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 // Copyright 2001, 2002, 2003 Ximian, Inc.
  10 // Copyright 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                 public abstract void MutateHoistedGenericType (AnonymousMethodStorey storey);
 120         }
 121
 122         //
 123         // This class is used during the Statement.Clone operation
 124         // to remap objects that have been cloned.
 125         //
 126         // Since blocks are cloned by Block.Clone, we need a way for
 127         // expressions that must reference the block to be cloned
 128         // pointing to the new cloned block.
 129         //
 130         public class CloneContext {
 131                 Hashtable block_map = new Hashtable ();
 132                 Hashtable variable_map;
 133
 134                 public void AddBlockMap (Block from, Block to)
 135                 {
 136                         if (block_map.Contains (from))
 137                                 return;
 138                         block_map [from] = to;
 139                 }
 140
 141                 public Block LookupBlock (Block from)
 142                 {
 143                         Block result = (Block) block_map [from];
 144
 145                         if (result == null){
 146                                 result = (Block) from.Clone (this);
 147                                 block_map [from] = result;
 148                         }
 149
 150                         return result;
 151                 }
 152
 153                 ///
 154                 /// Remaps block to cloned copy if one exists.
 155                 ///
 156                 public Block RemapBlockCopy (Block from)
 157                 {
 158                         Block mapped_to = (Block)block_map[from];
 159                         if (mapped_to == null)
 160                                 return from;
 161
 162                         return mapped_to;
 163                 }
 164
 165                 public void AddVariableMap (LocalInfo from, LocalInfo to)
 166                 {
 167                         if (variable_map == null)
 168                                 variable_map = new Hashtable ();
 169
 170                         if (variable_map.Contains (from))
 171                                 return;
 172                         variable_map [from] = to;
 173                 }
 174
 175                 public LocalInfo LookupVariable (LocalInfo from)
 176                 {
 177                         LocalInfo result = (LocalInfo) variable_map [from];
 178
 179                         if (result == null)
 180                                 throw new Exception ("LookupVariable: looking up a variable that has not been registered yet");
 181
 182                         return result;
 183                 }
 184         }
 185
 186         public sealed class EmptyStatement : Statement {
 187
 188                 private EmptyStatement () {}
 189
 190                 public static readonly EmptyStatement Value = new EmptyStatement ();
 191
 192                 public override bool Resolve (EmitContext ec)
 193                 {
 194                         return true;
 195                 }
 196
 197                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
 198                 {
 199                         return true;
 200                 }
 201
 202                 protected override void DoEmit (EmitContext ec)
 203                 {
 204                 }
 205
 206                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 207                 {
 208                 }
 209
 210                 protected override void CloneTo (CloneContext clonectx, Statement target)
 211                 {
 212                         // nothing needed.
 213                 }
 214         }
 215
 216         public class If : Statement {
 217                 Expression expr;
 218                 public Statement TrueStatement;
 219                 public Statement FalseStatement;
 220
 221                 bool is_true_ret;
 222
 223                 public If (Expression expr, Statement true_statement, Location l)
 224                 {
 225                         this.expr = expr;
 226                         TrueStatement = true_statement;
 227                         loc = l;
 228                 }
 229
 230                 public If (Expression expr,
 231                            Statement true_statement,
 232                            Statement false_statement,
 233                            Location l)
 234                 {
 235                         this.expr = expr;
 236                         TrueStatement = true_statement;
 237                         FalseStatement = false_statement;
 238                         loc = l;
 239                 }
 240
 241                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 242                 {
 243                         expr.MutateHoistedGenericType (storey);
 244                         TrueStatement.MutateHoistedGenericType (storey);
 245                         if (FalseStatement != null)
 246                                 FalseStatement.MutateHoistedGenericType (storey);
 247                 }
 248
 249                 public override bool Resolve (EmitContext ec)
 250                 {
 251                         bool ok = true;
 252
 253                         Report.Debug (1, "START IF BLOCK", loc);
 254
 255                         expr = Expression.ResolveBoolean (ec, expr, loc);
 256                         if (expr == null){
 257                                 ok = false;
 258                                 goto skip;
 259                         }
 260
 261                         Assign ass = expr as Assign;
 262                         if (ass != null && ass.Source is Constant) {
 263                                 Report.Warning (665, 3, loc, "Assignment in conditional expression is always constant; did you mean to use == instead of = ?");
 264                         }
 265
 266                         //
 267                         // Dead code elimination
 268                         //
 269                         if (expr is Constant){
 270                                 bool take = !((Constant) expr).IsDefaultValue;
 271
 272                                 if (take){
 273                                         if (!TrueStatement.Resolve (ec))
 274                                                 return false;
 275
 276                                         if ((FalseStatement != null) &&
 277                                             !FalseStatement.ResolveUnreachable (ec, true))
 278                                                 return false;
 279                                         FalseStatement = null;
 280                                 } else {
 281                                         if (!TrueStatement.ResolveUnreachable (ec, true))
 282                                                 return false;
 283                                         TrueStatement = null;
 284
 285                                         if ((FalseStatement != null) &&
 286                                             !FalseStatement.Resolve (ec))
 287                                                 return false;
 288                                 }
 289
 290                                 return true;
 291                         }
 292                 skip:
 293                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
 294
 295                         ok &= TrueStatement.Resolve (ec);
 296
 297                         is_true_ret = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 298
 299                         ec.CurrentBranching.CreateSibling ();
 300
 301                         if (FalseStatement != null)
 302                                 ok &= FalseStatement.Resolve (ec);
 303
 304                         ec.EndFlowBranching ();
 305
 306                         Report.Debug (1, "END IF BLOCK", loc);
 307
 308                         return ok;
 309                 }
 310
 311                 protected override void DoEmit (EmitContext ec)
 312                 {
 313                         ILGenerator ig = ec.ig;
 314                         Label false_target = ig.DefineLabel ();
 315                         Label end;
 316
 317                         //
 318                         // If we're a boolean constant, Resolve() already
 319                         // eliminated dead code for us.
 320                         //
 321                         Constant c = expr as Constant;
 322                         if (c != null){
 323                                 c.EmitSideEffect (ec);
 324
 325                                 if (!c.IsDefaultValue)
 326                                         TrueStatement.Emit (ec);
 327                                 else if (FalseStatement != null)
 328                                         FalseStatement.Emit (ec);
 329
 330                                 return;
 331                         }
 332
 333                         expr.EmitBranchable (ec, false_target, false);
 334
 335                         TrueStatement.Emit (ec);
 336
 337                         if (FalseStatement != null){
 338                                 bool branch_emitted = false;
 339
 340                                 end = ig.DefineLabel ();
 341                                 if (!is_true_ret){
 342                                         ig.Emit (OpCodes.Br, end);
 343                                         branch_emitted = true;
 344                                 }
 345
 346                                 ig.MarkLabel (false_target);
 347                                 FalseStatement.Emit (ec);
 348
 349                                 if (branch_emitted)
 350                                         ig.MarkLabel (end);
 351                         } else {
 352                                 ig.MarkLabel (false_target);
 353                         }
 354                 }
 355
 356                 protected override void CloneTo (CloneContext clonectx, Statement t)
 357                 {
 358                         If target = (If) t;
 359
 360                         target.expr = expr.Clone (clonectx);
 361                         target.TrueStatement = TrueStatement.Clone (clonectx);
 362                         if (FalseStatement != null)
 363                                 target.FalseStatement = FalseStatement.Clone (clonectx);
 364                 }
 365         }
 366
 367         public class Do : Statement {
 368                 public Expression expr;
 369                 public Statement  EmbeddedStatement;
 370
 371                 public Do (Statement statement, Expression bool_expr, Location l)
 372                 {
 373                         expr = bool_expr;
 374                         EmbeddedStatement = statement;
 375                         loc = l;
 376                 }
 377
 378                 public override bool Resolve (EmitContext ec)
 379                 {
 380                         bool ok = true;
 381
 382                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 383
 384                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 385
 386                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 387                         if (!EmbeddedStatement.Resolve (ec))
 388                                 ok = false;
 389                         ec.EndFlowBranching ();
 390
 391                         if (ec.CurrentBranching.CurrentUsageVector.IsUnreachable && !was_unreachable)
 392                                 Report.Warning (162, 2, expr.Location, "Unreachable code detected");
 393
 394                         expr = Expression.ResolveBoolean (ec, expr, loc);
 395                         if (expr == null)
 396                                 ok = false;
 397                         else if (expr is Constant){
 398                                 bool infinite = !((Constant) expr).IsDefaultValue;
 399                                 if (infinite)
 400                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 401                         }
 402
 403                         ec.EndFlowBranching ();
 404
 405                         return ok;
 406                 }
 407
 408                 protected override void DoEmit (EmitContext ec)
 409                 {
 410                         ILGenerator ig = ec.ig;
 411                         Label loop = ig.DefineLabel ();
 412                         Label old_begin = ec.LoopBegin;
 413                         Label old_end = ec.LoopEnd;
 414
 415                         ec.LoopBegin = ig.DefineLabel ();
 416                         ec.LoopEnd = ig.DefineLabel ();
 417
 418                         ig.MarkLabel (loop);
 419                         EmbeddedStatement.Emit (ec);
 420                         ig.MarkLabel (ec.LoopBegin);
 421
 422                         //
 423                         // Dead code elimination
 424                         //
 425                         if (expr is Constant){
 426                                 bool res = !((Constant) expr).IsDefaultValue;
 427
 428                                 expr.EmitSideEffect (ec);
 429                                 if (res)
 430                                         ec.ig.Emit (OpCodes.Br, loop);
 431                         } else
 432                                 expr.EmitBranchable (ec, loop, true);
 433
 434                         ig.MarkLabel (ec.LoopEnd);
 435
 436                         ec.LoopBegin = old_begin;
 437                         ec.LoopEnd = old_end;
 438                 }
 439
 440                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 441                 {
 442                         expr.MutateHoistedGenericType (storey);
 443                         EmbeddedStatement.MutateHoistedGenericType (storey);
 444                 }
 445
 446                 protected override void CloneTo (CloneContext clonectx, Statement t)
 447                 {
 448                         Do target = (Do) t;
 449
 450                         target.EmbeddedStatement = EmbeddedStatement.Clone (clonectx);
 451                         target.expr = expr.Clone (clonectx);
 452                 }
 453         }
 454
 455         public class While : Statement {
 456                 public Expression expr;
 457                 public Statement Statement;
 458                 bool infinite, empty;
 459
 460                 public While (Expression bool_expr, Statement statement, Location l)
 461                 {
 462                         this.expr = bool_expr;
 463                         Statement = statement;
 464                         loc = l;
 465                 }
 466
 467                 public override bool Resolve (EmitContext ec)
 468                 {
 469                         bool ok = true;
 470
 471                         expr = Expression.ResolveBoolean (ec, expr, loc);
 472                         if (expr == null)
 473                                 return false;
 474
 475                         //
 476                         // Inform whether we are infinite or not
 477                         //
 478                         if (expr is Constant){
 479                                 bool value = !((Constant) expr).IsDefaultValue;
 480
 481                                 if (value == false){
 482                                         if (!Statement.ResolveUnreachable (ec, true))
 483                                                 return false;
 484                                         empty = true;
 485                                         return true;
 486                                 } else
 487                                         infinite = true;
 488                         }
 489
 490                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 491                         if (!infinite)
 492                                 ec.CurrentBranching.CreateSibling ();
 493
 494                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 495                         if (!Statement.Resolve (ec))
 496                                 ok = false;
 497                         ec.EndFlowBranching ();
 498
 499                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 500                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 501
 502                         ec.EndFlowBranching ();
 503
 504                         return ok;
 505                 }
 506
 507                 protected override void DoEmit (EmitContext ec)
 508                 {
 509                         if (empty) {
 510                                 expr.EmitSideEffect (ec);
 511                                 return;
 512                         }
 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 Constant){
 525                                 // expr is 'true', since the 'empty' case above handles the 'false' case
 526                                 ig.MarkLabel (ec.LoopBegin);
 527                                 expr.EmitSideEffect (ec);
 528                                 Statement.Emit (ec);
 529                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 530
 531                                 //
 532                                 // Inform that we are infinite (ie, `we return'), only
 533                                 // if we do not `break' inside the code.
 534                                 //
 535                                 ig.MarkLabel (ec.LoopEnd);
 536                         } else {
 537                                 Label while_loop = ig.DefineLabel ();
 538
 539                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 540                                 ig.MarkLabel (while_loop);
 541
 542                                 Statement.Emit (ec);
 543
 544                                 ig.MarkLabel (ec.LoopBegin);
 545                                 ec.Mark (loc, true);
 546
 547                                 expr.EmitBranchable (ec, while_loop, true);
 548
 549                                 ig.MarkLabel (ec.LoopEnd);
 550                         }
 551
 552                         ec.LoopBegin = old_begin;
 553                         ec.LoopEnd = old_end;
 554                 }
 555
 556                 public override void Emit (EmitContext ec)
 557                 {
 558                         DoEmit (ec);
 559                 }
 560
 561                 protected override void CloneTo (CloneContext clonectx, Statement t)
 562                 {
 563                         While target = (While) t;
 564
 565                         target.expr = expr.Clone (clonectx);
 566                         target.Statement = Statement.Clone (clonectx);
 567                 }
 568
 569                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 570                 {
 571                         expr.MutateHoistedGenericType (storey);
 572                         Statement.MutateHoistedGenericType (storey);
 573                 }
 574         }
 575
 576         public class For : Statement {
 577                 Expression Test;
 578                 Statement InitStatement;
 579                 Statement Increment;
 580                 public Statement Statement;
 581                 bool infinite, empty;
 582
 583                 public For (Statement init_statement,
 584                             Expression test,
 585                             Statement increment,
 586                             Statement statement,
 587                             Location l)
 588                 {
 589                         InitStatement = init_statement;
 590                         Test = test;
 591                         Increment = increment;
 592                         Statement = statement;
 593                         loc = l;
 594                 }
 595
 596                 public override bool Resolve (EmitContext ec)
 597                 {
 598                         bool ok = true;
 599
 600                         if (InitStatement != null){
 601                                 if (!InitStatement.Resolve (ec))
 602                                         ok = false;
 603                         }
 604
 605                         if (Test != null){
 606                                 Test = Expression.ResolveBoolean (ec, Test, loc);
 607                                 if (Test == null)
 608                                         ok = false;
 609                                 else if (Test is Constant){
 610                                         bool value = !((Constant) Test).IsDefaultValue;
 611
 612                                         if (value == false){
 613                                                 if (!Statement.ResolveUnreachable (ec, true))
 614                                                         return false;
 615                                                 if ((Increment != null) &&
 616                                                     !Increment.ResolveUnreachable (ec, false))
 617                                                         return false;
 618                                                 empty = true;
 619                                                 return true;
 620                                         } else
 621                                                 infinite = true;
 622                                 }
 623                         } else
 624                                 infinite = true;
 625
 626                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 627                         if (!infinite)
 628                                 ec.CurrentBranching.CreateSibling ();
 629
 630                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 631
 632                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 633                         if (!Statement.Resolve (ec))
 634                                 ok = false;
 635                         ec.EndFlowBranching ();
 636
 637                         if (Increment != null){
 638                                 if (ec.CurrentBranching.CurrentUsageVector.IsUnreachable) {
 639                                         if (!Increment.ResolveUnreachable (ec, !was_unreachable))
 640                                                 ok = false;
 641                                 } else {
 642                                         if (!Increment.Resolve (ec))
 643                                                 ok = false;
 644                                 }
 645                         }
 646
 647                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 648                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 649
 650                         ec.EndFlowBranching ();
 651
 652                         return ok;
 653                 }
 654
 655                 protected override void DoEmit (EmitContext ec)
 656                 {
 657                         if (InitStatement != null && InitStatement != EmptyStatement.Value)
 658                                 InitStatement.Emit (ec);
 659
 660                         if (empty) {
 661                                 Test.EmitSideEffect (ec);
 662                                 return;
 663                         }
 664
 665                         ILGenerator ig = ec.ig;
 666                         Label old_begin = ec.LoopBegin;
 667                         Label old_end = ec.LoopEnd;
 668                         Label loop = ig.DefineLabel ();
 669                         Label test = ig.DefineLabel ();
 670
 671                         ec.LoopBegin = ig.DefineLabel ();
 672                         ec.LoopEnd = ig.DefineLabel ();
 673
 674                         ig.Emit (OpCodes.Br, test);
 675                         ig.MarkLabel (loop);
 676                         Statement.Emit (ec);
 677
 678                         ig.MarkLabel (ec.LoopBegin);
 679                         if (Increment != EmptyStatement.Value)
 680                                 Increment.Emit (ec);
 681
 682                         ig.MarkLabel (test);
 683                         //
 684                         // If test is null, there is no test, and we are just
 685                         // an infinite loop
 686                         //
 687                         if (Test != null){
 688                                 //
 689                                 // The Resolve code already catches the case for
 690                                 // Test == Constant (false) so we know that
 691                                 // this is true
 692                                 //
 693                                 if (Test is Constant) {
 694                                         Test.EmitSideEffect (ec);
 695                                         ig.Emit (OpCodes.Br, loop);
 696                                 } else {
 697                                         Test.EmitBranchable (ec, loop, true);
 698                                 }
 699
 700                         } else
 701                                 ig.Emit (OpCodes.Br, loop);
 702                         ig.MarkLabel (ec.LoopEnd);
 703
 704                         ec.LoopBegin = old_begin;
 705                         ec.LoopEnd = old_end;
 706                 }
 707
 708                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 709                 {
 710                         if (InitStatement != null)
 711                                 InitStatement.MutateHoistedGenericType (storey);
 712                         if (Test != null)
 713                                 Test.MutateHoistedGenericType (storey);
 714                         if (Increment != null)
 715                                 Increment.MutateHoistedGenericType (storey);
 716
 717                         Statement.MutateHoistedGenericType (storey);
 718                 }
 719
 720                 protected override void CloneTo (CloneContext clonectx, Statement t)
 721                 {
 722                         For target = (For) t;
 723
 724                         if (InitStatement != null)
 725                                 target.InitStatement = InitStatement.Clone (clonectx);
 726                         if (Test != null)
 727                                 target.Test = Test.Clone (clonectx);
 728                         if (Increment != null)
 729                                 target.Increment = Increment.Clone (clonectx);
 730                         target.Statement = Statement.Clone (clonectx);
 731                 }
 732         }
 733
 734         public class StatementExpression : Statement {
 735                 ExpressionStatement expr;
 736
 737                 public StatementExpression (ExpressionStatement expr)
 738                 {
 739                         this.expr = expr;
 740                         loc = expr.Location;
 741                 }
 742
 743                 public override bool Resolve (EmitContext ec)
 744                 {
 745                         if (expr != null)
 746                                 expr = expr.ResolveStatement (ec);
 747                         return expr != null;
 748                 }
 749
 750                 protected override void DoEmit (EmitContext ec)
 751                 {
 752                         expr.EmitStatement (ec);
 753                 }
 754
 755                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 756                 {
 757                         expr.MutateHoistedGenericType (storey);
 758                 }
 759
 760                 public override string ToString ()
 761                 {
 762                         return "StatementExpression (" + expr + ")";
 763                 }
 764
 765                 protected override void CloneTo (CloneContext clonectx, Statement t)
 766                 {
 767                         StatementExpression target = (StatementExpression) t;
 768
 769                         target.expr = (ExpressionStatement) expr.Clone (clonectx);
 770                 }
 771         }
 772
 773         // A 'return' or a 'yield break'
 774         public abstract class ExitStatement : Statement
 775         {
 776                 protected bool unwind_protect;
 777                 protected abstract bool DoResolve (EmitContext ec);
 778
 779                 public virtual void Error_FinallyClause ()
 780                 {
 781                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 782                 }
 783
 784                 public sealed override bool Resolve (EmitContext ec)
 785                 {
 786                         if (!DoResolve (ec))
 787                                 return false;
 788
 789                         unwind_protect = ec.CurrentBranching.AddReturnOrigin (ec.CurrentBranching.CurrentUsageVector, this);
 790                         if (unwind_protect)
 791                                 ec.NeedReturnLabel ();
 792                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 793                         return true;
 794                 }
 795         }
 796
 797         /// <summary>
 798         ///   Implements the return statement
 799         /// </summary>
 800         public class Return : ExitStatement {
 801                 protected Expression Expr;
 802                 public Return (Expression expr, Location l)
 803                 {
 804                         Expr = expr;
 805                         loc = l;
 806                 }
 807
 808                 protected override bool DoResolve (EmitContext ec)
 809                 {
 810                         if (Expr == null) {
 811                                 if (ec.ReturnType == TypeManager.void_type)
 812                                         return true;
 813
 814                                 Error (126, "An object of a type convertible to `{0}' is required " +
 815                                            "for the return statement",
 816                                            TypeManager.CSharpName (ec.ReturnType));
 817                                 return false;
 818                         }
 819
 820                         AnonymousExpression am = ec.CurrentAnonymousMethod;
 821                         if ((am != null) && am.IsIterator && ec.InIterator) {
 822                                 Report.Error (1622, loc, "Cannot return a value from iterators. Use the yield return " +
 823                                                   "statement to return a value, or yield break to end the iteration");
 824                         }
 825
 826                         if (am == null && ec.ReturnType == TypeManager.void_type) {
 827                                 MemberCore mc = ec.ResolveContext as MemberCore;
 828                                 Report.Error (127, loc, "`{0}': A return keyword must not be followed by any expression when method returns void",
 829                                         mc.GetSignatureForError ());
 830                         }
 831
 832                         Expr = Expr.Resolve (ec);
 833                         if (Expr == null)
 834                                 return false;
 835
 836                         if (Expr.Type != ec.ReturnType) {
 837                                 if (ec.InferReturnType) {
 838                                         //
 839                                         // void cannot be used in contextual return
 840                                         //
 841                                         if (Expr.Type == TypeManager.void_type)
 842                                                 return false;
 843
 844                                         ec.ReturnType = Expr.Type;
 845                                 } else {
 846                                         Expr = Convert.ImplicitConversionRequired (
 847                                                 ec, Expr, ec.ReturnType, loc);
 848
 849                                         if (Expr == null) {
 850                                                 if (am != null) {
 851                                                         Report.Error (1662, loc,
 852                                                                 "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",
 853                                                                 am.ContainerType, am.GetSignatureForError ());
 854                                                 }
 855                                                 return false;
 856                                         }
 857                                 }
 858                         }
 859
 860                         return true;
 861                 }
 862
 863                 protected override void DoEmit (EmitContext ec)
 864                 {
 865                         if (Expr != null) {
 866                                 Expr.Emit (ec);
 867
 868                                 if (unwind_protect)
 869                                         ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 870                         }
 871
 872                         if (unwind_protect)
 873                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 874                         else
 875                                 ec.ig.Emit (OpCodes.Ret);
 876                 }
 877
 878                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 879                 {
 880                         if (Expr != null)
 881                                 Expr.MutateHoistedGenericType (storey);
 882                 }
 883
 884                 protected override void CloneTo (CloneContext clonectx, Statement t)
 885                 {
 886                         Return target = (Return) t;
 887                         // It's null for simple return;
 888                         if (Expr != null)
 889                                 target.Expr = Expr.Clone (clonectx);
 890                 }
 891         }
 892
 893         public class Goto : Statement {
 894                 string target;
 895                 LabeledStatement label;
 896                 bool unwind_protect;
 897
 898                 public override bool Resolve (EmitContext ec)
 899                 {
 900                         int errors = Report.Errors;
 901                         unwind_protect = ec.CurrentBranching.AddGotoOrigin (ec.CurrentBranching.CurrentUsageVector, this);
 902                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 903                         return errors == Report.Errors;
 904                 }
 905
 906                 public Goto (string label, Location l)
 907                 {
 908                         loc = l;
 909                         target = label;
 910                 }
 911
 912                 public string Target {
 913                         get { return target; }
 914                 }
 915
 916                 public void SetResolvedTarget (LabeledStatement label)
 917                 {
 918                         this.label = label;
 919                         label.AddReference ();
 920                 }
 921
 922                 protected override void DoEmit (EmitContext ec)
 923                 {
 924                         if (label == null)
 925                                 throw new InternalErrorException ("goto emitted before target resolved");
 926                         Label l = label.LabelTarget (ec);
 927                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
 928                 }
 929
 930                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 931                 {
 932                 }
 933         }
 934
 935         public class LabeledStatement : Statement {
 936                 string name;
 937                 bool defined;
 938                 bool referenced;
 939                 Label label;
 940                 ILGenerator ig;
 941
 942                 FlowBranching.UsageVector vectors;
 943
 944                 public LabeledStatement (string name, Location l)
 945                 {
 946                         this.name = name;
 947                         this.loc = l;
 948                 }
 949
 950                 public Label LabelTarget (EmitContext ec)
 951                 {
 952                         if (defined)
 953                                 return label;
 954                         ig = ec.ig;
 955                         label = ec.ig.DefineLabel ();
 956                         defined = true;
 957
 958                         return label;
 959                 }
 960
 961                 public string Name {
 962                         get { return name; }
 963                 }
 964
 965                 public bool IsDefined {
 966                         get { return defined; }
 967                 }
 968
 969                 public bool HasBeenReferenced {
 970                         get { return referenced; }
 971                 }
 972
 973                 public FlowBranching.UsageVector JumpOrigins {
 974                         get { return vectors; }
 975                 }
 976
 977                 public void AddUsageVector (FlowBranching.UsageVector vector)
 978                 {
 979                         vector = vector.Clone ();
 980                         vector.Next = vectors;
 981                         vectors = vector;
 982                 }
 983
 984                 public override bool Resolve (EmitContext ec)
 985                 {
 986                         // this flow-branching will be terminated when the surrounding block ends
 987                         ec.StartFlowBranching (this);
 988                         return true;
 989                 }
 990
 991                 protected override void DoEmit (EmitContext ec)
 992                 {
 993                         if (ig != null && ig != ec.ig)
 994                                 throw new InternalErrorException ("cannot happen");
 995                         LabelTarget (ec);
 996                         ec.ig.MarkLabel (label);
 997                 }
 998
 999                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1000                 {
1001                 }
1002
1003                 public void AddReference ()
1004                 {
1005                         referenced = true;
1006                 }
1007         }
1008
1009
1010         /// <summary>
1011         ///   `goto default' statement
1012         /// </summary>
1013         public class GotoDefault : Statement {
1014
1015                 public GotoDefault (Location l)
1016                 {
1017                         loc = l;
1018                 }
1019
1020                 public override bool Resolve (EmitContext ec)
1021                 {
1022                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1023                         return true;
1024                 }
1025
1026                 protected override void DoEmit (EmitContext ec)
1027                 {
1028                         if (ec.Switch == null){
1029                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
1030                                 return;
1031                         }
1032
1033                         if (!ec.Switch.GotDefault){
1034                                 FlowBranchingBlock.Error_UnknownLabel (loc, "default");
1035                                 return;
1036                         }
1037                         ec.ig.Emit (OpCodes.Br, ec.Switch.DefaultTarget);
1038                 }
1039
1040                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1041                 {
1042                 }
1043         }
1044
1045         /// <summary>
1046         ///   `goto case' statement
1047         /// </summary>
1048         public class GotoCase : Statement {
1049                 Expression expr;
1050                 SwitchLabel sl;
1051
1052                 public GotoCase (Expression e, Location l)
1053                 {
1054                         expr = e;
1055                         loc = l;
1056                 }
1057
1058                 public override bool Resolve (EmitContext ec)
1059                 {
1060                         if (ec.Switch == null){
1061                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
1062                                 return false;
1063                         }
1064
1065                         expr = expr.Resolve (ec);
1066                         if (expr == null)
1067                                 return false;
1068
1069                         Constant c = expr as Constant;
1070                         if (c == null) {
1071                                 Error (150, "A constant value is expected");
1072                                 return false;
1073                         }
1074
1075                         Type type = ec.Switch.SwitchType;
1076                         if (!Convert.ImplicitStandardConversionExists (c, type))
1077                                 Report.Warning (469, 2, loc, "The `goto case' value is not implicitly " +
1078                                                 "convertible to type `{0}'", TypeManager.CSharpName (type));
1079
1080                         bool fail = false;
1081                         object val = c.GetValue ();
1082                         if ((val != null) && (c.Type != type) && (c.Type != TypeManager.object_type))
1083                                 val = TypeManager.ChangeType (val, type, out fail);
1084
1085                         if (fail) {
1086                                 Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
1087                                               c.GetSignatureForError (), TypeManager.CSharpName (type));
1088                                 return false;
1089                         }
1090
1091                         if (val == null)
1092                                 val = SwitchLabel.NullStringCase;
1093
1094                         sl = (SwitchLabel) ec.Switch.Elements [val];
1095
1096                         if (sl == null){
1097                                 FlowBranchingBlock.Error_UnknownLabel (loc, "case " +
1098                                         (c.GetValue () == null ? "null" : val.ToString ()));
1099                                 return false;
1100                         }
1101
1102                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1103                         return true;
1104                 }
1105
1106                 protected override void DoEmit (EmitContext ec)
1107                 {
1108                         ec.ig.Emit (OpCodes.Br, sl.GetILLabelCode (ec));
1109                 }
1110
1111                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1112                 {
1113                         expr.MutateHoistedGenericType (storey);
1114                 }
1115
1116                 protected override void CloneTo (CloneContext clonectx, Statement t)
1117                 {
1118                         GotoCase target = (GotoCase) t;
1119
1120                         target.expr = expr.Clone (clonectx);
1121                 }
1122         }
1123
1124         public class Throw : Statement {
1125                 Expression expr;
1126
1127                 public Throw (Expression expr, Location l)
1128                 {
1129                         this.expr = expr;
1130                         loc = l;
1131                 }
1132
1133                 public override bool Resolve (EmitContext ec)
1134                 {
1135                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1136
1137                         if (expr == null)
1138                                 return ec.CurrentBranching.CheckRethrow (loc);
1139
1140                         expr = expr.Resolve (ec);
1141                         if (expr == null)
1142                                 return false;
1143
1144                         ExprClass eclass = expr.eclass;
1145
1146                         if (!(eclass == ExprClass.Variable || eclass == ExprClass.PropertyAccess ||
1147                               eclass == ExprClass.Value || eclass == ExprClass.IndexerAccess)) {
1148                                 expr.Error_UnexpectedKind (ec.DeclContainer, "value, variable, property or indexer access ", loc);
1149                                 return false;
1150                         }
1151
1152                         Type t = expr.Type;
1153
1154                         if ((t != TypeManager.exception_type) &&
1155                             !TypeManager.IsSubclassOf (t, TypeManager.exception_type) &&
1156                             !(expr is NullLiteral)) {
1157                                 Error (155, "The type caught or thrown must be derived from System.Exception");
1158                                 return false;
1159                         }
1160                         return true;
1161                 }
1162
1163                 protected override void DoEmit (EmitContext ec)
1164                 {
1165                         if (expr == null)
1166                                 ec.ig.Emit (OpCodes.Rethrow);
1167                         else {
1168                                 expr.Emit (ec);
1169
1170                                 ec.ig.Emit (OpCodes.Throw);
1171                         }
1172                 }
1173
1174                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1175                 {
1176                         if (expr != null)
1177                                 expr.MutateHoistedGenericType (storey);
1178                 }
1179
1180                 protected override void CloneTo (CloneContext clonectx, Statement t)
1181                 {
1182                         Throw target = (Throw) t;
1183
1184                         if (expr != null)
1185                                 target.expr = expr.Clone (clonectx);
1186                 }
1187         }
1188
1189         public class Break : Statement {
1190
1191                 public Break (Location l)
1192                 {
1193                         loc = l;
1194                 }
1195
1196                 bool unwind_protect;
1197
1198                 public override bool Resolve (EmitContext ec)
1199                 {
1200                         int errors = Report.Errors;
1201                         unwind_protect = ec.CurrentBranching.AddBreakOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
1202                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1203                         return errors == Report.Errors;
1204                 }
1205
1206                 protected override void DoEmit (EmitContext ec)
1207                 {
1208                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopEnd);
1209                 }
1210
1211                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1212                 {
1213                 }
1214
1215                 protected override void CloneTo (CloneContext clonectx, Statement t)
1216                 {
1217                         // nothing needed
1218                 }
1219         }
1220
1221         public class Continue : Statement {
1222
1223                 public Continue (Location l)
1224                 {
1225                         loc = l;
1226                 }
1227
1228                 bool unwind_protect;
1229
1230                 public override bool Resolve (EmitContext ec)
1231                 {
1232                         int errors = Report.Errors;
1233                         unwind_protect = ec.CurrentBranching.AddContinueOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
1234                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1235                         return errors == Report.Errors;
1236                 }
1237
1238                 protected override void DoEmit (EmitContext ec)
1239                 {
1240                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopBegin);
1241                 }
1242
1243                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1244                 {
1245                 }
1246
1247                 protected override void CloneTo (CloneContext clonectx, Statement t)
1248                 {
1249                         // nothing needed.
1250                 }
1251         }
1252
1253         public interface ILocalVariable
1254         {
1255                 void Emit (EmitContext ec);
1256                 void EmitAssign (EmitContext ec);
1257                 void EmitAddressOf (EmitContext ec);
1258         }
1259
1260         public interface IKnownVariable {
1261                 Block Block { get; }
1262                 Location Location { get; }
1263         }
1264
1265         //
1266         // The information about a user-perceived local variable
1267         //
1268         public class LocalInfo : IKnownVariable, ILocalVariable {
1269                 public readonly Expression Type;
1270
1271                 public Type VariableType;
1272                 public readonly string Name;
1273                 public readonly Location Location;
1274                 public readonly Block Block;
1275
1276                 public VariableInfo VariableInfo;
1277                 public HoistedVariable HoistedVariableReference;
1278
1279                 [Flags]
1280                 enum Flags : byte {
1281                         Used = 1,
1282                         ReadOnly = 2,
1283                         Pinned = 4,
1284                         IsThis = 8,
1285                         AddressTaken = 32,
1286                         CompilerGenerated = 64,
1287                         IsConstant = 128
1288                 }
1289
1290                 public enum ReadOnlyContext: byte {
1291                         Using,
1292                         Foreach,
1293                         Fixed
1294                 }
1295
1296                 Flags flags;
1297                 ReadOnlyContext ro_context;
1298                 LocalBuilder builder;
1299
1300                 public LocalInfo (Expression type, string name, Block block, Location l)
1301                 {
1302                         Type = type;
1303                         Name = name;
1304                         Block = block;
1305                         Location = l;
1306                 }
1307
1308                 public LocalInfo (DeclSpace ds, Block block, Location l)
1309                 {
1310                         VariableType = ds.IsGeneric ? ds.CurrentType : ds.TypeBuilder;
1311                         Block = block;
1312                         Location = l;
1313                 }
1314
1315                 public void ResolveVariable (EmitContext ec)
1316                 {
1317                         if (HoistedVariableReference != null)
1318                                 return;
1319
1320                         if (builder == null) {
1321                                 if (Pinned)
1322                                         //
1323                                         // This is needed to compile on both .NET 1.x and .NET 2.x
1324                                         // the later introduced `DeclareLocal (Type t, bool pinned)'
1325                                         //
1326                                         builder = TypeManager.DeclareLocalPinned (ec.ig, VariableType);
1327                                 else
1328                                         builder = ec.ig.DeclareLocal (VariableType);
1329                         }
1330                 }
1331
1332                 public void Emit (EmitContext ec)
1333                 {
1334                         ec.ig.Emit (OpCodes.Ldloc, builder);
1335                 }
1336
1337                 public void EmitAssign (EmitContext ec)
1338                 {
1339                         ec.ig.Emit (OpCodes.Stloc, builder);
1340                 }
1341
1342                 public void EmitAddressOf (EmitContext ec)
1343                 {
1344                         ec.ig.Emit (OpCodes.Ldloca, builder);
1345                 }
1346
1347                 public void EmitSymbolInfo (EmitContext ec, string name)
1348                 {
1349                         if (builder != null)
1350                                 ec.DefineLocalVariable (Name, builder);
1351                 }
1352
1353                 public bool IsThisAssigned (EmitContext ec)
1354                 {
1355                         if (VariableInfo == null)
1356                                 throw new Exception ();
1357
1358                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo))
1359                                 return true;
1360
1361                         return VariableInfo.TypeInfo.IsFullyInitialized (ec.CurrentBranching, VariableInfo, ec.loc);
1362                 }
1363
1364                 public bool IsAssigned (EmitContext ec)
1365                 {
1366                         if (VariableInfo == null)
1367                                 throw new Exception ();
1368
1369                         return !ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo);
1370                 }
1371
1372                 public bool Resolve (EmitContext ec)
1373                 {
1374                         if (VariableType != null)
1375                                 return true;
1376
1377                         TypeExpr texpr = Type.ResolveAsContextualType (ec, false);
1378                         if (texpr == null)
1379                                 return false;
1380
1381                         VariableType = texpr.Type;
1382
1383                         if (TypeManager.IsGenericParameter (VariableType))
1384                                 return true;
1385
1386                         if (VariableType == TypeManager.void_type) {
1387                                 Expression.Error_VoidInvalidInTheContext (Location);
1388                                 return false;
1389                         }
1390
1391                         if (VariableType.IsAbstract && VariableType.IsSealed) {
1392                                 FieldBase.Error_VariableOfStaticClass (Location, Name, VariableType);
1393                                 return false;
1394                         }
1395
1396                         if (VariableType.IsPointer && !ec.InUnsafe)
1397                                 Expression.UnsafeError (Location);
1398
1399                         return true;
1400                 }
1401
1402                 public bool IsConstant {
1403                         get { return (flags & Flags.IsConstant) != 0; }
1404                         set { flags |= Flags.IsConstant; }
1405                 }
1406
1407                 public bool AddressTaken {
1408                         get { return (flags & Flags.AddressTaken) != 0; }
1409                         set { flags |= Flags.AddressTaken; }
1410                 }
1411
1412                 public bool CompilerGenerated {
1413                         get { return (flags & Flags.CompilerGenerated) != 0; }
1414                         set { flags |= Flags.CompilerGenerated; }
1415                 }
1416
1417                 public override string ToString ()
1418                 {
1419                         return String.Format ("LocalInfo ({0},{1},{2},{3})",
1420                                               Name, Type, VariableInfo, Location);
1421                 }
1422
1423                 public bool Used {
1424                         get { return (flags & Flags.Used) != 0; }
1425                         set { flags = value ? (flags | Flags.Used) : (unchecked (flags & ~Flags.Used)); }
1426                 }
1427
1428                 public bool ReadOnly {
1429                         get { return (flags & Flags.ReadOnly) != 0; }
1430                 }
1431
1432                 public void SetReadOnlyContext (ReadOnlyContext context)
1433                 {
1434                         flags |= Flags.ReadOnly;
1435                         ro_context = context;
1436                 }
1437
1438                 public string GetReadOnlyContext ()
1439                 {
1440                         if (!ReadOnly)
1441                                 throw new InternalErrorException ("Variable is not readonly");
1442
1443                         switch (ro_context) {
1444                                 case ReadOnlyContext.Fixed:
1445                                         return "fixed variable";
1446                                 case ReadOnlyContext.Foreach:
1447                                         return "foreach iteration variable";
1448                                 case ReadOnlyContext.Using:
1449                                         return "using variable";
1450                         }
1451                         throw new NotImplementedException ();
1452                 }
1453
1454                 //
1455                 // Whether the variable is pinned, if Pinned the variable has been
1456                 // allocated in a pinned slot with DeclareLocal.
1457                 //
1458                 public bool Pinned {
1459                         get { return (flags & Flags.Pinned) != 0; }
1460                         set { flags = value ? (flags | Flags.Pinned) : (flags & ~Flags.Pinned); }
1461                 }
1462
1463                 public bool IsThis {
1464                         get { return (flags & Flags.IsThis) != 0; }
1465                         set { flags = value ? (flags | Flags.IsThis) : (flags & ~Flags.IsThis); }
1466                 }
1467
1468                 Block IKnownVariable.Block {
1469                         get { return Block; }
1470                 }
1471
1472                 Location IKnownVariable.Location {
1473                         get { return Location; }
1474                 }
1475
1476                 public LocalInfo Clone (CloneContext clonectx)
1477                 {
1478                         //
1479                         // Variables in anonymous block are not resolved yet
1480                         //
1481                         if (VariableType == null)
1482                                 return new LocalInfo (Type.Clone (clonectx), Name, clonectx.LookupBlock (Block), Location);
1483
1484                         //
1485                         // Variables in method block are resolved
1486                         //
1487                         LocalInfo li = new LocalInfo (null, Name, clonectx.LookupBlock (Block), Location);
1488                         li.VariableType = VariableType;
1489                         return li;
1490                 }
1491         }
1492
1493         /// <summary>
1494         ///   Block represents a C# block.
1495         /// </summary>
1496         ///
1497         /// <remarks>
1498         ///   This class is used in a number of places: either to represent
1499         ///   explicit blocks that the programmer places or implicit blocks.
1500         ///
1501         ///   Implicit blocks are used as labels or to introduce variable
1502         ///   declarations.
1503         ///
1504         ///   Top-level blocks derive from Block, and they are called ToplevelBlock
1505         ///   they contain extra information that is not necessary on normal blocks.
1506         /// </remarks>
1507         public class Block : Statement {
1508                 public Block    Parent;
1509                 public readonly Location  StartLocation;
1510                 public Location EndLocation = Location.Null;
1511
1512                 public ExplicitBlock Explicit;
1513                 public ToplevelBlock Toplevel; // TODO: Use Explicit
1514
1515                 [Flags]
1516                 public enum Flags : byte {
1517                         Unchecked = 1,
1518                         BlockUsed = 2,
1519                         VariablesInitialized = 4,
1520                         HasRet = 8,
1521                         IsDestructor = 16,
1522                         Unsafe = 32
1523                 }
1524                 protected Flags flags;
1525
1526                 public bool Unchecked {
1527                         get { return (flags & Flags.Unchecked) != 0; }
1528                         set { flags |= Flags.Unchecked; }
1529                 }
1530
1531                 public bool Unsafe {
1532                         get { return (flags & Flags.Unsafe) != 0; }
1533                         set { flags |= Flags.Unsafe; }
1534                 }
1535
1536                 //
1537                 // The statements in this block
1538                 //
1539                 protected ArrayList statements;
1540
1541                 //
1542                 // An array of Blocks.  We keep track of children just
1543                 // to generate the local variable declarations.
1544                 //
1545                 // Statements and child statements are handled through the
1546                 // statements.
1547                 //
1548                 ArrayList children;
1549
1550                 //
1551                 // Labels.  (label, block) pairs.
1552                 //
1553                 HybridDictionary labels;
1554
1555                 //
1556                 // Keeps track of (name, type) pairs
1557                 //
1558                 IDictionary variables;
1559
1560                 //
1561                 // Keeps track of constants
1562                 HybridDictionary constants;
1563
1564                 //
1565                 // Temporary variables.
1566                 //
1567                 ArrayList temporary_variables;
1568
1569                 //
1570                 // If this is a switch section, the enclosing switch block.
1571                 //
1572                 Block switch_block;
1573
1574                 ArrayList scope_initializers;
1575
1576                 ArrayList anonymous_children;
1577
1578                 protected static int id;
1579
1580                 int this_id;
1581
1582                 int assignable_slots;
1583                 bool unreachable_shown;
1584                 bool unreachable;
1585
1586                 public Block (Block parent)
1587                         : this (parent, (Flags) 0, Location.Null, Location.Null)
1588                 { }
1589
1590                 public Block (Block parent, Flags flags)
1591                         : this (parent, flags, Location.Null, Location.Null)
1592                 { }
1593
1594                 public Block (Block parent, Location start, Location end)
1595                         : this (parent, (Flags) 0, start, end)
1596                 { }
1597
1598                 public Block (Block parent, Flags flags, Location start, Location end)
1599                 {
1600                         if (parent != null) {
1601                                 parent.AddChild (this);
1602
1603                                 // the appropriate constructors will fixup these fields
1604                                 Toplevel = parent.Toplevel;
1605                                 Explicit = parent.Explicit;
1606                         }
1607
1608                         this.Parent = parent;
1609                         this.flags = flags;
1610                         this.StartLocation = start;
1611                         this.EndLocation = end;
1612                         this.loc = start;
1613                         this_id = id++;
1614                         statements = new ArrayList (4);
1615                 }
1616
1617                 public Block CreateSwitchBlock (Location start)
1618                 {
1619                         // FIXME: should this be implicit?
1620                         Block new_block = new ExplicitBlock (this, start, start);
1621                         new_block.switch_block = this;
1622                         return new_block;
1623                 }
1624
1625                 public int ID {
1626                         get { return this_id; }
1627                 }
1628
1629                 public IDictionary Variables {
1630                         get {
1631                                 if (variables == null)
1632                                         variables = new ListDictionary ();
1633                                 return variables;
1634                         }
1635                 }
1636
1637                 void AddChild (Block b)
1638                 {
1639                         if (children == null)
1640                                 children = new ArrayList (1);
1641
1642                         children.Add (b);
1643                 }
1644
1645                 public void SetEndLocation (Location loc)
1646                 {
1647                         EndLocation = loc;
1648                 }
1649
1650                 protected static void Error_158 (string name, Location loc)
1651                 {
1652                         Report.Error (158, loc, "The label `{0}' shadows another label " +
1653                                       "by the same name in a contained scope", name);
1654                 }
1655
1656                 /// <summary>
1657                 ///   Adds a label to the current block.
1658                 /// </summary>
1659                 ///
1660                 /// <returns>
1661                 ///   false if the name already exists in this block. true
1662                 ///   otherwise.
1663                 /// </returns>
1664                 ///
1665                 public bool AddLabel (LabeledStatement target)
1666                 {
1667                         if (switch_block != null)
1668                                 return switch_block.AddLabel (target);
1669
1670                         string name = target.Name;
1671
1672                         Block cur = this;
1673                         while (cur != null) {
1674                                 LabeledStatement s = cur.DoLookupLabel (name);
1675                                 if (s != null) {
1676                                         Report.SymbolRelatedToPreviousError (s.loc, s.Name);
1677                                         Report.Error (140, target.loc, "The label `{0}' is a duplicate", name);
1678                                         return false;
1679                                 }
1680
1681                                 if (this == Explicit)
1682                                         break;
1683
1684                                 cur = cur.Parent;
1685                         }
1686
1687                         while (cur != null) {
1688                                 if (cur.DoLookupLabel (name) != null) {
1689                                         Error_158 (name, target.loc);
1690                                         return false;
1691                                 }
1692
1693                                 if (children != null) {
1694                                         foreach (Block b in children) {
1695                                                 LabeledStatement s = b.DoLookupLabel (name);
1696                                                 if (s == null)
1697                                                         continue;
1698
1699                                                 Report.SymbolRelatedToPreviousError (s.loc, s.Name);
1700                                                 Error_158 (name, target.loc);
1701                                                 return false;
1702                                         }
1703                                 }
1704
1705                                 cur = cur.Parent;
1706                         }
1707
1708                         Toplevel.CheckError158 (name, target.loc);
1709
1710                         if (labels == null)
1711                                 labels = new HybridDictionary();
1712
1713                         labels.Add (name, target);
1714                         return true;
1715                 }
1716
1717                 public LabeledStatement LookupLabel (string name)
1718                 {
1719                         LabeledStatement s = DoLookupLabel (name);
1720                         if (s != null)
1721                                 return s;
1722
1723                         if (children == null)
1724                                 return null;
1725
1726                         foreach (Block child in children) {
1727                                 if (Explicit != child.Explicit)
1728                                         continue;
1729
1730                                 s = child.LookupLabel (name);
1731                                 if (s != null)
1732                                         return s;
1733                         }
1734
1735                         return null;
1736                 }
1737
1738                 LabeledStatement DoLookupLabel (string name)
1739                 {
1740                         if (switch_block != null)
1741                                 return switch_block.LookupLabel (name);
1742
1743                         if (labels != null)
1744                                 if (labels.Contains (name))
1745                                         return ((LabeledStatement) labels [name]);
1746
1747                         return null;
1748                 }
1749
1750                 public bool CheckInvariantMeaningInBlock (string name, Expression e, Location loc)
1751                 {
1752                         Block b = this;
1753                         IKnownVariable kvi = b.Explicit.GetKnownVariable (name);
1754                         while (kvi == null) {
1755                                 b = b.Explicit.Parent;
1756                                 if (b == null)
1757                                         return true;
1758                                 kvi = b.Explicit.GetKnownVariable (name);
1759                         }
1760
1761                         if (kvi.Block == b)
1762                                 return true;
1763
1764                         // Is kvi.Block nested inside 'b'
1765                         if (b.Explicit != kvi.Block.Explicit) {
1766                                 //
1767                                 // If a variable by the same name it defined in a nested block of this
1768                                 // block, we violate the invariant meaning in a block.
1769                                 //
1770                                 if (b == this) {
1771                                         Report.SymbolRelatedToPreviousError (kvi.Location, name);
1772                                         Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", name);
1773                                         return false;
1774                                 }
1775
1776                                 //
1777                                 // It's ok if the definition is in a nested subblock of b, but not
1778                                 // nested inside this block -- a definition in a sibling block
1779                                 // should not affect us.
1780                                 //
1781                                 return true;
1782                         }
1783
1784                         //
1785                         // Block 'b' and kvi.Block are the same textual block.
1786                         // However, different variables are extant.
1787                         //
1788                         // Check if the variable is in scope in both blocks.  We use
1789                         // an indirect check that depends on AddVariable doing its
1790                         // part in maintaining the invariant-meaning-in-block property.
1791                         //
1792                         if (e is VariableReference || (e is Constant && b.GetLocalInfo (name) != null))
1793                                 return true;
1794
1795                         //
1796                         // Even though we detected the error when the name is used, we
1797                         // treat it as if the variable declaration was in error.
1798                         //
1799                         Report.SymbolRelatedToPreviousError (loc, name);
1800                         Error_AlreadyDeclared (kvi.Location, name, "parent or current");
1801                         return false;
1802                 }
1803
1804                 public LocalInfo AddVariable (Expression type, string name, Location l)
1805                 {
1806                         LocalInfo vi = GetLocalInfo (name);
1807                         if (vi != null) {
1808                                 Report.SymbolRelatedToPreviousError (vi.Location, name);
1809                                 if (Explicit == vi.Block.Explicit)
1810                                         Error_AlreadyDeclared (l, name, null);
1811                                 else
1812                                         Error_AlreadyDeclared (l, name, "parent");
1813                                 return null;
1814                         }
1815
1816                         ToplevelParameterInfo pi = Toplevel.GetParameterInfo (name);
1817                         if (pi != null) {
1818                                 Report.SymbolRelatedToPreviousError (pi.Location, name);
1819                                 Error_AlreadyDeclared (loc, name,
1820                                         pi.Block == Toplevel ? "method argument" : "parent or current");
1821                                 return null;
1822                         }
1823
1824                         if (Toplevel.GenericMethod != null) {
1825                                 foreach (TypeParameter tp in Toplevel.GenericMethod.CurrentTypeParameters) {
1826                                         if (tp.Name == name) {
1827                                                 Report.SymbolRelatedToPreviousError (tp);
1828                                                 Error_AlreadyDeclaredTypeParameter (loc, name);
1829                                                 return null;
1830                                         }
1831                                 }
1832                         }
1833
1834                         IKnownVariable kvi = Explicit.GetKnownVariable (name);
1835                         if (kvi != null) {
1836                                 Report.SymbolRelatedToPreviousError (kvi.Location, name);
1837                                 Error_AlreadyDeclared (l, name, "child");
1838                                 return null;
1839                         }
1840
1841                         vi = new LocalInfo (type, name, this, l);
1842                         AddVariable (vi);
1843
1844                         if ((flags & Flags.VariablesInitialized) != 0)
1845                                 throw new InternalErrorException ("block has already been resolved");
1846
1847                         return vi;
1848                 }
1849
1850                 protected virtual void AddVariable (LocalInfo li)
1851                 {
1852                         Variables.Add (li.Name, li);
1853                         Explicit.AddKnownVariable (li.Name, li);
1854                 }
1855
1856                 protected virtual void Error_AlreadyDeclared (Location loc, string var, string reason)
1857                 {
1858                         if (reason == null) {
1859                                 Error_AlreadyDeclared (loc, var);
1860                                 return;
1861                         }
1862
1863                         Report.Error (136, loc, "A local variable named `{0}' cannot be declared " +
1864                                       "in this scope because it would give a different meaning " +
1865                                       "to `{0}', which is already used in a `{1}' scope " +
1866                                       "to denote something else", var, reason);
1867                 }
1868
1869                 protected virtual void Error_AlreadyDeclared (Location loc, string name)
1870                 {
1871                         Report.Error (128, loc,
1872                                 "A local variable named `{0}' is already defined in this scope", name);
1873                 }
1874
1875                 protected virtual void Error_AlreadyDeclaredTypeParameter (Location loc, string name)
1876                 {
1877                         GenericMethod.Error_ParameterNameCollision (loc, name, "local variable");
1878                 }
1879
1880                 public bool AddConstant (Expression type, string name, Expression value, Location l)
1881                 {
1882                         if (AddVariable (type, name, l) == null)
1883                                 return false;
1884
1885                         if (constants == null)
1886                                 constants = new HybridDictionary();
1887
1888                         constants.Add (name, value);
1889
1890                         // A block is considered used if we perform an initialization in a local declaration, even if it is constant.
1891                         Use ();
1892                         return true;
1893                 }
1894
1895                 static int next_temp_id = 0;
1896
1897                 public LocalInfo AddTemporaryVariable (TypeExpr te, Location loc)
1898                 {
1899                         Report.Debug (64, "ADD TEMPORARY", this, Toplevel, loc);
1900
1901                         if (temporary_variables == null)
1902                                 temporary_variables = new ArrayList ();
1903
1904                         int id = ++next_temp_id;
1905                         string name = "$s_" + id.ToString ();
1906
1907                         LocalInfo li = new LocalInfo (te, name, this, loc);
1908                         li.CompilerGenerated = true;
1909                         temporary_variables.Add (li);
1910                         return li;
1911                 }
1912
1913                 public LocalInfo GetLocalInfo (string name)
1914                 {
1915                         for (Block b = this; b != null; b = b.Parent) {
1916                                 if (b.variables != null) {
1917                                         LocalInfo ret = b.variables [name] as LocalInfo;
1918                                         if (ret != null)
1919                                                 return ret;
1920                                 }
1921                         }
1922                         return null;
1923                 }
1924
1925                 public Expression GetVariableType (string name)
1926                 {
1927                         LocalInfo vi = GetLocalInfo (name);
1928                         return vi == null ? null : vi.Type;
1929                 }
1930
1931                 public Expression GetConstantExpression (string name)
1932                 {
1933                         for (Block b = this; b != null; b = b.Parent) {
1934                                 if (b.constants != null) {
1935                                         Expression ret = b.constants [name] as Expression;
1936                                         if (ret != null)
1937                                                 return ret;
1938                                 }
1939                         }
1940                         return null;
1941                 }
1942
1943                 //
1944                 // It should be used by expressions which require to
1945                 // register a statement during resolve process.
1946                 //
1947                 public void AddScopeStatement (StatementExpression s)
1948                 {
1949                         if (scope_initializers == null)
1950                                 scope_initializers = new ArrayList ();
1951
1952                         scope_initializers.Add (s);
1953                 }
1954
1955                 public void AddStatement (Statement s)
1956                 {
1957                         statements.Add (s);
1958                         flags |= Flags.BlockUsed;
1959                 }
1960
1961                 public bool Used {
1962                         get { return (flags & Flags.BlockUsed) != 0; }
1963                 }
1964
1965                 public void Use ()
1966                 {
1967                         flags |= Flags.BlockUsed;
1968                 }
1969
1970                 public bool HasRet {
1971                         get { return (flags & Flags.HasRet) != 0; }
1972                 }
1973
1974                 public bool IsDestructor {
1975                         get { return (flags & Flags.IsDestructor) != 0; }
1976                 }
1977
1978                 public void SetDestructor ()
1979                 {
1980                         flags |= Flags.IsDestructor;
1981                 }
1982
1983                 public int AssignableSlots {
1984                         get {
1985                                 if ((flags & Flags.VariablesInitialized) == 0)
1986                                         throw new Exception ("Variables have not been initialized yet");
1987                                 return assignable_slots;
1988                         }
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                         if (variables != null){
2099                                 foreach (LocalInfo vi in variables.Values)
2100                                         vi.ResolveVariable (ec);
2101                         }
2102
2103                         if (temporary_variables != null) {
2104                                 for (int i = 0; i < temporary_variables.Count; i++)
2105                                         ((LocalInfo)temporary_variables[i]).ResolveVariable(ec);
2106                         }
2107
2108                         if (children != null) {
2109                                 for (int i = 0; i < children.Count; i++)
2110                                         ((Block)children[i]).EmitMeta(ec);
2111                         }
2112                 }
2113
2114                 void UsageWarning ()
2115                 {
2116                         if (variables == null || Report.WarningLevel < 3)
2117                                 return;
2118
2119                         foreach (DictionaryEntry de in variables) {
2120                                 LocalInfo vi = (LocalInfo) de.Value;
2121
2122                                 if (!vi.Used) {
2123                                         string name = (string) de.Key;
2124
2125                                         // vi.VariableInfo can be null for 'catch' variables
2126                                         if (vi.VariableInfo != null && vi.VariableInfo.IsEverAssigned)
2127                                                 Report.Warning (219, 3, vi.Location, "The variable `{0}' is assigned but its value is never used", name);
2128                                         else
2129                                                 Report.Warning (168, 3, vi.Location, "The variable `{0}' is declared but never used", name);
2130                                 }
2131                         }
2132                 }
2133
2134                 private void CheckPossibleMistakenEmptyStatement (Statement s)
2135                 {
2136                         Statement body;
2137
2138                         // Some statements are wrapped by a Block. Since
2139                         // others' internal could be changed, here I treat
2140                         // them as possibly wrapped by Block equally.
2141                         Block b = s as Block;
2142                         if (b != null && b.statements.Count == 1)
2143                                 s = (Statement) b.statements [0];
2144
2145                         if (s is Lock)
2146                                 body = ((Lock) s).Statement;
2147                         else if (s is For)
2148                                 body = ((For) s).Statement;
2149                         else if (s is Foreach)
2150                                 body = ((Foreach) s).Statement;
2151                         else if (s is While)
2152                                 body = ((While) s).Statement;
2153                         else if (s is Fixed)
2154                                 body = ((Fixed) s).Statement;
2155                         else if (s is Using)
2156                                 body = ((Using) s).EmbeddedStatement;
2157                         else if (s is UsingTemporary)
2158                                 body = ((UsingTemporary) s).Statement;
2159                         else
2160                                 return;
2161
2162                         if (body == null || body is EmptyStatement)
2163                                 Report.Warning (642, 3, s.loc, "Possible mistaken empty statement");
2164                 }
2165
2166                 public override bool Resolve (EmitContext ec)
2167                 {
2168                         Block prev_block = ec.CurrentBlock;
2169                         bool ok = true;
2170
2171                         int errors = Report.Errors;
2172
2173                         ec.CurrentBlock = this;
2174                         ec.StartFlowBranching (this);
2175
2176                         Report.Debug (4, "RESOLVE BLOCK", StartLocation, ec.CurrentBranching);
2177
2178                         //
2179                         // This flag is used to notate nested statements as unreachable from the beginning of this block.
2180                         // For the purposes of this resolution, it doesn't matter that the whole block is unreachable
2181                         // from the beginning of the function.  The outer Resolve() that detected the unreachability is
2182                         // responsible for handling the situation.
2183                         //
2184                         int statement_count = statements.Count;
2185                         for (int ix = 0; ix < statement_count; ix++){
2186                                 Statement s = (Statement) statements [ix];
2187                                 // Check possible empty statement (CS0642)
2188                                 if (Report.WarningLevel >= 3 &&
2189                                         ix + 1 < statement_count &&
2190                                                 statements [ix + 1] is Block)
2191                                         CheckPossibleMistakenEmptyStatement (s);
2192
2193                                 //
2194                                 // Warn if we detect unreachable code.
2195                                 //
2196                                 if (unreachable) {
2197                                         if (s is EmptyStatement)
2198                                                 continue;
2199
2200                                         if (s is Block)
2201                                                 ((Block) s).unreachable = true;
2202
2203                                         if (!unreachable_shown && !(s is LabeledStatement)) {
2204                                                 Report.Warning (162, 2, s.loc, "Unreachable code detected");
2205                                                 unreachable_shown = true;
2206                                         }
2207                                 }
2208
2209                                 //
2210                                 // Note that we're not using ResolveUnreachable() for unreachable
2211                                 // statements here.  ResolveUnreachable() creates a temporary
2212                                 // flow branching and kills it afterwards.  This leads to problems
2213                                 // if you have two unreachable statements where the first one
2214                                 // assigns a variable and the second one tries to access it.
2215                                 //
2216
2217                                 if (!s.Resolve (ec)) {
2218                                         ok = false;
2219                                         if (ec.IsInProbingMode)
2220                                                 break;
2221
2222                                         statements [ix] = EmptyStatement.Value;
2223                                         continue;
2224                                 }
2225
2226                                 if (unreachable && !(s is LabeledStatement) && !(s is Block))
2227                                         statements [ix] = EmptyStatement.Value;
2228
2229                                 unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
2230                                 if (unreachable && s is LabeledStatement)
2231                                         throw new InternalErrorException ("should not happen");
2232                         }
2233
2234                         Report.Debug (4, "RESOLVE BLOCK DONE", StartLocation,
2235                                       ec.CurrentBranching, statement_count);
2236
2237                         while (ec.CurrentBranching is FlowBranchingLabeled)
2238                                 ec.EndFlowBranching ();
2239
2240                         bool flow_unreachable = ec.EndFlowBranching ();
2241
2242                         ec.CurrentBlock = prev_block;
2243
2244                         if (flow_unreachable)
2245                                 flags |= Flags.HasRet;
2246
2247                         // If we're a non-static `struct' constructor which doesn't have an
2248                         // initializer, then we must initialize all of the struct's fields.
2249                         if (this == Toplevel && !Toplevel.IsThisAssigned (ec) && !flow_unreachable)
2250                                 ok = false;
2251
2252                         if ((labels != null) && (Report.WarningLevel >= 2)) {
2253                                 foreach (LabeledStatement label in labels.Values)
2254                                         if (!label.HasBeenReferenced)
2255                                                 Report.Warning (164, 2, label.loc, "This label has not been referenced");
2256                         }
2257
2258                         if (ok && errors == Report.Errors)
2259                                 UsageWarning ();
2260
2261                         return ok;
2262                 }
2263
2264                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
2265                 {
2266                         unreachable_shown = true;
2267                         unreachable = true;
2268
2269                         if (warn)
2270                                 Report.Warning (162, 2, loc, "Unreachable code detected");
2271
2272                         ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
2273                         bool ok = Resolve (ec);
2274                         ec.KillFlowBranching ();
2275
2276                         return ok;
2277                 }
2278
2279                 protected override void DoEmit (EmitContext ec)
2280                 {
2281                         for (int ix = 0; ix < statements.Count; ix++){
2282                                 Statement s = (Statement) statements [ix];
2283                                 s.Emit (ec);
2284                         }
2285                 }
2286
2287                 public override void Emit (EmitContext ec)
2288                 {
2289                         Block prev_block = ec.CurrentBlock;
2290                         ec.CurrentBlock = this;
2291
2292                         if (scope_initializers != null) {
2293                                 SymbolWriter.OpenCompilerGeneratedBlock (ec.ig);
2294
2295                                 bool omit_debug_info = ec.OmitDebuggingInfo;
2296                                 ec.OmitDebuggingInfo = true;
2297                                 foreach (StatementExpression s in scope_initializers)
2298                                         s.Emit (ec);
2299                                 ec.OmitDebuggingInfo = omit_debug_info;
2300
2301                                 SymbolWriter.CloseCompilerGeneratedBlock (ec.ig);
2302                         }
2303
2304                         ec.Mark (StartLocation, true);
2305                         DoEmit (ec);
2306
2307                         ec.CurrentBlock = prev_block;
2308                 }
2309
2310                 protected virtual void EmitSymbolInfo (EmitContext ec)
2311                 {
2312                         if (variables != null) {
2313                                 foreach (DictionaryEntry de in variables) {
2314                                         string name = (string) de.Key;
2315                                         LocalInfo vi = (LocalInfo) de.Value;
2316
2317                                         vi.EmitSymbolInfo (ec, name);
2318                                 }
2319                         }
2320                 }
2321
2322                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
2323                 {
2324                         MutateVariables (storey);
2325
2326                         foreach (Statement s in statements)
2327                                 s.MutateHoistedGenericType (storey);
2328                 }
2329
2330                 void MutateVariables (AnonymousMethodStorey storey)
2331                 {
2332                         if (variables != null) {
2333                                 foreach (LocalInfo vi in variables.Values) {
2334                                         vi.VariableType = storey.MutateType (vi.VariableType);
2335                                 }
2336                         }
2337
2338                         if (temporary_variables != null) {
2339                                 foreach (LocalInfo vi in temporary_variables)
2340                                         vi.VariableType = storey.MutateType (vi.VariableType);
2341                         }
2342                 }
2343
2344                 public override string ToString ()
2345                 {
2346                         return String.Format ("{0} ({1}:{2})", GetType (),ID, StartLocation);
2347                 }
2348
2349                 protected override void CloneTo (CloneContext clonectx, Statement t)
2350                 {
2351                         Block target = (Block) t;
2352
2353                         clonectx.AddBlockMap (this, target);
2354
2355                         //target.Toplevel = (ToplevelBlock) clonectx.LookupBlock (Toplevel);
2356                         target.Explicit = (ExplicitBlock) clonectx.LookupBlock (Explicit);
2357                         if (Parent != null)
2358                                 target.Parent = clonectx.RemapBlockCopy (Parent);
2359
2360                         if (variables != null){
2361                                 target.variables = new Hashtable ();
2362
2363                                 foreach (DictionaryEntry de in variables){
2364                                         LocalInfo newlocal = ((LocalInfo) de.Value).Clone (clonectx);
2365                                         target.variables [de.Key] = newlocal;
2366                                         clonectx.AddVariableMap ((LocalInfo) de.Value, newlocal);
2367                                 }
2368                         }
2369
2370                         target.statements = new ArrayList (statements.Count);
2371                         foreach (Statement s in statements)
2372                                 target.statements.Add (s.Clone (clonectx));
2373
2374                         if (target.children != null){
2375                                 target.children = new ArrayList (children.Count);
2376                                 foreach (Block b in children){
2377                                         target.children.Add (clonectx.LookupBlock (b));
2378                                 }
2379                         }
2380
2381                         //
2382                         // TODO: labels, switch_block, constants (?), anonymous_children
2383                         //
2384                 }
2385         }
2386
2387         public class ExplicitBlock : Block {
2388                 HybridDictionary known_variables;
2389                 protected AnonymousMethodStorey am_storey;
2390
2391                 public ExplicitBlock (Block parent, Location start, Location end)
2392                         : this (parent, (Flags) 0, start, end)
2393                 {
2394                 }
2395
2396                 public ExplicitBlock (Block parent, Flags flags, Location start, Location end)
2397                         : base (parent, flags, start, end)
2398                 {
2399                         this.Explicit = this;
2400                 }
2401
2402                 // <summary>
2403                 //   Marks a variable with name @name as being used in this or a child block.
2404                 //   If a variable name has been used in a child block, it's illegal to
2405                 //   declare a variable with the same name in the current block.
2406                 // </summary>
2407                 internal void AddKnownVariable (string name, IKnownVariable info)
2408                 {
2409                         if (known_variables == null)
2410                                 known_variables = new HybridDictionary();
2411
2412                         known_variables [name] = info;
2413
2414                         if (Parent != null)
2415                                 Parent.Explicit.AddKnownVariable (name, info);
2416                 }
2417
2418                 public AnonymousMethodStorey AnonymousMethodStorey {
2419                         get { return am_storey; }
2420                 }
2421
2422                 //
2423                 // Creates anonymous method storey in current block
2424                 //
2425                 public AnonymousMethodStorey CreateAnonymousMethodStorey (EmitContext ec)
2426                 {
2427                         //
2428                         // When referencing a variable in iterator storey from children anonymous method
2429                         //
2430                         if (Toplevel.am_storey is IteratorStorey) {
2431                                 ec.CurrentAnonymousMethod.AddStoreyReference (Toplevel.am_storey);
2432                                 return Toplevel.am_storey;
2433                         }
2434
2435                         //
2436                         // An iterator has only 1 storey block
2437                         //
2438                         if (ec.CurrentIterator != null)
2439                             return ec.CurrentIterator.Storey;
2440
2441                         if (am_storey == null) {
2442                                 MemberBase mc = ec.ResolveContext as MemberBase;
2443                                 GenericMethod gm = mc == null ? null : mc.GenericMethod;
2444
2445                                 //
2446                                 // Create anonymous method storey for this block
2447                                 //
2448                                 am_storey = new AnonymousMethodStorey (this, ec.TypeContainer, mc, gm, "AnonStorey");
2449                         }
2450
2451                         //
2452                         // Creates a link between this block and the anonymous method
2453                         //
2454                         // An anonymous method can reference variables from any outer block, but they are
2455                         // hoisted in their own ExplicitBlock. When more than one block is referenced we
2456                         // need to create another link between those variable storeys
2457                         //
2458                         ec.CurrentAnonymousMethod.AddStoreyReference (am_storey);
2459                         return am_storey;
2460                 }
2461
2462                 public override void Emit (EmitContext ec)
2463                 {
2464                         if (am_storey != null)
2465                                 am_storey.EmitHoistedVariables (ec);
2466
2467                         bool emit_debug_info = SymbolWriter.HasSymbolWriter;
2468                         bool is_lexical_block = Parent != null && !(am_storey is IteratorStorey);
2469                         if (emit_debug_info && is_lexical_block)
2470                                 ec.BeginScope ();
2471
2472                         base.Emit (ec);
2473
2474                         if (emit_debug_info) {
2475                                 EmitSymbolInfo (ec);
2476                                 if (is_lexical_block)
2477                                         ec.EndScope ();
2478                         }
2479                 }
2480
2481                 public override void EmitMeta (EmitContext ec)
2482                 {
2483                         base.EmitMeta (ec);
2484
2485                         //
2486                         // It has to be done when all storey references are resolved
2487                         //
2488                         if (am_storey != null && am_storey.HasHoistedVariables)
2489                                 am_storey.DefineMembers ();
2490                 }
2491
2492                 protected override void EmitSymbolInfo (EmitContext ec)
2493                 {
2494                         if (am_storey != null)
2495                                 SymbolWriter.DefineScopeVariable (am_storey.ID);
2496
2497                         base.EmitSymbolInfo (ec);
2498                 }
2499
2500                 internal IKnownVariable GetKnownVariable (string name)
2501                 {
2502                         return known_variables == null ? null : (IKnownVariable) known_variables [name];
2503                 }
2504
2505                 public void PropagateStoreyReference (AnonymousMethodStorey s)
2506                 {
2507                         if (Parent != null && am_storey != s) {
2508                                 if (am_storey != null)
2509                                         am_storey.AddParentStoreyReference (s);
2510
2511                                 Parent.Explicit.PropagateStoreyReference (s);
2512                         }
2513                 }
2514
2515                 public override bool Resolve (EmitContext ec)
2516                 {
2517                         bool ok = base.Resolve (ec);
2518
2519                         //
2520                         // Define an anonymous method storey when this block has hoisted variables
2521                         //
2522                         if (am_storey != null && am_storey.HasHoistedVariables) {
2523                                 am_storey.DefineType ();
2524                                 am_storey.DefineMembers ();
2525                         }
2526
2527                         return ok;
2528                 }
2529
2530                 protected override void CloneTo (CloneContext clonectx, Statement t)
2531                 {
2532                         ExplicitBlock target = (ExplicitBlock) t;
2533                         target.known_variables = null;
2534                         base.CloneTo (clonectx, t);
2535                 }
2536         }
2537
2538         public class ToplevelParameterInfo : IKnownVariable {
2539                 public readonly ToplevelBlock Block;
2540                 public readonly int Index;
2541                 public VariableInfo VariableInfo;
2542
2543                 Block IKnownVariable.Block {
2544                         get { return Block; }
2545                 }
2546                 public Parameter Parameter {
2547                         get { return Block.Parameters [Index]; }
2548                 }
2549                 public Location Location {
2550                         get { return Parameter.Location; }
2551                 }
2552
2553                 public ToplevelParameterInfo (ToplevelBlock block, int idx)
2554                 {
2555                         this.Block = block;
2556                         this.Index = idx;
2557                 }
2558         }
2559
2560         //
2561         // A toplevel block contains extra information, the split is done
2562         // only to separate information that would otherwise bloat the more
2563         // lightweight Block.
2564         //
2565         // In particular, this was introduced when the support for Anonymous
2566         // Methods was implemented.
2567         //
2568         public class ToplevelBlock : ExplicitBlock {
2569                 GenericMethod generic;
2570                 FlowBranchingToplevel top_level_branching;
2571                 Parameters parameters;
2572                 ToplevelParameterInfo[] parameter_info;
2573                 LocalInfo this_variable;
2574
2575                 public HoistedVariable HoistedThisVariable;
2576
2577                 //
2578                 // The parameters for the block.
2579                 //
2580                 public Parameters Parameters {
2581                         get { return parameters; }
2582                 }
2583
2584                 public GenericMethod GenericMethod {
2585                         get { return generic; }
2586                 }
2587
2588                 public ToplevelBlock Container {
2589                         get { return Parent == null ? null : Parent.Toplevel; }
2590                 }
2591
2592                 public ToplevelBlock (Block parent, Parameters parameters, Location start) :
2593                         this (parent, (Flags) 0, parameters, start)
2594                 {
2595                 }
2596
2597                 public ToplevelBlock (Block parent, Parameters parameters, GenericMethod generic, Location start) :
2598                         this (parent, parameters, start)
2599                 {
2600                         this.generic = generic;
2601                 }
2602
2603                 public ToplevelBlock (Parameters parameters, Location start) :
2604                         this (null, (Flags) 0, parameters, start)
2605                 {
2606                 }
2607
2608                 ToplevelBlock (Flags flags, Parameters parameters, Location start) :
2609                         this (null, flags, parameters, start)
2610                 {
2611                 }
2612
2613                 // We use 'Parent' to hook up to the containing block, but don't want to register the current block as a child.
2614                 // So, we use a two-stage setup -- first pass a null parent to the base constructor, and then override 'Parent'.
2615                 public ToplevelBlock (Block parent, Flags flags, Parameters parameters, Location start) :
2616                         base (null, flags, start, Location.Null)
2617                 {
2618                         this.Toplevel = this;
2619
2620                         this.parameters = parameters == null ? Parameters.EmptyReadOnlyParameters : parameters;
2621                         this.Parent = parent;
2622                         if (parent != null)
2623                                 parent.AddAnonymousChild (this);
2624
2625                         if (this.parameters.Count != 0)
2626                                 ProcessParameters ();
2627                 }
2628
2629                 public ToplevelBlock (Location loc) : this (null, (Flags) 0, null, loc)
2630                 {
2631                 }
2632
2633                 protected override void CloneTo (CloneContext clonectx, Statement t)
2634                 {
2635                         ToplevelBlock target = (ToplevelBlock) t;
2636                         base.CloneTo (clonectx, t);
2637
2638                         if (parameters.Count != 0)
2639                                 target.parameter_info = new ToplevelParameterInfo [parameters.Count];
2640                         for (int i = 0; i < parameters.Count; ++i)
2641                                 target.parameter_info [i] = new ToplevelParameterInfo (target, i);
2642                 }
2643
2644                 public bool CheckError158 (string name, Location loc)
2645                 {
2646                         if (AnonymousChildren != null) {
2647                                 foreach (ToplevelBlock child in AnonymousChildren) {
2648                                         if (!child.CheckError158 (name, loc))
2649                                                 return false;
2650                                 }
2651                         }
2652
2653                         for (ToplevelBlock c = Container; c != null; c = c.Container) {
2654                                 if (!c.DoCheckError158 (name, loc))
2655                                         return false;
2656                         }
2657
2658                         return true;
2659                 }
2660
2661                 public virtual Expression GetTransparentIdentifier (string name)
2662                 {
2663                         return null;
2664                 }
2665
2666                 void ProcessParameters ()
2667                 {
2668                         int n = parameters.Count;
2669                         parameter_info = new ToplevelParameterInfo [n];
2670                         for (int i = 0; i < n; ++i) {
2671                                 parameter_info [i] = new ToplevelParameterInfo (this, i);
2672
2673                                 Parameter p = parameters [i];
2674                                 if (p == null)
2675                                         continue;
2676
2677                                 string name = p.Name;
2678                                 LocalInfo vi = GetLocalInfo (name);
2679                                 if (vi != null) {
2680                                         Report.SymbolRelatedToPreviousError (vi.Location, name);
2681                                         Error_AlreadyDeclared (loc, name, "parent or current");
2682                                         continue;
2683                                 }
2684
2685                                 ToplevelParameterInfo pi = Parent == null ? null : Parent.Toplevel.GetParameterInfo (name);
2686                                 if (pi != null) {
2687                                         Report.SymbolRelatedToPreviousError (pi.Location, name);
2688                                         Error_AlreadyDeclared (loc, name, "parent or current");
2689                                         continue;
2690                                 }
2691
2692                                 AddKnownVariable (name, parameter_info [i]);
2693                         }
2694
2695                         // mark this block as "used" so that we create local declarations in a sub-block
2696                         // FIXME: This appears to uncover a lot of bugs
2697                         //this.Use ();
2698                 }
2699
2700                 bool DoCheckError158 (string name, Location loc)
2701                 {
2702                         LabeledStatement s = LookupLabel (name);
2703                         if (s != null) {
2704                                 Report.SymbolRelatedToPreviousError (s.loc, s.Name);
2705                                 Error_158 (name, loc);
2706                                 return false;
2707                         }
2708
2709                         return true;
2710                 }
2711
2712                 public override Expression CreateExpressionTree (EmitContext ec)
2713                 {
2714                         return ((Statement) statements [0]).CreateExpressionTree (ec);
2715                 }
2716
2717                 //
2718                 // Reformats this block to be top-level iterator block
2719                 //
2720                 public IteratorStorey ChangeToIterator (Iterator iterator, ToplevelBlock source)
2721                 {
2722                         // Create block with original statements
2723                         ExplicitBlock iter_block = new ExplicitBlock (this, flags, StartLocation, EndLocation);
2724
2725                         // TODO: Change to iter_block.statements = statements;
2726                         foreach (Statement stmt in source.statements)
2727                                 iter_block.AddStatement (stmt);
2728
2729                         AddStatement (new IteratorStatement (iterator, iter_block));
2730
2731                         source.statements = new ArrayList (1);
2732                         source.AddStatement (new Return (iterator, iterator.Location));
2733
2734                         IteratorStorey iterator_storey = new IteratorStorey (iterator);
2735                         source.am_storey = iterator_storey;
2736                         return iterator_storey;
2737                 }
2738
2739                 public FlowBranchingToplevel TopLevelBranching {
2740                         get { return top_level_branching; }
2741                 }
2742
2743                 //
2744                 // Returns a `ParameterReference' for the given name, or null if there
2745                 // is no such parameter
2746                 //
2747                 public ParameterReference GetParameterReference (string name, Location loc)
2748                 {
2749                         ToplevelParameterInfo p = GetParameterInfo (name);
2750                         return p == null ? null : new ParameterReference (this, p, loc);
2751                 }
2752
2753                 public ToplevelParameterInfo GetParameterInfo (string name)
2754                 {
2755                         int idx;
2756                         for (ToplevelBlock t = this; t != null; t = t.Container) {
2757                                 Parameter par = t.Parameters.GetParameterByName (name, out idx);
2758                                 if (par != null)
2759                                         return t.parameter_info [idx];
2760                         }
2761                         return null;
2762                 }
2763
2764                 // <summary>
2765                 //   Returns the "this" instance variable of this block.
2766                 //   See AddThisVariable() for more information.
2767                 // </summary>
2768                 public LocalInfo ThisVariable {
2769                         get { return this_variable; }
2770                 }
2771
2772                 // <summary>
2773                 //   This is used by non-static `struct' constructors which do not have an
2774                 //   initializer - in this case, the constructor must initialize all of the
2775                 //   struct's fields.  To do this, we add a "this" variable and use the flow
2776                 //   analysis code to ensure that it's been fully initialized before control
2777                 //   leaves the constructor.
2778                 // </summary>
2779                 public LocalInfo AddThisVariable (DeclSpace ds, Location l)
2780                 {
2781                         if (this_variable == null) {
2782                                 this_variable = new LocalInfo (ds, this, l);
2783                                 this_variable.Used = true;
2784                                 this_variable.IsThis = true;
2785
2786                                 Variables.Add ("this", this_variable);
2787                         }
2788
2789                         return this_variable;
2790                 }
2791
2792                 public bool IsThisAssigned (EmitContext ec)
2793                 {
2794                         return this_variable == null || this_variable.IsThisAssigned (ec);
2795                 }
2796
2797                 public bool ResolveMeta (EmitContext ec, Parameters ip)
2798                 {
2799                         int errors = Report.Errors;
2800                         int orig_count = parameters.Count;
2801
2802                         if (top_level_branching != null)
2803                                 return true;
2804
2805                         if (ip != null)
2806                                 parameters = ip;
2807
2808                         // Assert: orig_count != parameter.Count => orig_count == 0
2809                         if (orig_count != 0 && orig_count != parameters.Count)
2810                                 throw new InternalErrorException ("parameter information mismatch");
2811
2812                         int offset = Parent == null ? 0 : Parent.AssignableSlots;
2813
2814                         for (int i = 0; i < orig_count; ++i) {
2815                                 Parameter.Modifier mod = parameters.ParameterModifier (i);
2816
2817                                 if ((mod & Parameter.Modifier.OUT) != Parameter.Modifier.OUT)
2818                                         continue;
2819
2820                                 VariableInfo vi = new VariableInfo (ip, i, offset);
2821                                 parameter_info [i].VariableInfo = vi;
2822                                 offset += vi.Length;
2823                         }
2824
2825                         ResolveMeta (ec, offset);
2826
2827                         top_level_branching = ec.StartFlowBranching (this);
2828
2829                         return Report.Errors == errors;
2830                 }
2831
2832                 // <summary>
2833                 //   Check whether all `out' parameters have been assigned.
2834                 // </summary>
2835                 public void CheckOutParameters (FlowBranching.UsageVector vector, Location loc)
2836                 {
2837                         if (vector.IsUnreachable)
2838                                 return;
2839
2840                         int n = parameter_info == null ? 0 : parameter_info.Length;
2841
2842                         for (int i = 0; i < n; i++) {
2843                                 VariableInfo var = parameter_info [i].VariableInfo;
2844
2845                                 if (var == null)
2846                                         continue;
2847
2848                                 if (vector.IsAssigned (var, false))
2849                                         continue;
2850
2851                                 Report.Error (177, loc, "The out parameter `{0}' must be assigned to before control leaves the current method",
2852                                         var.Name);
2853                         }
2854                 }
2855
2856                 public override void EmitMeta (EmitContext ec)
2857                 {
2858                         parameters.ResolveVariable ();
2859
2860                         // Avoid declaring an IL variable for this_variable since it is not accessed
2861                         // from the generated IL
2862                         if (this_variable != null)
2863                                 Variables.Remove ("this");
2864                         base.EmitMeta (ec);
2865                 }
2866
2867                 public override void Emit (EmitContext ec)
2868                 {
2869                         base.Emit (ec);
2870                         ec.Mark (EndLocation, true);
2871                 }
2872         }
2873
2874         public class SwitchLabel {
2875                 Expression label;
2876                 object converted;
2877                 Location loc;
2878
2879                 Label il_label;
2880                 bool  il_label_set;
2881                 Label il_label_code;
2882                 bool  il_label_code_set;
2883
2884                 public static readonly object NullStringCase = new object ();
2885
2886                 //
2887                 // if expr == null, then it is the default case.
2888                 //
2889                 public SwitchLabel (Expression expr, Location l)
2890                 {
2891                         label = expr;
2892                         loc = l;
2893                 }
2894
2895                 public Expression Label {
2896                         get {
2897                                 return label;
2898                         }
2899                 }
2900
2901                 public object Converted {
2902                         get {
2903                                 return converted;
2904                         }
2905                 }
2906
2907                 public Label GetILLabel (EmitContext ec)
2908                 {
2909                         if (!il_label_set){
2910                                 il_label = ec.ig.DefineLabel ();
2911                                 il_label_set = true;
2912                         }
2913                         return il_label;
2914                 }
2915
2916                 public Label GetILLabelCode (EmitContext ec)
2917                 {
2918                         if (!il_label_code_set){
2919                                 il_label_code = ec.ig.DefineLabel ();
2920                                 il_label_code_set = true;
2921                         }
2922                         return il_label_code;
2923                 }
2924
2925                 //
2926                 // Resolves the expression, reduces it to a literal if possible
2927                 // and then converts it to the requested type.
2928                 //
2929                 public bool ResolveAndReduce (EmitContext ec, Type required_type, bool allow_nullable)
2930                 {
2931                         Expression e = label.Resolve (ec);
2932
2933                         if (e == null)
2934                                 return false;
2935
2936                         Constant c = e as Constant;
2937                         if (c == null){
2938                                 Report.Error (150, loc, "A constant value is expected");
2939                                 return false;
2940                         }
2941
2942                         if (required_type == TypeManager.string_type && c.GetValue () == null) {
2943                                 converted = NullStringCase;
2944                                 return true;
2945                         }
2946
2947                         if (allow_nullable && c.GetValue () == null) {
2948                                 converted = NullStringCase;
2949                                 return true;
2950                         }
2951
2952                         c = c.ImplicitConversionRequired (required_type, loc);
2953                         if (c == null)
2954                                 return false;
2955
2956                         converted = c.GetValue ();
2957                         return true;
2958                 }
2959
2960                 public void Error_AlreadyOccurs (Type switch_type, SwitchLabel collision_with)
2961                 {
2962                         string label;
2963                         if (converted == null)
2964                                 label = "default";
2965                         else if (converted == NullStringCase)
2966                                 label = "null";
2967                         else if (TypeManager.IsEnumType (switch_type))
2968                                 label = TypeManager.CSharpEnumValue (switch_type, converted);
2969                         else
2970                                 label = converted.ToString ();
2971
2972                         Report.SymbolRelatedToPreviousError (collision_with.loc, null);
2973                         Report.Error (152, loc, "The label `case {0}:' already occurs in this switch statement", label);
2974                 }
2975
2976                 public SwitchLabel Clone (CloneContext clonectx)
2977                 {
2978                         return new SwitchLabel (label.Clone (clonectx), loc);
2979                 }
2980         }
2981
2982         public class SwitchSection {
2983                 // An array of SwitchLabels.
2984                 public readonly ArrayList Labels;
2985                 public readonly Block Block;
2986
2987                 public SwitchSection (ArrayList labels, Block block)
2988                 {
2989                         Labels = labels;
2990                         Block = block;
2991                 }
2992
2993                 public SwitchSection Clone (CloneContext clonectx)
2994                 {
2995                         ArrayList cloned_labels = new ArrayList ();
2996
2997                         foreach (SwitchLabel sl in cloned_labels)
2998                                 cloned_labels.Add (sl.Clone (clonectx));
2999
3000                         return new SwitchSection (cloned_labels, clonectx.LookupBlock (Block));
3001                 }
3002         }
3003
3004         public class Switch : Statement {
3005                 public ArrayList Sections;
3006                 public Expression Expr;
3007
3008                 /// <summary>
3009                 ///   Maps constants whose type type SwitchType to their  SwitchLabels.
3010                 /// </summary>
3011                 public IDictionary Elements;
3012
3013                 /// <summary>
3014                 ///   The governing switch type
3015                 /// </summary>
3016                 public Type SwitchType;
3017
3018                 //
3019                 // Computed
3020                 //
3021                 Label default_target;
3022                 Label null_target;
3023                 Expression new_expr;
3024                 bool is_constant;
3025                 SwitchSection constant_section;
3026                 SwitchSection default_section;
3027
3028 #if GMCS_SOURCE
3029                 //
3030                 // Nullable Types support for GMCS.
3031                 //
3032                 Nullable.Unwrap unwrap;
3033
3034                 protected bool HaveUnwrap {
3035                         get { return unwrap != null; }
3036                 }
3037 #else
3038                 protected bool HaveUnwrap {
3039                         get { return false; }
3040                 }
3041 #endif
3042
3043                 //
3044                 // The types allowed to be implicitly cast from
3045                 // on the governing type
3046                 //
3047                 static Type [] allowed_types;
3048
3049                 public Switch (Expression e, ArrayList sects, Location l)
3050                 {
3051                         Expr = e;
3052                         Sections = sects;
3053                         loc = l;
3054                 }
3055
3056                 public bool GotDefault {
3057                         get {
3058                                 return default_section != null;
3059                         }
3060                 }
3061
3062                 public Label DefaultTarget {
3063                         get {
3064                                 return default_target;
3065                         }
3066                 }
3067
3068                 //
3069                 // Determines the governing type for a switch.  The returned
3070                 // expression might be the expression from the switch, or an
3071                 // expression that includes any potential conversions to the
3072                 // integral types or to string.
3073                 //
3074                 Expression SwitchGoverningType (EmitContext ec, Expression expr)
3075                 {
3076                         Type t = expr.Type;
3077
3078                         if (t == TypeManager.byte_type ||
3079                             t == TypeManager.sbyte_type ||
3080                             t == TypeManager.ushort_type ||
3081                             t == TypeManager.short_type ||
3082                             t == TypeManager.uint32_type ||
3083                             t == TypeManager.int32_type ||
3084                             t == TypeManager.uint64_type ||
3085                             t == TypeManager.int64_type ||
3086                             t == TypeManager.char_type ||
3087                             t == TypeManager.string_type ||
3088                             t == TypeManager.bool_type ||
3089                             TypeManager.IsEnumType (t))
3090                                 return expr;
3091
3092                         if (allowed_types == null){
3093                                 allowed_types = new Type [] {
3094                                         TypeManager.sbyte_type,
3095                                         TypeManager.byte_type,
3096                                         TypeManager.short_type,
3097                                         TypeManager.ushort_type,
3098                                         TypeManager.int32_type,
3099                                         TypeManager.uint32_type,
3100                                         TypeManager.int64_type,
3101                                         TypeManager.uint64_type,
3102                                         TypeManager.char_type,
3103                                         TypeManager.string_type,
3104                                         TypeManager.bool_type
3105                                 };
3106                         }
3107
3108                         //
3109                         // Try to find a *user* defined implicit conversion.
3110                         //
3111                         // If there is no implicit conversion, or if there are multiple
3112                         // conversions, we have to report an error
3113                         //
3114                         Expression converted = null;
3115                         foreach (Type tt in allowed_types){
3116                                 Expression e;
3117
3118                                 e = Convert.ImplicitUserConversion (ec, expr, tt, loc);
3119                                 if (e == null)
3120                                         continue;
3121
3122                                 //
3123                                 // Ignore over-worked ImplicitUserConversions that do
3124                                 // an implicit conversion in addition to the user conversion.
3125                                 //
3126                                 if (!(e is UserCast))
3127                                         continue;
3128
3129                                 if (converted != null){
3130                                         Report.ExtraInformation (
3131                                                 loc,
3132                                                 String.Format ("reason: more than one conversion to an integral type exist for type {0}",
3133                                                                TypeManager.CSharpName (expr.Type)));
3134                                         return null;
3135                                 }
3136
3137                                 converted = e;
3138                         }
3139                         return converted;
3140                 }
3141
3142                 //
3143                 // Performs the basic sanity checks on the switch statement
3144                 // (looks for duplicate keys and non-constant expressions).
3145                 //
3146                 // It also returns a hashtable with the keys that we will later
3147                 // use to compute the switch tables
3148                 //
3149                 bool CheckSwitch (EmitContext ec)
3150                 {
3151                         bool error = false;
3152                         Elements = Sections.Count > 10 ?
3153                                 (IDictionary)new Hashtable () :
3154                                 (IDictionary)new ListDictionary ();
3155
3156                         foreach (SwitchSection ss in Sections){
3157                                 foreach (SwitchLabel sl in ss.Labels){
3158                                         if (sl.Label == null){
3159                                                 if (default_section != null){
3160                                                         sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)default_section.Labels [0]);
3161                                                         error = true;
3162                                                 }
3163                                                 default_section = ss;
3164                                                 continue;
3165                                         }
3166
3167                                         if (!sl.ResolveAndReduce (ec, SwitchType, HaveUnwrap)) {
3168                                                 error = true;
3169                                                 continue;
3170                                         }
3171
3172                                         object key = sl.Converted;
3173                                         try {
3174                                                 Elements.Add (key, sl);
3175                                         } catch (ArgumentException) {
3176                                                 sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)Elements [key]);
3177                                                 error = true;
3178                                         }
3179                                 }
3180                         }
3181                         return !error;
3182                 }
3183
3184                 void EmitObjectInteger (ILGenerator ig, object k)
3185                 {
3186                         if (k is int)
3187                                 IntConstant.EmitInt (ig, (int) k);
3188                         else if (k is Constant) {
3189                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
3190                         }
3191                         else if (k is uint)
3192                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
3193                         else if (k is long)
3194                         {
3195                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
3196                                 {
3197                                         IntConstant.EmitInt (ig, (int) (long) k);
3198                                         ig.Emit (OpCodes.Conv_I8);
3199                                 }
3200                                 else
3201                                         LongConstant.EmitLong (ig, (long) k);
3202                         }
3203                         else if (k is ulong)
3204                         {
3205                                 ulong ul = (ulong) k;
3206                                 if (ul < (1L<<32))
3207                                 {
3208                                         IntConstant.EmitInt (ig, unchecked ((int) ul));
3209                                         ig.Emit (OpCodes.Conv_U8);
3210                                 }
3211                                 else
3212                                 {
3213                                         LongConstant.EmitLong (ig, unchecked ((long) ul));
3214                                 }
3215                         }
3216                         else if (k is char)
3217                                 IntConstant.EmitInt (ig, (int) ((char) k));
3218                         else if (k is sbyte)
3219                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
3220                         else if (k is byte)
3221                                 IntConstant.EmitInt (ig, (int) ((byte) k));
3222                         else if (k is short)
3223                                 IntConstant.EmitInt (ig, (int) ((short) k));
3224                         else if (k is ushort)
3225                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
3226                         else if (k is bool)
3227                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
3228                         else
3229                                 throw new Exception ("Unhandled case");
3230                 }
3231
3232                 // structure used to hold blocks of keys while calculating table switch
3233                 class KeyBlock : IComparable
3234                 {
3235                         public KeyBlock (long _first)
3236                         {
3237                                 first = last = _first;
3238                         }
3239                         public long first;
3240                         public long last;
3241                         public ArrayList element_keys = null;
3242                         // how many items are in the bucket
3243                         public int Size = 1;
3244                         public int Length
3245                         {
3246                                 get { return (int) (last - first + 1); }
3247                         }
3248                         public static long TotalLength (KeyBlock kb_first, KeyBlock kb_last)
3249                         {
3250                                 return kb_last.last - kb_first.first + 1;
3251                         }
3252                         public int CompareTo (object obj)
3253                         {
3254                                 KeyBlock kb = (KeyBlock) obj;
3255                                 int nLength = Length;
3256                                 int nLengthOther = kb.Length;
3257                                 if (nLengthOther == nLength)
3258                                         return (int) (kb.first - first);
3259                                 return nLength - nLengthOther;
3260                         }
3261                 }
3262
3263                 /// <summary>
3264                 /// This method emits code for a lookup-based switch statement (non-string)
3265                 /// Basically it groups the cases into blocks that are at least half full,
3266                 /// and then spits out individual lookup opcodes for each block.
3267                 /// It emits the longest blocks first, and short blocks are just
3268                 /// handled with direct compares.
3269                 /// </summary>
3270                 /// <param name="ec"></param>
3271                 /// <param name="val"></param>
3272                 /// <returns></returns>
3273                 void TableSwitchEmit (EmitContext ec, LocalBuilder val)
3274                 {
3275                         int element_count = Elements.Count;
3276                         object [] element_keys = new object [element_count];
3277                         Elements.Keys.CopyTo (element_keys, 0);
3278                         Array.Sort (element_keys);
3279
3280                         // initialize the block list with one element per key
3281                         ArrayList key_blocks = new ArrayList ();
3282                         foreach (object key in element_keys)
3283                                 key_blocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));
3284
3285                         KeyBlock current_kb;
3286                         // iteratively merge the blocks while they are at least half full
3287                         // there's probably a really cool way to do this with a tree...
3288                         while (key_blocks.Count > 1)
3289                         {
3290                                 ArrayList key_blocks_new = new ArrayList ();
3291                                 current_kb = (KeyBlock) key_blocks [0];
3292                                 for (int ikb = 1; ikb < key_blocks.Count; ikb++)
3293                                 {
3294                                         KeyBlock kb = (KeyBlock) key_blocks [ikb];
3295                                         if ((current_kb.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (current_kb, kb))
3296                                         {
3297                                                 // merge blocks
3298                                                 current_kb.last = kb.last;
3299                                                 current_kb.Size += kb.Size;
3300                                         }
3301                                         else
3302                                         {
3303                                                 // start a new block
3304                                                 key_blocks_new.Add (current_kb);
3305                                                 current_kb = kb;
3306                                         }
3307                                 }
3308                                 key_blocks_new.Add (current_kb);
3309                                 if (key_blocks.Count == key_blocks_new.Count)
3310                                         break;
3311                                 key_blocks = key_blocks_new;
3312                         }
3313
3314                         // initialize the key lists
3315                         foreach (KeyBlock kb in key_blocks)
3316                                 kb.element_keys = new ArrayList ();
3317
3318                         // fill the key lists
3319                         int iBlockCurr = 0;
3320                         if (key_blocks.Count > 0) {
3321                                 current_kb = (KeyBlock) key_blocks [0];
3322                                 foreach (object key in element_keys)
3323                                 {
3324                                         bool next_block = (key is UInt64) ? (ulong) key > (ulong) current_kb.last :
3325                                                 System.Convert.ToInt64 (key) > current_kb.last;
3326                                         if (next_block)
3327                                                 current_kb = (KeyBlock) key_blocks [++iBlockCurr];
3328                                         current_kb.element_keys.Add (key);
3329                                 }
3330                         }
3331
3332                         // sort the blocks so we can tackle the largest ones first
3333                         key_blocks.Sort ();
3334
3335                         // okay now we can start...
3336                         ILGenerator ig = ec.ig;
3337                         Label lbl_end = ig.DefineLabel ();      // at the end ;-)
3338                         Label lbl_default = ig.DefineLabel ();
3339
3340                         Type type_keys = null;
3341                         if (element_keys.Length > 0)
3342                                 type_keys = element_keys [0].GetType ();        // used for conversions
3343
3344                         Type compare_type;
3345
3346                         if (TypeManager.IsEnumType (SwitchType))
3347                                 compare_type = TypeManager.GetEnumUnderlyingType (SwitchType);
3348                         else
3349                                 compare_type = SwitchType;
3350
3351                         for (int iBlock = key_blocks.Count - 1; iBlock >= 0; --iBlock)
3352                         {
3353                                 KeyBlock kb = ((KeyBlock) key_blocks [iBlock]);
3354                                 lbl_default = (iBlock == 0) ? DefaultTarget : ig.DefineLabel ();
3355                                 if (kb.Length <= 2)
3356                                 {
3357                                         foreach (object key in kb.element_keys)
3358                                         {
3359                                                 ig.Emit (OpCodes.Ldloc, val);
3360                                                 EmitObjectInteger (ig, key);
3361                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
3362                                                 ig.Emit (OpCodes.Beq, sl.GetILLabel (ec));
3363                                         }
3364                                 }
3365                                 else
3366                                 {
3367                                         // TODO: if all the keys in the block are the same and there are
3368                                         //       no gaps/defaults then just use a range-check.
3369                                         if (compare_type == TypeManager.int64_type ||
3370                                                 compare_type == TypeManager.uint64_type)
3371                                         {
3372                                                 // TODO: optimize constant/I4 cases
3373
3374                                                 // check block range (could be > 2^31)
3375                                                 ig.Emit (OpCodes.Ldloc, val);
3376                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3377                                                 ig.Emit (OpCodes.Blt, lbl_default);
3378                                                 ig.Emit (OpCodes.Ldloc, val);
3379                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.last, type_keys));
3380                                                 ig.Emit (OpCodes.Bgt, lbl_default);
3381
3382                                                 // normalize range
3383                                                 ig.Emit (OpCodes.Ldloc, val);
3384                                                 if (kb.first != 0)
3385                                                 {
3386                                                         EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3387                                                         ig.Emit (OpCodes.Sub);
3388                                                 }
3389                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
3390                                         }
3391                                         else
3392                                         {
3393                                                 // normalize range
3394                                                 ig.Emit (OpCodes.Ldloc, val);
3395                                                 int first = (int) kb.first;
3396                                                 if (first > 0)
3397                                                 {
3398                                                         IntConstant.EmitInt (ig, first);
3399                                                         ig.Emit (OpCodes.Sub);
3400                                                 }
3401                                                 else if (first < 0)
3402                                                 {
3403                                                         IntConstant.EmitInt (ig, -first);
3404                                                         ig.Emit (OpCodes.Add);
3405                                                 }
3406                                         }
3407
3408                                         // first, build the list of labels for the switch
3409                                         int iKey = 0;
3410                                         int cJumps = kb.Length;
3411                                         Label [] switch_labels = new Label [cJumps];
3412                                         for (int iJump = 0; iJump < cJumps; iJump++)
3413                                         {
3414                                                 object key = kb.element_keys [iKey];
3415                                                 if (System.Convert.ToInt64 (key) == kb.first + iJump)
3416                                                 {
3417                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
3418                                                         switch_labels [iJump] = sl.GetILLabel (ec);
3419                                                         iKey++;
3420                                                 }
3421                                                 else
3422                                                         switch_labels [iJump] = lbl_default;
3423                                         }
3424                                         // emit the switch opcode
3425                                         ig.Emit (OpCodes.Switch, switch_labels);
3426                                 }
3427
3428                                 // mark the default for this block
3429                                 if (iBlock != 0)
3430                                         ig.MarkLabel (lbl_default);
3431                         }
3432
3433                         // TODO: find the default case and emit it here,
3434                         //       to prevent having to do the following jump.
3435                         //       make sure to mark other labels in the default section
3436
3437                         // the last default just goes to the end
3438                         ig.Emit (OpCodes.Br, lbl_default);
3439
3440                         // now emit the code for the sections
3441                         bool found_default = false;
3442                         bool found_null = false;
3443                         foreach (SwitchSection ss in Sections)
3444                         {
3445                                 foreach (SwitchLabel sl in ss.Labels)
3446                                         if (sl.Converted == SwitchLabel.NullStringCase)
3447                                                 found_null = true;
3448                         }
3449
3450                         foreach (SwitchSection ss in Sections)
3451                         {
3452                                 foreach (SwitchLabel sl in ss.Labels)
3453                                 {
3454                                         ig.MarkLabel (sl.GetILLabel (ec));
3455                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3456                                         if (sl.Converted == SwitchLabel.NullStringCase)
3457                                                 ig.MarkLabel (null_target);
3458                                         else if (sl.Label == null) {
3459                                                 ig.MarkLabel (lbl_default);
3460                                                 found_default = true;
3461                                                 if (!found_null)
3462                                                         ig.MarkLabel (null_target);
3463                                         }
3464                                 }
3465                                 ss.Block.Emit (ec);
3466                         }
3467
3468                         if (!found_default) {
3469                                 ig.MarkLabel (lbl_default);
3470                                 if (HaveUnwrap && !found_null) {
3471                                         ig.MarkLabel (null_target);
3472                                 }
3473                         }
3474
3475                         ig.MarkLabel (lbl_end);
3476                 }
3477                 //
3478                 // This simple emit switch works, but does not take advantage of the
3479                 // `switch' opcode.
3480                 // TODO: remove non-string logic from here
3481                 // TODO: binary search strings?
3482                 //
3483                 void SimpleSwitchEmit (EmitContext ec, LocalBuilder val)
3484                 {
3485                         ILGenerator ig = ec.ig;
3486                         Label end_of_switch = ig.DefineLabel ();
3487                         Label next_test = ig.DefineLabel ();
3488                         bool first_test = true;
3489                         bool pending_goto_end = false;
3490                         bool null_marked = false;
3491                         bool null_found;
3492                         int section_count = Sections.Count;
3493
3494                         // TODO: implement switch optimization for string by using Hashtable
3495                         //if (SwitchType == TypeManager.string_type && section_count > 7)
3496                         //      Console.WriteLine ("Switch optimization possible " + loc);
3497
3498                         ig.Emit (OpCodes.Ldloc, val);
3499
3500                         if (Elements.Contains (SwitchLabel.NullStringCase)){
3501                                 ig.Emit (OpCodes.Brfalse, null_target);
3502                         } else
3503                                 ig.Emit (OpCodes.Brfalse, default_target);
3504
3505                         ig.Emit (OpCodes.Ldloc, val);
3506                         ig.Emit (OpCodes.Call, TypeManager.string_isinterned_string);
3507                         ig.Emit (OpCodes.Stloc, val);
3508
3509                         for (int section = 0; section < section_count; section++){
3510                                 SwitchSection ss = (SwitchSection) Sections [section];
3511
3512                                 if (ss == default_section)
3513                                         continue;
3514
3515                                 Label sec_begin = ig.DefineLabel ();
3516
3517                                 ig.Emit (OpCodes.Nop);
3518
3519                                 if (pending_goto_end)
3520                                         ig.Emit (OpCodes.Br, end_of_switch);
3521
3522                                 int label_count = ss.Labels.Count;
3523                                 null_found = false;
3524                                 for (int label = 0; label < label_count; label++){
3525                                         SwitchLabel sl = (SwitchLabel) ss.Labels [label];
3526                                         ig.MarkLabel (sl.GetILLabel (ec));
3527
3528                                         if (!first_test){
3529                                                 ig.MarkLabel (next_test);
3530                                                 next_test = ig.DefineLabel ();
3531                                         }
3532                                         //
3533                                         // If we are the default target
3534                                         //
3535                                         if (sl.Label != null){
3536                                                 object lit = sl.Converted;
3537
3538                                                 if (lit == SwitchLabel.NullStringCase){
3539                                                         null_found = true;
3540                                                         if (label + 1 == label_count)
3541                                                                 ig.Emit (OpCodes.Br, next_test);
3542                                                         continue;
3543                                                 }
3544
3545                                                 ig.Emit (OpCodes.Ldloc, val);
3546                                                 ig.Emit (OpCodes.Ldstr, (string)lit);
3547                                                 if (label_count == 1)
3548                                                         ig.Emit (OpCodes.Bne_Un, next_test);
3549                                                 else {
3550                                                         if (label+1 == label_count)
3551                                                                 ig.Emit (OpCodes.Bne_Un, next_test);
3552                                                         else
3553                                                                 ig.Emit (OpCodes.Beq, sec_begin);
3554                                                 }
3555                                         }
3556                                 }
3557                                 if (null_found) {
3558                                         ig.MarkLabel (null_target);
3559                                         null_marked = true;
3560                                 }
3561                                 ig.MarkLabel (sec_begin);
3562                                 foreach (SwitchLabel sl in ss.Labels)
3563                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3564
3565                                 ss.Block.Emit (ec);
3566                                 pending_goto_end = !ss.Block.HasRet;
3567                                 first_test = false;
3568                         }
3569                         ig.MarkLabel (next_test);
3570                         ig.MarkLabel (default_target);
3571                         if (!null_marked)
3572                                 ig.MarkLabel (null_target);
3573                         if (default_section != null)
3574                                 default_section.Block.Emit (ec);
3575                         ig.MarkLabel (end_of_switch);
3576                 }
3577
3578                 SwitchSection FindSection (SwitchLabel label)
3579                 {
3580                         foreach (SwitchSection ss in Sections){
3581                                 foreach (SwitchLabel sl in ss.Labels){
3582                                         if (label == sl)
3583                                                 return ss;
3584                                 }
3585                         }
3586
3587                         return null;
3588                 }
3589
3590                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
3591                 {
3592                         foreach (SwitchSection ss in Sections)
3593                                 ss.Block.MutateHoistedGenericType (storey);
3594                 }
3595
3596                 public override bool Resolve (EmitContext ec)
3597                 {
3598                         Expr = Expr.Resolve (ec);
3599                         if (Expr == null)
3600                                 return false;
3601
3602                         new_expr = SwitchGoverningType (ec, Expr);
3603
3604 #if GMCS_SOURCE
3605                         if ((new_expr == null) && TypeManager.IsNullableType (Expr.Type)) {
3606                                 unwrap = Nullable.Unwrap.Create (Expr, ec);
3607                                 if (unwrap == null)
3608                                         return false;
3609
3610                                 new_expr = SwitchGoverningType (ec, unwrap);
3611                         }
3612 #endif
3613
3614                         if (new_expr == null){
3615                                 Report.Error (151, loc, "A value of an integral type or string expected for switch");
3616                                 return false;
3617                         }
3618
3619                         // Validate switch.
3620                         SwitchType = new_expr.Type;
3621
3622                         if (RootContext.Version == LanguageVersion.ISO_1 && SwitchType == TypeManager.bool_type) {
3623                                 Report.FeatureIsNotAvailable (loc, "switch expression of boolean type");
3624                                 return false;
3625                         }
3626
3627                         if (!CheckSwitch (ec))
3628                                 return false;
3629
3630                         if (HaveUnwrap)
3631                                 Elements.Remove (SwitchLabel.NullStringCase);
3632
3633                         Switch old_switch = ec.Switch;
3634                         ec.Switch = this;
3635                         ec.Switch.SwitchType = SwitchType;
3636
3637                         Report.Debug (1, "START OF SWITCH BLOCK", loc, ec.CurrentBranching);
3638                         ec.StartFlowBranching (FlowBranching.BranchingType.Switch, loc);
3639
3640                         is_constant = new_expr is Constant;
3641                         if (is_constant) {
3642                                 object key = ((Constant) new_expr).GetValue ();
3643                                 SwitchLabel label = (SwitchLabel) Elements [key];
3644
3645                                 constant_section = FindSection (label);
3646                                 if (constant_section == null)
3647                                         constant_section = default_section;
3648                         }
3649
3650                         bool first = true;
3651                         bool ok = true;
3652                         foreach (SwitchSection ss in Sections){
3653                                 if (!first)
3654                                         ec.CurrentBranching.CreateSibling (
3655                                                 null, FlowBranching.SiblingType.SwitchSection);
3656                                 else
3657                                         first = false;
3658
3659                                 if (is_constant && (ss != constant_section)) {
3660                                         // If we're a constant switch, we're only emitting
3661                                         // one single section - mark all the others as
3662                                         // unreachable.
3663                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
3664                                         if (!ss.Block.ResolveUnreachable (ec, true)) {
3665                                                 ok = false;
3666                                         }
3667                                 } else {
3668                                         if (!ss.Block.Resolve (ec))
3669                                                 ok = false;
3670                                 }
3671                         }
3672
3673                         if (default_section == null)
3674                                 ec.CurrentBranching.CreateSibling (
3675                                         null, FlowBranching.SiblingType.SwitchSection);
3676
3677                         ec.EndFlowBranching ();
3678                         ec.Switch = old_switch;
3679
3680                         Report.Debug (1, "END OF SWITCH BLOCK", loc, ec.CurrentBranching);
3681
3682                         if (TypeManager.string_isinterned_string == null) {
3683                                 TypeManager.string_isinterned_string = TypeManager.GetPredefinedMethod (TypeManager.string_type,
3684                                         "IsInterned", loc, TypeManager.string_type);
3685                         }
3686
3687                         return ok;
3688                 }
3689
3690                 protected override void DoEmit (EmitContext ec)
3691                 {
3692                         ILGenerator ig = ec.ig;
3693
3694                         default_target = ig.DefineLabel ();
3695                         null_target = ig.DefineLabel ();
3696
3697                         // Store variable for comparission purposes
3698                         LocalBuilder value;
3699                         if (HaveUnwrap) {
3700                                 value = ig.DeclareLocal (SwitchType);
3701 #if GMCS_SOURCE
3702                                 unwrap.EmitCheck (ec);
3703                                 ig.Emit (OpCodes.Brfalse, null_target);
3704                                 new_expr.Emit (ec);
3705                                 ig.Emit (OpCodes.Stloc, value);
3706 #endif
3707                         } else if (!is_constant) {
3708                                 value = ig.DeclareLocal (SwitchType);
3709                                 new_expr.Emit (ec);
3710                                 ig.Emit (OpCodes.Stloc, value);
3711                         } else
3712                                 value = null;
3713
3714                         //
3715                         // Setup the codegen context
3716                         //
3717                         Label old_end = ec.LoopEnd;
3718                         Switch old_switch = ec.Switch;
3719
3720                         ec.LoopEnd = ig.DefineLabel ();
3721                         ec.Switch = this;
3722
3723                         // Emit Code.
3724                         if (is_constant) {
3725                                 if (constant_section != null)
3726                                         constant_section.Block.Emit (ec);
3727                         } else if (SwitchType == TypeManager.string_type)
3728                                 SimpleSwitchEmit (ec, value);
3729                         else
3730                                 TableSwitchEmit (ec, value);
3731
3732                         // Restore context state.
3733                         ig.MarkLabel (ec.LoopEnd);
3734
3735                         //
3736                         // Restore the previous context
3737                         //
3738                         ec.LoopEnd = old_end;
3739                         ec.Switch = old_switch;
3740                 }
3741
3742                 protected override void CloneTo (CloneContext clonectx, Statement t)
3743                 {
3744                         Switch target = (Switch) t;
3745
3746                         target.Expr = Expr.Clone (clonectx);
3747                         target.Sections = new ArrayList ();
3748                         foreach (SwitchSection ss in Sections){
3749                                 target.Sections.Add (ss.Clone (clonectx));
3750                         }
3751                 }
3752         }
3753
3754         // A place where execution can restart in an iterator
3755         public abstract class ResumableStatement : Statement
3756         {
3757                 bool prepared;
3758                 protected Label resume_point;
3759
3760                 public Label PrepareForEmit (EmitContext ec)
3761                 {
3762                         if (!prepared) {
3763                                 prepared = true;
3764                                 resume_point = ec.ig.DefineLabel ();
3765                         }
3766                         return resume_point;
3767                 }
3768
3769                 public virtual Label PrepareForDispose (EmitContext ec, Label end)
3770                 {
3771                         return end;
3772                 }
3773                 public virtual void EmitForDispose (EmitContext ec, Iterator iterator, Label end, bool have_dispatcher)
3774                 {
3775                 }
3776         }
3777
3778         // Base class for statements that are implemented in terms of try...finally
3779         public abstract class ExceptionStatement : ResumableStatement
3780         {
3781                 bool code_follows;
3782
3783                 protected abstract void EmitPreTryBody (EmitContext ec);
3784                 protected abstract void EmitTryBody (EmitContext ec);
3785                 protected abstract void EmitFinallyBody (EmitContext ec);
3786
3787                 protected sealed override void DoEmit (EmitContext ec)
3788                 {
3789                         ILGenerator ig = ec.ig;
3790
3791                         EmitPreTryBody (ec);
3792
3793                         if (resume_points != null) {
3794                                 IntConstant.EmitInt (ig, (int) Iterator.State.Running);
3795                                 ig.Emit (OpCodes.Stloc, ec.CurrentIterator.CurrentPC);
3796                         }
3797
3798                         ig.BeginExceptionBlock ();
3799
3800                         if (resume_points != null) {
3801                                 ig.MarkLabel (resume_point);
3802
3803                                 // For normal control flow, we want to fall-through the Switch
3804                                 // So, we use CurrentPC rather than the $PC field, and initialize it to an outside value above
3805                                 ig.Emit (OpCodes.Ldloc, ec.CurrentIterator.CurrentPC);
3806                                 IntConstant.EmitInt (ig, first_resume_pc);
3807                                 ig.Emit (OpCodes.Sub);
3808
3809                                 Label [] labels = new Label [resume_points.Count];
3810                                 for (int i = 0; i < resume_points.Count; ++i)
3811                                         labels [i] = ((ResumableStatement) resume_points [i]).PrepareForEmit (ec);
3812                                 ig.Emit (OpCodes.Switch, labels);
3813                         }
3814
3815                         EmitTryBody (ec);
3816
3817                         ig.BeginFinallyBlock ();
3818
3819                         Label start_finally = ec.ig.DefineLabel ();
3820                         if (resume_points != null) {
3821                                 ig.Emit (OpCodes.Ldloc, ec.CurrentIterator.SkipFinally);
3822                                 ig.Emit (OpCodes.Brfalse_S, start_finally);
3823                                 ig.Emit (OpCodes.Endfinally);
3824                         }
3825
3826                         ig.MarkLabel (start_finally);
3827                         EmitFinallyBody (ec);
3828
3829                         ig.EndExceptionBlock ();
3830                 }
3831
3832                 public void SomeCodeFollows ()
3833                 {
3834                         code_follows = true;
3835                 }
3836
3837                 protected void ResolveReachability (EmitContext ec)
3838                 {
3839                         // System.Reflection.Emit automatically emits a 'leave' at the end of a try clause
3840                         // So, ensure there's some IL code after this statement.
3841                         if (!code_follows && resume_points == null && ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
3842                                 ec.NeedReturnLabel ();
3843
3844                 }
3845
3846                 ArrayList resume_points;
3847                 int first_resume_pc;
3848                 public void AddResumePoint (ResumableStatement stmt, Location loc, int pc)
3849                 {
3850                         if (resume_points == null) {
3851                                 resume_points = new ArrayList ();
3852                                 first_resume_pc = pc;
3853                         }
3854
3855                         if (pc != first_resume_pc + resume_points.Count)
3856                                 throw new InternalErrorException ("missed an intervening AddResumePoint?");
3857
3858                         resume_points.Add (stmt);
3859                 }
3860
3861                 Label dispose_try_block;
3862                 bool prepared_for_dispose, emitted_dispose;
3863                 public override Label PrepareForDispose (EmitContext ec, Label end)
3864                 {
3865                         if (!prepared_for_dispose) {
3866                                 prepared_for_dispose = true;
3867                                 dispose_try_block = ec.ig.DefineLabel ();
3868                         }
3869                         return dispose_try_block;
3870                 }
3871
3872                 public override void EmitForDispose (EmitContext ec, Iterator iterator, Label end, bool have_dispatcher)
3873                 {
3874                         if (emitted_dispose)
3875                                 return;
3876
3877                         emitted_dispose = true;
3878
3879                         ILGenerator ig = ec.ig;
3880
3881                         Label end_of_try = ig.DefineLabel ();
3882
3883                         // Ensure that the only way we can get into this code is through a dispatcher
3884                         if (have_dispatcher)
3885                                 ig.Emit (OpCodes.Br, end);
3886
3887                         ig.BeginExceptionBlock ();
3888
3889                         ig.MarkLabel (dispose_try_block);
3890
3891                         Label [] labels = null;
3892                         for (int i = 0; i < resume_points.Count; ++i) {
3893                                 ResumableStatement s = (ResumableStatement) resume_points [i];
3894                                 Label ret = s.PrepareForDispose (ec, end_of_try);
3895                                 if (ret.Equals (end_of_try) && labels == null)
3896                                         continue;
3897                                 if (labels == null) {
3898                                         labels = new Label [resume_points.Count];
3899                                         for (int j = 0; j < i; ++j)
3900                                                 labels [j] = end_of_try;
3901                                 }
3902                                 labels [i] = ret;
3903                         }
3904
3905                         if (labels != null) {
3906                                 int j;
3907                                 for (j = 1; j < labels.Length; ++j)
3908                                         if (!labels [0].Equals (labels [j]))
3909                                                 break;
3910                                 bool emit_dispatcher = j < labels.Length;
3911
3912                                 if (emit_dispatcher) {
3913                                         //SymbolWriter.StartIteratorDispatcher (ec.ig);
3914                                         ig.Emit (OpCodes.Ldloc, iterator.CurrentPC);
3915                                         IntConstant.EmitInt (ig, first_resume_pc);
3916                                         ig.Emit (OpCodes.Sub);
3917                                         ig.Emit (OpCodes.Switch, labels);
3918                                         //SymbolWriter.EndIteratorDispatcher (ec.ig);
3919                                 }
3920
3921                                 foreach (ResumableStatement s in resume_points)
3922                                         s.EmitForDispose (ec, iterator, end_of_try, emit_dispatcher);
3923                         }
3924
3925                         ig.MarkLabel (end_of_try);
3926
3927                         ig.BeginFinallyBlock ();
3928
3929                         EmitFinallyBody (ec);
3930
3931                         ig.EndExceptionBlock ();
3932                 }
3933         }
3934
3935         public class Lock : ExceptionStatement {
3936                 Expression expr;
3937                 public Statement Statement;
3938                 TemporaryVariable temp;
3939
3940                 public Lock (Expression expr, Statement stmt, Location l)
3941                 {
3942                         this.expr = expr;
3943                         Statement = stmt;
3944                         loc = l;
3945                 }
3946
3947                 public override bool Resolve (EmitContext ec)
3948                 {
3949                         expr = expr.Resolve (ec);
3950                         if (expr == null)
3951                                 return false;
3952
3953                         if (expr.Type.IsValueType){
3954                                 Report.Error (185, loc,
3955                                               "`{0}' is not a reference type as required by the lock statement",
3956                                               TypeManager.CSharpName (expr.Type));
3957                                 return false;
3958                         }
3959
3960                         ec.StartFlowBranching (this);
3961                         bool ok = Statement.Resolve (ec);
3962                         ec.EndFlowBranching ();
3963
3964                         ResolveReachability (ec);
3965
3966                         // Avoid creating libraries that reference the internal
3967                         // mcs NullType:
3968                         Type t = expr.Type;
3969                         if (t == TypeManager.null_type)
3970                                 t = TypeManager.object_type;
3971
3972                         temp = new TemporaryVariable (t, loc);
3973                         temp.Resolve (ec);
3974
3975                         if (TypeManager.void_monitor_enter_object == null || TypeManager.void_monitor_exit_object == null) {
3976                                 Type monitor_type = TypeManager.CoreLookupType ("System.Threading", "Monitor", Kind.Class, true);
3977                                 TypeManager.void_monitor_enter_object = TypeManager.GetPredefinedMethod (
3978                                         monitor_type, "Enter", loc, TypeManager.object_type);
3979                                 TypeManager.void_monitor_exit_object = TypeManager.GetPredefinedMethod (
3980                                         monitor_type, "Exit", loc, TypeManager.object_type);
3981                         }
3982
3983                         return ok;
3984                 }
3985
3986                 protected override void EmitPreTryBody (EmitContext ec)
3987                 {
3988                         ILGenerator ig = ec.ig;
3989
3990                         temp.EmitAssign (ec, expr);
3991                         temp.Emit (ec);
3992                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
3993                 }
3994
3995                 protected override void EmitTryBody (EmitContext ec)
3996                 {
3997                         Statement.Emit (ec);
3998                 }
3999
4000                 protected override void EmitFinallyBody (EmitContext ec)
4001                 {
4002                         temp.Emit (ec);
4003                         ec.ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
4004                 }
4005
4006                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4007                 {
4008                         expr.MutateHoistedGenericType (storey);
4009                         temp.MutateHoistedGenericType (storey);
4010                         Statement.MutateHoistedGenericType (storey);
4011                 }
4012
4013                 protected override void CloneTo (CloneContext clonectx, Statement t)
4014                 {
4015                         Lock target = (Lock) t;
4016
4017                         target.expr = expr.Clone (clonectx);
4018                         target.Statement = Statement.Clone (clonectx);
4019                 }
4020         }
4021
4022         public class Unchecked : Statement {
4023                 public Block Block;
4024
4025                 public Unchecked (Block b)
4026                 {
4027                         Block = b;
4028                         b.Unchecked = true;
4029                 }
4030
4031                 public override bool Resolve (EmitContext ec)
4032                 {
4033                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
4034                                 return Block.Resolve (ec);
4035                 }
4036
4037                 protected override void DoEmit (EmitContext ec)
4038                 {
4039                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
4040                                 Block.Emit (ec);
4041                 }
4042
4043                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4044                 {
4045                         Block.MutateHoistedGenericType (storey);
4046                 }
4047
4048                 protected override void CloneTo (CloneContext clonectx, Statement t)
4049                 {
4050                         Unchecked target = (Unchecked) t;
4051
4052                         target.Block = clonectx.LookupBlock (Block);
4053                 }
4054         }
4055
4056         public class Checked : Statement {
4057                 public Block Block;
4058
4059                 public Checked (Block b)
4060                 {
4061                         Block = b;
4062                         b.Unchecked = false;
4063                 }
4064
4065                 public override bool Resolve (EmitContext ec)
4066                 {
4067                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
4068                                 return Block.Resolve (ec);
4069                 }
4070
4071                 protected override void DoEmit (EmitContext ec)
4072                 {
4073                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
4074                                 Block.Emit (ec);
4075                 }
4076
4077                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4078                 {
4079                         Block.MutateHoistedGenericType (storey);
4080                 }
4081
4082                 protected override void CloneTo (CloneContext clonectx, Statement t)
4083                 {
4084                         Checked target = (Checked) t;
4085
4086                         target.Block = clonectx.LookupBlock (Block);
4087                 }
4088         }
4089
4090         public class Unsafe : Statement {
4091                 public Block Block;
4092
4093                 public Unsafe (Block b)
4094                 {
4095                         Block = b;
4096                         Block.Unsafe = true;
4097                 }
4098
4099                 public override bool Resolve (EmitContext ec)
4100                 {
4101                         using (ec.With (EmitContext.Flags.InUnsafe, true))
4102                                 return Block.Resolve (ec);
4103                 }
4104
4105                 protected override void DoEmit (EmitContext ec)
4106                 {
4107                         using (ec.With (EmitContext.Flags.InUnsafe, true))
4108                                 Block.Emit (ec);
4109                 }
4110
4111                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4112                 {
4113                         Block.MutateHoistedGenericType (storey);
4114                 }
4115
4116                 protected override void CloneTo (CloneContext clonectx, Statement t)
4117                 {
4118                         Unsafe target = (Unsafe) t;
4119
4120                         target.Block = clonectx.LookupBlock (Block);
4121                 }
4122         }
4123
4124         //
4125         // Fixed statement
4126         //
4127         public class Fixed : Statement {
4128                 Expression type;
4129                 ArrayList declarators;
4130                 Statement statement;
4131                 Type expr_type;
4132                 Emitter[] data;
4133                 bool has_ret;
4134
4135                 abstract class Emitter
4136                 {
4137                         protected LocalInfo vi;
4138                         protected Expression converted;
4139
4140                         protected Emitter (Expression expr, LocalInfo li)
4141                         {
4142                                 converted = expr;
4143                                 vi = li;
4144                         }
4145
4146                         public abstract void Emit (EmitContext ec);
4147                         public abstract void EmitExit (EmitContext ec);
4148                 }
4149
4150                 class ExpressionEmitter : Emitter {
4151                         public ExpressionEmitter (Expression converted, LocalInfo li) :
4152                                 base (converted, li)
4153                         {
4154                         }
4155
4156                         public override void Emit (EmitContext ec) {
4157                                 //
4158                                 // Store pointer in pinned location
4159                                 //
4160                                 converted.Emit (ec);
4161                                 vi.EmitAssign (ec);
4162                         }
4163
4164                         public override void EmitExit (EmitContext ec)
4165                         {
4166                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
4167                                 ec.ig.Emit (OpCodes.Conv_U);
4168                                 vi.EmitAssign (ec);
4169                         }
4170                 }
4171
4172                 class StringEmitter : Emitter {
4173                         class StringPtr : Expression
4174                         {
4175                                 LocalBuilder b;
4176
4177                                 public StringPtr (LocalBuilder b, Location l)
4178                                 {
4179                                         this.b = b;
4180                                         eclass = ExprClass.Value;
4181                                         type = TypeManager.char_ptr_type;
4182                                         loc = l;
4183                                 }
4184
4185                                 public override Expression CreateExpressionTree (EmitContext ec)
4186                                 {
4187                                         throw new NotSupportedException ("ET");
4188                                 }
4189
4190                                 public override Expression DoResolve (EmitContext ec)
4191                                 {
4192                                         // This should never be invoked, we are born in fully
4193                                         // initialized state.
4194
4195                                         return this;
4196                                 }
4197
4198                                 public override void Emit (EmitContext ec)
4199                                 {
4200                                         if (TypeManager.int_get_offset_to_string_data == null) {
4201                                                 // TODO: Move to resolve !!
4202                                                 TypeManager.int_get_offset_to_string_data = TypeManager.GetPredefinedMethod (
4203                                                         TypeManager.runtime_helpers_type, "get_OffsetToStringData", loc, Type.EmptyTypes);
4204                                         }
4205
4206                                         ILGenerator ig = ec.ig;
4207
4208                                         ig.Emit (OpCodes.Ldloc, b);
4209                                         ig.Emit (OpCodes.Conv_I);
4210                                         ig.Emit (OpCodes.Call, TypeManager.int_get_offset_to_string_data);
4211                                         ig.Emit (OpCodes.Add);
4212                                 }
4213                         }
4214
4215                         LocalBuilder pinned_string;
4216                         Location loc;
4217
4218                         public StringEmitter (Expression expr, LocalInfo li, Location loc):
4219                                 base (expr, li)
4220                         {
4221                                 this.loc = loc;
4222                         }
4223
4224                         public override void Emit (EmitContext ec)
4225                         {
4226                                 ILGenerator ig = ec.ig;
4227                                 pinned_string = TypeManager.DeclareLocalPinned (ig, TypeManager.string_type);
4228
4229                                 converted.Emit (ec);
4230                                 ig.Emit (OpCodes.Stloc, pinned_string);
4231
4232                                 Expression sptr = new StringPtr (pinned_string, loc);
4233                                 converted = Convert.ImplicitConversionRequired (
4234                                         ec, sptr, vi.VariableType, loc);
4235
4236                                 if (converted == null)
4237                                         return;
4238
4239                                 converted.Emit (ec);
4240                                 vi.EmitAssign (ec);
4241                         }
4242
4243                         public override void EmitExit (EmitContext ec)
4244                         {
4245                                 ec.ig.Emit (OpCodes.Ldnull);
4246                                 ec.ig.Emit (OpCodes.Stloc, pinned_string);
4247                         }
4248                 }
4249
4250                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
4251                 {
4252                         this.type = type;
4253                         declarators = decls;
4254                         statement = stmt;
4255                         loc = l;
4256                 }
4257
4258                 public Statement Statement {
4259                         get { return statement; }
4260                 }
4261
4262                 public override bool Resolve (EmitContext ec)
4263                 {
4264                         if (!ec.InUnsafe){
4265                                 Expression.UnsafeError (loc);
4266                                 return false;
4267                         }
4268
4269                         TypeExpr texpr = type.ResolveAsContextualType (ec, false);
4270                         if (texpr == null) {
4271                                 if (type is VarExpr)
4272                                         Report.Error (821, type.Location, "A fixed statement cannot use an implicitly typed local variable");
4273
4274                                 return false;
4275                         }
4276
4277                         expr_type = texpr.Type;
4278
4279                         data = new Emitter [declarators.Count];
4280
4281                         if (!expr_type.IsPointer){
4282                                 Report.Error (209, loc, "The type of locals declared in a fixed statement must be a pointer type");
4283                                 return false;
4284                         }
4285
4286                         int i = 0;
4287                         foreach (Pair p in declarators){
4288                                 LocalInfo vi = (LocalInfo) p.First;
4289                                 Expression e = (Expression) p.Second;
4290
4291                                 vi.VariableInfo.SetAssigned (ec);
4292                                 vi.SetReadOnlyContext (LocalInfo.ReadOnlyContext.Fixed);
4293
4294                                 //
4295                                 // The rules for the possible declarators are pretty wise,
4296                                 // but the production on the grammar is more concise.
4297                                 //
4298                                 // So we have to enforce these rules here.
4299                                 //
4300                                 // We do not resolve before doing the case 1 test,
4301                                 // because the grammar is explicit in that the token &
4302                                 // is present, so we need to test for this particular case.
4303                                 //
4304
4305                                 if (e is Cast){
4306                                         Report.Error (254, loc, "The right hand side of a fixed statement assignment may not be a cast expression");
4307                                         return false;
4308                                 }
4309
4310                                 //
4311                                 // Case 1: & object.
4312                                 //
4313                                 if (e is Unary && ((Unary) e).Oper == Unary.Operator.AddressOf){
4314                                         Expression child = ((Unary) e).Expr;
4315
4316                                         if (child is ParameterReference || child is LocalVariableReference){
4317                                                 Report.Error (
4318                                                         213, loc,
4319                                                         "No need to use fixed statement for parameters or " +
4320                                                         "local variable declarations (address is already " +
4321                                                         "fixed)");
4322                                                 return false;
4323                                         }
4324
4325                                         ec.InFixedInitializer = true;
4326                                         e = e.Resolve (ec);
4327                                         ec.InFixedInitializer = false;
4328                                         if (e == null)
4329                                                 return false;
4330
4331                                         child = ((Unary) e).Expr;
4332
4333                                         if (!TypeManager.VerifyUnManaged (child.Type, loc))
4334                                                 return false;
4335
4336                                         if (!Convert.ImplicitConversionExists (ec, e, expr_type)) {
4337                                                 e.Error_ValueCannotBeConverted (ec, e.Location, expr_type, false);
4338                                                 return false;
4339                                         }
4340
4341                                         data [i] = new ExpressionEmitter (e, vi);
4342                                         i++;
4343
4344                                         continue;
4345                                 }
4346
4347                                 ec.InFixedInitializer = true;
4348                                 e = e.Resolve (ec);
4349                                 ec.InFixedInitializer = false;
4350                                 if (e == null)
4351                                         return false;
4352
4353                                 //
4354                                 // Case 2: Array
4355                                 //
4356                                 if (e.Type.IsArray){
4357                                         Type array_type = TypeManager.GetElementType (e.Type);
4358
4359                                         //
4360                                         // Provided that array_type is unmanaged,
4361                                         //
4362                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
4363                                                 return false;
4364
4365                                         //
4366                                         // and T* is implicitly convertible to the
4367                                         // pointer type given in the fixed statement.
4368                                         //
4369                                         ArrayPtr array_ptr = new ArrayPtr (e, array_type, loc);
4370
4371                                         Expression converted = Convert.ImplicitConversionRequired (
4372                                                 ec, array_ptr, vi.VariableType, loc);
4373                                         if (converted == null)
4374                                                 return false;
4375
4376                                         //
4377                                         // fixed (T* e_ptr = (e == null || e.Length == 0) ? null : converted [0])
4378                                         //
4379                                         converted = new Conditional (new Binary (Binary.Operator.LogicalOr,
4380                                                 new Binary (Binary.Operator.Equality, e, new NullLiteral (loc)),
4381                                                 new Binary (Binary.Operator.Equality, new MemberAccess (e, "Length"), new IntConstant (0, loc))),
4382                                                         NullPointer.Null,
4383                                                         converted);
4384
4385                                         converted = converted.Resolve (ec);
4386
4387                                         data [i] = new ExpressionEmitter (converted, vi);
4388                                         i++;
4389
4390                                         continue;
4391                                 }
4392
4393                                 //
4394                                 // Case 3: string
4395                                 //
4396                                 if (e.Type == TypeManager.string_type){
4397                                         data [i] = new StringEmitter (e, vi, loc);
4398                                         i++;
4399                                         continue;
4400                                 }
4401
4402                                 // Case 4: fixed buffer
4403                                 FixedBufferPtr fixed_buffer_ptr = e as FixedBufferPtr;
4404                                 if (fixed_buffer_ptr != null) {
4405                                         data [i++] = new ExpressionEmitter (fixed_buffer_ptr, vi);
4406                                         continue;
4407                                 }
4408
4409                                 //
4410                                 // For other cases, flag a `this is already fixed expression'
4411                                 //
4412                                 if (e is LocalVariableReference || e is ParameterReference ||
4413                                     Convert.ImplicitConversionExists (ec, e, vi.VariableType)){
4414
4415                                         Report.Error (245, loc, "right hand expression is already fixed, no need to use fixed statement ");
4416                                         return false;
4417                                 }
4418
4419                                 Report.Error (245, loc, "Fixed statement only allowed on strings, arrays or address-of expressions");
4420                                 return false;
4421                         }
4422
4423                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
4424                         bool ok = statement.Resolve (ec);
4425                         bool flow_unreachable = ec.EndFlowBranching ();
4426                         has_ret = flow_unreachable;
4427
4428                         return ok;
4429                 }
4430
4431                 protected override void DoEmit (EmitContext ec)
4432                 {
4433                         for (int i = 0; i < data.Length; i++) {
4434                                 data [i].Emit (ec);
4435                         }
4436
4437                         statement.Emit (ec);
4438
4439                         if (has_ret)
4440                                 return;
4441
4442                         //
4443                         // Clear the pinned variable
4444                         //
4445                         for (int i = 0; i < data.Length; i++) {
4446                                 data [i].EmitExit (ec);
4447                         }
4448                 }
4449
4450                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4451                 {
4452                         // Fixed statement cannot be used inside anonymous methods or lambdas
4453                         throw new NotSupportedException ();
4454                 }
4455
4456                 protected override void CloneTo (CloneContext clonectx, Statement t)
4457                 {
4458                         Fixed target = (Fixed) t;
4459
4460                         target.type = type.Clone (clonectx);
4461                         target.declarators = new ArrayList (declarators.Count);
4462                         foreach (Pair p in declarators) {
4463                                 LocalInfo vi = (LocalInfo) p.First;
4464                                 Expression e = (Expression) p.Second;
4465
4466                                 target.declarators.Add (
4467                                         new Pair (clonectx.LookupVariable (vi), e.Clone (clonectx)));
4468                         }
4469
4470                         target.statement = statement.Clone (clonectx);
4471                 }
4472         }
4473
4474         public class Catch : Statement {
4475                 public readonly string Name;
4476                 public Block  Block;
4477                 public Block  VarBlock;
4478
4479                 Expression type_expr;
4480                 Type type;
4481
4482                 public Catch (Expression type, string name, Block block, Block var_block, Location l)
4483                 {
4484                         type_expr = type;
4485                         Name = name;
4486                         Block = block;
4487                         VarBlock = var_block;
4488                         loc = l;
4489                 }
4490
4491                 public Type CatchType {
4492                         get {
4493                                 return type;
4494                         }
4495                 }
4496
4497                 public bool IsGeneral {
4498                         get {
4499                                 return type_expr == null;
4500                         }
4501                 }
4502
4503                 protected override void DoEmit (EmitContext ec)
4504                 {
4505                         ILGenerator ig = ec.ig;
4506
4507                         if (CatchType != null)
4508                                 ig.BeginCatchBlock (CatchType);
4509                         else
4510                                 ig.BeginCatchBlock (TypeManager.object_type);
4511
4512                         if (VarBlock != null)
4513                                 VarBlock.Emit (ec);
4514
4515                         if (Name != null) {
4516                                 // TODO: Move to resolve
4517                                 LocalVariableReference lvr = new LocalVariableReference (Block, Name, loc);
4518                                 lvr.Resolve (ec);
4519
4520                                 Expression source;
4521                                 if (lvr.IsHoisted) {
4522                                         LocalTemporary lt = new LocalTemporary (lvr.Type);
4523                                         lt.Store (ec);
4524                                         source = lt;
4525                                 } else {
4526                                         // Variable is at the top of the stack
4527                                         source = EmptyExpression.Null;
4528                                 }
4529
4530                                 lvr.EmitAssign (ec, source, false, false);
4531                         } else
4532                                 ig.Emit (OpCodes.Pop);
4533
4534                         Block.Emit (ec);
4535                 }
4536
4537                 public override bool Resolve (EmitContext ec)
4538                 {
4539                         using (ec.With (EmitContext.Flags.InCatch, true)) {
4540                                 if (type_expr != null) {
4541                                         TypeExpr te = type_expr.ResolveAsTypeTerminal (ec, false);
4542                                         if (te == null)
4543                                                 return false;
4544
4545                                         type = te.Type;
4546
4547                                         if (type != TypeManager.exception_type && !TypeManager.IsSubclassOf (type, TypeManager.exception_type)){
4548                                                 Error (155, "The type caught or thrown must be derived from System.Exception");
4549                                                 return false;
4550                                         }
4551                                 } else
4552                                         type = null;
4553
4554                                 if (!Block.Resolve (ec))
4555                                         return false;
4556
4557                                 // Even though VarBlock surrounds 'Block' we resolve it later, so that we can correctly
4558                                 // emit the "unused variable" warnings.
4559                                 if (VarBlock != null)
4560                                         return VarBlock.Resolve (ec);
4561
4562                                 return true;
4563                         }
4564                 }
4565
4566                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4567                 {
4568                         if (type != null)
4569                                 type = storey.MutateType (type);
4570                         if (VarBlock != null)
4571                                 VarBlock.MutateHoistedGenericType (storey);
4572                         Block.MutateHoistedGenericType (storey);
4573                 }
4574
4575                 protected override void CloneTo (CloneContext clonectx, Statement t)
4576                 {
4577                         Catch target = (Catch) t;
4578
4579                         if (type_expr != null)
4580                                 target.type_expr = type_expr.Clone (clonectx);
4581                         if (VarBlock != null)
4582                                 target.VarBlock = clonectx.LookupBlock (VarBlock);
4583                         target.Block = clonectx.LookupBlock (Block);
4584                 }
4585         }
4586
4587         public class TryFinally : ExceptionStatement {
4588                 Statement stmt;
4589                 Block fini;
4590
4591                 public TryFinally (Statement stmt, Block fini, Location l)
4592                 {
4593                         this.stmt = stmt;
4594                         this.fini = fini;
4595                         loc = l;
4596                 }
4597
4598                 public override bool Resolve (EmitContext ec)
4599                 {
4600                         bool ok = true;
4601
4602                         ec.StartFlowBranching (this);
4603
4604                         if (!stmt.Resolve (ec))
4605                                 ok = false;
4606
4607                         if (ok)
4608                                 ec.CurrentBranching.CreateSibling (fini, FlowBranching.SiblingType.Finally);
4609                         using (ec.With (EmitContext.Flags.InFinally, true)) {
4610                                 if (!fini.Resolve (ec))
4611                                         ok = false;
4612                         }
4613
4614                         ec.EndFlowBranching ();
4615
4616                         ResolveReachability (ec);
4617
4618                         return ok;
4619                 }
4620
4621                 protected override void EmitPreTryBody (EmitContext ec)
4622                 {
4623                 }
4624
4625                 protected override void EmitTryBody (EmitContext ec)
4626                 {
4627                         stmt.Emit (ec);
4628                 }
4629
4630                 protected override void EmitFinallyBody (EmitContext ec)
4631                 {
4632                         fini.Emit (ec);
4633                 }
4634
4635                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4636                 {
4637                         stmt.MutateHoistedGenericType (storey);
4638                         fini.MutateHoistedGenericType (storey);
4639                 }
4640
4641                 protected override void CloneTo (CloneContext clonectx, Statement t)
4642                 {
4643                         TryFinally target = (TryFinally) t;
4644
4645                         target.stmt = (Statement) stmt.Clone (clonectx);
4646                         if (fini != null)
4647                                 target.fini = clonectx.LookupBlock (fini);
4648                 }
4649         }
4650
4651         public class TryCatch : Statement {
4652                 public Block Block;
4653                 public ArrayList Specific;
4654                 public Catch General;
4655                 bool inside_try_finally, code_follows;
4656
4657                 public TryCatch (Block block, ArrayList catch_clauses, Location l, bool inside_try_finally)
4658                 {
4659                         this.Block = block;
4660                         this.Specific = catch_clauses;
4661                         this.General = null;
4662                         this.inside_try_finally = inside_try_finally;
4663
4664                         for (int i = 0; i < catch_clauses.Count; ++i) {
4665                                 Catch c = (Catch) catch_clauses [i];
4666                                 if (c.IsGeneral) {
4667                                         if (i != catch_clauses.Count - 1)
4668                                                 Report.Error (1017, c.loc, "Try statement already has an empty catch block");
4669                                         this.General = c;
4670                                         catch_clauses.RemoveAt (i);
4671                                         i--;
4672                                 }
4673                         }
4674
4675                         loc = l;
4676                 }
4677
4678                 public override bool Resolve (EmitContext ec)
4679                 {
4680                         bool ok = true;
4681
4682                         ec.StartFlowBranching (this);
4683
4684                         if (!Block.Resolve (ec))
4685                                 ok = false;
4686
4687                         Type[] prev_catches = new Type [Specific.Count];
4688                         int last_index = 0;
4689                         foreach (Catch c in Specific){
4690                                 ec.CurrentBranching.CreateSibling (c.Block, FlowBranching.SiblingType.Catch);
4691
4692                                 if (c.Name != null) {
4693                                         LocalInfo vi = c.Block.GetLocalInfo (c.Name);
4694                                         if (vi == null)
4695                                                 throw new Exception ();
4696
4697                                         vi.VariableInfo = null;
4698                                 }
4699
4700                                 if (!c.Resolve (ec))
4701                                         ok = false;
4702
4703                                 Type resolved_type = c.CatchType;
4704                                 for (int ii = 0; ii < last_index; ++ii) {
4705                                         if (resolved_type == prev_catches [ii] || TypeManager.IsSubclassOf (resolved_type, prev_catches [ii])) {
4706                                                 Report.Error (160, c.loc, "A previous catch clause already catches all exceptions of this or a super type `{0}'", prev_catches [ii].FullName);
4707                                                 ok = false;
4708                                         }
4709                                 }
4710
4711                                 prev_catches [last_index++] = resolved_type;
4712                         }
4713
4714                         if (General != null) {
4715                                 if (CodeGen.Assembly.WrapNonExceptionThrows) {
4716                                         foreach (Catch c in Specific){
4717                                                 if (c.CatchType == TypeManager.exception_type) {
4718                                                         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'");
4719                                                 }
4720                                         }
4721                                 }
4722
4723                                 ec.CurrentBranching.CreateSibling (General.Block, FlowBranching.SiblingType.Catch);
4724
4725                                 if (!General.Resolve (ec))
4726                                         ok = false;
4727                         }
4728
4729                         ec.EndFlowBranching ();
4730
4731                         // System.Reflection.Emit automatically emits a 'leave' at the end of a try/catch clause
4732                         // So, ensure there's some IL code after this statement
4733                         if (!inside_try_finally && !code_follows && ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
4734                                 ec.NeedReturnLabel ();
4735
4736                         return ok;
4737                 }
4738
4739                 public void SomeCodeFollows ()
4740                 {
4741                         code_follows = true;
4742                 }
4743
4744                 protected override void DoEmit (EmitContext ec)
4745                 {
4746                         ILGenerator ig = ec.ig;
4747
4748                         if (!inside_try_finally)
4749                                 ig.BeginExceptionBlock ();
4750
4751                         Block.Emit (ec);
4752
4753                         foreach (Catch c in Specific)
4754                                 c.Emit (ec);
4755
4756                         if (General != null)
4757                                 General.Emit (ec);
4758
4759                         if (!inside_try_finally)
4760                                 ig.EndExceptionBlock ();
4761                 }
4762
4763                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4764                 {
4765                         Block.MutateHoistedGenericType (storey);
4766
4767                         if (General != null)
4768                                 General.MutateHoistedGenericType (storey);
4769                         if (Specific != null) {
4770                                 foreach (Catch c in Specific)
4771                                         c.MutateHoistedGenericType (storey);
4772                         }
4773                 }
4774
4775                 protected override void CloneTo (CloneContext clonectx, Statement t)
4776                 {
4777                         TryCatch target = (TryCatch) t;
4778
4779                         target.Block = clonectx.LookupBlock (Block);
4780                         if (General != null)
4781                                 target.General = (Catch) General.Clone (clonectx);
4782                         if (Specific != null){
4783                                 target.Specific = new ArrayList ();
4784                                 foreach (Catch c in Specific)
4785                                         target.Specific.Add (c.Clone (clonectx));
4786                         }
4787                 }
4788         }
4789
4790         public class UsingTemporary : ExceptionStatement {
4791                 TemporaryVariable local_copy;
4792                 public Statement Statement;
4793                 Expression expr;
4794                 Type expr_type;
4795
4796                 public UsingTemporary (Expression expr, Statement stmt, Location l)
4797                 {
4798                         this.expr = expr;
4799                         Statement = stmt;
4800                         loc = l;
4801                 }
4802
4803                 public override bool Resolve (EmitContext ec)
4804                 {
4805                         expr = expr.Resolve (ec);
4806                         if (expr == null)
4807                                 return false;
4808
4809                         expr_type = expr.Type;
4810
4811                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)) {
4812                                 if (Convert.ImplicitConversion (ec, expr, TypeManager.idisposable_type, loc) == null) {
4813                                         Using.Error_IsNotConvertibleToIDisposable (expr);
4814                                         return false;
4815                                 }
4816                         }
4817
4818                         local_copy = new TemporaryVariable (expr_type, loc);
4819                         local_copy.Resolve (ec);
4820
4821                         ec.StartFlowBranching (this);
4822
4823                         bool ok = Statement.Resolve (ec);
4824
4825                         ec.EndFlowBranching ();
4826
4827                         ResolveReachability (ec);
4828
4829                         if (TypeManager.void_dispose_void == null) {
4830                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
4831                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
4832                         }
4833
4834                         return ok;
4835                 }
4836
4837                 protected override void EmitPreTryBody (EmitContext ec)
4838                 {
4839                         local_copy.EmitAssign (ec, expr);
4840                 }
4841
4842                 protected override void EmitTryBody (EmitContext ec)
4843                 {
4844                         Statement.Emit (ec);
4845                 }
4846
4847                 protected override void EmitFinallyBody (EmitContext ec)
4848                 {
4849                         ILGenerator ig = ec.ig;
4850                         if (!expr_type.IsValueType) {
4851                                 Label skip = ig.DefineLabel ();
4852                                 local_copy.Emit (ec);
4853                                 ig.Emit (OpCodes.Brfalse, skip);
4854                                 local_copy.Emit (ec);
4855                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4856                                 ig.MarkLabel (skip);
4857                                 return;
4858                         }
4859
4860                         Expression ml = Expression.MemberLookup (
4861                                 ec.ContainerType, TypeManager.idisposable_type, expr_type,
4862                                 "Dispose", Location.Null);
4863
4864                         if (!(ml is MethodGroupExpr)) {
4865                                 local_copy.Emit (ec);
4866                                 ig.Emit (OpCodes.Box, expr_type);
4867                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4868                                 return;
4869                         }
4870
4871                         MethodInfo mi = null;
4872
4873                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4874                                 if (TypeManager.GetParameterData (mk).Count == 0) {
4875                                         mi = mk;
4876                                         break;
4877                                 }
4878                         }
4879
4880                         if (mi == null) {
4881                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4882                                 return;
4883                         }
4884
4885                         local_copy.AddressOf (ec, AddressOp.Load);
4886                         ig.Emit (OpCodes.Call, mi);
4887                 }
4888
4889                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4890                 {
4891                         expr_type = storey.MutateType (expr_type);
4892                         local_copy.MutateHoistedGenericType (storey);
4893                         Statement.MutateHoistedGenericType (storey);
4894                 }
4895
4896                 protected override void CloneTo (CloneContext clonectx, Statement t)
4897                 {
4898                         UsingTemporary target = (UsingTemporary) t;
4899
4900                         target.expr = expr.Clone (clonectx);
4901                         target.Statement = Statement.Clone (clonectx);
4902                 }
4903         }
4904
4905         public class Using : ExceptionStatement {
4906                 Statement stmt;
4907                 public Statement EmbeddedStatement {
4908                         get { return stmt is Using ? ((Using) stmt).EmbeddedStatement : stmt; }
4909                 }
4910
4911                 Expression var;
4912                 Expression init;
4913
4914                 Expression converted_var;
4915                 ExpressionStatement assign;
4916
4917                 public Using (Expression var, Expression init, Statement stmt, Location l)
4918                 {
4919                         this.var = var;
4920                         this.init = init;
4921                         this.stmt = stmt;
4922                         loc = l;
4923                 }
4924
4925                 bool ResolveVariable (EmitContext ec)
4926                 {
4927                         ExpressionStatement a = new SimpleAssign (var, init, loc);
4928                         a = a.ResolveStatement (ec);
4929                         if (a == null)
4930                                 return false;
4931
4932                         assign = a;
4933
4934                         if (TypeManager.ImplementsInterface (a.Type, TypeManager.idisposable_type)) {
4935                                 converted_var = var;
4936                                 return true;
4937                         }
4938
4939                         Expression e = Convert.ImplicitConversionStandard (ec, a, TypeManager.idisposable_type, var.Location);
4940                         if (e == null) {
4941                                 Error_IsNotConvertibleToIDisposable (var);
4942                                 return false;
4943                         }
4944
4945                         converted_var = e;
4946
4947                         return true;
4948                 }
4949
4950                 static public void Error_IsNotConvertibleToIDisposable (Expression expr)
4951                 {
4952                         Report.SymbolRelatedToPreviousError (expr.Type);
4953                         Report.Error (1674, expr.Location, "`{0}': type used in a using statement must be implicitly convertible to `System.IDisposable'",
4954                                 expr.GetSignatureForError ());
4955                 }
4956
4957                 protected override void EmitPreTryBody (EmitContext ec)
4958                 {
4959                         assign.EmitStatement (ec);
4960                 }
4961
4962                 protected override void EmitTryBody (EmitContext ec)
4963                 {
4964                         stmt.Emit (ec);
4965                 }
4966
4967                 protected override void EmitFinallyBody (EmitContext ec)
4968                 {
4969                         ILGenerator ig = ec.ig;
4970
4971                         if (!var.Type.IsValueType) {
4972                                 Label skip = ig.DefineLabel ();
4973                                 var.Emit (ec);
4974                                 ig.Emit (OpCodes.Brfalse, skip);
4975                                 converted_var.Emit (ec);
4976                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4977                                 ig.MarkLabel (skip);
4978                         } else {
4979                                 Expression ml = Expression.MemberLookup(ec.ContainerType, TypeManager.idisposable_type, var.Type, "Dispose", Mono.CSharp.Location.Null);
4980
4981                                 if (!(ml is MethodGroupExpr)) {
4982                                         var.Emit (ec);
4983                                         ig.Emit (OpCodes.Box, var.Type);
4984                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4985                                 } else {
4986                                         MethodInfo mi = null;
4987
4988                                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4989                                                 if (TypeManager.GetParameterData (mk).Count == 0) {
4990                                                         mi = mk;
4991                                                         break;
4992                                                 }
4993                                         }
4994
4995                                         if (mi == null) {
4996                                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4997                                                 return;
4998                                         }
4999
5000                                         IMemoryLocation mloc = (IMemoryLocation) var;
5001
5002                                         mloc.AddressOf (ec, AddressOp.Load);
5003                                         ig.Emit (OpCodes.Call, mi);
5004                                 }
5005                         }
5006                 }
5007
5008                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5009                 {
5010                         assign.MutateHoistedGenericType (storey);
5011                         var.MutateHoistedGenericType (storey);
5012                         stmt.MutateHoistedGenericType (storey);
5013                 }
5014
5015                 public override bool Resolve (EmitContext ec)
5016                 {
5017                         if (!ResolveVariable (ec))
5018                                 return false;
5019
5020                         ec.StartFlowBranching (this);
5021
5022                         bool ok = stmt.Resolve (ec);
5023
5024                         ec.EndFlowBranching ();
5025
5026                         ResolveReachability (ec);
5027
5028                         if (TypeManager.void_dispose_void == null) {
5029                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
5030                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
5031                         }
5032
5033                         return ok;
5034                 }
5035
5036                 protected override void CloneTo (CloneContext clonectx, Statement t)
5037                 {
5038                         Using target = (Using) t;
5039
5040                         target.var = var.Clone (clonectx);
5041                         target.init = init.Clone (clonectx);
5042                         target.stmt = stmt.Clone (clonectx);
5043                 }
5044         }
5045
5046         /// <summary>
5047         ///   Implementation of the foreach C# statement
5048         /// </summary>
5049         public class Foreach : Statement {
5050                 Expression type;
5051                 Expression variable;
5052                 Expression expr;
5053                 Statement statement;
5054
5055                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
5056                                 Statement stmt, Location l)
5057                 {
5058                         this.type = type;
5059                         this.variable = var;
5060                         this.expr = expr;
5061                         statement = stmt;
5062                         loc = l;
5063                 }
5064
5065                 public Statement Statement {
5066                         get { return statement; }
5067                 }
5068
5069                 public override bool Resolve (EmitContext ec)
5070                 {
5071                         expr = expr.Resolve (ec);
5072                         if (expr == null)
5073                                 return false;
5074
5075                         if (expr.IsNull) {
5076                                 Report.Error (186, loc, "Use of null is not valid in this context");
5077                                 return false;
5078                         }
5079
5080                         if (expr.eclass == ExprClass.MethodGroup || expr is AnonymousMethodExpression) {
5081                                 Report.Error (446, expr.Location, "Foreach statement cannot operate on a `{0}'",
5082                                         expr.ExprClassName);
5083                                 return false;
5084                         }
5085
5086                         if (expr.Type.IsArray) {
5087                                 statement = new ArrayForeach (type, variable, expr, statement, loc);
5088                         } else {
5089                                 statement = new CollectionForeach (type, variable, expr, statement, loc);
5090                         }
5091
5092                         return statement.Resolve (ec);
5093                 }
5094
5095                 protected override void DoEmit (EmitContext ec)
5096                 {
5097                         ILGenerator ig = ec.ig;
5098
5099                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
5100                         ec.LoopBegin = ig.DefineLabel ();
5101                         ec.LoopEnd = ig.DefineLabel ();
5102
5103                         statement.Emit (ec);
5104
5105                         ec.LoopBegin = old_begin;
5106                         ec.LoopEnd = old_end;
5107                 }
5108
5109                 protected class ArrayCounter : TemporaryVariable
5110                 {
5111                         StatementExpression increment;
5112
5113                         public ArrayCounter (Location loc)
5114                                 : base (TypeManager.int32_type, loc)
5115                         {
5116                         }
5117
5118                         public void ResolveIncrement (EmitContext ec)
5119                         {
5120                                 increment = new StatementExpression (new UnaryMutator (UnaryMutator.Mode.PostIncrement, this, loc));
5121                                 increment.Resolve (ec);
5122                         }
5123
5124                         public void EmitIncrement (EmitContext ec)
5125                         {
5126                                 increment.Emit (ec);
5127                         }
5128                 }
5129
5130                 protected class ArrayForeach : Statement
5131                 {
5132                         Expression variable, expr, conv;
5133                         Statement statement;
5134                         Type array_type;
5135                         Expression var_type;
5136                         TemporaryVariable[] lengths;
5137                         ArrayCounter[] counter;
5138                         int rank;
5139
5140                         TemporaryVariable copy;
5141                         Expression access;
5142                         Expression[] length_exprs;
5143
5144                         public ArrayForeach (Expression var_type, Expression var,
5145                                              Expression expr, Statement stmt, Location l)
5146                         {
5147                                 this.var_type = var_type;
5148                                 this.variable = var;
5149                                 this.expr = expr;
5150                                 statement = stmt;
5151                                 loc = l;
5152                         }
5153
5154                         public override bool Resolve (EmitContext ec)
5155                         {
5156                                 array_type = expr.Type;
5157                                 rank = array_type.GetArrayRank ();
5158
5159                                 copy = new TemporaryVariable (array_type, loc);
5160                                 copy.Resolve (ec);
5161
5162                                 counter = new ArrayCounter [rank];
5163                                 lengths = new TemporaryVariable [rank];
5164                                 length_exprs = new Expression [rank];
5165
5166                                 ArrayList list = new ArrayList (rank);
5167                                 for (int i = 0; i < rank; i++) {
5168                                         counter [i] = new ArrayCounter (loc);
5169                                         counter [i].ResolveIncrement (ec);
5170
5171                                         lengths [i] = new TemporaryVariable (TypeManager.int32_type, loc);
5172                                         lengths [i].Resolve (ec);
5173
5174                                         if (rank == 1) {
5175                                                 length_exprs [i] = new MemberAccess (copy, "Length").Resolve (ec);
5176                                         } else {
5177                                                 ArrayList args = new ArrayList (1);
5178                                                 args.Add (new Argument (new IntConstant (i, loc)));
5179                                                 length_exprs [i] = new Invocation (new MemberAccess (copy, "GetLength"), args).Resolve (ec);
5180                                         }
5181
5182                                         list.Add (counter [i]);
5183                                 }
5184
5185                                 access = new ElementAccess (copy, list).Resolve (ec);
5186                                 if (access == null)
5187                                         return false;
5188
5189                                 VarExpr ve = var_type as VarExpr;
5190                                 if (ve != null) {
5191                                         // Infer implicitly typed local variable from foreach array type
5192                                         var_type = new TypeExpression (access.Type, ve.Location);
5193                                 }
5194
5195                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
5196                                 if (var_type == null)
5197                                         return false;
5198
5199                                 conv = Convert.ExplicitConversion (ec, access, var_type.Type, loc);
5200                                 if (conv == null)
5201                                         return false;
5202
5203                                 bool ok = true;
5204
5205                                 ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
5206                                 ec.CurrentBranching.CreateSibling ();
5207
5208                                 variable = variable.ResolveLValue (ec, conv, loc);
5209                                 if (variable == null)
5210                                         ok = false;
5211
5212                                 ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
5213                                 if (!statement.Resolve (ec))
5214                                         ok = false;
5215                                 ec.EndFlowBranching ();
5216
5217                                 // There's no direct control flow from the end of the embedded statement to the end of the loop
5218                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
5219
5220                                 ec.EndFlowBranching ();
5221
5222                                 return ok;
5223                         }
5224
5225                         protected override void DoEmit (EmitContext ec)
5226                         {
5227                                 ILGenerator ig = ec.ig;
5228
5229                                 copy.EmitAssign (ec, expr);
5230
5231                                 Label[] test = new Label [rank];
5232                                 Label[] loop = new Label [rank];
5233
5234                                 for (int i = 0; i < rank; i++) {
5235                                         test [i] = ig.DefineLabel ();
5236                                         loop [i] = ig.DefineLabel ();
5237
5238                                         lengths [i].EmitAssign (ec, length_exprs [i]);
5239                                 }
5240
5241                                 IntConstant zero = new IntConstant (0, loc);
5242                                 for (int i = 0; i < rank; i++) {
5243                                         counter [i].EmitAssign (ec, zero);
5244
5245                                         ig.Emit (OpCodes.Br, test [i]);
5246                                         ig.MarkLabel (loop [i]);
5247                                 }
5248
5249                                 ((IAssignMethod) variable).EmitAssign (ec, conv, false, false);
5250
5251                                 statement.Emit (ec);
5252
5253                                 ig.MarkLabel (ec.LoopBegin);
5254
5255                                 for (int i = rank - 1; i >= 0; i--){
5256                                         counter [i].EmitIncrement (ec);
5257
5258                                         ig.MarkLabel (test [i]);
5259                                         counter [i].Emit (ec);
5260                                         lengths [i].Emit (ec);
5261                                         ig.Emit (OpCodes.Blt, loop [i]);
5262                                 }
5263
5264                                 ig.MarkLabel (ec.LoopEnd);
5265                         }
5266
5267                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5268                         {
5269                                 copy.MutateHoistedGenericType (storey);
5270                                 conv.MutateHoistedGenericType (storey);
5271                                 variable.MutateHoistedGenericType (storey);
5272                                 statement.MutateHoistedGenericType (storey);
5273
5274                                 for (int i = 0; i < rank; i++) {
5275                                         counter [i].MutateHoistedGenericType (storey);
5276                                         lengths [i].MutateHoistedGenericType (storey);
5277                                 }
5278                         }
5279                 }
5280
5281                 protected class CollectionForeach : Statement
5282                 {
5283                         Expression variable, expr;
5284                         Statement statement;
5285
5286                         TemporaryVariable enumerator;
5287                         Expression init;
5288                         Statement loop;
5289                         Statement wrapper;
5290
5291                         MethodGroupExpr get_enumerator;
5292                         PropertyExpr get_current;
5293                         MethodInfo move_next;
5294                         Expression var_type;
5295                         Type enumerator_type;
5296                         bool enumerator_found;
5297
5298                         public CollectionForeach (Expression var_type, Expression var,
5299                                                   Expression expr, Statement stmt, Location l)
5300                         {
5301                                 this.var_type = var_type;
5302                                 this.variable = var;
5303                                 this.expr = expr;
5304                                 statement = stmt;
5305                                 loc = l;
5306                         }
5307
5308                         bool GetEnumeratorFilter (EmitContext ec, MethodInfo mi)
5309                         {
5310                                 Type return_type = mi.ReturnType;
5311
5312                                 if ((return_type == TypeManager.ienumerator_type) && (mi.DeclaringType == TypeManager.string_type))
5313                                         //
5314                                         // Apply the same optimization as MS: skip the GetEnumerator
5315                                         // returning an IEnumerator, and use the one returning a
5316                                         // CharEnumerator instead. This allows us to avoid the
5317                                         // try-finally block and the boxing.
5318                                         //
5319                                         return false;
5320
5321                                 //
5322                                 // Ok, we can access it, now make sure that we can do something
5323                                 // with this `GetEnumerator'
5324                                 //
5325
5326                                 if (return_type == TypeManager.ienumerator_type ||
5327                                     TypeManager.ienumerator_type.IsAssignableFrom (return_type) ||
5328                                     (!RootContext.StdLib && TypeManager.ImplementsInterface (return_type, TypeManager.ienumerator_type))) {
5329                                         //
5330                                         // If it is not an interface, lets try to find the methods ourselves.
5331                                         // For example, if we have:
5332                                         // public class Foo : IEnumerator { public bool MoveNext () {} public int Current { get {}}}
5333                                         // We can avoid the iface call. This is a runtime perf boost.
5334                                         // even bigger if we have a ValueType, because we avoid the cost
5335                                         // of boxing.
5336                                         //
5337                                         // We have to make sure that both methods exist for us to take
5338                                         // this path. If one of the methods does not exist, we will just
5339                                         // use the interface. Sadly, this complex if statement is the only
5340                                         // way I could do this without a goto
5341                                         //
5342
5343                                         if (TypeManager.bool_movenext_void == null) {
5344                                                 TypeManager.bool_movenext_void = TypeManager.GetPredefinedMethod (
5345                                                         TypeManager.ienumerator_type, "MoveNext", loc, Type.EmptyTypes);
5346                                         }
5347
5348                                         if (TypeManager.ienumerator_getcurrent == null) {
5349                                                 TypeManager.ienumerator_getcurrent = TypeManager.GetPredefinedProperty (
5350                                                         TypeManager.ienumerator_type, "Current", loc, TypeManager.object_type);
5351                                         }
5352
5353 #if GMCS_SOURCE
5354                                         //
5355                                         // Prefer a generic enumerator over a non-generic one.
5356                                         //
5357                                         if (return_type.IsInterface && return_type.IsGenericType) {
5358                                                 enumerator_type = return_type;
5359                                                 if (!FetchGetCurrent (ec, return_type))
5360                                                         get_current = new PropertyExpr (
5361                                                                 ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5362                                                 if (!FetchMoveNext (return_type))
5363                                                         move_next = TypeManager.bool_movenext_void;
5364                                                 return true;
5365                                         }
5366 #endif
5367
5368                                         if (return_type.IsInterface ||
5369                                             !FetchMoveNext (return_type) ||
5370                                             !FetchGetCurrent (ec, return_type)) {
5371                                                 enumerator_type = return_type;
5372                                                 move_next = TypeManager.bool_movenext_void;
5373                                                 get_current = new PropertyExpr (
5374                                                         ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5375                                                 return true;
5376                                         }
5377                                 } else {
5378                                         //
5379                                         // Ok, so they dont return an IEnumerable, we will have to
5380                                         // find if they support the GetEnumerator pattern.
5381                                         //
5382
5383                                         if (TypeManager.HasElementType (return_type) || !FetchMoveNext (return_type) || !FetchGetCurrent (ec, return_type)) {
5384                                                 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",
5385                                                         TypeManager.CSharpName (return_type), TypeManager.CSharpSignature (mi));
5386                                                 return false;
5387                                         }
5388                                 }
5389
5390                                 enumerator_type = return_type;
5391
5392                                 return true;
5393                         }
5394
5395                         //
5396                         // Retrieves a `public bool MoveNext ()' method from the Type `t'
5397                         //
5398                         bool FetchMoveNext (Type t)
5399                         {
5400                                 MemberList move_next_list;
5401
5402                                 move_next_list = TypeContainer.FindMembers (
5403                                         t, MemberTypes.Method,
5404                                         BindingFlags.Public | BindingFlags.Instance,
5405                                         Type.FilterName, "MoveNext");
5406                                 if (move_next_list.Count == 0)
5407                                         return false;
5408
5409                                 foreach (MemberInfo m in move_next_list){
5410                                         MethodInfo mi = (MethodInfo) m;
5411
5412                                         if ((TypeManager.GetParameterData (mi).Count == 0) &&
5413                                             TypeManager.TypeToCoreType (mi.ReturnType) == TypeManager.bool_type) {
5414                                                 move_next = mi;
5415                                                 return true;
5416                                         }
5417                                 }
5418
5419                                 return false;
5420                         }
5421
5422                         //
5423                         // Retrieves a `public T get_Current ()' method from the Type `t'
5424                         //
5425                         bool FetchGetCurrent (EmitContext ec, Type t)
5426                         {
5427                                 PropertyExpr pe = Expression.MemberLookup (
5428                                         ec.ContainerType, t, "Current", MemberTypes.Property,
5429                                         Expression.AllBindingFlags, loc) as PropertyExpr;
5430                                 if (pe == null)
5431                                         return false;
5432
5433                                 get_current = pe;
5434                                 return true;
5435                         }
5436
5437                         //
5438                         // Retrieves a `public void Dispose ()' method from the Type `t'
5439                         //
5440                         static MethodInfo FetchMethodDispose (Type t)
5441                         {
5442                                 MemberList dispose_list;
5443
5444                                 dispose_list = TypeContainer.FindMembers (
5445                                         t, MemberTypes.Method,
5446                                         BindingFlags.Public | BindingFlags.Instance,
5447                                         Type.FilterName, "Dispose");
5448                                 if (dispose_list.Count == 0)
5449                                         return null;
5450
5451                                 foreach (MemberInfo m in dispose_list){
5452                                         MethodInfo mi = (MethodInfo) m;
5453
5454                                         if (TypeManager.GetParameterData (mi).Count == 0){
5455                                                 if (mi.ReturnType == TypeManager.void_type)
5456                                                         return mi;
5457                                         }
5458                                 }
5459                                 return null;
5460                         }
5461
5462                         void Error_Enumerator ()
5463                         {
5464                                 if (enumerator_found) {
5465                                         return;
5466                                 }
5467
5468                             Report.Error (1579, loc,
5469                                         "foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `GetEnumerator' or is not accessible",
5470                                         TypeManager.CSharpName (expr.Type));
5471                         }
5472
5473                         bool IsOverride (MethodInfo m)
5474                         {
5475                                 m = (MethodInfo) TypeManager.DropGenericMethodArguments (m);
5476
5477                                 if (!m.IsVirtual || ((m.Attributes & MethodAttributes.NewSlot) != 0))
5478                                         return false;
5479                                 if (m is MethodBuilder)
5480                                         return true;
5481
5482                                 MethodInfo base_method = m.GetBaseDefinition ();
5483                                 return base_method != m;
5484                         }
5485
5486                         bool TryType (EmitContext ec, Type t)
5487                         {
5488                                 MethodGroupExpr mg = Expression.MemberLookup (
5489                                         ec.ContainerType, t, "GetEnumerator", MemberTypes.Method,
5490                                         Expression.AllBindingFlags, loc) as MethodGroupExpr;
5491                                 if (mg == null)
5492                                         return false;
5493
5494                                 MethodInfo result = null;
5495                                 MethodInfo tmp_move_next = null;
5496                                 PropertyExpr tmp_get_cur = null;
5497                                 Type tmp_enumerator_type = enumerator_type;
5498                                 foreach (MethodInfo mi in mg.Methods) {
5499                                         if (TypeManager.GetParameterData (mi).Count != 0)
5500                                                 continue;
5501
5502                                         // Check whether GetEnumerator is public
5503                                         if ((mi.Attributes & MethodAttributes.Public) != MethodAttributes.Public)
5504                                                 continue;
5505
5506                                         if (IsOverride (mi))
5507                                                 continue;
5508
5509                                         enumerator_found = true;
5510
5511                                         if (!GetEnumeratorFilter (ec, mi))
5512                                                 continue;
5513
5514                                         if (result != null) {
5515                                                 if (TypeManager.IsGenericType (result.ReturnType)) {
5516                                                         if (!TypeManager.IsGenericType (mi.ReturnType))
5517                                                                 continue;
5518
5519                                                         MethodBase mb = TypeManager.DropGenericMethodArguments (mi);
5520                                                         Report.SymbolRelatedToPreviousError (t);
5521                                                         Report.Error(1640, loc, "foreach statement cannot operate on variables of type `{0}' " +
5522                                                                      "because it contains multiple implementation of `{1}'. Try casting to a specific implementation",
5523                                                                      TypeManager.CSharpName (t), TypeManager.CSharpSignature (mb));
5524                                                         return false;
5525                                                 }
5526
5527                                                 // Always prefer generics enumerators
5528                                                 if (!TypeManager.IsGenericType (mi.ReturnType)) {
5529                                                         if (TypeManager.ImplementsInterface (mi.DeclaringType, result.DeclaringType) ||
5530                                                             TypeManager.ImplementsInterface (result.DeclaringType, mi.DeclaringType))
5531                                                                 continue;
5532
5533                                                         Report.SymbolRelatedToPreviousError (result);
5534                                                         Report.SymbolRelatedToPreviousError (mi);
5535                                                         Report.Warning (278, 2, loc, "`{0}' contains ambiguous implementation of `{1}' pattern. Method `{2}' is ambiguous with method `{3}'",
5536                                                                         TypeManager.CSharpName (t), "enumerable", TypeManager.CSharpSignature (result), TypeManager.CSharpSignature (mi));
5537                                                         return false;
5538                                                 }
5539                                         }
5540                                         result = mi;
5541                                         tmp_move_next = move_next;
5542                                         tmp_get_cur = get_current;
5543                                         tmp_enumerator_type = enumerator_type;
5544                                         if (mi.DeclaringType == t)
5545                                                 break;
5546                                 }
5547
5548                                 if (result != null) {
5549                                         move_next = tmp_move_next;
5550                                         get_current = tmp_get_cur;
5551                                         enumerator_type = tmp_enumerator_type;
5552                                         MethodInfo[] mi = new MethodInfo[] { (MethodInfo) result };
5553                                         get_enumerator = new MethodGroupExpr (mi, enumerator_type, loc);
5554
5555                                         if (t != expr.Type) {
5556                                                 expr = Convert.ExplicitConversion (
5557                                                         ec, expr, t, loc);
5558                                                 if (expr == null)
5559                                                         throw new InternalErrorException ();
5560                                         }
5561
5562                                         get_enumerator.InstanceExpression = expr;
5563                                         get_enumerator.IsBase = t != expr.Type;
5564
5565                                         return true;
5566                                 }
5567
5568                                 return false;
5569                         }
5570
5571                         bool ProbeCollectionType (EmitContext ec, Type t)
5572                         {
5573                                 int errors = Report.Errors;
5574                                 for (Type tt = t; tt != null && tt != TypeManager.object_type;){
5575                                         if (TryType (ec, tt))
5576                                                 return true;
5577                                         tt = tt.BaseType;
5578                                 }
5579
5580                                 if (Report.Errors > errors)
5581                                         return false;
5582
5583                                 //
5584                                 // Now try to find the method in the interfaces
5585                                 //
5586                                 Type [] ifaces = TypeManager.GetInterfaces (t);
5587                                 foreach (Type i in ifaces){
5588                                         if (TryType (ec, i))
5589                                                 return true;
5590                                 }
5591
5592                                 return false;
5593                         }
5594
5595                         public override bool Resolve (EmitContext ec)
5596                         {
5597                                 enumerator_type = TypeManager.ienumerator_type;
5598
5599                                 if (!ProbeCollectionType (ec, expr.Type)) {
5600                                         Error_Enumerator ();
5601                                         return false;
5602                                 }
5603
5604                                 bool is_disposable = !enumerator_type.IsSealed ||
5605                                         TypeManager.ImplementsInterface (enumerator_type, TypeManager.idisposable_type);
5606
5607                                 VarExpr ve = var_type as VarExpr;
5608                                 if (ve != null) {
5609                                         // Infer implicitly typed local variable from foreach enumerable type
5610                                         var_type = new TypeExpression (get_current.PropertyInfo.PropertyType, var_type.Location);
5611                                 }
5612
5613                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
5614                                 if (var_type == null)
5615                                         return false;
5616
5617                                 enumerator = new TemporaryVariable (enumerator_type, loc);
5618                                 enumerator.Resolve (ec);
5619
5620                                 init = new Invocation (get_enumerator, null);
5621                                 init = init.Resolve (ec);
5622                                 if (init == null)
5623                                         return false;
5624
5625                                 Expression move_next_expr;
5626                                 {
5627                                         MemberInfo[] mi = new MemberInfo[] { move_next };
5628                                         MethodGroupExpr mg = new MethodGroupExpr (mi, var_type.Type, loc);
5629                                         mg.InstanceExpression = enumerator;
5630
5631                                         move_next_expr = new Invocation (mg, null);
5632                                 }
5633
5634                                 get_current.InstanceExpression = enumerator;
5635
5636                                 Statement block = new CollectionForeachStatement (
5637                                         var_type.Type, variable, get_current, statement, loc);
5638
5639                                 loop = new While (move_next_expr, block, loc);
5640
5641                                 wrapper = is_disposable ?
5642                                         (Statement) new DisposableWrapper (this) :
5643                                         (Statement) new NonDisposableWrapper (this);
5644                                 return wrapper.Resolve (ec);
5645                         }
5646
5647                         protected override void DoEmit (EmitContext ec)
5648                         {
5649                                 wrapper.Emit (ec);
5650                         }
5651
5652                         class NonDisposableWrapper : Statement {
5653                                 CollectionForeach parent;
5654
5655                                 internal NonDisposableWrapper (CollectionForeach parent)
5656                                 {
5657                                         this.parent = parent;
5658                                 }
5659
5660                                 public override bool Resolve (EmitContext ec)
5661                                 {
5662                                         return parent.ResolveLoop (ec);
5663                                 }
5664
5665                                 protected override void DoEmit (EmitContext ec)
5666                                 {
5667                                         parent.EmitLoopInit (ec);
5668                                         parent.EmitLoopBody (ec);
5669                                 }
5670
5671                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5672                                 {
5673                                         throw new NotSupportedException ();
5674                                 }
5675                         }
5676
5677                         class DisposableWrapper : ExceptionStatement {
5678                                 CollectionForeach parent;
5679
5680                                 internal DisposableWrapper (CollectionForeach parent)
5681                                 {
5682                                         this.parent = parent;
5683                                 }
5684
5685                                 public override bool Resolve (EmitContext ec)
5686                                 {
5687                                         bool ok = true;
5688
5689                                         ec.StartFlowBranching (this);
5690
5691                                         if (!parent.ResolveLoop (ec))
5692                                                 ok = false;
5693
5694                                         ec.EndFlowBranching ();
5695
5696                                         ResolveReachability (ec);
5697
5698                                         if (TypeManager.void_dispose_void == null) {
5699                                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
5700                                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
5701                                         }
5702                                         return ok;
5703                                 }
5704
5705                                 protected override void EmitPreTryBody (EmitContext ec)
5706                                 {
5707                                         parent.EmitLoopInit (ec);
5708                                 }
5709
5710                                 protected override void EmitTryBody (EmitContext ec)
5711                                 {
5712                                         parent.EmitLoopBody (ec);
5713                                 }
5714
5715                                 protected override void EmitFinallyBody (EmitContext ec)
5716                                 {
5717                                         parent.EmitFinallyBody (ec);
5718                                 }
5719
5720                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5721                                 {
5722                                         throw new NotSupportedException ();
5723                                 }
5724                         }
5725
5726                         bool ResolveLoop (EmitContext ec)
5727                         {
5728                                 return loop.Resolve (ec);
5729                         }
5730
5731                         void EmitLoopInit (EmitContext ec)
5732                         {
5733                                 enumerator.EmitAssign (ec, init);
5734                         }
5735
5736                         void EmitLoopBody (EmitContext ec)
5737                         {
5738                                 loop.Emit (ec);
5739                         }
5740
5741                         void EmitFinallyBody (EmitContext ec)
5742                         {
5743                                 ILGenerator ig = ec.ig;
5744
5745                                 if (enumerator_type.IsValueType) {
5746                                         MethodInfo mi = FetchMethodDispose (enumerator_type);
5747                                         if (mi != null) {
5748                                                 enumerator.AddressOf (ec, AddressOp.Load);
5749                                                 ig.Emit (OpCodes.Call, mi);
5750                                         } else {
5751                                                 enumerator.Emit (ec);
5752                                                 ig.Emit (OpCodes.Box, enumerator_type);
5753                                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
5754                                         }
5755                                 } else {
5756                                         Label call_dispose = ig.DefineLabel ();
5757
5758                                         enumerator.Emit (ec);
5759                                         ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
5760                                         ig.Emit (OpCodes.Dup);
5761                                         ig.Emit (OpCodes.Brtrue_S, call_dispose);
5762
5763                                         // 'endfinally' empties the evaluation stack, and can appear anywhere inside a finally block
5764                                         // (Partition III, Section 3.35)
5765                                         ig.Emit (OpCodes.Endfinally);
5766
5767                                         ig.MarkLabel (call_dispose);
5768                                         ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
5769                                 }
5770                         }
5771
5772                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5773                         {
5774                                 enumerator_type = storey.MutateType (enumerator_type);
5775                                 init.MutateHoistedGenericType (storey);
5776                                 loop.MutateHoistedGenericType (storey);
5777                         }
5778                 }
5779
5780                 protected class CollectionForeachStatement : Statement
5781                 {
5782                         Type type;
5783                         Expression variable, current, conv;
5784                         Statement statement;
5785                         Assign assign;
5786
5787                         public CollectionForeachStatement (Type type, Expression variable,
5788                                                            Expression current, Statement statement,
5789                                                            Location loc)
5790                         {
5791                                 this.type = type;
5792                                 this.variable = variable;
5793                                 this.current = current;
5794                                 this.statement = statement;
5795                                 this.loc = loc;
5796                         }
5797
5798                         public override bool Resolve (EmitContext ec)
5799                         {
5800                                 current = current.Resolve (ec);
5801                                 if (current == null)
5802                                         return false;
5803
5804                                 conv = Convert.ExplicitConversion (ec, current, type, loc);
5805                                 if (conv == null)
5806                                         return false;
5807
5808                                 assign = new SimpleAssign (variable, conv, loc);
5809                                 if (assign.Resolve (ec) == null)
5810                                         return false;
5811
5812                                 if (!statement.Resolve (ec))
5813                                         return false;
5814
5815                                 return true;
5816                         }
5817
5818                         protected override void DoEmit (EmitContext ec)
5819                         {
5820                                 assign.EmitStatement (ec);
5821                                 statement.Emit (ec);
5822                         }
5823
5824                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5825                         {
5826                                 assign.MutateHoistedGenericType (storey);
5827                                 statement.MutateHoistedGenericType (storey);
5828                         }
5829                 }
5830
5831                 protected override void CloneTo (CloneContext clonectx, Statement t)
5832                 {
5833                         Foreach target = (Foreach) t;
5834
5835                         target.type = type.Clone (clonectx);
5836                         target.variable = variable.Clone (clonectx);
5837                         target.expr = expr.Clone (clonectx);
5838                         target.statement = statement.Clone (clonectx);
5839                 }
5840
5841                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5842                 {
5843                         statement.MutateHoistedGenericType (storey);
5844                 }
5845         }
5846 }