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);
  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 abstract void CloneTo (CloneContext clonectx, Statement target);
  95
  96                 public Statement Clone (CloneContext clonectx)
  97                 {
  98                         Statement s = (Statement) this.MemberwiseClone ();
  99                         CloneTo (clonectx, s);
 100                         return s;
 101                 }
 102
 103                 public virtual Expression CreateExpressionTree (EmitContext ec)
 104                 {
 105                         Report.Error (834, loc, "A lambda expression with statement body cannot be converted to an expresion tree");
 106                         return null;
 107                 }
 108
 109                 public Statement PerformClone ()
 110                 {
 111                         CloneContext clonectx = new CloneContext ();
 112
 113                         return Clone (clonectx);
 114                 }
 115
 116                 public abstract void MutateHoistedGenericType (AnonymousMethodStorey storey);
 117         }
 118
 119         //
 120         // This class is used during the Statement.Clone operation
 121         // to remap objects that have been cloned.
 122         //
 123         // Since blocks are cloned by Block.Clone, we need a way for
 124         // expressions that must reference the block to be cloned
 125         // pointing to the new cloned block.
 126         //
 127         public class CloneContext {
 128                 Hashtable block_map = new Hashtable ();
 129                 Hashtable variable_map;
 130
 131                 public void AddBlockMap (Block from, Block to)
 132                 {
 133                         if (block_map.Contains (from))
 134                                 return;
 135                         block_map [from] = to;
 136                 }
 137
 138                 public Block LookupBlock (Block from)
 139                 {
 140                         Block result = (Block) block_map [from];
 141
 142                         if (result == null){
 143                                 result = (Block) from.Clone (this);
 144                                 block_map [from] = result;
 145                         }
 146
 147                         return result;
 148                 }
 149
 150                 ///
 151                 /// Remaps block to cloned copy if one exists.
 152                 ///
 153                 public Block RemapBlockCopy (Block from)
 154                 {
 155                         Block mapped_to = (Block)block_map[from];
 156                         if (mapped_to == null)
 157                                 return from;
 158
 159                         return mapped_to;
 160                 }
 161
 162                 public void AddVariableMap (LocalInfo from, LocalInfo to)
 163                 {
 164                         if (variable_map == null)
 165                                 variable_map = new Hashtable ();
 166
 167                         if (variable_map.Contains (from))
 168                                 return;
 169                         variable_map [from] = to;
 170                 }
 171
 172                 public LocalInfo LookupVariable (LocalInfo from)
 173                 {
 174                         LocalInfo result = (LocalInfo) variable_map [from];
 175
 176                         if (result == null)
 177                                 throw new Exception ("LookupVariable: looking up a variable that has not been registered yet");
 178
 179                         return result;
 180                 }
 181         }
 182
 183         public sealed class EmptyStatement : Statement {
 184
 185                 private EmptyStatement () {}
 186
 187                 public static readonly EmptyStatement Value = new EmptyStatement ();
 188
 189                 public override bool Resolve (EmitContext ec)
 190                 {
 191                         return true;
 192                 }
 193
 194                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
 195                 {
 196                         return true;
 197                 }
 198
 199                 protected override void DoEmit (EmitContext ec)
 200                 {
 201                 }
 202
 203                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 204                 {
 205                 }
 206
 207                 protected override void CloneTo (CloneContext clonectx, Statement target)
 208                 {
 209                         // nothing needed.
 210                 }
 211         }
 212
 213         public class If : Statement {
 214                 Expression expr;
 215                 public Statement TrueStatement;
 216                 public Statement FalseStatement;
 217
 218                 bool is_true_ret;
 219
 220                 public If (Expression expr, Statement true_statement, Location l)
 221                 {
 222                         this.expr = expr;
 223                         TrueStatement = true_statement;
 224                         loc = l;
 225                 }
 226
 227                 public If (Expression expr,
 228                            Statement true_statement,
 229                            Statement false_statement,
 230                            Location l)
 231                 {
 232                         this.expr = expr;
 233                         TrueStatement = true_statement;
 234                         FalseStatement = false_statement;
 235                         loc = l;
 236                 }
 237
 238                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 239                 {
 240                         expr.MutateHoistedGenericType (storey);
 241                         TrueStatement.MutateHoistedGenericType (storey);
 242                         if (FalseStatement != null)
 243                                 FalseStatement.MutateHoistedGenericType (storey);
 244                 }
 245
 246                 public override bool Resolve (EmitContext ec)
 247                 {
 248                         bool ok = true;
 249
 250                         Report.Debug (1, "START IF BLOCK", loc);
 251
 252                         expr = Expression.ResolveBoolean (ec, expr, loc);
 253                         if (expr == null){
 254                                 ok = false;
 255                                 goto skip;
 256                         }
 257
 258                         Assign ass = expr as Assign;
 259                         if (ass != null && ass.Source is Constant) {
 260                                 Report.Warning (665, 3, loc, "Assignment in conditional expression is always constant; did you mean to use == instead of = ?");
 261                         }
 262
 263                         //
 264                         // Dead code elimination
 265                         //
 266                         if (expr is Constant){
 267                                 bool take = !((Constant) expr).IsDefaultValue;
 268
 269                                 if (take){
 270                                         if (!TrueStatement.Resolve (ec))
 271                                                 return false;
 272
 273                                         if ((FalseStatement != null) &&
 274                                             !FalseStatement.ResolveUnreachable (ec, true))
 275                                                 return false;
 276                                         FalseStatement = null;
 277                                 } else {
 278                                         if (!TrueStatement.ResolveUnreachable (ec, true))
 279                                                 return false;
 280                                         TrueStatement = null;
 281
 282                                         if ((FalseStatement != null) &&
 283                                             !FalseStatement.Resolve (ec))
 284                                                 return false;
 285                                 }
 286
 287                                 return true;
 288                         }
 289                 skip:
 290                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
 291
 292                         ok &= TrueStatement.Resolve (ec);
 293
 294                         is_true_ret = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 295
 296                         ec.CurrentBranching.CreateSibling ();
 297
 298                         if (FalseStatement != null)
 299                                 ok &= FalseStatement.Resolve (ec);
 300
 301                         ec.EndFlowBranching ();
 302
 303                         Report.Debug (1, "END IF BLOCK", loc);
 304
 305                         return ok;
 306                 }
 307
 308                 protected override void DoEmit (EmitContext ec)
 309                 {
 310                         ILGenerator ig = ec.ig;
 311                         Label false_target = ig.DefineLabel ();
 312                         Label end;
 313
 314                         //
 315                         // If we're a boolean constant, Resolve() already
 316                         // eliminated dead code for us.
 317                         //
 318                         Constant c = expr as Constant;
 319                         if (c != null){
 320                                 c.EmitSideEffect (ec);
 321
 322                                 if (!c.IsDefaultValue)
 323                                         TrueStatement.Emit (ec);
 324                                 else if (FalseStatement != null)
 325                                         FalseStatement.Emit (ec);
 326
 327                                 return;
 328                         }
 329
 330                         expr.EmitBranchable (ec, false_target, false);
 331
 332                         TrueStatement.Emit (ec);
 333
 334                         if (FalseStatement != null){
 335                                 bool branch_emitted = false;
 336
 337                                 end = ig.DefineLabel ();
 338                                 if (!is_true_ret){
 339                                         ig.Emit (OpCodes.Br, end);
 340                                         branch_emitted = true;
 341                                 }
 342
 343                                 ig.MarkLabel (false_target);
 344                                 FalseStatement.Emit (ec);
 345
 346                                 if (branch_emitted)
 347                                         ig.MarkLabel (end);
 348                         } else {
 349                                 ig.MarkLabel (false_target);
 350                         }
 351                 }
 352
 353                 protected override void CloneTo (CloneContext clonectx, Statement t)
 354                 {
 355                         If target = (If) t;
 356
 357                         target.expr = expr.Clone (clonectx);
 358                         target.TrueStatement = TrueStatement.Clone (clonectx);
 359                         if (FalseStatement != null)
 360                                 target.FalseStatement = FalseStatement.Clone (clonectx);
 361                 }
 362         }
 363
 364         public class Do : Statement {
 365                 public Expression expr;
 366                 public Statement  EmbeddedStatement;
 367
 368                 public Do (Statement statement, Expression bool_expr, Location l)
 369                 {
 370                         expr = bool_expr;
 371                         EmbeddedStatement = statement;
 372                         loc = l;
 373                 }
 374
 375                 public override bool Resolve (EmitContext ec)
 376                 {
 377                         bool ok = true;
 378
 379                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 380
 381                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 382
 383                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 384                         if (!EmbeddedStatement.Resolve (ec))
 385                                 ok = false;
 386                         ec.EndFlowBranching ();
 387
 388                         if (ec.CurrentBranching.CurrentUsageVector.IsUnreachable && !was_unreachable)
 389                                 Report.Warning (162, 2, expr.Location, "Unreachable code detected");
 390
 391                         expr = Expression.ResolveBoolean (ec, expr, loc);
 392                         if (expr == null)
 393                                 ok = false;
 394                         else if (expr is Constant){
 395                                 bool infinite = !((Constant) expr).IsDefaultValue;
 396                                 if (infinite)
 397                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 398                         }
 399
 400                         ec.EndFlowBranching ();
 401
 402                         return ok;
 403                 }
 404
 405                 protected override void DoEmit (EmitContext ec)
 406                 {
 407                         ILGenerator ig = ec.ig;
 408                         Label loop = ig.DefineLabel ();
 409                         Label old_begin = ec.LoopBegin;
 410                         Label old_end = ec.LoopEnd;
 411
 412                         ec.LoopBegin = ig.DefineLabel ();
 413                         ec.LoopEnd = ig.DefineLabel ();
 414
 415                         ig.MarkLabel (loop);
 416                         EmbeddedStatement.Emit (ec);
 417                         ig.MarkLabel (ec.LoopBegin);
 418
 419                         //
 420                         // Dead code elimination
 421                         //
 422                         if (expr is Constant){
 423                                 bool res = !((Constant) expr).IsDefaultValue;
 424
 425                                 expr.EmitSideEffect (ec);
 426                                 if (res)
 427                                         ec.ig.Emit (OpCodes.Br, loop);
 428                         } else
 429                                 expr.EmitBranchable (ec, loop, true);
 430
 431                         ig.MarkLabel (ec.LoopEnd);
 432
 433                         ec.LoopBegin = old_begin;
 434                         ec.LoopEnd = old_end;
 435                 }
 436
 437                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 438                 {
 439                         expr.MutateHoistedGenericType (storey);
 440                         EmbeddedStatement.MutateHoistedGenericType (storey);
 441                 }
 442
 443                 protected override void CloneTo (CloneContext clonectx, Statement t)
 444                 {
 445                         Do target = (Do) t;
 446
 447                         target.EmbeddedStatement = EmbeddedStatement.Clone (clonectx);
 448                         target.expr = expr.Clone (clonectx);
 449                 }
 450         }
 451
 452         public class While : Statement {
 453                 public Expression expr;
 454                 public Statement Statement;
 455                 bool infinite, empty;
 456
 457                 public While (Expression bool_expr, Statement statement, Location l)
 458                 {
 459                         this.expr = bool_expr;
 460                         Statement = statement;
 461                         loc = l;
 462                 }
 463
 464                 public override bool Resolve (EmitContext ec)
 465                 {
 466                         bool ok = true;
 467
 468                         expr = Expression.ResolveBoolean (ec, expr, loc);
 469                         if (expr == null)
 470                                 return false;
 471
 472                         //
 473                         // Inform whether we are infinite or not
 474                         //
 475                         if (expr is Constant){
 476                                 bool value = !((Constant) expr).IsDefaultValue;
 477
 478                                 if (value == false){
 479                                         if (!Statement.ResolveUnreachable (ec, true))
 480                                                 return false;
 481                                         empty = true;
 482                                         return true;
 483                                 } else
 484                                         infinite = true;
 485                         }
 486
 487                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 488                         if (!infinite)
 489                                 ec.CurrentBranching.CreateSibling ();
 490
 491                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 492                         if (!Statement.Resolve (ec))
 493                                 ok = false;
 494                         ec.EndFlowBranching ();
 495
 496                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 497                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 498
 499                         ec.EndFlowBranching ();
 500
 501                         return ok;
 502                 }
 503
 504                 protected override void DoEmit (EmitContext ec)
 505                 {
 506                         if (empty) {
 507                                 expr.EmitSideEffect (ec);
 508                                 return;
 509                         }
 510
 511                         ILGenerator ig = ec.ig;
 512                         Label old_begin = ec.LoopBegin;
 513                         Label old_end = ec.LoopEnd;
 514
 515                         ec.LoopBegin = ig.DefineLabel ();
 516                         ec.LoopEnd = ig.DefineLabel ();
 517
 518                         //
 519                         // Inform whether we are infinite or not
 520                         //
 521                         if (expr is Constant){
 522                                 // expr is 'true', since the 'empty' case above handles the 'false' case
 523                                 ig.MarkLabel (ec.LoopBegin);
 524                                 expr.EmitSideEffect (ec);
 525                                 Statement.Emit (ec);
 526                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 527
 528                                 //
 529                                 // Inform that we are infinite (ie, `we return'), only
 530                                 // if we do not `break' inside the code.
 531                                 //
 532                                 ig.MarkLabel (ec.LoopEnd);
 533                         } else {
 534                                 Label while_loop = ig.DefineLabel ();
 535
 536                                 ig.Emit (OpCodes.Br, ec.LoopBegin);
 537                                 ig.MarkLabel (while_loop);
 538
 539                                 Statement.Emit (ec);
 540
 541                                 ig.MarkLabel (ec.LoopBegin);
 542                                 ec.Mark (loc);
 543
 544                                 expr.EmitBranchable (ec, while_loop, true);
 545
 546                                 ig.MarkLabel (ec.LoopEnd);
 547                         }
 548
 549                         ec.LoopBegin = old_begin;
 550                         ec.LoopEnd = old_end;
 551                 }
 552
 553                 public override void Emit (EmitContext ec)
 554                 {
 555                         DoEmit (ec);
 556                 }
 557
 558                 protected override void CloneTo (CloneContext clonectx, Statement t)
 559                 {
 560                         While target = (While) t;
 561
 562                         target.expr = expr.Clone (clonectx);
 563                         target.Statement = Statement.Clone (clonectx);
 564                 }
 565
 566                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 567                 {
 568                         expr.MutateHoistedGenericType (storey);
 569                         Statement.MutateHoistedGenericType (storey);
 570                 }
 571         }
 572
 573         public class For : Statement {
 574                 Expression Test;
 575                 Statement InitStatement;
 576                 Statement Increment;
 577                 public Statement Statement;
 578                 bool infinite, empty;
 579
 580                 public For (Statement init_statement,
 581                             Expression test,
 582                             Statement increment,
 583                             Statement statement,
 584                             Location l)
 585                 {
 586                         InitStatement = init_statement;
 587                         Test = test;
 588                         Increment = increment;
 589                         Statement = statement;
 590                         loc = l;
 591                 }
 592
 593                 public override bool Resolve (EmitContext ec)
 594                 {
 595                         bool ok = true;
 596
 597                         if (InitStatement != null){
 598                                 if (!InitStatement.Resolve (ec))
 599                                         ok = false;
 600                         }
 601
 602                         if (Test != null){
 603                                 Test = Expression.ResolveBoolean (ec, Test, loc);
 604                                 if (Test == null)
 605                                         ok = false;
 606                                 else if (Test is Constant){
 607                                         bool value = !((Constant) Test).IsDefaultValue;
 608
 609                                         if (value == false){
 610                                                 if (!Statement.ResolveUnreachable (ec, true))
 611                                                         return false;
 612                                                 if ((Increment != null) &&
 613                                                     !Increment.ResolveUnreachable (ec, false))
 614                                                         return false;
 615                                                 empty = true;
 616                                                 return true;
 617                                         } else
 618                                                 infinite = true;
 619                                 }
 620                         } else
 621                                 infinite = true;
 622
 623                         ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
 624                         if (!infinite)
 625                                 ec.CurrentBranching.CreateSibling ();
 626
 627                         bool was_unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
 628
 629                         ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
 630                         if (!Statement.Resolve (ec))
 631                                 ok = false;
 632                         ec.EndFlowBranching ();
 633
 634                         if (Increment != null){
 635                                 if (ec.CurrentBranching.CurrentUsageVector.IsUnreachable) {
 636                                         if (!Increment.ResolveUnreachable (ec, !was_unreachable))
 637                                                 ok = false;
 638                                 } else {
 639                                         if (!Increment.Resolve (ec))
 640                                                 ok = false;
 641                                 }
 642                         }
 643
 644                         // There's no direct control flow from the end of the embedded statement to the end of the loop
 645                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 646
 647                         ec.EndFlowBranching ();
 648
 649                         return ok;
 650                 }
 651
 652                 protected override void DoEmit (EmitContext ec)
 653                 {
 654                         if (InitStatement != null && InitStatement != EmptyStatement.Value)
 655                                 InitStatement.Emit (ec);
 656
 657                         if (empty) {
 658                                 Test.EmitSideEffect (ec);
 659                                 return;
 660                         }
 661
 662                         ILGenerator ig = ec.ig;
 663                         Label old_begin = ec.LoopBegin;
 664                         Label old_end = ec.LoopEnd;
 665                         Label loop = ig.DefineLabel ();
 666                         Label test = ig.DefineLabel ();
 667
 668                         ec.LoopBegin = ig.DefineLabel ();
 669                         ec.LoopEnd = ig.DefineLabel ();
 670
 671                         ig.Emit (OpCodes.Br, test);
 672                         ig.MarkLabel (loop);
 673                         Statement.Emit (ec);
 674
 675                         ig.MarkLabel (ec.LoopBegin);
 676                         if (Increment != EmptyStatement.Value)
 677                                 Increment.Emit (ec);
 678
 679                         ig.MarkLabel (test);
 680                         //
 681                         // If test is null, there is no test, and we are just
 682                         // an infinite loop
 683                         //
 684                         if (Test != null){
 685                                 //
 686                                 // The Resolve code already catches the case for
 687                                 // Test == Constant (false) so we know that
 688                                 // this is true
 689                                 //
 690                                 if (Test is Constant) {
 691                                         Test.EmitSideEffect (ec);
 692                                         ig.Emit (OpCodes.Br, loop);
 693                                 } else {
 694                                         Test.EmitBranchable (ec, loop, true);
 695                                 }
 696
 697                         } else
 698                                 ig.Emit (OpCodes.Br, loop);
 699                         ig.MarkLabel (ec.LoopEnd);
 700
 701                         ec.LoopBegin = old_begin;
 702                         ec.LoopEnd = old_end;
 703                 }
 704
 705                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 706                 {
 707                         if (InitStatement != null)
 708                                 InitStatement.MutateHoistedGenericType (storey);
 709                         if (Test != null)
 710                                 Test.MutateHoistedGenericType (storey);
 711                         if (Increment != null)
 712                                 Increment.MutateHoistedGenericType (storey);
 713
 714                         Statement.MutateHoistedGenericType (storey);
 715                 }
 716
 717                 protected override void CloneTo (CloneContext clonectx, Statement t)
 718                 {
 719                         For target = (For) t;
 720
 721                         if (InitStatement != null)
 722                                 target.InitStatement = InitStatement.Clone (clonectx);
 723                         if (Test != null)
 724                                 target.Test = Test.Clone (clonectx);
 725                         if (Increment != null)
 726                                 target.Increment = Increment.Clone (clonectx);
 727                         target.Statement = Statement.Clone (clonectx);
 728                 }
 729         }
 730
 731         public class StatementExpression : Statement {
 732                 ExpressionStatement expr;
 733
 734                 public StatementExpression (ExpressionStatement expr)
 735                 {
 736                         this.expr = expr;
 737                         loc = expr.Location;
 738                 }
 739
 740                 public override bool Resolve (EmitContext ec)
 741                 {
 742                         if (expr != null)
 743                                 expr = expr.ResolveStatement (ec);
 744                         return expr != null;
 745                 }
 746
 747                 protected override void DoEmit (EmitContext ec)
 748                 {
 749                         expr.EmitStatement (ec);
 750                 }
 751
 752                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 753                 {
 754                         expr.MutateHoistedGenericType (storey);
 755                 }
 756
 757                 public override string ToString ()
 758                 {
 759                         return "StatementExpression (" + expr + ")";
 760                 }
 761
 762                 protected override void CloneTo (CloneContext clonectx, Statement t)
 763                 {
 764                         StatementExpression target = (StatementExpression) t;
 765
 766                         target.expr = (ExpressionStatement) expr.Clone (clonectx);
 767                 }
 768         }
 769
 770         // A 'return' or a 'yield break'
 771         public abstract class ExitStatement : Statement
 772         {
 773                 protected bool unwind_protect;
 774                 protected abstract bool DoResolve (EmitContext ec);
 775
 776                 public virtual void Error_FinallyClause ()
 777                 {
 778                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 779                 }
 780
 781                 public sealed override bool Resolve (EmitContext ec)
 782                 {
 783                         if (!DoResolve (ec))
 784                                 return false;
 785
 786                         unwind_protect = ec.CurrentBranching.AddReturnOrigin (ec.CurrentBranching.CurrentUsageVector, this);
 787                         if (unwind_protect)
 788                                 ec.NeedReturnLabel ();
 789                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 790                         return true;
 791                 }
 792         }
 793
 794         /// <summary>
 795         ///   Implements the return statement
 796         /// </summary>
 797         public class Return : ExitStatement {
 798                 protected Expression Expr;
 799                 public Return (Expression expr, Location l)
 800                 {
 801                         Expr = expr;
 802                         loc = l;
 803                 }
 804
 805                 protected override bool DoResolve (EmitContext ec)
 806                 {
 807                         if (Expr == null) {
 808                                 if (ec.ReturnType == TypeManager.void_type)
 809                                         return true;
 810
 811                                 Error (126, "An object of a type convertible to `{0}' is required " +
 812                                            "for the return statement",
 813                                            TypeManager.CSharpName (ec.ReturnType));
 814                                 return false;
 815                         }
 816
 817                         if (ec.CurrentBlock.Toplevel.IsIterator) {
 818                                 Report.Error (1622, loc, "Cannot return a value from iterators. Use the yield return " +
 819                                                   "statement to return a value, or yield break to end the iteration");
 820                         }
 821
 822                         AnonymousExpression am = ec.CurrentAnonymousMethod;
 823                         if (am == null && ec.ReturnType == TypeManager.void_type) {
 824                                 MemberCore mc = ec.ResolveContext as MemberCore;
 825                                 Report.Error (127, loc, "`{0}': A return keyword must not be followed by any expression when method returns void",
 826                                         mc.GetSignatureForError ());
 827                         }
 828
 829                         Expr = Expr.Resolve (ec);
 830                         if (Expr == null)
 831                                 return false;
 832
 833                         if (Expr.Type != ec.ReturnType) {
 834                                 if (ec.InferReturnType) {
 835                                         //
 836                                         // void cannot be used in contextual return
 837                                         //
 838                                         if (Expr.Type == TypeManager.void_type)
 839                                                 return false;
 840
 841                                         ec.ReturnType = Expr.Type;
 842                                 } else {
 843                                         Expr = Convert.ImplicitConversionRequired (
 844                                                 ec, Expr, ec.ReturnType, loc);
 845
 846                                         if (Expr == null) {
 847                                                 if (am != null) {
 848                                                         Report.Error (1662, loc,
 849                                                                 "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",
 850                                                                 am.ContainerType, am.GetSignatureForError ());
 851                                                 }
 852                                                 return false;
 853                                         }
 854                                 }
 855                         }
 856
 857                         return true;
 858                 }
 859
 860                 protected override void DoEmit (EmitContext ec)
 861                 {
 862                         if (Expr != null) {
 863                                 Expr.Emit (ec);
 864
 865                                 if (unwind_protect)
 866                                         ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 867                         }
 868
 869                         if (unwind_protect)
 870                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 871                         else
 872                                 ec.ig.Emit (OpCodes.Ret);
 873                 }
 874
 875                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 876                 {
 877                         if (Expr != null)
 878                                 Expr.MutateHoistedGenericType (storey);
 879                 }
 880
 881                 protected override void CloneTo (CloneContext clonectx, Statement t)
 882                 {
 883                         Return target = (Return) t;
 884                         // It's null for simple return;
 885                         if (Expr != null)
 886                                 target.Expr = Expr.Clone (clonectx);
 887                 }
 888         }
 889
 890         public class Goto : Statement {
 891                 string target;
 892                 LabeledStatement label;
 893                 bool unwind_protect;
 894
 895                 public override bool Resolve (EmitContext ec)
 896                 {
 897                         int errors = Report.Errors;
 898                         unwind_protect = ec.CurrentBranching.AddGotoOrigin (ec.CurrentBranching.CurrentUsageVector, this);
 899                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 900                         return errors == Report.Errors;
 901                 }
 902
 903                 public Goto (string label, Location l)
 904                 {
 905                         loc = l;
 906                         target = label;
 907                 }
 908
 909                 public string Target {
 910                         get { return target; }
 911                 }
 912
 913                 public void SetResolvedTarget (LabeledStatement label)
 914                 {
 915                         this.label = label;
 916                         label.AddReference ();
 917                 }
 918
 919                 protected override void CloneTo (CloneContext clonectx, Statement target)
 920                 {
 921                         // Nothing to clone
 922                 }
 923
 924                 protected override void DoEmit (EmitContext ec)
 925                 {
 926                         if (label == null)
 927                                 throw new InternalErrorException ("goto emitted before target resolved");
 928                         Label l = label.LabelTarget (ec);
 929                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
 930                 }
 931
 932                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 933                 {
 934                 }
 935         }
 936
 937         public class LabeledStatement : Statement {
 938                 string name;
 939                 bool defined;
 940                 bool referenced;
 941                 Label label;
 942                 ILGenerator ig;
 943
 944                 FlowBranching.UsageVector vectors;
 945
 946                 public LabeledStatement (string name, Location l)
 947                 {
 948                         this.name = name;
 949                         this.loc = l;
 950                 }
 951
 952                 public Label LabelTarget (EmitContext ec)
 953                 {
 954                         if (defined)
 955                                 return label;
 956                         ig = ec.ig;
 957                         label = ec.ig.DefineLabel ();
 958                         defined = true;
 959
 960                         return label;
 961                 }
 962
 963                 public string Name {
 964                         get { return name; }
 965                 }
 966
 967                 public bool IsDefined {
 968                         get { return defined; }
 969                 }
 970
 971                 public bool HasBeenReferenced {
 972                         get { return referenced; }
 973                 }
 974
 975                 public FlowBranching.UsageVector JumpOrigins {
 976                         get { return vectors; }
 977                 }
 978
 979                 public void AddUsageVector (FlowBranching.UsageVector vector)
 980                 {
 981                         vector = vector.Clone ();
 982                         vector.Next = vectors;
 983                         vectors = vector;
 984                 }
 985
 986                 protected override void CloneTo (CloneContext clonectx, Statement target)
 987                 {
 988                         // nothing to clone
 989                 }
 990
 991                 public override bool Resolve (EmitContext ec)
 992                 {
 993                         // this flow-branching will be terminated when the surrounding block ends
 994                         ec.StartFlowBranching (this);
 995                         return true;
 996                 }
 997
 998                 protected override void DoEmit (EmitContext ec)
 999                 {
1000                         if (ig != null && ig != ec.ig)
1001                                 throw new InternalErrorException ("cannot happen");
1002                         LabelTarget (ec);
1003                         ec.ig.MarkLabel (label);
1004                 }
1005
1006                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1007                 {
1008                 }
1009
1010                 public void AddReference ()
1011                 {
1012                         referenced = true;
1013                 }
1014         }
1015
1016
1017         /// <summary>
1018         ///   `goto default' statement
1019         /// </summary>
1020         public class GotoDefault : Statement {
1021
1022                 public GotoDefault (Location l)
1023                 {
1024                         loc = l;
1025                 }
1026
1027                 protected override void CloneTo (CloneContext clonectx, Statement target)
1028                 {
1029                         // nothing to clone
1030                 }
1031
1032                 public override bool Resolve (EmitContext ec)
1033                 {
1034                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1035                         return true;
1036                 }
1037
1038                 protected override void DoEmit (EmitContext ec)
1039                 {
1040                         if (ec.Switch == null){
1041                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
1042                                 return;
1043                         }
1044
1045                         if (!ec.Switch.GotDefault){
1046                                 FlowBranchingBlock.Error_UnknownLabel (loc, "default");
1047                                 return;
1048                         }
1049                         ec.ig.Emit (OpCodes.Br, ec.Switch.DefaultTarget);
1050                 }
1051
1052                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1053                 {
1054                 }
1055         }
1056
1057         /// <summary>
1058         ///   `goto case' statement
1059         /// </summary>
1060         public class GotoCase : Statement {
1061                 Expression expr;
1062                 SwitchLabel sl;
1063
1064                 public GotoCase (Expression e, Location l)
1065                 {
1066                         expr = e;
1067                         loc = l;
1068                 }
1069
1070                 public override bool Resolve (EmitContext ec)
1071                 {
1072                         if (ec.Switch == null){
1073                                 Report.Error (153, loc, "A goto case is only valid inside a switch statement");
1074                                 return false;
1075                         }
1076
1077                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1078
1079                         expr = expr.Resolve (ec);
1080                         if (expr == null)
1081                                 return false;
1082
1083                         Constant c = expr as Constant;
1084                         if (c == null) {
1085                                 Error (150, "A constant value is expected");
1086                                 return false;
1087                         }
1088
1089                         Type type = ec.Switch.SwitchType;
1090                         Constant res = c.TryReduce (ec, type, c.Location);
1091                         if (res == null) {
1092                                 c.Error_ValueCannotBeConverted (ec, loc, type, true);
1093                                 return false;
1094                         }
1095
1096                         if (!Convert.ImplicitStandardConversionExists (c, type))
1097                                 Report.Warning (469, 2, loc,
1098                                         "The `goto case' value is not implicitly convertible to type `{0}'",
1099                                         TypeManager.CSharpName (type));
1100
1101                         object val = res.GetValue ();
1102                         if (val == null)
1103                                 val = SwitchLabel.NullStringCase;
1104
1105                         sl = (SwitchLabel) ec.Switch.Elements [val];
1106
1107                         if (sl == null){
1108                                 FlowBranchingBlock.Error_UnknownLabel (loc, "case " +
1109                                         (c.GetValue () == null ? "null" : val.ToString ()));
1110                                 return false;
1111                         }
1112
1113                         return true;
1114                 }
1115
1116                 protected override void DoEmit (EmitContext ec)
1117                 {
1118                         ec.ig.Emit (OpCodes.Br, sl.GetILLabelCode (ec));
1119                 }
1120
1121                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1122                 {
1123                         expr.MutateHoistedGenericType (storey);
1124                 }
1125
1126                 protected override void CloneTo (CloneContext clonectx, Statement t)
1127                 {
1128                         GotoCase target = (GotoCase) t;
1129
1130                         target.expr = expr.Clone (clonectx);
1131                 }
1132         }
1133
1134         public class Throw : Statement {
1135                 Expression expr;
1136
1137                 public Throw (Expression expr, Location l)
1138                 {
1139                         this.expr = expr;
1140                         loc = l;
1141                 }
1142
1143                 public override bool Resolve (EmitContext ec)
1144                 {
1145                         if (expr == null) {
1146                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
1147                                 return ec.CurrentBranching.CheckRethrow (loc);
1148                         }
1149
1150                         expr = expr.Resolve (ec, ResolveFlags.Type | ResolveFlags.VariableOrValue);
1151                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1152
1153                         if (expr == null)
1154                                 return false;
1155
1156                         Type t = expr.Type;
1157
1158                         if ((t != TypeManager.exception_type) &&
1159                             !TypeManager.IsSubclassOf (t, TypeManager.exception_type) &&
1160                             t != TypeManager.null_type) {
1161                                 Error (155, "The type caught or thrown must be derived from System.Exception");
1162                                 return false;
1163                         }
1164                         return true;
1165                 }
1166
1167                 protected override void DoEmit (EmitContext ec)
1168                 {
1169                         if (expr == null)
1170                                 ec.ig.Emit (OpCodes.Rethrow);
1171                         else {
1172                                 expr.Emit (ec);
1173
1174                                 ec.ig.Emit (OpCodes.Throw);
1175                         }
1176                 }
1177
1178                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1179                 {
1180                         if (expr != null)
1181                                 expr.MutateHoistedGenericType (storey);
1182                 }
1183
1184                 protected override void CloneTo (CloneContext clonectx, Statement t)
1185                 {
1186                         Throw target = (Throw) t;
1187
1188                         if (expr != null)
1189                                 target.expr = expr.Clone (clonectx);
1190                 }
1191         }
1192
1193         public class Break : Statement {
1194
1195                 public Break (Location l)
1196                 {
1197                         loc = l;
1198                 }
1199
1200                 bool unwind_protect;
1201
1202                 public override bool Resolve (EmitContext ec)
1203                 {
1204                         int errors = Report.Errors;
1205                         unwind_protect = ec.CurrentBranching.AddBreakOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
1206                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1207                         return errors == Report.Errors;
1208                 }
1209
1210                 protected override void DoEmit (EmitContext ec)
1211                 {
1212                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopEnd);
1213                 }
1214
1215                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1216                 {
1217                 }
1218
1219                 protected override void CloneTo (CloneContext clonectx, Statement t)
1220                 {
1221                         // nothing needed
1222                 }
1223         }
1224
1225         public class Continue : Statement {
1226
1227                 public Continue (Location l)
1228                 {
1229                         loc = l;
1230                 }
1231
1232                 bool unwind_protect;
1233
1234                 public override bool Resolve (EmitContext ec)
1235                 {
1236                         int errors = Report.Errors;
1237                         unwind_protect = ec.CurrentBranching.AddContinueOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
1238                         ec.CurrentBranching.CurrentUsageVector.Goto ();
1239                         return errors == Report.Errors;
1240                 }
1241
1242                 protected override void DoEmit (EmitContext ec)
1243                 {
1244                         ec.ig.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.LoopBegin);
1245                 }
1246
1247                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
1248                 {
1249                 }
1250
1251                 protected override void CloneTo (CloneContext clonectx, Statement t)
1252                 {
1253                         // nothing needed.
1254                 }
1255         }
1256
1257         public interface ILocalVariable
1258         {
1259                 void Emit (EmitContext ec);
1260                 void EmitAssign (EmitContext ec);
1261                 void EmitAddressOf (EmitContext ec);
1262         }
1263
1264         public interface IKnownVariable {
1265                 Block Block { get; }
1266                 Location Location { get; }
1267         }
1268
1269         //
1270         // The information about a user-perceived local variable
1271         //
1272         public class LocalInfo : IKnownVariable, ILocalVariable {
1273                 public readonly FullNamedExpression Type;
1274
1275                 public Type VariableType;
1276                 public readonly string Name;
1277                 public readonly Location Location;
1278                 public readonly Block Block;
1279
1280                 public VariableInfo VariableInfo;
1281                 public HoistedVariable HoistedVariableReference;
1282
1283                 [Flags]
1284                 enum Flags : byte {
1285                         Used = 1,
1286                         ReadOnly = 2,
1287                         Pinned = 4,
1288                         IsThis = 8,
1289                         AddressTaken = 32,
1290                         CompilerGenerated = 64,
1291                         IsConstant = 128
1292                 }
1293
1294                 public enum ReadOnlyContext: byte {
1295                         Using,
1296                         Foreach,
1297                         Fixed
1298                 }
1299
1300                 Flags flags;
1301                 ReadOnlyContext ro_context;
1302                 LocalBuilder builder;
1303
1304                 public LocalInfo (FullNamedExpression type, string name, Block block, Location l)
1305                 {
1306                         Type = type;
1307                         Name = name;
1308                         Block = block;
1309                         Location = l;
1310                 }
1311
1312                 public LocalInfo (DeclSpace ds, Block block, Location l)
1313                 {
1314                         VariableType = ds.IsGeneric ? ds.CurrentType : ds.TypeBuilder;
1315                         Block = block;
1316                         Location = l;
1317                 }
1318
1319                 public void ResolveVariable (EmitContext ec)
1320                 {
1321                         if (HoistedVariableReference != null)
1322                                 return;
1323
1324                         if (builder == null) {
1325                                 if (Pinned)
1326                                         //
1327                                         // This is needed to compile on both .NET 1.x and .NET 2.x
1328                                         // the later introduced `DeclareLocal (Type t, bool pinned)'
1329                                         //
1330                                         builder = TypeManager.DeclareLocalPinned (ec.ig, VariableType);
1331                                 else
1332                                         builder = ec.ig.DeclareLocal (VariableType);
1333                         }
1334                 }
1335
1336                 public void Emit (EmitContext ec)
1337                 {
1338                         ec.ig.Emit (OpCodes.Ldloc, builder);
1339                 }
1340
1341                 public void EmitAssign (EmitContext ec)
1342                 {
1343                         ec.ig.Emit (OpCodes.Stloc, builder);
1344                 }
1345
1346                 public void EmitAddressOf (EmitContext ec)
1347                 {
1348                         ec.ig.Emit (OpCodes.Ldloca, builder);
1349                 }
1350
1351                 public void EmitSymbolInfo (EmitContext ec)
1352                 {
1353                         if (builder != null)
1354                                 ec.DefineLocalVariable (Name, builder);
1355                 }
1356
1357                 public bool IsThisAssigned (EmitContext ec)
1358                 {
1359                         if (VariableInfo == null)
1360                                 throw new Exception ();
1361
1362                         if (!ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo))
1363                                 return true;
1364
1365                         return VariableInfo.TypeInfo.IsFullyInitialized (ec.CurrentBranching, VariableInfo, ec.loc);
1366                 }
1367
1368                 public bool IsAssigned (EmitContext ec)
1369                 {
1370                         if (VariableInfo == null)
1371                                 throw new Exception ();
1372
1373                         return !ec.DoFlowAnalysis || ec.CurrentBranching.IsAssigned (VariableInfo);
1374                 }
1375
1376                 public bool Resolve (EmitContext ec)
1377                 {
1378                         if (VariableType != null)
1379                                 return true;
1380
1381                         TypeExpr texpr = Type.ResolveAsContextualType (ec, false);
1382                         if (texpr == null)
1383                                 return false;
1384
1385                         VariableType = texpr.Type;
1386
1387                         if (TypeManager.IsGenericParameter (VariableType))
1388                                 return true;
1389
1390                         if (VariableType.IsAbstract && VariableType.IsSealed) {
1391                                 FieldBase.Error_VariableOfStaticClass (Location, Name, VariableType);
1392                                 return false;
1393                         }
1394
1395                         if (VariableType.IsPointer && !ec.InUnsafe)
1396                                 Expression.UnsafeError (Location);
1397
1398                         return true;
1399                 }
1400
1401                 public bool IsConstant {
1402                         get { return (flags & Flags.IsConstant) != 0; }
1403                         set { flags |= Flags.IsConstant; }
1404                 }
1405
1406                 public bool AddressTaken {
1407                         get { return (flags & Flags.AddressTaken) != 0; }
1408                         set { flags |= Flags.AddressTaken; }
1409                 }
1410
1411                 public bool CompilerGenerated {
1412                         get { return (flags & Flags.CompilerGenerated) != 0; }
1413                         set { flags |= Flags.CompilerGenerated; }
1414                 }
1415
1416                 public override string ToString ()
1417                 {
1418                         return String.Format ("LocalInfo ({0},{1},{2},{3})",
1419                                               Name, Type, VariableInfo, Location);
1420                 }
1421
1422                 public bool Used {
1423                         get { return (flags & Flags.Used) != 0; }
1424                         set { flags = value ? (flags | Flags.Used) : (unchecked (flags & ~Flags.Used)); }
1425                 }
1426
1427                 public bool ReadOnly {
1428                         get { return (flags & Flags.ReadOnly) != 0; }
1429                 }
1430
1431                 public void SetReadOnlyContext (ReadOnlyContext context)
1432                 {
1433                         flags |= Flags.ReadOnly;
1434                         ro_context = context;
1435                 }
1436
1437                 public string GetReadOnlyContext ()
1438                 {
1439                         if (!ReadOnly)
1440                                 throw new InternalErrorException ("Variable is not readonly");
1441
1442                         switch (ro_context) {
1443                         case ReadOnlyContext.Fixed:
1444                                 return "fixed variable";
1445                         case ReadOnlyContext.Foreach:
1446                                 return "foreach iteration variable";
1447                         case ReadOnlyContext.Using:
1448                                 return "using variable";
1449                         }
1450                         throw new NotImplementedException ();
1451                 }
1452
1453                 //
1454                 // Whether the variable is pinned, if Pinned the variable has been
1455                 // allocated in a pinned slot with DeclareLocal.
1456                 //
1457                 public bool Pinned {
1458                         get { return (flags & Flags.Pinned) != 0; }
1459                         set { flags = value ? (flags | Flags.Pinned) : (flags & ~Flags.Pinned); }
1460                 }
1461
1462                 public bool IsThis {
1463                         get { return (flags & Flags.IsThis) != 0; }
1464                         set { flags = value ? (flags | Flags.IsThis) : (flags & ~Flags.IsThis); }
1465                 }
1466
1467                 Block IKnownVariable.Block {
1468                         get { return Block; }
1469                 }
1470
1471                 Location IKnownVariable.Location {
1472                         get { return Location; }
1473                 }
1474
1475                 public LocalInfo Clone (CloneContext clonectx)
1476                 {
1477                         //
1478                         // Variables in anonymous block are not resolved yet
1479                         //
1480                         if (VariableType == null)
1481                                 return new LocalInfo ((FullNamedExpression) Type.Clone (clonectx), Name, clonectx.LookupBlock (Block), Location);
1482
1483                         //
1484                         // Variables in method block are resolved
1485                         //
1486                         LocalInfo li = new LocalInfo (null, Name, clonectx.LookupBlock (Block), Location);
1487                         li.VariableType = VariableType;
1488                         return li;
1489                 }
1490         }
1491
1492         /// <summary>
1493         ///   Block represents a C# block.
1494         /// </summary>
1495         ///
1496         /// <remarks>
1497         ///   This class is used in a number of places: either to represent
1498         ///   explicit blocks that the programmer places or implicit blocks.
1499         ///
1500         ///   Implicit blocks are used as labels or to introduce variable
1501         ///   declarations.
1502         ///
1503         ///   Top-level blocks derive from Block, and they are called ToplevelBlock
1504         ///   they contain extra information that is not necessary on normal blocks.
1505         /// </remarks>
1506         public class Block : Statement {
1507                 public Block    Parent;
1508                 public Location StartLocation;
1509                 public Location EndLocation = Location.Null;
1510
1511                 public ExplicitBlock Explicit;
1512                 public ToplevelBlock Toplevel; // TODO: Use Explicit
1513
1514                 [Flags]
1515                 public enum Flags : byte {
1516                         Unchecked = 1,
1517                         BlockUsed = 2,
1518                         VariablesInitialized = 4,
1519                         HasRet = 8,
1520                         Unsafe = 16,
1521                         IsIterator = 32,
1522                         HasCapturedVariable = 64,
1523                         HasCapturedThis = 128
1524                 }
1525                 protected Flags flags;
1526
1527                 public bool Unchecked {
1528                         get { return (flags & Flags.Unchecked) != 0; }
1529                         set { flags = value ? flags | Flags.Unchecked : flags & ~Flags.Unchecked; }
1530                 }
1531
1532                 public bool Unsafe {
1533                         get { return (flags & Flags.Unsafe) != 0; }
1534                         set { flags |= Flags.Unsafe; }
1535                 }
1536
1537                 //
1538                 // The statements in this block
1539                 //
1540                 protected ArrayList statements;
1541
1542                 //
1543                 // An array of Blocks.  We keep track of children just
1544                 // to generate the local variable declarations.
1545                 //
1546                 // Statements and child statements are handled through the
1547                 // statements.
1548                 //
1549                 ArrayList children;
1550
1551                 //
1552                 // Labels.  (label, block) pairs.
1553                 //
1554                 protected HybridDictionary labels;
1555
1556                 //
1557                 // Keeps track of (name, type) pairs
1558                 //
1559                 IDictionary variables;
1560
1561                 //
1562                 // Keeps track of constants
1563                 HybridDictionary constants;
1564
1565                 //
1566                 // Temporary variables.
1567                 //
1568                 ArrayList temporary_variables;
1569
1570                 //
1571                 // If this is a switch section, the enclosing switch block.
1572                 //
1573                 Block switch_block;
1574
1575                 protected ArrayList scope_initializers;
1576
1577                 ArrayList anonymous_children;
1578
1579                 protected static int id;
1580
1581                 int this_id;
1582
1583                 int assignable_slots;
1584                 bool unreachable_shown;
1585                 bool unreachable;
1586
1587                 public Block (Block parent)
1588                         : this (parent, (Flags) 0, Location.Null, Location.Null)
1589                 { }
1590
1591                 public Block (Block parent, Flags flags)
1592                         : this (parent, flags, Location.Null, Location.Null)
1593                 { }
1594
1595                 public Block (Block parent, Location start, Location end)
1596                         : this (parent, (Flags) 0, start, end)
1597                 { }
1598
1599                 //
1600                 // Useful when TopLevel block is downgraded to normal block
1601                 //
1602                 public Block (ToplevelBlock parent, ToplevelBlock source)
1603                         : this (parent, source.flags, source.StartLocation, source.EndLocation)
1604                 {
1605                         statements = source.statements;
1606                         children = source.children;
1607                         labels = source.labels;
1608                         variables = source.variables;
1609                         constants = source.constants;
1610                         switch_block = source.switch_block;
1611                 }
1612
1613                 public Block (Block parent, Flags flags, Location start, Location end)
1614                 {
1615                         if (parent != null) {
1616                                 parent.AddChild (this);
1617
1618                                 // the appropriate constructors will fixup these fields
1619                                 Toplevel = parent.Toplevel;
1620                                 Explicit = parent.Explicit;
1621                         }
1622
1623                         this.Parent = parent;
1624                         this.flags = flags;
1625                         this.StartLocation = start;
1626                         this.EndLocation = end;
1627                         this.loc = start;
1628                         this_id = id++;
1629                         statements = new ArrayList (4);
1630                 }
1631
1632                 public Block CreateSwitchBlock (Location start)
1633                 {
1634                         // FIXME: should this be implicit?
1635                         Block new_block = new ExplicitBlock (this, start, start);
1636                         new_block.switch_block = this;
1637                         return new_block;
1638                 }
1639
1640                 public int ID {
1641                         get { return this_id; }
1642                 }
1643
1644                 public IDictionary Variables {
1645                         get {
1646                                 if (variables == null)
1647                                         variables = new ListDictionary ();
1648                                 return variables;
1649                         }
1650                 }
1651
1652                 void AddChild (Block b)
1653                 {
1654                         if (children == null)
1655                                 children = new ArrayList (1);
1656
1657                         children.Add (b);
1658                 }
1659
1660                 public void SetEndLocation (Location loc)
1661                 {
1662                         EndLocation = loc;
1663                 }
1664
1665                 protected static void Error_158 (string name, Location loc)
1666                 {
1667                         Report.Error (158, loc, "The label `{0}' shadows another label " +
1668                                       "by the same name in a contained scope", name);
1669                 }
1670
1671                 /// <summary>
1672                 ///   Adds a label to the current block.
1673                 /// </summary>
1674                 ///
1675                 /// <returns>
1676                 ///   false if the name already exists in this block. true
1677                 ///   otherwise.
1678                 /// </returns>
1679                 ///
1680                 public bool AddLabel (LabeledStatement target)
1681                 {
1682                         if (switch_block != null)
1683                                 return switch_block.AddLabel (target);
1684
1685                         string name = target.Name;
1686
1687                         Block cur = this;
1688                         while (cur != null) {
1689                                 LabeledStatement s = cur.DoLookupLabel (name);
1690                                 if (s != null) {
1691                                         Report.SymbolRelatedToPreviousError (s.loc, s.Name);
1692                                         Report.Error (140, target.loc, "The label `{0}' is a duplicate", name);
1693                                         return false;
1694                                 }
1695
1696                                 if (this == Explicit)
1697                                         break;
1698
1699                                 cur = cur.Parent;
1700                         }
1701
1702                         while (cur != null) {
1703                                 if (cur.DoLookupLabel (name) != null) {
1704                                         Error_158 (name, target.loc);
1705                                         return false;
1706                                 }
1707
1708                                 if (children != null) {
1709                                         foreach (Block b in children) {
1710                                                 LabeledStatement s = b.DoLookupLabel (name);
1711                                                 if (s == null)
1712                                                         continue;
1713
1714                                                 Report.SymbolRelatedToPreviousError (s.loc, s.Name);
1715                                                 Error_158 (name, target.loc);
1716                                                 return false;
1717                                         }
1718                                 }
1719
1720                                 cur = cur.Parent;
1721                         }
1722
1723                         Toplevel.CheckError158 (name, target.loc);
1724
1725                         if (labels == null)
1726                                 labels = new HybridDictionary();
1727
1728                         labels.Add (name, target);
1729                         return true;
1730                 }
1731
1732                 public LabeledStatement LookupLabel (string name)
1733                 {
1734                         LabeledStatement s = DoLookupLabel (name);
1735                         if (s != null)
1736                                 return s;
1737
1738                         if (children == null)
1739                                 return null;
1740
1741                         foreach (Block child in children) {
1742                                 if (Explicit != child.Explicit)
1743                                         continue;
1744
1745                                 s = child.LookupLabel (name);
1746                                 if (s != null)
1747                                         return s;
1748                         }
1749
1750                         return null;
1751                 }
1752
1753                 LabeledStatement DoLookupLabel (string name)
1754                 {
1755                         if (switch_block != null)
1756                                 return switch_block.LookupLabel (name);
1757
1758                         if (labels != null)
1759                                 if (labels.Contains (name))
1760                                         return ((LabeledStatement) labels [name]);
1761
1762                         return null;
1763                 }
1764
1765                 public bool CheckInvariantMeaningInBlock (string name, Expression e, Location loc)
1766                 {
1767                         Block b = this;
1768                         IKnownVariable kvi = b.Explicit.GetKnownVariable (name);
1769                         while (kvi == null) {
1770                                 b = b.Explicit.Parent;
1771                                 if (b == null)
1772                                         return true;
1773                                 kvi = b.Explicit.GetKnownVariable (name);
1774                         }
1775
1776                         if (kvi.Block == b)
1777                                 return true;
1778
1779                         // Is kvi.Block nested inside 'b'
1780                         if (b.Explicit != kvi.Block.Explicit) {
1781                                 //
1782                                 // If a variable by the same name it defined in a nested block of this
1783                                 // block, we violate the invariant meaning in a block.
1784                                 //
1785                                 if (b == this) {
1786                                         Report.SymbolRelatedToPreviousError (kvi.Location, name);
1787                                         Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", name);
1788                                         return false;
1789                                 }
1790
1791                                 //
1792                                 // It's ok if the definition is in a nested subblock of b, but not
1793                                 // nested inside this block -- a definition in a sibling block
1794                                 // should not affect us.
1795                                 //
1796                                 return true;
1797                         }
1798
1799                         //
1800                         // Block 'b' and kvi.Block are the same textual block.
1801                         // However, different variables are extant.
1802                         //
1803                         // Check if the variable is in scope in both blocks.  We use
1804                         // an indirect check that depends on AddVariable doing its
1805                         // part in maintaining the invariant-meaning-in-block property.
1806                         //
1807                         if (e is VariableReference || (e is Constant && b.GetLocalInfo (name) != null))
1808                                 return true;
1809
1810                         if (this is ToplevelBlock) {
1811                                 Report.SymbolRelatedToPreviousError (kvi.Location, name);
1812                                 e.Error_VariableIsUsedBeforeItIsDeclared (name);
1813                                 return false;
1814                         }
1815
1816                         //
1817                         // Even though we detected the error when the name is used, we
1818                         // treat it as if the variable declaration was in error.
1819                         //
1820                         Report.SymbolRelatedToPreviousError (loc, name);
1821                         Error_AlreadyDeclared (kvi.Location, name, "parent or current");
1822                         return false;
1823                 }
1824
1825                 protected virtual bool CheckParentConflictName (ToplevelBlock block, string name, Location l)
1826                 {
1827                         LocalInfo vi = GetLocalInfo (name);
1828                         if (vi != null) {
1829                                 Report.SymbolRelatedToPreviousError (vi.Location, name);
1830                                 if (Explicit == vi.Block.Explicit) {
1831                                         Error_AlreadyDeclared (l, name, null);
1832                                 } else {
1833                                         Error_AlreadyDeclared (l, name, this is ToplevelBlock ?
1834                                                 "parent or current" : "parent");
1835                                 }
1836                                 return false;
1837                         }
1838
1839                         if (block != null) {
1840                                 Expression e = block.GetParameterReference (name, Location.Null);
1841                                 if (e != null) {
1842                                         ParameterReference pr = e as ParameterReference;
1843                                         if (this is Linq.QueryBlock && (pr != null && pr.Parameter is Linq.QueryBlock.ImplicitQueryParameter || e is MemberAccess))
1844                                                 Error_AlreadyDeclared (loc, name);
1845                                         else
1846                                                 Error_AlreadyDeclared (loc, name, "parent or current");
1847                                         return false;
1848                                 }
1849                         }
1850
1851                         return true;
1852                 }
1853
1854                 public LocalInfo AddVariable (Expression type, string name, Location l)
1855                 {
1856                         if (!CheckParentConflictName (Toplevel, name, l))
1857                                 return null;
1858
1859                         if (Toplevel.GenericMethod != null) {
1860                                 foreach (TypeParameter tp in Toplevel.GenericMethod.CurrentTypeParameters) {
1861                                         if (tp.Name == name) {
1862                                                 Report.SymbolRelatedToPreviousError (tp);
1863                                                 Error_AlreadyDeclaredTypeParameter (loc, name, "local variable");
1864                                                 return null;
1865                                         }
1866                                 }
1867                         }
1868
1869                         IKnownVariable kvi = Explicit.GetKnownVariable (name);
1870                         if (kvi != null) {
1871                                 Report.SymbolRelatedToPreviousError (kvi.Location, name);
1872                                 Error_AlreadyDeclared (l, name, "child");
1873                                 return null;
1874                         }
1875
1876                         LocalInfo vi = new LocalInfo ((FullNamedExpression) type, name, this, l);
1877                         AddVariable (vi);
1878
1879                         if ((flags & Flags.VariablesInitialized) != 0)
1880                                 throw new InternalErrorException ("block has already been resolved");
1881
1882                         return vi;
1883                 }
1884
1885                 protected virtual void AddVariable (LocalInfo li)
1886                 {
1887                         Variables.Add (li.Name, li);
1888                         Explicit.AddKnownVariable (li.Name, li);
1889                 }
1890
1891                 protected virtual void Error_AlreadyDeclared (Location loc, string var, string reason)
1892                 {
1893                         if (reason == null) {
1894                                 Error_AlreadyDeclared (loc, var);
1895                                 return;
1896                         }
1897
1898                         Report.Error (136, loc, "A local variable named `{0}' cannot be declared " +
1899                                       "in this scope because it would give a different meaning " +
1900                                       "to `{0}', which is already used in a `{1}' scope " +
1901                                       "to denote something else", var, reason);
1902                 }
1903
1904                 protected virtual void Error_AlreadyDeclared (Location loc, string name)
1905                 {
1906                         Report.Error (128, loc,
1907                                 "A local variable named `{0}' is already defined in this scope", name);
1908                 }
1909
1910                 public virtual void Error_AlreadyDeclaredTypeParameter (Location loc, string name, string conflict)
1911                 {
1912                         Report.Error (412, loc, "The type parameter name `{0}' is the same as `{1}'",
1913                                 name, conflict);
1914                 }
1915
1916                 public bool AddConstant (Expression type, string name, Expression value, Location l)
1917                 {
1918                         if (AddVariable (type, name, l) == null)
1919                                 return false;
1920
1921                         if (constants == null)
1922                                 constants = new HybridDictionary();
1923
1924                         constants.Add (name, value);
1925
1926                         // A block is considered used if we perform an initialization in a local declaration, even if it is constant.
1927                         Use ();
1928                         return true;
1929                 }
1930
1931                 static int next_temp_id = 0;
1932
1933                 public LocalInfo AddTemporaryVariable (TypeExpr te, Location loc)
1934                 {
1935                         Report.Debug (64, "ADD TEMPORARY", this, Toplevel, loc);
1936
1937                         if (temporary_variables == null)
1938                                 temporary_variables = new ArrayList ();
1939
1940                         int id = ++next_temp_id;
1941                         string name = "$s_" + id.ToString ();
1942
1943                         LocalInfo li = new LocalInfo (te, name, this, loc);
1944                         li.CompilerGenerated = true;
1945                         temporary_variables.Add (li);
1946                         return li;
1947                 }
1948
1949                 public LocalInfo GetLocalInfo (string name)
1950                 {
1951                         LocalInfo ret;
1952                         for (Block b = this; b != null; b = b.Parent) {
1953                                 if (b.variables != null) {
1954                                         ret = (LocalInfo) b.variables [name];
1955                                         if (ret != null)
1956                                                 return ret;
1957                                 }
1958                         }
1959
1960                         return null;
1961                 }
1962
1963                 public Expression GetVariableType (string name)
1964                 {
1965                         LocalInfo vi = GetLocalInfo (name);
1966                         return vi == null ? null : vi.Type;
1967                 }
1968
1969                 public Expression GetConstantExpression (string name)
1970                 {
1971                         for (Block b = this; b != null; b = b.Parent) {
1972                                 if (b.constants != null) {
1973                                         Expression ret = b.constants [name] as Expression;
1974                                         if (ret != null)
1975                                                 return ret;
1976                                 }
1977                         }
1978                         return null;
1979                 }
1980
1981                 //
1982                 // It should be used by expressions which require to
1983                 // register a statement during resolve process.
1984                 //
1985                 public void AddScopeStatement (Statement s)
1986                 {
1987                         if (scope_initializers == null)
1988                                 scope_initializers = new ArrayList ();
1989
1990                         scope_initializers.Add (s);
1991                 }
1992
1993                 public void AddStatement (Statement s)
1994                 {
1995                         statements.Add (s);
1996                         flags |= Flags.BlockUsed;
1997                 }
1998
1999                 public bool Used {
2000                         get { return (flags & Flags.BlockUsed) != 0; }
2001                 }
2002
2003                 public void Use ()
2004                 {
2005                         flags |= Flags.BlockUsed;
2006                 }
2007
2008                 public bool HasRet {
2009                         get { return (flags & Flags.HasRet) != 0; }
2010                 }
2011
2012                 public int AssignableSlots {
2013                         get {
2014 // TODO: Re-enable
2015 //                              if ((flags & Flags.VariablesInitialized) == 0)
2016 //                                      throw new Exception ("Variables have not been initialized yet");
2017                                 return assignable_slots;
2018                         }
2019                 }
2020
2021                 public ArrayList AnonymousChildren {
2022                         get { return anonymous_children; }
2023                 }
2024
2025                 public void AddAnonymousChild (ToplevelBlock b)
2026                 {
2027                         if (anonymous_children == null)
2028                                 anonymous_children = new ArrayList ();
2029
2030                         anonymous_children.Add (b);
2031                 }
2032
2033                 void DoResolveConstants (EmitContext ec)
2034                 {
2035                         if (constants == null)
2036                                 return;
2037
2038                         if (variables == null)
2039                                 throw new InternalErrorException ("cannot happen");
2040
2041                         foreach (DictionaryEntry de in variables) {
2042                                 string name = (string) de.Key;
2043                                 LocalInfo vi = (LocalInfo) de.Value;
2044                                 Type variable_type = vi.VariableType;
2045
2046                                 if (variable_type == null) {
2047                                         if (vi.Type is VarExpr)
2048                                                 Report.Error (822, vi.Type.Location, "An implicitly typed local variable cannot be a constant");
2049
2050                                         continue;
2051                                 }
2052
2053                                 Expression cv = (Expression) constants [name];
2054                                 if (cv == null)
2055                                         continue;
2056
2057                                 // Don't let 'const int Foo = Foo;' succeed.
2058                                 // Removing the name from 'constants' ensures that we get a LocalVariableReference below,
2059                                 // which in turn causes the 'must be constant' error to be triggered.
2060                                 constants.Remove (name);
2061
2062                                 if (!Const.IsConstantTypeValid (variable_type)) {
2063                                         Const.Error_InvalidConstantType (variable_type, loc);
2064                                         continue;
2065                                 }
2066
2067                                 ec.CurrentBlock = this;
2068                                 Expression e;
2069                                 using (ec.With (EmitContext.Flags.ConstantCheckState, (flags & Flags.Unchecked) == 0)) {
2070                                         e = cv.Resolve (ec);
2071                                 }
2072                                 if (e == null)
2073                                         continue;
2074
2075                                 Constant ce = e as Constant;
2076                                 if (ce == null) {
2077                                         Const.Error_ExpressionMustBeConstant (vi.Location, name);
2078                                         continue;
2079                                 }
2080
2081                                 e = ce.ConvertImplicitly (variable_type);
2082                                 if (e == null) {
2083                                         if (TypeManager.IsReferenceType (variable_type))
2084                                                 Const.Error_ConstantCanBeInitializedWithNullOnly (variable_type, vi.Location, vi.Name);
2085                                         else
2086                                                 ce.Error_ValueCannotBeConverted (ec, vi.Location, variable_type, false);
2087                                         continue;
2088                                 }
2089
2090                                 constants.Add (name, e);
2091                                 vi.IsConstant = true;
2092                         }
2093                 }
2094
2095                 protected void ResolveMeta (EmitContext ec, int offset)
2096                 {
2097                         Report.Debug (64, "BLOCK RESOLVE META", this, Parent);
2098
2099                         // If some parent block was unsafe, we remain unsafe even if this block
2100                         // isn't explicitly marked as such.
2101                         using (ec.With (EmitContext.Flags.InUnsafe, ec.InUnsafe | Unsafe)) {
2102                                 flags |= Flags.VariablesInitialized;
2103
2104                                 if (variables != null) {
2105                                         foreach (LocalInfo li in variables.Values) {
2106                                                 if (!li.Resolve (ec))
2107                                                         continue;
2108                                                 li.VariableInfo = new VariableInfo (li, offset);
2109                                                 offset += li.VariableInfo.Length;
2110                                         }
2111                                 }
2112                                 assignable_slots = offset;
2113
2114                                 DoResolveConstants (ec);
2115
2116                                 if (children == null)
2117                                         return;
2118                                 foreach (Block b in children)
2119                                         b.ResolveMeta (ec, offset);
2120                         }
2121                 }
2122
2123                 //
2124                 // Emits the local variable declarations for a block
2125                 //
2126                 public virtual void EmitMeta (EmitContext ec)
2127                 {
2128                         if (variables != null){
2129                                 foreach (LocalInfo vi in variables.Values)
2130                                         vi.ResolveVariable (ec);
2131                         }
2132
2133                         if (temporary_variables != null) {
2134                                 for (int i = 0; i < temporary_variables.Count; i++)
2135                                         ((LocalInfo)temporary_variables[i]).ResolveVariable(ec);
2136                         }
2137
2138                         if (children != null) {
2139                                 for (int i = 0; i < children.Count; i++)
2140                                         ((Block)children[i]).EmitMeta(ec);
2141                         }
2142                 }
2143
2144                 void UsageWarning ()
2145                 {
2146                         if (variables == null || Report.WarningLevel < 3)
2147                                 return;
2148
2149                         foreach (DictionaryEntry de in variables) {
2150                                 LocalInfo vi = (LocalInfo) de.Value;
2151
2152                                 if (!vi.Used) {
2153                                         string name = (string) de.Key;
2154
2155                                         // vi.VariableInfo can be null for 'catch' variables
2156                                         if (vi.VariableInfo != null && vi.VariableInfo.IsEverAssigned)
2157                                                 Report.Warning (219, 3, vi.Location, "The variable `{0}' is assigned but its value is never used", name);
2158                                         else
2159                                                 Report.Warning (168, 3, vi.Location, "The variable `{0}' is declared but never used", name);
2160                                 }
2161                         }
2162                 }
2163
2164                 static void CheckPossibleMistakenEmptyStatement (Statement s)
2165                 {
2166                         Statement body;
2167
2168                         // Some statements are wrapped by a Block. Since
2169                         // others' internal could be changed, here I treat
2170                         // them as possibly wrapped by Block equally.
2171                         Block b = s as Block;
2172                         if (b != null && b.statements.Count == 1)
2173                                 s = (Statement) b.statements [0];
2174
2175                         if (s is Lock)
2176                                 body = ((Lock) s).Statement;
2177                         else if (s is For)
2178                                 body = ((For) s).Statement;
2179                         else if (s is Foreach)
2180                                 body = ((Foreach) s).Statement;
2181                         else if (s is While)
2182                                 body = ((While) s).Statement;
2183                         else if (s is Fixed)
2184                                 body = ((Fixed) s).Statement;
2185                         else if (s is Using)
2186                                 body = ((Using) s).EmbeddedStatement;
2187                         else if (s is UsingTemporary)
2188                                 body = ((UsingTemporary) s).Statement;
2189                         else
2190                                 return;
2191
2192                         if (body == null || body is EmptyStatement)
2193                                 Report.Warning (642, 3, s.loc, "Possible mistaken empty statement");
2194                 }
2195
2196                 public override bool Resolve (EmitContext ec)
2197                 {
2198                         Block prev_block = ec.CurrentBlock;
2199                         bool ok = true;
2200
2201                         int errors = Report.Errors;
2202
2203                         ec.CurrentBlock = this;
2204                         ec.StartFlowBranching (this);
2205
2206                         Report.Debug (4, "RESOLVE BLOCK", StartLocation, ec.CurrentBranching);
2207
2208                         //
2209                         // This flag is used to notate nested statements as unreachable from the beginning of this block.
2210                         // For the purposes of this resolution, it doesn't matter that the whole block is unreachable
2211                         // from the beginning of the function.  The outer Resolve() that detected the unreachability is
2212                         // responsible for handling the situation.
2213                         //
2214                         int statement_count = statements.Count;
2215                         for (int ix = 0; ix < statement_count; ix++){
2216                                 Statement s = (Statement) statements [ix];
2217                                 // Check possible empty statement (CS0642)
2218                                 if (Report.WarningLevel >= 3 &&
2219                                         ix + 1 < statement_count &&
2220                                                 statements [ix + 1] is ExplicitBlock)
2221                                         CheckPossibleMistakenEmptyStatement (s);
2222
2223                                 //
2224                                 // Warn if we detect unreachable code.
2225                                 //
2226                                 if (unreachable) {
2227                                         if (s is EmptyStatement)
2228                                                 continue;
2229
2230                                         if (!unreachable_shown && !(s is LabeledStatement)) {
2231                                                 Report.Warning (162, 2, s.loc, "Unreachable code detected");
2232                                                 unreachable_shown = true;
2233                                         }
2234
2235                                         Block c_block = s as Block;
2236                                         if (c_block != null)
2237                                                 c_block.unreachable = c_block.unreachable_shown = true;
2238                                 }
2239
2240                                 //
2241                                 // Note that we're not using ResolveUnreachable() for unreachable
2242                                 // statements here.  ResolveUnreachable() creates a temporary
2243                                 // flow branching and kills it afterwards.  This leads to problems
2244                                 // if you have two unreachable statements where the first one
2245                                 // assigns a variable and the second one tries to access it.
2246                                 //
2247
2248                                 if (!s.Resolve (ec)) {
2249                                         ok = false;
2250                                         if (ec.IsInProbingMode)
2251                                                 break;
2252
2253                                         statements [ix] = EmptyStatement.Value;
2254                                         continue;
2255                                 }
2256
2257                                 if (unreachable && !(s is LabeledStatement) && !(s is Block))
2258                                         statements [ix] = EmptyStatement.Value;
2259
2260                                 unreachable = ec.CurrentBranching.CurrentUsageVector.IsUnreachable;
2261                                 if (unreachable && s is LabeledStatement)
2262                                         throw new InternalErrorException ("should not happen");
2263                         }
2264
2265                         Report.Debug (4, "RESOLVE BLOCK DONE", StartLocation,
2266                                       ec.CurrentBranching, statement_count);
2267
2268                         while (ec.CurrentBranching is FlowBranchingLabeled)
2269                                 ec.EndFlowBranching ();
2270
2271                         bool flow_unreachable = ec.EndFlowBranching ();
2272
2273                         ec.CurrentBlock = prev_block;
2274
2275                         if (flow_unreachable)
2276                                 flags |= Flags.HasRet;
2277
2278                         // If we're a non-static `struct' constructor which doesn't have an
2279                         // initializer, then we must initialize all of the struct's fields.
2280                         if (this == Toplevel && !Toplevel.IsThisAssigned (ec) && !flow_unreachable)
2281                                 ok = false;
2282
2283                         if ((labels != null) && (Report.WarningLevel >= 2)) {
2284                                 foreach (LabeledStatement label in labels.Values)
2285                                         if (!label.HasBeenReferenced)
2286                                                 Report.Warning (164, 2, label.loc, "This label has not been referenced");
2287                         }
2288
2289                         if (ok && errors == Report.Errors)
2290                                 UsageWarning ();
2291
2292                         return ok;
2293                 }
2294
2295                 public override bool ResolveUnreachable (EmitContext ec, bool warn)
2296                 {
2297                         unreachable_shown = true;
2298                         unreachable = true;
2299
2300                         if (warn)
2301                                 Report.Warning (162, 2, loc, "Unreachable code detected");
2302
2303                         ec.StartFlowBranching (FlowBranching.BranchingType.Block, loc);
2304                         bool ok = Resolve (ec);
2305                         ec.KillFlowBranching ();
2306
2307                         return ok;
2308                 }
2309
2310                 protected override void DoEmit (EmitContext ec)
2311                 {
2312                         for (int ix = 0; ix < statements.Count; ix++){
2313                                 Statement s = (Statement) statements [ix];
2314                                 s.Emit (ec);
2315                         }
2316                 }
2317
2318                 public override void Emit (EmitContext ec)
2319                 {
2320                         Block prev_block = ec.CurrentBlock;
2321                         ec.CurrentBlock = this;
2322
2323                         if (scope_initializers != null)
2324                                 EmitScopeInitializers (ec);
2325
2326                         ec.Mark (StartLocation);
2327                         DoEmit (ec);
2328
2329                         if (SymbolWriter.HasSymbolWriter)
2330                                 EmitSymbolInfo (ec);
2331
2332                         ec.CurrentBlock = prev_block;
2333                 }
2334
2335                 protected void EmitScopeInitializers (EmitContext ec)
2336                 {
2337                         SymbolWriter.OpenCompilerGeneratedBlock (ec.ig);
2338
2339                         using (ec.Set (EmitContext.Flags.OmitDebuggingInfo)) {
2340                                 foreach (Statement s in scope_initializers)
2341                                         s.Emit (ec);
2342                         }
2343
2344                         SymbolWriter.CloseCompilerGeneratedBlock (ec.ig);
2345                 }
2346
2347                 protected virtual void EmitSymbolInfo (EmitContext ec)
2348                 {
2349                         if (variables != null) {
2350                                 foreach (LocalInfo vi in variables.Values) {
2351                                         vi.EmitSymbolInfo (ec);
2352                                 }
2353                         }
2354                 }
2355
2356                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
2357                 {
2358                         MutateVariables (storey);
2359
2360                         if (scope_initializers != null) {
2361                                 foreach (Statement s in scope_initializers)
2362                                         s.MutateHoistedGenericType (storey);
2363                         }
2364
2365                         foreach (Statement s in statements)
2366                                 s.MutateHoistedGenericType (storey);
2367                 }
2368
2369                 void MutateVariables (AnonymousMethodStorey storey)
2370                 {
2371                         if (variables != null) {
2372                                 foreach (LocalInfo vi in variables.Values) {
2373                                         vi.VariableType = storey.MutateType (vi.VariableType);
2374                                 }
2375                         }
2376
2377                         if (temporary_variables != null) {
2378                                 foreach (LocalInfo vi in temporary_variables)
2379                                         vi.VariableType = storey.MutateType (vi.VariableType);
2380                         }
2381                 }
2382
2383                 public override string ToString ()
2384                 {
2385                         return String.Format ("{0} ({1}:{2})", GetType (),ID, StartLocation);
2386                 }
2387
2388                 protected override void CloneTo (CloneContext clonectx, Statement t)
2389                 {
2390                         Block target = (Block) t;
2391
2392                         clonectx.AddBlockMap (this, target);
2393
2394                         //target.Toplevel = (ToplevelBlock) clonectx.LookupBlock (Toplevel);
2395                         target.Explicit = (ExplicitBlock) clonectx.LookupBlock (Explicit);
2396                         if (Parent != null)
2397                                 target.Parent = clonectx.RemapBlockCopy (Parent);
2398
2399                         if (variables != null){
2400                                 target.variables = new Hashtable ();
2401
2402                                 foreach (DictionaryEntry de in variables){
2403                                         LocalInfo newlocal = ((LocalInfo) de.Value).Clone (clonectx);
2404                                         target.variables [de.Key] = newlocal;
2405                                         clonectx.AddVariableMap ((LocalInfo) de.Value, newlocal);
2406                                 }
2407                         }
2408
2409                         target.statements = new ArrayList (statements.Count);
2410                         foreach (Statement s in statements)
2411                                 target.statements.Add (s.Clone (clonectx));
2412
2413                         if (target.children != null){
2414                                 target.children = new ArrayList (children.Count);
2415                                 foreach (Block b in children){
2416                                         target.children.Add (clonectx.LookupBlock (b));
2417                                 }
2418                         }
2419
2420                         //
2421                         // TODO: labels, switch_block, constants (?), anonymous_children
2422                         //
2423                 }
2424         }
2425
2426         public class ExplicitBlock : Block {
2427                 HybridDictionary known_variables;
2428                 protected AnonymousMethodStorey am_storey;
2429
2430                 public ExplicitBlock (Block parent, Location start, Location end)
2431                         : this (parent, (Flags) 0, start, end)
2432                 {
2433                 }
2434
2435                 public ExplicitBlock (Block parent, Flags flags, Location start, Location end)
2436                         : base (parent, flags, start, end)
2437                 {
2438                         this.Explicit = this;
2439                 }
2440
2441                 // <summary>
2442                 //   Marks a variable with name @name as being used in this or a child block.
2443                 //   If a variable name has been used in a child block, it's illegal to
2444                 //   declare a variable with the same name in the current block.
2445                 // </summary>
2446                 internal void AddKnownVariable (string name, IKnownVariable info)
2447                 {
2448                         if (known_variables == null)
2449                                 known_variables = new HybridDictionary();
2450
2451                         known_variables [name] = info;
2452
2453                         if (Parent != null)
2454                                 Parent.Explicit.AddKnownVariable (name, info);
2455                 }
2456
2457                 public AnonymousMethodStorey AnonymousMethodStorey {
2458                         get { return am_storey; }
2459                 }
2460
2461                 //
2462                 // Creates anonymous method storey in current block
2463                 //
2464                 public AnonymousMethodStorey CreateAnonymousMethodStorey (EmitContext ec)
2465                 {
2466                         //
2467                         // When referencing a variable in iterator storey from children anonymous method
2468                         //
2469                         if (Toplevel.am_storey is IteratorStorey) {
2470                                 return Toplevel.am_storey;
2471                         }
2472
2473                         //
2474                         // An iterator has only 1 storey block
2475                         //
2476                         if (ec.CurrentIterator != null)
2477                             return ec.CurrentIterator.Storey;
2478
2479                         if (am_storey == null) {
2480                                 MemberBase mc = ec.ResolveContext as MemberBase;
2481                                 GenericMethod gm = mc == null ? null : mc.GenericMethod;
2482
2483                                 //
2484                                 // Creates anonymous method storey for this block
2485                                 //
2486                                 am_storey = new AnonymousMethodStorey (this, ec.TypeContainer, mc, gm, "AnonStorey");
2487                         }
2488
2489                         return am_storey;
2490                 }
2491
2492                 public override void Emit (EmitContext ec)
2493                 {
2494                         if (am_storey != null)
2495                                 am_storey.EmitStoreyInstantiation (ec);
2496
2497                         bool emit_debug_info = SymbolWriter.HasSymbolWriter && Parent != null && !(am_storey is IteratorStorey);
2498                         if (emit_debug_info)
2499                                 ec.BeginScope ();
2500
2501                         base.Emit (ec);
2502
2503                         if (emit_debug_info)
2504                                 ec.EndScope ();
2505                 }
2506
2507                 public override void EmitMeta (EmitContext ec)
2508                 {
2509                         //
2510                         // Creates anonymous method storey
2511                         //
2512                         if (am_storey != null) {
2513                                 if (ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod.Storey != null) {
2514                                         //
2515                                         // Creates parent storey reference when hoisted this is accessible
2516                                         //
2517                                         if (am_storey.OriginalSourceBlock.Explicit.HasCapturedThis) {
2518                                                 ExplicitBlock parent = Toplevel.Parent.Explicit;
2519
2520                                                 //
2521                                                 // Hoisted this exists in top-level parent storey only
2522                                                 //
2523                                                 while (parent.am_storey == null || parent.am_storey.Parent is AnonymousMethodStorey)
2524                                                         parent = parent.Parent.Explicit;
2525
2526                                                 am_storey.AddParentStoreyReference (parent.am_storey);
2527                                         }
2528
2529                                         am_storey.ChangeParentStorey (ec.CurrentAnonymousMethod.Storey);
2530                                 }
2531
2532                                 am_storey.DefineType ();
2533                                 am_storey.ResolveType ();
2534                                 am_storey.Define ();
2535                                 am_storey.Parent.PartialContainer.AddCompilerGeneratedClass (am_storey);
2536
2537                                 ArrayList ref_blocks = am_storey.ReferencesFromChildrenBlock;
2538                                 if (ref_blocks != null) {
2539                                         foreach (ExplicitBlock ref_block in ref_blocks) {
2540                                                 for (ExplicitBlock b = ref_block.Explicit; b != this; b = b.Parent.Explicit) {
2541                                                         if (b.am_storey != null) {
2542                                                                 b.am_storey.AddParentStoreyReference (am_storey);
2543
2544                                                                 // Stop propagation inside same top block
2545                                                                 if (b.Toplevel == Toplevel)
2546                                                                         break;
2547
2548                                                                 b = b.Toplevel;
2549                                                     }
2550                                                         b.HasCapturedVariable = true;
2551                                                 }
2552                                         }
2553                                 }
2554                         }
2555
2556                         base.EmitMeta (ec);
2557                 }
2558
2559                 internal IKnownVariable GetKnownVariable (string name)
2560                 {
2561                         return known_variables == null ? null : (IKnownVariable) known_variables [name];
2562                 }
2563
2564                 public bool HasCapturedThis
2565                 {
2566                         set { flags = value ? flags | Flags.HasCapturedThis : flags & ~Flags.HasCapturedThis; }
2567                         get { return (flags & Flags.HasCapturedThis) != 0; }
2568                 }
2569
2570                 public bool HasCapturedVariable
2571                 {
2572                         set { flags = value ? flags | Flags.HasCapturedVariable : flags & ~Flags.HasCapturedVariable; }
2573                         get { return (flags & Flags.HasCapturedVariable) != 0; }
2574                 }
2575
2576                 protected override void CloneTo (CloneContext clonectx, Statement t)
2577                 {
2578                         ExplicitBlock target = (ExplicitBlock) t;
2579                         target.known_variables = null;
2580                         base.CloneTo (clonectx, t);
2581                 }
2582         }
2583
2584         public class ToplevelParameterInfo : IKnownVariable {
2585                 public readonly ToplevelBlock Block;
2586                 public readonly int Index;
2587                 public VariableInfo VariableInfo;
2588
2589                 Block IKnownVariable.Block {
2590                         get { return Block; }
2591                 }
2592                 public Parameter Parameter {
2593                         get { return Block.Parameters [Index]; }
2594                 }
2595
2596                 public Type ParameterType {
2597                         get { return Block.Parameters.Types [Index]; }
2598                 }
2599
2600                 public Location Location {
2601                         get { return Parameter.Location; }
2602                 }
2603
2604                 public ToplevelParameterInfo (ToplevelBlock block, int idx)
2605                 {
2606                         this.Block = block;
2607                         this.Index = idx;
2608                 }
2609         }
2610
2611         //
2612         // A toplevel block contains extra information, the split is done
2613         // only to separate information that would otherwise bloat the more
2614         // lightweight Block.
2615         //
2616         // In particular, this was introduced when the support for Anonymous
2617         // Methods was implemented.
2618         //
2619         public class ToplevelBlock : ExplicitBlock
2620         {
2621                 //
2622                 // Block is converted to an expression
2623                 //
2624                 sealed class BlockScopeExpression : Expression
2625                 {
2626                         Expression child;
2627                         readonly ToplevelBlock block;
2628
2629                         public BlockScopeExpression (Expression child, ToplevelBlock block)
2630                         {
2631                                 this.child = child;
2632                                 this.block = block;
2633                         }
2634
2635                         public override Expression CreateExpressionTree (EmitContext ec)
2636                         {
2637                                 throw new NotSupportedException ();
2638                         }
2639
2640                         public override Expression DoResolve (EmitContext ec)
2641                         {
2642                                 if (child == null)
2643                                         return null;
2644
2645                                 block.ResolveMeta (ec, ParametersCompiled.EmptyReadOnlyParameters);
2646                                 child = child.Resolve (ec);
2647                                 if (child == null)
2648                                         return null;
2649
2650                                 eclass = child.eclass;
2651                                 type = child.Type;
2652                                 return this;
2653                         }
2654
2655                         public override void Emit (EmitContext ec)
2656                         {
2657                                 block.EmitMeta (ec);
2658                                 block.EmitScopeInitializers (ec);
2659                                 child.Emit (ec);
2660                         }
2661
2662                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
2663                         {
2664                                 type = storey.MutateType (type);
2665                                 child.MutateHoistedGenericType (storey);
2666                                 block.MutateHoistedGenericType (storey);
2667                         }
2668                 }
2669
2670                 GenericMethod generic;
2671                 FlowBranchingToplevel top_level_branching;
2672                 protected ParametersCompiled parameters;
2673                 ToplevelParameterInfo[] parameter_info;
2674                 LocalInfo this_variable;
2675
2676                 public HoistedVariable HoistedThisVariable;
2677
2678                 //
2679                 // The parameters for the block.
2680                 //
2681                 public ParametersCompiled Parameters {
2682                         get { return parameters; }
2683                 }
2684
2685                 public GenericMethod GenericMethod {
2686                         get { return generic; }
2687                 }
2688
2689                 public ToplevelBlock Container {
2690                         get { return Parent == null ? null : Parent.Toplevel; }
2691                 }
2692
2693                 public ToplevelBlock (Block parent, ParametersCompiled parameters, Location start) :
2694                         this (parent, (Flags) 0, parameters, start)
2695                 {
2696                 }
2697
2698                 public ToplevelBlock (Block parent, ParametersCompiled parameters, GenericMethod generic, Location start) :
2699                         this (parent, parameters, start)
2700                 {
2701                         this.generic = generic;
2702                 }
2703
2704                 public ToplevelBlock (ParametersCompiled parameters, Location start) :
2705                         this (null, (Flags) 0, parameters, start)
2706                 {
2707                 }
2708
2709                 ToplevelBlock (Flags flags, ParametersCompiled parameters, Location start) :
2710                         this (null, flags, parameters, start)
2711                 {
2712                 }
2713
2714                 // We use 'Parent' to hook up to the containing block, but don't want to register the current block as a child.
2715                 // So, we use a two-stage setup -- first pass a null parent to the base constructor, and then override 'Parent'.
2716                 public ToplevelBlock (Block parent, Flags flags, ParametersCompiled parameters, Location start) :
2717                         base (null, flags, start, Location.Null)
2718                 {
2719                         this.Toplevel = this;
2720
2721                         this.parameters = parameters;
2722                         this.Parent = parent;
2723                         if (parent != null)
2724                                 parent.AddAnonymousChild (this);
2725
2726                         if (!this.parameters.IsEmpty)
2727                                 ProcessParameters ();
2728                 }
2729
2730                 public ToplevelBlock (Location loc)
2731                         : this (null, (Flags) 0, ParametersCompiled.EmptyReadOnlyParameters, loc)
2732                 {
2733                 }
2734
2735                 protected override void CloneTo (CloneContext clonectx, Statement t)
2736                 {
2737                         ToplevelBlock target = (ToplevelBlock) t;
2738                         base.CloneTo (clonectx, t);
2739
2740                         if (parameters.Count != 0)
2741                                 target.parameter_info = new ToplevelParameterInfo [parameters.Count];
2742                         for (int i = 0; i < parameters.Count; ++i)
2743                                 target.parameter_info [i] = new ToplevelParameterInfo (target, i);
2744                 }
2745
2746                 public bool CheckError158 (string name, Location loc)
2747                 {
2748                         if (AnonymousChildren != null) {
2749                                 foreach (ToplevelBlock child in AnonymousChildren) {
2750                                         if (!child.CheckError158 (name, loc))
2751                                                 return false;
2752                                 }
2753                         }
2754
2755                         for (ToplevelBlock c = Container; c != null; c = c.Container) {
2756                                 if (!c.DoCheckError158 (name, loc))
2757                                         return false;
2758                         }
2759
2760                         return true;
2761                 }
2762
2763                 void ProcessParameters ()
2764                 {
2765                         int n = parameters.Count;
2766                         parameter_info = new ToplevelParameterInfo [n];
2767                         ToplevelBlock top_parent = Parent == null ? null : Parent.Toplevel;
2768                         for (int i = 0; i < n; ++i) {
2769                                 parameter_info [i] = new ToplevelParameterInfo (this, i);
2770
2771                                 Parameter p = parameters [i];
2772                                 if (p == null)
2773                                         continue;
2774
2775                                 string name = p.Name;
2776                                 if (CheckParentConflictName (top_parent, name, loc))
2777                                         AddKnownVariable (name, parameter_info [i]);
2778                         }
2779
2780                         // mark this block as "used" so that we create local declarations in a sub-block
2781                         // FIXME: This appears to uncover a lot of bugs
2782                         //this.Use ();
2783                 }
2784
2785                 bool DoCheckError158 (string name, Location loc)
2786                 {
2787                         LabeledStatement s = LookupLabel (name);
2788                         if (s != null) {
2789                                 Report.SymbolRelatedToPreviousError (s.loc, s.Name);
2790                                 Error_158 (name, loc);
2791                                 return false;
2792                         }
2793
2794                         return true;
2795                 }
2796
2797                 public override Expression CreateExpressionTree (EmitContext ec)
2798                 {
2799                         if (statements.Count == 1) {
2800                                 Expression expr = ((Statement) statements[0]).CreateExpressionTree (ec);
2801                                 if (scope_initializers != null)
2802                                         expr = new BlockScopeExpression (expr, this);
2803
2804                                 return expr;
2805                         }
2806
2807                         return base.CreateExpressionTree (ec);
2808                 }
2809
2810                 //
2811                 // Reformats this block to be top-level iterator block
2812                 //
2813                 public IteratorStorey ChangeToIterator (Iterator iterator, ToplevelBlock source)
2814                 {
2815                         IsIterator = true;
2816
2817                         // Creates block with original statements
2818                         AddStatement (new IteratorStatement (iterator, new Block (this, source)));
2819
2820                         source.statements = new ArrayList (1);
2821                         source.AddStatement (new Return (iterator, iterator.Location));
2822                         source.IsIterator = false;
2823
2824                         IteratorStorey iterator_storey = new IteratorStorey (iterator);
2825                         source.am_storey = iterator_storey;
2826                         return iterator_storey;
2827                 }
2828
2829                 public FlowBranchingToplevel TopLevelBranching {
2830                         get { return top_level_branching; }
2831                 }
2832
2833                 //
2834                 // Returns a parameter reference expression for the given name,
2835                 // or null if there is no such parameter
2836                 //
2837                 public Expression GetParameterReference (string name, Location loc)
2838                 {
2839                         for (ToplevelBlock t = this; t != null; t = t.Container) {
2840                                 Expression expr = t.GetParameterReferenceExpression (name, loc);
2841                                 if (expr != null)
2842                                         return expr;
2843                         }
2844
2845                         return null;
2846                 }
2847
2848                 protected virtual Expression GetParameterReferenceExpression (string name, Location loc)
2849                 {
2850                         int idx = parameters.GetParameterIndexByName (name);
2851                         return idx < 0 ?
2852                                 null : new ParameterReference (parameter_info [idx], loc);
2853                 }
2854
2855                 // <summary>
2856                 //   Returns the "this" instance variable of this block.
2857                 //   See AddThisVariable() for more information.
2858                 // </summary>
2859                 public LocalInfo ThisVariable {
2860                         get { return this_variable; }
2861                 }
2862
2863                 // <summary>
2864                 //   This is used by non-static `struct' constructors which do not have an
2865                 //   initializer - in this case, the constructor must initialize all of the
2866                 //   struct's fields.  To do this, we add a "this" variable and use the flow
2867                 //   analysis code to ensure that it's been fully initialized before control
2868                 //   leaves the constructor.
2869                 // </summary>
2870                 public LocalInfo AddThisVariable (DeclSpace ds, Location l)
2871                 {
2872                         if (this_variable == null) {
2873                                 this_variable = new LocalInfo (ds, this, l);
2874                                 this_variable.Used = true;
2875                                 this_variable.IsThis = true;
2876
2877                                 Variables.Add ("this", this_variable);
2878                         }
2879
2880                         return this_variable;
2881                 }
2882
2883                 public bool IsIterator {
2884                         get { return (flags & Flags.IsIterator) != 0; }
2885                         set { flags = value ? flags | Flags.IsIterator : flags & ~Flags.IsIterator; }
2886                 }
2887
2888                 public bool IsThisAssigned (EmitContext ec)
2889                 {
2890                         return this_variable == null || this_variable.IsThisAssigned (ec);
2891                 }
2892
2893                 public bool ResolveMeta (EmitContext ec, ParametersCompiled ip)
2894                 {
2895                         int errors = Report.Errors;
2896                         int orig_count = parameters.Count;
2897
2898                         if (top_level_branching != null)
2899                                 return true;
2900
2901                         if (ip != null)
2902                                 parameters = ip;
2903
2904                         // Assert: orig_count != parameter.Count => orig_count == 0
2905                         if (orig_count != 0 && orig_count != parameters.Count)
2906                                 throw new InternalErrorException ("parameter information mismatch");
2907
2908                         int offset = Parent == null ? 0 : Parent.AssignableSlots;
2909
2910                         for (int i = 0; i < orig_count; ++i) {
2911                                 Parameter.Modifier mod = parameters.FixedParameters [i].ModFlags;
2912
2913                                 if ((mod & Parameter.Modifier.OUT) != Parameter.Modifier.OUT)
2914                                         continue;
2915
2916                                 VariableInfo vi = new VariableInfo (ip, i, offset);
2917                                 parameter_info [i].VariableInfo = vi;
2918                                 offset += vi.Length;
2919                         }
2920
2921                         ResolveMeta (ec, offset);
2922
2923                         top_level_branching = ec.StartFlowBranching (this);
2924
2925                         return Report.Errors == errors;
2926                 }
2927
2928                 // <summary>
2929                 //   Check whether all `out' parameters have been assigned.
2930                 // </summary>
2931                 public void CheckOutParameters (FlowBranching.UsageVector vector, Location loc)
2932                 {
2933                         if (vector.IsUnreachable)
2934                                 return;
2935
2936                         int n = parameter_info == null ? 0 : parameter_info.Length;
2937
2938                         for (int i = 0; i < n; i++) {
2939                                 VariableInfo var = parameter_info [i].VariableInfo;
2940
2941                                 if (var == null)
2942                                         continue;
2943
2944                                 if (vector.IsAssigned (var, false))
2945                                         continue;
2946
2947                                 Report.Error (177, loc, "The out parameter `{0}' must be assigned to before control leaves the current method",
2948                                         var.Name);
2949                         }
2950                 }
2951
2952                 public override void EmitMeta (EmitContext ec)
2953                 {
2954                         parameters.ResolveVariable ();
2955
2956                         // Avoid declaring an IL variable for this_variable since it is not accessed
2957                         // from the generated IL
2958                         if (this_variable != null)
2959                                 Variables.Remove ("this");
2960                         base.EmitMeta (ec);
2961                 }
2962
2963                 protected override void EmitSymbolInfo (EmitContext ec)
2964                 {
2965                         AnonymousExpression ae = ec.CurrentAnonymousMethod;
2966                         if ((ae != null) && (ae.Storey != null))
2967                                 SymbolWriter.DefineScopeVariable (ae.Storey.ID);
2968
2969                         base.EmitSymbolInfo (ec);
2970                 }
2971
2972                 public override void Emit (EmitContext ec)
2973                 {
2974                         base.Emit (ec);
2975                         ec.Mark (EndLocation);
2976                 }
2977         }
2978
2979         public class SwitchLabel {
2980                 Expression label;
2981                 object converted;
2982                 Location loc;
2983
2984                 Label il_label;
2985                 bool  il_label_set;
2986                 Label il_label_code;
2987                 bool  il_label_code_set;
2988
2989                 public static readonly object NullStringCase = new object ();
2990
2991                 //
2992                 // if expr == null, then it is the default case.
2993                 //
2994                 public SwitchLabel (Expression expr, Location l)
2995                 {
2996                         label = expr;
2997                         loc = l;
2998                 }
2999
3000                 public Expression Label {
3001                         get {
3002                                 return label;
3003                         }
3004                 }
3005
3006                 public Location Location {
3007                         get { return loc; }
3008                 }
3009
3010                 public object Converted {
3011                         get {
3012                                 return converted;
3013                         }
3014                 }
3015
3016                 public Label GetILLabel (EmitContext ec)
3017                 {
3018                         if (!il_label_set){
3019                                 il_label = ec.ig.DefineLabel ();
3020                                 il_label_set = true;
3021                         }
3022                         return il_label;
3023                 }
3024
3025                 public Label GetILLabelCode (EmitContext ec)
3026                 {
3027                         if (!il_label_code_set){
3028                                 il_label_code = ec.ig.DefineLabel ();
3029                                 il_label_code_set = true;
3030                         }
3031                         return il_label_code;
3032                 }
3033
3034                 //
3035                 // Resolves the expression, reduces it to a literal if possible
3036                 // and then converts it to the requested type.
3037                 //
3038                 public bool ResolveAndReduce (EmitContext ec, Type required_type, bool allow_nullable)
3039                 {
3040                         Expression e = label.Resolve (ec);
3041
3042                         if (e == null)
3043                                 return false;
3044
3045                         Constant c = e as Constant;
3046                         if (c == null){
3047                                 Report.Error (150, loc, "A constant value is expected");
3048                                 return false;
3049                         }
3050
3051                         if (required_type == TypeManager.string_type && c.GetValue () == null) {
3052                                 converted = NullStringCase;
3053                                 return true;
3054                         }
3055
3056                         if (allow_nullable && c.GetValue () == null) {
3057                                 converted = NullStringCase;
3058                                 return true;
3059                         }
3060
3061                         c = c.ImplicitConversionRequired (ec, required_type, loc);
3062                         if (c == null)
3063                                 return false;
3064
3065                         converted = c.GetValue ();
3066                         return true;
3067                 }
3068
3069                 public void Error_AlreadyOccurs (Type switch_type, SwitchLabel collision_with)
3070                 {
3071                         string label;
3072                         if (converted == null)
3073                                 label = "default";
3074                         else if (converted == NullStringCase)
3075                                 label = "null";
3076                         else
3077                                 label = converted.ToString ();
3078
3079                         Report.SymbolRelatedToPreviousError (collision_with.loc, null);
3080                         Report.Error (152, loc, "The label `case {0}:' already occurs in this switch statement", label);
3081                 }
3082
3083                 public SwitchLabel Clone (CloneContext clonectx)
3084                 {
3085                         return new SwitchLabel (label.Clone (clonectx), loc);
3086                 }
3087         }
3088
3089         public class SwitchSection {
3090                 // An array of SwitchLabels.
3091                 public readonly ArrayList Labels;
3092                 public readonly Block Block;
3093
3094                 public SwitchSection (ArrayList labels, Block block)
3095                 {
3096                         Labels = labels;
3097                         Block = block;
3098                 }
3099
3100                 public SwitchSection Clone (CloneContext clonectx)
3101                 {
3102                         ArrayList cloned_labels = new ArrayList ();
3103
3104                         foreach (SwitchLabel sl in cloned_labels)
3105                                 cloned_labels.Add (sl.Clone (clonectx));
3106
3107                         return new SwitchSection (cloned_labels, clonectx.LookupBlock (Block));
3108                 }
3109         }
3110
3111         public class Switch : Statement {
3112                 public ArrayList Sections;
3113                 public Expression Expr;
3114
3115                 /// <summary>
3116                 ///   Maps constants whose type type SwitchType to their  SwitchLabels.
3117                 /// </summary>
3118                 public IDictionary Elements;
3119
3120                 /// <summary>
3121                 ///   The governing switch type
3122                 /// </summary>
3123                 public Type SwitchType;
3124
3125                 //
3126                 // Computed
3127                 //
3128                 Label default_target;
3129                 Label null_target;
3130                 Expression new_expr;
3131                 bool is_constant;
3132                 bool has_null_case;
3133                 SwitchSection constant_section;
3134                 SwitchSection default_section;
3135
3136                 ExpressionStatement string_dictionary;
3137                 FieldExpr switch_cache_field;
3138                 static int unique_counter;
3139
3140 #if GMCS_SOURCE
3141                 //
3142                 // Nullable Types support for GMCS.
3143                 //
3144                 Nullable.Unwrap unwrap;
3145
3146                 protected bool HaveUnwrap {
3147                         get { return unwrap != null; }
3148                 }
3149 #else
3150                 protected bool HaveUnwrap {
3151                         get { return false; }
3152                 }
3153 #endif
3154
3155                 //
3156                 // The types allowed to be implicitly cast from
3157                 // on the governing type
3158                 //
3159                 static Type [] allowed_types;
3160
3161                 public Switch (Expression e, ArrayList sects, Location l)
3162                 {
3163                         Expr = e;
3164                         Sections = sects;
3165                         loc = l;
3166                 }
3167
3168                 public bool GotDefault {
3169                         get {
3170                                 return default_section != null;
3171                         }
3172                 }
3173
3174                 public Label DefaultTarget {
3175                         get {
3176                                 return default_target;
3177                         }
3178                 }
3179
3180                 //
3181                 // Determines the governing type for a switch.  The returned
3182                 // expression might be the expression from the switch, or an
3183                 // expression that includes any potential conversions to the
3184                 // integral types or to string.
3185                 //
3186                 Expression SwitchGoverningType (EmitContext ec, Expression expr)
3187                 {
3188                         Type t = expr.Type;
3189
3190                         if (t == TypeManager.byte_type ||
3191                             t == TypeManager.sbyte_type ||
3192                             t == TypeManager.ushort_type ||
3193                             t == TypeManager.short_type ||
3194                             t == TypeManager.uint32_type ||
3195                             t == TypeManager.int32_type ||
3196                             t == TypeManager.uint64_type ||
3197                             t == TypeManager.int64_type ||
3198                             t == TypeManager.char_type ||
3199                             t == TypeManager.string_type ||
3200                             t == TypeManager.bool_type ||
3201                             TypeManager.IsEnumType (t))
3202                                 return expr;
3203
3204                         if (allowed_types == null){
3205                                 allowed_types = new Type [] {
3206                                         TypeManager.sbyte_type,
3207                                         TypeManager.byte_type,
3208                                         TypeManager.short_type,
3209                                         TypeManager.ushort_type,
3210                                         TypeManager.int32_type,
3211                                         TypeManager.uint32_type,
3212                                         TypeManager.int64_type,
3213                                         TypeManager.uint64_type,
3214                                         TypeManager.char_type,
3215                                         TypeManager.string_type
3216                                 };
3217                         }
3218
3219                         //
3220                         // Try to find a *user* defined implicit conversion.
3221                         //
3222                         // If there is no implicit conversion, or if there are multiple
3223                         // conversions, we have to report an error
3224                         //
3225                         Expression converted = null;
3226                         foreach (Type tt in allowed_types){
3227                                 Expression e;
3228
3229                                 e = Convert.ImplicitUserConversion (ec, expr, tt, loc);
3230                                 if (e == null)
3231                                         continue;
3232
3233                                 //
3234                                 // Ignore over-worked ImplicitUserConversions that do
3235                                 // an implicit conversion in addition to the user conversion.
3236                                 //
3237                                 if (!(e is UserCast))
3238                                         continue;
3239
3240                                 if (converted != null){
3241                                         Report.ExtraInformation (loc, "(Ambiguous implicit user defined conversion in previous ");
3242                                         return null;
3243                                 }
3244
3245                                 converted = e;
3246                         }
3247                         return converted;
3248                 }
3249
3250                 //
3251                 // Performs the basic sanity checks on the switch statement
3252                 // (looks for duplicate keys and non-constant expressions).
3253                 //
3254                 // It also returns a hashtable with the keys that we will later
3255                 // use to compute the switch tables
3256                 //
3257                 bool CheckSwitch (EmitContext ec)
3258                 {
3259                         bool error = false;
3260                         Elements = Sections.Count > 10 ?
3261                                 (IDictionary)new Hashtable () :
3262                                 (IDictionary)new ListDictionary ();
3263
3264                         foreach (SwitchSection ss in Sections){
3265                                 foreach (SwitchLabel sl in ss.Labels){
3266                                         if (sl.Label == null){
3267                                                 if (default_section != null){
3268                                                         sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)default_section.Labels [0]);
3269                                                         error = true;
3270                                                 }
3271                                                 default_section = ss;
3272                                                 continue;
3273                                         }
3274
3275                                         if (!sl.ResolveAndReduce (ec, SwitchType, HaveUnwrap)) {
3276                                                 error = true;
3277                                                 continue;
3278                                         }
3279
3280                                         object key = sl.Converted;
3281                                         if (key == SwitchLabel.NullStringCase)
3282                                                 has_null_case = true;
3283
3284                                         try {
3285                                                 Elements.Add (key, sl);
3286                                         } catch (ArgumentException) {
3287                                                 sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)Elements [key]);
3288                                                 error = true;
3289                                         }
3290                                 }
3291                         }
3292                         return !error;
3293                 }
3294
3295                 void EmitObjectInteger (ILGenerator ig, object k)
3296                 {
3297                         if (k is int)
3298                                 IntConstant.EmitInt (ig, (int) k);
3299                         else if (k is Constant) {
3300                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
3301                         }
3302                         else if (k is uint)
3303                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
3304                         else if (k is long)
3305                         {
3306                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
3307                                 {
3308                                         IntConstant.EmitInt (ig, (int) (long) k);
3309                                         ig.Emit (OpCodes.Conv_I8);
3310                                 }
3311                                 else
3312                                         LongConstant.EmitLong (ig, (long) k);
3313                         }
3314                         else if (k is ulong)
3315                         {
3316                                 ulong ul = (ulong) k;
3317                                 if (ul < (1L<<32))
3318                                 {
3319                                         IntConstant.EmitInt (ig, unchecked ((int) ul));
3320                                         ig.Emit (OpCodes.Conv_U8);
3321                                 }
3322                                 else
3323                                 {
3324                                         LongConstant.EmitLong (ig, unchecked ((long) ul));
3325                                 }
3326                         }
3327                         else if (k is char)
3328                                 IntConstant.EmitInt (ig, (int) ((char) k));
3329                         else if (k is sbyte)
3330                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
3331                         else if (k is byte)
3332                                 IntConstant.EmitInt (ig, (int) ((byte) k));
3333                         else if (k is short)
3334                                 IntConstant.EmitInt (ig, (int) ((short) k));
3335                         else if (k is ushort)
3336                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
3337                         else if (k is bool)
3338                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
3339                         else
3340                                 throw new Exception ("Unhandled case");
3341                 }
3342
3343                 // structure used to hold blocks of keys while calculating table switch
3344                 class KeyBlock : IComparable
3345                 {
3346                         public KeyBlock (long _first)
3347                         {
3348                                 first = last = _first;
3349                         }
3350                         public long first;
3351                         public long last;
3352                         public ArrayList element_keys = null;
3353                         // how many items are in the bucket
3354                         public int Size = 1;
3355                         public int Length
3356                         {
3357                                 get { return (int) (last - first + 1); }
3358                         }
3359                         public static long TotalLength (KeyBlock kb_first, KeyBlock kb_last)
3360                         {
3361                                 return kb_last.last - kb_first.first + 1;
3362                         }
3363                         public int CompareTo (object obj)
3364                         {
3365                                 KeyBlock kb = (KeyBlock) obj;
3366                                 int nLength = Length;
3367                                 int nLengthOther = kb.Length;
3368                                 if (nLengthOther == nLength)
3369                                         return (int) (kb.first - first);
3370                                 return nLength - nLengthOther;
3371                         }
3372                 }
3373
3374                 /// <summary>
3375                 /// This method emits code for a lookup-based switch statement (non-string)
3376                 /// Basically it groups the cases into blocks that are at least half full,
3377                 /// and then spits out individual lookup opcodes for each block.
3378                 /// It emits the longest blocks first, and short blocks are just
3379                 /// handled with direct compares.
3380                 /// </summary>
3381                 /// <param name="ec"></param>
3382                 /// <param name="val"></param>
3383                 /// <returns></returns>
3384                 void TableSwitchEmit (EmitContext ec, Expression val)
3385                 {
3386                         int element_count = Elements.Count;
3387                         object [] element_keys = new object [element_count];
3388                         Elements.Keys.CopyTo (element_keys, 0);
3389                         Array.Sort (element_keys);
3390
3391                         // initialize the block list with one element per key
3392                         ArrayList key_blocks = new ArrayList (element_count);
3393                         foreach (object key in element_keys)
3394                                 key_blocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));
3395
3396                         KeyBlock current_kb;
3397                         // iteratively merge the blocks while they are at least half full
3398                         // there's probably a really cool way to do this with a tree...
3399                         while (key_blocks.Count > 1)
3400                         {
3401                                 ArrayList key_blocks_new = new ArrayList ();
3402                                 current_kb = (KeyBlock) key_blocks [0];
3403                                 for (int ikb = 1; ikb < key_blocks.Count; ikb++)
3404                                 {
3405                                         KeyBlock kb = (KeyBlock) key_blocks [ikb];
3406                                         if ((current_kb.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (current_kb, kb))
3407                                         {
3408                                                 // merge blocks
3409                                                 current_kb.last = kb.last;
3410                                                 current_kb.Size += kb.Size;
3411                                         }
3412                                         else
3413                                         {
3414                                                 // start a new block
3415                                                 key_blocks_new.Add (current_kb);
3416                                                 current_kb = kb;
3417                                         }
3418                                 }
3419                                 key_blocks_new.Add (current_kb);
3420                                 if (key_blocks.Count == key_blocks_new.Count)
3421                                         break;
3422                                 key_blocks = key_blocks_new;
3423                         }
3424
3425                         // initialize the key lists
3426                         foreach (KeyBlock kb in key_blocks)
3427                                 kb.element_keys = new ArrayList ();
3428
3429                         // fill the key lists
3430                         int iBlockCurr = 0;
3431                         if (key_blocks.Count > 0) {
3432                                 current_kb = (KeyBlock) key_blocks [0];
3433                                 foreach (object key in element_keys)
3434                                 {
3435                                         bool next_block = (key is UInt64) ? (ulong) key > (ulong) current_kb.last :
3436                                                 System.Convert.ToInt64 (key) > current_kb.last;
3437                                         if (next_block)
3438                                                 current_kb = (KeyBlock) key_blocks [++iBlockCurr];
3439                                         current_kb.element_keys.Add (key);
3440                                 }
3441                         }
3442
3443                         // sort the blocks so we can tackle the largest ones first
3444                         key_blocks.Sort ();
3445
3446                         // okay now we can start...
3447                         ILGenerator ig = ec.ig;
3448                         Label lbl_end = ig.DefineLabel ();      // at the end ;-)
3449                         Label lbl_default = default_target;
3450
3451                         Type type_keys = null;
3452                         if (element_keys.Length > 0)
3453                                 type_keys = element_keys [0].GetType ();        // used for conversions
3454
3455                         Type compare_type;
3456
3457                         if (TypeManager.IsEnumType (SwitchType))
3458                                 compare_type = TypeManager.GetEnumUnderlyingType (SwitchType);
3459                         else
3460                                 compare_type = SwitchType;
3461
3462                         for (int iBlock = key_blocks.Count - 1; iBlock >= 0; --iBlock)
3463                         {
3464                                 KeyBlock kb = ((KeyBlock) key_blocks [iBlock]);
3465                                 lbl_default = (iBlock == 0) ? default_target : ig.DefineLabel ();
3466                                 if (kb.Length <= 2)
3467                                 {
3468                                         foreach (object key in kb.element_keys) {
3469                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
3470                                                 if (key is int && (int) key == 0) {
3471                                                         val.EmitBranchable (ec, sl.GetILLabel (ec), false);
3472                                                 } else {
3473                                                         val.Emit (ec);
3474                                                         EmitObjectInteger (ig, key);
3475                                                         ig.Emit (OpCodes.Beq, sl.GetILLabel (ec));
3476                                                 }
3477                                         }
3478                                 }
3479                                 else
3480                                 {
3481                                         // TODO: if all the keys in the block are the same and there are
3482                                         //       no gaps/defaults then just use a range-check.
3483                                         if (compare_type == TypeManager.int64_type ||
3484                                                 compare_type == TypeManager.uint64_type)
3485                                         {
3486                                                 // TODO: optimize constant/I4 cases
3487
3488                                                 // check block range (could be > 2^31)
3489                                                 val.Emit (ec);
3490                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3491                                                 ig.Emit (OpCodes.Blt, lbl_default);
3492                                                 val.Emit (ec);
3493                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.last, type_keys));
3494                                                 ig.Emit (OpCodes.Bgt, lbl_default);
3495
3496                                                 // normalize range
3497                                                 val.Emit (ec);
3498                                                 if (kb.first != 0)
3499                                                 {
3500                                                         EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3501                                                         ig.Emit (OpCodes.Sub);
3502                                                 }
3503                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
3504                                         }
3505                                         else
3506                                         {
3507                                                 // normalize range
3508                                                 val.Emit (ec);
3509                                                 int first = (int) kb.first;
3510                                                 if (first > 0)
3511                                                 {
3512                                                         IntConstant.EmitInt (ig, first);
3513                                                         ig.Emit (OpCodes.Sub);
3514                                                 }
3515                                                 else if (first < 0)
3516                                                 {
3517                                                         IntConstant.EmitInt (ig, -first);
3518                                                         ig.Emit (OpCodes.Add);
3519                                                 }
3520                                         }
3521
3522                                         // first, build the list of labels for the switch
3523                                         int iKey = 0;
3524                                         int cJumps = kb.Length;
3525                                         Label [] switch_labels = new Label [cJumps];
3526                                         for (int iJump = 0; iJump < cJumps; iJump++)
3527                                         {
3528                                                 object key = kb.element_keys [iKey];
3529                                                 if (System.Convert.ToInt64 (key) == kb.first + iJump)
3530                                                 {
3531                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
3532                                                         switch_labels [iJump] = sl.GetILLabel (ec);
3533                                                         iKey++;
3534                                                 }
3535                                                 else
3536                                                         switch_labels [iJump] = lbl_default;
3537                                         }
3538                                         // emit the switch opcode
3539                                         ig.Emit (OpCodes.Switch, switch_labels);
3540                                 }
3541
3542                                 // mark the default for this block
3543                                 if (iBlock != 0)
3544                                         ig.MarkLabel (lbl_default);
3545                         }
3546
3547                         // TODO: find the default case and emit it here,
3548                         //       to prevent having to do the following jump.
3549                         //       make sure to mark other labels in the default section
3550
3551                         // the last default just goes to the end
3552                         if (element_keys.Length > 0)
3553                                 ig.Emit (OpCodes.Br, lbl_default);
3554
3555                         // now emit the code for the sections
3556                         bool found_default = false;
3557
3558                         foreach (SwitchSection ss in Sections) {
3559                                 foreach (SwitchLabel sl in ss.Labels) {
3560                                         if (sl.Converted == SwitchLabel.NullStringCase) {
3561                                                 ig.MarkLabel (null_target);
3562                                         } else if (sl.Label == null) {
3563                                                 ig.MarkLabel (lbl_default);
3564                                                 found_default = true;
3565                                                 if (!has_null_case)
3566                                                         ig.MarkLabel (null_target);
3567                                         }
3568                                         ig.MarkLabel (sl.GetILLabel (ec));
3569                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3570                                 }
3571                                 ss.Block.Emit (ec);
3572                         }
3573
3574                         if (!found_default) {
3575                                 ig.MarkLabel (lbl_default);
3576                                 if (!has_null_case) {
3577                                         ig.MarkLabel (null_target);
3578                                 }
3579                         }
3580
3581                         ig.MarkLabel (lbl_end);
3582                 }
3583
3584                 SwitchSection FindSection (SwitchLabel label)
3585                 {
3586                         foreach (SwitchSection ss in Sections){
3587                                 foreach (SwitchLabel sl in ss.Labels){
3588                                         if (label == sl)
3589                                                 return ss;
3590                                 }
3591                         }
3592
3593                         return null;
3594                 }
3595
3596                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
3597                 {
3598                         foreach (SwitchSection ss in Sections)
3599                                 ss.Block.MutateHoistedGenericType (storey);
3600                 }
3601
3602                 public static void Reset ()
3603                 {
3604                         unique_counter = 0;
3605                         allowed_types = null;
3606                 }
3607
3608                 public override bool Resolve (EmitContext ec)
3609                 {
3610                         Expr = Expr.Resolve (ec);
3611                         if (Expr == null)
3612                                 return false;
3613
3614                         new_expr = SwitchGoverningType (ec, Expr);
3615
3616 #if GMCS_SOURCE
3617                         if ((new_expr == null) && TypeManager.IsNullableType (Expr.Type)) {
3618                                 unwrap = Nullable.Unwrap.Create (Expr, false);
3619                                 if (unwrap == null)
3620                                         return false;
3621
3622                                 new_expr = SwitchGoverningType (ec, unwrap);
3623                         }
3624 #endif
3625
3626                         if (new_expr == null){
3627                                 Report.Error (151, loc, "A value of an integral type or string expected for switch");
3628                                 return false;
3629                         }
3630
3631                         // Validate switch.
3632                         SwitchType = new_expr.Type;
3633
3634                         if (RootContext.Version == LanguageVersion.ISO_1 && SwitchType == TypeManager.bool_type) {
3635                                 Report.FeatureIsNotAvailable (loc, "switch expression of boolean type");
3636                                 return false;
3637                         }
3638
3639                         if (!CheckSwitch (ec))
3640                                 return false;
3641
3642                         if (HaveUnwrap)
3643                                 Elements.Remove (SwitchLabel.NullStringCase);
3644
3645                         Switch old_switch = ec.Switch;
3646                         ec.Switch = this;
3647                         ec.Switch.SwitchType = SwitchType;
3648
3649                         Report.Debug (1, "START OF SWITCH BLOCK", loc, ec.CurrentBranching);
3650                         ec.StartFlowBranching (FlowBranching.BranchingType.Switch, loc);
3651
3652                         is_constant = new_expr is Constant;
3653                         if (is_constant) {
3654                                 object key = ((Constant) new_expr).GetValue ();
3655                                 SwitchLabel label = (SwitchLabel) Elements [key];
3656
3657                                 constant_section = FindSection (label);
3658                                 if (constant_section == null)
3659                                         constant_section = default_section;
3660                         }
3661
3662                         bool first = true;
3663                         bool ok = true;
3664                         foreach (SwitchSection ss in Sections){
3665                                 if (!first)
3666                                         ec.CurrentBranching.CreateSibling (
3667                                                 null, FlowBranching.SiblingType.SwitchSection);
3668                                 else
3669                                         first = false;
3670
3671                                 if (is_constant && (ss != constant_section)) {
3672                                         // If we're a constant switch, we're only emitting
3673                                         // one single section - mark all the others as
3674                                         // unreachable.
3675                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
3676                                         if (!ss.Block.ResolveUnreachable (ec, true)) {
3677                                                 ok = false;
3678                                         }
3679                                 } else {
3680                                         if (!ss.Block.Resolve (ec))
3681                                                 ok = false;
3682                                 }
3683                         }
3684
3685                         if (default_section == null)
3686                                 ec.CurrentBranching.CreateSibling (
3687                                         null, FlowBranching.SiblingType.SwitchSection);
3688
3689                         ec.EndFlowBranching ();
3690                         ec.Switch = old_switch;
3691
3692                         Report.Debug (1, "END OF SWITCH BLOCK", loc, ec.CurrentBranching);
3693
3694                         if (!ok)
3695                                 return false;
3696
3697                         if (SwitchType == TypeManager.string_type && !is_constant) {
3698                                 // TODO: Optimize single case, and single+default case
3699                                 ResolveStringSwitchMap (ec);
3700                         }
3701
3702                         return true;
3703                 }
3704
3705                 void ResolveStringSwitchMap (EmitContext ec)
3706                 {
3707                         FullNamedExpression string_dictionary_type;
3708 #if GMCS_SOURCE
3709                         MemberAccess system_collections_generic = new MemberAccess (new MemberAccess (
3710                                 new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Collections", loc), "Generic", loc);
3711
3712                         string_dictionary_type = new MemberAccess (system_collections_generic, "Dictionary",
3713                                 new TypeArguments (
3714                                         new TypeExpression (TypeManager.string_type, loc),
3715                                         new TypeExpression (TypeManager.int32_type, loc)), loc);
3716 #else
3717                         MemberAccess system_collections_generic = new MemberAccess (
3718                                 new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Collections", loc);
3719
3720                         string_dictionary_type = new MemberAccess (system_collections_generic, "Hashtable", loc);
3721 #endif
3722                         Field field = new Field (ec.TypeContainer, string_dictionary_type,
3723                                 Modifiers.STATIC | Modifiers.PRIVATE | Modifiers.COMPILER_GENERATED,
3724                                 new MemberName (CompilerGeneratedClass.MakeName (null, "f", "switch$map", unique_counter++), loc), null);
3725                         if (!field.Define ())
3726                                 return;
3727                         ec.TypeContainer.PartialContainer.AddField (field);
3728
3729                         ArrayList init = new ArrayList ();
3730                         int counter = 0;
3731                         Elements.Clear ();
3732                         string value = null;
3733                         foreach (SwitchSection section in Sections) {
3734                                 foreach (SwitchLabel sl in section.Labels) {
3735                                         if (sl.Label == null || sl.Converted == SwitchLabel.NullStringCase) {
3736                                                 value = null;
3737                                                 continue;
3738                                         }
3739
3740                                         value = (string) sl.Converted;
3741                                         ArrayList init_args = new ArrayList (2);
3742                                         init_args.Add (new StringLiteral (value, sl.Location));
3743                                         init_args.Add (new IntConstant (counter, loc));
3744                                         init.Add (new CollectionElementInitializer (init_args, loc));
3745                                 }
3746
3747                                 if (value == null)
3748                                         continue;
3749
3750                                 Elements.Add (counter, section.Labels [0]);
3751                                 ++counter;
3752                         }
3753
3754                         ArrayList args = new ArrayList (1);
3755                         args.Add (new Argument (new IntConstant (Sections.Count, loc)));
3756                         Expression initializer = new NewInitialize (string_dictionary_type, args,
3757                                 new CollectionOrObjectInitializers (init, loc), loc);
3758
3759                         switch_cache_field = new FieldExpr (field.FieldBuilder, loc);
3760                         string_dictionary = new SimpleAssign (switch_cache_field, initializer.Resolve (ec));
3761                 }
3762
3763                 void DoEmitStringSwitch (LocalTemporary value, EmitContext ec)
3764                 {
3765                         ILGenerator ig = ec.ig;
3766                         Label l_initialized = ig.DefineLabel ();
3767
3768                         //
3769                         // Skip initialization when value is null
3770                         //
3771                         value.EmitBranchable (ec, null_target, false);
3772
3773                         //
3774                         // Check if string dictionary is initialized and initialize
3775                         //
3776                         switch_cache_field.EmitBranchable (ec, l_initialized, true);
3777                         string_dictionary.EmitStatement (ec);
3778                         ig.MarkLabel (l_initialized);
3779
3780                         LocalTemporary string_switch_variable = new LocalTemporary (TypeManager.int32_type);
3781
3782 #if GMCS_SOURCE
3783                         ArrayList get_value_args = new ArrayList (2);
3784                         get_value_args.Add (new Argument (value));
3785                         get_value_args.Add (new Argument (string_switch_variable, Argument.AType.Out));
3786                         Expression get_item = new Invocation (new MemberAccess (switch_cache_field, "TryGetValue", loc), get_value_args).Resolve (ec);
3787                         if (get_item == null)
3788                                 return;
3789
3790                         //
3791                         // A value was not found, go to default case
3792                         //
3793                         get_item.EmitBranchable (ec, default_target, false);
3794 #else
3795                         ArrayList get_value_args = new ArrayList (1);
3796                         get_value_args.Add (value);
3797
3798                         Expression get_item = new IndexerAccess (new ElementAccess (switch_cache_field, get_value_args), loc).Resolve (ec);
3799                         if (get_item == null)
3800                                 return;
3801
3802                         LocalTemporary get_item_object = new LocalTemporary (TypeManager.object_type);
3803                         get_item_object.EmitAssign (ec, get_item, true, false);
3804                         ec.ig.Emit (OpCodes.Brfalse, default_target);
3805
3806                         ExpressionStatement get_item_int = (ExpressionStatement) new SimpleAssign (string_switch_variable,
3807                                 new Cast (new TypeExpression (TypeManager.int32_type, loc), get_item_object, loc)).Resolve (ec);
3808
3809                         get_item_int.EmitStatement (ec);
3810                         get_item_object.Release (ec);
3811 #endif
3812                         TableSwitchEmit (ec, string_switch_variable);
3813                         string_switch_variable.Release (ec);
3814                 }
3815
3816                 protected override void DoEmit (EmitContext ec)
3817                 {
3818                         ILGenerator ig = ec.ig;
3819
3820                         default_target = ig.DefineLabel ();
3821                         null_target = ig.DefineLabel ();
3822
3823                         // Store variable for comparission purposes
3824                         // TODO: Don't duplicate non-captured VariableReference
3825                         LocalTemporary value;
3826                         if (HaveUnwrap) {
3827                                 value = new LocalTemporary (SwitchType);
3828 #if GMCS_SOURCE
3829                                 unwrap.EmitCheck (ec);
3830                                 ig.Emit (OpCodes.Brfalse, null_target);
3831                                 new_expr.Emit (ec);
3832                                 value.Store (ec);
3833 #endif
3834                         } else if (!is_constant) {
3835                                 value = new LocalTemporary (SwitchType);
3836                                 new_expr.Emit (ec);
3837                                 value.Store (ec);
3838                         } else
3839                                 value = null;
3840
3841                         //
3842                         // Setup the codegen context
3843                         //
3844                         Label old_end = ec.LoopEnd;
3845                         Switch old_switch = ec.Switch;
3846
3847                         ec.LoopEnd = ig.DefineLabel ();
3848                         ec.Switch = this;
3849
3850                         // Emit Code.
3851                         if (is_constant) {
3852                                 if (constant_section != null)
3853                                         constant_section.Block.Emit (ec);
3854                         } else if (string_dictionary != null) {
3855                                 DoEmitStringSwitch (value, ec);
3856                         } else {
3857                                 TableSwitchEmit (ec, value);
3858                         }
3859
3860                         if (value != null)
3861                                 value.Release (ec);
3862
3863                         // Restore context state.
3864                         ig.MarkLabel (ec.LoopEnd);
3865
3866                         //
3867                         // Restore the previous context
3868                         //
3869                         ec.LoopEnd = old_end;
3870                         ec.Switch = old_switch;
3871                 }
3872
3873                 protected override void CloneTo (CloneContext clonectx, Statement t)
3874                 {
3875                         Switch target = (Switch) t;
3876
3877                         target.Expr = Expr.Clone (clonectx);
3878                         target.Sections = new ArrayList ();
3879                         foreach (SwitchSection ss in Sections){
3880                                 target.Sections.Add (ss.Clone (clonectx));
3881                         }
3882                 }
3883         }
3884
3885         // A place where execution can restart in an iterator
3886         public abstract class ResumableStatement : Statement
3887         {
3888                 bool prepared;
3889                 protected Label resume_point;
3890
3891                 public Label PrepareForEmit (EmitContext ec)
3892                 {
3893                         if (!prepared) {
3894                                 prepared = true;
3895                                 resume_point = ec.ig.DefineLabel ();
3896                         }
3897                         return resume_point;
3898                 }
3899
3900                 public virtual Label PrepareForDispose (EmitContext ec, Label end)
3901                 {
3902                         return end;
3903                 }
3904                 public virtual void EmitForDispose (EmitContext ec, Iterator iterator, Label end, bool have_dispatcher)
3905                 {
3906                 }
3907         }
3908
3909         // Base class for statements that are implemented in terms of try...finally
3910         public abstract class ExceptionStatement : ResumableStatement
3911         {
3912                 bool code_follows;
3913
3914                 protected abstract void EmitPreTryBody (EmitContext ec);
3915                 protected abstract void EmitTryBody (EmitContext ec);
3916                 protected abstract void EmitFinallyBody (EmitContext ec);
3917
3918                 protected sealed override void DoEmit (EmitContext ec)
3919                 {
3920                         ILGenerator ig = ec.ig;
3921
3922                         EmitPreTryBody (ec);
3923
3924                         if (resume_points != null) {
3925                                 IntConstant.EmitInt (ig, (int) Iterator.State.Running);
3926                                 ig.Emit (OpCodes.Stloc, ec.CurrentIterator.CurrentPC);
3927                         }
3928
3929                         ig.BeginExceptionBlock ();
3930
3931                         if (resume_points != null) {
3932                                 ig.MarkLabel (resume_point);
3933
3934                                 // For normal control flow, we want to fall-through the Switch
3935                                 // So, we use CurrentPC rather than the $PC field, and initialize it to an outside value above
3936                                 ig.Emit (OpCodes.Ldloc, ec.CurrentIterator.CurrentPC);
3937                                 IntConstant.EmitInt (ig, first_resume_pc);
3938                                 ig.Emit (OpCodes.Sub);
3939
3940                                 Label [] labels = new Label [resume_points.Count];
3941                                 for (int i = 0; i < resume_points.Count; ++i)
3942                                         labels [i] = ((ResumableStatement) resume_points [i]).PrepareForEmit (ec);
3943                                 ig.Emit (OpCodes.Switch, labels);
3944                         }
3945
3946                         EmitTryBody (ec);
3947
3948                         ig.BeginFinallyBlock ();
3949
3950                         Label start_finally = ec.ig.DefineLabel ();
3951                         if (resume_points != null) {
3952                                 ig.Emit (OpCodes.Ldloc, ec.CurrentIterator.SkipFinally);
3953                                 ig.Emit (OpCodes.Brfalse_S, start_finally);
3954                                 ig.Emit (OpCodes.Endfinally);
3955                         }
3956
3957                         ig.MarkLabel (start_finally);
3958                         EmitFinallyBody (ec);
3959
3960                         ig.EndExceptionBlock ();
3961                 }
3962
3963                 public void SomeCodeFollows ()
3964                 {
3965                         code_follows = true;
3966                 }
3967
3968                 protected void ResolveReachability (EmitContext ec)
3969                 {
3970                         // System.Reflection.Emit automatically emits a 'leave' at the end of a try clause
3971                         // So, ensure there's some IL code after this statement.
3972                         if (!code_follows && resume_points == null && ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
3973                                 ec.NeedReturnLabel ();
3974
3975                 }
3976
3977                 ArrayList resume_points;
3978                 int first_resume_pc;
3979                 public void AddResumePoint (ResumableStatement stmt, int pc)
3980                 {
3981                         if (resume_points == null) {
3982                                 resume_points = new ArrayList ();
3983                                 first_resume_pc = pc;
3984                         }
3985
3986                         if (pc != first_resume_pc + resume_points.Count)
3987                                 throw new InternalErrorException ("missed an intervening AddResumePoint?");
3988
3989                         resume_points.Add (stmt);
3990                 }
3991
3992                 Label dispose_try_block;
3993                 bool prepared_for_dispose, emitted_dispose;
3994                 public override Label PrepareForDispose (EmitContext ec, Label end)
3995                 {
3996                         if (!prepared_for_dispose) {
3997                                 prepared_for_dispose = true;
3998                                 dispose_try_block = ec.ig.DefineLabel ();
3999                         }
4000                         return dispose_try_block;
4001                 }
4002
4003                 public override void EmitForDispose (EmitContext ec, Iterator iterator, Label end, bool have_dispatcher)
4004                 {
4005                         if (emitted_dispose)
4006                                 return;
4007
4008                         emitted_dispose = true;
4009
4010                         ILGenerator ig = ec.ig;
4011
4012                         Label end_of_try = ig.DefineLabel ();
4013
4014                         // Ensure that the only way we can get into this code is through a dispatcher
4015                         if (have_dispatcher)
4016                                 ig.Emit (OpCodes.Br, end);
4017
4018                         ig.BeginExceptionBlock ();
4019
4020                         ig.MarkLabel (dispose_try_block);
4021
4022                         Label [] labels = null;
4023                         for (int i = 0; i < resume_points.Count; ++i) {
4024                                 ResumableStatement s = (ResumableStatement) resume_points [i];
4025                                 Label ret = s.PrepareForDispose (ec, end_of_try);
4026                                 if (ret.Equals (end_of_try) && labels == null)
4027                                         continue;
4028                                 if (labels == null) {
4029                                         labels = new Label [resume_points.Count];
4030                                         for (int j = 0; j < i; ++j)
4031                                                 labels [j] = end_of_try;
4032                                 }
4033                                 labels [i] = ret;
4034                         }
4035
4036                         if (labels != null) {
4037                                 int j;
4038                                 for (j = 1; j < labels.Length; ++j)
4039                                         if (!labels [0].Equals (labels [j]))
4040                                                 break;
4041                                 bool emit_dispatcher = j < labels.Length;
4042
4043                                 if (emit_dispatcher) {
4044                                         //SymbolWriter.StartIteratorDispatcher (ec.ig);
4045                                         ig.Emit (OpCodes.Ldloc, iterator.CurrentPC);
4046                                         IntConstant.EmitInt (ig, first_resume_pc);
4047                                         ig.Emit (OpCodes.Sub);
4048                                         ig.Emit (OpCodes.Switch, labels);
4049                                         //SymbolWriter.EndIteratorDispatcher (ec.ig);
4050                                 }
4051
4052                                 foreach (ResumableStatement s in resume_points)
4053                                         s.EmitForDispose (ec, iterator, end_of_try, emit_dispatcher);
4054                         }
4055
4056                         ig.MarkLabel (end_of_try);
4057
4058                         ig.BeginFinallyBlock ();
4059
4060                         EmitFinallyBody (ec);
4061
4062                         ig.EndExceptionBlock ();
4063                 }
4064         }
4065
4066         public class Lock : ExceptionStatement {
4067                 Expression expr;
4068                 public Statement Statement;
4069                 TemporaryVariable temp;
4070
4071                 public Lock (Expression expr, Statement stmt, Location l)
4072                 {
4073                         this.expr = expr;
4074                         Statement = stmt;
4075                         loc = l;
4076                 }
4077
4078                 public override bool Resolve (EmitContext ec)
4079                 {
4080                         expr = expr.Resolve (ec);
4081                         if (expr == null)
4082                                 return false;
4083
4084                         if (!TypeManager.IsReferenceType (expr.Type)){
4085                                 Report.Error (185, loc,
4086                                               "`{0}' is not a reference type as required by the lock statement",
4087                                               TypeManager.CSharpName (expr.Type));
4088                                 return false;
4089                         }
4090
4091                         ec.StartFlowBranching (this);
4092                         bool ok = Statement.Resolve (ec);
4093                         ec.EndFlowBranching ();
4094
4095                         ResolveReachability (ec);
4096
4097                         // Avoid creating libraries that reference the internal
4098                         // mcs NullType:
4099                         Type t = expr.Type;
4100                         if (t == TypeManager.null_type)
4101                                 t = TypeManager.object_type;
4102
4103                         temp = new TemporaryVariable (t, loc);
4104                         temp.Resolve (ec);
4105
4106                         if (TypeManager.void_monitor_enter_object == null || TypeManager.void_monitor_exit_object == null) {
4107                                 Type monitor_type = TypeManager.CoreLookupType ("System.Threading", "Monitor", Kind.Class, true);
4108                                 TypeManager.void_monitor_enter_object = TypeManager.GetPredefinedMethod (
4109                                         monitor_type, "Enter", loc, TypeManager.object_type);
4110                                 TypeManager.void_monitor_exit_object = TypeManager.GetPredefinedMethod (
4111                                         monitor_type, "Exit", loc, TypeManager.object_type);
4112                         }
4113
4114                         return ok;
4115                 }
4116
4117                 protected override void EmitPreTryBody (EmitContext ec)
4118                 {
4119                         ILGenerator ig = ec.ig;
4120
4121                         temp.EmitAssign (ec, expr);
4122                         temp.Emit (ec);
4123                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
4124                 }
4125
4126                 protected override void EmitTryBody (EmitContext ec)
4127                 {
4128                         Statement.Emit (ec);
4129                 }
4130
4131                 protected override void EmitFinallyBody (EmitContext ec)
4132                 {
4133                         temp.Emit (ec);
4134                         ec.ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
4135                 }
4136
4137                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4138                 {
4139                         expr.MutateHoistedGenericType (storey);
4140                         temp.MutateHoistedGenericType (storey);
4141                         Statement.MutateHoistedGenericType (storey);
4142                 }
4143
4144                 protected override void CloneTo (CloneContext clonectx, Statement t)
4145                 {
4146                         Lock target = (Lock) t;
4147
4148                         target.expr = expr.Clone (clonectx);
4149                         target.Statement = Statement.Clone (clonectx);
4150                 }
4151         }
4152
4153         public class Unchecked : Statement {
4154                 public Block Block;
4155
4156                 public Unchecked (Block b)
4157                 {
4158                         Block = b;
4159                         b.Unchecked = true;
4160                 }
4161
4162                 public override bool Resolve (EmitContext ec)
4163                 {
4164                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
4165                                 return Block.Resolve (ec);
4166                 }
4167
4168                 protected override void DoEmit (EmitContext ec)
4169                 {
4170                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
4171                                 Block.Emit (ec);
4172                 }
4173
4174                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4175                 {
4176                         Block.MutateHoistedGenericType (storey);
4177                 }
4178
4179                 protected override void CloneTo (CloneContext clonectx, Statement t)
4180                 {
4181                         Unchecked target = (Unchecked) t;
4182
4183                         target.Block = clonectx.LookupBlock (Block);
4184                 }
4185         }
4186
4187         public class Checked : Statement {
4188                 public Block Block;
4189
4190                 public Checked (Block b)
4191                 {
4192                         Block = b;
4193                         b.Unchecked = false;
4194                 }
4195
4196                 public override bool Resolve (EmitContext ec)
4197                 {
4198                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
4199                                 return Block.Resolve (ec);
4200                 }
4201
4202                 protected override void DoEmit (EmitContext ec)
4203                 {
4204                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
4205                                 Block.Emit (ec);
4206                 }
4207
4208                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4209                 {
4210                         Block.MutateHoistedGenericType (storey);
4211                 }
4212
4213                 protected override void CloneTo (CloneContext clonectx, Statement t)
4214                 {
4215                         Checked target = (Checked) t;
4216
4217                         target.Block = clonectx.LookupBlock (Block);
4218                 }
4219         }
4220
4221         public class Unsafe : Statement {
4222                 public Block Block;
4223
4224                 public Unsafe (Block b)
4225                 {
4226                         Block = b;
4227                         Block.Unsafe = true;
4228                 }
4229
4230                 public override bool Resolve (EmitContext ec)
4231                 {
4232                         using (ec.With (EmitContext.Flags.InUnsafe, true))
4233                                 return Block.Resolve (ec);
4234                 }
4235
4236                 protected override void DoEmit (EmitContext ec)
4237                 {
4238                         using (ec.With (EmitContext.Flags.InUnsafe, true))
4239                                 Block.Emit (ec);
4240                 }
4241
4242                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4243                 {
4244                         Block.MutateHoistedGenericType (storey);
4245                 }
4246
4247                 protected override void CloneTo (CloneContext clonectx, Statement t)
4248                 {
4249                         Unsafe target = (Unsafe) t;
4250
4251                         target.Block = clonectx.LookupBlock (Block);
4252                 }
4253         }
4254
4255         //
4256         // Fixed statement
4257         //
4258         public class Fixed : Statement {
4259                 Expression type;
4260                 ArrayList declarators;
4261                 Statement statement;
4262                 Type expr_type;
4263                 Emitter[] data;
4264                 bool has_ret;
4265
4266                 abstract class Emitter
4267                 {
4268                         protected LocalInfo vi;
4269                         protected Expression converted;
4270
4271                         protected Emitter (Expression expr, LocalInfo li)
4272                         {
4273                                 converted = expr;
4274                                 vi = li;
4275                         }
4276
4277                         public abstract void Emit (EmitContext ec);
4278                         public abstract void EmitExit (EmitContext ec);
4279                 }
4280
4281                 class ExpressionEmitter : Emitter {
4282                         public ExpressionEmitter (Expression converted, LocalInfo li) :
4283                                 base (converted, li)
4284                         {
4285                         }
4286
4287                         public override void Emit (EmitContext ec) {
4288                                 //
4289                                 // Store pointer in pinned location
4290                                 //
4291                                 converted.Emit (ec);
4292                                 vi.EmitAssign (ec);
4293                         }
4294
4295                         public override void EmitExit (EmitContext ec)
4296                         {
4297                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
4298                                 ec.ig.Emit (OpCodes.Conv_U);
4299                                 vi.EmitAssign (ec);
4300                         }
4301                 }
4302
4303                 class StringEmitter : Emitter
4304                 {
4305                         LocalInfo pinned_string;
4306
4307                         public StringEmitter (Expression expr, LocalInfo li, Location loc):
4308                                 base (expr, li)
4309                         {
4310                                 pinned_string = new LocalInfo (new TypeExpression (TypeManager.string_type, loc), null, null, loc);
4311                                 pinned_string.Pinned = true;
4312                         }
4313
4314                         public override void Emit (EmitContext ec)
4315                         {
4316                                 pinned_string.Resolve (ec);
4317                                 pinned_string.ResolveVariable (ec);
4318
4319                                 converted.Emit (ec);
4320                                 pinned_string.EmitAssign (ec);
4321
4322                                 PropertyInfo p = TypeManager.int_get_offset_to_string_data;
4323                                 if (p == null) {
4324                                         // TODO: Move to resolve
4325                                         p = TypeManager.int_get_offset_to_string_data = TypeManager.GetPredefinedProperty (
4326                                                 TypeManager.runtime_helpers_type, "OffsetToStringData", pinned_string.Location, TypeManager.int32_type);
4327
4328                                         if (p == null)
4329                                                 return;
4330                                 }
4331
4332                                 // TODO: Should use Binary::Add
4333                                 pinned_string.Emit (ec);
4334                                 ec.ig.Emit (OpCodes.Conv_I);
4335
4336                                 PropertyExpr pe = new PropertyExpr (pinned_string.VariableType, p, pinned_string.Location);
4337                                 //pe.InstanceExpression = pinned_string;
4338                                 pe.Resolve (ec).Emit (ec);
4339
4340                                 ec.ig.Emit (OpCodes.Add);
4341                                 vi.EmitAssign (ec);
4342                         }
4343
4344                         public override void EmitExit (EmitContext ec)
4345                         {
4346                                 ec.ig.Emit (OpCodes.Ldnull);
4347                                 pinned_string.EmitAssign (ec);
4348                         }
4349                 }
4350
4351                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
4352                 {
4353                         this.type = type;
4354                         declarators = decls;
4355                         statement = stmt;
4356                         loc = l;
4357                 }
4358
4359                 public Statement Statement {
4360                         get { return statement; }
4361                 }
4362
4363                 public override bool Resolve (EmitContext ec)
4364                 {
4365                         if (!ec.InUnsafe){
4366                                 Expression.UnsafeError (loc);
4367                                 return false;
4368                         }
4369
4370                         TypeExpr texpr = type.ResolveAsContextualType (ec, false);
4371                         if (texpr == null) {
4372                                 if (type is VarExpr)
4373                                         Report.Error (821, type.Location, "A fixed statement cannot use an implicitly typed local variable");
4374
4375                                 return false;
4376                         }
4377
4378                         expr_type = texpr.Type;
4379
4380                         data = new Emitter [declarators.Count];
4381
4382                         if (!expr_type.IsPointer){
4383                                 Report.Error (209, loc, "The type of locals declared in a fixed statement must be a pointer type");
4384                                 return false;
4385                         }
4386
4387                         int i = 0;
4388                         foreach (Pair p in declarators){
4389                                 LocalInfo vi = (LocalInfo) p.First;
4390                                 Expression e = (Expression) p.Second;
4391
4392                                 vi.VariableInfo.SetAssigned (ec);
4393                                 vi.SetReadOnlyContext (LocalInfo.ReadOnlyContext.Fixed);
4394
4395                                 //
4396                                 // The rules for the possible declarators are pretty wise,
4397                                 // but the production on the grammar is more concise.
4398                                 //
4399                                 // So we have to enforce these rules here.
4400                                 //
4401                                 // We do not resolve before doing the case 1 test,
4402                                 // because the grammar is explicit in that the token &
4403                                 // is present, so we need to test for this particular case.
4404                                 //
4405
4406                                 if (e is Cast){
4407                                         Report.Error (254, loc, "The right hand side of a fixed statement assignment may not be a cast expression");
4408                                         return false;
4409                                 }
4410
4411                                 ec.InFixedInitializer = true;
4412                                 e = e.Resolve (ec);
4413                                 ec.InFixedInitializer = false;
4414                                 if (e == null)
4415                                         return false;
4416
4417                                 //
4418                                 // Case 2: Array
4419                                 //
4420                                 if (e.Type.IsArray){
4421                                         Type array_type = TypeManager.GetElementType (e.Type);
4422
4423                                         //
4424                                         // Provided that array_type is unmanaged,
4425                                         //
4426                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
4427                                                 return false;
4428
4429                                         //
4430                                         // and T* is implicitly convertible to the
4431                                         // pointer type given in the fixed statement.
4432                                         //
4433                                         ArrayPtr array_ptr = new ArrayPtr (e, array_type, loc);
4434
4435                                         Expression converted = Convert.ImplicitConversionRequired (
4436                                                 ec, array_ptr, vi.VariableType, loc);
4437                                         if (converted == null)
4438                                                 return false;
4439
4440                                         //
4441                                         // fixed (T* e_ptr = (e == null || e.Length == 0) ? null : converted [0])
4442                                         //
4443                                         converted = new Conditional (new Binary (Binary.Operator.LogicalOr,
4444                                                 new Binary (Binary.Operator.Equality, e, new NullLiteral (loc)),
4445                                                 new Binary (Binary.Operator.Equality, new MemberAccess (e, "Length"), new IntConstant (0, loc))),
4446                                                         new NullPointer (loc),
4447                                                         converted);
4448
4449                                         converted = converted.Resolve (ec);
4450
4451                                         data [i] = new ExpressionEmitter (converted, vi);
4452                                         i++;
4453
4454                                         continue;
4455                                 }
4456
4457                                 //
4458                                 // Case 3: string
4459                                 //
4460                                 if (e.Type == TypeManager.string_type){
4461                                         data [i] = new StringEmitter (e, vi, loc);
4462                                         i++;
4463                                         continue;
4464                                 }
4465
4466                                 // Case 4: fixed buffer
4467                                 if (e is FixedBufferPtr) {
4468                                         data [i++] = new ExpressionEmitter (e, vi);
4469                                         continue;
4470                                 }
4471
4472                                 //
4473                                 // Case 1: & object.
4474                                 //
4475                                 Unary u = e as Unary;
4476                                 if (u != null && u.Oper == Unary.Operator.AddressOf) {
4477                                         IVariableReference vr = u.Expr as IVariableReference;
4478                                         if (vr == null || !vr.IsFixed) {
4479                                                 data [i] = new ExpressionEmitter (e, vi);
4480                                         }
4481                                 }
4482
4483                                 if (data [i++] == null)
4484                                         Report.Error (213, vi.Location, "You cannot use the fixed statement to take the address of an already fixed expression");
4485
4486                                 e = Convert.ImplicitConversionRequired (ec, e, expr_type, loc);
4487                         }
4488
4489                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
4490                         bool ok = statement.Resolve (ec);
4491                         bool flow_unreachable = ec.EndFlowBranching ();
4492                         has_ret = flow_unreachable;
4493
4494                         return ok;
4495                 }
4496
4497                 protected override void DoEmit (EmitContext ec)
4498                 {
4499                         for (int i = 0; i < data.Length; i++) {
4500                                 data [i].Emit (ec);
4501                         }
4502
4503                         statement.Emit (ec);
4504
4505                         if (has_ret)
4506                                 return;
4507
4508                         //
4509                         // Clear the pinned variable
4510                         //
4511                         for (int i = 0; i < data.Length; i++) {
4512                                 data [i].EmitExit (ec);
4513                         }
4514                 }
4515
4516                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4517                 {
4518                         // Fixed statement cannot be used inside anonymous methods or lambdas
4519                         throw new NotSupportedException ();
4520                 }
4521
4522                 protected override void CloneTo (CloneContext clonectx, Statement t)
4523                 {
4524                         Fixed target = (Fixed) t;
4525
4526                         target.type = type.Clone (clonectx);
4527                         target.declarators = new ArrayList (declarators.Count);
4528                         foreach (Pair p in declarators) {
4529                                 LocalInfo vi = (LocalInfo) p.First;
4530                                 Expression e = (Expression) p.Second;
4531
4532                                 target.declarators.Add (
4533                                         new Pair (clonectx.LookupVariable (vi), e.Clone (clonectx)));
4534                         }
4535
4536                         target.statement = statement.Clone (clonectx);
4537                 }
4538         }
4539
4540         public class Catch : Statement {
4541                 public readonly string Name;
4542                 public Block  Block;
4543                 public Block  VarBlock;
4544
4545                 Expression type_expr;
4546                 Type type;
4547
4548                 public Catch (Expression type, string name, Block block, Block var_block, Location l)
4549                 {
4550                         type_expr = type;
4551                         Name = name;
4552                         Block = block;
4553                         VarBlock = var_block;
4554                         loc = l;
4555                 }
4556
4557                 public Type CatchType {
4558                         get {
4559                                 return type;
4560                         }
4561                 }
4562
4563                 public bool IsGeneral {
4564                         get {
4565                                 return type_expr == null;
4566                         }
4567                 }
4568
4569                 protected override void DoEmit (EmitContext ec)
4570                 {
4571                         ILGenerator ig = ec.ig;
4572
4573                         if (CatchType != null)
4574                                 ig.BeginCatchBlock (CatchType);
4575                         else
4576                                 ig.BeginCatchBlock (TypeManager.object_type);
4577
4578                         if (VarBlock != null)
4579                                 VarBlock.Emit (ec);
4580
4581                         if (Name != null) {
4582                                 // TODO: Move to resolve
4583                                 LocalVariableReference lvr = new LocalVariableReference (Block, Name, loc);
4584                                 lvr.Resolve (ec);
4585
4586 #if GMCS_SOURCE
4587                                 // Only to make verifier happy
4588                                 if (TypeManager.IsGenericParameter (lvr.Type))
4589                                         ig.Emit (OpCodes.Unbox_Any, lvr.Type);
4590 #endif
4591
4592                                 Expression source;
4593                                 if (lvr.IsHoisted) {
4594                                         LocalTemporary lt = new LocalTemporary (lvr.Type);
4595                                         lt.Store (ec);
4596                                         source = lt;
4597                                 } else {
4598                                         // Variable is at the top of the stack
4599                                         source = EmptyExpression.Null;
4600                                 }
4601
4602                                 lvr.EmitAssign (ec, source, false, false);
4603                         } else
4604                                 ig.Emit (OpCodes.Pop);
4605
4606                         Block.Emit (ec);
4607                 }
4608
4609                 public override bool Resolve (EmitContext ec)
4610                 {
4611                         using (ec.With (EmitContext.Flags.InCatch, true)) {
4612                                 if (type_expr != null) {
4613                                         TypeExpr te = type_expr.ResolveAsTypeTerminal (ec, false);
4614                                         if (te == null)
4615                                                 return false;
4616
4617                                         type = te.Type;
4618
4619                                         if (type != TypeManager.exception_type && !TypeManager.IsSubclassOf (type, TypeManager.exception_type)){
4620                                                 Error (155, "The type caught or thrown must be derived from System.Exception");
4621                                                 return false;
4622                                         }
4623                                 } else
4624                                         type = null;
4625
4626                                 if (!Block.Resolve (ec))
4627                                         return false;
4628
4629                                 // Even though VarBlock surrounds 'Block' we resolve it later, so that we can correctly
4630                                 // emit the "unused variable" warnings.
4631                                 if (VarBlock != null)
4632                                         return VarBlock.Resolve (ec);
4633
4634                                 return true;
4635                         }
4636                 }
4637
4638                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4639                 {
4640                         if (type != null)
4641                                 type = storey.MutateType (type);
4642                         if (VarBlock != null)
4643                                 VarBlock.MutateHoistedGenericType (storey);
4644                         Block.MutateHoistedGenericType (storey);
4645                 }
4646
4647                 protected override void CloneTo (CloneContext clonectx, Statement t)
4648                 {
4649                         Catch target = (Catch) t;
4650
4651                         if (type_expr != null)
4652                                 target.type_expr = type_expr.Clone (clonectx);
4653                         if (VarBlock != null)
4654                                 target.VarBlock = clonectx.LookupBlock (VarBlock);
4655                         target.Block = clonectx.LookupBlock (Block);
4656                 }
4657         }
4658
4659         public class TryFinally : ExceptionStatement {
4660                 Statement stmt;
4661                 Block fini;
4662
4663                 public TryFinally (Statement stmt, Block fini, Location l)
4664                 {
4665                         this.stmt = stmt;
4666                         this.fini = fini;
4667                         loc = l;
4668                 }
4669
4670                 public override bool Resolve (EmitContext ec)
4671                 {
4672                         bool ok = true;
4673
4674                         ec.StartFlowBranching (this);
4675
4676                         if (!stmt.Resolve (ec))
4677                                 ok = false;
4678
4679                         if (ok)
4680                                 ec.CurrentBranching.CreateSibling (fini, FlowBranching.SiblingType.Finally);
4681                         using (ec.With (EmitContext.Flags.InFinally, true)) {
4682                                 if (!fini.Resolve (ec))
4683                                         ok = false;
4684                         }
4685
4686                         ec.EndFlowBranching ();
4687
4688                         ResolveReachability (ec);
4689
4690                         return ok;
4691                 }
4692
4693                 protected override void EmitPreTryBody (EmitContext ec)
4694                 {
4695                 }
4696
4697                 protected override void EmitTryBody (EmitContext ec)
4698                 {
4699                         stmt.Emit (ec);
4700                 }
4701
4702                 protected override void EmitFinallyBody (EmitContext ec)
4703                 {
4704                         fini.Emit (ec);
4705                 }
4706
4707                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4708                 {
4709                         stmt.MutateHoistedGenericType (storey);
4710                         fini.MutateHoistedGenericType (storey);
4711                 }
4712
4713                 protected override void CloneTo (CloneContext clonectx, Statement t)
4714                 {
4715                         TryFinally target = (TryFinally) t;
4716
4717                         target.stmt = (Statement) stmt.Clone (clonectx);
4718                         if (fini != null)
4719                                 target.fini = clonectx.LookupBlock (fini);
4720                 }
4721         }
4722
4723         public class TryCatch : Statement {
4724                 public Block Block;
4725                 public ArrayList Specific;
4726                 public Catch General;
4727                 bool inside_try_finally, code_follows;
4728
4729                 public TryCatch (Block block, ArrayList catch_clauses, Location l, bool inside_try_finally)
4730                 {
4731                         this.Block = block;
4732                         this.Specific = catch_clauses;
4733                         this.General = null;
4734                         this.inside_try_finally = inside_try_finally;
4735
4736                         for (int i = 0; i < catch_clauses.Count; ++i) {
4737                                 Catch c = (Catch) catch_clauses [i];
4738                                 if (c.IsGeneral) {
4739                                         if (i != catch_clauses.Count - 1)
4740                                                 Report.Error (1017, c.loc, "Try statement already has an empty catch block");
4741                                         this.General = c;
4742                                         catch_clauses.RemoveAt (i);
4743                                         i--;
4744                                 }
4745                         }
4746
4747                         loc = l;
4748                 }
4749
4750                 public override bool Resolve (EmitContext ec)
4751                 {
4752                         bool ok = true;
4753
4754                         ec.StartFlowBranching (this);
4755
4756                         if (!Block.Resolve (ec))
4757                                 ok = false;
4758
4759                         Type[] prev_catches = new Type [Specific.Count];
4760                         int last_index = 0;
4761                         foreach (Catch c in Specific){
4762                                 ec.CurrentBranching.CreateSibling (c.Block, FlowBranching.SiblingType.Catch);
4763
4764                                 if (c.Name != null) {
4765                                         LocalInfo vi = c.Block.GetLocalInfo (c.Name);
4766                                         if (vi == null)
4767                                                 throw new Exception ();
4768
4769                                         vi.VariableInfo = null;
4770                                 }
4771
4772                                 if (!c.Resolve (ec))
4773                                         ok = false;
4774
4775                                 Type resolved_type = c.CatchType;
4776                                 for (int ii = 0; ii < last_index; ++ii) {
4777                                         if (resolved_type == prev_catches [ii] || TypeManager.IsSubclassOf (resolved_type, prev_catches [ii])) {
4778                                                 Report.Error (160, c.loc,
4779                                                         "A previous catch clause already catches all exceptions of this or a super type `{0}'",
4780                                                         TypeManager.CSharpName (prev_catches [ii]));
4781                                                 ok = false;
4782                                         }
4783                                 }
4784
4785                                 prev_catches [last_index++] = resolved_type;
4786                         }
4787
4788                         if (General != null) {
4789                                 if (CodeGen.Assembly.WrapNonExceptionThrows) {
4790                                         foreach (Catch c in Specific){
4791                                                 if (c.CatchType == TypeManager.exception_type) {
4792                                                         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'");
4793                                                 }
4794                                         }
4795                                 }
4796
4797                                 ec.CurrentBranching.CreateSibling (General.Block, FlowBranching.SiblingType.Catch);
4798
4799                                 if (!General.Resolve (ec))
4800                                         ok = false;
4801                         }
4802
4803                         ec.EndFlowBranching ();
4804
4805                         // System.Reflection.Emit automatically emits a 'leave' at the end of a try/catch clause
4806                         // So, ensure there's some IL code after this statement
4807                         if (!inside_try_finally && !code_follows && ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
4808                                 ec.NeedReturnLabel ();
4809
4810                         return ok;
4811                 }
4812
4813                 public void SomeCodeFollows ()
4814                 {
4815                         code_follows = true;
4816                 }
4817
4818                 protected override void DoEmit (EmitContext ec)
4819                 {
4820                         ILGenerator ig = ec.ig;
4821
4822                         if (!inside_try_finally)
4823                                 ig.BeginExceptionBlock ();
4824
4825                         Block.Emit (ec);
4826
4827                         foreach (Catch c in Specific)
4828                                 c.Emit (ec);
4829
4830                         if (General != null)
4831                                 General.Emit (ec);
4832
4833                         if (!inside_try_finally)
4834                                 ig.EndExceptionBlock ();
4835                 }
4836
4837                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4838                 {
4839                         Block.MutateHoistedGenericType (storey);
4840
4841                         if (General != null)
4842                                 General.MutateHoistedGenericType (storey);
4843                         if (Specific != null) {
4844                                 foreach (Catch c in Specific)
4845                                         c.MutateHoistedGenericType (storey);
4846                         }
4847                 }
4848
4849                 protected override void CloneTo (CloneContext clonectx, Statement t)
4850                 {
4851                         TryCatch target = (TryCatch) t;
4852
4853                         target.Block = clonectx.LookupBlock (Block);
4854                         if (General != null)
4855                                 target.General = (Catch) General.Clone (clonectx);
4856                         if (Specific != null){
4857                                 target.Specific = new ArrayList ();
4858                                 foreach (Catch c in Specific)
4859                                         target.Specific.Add (c.Clone (clonectx));
4860                         }
4861                 }
4862         }
4863
4864         // FIXME: Why is it almost exact copy of Using ??
4865         public class UsingTemporary : ExceptionStatement {
4866                 TemporaryVariable local_copy;
4867                 public Statement Statement;
4868                 Expression expr;
4869                 Type expr_type;
4870
4871                 public UsingTemporary (Expression expr, Statement stmt, Location l)
4872                 {
4873                         this.expr = expr;
4874                         Statement = stmt;
4875                         loc = l;
4876                 }
4877
4878                 public override bool Resolve (EmitContext ec)
4879                 {
4880                         expr = expr.Resolve (ec);
4881                         if (expr == null)
4882                                 return false;
4883
4884                         expr_type = expr.Type;
4885
4886                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)) {
4887                                 if (Convert.ImplicitConversion (ec, expr, TypeManager.idisposable_type, loc) == null) {
4888                                         Using.Error_IsNotConvertibleToIDisposable (expr);
4889                                         return false;
4890                                 }
4891                         }
4892
4893                         local_copy = new TemporaryVariable (expr_type, loc);
4894                         local_copy.Resolve (ec);
4895
4896                         ec.StartFlowBranching (this);
4897
4898                         bool ok = Statement.Resolve (ec);
4899
4900                         ec.EndFlowBranching ();
4901
4902                         ResolveReachability (ec);
4903
4904                         if (TypeManager.void_dispose_void == null) {
4905                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
4906                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
4907                         }
4908
4909                         return ok;
4910                 }
4911
4912                 protected override void EmitPreTryBody (EmitContext ec)
4913                 {
4914                         local_copy.EmitAssign (ec, expr);
4915                 }
4916
4917                 protected override void EmitTryBody (EmitContext ec)
4918                 {
4919                         Statement.Emit (ec);
4920                 }
4921
4922                 protected override void EmitFinallyBody (EmitContext ec)
4923                 {
4924                         ILGenerator ig = ec.ig;
4925                         if (!TypeManager.IsStruct (expr_type)) {
4926                                 Label skip = ig.DefineLabel ();
4927                                 local_copy.Emit (ec);
4928                                 ig.Emit (OpCodes.Brfalse, skip);
4929                                 local_copy.Emit (ec);
4930                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4931                                 ig.MarkLabel (skip);
4932                                 return;
4933                         }
4934
4935                         Expression ml = Expression.MemberLookup (
4936                                 ec.ContainerType, TypeManager.idisposable_type, expr_type,
4937                                 "Dispose", Location.Null);
4938
4939                         if (!(ml is MethodGroupExpr)) {
4940                                 local_copy.Emit (ec);
4941                                 ig.Emit (OpCodes.Box, expr_type);
4942                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4943                                 return;
4944                         }
4945
4946                         MethodInfo mi = null;
4947
4948                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4949                                 if (TypeManager.GetParameterData (mk).Count == 0) {
4950                                         mi = mk;
4951                                         break;
4952                                 }
4953                         }
4954
4955                         if (mi == null) {
4956                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4957                                 return;
4958                         }
4959
4960                         local_copy.AddressOf (ec, AddressOp.Load);
4961                         ig.Emit (OpCodes.Call, mi);
4962                 }
4963
4964                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4965                 {
4966                         expr_type = storey.MutateType (expr_type);
4967                         local_copy.MutateHoistedGenericType (storey);
4968                         Statement.MutateHoistedGenericType (storey);
4969                 }
4970
4971                 protected override void CloneTo (CloneContext clonectx, Statement t)
4972                 {
4973                         UsingTemporary target = (UsingTemporary) t;
4974
4975                         target.expr = expr.Clone (clonectx);
4976                         target.Statement = Statement.Clone (clonectx);
4977                 }
4978         }
4979
4980         public class Using : ExceptionStatement {
4981                 Statement stmt;
4982                 public Statement EmbeddedStatement {
4983                         get { return stmt is Using ? ((Using) stmt).EmbeddedStatement : stmt; }
4984                 }
4985
4986                 Expression var;
4987                 Expression init;
4988
4989                 ExpressionStatement assign;
4990
4991                 public Using (Expression var, Expression init, Statement stmt, Location l)
4992                 {
4993                         this.var = var;
4994                         this.init = init;
4995                         this.stmt = stmt;
4996                         loc = l;
4997                 }
4998
4999                 static public void Error_IsNotConvertibleToIDisposable (Expression expr)
5000                 {
5001                         Report.SymbolRelatedToPreviousError (expr.Type);
5002                         Report.Error (1674, expr.Location, "`{0}': type used in a using statement must be implicitly convertible to `System.IDisposable'",
5003                                 expr.GetSignatureForError ());
5004                 }
5005
5006                 protected override void EmitPreTryBody (EmitContext ec)
5007                 {
5008                         assign.EmitStatement (ec);
5009                 }
5010
5011                 protected override void EmitTryBody (EmitContext ec)
5012                 {
5013                         stmt.Emit (ec);
5014                 }
5015
5016                 protected override void EmitFinallyBody (EmitContext ec)
5017                 {
5018                         ILGenerator ig = ec.ig;
5019                         Label skip = ig.DefineLabel ();
5020
5021                         bool emit_null_check = !TypeManager.IsValueType (var.Type);
5022                         if (emit_null_check) {
5023                                 var.Emit (ec);
5024                                 ig.Emit (OpCodes.Brfalse, skip);
5025                         }
5026
5027                         Invocation.EmitCall (ec, false, var, TypeManager.void_dispose_void, new ArrayList (0), loc);
5028
5029                         if (emit_null_check)
5030                                 ig.MarkLabel (skip);
5031                 }
5032
5033                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5034                 {
5035                         assign.MutateHoistedGenericType (storey);
5036                         var.MutateHoistedGenericType (storey);
5037                         stmt.MutateHoistedGenericType (storey);
5038                 }
5039
5040                 public override bool Resolve (EmitContext ec)
5041                 {
5042                         if (!ResolveVariable (ec))
5043                                 return false;
5044
5045                         ec.StartFlowBranching (this);
5046
5047                         bool ok = stmt.Resolve (ec);
5048
5049                         ec.EndFlowBranching ();
5050
5051                         ResolveReachability (ec);
5052
5053                         if (TypeManager.void_dispose_void == null) {
5054                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
5055                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
5056                         }
5057
5058                         return ok;
5059                 }
5060
5061                 bool ResolveVariable (EmitContext ec)
5062                 {
5063                         assign = new SimpleAssign (var, init, loc);
5064                         assign = assign.ResolveStatement (ec);
5065                         if (assign == null)
5066                                 return false;
5067
5068                         if (assign.Type == TypeManager.idisposable_type ||
5069                                 TypeManager.ImplementsInterface (assign.Type, TypeManager.idisposable_type)) {
5070                                 return true;
5071                         }
5072
5073                         Expression e = Convert.ImplicitConversionStandard (ec, assign, TypeManager.idisposable_type, var.Location);
5074                         if (e == null) {
5075                                 Error_IsNotConvertibleToIDisposable (var);
5076                                 return false;
5077                         }
5078
5079                         throw new NotImplementedException ("covariance?");
5080                 }
5081
5082                 protected override void CloneTo (CloneContext clonectx, Statement t)
5083                 {
5084                         Using target = (Using) t;
5085
5086                         target.var = var.Clone (clonectx);
5087                         target.init = init.Clone (clonectx);
5088                         target.stmt = stmt.Clone (clonectx);
5089                 }
5090         }
5091
5092         /// <summary>
5093         ///   Implementation of the foreach C# statement
5094         /// </summary>
5095         public class Foreach : Statement {
5096
5097                 sealed class ArrayForeach : Statement
5098                 {
5099                         class ArrayCounter : TemporaryVariable
5100                         {
5101                                 StatementExpression increment;
5102
5103                                 public ArrayCounter (Location loc)
5104                                         : base (TypeManager.int32_type, loc)
5105                                 {
5106                                 }
5107
5108                                 public void ResolveIncrement (EmitContext ec)
5109                                 {
5110                                         increment = new StatementExpression (new UnaryMutator (UnaryMutator.Mode.PostIncrement, this));
5111                                         increment.Resolve (ec);
5112                                 }
5113
5114                                 public void EmitIncrement (EmitContext ec)
5115                                 {
5116                                         increment.Emit (ec);
5117                                 }
5118                         }
5119
5120                         readonly Foreach for_each;
5121                         readonly Statement statement;
5122
5123                         Expression conv;
5124                         TemporaryVariable[] lengths;
5125                         Expression [] length_exprs;
5126                         ArrayCounter[] counter;
5127
5128                         TemporaryVariable copy;
5129                         Expression access;
5130
5131                         public ArrayForeach (Foreach @foreach, int rank)
5132                         {
5133                                 for_each = @foreach;
5134                                 statement = for_each.statement;
5135                                 loc = @foreach.loc;
5136
5137                                 counter = new ArrayCounter [rank];
5138                                 length_exprs = new Expression [rank];
5139
5140                                 //
5141                                 // Only use temporary length variables when dealing with
5142                                 // multi-dimensional arrays
5143                                 //
5144                                 if (rank > 1)
5145                                         lengths = new TemporaryVariable [rank];
5146                         }
5147
5148                         protected override void CloneTo (CloneContext clonectx, Statement target)
5149                         {
5150                                 throw new NotImplementedException ();
5151                         }
5152
5153                         public override bool Resolve (EmitContext ec)
5154                         {
5155                                 copy = new TemporaryVariable (for_each.expr.Type, loc);
5156                                 copy.Resolve (ec);
5157
5158                                 int rank = length_exprs.Length;
5159                                 ArrayList list = new ArrayList (rank);
5160                                 for (int i = 0; i < rank; i++) {
5161                                         counter [i] = new ArrayCounter (loc);
5162                                         counter [i].ResolveIncrement (ec);
5163
5164                                         if (rank == 1) {
5165                                                 length_exprs [i] = new MemberAccess (copy, "Length").Resolve (ec);
5166                                         } else {
5167                                                 lengths [i] = new TemporaryVariable (TypeManager.int32_type, loc);
5168                                                 lengths [i].Resolve (ec);
5169
5170                                                 ArrayList args = new ArrayList (1);
5171                                                 args.Add (new Argument (new IntConstant (i, loc)));
5172                                                 length_exprs [i] = new Invocation (new MemberAccess (copy, "GetLength"), args).Resolve (ec);
5173                                         }
5174
5175                                         list.Add (counter [i]);
5176                                 }
5177
5178                                 access = new ElementAccess (copy, list).Resolve (ec);
5179                                 if (access == null)
5180                                         return false;
5181
5182                                 Expression var_type = for_each.type;
5183                                 VarExpr ve = var_type as VarExpr;
5184                                 if (ve != null) {
5185                                         // Infer implicitly typed local variable from foreach array type
5186                                         var_type = new TypeExpression (access.Type, ve.Location);
5187                                 }
5188
5189                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
5190                                 if (var_type == null)
5191                                         return false;
5192
5193                                 conv = Convert.ExplicitConversion (ec, access, var_type.Type, loc);
5194                                 if (conv == null)
5195                                         return false;
5196
5197                                 bool ok = true;
5198
5199                                 ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
5200                                 ec.CurrentBranching.CreateSibling ();
5201
5202                                 for_each.variable = for_each.variable.ResolveLValue (ec, conv, loc);
5203                                 if (for_each.variable == null)
5204                                         ok = false;
5205
5206                                 ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
5207                                 if (!statement.Resolve (ec))
5208                                         ok = false;
5209                                 ec.EndFlowBranching ();
5210
5211                                 // There's no direct control flow from the end of the embedded statement to the end of the loop
5212                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
5213
5214                                 ec.EndFlowBranching ();
5215
5216                                 return ok;
5217                         }
5218
5219                         protected override void DoEmit (EmitContext ec)
5220                         {
5221                                 ILGenerator ig = ec.ig;
5222
5223                                 copy.EmitAssign (ec, for_each.expr);
5224
5225                                 int rank = length_exprs.Length;
5226                                 Label[] test = new Label [rank];
5227                                 Label[] loop = new Label [rank];
5228
5229                                 for (int i = 0; i < rank; i++) {
5230                                         test [i] = ig.DefineLabel ();
5231                                         loop [i] = ig.DefineLabel ();
5232
5233                                         if (lengths != null)
5234                                                 lengths [i].EmitAssign (ec, length_exprs [i]);
5235                                 }
5236
5237                                 IntConstant zero = new IntConstant (0, loc);
5238                                 for (int i = 0; i < rank; i++) {
5239                                         counter [i].EmitAssign (ec, zero);
5240
5241                                         ig.Emit (OpCodes.Br, test [i]);
5242                                         ig.MarkLabel (loop [i]);
5243                                 }
5244
5245                                 ((IAssignMethod) for_each.variable).EmitAssign (ec, conv, false, false);
5246
5247                                 statement.Emit (ec);
5248
5249                                 ig.MarkLabel (ec.LoopBegin);
5250
5251                                 for (int i = rank - 1; i >= 0; i--){
5252                                         counter [i].EmitIncrement (ec);
5253
5254                                         ig.MarkLabel (test [i]);
5255                                         counter [i].Emit (ec);
5256
5257                                         if (lengths != null)
5258                                                 lengths [i].Emit (ec);
5259                                         else
5260                                                 length_exprs [i].Emit (ec);
5261
5262                                         ig.Emit (OpCodes.Blt, loop [i]);
5263                                 }
5264
5265                                 ig.MarkLabel (ec.LoopEnd);
5266                         }
5267
5268                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5269                         {
5270                                 for_each.expr.MutateHoistedGenericType (storey);
5271
5272                                 copy.MutateHoistedGenericType (storey);
5273                                 conv.MutateHoistedGenericType (storey);
5274                                 statement.MutateHoistedGenericType (storey);
5275
5276                                 for (int i = 0; i < counter.Length; i++) {
5277                                         counter [i].MutateHoistedGenericType (storey);
5278                                         if (lengths != null)
5279                                                 lengths [i].MutateHoistedGenericType (storey);
5280                                 }
5281                         }
5282                 }
5283
5284                 sealed class CollectionForeach : Statement
5285                 {
5286                         class CollectionForeachStatement : Statement
5287                         {
5288                                 Type type;
5289                                 Expression variable, current, conv;
5290                                 Statement statement;
5291                                 Assign assign;
5292
5293                                 public CollectionForeachStatement (Type type, Expression variable,
5294                                                                    Expression current, Statement statement,
5295                                                                    Location loc)
5296                                 {
5297                                         this.type = type;
5298                                         this.variable = variable;
5299                                         this.current = current;
5300                                         this.statement = statement;
5301                                         this.loc = loc;
5302                                 }
5303
5304                                 protected override void CloneTo (CloneContext clonectx, Statement target)
5305                                 {
5306                                         throw new NotImplementedException ();
5307                                 }
5308
5309                                 public override bool Resolve (EmitContext ec)
5310                                 {
5311                                         current = current.Resolve (ec);
5312                                         if (current == null)
5313                                                 return false;
5314
5315                                         conv = Convert.ExplicitConversion (ec, current, type, loc);
5316                                         if (conv == null)
5317                                                 return false;
5318
5319                                         assign = new SimpleAssign (variable, conv, loc);
5320                                         if (assign.Resolve (ec) == null)
5321                                                 return false;
5322
5323                                         if (!statement.Resolve (ec))
5324                                                 return false;
5325
5326                                         return true;
5327                                 }
5328
5329                                 protected override void DoEmit (EmitContext ec)
5330                                 {
5331                                         assign.EmitStatement (ec);
5332                                         statement.Emit (ec);
5333                                 }
5334
5335                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5336                                 {
5337                                         assign.MutateHoistedGenericType (storey);
5338                                         statement.MutateHoistedGenericType (storey);
5339                                 }
5340                         }
5341
5342                         Expression variable, expr;
5343                         Statement statement;
5344
5345                         TemporaryVariable enumerator;
5346                         Expression init;
5347                         Statement loop;
5348                         Statement wrapper;
5349
5350                         MethodGroupExpr get_enumerator;
5351                         PropertyExpr get_current;
5352                         MethodInfo move_next;
5353                         Expression var_type;
5354                         Type enumerator_type;
5355                         bool enumerator_found;
5356
5357                         public CollectionForeach (Expression var_type, Expression var,
5358                                                   Expression expr, Statement stmt, Location l)
5359                         {
5360                                 this.var_type = var_type;
5361                                 this.variable = var;
5362                                 this.expr = expr;
5363                                 statement = stmt;
5364                                 loc = l;
5365                         }
5366
5367                         protected override void CloneTo (CloneContext clonectx, Statement target)
5368                         {
5369                                 throw new NotImplementedException ();
5370                         }
5371
5372                         bool GetEnumeratorFilter (EmitContext ec, MethodInfo mi)
5373                         {
5374                                 Type return_type = mi.ReturnType;
5375
5376                                 //
5377                                 // Ok, we can access it, now make sure that we can do something
5378                                 // with this `GetEnumerator'
5379                                 //
5380
5381                                 if (return_type == TypeManager.ienumerator_type ||
5382                                         TypeManager.ImplementsInterface (return_type, TypeManager.ienumerator_type)) {
5383                                         //
5384                                         // If it is not an interface, lets try to find the methods ourselves.
5385                                         // For example, if we have:
5386                                         // public class Foo : IEnumerator { public bool MoveNext () {} public int Current { get {}}}
5387                                         // We can avoid the iface call. This is a runtime perf boost.
5388                                         // even bigger if we have a ValueType, because we avoid the cost
5389                                         // of boxing.
5390                                         //
5391                                         // We have to make sure that both methods exist for us to take
5392                                         // this path. If one of the methods does not exist, we will just
5393                                         // use the interface. Sadly, this complex if statement is the only
5394                                         // way I could do this without a goto
5395                                         //
5396
5397                                         if (TypeManager.bool_movenext_void == null) {
5398                                                 TypeManager.bool_movenext_void = TypeManager.GetPredefinedMethod (
5399                                                         TypeManager.ienumerator_type, "MoveNext", loc, Type.EmptyTypes);
5400                                         }
5401
5402                                         if (TypeManager.ienumerator_getcurrent == null) {
5403                                                 TypeManager.ienumerator_getcurrent = TypeManager.GetPredefinedProperty (
5404                                                         TypeManager.ienumerator_type, "Current", loc, TypeManager.object_type);
5405                                         }
5406
5407 #if GMCS_SOURCE
5408                                         //
5409                                         // Prefer a generic enumerator over a non-generic one.
5410                                         //
5411                                         if (return_type.IsInterface && return_type.IsGenericType) {
5412                                                 enumerator_type = return_type;
5413                                                 if (!FetchGetCurrent (ec, return_type))
5414                                                         get_current = new PropertyExpr (
5415                                                                 ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5416                                                 if (!FetchMoveNext (return_type))
5417                                                         move_next = TypeManager.bool_movenext_void;
5418                                                 return true;
5419                                         }
5420 #endif
5421
5422                                         if (return_type.IsInterface ||
5423                                             !FetchMoveNext (return_type) ||
5424                                             !FetchGetCurrent (ec, return_type)) {
5425                                                 enumerator_type = return_type;
5426                                                 move_next = TypeManager.bool_movenext_void;
5427                                                 get_current = new PropertyExpr (
5428                                                         ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5429                                                 return true;
5430                                         }
5431                                 } else {
5432                                         //
5433                                         // Ok, so they dont return an IEnumerable, we will have to
5434                                         // find if they support the GetEnumerator pattern.
5435                                         //
5436
5437                                         if (TypeManager.HasElementType (return_type) || !FetchMoveNext (return_type) || !FetchGetCurrent (ec, return_type)) {
5438                                                 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",
5439                                                         TypeManager.CSharpName (return_type), TypeManager.CSharpSignature (mi));
5440                                                 return false;
5441                                         }
5442                                 }
5443
5444                                 enumerator_type = return_type;
5445
5446                                 return true;
5447                         }
5448
5449                         //
5450                         // Retrieves a `public bool MoveNext ()' method from the Type `t'
5451                         //
5452                         bool FetchMoveNext (Type t)
5453                         {
5454                                 MemberInfo[] move_next_list = TypeManager.MemberLookup (null, null, t,
5455                                         MemberTypes.Method,
5456                                         BindingFlags.Public | BindingFlags.Instance,
5457                                         "MoveNext", null);
5458
5459                                 foreach (MemberInfo m in move_next_list){
5460                                         MethodInfo mi = (MethodInfo) m;
5461
5462                                         if ((TypeManager.GetParameterData (mi).Count == 0) &&
5463                                             TypeManager.TypeToCoreType (mi.ReturnType) == TypeManager.bool_type) {
5464                                                 move_next = mi;
5465                                                 return true;
5466                                         }
5467                                 }
5468
5469                                 return false;
5470                         }
5471
5472                         //
5473                         // Retrieves a `public T get_Current ()' method from the Type `t'
5474                         //
5475                         bool FetchGetCurrent (EmitContext ec, Type t)
5476                         {
5477                                 PropertyExpr pe = Expression.MemberLookup (
5478                                         ec.ContainerType, t, "Current", MemberTypes.Property,
5479                                         Expression.AllBindingFlags, loc) as PropertyExpr;
5480                                 if (pe == null)
5481                                         return false;
5482
5483                                 get_current = pe;
5484                                 return true;
5485                         }
5486
5487                         void Error_Enumerator ()
5488                         {
5489                                 if (enumerator_found) {
5490                                         return;
5491                                 }
5492
5493                             Report.Error (1579, loc,
5494                                         "foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `GetEnumerator' or is not accessible",
5495                                         TypeManager.CSharpName (expr.Type));
5496                         }
5497
5498                         bool IsOverride (MethodInfo m)
5499                         {
5500                                 m = (MethodInfo) TypeManager.DropGenericMethodArguments (m);
5501
5502                                 if (!m.IsVirtual || ((m.Attributes & MethodAttributes.NewSlot) != 0))
5503                                         return false;
5504                                 if (m is MethodBuilder)
5505                                         return true;
5506
5507                                 MethodInfo base_method = m.GetBaseDefinition ();
5508                                 return base_method != m;
5509                         }
5510
5511                         bool TryType (EmitContext ec, Type t)
5512                         {
5513                                 MethodGroupExpr mg = Expression.MemberLookup (
5514                                         ec.ContainerType, t, "GetEnumerator", MemberTypes.Method,
5515                                         Expression.AllBindingFlags, loc) as MethodGroupExpr;
5516                                 if (mg == null)
5517                                         return false;
5518
5519                                 MethodInfo result = null;
5520                                 MethodInfo tmp_move_next = null;
5521                                 PropertyExpr tmp_get_cur = null;
5522                                 Type tmp_enumerator_type = enumerator_type;
5523                                 foreach (MethodInfo mi in mg.Methods) {
5524                                         if (TypeManager.GetParameterData (mi).Count != 0)
5525                                                 continue;
5526
5527                                         // Check whether GetEnumerator is public
5528                                         if ((mi.Attributes & MethodAttributes.Public) != MethodAttributes.Public)
5529                                                 continue;
5530
5531                                         if (IsOverride (mi))
5532                                                 continue;
5533
5534                                         enumerator_found = true;
5535
5536                                         if (!GetEnumeratorFilter (ec, mi))
5537                                                 continue;
5538
5539                                         if (result != null) {
5540                                                 if (TypeManager.IsGenericType (result.ReturnType)) {
5541                                                         if (!TypeManager.IsGenericType (mi.ReturnType))
5542                                                                 continue;
5543
5544                                                         MethodBase mb = TypeManager.DropGenericMethodArguments (mi);
5545                                                         Report.SymbolRelatedToPreviousError (t);
5546                                                         Report.Error(1640, loc, "foreach statement cannot operate on variables of type `{0}' " +
5547                                                                      "because it contains multiple implementation of `{1}'. Try casting to a specific implementation",
5548                                                                      TypeManager.CSharpName (t), TypeManager.CSharpSignature (mb));
5549                                                         return false;
5550                                                 }
5551
5552                                                 // Always prefer generics enumerators
5553                                                 if (!TypeManager.IsGenericType (mi.ReturnType)) {
5554                                                         if (TypeManager.ImplementsInterface (mi.DeclaringType, result.DeclaringType) ||
5555                                                             TypeManager.ImplementsInterface (result.DeclaringType, mi.DeclaringType))
5556                                                                 continue;
5557
5558                                                         Report.SymbolRelatedToPreviousError (result);
5559                                                         Report.SymbolRelatedToPreviousError (mi);
5560                                                         Report.Warning (278, 2, loc, "`{0}' contains ambiguous implementation of `{1}' pattern. Method `{2}' is ambiguous with method `{3}'",
5561                                                                         TypeManager.CSharpName (t), "enumerable", TypeManager.CSharpSignature (result), TypeManager.CSharpSignature (mi));
5562                                                         return false;
5563                                                 }
5564                                         }
5565                                         result = mi;
5566                                         tmp_move_next = move_next;
5567                                         tmp_get_cur = get_current;
5568                                         tmp_enumerator_type = enumerator_type;
5569                                         if (mi.DeclaringType == t)
5570                                                 break;
5571                                 }
5572
5573                                 if (result != null) {
5574                                         move_next = tmp_move_next;
5575                                         get_current = tmp_get_cur;
5576                                         enumerator_type = tmp_enumerator_type;
5577                                         MethodInfo[] mi = new MethodInfo[] { (MethodInfo) result };
5578                                         get_enumerator = new MethodGroupExpr (mi, enumerator_type, loc);
5579
5580                                         if (t != expr.Type) {
5581                                                 expr = Convert.ExplicitConversion (
5582                                                         ec, expr, t, loc);
5583                                                 if (expr == null)
5584                                                         throw new InternalErrorException ();
5585                                         }
5586
5587                                         get_enumerator.InstanceExpression = expr;
5588                                         get_enumerator.IsBase = t != expr.Type;
5589
5590                                         return true;
5591                                 }
5592
5593                                 return false;
5594                         }
5595
5596                         bool ProbeCollectionType (EmitContext ec, Type t)
5597                         {
5598                                 int errors = Report.Errors;
5599                                 for (Type tt = t; tt != null && tt != TypeManager.object_type;){
5600                                         if (TryType (ec, tt))
5601                                                 return true;
5602                                         tt = tt.BaseType;
5603                                 }
5604
5605                                 if (Report.Errors > errors)
5606                                         return false;
5607
5608                                 //
5609                                 // Now try to find the method in the interfaces
5610                                 //
5611                                 Type [] ifaces = TypeManager.GetInterfaces (t);
5612                                 foreach (Type i in ifaces){
5613                                         if (TryType (ec, i))
5614                                                 return true;
5615                                 }
5616
5617                                 return false;
5618                         }
5619
5620                         public override bool Resolve (EmitContext ec)
5621                         {
5622                                 enumerator_type = TypeManager.ienumerator_type;
5623
5624                                 if (!ProbeCollectionType (ec, expr.Type)) {
5625                                         Error_Enumerator ();
5626                                         return false;
5627                                 }
5628
5629                                 VarExpr ve = var_type as VarExpr;
5630                                 if (ve != null) {
5631                                         // Infer implicitly typed local variable from foreach enumerable type
5632                                         var_type = new TypeExpression (get_current.PropertyInfo.PropertyType, var_type.Location);
5633                                 }
5634
5635                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
5636                                 if (var_type == null)
5637                                         return false;
5638
5639                                 enumerator = new TemporaryVariable (enumerator_type, loc);
5640                                 enumerator.Resolve (ec);
5641
5642                                 init = new Invocation (get_enumerator, null);
5643                                 init = init.Resolve (ec);
5644                                 if (init == null)
5645                                         return false;
5646
5647                                 Expression move_next_expr;
5648                                 {
5649                                         MemberInfo[] mi = new MemberInfo[] { move_next };
5650                                         MethodGroupExpr mg = new MethodGroupExpr (mi, var_type.Type, loc);
5651                                         mg.InstanceExpression = enumerator;
5652
5653                                         move_next_expr = new Invocation (mg, null);
5654                                 }
5655
5656                                 get_current.InstanceExpression = enumerator;
5657
5658                                 Statement block = new CollectionForeachStatement (
5659                                         var_type.Type, variable, get_current, statement, loc);
5660
5661                                 loop = new While (move_next_expr, block, loc);
5662
5663
5664                                 bool implements_idisposable = TypeManager.ImplementsInterface (enumerator_type, TypeManager.idisposable_type);
5665                                 if (implements_idisposable || !enumerator_type.IsSealed) {
5666                                         wrapper = new DisposableWrapper (this, implements_idisposable);
5667                                 } else {
5668                                         wrapper = new NonDisposableWrapper (this);
5669                                 }
5670
5671                                 return wrapper.Resolve (ec);
5672                         }
5673
5674                         protected override void DoEmit (EmitContext ec)
5675                         {
5676                                 wrapper.Emit (ec);
5677                         }
5678
5679                         class NonDisposableWrapper : Statement {
5680                                 CollectionForeach parent;
5681
5682                                 internal NonDisposableWrapper (CollectionForeach parent)
5683                                 {
5684                                         this.parent = parent;
5685                                 }
5686
5687                                 protected override void CloneTo (CloneContext clonectx, Statement target)
5688                                 {
5689                                         throw new NotSupportedException ();
5690                                 }
5691
5692                                 public override bool Resolve (EmitContext ec)
5693                                 {
5694                                         return parent.ResolveLoop (ec);
5695                                 }
5696
5697                                 protected override void DoEmit (EmitContext ec)
5698                                 {
5699                                         parent.EmitLoopInit (ec);
5700                                         parent.EmitLoopBody (ec);
5701                                 }
5702
5703                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5704                                 {
5705                                         throw new NotSupportedException ();
5706                                 }
5707                         }
5708
5709                         sealed class DisposableWrapper : ExceptionStatement
5710                         {
5711                                 CollectionForeach parent;
5712                                 bool implements_idisposable;
5713
5714                                 internal DisposableWrapper (CollectionForeach parent, bool implements)
5715                                 {
5716                                         this.parent = parent;
5717                                         this.implements_idisposable = implements;
5718                                 }
5719
5720                                 protected override void CloneTo (CloneContext clonectx, Statement target)
5721                                 {
5722                                         throw new NotSupportedException ();
5723                                 }
5724
5725                                 public override bool Resolve (EmitContext ec)
5726                                 {
5727                                         bool ok = true;
5728
5729                                         ec.StartFlowBranching (this);
5730
5731                                         if (!parent.ResolveLoop (ec))
5732                                                 ok = false;
5733
5734                                         ec.EndFlowBranching ();
5735
5736                                         ResolveReachability (ec);
5737
5738                                         if (TypeManager.void_dispose_void == null) {
5739                                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
5740                                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
5741                                         }
5742                                         return ok;
5743                                 }
5744
5745                                 protected override void EmitPreTryBody (EmitContext ec)
5746                                 {
5747                                         parent.EmitLoopInit (ec);
5748                                 }
5749
5750                                 protected override void EmitTryBody (EmitContext ec)
5751                                 {
5752                                         parent.EmitLoopBody (ec);
5753                                 }
5754
5755                                 protected override void EmitFinallyBody (EmitContext ec)
5756                                 {
5757                                         Expression instance = parent.enumerator;
5758                                         if (!TypeManager.IsValueType (parent.enumerator_type)) {
5759                                                 ILGenerator ig = ec.ig;
5760
5761                                                 parent.enumerator.Emit (ec);
5762
5763                                                 Label call_dispose = ig.DefineLabel ();
5764
5765                                                 if (!implements_idisposable) {
5766                                                         ec.ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
5767                                                         LocalTemporary temp = new LocalTemporary (TypeManager.idisposable_type);
5768                                                         temp.Store (ec);
5769                                                         temp.Emit (ec);
5770                                                         instance = temp;
5771                                                 }
5772
5773                                                 ig.Emit (OpCodes.Brtrue_S, call_dispose);
5774
5775                                                 // using 'endfinally' to empty the evaluation stack
5776                                                 ig.Emit (OpCodes.Endfinally);
5777                                                 ig.MarkLabel (call_dispose);
5778                                         }
5779
5780                                         Invocation.EmitCall (ec, false, instance, TypeManager.void_dispose_void, new ArrayList (0), loc);
5781                                 }
5782
5783                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5784                                 {
5785                                         throw new NotSupportedException ();
5786                                 }
5787                         }
5788
5789                         bool ResolveLoop (EmitContext ec)
5790                         {
5791                                 return loop.Resolve (ec);
5792                         }
5793
5794                         void EmitLoopInit (EmitContext ec)
5795                         {
5796                                 enumerator.EmitAssign (ec, init);
5797                         }
5798
5799                         void EmitLoopBody (EmitContext ec)
5800                         {
5801                                 loop.Emit (ec);
5802                         }
5803
5804                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5805                         {
5806                                 enumerator_type = storey.MutateType (enumerator_type);
5807                                 init.MutateHoistedGenericType (storey);
5808                                 loop.MutateHoistedGenericType (storey);
5809                         }
5810                 }
5811
5812                 Expression type;
5813                 Expression variable;
5814                 Expression expr;
5815                 Statement statement;
5816
5817                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
5818                                 Statement stmt, Location l)
5819                 {
5820                         this.type = type;
5821                         this.variable = var;
5822                         this.expr = expr;
5823                         statement = stmt;
5824                         loc = l;
5825                 }
5826
5827                 public Statement Statement {
5828                         get { return statement; }
5829                 }
5830
5831                 public override bool Resolve (EmitContext ec)
5832                 {
5833                         expr = expr.Resolve (ec);
5834                         if (expr == null)
5835                                 return false;
5836
5837                         if (expr.IsNull) {
5838                                 Report.Error (186, loc, "Use of null is not valid in this context");
5839                                 return false;
5840                         }
5841
5842                         if (expr.Type == TypeManager.string_type) {
5843                                 statement = new ArrayForeach (this, 1);
5844                         } else if (expr.Type.IsArray) {
5845                                 statement = new ArrayForeach (this, expr.Type.GetArrayRank ());
5846                         } else {
5847                                 if (expr.eclass == ExprClass.MethodGroup || expr is AnonymousMethodExpression) {
5848                                         Report.Error (446, expr.Location, "Foreach statement cannot operate on a `{0}'",
5849                                                 expr.ExprClassName);
5850                                         return false;
5851                                 }
5852
5853                                 statement = new CollectionForeach (type, variable, expr, statement, loc);
5854                         }
5855
5856                         return statement.Resolve (ec);
5857                 }
5858
5859                 protected override void DoEmit (EmitContext ec)
5860                 {
5861                         ILGenerator ig = ec.ig;
5862
5863                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
5864                         ec.LoopBegin = ig.DefineLabel ();
5865                         ec.LoopEnd = ig.DefineLabel ();
5866
5867                         statement.Emit (ec);
5868
5869                         ec.LoopBegin = old_begin;
5870                         ec.LoopEnd = old_end;
5871                 }
5872
5873                 protected override void CloneTo (CloneContext clonectx, Statement t)
5874                 {
5875                         Foreach target = (Foreach) t;
5876
5877                         target.type = type.Clone (clonectx);
5878                         target.variable = variable.Clone (clonectx);
5879                         target.expr = expr.Clone (clonectx);
5880                         target.statement = statement.Clone (clonectx);
5881                 }
5882
5883                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5884                 {
5885                         statement.MutateHoistedGenericType (storey);
5886                 }
5887         }
5888 }