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                                 return;
  87                         }
  88                         container.SetHaveAnonymousMethods (l, this);
  89                         block.SetHaveAnonymousMethods (l, this);
  90                 }
  91
  92                 protected AnonymousContainer (Parameters parameters, ToplevelBlock container,
  93                                               Location l):
  94                         this (parameters, container, new ToplevelBlock (container, parameters, l), l)
  95                 {
  96                 }
  97
  98                 public override Expression DoResolve (EmitContext ec)
  99                 {
 100                         //
 101                         // Set class type, set type
 102                         //
 103
 104                         eclass = ExprClass.Value;
 105
 106                         //
 107                         // This hack means `The type is not accessible
 108                         // anywhere', we depend on special conversion
 109                         // rules.
 110                         //
 111                         type = TypeManager.anonymous_method_type;
 112
 113                         return this;
 114                 }
 115
 116                 public void RegisterScope (ScopeInfo scope)
 117                 {
 118                         if (scopes_used.Contains (scope))
 119                                 return;
 120                         scopes_used.Add (scope);
 121                 }
 122
 123                 // Returns the deepest of two scopes
 124                 ScopeInfo Deepest (ScopeInfo a, ScopeInfo b)
 125                 {
 126                         ScopeInfo p;
 127
 128                         if (a == null)
 129                                 return b;
 130                         if (b == null)
 131                                 return a;
 132                         if (a == b)
 133                                 return a;
 134
 135                         //
 136                         // If they Scopes are on the same CaptureContext, we do the double
 137                         // checks just so if there is an invariant change in the future,
 138                         // we get the exception at the end
 139                         //
 140                         for (p = a; p != null; p = p.ParentScope)
 141                                 if (p == b)
 142                                         return a;
 143
 144                         for (p = b; p != null; p = p.ParentScope)
 145                                 if (p == a)
 146                                         return b;
 147
 148                         CaptureContext ca = a.CaptureContext;
 149                         CaptureContext cb = b.CaptureContext;
 150
 151                         for (CaptureContext c = ca; c != null; c = c.ParentCaptureContext)
 152                                 if (c == cb)
 153                                         return a;
 154
 155                         for (CaptureContext c = cb; c != null; c = c.ParentCaptureContext)
 156                                 if (c == ca)
 157                                         return b;
 158                         throw new Exception ("Should never be reached");
 159                 }
 160
 161                 //
 162                 // Determines the proper host for a method considering the
 163                 // scopes it references
 164                 //
 165                 public void ComputeMethodHost ()
 166                 {
 167                         if (computed_method_scope)
 168                                 return;
 169
 170                         method_scope = null;
 171                         int top = scopes_used.Count;
 172                         computed_method_scope = true;
 173
 174                         if (top == 0)
 175                                 return;
 176
 177                         method_scope = (ScopeInfo) scopes_used [0];
 178                         if (top == 1)
 179                                 return;
 180
 181                         for (int i = 1; i < top; i++)
 182                                 method_scope = Deepest (method_scope, (ScopeInfo) scopes_used [i]);
 183                 }
 184
 185                 public ScopeInfo Scope {
 186                         get {
 187                                 if (computed_method_scope)
 188                                         return method_scope;
 189
 190                                 //
 191                                 // This means that ComputeMethodHost is not being called, most
 192                                 // likely by someone who overwrote the CreateMethodHost method
 193                                 //
 194                                 throw new Exception ("Internal error, AnonymousContainer.Scope is being used before its container is computed");
 195                         }
 196                 }
 197
 198
 199                 protected abstract bool CreateMethodHost (EmitContext ec);
 200
 201                 public abstract void CreateScopeType (EmitContext ec, ScopeInfo scope);
 202
 203                 public abstract Iterator Iterator {
 204                         get;
 205                 }
 206
 207                 public abstract bool IsIterator {
 208                         get;
 209                 }
 210         }
 211
 212         public class AnonymousMethod : AnonymousContainer
 213         {
 214                 TypeContainer host;
 215
 216                 public AnonymousMethod (TypeContainer host, Parameters parameters, ToplevelBlock container,
 217                                         ToplevelBlock block, Location l)
 218                         : base (parameters, container, block, l)
 219                 {
 220                         this.host = host;
 221                 }
 222
 223                 public override Iterator Iterator {
 224                         get { return null; }
 225                 }
 226
 227                 public override bool IsIterator {
 228                         get { return false; }
 229                 }
 230
 231                 public override void Emit (EmitContext ec)
 232                 {
 233                         // nothing, as we only exist to not do anything.
 234                 }
 235
 236                 //
 237                 // Creates the host for the anonymous method
 238                 //
 239                 protected override bool CreateMethodHost (EmitContext ec)
 240                 {
 241                         ComputeMethodHost ();
 242
 243                         //
 244                         // Crude hack follows: we replace the TypeBuilder during the
 245                         // definition to get the method hosted in the right class
 246                         //
 247                         TypeBuilder current_type = ec.TypeContainer.TypeBuilder;
 248                         TypeBuilder type_host = (Scope == null ) ? current_type : Scope.ScopeTypeBuilder;
 249
 250                         if (current_type == null)
 251                                 throw new Exception ("The current_type is null");
 252
 253                         if (type_host == null)
 254                                 throw new Exception (String.Format ("Type host is null, method_host is {0}", Scope == null ? "null" : "Not null"));
 255
 256                         if (current_type != type_host)
 257                                 method_modifiers = Modifiers.INTERNAL;
 258
 259                         if (current_type == type_host && ec.IsStatic){
 260                                 method_modifiers |= Modifiers.STATIC;
 261                                 current_type = null;
 262                         }
 263
 264                         string name = "<#AnonymousMethod>" + anonymous_method_count++;
 265                         MemberName member_name;
 266
 267                         GenericMethod generic_method = null;
 268                         if (TypeParameters != null) {
 269                                 TypeArguments args = new TypeArguments (loc);
 270                                 foreach (string t in TypeParameters)
 271                                         args.Add (new SimpleName (t, loc));
 272
 273                                 member_name = new MemberName (name, args, loc);
 274
 275                                 generic_method = new GenericMethod (
 276                                         ec.DeclContainer.NamespaceEntry,
 277                                         (TypeContainer) ec.TypeContainer, member_name,
 278                                         new TypeExpression (invoke_mb.ReturnType, loc),
 279                                         Parameters);
 280
 281                                 generic_method.SetParameterInfo (null);
 282                         } else
 283                                 member_name = new MemberName (name, loc);
 284
 285                         method = new Method (
 286                                 (TypeContainer) ec.TypeContainer, generic_method,
 287                                 new TypeExpression (invoke_mb.ReturnType, loc),
 288                                 method_modifiers, false, member_name, Parameters, null);
 289                         method.Block = Block;
 290
 291                         //
 292                         // Swap the TypeBuilder while we define the method, then restore
 293                         //
 294                         if (current_type != null)
 295                                 ec.TypeContainer.TypeBuilder = type_host;
 296                         bool res = method.Define ();
 297                         if (current_type != null)
 298                                 ec.TypeContainer.TypeBuilder = current_type;
 299
 300                         return res;
 301                 }
 302
 303                 void Error_ParameterMismatch (Type t)
 304                 {
 305                         Report.Error (1661, loc, "Anonymous method could not be converted to delegate `" +
 306                                       "{0}' since there is a parameter mismatch", TypeManager.CSharpName (t));
 307                 }
 308
 309                 public bool ImplicitStandardConversionExists (Type delegate_type)
 310                 {
 311                         if (Parameters == null)
 312                                 return true;
 313
 314                         MethodGroupExpr invoke_mg = Delegate.GetInvokeMethod (host.TypeBuilder, delegate_type, loc);
 315                         invoke_mb = (MethodInfo) invoke_mg.Methods [0];
 316                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 317
 318                         if (Parameters.Count != invoke_pd.Count)
 319                                 return false;
 320
 321                         for (int i = 0; i < Parameters.Count; ++i) {
 322                                 if (invoke_pd.ParameterType (i) != Parameters.ParameterType (i))
 323                                         return false;
 324                         }
 325                         return true;
 326                 }
 327
 328                 //
 329                 // Returns true if this anonymous method can be implicitly
 330                 // converted to the delegate type `delegate_type'
 331                 //
 332                 public Expression Compatible (EmitContext ec, Type delegate_type)
 333                 {
 334                         //
 335                         // At this point its the first time we know the return type that is
 336                         // needed for the anonymous method.  We create the method here.
 337                         //
 338
 339                         MethodGroupExpr invoke_mg = Delegate.GetInvokeMethod (ec.ContainerType, delegate_type, loc);
 340                         invoke_mb = (MethodInfo) invoke_mg.Methods [0];
 341                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 342
 343                         if (delegate_type.IsGenericType) {
 344                                 Type def = delegate_type.GetGenericTypeDefinition ();
 345
 346                                 if (def != delegate_type) {
 347                                         Type[] tparam = TypeManager.GetTypeArguments (def);
 348
 349                                         TypeArguments = TypeManager.GetTypeArguments (delegate_type);
 350                                         TypeParameters = new string [tparam.Length];
 351                                         for (int i = 0; i < tparam.Length; i++)
 352                                                 TypeParameters [i] = tparam [i].Name;
 353                                 }
 354                         }
 355
 356                         if (Parameters == null) {
 357                                 //
 358                                 // We provide a set of inaccessible parameters
 359                                 //
 360                                 Parameter [] fixedpars = new Parameter [invoke_pd.Count];
 361
 362                                 for (int i = 0; i < invoke_pd.Count; i++){
 363                                         fixedpars [i] = new Parameter (
 364                                                 invoke_pd.ParameterType (i),
 365                                                 "+" + i, invoke_pd.ParameterModifier (i), null, loc);
 366                                 }
 367
 368                                 Parameters = new Parameters (fixedpars);
 369                         } else {
 370                                 if (Parameters.Count != invoke_pd.Count) {
 371                                         Report.SymbolRelatedToPreviousError (delegate_type);
 372                                         Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
 373                                                 TypeManager.CSharpName (delegate_type), Parameters.Count.ToString ());
 374                                         Error_ParameterMismatch (delegate_type);
 375                                         return null;
 376                                 }
 377
 378                                 for (int i = 0; i < Parameters.Count; ++i) {
 379                                         Parameter.Modifier p_mod = invoke_pd.ParameterModifier (i);
 380                                         if (Parameters.ParameterModifier (i) != p_mod && p_mod != Parameter.Modifier.PARAMS) {
 381                                                 if (p_mod == Parameter.Modifier.NONE)
 382                                                         Report.Error (1677, loc, "Parameter `{0}' should not be declared with the `{1}' keyword",
 383                                                                 (i + 1).ToString (), Parameter.GetModifierSignature (Parameters.ParameterModifier (i)));
 384                                                 else
 385                                                         Report.Error (1676, loc, "Parameter `{0}' must be declared with the `{1}' keyword",
 386                                                                 (i+1).ToString (), Parameter.GetModifierSignature (p_mod));
 387                                                 Error_ParameterMismatch (delegate_type);
 388                                                 return null;
 389                                         }
 390
 391                                         if (invoke_pd.ParameterType (i) != Parameters.ParameterType (i)) {
 392                                                 Report.Error (1678, loc, "Parameter `{0}' is declared as type `{1}' but should be `{2}'",
 393                                                         (i+1).ToString (),
 394                                                         TypeManager.CSharpName (Parameters.ParameterType (i)),
 395                                                         TypeManager.CSharpName (invoke_pd.ParameterType (i)));
 396                                                 Error_ParameterMismatch (delegate_type);
 397                                                 return null;
 398                                         }
 399                                 }
 400                         }
 401
 402                         //
 403                         // Second: the return type of the delegate must be compatible with
 404                         // the anonymous type.   Instead of doing a pass to examine the block
 405                         // we satisfy the rule by setting the return type on the EmitContext
 406                         // to be the delegate type return type.
 407                         //
 408
 409                         //MethodBuilder builder = method_data.MethodBuilder;
 410                         //ILGenerator ig = builder.GetILGenerator ();
 411
 412                         aec = new EmitContext (ec.ResolveContext,
 413                                 ec.TypeContainer, ec.DeclContainer, loc, null,
 414                                 invoke_mb.ReturnType,
 415                                 /* REVIEW */ (ec.InIterator ? Modifiers.METHOD_YIELDS : 0) |
 416                                 (ec.InUnsafe ? Modifiers.UNSAFE : 0) |
 417                                 (ec.IsStatic ? Modifiers.STATIC : 0),
 418                                 /* No constructor */ false);
 419
 420                         aec.CurrentAnonymousMethod = this;
 421                         ContainerAnonymousMethod = ec.CurrentAnonymousMethod;
 422                         ContainingBlock = ec.CurrentBlock;
 423
 424                         if (aec.ResolveTopBlock (ec, Block, Parameters, null, out unreachable))
 425                                 return new AnonymousDelegate (this, delegate_type, loc).Resolve (ec);
 426
 427                         return null;
 428                 }
 429
 430                 public override Expression DoResolve (EmitContext ec)
 431                 {
 432                         if (!ec.IsAnonymousMethodAllowed) {
 433                                 Report.Error (1706, loc, "Anonymous methods are not allowed in the attribute declaration");
 434                                 return null;
 435                         }
 436
 437                         if (Parameters != null && !Parameters.Resolve (ec)) {
 438                                 return null;
 439                         }
 440
 441                         return base.DoResolve (ec);
 442                 }
 443
 444
 445                 public override string ExprClassName {
 446                         get {
 447                                 return "anonymous method";
 448                         }
 449                 }
 450
 451                 public MethodInfo GetMethodBuilder ()
 452                 {
 453                         MethodInfo builder = method.MethodBuilder;
 454                         if (TypeArguments != null)
 455                                 return builder.MakeGenericMethod (TypeArguments);
 456                         else
 457                                 return builder;
 458                 }
 459
 460                 public override string GetSignatureForError ()
 461                 {
 462                         string s = TypeManager.CSharpSignature (invoke_mb);
 463                         return s.Substring (0, s.IndexOf (".Invoke("));
 464                 }
 465
 466                 public bool EmitMethod (EmitContext ec)
 467                 {
 468                         if (!CreateMethodHost (ec))
 469                                 return false;
 470
 471                         MethodBuilder builder = method.MethodBuilder;
 472                         ILGenerator ig = builder.GetILGenerator ();
 473                         aec.ig = ig;
 474
 475                         Parameters.ApplyAttributes (builder);
 476
 477                         //
 478                         // Adjust based on the computed state of the
 479                         // method from CreateMethodHost
 480
 481                         aec.MethodIsStatic = (method_modifiers & Modifiers.STATIC) != 0;
 482
 483                         aec.EmitMeta (Block);
 484                         aec.EmitResolvedTopBlock (Block, unreachable);
 485                         return true;
 486                 }
 487
 488                 public override void CreateScopeType (EmitContext ec, ScopeInfo scope)
 489                 {
 490                         TypeBuilder container = ec.TypeContainer.TypeBuilder;
 491                         string name = String.Format ("<>AnonHelp<{0}>", scope.id);
 492
 493                         scope.ScopeTypeBuilder = container.DefineNestedType (
 494                                 name, TypeAttributes.AutoLayout | TypeAttributes.Class |
 495                                 TypeAttributes.NestedAssembly, TypeManager.object_type, null);
 496
 497                         Type [] constructor_types = Type.EmptyTypes;
 498                         ConstructorBuilder ctor = scope.ScopeTypeBuilder.DefineConstructor (
 499                                 MethodAttributes.Public | MethodAttributes.HideBySig |
 500                                 MethodAttributes.SpecialName | MethodAttributes.RTSpecialName,
 501                                 CallingConventions.HasThis, constructor_types);
 502                         TypeManager.RegisterMethod (ctor, Parameters.EmptyReadOnlyParameters);
 503
 504                         ILGenerator cig = ctor.GetILGenerator ();
 505                         cig.Emit (OpCodes.Ldarg_0);
 506                         cig.Emit (OpCodes.Call, TypeManager.object_ctor);
 507                         cig.Emit (OpCodes.Ret);
 508
 509                         if (ec.TypeContainer.IsGeneric) {
 510                                 TypeParameter[] tparam = ec.TypeContainer.TypeParameters;
 511                                 string[] names = new string [tparam.Length];
 512                                 Type[] types = new Type [tparam.Length];
 513
 514                                 for (int i = 0; i < names.Length; i++) {
 515                                         names [i] = tparam [i].Name;
 516                                         types [i] = tparam [i].Type;
 517                                 }
 518
 519                                 scope.ScopeTypeBuilder.DefineGenericParameters (names);
 520                                 scope.ScopeTypeBuilder.GetGenericTypeDefinition ();
 521
 522                                 scope.ScopeType = scope.ScopeTypeBuilder.MakeGenericType (types);
 523                         } else
 524                                 scope.ScopeType = scope.ScopeTypeBuilder;
 525
 526
 527                         if (ec.TypeContainer.IsGeneric)
 528                                 scope.ScopeConstructor = TypeBuilder.GetConstructor (
 529                                         scope.ScopeType, ctor);
 530                         else
 531                                 scope.ScopeConstructor = ctor;
 532                 }
 533
 534                 public static void Error_AddressOfCapturedVar (string name, Location loc)
 535                 {
 536                         Report.Error (1686, loc,
 537                                 "Local variable `{0}' or its members cannot have their address taken and be used inside an anonymous method block",
 538                                 name);
 539                 }
 540         }
 541
 542         //
 543         // This will emit the code for the delegate, as well delegate creation on the host
 544         //
 545         public class AnonymousDelegate : DelegateCreation {
 546                 AnonymousMethod am;
 547
 548                 public AnonymousDelegate (AnonymousMethod am, Type target_type, Location l)
 549                 {
 550                         type = target_type;
 551                         loc = l;
 552                         this.am = am;
 553                 }
 554
 555                 public override Expression DoResolve (EmitContext ec)
 556                 {
 557                         eclass = ExprClass.Value;
 558
 559                         return this;
 560                 }
 561
 562                 public override void Emit (EmitContext ec)
 563                 {
 564                         if (!am.EmitMethod (ec))
 565                                 return;
 566
 567                         //
 568                         // Now emit the delegate creation.
 569                         //
 570                         if ((am.method.ModFlags & Modifiers.STATIC) == 0)
 571                                 delegate_instance_expression = new AnonymousInstance (am);
 572
 573                         Expression ml = Expression.MemberLookup (ec.ContainerType, type, ".ctor", loc);
 574                         constructor_method = ((MethodGroupExpr) ml).Methods [0];
 575                         delegate_method = am.GetMethodBuilder ();
 576                         base.Emit (ec);
 577                 }
 578
 579                 class AnonymousInstance : Expression {
 580                         AnonymousMethod am;
 581
 582                         public AnonymousInstance (AnonymousMethod am)
 583                         {
 584                                 this.am = am;
 585                                 eclass = ExprClass.Value;
 586                         }
 587
 588                         public override Expression DoResolve (EmitContext ec)
 589                         {
 590                                 return this;
 591                         }
 592
 593                         public override void Emit (EmitContext ec)
 594                         {
 595                                 am.aec.EmitMethodHostInstance (ec, am);
 596                         }
 597                 }
 598         }
 599
 600         class CapturedParameter {
 601                 public Type Type;
 602                 public FieldBuilder FieldBuilder;
 603                 public int Idx;
 604
 605                 public CapturedParameter (Type type, int idx)
 606                 {
 607                         Type = type;
 608                         Idx = idx;
 609                 }
 610         }
 611
 612         //
 613         // Here we cluster all the variables captured on a given scope, we also
 614         // keep some extra information that might be required on each scope.
 615         //
 616         public class ScopeInfo {
 617                 public CaptureContext CaptureContext;
 618                 public ScopeInfo ParentScope;
 619                 public Block ScopeBlock;
 620                 public bool NeedThis = false;
 621                 public bool HostsParameters = false;
 622
 623                 // For tracking the number of scopes created.
 624                 public int id;
 625                 static int count;
 626                 bool inited = false;
 627
 628                 ArrayList locals = new ArrayList ();
 629                 ArrayList children = new ArrayList ();
 630
 631                 //
 632                 // The types and fields generated
 633                 //
 634                 public TypeBuilder ScopeTypeBuilder;
 635                 public Type ScopeType;
 636                 public ConstructorInfo ScopeConstructor;
 637                 public FieldBuilder THIS;
 638                 public FieldBuilder ParentLink;
 639
 640                 //
 641                 // Points to the object of type `ScopeTypeBuilder' that
 642                 // holds the data for the scope
 643                 //
 644                 LocalBuilder scope_instance;
 645
 646                 public ScopeInfo (CaptureContext cc, Block b)
 647                 {
 648                         CaptureContext = cc;
 649                         ScopeBlock = b;
 650                         id = count++;
 651
 652                         cc.RegisterCaptureContext ();
 653                 }
 654
 655                 public void AddLocal (LocalInfo li)
 656                 {
 657                         if (locals.Contains (li))
 658                                 return;
 659
 660                         locals.Add (li);
 661 }
 662
 663                 public bool IsCaptured (LocalInfo li)
 664                 {
 665                         return locals.Contains (li);
 666                 }
 667
 668                 internal void AddChild (ScopeInfo si)
 669                 {
 670                         if (children.Contains (si))
 671                                 return;
 672
 673                         //
 674                         // If any of the current children should be a children of `si', move them there
 675                         //
 676                         ArrayList move_queue = null;
 677                         foreach (ScopeInfo child in children){
 678                                 if (child.ScopeBlock.IsChildOf (si.ScopeBlock)){
 679                                         if (move_queue == null)
 680                                                 move_queue = new ArrayList ();
 681                                         move_queue.Add (child);
 682                                         child.ParentScope = si;
 683                                         si.AddChild (child);
 684                                 }
 685                         }
 686
 687                         children.Add (si);
 688
 689                         if (move_queue != null){
 690                                 foreach (ScopeInfo child in move_queue){
 691                                         children.Remove (child);
 692                                 }
 693                         }
 694                 }
 695
 696                 static int indent = 0;
 697
 698                 void Pad ()
 699                 {
 700                         for (int i = 0; i < indent; i++)
 701                                 Console.Write ("    ");
 702                 }
 703
 704                 void EmitDebug ()
 705                 {
 706                         //Console.WriteLine (Environment.StackTrace);
 707                         Pad ();
 708                         Console.WriteLine ("START");
 709                         indent++;
 710                         Pad ();
 711                         Console.WriteLine ("NeedThis=" + NeedThis);
 712                         foreach (LocalInfo li in locals){
 713                                 Pad ();
 714                                 Console.WriteLine ("var {0}", MakeFieldName (li.Name));
 715                         }
 716
 717                         foreach (ScopeInfo si in children)
 718                                 si.EmitDebug ();
 719                         indent--;
 720                         Pad ();
 721                         Console.WriteLine ("END");
 722                 }
 723
 724                 public string MakeHelperName ()
 725                 {
 726                         return String.Format ("<>AnonHelp<{0}>", id);
 727                 }
 728
 729                 private string MakeFieldName (string local_name)
 730                 {
 731                         return "<" + id + ":" + local_name + ">";
 732                 }
 733
 734                 public void EmitScopeType (EmitContext ec)
 735                 {
 736                         // EmitDebug ();
 737
 738                         if (ScopeTypeBuilder != null)
 739                                 return;
 740
 741                         Type container;
 742                         if (ec.TypeContainer.CurrentType != null)
 743                                 container = ec.TypeContainer.CurrentType;
 744                         else
 745                                 container = ec.TypeContainer.TypeBuilder;
 746
 747                         CaptureContext.Host.CreateScopeType (ec, this);
 748
 749                         if (NeedThis)
 750                                 THIS = ScopeTypeBuilder.DefineField ("<>THIS", container, FieldAttributes.Assembly);
 751
 752                         if (ParentScope != null){
 753                                 if (ParentScope.ScopeTypeBuilder == null){
 754                                         throw new Exception (String.Format ("My parent has not been initialized {0} and {1}", ParentScope, this));
 755                                 }
 756
 757                                 if (ParentScope.ScopeTypeBuilder != ScopeTypeBuilder)
 758                                         ParentLink = ScopeTypeBuilder.DefineField (
 759                                                 "<>parent", ParentScope.ScopeType, FieldAttributes.Assembly);
 760                         }
 761
 762                         if (NeedThis && ParentScope != null)
 763                                 throw new Exception ("I was not expecting THIS && having a parent");
 764
 765                         foreach (LocalInfo info in locals)
 766                                 info.FieldBuilder = ScopeTypeBuilder.DefineField (
 767                                         MakeFieldName (info.Name), info.VariableType, FieldAttributes.Assembly);
 768
 769                         if (HostsParameters){
 770                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 771
 772                                 foreach (DictionaryEntry de in captured_parameters){
 773                                         string name = (string) de.Key;
 774                                         CapturedParameter cp = (CapturedParameter) de.Value;
 775                                         FieldBuilder fb;
 776
 777                                         fb = ScopeTypeBuilder.DefineField ("<p:" + name + ">", cp.Type, FieldAttributes.Assembly);
 778                                         cp.FieldBuilder = fb;
 779                                 }
 780                         }
 781
 782                         foreach (ScopeInfo si in children){
 783                                 si.EmitScopeType (ec);
 784                         }
 785                 }
 786
 787                 public void CloseTypes ()
 788                 {
 789                         RootContext.RegisterCompilerGeneratedType (ScopeTypeBuilder);
 790                         foreach (ScopeInfo si in children)
 791                                 si.CloseTypes ();
 792                 }
 793
 794                 //
 795                 // Emits the initialization code for the scope
 796                 //
 797                 public void EmitInitScope (EmitContext ec)
 798                 {
 799                         ILGenerator ig = ec.ig;
 800
 801                         if (inited)
 802                                 return;
 803
 804                         if (ScopeConstructor == null)
 805                                 throw new Exception ("ScopeConstructor is null for" + this.ToString ());
 806
 807                         if (!CaptureContext.Host.IsIterator) {
 808                                 scope_instance = ig.DeclareLocal (ScopeType);
 809                                 ig.Emit (OpCodes.Newobj, ScopeConstructor);
 810                                 ig.Emit (OpCodes.Stloc, scope_instance);
 811                         }
 812
 813                         if (THIS != null){
 814                                 if (CaptureContext.Host.IsIterator) {
 815                                         ig.Emit (OpCodes.Ldarg_0);
 816                                         ig.Emit (OpCodes.Ldarg_1);
 817                                 } else {
 818                                         ig.Emit (OpCodes.Ldloc, scope_instance);
 819                                         ig.Emit (OpCodes.Ldarg_0);
 820                                 }
 821                                 ig.Emit (OpCodes.Stfld, THIS);
 822                         }
 823
 824                         //
 825                         // Copy the parameter values, if any
 826                         //
 827                         int extra = ec.IsStatic ? 0 : 1;
 828                         if (CaptureContext.Host.IsIterator)
 829                                 extra++;
 830                         if (HostsParameters){
 831                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 832
 833                                 foreach (DictionaryEntry de in captured_parameters){
 834                                         CapturedParameter cp = (CapturedParameter) de.Value;
 835
 836                                         EmitScopeInstance (ig);
 837                                         ParameterReference.EmitLdArg (ig, cp.Idx + extra);
 838                                         ig.Emit (OpCodes.Stfld, cp.FieldBuilder);
 839                                 }
 840                         }
 841
 842                         if (ParentScope != null){
 843                                 if (!ParentScope.inited)
 844                                         ParentScope.EmitInitScope (ec);
 845
 846                                 if (ParentScope.ScopeTypeBuilder != ScopeTypeBuilder) {
 847                                         //
 848                                         // Only emit initialization in our capturecontext world
 849                                         //
 850                                         if (ParentScope.CaptureContext == CaptureContext){
 851                                                 EmitScopeInstance (ig);
 852                                                 ParentScope.EmitScopeInstance (ig);
 853                                                 ig.Emit (OpCodes.Stfld, ParentLink);
 854                                         } else {
 855                                                 EmitScopeInstance (ig);
 856                                                 ig.Emit (OpCodes.Ldarg_0);
 857                                                 ig.Emit (OpCodes.Stfld, ParentLink);
 858                                         }
 859                                 }
 860                         }
 861                         inited = true;
 862                 }
 863
 864                 public void EmitScopeInstance (ILGenerator ig)
 865                 {
 866                         if (CaptureContext.Host.IsIterator)
 867                                 ig.Emit (OpCodes.Ldarg_0);
 868                         else {
 869                                 if (scope_instance == null){
 870                                         //
 871                                         // This is needed if someone overwrites the Emit method
 872                                         // of Statement and manually calls Block.Emit without
 873                                         // this snippet first:
 874                                         //
 875                                         //   ec.EmitScopeInitFromBlock (The_Block);
 876                                         //   The_Block.Emit (ec);
 877                                         //
 878
 879                                         Console.WriteLine (
 880                                                 "The scope_instance has not been emitted, this typically means\n" +
 881                                                 "that inside the compiler someone is calling Block.Emit without\n" +
 882                                                 "first calling EmitScopeInitFromBlock for the block.  See compiler" +
 883                                                 "source code for an explanation");
 884                                         throw new Exception ("Internal compiler error");
 885
 886                                 }
 887                                 ig.Emit (OpCodes.Ldloc, scope_instance);
 888                         }
 889                 }
 890
 891                 public static void CheckCycles (string msg, ScopeInfo s)
 892                 {
 893                         ArrayList l = new ArrayList ();
 894                         int n = 0;
 895
 896                         for (ScopeInfo p = s; p != null; p = p.ParentScope,n++){
 897                                 if (l.Contains (p)){
 898                                         Console.WriteLine ("Loop detected {0} in {1}", n, msg);
 899                                         throw new Exception ();
 900                                 }
 901                                 l.Add (p);
 902                         }
 903                 }
 904
 905                 static void DoPath (StringBuilder sb, ScopeInfo start)
 906                 {
 907                         CheckCycles ("print", start);
 908
 909                         if (start.ParentScope != null){
 910                                 DoPath (sb, start.ParentScope);
 911                                 sb.Append (", ");
 912                         }
 913                         sb.Append ((start.id).ToString ());
 914                 }
 915
 916                 public override string ToString ()
 917                 {
 918                         StringBuilder sb = new StringBuilder ();
 919
 920                         sb.Append ("{");
 921                         if (CaptureContext != null){
 922                                 sb.Append (CaptureContext.ToString ());
 923                                 sb.Append (":");
 924                         }
 925
 926                         DoPath (sb, this);
 927                         sb.Append ("}");
 928
 929                         return sb.ToString ();
 930                 }
 931         }
 932
 933         //
 934         // CaptureContext objects are created on demand if a method has
 935         // anonymous methods and kept on the ToplevelBlock.
 936         //
 937         // If they exist, all ToplevelBlocks in the containing block are
 938         // linked together (children pointing to their parents).
 939         //
 940         public class CaptureContext {
 941                 public static int count;
 942                 public int cc_id;
 943                 public Location loc;
 944
 945                 //
 946                 // Points to the toplevel block that owns this CaptureContext
 947                 //
 948                 ToplevelBlock toplevel_owner;
 949
 950                 //
 951                 // All the scopes we capture
 952                 //
 953                 Hashtable scopes = new Hashtable ();
 954
 955                 //
 956                 // All the root scopes
 957                 //
 958                 ArrayList roots = new ArrayList ();
 959
 960                 bool have_captured_vars = false;
 961                 bool referenced_this = false;
 962
 963                 //
 964                 // Captured fields
 965                 //
 966                 Hashtable captured_fields = new Hashtable ();
 967                 Hashtable captured_variables = new Hashtable ();
 968                 public Hashtable captured_parameters = new Hashtable ();
 969                 public AnonymousContainer Host;
 970
 971                 public CaptureContext (ToplevelBlock toplevel_owner, Location loc,
 972                                        AnonymousContainer host)
 973                 {
 974                         cc_id = count++;
 975                         this.toplevel_owner = toplevel_owner;
 976                         this.loc = loc;
 977
 978                         if (host != null)
 979                                 Host = host;
 980                 }
 981
 982                 void DoPath (StringBuilder sb, CaptureContext cc)
 983                 {
 984                         if (cc.ParentCaptureContext != null){
 985                                 DoPath (sb, cc.ParentCaptureContext);
 986                                 sb.Append (".");
 987                         }
 988                         sb.Append (cc.cc_id.ToString ());
 989                 }
 990
 991                 public void ReParent (ToplevelBlock new_toplevel, AnonymousContainer new_host)
 992                 {
 993                         toplevel_owner = new_toplevel;
 994                         Host = new_host;
 995
 996                         for (CaptureContext cc = ParentCaptureContext; cc != null;
 997                              cc = cc.ParentCaptureContext) {
 998                                 cc.Host = new_host;
 999                         }
1000                 }
1001
1002                 public override string ToString ()
1003                 {
1004                         StringBuilder sb = new StringBuilder ();
1005                         sb.Append ("[");
1006                         DoPath (sb, this);
1007                         sb.Append ("]");
1008                         return sb.ToString ();
1009                 }
1010
1011                 public ToplevelBlock ParentToplevel {
1012                         get {
1013                                 return toplevel_owner.Container;
1014                         }
1015                 }
1016
1017                 public CaptureContext ParentCaptureContext {
1018                         get {
1019                                 ToplevelBlock parent = ParentToplevel;
1020
1021                                 return (parent == null) ? null : parent.CaptureContext;
1022                         }
1023                 }
1024
1025                 ScopeInfo GetScopeForBlock (Block block)
1026                 {
1027                         ScopeInfo si = (ScopeInfo) scopes [block.ID];
1028                         if (si != null)
1029                                 return si;
1030                         si = new ScopeInfo (this, block);
1031                         scopes [block.ID] = si;
1032                         return si;
1033                 }
1034
1035                 public void AddLocal (AnonymousContainer am, LocalInfo li)
1036                 {
1037                         if (li.Block.Toplevel != toplevel_owner){
1038                                 ParentCaptureContext.AddLocal (am, li);
1039                                 return;
1040                         }
1041                         ScopeInfo scope = GetScopeForBlock (li.Block);
1042
1043                         //
1044                         // Adjust the owner
1045                         //
1046                         if (Host != null)
1047                                 Host.RegisterScope (scope);
1048
1049                         //
1050                         // Adjust the user
1051                         //
1052                         am.RegisterScope (scope);
1053
1054                         if (captured_variables [li] != null)
1055                                 return;
1056
1057                         have_captured_vars = true;
1058                         captured_variables [li] = li;
1059                         scope.AddLocal (li);
1060                 }
1061
1062                 //
1063                 // Retursn the CaptureContext for the block that defines the parameter `name'
1064                 //
1065                 static CaptureContext _ContextForParameter (ToplevelBlock current, string name)
1066                 {
1067                         ToplevelBlock container = current.Container;
1068                         if (container != null){
1069                                 CaptureContext cc = _ContextForParameter (container, name);
1070                                 if (cc != null)
1071                                         return cc;
1072                         }
1073                         if (current.IsParameterReference (name))
1074                                 return current.ToplevelBlockCaptureContext;
1075                         return null;
1076                 }
1077
1078                 static CaptureContext ContextForParameter (ToplevelBlock current, string name)
1079                 {
1080                         CaptureContext cc = _ContextForParameter (current, name);
1081                         if (cc == null)
1082                                 throw new Exception (String.Format ("request for parameteter {0} failed: not found", name));
1083                         return cc;
1084                 }
1085
1086                 //
1087                 // Records the captured parameter at the appropriate CaptureContext
1088                 //
1089                 public void AddParameter (EmitContext ec, AnonymousContainer am,
1090                                           string name, Type t, int idx)
1091                 {
1092                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1093
1094                         cc.AddParameterToContext (am, name, t, idx);
1095                 }
1096
1097                 //
1098                 // Records the parameters in the context
1099                 //
1100                 public void AddParameterToContext (AnonymousContainer am, string name, Type t, int idx)
1101                 {
1102                         if (captured_parameters == null)
1103                                 captured_parameters = new Hashtable ();
1104                         if (captured_parameters [name] == null)
1105                                 captured_parameters [name] = new CapturedParameter (t, idx);
1106
1107                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1108                         scope.HostsParameters = true;
1109                         am.RegisterScope (scope);
1110                 }
1111
1112                 //
1113                 // Captured fields are only recorded on the topmost CaptureContext, because that
1114                 // one is the one linked to the owner of instance fields
1115                 //
1116                 public void AddField (EmitContext ec, AnonymousContainer am, FieldExpr fe)
1117                 {
1118                         if (fe.FieldInfo.IsStatic)
1119                                 throw new Exception ("Attempt to register a static field as a captured field");
1120                         CaptureContext parent = ParentCaptureContext;
1121                         if (parent != null) {
1122                                 parent.AddField (ec, am, fe);
1123                                 return;
1124                         }
1125
1126                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1127                         am.RegisterScope (scope);
1128                 }
1129
1130                 public void CaptureThis (AnonymousContainer am)
1131                 {
1132                         if (am == null)
1133                                 throw new Exception ("Internal Compiler error: Capturethis called with a null method");
1134                         CaptureContext parent = ParentCaptureContext;
1135                         if (parent != null) {
1136                                 parent.CaptureThis (am);
1137                                 return;
1138                         }
1139                         referenced_this = true;
1140
1141                         ScopeInfo scope = GetScopeForBlock (toplevel_owner);
1142                         am.RegisterScope (scope);
1143                 }
1144
1145                 public bool HaveCapturedVariables {
1146                         get {
1147                                 return have_captured_vars;
1148                         }
1149                 }
1150
1151                 public bool HaveCapturedFields {
1152                         get {
1153                                 CaptureContext parent = ParentCaptureContext;
1154                                 if (parent != null)
1155                                         return parent.HaveCapturedFields;
1156                                 return captured_fields.Count > 0;
1157                         }
1158                 }
1159
1160                 public bool IsCaptured (LocalInfo local)
1161                 {
1162                         foreach (ScopeInfo si in scopes.Values){
1163                                 if (si.IsCaptured (local))
1164                                         return true;
1165                         }
1166                         return false;
1167                 }
1168
1169                 //
1170                 // Returns whether the parameter is captured
1171                 //
1172                 public bool IsParameterCaptured (string name)
1173                 {
1174                         if (ParentCaptureContext != null && ParentCaptureContext.IsParameterCaptured (name))
1175                                 return true;
1176
1177                         if (captured_parameters != null)
1178                                 return captured_parameters [name] != null;
1179                         return false;
1180                 }
1181
1182                 public void EmitAnonymousHelperClasses (EmitContext ec)
1183                 {
1184                         if (roots.Count != 0){
1185                                 foreach (ScopeInfo root in roots){
1186                                         //
1187                                         // FIXME: We really should do this in a per-ScopeInfo
1188                                         // basis, instead of having the NeedThis applied to
1189                                         // all of the roots.
1190                                         //
1191                                         root.NeedThis = HaveCapturedFields || referenced_this;
1192
1193                                         root.EmitScopeType (ec);
1194                                 }
1195                         }
1196                 }
1197
1198                 public void CloseAnonymousHelperClasses ()
1199                 {
1200                         if (roots.Count != 0)
1201                                 foreach (ScopeInfo root in roots)
1202                                         root.CloseTypes ();
1203                 }
1204
1205                 public void EmitInitScope (EmitContext ec)
1206                 {
1207                         EmitAnonymousHelperClasses (ec);
1208                         if (roots.Count != 0)
1209                                 foreach (ScopeInfo root in roots)
1210                                         root.EmitInitScope (ec);                }
1211
1212                 //
1213                 // This is called externally when we start emitting code for a block
1214                 // if the block has a ScopeInfo associated, emit the init code
1215                 //
1216                 public void EmitScopeInitFromBlock (EmitContext ec, Block b)
1217                 {
1218                         ScopeInfo si = (ScopeInfo) scopes [b.ID];
1219                         if (si == null)
1220                                 return;
1221
1222                         si.EmitInitScope (ec);
1223                 }
1224
1225                 //
1226                 // Emits the opcodes necessary to load the instance of the captured
1227                 // variable in `li'
1228                 //
1229                 public void EmitCapturedVariableInstance (EmitContext ec, LocalInfo li,
1230                                                           AnonymousContainer am)
1231                 {
1232                         ILGenerator ig = ec.ig;
1233                         ScopeInfo si;
1234
1235                         if (li.Block.Toplevel == toplevel_owner){
1236                                 si = (ScopeInfo) scopes [li.Block.ID];
1237                                 si.EmitScopeInstance (ig);
1238                                 return;
1239                         }
1240
1241                         si = am.Scope;
1242                         ig.Emit (OpCodes.Ldarg_0);
1243                         if (si != null){
1244                                 if (am.IsIterator && (si.ScopeBlock.Toplevel == li.Block.Toplevel)) {
1245                                         return;
1246                                 }
1247
1248                                 while (si.ScopeBlock.ID != li.Block.ID){
1249                                         if (si.ParentLink != null)
1250                                                 ig.Emit (OpCodes.Ldfld, si.ParentLink);
1251                                         si = si.ParentScope;
1252                                         if (si == null) {
1253                                                 si = am.Scope;
1254                                                 Console.WriteLine ("Target: {0} {1}", li.Block.ID, li.Name);
1255                                                 while (si.ScopeBlock.ID != li.Block.ID){
1256                                                         Console.WriteLine ("Trying: {0}", si.ScopeBlock.ID);
1257                                                         si = si.ParentScope;
1258                                                 }
1259
1260                                                 throw new Exception (
1261                                                              String.Format ("Never found block {0} starting at {1} while looking up {2}",
1262                                                                             li.Block.ID, am.Scope.ScopeBlock.ID, li.Name));
1263                                         }
1264                                 }
1265                         }
1266                 }
1267
1268                 //
1269                 // Internal routine that loads the instance to reach parameter `name'
1270                 //
1271                 void EmitParameterInstance (EmitContext ec, string name)
1272                 {
1273                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1274                         if (cc != this){
1275                                 cc.EmitParameterInstance (ec, name);
1276                                 return;
1277                         }
1278
1279                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1280                         if (par_info != null){
1281                                 //
1282                                 // FIXME: implementing this.
1283                                 //
1284                         }
1285                         ILGenerator ig = ec.ig;
1286
1287                         ScopeInfo si;
1288
1289                         if (ec.CurrentBlock.Toplevel == toplevel_owner) {
1290                                 si = (ScopeInfo) scopes [toplevel_owner.ID];
1291                                 si.EmitScopeInstance (ig);
1292                         } else {
1293                                 si = ec.CurrentAnonymousMethod.Scope;
1294                                 ig.Emit (OpCodes.Ldarg_0);
1295                         }
1296
1297                         if (si != null){
1298                                 while (si.ParentLink != null) {
1299                                         ig.Emit (OpCodes.Ldfld, si.ParentLink);
1300                                         si = si.ParentScope;
1301                                 }
1302                         }
1303                 }
1304
1305                 //
1306                 // Emits the code necessary to load the parameter named `name' within
1307                 // an anonymous method.
1308                 //
1309                 public void EmitParameter (EmitContext ec, string name, bool leave_copy, bool prepared, ref LocalTemporary temp)
1310                 {
1311                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1312                         if (cc != this){
1313                                 cc.EmitParameter (ec, name, leave_copy, prepared, ref temp);
1314                                 return;
1315                         }
1316                         if (!prepared)
1317                                 EmitParameterInstance (ec, name);
1318                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1319                         if (par_info != null){
1320                                 //
1321                                 // FIXME: implementing this.
1322                                 //
1323                         }
1324                         ec.ig.Emit (OpCodes.Ldfld, par_info.FieldBuilder);
1325
1326                         if (leave_copy){
1327                                 ec.ig.Emit (OpCodes.Dup);
1328                                 temp = new LocalTemporary (par_info.FieldBuilder.FieldType);
1329                                 temp.Store (ec);
1330                         }
1331                 }
1332
1333                 //
1334                 // Implements the assignment of `source' to the paramenter named `name' within
1335                 // an anonymous method.
1336                 //
1337                 public void EmitAssignParameter (EmitContext ec, string name, Expression source, bool leave_copy, bool prepare_for_load, ref LocalTemporary temp)
1338                 {
1339                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1340                         if (cc != this){
1341                                 cc.EmitAssignParameter (ec, name, source, leave_copy, prepare_for_load, ref temp);
1342                                 return;
1343                         }
1344                         ILGenerator ig = ec.ig;
1345                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1346
1347                         EmitParameterInstance (ec, name);
1348                         if (prepare_for_load)
1349                                 ig.Emit (OpCodes.Dup);
1350                         source.Emit (ec);
1351                         if (leave_copy){
1352                                 ig.Emit (OpCodes.Dup);
1353                                 temp = new LocalTemporary (par_info.FieldBuilder.FieldType);
1354                                 temp.Store (ec);
1355                         }
1356                         ig.Emit (OpCodes.Stfld, par_info.FieldBuilder);
1357                         if (temp != null)
1358                                 temp.Emit (ec);
1359                 }
1360
1361                 //
1362                 // Emits the address for the parameter named `name' within
1363                 // an anonymous method.
1364                 //
1365                 public void EmitAddressOfParameter (EmitContext ec, string name)
1366                 {
1367                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1368                         if (cc != this){
1369                                 cc.EmitAddressOfParameter (ec, name);
1370                                 return;
1371                         }
1372                         EmitParameterInstance (ec, name);
1373                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1374                         ec.ig.Emit (OpCodes.Ldflda, par_info.FieldBuilder);
1375                 }
1376
1377                 //
1378                 // The following methods are only invoked on the host for the
1379                 // anonymous method.
1380                 //
1381                 public void EmitMethodHostInstance (EmitContext target, AnonymousContainer am)
1382                 {
1383                         ILGenerator ig = target.ig;
1384                         ScopeInfo si = am.Scope;
1385
1386                         AnonymousContainer container = am.ContainerAnonymousMethod;
1387
1388                         if ((si == null) || ((container != null) && (si == container.Scope))) {
1389                                 ig.Emit (OpCodes.Ldarg_0);
1390                                 return;
1391                         }
1392
1393                         si.EmitInitScope (target);
1394                         si.EmitScopeInstance (ig);
1395                 }
1396
1397                 public void RegisterCaptureContext ()
1398                 {
1399                         toplevel_owner.RegisterCaptureContext (this);
1400                 }
1401
1402                 //
1403                 // Returs true if `probe' is an ancestor of `scope' in the
1404                 // scope chain
1405                 //
1406                 bool IsAncestor (ScopeInfo probe, ScopeInfo scope)
1407                 {
1408                         for (Block b = scope.ScopeBlock.Parent; b != null; b = b.Parent){
1409                                 if (probe.ScopeBlock == b)
1410                                         return true;
1411                         }
1412                         return false;
1413                 }
1414
1415                 //
1416                 // Returns an ArrayList of ScopeInfos that enumerates all the ancestors
1417                 // of `scope' found in `scope_list'.
1418                 //
1419                 // The value returned is either a ScopeInfo or an Arraylist of ScopeInfos
1420                 //
1421                 object GetAncestorScopes (ScopeInfo scope, ScopeInfo [] scope_list)
1422                 {
1423                         object ancestors = null;
1424
1425                         for (int i = 0; i < scope_list.Length; i++){
1426                                 // Ignore the same scope
1427                                 if (scope_list [i] == scope)
1428                                         continue;
1429
1430                                 if (IsAncestor (scope_list [i], scope)){
1431                                         if (ancestors == null){
1432                                                 ancestors = scope_list [i];
1433                                                 continue;
1434                                         }
1435
1436                                         if (ancestors is ScopeInfo){
1437                                                 object old = ancestors;
1438                                                 ancestors = new ArrayList (4);
1439                                                 ((ArrayList)ancestors).Add (old);
1440                                         }
1441
1442                                         ((ArrayList)ancestors).Add (scope_list [i]);
1443                                 }
1444                         }
1445                         return ancestors;
1446                 }
1447
1448                 //
1449                 // Returns the immediate parent of `scope' from all the captured
1450                 // scopes found in `scope_list', or null if this is a toplevel scope.
1451                 //
1452                 ScopeInfo GetParentScope (ScopeInfo scope, ScopeInfo [] scope_list)
1453                 {
1454                         object ancestors = GetAncestorScopes (scope, scope_list);
1455                         if (ancestors == null)
1456                                 return null;
1457
1458                         // Single match, thats the parent.
1459                         if (ancestors is ScopeInfo)
1460                                 return (ScopeInfo) ancestors;
1461
1462                         ArrayList candidates = (ArrayList) ancestors;
1463                         ScopeInfo parent = (ScopeInfo) candidates [0];
1464                         for (int i = 1; i < candidates.Count; i++){
1465                                 if (IsAncestor (parent, (ScopeInfo) candidates [i]))
1466                                         parent = (ScopeInfo) candidates [i];
1467                         }
1468                         return parent;
1469                 }
1470
1471                 //
1472                 // Links all the scopes
1473                 //
1474                 bool linked;
1475                 public void LinkScopes ()
1476                 {
1477                         if (linked)
1478                                 return;
1479
1480                         linked = true;
1481                         if (ParentCaptureContext != null)
1482                                 ParentCaptureContext.LinkScopes ();
1483
1484                         int scope_count = scopes.Keys.Count;
1485                         ScopeInfo [] scope_list = new ScopeInfo [scope_count];
1486                         scopes.Values.CopyTo (scope_list, 0);
1487
1488                         for (int i = 0; i < scope_count; i++){
1489                                 ScopeInfo parent = GetParentScope (scope_list [i], scope_list);
1490
1491                                 if (parent == null){
1492                                         roots.Add (scope_list [i]);
1493                                         continue;
1494                                 }
1495
1496                                 scope_list [i].ParentScope = parent;
1497                                 parent.AddChild (scope_list [i]);
1498                         }
1499
1500                         //
1501                         // Link the roots to their parent containers if any.
1502                         //
1503                         if (ParentCaptureContext != null && roots.Count != 0){
1504                                 ScopeInfo one_root = (ScopeInfo) roots [0];
1505                                 bool found = false;
1506
1507                                 foreach (ScopeInfo a_parent_root in ParentCaptureContext.roots){
1508                                         if (!IsAncestor (a_parent_root, one_root))
1509                                                 continue;
1510
1511                                         found = true;
1512
1513                                         // Found, link all the roots to this root
1514                                         foreach (ScopeInfo root in roots){
1515                                                 root.ParentScope = a_parent_root;
1516                                                 a_parent_root.AddChild (root);
1517                                         }
1518                                         break;
1519                                 }
1520                                 if (!found){
1521                                         //
1522                                         // This is to catch a condition in which it is
1523                                         // not possible to determine the containing ScopeInfo
1524                                         // from an encapsulating CaptureContext
1525                                         //
1526                                         throw new Exception ("Internal compiler error: Did not find the parent for the root in the chain");
1527                                 }
1528                         }
1529                 }
1530         }
1531 }