mcs/gmcs/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                 public string[] TypeParameters;
  51                 public Type[] TypeArguments;
  52                 protected bool unreachable;
  53
  54                 // The method scope
  55                 ScopeInfo method_scope;
  56                 bool computed_method_scope = false;
  57
  58                 //
  59                 // The modifiers applied to the method, we aggregate them
  60                 //
  61                 protected int method_modifiers = Modifiers.PRIVATE;
  62
  63                 //
  64                 // Track the scopes that this method has used.  At the
  65                 // end this is used to determine the ScopeInfo that will
  66                 // host the method
  67                 //
  68                 ArrayList scopes_used = new ArrayList ();
  69
  70                 //
  71                 // Points to our container anonymous method if its present
  72                 //
  73                 public AnonymousContainer ContainerAnonymousMethod;
  74
  75                 protected AnonymousContainer (Parameters parameters, ToplevelBlock container,
  76                                               ToplevelBlock block, Location l)
  77                 {
  78                         Parameters = parameters;
  79                         Block = block;
  80                         loc = l;
  81
  82                         //
  83                         // The order is important: this setups the CaptureContext tree hierarchy.
  84                         //
  85                         if (container == null) {
  86                                 Report.Error (1706, l, "Anonymous methods are not allowed in attribute declaration");
  87                                 return;
  88                         }
  89                         container.SetHaveAnonymousMethods (l, this);
  90                         block.SetHaveAnonymousMethods (l, this);
  91                 }
  92
  93                 protected AnonymousContainer (Parameters parameters, ToplevelBlock container,
  94                                               Location l):
  95                         this (parameters, container, new ToplevelBlock (container, parameters, l), l)
  96                 {
  97                 }
  98
  99                 public override Expression DoResolve (EmitContext ec)
 100                 {
 101                         //
 102                         // Set class type, set type
 103                         //
 104
 105                         eclass = ExprClass.Value;
 106
 107                         //
 108                         // This hack means `The type is not accessible
 109                         // anywhere', we depend on special conversion
 110                         // rules.
 111                         //
 112                         type = TypeManager.anonymous_method_type;
 113
 114                         return this;
 115                 }
 116
 117                 public void RegisterScope (ScopeInfo scope)
 118                 {
 119                         if (scopes_used.Contains (scope))
 120                                 return;
 121                         scopes_used.Add (scope);
 122                 }
 123
 124                 // Returns the deepest of two scopes
 125                 ScopeInfo Deepest (ScopeInfo a, ScopeInfo b)
 126                 {
 127                         ScopeInfo p;
 128
 129                         if (a == null)
 130                                 return b;
 131                         if (b == null)
 132                                 return a;
 133                         if (a == b)
 134                                 return a;
 135
 136                         //
 137                         // If they Scopes are on the same CaptureContext, we do the double
 138                         // checks just so if there is an invariant change in the future,
 139                         // we get the exception at the end
 140                         //
 141                         for (p = a; p != null; p = p.ParentScope)
 142                                 if (p == b)
 143                                         return a;
 144
 145                         for (p = b; p != null; p = p.ParentScope)
 146                                 if (p == a)
 147                                         return b;
 148
 149                         CaptureContext ca = a.CaptureContext;
 150                         CaptureContext cb = b.CaptureContext;
 151
 152                         for (CaptureContext c = ca; c != null; c = c.ParentCaptureContext)
 153                                 if (c == cb)
 154                                         return a;
 155
 156                         for (CaptureContext c = cb; c != null; c = c.ParentCaptureContext)
 157                                 if (c == ca)
 158                                         return b;
 159                         throw new Exception ("Should never be reached");
 160                 }
 161
 162                 //
 163                 // Determines the proper host for a method considering the
 164                 // scopes it references
 165                 //
 166                 public void ComputeMethodHost ()
 167                 {
 168                         if (computed_method_scope)
 169                                 return;
 170
 171                         method_scope = null;
 172                         int top = scopes_used.Count;
 173                         computed_method_scope = true;
 174
 175                         if (top == 0)
 176                                 return;
 177
 178                         method_scope = (ScopeInfo) scopes_used [0];
 179                         if (top == 1)
 180                                 return;
 181
 182                         for (int i = 1; i < top; i++)
 183                                 method_scope = Deepest (method_scope, (ScopeInfo) scopes_used [i]);
 184                 }
 185
 186                 public ScopeInfo Scope {
 187                         get {
 188                                 if (computed_method_scope)
 189                                         return method_scope;
 190
 191                                 //
 192                                 // This means that ComputeMethodHost is not being called, most
 193                                 // likely by someone who overwrote the CreateMethodHost method
 194                                 //
 195                                 throw new Exception ("Internal error, AnonymousContainer.Scope is being used before its container is computed");
 196                         }
 197                 }
 198
 199
 200                 protected abstract bool CreateMethodHost (EmitContext ec);
 201
 202                 public abstract void CreateScopeType (EmitContext ec, ScopeInfo scope);
 203
 204                 public abstract Iterator Iterator {
 205                         get;
 206                 }
 207
 208                 public abstract bool IsIterator {
 209                         get;
 210                 }
 211         }
 212
 213         public class AnonymousMethod : AnonymousContainer
 214         {
 215                 TypeContainer host;
 216
 217                 public AnonymousMethod (TypeContainer host, Parameters parameters, ToplevelBlock container,
 218                                         ToplevelBlock block, Location l)
 219                         : base (parameters, container, block, l)
 220                 {
 221                         this.host = host;
 222                 }
 223
 224                 public override Iterator Iterator {
 225                         get { return null; }
 226                 }
 227
 228                 public override bool IsIterator {
 229                         get { return false; }
 230                 }
 231
 232                 public override void Emit (EmitContext ec)
 233                 {
 234                         // nothing, as we only exist to not do anything.
 235                 }
 236
 237                 //
 238                 // Creates the host for the anonymous method
 239                 //
 240                 protected override bool CreateMethodHost (EmitContext ec)
 241                 {
 242                         ComputeMethodHost ();
 243
 244                         //
 245                         // Crude hack follows: we replace the TypeBuilder during the
 246                         // definition to get the method hosted in the right class
 247                         //
 248                         TypeBuilder current_type = ec.TypeContainer.TypeBuilder;
 249                         TypeBuilder type_host = (Scope == null ) ? current_type : Scope.ScopeTypeBuilder;
 250
 251                         if (current_type == null)
 252                                 throw new Exception ("The current_type is null");
 253
 254                         if (type_host == null)
 255                                 throw new Exception (String.Format ("Type host is null, method_host is {0}", Scope == null ? "null" : "Not null"));
 256
 257                         if (current_type != type_host)
 258                                 method_modifiers = Modifiers.INTERNAL;
 259
 260                         if (current_type == type_host && ec.IsStatic){
 261                                 method_modifiers |= Modifiers.STATIC;
 262                                 current_type = null;
 263                         }
 264
 265                         string name = "<#AnonymousMethod>" + anonymous_method_count++;
 266                         MemberName member_name;
 267
 268                         GenericMethod generic_method = null;
 269                         if (TypeParameters != null) {
 270                                 TypeArguments args = new TypeArguments (loc);
 271                                 foreach (string t in TypeParameters)
 272                                         args.Add (new SimpleName (t, loc));
 273
 274                                 member_name = new MemberName (name, args, loc);
 275
 276                                 generic_method = new GenericMethod (
 277                                         ec.DeclContainer.NamespaceEntry,
 278                                         (TypeContainer) ec.TypeContainer, member_name,
 279                                         new TypeExpression (invoke_mb.ReturnType, loc),
 280                                         Parameters);
 281
 282                                 generic_method.SetParameterInfo (null);
 283                         } else
 284                                 member_name = new MemberName (name, loc);
 285
 286                         method = new Method (
 287                                 (TypeContainer) ec.TypeContainer, generic_method,
 288                                 new TypeExpression (invoke_mb.ReturnType, loc),
 289                                 method_modifiers, false, member_name, Parameters, null);
 290                         method.Block = Block;
 291
 292                         //
 293                         // Swap the TypeBuilder while we define the method, then restore
 294                         //
 295                         if (current_type != null)
 296                                 ec.TypeContainer.TypeBuilder = type_host;
 297                         bool res = method.Define ();
 298                         if (current_type != null)
 299                                 ec.TypeContainer.TypeBuilder = current_type;
 300
 301                         return res;
 302                 }
 303
 304                 void Error_ParameterMismatch (Type t)
 305                 {
 306                         Report.Error (1661, loc, "Anonymous method could not be converted to delegate `" +
 307                                       "{0}' since there is a parameter mismatch", TypeManager.CSharpName (t));
 308                 }
 309
 310                 public bool ImplicitStandardConversionExists (Type delegate_type)
 311                 {
 312                         if (Parameters == null)
 313                                 return true;
 314
 315                         MethodGroupExpr invoke_mg = Delegate.GetInvokeMethod (host.TypeBuilder, delegate_type, loc);
 316                         invoke_mb = (MethodInfo) invoke_mg.Methods [0];
 317                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 318
 319                         if (Parameters.Count != invoke_pd.Count)
 320                                 return false;
 321
 322                         for (int i = 0; i < Parameters.Count; ++i) {
 323                                 if (invoke_pd.ParameterType (i) != Parameters.ParameterType (i))
 324                                         return false;
 325                         }
 326                         return true;
 327                 }
 328
 329                 //
 330                 // Returns true if this anonymous method can be implicitly
 331                 // converted to the delegate type `delegate_type'
 332                 //
 333                 public Expression Compatible (EmitContext ec, Type delegate_type)
 334                 {
 335                         //
 336                         // At this point its the first time we know the return type that is
 337                         // needed for the anonymous method.  We create the method here.
 338                         //
 339
 340                         MethodGroupExpr invoke_mg = Delegate.GetInvokeMethod (ec.ContainerType, delegate_type, loc);
 341                         invoke_mb = (MethodInfo) invoke_mg.Methods [0];
 342                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 343
 344                         if (delegate_type.IsGenericType) {
 345                                 Type def = delegate_type.GetGenericTypeDefinition ();
 346
 347                                 if (def != delegate_type) {
 348                                         Type[] tparam = TypeManager.GetTypeArguments (def);
 349
 350                                         TypeArguments = TypeManager.GetTypeArguments (delegate_type);
 351                                         TypeParameters = new string [tparam.Length];
 352                                         for (int i = 0; i < tparam.Length; i++)
 353                                                 TypeParameters [i] = tparam [i].Name;
 354                                 }
 355                         }
 356
 357                         if (Parameters == null) {
 358                                 //
 359                                 // We provide a set of inaccessible parameters
 360                                 //
 361                                 Parameter [] fixedpars = new Parameter [invoke_pd.Count];
 362
 363                                 for (int i = 0; i < invoke_pd.Count; i++){
 364                                         fixedpars [i] = new Parameter (
 365                                                 invoke_pd.ParameterType (i),
 366                                                 "+" + i, invoke_pd.ParameterModifier (i), null, loc);
 367                                 }
 368
 369                                 Parameters = new Parameters (fixedpars);
 370                         } else {
 371                                 if (Parameters.Count != invoke_pd.Count) {
 372                                         Report.SymbolRelatedToPreviousError (delegate_type);
 373                                         Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
 374                                                 TypeManager.CSharpName (delegate_type), Parameters.Count.ToString ());
 375                                         Error_ParameterMismatch (delegate_type);
 376                                         return null;
 377                                 }
 378
 379                                 for (int i = 0; i < Parameters.Count; ++i) {
 380                                         Parameter.Modifier p_mod = invoke_pd.ParameterModifier (i);
 381                                         if (Parameters.ParameterModifier (i) != p_mod && p_mod != Parameter.Modifier.PARAMS) {
 382                                                 if (p_mod == Parameter.Modifier.NONE)
 383                                                         Report.Error (1677, loc, "Parameter `{0}' should not be declared with the `{1}' keyword",
 384                                                                 (i + 1).ToString (), Parameter.GetModifierSignature (Parameters.ParameterModifier (i)));
 385                                                 else
 386                                                         Report.Error (1676, loc, "Parameter `{0}' must be declared with the `{1}' keyword",
 387                                                                 (i+1).ToString (), Parameter.GetModifierSignature (p_mod));
 388                                                 Error_ParameterMismatch (delegate_type);
 389                                                 return null;
 390                                         }
 391
 392                                         if (invoke_pd.ParameterType (i) != Parameters.ParameterType (i)) {
 393                                                 Report.Error (1678, loc, "Parameter `{0}' is declared as type `{1}' but should be `{2}'",
 394                                                         (i+1).ToString (),
 395                                                         TypeManager.CSharpName (Parameters.ParameterType (i)),
 396                                                         TypeManager.CSharpName (invoke_pd.ParameterType (i)));
 397                                                 Error_ParameterMismatch (delegate_type);
 398                                                 return null;
 399                                         }
 400                                 }
 401                         }
 402
 403                         //
 404                         // Second: the return type of the delegate must be compatible with
 405                         // the anonymous type.   Instead of doing a pass to examine the block
 406                         // we satisfy the rule by setting the return type on the EmitContext
 407                         // to be the delegate type return type.
 408                         //
 409
 410                         //MethodBuilder builder = method_data.MethodBuilder;
 411                         //ILGenerator ig = builder.GetILGenerator ();
 412
 413                         aec = new EmitContext (ec.ResolveContext,
 414                                 ec.TypeContainer, ec.DeclContainer, loc, null,
 415                                 invoke_mb.ReturnType,
 416                                 /* REVIEW */ (ec.InIterator ? Modifiers.METHOD_YIELDS : 0) |
 417                                 (ec.InUnsafe ? Modifiers.UNSAFE : 0) |
 418                                 (ec.IsStatic ? Modifiers.STATIC : 0),
 419                                 /* No constructor */ false);
 420
 421                         aec.CurrentAnonymousMethod = this;
 422                         ContainerAnonymousMethod = ec.CurrentAnonymousMethod;
 423                         ContainingBlock = ec.CurrentBlock;
 424
 425                         if (aec.ResolveTopBlock (ec, Block, Parameters, null, out unreachable))
 426                                 return new AnonymousDelegate (this, delegate_type, loc).Resolve (ec);
 427
 428                         return null;
 429                 }
 430
 431                 public override Expression DoResolve (EmitContext ec)
 432                 {
 433                         if (Parameters != null && !Parameters.Resolve (ec)) {
 434                                 return null;
 435                         }
 436
 437                         return base.DoResolve (ec);
 438                 }
 439
 440
 441                 public override string ExprClassName {
 442                         get {
 443                                 return "anonymous method";
 444                         }
 445                 }
 446
 447                 public MethodInfo GetMethodBuilder ()
 448                 {
 449                         MethodInfo builder = method.MethodData.MethodBuilder;
 450                         if (TypeArguments != null)
 451                                 return builder.MakeGenericMethod (TypeArguments);
 452                         else
 453                                 return builder;
 454                 }
 455
 456                 public override string GetSignatureForError ()
 457                 {
 458                         string s = TypeManager.CSharpSignature (invoke_mb);
 459                         return s.Substring (0, s.IndexOf (".Invoke("));
 460                 }
 461
 462                 public bool EmitMethod (EmitContext ec)
 463                 {
 464                         if (!CreateMethodHost (ec))
 465                                 return false;
 466
 467                         MethodBuilder builder = method.MethodData.MethodBuilder;
 468                         ILGenerator ig = builder.GetILGenerator ();
 469                         aec.ig = ig;
 470
 471                         Parameters.ApplyAttributes (builder);
 472
 473                         //
 474                         // Adjust based on the computed state of the
 475                         // method from CreateMethodHost
 476
 477                         aec.MethodIsStatic = (method_modifiers & Modifiers.STATIC) != 0;
 478
 479                         aec.EmitMeta (Block);
 480                         aec.EmitResolvedTopBlock (Block, unreachable);
 481                         return true;
 482                 }
 483
 484                 public override void CreateScopeType (EmitContext ec, ScopeInfo scope)
 485                 {
 486                         TypeBuilder container = ec.TypeContainer.TypeBuilder;
 487                         string name = String.Format ("<>AnonHelp<{0}>", scope.id);
 488
 489                         scope.ScopeTypeBuilder = container.DefineNestedType (
 490                                 name, TypeAttributes.AutoLayout | TypeAttributes.Class |
 491                                 TypeAttributes.NestedAssembly, TypeManager.object_type, null);
 492
 493                         Type [] constructor_types = Type.EmptyTypes;
 494                         ConstructorBuilder ctor = scope.ScopeTypeBuilder.DefineConstructor (
 495                                 MethodAttributes.Public | MethodAttributes.HideBySig |
 496                                 MethodAttributes.SpecialName | MethodAttributes.RTSpecialName,
 497                                 CallingConventions.HasThis, constructor_types);
 498                         TypeManager.RegisterMethod (ctor, Parameters.EmptyReadOnlyParameters);
 499
 500                         ILGenerator cig = ctor.GetILGenerator ();
 501                         cig.Emit (OpCodes.Ldarg_0);
 502                         cig.Emit (OpCodes.Call, TypeManager.object_ctor);
 503                         cig.Emit (OpCodes.Ret);
 504
 505                         if (ec.TypeContainer.IsGeneric) {
 506                                 TypeParameter[] tparam = ec.TypeContainer.TypeParameters;
 507                                 string[] names = new string [tparam.Length];
 508                                 Type[] types = new Type [tparam.Length];
 509
 510                                 for (int i = 0; i < names.Length; i++) {
 511                                         names [i] = tparam [i].Name;
 512                                         types [i] = tparam [i].Type;
 513                                 }
 514
 515                                 scope.ScopeTypeBuilder.DefineGenericParameters (names);
 516                                 scope.ScopeTypeBuilder.GetGenericTypeDefinition ();
 517
 518                                 scope.ScopeType = scope.ScopeTypeBuilder.MakeGenericType (types);
 519                         } else
 520                                 scope.ScopeType = scope.ScopeTypeBuilder;
 521
 522
 523                         if (ec.TypeContainer.IsGeneric)
 524                                 scope.ScopeConstructor = TypeBuilder.GetConstructor (
 525                                         scope.ScopeType, ctor);
 526                         else
 527                                 scope.ScopeConstructor = ctor;
 528                 }
 529
 530                 public static void Error_AddressOfCapturedVar (string name, Location loc)
 531                 {
 532                         Report.Error (1686, loc,
 533                                 "Local variable `{0}' or its members cannot have their address taken and be used inside an anonymous method block",
 534                                 name);
 535                 }
 536         }
 537
 538         //
 539         // This will emit the code for the delegate, as well delegate creation on the host
 540         //
 541         public class AnonymousDelegate : DelegateCreation {
 542                 AnonymousMethod am;
 543
 544                 public AnonymousDelegate (AnonymousMethod am, Type target_type, Location l)
 545                 {
 546                         type = target_type;
 547                         loc = l;
 548                         this.am = am;
 549                 }
 550
 551                 public override Expression DoResolve (EmitContext ec)
 552                 {
 553                         eclass = ExprClass.Value;
 554
 555                         return this;
 556                 }
 557
 558                 public override void Emit (EmitContext ec)
 559                 {
 560                         if (!am.EmitMethod (ec))
 561                                 return;
 562
 563                         //
 564                         // Now emit the delegate creation.
 565                         //
 566                         if ((am.method.ModFlags & Modifiers.STATIC) == 0)
 567                                 delegate_instance_expression = new AnonymousInstance (am);
 568
 569                         Expression ml = Expression.MemberLookup (ec.ContainerType, type, ".ctor", loc);
 570                         constructor_method = ((MethodGroupExpr) ml).Methods [0];
 571                         delegate_method = am.GetMethodBuilder ();
 572                         base.Emit (ec);
 573                 }
 574
 575                 class AnonymousInstance : Expression {
 576                         AnonymousMethod am;
 577
 578                         public AnonymousInstance (AnonymousMethod am)
 579                         {
 580                                 this.am = am;
 581                                 eclass = ExprClass.Value;
 582                         }
 583
 584                         public override Expression DoResolve (EmitContext ec)
 585                         {
 586                                 return this;
 587                         }
 588
 589                         public override void Emit (EmitContext ec)
 590                         {
 591                                 am.aec.EmitMethodHostInstance (ec, am);
 592                         }
 593                 }
 594         }
 595
 596         class CapturedParameter {
 597                 public Type Type;
 598                 public FieldBuilder FieldBuilder;
 599                 public int Idx;
 600
 601                 public CapturedParameter (Type type, int idx)
 602                 {
 603                         Type = type;
 604                         Idx = idx;
 605                 }
 606         }
 607
 608         //
 609         // Here we cluster all the variables captured on a given scope, we also
 610         // keep some extra information that might be required on each scope.
 611         //
 612         public class ScopeInfo {
 613                 public CaptureContext CaptureContext;
 614                 public ScopeInfo ParentScope;
 615                 public Block ScopeBlock;
 616                 public bool NeedThis = false;
 617                 public bool HostsParameters = false;
 618
 619                 // For tracking the number of scopes created.
 620                 public int id;
 621                 static int count;
 622                 bool inited = false;
 623
 624                 ArrayList locals = new ArrayList ();
 625                 ArrayList children = new ArrayList ();
 626
 627                 //
 628                 // The types and fields generated
 629                 //
 630                 public TypeBuilder ScopeTypeBuilder;
 631                 public Type ScopeType;
 632                 public ConstructorInfo ScopeConstructor;
 633                 public FieldBuilder THIS;
 634                 public FieldBuilder ParentLink;
 635
 636                 //
 637                 // Points to the object of type `ScopeTypeBuilder' that
 638                 // holds the data for the scope
 639                 //
 640                 LocalBuilder scope_instance;
 641
 642                 public ScopeInfo (CaptureContext cc, Block b)
 643                 {
 644                         CaptureContext = cc;
 645                         ScopeBlock = b;
 646                         id = count++;
 647
 648                         cc.RegisterCaptureContext ();
 649                 }
 650
 651                 public void AddLocal (LocalInfo li)
 652                 {
 653                         if (locals.Contains (li))
 654                                 return;
 655
 656                         locals.Add (li);
 657 }
 658
 659                 public bool IsCaptured (LocalInfo li)
 660                 {
 661                         return locals.Contains (li);
 662                 }
 663
 664                 internal void AddChild (ScopeInfo si)
 665                 {
 666                         if (children.Contains (si))
 667                                 return;
 668
 669                         //
 670                         // If any of the current children should be a children of `si', move them there
 671                         //
 672                         ArrayList move_queue = null;
 673                         foreach (ScopeInfo child in children){
 674                                 if (child.ScopeBlock.IsChildOf (si.ScopeBlock)){
 675                                         if (move_queue == null)
 676                                                 move_queue = new ArrayList ();
 677                                         move_queue.Add (child);
 678                                         child.ParentScope = si;
 679                                         si.AddChild (child);
 680                                 }
 681                         }
 682
 683                         children.Add (si);
 684
 685                         if (move_queue != null){
 686                                 foreach (ScopeInfo child in move_queue){
 687                                         children.Remove (child);
 688                                 }
 689                         }
 690                 }
 691
 692                 static int indent = 0;
 693
 694                 void Pad ()
 695                 {
 696                         for (int i = 0; i < indent; i++)
 697                                 Console.Write ("    ");
 698                 }
 699
 700                 void EmitDebug ()
 701                 {
 702                         //Console.WriteLine (Environment.StackTrace);
 703                         Pad ();
 704                         Console.WriteLine ("START");
 705                         indent++;
 706                         Pad ();
 707                         Console.WriteLine ("NeedThis=" + NeedThis);
 708                         foreach (LocalInfo li in locals){
 709                                 Pad ();
 710                                 Console.WriteLine ("var {0}", MakeFieldName (li.Name));
 711                         }
 712
 713                         foreach (ScopeInfo si in children)
 714                                 si.EmitDebug ();
 715                         indent--;
 716                         Pad ();
 717                         Console.WriteLine ("END");
 718                 }
 719
 720                 public string MakeHelperName ()
 721                 {
 722                         return String.Format ("<>AnonHelp<{0}>", id);
 723                 }
 724
 725                 private string MakeFieldName (string local_name)
 726                 {
 727                         return "<" + id + ":" + local_name + ">";
 728                 }
 729
 730                 public void EmitScopeType (EmitContext ec)
 731                 {
 732                         // EmitDebug ();
 733
 734                         if (ScopeTypeBuilder != null)
 735                                 return;
 736
 737                         Type container;
 738                         if (ec.TypeContainer.CurrentType != null)
 739                                 container = ec.TypeContainer.CurrentType;
 740                         else
 741                                 container = ec.TypeContainer.TypeBuilder;
 742
 743                         CaptureContext.Host.CreateScopeType (ec, this);
 744
 745                         if (NeedThis)
 746                                 THIS = ScopeTypeBuilder.DefineField ("<>THIS", container, FieldAttributes.Assembly);
 747
 748                         if (ParentScope != null){
 749                                 if (ParentScope.ScopeTypeBuilder == null){
 750                                         throw new Exception (String.Format ("My parent has not been initialized {0} and {1}", ParentScope, this));
 751                                 }
 752
 753                                 if (ParentScope.ScopeTypeBuilder != ScopeTypeBuilder)
 754                                         ParentLink = ScopeTypeBuilder.DefineField (
 755                                                 "<>parent", ParentScope.ScopeType, FieldAttributes.Assembly);
 756                         }
 757
 758                         if (NeedThis && ParentScope != null)
 759                                 throw new Exception ("I was not expecting THIS && having a parent");
 760
 761                         foreach (LocalInfo info in locals)
 762                                 info.FieldBuilder = ScopeTypeBuilder.DefineField (
 763                                         MakeFieldName (info.Name), info.VariableType, FieldAttributes.Assembly);
 764
 765                         if (HostsParameters){
 766                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 767
 768                                 foreach (DictionaryEntry de in captured_parameters){
 769                                         string name = (string) de.Key;
 770                                         CapturedParameter cp = (CapturedParameter) de.Value;
 771                                         FieldBuilder fb;
 772
 773                                         fb = ScopeTypeBuilder.DefineField ("<p:" + name + ">", cp.Type, FieldAttributes.Assembly);
 774                                         cp.FieldBuilder = fb;
 775                                 }
 776                         }
 777
 778                         foreach (ScopeInfo si in children){
 779                                 si.EmitScopeType (ec);
 780                         }
 781                 }
 782
 783                 public void CloseTypes ()
 784                 {
 785                         RootContext.RegisterCompilerGeneratedType (ScopeTypeBuilder);
 786                         foreach (ScopeInfo si in children)
 787                                 si.CloseTypes ();
 788                 }
 789
 790                 //
 791                 // Emits the initialization code for the scope
 792                 //
 793                 public void EmitInitScope (EmitContext ec)
 794                 {
 795                         ILGenerator ig = ec.ig;
 796
 797                         if (inited)
 798                                 return;
 799
 800                         if (ScopeConstructor == null)
 801                                 throw new Exception ("ScopeConstructor is null for" + this.ToString ());
 802
 803                         if (!CaptureContext.Host.IsIterator) {
 804                                 scope_instance = ig.DeclareLocal (ScopeType);
 805                                 ig.Emit (OpCodes.Newobj, ScopeConstructor);
 806                                 ig.Emit (OpCodes.Stloc, scope_instance);
 807                         }
 808
 809                         if (THIS != null){
 810                                 if (CaptureContext.Host.IsIterator) {
 811                                         ig.Emit (OpCodes.Ldarg_0);
 812                                         ig.Emit (OpCodes.Ldarg_1);
 813                                 } else {
 814                                         ig.Emit (OpCodes.Ldloc, scope_instance);
 815                                         ig.Emit (OpCodes.Ldarg_0);
 816                                 }
 817                                 ig.Emit (OpCodes.Stfld, THIS);
 818                         }
 819
 820                         //
 821                         // Copy the parameter values, if any
 822                         //
 823                         int extra = ec.IsStatic ? 0 : 1;
 824                         if (CaptureContext.Host.IsIterator)
 825                                 extra++;
 826                         if (HostsParameters){
 827                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 828
 829                                 foreach (DictionaryEntry de in captured_parameters){
 830                                         CapturedParameter cp = (CapturedParameter) de.Value;
 831
 832                                         EmitScopeInstance (ig);
 833                                         ParameterReference.EmitLdArg (ig, cp.Idx + extra);
 834                                         ig.Emit (OpCodes.Stfld, cp.FieldBuilder);
 835                                 }
 836                         }
 837
 838                         if (ParentScope != null){
 839                                 if (!ParentScope.inited)
 840                                         ParentScope.EmitInitScope (ec);
 841
 842                                 if (ParentScope.ScopeTypeBuilder != ScopeTypeBuilder) {
 843                                         //
 844                                         // Only emit initialization in our capturecontext world
 845                                         //
 846                                         if (ParentScope.CaptureContext == CaptureContext){
 847                                                 EmitScopeInstance (ig);
 848                                                 ParentScope.EmitScopeInstance (ig);
 849                                                 ig.Emit (OpCodes.Stfld, ParentLink);
 850                                         } else {
 851                                                 EmitScopeInstance (ig);
 852                                                 ig.Emit (OpCodes.Ldarg_0);
 853                                                 ig.Emit (OpCodes.Stfld, ParentLink);
 854                                         }
 855                                 }
 856                         }
 857                         inited = true;
 858                 }
 859
 860                 public void EmitScopeInstance (ILGenerator ig)
 861                 {
 862                         if (CaptureContext.Host.IsIterator)
 863                                 ig.Emit (OpCodes.Ldarg_0);
 864                         else {
 865                                 if (scope_instance == null){
 866                                         //
 867                                         // This is needed if someone overwrites the Emit method
 868                                         // of Statement and manually calls Block.Emit without
 869                                         // this snippet first:
 870                                         //
 871                                         //   ec.EmitScopeInitFromBlock (The_Block);
 872                                         //   The_Block.Emit (ec);
 873                                         //
 874
 875                                         Console.WriteLine (
 876                                                 "The scope_instance has not been emitted, this typically means\n" +
 877                                                 "that inside the compiler someone is calling Block.Emit without\n" +
 878                                                 "first calling EmitScopeInitFromBlock for the block.  See compiler" +
 879                                                 "source code for an explanation");
 880                                         throw new Exception ("Internal compiler error");
 881
 882                                 }
 883                                 ig.Emit (OpCodes.Ldloc, scope_instance);
 884                         }
 885                 }
 886
 887                 public static void CheckCycles (string msg, ScopeInfo s)
 888                 {
 889                         ArrayList l = new ArrayList ();
 890                         int n = 0;
 891
 892                         for (ScopeInfo p = s; p != null; p = p.ParentScope,n++){
 893                                 if (l.Contains (p)){
 894                                         Console.WriteLine ("Loop detected {0} in {1}", n, msg);
 895                                         throw new Exception ();
 896                                 }
 897                                 l.Add (p);
 898                         }
 899                 }
 900
 901                 static void DoPath (StringBuilder sb, ScopeInfo start)
 902                 {
 903                         CheckCycles ("print", start);
 904
 905                         if (start.ParentScope != null){
 906                                 DoPath (sb, start.ParentScope);
 907                                 sb.Append (", ");
 908                         }
 909                         sb.Append ((start.id).ToString ());
 910                 }
 911
 912                 public override string ToString ()
 913                 {
 914                         StringBuilder sb = new StringBuilder ();
 915
 916                         sb.Append ("{");
 917                         if (CaptureContext != null){
 918                                 sb.Append (CaptureContext.ToString ());
 919                                 sb.Append (":");
 920                         }
 921
 922                         DoPath (sb, this);
 923                         sb.Append ("}");
 924
 925                         return sb.ToString ();
 926                 }
 927         }
 928
 929         //
 930         // CaptureContext objects are created on demand if a method has
 931         // anonymous methods and kept on the ToplevelBlock.
 932         //
 933         // If they exist, all ToplevelBlocks in the containing block are
 934         // linked together (children pointing to their parents).
 935         //
 936         public class CaptureContext {
 937                 public static int count;
 938                 public int cc_id;
 939                 public Location loc;
 940
 941                 //
 942                 // Points to the toplevel block that owns this CaptureContext
 943                 //
 944                 ToplevelBlock toplevel_owner;
 945
 946                 //
 947                 // All the scopes we capture
 948                 //
 949                 Hashtable scopes = new Hashtable ();
 950
 951                 //
 952                 // All the root scopes
 953                 //
 954                 ArrayList roots = new ArrayList ();
 955
 956                 bool have_captured_vars = false;
 957                 bool referenced_this = false;
 958
 959                 //
 960                 // Captured fields
 961                 //
 962                 Hashtable captured_fields = new Hashtable ();
 963                 Hashtable captured_variables = new Hashtable ();
 964                 public Hashtable captured_parameters = new Hashtable ();
 965                 public AnonymousContainer Host;
 966
 967                 public CaptureContext (ToplevelBlock toplevel_owner, Location loc,
 968                                        AnonymousContainer host)
 969                 {
 970                         cc_id = count++;
 971                         this.toplevel_owner = toplevel_owner;
 972                         this.loc = loc;
 973
 974                         if (host != null)
 975                                 Host = host;
 976                 }
 977
 978                 void DoPath (StringBuilder sb, CaptureContext cc)
 979                 {
 980                         if (cc.ParentCaptureContext != null){
 981                                 DoPath (sb, cc.ParentCaptureContext);
 982                                 sb.Append (".");
 983                         }
 984                         sb.Append (cc.cc_id.ToString ());
 985                 }
 986
 987                 public void ReParent (ToplevelBlock new_toplevel, AnonymousContainer new_host)
 988                 {
 989                         toplevel_owner = new_toplevel;
 990                         Host = new_host;
 991
 992                         for (CaptureContext cc = ParentCaptureContext; cc != null;
 993                              cc = cc.ParentCaptureContext) {
 994                                 cc.Host = new_host;
 995                         }
 996                 }
 997
 998                 public override string ToString ()
 999                 {
1000                         StringBuilder sb = new StringBuilder ();
1001                         sb.Append ("[");
1002                         DoPath (sb, this);
1003                         sb.Append ("]");
1004                         return sb.ToString ();
1005                 }
1006
1007                 public ToplevelBlock ParentToplevel {
1008                         get {
1009                                 return toplevel_owner.Container;
1010                         }
1011                 }
1012
1013                 public CaptureContext ParentCaptureContext {
1014                         get {
1015                                 ToplevelBlock parent = ParentToplevel;
1016
1017                                 return (parent == null) ? null : parent.CaptureContext;
1018                         }
1019                 }
1020
1021                 ScopeInfo GetScopeForBlock (Block block)
1022                 {
1023                         ScopeInfo si = (ScopeInfo) scopes [block.ID];
1024                         if (si != null)
1025                                 return si;
1026                         si = new ScopeInfo (this, block);
1027                         scopes [block.ID] = si;
1028                         return si;
1029                 }
1030
1031                 public void AddLocal (AnonymousContainer am, LocalInfo li)
1032                 {
1033                         if (li.Block.Toplevel != toplevel_owner){
1034                                 ParentCaptureContext.AddLocal (am, li);
1035                                 return;
1036                         }
1037                         ScopeInfo scope = GetScopeForBlock (li.Block);
1038
1039                         //
1040                         // Adjust the owner
1041                         //
1042                         if (Host != null)
1043                                 Host.RegisterScope (scope);
1044
1045                         //
1046                         // Adjust the user
1047                         //
1048                         am.RegisterScope (scope);
1049
1050                         if (captured_variables [li] != null)
1051                                 return;
1052
1053                         have_captured_vars = true;
1054                         captured_variables [li] = li;
1055                         scope.AddLocal (li);
1056                 }
1057
1058                 //
1059                 // Retursn the CaptureContext for the block that defines the parameter `name'
1060                 //
1061                 static CaptureContext _ContextForParameter (ToplevelBlock current, string name)
1062                 {
1063                         ToplevelBlock container = current.Container;
1064                         if (container != null){
1065                                 CaptureContext cc = _ContextForParameter (container, name);
1066                                 if (cc != null)
1067                                         return cc;
1068                         }
1069                         if (current.IsParameterReference (name))
1070                                 return current.ToplevelBlockCaptureContext;
1071                         return null;
1072                 }
1073
1074                 static CaptureContext ContextForParameter (ToplevelBlock current, string name)
1075                 {
1076                         CaptureContext cc = _ContextForParameter (current, name);
1077                         if (cc == null)
1078                                 throw new Exception (String.Format ("request for parameteter {0} failed: not found", name));
1079                         return cc;
1080                 }
1081
1082                 //
1083                 // Records the captured parameter at the appropriate CaptureContext
1084                 //
1085                 public void AddParameter (EmitContext ec, AnonymousContainer am,
1086                                           string name, Type t, int idx)
1087                 {
1088                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1089
1090                         cc.AddParameterToContext (am, name, t, idx);
1091                 }
1092
1093                 //
1094                 // Records the parameters in the context
1095                 //
1096                 public void AddParameterToContext (AnonymousContainer am, string name, Type t, int idx)
1097                 {
1098                         if (captured_parameters == null)
1099                                 captured_parameters = new Hashtable ();
1100                         if (captured_parameters [name] == null)
1101                                 captured_parameters [name] = new CapturedParameter (t, idx);
1102
1103                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1104                         scope.HostsParameters = true;
1105                         am.RegisterScope (scope);
1106                 }
1107
1108                 //
1109                 // Captured fields are only recorded on the topmost CaptureContext, because that
1110                 // one is the one linked to the owner of instance fields
1111                 //
1112                 public void AddField (EmitContext ec, AnonymousContainer am, FieldExpr fe)
1113                 {
1114                         if (fe.FieldInfo.IsStatic)
1115                                 throw new Exception ("Attempt to register a static field as a captured field");
1116                         CaptureContext parent = ParentCaptureContext;
1117                         if (parent != null) {
1118                                 parent.AddField (ec, am, fe);
1119                                 return;
1120                         }
1121
1122                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1123                         am.RegisterScope (scope);
1124                 }
1125
1126                 public void CaptureThis (AnonymousContainer am)
1127                 {
1128                         if (am == null)
1129                                 throw new Exception ("Internal Compiler error: Capturethis called with a null method");
1130                         CaptureContext parent = ParentCaptureContext;
1131                         if (parent != null) {
1132                                 parent.CaptureThis (am);
1133                                 return;
1134                         }
1135                         referenced_this = true;
1136
1137                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1138                         am.RegisterScope (scope);
1139                 }
1140
1141                 public bool HaveCapturedVariables {
1142                         get {
1143                                 return have_captured_vars;
1144                         }
1145                 }
1146
1147                 public bool HaveCapturedFields {
1148                         get {
1149                                 CaptureContext parent = ParentCaptureContext;
1150                                 if (parent != null)
1151                                         return parent.HaveCapturedFields;
1152                                 return captured_fields.Count > 0;
1153                         }
1154                 }
1155
1156                 public bool IsCaptured (LocalInfo local)
1157                 {
1158                         foreach (ScopeInfo si in scopes.Values){
1159                                 if (si.IsCaptured (local))
1160                                         return true;
1161                         }
1162                         return false;
1163                 }
1164
1165                 //
1166                 // Returns whether the parameter is captured
1167                 //
1168                 public bool IsParameterCaptured (string name)
1169                 {
1170                         if (ParentCaptureContext != null && ParentCaptureContext.IsParameterCaptured (name))
1171                                 return true;
1172
1173                         if (captured_parameters != null)
1174                                 return captured_parameters [name] != null;
1175                         return false;
1176                 }
1177
1178                 public void EmitAnonymousHelperClasses (EmitContext ec)
1179                 {
1180                         if (roots.Count != 0){
1181                                 foreach (ScopeInfo root in roots){
1182                                         //
1183                                         // FIXME: We really should do this in a per-ScopeInfo
1184                                         // basis, instead of having the NeedThis applied to
1185                                         // all of the roots.
1186                                         //
1187                                         root.NeedThis = HaveCapturedFields || referenced_this;
1188
1189                                         root.EmitScopeType (ec);
1190                                 }
1191                         }
1192                 }
1193
1194                 public void CloseAnonymousHelperClasses ()
1195                 {
1196                         if (roots.Count != 0)
1197                                 foreach (ScopeInfo root in roots)
1198                                         root.CloseTypes ();
1199                 }
1200
1201                 public void EmitInitScope (EmitContext ec)
1202                 {
1203                         EmitAnonymousHelperClasses (ec);
1204                         if (roots.Count != 0)
1205                                 foreach (ScopeInfo root in roots)
1206                                         root.EmitInitScope (ec);                }
1207
1208                 //
1209                 // This is called externally when we start emitting code for a block
1210                 // if the block has a ScopeInfo associated, emit the init code
1211                 //
1212                 public void EmitScopeInitFromBlock (EmitContext ec, Block b)
1213                 {
1214                         ScopeInfo si = (ScopeInfo) scopes [b.ID];
1215                         if (si == null)
1216                                 return;
1217
1218                         si.EmitInitScope (ec);
1219                 }
1220
1221                 //
1222                 // Emits the opcodes necessary to load the instance of the captured
1223                 // variable in `li'
1224                 //
1225                 public void EmitCapturedVariableInstance (EmitContext ec, LocalInfo li,
1226                                                           AnonymousContainer am)
1227                 {
1228                         ILGenerator ig = ec.ig;
1229                         ScopeInfo si;
1230
1231                         if (li.Block.Toplevel == toplevel_owner){
1232                                 si = (ScopeInfo) scopes [li.Block.ID];
1233                                 si.EmitScopeInstance (ig);
1234                                 return;
1235                         }
1236
1237                         si = am.Scope;
1238                         ig.Emit (OpCodes.Ldarg_0);
1239                         if (si != null){
1240                                 if (am.IsIterator && (si.ScopeBlock.Toplevel == li.Block.Toplevel)) {
1241                                         return;
1242                                 }
1243
1244                                 while (si.ScopeBlock.ID != li.Block.ID){
1245                                         if (si.ParentLink != null)
1246                                                 ig.Emit (OpCodes.Ldfld, si.ParentLink);
1247                                         si = si.ParentScope;
1248                                         if (si == null) {
1249                                                 si = am.Scope;
1250                                                 Console.WriteLine ("Target: {0} {1}", li.Block.ID, li.Name);
1251                                                 while (si.ScopeBlock.ID != li.Block.ID){
1252                                                         Console.WriteLine ("Trying: {0}", si.ScopeBlock.ID);
1253                                                         si = si.ParentScope;
1254                                                 }
1255
1256                                                 throw new Exception (
1257                                                              String.Format ("Never found block {0} starting at {1} while looking up {2}",
1258                                                                             li.Block.ID, am.Scope.ScopeBlock.ID, li.Name));
1259                                         }
1260                                 }
1261                         }
1262                 }
1263
1264                 //
1265                 // Internal routine that loads the instance to reach parameter `name'
1266                 //
1267                 void EmitParameterInstance (EmitContext ec, string name)
1268                 {
1269                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1270                         if (cc != this){
1271                                 cc.EmitParameterInstance (ec, name);
1272                                 return;
1273                         }
1274
1275                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1276                         if (par_info != null){
1277                                 //
1278                                 // FIXME: implementing this.
1279                                 //
1280                         }
1281                         ILGenerator ig = ec.ig;
1282
1283                         ScopeInfo si;
1284
1285                         if (ec.CurrentBlock.Toplevel == toplevel_owner) {
1286                                 si = (ScopeInfo) scopes [toplevel_owner.ID];
1287                                 si.EmitScopeInstance (ig);
1288                         } else {
1289                                 si = ec.CurrentAnonymousMethod.Scope;
1290                                 ig.Emit (OpCodes.Ldarg_0);
1291                         }
1292
1293                         if (si != null){
1294                                 while (si.ParentLink != null) {
1295                                         ig.Emit (OpCodes.Ldfld, si.ParentLink);
1296                                         si = si.ParentScope;
1297                                 }
1298                         }
1299                 }
1300
1301                 //
1302                 // Emits the code necessary to load the parameter named `name' within
1303                 // an anonymous method.
1304                 //
1305                 public void EmitParameter (EmitContext ec, string name, bool leave_copy, bool prepared, ref LocalTemporary temp)
1306                 {
1307                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1308                         if (cc != this){
1309                                 cc.EmitParameter (ec, name, leave_copy, prepared, ref temp);
1310                                 return;
1311                         }
1312                         if (!prepared)
1313                                 EmitParameterInstance (ec, name);
1314                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1315                         if (par_info != null){
1316                                 //
1317                                 // FIXME: implementing this.
1318                                 //
1319                         }
1320                         ec.ig.Emit (OpCodes.Ldfld, par_info.FieldBuilder);
1321
1322                         if (leave_copy){
1323                                 ec.ig.Emit (OpCodes.Dup);
1324                                 temp = new LocalTemporary (par_info.FieldBuilder.FieldType);
1325                                 temp.Store (ec);
1326                         }
1327                 }
1328
1329                 //
1330                 // Implements the assignment of `source' to the paramenter named `name' within
1331                 // an anonymous method.
1332                 //
1333                 public void EmitAssignParameter (EmitContext ec, string name, Expression source, bool leave_copy, bool prepare_for_load, ref LocalTemporary temp)
1334                 {
1335                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1336                         if (cc != this){
1337                                 cc.EmitAssignParameter (ec, name, source, leave_copy, prepare_for_load, ref temp);
1338                                 return;
1339                         }
1340                         ILGenerator ig = ec.ig;
1341                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1342
1343                         EmitParameterInstance (ec, name);
1344                         if (prepare_for_load)
1345                                 ig.Emit (OpCodes.Dup);
1346                         source.Emit (ec);
1347                         if (leave_copy){
1348                                 ig.Emit (OpCodes.Dup);
1349                                 temp = new LocalTemporary (par_info.FieldBuilder.FieldType);
1350                                 temp.Store (ec);
1351                         }
1352                         ig.Emit (OpCodes.Stfld, par_info.FieldBuilder);
1353                         if (temp != null)
1354                                 temp.Emit (ec);
1355                 }
1356
1357                 //
1358                 // Emits the address for the parameter named `name' within
1359                 // an anonymous method.
1360                 //
1361                 public void EmitAddressOfParameter (EmitContext ec, string name)
1362                 {
1363                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1364                         if (cc != this){
1365                                 cc.EmitAddressOfParameter (ec, name);
1366                                 return;
1367                         }
1368                         EmitParameterInstance (ec, name);
1369                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1370                         ec.ig.Emit (OpCodes.Ldflda, par_info.FieldBuilder);
1371                 }
1372
1373                 //
1374                 // The following methods are only invoked on the host for the
1375                 // anonymous method.
1376                 //
1377                 public void EmitMethodHostInstance (EmitContext target, AnonymousContainer am)
1378                 {
1379                         ILGenerator ig = target.ig;
1380                         ScopeInfo si = am.Scope;
1381
1382                         AnonymousContainer container = am.ContainerAnonymousMethod;
1383
1384                         if ((si == null) || ((container != null) && (si == container.Scope))) {
1385                                 ig.Emit (OpCodes.Ldarg_0);
1386                                 return;
1387                         }
1388
1389                         si.EmitInitScope (target);
1390                         si.EmitScopeInstance (ig);
1391                 }
1392
1393                 public void RegisterCaptureContext ()
1394                 {
1395                         toplevel_owner.RegisterCaptureContext (this);
1396                 }
1397
1398                 //
1399                 // Returs true if `probe' is an ancestor of `scope' in the
1400                 // scope chain
1401                 //
1402                 bool IsAncestor (ScopeInfo probe, ScopeInfo scope)
1403                 {
1404                         for (Block b = scope.ScopeBlock.Parent; b != null; b = b.Parent){
1405                                 if (probe.ScopeBlock == b)
1406                                         return true;
1407                         }
1408                         return false;
1409                 }
1410
1411                 //
1412                 // Returns an ArrayList of ScopeInfos that enumerates all the ancestors
1413                 // of `scope' found in `scope_list'.
1414                 //
1415                 // The value returned is either a ScopeInfo or an Arraylist of ScopeInfos
1416                 //
1417                 object GetAncestorScopes (ScopeInfo scope, ScopeInfo [] scope_list)
1418                 {
1419                         object ancestors = null;
1420
1421                         for (int i = 0; i < scope_list.Length; i++){
1422                                 // Ignore the same scope
1423                                 if (scope_list [i] == scope)
1424                                         continue;
1425
1426                                 if (IsAncestor (scope_list [i], scope)){
1427                                         if (ancestors == null){
1428                                                 ancestors = scope_list [i];
1429                                                 continue;
1430                                         }
1431
1432                                         if (ancestors is ScopeInfo){
1433                                                 object old = ancestors;
1434                                                 ancestors = new ArrayList (4);
1435                                                 ((ArrayList)ancestors).Add (old);
1436                                         }
1437
1438                                         ((ArrayList)ancestors).Add (scope_list [i]);
1439                                 }
1440                         }
1441                         return ancestors;
1442                 }
1443
1444                 //
1445                 // Returns the immediate parent of `scope' from all the captured
1446                 // scopes found in `scope_list', or null if this is a toplevel scope.
1447                 //
1448                 ScopeInfo GetParentScope (ScopeInfo scope, ScopeInfo [] scope_list)
1449                 {
1450                         object ancestors = GetAncestorScopes (scope, scope_list);
1451                         if (ancestors == null)
1452                                 return null;
1453
1454                         // Single match, thats the parent.
1455                         if (ancestors is ScopeInfo)
1456                                 return (ScopeInfo) ancestors;
1457
1458                         ArrayList candidates = (ArrayList) ancestors;
1459                         ScopeInfo parent = (ScopeInfo) candidates [0];
1460                         for (int i = 1; i < candidates.Count; i++){
1461                                 if (IsAncestor (parent, (ScopeInfo) candidates [i]))
1462                                         parent = (ScopeInfo) candidates [i];
1463                         }
1464                         return parent;
1465                 }
1466
1467                 //
1468                 // Links all the scopes
1469                 //
1470                 bool linked;
1471                 public void LinkScopes ()
1472                 {
1473                         if (linked)
1474                                 return;
1475
1476                         linked = true;
1477                         if (ParentCaptureContext != null)
1478                                 ParentCaptureContext.LinkScopes ();
1479
1480                         int scope_count = scopes.Keys.Count;
1481                         ScopeInfo [] scope_list = new ScopeInfo [scope_count];
1482                         scopes.Values.CopyTo (scope_list, 0);
1483
1484                         for (int i = 0; i < scope_count; i++){
1485                                 ScopeInfo parent = GetParentScope (scope_list [i], scope_list);
1486
1487                                 if (parent == null){
1488                                         roots.Add (scope_list [i]);
1489                                         continue;
1490                                 }
1491
1492                                 scope_list [i].ParentScope = parent;
1493                                 parent.AddChild (scope_list [i]);
1494                         }
1495
1496                         //
1497                         // Link the roots to their parent containers if any.
1498                         //
1499                         if (ParentCaptureContext != null && roots.Count != 0){
1500                                 ScopeInfo one_root = (ScopeInfo) roots [0];
1501                                 bool found = false;
1502
1503                                 foreach (ScopeInfo a_parent_root in ParentCaptureContext.roots){
1504                                         if (!IsAncestor (a_parent_root, one_root))
1505                                                 continue;
1506
1507                                         found = true;
1508
1509                                         // Found, link all the roots to this root
1510                                         foreach (ScopeInfo root in roots){
1511                                                 root.ParentScope = a_parent_root;
1512                                                 a_parent_root.AddChild (root);
1513                                         }
1514                                         break;
1515                                 }
1516                                 if (!found){
1517                                         //
1518                                         // This is to catch a condition in which it is
1519                                         // not possible to determine the containing ScopeInfo
1520                                         // from an encapsulating CaptureContext
1521                                         //
1522                                         throw new Exception ("Internal compiler error: Did not find the parent for the root in the chain");
1523                                 }
1524                         }
1525                 }
1526         }
1527 }