mcs/mcs/statement.cs

   1 //
   2 // statement.cs: Statement representation for the IL tree.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Martin Baulig (martin@ximian.com)
   7 //   Marek Safar (marek.safar@seznam.cz)
   8 //
   9 // (C) 2001, 2002, 2003 Ximian, Inc.
  10 // (C) 2003, 2004 Novell, Inc.
  11 //
  12
  13 using System;
  14 using System.Text;
  15 using System.Reflection;
  16 using System.Reflection.Emit;
  17 using System.Diagnostics;
  18 using System.Collections;
  19 using System.Collections.Specialized;
  20
  21 namespace Mono.CSharp {
  22
  23         public abstract class Statement {
  24                 public Location loc;
  25
  26                 /// <summary>
  27                 ///   Resolves the statement, true means that all sub-statements
  28                 ///   did resolve ok.
  29                 //  </summary>
  30                 public virtual bool Resolve (EmitContext ec)
  31                 {
  32                         return true;
  33                 }
  34
  35                 /// <summary>
  36                 ///   We already know that the statement is unreachable, but we still
  37                 ///   need to resolve it to catch errors.
  38                 /// </summary>
  39                 public virtual bool ResolveUnreachable (EmitContext ec, bool warn)
  40                 {
  41                         //
  42                         // This conflicts with csc's way of doing this, but IMHO it's
  43                         // the right thing to do.
  44                         //
  45                         // If something is unreachable, we still check whether it's
  46                         // correct.  This means that you cannot use unassigned variables
  47                         // in unreachable code, for instance.
  48                         //
  49
  50                         if (warn)
  51                                 Report.Warning (162, 2, loc, "Unreachable code detected");
  52
  53                         ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
  54                         bool ok = Resolve (ec);
  55                         ec.KillFlowBranching ();
  56
  57                         return ok;
  58                 }
  59
  60                 /// <summary>
  61                 ///   Return value indicates whether all code paths emitted return.
  62                 /// </summary>
  63                 protected abstract void DoEmit (EmitContext ec);
  64
  65                 /// <summary>
  66                 ///   Utility wrapper routine for Error, just to beautify the code
  67                 /// </summary>
  68                 public void Error (int error, string format, params object[] args)
  69                 {
  70                         Error (error, String.Format (format, args));
  71                 }
  72
  73                 public void Error (int error, string s)
  74                 {
  75                         if (!loc.IsNull)
  76                                 Report.Error (error, loc, s);
  77                         else
  78                                 Report.Error (error, s);
  79                 }
  80
  81                 /// <summary>
  82                 ///   Return value indicates whether all code paths emitted return.
  83                 /// </summary>
  84                 public virtual void Emit (EmitContext ec)
  85                 {
  86                         ec.Mark (loc, true);
  87                         DoEmit (ec);
  88                 }
  89
  90                 //
  91                 // This routine must be overrided in derived classes and make copies
  92                 // of all the data that might be modified if resolved
  93                 //
  94                 protected virtual void CloneTo (CloneContext clonectx, Statement target)
  95                 {
  96                         throw new InternalErrorException ("{0} does not implement Statement.CloneTo", this.GetType ());
  97                 }
  98
  99                 public Statement Clone (CloneContext clonectx)
 100                 {
 101                         Statement s = (Statement) this.MemberwiseClone ();
 102                         CloneTo (clonectx, s);
 103                         return s;
 104                 }
 105
 106                 public virtual Expression CreateExpressionTree (EmitContext ec)
 107                 {
 108                         Report.Error (834, loc, "A lambda expression with statement body cannot be converted to an expresion tree");
 109                         return null;
 110                 }
 111
 112                 public Statement PerformClone ()
 113                 {
 114                         CloneContext clonectx = new CloneContext ();
 115
 116                         return Clone (clonectx);
 117                 }
 118
 119         }
 120
 121         //
 122         // This class is used during the Statement.Clone operation
 123         // to remap objects that have been cloned.
 124         //
 125         // Since blocks are cloned by Block.Clone, we need a way for
 126         // expressions that must reference the block to be cloned
 127         // pointing to the new cloned block.
 128         //
 129         public class CloneContext {
 130                 Hashtable block_map = new Hashtable ();
 131                 Hashtable variable_map;
 132
 133                 public void AddBlockMap (Block from, Block to)
 134                 {
 135                         if (block_map.Contains (from))
 136                                 return;
 137                         block_map [from] = to;
 138                 }
 139
 140                 public Block LookupBlock (Block from)
 141                 {
 142                         Block result = (Block) block_map [from];
 143
 144                         if (result == null){
 145                                 result = (Block) from.Clone (this);
 146                                 block_map [from] = result;
 147                         }
 148
 149                         return result;
 150                 }
 151
 152                 ///
 153                 /// Remaps block to cloned copy if one exists.
 154                 ///
 155                 public Block RemapBlockCopy (Block from)
 156                 {
 157                         Block mapped_to = (Block)block_map[from];
 158                         if (mapped_to == null)
 159                                 return from;
 160
 161                         return mapped_to;
 162                 }
 163
 164                 public void AddVariableMap (LocalInfo from, LocalInfo to)
 165                 {
 166                         if (variable_map == null)
 167                                 variable_map = new Hashtable ();
 168
 169                         if (variable_map.Contains (from))
 170                                 return;
 171                         variable_map [from] = to;
 172                 }
 173
 174                 public LocalInfo LookupVariable (LocalInfo from)
 175                 {
 176                         LocalInfo result = (LocalInfo) variable_map [from];
 177
 178                         if (result == null)
 179                                 throw new Exception ("LookupVariable: looking up a variable that has not been registered yet");
 180
 181                         return result;
 182                 }
 183         }
 184
 185         public sealed class EmptyStatement : Statement {
 186
 187                 private EmptyStatement () {}
 188
 189                 public static readonly EmptyStatement Value = new EmptyStatement ();
 190
 191                 public override bool Resolve (EmitContext ec)
 192                 {
 193                         return true;
 194                 }
 195
 196                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
 197                 {
 198                         return true;
 199                 }
 200
 201                 protected override void DoEmit (EmitContext ec)
 202                 {
 203                 }
 204
 205                 protected override void CloneTo (CloneContext clonectx, Statement target)
 206                 {
 207                         // nothing needed.
 208                 }
 209         }
 210
 211         public class If : Statement {
 212                 Expression expr;
 213                 public Statement TrueStatement;
 214                 public Statement FalseStatement;
 215
 216                 bool is_true_ret;
 217
 218                 public If (Expression expr, Statement true_statement, Location l)
 219                 {
 220                         this.expr = expr;
 221                         TrueStatement = true_statement;
 222                         loc = l;
 223                 }
 224
 225                 public If (Expression expr,
 226                            Statement true_statement,
 227                            Statement false_statement,
 228                            Location l)
 229                 {
 230                         this.expr = expr;
 231                         TrueStatement = true_statement;
 232                         FalseStatement = false_statement;
 233                         loc = l;
 234                 }
 235
 236                 public override bool Resolve (EmitContext ec)
 237                 {
 238                         bool ok = true;
 239
 240                         Report.Debug (1, "START IF BLOCK", loc);
 241
 242                         expr = Expression.ResolveBoolean (ec, expr, loc);
 243                         if (expr == null){
 244                                 ok = false;
 245                                 goto skip;
 246                         }
 247
 248                         Assign ass = expr as Assign;
 249                         if (ass != null && ass.Source is Constant) {
 250                                 Report.Warning (665, 3, loc, "Assignment in conditional expression is always constant; did you mean to use == instead of = ?");
 251                         }
 252
 253                         //
 254                         // Dead code elimination
 255                         //
 256                         if (expr is Constant){
 257                                 bool take = !((Constant) expr).IsDefaultValue;
 258
 259                                 if (take){
 260                                         if (!TrueStatement.Resolve (ec))
 261                                                 return false;
 262
 263                                         if ((FalseStatement != null) &&
 264                                             !FalseStatement.ResolveUnreachable (ec, true))
 265                                                 return false;
 266                                         FalseStatement = null;
 267                                 } else {
 268                                         if (!TrueStatement.ResolveUnreachable (ec, true))
 269                                                 return false;
 270                                         TrueStatement = null;
 271
 272                                         if ((FalseStatement != null) &&
 273                                             !FalseStatement.Resolve (ec))
 274                                                 return false;
 275                                 }
 276
 277                                 return true;
 278                         }
 279                 skip:
 280                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
 281
 282                         ok &= TrueStatement.Resolve (ec);
 283
 284                         is_true_ret = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 285
 286                         ec.CurrentBranching.CreateSibling ();
 287
 288                         if (FalseStatement != null)
 289                                 ok &= FalseStatement.Resolve (ec);
 290
 291                         ec.EndFlowBranching ();
 292
 293                         Report.Debug (1, "END IF BLOCK", loc);
 294
 295                         return ok;
 296                 }
 297
 298                 protected override void DoEmit (EmitContext ec)
 299                 {
 300                         ILGenerator ig = ec.ig;
 301                         Label false_target = ig.DefineLabel ();
 302                         Label end;
 303
 304                         //
 305                         // If we're a boolean constant, Resolve() already
 306                         // eliminated dead code for us.
 307                         //
 308                         if (expr is Constant){
 309
 310                                 //
 311                                 // Simple bool constant
 312                                 //
 313                                 if (expr is BoolConstant) {
 314                                         bool take = ((BoolConstant) expr).Value;
 315
 316                                         if (take)
 317                                                 TrueStatement.Emit (ec);
 318                                         else if (FalseStatement != null)
 319                                                 FalseStatement.Emit (ec);
 320
 321                                         return;
 322                                 }
 323
 324                                 //
 325                                 // Bool constant with side-effects
 326                                 //
 327                                 expr.Emit (ec);
 328                                 ig.Emit (OpCodes.Pop);
 329
 330                                 if (TrueStatement != null)
 331                                         TrueStatement.Emit (ec);
 332                                 if (FalseStatement != null)
 333                                         FalseStatement.Emit (ec);
 334
 335                                 return;
 336                         }
 337
 338                         expr.EmitBranchable (ec, false_target, false);
 339
 340                         TrueStatement.Emit (ec);
 341
 342                         if (FalseStatement != null){
 343                                 bool branch_emitted = false;
 344
 345                                 end = ig.DefineLabel ();
 346                                 if (!is_true_ret){
 347                                         ig.Emit (OpCodes.Br, end);
 348                                         branch_emitted = true;
 349                                 }
 350
 351                                 ig.MarkLabel (false_target);
 352                                 FalseStatement.Emit (ec);
 353
 354                                 if (branch_emitted)
 355                                         ig.MarkLabel (end);
 356                         } else {
 357                                 ig.MarkLabel (false_target);
 358                         }
 359                 }
 360
 361                 protected override void CloneTo (CloneContext clonectx, Statement t)
 362                 {
 363                         If target = (If) t;
 364
 365                         target.expr = expr.Clone (clonectx);
 366                         target.TrueStatement = TrueStatement.Clone (clonectx);
 367                         if (FalseStatement != null)
 368                                 target.FalseStatement = FalseStatement.Clone (clonectx);
 369                 }
 370         }
 371
 372         public class Do : Statement {
 373                 public Expression expr;
 374                 public Statement  EmbeddedStatement;
 375                 bool infinite;
 376
 377                 public Do (Statement statement, Expression bool_expr, Location l)
 378                 {
 379                         expr = bool_expr;
 380                         EmbeddedStatement = statement;
 381                         loc = l;
 382                 }
 383
 384                 public override bool Resolve (EmitContext ec)
 385                 {
 386                         bool ok = true;
 387
 388                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 389
 390                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 391
 392                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 393                         if (!EmbeddedStatement.Resolve (ec))
 394                                 ok = false;
 395                         ec.EndFlowBranching ();
 396
 397                         if (ec.CurrentBranching.CurrentUsageVector.IsUnreachable && !was_unreachable)
 398                                 Report.Warning (162, 2, expr.Location, "Unreachable code detected");
 399
 400                         expr = Expression.ResolveBoolean (ec, expr, loc);
 401                         if (expr == null)
 402                                 ok = false;
 403                         else if (expr is BoolConstant){
 404                                 bool res = ((BoolConstant) expr).Value;
 405
 406                                 if (res)
 407                                         infinite = true;
 408                         }
 409                         if (infinite)
 410                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
 411
 412                         ec.EndFlowBranching ();
 413
 414                         return ok;
 415                 }
 416
 417                 protected override void DoEmit (EmitContext ec)
 418                 {
 419                         ILGenerator ig = ec.ig;
 420                         Label loop = ig.DefineLabel ();
 421                         Label old_begin = ec.LoopBegin;
 422                         Label old_end = ec.LoopEnd;
 423
 424                         ec.LoopBegin = ig.DefineLabel ();
 425                         ec.LoopEnd = ig.DefineLabel ();
 426
 427                         ig.MarkLabel (loop);
 428                         EmbeddedStatement.Emit (ec);
 429                         ig.MarkLabel (ec.LoopBegin);
 430
 431                         //
 432                         // Dead code elimination
 433                         //
 434                         if (expr is BoolConstant){
 435                                 bool res = ((BoolConstant) expr).Value;
 436
 437                                 if (res)
 438                                         ec.ig.Emit (OpCodes.Br, loop);
 439                         } else
 440                                 expr.EmitBranchable (ec, loop, true);
 441
 442                         ig.MarkLabel (ec.LoopEnd);
 443
 444                         ec.LoopBegin = old_begin;
 445                         ec.LoopEnd = old_end;
 446                 }
 447
 448                 protected override void CloneTo (CloneContext clonectx, Statement t)
 449                 {
 450                         Do target = (Do) t;
 451
 452                         target.EmbeddedStatement = EmbeddedStatement.Clone (clonectx);
 453                         target.expr = expr.Clone (clonectx);
 454                 }
 455         }
 456
 457         public class While : Statement {
 458                 public Expression expr;
 459                 public Statement Statement;
 460                 bool infinite, empty;
 461
 462                 public While (Expression bool_expr, Statement statement, Location l)
 463                 {
 464                         this.expr = bool_expr;
 465                         Statement = statement;
 466                         loc = l;
 467                 }
 468
 469                 public override bool Resolve (EmitContext ec)
 470                 {
 471                         bool ok = true;
 472
 473                         expr = Expression.ResolveBoolean (ec, expr, loc);
 474                         if (expr == null)
 475                                 return false;
 476
 477                         //
 478                         // Inform whether we are infinite or not
 479                         //
 480                         if (expr is BoolConstant){
 481                                 BoolConstant bc = (BoolConstant) expr;
 482
 483                                 if (bc.Value == false){
 484                                         if (!Statement.ResolveUnreachable (ec, true))
 485                                                 return false;
 486                                         empty = true;
 487                                         return true;
 488                                 } else
 489                                         infinite = true;
 490                         }
 491
 492                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 493                         if (!infinite)
 494                                 ec.CurrentBranching.CreateSibling ();
 495
 496                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 497                         if (!Statement.Resolve (ec))
 498                                 ok = false;
 499                         ec.EndFlowBranching ();
 500
 501                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 502                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 503
 504                         ec.EndFlowBranching ();
 505
 506                         return ok;
 507                 }
 508
 509                 protected override void DoEmit (EmitContext ec)
 510                 {
 511                         if (empty)
 512                                 return;
 513
 514                         ILGenerator ig = ec.ig;
 515                         Label old_begin = ec.LoopBegin;
 516                         Label old_end = ec.LoopEnd;
 517
 518                         ec.LoopBegin = ig.DefineLabel ();
 519                         ec.LoopEnd = ig.DefineLabel ();
 520
 521                         //
 522                         // Inform whether we are infinite or not
 523                         //
 524                         if (expr is BoolConstant){
 525                                 ig.MarkLabel (ec.LoopBegin);
 526                                 Statement.Emit (ec);
 527                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 528
 529                                 //
 530                                 // Inform that we are infinite (ie, `we return'), only
 531                                 // if we do not `break' inside the code.
 532                                 //
 533                                 ig.MarkLabel (ec.LoopEnd);
 534                         } else {
 535                                 Label while_loop = ig.DefineLabel ();
 536
 537                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 538                                 ig.MarkLabel (while_loop);
 539
 540                                 Statement.Emit (ec);
 541
 542                                 ig.MarkLabel (ec.LoopBegin);
 543
 544                                 expr.EmitBranchable (ec, while_loop, true);
 545
 546                                 ig.MarkLabel (ec.LoopEnd);
 547                         }
 548
 549                         ec.LoopBegin = old_begin;
 550                         ec.LoopEnd = old_end;
 551                 }
 552
 553                 protected override void CloneTo (CloneContext clonectx, Statement t)
 554                 {
 555                         While target = (While) t;
 556
 557                         target.expr = expr.Clone (clonectx);
 558                         target.Statement = Statement.Clone (clonectx);
 559                 }
 560         }
 561
 562         public class For : Statement {
 563                 Expression Test;
 564                 Statement InitStatement;
 565                 Statement Increment;
 566                 public Statement Statement;
 567                 bool infinite, empty;
 568
 569                 public For (Statement init_statement,
 570                             Expression test,
 571                             Statement increment,
 572                             Statement statement,
 573                             Location l)
 574                 {
 575                         InitStatement = init_statement;
 576                         Test = test;
 577                         Increment = increment;
 578                         Statement = statement;
 579                         loc = l;
 580                 }
 581
 582                 public override bool Resolve (EmitContext ec)
 583                 {
 584                         bool ok = true;
 585
 586                         if (InitStatement != null){
 587                                 if (!InitStatement.Resolve (ec))
 588                                         ok = false;
 589                         }
 590
 591                         if (Test != null){
 592                                 Test = Expression.ResolveBoolean (ec, Test, loc);
 593                                 if (Test == null)
 594                                         ok = false;
 595                                 else if (Test is BoolConstant){
 596                                         BoolConstant bc = (BoolConstant) Test;
 597
 598                                         if (bc.Value == false){
 599                                                 if (!Statement.ResolveUnreachable (ec, true))
 600                                                         return false;
 601                                                 if ((Increment != null) &&
 602                                                     !Increment.ResolveUnreachable (ec, false))
 603                                                         return false;
 604                                                 empty = true;
 605                                                 return true;
 606                                         } else
 607                                                 infinite = true;
 608                                 }
 609                         } else
 610                                 infinite = true;
 611
 612                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 613                         if (!infinite)
 614                                 ec.CurrentBranching.CreateSibling ();
 615
 616                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 617
 618                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 619                         if (!Statement.Resolve (ec))
 620                                 ok = false;
 621                         ec.EndFlowBranching ();
 622
 623                         if (Increment != null){
 624                                 if (ec.CurrentBranching.CurrentUsageVector.IsUnreachable) {
 625                                         if (!Increment.ResolveUnreachable (ec, !was_unreachable))
 626                                                 ok = false;
 627                                 } else {
 628                                         if (!Increment.Resolve (ec))
 629                                                 ok = false;
 630                                 }
 631                         }
 632
 633                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 634                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 635
 636                         ec.EndFlowBranching ();
 637
 638                         return ok;
 639                 }
 640
 641                 protected override void DoEmit (EmitContext ec)
 642                 {
 643                         if (empty)
 644                                 return;
 645
 646                         ILGenerator ig = ec.ig;
 647                         Label old_begin = ec.LoopBegin;
 648                         Label old_end = ec.LoopEnd;
 649                         Label loop = ig.DefineLabel ();
 650                         Label test = ig.DefineLabel ();
 651
 652                         if (InitStatement != null && InitStatement != EmptyStatement.Value)
 653                                 InitStatement.Emit (ec);
 654
 655                         ec.LoopBegin = ig.DefineLabel ();
 656                         ec.LoopEnd = ig.DefineLabel ();
 657
 658                         ig.Emit (OpCodes.Br, test);
 659                         ig.MarkLabel (loop);
 660                         Statement.Emit (ec);
 661
 662                         ig.MarkLabel (ec.LoopBegin);
 663                         if (Increment != EmptyStatement.Value)
 664                                 Increment.Emit (ec);
 665
 666                         ig.MarkLabel (test);
 667                         //
 668                         // If test is null, there is no test, and we are just
 669                         // an infinite loop
 670                         //
 671                         if (Test != null){
 672                                 //
 673                                 // The Resolve code already catches the case for
 674                                 // Test == BoolConstant (false) so we know that
 675                                 // this is true
 676                                 //
 677                                 if (Test is BoolConstant)
 678                                         ig.Emit (OpCodes.Br, loop);
 679                                 else
 680                                         Test.EmitBranchable (ec, loop, true);
 681
 682                         } else
 683                                 ig.Emit (OpCodes.Br, loop);
 684                         ig.MarkLabel (ec.LoopEnd);
 685
 686                         ec.LoopBegin = old_begin;
 687                         ec.LoopEnd = old_end;
 688                 }
 689
 690                 protected override void CloneTo (CloneContext clonectx, Statement t)
 691                 {
 692                         For target = (For) t;
 693
 694                         if (InitStatement != null)
 695                                 target.InitStatement = InitStatement.Clone (clonectx);
 696                         if (Test != null)
 697                                 target.Test = Test.Clone (clonectx);
 698                         if (Increment != null)
 699                                 target.Increment = Increment.Clone (clonectx);
 700                         target.Statement = Statement.Clone (clonectx);
 701                 }
 702         }
 703
 704         public class StatementExpression : Statement {
 705                 ExpressionStatement expr;
 706
 707                 public StatementExpression (ExpressionStatement expr)
 708                 {
 709                         this.expr = expr;
 710                         loc = expr.Location;
 711                 }
 712
 713                 public override bool Resolve (EmitContext ec)
 714                 {
 715                         if (expr != null)
 716                                 expr = expr.ResolveStatement (ec);
 717                         return expr != null;
 718                 }
 719
 720                 protected override void DoEmit (EmitContext ec)
 721                 {
 722                         expr.EmitStatement (ec);
 723                 }
 724
 725                 public override string ToString ()
 726                 {
 727                         return "StatementExpression (" + expr + ")";
 728                 }
 729
 730                 protected override void CloneTo (CloneContext clonectx, Statement t)
 731                 {
 732                         StatementExpression target = (StatementExpression) t;
 733
 734                         target.expr = (ExpressionStatement) expr.Clone (clonectx);
 735                 }
 736         }
 737
 738         /// <summary>
 739         ///   Implements the return statement
 740         /// </summary>
 741         public class Return : Statement {
 742                 protected Expression Expr;
 743                 bool unwind_protect;
 744
 745                 public Return (Expression expr, Location l)
 746                 {
 747                         Expr = expr;
 748                         loc = l;
 749                 }
 750
 751                 bool DoResolve (EmitContext ec)
 752                 {
 753                         if (Expr == null) {
 754                                 if (ec.ReturnType == TypeManager.void_type)
 755                                         return true;
 756
 757                                 Error (126, "An object of a type convertible to `{0}' is required " +
 758                                            "for the return statement",
 759                                            TypeManager.CSharpName (ec.ReturnType));
 760                                 return false;
 761                         }
 762
 763                         AnonymousContainer am = ec.CurrentAnonymousMethod;
 764                         if ((am != null) && am.IsIterator && ec.InIterator) {
 765                                 Report.Error (1622, loc, "Cannot return a value from iterators. Use the yield return " +
 766                                                   "statement to return a value, or yield break to end the iteration");
 767                         }
 768
 769                         if (am == null && ec.ReturnType == TypeManager.void_type) {
 770                                 MemberCore mc = ec.ResolveContext as MemberCore;
 771                                 Report.Error (127, loc, "`{0}': A return keyword must not be followed by any expression when method returns void",
 772                                         mc.GetSignatureForError ());
 773                         }
 774
 775                         Expr = Expr.Resolve (ec);
 776                         if (Expr == null)
 777                                 return false;
 778
 779                         if (Expr.Type != ec.ReturnType) {
 780                                 if (ec.InferReturnType) {
 781                                         ec.ReturnType = Expr.Type;
 782                                 } else {
 783                                         Expr = Convert.ImplicitConversionRequired (
 784                                                 ec, Expr, ec.ReturnType, loc);
 785
 786                                         if (Expr == null) {
 787                                                 if (am != null) {
 788                                                         Report.Error (1662, loc,
 789                                                                 "Cannot convert `{0}' to delegate type `{1}' because some of the return types in the block are not implicitly convertible to the delegate return type",
 790                                                                 am.ContainerType, am.GetSignatureForError ());
 791                                                 }
 792                                                 return false;
 793                                         }
 794                                 }
 795                         }
 796
 797                         return true;
 798                 }
 799
 800                 public override bool Resolve (EmitContext ec)
 801                 {
 802                         if (!DoResolve (ec))
 803                                 return false;
 804
 805                         unwind_protect = ec.CurrentBranching.AddReturnOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
 806                         if (unwind_protect)
 807                                 ec.NeedReturnLabel ();
 808                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 809                         return true;
 810                 }
 811
 812                 protected override void DoEmit (EmitContext ec)
 813                 {
 814                         if (Expr != null) {
 815                                 Expr.Emit (ec);
 816
 817                                 if (unwind_protect)
 818                                         ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 819                         }
 820
 821                         if (unwind_protect)
 822                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 823                         else
 824                                 ec.ig.Emit (OpCodes.Ret);
 825                 }
 826
 827                 protected override void CloneTo (CloneContext clonectx, Statement t)
 828                 {
 829                         Return target = (Return) t;
 830                         // It's null for simple return;
 831                         if (Expr != null)
 832                                 target.Expr = Expr.Clone (clonectx);
 833                 }
 834         }
 835
 836         public class Goto : Statement {
 837                 string target;
 838                 LabeledStatement label;
 839                 bool unwind_protect;
 840
 841                 public override bool Resolve (EmitContext ec)
 842                 {
 843                         int errors = Report.Errors;
 844                         unwind_protect = ec.CurrentBranching.AddGotoOrigin (ec.CurrentBranching.CurrentUsageVector, this);
 845                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 846                         return errors == Report.Errors;
 847                 }
 848
 849                 public Goto (string label, Location l)
 850                 {
 851                         loc = l;
 852                         target = label;
 853                 }
 854
 855                 public string Target {
 856                         get { return target; }
 857                 }
 858
 859                 public void SetResolvedTarget (LabeledStatement label)
 860                 {
 861                         this.label = label;
 862                         label.AddReference ();
 863                 }
 864
 865                 protected override void DoEmit (EmitContext ec)
 866                 {
 867                         if (label == null)
 868                                 throw new InternalErrorException ("goto emitted before target resolved");
 869                         Label l = label.LabelTarget (ec);
 870                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
 871                 }
 872         }
 873
 874         public class LabeledStatement : Statement {
 875                 string name;
 876                 bool defined;
 877                 bool referenced;
 878                 Label label;
 879                 ILGenerator ig;
 880
 881                 FlowBranching.UsageVector vectors;
 882
 883                 public LabeledStatement (string name, Location l)
 884                 {
 885                         this.name = name;
 886                         this.loc = l;
 887                 }
 888
 889                 public Label LabelTarget (EmitContext ec)
 890                 {
 891                         if (defined)
 892                                 return label;
 893                         ig = ec.ig;
 894                         label = ec.ig.DefineLabel ();
 895                         defined = true;
 896
 897                         return label;
 898                 }
 899
 900                 public string Name {
 901                         get { return name; }
 902                 }
 903
 904                 public bool IsDefined {
 905                         get { return defined; }
 906                 }
 907
 908                 public bool HasBeenReferenced {
 909                         get { return referenced; }
 910                 }
 911
 912                 public FlowBranching.UsageVector JumpOrigins {
 913                         get { return vectors; }
 914                 }
 915
 916                 public void AddUsageVector (FlowBranching.UsageVector vector)
 917                 {
 918                         vector = vector.Clone ();
 919                         vector.Next = vectors;
 920                         vectors = vector;
 921                 }
 922
 923                 public override bool Resolve (EmitContext ec)
 924                 {
 925                         // this flow-branching will be terminated when the surrounding block ends
 926                         ec.StartFlowBranching (this);
 927                         return true;
 928                 }
 929
 930                 protected override void DoEmit (EmitContext ec)
 931                 {
 932                         if (ig != null && ig != ec.ig)
 933                                 throw new InternalErrorException ("cannot happen");
 934                         LabelTarget (ec);
 935                         ec.ig.MarkLabel (label);
 936                 }
 937
 938                 public void AddReference ()
 939                 {
 940                         referenced = true;
 941                 }
 942         }
 943
 944
 945         /// <summary>
 946         ///   `goto default' statement
 947         /// </summary>
 948         public class GotoDefault : Statement {
 949
 950                 public GotoDefault (Location l)
 951                 {
 952                         loc = l;
 953                 }
 954
 955                 public override bool Resolve (EmitContext ec)
 956                 {
 957                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 958                         return true;
 959                 }
 960
 961                 protected override void DoEmit (EmitContext ec)
 962                 {
 963                         if (ec.Switch == null){
 964                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
 965                                 return;
 966                         }
 967
 968                         if (!ec.Switch.GotDefault){
 969                                 FlowBranchingBlock.Error_UnknownLabel (loc, "default");
 970                                 return;
 971                         }
 972                         ec.ig.Emit (OpCodes.Br, ec.Switch.DefaultTarget);
 973                 }
 974         }
 975
 976         /// <summary>
 977         ///   `goto case' statement
 978         /// </summary>
 979         public class GotoCase : Statement {
 980                 Expression expr;
 981                 SwitchLabel sl;
 982
 983                 public GotoCase (Expression e, Location l)
 984                 {
 985                         expr = e;
 986                         loc = l;
 987                 }
 988
 989                 public override bool Resolve (EmitContext ec)
 990                 {
 991                         if (ec.Switch == null){
 992                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
 993                                 return false;
 994                         }
 995
 996                         expr = expr.Resolve (ec);
 997                         if (expr == null)
 998                                 return false;
 999
1000                         Constant c = expr as Constant;
1001                         if (c == null) {
1002                                 Error (150, "A constant value is expected");
1003                                 return false;
1004                         }
1005
1006                         Type type = ec.Switch.SwitchType;
1007                         if (!Convert.ImplicitStandardConversionExists (c, type))
1008                                 Report.Warning (469, 2, loc, "The `goto case' value is not implicitly " +
1009                                                 "convertible to type `{0}'", TypeManager.CSharpName (type));
1010
1011                         bool fail = false;
1012                         object val = c.GetValue ();
1013                         if ((val != null) && (c.Type != type) && (c.Type != TypeManager.object_type))
1014                                 val = TypeManager.ChangeType (val, type, out fail);
1015
1016                         if (fail) {
1017                                 Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
1018                                               c.GetSignatureForError (), TypeManager.CSharpName (type));
1019                                 return false;
1020                         }
1021
1022                         if (val == null)
1023                                 val = SwitchLabel.NullStringCase;
1024
1025                         sl = (SwitchLabel) ec.Switch.Elements [val];
1026
1027                         if (sl == null){
1028                                 FlowBranchingBlock.Error_UnknownLabel (loc, "case " +
1029                                         (c.GetValue () == null ? "null" : val.ToString ()));
1030                                 return false;
1031                         }
1032
1033                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1034                         return true;
1035                 }
1036
1037                 protected override void DoEmit (EmitContext ec)
1038                 {
1039                         ec.ig.Emit (OpCodes.Br, sl.GetILLabelCode (ec));
1040                 }
1041
1042                 protected override void CloneTo (CloneContext clonectx, Statement t)
1043                 {
1044                         GotoCase target = (GotoCase) t;
1045
1046                         target.expr = expr.Clone (clonectx);
1047                         target.sl = sl.Clone (clonectx);
1048                 }
1049         }
1050
1051         public class Throw : Statement {
1052                 Expression expr;
1053
1054                 public Throw (Expression expr, Location l)
1055                 {
1056                         this.expr = expr;
1057                         loc = l;
1058                 }
1059
1060                 public override bool Resolve (EmitContext ec)
1061                 {
1062                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1063
1064                         if (expr != null){
1065                                 expr = expr.Resolve (ec);
1066                                 if (expr == null)
1067                                         return false;
1068
1069                                 ExprClass eclass = expr.eclass;
1070
1071                                 if (!(eclass == ExprClass.Variable || eclass == ExprClass.PropertyAccess ||
1072                                         eclass == ExprClass.Value || eclass == ExprClass.IndexerAccess)) {
1073                                         expr.Error_UnexpectedKind (ec.DeclContainer, "value, variable, property or indexer access ", loc);
1074                                         return false;
1075                                 }
1076
1077                                 Type t = expr.Type;
1078
1079                                 if ((t != TypeManager.exception_type) &&
1080                                     !TypeManager.IsSubclassOf (t, TypeManager.exception_type) &&
1081                                     !(expr is NullLiteral)) {
1082                                         Error (155,
1083                                                 "The type caught or thrown must be derived " +
1084                                                 "from System.Exception");
1085                                         return false;
1086                                 }
1087                                 return true;
1088                         }
1089
1090                         if (!ec.InCatch) {
1091                                 Error (156, "A throw statement with no arguments is not allowed outside of a catch clause");
1092                                 return false;
1093                         }
1094
1095                         if (ec.InFinally) {
1096                                 Error (724, "A throw statement with no arguments is not allowed inside of a finally clause nested inside of the innermost catch clause");
1097                                 return false;
1098                         }
1099                         return true;
1100                 }
1101
1102                 protected override void DoEmit (EmitContext ec)
1103                 {
1104                         if (expr == null)
1105                                 ec.ig.Emit (OpCodes.Rethrow);
1106                         else {
1107                                 expr.Emit (ec);
1108
1109                                 ec.ig.Emit (OpCodes.Throw);
1110                         }
1111                 }
1112
1113                 protected override void CloneTo (CloneContext clonectx, Statement t)
1114                 {
1115                         Throw target = (Throw) t;
1116
1117                         if (expr != null)
1118                                 target.expr = expr.Clone (clonectx);
1119                 }
1120         }
1121
1122         public class Break : Statement {
1123
1124                 public Break (Location l)
1125                 {
1126                         loc = l;
1127                 }
1128
1129                 bool unwind_protect;
1130
1131                 public override bool Resolve (EmitContext ec)
1132                 {
1133                         int errors = Report.Errors;
1134                         unwind_protect = ec.CurrentBranching.AddBreakOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
1135                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1136                         return errors == Report.Errors;
1137                 }
1138
1139                 protected override void DoEmit (EmitContext ec)
1140                 {
1141                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopEnd);
1142                 }
1143
1144                 protected override void CloneTo (CloneContext clonectx, Statement t)
1145                 {
1146                         // nothing needed
1147                 }
1148         }
1149
1150         public class Continue : Statement {
1151
1152                 public Continue (Location l)
1153                 {
1154                         loc = l;
1155                 }
1156
1157                 bool unwind_protect;
1158
1159                 public override bool Resolve (EmitContext ec)
1160                 {
1161                         int errors = Report.Errors;
1162                         unwind_protect = ec.CurrentBranching.AddContinueOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
1163                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1164                         return errors == Report.Errors;
1165                 }
1166
1167                 protected override void DoEmit (EmitContext ec)
1168                 {
1169                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopBegin);
1170                 }
1171
1172                 protected override void CloneTo (CloneContext clonectx, Statement t)
1173                 {
1174                         // nothing needed.
1175                 }
1176         }
1177
1178         public abstract class Variable
1179         {
1180                 public abstract Type Type {
1181                         get;
1182                 }
1183
1184                 public abstract bool HasInstance {
1185                         get;
1186                 }
1187
1188                 public abstract bool NeedsTemporary {
1189                         get;
1190                 }
1191
1192                 public abstract void EmitInstance (EmitContext ec);
1193
1194                 public abstract void Emit (EmitContext ec);
1195
1196                 public abstract void EmitAssign (EmitContext ec);
1197
1198                 public abstract void EmitAddressOf (EmitContext ec);
1199         }
1200
1201         public interface IKnownVariable {
1202                 Block Block { get; }
1203                 Location Location { get; }
1204         }
1205
1206         //
1207         // The information about a user-perceived local variable
1208         //
1209         public class LocalInfo : IKnownVariable {
1210                 public Expression Type;
1211
1212                 public Type VariableType;
1213                 public readonly string Name;
1214                 public readonly Location Location;
1215                 public readonly Block Block;
1216
1217                 public VariableInfo VariableInfo;
1218
1219                 Variable var;
1220                 public Variable Variable {
1221                         get { return var; }
1222                 }
1223
1224                 [Flags]
1225                 enum Flags : byte {
1226                         Used = 1,
1227                         ReadOnly = 2,
1228                         Pinned = 4,
1229                         IsThis = 8,
1230                         Captured = 16,
1231                         AddressTaken = 32,
1232                         CompilerGenerated = 64,
1233                         IsConstant = 128
1234                 }
1235
1236                 public enum ReadOnlyContext: byte {
1237                         Using,
1238                         Foreach,
1239                         Fixed
1240                 }
1241
1242                 Flags flags;
1243                 ReadOnlyContext ro_context;
1244                 LocalBuilder builder;
1245
1246                 public LocalInfo (Expression type, string name, Block block, Location l)
1247                 {
1248                         Type = type;
1249                         Name = name;
1250                         Block = block;
1251                         Location = l;
1252                 }
1253
1254                 public LocalInfo (DeclSpace ds, Block block, Location l)
1255                 {
1256                         VariableType = ds.IsGeneric ? ds.CurrentType : ds.TypeBuilder;
1257                         Block = block;
1258                         Location = l;
1259                 }
1260
1261                 public void ResolveVariable (EmitContext ec)
1262                 {
1263                         Block theblock = Block;
1264                         if (theblock.ScopeInfo != null)
1265                                 var = theblock.ScopeInfo.GetCapturedVariable (this);
1266
1267                         if (var == null) {
1268                                 if (Pinned)
1269                                         //
1270                                         // This is needed to compile on both .NET 1.x and .NET 2.x
1271                                         // the later introduced `DeclareLocal (Type t, bool pinned)'
1272                                         //
1273                                         builder = TypeManager.DeclareLocalPinned (ec.ig, VariableType);
1274                                 else
1275                                         builder = ec.ig.DeclareLocal (VariableType);
1276
1277                                 var = new LocalVariable (this, builder);
1278                         }
1279                 }
1280
1281                 public void EmitSymbolInfo (EmitContext ec, string name)
1282                 {
1283                         if (builder != null)
1284                                 ec.DefineLocalVariable (name, builder);
1285                 }
1286
1287                 public bool IsThisAssigned (EmitContext ec)
1288                 {
1289                         if (VariableInfo == null)
1290                                 throw new Exception ();
1291
1292                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo))
1293                                 return true;
1294
1295                         return VariableInfo.TypeInfo.IsFullyInitialized (ec.CurrentBranching, VariableInfo, ec.loc);
1296                 }
1297
1298                 public bool IsAssigned (EmitContext ec)
1299                 {
1300                         if (VariableInfo == null)
1301                                 throw new Exception ();
1302
1303                         return !ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo);
1304                 }
1305
1306                 public bool Resolve (EmitContext ec)
1307                 {
1308                         if (VariableType == null) {
1309                                 TypeExpr texpr = Type.ResolveAsContextualType (ec, false);
1310                                 if (texpr == null)
1311                                         return false;
1312
1313                                 VariableType = texpr.Type;
1314                         }
1315
1316                         if (TypeManager.IsGenericParameter (VariableType))
1317                                 return true;
1318
1319                         if (VariableType == TypeManager.void_type) {
1320                                 Expression.Error_VoidInvalidInTheContext (Location);
1321                                 return false;
1322                         }
1323
1324                         if (VariableType.IsAbstract && VariableType.IsSealed) {
1325                                 FieldBase.Error_VariableOfStaticClass (Location, Name, VariableType);
1326                                 return false;
1327                         }
1328
1329                         if (VariableType.IsPointer && !ec.InUnsafe)
1330                                 Expression.UnsafeError (Location);
1331
1332                         return true;
1333                 }
1334
1335                 public bool IsCaptured {
1336                         get { return (flags & Flags.Captured) != 0; }
1337                         set { flags |= Flags.Captured; }
1338                 }
1339
1340                 public bool IsConstant {
1341                         get { return (flags & Flags.IsConstant) != 0; }
1342                         set { flags |= Flags.IsConstant; }
1343                 }
1344
1345                 public bool AddressTaken {
1346                         get { return (flags & Flags.AddressTaken) != 0; }
1347                         set { flags |= Flags.AddressTaken; }
1348                 }
1349
1350                 public bool CompilerGenerated {
1351                         get { return (flags & Flags.CompilerGenerated) != 0; }
1352                         set { flags |= Flags.CompilerGenerated; }
1353                 }
1354
1355                 public override string ToString ()
1356                 {
1357                         return String.Format ("LocalInfo ({0},{1},{2},{3})",
1358                                               Name, Type, VariableInfo, Location);
1359                 }
1360
1361                 public bool Used {
1362                         get { return (flags & Flags.Used) != 0; }
1363                         set { flags = value ? (flags | Flags.Used) : (unchecked (flags & ~Flags.Used)); }
1364                 }
1365
1366                 public bool ReadOnly {
1367                         get { return (flags & Flags.ReadOnly) != 0; }
1368                 }
1369
1370                 public void SetReadOnlyContext (ReadOnlyContext context)
1371                 {
1372                         flags |= Flags.ReadOnly;
1373                         ro_context = context;
1374                 }
1375
1376                 public string GetReadOnlyContext ()
1377                 {
1378                         if (!ReadOnly)
1379                                 throw new InternalErrorException ("Variable is not readonly");
1380
1381                         switch (ro_context) {
1382                                 case ReadOnlyContext.Fixed:
1383                                         return "fixed variable";
1384                                 case ReadOnlyContext.Foreach:
1385                                         return "foreach iteration variable";
1386                                 case ReadOnlyContext.Using:
1387                                         return "using variable";
1388                         }
1389                         throw new NotImplementedException ();
1390                 }
1391
1392                 //
1393                 // Whether the variable is pinned, if Pinned the variable has been
1394                 // allocated in a pinned slot with DeclareLocal.
1395                 //
1396                 public bool Pinned {
1397                         get { return (flags & Flags.Pinned) != 0; }
1398                         set { flags = value ? (flags | Flags.Pinned) : (flags & ~Flags.Pinned); }
1399                 }
1400
1401                 public bool IsThis {
1402                         get { return (flags & Flags.IsThis) != 0; }
1403                         set { flags = value ? (flags | Flags.IsThis) : (flags & ~Flags.IsThis); }
1404                 }
1405
1406                 Block IKnownVariable.Block {
1407                         get { return Block; }
1408                 }
1409
1410                 Location IKnownVariable.Location {
1411                         get { return Location; }
1412                 }
1413
1414                 protected class LocalVariable : Variable
1415                 {
1416                         public readonly LocalInfo LocalInfo;
1417                         LocalBuilder builder;
1418
1419                         public LocalVariable (LocalInfo local, LocalBuilder builder)
1420                         {
1421                                 this.LocalInfo = local;
1422                                 this.builder = builder;
1423                         }
1424
1425                         public override Type Type {
1426                                 get { return LocalInfo.VariableType; }
1427                         }
1428
1429                         public override bool HasInstance {
1430                                 get { return false; }
1431                         }
1432
1433                         public override bool NeedsTemporary {
1434                                 get { return false; }
1435                         }
1436
1437                         public override void EmitInstance (EmitContext ec)
1438                         {
1439                                 // Do nothing.
1440                         }
1441
1442                         public override void Emit (EmitContext ec)
1443                         {
1444                                 ec.ig.Emit (OpCodes.Ldloc, builder);
1445                         }
1446
1447                         public override void EmitAssign (EmitContext ec)
1448                         {
1449                                 ec.ig.Emit (OpCodes.Stloc, builder);
1450                         }
1451
1452                         public override void EmitAddressOf (EmitContext ec)
1453                         {
1454                                 ec.ig.Emit (OpCodes.Ldloca, builder);
1455                         }
1456                 }
1457
1458                 public LocalInfo Clone (CloneContext clonectx)
1459                 {
1460                         //
1461                         // Variables in anonymous block are not resolved yet
1462                         //
1463                         if (VariableType == null)
1464                                 return new LocalInfo (Type.Clone (clonectx), Name, clonectx.LookupBlock (Block), Location);
1465
1466                         //
1467                         // Variables in method block are resolved
1468                         //
1469                         LocalInfo li = new LocalInfo (null, Name, clonectx.LookupBlock (Block), Location);
1470                         li.VariableType = VariableType;
1471                         return li;
1472                 }
1473         }
1474
1475         /// <summary>
1476         ///   Block represents a C# block.
1477         /// </summary>
1478         ///
1479         /// <remarks>
1480         ///   This class is used in a number of places: either to represent
1481         ///   explicit blocks that the programmer places or implicit blocks.
1482         ///
1483         ///   Implicit blocks are used as labels or to introduce variable
1484         ///   declarations.
1485         ///
1486         ///   Top-level blocks derive from Block, and they are called ToplevelBlock
1487         ///   they contain extra information that is not necessary on normal blocks.
1488         /// </remarks>
1489         public class Block : Statement {
1490                 public Block    Parent;
1491                 public readonly Location  StartLocation;
1492                 public Location EndLocation = Location.Null;
1493
1494                 public ExplicitBlock Explicit;
1495                 public ToplevelBlock Toplevel;
1496
1497                 [Flags]
1498                 public enum Flags : byte {
1499                         Unchecked = 1,
1500                         BlockUsed = 2,
1501                         VariablesInitialized = 4,
1502                         HasRet = 8,
1503                         IsDestructor = 16,
1504                         Unsafe = 32,
1505                         HasVarargs = 64, // Used in ToplevelBlock
1506                         IsIterator = 128
1507                 }
1508                 protected Flags flags;
1509
1510                 public bool Unchecked {
1511                         get { return (flags & Flags.Unchecked) != 0; }
1512                         set { flags |= Flags.Unchecked; }
1513                 }
1514
1515                 public bool Unsafe {
1516                         get { return (flags & Flags.Unsafe) != 0; }
1517                         set { flags |= Flags.Unsafe; }
1518                 }
1519
1520                 //
1521                 // The statements in this block
1522                 //
1523                 protected ArrayList statements;
1524                 int num_statements;
1525
1526                 //
1527                 // An array of Blocks.  We keep track of children just
1528                 // to generate the local variable declarations.
1529                 //
1530                 // Statements and child statements are handled through the
1531                 // statements.
1532                 //
1533                 ArrayList children;
1534
1535                 //
1536                 // Labels.  (label, block) pairs.
1537                 //
1538                 HybridDictionary labels;
1539
1540                 //
1541                 // Keeps track of (name, type) pairs
1542                 //
1543                 IDictionary variables;
1544
1545                 //
1546                 // Keeps track of constants
1547                 HybridDictionary constants;
1548
1549                 //
1550                 // Temporary variables.
1551                 //
1552                 ArrayList temporary_variables;
1553
1554                 //
1555                 // If this is a switch section, the enclosing switch block.
1556                 //
1557                 Block switch_block;
1558
1559                 // TODO: merge with scope_initializers
1560                 ExpressionStatement scope_init;
1561                 ArrayList scope_initializers;
1562
1563                 ArrayList anonymous_children;
1564
1565                 protected static int id;
1566
1567                 int this_id;
1568
1569                 int assignable_slots;
1570                 protected ScopeInfo scope_info;
1571                 bool unreachable_shown;
1572                 bool unreachable;
1573
1574                 public Block (Block parent)
1575                         : this (parent, (Flags) 0, Location.Null, Location.Null)
1576                 { }
1577
1578                 public Block (Block parent, Flags flags)
1579                         : this (parent, flags, Location.Null, Location.Null)
1580                 { }
1581
1582                 public Block (Block parent, Location start, Location end)
1583                         : this (parent, (Flags) 0, start, end)
1584                 { }
1585
1586                 public Block (Block parent, Flags flags, Location start, Location end)
1587                 {
1588                         if (parent != null) {
1589                                 parent.AddChild (this);
1590
1591                                 // the appropriate constructors will fixup these fields
1592                                 Toplevel = parent.Toplevel;
1593                                 Explicit = parent.Explicit;
1594                         }
1595
1596                         this.Parent = parent;
1597                         this.flags = flags;
1598                         this.StartLocation = start;
1599                         this.EndLocation = end;
1600                         this.loc = start;
1601                         this_id = id++;
1602                         statements = new ArrayList (4);
1603                 }
1604
1605                 public Block CreateSwitchBlock (Location start)
1606                 {
1607                         // FIXME: should this be implicit?
1608                         Block new_block = new ExplicitBlock (this, start, start);
1609                         new_block.switch_block = this;
1610                         return new_block;
1611                 }
1612
1613                 public int ID {
1614                         get { return this_id; }
1615                 }
1616
1617                 public IDictionary Variables {
1618                         get {
1619                                 if (variables == null)
1620                                         variables = new ListDictionary ();
1621                                 return variables;
1622                         }
1623                 }
1624
1625                 void AddChild (Block b)
1626                 {
1627                         if (children == null)
1628                                 children = new ArrayList (1);
1629
1630                         children.Add (b);
1631                 }
1632
1633                 public void SetEndLocation (Location loc)
1634                 {
1635                         EndLocation = loc;
1636                 }
1637
1638                 protected static void Error_158 (string name, Location loc)
1639                 {
1640                         Report.Error (158, loc, "The label `{0}' shadows another label " +
1641                                       "by the same name in a contained scope", name);
1642                 }
1643
1644                 /// <summary>
1645                 ///   Adds a label to the current block.
1646                 /// </summary>
1647                 ///
1648                 /// <returns>
1649                 ///   false if the name already exists in this block. true
1650                 ///   otherwise.
1651                 /// </returns>
1652                 ///
1653                 public bool AddLabel (LabeledStatement target)
1654                 {
1655                         if (switch_block != null)
1656                                 return switch_block.AddLabel (target);
1657
1658                         string name = target.Name;
1659
1660                         Block cur = this;
1661                         while (cur != null) {
1662                                 LabeledStatement s = cur.DoLookupLabel (name);
1663                                 if (s != null) {
1664                                         Report.SymbolRelatedToPreviousError (s.loc, s.Name);
1665                                         Report.Error (140, target.loc, "The label `{0}' is a duplicate", name);
1666                                         return false;
1667                                 }
1668
1669                                 if (this == Explicit)
1670                                         break;
1671
1672                                 cur = cur.Parent;
1673                         }
1674
1675                         while (cur != null) {
1676                                 if (cur.DoLookupLabel (name) != null) {
1677                                         Error_158 (name, target.loc);
1678                                         return false;
1679                                 }
1680
1681                                 if (children != null) {
1682                                         foreach (Block b in children) {
1683                                                 LabeledStatement s = b.DoLookupLabel (name);
1684                                                 if (s == null)
1685                                                         continue;
1686
1687                                                 Report.SymbolRelatedToPreviousError (s.loc, s.Name);
1688                                                 Error_158 (name, target.loc);
1689                                                 return false;
1690                                         }
1691                                 }
1692
1693                                 cur = cur.Parent;
1694                         }
1695
1696                         Toplevel.CheckError158 (name, target.loc);
1697
1698                         if (labels == null)
1699                                 labels = new HybridDictionary();
1700
1701                         labels.Add (name, target);
1702                         return true;
1703                 }
1704
1705                 public LabeledStatement LookupLabel (string name)
1706                 {
1707                         LabeledStatement s = DoLookupLabel (name);
1708                         if (s != null)
1709                                 return s;
1710
1711                         if (children == null)
1712                                 return null;
1713
1714                         foreach (Block child in children) {
1715                                 if (Explicit != child.Explicit)
1716                                         continue;
1717
1718                                 s = child.LookupLabel (name);
1719                                 if (s != null)
1720                                         return s;
1721                         }
1722
1723                         return null;
1724                 }
1725
1726                 LabeledStatement DoLookupLabel (string name)
1727                 {
1728                         if (switch_block != null)
1729                                 return switch_block.LookupLabel (name);
1730
1731                         if (labels != null)
1732                                 if (labels.Contains (name))
1733                                         return ((LabeledStatement) labels [name]);
1734
1735                         return null;
1736                 }
1737
1738                 public bool CheckInvariantMeaningInBlock (string name, Expression e, Location loc)
1739                 {
1740                         Block b = this;
1741                         IKnownVariable kvi = b.Explicit.GetKnownVariable (name);
1742                         while (kvi == null) {
1743                                 b = b.Explicit.Parent;
1744                                 if (b == null)
1745                                         return true;
1746                                 kvi = b.Explicit.GetKnownVariable (name);
1747                         }
1748
1749                         if (kvi.Block == b)
1750                                 return true;
1751
1752                         // Is kvi.Block nested inside 'b'
1753                         if (b.Explicit != kvi.Block.Explicit) {
1754                                 //
1755                                 // If a variable by the same name it defined in a nested block of this
1756                                 // block, we violate the invariant meaning in a block.
1757                                 //
1758                                 if (b == this) {
1759                                         Report.SymbolRelatedToPreviousError (kvi.Location, name);
1760                                         Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", name);
1761                                         return false;
1762                                 }
1763
1764                                 //
1765                                 // It's ok if the definition is in a nested subblock of b, but not
1766                                 // nested inside this block -- a definition in a sibling block
1767                                 // should not affect us.
1768                                 //
1769                                 return true;
1770                         }
1771
1772                         //
1773                         // Block 'b' and kvi.Block are the same textual block.
1774                         // However, different variables are extant.
1775                         //
1776                         // Check if the variable is in scope in both blocks.  We use
1777                         // an indirect check that depends on AddVariable doing its
1778                         // part in maintaining the invariant-meaning-in-block property.
1779                         //
1780                         if (e is VariableReference || (e is Constant && b.GetLocalInfo (name) != null))
1781                                 return true;
1782
1783                         //
1784                         // Even though we detected the error when the name is used, we
1785                         // treat it as if the variable declaration was in error.
1786                         //
1787                         Report.SymbolRelatedToPreviousError (loc, name);
1788                         Error_AlreadyDeclared (kvi.Location, name, "parent or current");
1789                         return false;
1790                 }
1791
1792                 public LocalInfo AddVariable (Expression type, string name, Location l)
1793                 {
1794                         LocalInfo vi = GetLocalInfo (name);
1795                         if (vi != null) {
1796                                 Report.SymbolRelatedToPreviousError (vi.Location, name);
1797                                 if (Explicit == vi.Block.Explicit)
1798                                         Error_AlreadyDeclared (l, name, null);
1799                                 else
1800                                         Error_AlreadyDeclared (l, name, "parent");
1801                                 return null;
1802                         }
1803
1804                         ToplevelParameterInfo pi = Toplevel.GetParameterInfo (name);
1805                         if (pi != null) {
1806                                 Report.SymbolRelatedToPreviousError (pi.Location, name);
1807                                 Error_AlreadyDeclared (loc, name,
1808                                         pi.Block == Toplevel ? "method argument" : "parent or current");
1809                                 return null;
1810                         }
1811
1812                         if (Toplevel.GenericMethod != null) {
1813                                 foreach (TypeParameter tp in Toplevel.GenericMethod.CurrentTypeParameters) {
1814                                         if (tp.Name == name) {
1815                                                 Report.SymbolRelatedToPreviousError (tp);
1816                                                 Error_AlreadyDeclaredTypeParameter (loc, name);
1817                                                 return null;
1818                                         }
1819                                 }
1820                         }
1821
1822                         IKnownVariable kvi = Explicit.GetKnownVariable (name);
1823                         if (kvi != null) {
1824                                 Report.SymbolRelatedToPreviousError (kvi.Location, name);
1825                                 Error_AlreadyDeclared (l, name, "child");
1826                                 return null;
1827                         }
1828
1829                         vi = new LocalInfo (type, name, this, l);
1830                         AddVariable (vi);
1831
1832                         if ((flags & Flags.VariablesInitialized) != 0)
1833                                 throw new InternalErrorException ("block has already been resolved");
1834
1835                         return vi;
1836                 }
1837
1838                 protected virtual void AddVariable (LocalInfo li)
1839                 {
1840                         Variables.Add (li.Name, li);
1841                         Explicit.AddKnownVariable (li.Name, li);
1842                 }
1843
1844                 protected virtual void Error_AlreadyDeclared (Location loc, string var, string reason)
1845                 {
1846                         if (reason == null) {
1847                                 Error_AlreadyDeclared (loc, var);
1848                                 return;
1849                         }
1850
1851                         Report.Error (136, loc, "A local variable named `{0}' cannot be declared " +
1852                                       "in this scope because it would give a different meaning " +
1853                                       "to `{0}', which is already used in a `{1}' scope " +
1854                                       "to denote something else", var, reason);
1855                 }
1856
1857                 protected virtual void Error_AlreadyDeclared (Location loc, string name)
1858                 {
1859                         Report.Error (128, loc,
1860                                 "A local variable named `{0}' is already defined in this scope", name);
1861                 }
1862
1863                 protected virtual void Error_AlreadyDeclaredTypeParameter (Location loc, string name)
1864                 {
1865                         GenericMethod.Error_ParameterNameCollision (loc, name, "local variable");
1866                 }
1867
1868                 public bool AddConstant (Expression type, string name, Expression value, Location l)
1869                 {
1870                         if (AddVariable (type, name, l) == null)
1871                                 return false;
1872
1873                         if (constants == null)
1874                                 constants = new HybridDictionary();
1875
1876                         constants.Add (name, value);
1877
1878                         // A block is considered used if we perform an initialization in a local declaration, even if it is constant.
1879                         Use ();
1880                         return true;
1881                 }
1882
1883                 static int next_temp_id = 0;
1884
1885                 public LocalInfo AddTemporaryVariable (TypeExpr te, Location loc)
1886                 {
1887                         Report.Debug (64, "ADD TEMPORARY", this, Toplevel, loc);
1888
1889                         if (temporary_variables == null)
1890                                 temporary_variables = new ArrayList ();
1891
1892                         int id = ++next_temp_id;
1893                         string name = "$s_" + id.ToString ();
1894
1895                         LocalInfo li = new LocalInfo (te, name, this, loc);
1896                         li.CompilerGenerated = true;
1897                         temporary_variables.Add (li);
1898                         return li;
1899                 }
1900
1901                 public LocalInfo GetLocalInfo (string name)
1902                 {
1903                         for (Block b = this; b != null; b = b.Parent) {
1904                                 if (b.variables != null) {
1905                                         LocalInfo ret = b.variables [name] as LocalInfo;
1906                                         if (ret != null)
1907                                                 return ret;
1908                                 }
1909                         }
1910                         return null;
1911                 }
1912
1913                 public Expression GetVariableType (string name)
1914                 {
1915                         LocalInfo vi = GetLocalInfo (name);
1916                         return vi == null ? null : vi.Type;
1917                 }
1918
1919                 public Expression GetConstantExpression (string name)
1920                 {
1921                         for (Block b = this; b != null; b = b.Parent) {
1922                                 if (b.constants != null) {
1923                                         Expression ret = b.constants [name] as Expression;
1924                                         if (ret != null)
1925                                                 return ret;
1926                                 }
1927                         }
1928                         return null;
1929                 }
1930
1931                 //
1932                 // It should be used by expressions which require to
1933                 // register a statement during resolve process.
1934                 //
1935                 public void AddScopeStatement (StatementExpression s)
1936                 {
1937                         if (scope_initializers == null)
1938                                 scope_initializers = new ArrayList ();
1939
1940                         scope_initializers.Add (s);
1941                 }
1942
1943                 public void AddStatement (Statement s)
1944                 {
1945                         statements.Add (s);
1946                         flags |= Flags.BlockUsed;
1947                 }
1948
1949                 public bool Used {
1950                         get { return (flags & Flags.BlockUsed) != 0; }
1951                 }
1952
1953                 public void Use ()
1954                 {
1955                         flags |= Flags.BlockUsed;
1956                 }
1957
1958                 public bool HasRet {
1959                         get { return (flags & Flags.HasRet) != 0; }
1960                 }
1961
1962                 public bool IsDestructor {
1963                         get { return (flags & Flags.IsDestructor) != 0; }
1964                 }
1965
1966                 public void SetDestructor ()
1967                 {
1968                         flags |= Flags.IsDestructor;
1969                 }
1970
1971                 public int AssignableSlots {
1972                         get {
1973                                 if ((flags & Flags.VariablesInitialized) == 0)
1974                                         throw new Exception ("Variables have not been initialized yet");
1975                                 return assignable_slots;
1976                         }
1977                 }
1978
1979                 public ScopeInfo ScopeInfo {
1980                         get { return scope_info; }
1981                 }
1982
1983                 public ScopeInfo CreateScopeInfo ()
1984                 {
1985                         if (scope_info == null)
1986                                 scope_info = ScopeInfo.CreateScope (this);
1987
1988                         return scope_info;
1989                 }
1990
1991                 public ArrayList AnonymousChildren {
1992                         get { return anonymous_children; }
1993                 }
1994
1995                 public void AddAnonymousChild (ToplevelBlock b)
1996                 {
1997                         if (anonymous_children == null)
1998                                 anonymous_children = new ArrayList ();
1999
2000                         anonymous_children.Add (b);
2001                 }
2002
2003                 void DoResolveConstants (EmitContext ec)
2004                 {
2005                         if (constants == null)
2006                                 return;
2007
2008                         if (variables == null)
2009                                 throw new InternalErrorException ("cannot happen");
2010
2011                         foreach (DictionaryEntry de in variables) {
2012                                 string name = (string) de.Key;
2013                                 LocalInfo vi = (LocalInfo) de.Value;
2014                                 Type variable_type = vi.VariableType;
2015
2016                                 if (variable_type == null) {
2017                                         if (vi.Type is VarExpr)
2018                                                 Report.Error (822, vi.Type.Location, "An implicitly typed local variable cannot be a constant");
2019
2020                                         continue;
2021                                 }
2022
2023                                 Expression cv = (Expression) constants [name];
2024                                 if (cv == null)
2025                                         continue;
2026
2027                                 // Don't let 'const int Foo = Foo;' succeed.
2028                                 // Removing the name from 'constants' ensures that we get a LocalVariableReference below,
2029                                 // which in turn causes the 'must be constant' error to be triggered.
2030                                 constants.Remove (name);
2031
2032                                 if (!Const.IsConstantTypeValid (variable_type)) {
2033                                         Const.Error_InvalidConstantType (variable_type, loc);
2034                                         continue;
2035                                 }
2036
2037                                 ec.CurrentBlock = this;
2038                                 Expression e;
2039                                 using (ec.With (EmitContext.Flags.ConstantCheckState, (flags & Flags.Unchecked) == 0)) {
2040                                         e = cv.Resolve (ec);
2041                                 }
2042                                 if (e == null)
2043                                         continue;
2044
2045                                 Constant ce = e as Constant;
2046                                 if (ce == null) {
2047                                         Const.Error_ExpressionMustBeConstant (vi.Location, name);
2048                                         continue;
2049                                 }
2050
2051                                 e = ce.ConvertImplicitly (variable_type);
2052                                 if (e == null) {
2053                                         if (!variable_type.IsValueType && variable_type != TypeManager.string_type && !ce.IsDefaultValue)
2054                                                 Const.Error_ConstantCanBeInitializedWithNullOnly (vi.Location, vi.Name);
2055                                         else
2056                                                 ce.Error_ValueCannotBeConverted (null, vi.Location, variable_type, false);
2057                                         continue;
2058                                 }
2059
2060                                 constants.Add (name, e);
2061                                 vi.IsConstant = true;
2062                         }
2063                 }
2064
2065                 protected void ResolveMeta (EmitContext ec, int offset)
2066                 {
2067                         Report.Debug (64, "BLOCK RESOLVE META", this, Parent);
2068
2069                         // If some parent block was unsafe, we remain unsafe even if this block
2070                         // isn't explicitly marked as such.
2071                         using (ec.With (EmitContext.Flags.InUnsafe, ec.InUnsafe | Unsafe)) {
2072                                 flags |= Flags.VariablesInitialized;
2073
2074                                 if (variables != null) {
2075                                         foreach (LocalInfo li in variables.Values) {
2076                                                 if (!li.Resolve (ec))
2077                                                         continue;
2078                                                 li.VariableInfo = new VariableInfo (li, offset);
2079                                                 offset += li.VariableInfo.Length;
2080                                         }
2081                                 }
2082                                 assignable_slots = offset;
2083
2084                                 DoResolveConstants (ec);
2085
2086                                 if (children == null)
2087                                         return;
2088                                 foreach (Block b in children)
2089                                         b.ResolveMeta (ec, offset);
2090                         }
2091                 }
2092
2093                 //
2094                 // Emits the local variable declarations for a block
2095                 //
2096                 public virtual void EmitMeta (EmitContext ec)
2097                 {
2098                         Report.Debug (64, "BLOCK EMIT META", this, Parent, Toplevel, ScopeInfo, ec);
2099                         if (ScopeInfo != null) {
2100                                 scope_init = ScopeInfo.GetScopeInitializer (ec);
2101                                 Report.Debug (64, "BLOCK EMIT META #1", this, Toplevel, ScopeInfo,
2102                                               ec, scope_init);
2103                         }
2104
2105                         if (variables != null){
2106                                 foreach (LocalInfo vi in variables.Values)
2107                                         vi.ResolveVariable (ec);
2108                         }
2109
2110                         if (temporary_variables != null) {
2111                                 for (int i = 0; i < temporary_variables.Count; i++)
2112                                         ((LocalInfo)temporary_variables[i]).ResolveVariable(ec);
2113                         }
2114
2115                         if (children != null){
2116                                 for (int i = 0; i < children.Count; i++)
2117                                         ((Block)children[i]).EmitMeta(ec);
2118                         }
2119                 }
2120
2121                 void UsageWarning (FlowBranching.UsageVector vector)
2122                 {
2123                         string name;
2124
2125                         if ((variables != null) && (Report.WarningLevel >= 3)) {
2126                                 foreach (DictionaryEntry de in variables){
2127                                         LocalInfo vi = (LocalInfo) de.Value;
2128
2129                                         if (vi.Used)
2130                                                 continue;
2131
2132                                         name = (string) de.Key;
2133
2134                                         // vi.VariableInfo can be null for 'catch' variables
2135                                         if (vi.VariableInfo != null && vector.IsAssigned (vi.VariableInfo, true)){
2136                                                 Report.Warning (219, 3, vi.Location, "The variable `{0}' is assigned but its value is never used", name);
2137                                         } else {
2138                                                 Report.Warning (168, 3, vi.Location, "The variable `{0}' is declared but never used", name);
2139                                         }
2140                                 }
2141                         }
2142                 }
2143
2144                 private void CheckPossibleMistakenEmptyStatement (Statement s)
2145                 {
2146                         Statement body;
2147
2148                         // Some statements are wrapped by a Block. Since
2149                         // others' internal could be changed, here I treat
2150                         // them as possibly wrapped by Block equally.
2151                         Block b = s as Block;
2152                         if (b != null && b.statements.Count == 1)
2153                                 s = (Statement) b.statements [0];
2154
2155                         if (s is Lock)
2156                                 body = ((Lock) s).Statement;
2157                         else if (s is For)
2158                                 body = ((For) s).Statement;
2159                         else if (s is Foreach)
2160                                 body = ((Foreach) s).Statement;
2161                         else if (s is While)
2162                                 body = ((While) s).Statement;
2163                         else if (s is Using)
2164                                 body = ((Using) s).Statement;
2165                         else if (s is Fixed)
2166                                 body = ((Fixed) s).Statement;
2167                         else
2168                                 return;
2169
2170                         if (body == null || body is EmptyStatement)
2171                                 Report.Warning (642, 3, s.loc, "Possible mistaken empty statement");
2172                 }
2173
2174                 public override bool Resolve (EmitContext ec)
2175                 {
2176                         Block prev_block = ec.CurrentBlock;
2177                         bool ok = true;
2178
2179                         int errors = Report.Errors;
2180
2181                         ec.CurrentBlock = this;
2182                         ec.StartFlowBranching (this);
2183
2184                         Report.Debug (4, "RESOLVE BLOCK", StartLocation, ec.CurrentBranching);
2185
2186                         //
2187                         // This flag is used to notate nested statements as unreachable from the beginning of this block.
2188                         // For the purposes of this resolution, it doesn't matter that the whole block is unreachable
2189                         // from the beginning of the function.  The outer Resolve() that detected the unreachability is
2190                         // responsible for handling the situation.
2191                         //
2192                         int statement_count = statements.Count;
2193                         for (int ix = 0; ix < statement_count; ix++){
2194                                 Statement s = (Statement) statements [ix];
2195                                 // Check possible empty statement (CS0642)
2196                                 if (Report.WarningLevel >= 3 &&
2197                                         ix + 1 < statement_count &&
2198                                                 statements [ix + 1] is Block)
2199                                         CheckPossibleMistakenEmptyStatement (s);
2200
2201                                 //
2202                                 // Warn if we detect unreachable code.
2203                                 //
2204                                 if (unreachable) {
2205                                         if (s is EmptyStatement)
2206                                                 continue;
2207
2208                                         if (s is Block)
2209                                                 ((Block) s).unreachable = true;
2210
2211                                         if (!unreachable_shown && !(s is LabeledStatement)) {
2212                                                 Report.Warning (162, 2, s.loc, "Unreachable code detected");
2213                                                 unreachable_shown = true;
2214                                         }
2215                                 }
2216
2217                                 //
2218                                 // Note that we're not using ResolveUnreachable() for unreachable
2219                                 // statements here.  ResolveUnreachable() creates a temporary
2220                                 // flow branching and kills it afterwards.  This leads to problems
2221                                 // if you have two unreachable statements where the first one
2222                                 // assigns a variable and the second one tries to access it.
2223                                 //
2224
2225                                 if (!s.Resolve (ec)) {
2226                                         ok = false;
2227                                         if (ec.IsInProbingMode)
2228                                                 break;
2229
2230                                         statements [ix] = EmptyStatement.Value;
2231                                         continue;
2232                                 }
2233
2234                                 if (unreachable && !(s is LabeledStatement) && !(s is Block))
2235                                         statements [ix] = EmptyStatement.Value;
2236
2237                                 num_statements = ix + 1;
2238
2239                                 unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
2240                                 if (unreachable && s is LabeledStatement)
2241                                         throw new InternalErrorException ("should not happen");
2242                         }
2243
2244                         Report.Debug (4, "RESOLVE BLOCK DONE", StartLocation,
2245                                       ec.CurrentBranching, statement_count, num_statements);
2246
2247                         while (ec.CurrentBranching is FlowBranchingLabeled)
2248                                 ec.EndFlowBranching ();
2249
2250                         FlowBranching.UsageVector vector = ec.DoEndFlowBranching ();
2251
2252                         ec.CurrentBlock = prev_block;
2253
2254                         // If we're a non-static `struct' constructor which doesn't have an
2255                         // initializer, then we must initialize all of the struct's fields.
2256                         if (this == Toplevel && !Toplevel.IsThisAssigned (ec) && !vector.IsUnreachable)
2257                                 ok = false;
2258
2259                         if ((labels != null) && (Report.WarningLevel >= 2)) {
2260                                 foreach (LabeledStatement label in labels.Values)
2261                                         if (!label.HasBeenReferenced)
2262                                                 Report.Warning (164, 2, label.loc,
2263                                                                 "This label has not been referenced");
2264                         }
2265
2266                         Report.Debug (4, "RESOLVE BLOCK DONE #2", StartLocation, vector);
2267
2268                         if (vector.IsUnreachable)
2269                                 flags |= Flags.HasRet;
2270
2271                         if (ok && (errors == Report.Errors)) {
2272                                 UsageWarning (vector);
2273                         }
2274
2275                         return ok;
2276                 }
2277
2278                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
2279                 {
2280                         unreachable_shown = true;
2281                         unreachable = true;
2282
2283                         if (warn)
2284                                 Report.Warning (162, 2, loc, "Unreachable code detected");
2285
2286                         ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
2287                         bool ok = Resolve (ec);
2288                         ec.KillFlowBranching ();
2289
2290                         return ok;
2291                 }
2292
2293                 protected override void DoEmit (EmitContext ec)
2294                 {
2295                         for (int ix = 0; ix < num_statements; ix++){
2296                                 Statement s = (Statement) statements [ix];
2297                                 s.Emit (ec);
2298                         }
2299                 }
2300
2301                 public override void Emit (EmitContext ec)
2302                 {
2303                         Block prev_block = ec.CurrentBlock;
2304
2305                         ec.CurrentBlock = this;
2306
2307                         bool emit_debug_info = (CodeGen.SymbolWriter != null);
2308                         bool is_lexical_block = this == Explicit && Parent != null;
2309
2310                         if (emit_debug_info) {
2311                                 if (is_lexical_block)
2312                                         ec.BeginScope ();
2313                         }
2314                         ec.Mark (StartLocation, true);
2315                         if (scope_init != null)
2316                                 scope_init.EmitStatement (ec);
2317                         if (scope_initializers != null) {
2318                                 foreach (StatementExpression s in scope_initializers)
2319                                         s.Emit (ec);
2320                         }
2321
2322                         DoEmit (ec);
2323                         ec.Mark (EndLocation, true);
2324
2325                         if (emit_debug_info) {
2326                                 if (is_lexical_block)
2327                                         ec.EndScope ();
2328
2329                                 if (variables != null) {
2330                                         foreach (DictionaryEntry de in variables) {
2331                                                 string name = (string) de.Key;
2332                                                 LocalInfo vi = (LocalInfo) de.Value;
2333
2334                                                 vi.EmitSymbolInfo (ec, name);
2335                                         }
2336                                 }
2337                         }
2338
2339                         ec.CurrentBlock = prev_block;
2340                 }
2341
2342                 public override string ToString ()
2343                 {
2344                         return String.Format ("{0} ({1}:{2})", GetType (),ID, StartLocation);
2345                 }
2346
2347                 protected override void CloneTo (CloneContext clonectx, Statement t)
2348                 {
2349                         Block target = (Block) t;
2350
2351                         clonectx.AddBlockMap (this, target);
2352
2353                         //target.Toplevel = (ToplevelBlock) clonectx.LookupBlock (Toplevel);
2354                         target.Explicit = (ExplicitBlock) clonectx.LookupBlock (Explicit);
2355                         if (Parent != null)
2356                                 target.Parent = clonectx.RemapBlockCopy (Parent);
2357
2358                         if (variables != null){
2359                                 target.variables = new Hashtable ();
2360
2361                                 foreach (DictionaryEntry de in variables){
2362                                         LocalInfo newlocal = ((LocalInfo) de.Value).Clone (clonectx);
2363                                         target.variables [de.Key] = newlocal;
2364                                         clonectx.AddVariableMap ((LocalInfo) de.Value, newlocal);
2365                                 }
2366                         }
2367
2368                         target.statements = new ArrayList (statements.Count);
2369                         foreach (Statement s in statements)
2370                                 target.statements.Add (s.Clone (clonectx));
2371
2372                         if (target.children != null){
2373                                 target.children = new ArrayList (children.Count);
2374                                 foreach (Block b in children){
2375                                         target.children.Add (clonectx.LookupBlock (b));
2376                                 }
2377                         }
2378
2379                         //
2380                         // TODO: labels, switch_block, constants (?), anonymous_children
2381                         //
2382                 }
2383         }
2384
2385         public class ExplicitBlock : Block {
2386                 public ExplicitBlock (Block parent, Location start, Location end)
2387                         : this (parent, (Flags) 0, start, end)
2388                 {
2389                 }
2390
2391                 public ExplicitBlock (Block parent, Flags flags, Location start, Location end)
2392                         : base (parent, flags, start, end)
2393                 {
2394                         this.Explicit = this;
2395                 }
2396
2397                 HybridDictionary known_variables;
2398
2399                 // <summary>
2400                 //   Marks a variable with name @name as being used in this or a child block.
2401                 //   If a variable name has been used in a child block, it's illegal to
2402                 //   declare a variable with the same name in the current block.
2403                 // </summary>
2404                 internal void AddKnownVariable (string name, IKnownVariable info)
2405                 {
2406                         if (known_variables == null)
2407                                 known_variables = new HybridDictionary();
2408
2409                         known_variables [name] = info;
2410
2411                         if (Parent != null)
2412                                 Parent.Explicit.AddKnownVariable (name, info);
2413                 }
2414
2415                 internal IKnownVariable GetKnownVariable (string name)
2416                 {
2417                         return known_variables == null ? null : (IKnownVariable) known_variables [name];
2418                 }
2419
2420                 protected override void CloneTo (CloneContext clonectx, Statement t)
2421                 {
2422                         ExplicitBlock target = (ExplicitBlock) t;
2423                         target.known_variables = null;
2424                         base.CloneTo (clonectx, t);
2425                 }
2426         }
2427
2428         public class ToplevelParameterInfo : IKnownVariable {
2429                 public readonly ToplevelBlock Block;
2430                 public readonly int Index;
2431                 public VariableInfo VariableInfo;
2432
2433                 Block IKnownVariable.Block {
2434                         get { return Block; }
2435                 }
2436                 public Parameter Parameter {
2437                         get { return Block.Parameters [Index]; }
2438                 }
2439                 public Location Location {
2440                         get { return Parameter.Location; }
2441                 }
2442
2443                 public ToplevelParameterInfo (ToplevelBlock block, int idx)
2444                 {
2445                         this.Block = block;
2446                         this.Index = idx;
2447                 }
2448         }
2449
2450         //
2451         // A toplevel block contains extra information, the split is done
2452         // only to separate information that would otherwise bloat the more
2453         // lightweight Block.
2454         //
2455         // In particular, this was introduced when the support for Anonymous
2456         // Methods was implemented.
2457         //
2458         public class ToplevelBlock : ExplicitBlock {
2459                 GenericMethod generic;
2460                 FlowBranchingToplevel top_level_branching;
2461                 AnonymousContainer anonymous_container;
2462                 RootScopeInfo root_scope;
2463                 Parameters parameters;
2464                 ToplevelParameterInfo[] parameter_info;
2465
2466                 public bool HasVarargs {
2467                         get { return (flags & Flags.HasVarargs) != 0; }
2468                         set { flags |= Flags.HasVarargs; }
2469                 }
2470
2471                 public bool IsIterator {
2472                         get { return (flags & Flags.IsIterator) != 0; }
2473                 }
2474
2475                 //
2476                 // The parameters for the block.
2477                 //
2478                 public Parameters Parameters {
2479                         get { return parameters; }
2480                 }
2481
2482                 public bool CompleteContexts (EmitContext ec)
2483                 {
2484                         Report.Debug (64, "TOPLEVEL COMPLETE CONTEXTS", this, Parent, root_scope);
2485
2486                         if (root_scope != null)
2487                                 root_scope.LinkScopes ();
2488
2489                         if (Parent == null && root_scope != null) {
2490                                 Report.Debug (64, "TOPLEVEL COMPLETE CONTEXTS #1", this, root_scope);
2491
2492                                 if (root_scope.DefineType () == null)
2493                                         return false;
2494                                 if (!root_scope.ResolveType ())
2495                                         return false;
2496                                 if (!root_scope.ResolveMembers ())
2497                                         return false;
2498                                 if (!root_scope.DefineMembers ())
2499                                         return false;
2500                         }
2501
2502                         return true;
2503                 }
2504
2505                 public GenericMethod GenericMethod {
2506                         get { return generic; }
2507                 }
2508
2509                 public ToplevelBlock Container {
2510                         get { return Parent == null ? null : Parent.Toplevel; }
2511                 }
2512
2513                 public AnonymousContainer AnonymousContainer {
2514                         get { return anonymous_container; }
2515                         set { anonymous_container = value; }
2516                 }
2517
2518                 public ToplevelBlock (Block parent, Parameters parameters, Location start) :
2519                         this (parent, (Flags) 0, parameters, start)
2520                 {
2521                 }
2522
2523                 public ToplevelBlock (Block parent, Parameters parameters, GenericMethod generic, Location start) :
2524                         this (parent, parameters, start)
2525                 {
2526                         this.generic = generic;
2527                 }
2528
2529                 public ToplevelBlock (Parameters parameters, Location start) :
2530                         this (null, (Flags) 0, parameters, start)
2531                 {
2532                 }
2533
2534                 public ToplevelBlock (Flags flags, Parameters parameters, Location start) :
2535                         this (null, flags, parameters, start)
2536                 {
2537                 }
2538
2539                 // We use 'Parent' to hook up to the containing block, but don't want to register the current block as a child.
2540                 // So, we use a two-stage setup -- first pass a null parent to the base constructor, and then override 'Parent'.
2541                 public ToplevelBlock (Block parent, Flags flags, Parameters parameters, Location start) :
2542                         base (null, flags, start, Location.Null)
2543                 {
2544                         this.Toplevel = this;
2545
2546                         this.parameters = parameters == null ? Parameters.EmptyReadOnlyParameters : parameters;
2547                         this.Parent = parent;
2548                         if (parent != null)
2549                                 parent.AddAnonymousChild (this);
2550
2551                         if (this.parameters.Count != 0)
2552                                 ProcessParameters ();
2553                 }
2554
2555                 public ToplevelBlock (Location loc) : this (null, (Flags) 0, null, loc)
2556                 {
2557                 }
2558
2559                 protected override void CloneTo (CloneContext clonectx, Statement t)
2560                 {
2561                         ToplevelBlock target = (ToplevelBlock) t;
2562                         base.CloneTo (clonectx, t);
2563
2564                         if (parameters.Count != 0)
2565                                 target.parameter_info = new ToplevelParameterInfo [parameters.Count];
2566                         for (int i = 0; i < parameters.Count; ++i)
2567                                 target.parameter_info [i] = new ToplevelParameterInfo (target, i);
2568                 }
2569
2570                 public bool CheckError158 (string name, Location loc)
2571                 {
2572                         if (AnonymousChildren != null) {
2573                                 foreach (ToplevelBlock child in AnonymousChildren) {
2574                                         if (!child.CheckError158 (name, loc))
2575                                                 return false;
2576                                 }
2577                         }
2578
2579                         for (ToplevelBlock c = Container; c != null; c = c.Container) {
2580                                 if (!c.DoCheckError158 (name, loc))
2581                                         return false;
2582                         }
2583
2584                         return true;
2585                 }
2586
2587                 public virtual Expression GetTransparentIdentifier (string name)
2588                 {
2589                         return null;
2590                 }
2591
2592                 void ProcessParameters ()
2593                 {
2594                         int n = parameters.Count;
2595                         parameter_info = new ToplevelParameterInfo [n];
2596                         for (int i = 0; i < n; ++i) {
2597                                 parameter_info [i] = new ToplevelParameterInfo (this, i);
2598
2599                                 Parameter p = parameters [i];
2600                                 if (p == null)
2601                                         continue;
2602
2603                                 string name = p.Name;
2604                                 LocalInfo vi = GetLocalInfo (name);
2605                                 if (vi != null) {
2606                                         Report.SymbolRelatedToPreviousError (vi.Location, name);
2607                                         Error_AlreadyDeclared (loc, name, "parent or current");
2608                                         continue;
2609                                 }
2610
2611                                 ToplevelParameterInfo pi = Parent == null ? null : Parent.Toplevel.GetParameterInfo (name);
2612                                 if (pi != null) {
2613                                         Report.SymbolRelatedToPreviousError (pi.Location, name);
2614                                         Error_AlreadyDeclared (loc, name, "parent or current");
2615                                         continue;
2616                                 }
2617
2618                                 AddKnownVariable (name, parameter_info [i]);
2619                         }
2620
2621                         // mark this block as "used" so that we create local declarations in a sub-block
2622                         // FIXME: This appears to uncover a lot of bugs
2623                         //this.Use ();
2624                 }
2625
2626                 bool DoCheckError158 (string name, Location loc)
2627                 {
2628                         LabeledStatement s = LookupLabel (name);
2629                         if (s != null) {
2630                                 Report.SymbolRelatedToPreviousError (s.loc, s.Name);
2631                                 Error_158 (name, loc);
2632                                 return false;
2633                         }
2634
2635                         return true;
2636                 }
2637
2638                 public RootScopeInfo CreateRootScope (TypeContainer host)
2639                 {
2640                         if (root_scope != null)
2641                                 return root_scope;
2642
2643                         if (Container == null)
2644                                 root_scope = new RootScopeInfo (
2645                                         this, host, generic, StartLocation);
2646
2647                         if (scope_info != null)
2648                                 throw new InternalErrorException ();
2649
2650                         scope_info = root_scope;
2651                         return root_scope;
2652                 }
2653
2654                 public override Expression CreateExpressionTree (EmitContext ec)
2655                 {
2656                         return ((Statement) statements [0]).CreateExpressionTree (ec);
2657                 }
2658
2659                 public void CreateIteratorHost (RootScopeInfo root)
2660                 {
2661                         Report.Debug (64, "CREATE ITERATOR HOST", this, root, Parent, root_scope);
2662
2663                         if (Parent != null || root_scope != null)
2664                                 throw new InternalErrorException ();
2665
2666                         scope_info = root_scope = root;
2667                 }
2668
2669                 public RootScopeInfo RootScope {
2670                         get {
2671                                 if (root_scope != null)
2672                                         return root_scope;
2673                                 else if (Container != null)
2674                                         return Container.RootScope;
2675                                 else
2676                                         return null;
2677                         }
2678                 }
2679
2680                 public FlowBranchingToplevel TopLevelBranching {
2681                         get { return top_level_branching; }
2682                 }
2683
2684                 //
2685                 // This is used if anonymous methods are used inside an iterator
2686                 // (see 2test-22.cs for an example).
2687                 //
2688                 // The AnonymousMethod is created while parsing - at a time when we don't
2689                 // know yet that we're inside an iterator, so it's `Container' is initially
2690                 // null.  Later on, when resolving the iterator, we need to move the
2691                 // anonymous method into that iterator.
2692                 //
2693                 public void ReParent (ToplevelBlock new_parent)
2694                 {
2695                         if ((flags & Flags.VariablesInitialized) != 0)
2696                                 throw new InternalErrorException ("block has already been resolved");
2697
2698                         Parent = new_parent;
2699                 }
2700
2701                 //
2702                 // Returns a `ParameterReference' for the given name, or null if there
2703                 // is no such parameter
2704                 //
2705                 public ParameterReference GetParameterReference (string name, Location loc)
2706                 {
2707                         ToplevelParameterInfo p = GetParameterInfo (name);
2708                         return p == null ? null : new ParameterReference (this, p, loc);
2709                 }
2710
2711                 public ToplevelParameterInfo GetParameterInfo (string name)
2712                 {
2713                         int idx;
2714                         for (ToplevelBlock t = this; t != null; t = t.Container) {
2715                                 Parameter par = t.Parameters.GetParameterByName (name, out idx);
2716                                 if (par != null)
2717                                         return t.parameter_info [idx];
2718                         }
2719                         return null;
2720                 }
2721
2722                 LocalInfo this_variable = null;
2723
2724                 // <summary>
2725                 //   Returns the "this" instance variable of this block.
2726                 //   See AddThisVariable() for more information.
2727                 // </summary>
2728                 public LocalInfo ThisVariable {
2729                         get { return this_variable; }
2730                 }
2731
2732
2733                 // <summary>
2734                 //   This is used by non-static `struct' constructors which do not have an
2735                 //   initializer - in this case, the constructor must initialize all of the
2736                 //   struct's fields.  To do this, we add a "this" variable and use the flow
2737                 //   analysis code to ensure that it's been fully initialized before control
2738                 //   leaves the constructor.
2739                 // </summary>
2740                 public LocalInfo AddThisVariable (DeclSpace ds, Location l)
2741                 {
2742                         if (this_variable == null) {
2743                                 this_variable = new LocalInfo (ds, this, l);
2744                                 this_variable.Used = true;
2745                                 this_variable.IsThis = true;
2746
2747                                 Variables.Add ("this", this_variable);
2748                         }
2749
2750                         return this_variable;
2751                 }
2752
2753                 public bool IsThisAssigned (EmitContext ec)
2754                 {
2755                         return this_variable == null || this_variable.IsThisAssigned (ec);
2756                 }
2757
2758                 public bool ResolveMeta (EmitContext ec, Parameters ip)
2759                 {
2760                         int errors = Report.Errors;
2761                         int orig_count = parameters.Count;
2762
2763                         if (top_level_branching != null)
2764                                 return true;
2765
2766                         if (ip != null)
2767                                 parameters = ip;
2768
2769                         // Assert: orig_count != parameter.Count => orig_count == 0
2770                         if (orig_count != 0 && orig_count != parameters.Count)
2771                                 throw new InternalErrorException ("parameter information mismatch");
2772
2773                         int offset = Parent == null ? 0 : Parent.AssignableSlots;
2774
2775                         for (int i = 0; i < orig_count; ++i) {
2776                                 Parameter.Modifier mod = parameters.ParameterModifier (i);
2777
2778                                 if ((mod & Parameter.Modifier.OUT) != Parameter.Modifier.OUT)
2779                                         continue;
2780
2781                                 VariableInfo vi = new VariableInfo (ip, i, offset);
2782                                 parameter_info [i].VariableInfo = vi;
2783                                 offset += vi.Length;
2784                         }
2785
2786                         ResolveMeta (ec, offset);
2787
2788                         top_level_branching = ec.StartFlowBranching (this);
2789
2790                         return Report.Errors == errors;
2791                 }
2792
2793                 // <summary>
2794                 //   Check whether all `out' parameters have been assigned.
2795                 // </summary>
2796                 public void CheckOutParameters (FlowBranching.UsageVector vector, Location loc)
2797                 {
2798                         if (vector.IsUnreachable)
2799                                 return;
2800
2801                         int n = parameter_info == null ? 0 : parameter_info.Length;
2802
2803                         for (int i = 0; i < n; i++) {
2804                                 VariableInfo var = parameter_info [i].VariableInfo;
2805
2806                                 if (var == null)
2807                                         continue;
2808
2809                                 if (vector.IsAssigned (var, false))
2810                                         continue;
2811
2812                                 Report.Error (177, loc, "The out parameter `{0}' must be assigned to before control leaves the current method",
2813                                         var.Name);
2814                         }
2815                 }
2816
2817                 public override void EmitMeta (EmitContext ec)
2818                 {
2819                         // Avoid declaring an IL variable for this_variable since it is not accessed
2820                         // from the generated IL
2821                         if (this_variable != null)
2822                                 Variables.Remove ("this");
2823                         base.EmitMeta (ec);
2824                         parameters.ResolveVariable (this);
2825                 }
2826
2827                 public void MakeIterator (Iterator iterator)
2828                 {
2829                         flags |= Flags.IsIterator;
2830
2831                         Block block = new ExplicitBlock (this, StartLocation, EndLocation);
2832                         foreach (Statement stmt in statements)
2833                                 block.AddStatement (stmt);
2834                         statements.Clear ();
2835                         statements.Add (new MoveNextStatement (iterator, block));
2836                 }
2837
2838                 protected class MoveNextStatement : Statement {
2839                         Iterator iterator;
2840                         Block block;
2841
2842                         public MoveNextStatement (Iterator iterator, Block block)
2843                         {
2844                                 this.iterator = iterator;
2845                                 this.block = block;
2846                                 this.loc = iterator.Location;
2847                         }
2848
2849                         public override bool Resolve (EmitContext ec)
2850                         {
2851                                 return block.Resolve (ec);
2852                         }
2853
2854                         protected override void DoEmit (EmitContext ec)
2855                         {
2856                                 iterator.EmitMoveNext (ec, block);
2857                         }
2858                 }
2859
2860                 public override string ToString ()
2861                 {
2862                         return String.Format ("{0} ({1}:{2}{3}:{4})", GetType (), ID, StartLocation,
2863                                               root_scope, anonymous_container != null ?
2864                                               anonymous_container.Scope : null);
2865                 }
2866         }
2867
2868         public class SwitchLabel {
2869                 Expression label;
2870                 object converted;
2871                 Location loc;
2872
2873                 Label il_label;
2874                 bool  il_label_set;
2875                 Label il_label_code;
2876                 bool  il_label_code_set;
2877
2878                 public static readonly object NullStringCase = new object ();
2879
2880                 //
2881                 // if expr == null, then it is the default case.
2882                 //
2883                 public SwitchLabel (Expression expr, Location l)
2884                 {
2885                         label = expr;
2886                         loc = l;
2887                 }
2888
2889                 public Expression Label {
2890                         get {
2891                                 return label;
2892                         }
2893                 }
2894
2895                 public object Converted {
2896                         get {
2897                                 return converted;
2898                         }
2899                 }
2900
2901                 public Label GetILLabel (EmitContext ec)
2902                 {
2903                         if (!il_label_set){
2904                                 il_label = ec.ig.DefineLabel ();
2905                                 il_label_set = true;
2906                         }
2907                         return il_label;
2908                 }
2909
2910                 public Label GetILLabelCode (EmitContext ec)
2911                 {
2912                         if (!il_label_code_set){
2913                                 il_label_code = ec.ig.DefineLabel ();
2914                                 il_label_code_set = true;
2915                         }
2916                         return il_label_code;
2917                 }
2918
2919                 //
2920                 // Resolves the expression, reduces it to a literal if possible
2921                 // and then converts it to the requested type.
2922                 //
2923                 public bool ResolveAndReduce (EmitContext ec, Type required_type, bool allow_nullable)
2924                 {
2925                         Expression e = label.Resolve (ec);
2926
2927                         if (e == null)
2928                                 return false;
2929
2930                         Constant c = e as Constant;
2931                         if (c == null){
2932                                 Report.Error (150, loc, "A constant value is expected");
2933                                 return false;
2934                         }
2935
2936                         if (required_type == TypeManager.string_type && c.GetValue () == null) {
2937                                 converted = NullStringCase;
2938                                 return true;
2939                         }
2940
2941                         if (allow_nullable && c.GetValue () == null) {
2942                                 converted = NullStringCase;
2943                                 return true;
2944                         }
2945
2946                         c = c.ImplicitConversionRequired (required_type, loc);
2947                         if (c == null)
2948                                 return false;
2949
2950                         converted = c.GetValue ();
2951                         return true;
2952                 }
2953
2954                 public void Error_AlreadyOccurs (Type switch_type, SwitchLabel collision_with)
2955                 {
2956                         string label;
2957                         if (converted == null)
2958                                 label = "default";
2959                         else if (converted == NullStringCase)
2960                                 label = "null";
2961                         else if (TypeManager.IsEnumType (switch_type))
2962                                 label = TypeManager.CSharpEnumValue (switch_type, converted);
2963                         else
2964                                 label = converted.ToString ();
2965
2966                         Report.SymbolRelatedToPreviousError (collision_with.loc, null);
2967                         Report.Error (152, loc, "The label `case {0}:' already occurs in this switch statement", label);
2968                 }
2969
2970                 public SwitchLabel Clone (CloneContext clonectx)
2971                 {
2972                         return new SwitchLabel (label.Clone (clonectx), loc);
2973                 }
2974         }
2975
2976         public class SwitchSection {
2977                 // An array of SwitchLabels.
2978                 public readonly ArrayList Labels;
2979                 public readonly Block Block;
2980
2981                 public SwitchSection (ArrayList labels, Block block)
2982                 {
2983                         Labels = labels;
2984                         Block = block;
2985                 }
2986
2987                 public SwitchSection Clone (CloneContext clonectx)
2988                 {
2989                         ArrayList cloned_labels = new ArrayList ();
2990
2991                         foreach (SwitchLabel sl in cloned_labels)
2992                                 cloned_labels.Add (sl.Clone (clonectx));
2993
2994                         return new SwitchSection (cloned_labels, clonectx.LookupBlock (Block));
2995                 }
2996         }
2997
2998         public class Switch : Statement {
2999                 public ArrayList Sections;
3000                 public Expression Expr;
3001
3002                 /// <summary>
3003                 ///   Maps constants whose type type SwitchType to their  SwitchLabels.
3004                 /// </summary>
3005                 public IDictionary Elements;
3006
3007                 /// <summary>
3008                 ///   The governing switch type
3009                 /// </summary>
3010                 public Type SwitchType;
3011
3012                 //
3013                 // Computed
3014                 //
3015                 Label default_target;
3016                 Label null_target;
3017                 Expression new_expr;
3018                 bool is_constant;
3019                 SwitchSection constant_section;
3020                 SwitchSection default_section;
3021
3022 #if GMCS_SOURCE
3023                 //
3024                 // Nullable Types support for GMCS.
3025                 //
3026                 Nullable.Unwrap unwrap;
3027
3028                 protected bool HaveUnwrap {
3029                         get { return unwrap != null; }
3030                 }
3031 #else
3032                 protected bool HaveUnwrap {
3033                         get { return false; }
3034                 }
3035 #endif
3036
3037                 //
3038                 // The types allowed to be implicitly cast from
3039                 // on the governing type
3040                 //
3041                 static Type [] allowed_types;
3042
3043                 public Switch (Expression e, ArrayList sects, Location l)
3044                 {
3045                         Expr = e;
3046                         Sections = sects;
3047                         loc = l;
3048                 }
3049
3050                 public bool GotDefault {
3051                         get {
3052                                 return default_section != null;
3053                         }
3054                 }
3055
3056                 public Label DefaultTarget {
3057                         get {
3058                                 return default_target;
3059                         }
3060                 }
3061
3062                 //
3063                 // Determines the governing type for a switch.  The returned
3064                 // expression might be the expression from the switch, or an
3065                 // expression that includes any potential conversions to the
3066                 // integral types or to string.
3067                 //
3068                 Expression SwitchGoverningType (EmitContext ec, Expression expr)
3069                 {
3070                         Type t = expr.Type;
3071
3072                         if (t == TypeManager.byte_type ||
3073                             t == TypeManager.sbyte_type ||
3074                             t == TypeManager.ushort_type ||
3075                             t == TypeManager.short_type ||
3076                             t == TypeManager.uint32_type ||
3077                             t == TypeManager.int32_type ||
3078                             t == TypeManager.uint64_type ||
3079                             t == TypeManager.int64_type ||
3080                             t == TypeManager.char_type ||
3081                             t == TypeManager.string_type ||
3082                             t == TypeManager.bool_type ||
3083                             TypeManager.IsEnumType (t))
3084                                 return expr;
3085
3086                         if (allowed_types == null){
3087                                 allowed_types = new Type [] {
3088                                         TypeManager.sbyte_type,
3089                                         TypeManager.byte_type,
3090                                         TypeManager.short_type,
3091                                         TypeManager.ushort_type,
3092                                         TypeManager.int32_type,
3093                                         TypeManager.uint32_type,
3094                                         TypeManager.int64_type,
3095                                         TypeManager.uint64_type,
3096                                         TypeManager.char_type,
3097                                         TypeManager.string_type,
3098                                         TypeManager.bool_type
3099                                 };
3100                         }
3101
3102                         //
3103                         // Try to find a *user* defined implicit conversion.
3104                         //
3105                         // If there is no implicit conversion, or if there are multiple
3106                         // conversions, we have to report an error
3107                         //
3108                         Expression converted = null;
3109                         foreach (Type tt in allowed_types){
3110                                 Expression e;
3111
3112                                 e = Convert.ImplicitUserConversion (ec, expr, tt, loc);
3113                                 if (e == null)
3114                                         continue;
3115
3116                                 //
3117                                 // Ignore over-worked ImplicitUserConversions that do
3118                                 // an implicit conversion in addition to the user conversion.
3119                                 //
3120                                 if (!(e is UserCast))
3121                                         continue;
3122
3123                                 if (converted != null){
3124                                         Report.ExtraInformation (
3125                                                 loc,
3126                                                 String.Format ("reason: more than one conversion to an integral type exist for type {0}",
3127                                                                TypeManager.CSharpName (expr.Type)));
3128                                         return null;
3129                                 }
3130
3131                                 converted = e;
3132                         }
3133                         return converted;
3134                 }
3135
3136                 //
3137                 // Performs the basic sanity checks on the switch statement
3138                 // (looks for duplicate keys and non-constant expressions).
3139                 //
3140                 // It also returns a hashtable with the keys that we will later
3141                 // use to compute the switch tables
3142                 //
3143                 bool CheckSwitch (EmitContext ec)
3144                 {
3145                         bool error = false;
3146                         Elements = Sections.Count > 10 ?
3147                                 (IDictionary)new Hashtable () :
3148                                 (IDictionary)new ListDictionary ();
3149
3150                         foreach (SwitchSection ss in Sections){
3151                                 foreach (SwitchLabel sl in ss.Labels){
3152                                         if (sl.Label == null){
3153                                                 if (default_section != null){
3154                                                         sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)default_section.Labels [0]);
3155                                                         error = true;
3156                                                 }
3157                                                 default_section = ss;
3158                                                 continue;
3159                                         }
3160
3161                                         if (!sl.ResolveAndReduce (ec, SwitchType, HaveUnwrap)) {
3162                                                 error = true;
3163                                                 continue;
3164                                         }
3165
3166                                         object key = sl.Converted;
3167                                         try {
3168                                                 Elements.Add (key, sl);
3169                                         } catch (ArgumentException) {
3170                                                 sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)Elements [key]);
3171                                                 error = true;
3172                                         }
3173                                 }
3174                         }
3175                         return !error;
3176                 }
3177
3178                 void EmitObjectInteger (ILGenerator ig, object k)
3179                 {
3180                         if (k is int)
3181                                 IntConstant.EmitInt (ig, (int) k);
3182                         else if (k is Constant) {
3183                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
3184                         }
3185                         else if (k is uint)
3186                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
3187                         else if (k is long)
3188                         {
3189                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
3190                                 {
3191                                         IntConstant.EmitInt (ig, (int) (long) k);
3192                                         ig.Emit (OpCodes.Conv_I8);
3193                                 }
3194                                 else
3195                                         LongConstant.EmitLong (ig, (long) k);
3196                         }
3197                         else if (k is ulong)
3198                         {
3199                                 ulong ul = (ulong) k;
3200                                 if (ul < (1L<<32))
3201                                 {
3202                                         IntConstant.EmitInt (ig, unchecked ((int) ul));
3203                                         ig.Emit (OpCodes.Conv_U8);
3204                                 }
3205                                 else
3206                                 {
3207                                         LongConstant.EmitLong (ig, unchecked ((long) ul));
3208                                 }
3209                         }
3210                         else if (k is char)
3211                                 IntConstant.EmitInt (ig, (int) ((char) k));
3212                         else if (k is sbyte)
3213                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
3214                         else if (k is byte)
3215                                 IntConstant.EmitInt (ig, (int) ((byte) k));
3216                         else if (k is short)
3217                                 IntConstant.EmitInt (ig, (int) ((short) k));
3218                         else if (k is ushort)
3219                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
3220                         else if (k is bool)
3221                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
3222                         else
3223                                 throw new Exception ("Unhandled case");
3224                 }
3225
3226                 // structure used to hold blocks of keys while calculating table switch
3227                 class KeyBlock : IComparable
3228                 {
3229                         public KeyBlock (long _first)
3230                         {
3231                                 first = last = _first;
3232                         }
3233                         public long first;
3234                         public long last;
3235                         public ArrayList element_keys = null;
3236                         // how many items are in the bucket
3237                         public int Size = 1;
3238                         public int Length
3239                         {
3240                                 get { return (int) (last - first + 1); }
3241                         }
3242                         public static long TotalLength (KeyBlock kb_first, KeyBlock kb_last)
3243                         {
3244                                 return kb_last.last - kb_first.first + 1;
3245                         }
3246                         public int CompareTo (object obj)
3247                         {
3248                                 KeyBlock kb = (KeyBlock) obj;
3249                                 int nLength = Length;
3250                                 int nLengthOther = kb.Length;
3251                                 if (nLengthOther == nLength)
3252                                         return (int) (kb.first - first);
3253                                 return nLength - nLengthOther;
3254                         }
3255                 }
3256
3257                 /// <summary>
3258                 /// This method emits code for a lookup-based switch statement (non-string)
3259                 /// Basically it groups the cases into blocks that are at least half full,
3260                 /// and then spits out individual lookup opcodes for each block.
3261                 /// It emits the longest blocks first, and short blocks are just
3262                 /// handled with direct compares.
3263                 /// </summary>
3264                 /// <param name="ec"></param>
3265                 /// <param name="val"></param>
3266                 /// <returns></returns>
3267                 void TableSwitchEmit (EmitContext ec, LocalBuilder val)
3268                 {
3269                         int element_count = Elements.Count;
3270                         object [] element_keys = new object [element_count];
3271                         Elements.Keys.CopyTo (element_keys, 0);
3272                         Array.Sort (element_keys);
3273
3274                         // initialize the block list with one element per key
3275                         ArrayList key_blocks = new ArrayList ();
3276                         foreach (object key in element_keys)
3277                                 key_blocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));
3278
3279                         KeyBlock current_kb;
3280                         // iteratively merge the blocks while they are at least half full
3281                         // there's probably a really cool way to do this with a tree...
3282                         while (key_blocks.Count > 1)
3283                         {
3284                                 ArrayList key_blocks_new = new ArrayList ();
3285                                 current_kb = (KeyBlock) key_blocks [0];
3286                                 for (int ikb = 1; ikb < key_blocks.Count; ikb++)
3287                                 {
3288                                         KeyBlock kb = (KeyBlock) key_blocks [ikb];
3289                                         if ((current_kb.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (current_kb, kb))
3290                                         {
3291                                                 // merge blocks
3292                                                 current_kb.last = kb.last;
3293                                                 current_kb.Size += kb.Size;
3294                                         }
3295                                         else
3296                                         {
3297                                                 // start a new block
3298                                                 key_blocks_new.Add (current_kb);
3299                                                 current_kb = kb;
3300                                         }
3301                                 }
3302                                 key_blocks_new.Add (current_kb);
3303                                 if (key_blocks.Count == key_blocks_new.Count)
3304                                         break;
3305                                 key_blocks = key_blocks_new;
3306                         }
3307
3308                         // initialize the key lists
3309                         foreach (KeyBlock kb in key_blocks)
3310                                 kb.element_keys = new ArrayList ();
3311
3312                         // fill the key lists
3313                         int iBlockCurr = 0;
3314                         if (key_blocks.Count > 0) {
3315                                 current_kb = (KeyBlock) key_blocks [0];
3316                                 foreach (object key in element_keys)
3317                                 {
3318                                         bool next_block = (key is UInt64) ? (ulong) key > (ulong) current_kb.last :
3319                                                 System.Convert.ToInt64 (key) > current_kb.last;
3320                                         if (next_block)
3321                                                 current_kb = (KeyBlock) key_blocks [++iBlockCurr];
3322                                         current_kb.element_keys.Add (key);
3323                                 }
3324                         }
3325
3326                         // sort the blocks so we can tackle the largest ones first
3327                         key_blocks.Sort ();
3328
3329                         // okay now we can start...
3330                         ILGenerator ig = ec.ig;
3331                         Label lbl_end = ig.DefineLabel ();      // at the end ;-)
3332                         Label lbl_default = ig.DefineLabel ();
3333
3334                         Type type_keys = null;
3335                         if (element_keys.Length > 0)
3336                                 type_keys = element_keys [0].GetType ();        // used for conversions
3337
3338                         Type compare_type;
3339
3340                         if (TypeManager.IsEnumType (SwitchType))
3341                                 compare_type = TypeManager.GetEnumUnderlyingType (SwitchType);
3342                         else
3343                                 compare_type = SwitchType;
3344
3345                         for (int iBlock = key_blocks.Count - 1; iBlock >= 0; --iBlock)
3346                         {
3347                                 KeyBlock kb = ((KeyBlock) key_blocks [iBlock]);
3348                                 lbl_default = (iBlock == 0) ? DefaultTarget : ig.DefineLabel ();
3349                                 if (kb.Length <= 2)
3350                                 {
3351                                         foreach (object key in kb.element_keys)
3352                                         {
3353                                                 ig.Emit (OpCodes.Ldloc, val);
3354                                                 EmitObjectInteger (ig, key);
3355                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
3356                                                 ig.Emit (OpCodes.Beq, sl.GetILLabel (ec));
3357                                         }
3358                                 }
3359                                 else
3360                                 {
3361                                         // TODO: if all the keys in the block are the same and there are
3362                                         //       no gaps/defaults then just use a range-check.
3363                                         if (compare_type == TypeManager.int64_type ||
3364                                                 compare_type == TypeManager.uint64_type)
3365                                         {
3366                                                 // TODO: optimize constant/I4 cases
3367
3368                                                 // check block range (could be > 2^31)
3369                                                 ig.Emit (OpCodes.Ldloc, val);
3370                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3371                                                 ig.Emit (OpCodes.Blt, lbl_default);
3372                                                 ig.Emit (OpCodes.Ldloc, val);
3373                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.last, type_keys));
3374                                                 ig.Emit (OpCodes.Bgt, lbl_default);
3375
3376                                                 // normalize range
3377                                                 ig.Emit (OpCodes.Ldloc, val);
3378                                                 if (kb.first != 0)
3379                                                 {
3380                                                         EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3381                                                         ig.Emit (OpCodes.Sub);
3382                                                 }
3383                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
3384                                         }
3385                                         else
3386                                         {
3387                                                 // normalize range
3388                                                 ig.Emit (OpCodes.Ldloc, val);
3389                                                 int first = (int) kb.first;
3390                                                 if (first > 0)
3391                                                 {
3392                                                         IntConstant.EmitInt (ig, first);
3393                                                         ig.Emit (OpCodes.Sub);
3394                                                 }
3395                                                 else if (first < 0)
3396                                                 {
3397                                                         IntConstant.EmitInt (ig, -first);
3398                                                         ig.Emit (OpCodes.Add);
3399                                                 }
3400                                         }
3401
3402                                         // first, build the list of labels for the switch
3403                                         int iKey = 0;
3404                                         int cJumps = kb.Length;
3405                                         Label [] switch_labels = new Label [cJumps];
3406                                         for (int iJump = 0; iJump < cJumps; iJump++)
3407                                         {
3408                                                 object key = kb.element_keys [iKey];
3409                                                 if (System.Convert.ToInt64 (key) == kb.first + iJump)
3410                                                 {
3411                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
3412                                                         switch_labels [iJump] = sl.GetILLabel (ec);
3413                                                         iKey++;
3414                                                 }
3415                                                 else
3416                                                         switch_labels [iJump] = lbl_default;
3417                                         }
3418                                         // emit the switch opcode
3419                                         ig.Emit (OpCodes.Switch, switch_labels);
3420                                 }
3421
3422                                 // mark the default for this block
3423                                 if (iBlock != 0)
3424                                         ig.MarkLabel (lbl_default);
3425                         }
3426
3427                         // TODO: find the default case and emit it here,
3428                         //       to prevent having to do the following jump.
3429                         //       make sure to mark other labels in the default section
3430
3431                         // the last default just goes to the end
3432                         ig.Emit (OpCodes.Br, lbl_default);
3433
3434                         // now emit the code for the sections
3435                         bool found_default = false;
3436                         bool found_null = false;
3437                         foreach (SwitchSection ss in Sections)
3438                         {
3439                                 foreach (SwitchLabel sl in ss.Labels)
3440                                         if (sl.Converted == SwitchLabel.NullStringCase)
3441                                                 found_null = true;
3442                         }
3443
3444                         foreach (SwitchSection ss in Sections)
3445                         {
3446                                 foreach (SwitchLabel sl in ss.Labels)
3447                                 {
3448                                         ig.MarkLabel (sl.GetILLabel (ec));
3449                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3450                                         if (sl.Converted == SwitchLabel.NullStringCase)
3451                                                 ig.MarkLabel (null_target);
3452                                         else if (sl.Label == null) {
3453                                                 ig.MarkLabel (lbl_default);
3454                                                 found_default = true;
3455                                                 if (!found_null)
3456                                                         ig.MarkLabel (null_target);
3457                                         }
3458                                 }
3459                                 ss.Block.Emit (ec);
3460                         }
3461
3462                         if (!found_default) {
3463                                 ig.MarkLabel (lbl_default);
3464                                 if (HaveUnwrap && !found_null) {
3465                                         ig.MarkLabel (null_target);
3466                                 }
3467                         }
3468
3469                         ig.MarkLabel (lbl_end);
3470                 }
3471                 //
3472                 // This simple emit switch works, but does not take advantage of the
3473                 // `switch' opcode.
3474                 // TODO: remove non-string logic from here
3475                 // TODO: binary search strings?
3476                 //
3477                 void SimpleSwitchEmit (EmitContext ec, LocalBuilder val)
3478                 {
3479                         ILGenerator ig = ec.ig;
3480                         Label end_of_switch = ig.DefineLabel ();
3481                         Label next_test = ig.DefineLabel ();
3482                         bool first_test = true;
3483                         bool pending_goto_end = false;
3484                         bool null_marked = false;
3485                         bool null_found;
3486                         int section_count = Sections.Count;
3487
3488                         // TODO: implement switch optimization for string by using Hashtable
3489                         //if (SwitchType == TypeManager.string_type && section_count > 7)
3490                         //      Console.WriteLine ("Switch optimization possible " + loc);
3491
3492                         ig.Emit (OpCodes.Ldloc, val);
3493
3494                         if (Elements.Contains (SwitchLabel.NullStringCase)){
3495                                 ig.Emit (OpCodes.Brfalse, null_target);
3496                         } else
3497                                 ig.Emit (OpCodes.Brfalse, default_target);
3498
3499                         ig.Emit (OpCodes.Ldloc, val);
3500                         ig.Emit (OpCodes.Call, TypeManager.string_isinterned_string);
3501                         ig.Emit (OpCodes.Stloc, val);
3502
3503                         for (int section = 0; section < section_count; section++){
3504                                 SwitchSection ss = (SwitchSection) Sections [section];
3505
3506                                 if (ss == default_section)
3507                                         continue;
3508
3509                                 Label sec_begin = ig.DefineLabel ();
3510
3511                                 ig.Emit (OpCodes.Nop);
3512
3513                                 if (pending_goto_end)
3514                                         ig.Emit (OpCodes.Br, end_of_switch);
3515
3516                                 int label_count = ss.Labels.Count;
3517                                 null_found = false;
3518                                 for (int label = 0; label < label_count; label++){
3519                                         SwitchLabel sl = (SwitchLabel) ss.Labels [label];
3520                                         ig.MarkLabel (sl.GetILLabel (ec));
3521
3522                                         if (!first_test){
3523                                                 ig.MarkLabel (next_test);
3524                                                 next_test = ig.DefineLabel ();
3525                                         }
3526                                         //
3527                                         // If we are the default target
3528                                         //
3529                                         if (sl.Label != null){
3530                                                 object lit = sl.Converted;
3531
3532                                                 if (lit == SwitchLabel.NullStringCase){
3533                                                         null_found = true;
3534                                                         if (label + 1 == label_count)
3535                                                                 ig.Emit (OpCodes.Br, next_test);
3536                                                         continue;
3537                                                 }
3538
3539                                                 ig.Emit (OpCodes.Ldloc, val);
3540                                                 ig.Emit (OpCodes.Ldstr, (string)lit);
3541                                                 if (label_count == 1)
3542                                                         ig.Emit (OpCodes.Bne_Un, next_test);
3543                                                 else {
3544                                                         if (label+1 == label_count)
3545                                                                 ig.Emit (OpCodes.Bne_Un, next_test);
3546                                                         else
3547                                                                 ig.Emit (OpCodes.Beq, sec_begin);
3548                                                 }
3549                                         }
3550                                 }
3551                                 if (null_found) {
3552                                         ig.MarkLabel (null_target);
3553                                         null_marked = true;
3554                                 }
3555                                 ig.MarkLabel (sec_begin);
3556                                 foreach (SwitchLabel sl in ss.Labels)
3557                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3558
3559                                 ss.Block.Emit (ec);
3560                                 pending_goto_end = !ss.Block.HasRet;
3561                                 first_test = false;
3562                         }
3563                         ig.MarkLabel (next_test);
3564                         ig.MarkLabel (default_target);
3565                         if (!null_marked)
3566                                 ig.MarkLabel (null_target);
3567                         if (default_section != null)
3568                                 default_section.Block.Emit (ec);
3569                         ig.MarkLabel (end_of_switch);
3570                 }
3571
3572                 SwitchSection FindSection (SwitchLabel label)
3573                 {
3574                         foreach (SwitchSection ss in Sections){
3575                                 foreach (SwitchLabel sl in ss.Labels){
3576                                         if (label == sl)
3577                                                 return ss;
3578                                 }
3579                         }
3580
3581                         return null;
3582                 }
3583
3584                 public override bool Resolve (EmitContext ec)
3585                 {
3586                         Expr = Expr.Resolve (ec);
3587                         if (Expr == null)
3588                                 return false;
3589
3590                         new_expr = SwitchGoverningType (ec, Expr);
3591
3592 #if GMCS_SOURCE
3593                         if ((new_expr == null) && TypeManager.IsNullableType (Expr.Type)) {
3594                                 unwrap = Nullable.Unwrap.Create (Expr, ec);
3595                                 if (unwrap == null)
3596                                         return false;
3597
3598                                 new_expr = SwitchGoverningType (ec, unwrap);
3599                         }
3600 #endif
3601
3602                         if (new_expr == null){
3603                                 Report.Error (151, loc, "A value of an integral type or string expected for switch");
3604                                 return false;
3605                         }
3606
3607                         // Validate switch.
3608                         SwitchType = new_expr.Type;
3609
3610                         if (RootContext.Version == LanguageVersion.ISO_1 && SwitchType == TypeManager.bool_type) {
3611                                 Report.FeatureIsNotAvailable (loc, "switch expression of boolean type");
3612                                 return false;
3613                         }
3614
3615                         if (!CheckSwitch (ec))
3616                                 return false;
3617
3618                         if (HaveUnwrap)
3619                                 Elements.Remove (SwitchLabel.NullStringCase);
3620
3621                         Switch old_switch = ec.Switch;
3622                         ec.Switch = this;
3623                         ec.Switch.SwitchType = SwitchType;
3624
3625                         Report.Debug (1, "START OF SWITCH BLOCK", loc, ec.CurrentBranching);
3626                         ec.StartFlowBranching (FlowBranching.BranchingType.Switch, loc);
3627
3628                         is_constant = new_expr is Constant;
3629                         if (is_constant) {
3630                                 object key = ((Constant) new_expr).GetValue ();
3631                                 SwitchLabel label = (SwitchLabel) Elements [key];
3632
3633                                 constant_section = FindSection (label);
3634                                 if (constant_section == null)
3635                                         constant_section = default_section;
3636                         }
3637
3638                         bool first = true;
3639                         bool ok = true;
3640                         foreach (SwitchSection ss in Sections){
3641                                 if (!first)
3642                                         ec.CurrentBranching.CreateSibling (
3643                                                 null, FlowBranching.SiblingType.SwitchSection);
3644                                 else
3645                                         first = false;
3646
3647                                 if (is_constant && (ss != constant_section)) {
3648                                         // If we're a constant switch, we're only emitting
3649                                         // one single section - mark all the others as
3650                                         // unreachable.
3651                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
3652                                         if (!ss.Block.ResolveUnreachable (ec, true)) {
3653                                                 ok = false;
3654                                         }
3655                                 } else {
3656                                         if (!ss.Block.Resolve (ec))
3657                                                 ok = false;
3658                                 }
3659                         }
3660
3661                         if (default_section == null)
3662                                 ec.CurrentBranching.CreateSibling (
3663                                         null, FlowBranching.SiblingType.SwitchSection);
3664
3665                         ec.EndFlowBranching ();
3666                         ec.Switch = old_switch;
3667
3668                         Report.Debug (1, "END OF SWITCH BLOCK", loc, ec.CurrentBranching);
3669
3670                         if (TypeManager.string_isinterned_string == null) {
3671                                 TypeManager.string_isinterned_string = TypeManager.GetPredefinedMethod (TypeManager.string_type,
3672                                         "IsInterned", loc, TypeManager.string_type);
3673                         }
3674
3675                         return ok;
3676                 }
3677
3678                 protected override void DoEmit (EmitContext ec)
3679                 {
3680                         ILGenerator ig = ec.ig;
3681
3682                         default_target = ig.DefineLabel ();
3683                         null_target = ig.DefineLabel ();
3684
3685                         // Store variable for comparission purposes
3686                         LocalBuilder value;
3687                         if (HaveUnwrap) {
3688                                 value = ig.DeclareLocal (SwitchType);
3689 #if GMCS_SOURCE
3690                                 unwrap.EmitCheck (ec);
3691                                 ig.Emit (OpCodes.Brfalse, null_target);
3692                                 new_expr.Emit (ec);
3693                                 ig.Emit (OpCodes.Stloc, value);
3694 #endif
3695                         } else if (!is_constant) {
3696                                 value = ig.DeclareLocal (SwitchType);
3697                                 new_expr.Emit (ec);
3698                                 ig.Emit (OpCodes.Stloc, value);
3699                         } else
3700                                 value = null;
3701
3702                         //
3703                         // Setup the codegen context
3704                         //
3705                         Label old_end = ec.LoopEnd;
3706                         Switch old_switch = ec.Switch;
3707
3708                         ec.LoopEnd = ig.DefineLabel ();
3709                         ec.Switch = this;
3710
3711                         // Emit Code.
3712                         if (is_constant) {
3713                                 if (constant_section != null)
3714                                         constant_section.Block.Emit (ec);
3715                         } else if (SwitchType == TypeManager.string_type)
3716                                 SimpleSwitchEmit (ec, value);
3717                         else
3718                                 TableSwitchEmit (ec, value);
3719
3720                         // Restore context state.
3721                         ig.MarkLabel (ec.LoopEnd);
3722
3723                         //
3724                         // Restore the previous context
3725                         //
3726                         ec.LoopEnd = old_end;
3727                         ec.Switch = old_switch;
3728                 }
3729
3730                 protected override void CloneTo (CloneContext clonectx, Statement t)
3731                 {
3732                         Switch target = (Switch) t;
3733
3734                         target.Expr = Expr.Clone (clonectx);
3735                         target.Sections = new ArrayList ();
3736                         foreach (SwitchSection ss in Sections){
3737                                 target.Sections.Add (ss.Clone (clonectx));
3738                         }
3739                 }
3740         }
3741
3742         public abstract class ExceptionStatement : Statement
3743         {
3744                 public abstract void EmitFinally (EmitContext ec);
3745
3746                 protected bool emit_finally = true;
3747                 ArrayList parent_vectors;
3748
3749                 protected void DoEmitFinally (EmitContext ec)
3750                 {
3751                         if (emit_finally)
3752                                 ec.ig.BeginFinallyBlock ();
3753                         else if (ec.InIterator)
3754                                 ec.CurrentIterator.MarkFinally (ec, parent_vectors);
3755                         EmitFinally (ec);
3756                 }
3757
3758                 protected void ResolveFinally (FlowBranchingException branching)
3759                 {
3760                         emit_finally = branching.EmitFinally;
3761                         if (!emit_finally)
3762                                 branching.Parent.StealFinallyClauses (ref parent_vectors);
3763                 }
3764         }
3765
3766         public class Lock : ExceptionStatement {
3767                 Expression expr;
3768                 public Statement Statement;
3769                 TemporaryVariable temp;
3770
3771                 public Lock (Expression expr, Statement stmt, Location l)
3772                 {
3773                         this.expr = expr;
3774                         Statement = stmt;
3775                         loc = l;
3776                 }
3777
3778                 public override bool Resolve (EmitContext ec)
3779                 {
3780                         expr = expr.Resolve (ec);
3781                         if (expr == null)
3782                                 return false;
3783
3784                         if (expr.Type.IsValueType){
3785                                 Report.Error (185, loc,
3786                                               "`{0}' is not a reference type as required by the lock statement",
3787                                               TypeManager.CSharpName (expr.Type));
3788                                 return false;
3789                         }
3790
3791                         FlowBranchingException branching = ec.StartFlowBranching (this);
3792                         bool ok = Statement.Resolve (ec);
3793
3794                         ResolveFinally (branching);
3795
3796                         ec.EndFlowBranching ();
3797
3798                         // System.Reflection.Emit automatically emits a 'leave' to the end of the finally block.
3799                         // So, ensure there's some IL code after the finally block.
3800                         ec.NeedReturnLabel ();
3801
3802                         // Avoid creating libraries that reference the internal
3803                         // mcs NullType:
3804                         Type t = expr.Type;
3805                         if (t == TypeManager.null_type)
3806                                 t = TypeManager.object_type;
3807
3808                         temp = new TemporaryVariable (t, loc);
3809                         temp.Resolve (ec);
3810
3811                         if (TypeManager.void_monitor_enter_object == null || TypeManager.void_monitor_exit_object == null) {
3812                                 Type monitor_type = TypeManager.CoreLookupType ("System.Threading", "Monitor", Kind.Class, true);
3813                                 TypeManager.void_monitor_enter_object = TypeManager.GetPredefinedMethod (
3814                                         monitor_type, "Enter", loc, TypeManager.object_type);
3815                                 TypeManager.void_monitor_exit_object = TypeManager.GetPredefinedMethod (
3816                                         monitor_type, "Exit", loc, TypeManager.object_type);
3817                         }
3818
3819                         return ok;
3820                 }
3821
3822                 protected override void DoEmit (EmitContext ec)
3823                 {
3824                         ILGenerator ig = ec.ig;
3825
3826                         temp.Store (ec, expr);
3827                         temp.Emit (ec);
3828                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
3829
3830                         // try
3831                         if (emit_finally)
3832                                 ig.BeginExceptionBlock ();
3833                         Statement.Emit (ec);
3834
3835                         // finally
3836                         DoEmitFinally (ec);
3837                         if (emit_finally)
3838                                 ig.EndExceptionBlock ();
3839                 }
3840
3841                 public override void EmitFinally (EmitContext ec)
3842                 {
3843                         temp.Emit (ec);
3844                         ec.ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
3845                 }
3846
3847                 protected override void CloneTo (CloneContext clonectx, Statement t)
3848                 {
3849                         Lock target = (Lock) t;
3850
3851                         target.expr = expr.Clone (clonectx);
3852                         target.Statement = Statement.Clone (clonectx);
3853                 }
3854         }
3855
3856         public class Unchecked : Statement {
3857                 public Block Block;
3858
3859                 public Unchecked (Block b)
3860                 {
3861                         Block = b;
3862                         b.Unchecked = true;
3863                 }
3864
3865                 public override bool Resolve (EmitContext ec)
3866                 {
3867                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
3868                                 return Block.Resolve (ec);
3869                 }
3870
3871                 protected override void DoEmit (EmitContext ec)
3872                 {
3873                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
3874                                 Block.Emit (ec);
3875                 }
3876
3877                 protected override void CloneTo (CloneContext clonectx, Statement t)
3878                 {
3879                         Unchecked target = (Unchecked) t;
3880
3881                         target.Block = clonectx.LookupBlock (Block);
3882                 }
3883         }
3884
3885         public class Checked : Statement {
3886                 public Block Block;
3887
3888                 public Checked (Block b)
3889                 {
3890                         Block = b;
3891                         b.Unchecked = false;
3892                 }
3893
3894                 public override bool Resolve (EmitContext ec)
3895                 {
3896                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
3897                                 return Block.Resolve (ec);
3898                 }
3899
3900                 protected override void DoEmit (EmitContext ec)
3901                 {
3902                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
3903                                 Block.Emit (ec);
3904                 }
3905
3906                 protected override void CloneTo (CloneContext clonectx, Statement t)
3907                 {
3908                         Checked target = (Checked) t;
3909
3910                         target.Block = clonectx.LookupBlock (Block);
3911                 }
3912         }
3913
3914         public class Unsafe : Statement {
3915                 public Block Block;
3916
3917                 public Unsafe (Block b)
3918                 {
3919                         Block = b;
3920                         Block.Unsafe = true;
3921                 }
3922
3923                 public override bool Resolve (EmitContext ec)
3924                 {
3925                         using (ec.With (EmitContext.Flags.InUnsafe, true))
3926                                 return Block.Resolve (ec);
3927                 }
3928
3929                 protected override void DoEmit (EmitContext ec)
3930                 {
3931                         using (ec.With (EmitContext.Flags.InUnsafe, true))
3932                                 Block.Emit (ec);
3933                 }
3934                 protected override void CloneTo (CloneContext clonectx, Statement t)
3935                 {
3936                         Unsafe target = (Unsafe) t;
3937
3938                         target.Block = clonectx.LookupBlock (Block);
3939                 }
3940         }
3941
3942         //
3943         // Fixed statement
3944         //
3945         public class Fixed : Statement {
3946                 Expression type;
3947                 ArrayList declarators;
3948                 Statement statement;
3949                 Type expr_type;
3950                 Emitter[] data;
3951                 bool has_ret;
3952
3953                 abstract class Emitter
3954                 {
3955                         protected LocalInfo vi;
3956                         protected Expression converted;
3957
3958                         protected Emitter (Expression expr, LocalInfo li)
3959                         {
3960                                 converted = expr;
3961                                 vi = li;
3962                         }
3963
3964                         public abstract void Emit (EmitContext ec);
3965                         public abstract void EmitExit (EmitContext ec);
3966                 }
3967
3968                 class ExpressionEmitter : Emitter {
3969                         public ExpressionEmitter (Expression converted, LocalInfo li) :
3970                                 base (converted, li)
3971                         {
3972                         }
3973
3974                         public override void Emit (EmitContext ec) {
3975                                 //
3976                                 // Store pointer in pinned location
3977                                 //
3978                                 converted.Emit (ec);
3979                                 vi.Variable.EmitAssign (ec);
3980                         }
3981
3982                         public override void EmitExit (EmitContext ec)
3983                         {
3984                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
3985                                 ec.ig.Emit (OpCodes.Conv_U);
3986                                 vi.Variable.EmitAssign (ec);
3987                         }
3988                 }
3989
3990                 class StringEmitter : Emitter {
3991                         LocalBuilder pinned_string;
3992                         Location loc;
3993
3994                         public StringEmitter (Expression expr, LocalInfo li, Location loc):
3995                                 base (expr, li)
3996                         {
3997                                 this.loc = loc;
3998                         }
3999
4000                         public override void Emit (EmitContext ec)
4001                         {
4002                                 ILGenerator ig = ec.ig;
4003                                 pinned_string = TypeManager.DeclareLocalPinned (ig, TypeManager.string_type);
4004
4005                                 converted.Emit (ec);
4006                                 ig.Emit (OpCodes.Stloc, pinned_string);
4007
4008                                 Expression sptr = new StringPtr (pinned_string, loc);
4009                                 converted = Convert.ImplicitConversionRequired (
4010                                         ec, sptr, vi.VariableType, loc);
4011
4012                                 if (converted == null)
4013                                         return;
4014
4015                                 converted.Emit (ec);
4016                                 vi.Variable.EmitAssign (ec);
4017                         }
4018
4019                         public override void EmitExit (EmitContext ec)
4020                         {
4021                                 ec.ig.Emit (OpCodes.Ldnull);
4022                                 ec.ig.Emit (OpCodes.Stloc, pinned_string);
4023                         }
4024                 }
4025
4026                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
4027                 {
4028                         this.type = type;
4029                         declarators = decls;
4030                         statement = stmt;
4031                         loc = l;
4032                 }
4033
4034                 public Statement Statement {
4035                         get { return statement; }
4036                 }
4037
4038                 public override bool Resolve (EmitContext ec)
4039                 {
4040                         if (!ec.InUnsafe){
4041                                 Expression.UnsafeError (loc);
4042                                 return false;
4043                         }
4044
4045                         TypeExpr texpr = type.ResolveAsContextualType (ec, false);
4046                         if (texpr == null) {
4047                                 if (type is VarExpr)
4048                                         Report.Error (821, type.Location, "A fixed statement cannot use an implicitly typed local variable");
4049
4050                                 return false;
4051                         }
4052
4053                         expr_type = texpr.Type;
4054
4055                         data = new Emitter [declarators.Count];
4056
4057                         if (!expr_type.IsPointer){
4058                                 Report.Error (209, loc, "The type of locals declared in a fixed statement must be a pointer type");
4059                                 return false;
4060                         }
4061
4062                         int i = 0;
4063                         foreach (Pair p in declarators){
4064                                 LocalInfo vi = (LocalInfo) p.First;
4065                                 Expression e = (Expression) p.Second;
4066
4067                                 vi.VariableInfo.SetAssigned (ec);
4068                                 vi.SetReadOnlyContext (LocalInfo.ReadOnlyContext.Fixed);
4069
4070                                 //
4071                                 // The rules for the possible declarators are pretty wise,
4072                                 // but the production on the grammar is more concise.
4073                                 //
4074                                 // So we have to enforce these rules here.
4075                                 //
4076                                 // We do not resolve before doing the case 1 test,
4077                                 // because the grammar is explicit in that the token &
4078                                 // is present, so we need to test for this particular case.
4079                                 //
4080
4081                                 if (e is Cast){
4082                                         Report.Error (254, loc, "The right hand side of a fixed statement assignment may not be a cast expression");
4083                                         return false;
4084                                 }
4085
4086                                 //
4087                                 // Case 1: & object.
4088                                 //
4089                                 if (e is Unary && ((Unary) e).Oper == Unary.Operator.AddressOf){
4090                                         Expression child = ((Unary) e).Expr;
4091
4092                                         if (child is ParameterReference || child is LocalVariableReference){
4093                                                 Report.Error (
4094                                                         213, loc,
4095                                                         "No need to use fixed statement for parameters or " +
4096                                                         "local variable declarations (address is already " +
4097                                                         "fixed)");
4098                                                 return false;
4099                                         }
4100
4101                                         ec.InFixedInitializer = true;
4102                                         e = e.Resolve (ec);
4103                                         ec.InFixedInitializer = false;
4104                                         if (e == null)
4105                                                 return false;
4106
4107                                         child = ((Unary) e).Expr;
4108
4109                                         if (!TypeManager.VerifyUnManaged (child.Type, loc))
4110                                                 return false;
4111
4112                                         if (!Convert.ImplicitConversionExists (ec, e, expr_type)) {
4113                                                 e.Error_ValueCannotBeConverted (ec, e.Location, expr_type, false);
4114                                                 return false;
4115                                         }
4116
4117                                         data [i] = new ExpressionEmitter (e, vi);
4118                                         i++;
4119
4120                                         continue;
4121                                 }
4122
4123                                 ec.InFixedInitializer = true;
4124                                 e = e.Resolve (ec);
4125                                 ec.InFixedInitializer = false;
4126                                 if (e == null)
4127                                         return false;
4128
4129                                 //
4130                                 // Case 2: Array
4131                                 //
4132                                 if (e.Type.IsArray){
4133                                         Type array_type = TypeManager.GetElementType (e.Type);
4134
4135                                         //
4136                                         // Provided that array_type is unmanaged,
4137                                         //
4138                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
4139                                                 return false;
4140
4141                                         //
4142                                         // and T* is implicitly convertible to the
4143                                         // pointer type given in the fixed statement.
4144                                         //
4145                                         ArrayPtr array_ptr = new ArrayPtr (e, array_type, loc);
4146
4147                                         Expression converted = Convert.ImplicitConversionRequired (
4148                                                 ec, array_ptr, vi.VariableType, loc);
4149                                         if (converted == null)
4150                                                 return false;
4151
4152                                         //
4153                                         // fixed (T* e_ptr = (e == null || e.Length == 0) ? null : converted [0])
4154                                         //
4155                                         converted = new Conditional (new Binary (Binary.Operator.LogicalOr,
4156                                                 new Binary (Binary.Operator.Equality, e, new NullLiteral (loc)),
4157                                                 new Binary (Binary.Operator.Equality, new MemberAccess (e, "Length"), new IntConstant (0, loc))),
4158                                                         NullPointer.Null,
4159                                                         converted);
4160
4161                                         converted = converted.Resolve (ec);
4162
4163                                         data [i] = new ExpressionEmitter (converted, vi);
4164                                         i++;
4165
4166                                         continue;
4167                                 }
4168
4169                                 //
4170                                 // Case 3: string
4171                                 //
4172                                 if (e.Type == TypeManager.string_type){
4173                                         data [i] = new StringEmitter (e, vi, loc);
4174                                         i++;
4175                                         continue;
4176                                 }
4177
4178                                 // Case 4: fixed buffer
4179                                 FixedBufferPtr fixed_buffer_ptr = e as FixedBufferPtr;
4180                                 if (fixed_buffer_ptr != null) {
4181                                         data [i++] = new ExpressionEmitter (fixed_buffer_ptr, vi);
4182                                         continue;
4183                                 }
4184
4185                                 //
4186                                 // For other cases, flag a `this is already fixed expression'
4187                                 //
4188                                 if (e is LocalVariableReference || e is ParameterReference ||
4189                                     Convert.ImplicitConversionExists (ec, e, vi.VariableType)){
4190
4191                                         Report.Error (245, loc, "right hand expression is already fixed, no need to use fixed statement ");
4192                                         return false;
4193                                 }
4194
4195                                 Report.Error (245, loc, "Fixed statement only allowed on strings, arrays or address-of expressions");
4196                                 return false;
4197                         }
4198
4199                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
4200                         bool ok = statement.Resolve (ec);
4201                         bool flow_unreachable = ec.EndFlowBranching ();
4202                         has_ret = flow_unreachable;
4203
4204                         return ok;
4205                 }
4206
4207                 protected override void DoEmit (EmitContext ec)
4208                 {
4209                         for (int i = 0; i < data.Length; i++) {
4210                                 data [i].Emit (ec);
4211                         }
4212
4213                         statement.Emit (ec);
4214
4215                         if (has_ret)
4216                                 return;
4217
4218                         //
4219                         // Clear the pinned variable
4220                         //
4221                         for (int i = 0; i < data.Length; i++) {
4222                                 data [i].EmitExit (ec);
4223                         }
4224                 }
4225
4226                 protected override void CloneTo (CloneContext clonectx, Statement t)
4227                 {
4228                         Fixed target = (Fixed) t;
4229
4230                         target.type = type.Clone (clonectx);
4231                         target.declarators = new ArrayList (declarators.Count);
4232                         foreach (Pair p in declarators) {
4233                                 LocalInfo vi = (LocalInfo) p.First;
4234                                 Expression e = (Expression) p.Second;
4235
4236                                 target.declarators.Add (
4237                                         new Pair (clonectx.LookupVariable (vi), e.Clone (clonectx)));
4238                         }
4239
4240                         target.statement = statement.Clone (clonectx);
4241                 }
4242         }
4243
4244         public class Catch : Statement {
4245                 public readonly string Name;
4246                 public Block  Block;
4247                 public Block  VarBlock;
4248
4249                 Expression type_expr;
4250                 Type type;
4251
4252                 public Catch (Expression type, string name, Block block, Block var_block, Location l)
4253                 {
4254                         type_expr = type;
4255                         Name = name;
4256                         Block = block;
4257                         VarBlock = var_block;
4258                         loc = l;
4259                 }
4260
4261                 public Type CatchType {
4262                         get {
4263                                 return type;
4264                         }
4265                 }
4266
4267                 public bool IsGeneral {
4268                         get {
4269                                 return type_expr == null;
4270                         }
4271                 }
4272
4273                 protected override void DoEmit(EmitContext ec)
4274                 {
4275                         ILGenerator ig = ec.ig;
4276
4277                         if (CatchType != null)
4278                                 ig.BeginCatchBlock (CatchType);
4279                         else
4280                                 ig.BeginCatchBlock (TypeManager.object_type);
4281
4282                         if (VarBlock != null)
4283                                 VarBlock.Emit (ec);
4284
4285                         if (Name != null) {
4286                                 LocalInfo vi = Block.GetLocalInfo (Name);
4287                                 if (vi == null)
4288                                         throw new Exception ("Variable does not exist in this block");
4289
4290                                 if (vi.Variable.NeedsTemporary) {
4291                                         LocalBuilder e = ig.DeclareLocal (vi.VariableType);
4292                                         ig.Emit (OpCodes.Stloc, e);
4293
4294                                         vi.Variable.EmitInstance (ec);
4295                                         ig.Emit (OpCodes.Ldloc, e);
4296                                         vi.Variable.EmitAssign (ec);
4297                                 } else
4298                                         vi.Variable.EmitAssign (ec);
4299                         } else
4300                                 ig.Emit (OpCodes.Pop);
4301
4302                         Block.Emit (ec);
4303                 }
4304
4305                 public override bool Resolve (EmitContext ec)
4306                 {
4307                         using (ec.With (EmitContext.Flags.InCatch, true)) {
4308                                 if (type_expr != null) {
4309                                         TypeExpr te = type_expr.ResolveAsTypeTerminal (ec, false);
4310                                         if (te == null)
4311                                                 return false;
4312
4313                                         type = te.Type;
4314
4315                                         if (type != TypeManager.exception_type && !TypeManager.IsSubclassOf (type, TypeManager.exception_type)){
4316                                                 Error (155, "The type caught or thrown must be derived from System.Exception");
4317                                                 return false;
4318                                         }
4319                                 } else
4320                                         type = null;
4321
4322                                 if (!Block.Resolve (ec))
4323                                         return false;
4324
4325                                 // Even though VarBlock surrounds 'Block' we resolve it later, so that we can correctly
4326                                 // emit the "unused variable" warnings.
4327                                 if (VarBlock != null)
4328                                         return VarBlock.Resolve (ec);
4329
4330                                 return true;
4331                         }
4332                 }
4333
4334                 protected override void CloneTo (CloneContext clonectx, Statement t)
4335                 {
4336                         Catch target = (Catch) t;
4337
4338                         if (type_expr != null)
4339                                 target.type_expr = type_expr.Clone (clonectx);
4340                         if (VarBlock != null)
4341                                 target.VarBlock = clonectx.LookupBlock (VarBlock);
4342                         target.Block = clonectx.LookupBlock (Block);
4343                 }
4344         }
4345
4346         public class Try : ExceptionStatement {
4347                 public Block Fini, Block;
4348                 public ArrayList Specific;
4349                 public Catch General;
4350
4351                 bool need_exc_block;
4352
4353                 //
4354                 // specific, general and fini might all be null.
4355                 //
4356                 public Try (Block block, ArrayList specific, Catch general, Block fini, Location l)
4357                 {
4358                         if (specific == null && general == null){
4359                                 Console.WriteLine ("CIR.Try: Either specific or general have to be non-null");
4360                         }
4361
4362                         this.Block = block;
4363                         this.Specific = specific;
4364                         this.General = general;
4365                         this.Fini = fini;
4366                         loc = l;
4367                 }
4368
4369                 public override bool Resolve (EmitContext ec)
4370                 {
4371                         bool ok = true;
4372
4373                         FlowBranchingException branching = ec.StartFlowBranching (this);
4374
4375                         Report.Debug (1, "START OF TRY BLOCK", Block.StartLocation);
4376
4377                         if (!Block.Resolve (ec))
4378                                 ok = false;
4379
4380                         FlowBranching.UsageVector vector = ec.CurrentBranching.CurrentUsageVector;
4381
4382                         Report.Debug (1, "START OF CATCH BLOCKS", vector);
4383
4384                         Type[] prev_catches = new Type [Specific.Count];
4385                         int last_index = 0;
4386                         foreach (Catch c in Specific){
4387                                 ec.CurrentBranching.CreateSibling (
4388                                         c.Block, FlowBranching.SiblingType.Catch);
4389
4390                                 Report.Debug (1, "STARTED SIBLING FOR CATCH", ec.CurrentBranching);
4391
4392                                 if (c.Name != null) {
4393                                         LocalInfo vi = c.Block.GetLocalInfo (c.Name);
4394                                         if (vi == null)
4395                                                 throw new Exception ();
4396
4397                                         vi.VariableInfo = null;
4398                                 }
4399
4400                                 if (!c.Resolve (ec))
4401                                         return false;
4402
4403                                 Type resolved_type = c.CatchType;
4404                                 for (int ii = 0; ii < last_index; ++ii) {
4405                                         if (resolved_type == prev_catches [ii] || TypeManager.IsSubclassOf (resolved_type, prev_catches [ii])) {
4406                                                 Report.Error (160, c.loc, "A previous catch clause already catches all exceptions of this or a super type `{0}'", prev_catches [ii].FullName);
4407                                                 return false;
4408                                         }
4409                                 }
4410
4411                                 prev_catches [last_index++] = resolved_type;
4412                                 need_exc_block = true;
4413                         }
4414
4415                         Report.Debug (1, "END OF CATCH BLOCKS", ec.CurrentBranching);
4416
4417                         if (General != null){
4418                                 if (CodeGen.Assembly.WrapNonExceptionThrows) {
4419                                         foreach (Catch c in Specific){
4420                                                 if (c.CatchType == TypeManager.exception_type) {
4421                                                         Report.Warning (1058, 1, c.loc, "A previous catch clause already catches all exceptions. All non-exceptions thrown will be wrapped in a `System.Runtime.CompilerServices.RuntimeWrappedException'");
4422                                                 }
4423                                         }
4424                                 }
4425
4426                                 ec.CurrentBranching.CreateSibling (
4427                                         General.Block, FlowBranching.SiblingType.Catch);
4428
4429                                 Report.Debug (1, "STARTED SIBLING FOR GENERAL", ec.CurrentBranching);
4430
4431                                 if (!General.Resolve (ec))
4432                                         ok = false;
4433
4434                                 need_exc_block = true;
4435                         }
4436
4437                         Report.Debug (1, "END OF GENERAL CATCH BLOCKS", ec.CurrentBranching);
4438
4439                         if (Fini != null) {
4440                                 if (ok)
4441                                         ec.CurrentBranching.CreateSibling (Fini, FlowBranching.SiblingType.Finally);
4442
4443                                 Report.Debug (1, "STARTED SIBLING FOR FINALLY", ec.CurrentBranching, vector);
4444                                 using (ec.With (EmitContext.Flags.InFinally, true)) {
4445                                         if (!Fini.Resolve (ec))
4446                                                 ok = false;
4447                                 }
4448
4449                                 if (!ec.InIterator)
4450                                         need_exc_block = true;
4451                         }
4452
4453                         if (ec.InIterator) {
4454                                 ResolveFinally (branching);
4455                                 need_exc_block |= emit_finally;
4456                         } else
4457                                 emit_finally = Fini != null;
4458
4459                         ec.EndFlowBranching ();
4460
4461                         // System.Reflection.Emit automatically emits a 'leave' to the end of the finally block.
4462                         // So, ensure there's some IL code after the finally block.
4463                         ec.NeedReturnLabel ();
4464
4465                         FlowBranching.UsageVector f_vector = ec.CurrentBranching.CurrentUsageVector;
4466
4467                         Report.Debug (1, "END OF TRY", ec.CurrentBranching, vector, f_vector);
4468
4469                         return ok;
4470                 }
4471
4472                 protected override void DoEmit (EmitContext ec)
4473                 {
4474                         ILGenerator ig = ec.ig;
4475
4476                         if (need_exc_block)
4477                                 ig.BeginExceptionBlock ();
4478                         Block.Emit (ec);
4479
4480                         foreach (Catch c in Specific)
4481                                 c.Emit (ec);
4482
4483                         if (General != null)
4484                                 General.Emit (ec);
4485
4486                         DoEmitFinally (ec);
4487                         if (need_exc_block)
4488                                 ig.EndExceptionBlock ();
4489                 }
4490
4491                 public override void EmitFinally (EmitContext ec)
4492                 {
4493                         if (Fini != null)
4494                                 Fini.Emit (ec);
4495                 }
4496
4497                 public bool HasCatch
4498                 {
4499                         get {
4500                                 return General != null || Specific.Count > 0;
4501                         }
4502                 }
4503
4504                 protected override void CloneTo (CloneContext clonectx, Statement t)
4505                 {
4506                         Try target = (Try) t;
4507
4508                         target.Block = clonectx.LookupBlock (Block);
4509                         if (Fini != null)
4510                                 target.Fini = clonectx.LookupBlock (Fini);
4511                         if (General != null)
4512                                 target.General = (Catch) General.Clone (clonectx);
4513                         if (Specific != null){
4514                                 target.Specific = new ArrayList ();
4515                                 foreach (Catch c in Specific)
4516                                         target.Specific.Add (c.Clone (clonectx));
4517                         }
4518                 }
4519         }
4520
4521         public class Using : ExceptionStatement {
4522                 object expression_or_block;
4523                 public Statement Statement;
4524                 ArrayList var_list;
4525                 Expression expr;
4526                 Type expr_type;
4527                 Expression [] resolved_vars;
4528                 Expression [] converted_vars;
4529                 Expression [] assign;
4530                 TemporaryVariable local_copy;
4531
4532                 public Using (object expression_or_block, Statement stmt, Location l)
4533                 {
4534                         this.expression_or_block = expression_or_block;
4535                         Statement = stmt;
4536                         loc = l;
4537                 }
4538
4539                 //
4540                 // Resolves for the case of using using a local variable declaration.
4541                 //
4542                 bool ResolveLocalVariableDecls (EmitContext ec)
4543                 {
4544                         resolved_vars = new Expression[var_list.Count];
4545                         assign = new Expression [var_list.Count];
4546                         converted_vars = new Expression[var_list.Count];
4547
4548                         for (int i = 0; i < assign.Length; ++i) {
4549                                 DictionaryEntry e = (DictionaryEntry) var_list [i];
4550                                 Expression var = (Expression) e.Key;
4551                                 Expression new_expr = (Expression) e.Value;
4552
4553                                 Expression a = new Assign (var, new_expr, loc);
4554                                 a = a.Resolve (ec);
4555                                 if (a == null)
4556                                         return false;
4557
4558                                 resolved_vars [i] = var;
4559                                 assign [i] = a;
4560
4561                                 if (TypeManager.ImplementsInterface (a.Type, TypeManager.idisposable_type)) {
4562                                         converted_vars [i] = var;
4563                                         continue;
4564                                 }
4565
4566                                 a = Convert.ImplicitConversionStandard (ec, a, TypeManager.idisposable_type, var.Location);
4567                                 if (a == null) {
4568                                         Error_IsNotConvertibleToIDisposable (var);
4569                                         return false;
4570                                 }
4571
4572                                 converted_vars [i] = a;
4573                         }
4574
4575                         return true;
4576                 }
4577
4578                 static void Error_IsNotConvertibleToIDisposable (Expression expr)
4579                 {
4580                         Report.SymbolRelatedToPreviousError (expr.Type);
4581                         Report.Error (1674, expr.Location, "`{0}': type used in a using statement must be implicitly convertible to `System.IDisposable'",
4582                                 expr.GetSignatureForError ());
4583                 }
4584
4585                 bool ResolveExpression (EmitContext ec)
4586                 {
4587                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)){
4588                                 if (Convert.ImplicitConversion (ec, expr, TypeManager.idisposable_type, loc) == null) {
4589                                         Error_IsNotConvertibleToIDisposable (expr);
4590                                         return false;
4591                                 }
4592                         }
4593
4594                         local_copy = new TemporaryVariable (expr_type, loc);
4595                         local_copy.Resolve (ec);
4596
4597                         return true;
4598                 }
4599
4600                 //
4601                 // Emits the code for the case of using using a local variable declaration.
4602                 //
4603                 void EmitLocalVariableDecls (EmitContext ec)
4604                 {
4605                         ILGenerator ig = ec.ig;
4606                         int i = 0;
4607
4608                         for (i = 0; i < assign.Length; i++) {
4609                                 ExpressionStatement es = assign [i] as ExpressionStatement;
4610
4611                                 if (es != null)
4612                                         es.EmitStatement (ec);
4613                                 else {
4614                                         assign [i].Emit (ec);
4615                                         ig.Emit (OpCodes.Pop);
4616                                 }
4617
4618                                 if (emit_finally)
4619                                         ig.BeginExceptionBlock ();
4620                         }
4621                         Statement.Emit (ec);
4622
4623                         var_list.Reverse ();
4624
4625                         DoEmitFinally (ec);
4626                 }
4627
4628                 void EmitLocalVariableDeclFinally (EmitContext ec)
4629                 {
4630                         ILGenerator ig = ec.ig;
4631
4632                         int i = assign.Length;
4633                         for (int ii = 0; ii < var_list.Count; ++ii){
4634                                 Expression var = resolved_vars [--i];
4635                                 Label skip = ig.DefineLabel ();
4636
4637                                 if (emit_finally)
4638                                         ig.BeginFinallyBlock ();
4639
4640                                 if (!var.Type.IsValueType) {
4641                                         var.Emit (ec);
4642                                         ig.Emit (OpCodes.Brfalse, skip);
4643                                         converted_vars [i].Emit (ec);
4644                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4645                                 } else {
4646                                         Expression ml = Expression.MemberLookup(ec.ContainerType, TypeManager.idisposable_type, var.Type, "Dispose", Mono.CSharp.Location.Null);
4647
4648                                         if (!(ml is MethodGroupExpr)) {
4649                                                 var.Emit (ec);
4650                                                 ig.Emit (OpCodes.Box, var.Type);
4651                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4652                                         } else {
4653                                                 MethodInfo mi = null;
4654
4655                                                 foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4656                                                         if (TypeManager.GetParameterData (mk).Count == 0) {
4657                                                                 mi = mk;
4658                                                                 break;
4659                                                         }
4660                                                 }
4661
4662                                                 if (mi == null) {
4663                                                         Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4664                                                         return;
4665                                                 }
4666
4667                                                 IMemoryLocation mloc = (IMemoryLocation) var;
4668
4669                                                 mloc.AddressOf (ec, AddressOp.Load);
4670                                                 ig.Emit (OpCodes.Call, mi);
4671                                         }
4672                                 }
4673
4674                                 ig.MarkLabel (skip);
4675
4676                                 if (emit_finally) {
4677                                         ig.EndExceptionBlock ();
4678                                         if (i > 0)
4679                                                 ig.BeginFinallyBlock ();
4680                                 }
4681                         }
4682                 }
4683
4684                 void EmitExpression (EmitContext ec)
4685                 {
4686                         //
4687                         // Make a copy of the expression and operate on that.
4688                         //
4689                         ILGenerator ig = ec.ig;
4690
4691                         local_copy.Store (ec, expr);
4692
4693                         if (emit_finally)
4694                                 ig.BeginExceptionBlock ();
4695
4696                         Statement.Emit (ec);
4697
4698                         DoEmitFinally (ec);
4699                         if (emit_finally)
4700                                 ig.EndExceptionBlock ();
4701                 }
4702
4703                 void EmitExpressionFinally (EmitContext ec)
4704                 {
4705                         ILGenerator ig = ec.ig;
4706                         if (!expr_type.IsValueType) {
4707                                 Label skip = ig.DefineLabel ();
4708                                 local_copy.Emit (ec);
4709                                 ig.Emit (OpCodes.Brfalse, skip);
4710                                 local_copy.Emit (ec);
4711                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4712                                 ig.MarkLabel (skip);
4713                         } else {
4714                                 Expression ml = Expression.MemberLookup (
4715                                         ec.ContainerType, TypeManager.idisposable_type, expr_type,
4716                                         "Dispose", Location.Null);
4717
4718                                 if (!(ml is MethodGroupExpr)) {
4719                                         local_copy.Emit (ec);
4720                                         ig.Emit (OpCodes.Box, expr_type);
4721                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4722                                 } else {
4723                                         MethodInfo mi = null;
4724
4725                                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4726                                                 if (TypeManager.GetParameterData (mk).Count == 0) {
4727                                                         mi = mk;
4728                                                         break;
4729                                                 }
4730                                         }
4731
4732                                         if (mi == null) {
4733                                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4734                                                 return;
4735                                         }
4736
4737                                         local_copy.AddressOf (ec, AddressOp.Load);
4738                                         ig.Emit (OpCodes.Call, mi);
4739                                 }
4740                         }
4741                 }
4742
4743                 public override bool Resolve (EmitContext ec)
4744                 {
4745                         if (expression_or_block is DictionaryEntry){
4746                                 expr = (Expression) ((DictionaryEntry) expression_or_block).Key;
4747                                 var_list = (ArrayList)((DictionaryEntry)expression_or_block).Value;
4748
4749                                 if (!ResolveLocalVariableDecls (ec))
4750                                         return false;
4751
4752                         } else if (expression_or_block is Expression){
4753                                 expr = (Expression) expression_or_block;
4754
4755                                 expr = expr.Resolve (ec);
4756                                 if (expr == null)
4757                                         return false;
4758
4759                                 expr_type = expr.Type;
4760
4761                                 if (!ResolveExpression (ec))
4762                                         return false;
4763                         }
4764
4765                         FlowBranchingException branching = ec.StartFlowBranching (this);
4766
4767                         bool ok = Statement.Resolve (ec);
4768
4769                         ResolveFinally (branching);
4770
4771                         ec.EndFlowBranching ();
4772
4773                         // System.Reflection.Emit automatically emits a 'leave' to the end of the finally block.
4774                         // So, ensure there's some IL code after the finally block.
4775                         ec.NeedReturnLabel ();
4776
4777                         if (TypeManager.void_dispose_void == null) {
4778                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
4779                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
4780                         }
4781
4782                         return ok;
4783                 }
4784
4785                 protected override void DoEmit (EmitContext ec)
4786                 {
4787                         if (expression_or_block is DictionaryEntry)
4788                                 EmitLocalVariableDecls (ec);
4789                         else if (expression_or_block is Expression)
4790                                 EmitExpression (ec);
4791                 }
4792
4793                 public override void EmitFinally (EmitContext ec)
4794                 {
4795                         if (expression_or_block is DictionaryEntry)
4796                                 EmitLocalVariableDeclFinally (ec);
4797                         else if (expression_or_block is Expression)
4798                                 EmitExpressionFinally (ec);
4799                 }
4800
4801                 protected override void CloneTo (CloneContext clonectx, Statement t)
4802                 {
4803                         Using target = (Using) t;
4804
4805                         if (expression_or_block is Expression) {
4806                                 target.expression_or_block = ((Expression) expression_or_block).Clone (clonectx);
4807                         } else {
4808                                 DictionaryEntry de = (DictionaryEntry) expression_or_block;
4809                                 ArrayList var_list = (ArrayList) de.Value;
4810                                 ArrayList target_var_list = new ArrayList (var_list.Count);
4811
4812                                 foreach (DictionaryEntry de_variable in var_list)
4813                                         target_var_list.Add (new DictionaryEntry (
4814                                                 ((Expression) de_variable.Key).Clone (clonectx),
4815                                                 ((Expression) de_variable.Value).Clone (clonectx)));
4816
4817                                 target.expression_or_block = new DictionaryEntry (
4818                                         ((Expression) de.Key).Clone (clonectx),
4819                                         target_var_list);
4820                         }
4821
4822                         target.Statement = Statement.Clone (clonectx);
4823                 }
4824         }
4825
4826         /// <summary>
4827         ///   Implementation of the foreach C# statement
4828         /// </summary>
4829         public class Foreach : Statement {
4830                 Expression type;
4831                 Expression variable;
4832                 Expression expr;
4833                 Statement statement;
4834                 ArrayForeach array;
4835                 CollectionForeach collection;
4836
4837                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
4838                                 Statement stmt, Location l)
4839                 {
4840                         this.type = type;
4841                         this.variable = var;
4842                         this.expr = expr;
4843                         statement = stmt;
4844                         loc = l;
4845                 }
4846
4847                 public Statement Statement {
4848                         get { return statement; }
4849                 }
4850
4851                 public override bool Resolve (EmitContext ec)
4852                 {
4853                         expr = expr.Resolve (ec);
4854                         if (expr == null)
4855                                 return false;
4856
4857                         if (expr.IsNull) {
4858                                 Report.Error (186, loc, "Use of null is not valid in this context");
4859                                 return false;
4860                         }
4861
4862                         if (expr.eclass == ExprClass.MethodGroup || expr is AnonymousMethodExpression) {
4863                                 Report.Error (446, expr.Location, "Foreach statement cannot operate on a `{0}'",
4864                                         expr.ExprClassName);
4865                                 return false;
4866                         }
4867
4868                         //
4869                         // We need an instance variable.  Not sure this is the best
4870                         // way of doing this.
4871                         //
4872                         // FIXME: When we implement propertyaccess, will those turn
4873                         // out to return values in ExprClass?  I think they should.
4874                         //
4875                         if (!(expr.eclass == ExprClass.Variable || expr.eclass == ExprClass.Value ||
4876                               expr.eclass == ExprClass.PropertyAccess || expr.eclass == ExprClass.IndexerAccess)){
4877                                 collection.Error_Enumerator ();
4878                                 return false;
4879                         }
4880
4881                         if (expr.Type.IsArray) {
4882                                 array = new ArrayForeach (type, variable, expr, statement, loc);
4883                                 return array.Resolve (ec);
4884                         }
4885
4886                         collection = new CollectionForeach (type, variable, expr, statement, loc);
4887                         return collection.Resolve (ec);
4888                 }
4889
4890                 protected override void DoEmit (EmitContext ec)
4891                 {
4892                         ILGenerator ig = ec.ig;
4893
4894                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
4895                         ec.LoopBegin = ig.DefineLabel ();
4896                         ec.LoopEnd = ig.DefineLabel ();
4897
4898                         if (collection != null)
4899                                 collection.Emit (ec);
4900                         else
4901                                 array.Emit (ec);
4902
4903                         ec.LoopBegin = old_begin;
4904                         ec.LoopEnd = old_end;
4905                 }
4906
4907                 protected class ArrayCounter : TemporaryVariable
4908                 {
4909                         public ArrayCounter (Location loc)
4910                                 : base (TypeManager.int32_type, loc)
4911                         { }
4912
4913                         public void Initialize (EmitContext ec)
4914                         {
4915                                 EmitThis (ec);
4916                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
4917                                 EmitStore (ec);
4918                         }
4919
4920                         public void Increment (EmitContext ec)
4921                         {
4922                                 EmitThis (ec);
4923                                 Emit (ec);
4924                                 ec.ig.Emit (OpCodes.Ldc_I4_1);
4925                                 ec.ig.Emit (OpCodes.Add);
4926                                 EmitStore (ec);
4927                         }
4928                 }
4929
4930                 protected class ArrayForeach : Statement
4931                 {
4932                         Expression variable, expr, conv;
4933                         Statement statement;
4934                         Type array_type;
4935                         Expression var_type;
4936                         TemporaryVariable[] lengths;
4937                         ArrayCounter[] counter;
4938                         int rank;
4939
4940                         TemporaryVariable copy;
4941                         Expression access;
4942
4943                         public ArrayForeach (Expression var_type, Expression var,
4944                                              Expression expr, Statement stmt, Location l)
4945                         {
4946                                 this.var_type = var_type;
4947                                 this.variable = var;
4948                                 this.expr = expr;
4949                                 statement = stmt;
4950                                 loc = l;
4951                         }
4952
4953                         public override bool Resolve (EmitContext ec)
4954                         {
4955                                 array_type = expr.Type;
4956                                 rank = array_type.GetArrayRank ();
4957
4958                                 copy = new TemporaryVariable (array_type, loc);
4959                                 copy.Resolve (ec);
4960
4961                                 counter = new ArrayCounter [rank];
4962                                 lengths = new TemporaryVariable [rank];
4963
4964                                 ArrayList list = new ArrayList ();
4965                                 for (int i = 0; i < rank; i++) {
4966                                         counter [i] = new ArrayCounter (loc);
4967                                         counter [i].Resolve (ec);
4968
4969                                         lengths [i] = new TemporaryVariable (TypeManager.int32_type, loc);
4970                                         lengths [i].Resolve (ec);
4971
4972                                         list.Add (counter [i]);
4973                                 }
4974
4975                                 access = new ElementAccess (copy, list).Resolve (ec);
4976                                 if (access == null)
4977                                         return false;
4978
4979                                 VarExpr ve = var_type as VarExpr;
4980                                 if (ve != null) {
4981                                         // Infer implicitly typed local variable from foreach array type
4982                                         var_type = new TypeExpression (access.Type, ve.Location);
4983                                 }
4984
4985                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
4986                                 if (var_type == null)
4987                                         return false;
4988
4989                                 conv = Convert.ExplicitConversion (ec, access, var_type.Type, loc);
4990                                 if (conv == null)
4991                                         return false;
4992
4993                                 bool ok = true;
4994
4995                                 ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
4996                                 ec.CurrentBranching.CreateSibling ();
4997
4998                                 variable = variable.ResolveLValue (ec, conv, loc);
4999                                 if (variable == null)
5000                                         ok = false;
5001
5002                                 ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
5003                                 if (!statement.Resolve (ec))
5004                                         ok = false;
5005                                 ec.EndFlowBranching ();
5006
5007                                 // There's no direct control flow from the end of the embedded statement to the end of the loop
5008                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
5009
5010                                 ec.EndFlowBranching ();
5011
5012                                 return ok;
5013                         }
5014
5015                         protected override void DoEmit (EmitContext ec)
5016                         {
5017                                 ILGenerator ig = ec.ig;
5018
5019                                 copy.Store (ec, expr);
5020
5021                                 Label[] test = new Label [rank];
5022                                 Label[] loop = new Label [rank];
5023
5024                                 for (int i = 0; i < rank; i++) {
5025                                         test [i] = ig.DefineLabel ();
5026                                         loop [i] = ig.DefineLabel ();
5027
5028                                         lengths [i].EmitThis (ec);
5029                                         ((ArrayAccess) access).EmitGetLength (ec, i);
5030                                         lengths [i].EmitStore (ec);
5031                                 }
5032
5033                                 for (int i = 0; i < rank; i++) {
5034                                         counter [i].Initialize (ec);
5035
5036                                         ig.Emit (OpCodes.Br, test [i]);
5037                                         ig.MarkLabel (loop [i]);
5038                                 }
5039
5040                                 ((IAssignMethod) variable).EmitAssign (ec, conv, false, false);
5041
5042                                 statement.Emit (ec);
5043
5044                                 ig.MarkLabel (ec.LoopBegin);
5045
5046                                 for (int i = rank - 1; i >= 0; i--){
5047                                         counter [i].Increment (ec);
5048
5049                                         ig.MarkLabel (test [i]);
5050                                         counter [i].Emit (ec);
5051                                         lengths [i].Emit (ec);
5052                                         ig.Emit (OpCodes.Blt, loop [i]);
5053                                 }
5054
5055                                 ig.MarkLabel (ec.LoopEnd);
5056                         }
5057                 }
5058
5059                 protected class CollectionForeach : ExceptionStatement
5060                 {
5061                         Expression variable, expr;
5062                         Statement statement;
5063
5064                         TemporaryVariable enumerator;
5065                         Expression init;
5066                         Statement loop;
5067
5068                         MethodGroupExpr get_enumerator;
5069                         PropertyExpr get_current;
5070                         MethodInfo move_next;
5071                         Expression var_type;
5072                         Type enumerator_type;
5073                         bool is_disposable;
5074                         bool enumerator_found;
5075
5076                         public CollectionForeach (Expression var_type, Expression var,
5077                                                   Expression expr, Statement stmt, Location l)
5078                         {
5079                                 this.var_type = var_type;
5080                                 this.variable = var;
5081                                 this.expr = expr;
5082                                 statement = stmt;
5083                                 loc = l;
5084                         }
5085
5086                         bool GetEnumeratorFilter (EmitContext ec, MethodInfo mi)
5087                         {
5088                                 Type return_type = mi.ReturnType;
5089
5090                                 if ((return_type == TypeManager.ienumerator_type) && (mi.DeclaringType == TypeManager.string_type))
5091                                         //
5092                                         // Apply the same optimization as MS: skip the GetEnumerator
5093                                         // returning an IEnumerator, and use the one returning a
5094                                         // CharEnumerator instead. This allows us to avoid the
5095                                         // try-finally block and the boxing.
5096                                         //
5097                                         return false;
5098
5099                                 //
5100                                 // Ok, we can access it, now make sure that we can do something
5101                                 // with this `GetEnumerator'
5102                                 //
5103
5104                                 if (return_type == TypeManager.ienumerator_type ||
5105                                     TypeManager.ienumerator_type.IsAssignableFrom (return_type) ||
5106                                     (!RootContext.StdLib && TypeManager.ImplementsInterface (return_type, TypeManager.ienumerator_type))) {
5107                                         //
5108                                         // If it is not an interface, lets try to find the methods ourselves.
5109                                         // For example, if we have:
5110                                         // public class Foo : IEnumerator { public bool MoveNext () {} public int Current { get {}}}
5111                                         // We can avoid the iface call. This is a runtime perf boost.
5112                                         // even bigger if we have a ValueType, because we avoid the cost
5113                                         // of boxing.
5114                                         //
5115                                         // We have to make sure that both methods exist for us to take
5116                                         // this path. If one of the methods does not exist, we will just
5117                                         // use the interface. Sadly, this complex if statement is the only
5118                                         // way I could do this without a goto
5119                                         //
5120
5121                                         if (TypeManager.bool_movenext_void == null) {
5122                                                 TypeManager.bool_movenext_void = TypeManager.GetPredefinedMethod (
5123                                                         TypeManager.ienumerator_type, "MoveNext", loc, Type.EmptyTypes);
5124                                         }
5125
5126                                         if (TypeManager.ienumerator_getcurrent == null) {
5127                                                 TypeManager.ienumerator_getcurrent = TypeManager.GetPredefinedProperty (
5128                                                         TypeManager.ienumerator_type, "Current", loc, TypeManager.object_type);
5129                                         }
5130
5131 #if GMCS_SOURCE
5132                                         //
5133                                         // Prefer a generic enumerator over a non-generic one.
5134                                         //
5135                                         if (return_type.IsInterface && return_type.IsGenericType) {
5136                                                 enumerator_type = return_type;
5137                                                 if (!FetchGetCurrent (ec, return_type))
5138                                                         get_current = new PropertyExpr (
5139                                                                 ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5140                                                 if (!FetchMoveNext (return_type))
5141                                                         move_next = TypeManager.bool_movenext_void;
5142                                                 return true;
5143                                         }
5144 #endif
5145
5146                                         if (return_type.IsInterface ||
5147                                             !FetchMoveNext (return_type) ||
5148                                             !FetchGetCurrent (ec, return_type)) {
5149                                                 enumerator_type = return_type;
5150                                                 move_next = TypeManager.bool_movenext_void;
5151                                                 get_current = new PropertyExpr (
5152                                                         ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5153                                                 return true;
5154                                         }
5155                                 } else {
5156                                         //
5157                                         // Ok, so they dont return an IEnumerable, we will have to
5158                                         // find if they support the GetEnumerator pattern.
5159                                         //
5160
5161                                         if (TypeManager.HasElementType (return_type) || !FetchMoveNext (return_type) || !FetchGetCurrent (ec, return_type)) {
5162                                                 Report.Error (202, loc, "foreach statement requires that the return type `{0}' of `{1}' must have a suitable public MoveNext method and public Current property",
5163                                                         TypeManager.CSharpName (return_type), TypeManager.CSharpSignature (mi));
5164                                                 return false;
5165                                         }
5166                                 }
5167
5168                                 enumerator_type = return_type;
5169                                 is_disposable = !enumerator_type.IsSealed ||
5170                                         TypeManager.ImplementsInterface (
5171                                                 enumerator_type, TypeManager.idisposable_type);
5172
5173                                 return true;
5174                         }
5175
5176                         //
5177                         // Retrieves a `public bool MoveNext ()' method from the Type `t'
5178                         //
5179                         bool FetchMoveNext (Type t)
5180                         {
5181                                 MemberList move_next_list;
5182
5183                                 move_next_list = TypeContainer.FindMembers (
5184                                         t, MemberTypes.Method,
5185                                         BindingFlags.Public | BindingFlags.Instance,
5186                                         Type.FilterName, "MoveNext");
5187                                 if (move_next_list.Count == 0)
5188                                         return false;
5189
5190                                 foreach (MemberInfo m in move_next_list){
5191                                         MethodInfo mi = (MethodInfo) m;
5192
5193                                         if ((TypeManager.GetParameterData (mi).Count == 0) &&
5194                                             TypeManager.TypeToCoreType (mi.ReturnType) == TypeManager.bool_type) {
5195                                                 move_next = mi;
5196                                                 return true;
5197                                         }
5198                                 }
5199
5200                                 return false;
5201                         }
5202
5203                         //
5204                         // Retrieves a `public T get_Current ()' method from the Type `t'
5205                         //
5206                         bool FetchGetCurrent (EmitContext ec, Type t)
5207                         {
5208                                 PropertyExpr pe = Expression.MemberLookup (
5209                                         ec.ContainerType, t, "Current", MemberTypes.Property,
5210                                         Expression.AllBindingFlags, loc) as PropertyExpr;
5211                                 if (pe == null)
5212                                         return false;
5213
5214                                 get_current = pe;
5215                                 return true;
5216                         }
5217
5218                         //
5219                         // Retrieves a `public void Dispose ()' method from the Type `t'
5220                         //
5221                         static MethodInfo FetchMethodDispose (Type t)
5222                         {
5223                                 MemberList dispose_list;
5224
5225                                 dispose_list = TypeContainer.FindMembers (
5226                                         t, MemberTypes.Method,
5227                                         BindingFlags.Public | BindingFlags.Instance,
5228                                         Type.FilterName, "Dispose");
5229                                 if (dispose_list.Count == 0)
5230                                         return null;
5231
5232                                 foreach (MemberInfo m in dispose_list){
5233                                         MethodInfo mi = (MethodInfo) m;
5234
5235                                         if (TypeManager.GetParameterData (mi).Count == 0){
5236                                                 if (mi.ReturnType == TypeManager.void_type)
5237                                                         return mi;
5238                                         }
5239                                 }
5240                                 return null;
5241                         }
5242
5243                         public void Error_Enumerator ()
5244                         {
5245                                 if (enumerator_found) {
5246                                         return;
5247                                 }
5248
5249                             Report.Error (1579, loc,
5250                                         "foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `GetEnumerator' or is not accessible",
5251                                         TypeManager.CSharpName (expr.Type));
5252                         }
5253
5254                         bool IsOverride (MethodInfo m)
5255                         {
5256                                 m = (MethodInfo) TypeManager.DropGenericMethodArguments (m);
5257
5258                                 if (!m.IsVirtual || ((m.Attributes & MethodAttributes.NewSlot) != 0))
5259                                         return false;
5260                                 if (m is MethodBuilder)
5261                                         return true;
5262
5263                                 MethodInfo base_method = m.GetBaseDefinition ();
5264                                 return base_method != m;
5265                         }
5266
5267                         bool TryType (EmitContext ec, Type t)
5268                         {
5269                                 MethodGroupExpr mg = Expression.MemberLookup (
5270                                         ec.ContainerType, t, "GetEnumerator", MemberTypes.Method,
5271                                         Expression.AllBindingFlags, loc) as MethodGroupExpr;
5272                                 if (mg == null)
5273                                         return false;
5274
5275                                 MethodInfo result = null;
5276                                 MethodInfo tmp_move_next = null;
5277                                 PropertyExpr tmp_get_cur = null;
5278                                 Type tmp_enumerator_type = enumerator_type;
5279                                 foreach (MethodInfo mi in mg.Methods) {
5280                                         if (TypeManager.GetParameterData (mi).Count != 0)
5281                                                 continue;
5282
5283                                         // Check whether GetEnumerator is public
5284                                         if ((mi.Attributes & MethodAttributes.Public) != MethodAttributes.Public)
5285                                                 continue;
5286
5287                                         if (IsOverride (mi))
5288                                                 continue;
5289
5290                                         enumerator_found = true;
5291
5292                                         if (!GetEnumeratorFilter (ec, mi))
5293                                                 continue;
5294
5295                                         if (result != null) {
5296                                                 if (TypeManager.IsGenericType (result.ReturnType)) {
5297                                                         if (!TypeManager.IsGenericType (mi.ReturnType))
5298                                                                 continue;
5299
5300                                                         MethodBase mb = TypeManager.DropGenericMethodArguments (mi);
5301                                                         Report.SymbolRelatedToPreviousError (t);
5302                                                         Report.Error(1640, loc, "foreach statement cannot operate on variables of type `{0}' " +
5303                                                                      "because it contains multiple implementation of `{1}'. Try casting to a specific implementation",
5304                                                                      TypeManager.CSharpName (t), TypeManager.CSharpSignature (mb));
5305                                                         return false;
5306                                                 }
5307
5308                                                 // Always prefer generics enumerators
5309                                                 if (!TypeManager.IsGenericType (mi.ReturnType)) {
5310                                                         if (TypeManager.ImplementsInterface (mi.DeclaringType, result.DeclaringType) ||
5311                                                             TypeManager.ImplementsInterface (result.DeclaringType, mi.DeclaringType))
5312                                                                 continue;
5313
5314                                                         Report.SymbolRelatedToPreviousError (result);
5315                                                         Report.SymbolRelatedToPreviousError (mi);
5316                                                         Report.Warning (278, 2, loc, "`{0}' contains ambiguous implementation of `{1}' pattern. Method `{2}' is ambiguous with method `{3}'",
5317                                                                         TypeManager.CSharpName (t), "enumerable", TypeManager.CSharpSignature (result), TypeManager.CSharpSignature (mi));
5318                                                         return false;
5319                                                 }
5320                                         }
5321                                         result = mi;
5322                                         tmp_move_next = move_next;
5323                                         tmp_get_cur = get_current;
5324                                         tmp_enumerator_type = enumerator_type;
5325                                         if (mi.DeclaringType == t)
5326                                                 break;
5327                                 }
5328
5329                                 if (result != null) {
5330                                         move_next = tmp_move_next;
5331                                         get_current = tmp_get_cur;
5332                                         enumerator_type = tmp_enumerator_type;
5333                                         MethodInfo[] mi = new MethodInfo[] { (MethodInfo) result };
5334                                         get_enumerator = new MethodGroupExpr (mi, enumerator_type, loc);
5335
5336                                         if (t != expr.Type) {
5337                                                 expr = Convert.ExplicitConversion (
5338                                                         ec, expr, t, loc);
5339                                                 if (expr == null)
5340                                                         throw new InternalErrorException ();
5341                                         }
5342
5343                                         get_enumerator.InstanceExpression = expr;
5344                                         get_enumerator.IsBase = t != expr.Type;
5345
5346                                         return true;
5347                                 }
5348
5349                                 return false;
5350                         }
5351
5352                         bool ProbeCollectionType (EmitContext ec, Type t)
5353                         {
5354                                 int errors = Report.Errors;
5355                                 for (Type tt = t; tt != null && tt != TypeManager.object_type;){
5356                                         if (TryType (ec, tt))
5357                                                 return true;
5358                                         tt = tt.BaseType;
5359                                 }
5360
5361                                 if (Report.Errors > errors)
5362                                         return false;
5363
5364                                 //
5365                                 // Now try to find the method in the interfaces
5366                                 //
5367                                 Type [] ifaces = TypeManager.GetInterfaces (t);
5368                                 foreach (Type i in ifaces){
5369                                         if (TryType (ec, i))
5370                                                 return true;
5371                                 }
5372
5373                                 return false;
5374                         }
5375
5376                         public override bool Resolve (EmitContext ec)
5377                         {
5378                                 enumerator_type = TypeManager.ienumerator_type;
5379                                 is_disposable = true;
5380
5381                                 if (!ProbeCollectionType (ec, expr.Type)) {
5382                                         Error_Enumerator ();
5383                                         return false;
5384                                 }
5385
5386                                 VarExpr ve = var_type as VarExpr;
5387                                 if (ve != null) {
5388                                         // Infer implicitly typed local variable from foreach enumerable type
5389                                         var_type = new TypeExpression (get_current.PropertyInfo.PropertyType, var_type.Location);
5390                                 }
5391
5392                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
5393                                 if (var_type == null)
5394                                         return false;
5395
5396                                 enumerator = new TemporaryVariable (enumerator_type, loc);
5397                                 enumerator.Resolve (ec);
5398
5399                                 init = new Invocation (get_enumerator, null);
5400                                 init = init.Resolve (ec);
5401                                 if (init == null)
5402                                         return false;
5403
5404                                 Expression move_next_expr;
5405                                 {
5406                                         MemberInfo[] mi = new MemberInfo[] { move_next };
5407                                         MethodGroupExpr mg = new MethodGroupExpr (mi, var_type.Type, loc);
5408                                         mg.InstanceExpression = enumerator;
5409
5410                                         move_next_expr = new Invocation (mg, null);
5411                                 }
5412
5413                                 get_current.InstanceExpression = enumerator;
5414
5415                                 Statement block = new CollectionForeachStatement (
5416                                         var_type.Type, variable, get_current, statement, loc);
5417
5418                                 loop = new While (move_next_expr, block, loc);
5419
5420                                 bool ok = true;
5421
5422                                 FlowBranchingException branching = null;
5423                                 if (is_disposable)
5424                                         branching = ec.StartFlowBranching (this);
5425
5426                                 if (!loop.Resolve (ec))
5427                                         ok = false;
5428
5429                                 if (is_disposable) {
5430                                         ResolveFinally (branching);
5431                                         ec.EndFlowBranching ();
5432
5433                                         if (TypeManager.void_dispose_void == null) {
5434                                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
5435                                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
5436                                         }
5437                                 } else
5438                                         emit_finally = true;
5439
5440                                 return ok;
5441                         }
5442
5443                         protected override void DoEmit (EmitContext ec)
5444                         {
5445                                 ILGenerator ig = ec.ig;
5446
5447                                 enumerator.Store (ec, init);
5448
5449                                 //
5450                                 // Protect the code in a try/finalize block, so that
5451                                 // if the beast implement IDisposable, we get rid of it
5452                                 //
5453                                 if (is_disposable && emit_finally)
5454                                         ig.BeginExceptionBlock ();
5455
5456                                 loop.Emit (ec);
5457
5458                                 //
5459                                 // Now the finally block
5460                                 //
5461                                 if (is_disposable) {
5462                                         DoEmitFinally (ec);
5463                                         if (emit_finally)
5464                                                 ig.EndExceptionBlock ();
5465                                 }
5466                         }
5467
5468
5469                         public override void EmitFinally (EmitContext ec)
5470                         {
5471                                 ILGenerator ig = ec.ig;
5472
5473                                 if (enumerator_type.IsValueType) {
5474                                         MethodInfo mi = FetchMethodDispose (enumerator_type);
5475                                         if (mi != null) {
5476                                                 enumerator.EmitLoadAddress (ec);
5477                                                 ig.Emit (OpCodes.Call, mi);
5478                                         } else {
5479                                                 enumerator.Emit (ec);
5480                                                 ig.Emit (OpCodes.Box, enumerator_type);
5481                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
5482                                         }
5483                                 } else {
5484                                         Label call_dispose = ig.DefineLabel ();
5485
5486                                         enumerator.Emit (ec);
5487                                         ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
5488                                         ig.Emit (OpCodes.Dup);
5489                                         ig.Emit (OpCodes.Brtrue_S, call_dispose);
5490                                         ig.Emit (OpCodes.Pop);
5491
5492                                         Label end_finally = ig.DefineLabel ();
5493                                         ig.Emit (OpCodes.Br, end_finally);
5494
5495                                         ig.MarkLabel (call_dispose);
5496                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
5497                                         ig.MarkLabel (end_finally);
5498                                 }
5499                         }
5500                 }
5501
5502                 protected class CollectionForeachStatement : Statement
5503                 {
5504                         Type type;
5505                         Expression variable, current, conv;
5506                         Statement statement;
5507                         Assign assign;
5508
5509                         public CollectionForeachStatement (Type type, Expression variable,
5510                                                            Expression current, Statement statement,
5511                                                            Location loc)
5512                         {
5513                                 this.type = type;
5514                                 this.variable = variable;
5515                                 this.current = current;
5516                                 this.statement = statement;
5517                                 this.loc = loc;
5518                         }
5519
5520                         public override bool Resolve (EmitContext ec)
5521                         {
5522                                 current = current.Resolve (ec);
5523                                 if (current == null)
5524                                         return false;
5525
5526                                 conv = Convert.ExplicitConversion (ec, current, type, loc);
5527                                 if (conv == null)
5528                                         return false;
5529
5530                                 assign = new Assign (variable, conv, loc);
5531                                 if (assign.Resolve (ec) == null)
5532                                         return false;
5533
5534                                 if (!statement.Resolve (ec))
5535                                         return false;
5536
5537                                 return true;
5538                         }
5539
5540                         protected override void DoEmit (EmitContext ec)
5541                         {
5542                                 assign.EmitStatement (ec);
5543                                 statement.Emit (ec);
5544                         }
5545                 }
5546
5547                 protected override void CloneTo (CloneContext clonectx, Statement t)
5548                 {
5549                         Foreach target = (Foreach) t;
5550
5551                         target.type = type.Clone (clonectx);
5552                         target.variable = variable.Clone (clonectx);
5553                         target.expr = expr.Clone (clonectx);
5554                         target.statement = statement.Clone (clonectx);
5555                 }
5556         }
5557 }