mcs/mcs/anonymous.cs

   1 //
   2 // anonymous.cs: Support for anonymous methods
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximain.com)
   6 //
   7 // (C) 2003, 2004 Novell, Inc.
   8 //
   9 // TODO: Ideally, we should have the helper classes emited as a hierarchy to map
  10 // their nesting, and have the visibility set to private, instead of NestedAssembly
  11 //
  12 //
  13 //
  14
  15 using System;
  16 using System.Text;
  17 using System.Collections;
  18 using System.Reflection;
  19 using System.Reflection.Emit;
  20
  21 namespace Mono.CSharp {
  22
  23         public abstract class AnonymousContainer : Expression
  24         {
  25                 // Used to generate unique method names.
  26                 protected static int anonymous_method_count;
  27
  28                 // An array list of AnonymousMethodParameter or null
  29                 public Parameters Parameters;
  30
  31                 //
  32                 // The block that makes up the body for the anonymous mehtod
  33                 //
  34                 public ToplevelBlock Block;
  35
  36                 //
  37                 // The container block for this anonymous method.
  38                 //
  39                 public Block ContainingBlock;
  40
  41                 //
  42                 // The implicit method we create
  43                 //
  44                 public Method method;
  45
  46                 protected MethodInfo invoke_mb;
  47
  48                 // The emit context for the anonymous method
  49                 public EmitContext aec;
  50                 protected bool unreachable;
  51
  52                 // The method scope
  53                 ScopeInfo method_scope;
  54                 bool computed_method_scope = false;
  55
  56                 //
  57                 // The modifiers applied to the method, we aggregate them
  58                 //
  59                 protected int method_modifiers = Modifiers.PRIVATE;
  60
  61                 //
  62                 // Track the scopes that this method has used.  At the
  63                 // end this is used to determine the ScopeInfo that will
  64                 // host the method
  65                 //
  66                 ArrayList scopes_used = new ArrayList ();
  67
  68                 //
  69                 // Points to our container anonymous method if its present
  70                 //
  71                 public AnonymousContainer ContainerAnonymousMethod;
  72
  73                 protected AnonymousContainer (Parameters parameters, ToplevelBlock container,
  74                                               ToplevelBlock block, Location l)
  75                 {
  76                         Parameters = parameters;
  77                         Block = block;
  78                         loc = l;
  79
  80                         //
  81                         // The order is important: this setups the CaptureContext tree hierarchy.
  82                         //
  83                         if (container == null) {
  84                                 return;
  85                         }
  86                         container.SetHaveAnonymousMethods (l, this);
  87                         block.SetHaveAnonymousMethods (l, this);
  88                 }
  89
  90                 protected AnonymousContainer (Parameters parameters, ToplevelBlock container,
  91                                               Location l):
  92                         this (parameters, container, new ToplevelBlock (container, parameters, l), l)
  93                 {
  94                 }
  95
  96                 public override Expression DoResolve (EmitContext ec)
  97                 {
  98                         //
  99                         // Set class type, set type
 100                         //
 101
 102                         eclass = ExprClass.Value;
 103
 104                         //
 105                         // This hack means `The type is not accessible
 106                         // anywhere', we depend on special conversion
 107                         // rules.
 108                         //
 109                         type = TypeManager.anonymous_method_type;
 110
 111                         return this;
 112                 }
 113
 114                 public void RegisterScope (ScopeInfo scope)
 115                 {
 116                         if (scopes_used.Contains (scope))
 117                                 return;
 118                         scopes_used.Add (scope);
 119                 }
 120
 121                 // Returns the deepest of two scopes
 122                 ScopeInfo Deepest (ScopeInfo a, ScopeInfo b)
 123                 {
 124                         ScopeInfo p;
 125
 126                         if (a == null)
 127                                 return b;
 128                         if (b == null)
 129                                 return a;
 130                         if (a == b)
 131                                 return a;
 132
 133                         //
 134                         // If they Scopes are on the same CaptureContext, we do the double
 135                         // checks just so if there is an invariant change in the future,
 136                         // we get the exception at the end
 137                         //
 138                         for (p = a; p != null; p = p.ParentScope)
 139                                 if (p == b)
 140                                         return a;
 141
 142                         for (p = b; p != null; p = p.ParentScope)
 143                                 if (p == a)
 144                                         return b;
 145
 146                         CaptureContext ca = a.CaptureContext;
 147                         CaptureContext cb = b.CaptureContext;
 148
 149                         for (CaptureContext c = ca; c != null; c = c.ParentCaptureContext)
 150                                 if (c == cb)
 151                                         return a;
 152
 153                         for (CaptureContext c = cb; c != null; c = c.ParentCaptureContext)
 154                                 if (c == ca)
 155                                         return b;
 156                         throw new Exception ("Should never be reached");
 157                 }
 158
 159                 //
 160                 // Determines the proper host for a method considering the
 161                 // scopes it references
 162                 //
 163                 public void ComputeMethodHost ()
 164                 {
 165                         if (computed_method_scope)
 166                                 return;
 167
 168                         method_scope = null;
 169                         int top = scopes_used.Count;
 170                         computed_method_scope = true;
 171
 172                         if (top == 0)
 173                                 return;
 174
 175                         method_scope = (ScopeInfo) scopes_used [0];
 176                         if (top == 1)
 177                                 return;
 178
 179                         for (int i = 1; i < top; i++)
 180                                 method_scope = Deepest (method_scope, (ScopeInfo) scopes_used [i]);
 181                 }
 182
 183                 public ScopeInfo Scope {
 184                         get {
 185                                 if (computed_method_scope)
 186                                         return method_scope;
 187
 188                                 //
 189                                 // This means that ComputeMethodHost is not being called, most
 190                                 // likely by someone who overwrote the CreateMethodHost method
 191                                 //
 192                                 throw new Exception ("Internal error, AnonymousContainer.Scope is being used before its container is computed");
 193                         }
 194                 }
 195
 196
 197                 protected abstract bool CreateMethodHost (EmitContext ec);
 198
 199                 public abstract void CreateScopeType (EmitContext ec, ScopeInfo scope);
 200
 201                 public abstract bool IsIterator {
 202                         get;
 203                 }
 204         }
 205
 206         public class AnonymousMethod : AnonymousContainer
 207         {
 208                 TypeContainer host;
 209
 210                 public AnonymousMethod (TypeContainer host, Parameters parameters, ToplevelBlock container,
 211                                         ToplevelBlock block, Location l)
 212                         : base (parameters, container, block, l)
 213                 {
 214                         this.host = host;
 215                 }
 216
 217                 public override bool IsIterator {
 218                         get { return false; }
 219                 }
 220
 221                 public override void Emit (EmitContext ec)
 222                 {
 223                         // nothing, as we only exist to not do anything.
 224                 }
 225
 226                 //
 227                 // Creates the host for the anonymous method
 228                 //
 229                 protected override bool CreateMethodHost (EmitContext ec)
 230                 {
 231                         ComputeMethodHost ();
 232
 233                         //
 234                         // Crude hack follows: we replace the TypeBuilder during the
 235                         // definition to get the method hosted in the right class
 236                         //
 237                         TypeBuilder current_type = ec.TypeContainer.TypeBuilder;
 238                         TypeBuilder type_host = (Scope == null ) ? current_type : Scope.ScopeTypeBuilder;
 239
 240                         if (current_type == null)
 241                                 throw new Exception ("The current_type is null");
 242
 243                         if (type_host == null)
 244                                 throw new Exception (String.Format ("Type host is null, method_host is {0}", Scope == null ? "null" : "Not null"));
 245
 246                         if (current_type != type_host)
 247                                 method_modifiers = Modifiers.INTERNAL;
 248
 249                         if (current_type == type_host && ec.IsStatic){
 250                                 method_modifiers |= Modifiers.STATIC;
 251                                 current_type = null;
 252                         }
 253
 254                         method = new Method (
 255                                 (TypeContainer) ec.TypeContainer,
 256                                 new TypeExpression (invoke_mb.ReturnType, loc),
 257                                 method_modifiers, false, new MemberName ("<#AnonymousMethod>" + anonymous_method_count++, loc),
 258                                 Parameters, null);
 259                         method.Block = Block;
 260
 261                         //
 262                         // Swap the TypeBuilder while we define the method, then restore
 263                         //
 264                         if (current_type != null)
 265                                 ec.TypeContainer.TypeBuilder = type_host;
 266                         bool res = method.Define ();
 267                         if (current_type != null)
 268                                 ec.TypeContainer.TypeBuilder = current_type;
 269                         return res;
 270                 }
 271
 272                 void Error_ParameterMismatch (Type t)
 273                 {
 274                         Report.Error (1661, loc, "Anonymous method could not be converted to delegate `" +
 275                                       "{0}' since there is a parameter mismatch", TypeManager.CSharpName (t));
 276                 }
 277
 278                 public bool ImplicitStandardConversionExists (Type delegate_type)
 279                 {
 280                         if (Parameters == null)
 281                                 return true;
 282
 283                         invoke_mb = (MethodInfo) Delegate.GetInvokeMethod (host.TypeBuilder, delegate_type, loc);
 284                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 285
 286                         if (Parameters.Count != invoke_pd.Count)
 287                                 return false;
 288
 289                         for (int i = 0; i < Parameters.Count; ++i) {
 290                                 if (invoke_pd.ParameterType (i) != Parameters.ParameterType (i))
 291                                         return false;
 292                         }
 293                         return true;
 294                 }
 295
 296                 //
 297                 // Returns true if this anonymous method can be implicitly
 298                 // converted to the delegate type `delegate_type'
 299                 //
 300                 public Expression Compatible (EmitContext ec, Type delegate_type)
 301                 {
 302                         //
 303                         // At this point its the first time we know the return type that is
 304                         // needed for the anonymous method.  We create the method here.
 305                         //
 306
 307                         invoke_mb = (MethodInfo) Delegate.GetInvokeMethod (ec.ContainerType, delegate_type, loc);
 308                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 309
 310                         if (Parameters == null) {
 311                                 //
 312                                 // We provide a set of inaccessible parameters
 313                                 //
 314                                 Parameter [] fixedpars = new Parameter [invoke_pd.Count];
 315
 316                                 for (int i = 0; i < invoke_pd.Count; i++){
 317                                         fixedpars [i] = new Parameter (
 318                                                 invoke_pd.ParameterType (i),
 319                                                 "+" + i, invoke_pd.ParameterModifier (i), null, loc);
 320                                 }
 321
 322                                 Parameters = new Parameters (fixedpars);
 323                         } else {
 324                                 if (Parameters.Count != invoke_pd.Count) {
 325                                         Report.SymbolRelatedToPreviousError (delegate_type);
 326                                         Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
 327                                                 TypeManager.CSharpName (delegate_type), Parameters.Count.ToString ());
 328                                         Error_ParameterMismatch (delegate_type);
 329                                         return null;
 330                                 }
 331
 332                                 for (int i = 0; i < Parameters.Count; ++i) {
 333                                         Parameter.Modifier p_mod = invoke_pd.ParameterModifier (i);
 334                                         if (Parameters.ParameterModifier (i) != p_mod && p_mod != Parameter.Modifier.PARAMS) {
 335                                                 if (p_mod == Parameter.Modifier.NONE)
 336                                                         Report.Error (1677, loc, "Parameter `{0}' should not be declared with the `{1}' keyword",
 337                                                                 (i + 1).ToString (), Parameter.GetModifierSignature (Parameters.ParameterModifier (i)));
 338                                                 else
 339                                                         Report.Error (1676, loc, "Parameter `{0}' must be declared with the `{1}' keyword",
 340                                                                 (i+1).ToString (), Parameter.GetModifierSignature (p_mod));
 341                                                 Error_ParameterMismatch (delegate_type);
 342                                                 return null;
 343                                         }
 344
 345                                         if (invoke_pd.ParameterType (i) != Parameters.ParameterType (i)) {
 346                                                 Report.Error (1678, loc, "Parameter `{0}' is declared as type `{1}' but should be `{2}'",
 347                                                         (i+1).ToString (),
 348                                                         TypeManager.CSharpName (Parameters.ParameterType (i)),
 349                                                         TypeManager.CSharpName (invoke_pd.ParameterType (i)));
 350                                                 Error_ParameterMismatch (delegate_type);
 351                                                 return null;
 352                                         }
 353                                 }
 354                         }
 355
 356                         //
 357                         // Second: the return type of the delegate must be compatible with
 358                         // the anonymous type.   Instead of doing a pass to examine the block
 359                         // we satisfy the rule by setting the return type on the EmitContext
 360                         // to be the delegate type return type.
 361                         //
 362
 363                         //MethodBuilder builder = method_data.MethodBuilder;
 364                         //ILGenerator ig = builder.GetILGenerator ();
 365
 366                         aec = new EmitContext (ec.ResolveContext,
 367                                 ec.TypeContainer, ec.DeclContainer, loc, null,
 368                                 invoke_mb.ReturnType,
 369                                 /* REVIEW */ (ec.InIterator ? Modifiers.METHOD_YIELDS : 0) |
 370                                 (ec.InUnsafe ? Modifiers.UNSAFE : 0) |
 371                                 (ec.IsStatic ? Modifiers.STATIC : 0),
 372                                 /* No constructor */ false);
 373
 374                         aec.CurrentAnonymousMethod = this;
 375                         ContainerAnonymousMethod = ec.CurrentAnonymousMethod;
 376                         ContainingBlock = ec.CurrentBlock;
 377
 378                         if (aec.ResolveTopBlock (ec, Block, Parameters, null, out unreachable))
 379                                 return new AnonymousDelegate (this, delegate_type, loc).Resolve (ec);
 380
 381                         return null;
 382                 }
 383
 384                 public override Expression DoResolve (EmitContext ec)
 385                 {
 386                         if (!ec.IsAnonymousMethodAllowed) {
 387                                 Report.Error (1706, loc, "Anonymous methods are not allowed in the attribute declaration");
 388                                 return null;
 389                         }
 390
 391                         if (Parameters != null && !Parameters.Resolve (ec)) {
 392                                 return null;
 393                         }
 394
 395                         return base.DoResolve (ec);
 396                 }
 397
 398
 399                 public override string ExprClassName {
 400                         get {
 401                                 return "anonymous method";
 402                         }
 403                 }
 404
 405                 public MethodBuilder GetMethodBuilder ()
 406                 {
 407                         return method.MethodBuilder;
 408                 }
 409
 410                 public override string GetSignatureForError ()
 411                 {
 412                         string s = TypeManager.CSharpSignature (invoke_mb);
 413                         return s.Substring (0, s.IndexOf (".Invoke("));
 414                 }
 415
 416                 public bool EmitMethod (EmitContext ec)
 417                 {
 418                         if (!CreateMethodHost (ec))
 419                                 return false;
 420
 421                         MethodBuilder builder = GetMethodBuilder ();
 422                         ILGenerator ig = builder.GetILGenerator ();
 423                         aec.ig = ig;
 424
 425                         Parameters.ApplyAttributes (builder);
 426
 427                         //
 428                         // Adjust based on the computed state of the
 429                         // method from CreateMethodHost
 430
 431                         aec.MethodIsStatic = (method_modifiers & Modifiers.STATIC) != 0;
 432
 433                         aec.EmitMeta (Block);
 434                         aec.EmitResolvedTopBlock (Block, unreachable);
 435                         return true;
 436                 }
 437
 438                 public override void CreateScopeType (EmitContext ec, ScopeInfo scope)
 439                 {
 440                         TypeBuilder container = ec.TypeContainer.TypeBuilder;
 441                         string name = String.Format ("<>AnonHelp<{0}>", scope.id);
 442
 443                         scope.ScopeTypeBuilder = container.DefineNestedType (
 444                                 name, TypeAttributes.AutoLayout | TypeAttributes.Class |
 445                                 TypeAttributes.NestedAssembly, TypeManager.object_type, null);
 446
 447                         Type [] constructor_types = Type.EmptyTypes;
 448                         scope.ScopeConstructor = scope.ScopeTypeBuilder.DefineConstructor (
 449                                 MethodAttributes.Public | MethodAttributes.HideBySig |
 450                                 MethodAttributes.SpecialName | MethodAttributes.RTSpecialName,
 451                                 CallingConventions.HasThis, constructor_types);
 452
 453                         TypeManager.RegisterMethod (scope.ScopeConstructor, Parameters.EmptyReadOnlyParameters);
 454
 455                         ILGenerator cig = scope.ScopeConstructor.GetILGenerator ();
 456                         cig.Emit (OpCodes.Ldarg_0);
 457                         cig.Emit (OpCodes.Call, TypeManager.object_ctor);
 458                         cig.Emit (OpCodes.Ret);
 459                 }
 460
 461                 public static void Error_AddressOfCapturedVar (string name, Location loc)
 462                 {
 463                         Report.Error (1686, loc,
 464                                 "Local variable `{0}' or its members cannot have their address taken and be used inside an anonymous method block",
 465                                 name);
 466                 }
 467         }
 468
 469         //
 470         // This will emit the code for the delegate, as well delegate creation on the host
 471         //
 472         public class AnonymousDelegate : DelegateCreation {
 473                 AnonymousMethod am;
 474
 475                 public AnonymousDelegate (AnonymousMethod am, Type target_type, Location l)
 476                 {
 477                         type = target_type;
 478                         loc = l;
 479                         this.am = am;
 480                 }
 481
 482                 public override Expression DoResolve (EmitContext ec)
 483                 {
 484                         eclass = ExprClass.Value;
 485
 486                         return this;
 487                 }
 488
 489                 public override void Emit (EmitContext ec)
 490                 {
 491                         if (!am.EmitMethod (ec))
 492                                 return;
 493
 494                         //
 495                         // Now emit the delegate creation.
 496                         //
 497                         if ((am.method.ModFlags & Modifiers.STATIC) == 0)
 498                                 delegate_instance_expression = new AnonymousInstance (am);
 499
 500                         Expression ml = Expression.MemberLookup (ec.ContainerType, type, ".ctor", loc);
 501                         constructor_method = ((MethodGroupExpr) ml).Methods [0];
 502                         delegate_method = am.GetMethodBuilder ();
 503                         base.Emit (ec);
 504                 }
 505
 506                 class AnonymousInstance : Expression {
 507                         AnonymousMethod am;
 508
 509                         public AnonymousInstance (AnonymousMethod am)
 510                         {
 511                                 this.am = am;
 512                                 eclass = ExprClass.Value;
 513                         }
 514
 515                         public override Expression DoResolve (EmitContext ec)
 516                         {
 517                                 return this;
 518                         }
 519
 520                         public override void Emit (EmitContext ec)
 521                         {
 522                                 am.aec.EmitMethodHostInstance (ec, am);
 523                         }
 524                 }
 525         }
 526
 527         class CapturedParameter {
 528                 public Type Type;
 529                 public FieldBuilder FieldBuilder;
 530                 public int Idx;
 531
 532                 public CapturedParameter (Type type, int idx)
 533                 {
 534                         Type = type;
 535                         Idx = idx;
 536                 }
 537         }
 538
 539         //
 540         // Here we cluster all the variables captured on a given scope, we also
 541         // keep some extra information that might be required on each scope.
 542         //
 543         public class ScopeInfo {
 544                 public CaptureContext CaptureContext;
 545                 public ScopeInfo ParentScope;
 546                 public Block ScopeBlock;
 547                 public bool NeedThis = false;
 548                 public bool HostsParameters = false;
 549
 550                 // For tracking the number of scopes created.
 551                 public int id;
 552                 static int count;
 553                 bool inited = false;
 554
 555                 ArrayList locals = new ArrayList ();
 556                 ArrayList children = new ArrayList ();
 557
 558                 //
 559                 // The types and fields generated
 560                 //
 561                 public TypeBuilder ScopeTypeBuilder;
 562                 public ConstructorBuilder ScopeConstructor;
 563                 public FieldBuilder THIS;
 564                 public FieldBuilder ParentLink;
 565
 566                 //
 567                 // Points to the object of type `ScopeTypeBuilder' that
 568                 // holds the data for the scope
 569                 //
 570                 LocalBuilder scope_instance;
 571
 572                 public ScopeInfo (CaptureContext cc, Block b)
 573                 {
 574                         CaptureContext = cc;
 575                         ScopeBlock = b;
 576                         id = count++;
 577
 578                         cc.RegisterCaptureContext ();
 579                 }
 580
 581                 public void AddLocal (LocalInfo li)
 582                 {
 583                         if (locals.Contains (li))
 584                                 return;
 585
 586                         locals.Add (li);
 587                 }
 588
 589                 public bool IsCaptured (LocalInfo li)
 590                 {
 591                         return locals.Contains (li);
 592                 }
 593
 594                 internal void AddChild (ScopeInfo si)
 595                 {
 596                         if (children.Contains (si))
 597                                 return;
 598
 599                         //
 600                         // If any of the current children should be a children of `si', move them there
 601                         //
 602                         ArrayList move_queue = null;
 603                         foreach (ScopeInfo child in children){
 604                                 if (child.ScopeBlock.IsChildOf (si.ScopeBlock)){
 605                                         if (move_queue == null)
 606                                                 move_queue = new ArrayList ();
 607                                         move_queue.Add (child);
 608                                         child.ParentScope = si;
 609                                         si.AddChild (child);
 610                                 }
 611                         }
 612
 613                         children.Add (si);
 614
 615                         if (move_queue != null){
 616                                 foreach (ScopeInfo child in move_queue){
 617                                         children.Remove (child);
 618                                 }
 619                         }
 620                 }
 621
 622                 static int indent = 0;
 623
 624                 void Pad ()
 625                 {
 626                         for (int i = 0; i < indent; i++)
 627                                 Console.Write ("    ");
 628                 }
 629
 630                 void EmitDebug ()
 631                 {
 632                         //Console.WriteLine (Environment.StackTrace);
 633                         Pad ();
 634                         Console.WriteLine ("START");
 635                         indent++;
 636                         Pad ();
 637                         Console.WriteLine ("NeedThis=" + NeedThis);
 638                         foreach (LocalInfo li in locals){
 639                                 Pad ();
 640                                 Console.WriteLine ("var {0}", MakeFieldName (li.Name));
 641                         }
 642
 643                         foreach (ScopeInfo si in children)
 644                                 si.EmitDebug ();
 645                         indent--;
 646                         Pad ();
 647                         Console.WriteLine ("END");
 648                 }
 649
 650                 public string MakeHelperName ()
 651                 {
 652                         return String.Format ("<>AnonHelp<{0}>", id);
 653                 }
 654
 655                 private string MakeFieldName (string local_name)
 656                 {
 657                         return "<" + id + ":" + local_name + ">";
 658                 }
 659
 660                 public void EmitScopeType (EmitContext ec)
 661                 {
 662                         // EmitDebug ();
 663
 664                         if (ScopeTypeBuilder != null)
 665                                 return;
 666
 667                         TypeBuilder container = ec.TypeContainer.TypeBuilder;
 668
 669                         CaptureContext.Host.CreateScopeType (ec, this);
 670
 671                         if (NeedThis)
 672                                 THIS = ScopeTypeBuilder.DefineField ("<>THIS", container, FieldAttributes.Assembly);
 673
 674                         if (ParentScope != null){
 675                                 if (ParentScope.ScopeTypeBuilder == null){
 676                                         throw new Exception (String.Format ("My parent has not been initialized {0} and {1}", ParentScope, this));
 677                                 }
 678
 679                                 if (ParentScope.ScopeTypeBuilder != ScopeTypeBuilder)
 680                                         ParentLink = ScopeTypeBuilder.DefineField ("<>parent", ParentScope.ScopeTypeBuilder,
 681                                                                                    FieldAttributes.Assembly);
 682                         }
 683
 684                         if (NeedThis && ParentScope != null)
 685                                 throw new Exception ("I was not expecting THIS && having a parent");
 686
 687                         foreach (LocalInfo info in locals)
 688                                 info.FieldBuilder = ScopeTypeBuilder.DefineField (
 689                                         MakeFieldName (info.Name), info.VariableType, FieldAttributes.Assembly);
 690
 691                         if (HostsParameters){
 692                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 693
 694                                 foreach (DictionaryEntry de in captured_parameters){
 695                                         string name = (string) de.Key;
 696                                         CapturedParameter cp = (CapturedParameter) de.Value;
 697                                         FieldBuilder fb;
 698
 699                                         fb = ScopeTypeBuilder.DefineField ("<p:" + name + ">", cp.Type, FieldAttributes.Assembly);
 700                                         cp.FieldBuilder = fb;
 701                                 }
 702                         }
 703
 704                         foreach (ScopeInfo si in children){
 705                                 si.EmitScopeType (ec);
 706                         }
 707                 }
 708
 709                 public void CloseTypes ()
 710                 {
 711                         RootContext.RegisterCompilerGeneratedType (ScopeTypeBuilder);
 712                         foreach (ScopeInfo si in children)
 713                                 si.CloseTypes ();
 714                 }
 715
 716                 //
 717                 // Emits the initialization code for the scope
 718                 //
 719                 public void EmitInitScope (EmitContext ec)
 720                 {
 721                         ILGenerator ig = ec.ig;
 722
 723                         if (inited)
 724                                 return;
 725
 726                         if (ScopeConstructor == null)
 727                                 throw new Exception ("ScopeConstructor is null for" + this.ToString ());
 728
 729                         if (!CaptureContext.Host.IsIterator) {
 730                                 scope_instance = ig.DeclareLocal (ScopeTypeBuilder);
 731                                 ig.Emit (OpCodes.Newobj, (ConstructorInfo) ScopeConstructor);
 732                                 ig.Emit (OpCodes.Stloc, scope_instance);
 733                         }
 734
 735                         if (THIS != null){
 736                                 if (CaptureContext.Host.IsIterator) {
 737                                         ig.Emit (OpCodes.Ldarg_0);
 738                                         ig.Emit (OpCodes.Ldarg_1);
 739                                 } else {
 740                                         ig.Emit (OpCodes.Ldloc, scope_instance);
 741                                         ig.Emit (OpCodes.Ldarg_0);
 742                                 }
 743                                 ig.Emit (OpCodes.Stfld, THIS);
 744                         }
 745
 746                         //
 747                         // Copy the parameter values, if any
 748                         //
 749                         int extra = ec.IsStatic ? 0 : 1;
 750                         if (CaptureContext.Host.IsIterator)
 751                                 extra++;
 752                         if (HostsParameters){
 753                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 754
 755                                 foreach (DictionaryEntry de in captured_parameters){
 756                                         CapturedParameter cp = (CapturedParameter) de.Value;
 757
 758                                         EmitScopeInstance (ig);
 759                                         ParameterReference.EmitLdArg (ig, cp.Idx + extra);
 760                                         ig.Emit (OpCodes.Stfld, cp.FieldBuilder);
 761                                 }
 762                         }
 763
 764                         if (ParentScope != null){
 765                                 if (!ParentScope.inited)
 766                                         ParentScope.EmitInitScope (ec);
 767
 768                                 if (ParentScope.ScopeTypeBuilder != ScopeTypeBuilder) {
 769                                         //
 770                                         // Only emit initialization in our capturecontext world
 771                                         //
 772                                         if (ParentScope.CaptureContext == CaptureContext){
 773                                                 EmitScopeInstance (ig);
 774                                                 ParentScope.EmitScopeInstance (ig);
 775                                                 ig.Emit (OpCodes.Stfld, ParentLink);
 776                                         } else {
 777                                                 EmitScopeInstance (ig);
 778                                                 ig.Emit (OpCodes.Ldarg_0);
 779                                                 ig.Emit (OpCodes.Stfld, ParentLink);
 780                                         }
 781                                 }
 782                         }
 783                         inited = true;
 784                 }
 785
 786                 public void EmitScopeInstance (ILGenerator ig)
 787                 {
 788                         if (CaptureContext.Host.IsIterator)
 789                                 ig.Emit (OpCodes.Ldarg_0);
 790                         else {
 791                                 if (scope_instance == null){
 792                                         //
 793                                         // This is needed if someone overwrites the Emit method
 794                                         // of Statement and manually calls Block.Emit without
 795                                         // this snippet first:
 796                                         //
 797                                         //   ec.EmitScopeInitFromBlock (The_Block);
 798                                         //   The_Block.Emit (ec);
 799                                         //
 800
 801                                         Console.WriteLine (
 802                                                 "The scope_instance has not been emitted, this typically means\n" +
 803                                                 "that inside the compiler someone is calling Block.Emit without\n" +
 804                                                 "first calling EmitScopeInitFromBlock for the block.  See compiler" +
 805                                                 "source code for an explanation");
 806                                         throw new Exception ("Internal compiler error");
 807
 808                                 }
 809                                 ig.Emit (OpCodes.Ldloc, scope_instance);
 810                         }
 811                 }
 812
 813                 public static void CheckCycles (string msg, ScopeInfo s)
 814                 {
 815                         ArrayList l = new ArrayList ();
 816                         int n = 0;
 817
 818                         for (ScopeInfo p = s; p != null; p = p.ParentScope,n++){
 819                                 if (l.Contains (p)){
 820                                         Console.WriteLine ("Loop detected {0} in {1}", n, msg);
 821                                         throw new Exception ();
 822                                 }
 823                                 l.Add (p);
 824                         }
 825                 }
 826
 827                 static void DoPath (StringBuilder sb, ScopeInfo start)
 828                 {
 829                         CheckCycles ("print", start);
 830
 831                         if (start.ParentScope != null){
 832                                 DoPath (sb, start.ParentScope);
 833                                 sb.Append (", ");
 834                         }
 835                         sb.Append ((start.id).ToString ());
 836                 }
 837
 838                 public override string ToString ()
 839                 {
 840                         StringBuilder sb = new StringBuilder ();
 841
 842                         sb.Append ("{");
 843                         if (CaptureContext != null){
 844                                 sb.Append (CaptureContext.ToString ());
 845                                 sb.Append (":");
 846                         }
 847
 848                         DoPath (sb, this);
 849                         sb.Append ("}");
 850
 851                         return sb.ToString ();
 852                 }
 853         }
 854
 855         //
 856         // CaptureContext objects are created on demand if a method has
 857         // anonymous methods and kept on the ToplevelBlock.
 858         //
 859         // If they exist, all ToplevelBlocks in the containing block are
 860         // linked together (children pointing to their parents).
 861         //
 862         public class CaptureContext {
 863                 public static int count;
 864                 public int cc_id;
 865                 public Location loc;
 866
 867                 //
 868                 // Points to the toplevel block that owns this CaptureContext
 869                 //
 870                 ToplevelBlock toplevel_owner;
 871
 872                 //
 873                 // All the scopes we capture
 874                 //
 875                 Hashtable scopes = new Hashtable ();
 876
 877                 //
 878                 // All the root scopes
 879                 //
 880                 ArrayList roots = new ArrayList ();
 881
 882                 bool have_captured_vars = false;
 883                 bool referenced_this = false;
 884
 885                 //
 886                 // Captured fields
 887                 //
 888                 Hashtable captured_fields = new Hashtable ();
 889                 Hashtable captured_variables = new Hashtable ();
 890                 public Hashtable captured_parameters = new Hashtable ();
 891                 public AnonymousContainer Host;
 892
 893                 public CaptureContext (ToplevelBlock toplevel_owner, Location loc,
 894                                        AnonymousContainer host)
 895                 {
 896                         cc_id = count++;
 897                         this.toplevel_owner = toplevel_owner;
 898                         this.loc = loc;
 899
 900                         if (host != null)
 901                                 Host = host;
 902                 }
 903
 904                 void DoPath (StringBuilder sb, CaptureContext cc)
 905                 {
 906                         if (cc.ParentCaptureContext != null){
 907                                 DoPath (sb, cc.ParentCaptureContext);
 908                                 sb.Append (".");
 909                         }
 910                         sb.Append (cc.cc_id.ToString ());
 911                 }
 912
 913                 public void ReParent (ToplevelBlock new_toplevel, AnonymousContainer new_host)
 914                 {
 915                         toplevel_owner = new_toplevel;
 916                         Host = new_host;
 917
 918                         for (CaptureContext cc = ParentCaptureContext; cc != null;
 919                              cc = cc.ParentCaptureContext) {
 920                                 cc.Host = new_host;
 921                         }
 922                 }
 923
 924                 public override string ToString ()
 925                 {
 926                         StringBuilder sb = new StringBuilder ();
 927                         sb.Append ("[");
 928                         DoPath (sb, this);
 929                         sb.Append ("]");
 930                         return sb.ToString ();
 931                 }
 932
 933                 public ToplevelBlock ParentToplevel {
 934                         get {
 935                                 return toplevel_owner.Container;
 936                         }
 937                 }
 938
 939                 public CaptureContext ParentCaptureContext {
 940                         get {
 941                                 ToplevelBlock parent = ParentToplevel;
 942
 943                                 return (parent == null) ? null : parent.CaptureContext;
 944                         }
 945                 }
 946
 947                 ScopeInfo GetScopeForBlock (Block block)
 948                 {
 949                         ScopeInfo si = (ScopeInfo) scopes [block.ID];
 950                         if (si != null)
 951                                 return si;
 952                         si = new ScopeInfo (this, block);
 953                         scopes [block.ID] = si;
 954                         return si;
 955                 }
 956
 957                 public void AddLocal (AnonymousContainer am, LocalInfo li)
 958                 {
 959                         if (li.Block.Toplevel != toplevel_owner){
 960                                 ParentCaptureContext.AddLocal (am, li);
 961                                 return;
 962                         }
 963                         ScopeInfo scope = GetScopeForBlock (li.Block);
 964
 965                         //
 966                         // Adjust the owner
 967                         //
 968                         if (Host != null)
 969                                 Host.RegisterScope (scope);
 970
 971                         //
 972                         // Adjust the user
 973                         //
 974                         am.RegisterScope (scope);
 975
 976                         if (captured_variables [li] != null)
 977                                 return;
 978
 979                         have_captured_vars = true;
 980                         captured_variables [li] = li;
 981                         scope.AddLocal (li);
 982                 }
 983
 984                 //
 985                 // Retursn the CaptureContext for the block that defines the parameter `name'
 986                 //
 987                 static CaptureContext _ContextForParameter (ToplevelBlock current, string name)
 988                 {
 989                         ToplevelBlock container = current.Container;
 990                         if (container != null){
 991                                 CaptureContext cc = _ContextForParameter (container, name);
 992                                 if (cc != null)
 993                                         return cc;
 994                         }
 995                         if (current.IsParameterReference (name))
 996                                 return current.ToplevelBlockCaptureContext;
 997                         return null;
 998                 }
 999
1000                 static CaptureContext ContextForParameter (ToplevelBlock current, string name)
1001                 {
1002                         CaptureContext cc = _ContextForParameter (current, name);
1003                         if (cc == null)
1004                                 throw new Exception (String.Format ("request for parameteter {0} failed: not found", name));
1005                         return cc;
1006                 }
1007
1008                 //
1009                 // Records the captured parameter at the appropriate CaptureContext
1010                 //
1011                 public void AddParameter (EmitContext ec, AnonymousContainer am,
1012                                           string name, Type t, int idx)
1013                 {
1014                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1015
1016                         cc.AddParameterToContext (am, name, t, idx);
1017                 }
1018
1019                 //
1020                 // Records the parameters in the context
1021                 //
1022                 public void AddParameterToContext (AnonymousContainer am, string name, Type t, int idx)
1023                 {
1024                         if (captured_parameters == null)
1025                                 captured_parameters = new Hashtable ();
1026                         if (captured_parameters [name] == null)
1027                                 captured_parameters [name] = new CapturedParameter (t, idx);
1028
1029                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1030                         scope.HostsParameters = true;
1031                         am.RegisterScope (scope);
1032                 }
1033
1034                 //
1035                 // Captured fields are only recorded on the topmost CaptureContext, because that
1036                 // one is the one linked to the owner of instance fields
1037                 //
1038                 public void AddField (EmitContext ec, AnonymousContainer am, FieldExpr fe)
1039                 {
1040                         if (fe.FieldInfo.IsStatic)
1041                                 throw new Exception ("Attempt to register a static field as a captured field");
1042                         CaptureContext parent = ParentCaptureContext;
1043                         if (parent != null) {
1044                                 parent.AddField (ec, am, fe);
1045                                 return;
1046                         }
1047
1048                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1049                         am.RegisterScope (scope);
1050                 }
1051
1052                 public void CaptureThis (AnonymousContainer am)
1053                 {
1054                         if (am == null)
1055                                 throw new Exception ("Internal Compiler error: Capturethis called with a null method");
1056                         CaptureContext parent = ParentCaptureContext;
1057                         if (parent != null) {
1058                                 parent.CaptureThis (am);
1059                                 return;
1060                         }
1061                         referenced_this = true;
1062
1063                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1064                         am.RegisterScope (scope);
1065                 }
1066
1067                 public bool HaveCapturedVariables {
1068                         get {
1069                                 return have_captured_vars;
1070                         }
1071                 }
1072
1073                 public bool HaveCapturedFields {
1074                         get {
1075                                 CaptureContext parent = ParentCaptureContext;
1076                                 if (parent != null)
1077                                         return parent.HaveCapturedFields;
1078                                 return captured_fields.Count > 0;
1079                         }
1080                 }
1081
1082                 public bool IsCaptured (LocalInfo local)
1083                 {
1084                         foreach (ScopeInfo si in scopes.Values){
1085                                 if (si.IsCaptured (local))
1086                                         return true;
1087                         }
1088                         return false;
1089                 }
1090
1091                 //
1092                 // Returns whether the parameter is captured
1093                 //
1094                 public bool IsParameterCaptured (string name)
1095                 {
1096                         if (ParentCaptureContext != null && ParentCaptureContext.IsParameterCaptured (name))
1097                                 return true;
1098
1099                         if (captured_parameters != null)
1100                                 return captured_parameters [name] != null;
1101                         return false;
1102                 }
1103
1104                 public void EmitAnonymousHelperClasses (EmitContext ec)
1105                 {
1106                         if (roots.Count != 0){
1107                                 foreach (ScopeInfo root in roots){
1108                                         //
1109                                         // FIXME: We really should do this in a per-ScopeInfo
1110                                         // basis, instead of having the NeedThis applied to
1111                                         // all of the roots.
1112                                         //
1113                                         root.NeedThis = HaveCapturedFields || referenced_this;
1114
1115                                         root.EmitScopeType (ec);
1116                                 }
1117                         }
1118                 }
1119
1120                 public void CloseAnonymousHelperClasses ()
1121                 {
1122                         if (roots.Count != 0)
1123                                 foreach (ScopeInfo root in roots)
1124                                         root.CloseTypes ();
1125                 }
1126
1127                 public void EmitInitScope (EmitContext ec)
1128                 {
1129                         EmitAnonymousHelperClasses (ec);
1130                         if (roots.Count != 0)
1131                                 foreach (ScopeInfo root in roots)
1132                                         root.EmitInitScope (ec);                }
1133
1134                 //
1135                 // This is called externally when we start emitting code for a block
1136                 // if the block has a ScopeInfo associated, emit the init code
1137                 //
1138                 public void EmitScopeInitFromBlock (EmitContext ec, Block b)
1139                 {
1140                         ScopeInfo si = (ScopeInfo) scopes [b.ID];
1141                         if (si == null)
1142                                 return;
1143
1144                         si.EmitInitScope (ec);
1145                 }
1146
1147                 //
1148                 // Emits the opcodes necessary to load the instance of the captured
1149                 // variable in `li'
1150                 //
1151                 public void EmitCapturedVariableInstance (EmitContext ec, LocalInfo li,
1152                                                           AnonymousContainer am)
1153                 {
1154                         ILGenerator ig = ec.ig;
1155                         ScopeInfo si;
1156
1157                         if (li.Block.Toplevel == toplevel_owner){
1158                                 si = (ScopeInfo) scopes [li.Block.ID];
1159                                 si.EmitScopeInstance (ig);
1160                                 return;
1161                         }
1162
1163                         si = am.Scope;
1164                         ig.Emit (OpCodes.Ldarg_0);
1165                         if (si != null){
1166                                 if (am.IsIterator && (si.ScopeBlock.Toplevel == li.Block.Toplevel)) {
1167                                         return;
1168                                 }
1169
1170                                 while (si.ScopeBlock.ID != li.Block.ID){
1171                                         if (si.ParentLink != null)
1172                                                 ig.Emit (OpCodes.Ldfld, si.ParentLink);
1173                                         si = si.ParentScope;
1174                                         if (si == null) {
1175                                                 si = am.Scope;
1176                                                 Console.WriteLine ("Target: {0} {1}", li.Block.ID, li.Name);
1177                                                 while (si.ScopeBlock.ID != li.Block.ID){
1178                                                         Console.WriteLine ("Trying: {0}", si.ScopeBlock.ID);
1179                                                         si = si.ParentScope;
1180                                                 }
1181
1182                                                 throw new Exception (
1183                                                              String.Format ("Never found block {0} starting at {1} while looking up {2}",
1184                                                                             li.Block.ID, am.Scope.ScopeBlock.ID, li.Name));
1185                                         }
1186                                 }
1187                         }
1188                 }
1189
1190                 //
1191                 // Internal routine that loads the instance to reach parameter `name'
1192                 //
1193                 void EmitParameterInstance (EmitContext ec, string name)
1194                 {
1195                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1196                         if (cc != this){
1197                                 cc.EmitParameterInstance (ec, name);
1198                                 return;
1199                         }
1200
1201                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1202                         if (par_info != null){
1203                                 //
1204                                 // FIXME: implementing this.
1205                                 //
1206                         }
1207                         ILGenerator ig = ec.ig;
1208
1209                         ScopeInfo si;
1210
1211                         if (ec.CurrentBlock.Toplevel == toplevel_owner) {
1212                                 si = (ScopeInfo) scopes [toplevel_owner.ID];
1213                                 si.EmitScopeInstance (ig);
1214                         } else {
1215                                 si = ec.CurrentAnonymousMethod.Scope;
1216                                 ig.Emit (OpCodes.Ldarg_0);
1217                         }
1218
1219                         if (si != null){
1220                                 while (si.ParentLink != null) {
1221                                         ig.Emit (OpCodes.Ldfld, si.ParentLink);
1222                                         si = si.ParentScope;
1223                                 }
1224                         }
1225                 }
1226
1227                 //
1228                 // Emits the code necessary to load the parameter named `name' within
1229                 // an anonymous method.
1230                 //
1231                 public void EmitParameter (EmitContext ec, string name, bool leave_copy, bool prepared, ref LocalTemporary temp)
1232                 {
1233                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1234                         if (cc != this){
1235                                 cc.EmitParameter (ec, name, leave_copy, prepared, ref temp);
1236                                 return;
1237                         }
1238                         if (!prepared)
1239                                 EmitParameterInstance (ec, name);
1240                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1241                         if (par_info != null){
1242                                 //
1243                                 // FIXME: implementing this.
1244                                 //
1245                         }
1246                         ec.ig.Emit (OpCodes.Ldfld, par_info.FieldBuilder);
1247
1248                         if (leave_copy){
1249                                 ec.ig.Emit (OpCodes.Dup);
1250                                 temp = new LocalTemporary (par_info.FieldBuilder.FieldType);
1251                                 temp.Store (ec);
1252                         }
1253                 }
1254
1255                 //
1256                 // Implements the assignment of `source' to the paramenter named `name' within
1257                 // an anonymous method.
1258                 //
1259                 public void EmitAssignParameter (EmitContext ec, string name, Expression source, bool leave_copy, bool prepare_for_load, ref LocalTemporary temp)
1260                 {
1261                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1262                         if (cc != this){
1263                                 cc.EmitAssignParameter (ec, name, source, leave_copy, prepare_for_load, ref temp);
1264                                 return;
1265                         }
1266                         ILGenerator ig = ec.ig;
1267                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1268
1269                         EmitParameterInstance (ec, name);
1270                         if (prepare_for_load)
1271                                 ig.Emit (OpCodes.Dup);
1272                         source.Emit (ec);
1273                         if (leave_copy){
1274                                 ig.Emit (OpCodes.Dup);
1275                                 temp = new LocalTemporary (par_info.FieldBuilder.FieldType);
1276                                 temp.Store (ec);
1277                         }
1278                         ig.Emit (OpCodes.Stfld, par_info.FieldBuilder);
1279                         if (temp != null)
1280                                 temp.Emit (ec);
1281                 }
1282
1283                 //
1284                 // Emits the address for the parameter named `name' within
1285                 // an anonymous method.
1286                 //
1287                 public void EmitAddressOfParameter (EmitContext ec, string name)
1288                 {
1289                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1290                         if (cc != this){
1291                                 cc.EmitAddressOfParameter (ec, name);
1292                                 return;
1293                         }
1294                         EmitParameterInstance (ec, name);
1295                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1296                         ec.ig.Emit (OpCodes.Ldflda, par_info.FieldBuilder);
1297                 }
1298
1299                 //
1300                 // The following methods are only invoked on the host for the
1301                 // anonymous method.
1302                 //
1303                 public void EmitMethodHostInstance (EmitContext target, AnonymousContainer am)
1304                 {
1305                         ILGenerator ig = target.ig;
1306                         ScopeInfo si = am.Scope;
1307
1308                         AnonymousContainer container = am.ContainerAnonymousMethod;
1309
1310                         if ((si == null) || ((container != null) && (si == container.Scope))) {
1311                                 ig.Emit (OpCodes.Ldarg_0);
1312                                 return;
1313                         }
1314
1315                         si.EmitInitScope (target);
1316                         si.EmitScopeInstance (ig);
1317                 }
1318
1319                 public void RegisterCaptureContext ()
1320                 {
1321                         toplevel_owner.RegisterCaptureContext (this);
1322                 }
1323
1324                 //
1325                 // Returs true if `probe' is an ancestor of `scope' in the
1326                 // scope chain
1327                 //
1328                 bool IsAncestor (ScopeInfo probe, ScopeInfo scope)
1329                 {
1330                         for (Block b = scope.ScopeBlock.Parent; b != null; b = b.Parent){
1331                                 if (probe.ScopeBlock == b)
1332                                         return true;
1333                         }
1334                         return false;
1335                 }
1336
1337                 //
1338                 // Returns an ArrayList of ScopeInfos that enumerates all the ancestors
1339                 // of `scope' found in `scope_list'.
1340                 //
1341                 // The value returned is either a ScopeInfo or an Arraylist of ScopeInfos
1342                 //
1343                 object GetAncestorScopes (ScopeInfo scope, ScopeInfo [] scope_list)
1344                 {
1345                         object ancestors = null;
1346
1347                         for (int i = 0; i < scope_list.Length; i++){
1348                                 // Ignore the same scope
1349                                 if (scope_list [i] == scope)
1350                                         continue;
1351
1352                                 if (IsAncestor (scope_list [i], scope)){
1353                                         if (ancestors == null){
1354                                                 ancestors = scope_list [i];
1355                                                 continue;
1356                                         }
1357
1358                                         if (ancestors is ScopeInfo){
1359                                                 object old = ancestors;
1360                                                 ancestors = new ArrayList (4);
1361                                                 ((ArrayList)ancestors).Add (old);
1362                                         }
1363
1364                                         ((ArrayList)ancestors).Add (scope_list [i]);
1365                                 }
1366                         }
1367                         return ancestors;
1368                 }
1369
1370                 //
1371                 // Returns the immediate parent of `scope' from all the captured
1372                 // scopes found in `scope_list', or null if this is a toplevel scope.
1373                 //
1374                 ScopeInfo GetParentScope (ScopeInfo scope, ScopeInfo [] scope_list)
1375                 {
1376                         object ancestors = GetAncestorScopes (scope, scope_list);
1377                         if (ancestors == null)
1378                                 return null;
1379
1380                         // Single match, thats the parent.
1381                         if (ancestors is ScopeInfo)
1382                                 return (ScopeInfo) ancestors;
1383
1384                         ArrayList candidates = (ArrayList) ancestors;
1385                         ScopeInfo parent = (ScopeInfo) candidates [0];
1386                         for (int i = 1; i < candidates.Count; i++){
1387                                 if (IsAncestor (parent, (ScopeInfo) candidates [i]))
1388                                         parent = (ScopeInfo) candidates [i];
1389                         }
1390                         return parent;
1391                 }
1392
1393                 //
1394                 // Links all the scopes
1395                 //
1396                 bool linked;
1397                 public void LinkScopes ()
1398                 {
1399                         if (linked)
1400                                 return;
1401
1402                         linked = true;
1403                         if (ParentCaptureContext != null)
1404                                 ParentCaptureContext.LinkScopes ();
1405
1406                         int scope_count = scopes.Keys.Count;
1407                         ScopeInfo [] scope_list = new ScopeInfo [scope_count];
1408                         scopes.Values.CopyTo (scope_list, 0);
1409
1410                         for (int i = 0; i < scope_count; i++){
1411                                 ScopeInfo parent = GetParentScope (scope_list [i], scope_list);
1412
1413                                 if (parent == null){
1414                                         roots.Add (scope_list [i]);
1415                                         continue;
1416                                 }
1417
1418                                 scope_list [i].ParentScope = parent;
1419                                 parent.AddChild (scope_list [i]);
1420                         }
1421
1422                         //
1423                         // Link the roots to their parent containers if any.
1424                         //
1425                         if (ParentCaptureContext != null && roots.Count != 0){
1426                                 ScopeInfo one_root = (ScopeInfo) roots [0];
1427                                 bool found = false;
1428
1429                                 foreach (ScopeInfo a_parent_root in ParentCaptureContext.roots){
1430                                         if (!IsAncestor (a_parent_root, one_root))
1431                                                 continue;
1432
1433                                         found = true;
1434
1435                                         // Found, link all the roots to this root
1436                                         foreach (ScopeInfo root in roots){
1437                                                 root.ParentScope = a_parent_root;
1438                                                 a_parent_root.AddChild (root);
1439                                         }
1440                                         break;
1441                                 }
1442                                 if (!found){
1443                                         //
1444                                         // This is to catch a condition in which it is
1445                                         // not possible to determine the containing ScopeInfo
1446                                         // from an encapsulating CaptureContext
1447                                         //
1448                                         throw new Exception ("Internal compiler error: Did not find the parent for the root in the chain");
1449                                 }
1450                         }
1451                 }
1452         }
1453 }