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                 //
3141                 // Nullable Types support
3142                 //
3143                 Nullable.Unwrap unwrap;
3144
3145                 protected bool HaveUnwrap {
3146                         get { return unwrap != null; }
3147                 }
3148
3149                 //
3150                 // The types allowed to be implicitly cast from
3151                 // on the governing type
3152                 //
3153                 static Type [] allowed_types;
3154
3155                 public Switch (Expression e, ArrayList sects, Location l)
3156                 {
3157                         Expr = e;
3158                         Sections = sects;
3159                         loc = l;
3160                 }
3161
3162                 public bool GotDefault {
3163                         get {
3164                                 return default_section != null;
3165                         }
3166                 }
3167
3168                 public Label DefaultTarget {
3169                         get {
3170                                 return default_target;
3171                         }
3172                 }
3173
3174                 //
3175                 // Determines the governing type for a switch.  The returned
3176                 // expression might be the expression from the switch, or an
3177                 // expression that includes any potential conversions to the
3178                 // integral types or to string.
3179                 //
3180                 Expression SwitchGoverningType (EmitContext ec, Expression expr)
3181                 {
3182                         Type t = expr.Type;
3183
3184                         if (t == TypeManager.byte_type ||
3185                             t == TypeManager.sbyte_type ||
3186                             t == TypeManager.ushort_type ||
3187                             t == TypeManager.short_type ||
3188                             t == TypeManager.uint32_type ||
3189                             t == TypeManager.int32_type ||
3190                             t == TypeManager.uint64_type ||
3191                             t == TypeManager.int64_type ||
3192                             t == TypeManager.char_type ||
3193                             t == TypeManager.string_type ||
3194                             t == TypeManager.bool_type ||
3195                             TypeManager.IsEnumType (t))
3196                                 return expr;
3197
3198                         if (allowed_types == null){
3199                                 allowed_types = new Type [] {
3200                                         TypeManager.sbyte_type,
3201                                         TypeManager.byte_type,
3202                                         TypeManager.short_type,
3203                                         TypeManager.ushort_type,
3204                                         TypeManager.int32_type,
3205                                         TypeManager.uint32_type,
3206                                         TypeManager.int64_type,
3207                                         TypeManager.uint64_type,
3208                                         TypeManager.char_type,
3209                                         TypeManager.string_type
3210                                 };
3211                         }
3212
3213                         //
3214                         // Try to find a *user* defined implicit conversion.
3215                         //
3216                         // If there is no implicit conversion, or if there are multiple
3217                         // conversions, we have to report an error
3218                         //
3219                         Expression converted = null;
3220                         foreach (Type tt in allowed_types){
3221                                 Expression e;
3222
3223                                 e = Convert.ImplicitUserConversion (ec, expr, tt, loc);
3224                                 if (e == null)
3225                                         continue;
3226
3227                                 //
3228                                 // Ignore over-worked ImplicitUserConversions that do
3229                                 // an implicit conversion in addition to the user conversion.
3230                                 //
3231                                 if (!(e is UserCast))
3232                                         continue;
3233
3234                                 if (converted != null){
3235                                         Report.ExtraInformation (loc, "(Ambiguous implicit user defined conversion in previous ");
3236                                         return null;
3237                                 }
3238
3239                                 converted = e;
3240                         }
3241                         return converted;
3242                 }
3243
3244                 //
3245                 // Performs the basic sanity checks on the switch statement
3246                 // (looks for duplicate keys and non-constant expressions).
3247                 //
3248                 // It also returns a hashtable with the keys that we will later
3249                 // use to compute the switch tables
3250                 //
3251                 bool CheckSwitch (EmitContext ec)
3252                 {
3253                         bool error = false;
3254                         Elements = Sections.Count > 10 ?
3255                                 (IDictionary)new Hashtable () :
3256                                 (IDictionary)new ListDictionary ();
3257
3258                         foreach (SwitchSection ss in Sections){
3259                                 foreach (SwitchLabel sl in ss.Labels){
3260                                         if (sl.Label == null){
3261                                                 if (default_section != null){
3262                                                         sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)default_section.Labels [0]);
3263                                                         error = true;
3264                                                 }
3265                                                 default_section = ss;
3266                                                 continue;
3267                                         }
3268
3269                                         if (!sl.ResolveAndReduce (ec, SwitchType, HaveUnwrap)) {
3270                                                 error = true;
3271                                                 continue;
3272                                         }
3273
3274                                         object key = sl.Converted;
3275                                         if (key == SwitchLabel.NullStringCase)
3276                                                 has_null_case = true;
3277
3278                                         try {
3279                                                 Elements.Add (key, sl);
3280                                         } catch (ArgumentException) {
3281                                                 sl.Error_AlreadyOccurs (SwitchType, (SwitchLabel)Elements [key]);
3282                                                 error = true;
3283                                         }
3284                                 }
3285                         }
3286                         return !error;
3287                 }
3288
3289                 void EmitObjectInteger (ILGenerator ig, object k)
3290                 {
3291                         if (k is int)
3292                                 IntConstant.EmitInt (ig, (int) k);
3293                         else if (k is Constant) {
3294                                 EmitObjectInteger (ig, ((Constant) k).GetValue ());
3295                         }
3296                         else if (k is uint)
3297                                 IntConstant.EmitInt (ig, unchecked ((int) (uint) k));
3298                         else if (k is long)
3299                         {
3300                                 if ((long) k >= int.MinValue && (long) k <= int.MaxValue)
3301                                 {
3302                                         IntConstant.EmitInt (ig, (int) (long) k);
3303                                         ig.Emit (OpCodes.Conv_I8);
3304                                 }
3305                                 else
3306                                         LongConstant.EmitLong (ig, (long) k);
3307                         }
3308                         else if (k is ulong)
3309                         {
3310                                 ulong ul = (ulong) k;
3311                                 if (ul < (1L<<32))
3312                                 {
3313                                         IntConstant.EmitInt (ig, unchecked ((int) ul));
3314                                         ig.Emit (OpCodes.Conv_U8);
3315                                 }
3316                                 else
3317                                 {
3318                                         LongConstant.EmitLong (ig, unchecked ((long) ul));
3319                                 }
3320                         }
3321                         else if (k is char)
3322                                 IntConstant.EmitInt (ig, (int) ((char) k));
3323                         else if (k is sbyte)
3324                                 IntConstant.EmitInt (ig, (int) ((sbyte) k));
3325                         else if (k is byte)
3326                                 IntConstant.EmitInt (ig, (int) ((byte) k));
3327                         else if (k is short)
3328                                 IntConstant.EmitInt (ig, (int) ((short) k));
3329                         else if (k is ushort)
3330                                 IntConstant.EmitInt (ig, (int) ((ushort) k));
3331                         else if (k is bool)
3332                                 IntConstant.EmitInt (ig, ((bool) k) ? 1 : 0);
3333                         else
3334                                 throw new Exception ("Unhandled case");
3335                 }
3336
3337                 // structure used to hold blocks of keys while calculating table switch
3338                 class KeyBlock : IComparable
3339                 {
3340                         public KeyBlock (long _first)
3341                         {
3342                                 first = last = _first;
3343                         }
3344                         public long first;
3345                         public long last;
3346                         public ArrayList element_keys = null;
3347                         // how many items are in the bucket
3348                         public int Size = 1;
3349                         public int Length
3350                         {
3351                                 get { return (int) (last - first + 1); }
3352                         }
3353                         public static long TotalLength (KeyBlock kb_first, KeyBlock kb_last)
3354                         {
3355                                 return kb_last.last - kb_first.first + 1;
3356                         }
3357                         public int CompareTo (object obj)
3358                         {
3359                                 KeyBlock kb = (KeyBlock) obj;
3360                                 int nLength = Length;
3361                                 int nLengthOther = kb.Length;
3362                                 if (nLengthOther == nLength)
3363                                         return (int) (kb.first - first);
3364                                 return nLength - nLengthOther;
3365                         }
3366                 }
3367
3368                 /// <summary>
3369                 /// This method emits code for a lookup-based switch statement (non-string)
3370                 /// Basically it groups the cases into blocks that are at least half full,
3371                 /// and then spits out individual lookup opcodes for each block.
3372                 /// It emits the longest blocks first, and short blocks are just
3373                 /// handled with direct compares.
3374                 /// </summary>
3375                 /// <param name="ec"></param>
3376                 /// <param name="val"></param>
3377                 /// <returns></returns>
3378                 void TableSwitchEmit (EmitContext ec, Expression val)
3379                 {
3380                         int element_count = Elements.Count;
3381                         object [] element_keys = new object [element_count];
3382                         Elements.Keys.CopyTo (element_keys, 0);
3383                         Array.Sort (element_keys);
3384
3385                         // initialize the block list with one element per key
3386                         ArrayList key_blocks = new ArrayList (element_count);
3387                         foreach (object key in element_keys)
3388                                 key_blocks.Add (new KeyBlock (System.Convert.ToInt64 (key)));
3389
3390                         KeyBlock current_kb;
3391                         // iteratively merge the blocks while they are at least half full
3392                         // there's probably a really cool way to do this with a tree...
3393                         while (key_blocks.Count > 1)
3394                         {
3395                                 ArrayList key_blocks_new = new ArrayList ();
3396                                 current_kb = (KeyBlock) key_blocks [0];
3397                                 for (int ikb = 1; ikb < key_blocks.Count; ikb++)
3398                                 {
3399                                         KeyBlock kb = (KeyBlock) key_blocks [ikb];
3400                                         if ((current_kb.Size + kb.Size) * 2 >=  KeyBlock.TotalLength (current_kb, kb))
3401                                         {
3402                                                 // merge blocks
3403                                                 current_kb.last = kb.last;
3404                                                 current_kb.Size += kb.Size;
3405                                         }
3406                                         else
3407                                         {
3408                                                 // start a new block
3409                                                 key_blocks_new.Add (current_kb);
3410                                                 current_kb = kb;
3411                                         }
3412                                 }
3413                                 key_blocks_new.Add (current_kb);
3414                                 if (key_blocks.Count == key_blocks_new.Count)
3415                                         break;
3416                                 key_blocks = key_blocks_new;
3417                         }
3418
3419                         // initialize the key lists
3420                         foreach (KeyBlock kb in key_blocks)
3421                                 kb.element_keys = new ArrayList ();
3422
3423                         // fill the key lists
3424                         int iBlockCurr = 0;
3425                         if (key_blocks.Count > 0) {
3426                                 current_kb = (KeyBlock) key_blocks [0];
3427                                 foreach (object key in element_keys)
3428                                 {
3429                                         bool next_block = (key is UInt64) ? (ulong) key > (ulong) current_kb.last :
3430                                                 System.Convert.ToInt64 (key) > current_kb.last;
3431                                         if (next_block)
3432                                                 current_kb = (KeyBlock) key_blocks [++iBlockCurr];
3433                                         current_kb.element_keys.Add (key);
3434                                 }
3435                         }
3436
3437                         // sort the blocks so we can tackle the largest ones first
3438                         key_blocks.Sort ();
3439
3440                         // okay now we can start...
3441                         ILGenerator ig = ec.ig;
3442                         Label lbl_end = ig.DefineLabel ();      // at the end ;-)
3443                         Label lbl_default = default_target;
3444
3445                         Type type_keys = null;
3446                         if (element_keys.Length > 0)
3447                                 type_keys = element_keys [0].GetType ();        // used for conversions
3448
3449                         Type compare_type;
3450
3451                         if (TypeManager.IsEnumType (SwitchType))
3452                                 compare_type = TypeManager.GetEnumUnderlyingType (SwitchType);
3453                         else
3454                                 compare_type = SwitchType;
3455
3456                         for (int iBlock = key_blocks.Count - 1; iBlock >= 0; --iBlock)
3457                         {
3458                                 KeyBlock kb = ((KeyBlock) key_blocks [iBlock]);
3459                                 lbl_default = (iBlock == 0) ? default_target : ig.DefineLabel ();
3460                                 if (kb.Length <= 2)
3461                                 {
3462                                         foreach (object key in kb.element_keys) {
3463                                                 SwitchLabel sl = (SwitchLabel) Elements [key];
3464                                                 if (key is int && (int) key == 0) {
3465                                                         val.EmitBranchable (ec, sl.GetILLabel (ec), false);
3466                                                 } else {
3467                                                         val.Emit (ec);
3468                                                         EmitObjectInteger (ig, key);
3469                                                         ig.Emit (OpCodes.Beq, sl.GetILLabel (ec));
3470                                                 }
3471                                         }
3472                                 }
3473                                 else
3474                                 {
3475                                         // TODO: if all the keys in the block are the same and there are
3476                                         //       no gaps/defaults then just use a range-check.
3477                                         if (compare_type == TypeManager.int64_type ||
3478                                                 compare_type == TypeManager.uint64_type)
3479                                         {
3480                                                 // TODO: optimize constant/I4 cases
3481
3482                                                 // check block range (could be > 2^31)
3483                                                 val.Emit (ec);
3484                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3485                                                 ig.Emit (OpCodes.Blt, lbl_default);
3486                                                 val.Emit (ec);
3487                                                 EmitObjectInteger (ig, System.Convert.ChangeType (kb.last, type_keys));
3488                                                 ig.Emit (OpCodes.Bgt, lbl_default);
3489
3490                                                 // normalize range
3491                                                 val.Emit (ec);
3492                                                 if (kb.first != 0)
3493                                                 {
3494                                                         EmitObjectInteger (ig, System.Convert.ChangeType (kb.first, type_keys));
3495                                                         ig.Emit (OpCodes.Sub);
3496                                                 }
3497                                                 ig.Emit (OpCodes.Conv_I4);      // assumes < 2^31 labels!
3498                                         }
3499                                         else
3500                                         {
3501                                                 // normalize range
3502                                                 val.Emit (ec);
3503                                                 int first = (int) kb.first;
3504                                                 if (first > 0)
3505                                                 {
3506                                                         IntConstant.EmitInt (ig, first);
3507                                                         ig.Emit (OpCodes.Sub);
3508                                                 }
3509                                                 else if (first < 0)
3510                                                 {
3511                                                         IntConstant.EmitInt (ig, -first);
3512                                                         ig.Emit (OpCodes.Add);
3513                                                 }
3514                                         }
3515
3516                                         // first, build the list of labels for the switch
3517                                         int iKey = 0;
3518                                         int cJumps = kb.Length;
3519                                         Label [] switch_labels = new Label [cJumps];
3520                                         for (int iJump = 0; iJump < cJumps; iJump++)
3521                                         {
3522                                                 object key = kb.element_keys [iKey];
3523                                                 if (System.Convert.ToInt64 (key) == kb.first + iJump)
3524                                                 {
3525                                                         SwitchLabel sl = (SwitchLabel) Elements [key];
3526                                                         switch_labels [iJump] = sl.GetILLabel (ec);
3527                                                         iKey++;
3528                                                 }
3529                                                 else
3530                                                         switch_labels [iJump] = lbl_default;
3531                                         }
3532                                         // emit the switch opcode
3533                                         ig.Emit (OpCodes.Switch, switch_labels);
3534                                 }
3535
3536                                 // mark the default for this block
3537                                 if (iBlock != 0)
3538                                         ig.MarkLabel (lbl_default);
3539                         }
3540
3541                         // TODO: find the default case and emit it here,
3542                         //       to prevent having to do the following jump.
3543                         //       make sure to mark other labels in the default section
3544
3545                         // the last default just goes to the end
3546                         if (element_keys.Length > 0)
3547                                 ig.Emit (OpCodes.Br, lbl_default);
3548
3549                         // now emit the code for the sections
3550                         bool found_default = false;
3551
3552                         foreach (SwitchSection ss in Sections) {
3553                                 foreach (SwitchLabel sl in ss.Labels) {
3554                                         if (sl.Converted == SwitchLabel.NullStringCase) {
3555                                                 ig.MarkLabel (null_target);
3556                                         } else if (sl.Label == null) {
3557                                                 ig.MarkLabel (lbl_default);
3558                                                 found_default = true;
3559                                                 if (!has_null_case)
3560                                                         ig.MarkLabel (null_target);
3561                                         }
3562                                         ig.MarkLabel (sl.GetILLabel (ec));
3563                                         ig.MarkLabel (sl.GetILLabelCode (ec));
3564                                 }
3565                                 ss.Block.Emit (ec);
3566                         }
3567
3568                         if (!found_default) {
3569                                 ig.MarkLabel (lbl_default);
3570                                 if (!has_null_case) {
3571                                         ig.MarkLabel (null_target);
3572                                 }
3573                         }
3574
3575                         ig.MarkLabel (lbl_end);
3576                 }
3577
3578                 SwitchSection FindSection (SwitchLabel label)
3579                 {
3580                         foreach (SwitchSection ss in Sections){
3581                                 foreach (SwitchLabel sl in ss.Labels){
3582                                         if (label == sl)
3583                                                 return ss;
3584                                 }
3585                         }
3586
3587                         return null;
3588                 }
3589
3590                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
3591                 {
3592                         foreach (SwitchSection ss in Sections)
3593                                 ss.Block.MutateHoistedGenericType (storey);
3594                 }
3595
3596                 public static void Reset ()
3597                 {
3598                         unique_counter = 0;
3599                         allowed_types = null;
3600                 }
3601
3602                 public override bool Resolve (EmitContext ec)
3603                 {
3604                         Expr = Expr.Resolve (ec);
3605                         if (Expr == null)
3606                                 return false;
3607
3608                         new_expr = SwitchGoverningType (ec, Expr);
3609
3610                         if ((new_expr == null) && TypeManager.IsNullableType (Expr.Type)) {
3611                                 unwrap = Nullable.Unwrap.Create (Expr, false);
3612                                 if (unwrap == null)
3613                                         return false;
3614
3615                                 new_expr = SwitchGoverningType (ec, unwrap);
3616                         }
3617
3618                         if (new_expr == null){
3619                                 Report.Error (151, loc, "A value of an integral type or string expected for switch");
3620                                 return false;
3621                         }
3622
3623                         // Validate switch.
3624                         SwitchType = new_expr.Type;
3625
3626                         if (RootContext.Version == LanguageVersion.ISO_1 && SwitchType == TypeManager.bool_type) {
3627                                 Report.FeatureIsNotAvailable (loc, "switch expression of boolean type");
3628                                 return false;
3629                         }
3630
3631                         if (!CheckSwitch (ec))
3632                                 return false;
3633
3634                         if (HaveUnwrap)
3635                                 Elements.Remove (SwitchLabel.NullStringCase);
3636
3637                         Switch old_switch = ec.Switch;
3638                         ec.Switch = this;
3639                         ec.Switch.SwitchType = SwitchType;
3640
3641                         Report.Debug (1, "START OF SWITCH BLOCK", loc, ec.CurrentBranching);
3642                         ec.StartFlowBranching (FlowBranching.BranchingType.Switch, loc);
3643
3644                         is_constant = new_expr is Constant;
3645                         if (is_constant) {
3646                                 object key = ((Constant) new_expr).GetValue ();
3647                                 SwitchLabel label = (SwitchLabel) Elements [key];
3648
3649                                 constant_section = FindSection (label);
3650                                 if (constant_section == null)
3651                                         constant_section = default_section;
3652                         }
3653
3654                         bool first = true;
3655                         bool ok = true;
3656                         foreach (SwitchSection ss in Sections){
3657                                 if (!first)
3658                                         ec.CurrentBranching.CreateSibling (
3659                                                 null, FlowBranching.SiblingType.SwitchSection);
3660                                 else
3661                                         first = false;
3662
3663                                 if (is_constant && (ss != constant_section)) {
3664                                         // If we're a constant switch, we're only emitting
3665                                         // one single section - mark all the others as
3666                                         // unreachable.
3667                                         ec.CurrentBranching.CurrentUsageVector.Goto ();
3668                                         if (!ss.Block.ResolveUnreachable (ec, true)) {
3669                                                 ok = false;
3670                                         }
3671                                 } else {
3672                                         if (!ss.Block.Resolve (ec))
3673                                                 ok = false;
3674                                 }
3675                         }
3676
3677                         if (default_section == null)
3678                                 ec.CurrentBranching.CreateSibling (
3679                                         null, FlowBranching.SiblingType.SwitchSection);
3680
3681                         ec.EndFlowBranching ();
3682                         ec.Switch = old_switch;
3683
3684                         Report.Debug (1, "END OF SWITCH BLOCK", loc, ec.CurrentBranching);
3685
3686                         if (!ok)
3687                                 return false;
3688
3689                         if (SwitchType == TypeManager.string_type && !is_constant) {
3690                                 // TODO: Optimize single case, and single+default case
3691                                 ResolveStringSwitchMap (ec);
3692                         }
3693
3694                         return true;
3695                 }
3696
3697                 void ResolveStringSwitchMap (EmitContext ec)
3698                 {
3699                         FullNamedExpression string_dictionary_type;
3700                         if (TypeManager.generic_ienumerable_type != null) {
3701                                 MemberAccess system_collections_generic = new MemberAccess (new MemberAccess (
3702                                         new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Collections", loc), "Generic", loc);
3703
3704                                 string_dictionary_type = new MemberAccess (system_collections_generic, "Dictionary",
3705                                         new TypeArguments (
3706                                                 new TypeExpression (TypeManager.string_type, loc),
3707                                                 new TypeExpression (TypeManager.int32_type, loc)), loc);
3708                         } else {
3709                                 MemberAccess system_collections_generic = new MemberAccess (
3710                                         new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Collections", loc);
3711
3712                                 string_dictionary_type = new MemberAccess (system_collections_generic, "Hashtable", loc);
3713                         }
3714
3715                         Field field = new Field (ec.TypeContainer, string_dictionary_type,
3716                                 Modifiers.STATIC | Modifiers.PRIVATE | Modifiers.COMPILER_GENERATED,
3717                                 new MemberName (CompilerGeneratedClass.MakeName (null, "f", "switch$map", unique_counter++), loc), null);
3718                         if (!field.Define ())
3719                                 return;
3720                         ec.TypeContainer.PartialContainer.AddField (field);
3721
3722                         ArrayList init = new ArrayList ();
3723                         int counter = 0;
3724                         Elements.Clear ();
3725                         string value = null;
3726                         foreach (SwitchSection section in Sections) {
3727                                 int last_count = init.Count;
3728                                 foreach (SwitchLabel sl in section.Labels) {
3729                                         if (sl.Label == null || sl.Converted == SwitchLabel.NullStringCase)
3730                                                 continue;
3731
3732                                         value = (string) sl.Converted;
3733                                         ArrayList init_args = new ArrayList (2);
3734                                         init_args.Add (new StringLiteral (value, sl.Location));
3735                                         init_args.Add (new IntConstant (counter, loc));
3736                                         init.Add (new CollectionElementInitializer (init_args, loc));
3737                                 }
3738
3739                                 //
3740                                 // Don't add empty sections
3741                                 //
3742                                 if (last_count == init.Count)
3743                                         continue;
3744
3745                                 Elements.Add (counter, section.Labels [0]);
3746                                 ++counter;
3747                         }
3748
3749                         ArrayList args = new ArrayList (1);
3750                         args.Add (new Argument (new IntConstant (init.Count, loc)));
3751                         Expression initializer = new NewInitialize (string_dictionary_type, args,
3752                                 new CollectionOrObjectInitializers (init, loc), loc);
3753
3754                         switch_cache_field = new FieldExpr (field.FieldBuilder, loc);
3755                         string_dictionary = new SimpleAssign (switch_cache_field, initializer.Resolve (ec));
3756                 }
3757
3758                 void DoEmitStringSwitch (LocalTemporary value, EmitContext ec)
3759                 {
3760                         ILGenerator ig = ec.ig;
3761                         Label l_initialized = ig.DefineLabel ();
3762
3763                         //
3764                         // Skip initialization when value is null
3765                         //
3766                         value.EmitBranchable (ec, null_target, false);
3767
3768                         //
3769                         // Check if string dictionary is initialized and initialize
3770                         //
3771                         switch_cache_field.EmitBranchable (ec, l_initialized, true);
3772                         string_dictionary.EmitStatement (ec);
3773                         ig.MarkLabel (l_initialized);
3774
3775                         LocalTemporary string_switch_variable = new LocalTemporary (TypeManager.int32_type);
3776
3777                         if (TypeManager.generic_ienumerable_type != null) {
3778                                 ArrayList get_value_args = new ArrayList (2);
3779                                 get_value_args.Add (new Argument (value));
3780                                 get_value_args.Add (new Argument (string_switch_variable, Argument.AType.Out));
3781                                 Expression get_item = new Invocation (new MemberAccess (switch_cache_field, "TryGetValue", loc), get_value_args).Resolve (ec);
3782                                 if (get_item == null)
3783                                         return;
3784
3785                                 //
3786                                 // A value was not found, go to default case
3787                                 //
3788                                 get_item.EmitBranchable (ec, default_target, false);
3789                         } else {
3790                                 ArrayList get_value_args = new ArrayList (1);
3791                                 get_value_args.Add (value);
3792
3793                                 Expression get_item = new IndexerAccess (new ElementAccess (switch_cache_field, get_value_args), loc).Resolve (ec);
3794                                 if (get_item == null)
3795                                         return;
3796
3797                                 LocalTemporary get_item_object = new LocalTemporary (TypeManager.object_type);
3798                                 get_item_object.EmitAssign (ec, get_item, true, false);
3799                                 ec.ig.Emit (OpCodes.Brfalse, default_target);
3800
3801                                 ExpressionStatement get_item_int = (ExpressionStatement) new SimpleAssign (string_switch_variable,
3802                                         new Cast (new TypeExpression (TypeManager.int32_type, loc), get_item_object, loc)).Resolve (ec);
3803
3804                                 get_item_int.EmitStatement (ec);
3805                                 get_item_object.Release (ec);
3806                         }
3807
3808                         TableSwitchEmit (ec, string_switch_variable);
3809                         string_switch_variable.Release (ec);
3810                 }
3811
3812                 protected override void DoEmit (EmitContext ec)
3813                 {
3814                         ILGenerator ig = ec.ig;
3815
3816                         default_target = ig.DefineLabel ();
3817                         null_target = ig.DefineLabel ();
3818
3819                         // Store variable for comparission purposes
3820                         // TODO: Don't duplicate non-captured VariableReference
3821                         LocalTemporary value;
3822                         if (HaveUnwrap) {
3823                                 value = new LocalTemporary (SwitchType);
3824                                 unwrap.EmitCheck (ec);
3825                                 ig.Emit (OpCodes.Brfalse, null_target);
3826                                 new_expr.Emit (ec);
3827                                 value.Store (ec);
3828                         } else if (!is_constant) {
3829                                 value = new LocalTemporary (SwitchType);
3830                                 new_expr.Emit (ec);
3831                                 value.Store (ec);
3832                         } else
3833                                 value = null;
3834
3835                         //
3836                         // Setup the codegen context
3837                         //
3838                         Label old_end = ec.LoopEnd;
3839                         Switch old_switch = ec.Switch;
3840
3841                         ec.LoopEnd = ig.DefineLabel ();
3842                         ec.Switch = this;
3843
3844                         // Emit Code.
3845                         if (is_constant) {
3846                                 if (constant_section != null)
3847                                         constant_section.Block.Emit (ec);
3848                         } else if (string_dictionary != null) {
3849                                 DoEmitStringSwitch (value, ec);
3850                         } else {
3851                                 TableSwitchEmit (ec, value);
3852                         }
3853
3854                         if (value != null)
3855                                 value.Release (ec);
3856
3857                         // Restore context state.
3858                         ig.MarkLabel (ec.LoopEnd);
3859
3860                         //
3861                         // Restore the previous context
3862                         //
3863                         ec.LoopEnd = old_end;
3864                         ec.Switch = old_switch;
3865                 }
3866
3867                 protected override void CloneTo (CloneContext clonectx, Statement t)
3868                 {
3869                         Switch target = (Switch) t;
3870
3871                         target.Expr = Expr.Clone (clonectx);
3872                         target.Sections = new ArrayList ();
3873                         foreach (SwitchSection ss in Sections){
3874                                 target.Sections.Add (ss.Clone (clonectx));
3875                         }
3876                 }
3877         }
3878
3879         // A place where execution can restart in an iterator
3880         public abstract class ResumableStatement : Statement
3881         {
3882                 bool prepared;
3883                 protected Label resume_point;
3884
3885                 public Label PrepareForEmit (EmitContext ec)
3886                 {
3887                         if (!prepared) {
3888                                 prepared = true;
3889                                 resume_point = ec.ig.DefineLabel ();
3890                         }
3891                         return resume_point;
3892                 }
3893
3894                 public virtual Label PrepareForDispose (EmitContext ec, Label end)
3895                 {
3896                         return end;
3897                 }
3898                 public virtual void EmitForDispose (EmitContext ec, Iterator iterator, Label end, bool have_dispatcher)
3899                 {
3900                 }
3901         }
3902
3903         // Base class for statements that are implemented in terms of try...finally
3904         public abstract class ExceptionStatement : ResumableStatement
3905         {
3906                 bool code_follows;
3907
3908                 protected abstract void EmitPreTryBody (EmitContext ec);
3909                 protected abstract void EmitTryBody (EmitContext ec);
3910                 protected abstract void EmitFinallyBody (EmitContext ec);
3911
3912                 protected sealed override void DoEmit (EmitContext ec)
3913                 {
3914                         ILGenerator ig = ec.ig;
3915
3916                         EmitPreTryBody (ec);
3917
3918                         if (resume_points != null) {
3919                                 IntConstant.EmitInt (ig, (int) Iterator.State.Running);
3920                                 ig.Emit (OpCodes.Stloc, ec.CurrentIterator.CurrentPC);
3921                         }
3922
3923                         ig.BeginExceptionBlock ();
3924
3925                         if (resume_points != null) {
3926                                 ig.MarkLabel (resume_point);
3927
3928                                 // For normal control flow, we want to fall-through the Switch
3929                                 // So, we use CurrentPC rather than the $PC field, and initialize it to an outside value above
3930                                 ig.Emit (OpCodes.Ldloc, ec.CurrentIterator.CurrentPC);
3931                                 IntConstant.EmitInt (ig, first_resume_pc);
3932                                 ig.Emit (OpCodes.Sub);
3933
3934                                 Label [] labels = new Label [resume_points.Count];
3935                                 for (int i = 0; i < resume_points.Count; ++i)
3936                                         labels [i] = ((ResumableStatement) resume_points [i]).PrepareForEmit (ec);
3937                                 ig.Emit (OpCodes.Switch, labels);
3938                         }
3939
3940                         EmitTryBody (ec);
3941
3942                         ig.BeginFinallyBlock ();
3943
3944                         Label start_finally = ec.ig.DefineLabel ();
3945                         if (resume_points != null) {
3946                                 ig.Emit (OpCodes.Ldloc, ec.CurrentIterator.SkipFinally);
3947                                 ig.Emit (OpCodes.Brfalse_S, start_finally);
3948                                 ig.Emit (OpCodes.Endfinally);
3949                         }
3950
3951                         ig.MarkLabel (start_finally);
3952                         EmitFinallyBody (ec);
3953
3954                         ig.EndExceptionBlock ();
3955                 }
3956
3957                 public void SomeCodeFollows ()
3958                 {
3959                         code_follows = true;
3960                 }
3961
3962                 protected void ResolveReachability (EmitContext ec)
3963                 {
3964                         // System.Reflection.Emit automatically emits a 'leave' at the end of a try clause
3965                         // So, ensure there's some IL code after this statement.
3966                         if (!code_follows && resume_points == null && ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
3967                                 ec.NeedReturnLabel ();
3968
3969                 }
3970
3971                 ArrayList resume_points;
3972                 int first_resume_pc;
3973                 public void AddResumePoint (ResumableStatement stmt, int pc)
3974                 {
3975                         if (resume_points == null) {
3976                                 resume_points = new ArrayList ();
3977                                 first_resume_pc = pc;
3978                         }
3979
3980                         if (pc != first_resume_pc + resume_points.Count)
3981                                 throw new InternalErrorException ("missed an intervening AddResumePoint?");
3982
3983                         resume_points.Add (stmt);
3984                 }
3985
3986                 Label dispose_try_block;
3987                 bool prepared_for_dispose, emitted_dispose;
3988                 public override Label PrepareForDispose (EmitContext ec, Label end)
3989                 {
3990                         if (!prepared_for_dispose) {
3991                                 prepared_for_dispose = true;
3992                                 dispose_try_block = ec.ig.DefineLabel ();
3993                         }
3994                         return dispose_try_block;
3995                 }
3996
3997                 public override void EmitForDispose (EmitContext ec, Iterator iterator, Label end, bool have_dispatcher)
3998                 {
3999                         if (emitted_dispose)
4000                                 return;
4001
4002                         emitted_dispose = true;
4003
4004                         ILGenerator ig = ec.ig;
4005
4006                         Label end_of_try = ig.DefineLabel ();
4007
4008                         // Ensure that the only way we can get into this code is through a dispatcher
4009                         if (have_dispatcher)
4010                                 ig.Emit (OpCodes.Br, end);
4011
4012                         ig.BeginExceptionBlock ();
4013
4014                         ig.MarkLabel (dispose_try_block);
4015
4016                         Label [] labels = null;
4017                         for (int i = 0; i < resume_points.Count; ++i) {
4018                                 ResumableStatement s = (ResumableStatement) resume_points [i];
4019                                 Label ret = s.PrepareForDispose (ec, end_of_try);
4020                                 if (ret.Equals (end_of_try) && labels == null)
4021                                         continue;
4022                                 if (labels == null) {
4023                                         labels = new Label [resume_points.Count];
4024                                         for (int j = 0; j < i; ++j)
4025                                                 labels [j] = end_of_try;
4026                                 }
4027                                 labels [i] = ret;
4028                         }
4029
4030                         if (labels != null) {
4031                                 int j;
4032                                 for (j = 1; j < labels.Length; ++j)
4033                                         if (!labels [0].Equals (labels [j]))
4034                                                 break;
4035                                 bool emit_dispatcher = j < labels.Length;
4036
4037                                 if (emit_dispatcher) {
4038                                         //SymbolWriter.StartIteratorDispatcher (ec.ig);
4039                                         ig.Emit (OpCodes.Ldloc, iterator.CurrentPC);
4040                                         IntConstant.EmitInt (ig, first_resume_pc);
4041                                         ig.Emit (OpCodes.Sub);
4042                                         ig.Emit (OpCodes.Switch, labels);
4043                                         //SymbolWriter.EndIteratorDispatcher (ec.ig);
4044                                 }
4045
4046                                 foreach (ResumableStatement s in resume_points)
4047                                         s.EmitForDispose (ec, iterator, end_of_try, emit_dispatcher);
4048                         }
4049
4050                         ig.MarkLabel (end_of_try);
4051
4052                         ig.BeginFinallyBlock ();
4053
4054                         EmitFinallyBody (ec);
4055
4056                         ig.EndExceptionBlock ();
4057                 }
4058         }
4059
4060         public class Lock : ExceptionStatement {
4061                 Expression expr;
4062                 public Statement Statement;
4063                 TemporaryVariable temp;
4064
4065                 public Lock (Expression expr, Statement stmt, Location l)
4066                 {
4067                         this.expr = expr;
4068                         Statement = stmt;
4069                         loc = l;
4070                 }
4071
4072                 public override bool Resolve (EmitContext ec)
4073                 {
4074                         expr = expr.Resolve (ec);
4075                         if (expr == null)
4076                                 return false;
4077
4078                         if (!TypeManager.IsReferenceType (expr.Type)){
4079                                 Report.Error (185, loc,
4080                                               "`{0}' is not a reference type as required by the lock statement",
4081                                               TypeManager.CSharpName (expr.Type));
4082                                 return false;
4083                         }
4084
4085                         ec.StartFlowBranching (this);
4086                         bool ok = Statement.Resolve (ec);
4087                         ec.EndFlowBranching ();
4088
4089                         ResolveReachability (ec);
4090
4091                         // Avoid creating libraries that reference the internal
4092                         // mcs NullType:
4093                         Type t = expr.Type;
4094                         if (t == TypeManager.null_type)
4095                                 t = TypeManager.object_type;
4096
4097                         temp = new TemporaryVariable (t, loc);
4098                         temp.Resolve (ec);
4099
4100                         if (TypeManager.void_monitor_enter_object == null || TypeManager.void_monitor_exit_object == null) {
4101                                 Type monitor_type = TypeManager.CoreLookupType ("System.Threading", "Monitor", Kind.Class, true);
4102                                 TypeManager.void_monitor_enter_object = TypeManager.GetPredefinedMethod (
4103                                         monitor_type, "Enter", loc, TypeManager.object_type);
4104                                 TypeManager.void_monitor_exit_object = TypeManager.GetPredefinedMethod (
4105                                         monitor_type, "Exit", loc, TypeManager.object_type);
4106                         }
4107
4108                         return ok;
4109                 }
4110
4111                 protected override void EmitPreTryBody (EmitContext ec)
4112                 {
4113                         ILGenerator ig = ec.ig;
4114
4115                         temp.EmitAssign (ec, expr);
4116                         temp.Emit (ec);
4117                         ig.Emit (OpCodes.Call, TypeManager.void_monitor_enter_object);
4118                 }
4119
4120                 protected override void EmitTryBody (EmitContext ec)
4121                 {
4122                         Statement.Emit (ec);
4123                 }
4124
4125                 protected override void EmitFinallyBody (EmitContext ec)
4126                 {
4127                         temp.Emit (ec);
4128                         ec.ig.Emit (OpCodes.Call, TypeManager.void_monitor_exit_object);
4129                 }
4130
4131                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4132                 {
4133                         expr.MutateHoistedGenericType (storey);
4134                         temp.MutateHoistedGenericType (storey);
4135                         Statement.MutateHoistedGenericType (storey);
4136                 }
4137
4138                 protected override void CloneTo (CloneContext clonectx, Statement t)
4139                 {
4140                         Lock target = (Lock) t;
4141
4142                         target.expr = expr.Clone (clonectx);
4143                         target.Statement = Statement.Clone (clonectx);
4144                 }
4145         }
4146
4147         public class Unchecked : Statement {
4148                 public Block Block;
4149
4150                 public Unchecked (Block b)
4151                 {
4152                         Block = b;
4153                         b.Unchecked = true;
4154                 }
4155
4156                 public override bool Resolve (EmitContext ec)
4157                 {
4158                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
4159                                 return Block.Resolve (ec);
4160                 }
4161
4162                 protected override void DoEmit (EmitContext ec)
4163                 {
4164                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, false))
4165                                 Block.Emit (ec);
4166                 }
4167
4168                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4169                 {
4170                         Block.MutateHoistedGenericType (storey);
4171                 }
4172
4173                 protected override void CloneTo (CloneContext clonectx, Statement t)
4174                 {
4175                         Unchecked target = (Unchecked) t;
4176
4177                         target.Block = clonectx.LookupBlock (Block);
4178                 }
4179         }
4180
4181         public class Checked : Statement {
4182                 public Block Block;
4183
4184                 public Checked (Block b)
4185                 {
4186                         Block = b;
4187                         b.Unchecked = false;
4188                 }
4189
4190                 public override bool Resolve (EmitContext ec)
4191                 {
4192                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
4193                                 return Block.Resolve (ec);
4194                 }
4195
4196                 protected override void DoEmit (EmitContext ec)
4197                 {
4198                         using (ec.With (EmitContext.Flags.AllCheckStateFlags, true))
4199                                 Block.Emit (ec);
4200                 }
4201
4202                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4203                 {
4204                         Block.MutateHoistedGenericType (storey);
4205                 }
4206
4207                 protected override void CloneTo (CloneContext clonectx, Statement t)
4208                 {
4209                         Checked target = (Checked) t;
4210
4211                         target.Block = clonectx.LookupBlock (Block);
4212                 }
4213         }
4214
4215         public class Unsafe : Statement {
4216                 public Block Block;
4217
4218                 public Unsafe (Block b)
4219                 {
4220                         Block = b;
4221                         Block.Unsafe = true;
4222                 }
4223
4224                 public override bool Resolve (EmitContext ec)
4225                 {
4226                         using (ec.With (EmitContext.Flags.InUnsafe, true))
4227                                 return Block.Resolve (ec);
4228                 }
4229
4230                 protected override void DoEmit (EmitContext ec)
4231                 {
4232                         using (ec.With (EmitContext.Flags.InUnsafe, true))
4233                                 Block.Emit (ec);
4234                 }
4235
4236                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4237                 {
4238                         Block.MutateHoistedGenericType (storey);
4239                 }
4240
4241                 protected override void CloneTo (CloneContext clonectx, Statement t)
4242                 {
4243                         Unsafe target = (Unsafe) t;
4244
4245                         target.Block = clonectx.LookupBlock (Block);
4246                 }
4247         }
4248
4249         //
4250         // Fixed statement
4251         //
4252         public class Fixed : Statement {
4253                 Expression type;
4254                 ArrayList declarators;
4255                 Statement statement;
4256                 Type expr_type;
4257                 Emitter[] data;
4258                 bool has_ret;
4259
4260                 abstract class Emitter
4261                 {
4262                         protected LocalInfo vi;
4263                         protected Expression converted;
4264
4265                         protected Emitter (Expression expr, LocalInfo li)
4266                         {
4267                                 converted = expr;
4268                                 vi = li;
4269                         }
4270
4271                         public abstract void Emit (EmitContext ec);
4272                         public abstract void EmitExit (EmitContext ec);
4273                 }
4274
4275                 class ExpressionEmitter : Emitter {
4276                         public ExpressionEmitter (Expression converted, LocalInfo li) :
4277                                 base (converted, li)
4278                         {
4279                         }
4280
4281                         public override void Emit (EmitContext ec) {
4282                                 //
4283                                 // Store pointer in pinned location
4284                                 //
4285                                 converted.Emit (ec);
4286                                 vi.EmitAssign (ec);
4287                         }
4288
4289                         public override void EmitExit (EmitContext ec)
4290                         {
4291                                 ec.ig.Emit (OpCodes.Ldc_I4_0);
4292                                 ec.ig.Emit (OpCodes.Conv_U);
4293                                 vi.EmitAssign (ec);
4294                         }
4295                 }
4296
4297                 class StringEmitter : Emitter
4298                 {
4299                         LocalInfo pinned_string;
4300
4301                         public StringEmitter (Expression expr, LocalInfo li, Location loc):
4302                                 base (expr, li)
4303                         {
4304                                 pinned_string = new LocalInfo (new TypeExpression (TypeManager.string_type, loc), null, null, loc);
4305                                 pinned_string.Pinned = true;
4306                         }
4307
4308                         public override void Emit (EmitContext ec)
4309                         {
4310                                 pinned_string.Resolve (ec);
4311                                 pinned_string.ResolveVariable (ec);
4312
4313                                 converted.Emit (ec);
4314                                 pinned_string.EmitAssign (ec);
4315
4316                                 PropertyInfo p = TypeManager.int_get_offset_to_string_data;
4317                                 if (p == null) {
4318                                         // TODO: Move to resolve
4319                                         p = TypeManager.int_get_offset_to_string_data = TypeManager.GetPredefinedProperty (
4320                                                 TypeManager.runtime_helpers_type, "OffsetToStringData", pinned_string.Location, TypeManager.int32_type);
4321
4322                                         if (p == null)
4323                                                 return;
4324                                 }
4325
4326                                 // TODO: Should use Binary::Add
4327                                 pinned_string.Emit (ec);
4328                                 ec.ig.Emit (OpCodes.Conv_I);
4329
4330                                 PropertyExpr pe = new PropertyExpr (pinned_string.VariableType, p, pinned_string.Location);
4331                                 //pe.InstanceExpression = pinned_string;
4332                                 pe.Resolve (ec).Emit (ec);
4333
4334                                 ec.ig.Emit (OpCodes.Add);
4335                                 vi.EmitAssign (ec);
4336                         }
4337
4338                         public override void EmitExit (EmitContext ec)
4339                         {
4340                                 ec.ig.Emit (OpCodes.Ldnull);
4341                                 pinned_string.EmitAssign (ec);
4342                         }
4343                 }
4344
4345                 public Fixed (Expression type, ArrayList decls, Statement stmt, Location l)
4346                 {
4347                         this.type = type;
4348                         declarators = decls;
4349                         statement = stmt;
4350                         loc = l;
4351                 }
4352
4353                 public Statement Statement {
4354                         get { return statement; }
4355                 }
4356
4357                 public override bool Resolve (EmitContext ec)
4358                 {
4359                         if (!ec.InUnsafe){
4360                                 Expression.UnsafeError (loc);
4361                                 return false;
4362                         }
4363
4364                         TypeExpr texpr = type.ResolveAsContextualType (ec, false);
4365                         if (texpr == null) {
4366                                 if (type is VarExpr)
4367                                         Report.Error (821, type.Location, "A fixed statement cannot use an implicitly typed local variable");
4368
4369                                 return false;
4370                         }
4371
4372                         expr_type = texpr.Type;
4373
4374                         data = new Emitter [declarators.Count];
4375
4376                         if (!expr_type.IsPointer){
4377                                 Report.Error (209, loc, "The type of locals declared in a fixed statement must be a pointer type");
4378                                 return false;
4379                         }
4380
4381                         int i = 0;
4382                         foreach (Pair p in declarators){
4383                                 LocalInfo vi = (LocalInfo) p.First;
4384                                 Expression e = (Expression) p.Second;
4385
4386                                 vi.VariableInfo.SetAssigned (ec);
4387                                 vi.SetReadOnlyContext (LocalInfo.ReadOnlyContext.Fixed);
4388
4389                                 //
4390                                 // The rules for the possible declarators are pretty wise,
4391                                 // but the production on the grammar is more concise.
4392                                 //
4393                                 // So we have to enforce these rules here.
4394                                 //
4395                                 // We do not resolve before doing the case 1 test,
4396                                 // because the grammar is explicit in that the token &
4397                                 // is present, so we need to test for this particular case.
4398                                 //
4399
4400                                 if (e is Cast){
4401                                         Report.Error (254, loc, "The right hand side of a fixed statement assignment may not be a cast expression");
4402                                         return false;
4403                                 }
4404
4405                                 ec.InFixedInitializer = true;
4406                                 e = e.Resolve (ec);
4407                                 ec.InFixedInitializer = false;
4408                                 if (e == null)
4409                                         return false;
4410
4411                                 //
4412                                 // Case 2: Array
4413                                 //
4414                                 if (e.Type.IsArray){
4415                                         Type array_type = TypeManager.GetElementType (e.Type);
4416
4417                                         //
4418                                         // Provided that array_type is unmanaged,
4419                                         //
4420                                         if (!TypeManager.VerifyUnManaged (array_type, loc))
4421                                                 return false;
4422
4423                                         //
4424                                         // and T* is implicitly convertible to the
4425                                         // pointer type given in the fixed statement.
4426                                         //
4427                                         ArrayPtr array_ptr = new ArrayPtr (e, array_type, loc);
4428
4429                                         Expression converted = Convert.ImplicitConversionRequired (
4430                                                 ec, array_ptr, vi.VariableType, loc);
4431                                         if (converted == null)
4432                                                 return false;
4433
4434                                         //
4435                                         // fixed (T* e_ptr = (e == null || e.Length == 0) ? null : converted [0])
4436                                         //
4437                                         converted = new Conditional (new Binary (Binary.Operator.LogicalOr,
4438                                                 new Binary (Binary.Operator.Equality, e, new NullLiteral (loc)),
4439                                                 new Binary (Binary.Operator.Equality, new MemberAccess (e, "Length"), new IntConstant (0, loc))),
4440                                                         new NullPointer (loc),
4441                                                         converted);
4442
4443                                         converted = converted.Resolve (ec);
4444
4445                                         data [i] = new ExpressionEmitter (converted, vi);
4446                                         i++;
4447
4448                                         continue;
4449                                 }
4450
4451                                 //
4452                                 // Case 3: string
4453                                 //
4454                                 if (e.Type == TypeManager.string_type){
4455                                         data [i] = new StringEmitter (e, vi, loc);
4456                                         i++;
4457                                         continue;
4458                                 }
4459
4460                                 // Case 4: fixed buffer
4461                                 if (e is FixedBufferPtr) {
4462                                         data [i++] = new ExpressionEmitter (e, vi);
4463                                         continue;
4464                                 }
4465
4466                                 //
4467                                 // Case 1: & object.
4468                                 //
4469                                 Unary u = e as Unary;
4470                                 if (u != null && u.Oper == Unary.Operator.AddressOf) {
4471                                         IVariableReference vr = u.Expr as IVariableReference;
4472                                         if (vr == null || !vr.IsFixed) {
4473                                                 data [i] = new ExpressionEmitter (e, vi);
4474                                         }
4475                                 }
4476
4477                                 if (data [i++] == null)
4478                                         Report.Error (213, vi.Location, "You cannot use the fixed statement to take the address of an already fixed expression");
4479
4480                                 e = Convert.ImplicitConversionRequired (ec, e, expr_type, loc);
4481                         }
4482
4483                         ec.StartFlowBranching (FlowBranching.BranchingType.Conditional, loc);
4484                         bool ok = statement.Resolve (ec);
4485                         bool flow_unreachable = ec.EndFlowBranching ();
4486                         has_ret = flow_unreachable;
4487
4488                         return ok;
4489                 }
4490
4491                 protected override void DoEmit (EmitContext ec)
4492                 {
4493                         for (int i = 0; i < data.Length; i++) {
4494                                 data [i].Emit (ec);
4495                         }
4496
4497                         statement.Emit (ec);
4498
4499                         if (has_ret)
4500                                 return;
4501
4502                         //
4503                         // Clear the pinned variable
4504                         //
4505                         for (int i = 0; i < data.Length; i++) {
4506                                 data [i].EmitExit (ec);
4507                         }
4508                 }
4509
4510                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4511                 {
4512                         // Fixed statement cannot be used inside anonymous methods or lambdas
4513                         throw new NotSupportedException ();
4514                 }
4515
4516                 protected override void CloneTo (CloneContext clonectx, Statement t)
4517                 {
4518                         Fixed target = (Fixed) t;
4519
4520                         target.type = type.Clone (clonectx);
4521                         target.declarators = new ArrayList (declarators.Count);
4522                         foreach (Pair p in declarators) {
4523                                 LocalInfo vi = (LocalInfo) p.First;
4524                                 Expression e = (Expression) p.Second;
4525
4526                                 target.declarators.Add (
4527                                         new Pair (clonectx.LookupVariable (vi), e.Clone (clonectx)));
4528                         }
4529
4530                         target.statement = statement.Clone (clonectx);
4531                 }
4532         }
4533
4534         public class Catch : Statement {
4535                 public readonly string Name;
4536                 public Block  Block;
4537                 public Block  VarBlock;
4538
4539                 Expression type_expr;
4540                 Type type;
4541
4542                 public Catch (Expression type, string name, Block block, Block var_block, Location l)
4543                 {
4544                         type_expr = type;
4545                         Name = name;
4546                         Block = block;
4547                         VarBlock = var_block;
4548                         loc = l;
4549                 }
4550
4551                 public Type CatchType {
4552                         get {
4553                                 return type;
4554                         }
4555                 }
4556
4557                 public bool IsGeneral {
4558                         get {
4559                                 return type_expr == null;
4560                         }
4561                 }
4562
4563                 protected override void DoEmit (EmitContext ec)
4564                 {
4565                         ILGenerator ig = ec.ig;
4566
4567                         if (CatchType != null)
4568                                 ig.BeginCatchBlock (CatchType);
4569                         else
4570                                 ig.BeginCatchBlock (TypeManager.object_type);
4571
4572                         if (VarBlock != null)
4573                                 VarBlock.Emit (ec);
4574
4575                         if (Name != null) {
4576                                 // TODO: Move to resolve
4577                                 LocalVariableReference lvr = new LocalVariableReference (Block, Name, loc);
4578                                 lvr.Resolve (ec);
4579
4580 #if GMCS_SOURCE
4581                                 // Only to make verifier happy
4582                                 if (TypeManager.IsGenericParameter (lvr.Type))
4583                                         ig.Emit (OpCodes.Unbox_Any, lvr.Type);
4584 #endif
4585
4586                                 Expression source;
4587                                 if (lvr.IsHoisted) {
4588                                         LocalTemporary lt = new LocalTemporary (lvr.Type);
4589                                         lt.Store (ec);
4590                                         source = lt;
4591                                 } else {
4592                                         // Variable is at the top of the stack
4593                                         source = EmptyExpression.Null;
4594                                 }
4595
4596                                 lvr.EmitAssign (ec, source, false, false);
4597                         } else
4598                                 ig.Emit (OpCodes.Pop);
4599
4600                         Block.Emit (ec);
4601                 }
4602
4603                 public override bool Resolve (EmitContext ec)
4604                 {
4605                         using (ec.With (EmitContext.Flags.InCatch, true)) {
4606                                 if (type_expr != null) {
4607                                         TypeExpr te = type_expr.ResolveAsTypeTerminal (ec, false);
4608                                         if (te == null)
4609                                                 return false;
4610
4611                                         type = te.Type;
4612
4613                                         if (type != TypeManager.exception_type && !TypeManager.IsSubclassOf (type, TypeManager.exception_type)){
4614                                                 Error (155, "The type caught or thrown must be derived from System.Exception");
4615                                                 return false;
4616                                         }
4617                                 } else
4618                                         type = null;
4619
4620                                 if (!Block.Resolve (ec))
4621                                         return false;
4622
4623                                 // Even though VarBlock surrounds 'Block' we resolve it later, so that we can correctly
4624                                 // emit the "unused variable" warnings.
4625                                 if (VarBlock != null)
4626                                         return VarBlock.Resolve (ec);
4627
4628                                 return true;
4629                         }
4630                 }
4631
4632                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4633                 {
4634                         if (type != null)
4635                                 type = storey.MutateType (type);
4636                         if (VarBlock != null)
4637                                 VarBlock.MutateHoistedGenericType (storey);
4638                         Block.MutateHoistedGenericType (storey);
4639                 }
4640
4641                 protected override void CloneTo (CloneContext clonectx, Statement t)
4642                 {
4643                         Catch target = (Catch) t;
4644
4645                         if (type_expr != null)
4646                                 target.type_expr = type_expr.Clone (clonectx);
4647                         if (VarBlock != null)
4648                                 target.VarBlock = clonectx.LookupBlock (VarBlock);
4649                         target.Block = clonectx.LookupBlock (Block);
4650                 }
4651         }
4652
4653         public class TryFinally : ExceptionStatement {
4654                 Statement stmt;
4655                 Block fini;
4656
4657                 public TryFinally (Statement stmt, Block fini, Location l)
4658                 {
4659                         this.stmt = stmt;
4660                         this.fini = fini;
4661                         loc = l;
4662                 }
4663
4664                 public override bool Resolve (EmitContext ec)
4665                 {
4666                         bool ok = true;
4667
4668                         ec.StartFlowBranching (this);
4669
4670                         if (!stmt.Resolve (ec))
4671                                 ok = false;
4672
4673                         if (ok)
4674                                 ec.CurrentBranching.CreateSibling (fini, FlowBranching.SiblingType.Finally);
4675                         using (ec.With (EmitContext.Flags.InFinally, true)) {
4676                                 if (!fini.Resolve (ec))
4677                                         ok = false;
4678                         }
4679
4680                         ec.EndFlowBranching ();
4681
4682                         ResolveReachability (ec);
4683
4684                         return ok;
4685                 }
4686
4687                 protected override void EmitPreTryBody (EmitContext ec)
4688                 {
4689                 }
4690
4691                 protected override void EmitTryBody (EmitContext ec)
4692                 {
4693                         stmt.Emit (ec);
4694                 }
4695
4696                 protected override void EmitFinallyBody (EmitContext ec)
4697                 {
4698                         fini.Emit (ec);
4699                 }
4700
4701                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4702                 {
4703                         stmt.MutateHoistedGenericType (storey);
4704                         fini.MutateHoistedGenericType (storey);
4705                 }
4706
4707                 protected override void CloneTo (CloneContext clonectx, Statement t)
4708                 {
4709                         TryFinally target = (TryFinally) t;
4710
4711                         target.stmt = (Statement) stmt.Clone (clonectx);
4712                         if (fini != null)
4713                                 target.fini = clonectx.LookupBlock (fini);
4714                 }
4715         }
4716
4717         public class TryCatch : Statement {
4718                 public Block Block;
4719                 public ArrayList Specific;
4720                 public Catch General;
4721                 bool inside_try_finally, code_follows;
4722
4723                 public TryCatch (Block block, ArrayList catch_clauses, Location l, bool inside_try_finally)
4724                 {
4725                         this.Block = block;
4726                         this.Specific = catch_clauses;
4727                         this.General = null;
4728                         this.inside_try_finally = inside_try_finally;
4729
4730                         for (int i = 0; i < catch_clauses.Count; ++i) {
4731                                 Catch c = (Catch) catch_clauses [i];
4732                                 if (c.IsGeneral) {
4733                                         if (i != catch_clauses.Count - 1)
4734                                                 Report.Error (1017, c.loc, "Try statement already has an empty catch block");
4735                                         this.General = c;
4736                                         catch_clauses.RemoveAt (i);
4737                                         i--;
4738                                 }
4739                         }
4740
4741                         loc = l;
4742                 }
4743
4744                 public override bool Resolve (EmitContext ec)
4745                 {
4746                         bool ok = true;
4747
4748                         ec.StartFlowBranching (this);
4749
4750                         if (!Block.Resolve (ec))
4751                                 ok = false;
4752
4753                         Type[] prev_catches = new Type [Specific.Count];
4754                         int last_index = 0;
4755                         foreach (Catch c in Specific){
4756                                 ec.CurrentBranching.CreateSibling (c.Block, FlowBranching.SiblingType.Catch);
4757
4758                                 if (c.Name != null) {
4759                                         LocalInfo vi = c.Block.GetLocalInfo (c.Name);
4760                                         if (vi == null)
4761                                                 throw new Exception ();
4762
4763                                         vi.VariableInfo = null;
4764                                 }
4765
4766                                 if (!c.Resolve (ec))
4767                                         ok = false;
4768
4769                                 Type resolved_type = c.CatchType;
4770                                 for (int ii = 0; ii < last_index; ++ii) {
4771                                         if (resolved_type == prev_catches [ii] || TypeManager.IsSubclassOf (resolved_type, prev_catches [ii])) {
4772                                                 Report.Error (160, c.loc,
4773                                                         "A previous catch clause already catches all exceptions of this or a super type `{0}'",
4774                                                         TypeManager.CSharpName (prev_catches [ii]));
4775                                                 ok = false;
4776                                         }
4777                                 }
4778
4779                                 prev_catches [last_index++] = resolved_type;
4780                         }
4781
4782                         if (General != null) {
4783                                 if (CodeGen.Assembly.WrapNonExceptionThrows) {
4784                                         foreach (Catch c in Specific){
4785                                                 if (c.CatchType == TypeManager.exception_type && PredefinedAttributes.Get.RuntimeCompatibility.IsDefined) {
4786                                                         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'");
4787                                                 }
4788                                         }
4789                                 }
4790
4791                                 ec.CurrentBranching.CreateSibling (General.Block, FlowBranching.SiblingType.Catch);
4792
4793                                 if (!General.Resolve (ec))
4794                                         ok = false;
4795                         }
4796
4797                         ec.EndFlowBranching ();
4798
4799                         // System.Reflection.Emit automatically emits a 'leave' at the end of a try/catch clause
4800                         // So, ensure there's some IL code after this statement
4801                         if (!inside_try_finally && !code_follows && ec.CurrentBranching.CurrentUsageVector.IsUnreachable)
4802                                 ec.NeedReturnLabel ();
4803
4804                         return ok;
4805                 }
4806
4807                 public void SomeCodeFollows ()
4808                 {
4809                         code_follows = true;
4810                 }
4811
4812                 protected override void DoEmit (EmitContext ec)
4813                 {
4814                         ILGenerator ig = ec.ig;
4815
4816                         if (!inside_try_finally)
4817                                 ig.BeginExceptionBlock ();
4818
4819                         Block.Emit (ec);
4820
4821                         foreach (Catch c in Specific)
4822                                 c.Emit (ec);
4823
4824                         if (General != null)
4825                                 General.Emit (ec);
4826
4827                         if (!inside_try_finally)
4828                                 ig.EndExceptionBlock ();
4829                 }
4830
4831                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4832                 {
4833                         Block.MutateHoistedGenericType (storey);
4834
4835                         if (General != null)
4836                                 General.MutateHoistedGenericType (storey);
4837                         if (Specific != null) {
4838                                 foreach (Catch c in Specific)
4839                                         c.MutateHoistedGenericType (storey);
4840                         }
4841                 }
4842
4843                 protected override void CloneTo (CloneContext clonectx, Statement t)
4844                 {
4845                         TryCatch target = (TryCatch) t;
4846
4847                         target.Block = clonectx.LookupBlock (Block);
4848                         if (General != null)
4849                                 target.General = (Catch) General.Clone (clonectx);
4850                         if (Specific != null){
4851                                 target.Specific = new ArrayList ();
4852                                 foreach (Catch c in Specific)
4853                                         target.Specific.Add (c.Clone (clonectx));
4854                         }
4855                 }
4856         }
4857
4858         // FIXME: Why is it almost exact copy of Using ??
4859         public class UsingTemporary : ExceptionStatement {
4860                 TemporaryVariable local_copy;
4861                 public Statement Statement;
4862                 Expression expr;
4863                 Type expr_type;
4864
4865                 public UsingTemporary (Expression expr, Statement stmt, Location l)
4866                 {
4867                         this.expr = expr;
4868                         Statement = stmt;
4869                         loc = l;
4870                 }
4871
4872                 public override bool Resolve (EmitContext ec)
4873                 {
4874                         expr = expr.Resolve (ec);
4875                         if (expr == null)
4876                                 return false;
4877
4878                         expr_type = expr.Type;
4879
4880                         if (!TypeManager.ImplementsInterface (expr_type, TypeManager.idisposable_type)) {
4881                                 if (Convert.ImplicitConversion (ec, expr, TypeManager.idisposable_type, loc) == null) {
4882                                         Using.Error_IsNotConvertibleToIDisposable (expr);
4883                                         return false;
4884                                 }
4885                         }
4886
4887                         local_copy = new TemporaryVariable (expr_type, loc);
4888                         local_copy.Resolve (ec);
4889
4890                         ec.StartFlowBranching (this);
4891
4892                         bool ok = Statement.Resolve (ec);
4893
4894                         ec.EndFlowBranching ();
4895
4896                         ResolveReachability (ec);
4897
4898                         if (TypeManager.void_dispose_void == null) {
4899                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
4900                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
4901                         }
4902
4903                         return ok;
4904                 }
4905
4906                 protected override void EmitPreTryBody (EmitContext ec)
4907                 {
4908                         local_copy.EmitAssign (ec, expr);
4909                 }
4910
4911                 protected override void EmitTryBody (EmitContext ec)
4912                 {
4913                         Statement.Emit (ec);
4914                 }
4915
4916                 protected override void EmitFinallyBody (EmitContext ec)
4917                 {
4918                         ILGenerator ig = ec.ig;
4919                         if (!TypeManager.IsStruct (expr_type)) {
4920                                 Label skip = ig.DefineLabel ();
4921                                 local_copy.Emit (ec);
4922                                 ig.Emit (OpCodes.Brfalse, skip);
4923                                 local_copy.Emit (ec);
4924                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4925                                 ig.MarkLabel (skip);
4926                                 return;
4927                         }
4928
4929                         Expression ml = Expression.MemberLookup (
4930                                 ec.ContainerType, TypeManager.idisposable_type, expr_type,
4931                                 "Dispose", Location.Null);
4932
4933                         if (!(ml is MethodGroupExpr)) {
4934                                 local_copy.Emit (ec);
4935                                 ig.Emit (OpCodes.Box, expr_type);
4936                                 ig.Emit (OpCodes.Callvirt, TypeManager.void_dispose_void);
4937                                 return;
4938                         }
4939
4940                         MethodInfo mi = null;
4941
4942                         foreach (MethodInfo mk in ((MethodGroupExpr) ml).Methods) {
4943                                 if (TypeManager.GetParameterData (mk).Count == 0) {
4944                                         mi = mk;
4945                                         break;
4946                                 }
4947                         }
4948
4949                         if (mi == null) {
4950                                 Report.Error(-100, Mono.CSharp.Location.Null, "Internal error: No Dispose method which takes 0 parameters.");
4951                                 return;
4952                         }
4953
4954                         local_copy.AddressOf (ec, AddressOp.Load);
4955                         ig.Emit (OpCodes.Call, mi);
4956                 }
4957
4958                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
4959                 {
4960                         expr_type = storey.MutateType (expr_type);
4961                         local_copy.MutateHoistedGenericType (storey);
4962                         Statement.MutateHoistedGenericType (storey);
4963                 }
4964
4965                 protected override void CloneTo (CloneContext clonectx, Statement t)
4966                 {
4967                         UsingTemporary target = (UsingTemporary) t;
4968
4969                         target.expr = expr.Clone (clonectx);
4970                         target.Statement = Statement.Clone (clonectx);
4971                 }
4972         }
4973
4974         public class Using : ExceptionStatement {
4975                 Statement stmt;
4976                 public Statement EmbeddedStatement {
4977                         get { return stmt is Using ? ((Using) stmt).EmbeddedStatement : stmt; }
4978                 }
4979
4980                 Expression var;
4981                 Expression init;
4982
4983                 ExpressionStatement assign;
4984
4985                 public Using (Expression var, Expression init, Statement stmt, Location l)
4986                 {
4987                         this.var = var;
4988                         this.init = init;
4989                         this.stmt = stmt;
4990                         loc = l;
4991                 }
4992
4993                 static public void Error_IsNotConvertibleToIDisposable (Expression expr)
4994                 {
4995                         Report.SymbolRelatedToPreviousError (expr.Type);
4996                         Report.Error (1674, expr.Location, "`{0}': type used in a using statement must be implicitly convertible to `System.IDisposable'",
4997                                 expr.GetSignatureForError ());
4998                 }
4999
5000                 protected override void EmitPreTryBody (EmitContext ec)
5001                 {
5002                         assign.EmitStatement (ec);
5003                 }
5004
5005                 protected override void EmitTryBody (EmitContext ec)
5006                 {
5007                         stmt.Emit (ec);
5008                 }
5009
5010                 protected override void EmitFinallyBody (EmitContext ec)
5011                 {
5012                         ILGenerator ig = ec.ig;
5013                         Label skip = ig.DefineLabel ();
5014
5015                         bool emit_null_check = !TypeManager.IsValueType (var.Type);
5016                         if (emit_null_check) {
5017                                 var.Emit (ec);
5018                                 ig.Emit (OpCodes.Brfalse, skip);
5019                         }
5020
5021                         Invocation.EmitCall (ec, false, var, TypeManager.void_dispose_void, new ArrayList (0), loc);
5022
5023                         if (emit_null_check)
5024                                 ig.MarkLabel (skip);
5025                 }
5026
5027                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5028                 {
5029                         assign.MutateHoistedGenericType (storey);
5030                         var.MutateHoistedGenericType (storey);
5031                         stmt.MutateHoistedGenericType (storey);
5032                 }
5033
5034                 public override bool Resolve (EmitContext ec)
5035                 {
5036                         if (!ResolveVariable (ec))
5037                                 return false;
5038
5039                         ec.StartFlowBranching (this);
5040
5041                         bool ok = stmt.Resolve (ec);
5042
5043                         ec.EndFlowBranching ();
5044
5045                         ResolveReachability (ec);
5046
5047                         if (TypeManager.void_dispose_void == null) {
5048                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
5049                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
5050                         }
5051
5052                         return ok;
5053                 }
5054
5055                 bool ResolveVariable (EmitContext ec)
5056                 {
5057                         assign = new SimpleAssign (var, init, loc);
5058                         assign = assign.ResolveStatement (ec);
5059                         if (assign == null)
5060                                 return false;
5061
5062                         if (assign.Type == TypeManager.idisposable_type ||
5063                                 TypeManager.ImplementsInterface (assign.Type, TypeManager.idisposable_type)) {
5064                                 return true;
5065                         }
5066
5067                         Expression e = Convert.ImplicitConversionStandard (ec, assign, TypeManager.idisposable_type, var.Location);
5068                         if (e == null) {
5069                                 Error_IsNotConvertibleToIDisposable (var);
5070                                 return false;
5071                         }
5072
5073                         throw new NotImplementedException ("covariance?");
5074                 }
5075
5076                 protected override void CloneTo (CloneContext clonectx, Statement t)
5077                 {
5078                         Using target = (Using) t;
5079
5080                         target.var = var.Clone (clonectx);
5081                         target.init = init.Clone (clonectx);
5082                         target.stmt = stmt.Clone (clonectx);
5083                 }
5084         }
5085
5086         /// <summary>
5087         ///   Implementation of the foreach C# statement
5088         /// </summary>
5089         public class Foreach : Statement {
5090
5091                 sealed class ArrayForeach : Statement
5092                 {
5093                         class ArrayCounter : TemporaryVariable
5094                         {
5095                                 StatementExpression increment;
5096
5097                                 public ArrayCounter (Location loc)
5098                                         : base (TypeManager.int32_type, loc)
5099                                 {
5100                                 }
5101
5102                                 public void ResolveIncrement (EmitContext ec)
5103                                 {
5104                                         increment = new StatementExpression (new UnaryMutator (UnaryMutator.Mode.PostIncrement, this));
5105                                         increment.Resolve (ec);
5106                                 }
5107
5108                                 public void EmitIncrement (EmitContext ec)
5109                                 {
5110                                         increment.Emit (ec);
5111                                 }
5112                         }
5113
5114                         readonly Foreach for_each;
5115                         readonly Statement statement;
5116
5117                         Expression conv;
5118                         TemporaryVariable[] lengths;
5119                         Expression [] length_exprs;
5120                         ArrayCounter[] counter;
5121
5122                         TemporaryVariable copy;
5123                         Expression access;
5124
5125                         public ArrayForeach (Foreach @foreach, int rank)
5126                         {
5127                                 for_each = @foreach;
5128                                 statement = for_each.statement;
5129                                 loc = @foreach.loc;
5130
5131                                 counter = new ArrayCounter [rank];
5132                                 length_exprs = new Expression [rank];
5133
5134                                 //
5135                                 // Only use temporary length variables when dealing with
5136                                 // multi-dimensional arrays
5137                                 //
5138                                 if (rank > 1)
5139                                         lengths = new TemporaryVariable [rank];
5140                         }
5141
5142                         protected override void CloneTo (CloneContext clonectx, Statement target)
5143                         {
5144                                 throw new NotImplementedException ();
5145                         }
5146
5147                         public override bool Resolve (EmitContext ec)
5148                         {
5149                                 copy = new TemporaryVariable (for_each.expr.Type, loc);
5150                                 copy.Resolve (ec);
5151
5152                                 int rank = length_exprs.Length;
5153                                 ArrayList list = new ArrayList (rank);
5154                                 for (int i = 0; i < rank; i++) {
5155                                         counter [i] = new ArrayCounter (loc);
5156                                         counter [i].ResolveIncrement (ec);
5157
5158                                         if (rank == 1) {
5159                                                 length_exprs [i] = new MemberAccess (copy, "Length").Resolve (ec);
5160                                         } else {
5161                                                 lengths [i] = new TemporaryVariable (TypeManager.int32_type, loc);
5162                                                 lengths [i].Resolve (ec);
5163
5164                                                 ArrayList args = new ArrayList (1);
5165                                                 args.Add (new Argument (new IntConstant (i, loc)));
5166                                                 length_exprs [i] = new Invocation (new MemberAccess (copy, "GetLength"), args).Resolve (ec);
5167                                         }
5168
5169                                         list.Add (counter [i]);
5170                                 }
5171
5172                                 access = new ElementAccess (copy, list).Resolve (ec);
5173                                 if (access == null)
5174                                         return false;
5175
5176                                 Expression var_type = for_each.type;
5177                                 VarExpr ve = var_type as VarExpr;
5178                                 if (ve != null) {
5179                                         // Infer implicitly typed local variable from foreach array type
5180                                         var_type = new TypeExpression (access.Type, ve.Location);
5181                                 }
5182
5183                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
5184                                 if (var_type == null)
5185                                         return false;
5186
5187                                 conv = Convert.ExplicitConversion (ec, access, var_type.Type, loc);
5188                                 if (conv == null)
5189                                         return false;
5190
5191                                 bool ok = true;
5192
5193                                 ec.StartFlowBranching (FlowBranching.BranchingType.Loop, loc);
5194                                 ec.CurrentBranching.CreateSibling ();
5195
5196                                 for_each.variable = for_each.variable.ResolveLValue (ec, conv, loc);
5197                                 if (for_each.variable == null)
5198                                         ok = false;
5199
5200                                 ec.StartFlowBranching (FlowBranching.BranchingType.Embedded, loc);
5201                                 if (!statement.Resolve (ec))
5202                                         ok = false;
5203                                 ec.EndFlowBranching ();
5204
5205                                 // There's no direct control flow from the end of the embedded statement to the end of the loop
5206                                 ec.CurrentBranching.CurrentUsageVector.Goto ();
5207
5208                                 ec.EndFlowBranching ();
5209
5210                                 return ok;
5211                         }
5212
5213                         protected override void DoEmit (EmitContext ec)
5214                         {
5215                                 ILGenerator ig = ec.ig;
5216
5217                                 copy.EmitAssign (ec, for_each.expr);
5218
5219                                 int rank = length_exprs.Length;
5220                                 Label[] test = new Label [rank];
5221                                 Label[] loop = new Label [rank];
5222
5223                                 for (int i = 0; i < rank; i++) {
5224                                         test [i] = ig.DefineLabel ();
5225                                         loop [i] = ig.DefineLabel ();
5226
5227                                         if (lengths != null)
5228                                                 lengths [i].EmitAssign (ec, length_exprs [i]);
5229                                 }
5230
5231                                 IntConstant zero = new IntConstant (0, loc);
5232                                 for (int i = 0; i < rank; i++) {
5233                                         counter [i].EmitAssign (ec, zero);
5234
5235                                         ig.Emit (OpCodes.Br, test [i]);
5236                                         ig.MarkLabel (loop [i]);
5237                                 }
5238
5239                                 ((IAssignMethod) for_each.variable).EmitAssign (ec, conv, false, false);
5240
5241                                 statement.Emit (ec);
5242
5243                                 ig.MarkLabel (ec.LoopBegin);
5244
5245                                 for (int i = rank - 1; i >= 0; i--){
5246                                         counter [i].EmitIncrement (ec);
5247
5248                                         ig.MarkLabel (test [i]);
5249                                         counter [i].Emit (ec);
5250
5251                                         if (lengths != null)
5252                                                 lengths [i].Emit (ec);
5253                                         else
5254                                                 length_exprs [i].Emit (ec);
5255
5256                                         ig.Emit (OpCodes.Blt, loop [i]);
5257                                 }
5258
5259                                 ig.MarkLabel (ec.LoopEnd);
5260                         }
5261
5262                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5263                         {
5264                                 for_each.expr.MutateHoistedGenericType (storey);
5265
5266                                 copy.MutateHoistedGenericType (storey);
5267                                 conv.MutateHoistedGenericType (storey);
5268                                 statement.MutateHoistedGenericType (storey);
5269
5270                                 for (int i = 0; i < counter.Length; i++) {
5271                                         counter [i].MutateHoistedGenericType (storey);
5272                                         if (lengths != null)
5273                                                 lengths [i].MutateHoistedGenericType (storey);
5274                                 }
5275                         }
5276                 }
5277
5278                 sealed class CollectionForeach : Statement
5279                 {
5280                         class CollectionForeachStatement : Statement
5281                         {
5282                                 Type type;
5283                                 Expression variable, current, conv;
5284                                 Statement statement;
5285                                 Assign assign;
5286
5287                                 public CollectionForeachStatement (Type type, Expression variable,
5288                                                                    Expression current, Statement statement,
5289                                                                    Location loc)
5290                                 {
5291                                         this.type = type;
5292                                         this.variable = variable;
5293                                         this.current = current;
5294                                         this.statement = statement;
5295                                         this.loc = loc;
5296                                 }
5297
5298                                 protected override void CloneTo (CloneContext clonectx, Statement target)
5299                                 {
5300                                         throw new NotImplementedException ();
5301                                 }
5302
5303                                 public override bool Resolve (EmitContext ec)
5304                                 {
5305                                         current = current.Resolve (ec);
5306                                         if (current == null)
5307                                                 return false;
5308
5309                                         conv = Convert.ExplicitConversion (ec, current, type, loc);
5310                                         if (conv == null)
5311                                                 return false;
5312
5313                                         assign = new SimpleAssign (variable, conv, loc);
5314                                         if (assign.Resolve (ec) == null)
5315                                                 return false;
5316
5317                                         if (!statement.Resolve (ec))
5318                                                 return false;
5319
5320                                         return true;
5321                                 }
5322
5323                                 protected override void DoEmit (EmitContext ec)
5324                                 {
5325                                         assign.EmitStatement (ec);
5326                                         statement.Emit (ec);
5327                                 }
5328
5329                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5330                                 {
5331                                         assign.MutateHoistedGenericType (storey);
5332                                         statement.MutateHoistedGenericType (storey);
5333                                 }
5334                         }
5335
5336                         Expression variable, expr;
5337                         Statement statement;
5338
5339                         TemporaryVariable enumerator;
5340                         Expression init;
5341                         Statement loop;
5342                         Statement wrapper;
5343
5344                         MethodGroupExpr get_enumerator;
5345                         PropertyExpr get_current;
5346                         MethodInfo move_next;
5347                         Expression var_type;
5348                         Type enumerator_type;
5349                         bool enumerator_found;
5350
5351                         public CollectionForeach (Expression var_type, Expression var,
5352                                                   Expression expr, Statement stmt, Location l)
5353                         {
5354                                 this.var_type = var_type;
5355                                 this.variable = var;
5356                                 this.expr = expr;
5357                                 statement = stmt;
5358                                 loc = l;
5359                         }
5360
5361                         protected override void CloneTo (CloneContext clonectx, Statement target)
5362                         {
5363                                 throw new NotImplementedException ();
5364                         }
5365
5366                         bool GetEnumeratorFilter (EmitContext ec, MethodInfo mi)
5367                         {
5368                                 Type return_type = mi.ReturnType;
5369
5370                                 //
5371                                 // Ok, we can access it, now make sure that we can do something
5372                                 // with this `GetEnumerator'
5373                                 //
5374
5375                                 if (return_type == TypeManager.ienumerator_type ||
5376                                         TypeManager.ImplementsInterface (return_type, TypeManager.ienumerator_type)) {
5377                                         //
5378                                         // If it is not an interface, lets try to find the methods ourselves.
5379                                         // For example, if we have:
5380                                         // public class Foo : IEnumerator { public bool MoveNext () {} public int Current { get {}}}
5381                                         // We can avoid the iface call. This is a runtime perf boost.
5382                                         // even bigger if we have a ValueType, because we avoid the cost
5383                                         // of boxing.
5384                                         //
5385                                         // We have to make sure that both methods exist for us to take
5386                                         // this path. If one of the methods does not exist, we will just
5387                                         // use the interface. Sadly, this complex if statement is the only
5388                                         // way I could do this without a goto
5389                                         //
5390
5391                                         if (TypeManager.bool_movenext_void == null) {
5392                                                 TypeManager.bool_movenext_void = TypeManager.GetPredefinedMethod (
5393                                                         TypeManager.ienumerator_type, "MoveNext", loc, Type.EmptyTypes);
5394                                         }
5395
5396                                         if (TypeManager.ienumerator_getcurrent == null) {
5397                                                 TypeManager.ienumerator_getcurrent = TypeManager.GetPredefinedProperty (
5398                                                         TypeManager.ienumerator_type, "Current", loc, TypeManager.object_type);
5399                                         }
5400
5401                                         //
5402                                         // Prefer a generic enumerator over a non-generic one.
5403                                         //
5404                                         if (return_type.IsInterface && TypeManager.IsGenericType (return_type)) {
5405                                                 enumerator_type = return_type;
5406                                                 if (!FetchGetCurrent (ec, return_type))
5407                                                         get_current = new PropertyExpr (
5408                                                                 ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5409                                                 if (!FetchMoveNext (return_type))
5410                                                         move_next = TypeManager.bool_movenext_void;
5411                                                 return true;
5412                                         }
5413
5414                                         if (return_type.IsInterface ||
5415                                             !FetchMoveNext (return_type) ||
5416                                             !FetchGetCurrent (ec, return_type)) {
5417                                                 enumerator_type = return_type;
5418                                                 move_next = TypeManager.bool_movenext_void;
5419                                                 get_current = new PropertyExpr (
5420                                                         ec.ContainerType, TypeManager.ienumerator_getcurrent, loc);
5421                                                 return true;
5422                                         }
5423                                 } else {
5424                                         //
5425                                         // Ok, so they dont return an IEnumerable, we will have to
5426                                         // find if they support the GetEnumerator pattern.
5427                                         //
5428
5429                                         if (TypeManager.HasElementType (return_type) || !FetchMoveNext (return_type) || !FetchGetCurrent (ec, return_type)) {
5430                                                 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",
5431                                                         TypeManager.CSharpName (return_type), TypeManager.CSharpSignature (mi));
5432                                                 return false;
5433                                         }
5434                                 }
5435
5436                                 enumerator_type = return_type;
5437
5438                                 return true;
5439                         }
5440
5441                         //
5442                         // Retrieves a `public bool MoveNext ()' method from the Type `t'
5443                         //
5444                         bool FetchMoveNext (Type t)
5445                         {
5446                                 MemberInfo[] move_next_list = TypeManager.MemberLookup (null, null, t,
5447                                         MemberTypes.Method,
5448                                         BindingFlags.Public | BindingFlags.Instance,
5449                                         "MoveNext", null);
5450
5451                                 foreach (MemberInfo m in move_next_list){
5452                                         MethodInfo mi = (MethodInfo) m;
5453
5454                                         if ((TypeManager.GetParameterData (mi).Count == 0) &&
5455                                             TypeManager.TypeToCoreType (mi.ReturnType) == TypeManager.bool_type) {
5456                                                 move_next = mi;
5457                                                 return true;
5458                                         }
5459                                 }
5460
5461                                 return false;
5462                         }
5463
5464                         //
5465                         // Retrieves a `public T get_Current ()' method from the Type `t'
5466                         //
5467                         bool FetchGetCurrent (EmitContext ec, Type t)
5468                         {
5469                                 PropertyExpr pe = Expression.MemberLookup (
5470                                         ec.ContainerType, t, "Current", MemberTypes.Property,
5471                                         Expression.AllBindingFlags, loc) as PropertyExpr;
5472                                 if (pe == null)
5473                                         return false;
5474
5475                                 get_current = pe;
5476                                 return true;
5477                         }
5478
5479                         void Error_Enumerator ()
5480                         {
5481                                 if (enumerator_found) {
5482                                         return;
5483                                 }
5484
5485                             Report.Error (1579, loc,
5486                                         "foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `GetEnumerator' or is not accessible",
5487                                         TypeManager.CSharpName (expr.Type));
5488                         }
5489
5490                         bool IsOverride (MethodInfo m)
5491                         {
5492                                 m = (MethodInfo) TypeManager.DropGenericMethodArguments (m);
5493
5494                                 if (!m.IsVirtual || ((m.Attributes & MethodAttributes.NewSlot) != 0))
5495                                         return false;
5496                                 if (m is MethodBuilder)
5497                                         return true;
5498
5499                                 MethodInfo base_method = m.GetBaseDefinition ();
5500                                 return base_method != m;
5501                         }
5502
5503                         bool TryType (EmitContext ec, Type t)
5504                         {
5505                                 MethodGroupExpr mg = Expression.MemberLookup (
5506                                         ec.ContainerType, t, "GetEnumerator", MemberTypes.Method,
5507                                         Expression.AllBindingFlags, loc) as MethodGroupExpr;
5508                                 if (mg == null)
5509                                         return false;
5510
5511                                 MethodInfo result = null;
5512                                 MethodInfo tmp_move_next = null;
5513                                 PropertyExpr tmp_get_cur = null;
5514                                 Type tmp_enumerator_type = enumerator_type;
5515                                 foreach (MethodInfo mi in mg.Methods) {
5516                                         if (TypeManager.GetParameterData (mi).Count != 0)
5517                                                 continue;
5518
5519                                         // Check whether GetEnumerator is public
5520                                         if ((mi.Attributes & MethodAttributes.Public) != MethodAttributes.Public)
5521                                                 continue;
5522
5523                                         if (IsOverride (mi))
5524                                                 continue;
5525
5526                                         enumerator_found = true;
5527
5528                                         if (!GetEnumeratorFilter (ec, mi))
5529                                                 continue;
5530
5531                                         if (result != null) {
5532                                                 if (TypeManager.IsGenericType (result.ReturnType)) {
5533                                                         if (!TypeManager.IsGenericType (mi.ReturnType))
5534                                                                 continue;
5535
5536                                                         MethodBase mb = TypeManager.DropGenericMethodArguments (mi);
5537                                                         Report.SymbolRelatedToPreviousError (t);
5538                                                         Report.Error(1640, loc, "foreach statement cannot operate on variables of type `{0}' " +
5539                                                                      "because it contains multiple implementation of `{1}'. Try casting to a specific implementation",
5540                                                                      TypeManager.CSharpName (t), TypeManager.CSharpSignature (mb));
5541                                                         return false;
5542                                                 }
5543
5544                                                 // Always prefer generics enumerators
5545                                                 if (!TypeManager.IsGenericType (mi.ReturnType)) {
5546                                                         if (TypeManager.ImplementsInterface (mi.DeclaringType, result.DeclaringType) ||
5547                                                             TypeManager.ImplementsInterface (result.DeclaringType, mi.DeclaringType))
5548                                                                 continue;
5549
5550                                                         Report.SymbolRelatedToPreviousError (result);
5551                                                         Report.SymbolRelatedToPreviousError (mi);
5552                                                         Report.Warning (278, 2, loc, "`{0}' contains ambiguous implementation of `{1}' pattern. Method `{2}' is ambiguous with method `{3}'",
5553                                                                         TypeManager.CSharpName (t), "enumerable", TypeManager.CSharpSignature (result), TypeManager.CSharpSignature (mi));
5554                                                         return false;
5555                                                 }
5556                                         }
5557                                         result = mi;
5558                                         tmp_move_next = move_next;
5559                                         tmp_get_cur = get_current;
5560                                         tmp_enumerator_type = enumerator_type;
5561                                         if (mi.DeclaringType == t)
5562                                                 break;
5563                                 }
5564
5565                                 if (result != null) {
5566                                         move_next = tmp_move_next;
5567                                         get_current = tmp_get_cur;
5568                                         enumerator_type = tmp_enumerator_type;
5569                                         MethodInfo[] mi = new MethodInfo[] { (MethodInfo) result };
5570                                         get_enumerator = new MethodGroupExpr (mi, enumerator_type, loc);
5571
5572                                         if (t != expr.Type) {
5573                                                 expr = Convert.ExplicitConversion (
5574                                                         ec, expr, t, loc);
5575                                                 if (expr == null)
5576                                                         throw new InternalErrorException ();
5577                                         }
5578
5579                                         get_enumerator.InstanceExpression = expr;
5580                                         get_enumerator.IsBase = t != expr.Type;
5581
5582                                         return true;
5583                                 }
5584
5585                                 return false;
5586                         }
5587
5588                         bool ProbeCollectionType (EmitContext ec, Type t)
5589                         {
5590                                 int errors = Report.Errors;
5591                                 for (Type tt = t; tt != null && tt != TypeManager.object_type;){
5592                                         if (TryType (ec, tt))
5593                                                 return true;
5594                                         tt = tt.BaseType;
5595                                 }
5596
5597                                 if (Report.Errors > errors)
5598                                         return false;
5599
5600                                 //
5601                                 // Now try to find the method in the interfaces
5602                                 //
5603                                 Type [] ifaces = TypeManager.GetInterfaces (t);
5604                                 foreach (Type i in ifaces){
5605                                         if (TryType (ec, i))
5606                                                 return true;
5607                                 }
5608
5609                                 return false;
5610                         }
5611
5612                         public override bool Resolve (EmitContext ec)
5613                         {
5614                                 enumerator_type = TypeManager.ienumerator_type;
5615
5616                                 if (!ProbeCollectionType (ec, expr.Type)) {
5617                                         Error_Enumerator ();
5618                                         return false;
5619                                 }
5620
5621                                 VarExpr ve = var_type as VarExpr;
5622                                 if (ve != null) {
5623                                         // Infer implicitly typed local variable from foreach enumerable type
5624                                         var_type = new TypeExpression (get_current.PropertyInfo.PropertyType, var_type.Location);
5625                                 }
5626
5627                                 var_type = var_type.ResolveAsTypeTerminal (ec, false);
5628                                 if (var_type == null)
5629                                         return false;
5630
5631                                 enumerator = new TemporaryVariable (enumerator_type, loc);
5632                                 enumerator.Resolve (ec);
5633
5634                                 init = new Invocation (get_enumerator, null);
5635                                 init = init.Resolve (ec);
5636                                 if (init == null)
5637                                         return false;
5638
5639                                 Expression move_next_expr;
5640                                 {
5641                                         MemberInfo[] mi = new MemberInfo[] { move_next };
5642                                         MethodGroupExpr mg = new MethodGroupExpr (mi, var_type.Type, loc);
5643                                         mg.InstanceExpression = enumerator;
5644
5645                                         move_next_expr = new Invocation (mg, null);
5646                                 }
5647
5648                                 get_current.InstanceExpression = enumerator;
5649
5650                                 Statement block = new CollectionForeachStatement (
5651                                         var_type.Type, variable, get_current, statement, loc);
5652
5653                                 loop = new While (move_next_expr, block, loc);
5654
5655
5656                                 bool implements_idisposable = TypeManager.ImplementsInterface (enumerator_type, TypeManager.idisposable_type);
5657                                 if (implements_idisposable || !enumerator_type.IsSealed) {
5658                                         wrapper = new DisposableWrapper (this, implements_idisposable);
5659                                 } else {
5660                                         wrapper = new NonDisposableWrapper (this);
5661                                 }
5662
5663                                 return wrapper.Resolve (ec);
5664                         }
5665
5666                         protected override void DoEmit (EmitContext ec)
5667                         {
5668                                 wrapper.Emit (ec);
5669                         }
5670
5671                         class NonDisposableWrapper : Statement {
5672                                 CollectionForeach parent;
5673
5674                                 internal NonDisposableWrapper (CollectionForeach parent)
5675                                 {
5676                                         this.parent = parent;
5677                                 }
5678
5679                                 protected override void CloneTo (CloneContext clonectx, Statement target)
5680                                 {
5681                                         throw new NotSupportedException ();
5682                                 }
5683
5684                                 public override bool Resolve (EmitContext ec)
5685                                 {
5686                                         return parent.ResolveLoop (ec);
5687                                 }
5688
5689                                 protected override void DoEmit (EmitContext ec)
5690                                 {
5691                                         parent.EmitLoopInit (ec);
5692                                         parent.EmitLoopBody (ec);
5693                                 }
5694
5695                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5696                                 {
5697                                         throw new NotSupportedException ();
5698                                 }
5699                         }
5700
5701                         sealed class DisposableWrapper : ExceptionStatement
5702                         {
5703                                 CollectionForeach parent;
5704                                 bool implements_idisposable;
5705
5706                                 internal DisposableWrapper (CollectionForeach parent, bool implements)
5707                                 {
5708                                         this.parent = parent;
5709                                         this.implements_idisposable = implements;
5710                                 }
5711
5712                                 protected override void CloneTo (CloneContext clonectx, Statement target)
5713                                 {
5714                                         throw new NotSupportedException ();
5715                                 }
5716
5717                                 public override bool Resolve (EmitContext ec)
5718                                 {
5719                                         bool ok = true;
5720
5721                                         ec.StartFlowBranching (this);
5722
5723                                         if (!parent.ResolveLoop (ec))
5724                                                 ok = false;
5725
5726                                         ec.EndFlowBranching ();
5727
5728                                         ResolveReachability (ec);
5729
5730                                         if (TypeManager.void_dispose_void == null) {
5731                                                 TypeManager.void_dispose_void = TypeManager.GetPredefinedMethod (
5732                                                         TypeManager.idisposable_type, "Dispose", loc, Type.EmptyTypes);
5733                                         }
5734                                         return ok;
5735                                 }
5736
5737                                 protected override void EmitPreTryBody (EmitContext ec)
5738                                 {
5739                                         parent.EmitLoopInit (ec);
5740                                 }
5741
5742                                 protected override void EmitTryBody (EmitContext ec)
5743                                 {
5744                                         parent.EmitLoopBody (ec);
5745                                 }
5746
5747                                 protected override void EmitFinallyBody (EmitContext ec)
5748                                 {
5749                                         Expression instance = parent.enumerator;
5750                                         if (!TypeManager.IsValueType (parent.enumerator_type)) {
5751                                                 ILGenerator ig = ec.ig;
5752
5753                                                 parent.enumerator.Emit (ec);
5754
5755                                                 Label call_dispose = ig.DefineLabel ();
5756
5757                                                 if (!implements_idisposable) {
5758                                                         ec.ig.Emit (OpCodes.Isinst, TypeManager.idisposable_type);
5759                                                         LocalTemporary temp = new LocalTemporary (TypeManager.idisposable_type);
5760                                                         temp.Store (ec);
5761                                                         temp.Emit (ec);
5762                                                         instance = temp;
5763                                                 }
5764
5765                                                 ig.Emit (OpCodes.Brtrue_S, call_dispose);
5766
5767                                                 // using 'endfinally' to empty the evaluation stack
5768                                                 ig.Emit (OpCodes.Endfinally);
5769                                                 ig.MarkLabel (call_dispose);
5770                                         }
5771
5772                                         Invocation.EmitCall (ec, false, instance, TypeManager.void_dispose_void, new ArrayList (0), loc);
5773                                 }
5774
5775                                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5776                                 {
5777                                         throw new NotSupportedException ();
5778                                 }
5779                         }
5780
5781                         bool ResolveLoop (EmitContext ec)
5782                         {
5783                                 return loop.Resolve (ec);
5784                         }
5785
5786                         void EmitLoopInit (EmitContext ec)
5787                         {
5788                                 enumerator.EmitAssign (ec, init);
5789                         }
5790
5791                         void EmitLoopBody (EmitContext ec)
5792                         {
5793                                 loop.Emit (ec);
5794                         }
5795
5796                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5797                         {
5798                                 enumerator_type = storey.MutateType (enumerator_type);
5799                                 init.MutateHoistedGenericType (storey);
5800                                 loop.MutateHoistedGenericType (storey);
5801                         }
5802                 }
5803
5804                 Expression type;
5805                 Expression variable;
5806                 Expression expr;
5807                 Statement statement;
5808
5809                 public Foreach (Expression type, LocalVariableReference var, Expression expr,
5810                                 Statement stmt, Location l)
5811                 {
5812                         this.type = type;
5813                         this.variable = var;
5814                         this.expr = expr;
5815                         statement = stmt;
5816                         loc = l;
5817                 }
5818
5819                 public Statement Statement {
5820                         get { return statement; }
5821                 }
5822
5823                 public override bool Resolve (EmitContext ec)
5824                 {
5825                         expr = expr.Resolve (ec);
5826                         if (expr == null)
5827                                 return false;
5828
5829                         if (expr.IsNull) {
5830                                 Report.Error (186, loc, "Use of null is not valid in this context");
5831                                 return false;
5832                         }
5833
5834                         if (expr.Type == TypeManager.string_type) {
5835                                 statement = new ArrayForeach (this, 1);
5836                         } else if (expr.Type.IsArray) {
5837                                 statement = new ArrayForeach (this, expr.Type.GetArrayRank ());
5838                         } else {
5839                                 if (expr.eclass == ExprClass.MethodGroup || expr is AnonymousMethodExpression) {
5840                                         Report.Error (446, expr.Location, "Foreach statement cannot operate on a `{0}'",
5841                                                 expr.ExprClassName);
5842                                         return false;
5843                                 }
5844
5845                                 statement = new CollectionForeach (type, variable, expr, statement, loc);
5846                         }
5847
5848                         return statement.Resolve (ec);
5849                 }
5850
5851                 protected override void DoEmit (EmitContext ec)
5852                 {
5853                         ILGenerator ig = ec.ig;
5854
5855                         Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
5856                         ec.LoopBegin = ig.DefineLabel ();
5857                         ec.LoopEnd = ig.DefineLabel ();
5858
5859                         statement.Emit (ec);
5860
5861                         ec.LoopBegin = old_begin;
5862                         ec.LoopEnd = old_end;
5863                 }
5864
5865                 protected override void CloneTo (CloneContext clonectx, Statement t)
5866                 {
5867                         Foreach target = (Foreach) t;
5868
5869                         target.type = type.Clone (clonectx);
5870                         target.variable = variable.Clone (clonectx);
5871                         target.expr = expr.Clone (clonectx);
5872                         target.statement = statement.Clone (clonectx);
5873                 }
5874
5875                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
5876                 {
5877                         statement.MutateHoistedGenericType (storey);
5878                 }
5879         }
5880 }