 // Keeps track of (name, type) pairs
2360                 //
2361                 Hashtable variables;
2362
2363                 //
2364                 // Keeps track of constants
2365                 Hashtable constants;
2366
2367                 //
2368                 // Maps variable names to ILGenerator.LocalBuilders
2369                 //
2370                 Hashtable local_builders;
2371
2372                 bool used = false;
2373
2374                 static int id;
2375
2376                 int this_id;
2377
2378                 public Block (Block parent)
2379                         : this (parent, false, Location.Null, Location.Null)
2380                 { }
2381
2382                 public Block (Block parent, bool implicit_block)
2383                         : this (parent, implicit_block, Location.Null, Location.Null)
2384                 { }
2385
2386                 public Block (Block parent, bool implicit_block, Parameters parameters)
2387                         : this (parent, implicit_block, parameters, Location.Null, Location.Null)
2388                 { }
2389
2390                 public Block (Block parent, Location start, Location end)
2391                         : this (parent, false, start, end)
2392                 { }
2393
2394                 public Block (Block parent, Parameters parameters, Location start, Location end)
2395                         : this (parent, false, parameters, start, end)
2396                 { }
2397
2398                 public Block (Block parent, bool implicit_block, Location start, Location end)
2399                         : this (parent, implicit_block, Parameters.EmptyReadOnlyParameters,
2400                                 start, end)
2401                 { }
2402
2403                 public Block (Block parent, bool implicit_block, Parameters parameters,
2404                               Location start, Location end)
2405                 {
2406                         if (parent != null)
2407                                 parent.AddChild (this);
2408
2409                         this.Parent = parent;
2410                         this.Implicit = implicit_block;
2411                         this.parameters = parameters;
2412                         this.StartLocation = start;
2413                         this.EndLocation = end;
2414                         this.loc = start;
2415                         this_id = id++;
2416                         statements = new ArrayList ();
2417                 }
2418
2419                 public int ID {
2420                         get {
2421                                 if (Implicit)
2422                                         return Parent.ID;
2423                                 else
2424                                         return this_id;
2425                         }
2426                 }
2427
2428                 void AddChild (Block b)
2429                 {
2430                         if (children == null)
2431                                 children = new ArrayList ();
2432
2433                         children.Add (b);
2434                 }
2435
2436                 public void SetEndLocation (Location loc)
2437                 {
2438                         EndLocation = loc;
2439                 }
2440
2441                 /// <summary>
2442                 ///   Adds a label to the current block.
2443                 /// </summary>
2444                 ///
2445                 /// <returns>
2446                 ///   false if the name already exists in this block. true
2447                 ///   otherwise.
2448                 /// </returns>
2449                 ///
2450                 public bool AddLabel (string name, LabeledStatement target)
2451                 {
2452                         if (labels == null)
2453                                 labels = new Hashtable ();
2454                         if (labels.Contains (name))
2455                                 return false;
2456
2457                         labels.Add (name, target);
2458                         return true;
2459                 }
2460
2461                 public LabeledStatement LookupLabel (string name)
2462                 {
2463                         if (labels != null){
2464                                 if (labels.Contains (name))
2465                                         return ((LabeledStatement) labels [name]);
2466                         }
2467
2468                         if (Parent != null)
2469                                 return Parent.LookupLabel (name);
2470
2471                         return null;
2472                 }
2473
2474                 VariableInfo this_variable = null;
2475
2476                 // <summary>
2477                 //   Returns the "this" instance variable of this block.
2478                 //   See AddThisVariable() for more information.
2479                 // </summary>
2480                 public VariableInfo ThisVariable {
2481                         get {
2482                                 if (this_variable != null)
2483                                         return this_variable;
2484                                 else if (Parent != null)
2485                                         return Parent.ThisVariable;
2486                                 else
2487                                         return null;
2488                         }
2489                 }
2490
2491                 // <summary>
2492                 //   This is used by non-static `struct' constructors which do not have an
2493                 //   initializer - in this case, the constructor must initialize all of the
2494                 //   struct's fields.  To do this, we add a "this" variable and use the flow
2495                 //   analysis code to ensure that it's been fully initialized before control
2496                 //   leaves the constructor.
2497                 // </summary>
2498                 public VariableInfo AddThisVariable (TypeContainer tc, Location l)
2499                 {
2500                         if (this_variable != null)
2501                                 return this_variable;
2502
2503                         this_variable = new VariableInfo (tc, ID, l);
2504
2505                         if (variables == null)
2506                                 variables = new Hashtable ();
2507                         variables.Add ("this", this_variable);
2508
2509                         return this_variable;
2510                 }
2511
2512                 public VariableInfo AddVariable (Expression type, string name, Parameters pars, Location l)
2513                 {
2514                         if (variables == null)
2515                                 variables = new Hashtable ();
2516
2517                         VariableInfo vi = GetVariableInfo (name);
2518                         if (vi != null) {
2519                                 if (vi.Block != ID)
2520                                         Report.Error (136, l, "A local variable named `" + name + "' " +
2521                                                       "cannot be declared in this scope since it would " +
2522                                                       "give a different meaning to `" + name + "', which " +
2523                                                       "is already used in a `parent or current' scope to " +
2524                                                       "denote something else");
2525                                 else
2526                                         Report.Error (128, l, "A local variable `" + name + "' is already " +
2527                                                       "defined in this scope");
2528                                 return null;
2529                         }
2530
2531                         if (pars != null) {
2532                                 int idx = 0;
2533                                 Parameter p = pars.GetParameterByName (name, out idx);
2534                                 if (p != null) {
2535                                         Report.Error (136, l, "A local variable named `" + name + "' " +
2536                                                       "cannot be declared in this scope since it would " +
2537                                                       "give a different meaning to `" + name + "', which " +
2538                                                       "is already used in a `parent or current' scope to " +
2539                                                       "denote something else");
2540                                         return null;
2541                                 }
2542                         }
2543
2544                         vi = new VariableInfo (type, name, ID, l);
2545
2546                         variables.Add (name, vi);
2547
2548                         if (variables_initialized)
2549                                 throw new Exception ();
2550
2551                         // Console.WriteLine ("Adding {0} to {1}", name, ID);
2552                         return vi;
2553                 }
2554
2555                 public bool AddConstant (Expression type, string name, Expression value, Parameters pars, Location l)
2556                 {
2557                         if (AddVariable (type, name, pars, l) == null)
2558                                 return false;
2559
2560                         if (constants == null)
2561                                 constants = new Hashtable ();
2562
2563                         constants.Add (name, value);
2564                         return true;
2565                 }
2566
2567                 public Hashtable Variables {
2568                         get {
2569                                 return variables;
2570                         }
2571                 }
2572
2573                 public VariableInfo GetVariableInfo (string name)
2574                 {
2575                         if (variables != null) {
2576                                 object temp;
2577                                 temp = variables [name];
2578
2579                                 if (temp != null){
2580                                         return (VariableInfo) temp;
2581                                 }
2582                         }
2583
2584                         if (Parent != null)
2585                                 return Parent.GetVariableInfo (name);
2586
2587                         return null;
2588                 }
2589
2590                 public Expression GetVariableType (string name)
2591                 {
2592                         VariableInfo vi = GetVariableInfo (name);
2593
2594                         if (vi != null)
2595                                 return vi.Type;
2596
2597                         return null;
2598                 }
2599
2600                 public Expression GetConstantExpression (string name)
2601                 {
2602                         if (constants != null) {
2603                                 object temp;
2604                                 temp = constants [name];
2605
2606                                 if (temp != null)
2607                                         return (Expression) temp;
2608                         }
2609
2610                         if (Parent != null)
2611                                 return Parent.GetConstantExpression (name);
2612
2613                         return null;
2614                 }
2615
2616                 /// <summary>
2617                 ///   True if the variable named @name has been defined
2618                 ///   in this block
2619                 /// </summary>
2620                 public bool IsVariableDefined (string name)
2621                 {
2622                         // Console.WriteLine ("Looking up {0} in {1}", name, ID);
2623                         if (variables != null) {
2624                                 if (variables.Contains (name))
2625                                         return true;
2626                         }
2627
2628                         if (Parent != null)
2629                                 return Parent.IsVariableDefined (name);
2630
2631                         return false;
2632                 }
2633
2634                 /// <summary>
2635                 ///   True if the variable named @name is a constant
2636                 ///  </summary>
2637                 public bool IsConstant (string name)
2638                 {
2639                         Expression e = null;
2640
2641                         e = GetConstantExpression (name);
2642
2643                         return e != null;
2644                 }
2645
2646                 /// <summary>
2647                 ///   Use to fetch the statement associated with this label
2648                 /// </summary>
2649                 public Statement this [string name] {
2650                         get {
2651                                 return (Statement) labels [name];
2652                         }
2653                 }
2654
2655                 Parameters parameters = null;
2656                 public Parameters Parameters {
2657                         get {
2658                                 if (Parent != null)
2659                                         return Parent.Parameters;
2660
2661                                 return parameters;
2662                         }
2663                 }
2664
2665                 /// <returns>
2666                 ///   A list of labels that were not used within this block
2667                 /// </returns>
2668                 public string [] GetUnreferenced ()
2669                 {
2670                         // FIXME: Implement me
2671                         return null;
2672                 }
2673
2674                 public void AddStatement (Statement s)
2675                 {
2676                         statements.Add (s);
2677                         used = true;
2678                 }
2679
2680                 public bool Used {
2681                         get {
2682                                 return used;
2683                         }
2684                 }
2685
2686                 public void Use ()
2687                 {
2688                         used = true;
2689                 }
2690
2691                 bool variables_initialized = false;
2692                 int count_variables = 0, first_variable = 0;
2693
2694                 void UpdateVariableInfo (EmitContext ec)
2695                 {
2696                         DeclSpace ds = ec.DeclSpace;
2697
2698                         first_variable = 0;
2699
2700                         if (Parent != null)
2701                                 first_variable += Parent.CountVariables;
2702
2703                         count_variables = first_variable;
2704                         if (variables != null) {
2705                                 foreach (VariableInfo vi in variables.Values) {
2706                                         if (!vi.Resolve (ds)) {
2707                                                 vi.Number = -1;
2708                                                 continue;
2709                                         }
2710
2711                                         vi.Number = ++count_variables;
2712
2713                                         if (vi.StructInfo != null)
2714                                                 count_variables += vi.StructInfo.Count;
2715                                 }
2716                         }
2717
2718                         variables_initialized = true;
2719                 }
2720
2721                 //
2722                 // <returns>
2723                 //   The number of local variables in this block
2724                 // </returns>
2725                 public int CountVariables
2726                 {
2727                         get {
2728                                 if (!variables_initialized)
2729                                         throw new Exception ();
2730
2731                                 return count_variables;
2732                         }
2733                 }
2734
2735                 /// <summary>
2736                 ///   Emits the variable declarations and labels.
2737                 /// </summary>
2738                 /// <remarks>
2739                 ///   tc: is our typecontainer (to resolve type references)
2740                 ///   ig: is the code generator:
2741                 ///   toplevel: the toplevel block.  This is used for checking
2742                 ///             that no two labels with the same name are used.
2743                 /// </remarks>
2744                 public void EmitMeta (EmitContext ec, Block toplevel)
2745                 {
2746                         DeclSpace ds = ec.DeclSpace;
2747                         ILGenerator ig = ec.ig;
2748
2749                         if (!variables_initialized)
2750                                 UpdateVariableInfo (ec);
2751
2752                         //
2753                         // Process this block variables
2754                         //
2755                         if (variables != null){
2756                                 local_builders = new Hashtable ();
2757
2758                                 foreach (DictionaryEntry de in variables){
2759                                         string name = (string) de.Key;
2760                                         VariableInfo vi = (VariableInfo) de.Value;
2761
2762                                         if (vi.VariableType == null)
2763                                                 continue;
2764
2765                                         vi.LocalBuilder = ig.DeclareLocal (vi.VariableType);
2766
2767                                         if (CodeGen.SymbolWriter != null)
2768                                                 vi.LocalBuilder.SetLocalSymInfo (name);
2769
2770                                         if (constants == null)
2771                                                 continue;
2772
2773                                         Expression cv = (Expression) constants [name];
2774                                         if (cv == null)
2775                                                 continue;
2776
2777                                         Expression e = cv.Resolve (ec);
2778                                         if (e == null)
2779                                                 continue;
2780
2781                                         if (!(e is Constant)){
2782                                                 Report.Error (133, vi.Location,
2783                                                               "The expression being assigned to `" +
2784                                                               name + "' must be constant (" + e + ")");
2785                                                 continue;
2786                                         }
2787
2788                                         constants.Remove (name);
2789                                         constants.Add (name, e);
2790                                 }
2791                         }
2792
2793                         //
2794                         // Now, handle the children
2795                         //
2796                         if (children != null){
2797                                 foreach (Block b in children)
2798                                         b.EmitMeta (ec, toplevel);
2799                         }
2800                 }
2801
2802                 public void UsageWarning ()
2803                 {
2804                         string name;
2805
2806                         if (variables != null){
2807                                 foreach (DictionaryEntry de in variables){
2808                                         VariableInfo vi = (VariableInfo) de.Value;
2809
2810                                         if (vi.Used)
2811                                                 continue;
2812
2813                                         name = (string) de.Key;
2814
2815                                         if (vi.Assigned){
2816                                                 Report.Warning (
2817                                                         219, vi.Location, "The variable `" + name +
2818                                                         "' is assigned but its value is never used");
2819                                         } else {
2820                                                 Report.Warning (
2821                                                         168, vi.Location, "The variable `" +
2822                                                         name +
2823                                                         "' is declared but never used");
2824                                         }
2825                                 }
2826                         }
2827
2828                         if (children != null)
2829                                 foreach (Block b in children)
2830                                         b.UsageWarning ();
2831                 }
2832
2833                 public override bool Resolve (EmitContext ec)
2834                 {
2835                         Block prev_block = ec.CurrentBlock;
2836                         bool ok = true;
2837
2838                         ec.CurrentBlock = this;
2839                         ec.StartFlowBranching (this);
2840
2841                         Report.Debug (1, "RESOLVE BLOCK", StartLocation);
2842
2843                         if (!variables_initialized)
2844                                 UpdateVariableInfo (ec);
2845
2846                         foreach (Statement s in statements){
2847                                 if (s.Resolve (ec) == false)
2848                                         ok = false;
2849                         }
2850
2851                         Report.Debug (1, "RESOLVE BLOCK DONE", StartLocation);
2852
2853                         FlowReturns returns = ec.EndFlowBranching ();
2854                         ec.CurrentBlock = prev_block;
2855
2856                         // If we're a non-static `struct' constructor which doesn't have an
2857                         // initializer, then we must initialize all of the struct's fields.
2858                         if ((this_variable != null) && (returns != FlowReturns.EXCEPTION) &&
2859                             !this_variable.IsAssigned (ec, loc))
2860                                 ok = false;
2861
2862                         if ((labels != null) && (RootContext.WarningLevel >= 2)) {
2863                                 foreach (LabeledStatement label in labels.Values)
2864                                         if (!label.HasBeenReferenced)
2865                                                 Report.Warning (164, label.Location,
2866                                                                 "This label has not been referenced");
2867                         }
2868
2869                         return ok;
2870                 }
2871
2872                 public override bool Emit (EmitContext ec)
2873                 {
2874                         bool is_ret = false, this_ret = false;
2875                         Block prev_block = ec.CurrentBlock;
2876                         bool warning_shown = false;
2877
2878                         ec.CurrentBlock = this;
2879
2880                         if (CodeGen.SymbolWriter != null) {
2881                                 ec.Mark (StartLocation);
2882
2883                                 foreach (Statement s in statements) {
2884                                         ec.Mark (s.loc);
2885
2886                                         if (is_ret && !warning_shown && !(s is EmptyStatement)){
2887                                                 warning_shown = true;
2888                                                 Warning_DeadCodeFound (s.loc);
2889                                         }
2890                                         this_ret = s.Emit (ec);
2891                                         if (this_ret)
2892                                                 is_ret = true;
2893                                 }
2894
2895                                 ec.Mark (EndLocation);
2896                         } else {
2897                                 foreach (Statement s in statements){
2898                                         if (is_ret && !warning_shown && !(s is EmptyStatement)){
2899                                                 warning_shown = true;
2900                                                 Warning_DeadCodeFound (s.loc);
2901                                         }
2902                                         this_ret = s.Emit (ec);
2903                                         if (this_ret)
2904                                                 is_ret = true;
2905                                 }
2906                         }
2907
2908                         ec.CurrentBlock = prev_block;
2909                         return is_ret;
2910                 }
2911         }
2912
2913         public class SwitchLabel {
2914                 Expression label;
2915                 object converted;
2916                 public Location loc;
2917                 public Label ILLabel;
2918                 public Label ILLabelCode;
2919
2920                 //
2921                 // if expr == null, then it is the default case.
2922                 //
2923                 public SwitchLabel (Expression expr, Location l)
2924                 {
2925                         label = expr;
2926                         loc = l;
2927                 }
2928
2929                 public Expression Label {
2930                         get {
2931                                 return label;
2932                         }
2933                 }
2934
2935                 public object Converted {
2936                         get {
2937                                 return converted;
2938                         }
2939                 }
2940
2941                 //
2942                 // Resolves the expression, reduces it to a literal if possible
2943                 // and then converts it to the requested type.
2944                 //
2945                 public bool ResolveAndReduce (EmitContext ec, Type required_type)
2946                 {
2947                         ILLabel = ec.ig.DefineLabel ();
2948                         ILLabelCode = ec.ig.DefineLabel ();
2949
2950                         if (label == null)
2951                                 return true;
2952
2953                         Expression e = label.Resolve (ec);
2954
2955                         if (e == null)
2956                                 return false;
2957
2958                         if (!(e is Constant)){
2959                                 Console.WriteLine ("Value is: " + label);
2960                                 Report.Error (150, loc, "A constant value is expected");
2961                                 return false;
2962                         }
2963
2964                         if (e is StringConstant || e is NullLiteral){
2965                                 if (required_type == TypeManager.string_type){
2966                                         converted = label;
2967                                         ILLabel = ec.ig.DefineLabel ();
2968                                         return true;
2969                                 }
2970                         }
2971
2972                         converted = Expression.ConvertIntLiteral ((Constant) e, required_type, loc);
2973                         if (converted == null)
2974                                 return false;
2975
2976                         return true;
2977                 }
2978         }
2979
2980         public class SwitchSection {
2981                 // An array of SwitchLabels.
2982                 public readonly ArrayList Labels;
2983                 public readonly Block Block;
2984
2985                 public SwitchSection (ArrayList labels, Block block)
2986                 {
2987                         Labels = labels;
2988                         Block = block;
2989                 }
2990         }
2991
2992         public class Switch : Statement {
2993                 public readonly ArrayList Sections;
2994                 public Expression Expr;
2995
2996                 /// <summary>
2997                 ///   Maps constants whose type type SwitchType to their  SwitchLabels.
2998                 /// </summary>
2999                 public Hashtable Elements;
3000
3001                 /// <summary>
3002                 ///   The governing switch type
3003                 /// </summary>
3004                 public Type SwitchType;
3005
3006                 //
3007                 // Computed
3008                 //
3009                 bool got_default;
3010                 Label default_target;
3011                 Expression new_expr;
3012
3013                 //
3014                 // The types allowed to be implicitly cast from
3015                 // on the governing type
3016                 //
3017                 static Type [] allowed_types;
3018
3019                 public Switch (Expression e, ArrayList sects, Location l)
3020                 {
3021                         Expr = e;
3022                         Sections = sects;
3023                         loc = l;
3024                 }
3025
3026                 public bool GotDefault {
3027                         get {
3028                                 return got_default;
3029                         }
3030                 }
3031
3032                 public Label DefaultTarget {
3033                         get {
3034                                 return default_target;
3035                         }
3036                 }
3037
3038                 //
3039                 // Determines the governing type for a switch.  The returned
3040                 // expression might be the expression from the switch, or an
3041                 // expression that includes any potential conversions to the
3042                 // integral types or to string.
3043                 //
3044                 Expression SwitchGoverningType (EmitContext ec, Type t)
3045                 {
3046                         if (t == TypeManager.int32_type ||
3047                             t == TypeManager.uint32_type ||
3048                             t == TypeManager.char_type ||
3049                             t == TypeManager.byte_type ||
3050                             t == TypeManager.sbyte_type ||
3051                             t == TypeManager.ushort_type ||
3052                             t == TypeManager.short_type ||
3053                             t == TypeManager.uint64_type ||
3054                             t == TypeManager.int64_type ||
3055                             t == TypeManager.string_type ||
3056                                 t == TypeManager.bool_type ||
3057                                 t.IsSubclassOf (TypeManager.enum_type))
3058                                 return Expr;
3059
3060                         if (allowed_types == null){
3061                                 allowed_types = new Type [] {
3062                                         TypeManager.sbyte_type,
3063                                         TypeManager.byte_type,
3064                                         TypeManager.short_type,
3065                                         TypeManager.ushort_type,
3066                                         TypeManager.int32_type,
3067                                         TypeManager.uint32_type,
3068                                         TypeManager.int64_type,
3069                                         TypeManager.uint64_type,
3070                                         TypeManager.char_type,
3071                                         TypeManager.bool_type,
3072                                         TypeManager.string_type
3073                                 };
3074                         }
3075
3076                         //
3077                         // Try to find a *user* defined implicit conversion.
3078                         //
3079                         // If there is no implicit conversion, or if there are multiple
3080                         // conversions, we have to report an error
3081                         //
3082                         Expression converted = null;
3083                         foreach (Type tt in allowed_types){
3084                                 Expression e;
3085
3086                                 e = Expression.ImplicitUserConversion (ec, Expr, tt, loc);
3087                                 if (e == null)
3088                                         continue;
3089
3090                                 if (converted != null){
3091                                         Report.Error (-12, loc, "More than one conversion to an integral " +
3092                                                       " type exists for type `" +
3093                                                       TypeManager.CSharpName (Expr.Type)+"'");
3094                                         return null;
3095                                 } else
3096                                         converted = e;
3097                         }
3098                         return converted;
3099                 }
3100
3101                 void error152 (string n)
3102                 {
3103                         Report.Error (
3104                                 152, "The label `" + n + ":' " +
3105                                 "is already present on this switch statement");
3106                 }
3107
3108                 //
3109                 // Performs the basic sanity checks on the switch statement
3110                 // (looks for duplicate keys and non-constant expressions).
3111                 //
3112                 // It also returns a hashtable with the keys that we will later
3113                 // use to compute the switch tables
3114                 //
3115                 bool CheckSwitch (EmitContext ec)
3116                 {
3117                         Type compare_type;
3118                         bool error = false;
3119                         Elements = new Hashtable ();
3120
3121                         got_default = false;
3122
3123                         if (TypeManager.IsEnumType (SwitchType)){
3124                                 compare_type = TypeManager.EnumToUnderlying (SwitchType);
3125                         } else
3126                                 compare_type = SwitchType;
3127
3128                         foreach (SwitchSection ss in Sections){
3129                                 foreach (SwitchLabel sl in ss.Labels){
3130                                         if (!sl.ResolveAndReduce (ec, SwitchType)){
3131                                                 error = true;
3132                                                 continue;
3133                                         }
3134
3135                                         if (sl.Label == null){
3136                                                 if (got_default){
3137                                                         error152 ("default");
3138                                                         error = true;
3139                                                 }
3140                                                 got_default = true;
3141                                                 continue;
3142                                         }
3143
3144                                         object key = sl.Converted;
3145
3146                                         if (key is Constant)
3147                                                 key = ((Constant) key).GetValue ();
3148
3149                                         if (key == null)
3150                                                 key = NullLiteral.Null;
3151
3152                                         string lname = null;
3153                                         if (compare_type == TypeManager.uint64_type){
3154                                                 ulong v = (ulong) key;
3155
3156                                                 if (Elements.Contains (v))
3157                                                         lname = v.ToString ();
3158                                                 else
3159                                                         Elements.Add (v, sl);
3160                                         } else if (compare_type == TypeManager.int64_type){
3161                                                 long v = (long) key;
3162
3163                                                 if (Elements.Contains (v))
3164                                                         lname = v.ToString ();
3165                                                 else
3166                                                         Elements.Add (v, sl);
3167                                         } else if (compare_type == TypeManager.uint32_type){
3168                                                 uint v = (uint) key;
3169
3170                                                 if (Elements.Contains (v))
3171                                                         lname = v.ToString ();
3172                                                 else
3173                                                         Elements.Add (v, sl);
3174                                         } else if (compare_type == TypeManager.char_type){
3175                                                 char v = (char) key;
3176
3177                                                 if (Elements.Contains (v))
3178                                                         lname = v.ToString ();
3179                                                 else
3180                                                         Elements.Add (v, sl);
3181                                         } else if (compare_type == TypeManager.byte_type){
3182                                                 byte v = (byte) key;
3183
3184                                                 if (Elements.Contains (v))
3185                                                         lname = v.ToString ();
3186                                                 else
3187                                                         Elements.Add (v, sl);
3188                                         } else if (compare_type == TypeManager.sbyte_type){
3189                                                 sbyte v = (sbyte) key;
3190
3191                                                 if (Elements.Contains (v))
3192                                                         lname = v.ToString ();
3193                                                 else
3194                                                         Elements.Add (v, sl);
3195                                         } else if (compare_type == TypeManager.short_type){
3196                                                 short v = (short) key;
3197
3198                                                 if (Elements.Contains (v))
3199                                                         lname = v.ToString ();
3200                                                 else
3201                                                         Elements.Add (v, sl);
3202                                         } else if (compare_type == TypeManager.ushort_type){
3203                                                 ushort v = (ushort) key;
3204
3205                                                 if (Elements.Contains (v))
3206                                                         lname = v.ToString ();
3207                                                 else
3208                                                         Elements.Add (v, sl);
3209                                         } else if (compare_type == TypeManager.string_type){
3210                                                 if (key is NullLiteral){
3211                                                         if (Elements.Contains (NullLiteral.Null))
3212                                                                 lname = "null";
3213                                                         else
3214                                                                 Elements.Add (NullLiteral.Null, null);
3215                                                 } else {
3216                                                         string s = (string) key;
3217
3218                                                         if (Elements.Contains (s))
3219                                                                 lname = s;
3220                                                         else
3221                                                                 Elements.Add (s, sl);
3222                                                 }
3223                                         } else if (compare_type == TypeManager.int32_type) {
3224                                                 int v = (int) key;
3225
3226                                                 if (Elements.Contains (v))
3227                                                         lname = v.ToString ();
3228                                                 else
3229                                                         Elements.Add (v, sl);
3230                                         } else if (compare_type == TypeManager.bool_type) {
3231                                                 bool v = (bool) key;
3232
3233                                                 if (Elements.Contains (v))
3234                                                         lname = v.ToString ();
3235                                                 else
3236                                                         Elements.Add (v, sl);
3237                                         }
3238                                         else
3239                                         {
3240                                                 throw new Exception ("Unknown switch type!" +
3241                                                                      SwitchType + " " + compare_type);
3242                                         }
3243
3244                                         if (lname != null){
3245                                                 error152 ("case + " + lname);
3246                                                 error = true;
3247                                         }
3248                                 }
3249                         }
3250                         if (error)
3251                                 return false;
3252
3253                         return true;
3254                 }
3255
3256                 void EmitObjectInteger (ILGenerator ig, object k)
3257                 {
3258                         if (k is int)
3259                                 IntConstant.EmitInt (ig, (int) k);
3260                         else if (k is Constant) {
3261                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
3262                         }
3263                         else if (k is uint)
3264                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
3265                         else if (k is long)
3266                         {
3267                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
3268                                 {
3269                                         IntConstant.EmitInt (ig, (int) (long) k);
3270                                         ig.Emit (OpCodes.Conv_I8);
3271                                 }
3272                                 else
3273                                         LongConstant.EmitLong (ig, (long) k);
3274                         }
3275                         else if (k is ulong)
3276                         {
3277                                 if ((ulong) k < (1L<<32))
3278                                 {
3279                                         IntConstant.EmitInt (ig, (int) (long) k);
3280                                         ig.Emit (OpCodes.Conv_U8);
3281                                 }
3282                                 else
3283                                 {
3284                                         LongConstant.EmitLong (ig, unchecked ((long) (ulong) k));
3285                                 }
3286                         }
3287                         else if (k is char)
3288                                 IntConstant.EmitInt (ig, (int) ((char) k));
3289                         else if (k is sbyte)
3290                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
3291                         else if (k is byte)
3292                                 IntConstant.EmitInt (ig, (int) ((byte) k));
3293                         else if (k is short)
3294                                 IntConstant.EmitInt (ig, (int) ((short) k));
3295                         else if (k is ushort)
3296                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
3297                         else if (k is bool)
3298                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
3299                         else
3300                                 throw new Exception ("Unhandled case");
3301                 }
3302
3303                 // structure used to hold blocks of keys while calculating table switch
3304                 class KeyBlock : IComparable
3305                 {
3306                         public KeyBlock (long _nFirst)
3307                         {
3308                                 nFirst = nLast = _nFirst;
3309                         }
3310                         public long nFirst;
3311                         public long nLast;
3312                         public ArrayList rgKeys = null;
3313                         public int Length
3314                         {
3315                                 get { return (int) (nLast - nFirst + 1); }
3316                         }
3317                         public static long TotalLength (KeyBlock kbFirst, KeyBlock kbLast)
3318                         {
3319                                 return kbLast.nLast - kbFirst.nFirst + 1;
3320                         }
3321                         public int CompareTo (object obj)
3322                         {
3323                                 KeyBlock kb = (KeyBlock) obj;
3324                                 int nLength = Length;
3325                                 int nLengthOther = kb.Length;
3326                                 if (nLengthOther == nLength)
3327                                         return (int) (kb.nFirst - nFirst);
3328                                 return nLength - nLengthOther;
3329                         }
3330                 }
3331
3332                 /// <summary>
3333                 /// This method emits code for a lookup-based switch statement (non-string)
3334                 /// Basically it groups the cases into blocks that are at least half full,
3335                 /// and then spits out individual lookup opcodes for each block.
3336                 /// It emits the longest blocks first, and short blocks are just
3337                 /// handled with direct compares.
3338                 /// </summary>
3339                 /// <param name="ec"></param>
3340                 /// <param name="val"></param>
3341                 /// <returns></returns>
3342                 bool TableSwitchEmit (EmitContext ec, LocalBuilder val)
3343                 {
3344                         int cElements = Elements.Count;
3345                         object [] rgKeys = new object [cElements];
3346                         Elements.Keys.CopyTo (rgKeys, 0);
3347                         Array.Sort (rgKeys);
3348
3349                         // initialize the block list with one element per key
3350                         ArrayList rgKeyBlocks = new ArrayList ();
3351                         foreach (object key in rgKeys)
3352                                 rgKeyBlocks.Add (new KeyBlock (Convert.ToInt64 (key)));
3353
3354                         KeyBlock kbCurr;
3355                         // iteratively merge the blocks while they are at least half full
3356                         // there's probably a really cool way to do this with a tree...
3357                         while (rgKeyBlocks.Count > 1)
3358                         {
3359                                 ArrayList rgKeyBlocksNew = new ArrayList ();
3360                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
3361                                 for (int ikb = 1; ikb < rgKeyBlocks.Count; ikb++)
3362                                 {
3363                                         KeyBlock kb = (KeyBlock) rgKeyBlocks [ikb];
3364                                         if ((kbCurr.Length + kb.Length) * 2 >=  KeyBlock.TotalLength (kbCurr, kb))
3365                                         {
3366                                                 // merge blocks
3367                                                 kbCurr.nLast = kb.nLast;
3368                                         }
3369                                         else
3370                                         {
3371                                                 // start a new block
3372                                                 rgKeyBlocksNew.Add (kbCurr);
3373                                                 kbCurr = kb;
3374                                         }
3375                                 }
3376                                 rgKeyBlocksNew.Add (kbCurr);
3377                                 if (rgKeyBlocks.Count == rgKeyBlocksNew.Count)
3378                                         break;
3379                                 rgKeyBlocks = rgKeyBlocksNew;
3380                         }
3381
3382                         // initialize the key lists
3383                         foreach (KeyBlock kb in rgKeyBlocks)
3384                                 kb.rgKeys = new ArrayList ();
3385
3386                         // fill the key lists
3387                         int iBlockCurr = 0;
3388                         if (rgKeyBlocks.Count > 0) {
3389                                 kbCurr = (KeyBlock) rgKeyBlocks [0];
3390                                 foreach (object key in rgKeys)
3391                                 {
3392                                         bool fNextBlock = (key is UInt64) ? (ulong) key > (ulong) kbCurr.nLast : Convert.ToInt64 (key) > kbCurr.nLast;
3393                                         if (fNextBlock)
3394                                                 kbCurr = (KeyBlock) rgKeyBlocks [++iBlockCurr];
3395                                         kbCurr.rgKeys.Add (key);
3396                                 }
3397                         }
3398
3399                         // sort the blocks so we can tackle the largest ones first
3400                         rgKeyBlocks.Sort ();
3401
3402                         // okay now we can start...
3403                         ILGenerator ig = ec.ig;
3404                         Label lblEnd = ig.DefineLabel ();       // at the end ;-)
3405                         Label lblDefault = ig.DefineLabel ();
3406
3407                         Type typeKeys = null;
3408                         if (rgKeys.Length > 0)
3409                                 typeKeys = rgKeys [0].GetType ();       // used for conversions
3410
3411                         for (int iBlock = rgKeyBlocks.Count - 1; iBlock >= 0; --iBlock)
3412                         {
3413                                 KeyBlock kb = ((KeyBlock) rgKeyBlocks [iBlock]);
3414                                 lblDefault = (iBlock == 0) ? DefaultTarget : ig.DefineLabel ();
3415                                 if (kb.Length <= 2)
3416                                 {
3417                                         foreach (object key in kb.rgKeys)
3418                                         {
3419                                                 ig.Emit (OpCodes.Ldloc, val);
3420                                                 EmitObjectInteger (ig, key);
3421                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
3422                                                 ig.Emit (OpCodes.Beq, sl.ILLabel);
3423                                         }
3424                                 }
3425                                 else
3426                                 {
3427                                         // TODO: if all the keys in the block are the same and there are
3428                                         //       no gaps/defaults then just use a range-check.
3429                                         if (SwitchType == TypeManager.int64_type ||
3430                                                 SwitchType == TypeManager.uint64_type)
3431                                         {
3432                                                 // TODO: optimize constant/I4 cases
3433
3434                                                 // check block range (could be > 2^31)
3435                                                 ig.Emit (OpCodes.Ldloc, val);
3436                                                 EmitObjectInteger (ig, Convert.ChangeType (kb.nFirst, typeKeys));
3437                                                 ig.Emit (OpCodes.Blt, lblDefault);
3438                                                 ig.Emit (OpCodes.Ldloc, val);
3439                                                 EmitObjectInteger (ig, Convert.ChangeType (kb.nFirst, typeKeys));
3440                                                 ig.Emit (OpCodes.Bgt, lblDefault);
3441
3442                                                 // normalize range
3443                                                 ig.Emit (OpCodes.Ldloc, val);
3444                                                 if (kb.nFirst != 0)
3445                                                 {
3446                                                         EmitObjectInteger (ig, Convert.ChangeType (kb.nFirst, typeKeys));
3447                                                         ig.Emit (OpCodes.Sub);
3448                                                 }
3449                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
3450                                         }
3451                                         else
3452                                         {
3453                                                 // normalize range
3454                                                 ig.Emit (OpCodes.Ldloc, val);
3455                                                 int nFirst = (int) kb.nFirst;
3456                                                 if (nFirst > 0)
3457                                                 {
3458                                                         IntConstant.EmitInt (ig, nFirst);
3459                                                         ig.Emit (OpCodes.Sub);
3460                                                 }
3461                                                 else if (nFirst < 0)
3462                                                 {
3463                                                         IntConstant.EmitInt (ig, -nFirst);
3464                                                         ig.Emit (OpCodes.Add);
3465                                                 }
3466                                         }
3467
3468                                         // first, build the list of labels for the switch
3469                                         int iKey = 0;
3470                                         int cJumps = kb.Length;
3471                                         Label [] rgLabels = new Label [cJumps];
3472                                         for (int iJump = 0; iJump < cJumps; iJump++)
3473                                         {
3474                                                 object key = kb.rgKeys [iKey];
3475                                                 if (Convert.ToInt64 (key) == kb.nFirst + iJump)
3476                                                 {
3477                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
3478                                                         rgLabels [iJump] = sl.ILLabel;
3479                                                         iKey++;
3480                                                 }
3481                                                 else
3482                                                         rgLabels [iJump] = lblDefault;
3483                                         }
3484                                         // emit the switch opcode
3485                                         ig.Emit (OpCodes.Switch, rgLabels);
3486                                 }
3487
3488                                 // mark the default for this block
3489                                 if (iBlock != 0)
3490                                         ig.MarkLabel (lblDefault);
3491                         }
3492
3493                         // TODO: find the default case and emit it here,
3494                         //       to prevent having to do the following jump.
3495                         //       make sure to mark other labels in the default section
3496
3497                         // the last default just goes to the end
3498                         ig.Emit (OpCodes.Br, lblDefault);
3499
3500                         // now emit the code for the sections
3501                         bool fFoundDefault = false;
3502                         bool fAllReturn = true;
3503                         foreach (SwitchSection ss in Sections)
3504                         {
3505                                 foreach (SwitchLabel sl in ss.Labels)
3506                                 {
3507                                         ig.MarkLabel (sl.ILLabel);
3508                                         ig.MarkLabel (sl.ILLabelCode);
3509                                         if (sl.Label == null)
3510                                         {
3511                                                 ig.MarkLabel (lblDefault);
3512                                                 fFoundDefault = true;
3513                                         }
3514                                 }
3515                                 fAllReturn &= ss.Block.Emit (ec);
3516                                 //ig.Emit (OpCodes.Br, lblEnd);
3517                         }
3518
3519                         if (!fFoundDefault) {
3520                                 ig.MarkLabel (lblDefault);
3521                                 fAllReturn = false;
3522                         }
3523                         ig.MarkLabel (lblEnd);
3524
3525                         return fAllReturn;
3526                 }
3527                 //
3528                 // This simple emit switch works, but does not take advantage of the
3529                 // `switch' opcode.
3530                 // TODO: remove non-string logic from here
3531                 // TODO: binary search strings?
3532                 //
3533                 bool SimpleSwitchEmit (EmitContext ec, LocalBuilder val)
3534                 {
3535                         ILGenerator ig = ec.ig;
3536                         Label end_of_switch = ig.DefineLabel ();
3537                         Label next_test = ig.DefineLabel ();
3538                         Label null_target = ig.DefineLabel ();
3539                         bool default_found = false;
3540                         bool first_test = true;
3541                         bool pending_goto_end = false;
3542                         bool all_return = true;
3543                         bool is_string = false;
3544                         bool null_found;
3545
3546                         //
3547                         // Special processing for strings: we cant compare
3548                         // against null.
3549                         //
3550                         if (SwitchType == TypeManager.string_type){
3551                                 ig.Emit (OpCodes.Ldloc, val);
3552                                 is_string = true;
3553
3554                                 if (Elements.Contains (NullLiteral.Null)){
3555                                         ig.Emit (OpCodes.Brfalse, null_target);
3556                                 } else
3557                                         ig.Emit (OpCodes.Brfalse, default_target);
3558
3559                                 ig.Emit (OpCodes.Ldloc, val);
3560                                 ig.Emit (OpCodes.Call, TypeManager.string_isinterneted_string);
3561                                 ig.Emit (OpCodes.Stloc, val);
3562                         }
3563
3564                         SwitchSection last_section;
3565                         last_section = (SwitchSection) Sections [Sections.Count-1];
3566
3567                         foreach (SwitchSection ss in Sections){
3568                                 Label sec_begin = ig.DefineLabel ();
3569
3570                                 if (pending_goto_end)
3571                                         ig.Emit (OpCodes.Br, end_of_switch);
3572
3573                                 int label_count = ss.Labels.Count;
3574                                 null_found = false;
3575                                 foreach (SwitchLabel sl in ss.Labels){
3576                                         ig.MarkLabel (sl.ILLabel);
3577
3578                                         if (!first_test){
3579                                                 ig.MarkLabel (next_test);
3580                                                 next_test = ig.DefineLabel ();
3581                                         }
3582                                         //
3583                                         // If we are the default target
3584                                         //
3585                                         if (sl.Label == null){
3586                                                 ig.MarkLabel (default_target);
3587                                                 default_found = true;
3588                                         } else {
3589                                                 object lit = sl.Converted;
3590
3591                                                 if (lit is NullLiteral){
3592                                                         null_found = true;
3593                                                         if (label_count == 1)
3594                                                                 ig.Emit (OpCodes.Br, next_test);
3595                                                         continue;
3596
3597                                                 }
3598                                                 if (is_string){
3599                                                         StringConstant str = (StringConstant) lit;
3600
3601                                                         ig.Emit (OpCodes.Ldloc, val);
3602                                                         ig.Emit (OpCodes.Ldstr, str.Value);
3603                                                         if (label_count == 1)
3604                                                                 ig.Emit (OpCodes.Bne_Un, next_test);
3605                                                         else
3606                                                                 ig.Emit (OpCodes.Beq, sec_begin);
3607                                                 } else {
3608                                                         ig.Emit (OpCodes.Ldloc, val);
3609                                                         EmitObjectInteger (ig, lit);
3610                                                         ig.Emit (OpCodes.Ceq);
3611                                                         if (label_count == 1)
3612                                                                 ig.Emit (OpCodes.Brfalse, next_test);
3613                                                         else
3614                                                                 ig.Emit (OpCodes.Brtrue, sec_begin);
3615                                                 }
3616                                         }
3617                                 }
3618                                 if (label_count != 1 && ss != last_section)
3619                                         ig.Emit (OpCodes.Br, next_test);
3620
3621                                 if (null_found)
3622                                         ig.MarkLabel (null_target);
3623                                 ig.MarkLabel (sec_begin);
3624                                 foreach (SwitchLabel sl in ss.Labels)\r
3625                                         ig.MarkLabel (sl.ILLabelCode);
3626                                 if (ss.Block.Emit (ec))
3627                                         pending_goto_end = false;
3628                                 else {
3629                                         all_return = false;
3630                                         pending_goto_end = true;
3631                                 }
3632                                 first_test = false;
3633                         }
3634                         if (!default_found){
3635                                 ig.MarkLabel (default_target);
3636                                 all_return = false;
3637                         }
3638                         ig.MarkLabel (next_test);
3639                         ig.MarkLabel (end_of_switch);
3640
3641                         return all_return;
3642                 }
3643
3644                 public override bool Resolve (EmitContext ec)
3645                 {
3646                         Expr = Expr.Resolve (ec);
3647                         if (Expr == null)
3648                                 return false;
3649
3650                         new_expr = SwitchGoverningType (ec, Expr.Type);
3651                         if (new_expr == null){
3652                                 Report.Error (151, loc, "An integer type or string was expected for switch");
3653                                 return false;
3654                         }
3655
3656                         // Validate switch.
3657                         SwitchType = new_expr.Type;
3658
3659                         if (!CheckSwitch (ec))
3660                                 return false;
3661
3662                         Switch old_switch = ec.Switch;
3663                         ec.Switch = this;
3664                         ec.Switch.SwitchType = SwitchType;
3665
3666                         ec.StartFlowBranching (FlowBranchingType.SWITCH, loc);
3667
3668                         bool first = true;
3669                         foreach (SwitchSection ss in Sections){
3670                                 if (!first)
3671                                         ec.CurrentBranching.CreateSibling ();
3672                                 else
3673                                         first = false;
3674
3675                                 if (ss.Block.Resolve (ec) != true)
3676                                         return false;
3677                         }
3678
3679                         ec.EndFlowBranching ();
3680                         ec.Switch = old_switch;
3681
3682                         return true;
3683                 }
3684
3685                 public override bool Emit (EmitContext ec)
3686                 {
3687                         // Store variable for comparission purposes
3688                         LocalBuilder value = ec.ig.DeclareLocal (SwitchType);
3689                         new_expr.Emit (ec);
3690                         ec.ig.Emit (OpCodes.Stloc, value);
3691
3692                         ILGenerator ig = ec.ig;
3693
3694                         default_target = ig.DefineLabel ();
3695
3696                         //
3697                         // Setup the codegen context
3698                         //
3699                         Label old_end = ec.LoopEnd;
3700                         Switch old_switch = ec.Switch;
3701
3702                         ec.LoopEnd = ig.DefineLabel ();
3703                         ec.Switch = this;
3704
3705                         // Emit Code.
3706                         bool all_return;
3707                         if (SwitchType == TypeManager.string_type)
3708                                 all_return = SimpleSwitchEmit (ec, value);
3709                         else
3710                                 all_return = TableSwitchEmit (ec, value);
3711
3712                         // Restore context state.
3713                         ig.MarkLabel (ec.LoopEnd);
3714
3715                         //
3716                         // Restore the previous context
3717                         //
3718                         ec.LoopEnd = old_end;
3719                         ec.Switch = old_switch;
3720
3721                         return all_return;
3722                 }
3723         }
3724
3725         public class Lock : Statement {
3726                 Expression expr;
3727                 Statement Statement;
3728
3729                 public Lock (Expression expr, Statement stmt, Location l)
3730                 {
3731                         this.expr = expr;
3732                         Statement = stmt;
3733                         loc = l;
3734                 }
3735
3736                 public override bool Resolve (EmitContext ec)
3737                 {
3738                         expr = expr.Resolve (ec);
3739                         return Statement.Resolve (ec) && expr != null;
3740                 }
3741
3742                 public override bool Emit (EmitContext ec)
3743                 {
3744                         Type type = expr.Type;
3745                         bool val;
3746
3747                         if (type.IsValueType){
3748                                 Report.Error (185, loc, "lock statement requires the expression to be " +
3749                                               " a reference type (type is: `" +
3750                                               TypeManager.CSharpName (type) + "'");
3751                                 return false;
3752                         }
3753
3754                         ILGenerator ig = ec.ig;
3755                         LocalBuilder temp = ig.DeclareLocal (type);
3756
3757                         expr.Emit (ec);
3758                         ig.Emit (OpCodes.Dup);
3759                         ig.Emit (OpCodes.Stloc, temp);
3760                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
3761
3762                         // try
3763                         Label end = ig.BeginExceptionBlock ();
3764                         bool old_in_try = ec.InTry;
3765                         ec.InTry = true;
3766                         Label finish = ig.DefineLabel ();
3767                         val = Statement.Emit (ec);
3768                         ec.InTry = old_in_try;
3769                         // ig.Emit (OpCodes.Leave, finish);
3770
3771                         ig.MarkLabel (finish);
3772
3773                         // finally
3774                         ig.BeginFinallyBlock ();
3775                         ig.Emit (OpCodes.Ldloc, temp);
3776                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
3777                         ig.EndExceptionBlock ();
3778
3779                         return val;
3780                 }
3781         }
3782
3783         public class Unchecked : Statement {
3784                 public readonly Block Block;
3785
3786                 public Unchecked (Block b)
3787                 {
3788                         Block = b;
3789                 }
3790
3791                 public override bool Resolve (EmitContext ec)
3792                 {
3793                         return Block.Resolve (ec);
3794                 }
3795
3796                 public override bool Emit (EmitContext ec)
3797                 {
3798                         bool previous_state = ec.CheckState;
3799                         bool previous_state_const = ec.ConstantCheckState;
3800                         bool val;
3801
3802                         ec.CheckState = false;
3803                         ec.ConstantCheckState = false;
3804                         val = Block.Emit (ec);
3805                         ec.CheckState = previous_state;
3806                         ec.ConstantCheckState = previous_state_const;
3807
3808                         return val;
3809                 }
3810         }
3811
3812         public class Checked : Statement {
3813                 public readonly Block Block;
3814
3815                 public Checked (Block b)
3816                 {
3817                         Block = b;
3818                 }
3819
3820                 public override bool Resolve (EmitContext ec)
3821                 {
3822                         bool previous_state = ec.CheckState;
3823                         bool previous_state_const = ec.ConstantCheckState;
3824
3825                         ec.CheckState = true;
3826                         ec.ConstantCheckState = true;
3827                         bool ret = Block.Resolve (ec);
3828                         ec.CheckState = previous_state;
3829                         ec.ConstantCheckState = previous_state_const;
3830
3831                         return ret;
3832                 }
3833
3834                 public override bool Emit (EmitContext ec)
3835                 {
3836                         bool previous_state = ec.CheckState;
3837                         bool previous_state_const = ec.ConstantCheckState;
3838                         bool val;
3839
3840                         ec.CheckState = true;
3841                         ec.ConstantCheckState = true;
3842                         val = Block.Emit (ec);
3843                         ec.CheckState = previous_state;
3844                         ec.ConstantCheckState = previous_state_const;
3845
3846                         return val;
3847                 }
3848         }
3849
3850         public class Unsafe : Statement {
3851                 public readonly Block Block;
3852
3853                 public Unsafe (Block b)
3854                 {
3855                         Block = b;
3856                 }
3857
3858                 public override bool Resolve (EmitContext ec)
3859                 {
3860                         bool previous_state = ec.InUnsafe;
3861                         bool val;
3862
3863                         ec.InUnsafe = true;
3864                         val = Block.Resolve (ec);
3865                         ec.InUnsafe = previous_state;
3866
3867                         return val;
3868                 }
3869
3870                 public override bool Emit (EmitContext ec)
3871                 {
3872                         bool previous_state = ec.InUnsafe;
3873                         bool val;
3874
3875                         ec.InUnsafe = true;
3876                         val = Block.Emit (ec);
3877                         ec.InUnsafe = previous_state;
3878
3879                         return val;
3880                 }
3881         }
3882
3883         //
3884         // Fixed statement
3885         //
3886         public class Fixed : Statement {
3887                 Expression type;
3888                 ArrayList declarators;
3889                 Statement statement;
3890                 Type expr_type;
3891                 FixedData[] data;
3892
3893                 struct FixedData {
3894                         public bool is_object;
3895                         public VariableInfo vi;
3896                         public Expression expr;
3897                         public Expression converted;
3898                 }
3899
3900                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
3901                 {
3902                         this.type = type;
3903                         declarators = decls;
3904                         statement = stmt;
3905                         loc = l;
3906                 }
3907
3908                 public override bool Resolve (EmitContext ec)
3909                 {
3910                         expr_type = ec.DeclSpace.ResolveType (type, false, loc);
3911                         if (expr_type == null)
3912                                 return false;
3913
3914                         data = new FixedData [declarators.Count];
3915
3916                         int i = 0;
3917                         foreach (Pair p in declarators){
3918                                 VariableInfo vi = (VariableInfo) p.First;
3919                                 Expression e = (Expression) p.Second;
3920
3921                                 vi.Number = -1;
3922
3923                                 //
3924                                 // The rules for the possible declarators are pretty wise,
3925                                 // but the production on the grammar is more concise.
3926                                 //
3927                                 // So we have to enforce these rules here.
3928                                 //
3929                                 // We do not resolve before doing the case 1 test,
3930                                 // because the grammar is explicit in that the token &
3931                                 // is present, so we need to test for this particular case.
3932                                 //
3933
3934                                 //
3935                                 // Case 1: & object.
3936                                 //
3937                                 if (e is Unary && ((Unary) e).Oper == Unary.Operator.AddressOf){
3938                                         Expression child = ((Unary) e).Expr;
3939
3940                                         vi.MakePinned ();
3941                                         if (child is ParameterReference || child is LocalVariableReference){
3942                                                 Report.Error (
3943                                                         213, loc,
3944                                                         "No need to use fixed statement for parameters or " +
3945                                                         "local variable declarations (address is already " +
3946                                                         "fixed)");
3947                                                 return false;
3948                                         }
3949
3950                                         e = e.Resolve (ec);
3951                                         if (e == null)
3952                                                 return false;
3953
3954                                         child = ((Unary) e).Expr;
3955
3956                                         if (!TypeManager.VerifyUnManaged (child.Type, loc))
3957                                                 return false;
3958
3959                                         data [i].is_object = true;
3960                                         data [i].expr = e;
3961                                         data [i].converted = null;
3962                                         data [i].vi = vi;
3963                                         i++;
3964
3965                                         continue;
3966                                 }
3967
3968                                 e = e.Resolve (ec);
3969                                 if (e == null)
3970                                         return false;
3971
3972                                 //
3973                                 // Case 2: Array
3974                                 //
3975                                 if (e.Type.IsArray){
3976                                         Type array_type = e.Type.GetElementType ();
3977
3978                                         vi.MakePinned ();
3979                                         //
3980                                         // Provided that array_type is unmanaged,
3981                                         //
3982                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
3983                                                 return false;
3984
3985                                         //
3986                                         // and T* is implicitly convertible to the
3987                                         // pointer type given in the fixed statement.
3988                                         //
3989                                         ArrayPtr array_ptr = new ArrayPtr (e, loc);
3990
3991                                         Expression converted = Expression.ConvertImplicitRequired (
3992                                                 ec, array_ptr, vi.VariableType, loc);
3993                                         if (converted == null)
3994                                                 return false;
3995
3996                                         data [i].is_object = false;
3997                                         data [i].expr = e;
3998                                         data [i].converted = converted;
3999                                         data [i].vi = vi;
4000                                         i++;
4001
4002                                         continue;
4003                                 }
4004
4005                                 //
4006                                 // Case 3: string
4007                                 //
4008                                 if (e.Type == TypeManager.string_type){
4009                                         data [i].is_object = false;
4010                                         data [i].expr = e;
4011                                         data [i].converted = null;
4012                                         data [i].vi = vi;
4013                                         i++;
4014                                 }
4015                         }
4016
4017                         return statement.Resolve (ec);
4018                 }
4019
4020                 public override bool Emit (EmitContext ec)
4021                 {
4022                         ILGenerator ig = ec.ig;
4023
4024                         bool is_ret = false;
4025
4026                         for (int i = 0; i < data.Length; i++) {
4027                                 VariableInfo vi = data [i].vi;
4028
4029                                 //
4030                                 // Case 1: & object.
4031                                 //
4032                                 if (data [i].is_object) {
4033                                         //
4034                                         // Store pointer in pinned location
4035                                         //
4036                                         data [i].expr.Emit (ec);
4037                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
4038
4039                                         is_ret = statement.Emit (ec);
4040
4041                                         // Clear the pinned variable.
4042                                         ig.Emit (OpCodes.Ldc_I4_0);
4043                                         ig.Emit (OpCodes.Conv_U);
4044                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
4045
4046                                         continue;
4047                                 }
4048
4049                                 //
4050                                 // Case 2: Array
4051                                 //
4052                                 if (data [i].expr.Type.IsArray){
4053                                         //
4054                                         // Store pointer in pinned location
4055                                         //
4056                                         data [i].converted.Emit (ec);
4057
4058                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
4059
4060                                         is_ret = statement.Emit (ec);
4061
4062                                         // Clear the pinned variable.
4063                                         ig.Emit (OpCodes.Ldc_I4_0);
4064                                         ig.Emit (OpCodes.Conv_U);
4065                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
4066
4067                                         continue;
4068                                 }
4069
4070                                 //
4071                                 // Case 3: string
4072                                 //
4073                                 if (data [i].expr.Type == TypeManager.string_type){
4074                                         LocalBuilder pinned_string = ig.DeclareLocal (TypeManager.string_type);
4075                                         TypeManager.MakePinned (pinned_string);
4076
4077                                         data [i].expr.Emit (ec);
4078                                         ig.Emit (OpCodes.Stloc, pinned_string);
4079
4080                                         Expression sptr = new StringPtr (pinned_string, loc);
4081                                         Expression converted = Expression.ConvertImplicitRequired (
4082                                                 ec, sptr, vi.VariableType, loc);
4083
4084                                         if (converted == null)
4085                                                 continue;
4086
4087                                         converted.Emit (ec);
4088                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
4089
4090                                         is_ret = statement.Emit (ec);
4091
4092                                         // Clear the pinned variable
4093                                         ig.Emit (OpCodes.Ldnull);
4094                                         ig.Emit (OpCodes.Stloc, pinned_string);
4095                                 }
4096                         }
4097
4098                         return is_ret;
4099                 }
4100         }
4101
4102         public class Catch {
4103                 public readonly string Name;
4104                 public readonly Block  Block;
4105                 public readonly Location Location;
4106
4107                 Expression type;
4108
4109                 public Catch (Expression type, string name, Block block, Location l)
4110                 {
4111                         this.type = type;
4112                         Name = name;
4113                         Block = block;
4114                         Location = l;
4115                 }
4116
4117                 public Type CatchType {
4118                         get {
4119                                 if (type == null)
4120                                         throw new InvalidOperationException ();
4121
4122                                 return type.Type;
4123                         }
4124                 }
4125
4126                 public bool IsGeneral {
4127                         get {
4128                                 return type == null;
4129                         }
4130                 }
4131
4132                 public bool Resolve (EmitContext ec)
4133                 {
4134                         if (type != null) {
4135                                 type = type.DoResolve (ec);
4136                                 if (type == null)
4137                                         return false;
4138
4139                                 Type t = type.Type;
4140                                 if (t != TypeManager.exception_type && !t.IsSubclassOf (TypeManager.exception_type)){
4141                                         Report.Error (155, Location,
4142                                                       "The type caught or thrown must be derived " +
4143                                                       "from System.Exception");
4144                                         return false;
4145                                 }
4146                         }
4147
4148                         if (!Block.Resolve (ec))
4149                                 return false;
4150
4151                         return true;
4152                 }
4153         }
4154
4155         public class Try : Statement {
4156                 public readonly Block Fini, Block;
4157                 public readonly ArrayList Specific;
4158                 public readonly Catch General;
4159
4160                 //
4161                 // specific, general and fini might all be null.
4162                 //
4163                 public Try (Block block, ArrayList specific, Catch general, Block fini, Location l)
4164                 {
4165                         if (specific == null && general == null){
4166                                 Console.WriteLine ("CIR.Try: Either specific or general have to be non-null");
4167                         }
4168
4169                         this.Block = block;
4170                         this.Specific = specific;
4171                         this.General = general;
4172                         this.Fini = fini;
4173                         loc = l;
4174                 }
4175
4176                 public override bool Resolve (EmitContext ec)
4177                 {
4178                         bool ok = true;
4179
4180                         ec.StartFlowBranching (FlowBranchingType.EXCEPTION, Block.StartLocation);
4181
4182                         Report.Debug (1, "START OF TRY BLOCK", Block.StartLocation);
4183
4184                         bool old_in_try = ec.InTry;
4185                         ec.InTry = true;
4186
4187                         if (!Block.Resolve (ec))
4188                                 ok = false;
4189
4190                         ec.InTry = old_in_try;
4191
4192                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
4193
4194                         Report.Debug (1, "START OF CATCH BLOCKS", vector);
4195
4196                         foreach (Catch c in Specific){
4197                                 ec.CurrentBranching.CreateSibling ();
4198                                 Report.Debug (1, "STARTED SIBLING FOR CATCH", ec.CurrentBranching);
4199
4200                                 if (c.Name != null) {
4201                                         VariableInfo vi = c.Block.GetVariableInfo (c.Name);
4202                                         if (vi == null)
4203                                                 throw new Exception ();
4204
4205                                         vi.Number = -1;
4206                                 }
4207
4208                                 bool old_in_catch = ec.InCatch;
4209                                 ec.InCatch = true;
4210
4211                                 if (!c.Resolve (ec))
4212                                         ok = false;
4213
4214                                 ec.InCatch = old_in_catch;
4215
4216                                 FlowBranching.UsageVector current = ec.CurrentBranching.CurrentUsageVector;
4217
4218                                 if ((current.Returns == FlowReturns.NEVER) ||
4219                                     (current.Returns == FlowReturns.SOMETIMES)) {
4220                                         vector.AndLocals (current);
4221                                 }
4222                         }
4223
4224                         if (General != null){
4225                                 ec.CurrentBranching.CreateSibling ();
4226                                 Report.Debug (1, "STARTED SIBLING FOR GENERAL", ec.CurrentBranching);
4227
4228                                 bool old_in_catch = ec.InCatch;
4229                                 ec.InCatch = true;
4230
4231                                 if (!General.Resolve (ec))
4232                                         ok = false;
4233
4234                                 ec.InCatch = old_in_catch;
4235
4236                                 FlowBranching.UsageVector current = ec.CurrentBranching.CurrentUsageVector;
4237
4238                                 if ((current.Returns == FlowReturns.NEVER) ||
4239                                     (current.Returns == FlowReturns.SOMETIMES)) {
4240                                         vector.AndLocals (current);
4241                                 }
4242                         }
4243
4244                         ec.CurrentBranching.CreateSiblingForFinally ();
4245                         Report.Debug (1, "STARTED SIBLING FOR FINALLY", ec.CurrentBranching, vector);
4246
4247                         if (Fini != null) {
4248                                 bool old_in_finally = ec.InFinally;
4249                                 ec.InFinally = true;
4250
4251                                 if (!Fini.Resolve (ec))
4252                                         ok = false;
4253
4254                                 ec.InFinally = old_in_finally;
4255                         }
4256
4257                         FlowBranching.UsageVector f_vector = ec.CurrentBranching.CurrentUsageVector;
4258
4259                         FlowReturns returns = ec.EndFlowBranching ();
4260
4261                         Report.Debug (1, "END OF FINALLY", ec.CurrentBranching, returns, vector, f_vector);
4262
4263                         if ((returns == FlowReturns.SOMETIMES) || (returns == FlowReturns.ALWAYS)) {
4264                                 ec.CurrentBranching.CheckOutParameters (f_vector.Parameters, loc);
4265                         }
4266
4267                         ec.CurrentBranching.CurrentUsageVector.Or (vector);
4268
4269                         Report.Debug (1, "END OF TRY", ec.CurrentBranching);
4270
4271                         return ok;
4272                 }
4273
4274                 public override bool Emit (EmitContext ec)
4275                 {
4276                         ILGenerator ig = ec.ig;
4277                         Label end;
4278                         Label finish = ig.DefineLabel ();;
4279                         bool returns;
4280
4281                         ec.TryCatchLevel++;
4282                         end = ig.BeginExceptionBlock ();
4283                         bool old_in_try = ec.InTry;
4284                         ec.InTry = true;
4285                         returns = Block.Emit (ec);
4286                         ec.InTry = old_in_try;
4287
4288                         //
4289                         // System.Reflection.Emit provides this automatically:
4290                         // ig.Emit (OpCodes.Leave, finish);
4291
4292                         bool old_in_catch = ec.InCatch;
4293                         ec.InCatch = true;
4294                         DeclSpace ds = ec.DeclSpace;
4295
4296                         foreach (Catch c in Specific){
4297                                 VariableInfo vi;
4298
4299                                 ig.BeginCatchBlock (c.CatchType);
4300
4301                                 if (c.Name != null){
4302                                         vi = c.Block.GetVariableInfo (c.Name);
4303                                         if (vi == null)
4304                                                 throw new Exception ("Variable does not exist in this block");
4305
4306                                         ig.Emit (OpCodes.Stloc, vi.LocalBuilder);
4307                                 } else
4308                                         ig.Emit (OpCodes.Pop);
4309
4310                                 if (!c.Block.Emit (ec))
4311                                         returns = false;
4312                         }
4313
4314                         if (General != null){
4315                                 ig.BeginCatchBlock (TypeManager.object_type);
4316                                 ig.Emit (OpCodes.Pop);
4317                                 if (!General.Block.Emit (ec))
4318                                         returns = false;
4319                         }
4320                         ec.InCatch = old_in_catch;
4321
4322                         ig.MarkLabel (finish);
4323                         if (Fini != null){
4324                                 ig.BeginFinallyBlock ();
4325                                 bool old_in_finally = ec.InFinally;
4326                                 ec.InFinally = true;
4327                                 Fini.Emit (ec);
4328                                 ec.InFinally = old_in_finally;
4329                         }
4330
4331                         ig.EndExceptionBlock ();
4332                         ec.TryCatchLevel--;
4333
4334                         if (!returns || ec.InTry || ec.InCatch)
4335                                 return returns;
4336
4337                         // Unfortunately, System.Reflection.Emit automatically emits a leave
4338                         // to the end of the finally block.  This is a problem if `returns'
4339                         // is true since we may jump to a point after the end of the method.
4340                         // As a workaround, emit an explicit ret here.
4341
4342                         if (ec.ReturnType != null)
4343                                 ec.ig.Emit (OpCodes.Ldloc, ec.TemporaryReturn ());
4344                         ec.ig.Emit (OpCodes.Ret);
4345
4346                         return true;
4347                 }
4348         }
4349
4350         //
4351         // FIXME: We still do not support the expression variant of the using
4352         // statement.
4353         //
4354         public class Using : Statement {
4355                 object expression_or_block;
4356                 Statement Statement;
4357                 ArrayList var_list;
4358                 Expression expr;
4359                 Type expr_type;
4360                 Expression conv;
4361                 Expression [] converted_vars;
4362                 ExpressionStatement [] assign;
4363
4364                 public Using (object expression_or_block, Statement stmt, Location l)
4365                 {
4366                         this.expression_or_block = expression_or_block;
4367                         Statement = stmt;
4368                         loc = l;
4369                 }
4370
4371                 //
4372                 // Resolves for the case of using using a local variable declaration.
4373                 //
4374                 bool ResolveLocalVariableDecls (EmitContext ec)
4375                 {
4376                         bool need_conv = false;
4377                         expr_type = ec.DeclSpace.ResolveType (expr, false, loc);
4378                         int i = 0;
4379
4380                         if (expr_type == null)
4381                                 return false;
4382
4383                         //
4384                         // The type must be an IDisposable or an implicit conversion
4385                         // must exist.
4386                         //
4387                         converted_vars = new Expression [var_list.Count];
4388                         assign = new ExpressionStatement [var_list.Count];
4389                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)){
4390                                 foreach (DictionaryEntry e in var_list){
4391                                         Expression var = (Expression) e.Key;
4392
4393                                         var = var.ResolveLValue (ec, new EmptyExpression ());
4394                                         if (var == null)
4395                                                 return false;
4396
4397                                         converted_vars [i] = Expression.ConvertImplicit (
4398                                                 ec, var, TypeManager.idisposable_type, loc);
4399
4400                                         if (converted_vars [i] == null)
4401                                                 return false;
4402                                         i++;
4403                                 }
4404                                 need_conv = true;
4405                         }
4406
4407                         i = 0;
4408                         foreach (DictionaryEntry e in var_list){
4409                                 LocalVariableReference var = (LocalVariableReference) e.Key;
4410                                 Expression new_expr = (Expression) e.Value;
4411                                 Expression a;
4412
4413                                 a = new Assign (var, new_expr, loc);
4414                                 a = a.Resolve (ec);
4415                                 if (a == null)
4416                                         return false;
4417
4418                                 if (!need_conv)
4419                                         converted_vars [i] = var;
4420                                 assign [i] = (ExpressionStatement) a;
4421                                 i++;
4422                         }
4423
4424                         return true;
4425                 }
4426
4427                 bool ResolveExpression (EmitContext ec)
4428                 {
4429                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)){
4430                                 conv = Expression.ConvertImplicit (
4431                                         ec, expr, TypeManager.idisposable_type, loc);
4432
4433                                 if (conv == null)
4434                                         return false;
4435                         }
4436
4437                         return true;
4438                 }
4439
4440                 //
4441                 // Emits the code for the case of using using a local variable declaration.
4442                 //
4443                 bool EmitLocalVariableDecls (EmitContext ec)
4444                 {
4445                         ILGenerator ig = ec.ig;
4446                         int i = 0;
4447
4448                         bool old_in_try = ec.InTry;
4449                         ec.InTry = true;
4450                         for (i = 0; i < assign.Length; i++) {
4451                                 assign [i].EmitStatement (ec);
4452
4453                                 ig.BeginExceptionBlock ();
4454                         }
4455                         Statement.Emit (ec);
4456                         ec.InTry = old_in_try;
4457
4458                         bool old_in_finally = ec.InFinally;
4459                         ec.InFinally = true;
4460                         var_list.Reverse ();
4461                         foreach (DictionaryEntry e in var_list){
4462                                 LocalVariableReference var = (LocalVariableReference) e.Key;
4463                                 Label skip = ig.DefineLabel ();
4464                                 i--;
4465
4466                                 ig.BeginFinallyBlock ();
4467
4468                                 var.Emit (ec);
4469                                 ig.Emit (OpCodes.Brfalse, skip);
4470                                 converted_vars [i].Emit (ec);
4471                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4472                                 ig.MarkLabel (skip);
4473                                 ig.EndExceptionBlock ();
4474                         }
4475                         ec.InFinally = old_in_finally;
4476
4477                         return false;
4478                 }
4479
4480                 bool EmitExpression (EmitContext ec)
4481                 {
4482                         //
4483                         // Make a copy of the expression and operate on that.
4484                         //
4485                         ILGenerator ig = ec.ig;
4486                         LocalBuilder local_copy = ig.DeclareLocal (expr_type);
4487                         if (conv != null)
4488                                 conv.Emit (ec);
4489                         else
4490                                 expr.Emit (ec);
4491                         ig.Emit (OpCodes.Stloc, local_copy);
4492
4493                         bool old_in_try = ec.InTry;
4494                         ec.InTry = true;
4495                         ig.BeginExceptionBlock ();
4496                         Statement.Emit (ec);
4497                         ec.InTry = old_in_try;
4498
4499                         Label skip = ig.DefineLabel ();
4500                         bool old_in_finally = ec.InFinally;
4501                         ig.BeginFinallyBlock ();
4502                         ig.Emit (OpCodes.Ldloc, local_copy);
4503                         ig.Emit (OpCodes.Brfalse, skip);
4504                         ig.Emit (OpCodes.Ldloc, local_copy);
4505                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4506                         ig.MarkLabel (skip);
4507                         ec.InFinally = old_in_finally;
4508                         ig.EndExceptionBlock ();
4509
4510                         return false;
4511                 }
4512
4513                 public override bool Resolve (EmitContext ec)
4514                 {
4515                         if (expression_or_block is DictionaryEntry){
4516                                 expr = (Expression) ((DictionaryEntry) expression_or_block).Key;
4517                                 var_list = (ArrayList)((DictionaryEntry)expression_or_block).Value;
4518
4519                                 if (!ResolveLocalVariableDecls (ec))
4520                                         return false;
4521
4522                         } else if (expression_or_block is Expression){
4523                                 expr = (Expression) expression_or_block;
4524
4525                                 expr = expr.Resolve (ec);
4526                                 if (expr == null)
4527                                         return false;
4528
4529                                 expr_type = expr.Type;
4530
4531                                 if (!ResolveExpression (ec))
4532                                         return false;
4533                         }
4534
4535                         return Statement.Resolve (ec);
4536                 }
4537
4538                 public override bool Emit (EmitContext ec)
4539                 {
4540                         if (expression_or_block is DictionaryEntry)
4541                                 return EmitLocalVariableDecls (ec);
4542                         else if (expression_or_block is Expression)
4543                                 return EmitExpression (ec);
4544
4545                         return false;
4546                 }
4547         }
4548
4549         /// <summary>
4550         ///   Implementation of the foreach C# statement
4551         /// </summary>
4552         public class Foreach : Statement {
4553                 Expression type;
4554                 LocalVariableReference variable;
4555                 Expression expr;
4556                 Statement statement;
4557                 ForeachHelperMethods hm;
4558                 Expression empty, conv;
4559                 Type array_type, element_type;
4560                 Type var_type;
4561
4562                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
4563                                 Statement stmt, Location l)
4564                 {
4565                         this.type = type;
4566                         this.variable = var;
4567                         this.expr = expr;
4568                         statement = stmt;
4569                         loc = l;
4570                 }
4571
4572                 public override bool Resolve (EmitContext ec)
4573                 {
4574                         expr = expr.Resolve (ec);
4575                         if (expr == null)
4576                                 return false;
4577
4578                         var_type = ec.DeclSpace.ResolveType (type, false, loc);
4579                         if (var_type == null)
4580                                 return false;
4581
4582                         //
4583                         // We need an instance variable.  Not sure this is the best
4584                         // way of doing this.
4585                         //
4586                         // FIXME: When we implement propertyaccess, will those turn
4587                         // out to return values in ExprClass?  I think they should.
4588                         //
4589                         if (!(expr.eclass == ExprClass.Variable || expr.eclass == ExprClass.Value ||
4590                               expr.eclass == ExprClass.PropertyAccess)){
4591                                 error1579 (expr.Type);
4592                                 return false;
4593                         }
4594
4595                         if (expr.Type.IsArray) {
4596                                 array_type = expr.Type;
4597                                 element_type = array_type.GetElementType ();
4598
4599                                 empty = new EmptyExpression (element_type);
4600                         } else {
4601                                 hm = ProbeCollectionType (ec, expr.Type);
4602                                 if (hm == null){
4603                                         error1579 (expr.Type);
4604                                         return false;
4605                                 }
4606
4607                                 array_type = expr.Type;
4608                                 element_type = hm.element_type;
4609
4610                                 empty = new EmptyExpression (hm.element_type);
4611                         }
4612
4613                         //
4614                         // FIXME: maybe we can apply the same trick we do in the
4615                         // array handling to avoid creating empty and conv in some cases.
4616                         //
4617                         // Although it is not as important in this case, as the type
4618                         // will not likely be object (what the enumerator will return).
4619                         //
4620                         conv = Expression.ConvertExplicit (ec, empty, var_type, loc);
4621                         if (conv == null)
4622                                 return false;
4623
4624                         if (variable.ResolveLValue (ec, empty) == null)
4625                                 return false;
4626
4627                         if (!statement.Resolve (ec))
4628                                 return false;
4629
4630                         return true;
4631                 }
4632
4633                 //
4634                 // Retrieves a `public bool MoveNext ()' method from the Type `t'
4635                 //
4636                 static MethodInfo FetchMethodMoveNext (Type t)
4637                 {
4638                         MemberList move_next_list;
4639
4640                         move_next_list = TypeContainer.FindMembers (
4641                                 t, MemberTypes.Method,
4642                                 BindingFlags.Public | BindingFlags.Instance,
4643                                 Type.FilterName, "MoveNext");
4644                         if (move_next_list.Count == 0)
4645                                 return null;
4646
4647                         foreach (MemberInfo m in move_next_list){
4648                                 MethodInfo mi = (MethodInfo) m;
4649                                 Type [] args;
4650
4651                                 args = TypeManager.GetArgumentTypes (mi);
4652                                 if (args != null && args.Length == 0){
4653                                         if (mi.ReturnType == TypeManager.bool_type)
4654                                                 return mi;
4655                                 }
4656                         }
4657                         return null;
4658                 }
4659
4660                 //
4661                 // Retrieves a `public T get_Current ()' method from the Type `t'
4662                 //
4663                 static MethodInfo FetchMethodGetCurrent (Type t)
4664                 {
4665                         MemberList move_next_list;
4666
4667                         move_next_list = TypeContainer.FindMembers (
4668                                 t, MemberTypes.Method,
4669                                 BindingFlags.Public | BindingFlags.Instance,
4670                                 Type.FilterName, "get_Current");
4671                         if (move_next_list.Count == 0)
4672                                 return null;
4673
4674                         foreach (MemberInfo m in move_next_list){
4675                                 MethodInfo mi = (MethodInfo) m;
4676                                 Type [] args;
4677
4678                                 args = TypeManager.GetArgumentTypes (mi);
4679                                 if (args != null && args.Length == 0)
4680                                         return mi;
4681                         }
4682                         return null;
4683                 }
4684
4685                 //
4686                 // This struct records the helper methods used by the Foreach construct
4687                 //
4688                 class ForeachHelperMethods {
4689                         public EmitContext ec;
4690                         public MethodInfo get_enumerator;
4691                         public MethodInfo move_next;
4692                         public MethodInfo get_current;
4693                         public Type element_type;
4694                         public Type enumerator_type;
4695                         public bool is_disposable;
4696
4697                         public ForeachHelperMethods (EmitContext ec)
4698                         {
4699                                 this.ec = ec;
4700                                 this.element_type = TypeManager.object_type;
4701                                 this.enumerator_type = TypeManager.ienumerator_type;
4702                                 this.is_disposable = true;
4703                         }
4704                 }
4705
4706                 static bool GetEnumeratorFilter (MemberInfo m, object criteria)
4707                 {
4708                         if (m == null)
4709                                 return false;
4710
4711                         if (!(m is MethodInfo))
4712                                 return false;
4713
4714                         if (m.Name != "GetEnumerator")
4715                                 return false;
4716
4717                         MethodInfo mi = (MethodInfo) m;
4718                         Type [] args = TypeManager.GetArgumentTypes (mi);
4719                         if (args != null){
4720                                 if (args.Length != 0)
4721                                         return false;
4722                         }
4723                         ForeachHelperMethods hm = (ForeachHelperMethods) criteria;
4724                         EmitContext ec = hm.ec;
4725
4726                         //
4727                         // Check whether GetEnumerator is accessible to us
4728                         //
4729                         MethodAttributes prot = mi.Attributes & MethodAttributes.MemberAccessMask;
4730
4731                         Type declaring = mi.DeclaringType;
4732                         if (prot == MethodAttributes.Private){
4733                                 if (declaring != ec.ContainerType)
4734                                         return false;
4735                         } else if (prot == MethodAttributes.FamANDAssem){
4736                                 // If from a different assembly, false
4737                                 if (!(mi is MethodBuilder))
4738                                         return false;
4739                                 //
4740                                 // Are we being invoked from the same class, or from a derived method?
4741                                 //
4742                                 if (ec.ContainerType != declaring){
4743                                         if (!ec.ContainerType.IsSubclassOf (declaring))
4744                                                 return false;
4745                                 }
4746                         } else if (prot == MethodAttributes.FamORAssem){
4747                                 if (!(mi is MethodBuilder ||
4748                                       ec.ContainerType == declaring ||
4749                                       ec.ContainerType.IsSubclassOf (declaring)))
4750                                         return false;
4751                         } if (prot == MethodAttributes.Family){
4752                                 if (!(ec.ContainerType == declaring ||
4753                                       ec.ContainerType.IsSubclassOf (declaring)))
4754                                         return false;
4755                         }
4756
4757                         //
4758                         // Ok, we can access it, now make sure that we can do something
4759                         // with this `GetEnumerator'
4760                         //
4761
4762                         if (mi.ReturnType == TypeManager.ienumerator_type ||
4763                             TypeManager.ienumerator_type.IsAssignableFrom (mi.ReturnType) ||
4764                             (!RootContext.StdLib && TypeManager.ImplementsInterface (mi.ReturnType, TypeManager.ienumerator_type))) {
4765                                 hm.move_next = TypeManager.bool_movenext_void;
4766                                 hm.get_current = TypeManager.object_getcurrent_void;
4767                                 return true;
4768                         }
4769
4770                         //
4771                         // Ok, so they dont return an IEnumerable, we will have to
4772                         // find if they support the GetEnumerator pattern.
4773                         //
4774                         Type return_type = mi.ReturnType;
4775
4776                         hm.move_next = FetchMethodMoveNext (return_type);
4777                         if (hm.move_next == null)
4778                                 return false;
4779                         hm.get_current = FetchMethodGetCurrent (return_type);
4780                         if (hm.get_current == null)
4781                                 return false;
4782
4783                         hm.element_type = hm.get_current.ReturnType;
4784                         hm.enumerator_type = return_type;
4785                         hm.is_disposable = TypeManager.ImplementsInterface (
4786                                 hm.enumerator_type, TypeManager.idisposable_type);
4787
4788                         return true;
4789                 }
4790
4791                 /// <summary>
4792                 ///   This filter is used to find the GetEnumerator method
4793                 ///   on which IEnumerator operates
4794                 /// </summary>
4795                 static MemberFilter FilterEnumerator;
4796
4797                 static Foreach ()
4798                 {
4799                         FilterEnumerator = new MemberFilter (GetEnumeratorFilter);
4800                 }
4801
4802                 void error1579 (Type t)
4803                 {
4804                         Report.Error (1579, loc,
4805                                       "foreach statement cannot operate on variables of type `" +
4806                                       t.FullName + "' because that class does not provide a " +
4807                                       " GetEnumerator method or it is inaccessible");
4808                 }
4809
4810                 static bool TryType (Type t, ForeachHelperMethods hm)
4811                 {
4812                         MemberList mi;
4813
4814                         mi = TypeContainer.FindMembers (t, MemberTypes.Method,
4815                                                         BindingFlags.Public | BindingFlags.NonPublic |
4816                                                         BindingFlags.Instance,
4817                                                         FilterEnumerator, hm);
4818
4819                         if (mi.Count == 0)
4820                                 return false;
4821
4822                         hm.get_enumerator = (MethodInfo) mi [0];
4823                         return true;
4824                 }
4825
4826                 //
4827                 // Looks for a usable GetEnumerator in the Type, and if found returns
4828                 // the three methods that participate: GetEnumerator, MoveNext and get_Current
4829                 //
4830                 ForeachHelperMethods ProbeCollectionType (EmitContext ec, Type t)
4831                 {
4832                         ForeachHelperMethods hm = new ForeachHelperMethods (ec);
4833
4834                         if (TryType (t, hm))
4835                                 return hm;
4836
4837                         //
4838                         // Now try to find the method in the interfaces
4839                         //
4840                         while (t != null){
4841                                 Type [] ifaces = t.GetInterfaces ();
4842
4843                                 foreach (Type i in ifaces){
4844                                         if (TryType (i, hm))
4845                                                 return hm;
4846                                 }
4847
4848                                 //
4849                                 // Since TypeBuilder.GetInterfaces only returns the interface
4850                                 // types for this type, we have to keep looping, but once
4851                                 // we hit a non-TypeBuilder (ie, a Type), then we know we are
4852                                 // done, because it returns all the types
4853                                 //
4854                                 if ((t is TypeBuilder))
4855                                         t = t.BaseType;
4856                                 else
4857                                         break;
4858                         }
4859
4860                         return null;
4861                 }
4862
4863                 //
4864                 // FIXME: possible optimization.
4865                 // We might be able to avoid creating `empty' if the type is the sam
4866                 //
4867                 bool EmitCollectionForeach (EmitContext ec)
4868                 {
4869                         ILGenerator ig = ec.ig;
4870                         LocalBuilder enumerator, disposable;
4871
4872                         enumerator = ig.DeclareLocal (hm.enumerator_type);
4873                         if (hm.is_disposable)
4874                                 disposable = ig.DeclareLocal (TypeManager.idisposable_type);
4875                         else
4876                                 disposable = null;
4877
4878                         //
4879                         // Instantiate the enumerator
4880                         //
4881                         if (expr.Type.IsValueType){
4882                                 if (expr is IMemoryLocation){
4883                                         IMemoryLocation ml = (IMemoryLocation) expr;
4884
4885                                         ml.AddressOf (ec, AddressOp.Load);
4886                                 } else
4887                                         throw new Exception ("Expr " + expr + " of type " + expr.Type +
4888                                                              " does not implement IMemoryLocation");
4889                                 ig.Emit (OpCodes.Call, hm.get_enumerator);
4890                         } else {
4891                                 expr.Emit (ec);
4892                                 ig.Emit (OpCodes.Callvirt, hm.get_enumerator);
4893                         }
4894                         ig.Emit (OpCodes.Stloc, enumerator);
4895
4896                         //
4897                         // Protect the code in a try/finalize block, so that
4898                         // if the beast implement IDisposable, we get rid of it
4899                         //
4900                         Label l;
4901                         bool old_in_try = ec.InTry;
4902
4903                         if (hm.is_disposable) {
4904                                 l = ig.BeginExceptionBlock ();
4905                                 ec.InTry = true;
4906                         }
4907
4908                         Label end_try = ig.DefineLabel ();
4909
4910                         ig.MarkLabel (ec.LoopBegin);
4911                         ig.Emit (OpCodes.Ldloc, enumerator);
4912                         ig.Emit (OpCodes.Callvirt, hm.move_next);
4913                         ig.Emit (OpCodes.Brfalse, end_try);
4914                         ig.Emit (OpCodes.Ldloc, enumerator);
4915                         ig.Emit (OpCodes.Callvirt, hm.get_current);
4916                         variable.EmitAssign (ec, conv);
4917                         statement.Emit (ec);
4918                         ig.Emit (OpCodes.Br, ec.LoopBegin);
4919                         ig.MarkLabel (end_try);
4920                         ec.InTry = old_in_try;
4921
4922                         // The runtime provides this for us.
4923                         // ig.Emit (OpCodes.Leave, end);
4924
4925                         //
4926                         // Now the finally block
4927                         //
4928                         if (hm.is_disposable) {
4929                                 Label end_finally = ig.DefineLabel ();
4930                                 bool old_in_finally = ec.InFinally;
4931                                 ec.InFinally = true;
4932                                 ig.BeginFinallyBlock ();
4933
4934                                 ig.Emit (OpCodes.Ldloc, enumerator);
4935                                 ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
4936                                 ig.Emit (OpCodes.Stloc, disposable);
4937                                 ig.Emit (OpCodes.Ldloc, disposable);
4938                                 ig.Emit (OpCodes.Brfalse, end_finally);
4939                                 ig.Emit (OpCodes.Ldloc, disposable);
4940                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4941                                 ig.MarkLabel (end_finally);
4942                                 ec.InFinally = old_in_finally;
4943
4944                                 // The runtime generates this anyways.
4945                                 // ig.Emit (OpCodes.Endfinally);
4946
4947                                 ig.EndExceptionBlock ();
4948                         }
4949
4950                         ig.MarkLabel (ec.LoopEnd);
4951                         return false;
4952                 }
4953
4954                 //
4955                 // FIXME: possible optimization.
4956                 // We might be able to avoid creating `empty' if the type is the sam
4957                 //
4958                 bool EmitArrayForeach (EmitContext ec)
4959                 {
4960                         int rank = array_type.GetArrayRank ();
4961                         ILGenerator ig = ec.ig;
4962
4963                         LocalBuilder copy = ig.DeclareLocal (array_type);
4964
4965                         //
4966                         // Make our copy of the array
4967                         //
4968                         expr.Emit (ec);
4969                         ig.Emit (OpCodes.Stloc, copy);
4970
4971                         if (rank == 1){
4972                                 LocalBuilder counter = ig.DeclareLocal (TypeManager.int32_type);
4973
4974                                 Label loop, test;
4975
4976                                 ig.Emit (OpCodes.Ldc_I4_0);
4977                                 ig.Emit (OpCodes.Stloc, counter);
4978                                 test = ig.DefineLabel ();
4979                                 ig.Emit (OpCodes.Br, test);
4980
4981                                 loop = ig.DefineLabel ();
4982                                 ig.MarkLabel (loop);
4983
4984                                 ig.Emit (OpCodes.Ldloc, copy);
4985                                 ig.Emit (OpCodes.Ldloc, counter);
4986                                 ArrayAccess.EmitLoadOpcode (ig, var_type);
4987
4988                                 variable.EmitAssign (ec, conv);
4989
4990                                 statement.Emit (ec);
4991
4992                                 ig.MarkLabel (ec.LoopBegin);
4993                                 ig.Emit (OpCodes.Ldloc, counter);
4994                                 ig.Emit (OpCodes.Ldc_I4_1);
4995                                 ig.Emit (OpCodes.Add);
4996                                 ig.Emit (OpCodes.Stloc, counter);
4997
4998                                 ig.MarkLabel (test);
4999                                 ig.Emit (OpCodes.Ldloc, counter);
5000                                 ig.Emit (OpCodes.Ldloc, copy);
5001                                 ig.Emit (OpCodes.Ldlen);
5002                                 ig.Emit (OpCodes.Conv_I4);
5003                                 ig.Emit (OpCodes.Blt, loop);
5004                         } else {
5005                                 LocalBuilder [] dim_len   = new LocalBuilder [rank];
5006                                 LocalBuilder [] dim_count = new LocalBuilder [rank];
5007                                 Label [] loop = new Label [rank];
5008                                 Label [] test = new Label [rank];
5009                                 int dim;
5010
5011                                 for (dim = 0; dim < rank; dim++){
5012                                         dim_len [dim] = ig.DeclareLocal (TypeManager.int32_type);
5013                                         dim_count [dim] = ig.DeclareLocal (TypeManager.int32_type);
5014                                         test [dim] = ig.DefineLabel ();
5015                                         loop [dim] = ig.DefineLabel ();
5016                                 }
5017
5018                                 for (dim = 0; dim < rank; dim++){
5019                                         ig.Emit (OpCodes.Ldloc, copy);
5020                                         IntLiteral.EmitInt (ig, dim);
5021                                         ig.Emit (OpCodes.Callvirt, TypeManager.int_getlength_int);
5022                                         ig.Emit (OpCodes.Stloc, dim_len [dim]);
5023                                 }
5024
5025                                 for (dim = 0; dim < rank; dim++){
5026                                         ig.Emit (OpCodes.Ldc_I4_0);
5027                                         ig.Emit (OpCodes.Stloc, dim_count [dim]);
5028                                         ig.Emit (OpCodes.Br, test [dim]);
5029                                         ig.MarkLabel (loop [dim]);
5030                                 }
5031
5032                                 ig.Emit (OpCodes.Ldloc, copy);
5033                                 for (dim = 0; dim < rank; dim++)
5034                                         ig.Emit (OpCodes.Ldloc, dim_count [dim]);
5035
5036                                 //
5037                                 // FIXME: Maybe we can cache the computation of `get'?
5038                                 //
5039                                 Type [] args = new Type [rank];
5040                                 MethodInfo get;
5041
5042                                 for (int i = 0; i < rank; i++)
5043                                         args [i] = TypeManager.int32_type;
5044
5045                                 ModuleBuilder mb = CodeGen.ModuleBuilder;
5046                                 get = mb.GetArrayMethod (
5047                                         array_type, "Get",
5048                                         CallingConventions.HasThis| CallingConventions.Standard,
5049                                         var_type, args);
5050                                 ig.Emit (OpCodes.Call, get);
5051                                 variable.EmitAssign (ec, conv);
5052                                 statement.Emit (ec);
5053                                 ig.MarkLabel (ec.LoopBegin);
5054                                 for (dim = rank - 1; dim >= 0; dim--){
5055                                         ig.Emit (OpCodes.Ldloc, dim_count [dim]);
5056                                         ig.Emit (OpCodes.Ldc_I4_1);
5057                                         ig.Emit (OpCodes.Add);
5058                                         ig.Emit (OpCodes.Stloc, dim_count [dim]);
5059
5060                                         ig.MarkLabel (test [dim]);
5061                                         ig.Emit (OpCodes.Ldloc, dim_count [dim]);
5062                                         ig.Emit (OpCodes.Ldloc, dim_len [dim]);
5063                                         ig.Emit (OpCodes.Blt, loop [dim]);
5064                                 }
5065                         }
5066                         ig.MarkLabel (ec.LoopEnd);
5067
5068                         return false;
5069                 }
5070
5071                 public override bool Emit (EmitContext ec)
5072                 {
5073                         bool ret_val;
5074
5075                         ILGenerator ig = ec.ig;
5076
5077                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
5078                         bool old_inloop = ec.InLoop;
5079                         int old_loop_begin_try_catch_level = ec.LoopBeginTryCatchLevel;
5080                         ec.LoopBegin = ig.DefineLabel ();
5081                         ec.LoopEnd = ig.DefineLabel ();
5082                         ec.InLoop = true;
5083                         ec.LoopBeginTryCatchLevel = ec.TryCatchLevel;
5084
5085                         if (hm != null)
5086                                 ret_val = EmitCollectionForeach (ec);
5087                         else
5088                                 ret_val = EmitArrayForeach (ec);
5089
5090                         ec.LoopBegin = old_begin;
5091                         ec.LoopEnd = old_end;
5092                         ec.InLoop = old_inloop;
5093                         ec.LoopBeginTryCatchLevel = old_loop_begin_try_catch_level;
5094
5095                         return ret_val;
5096                 }
5097         }
5098 }
5099