mcs/mcs/anonymous.cs

   1 //
   2 // anonymous.cs: Support for anonymous methods
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximain.com)
   6 //
   7 // (C) 2003, 2004 Novell, Inc.
   8 //
   9 // TODO: Ideally, we should have the helper classes emited as a hierarchy to map
  10 // their nesting, and have the visibility set to private, instead of NestedAssembly
  11 //
  12 //
  13 //
  14
  15 using System;
  16 using System.Text;
  17 using System.Collections;
  18 using System.Reflection;
  19 using System.Reflection.Emit;
  20
  21 namespace Mono.CSharp {
  22
  23         public class AnonymousMethod : Expression {
  24                 // Used to generate unique method names.
  25                 static int anonymous_method_count;
  26
  27                 // An array list of AnonymousMethodParameter or null
  28                 public Parameters Parameters;
  29
  30                 //
  31                 // The block that makes up the body for the anonymous mehtod
  32                 //
  33                 public ToplevelBlock Block;
  34
  35                 //
  36                 // The container block for this anonymous method.
  37                 //
  38                 public Block ContainingBlock;
  39
  40                 //
  41                 // The implicit method we create
  42                 //
  43                 public Method method;
  44
  45                 MethodInfo invoke_mb;
  46
  47                 // The emit context for the anonymous method
  48                 public EmitContext aec;
  49                 public InternalParameters amp;
  50                 bool unreachable;
  51
  52                 //
  53                 // The modifiers applied to the method, we aggregate them
  54                 //
  55                 int method_modifiers = Modifiers.PRIVATE;
  56
  57                 //
  58                 // During the resolve stage of the anonymous method body,
  59                 // we discover the actual scope where we are hosted, or
  60                 // null to host the method in the same class
  61                 //
  62                 public ScopeInfo Scope;
  63
  64                 //
  65                 // Points to our container anonymous method if its present
  66                 //
  67                 public AnonymousMethod ContainerAnonymousMethod;
  68
  69                 public AnonymousMethod (Parameters parameters, ToplevelBlock container, ToplevelBlock block, Location l)
  70                 {
  71                         Parameters = parameters;
  72                         Block = block;
  73                         loc = l;
  74
  75                         //
  76                         // The order is important: this setups the CaptureContext tree hierarchy.
  77                         //
  78                         container.SetHaveAnonymousMethods (l, this);
  79                         block.SetHaveAnonymousMethods (l, this);
  80                 }
  81
  82                 public override Expression DoResolve (EmitContext ec)
  83                 {
  84                         //
  85                         // Set class type, set type
  86                         //
  87
  88                         eclass = ExprClass.Value;
  89
  90                         //
  91                         // This hack means `The type is not accessible
  92                         // anywhere', we depend on special conversion
  93                         // rules.
  94                         //
  95                         type = TypeManager.anonymous_method_type;
  96
  97                         return this;
  98                 }
  99
 100                 public override void Emit (EmitContext ec)
 101                 {
 102                         // nothing, as we only exist to not do anything.
 103                 }
 104
 105                 //
 106                 // Creates the host for the anonymous method
 107                 //
 108                 bool CreateMethodHost (EmitContext ec, Type return_type)
 109                 {
 110                         //
 111                         // Crude hack follows: we replace the TypeBuilder during the
 112                         // definition to get the method hosted in the right class
 113                         //
 114
 115                         TypeBuilder current_type = ec.TypeContainer.TypeBuilder;
 116                         TypeBuilder type_host = (Scope == null ) // || Scope.ScopeTypeBuilder == null)
 117                                 ? current_type : Scope.ScopeTypeBuilder;
 118
 119                         if (current_type == null)
 120                                 throw new Exception ("The current_type is null");
 121
 122                         if (type_host == null)
 123                                 throw new Exception ("Type host is null");
 124
 125                         if (current_type == type_host && ec.IsStatic){
 126                                 if (ec.IsStatic){
 127                                         method_modifiers |= Modifiers.STATIC;
 128                                 }
 129                                 current_type = null;
 130                         }
 131
 132                         method = new Method (
 133                                 (TypeContainer) ec.TypeContainer,
 134                                 new TypeExpression (return_type, loc),
 135                                 method_modifiers, false, new MemberName ("<#AnonymousMethod>" + anonymous_method_count++),
 136                                 Parameters, null, loc);
 137                         method.Block = Block;
 138
 139                         //
 140                         // Swap the TypeBuilder while we define the method, then restore
 141                         //
 142                         if (current_type != null)
 143                                 ec.TypeContainer.TypeBuilder = type_host;
 144                         bool res = method.Define ();
 145                         if (current_type != null)
 146                                 ec.TypeContainer.TypeBuilder = current_type;
 147                         return res;
 148                 }
 149
 150                 void Error_ParameterMismatch (Type t)
 151                 {
 152                         Report.Error (1661, loc, "Anonymous method could not be converted to delegate `" +
 153                                       "{0}' since there is a parameter mismatch", t);
 154                 }
 155
 156                 //
 157                 // Returns true if this anonymous method can be implicitly
 158                 // converted to the delegate type `delegate_type'
 159                 //
 160                 public Expression Compatible (EmitContext ec, Type delegate_type, bool probe)
 161                 {
 162                         //
 163                         // At this point its the first time we know the return type that is
 164                         // needed for the anonymous method.  We create the method here.
 165                         //
 166
 167                         invoke_mb = (MethodInfo) Delegate.GetInvokeMethod (ec, delegate_type, loc);
 168                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 169
 170                         if (Parameters == null){
 171                                 int i, j;
 172
 173                                 //
 174                                 // We provide a set of inaccessible parameters
 175                                 //
 176                                 int params_idx = -1;
 177                                 for (i = 0; i < invoke_pd.Count; i++){
 178                                         if (invoke_pd.ParameterModifier (i) == Parameter.Modifier.PARAMS)
 179                                                 params_idx = i;
 180                                 }
 181                                 int n = invoke_pd.Count - (params_idx != -1 ? 1 : 0);
 182                                 Parameter [] fixedpars = new Parameter [n];
 183
 184                                 for (i =  j = 0; i < invoke_pd.Count; i++){
 185                                         if (invoke_pd.ParameterModifier (i) == Parameter.Modifier.PARAMS)
 186                                                 continue;
 187                                         fixedpars [j] = new Parameter (
 188                                                 new TypeExpression (invoke_pd.ParameterType (i), loc),
 189                                                 "+" + j, invoke_pd.ParameterModifier (i), null);
 190                                         j++;
 191                                 }
 192
 193                                 Parameter variable = null;
 194                                 if (params_idx != -1){
 195                                         variable = new Parameter (
 196                                                 new TypeExpression (invoke_pd.ParameterType (params_idx), loc),
 197                                                 "+" + params_idx, invoke_pd.ParameterModifier (params_idx), null);
 198                                 }
 199
 200                                 Parameters = new Parameters (fixedpars, variable, loc);
 201                         }
 202
 203                         //
 204                         // First, parameter types of `delegate_type' must be compatible
 205                         // with the anonymous method.
 206                         //
 207                         amp = new InternalParameters (Parameters.GetParameterInfo (ec), Parameters);
 208
 209                         if (amp.Count != invoke_pd.Count){
 210                                 if (!probe){
 211                                         Report.Error (1593, loc,
 212                                               "Anonymous method has {0} parameters, while delegate requires {1}",
 213                                               amp.Count, invoke_pd.Count);
 214                                         Error_ParameterMismatch (delegate_type);
 215                                 }
 216                                 return null;
 217                         }
 218
 219                         for (int i = 0; i < amp.Count; i++){
 220                                 Parameter.Modifier amp_mod = amp.ParameterModifier (i);
 221
 222                                 if ((amp_mod & (Parameter.Modifier.OUT | Parameter.Modifier.REF)) != 0){
 223                                         if (!probe){
 224                                                 Error_ParameterMismatch (delegate_type);
 225                                                 Report.Error (1677, loc, "Parameter '{0}' should not be declared with the '{1}' keyword",
 226                                                         i+1, amp.ModifierDesc (i));
 227                                         }
 228                                         return null;
 229                                 }
 230
 231                                 if (amp_mod != invoke_pd.ParameterModifier (i)){
 232                                         if (!probe){
 233                                                 Report.Error (1676, loc,
 234                                                       "Signature mismatch in parameter modifier for parameter #0", i + 1);
 235                                                 Error_ParameterMismatch (delegate_type);
 236                                         }
 237                                         return null;
 238                                 }
 239
 240                                 if (amp.ParameterType (i) != invoke_pd.ParameterType (i)){
 241                                         if (!probe){
 242                                                 Report.Error (1678, loc,
 243                                                                       "Signature mismatch in parameter {0}: need `{1}' got `{2}'", i + 1,
 244                                                                       TypeManager.CSharpName (invoke_pd.ParameterType (i)),
 245                                                                       TypeManager.CSharpName (amp.ParameterType (i)));
 246                                                 Error_ParameterMismatch (delegate_type);
 247                                         }
 248                                         return null;
 249                                 }
 250                         }
 251
 252                         //
 253                         // If we are only probing, return ourselves
 254                         //
 255                         if (probe)
 256                                 return this;
 257
 258                         //
 259                         // Second: the return type of the delegate must be compatible with
 260                         // the anonymous type.   Instead of doing a pass to examine the block
 261                         // we satisfy the rule by setting the return type on the EmitContext
 262                         // to be the delegate type return type.
 263                         //
 264
 265                         //MethodBuilder builder = method_data.MethodBuilder;
 266                         //ILGenerator ig = builder.GetILGenerator ();
 267
 268
 269                         aec = new EmitContext (
 270                                 ec.TypeContainer, ec.DeclSpace, loc, null,
 271                                 invoke_mb.ReturnType,
 272                                 /* REVIEW */ (ec.InIterator ? Modifiers.METHOD_YIELDS : 0) |
 273                                 (ec.InUnsafe ? Modifiers.UNSAFE : 0) |
 274                                 (ec.IsStatic ? Modifiers.STATIC : 0),
 275                                 /* No constructor */ false);
 276
 277                         aec.CurrentAnonymousMethod = this;
 278                         ContainerAnonymousMethod = ec.CurrentAnonymousMethod;
 279                         ContainingBlock = ec.CurrentBlock;
 280
 281                         if (aec.ResolveTopBlock (ec, Block, amp, loc, out unreachable))
 282                                 return new AnonymousDelegate (this, delegate_type, loc).Resolve (ec);
 283
 284                         return null;
 285                 }
 286
 287                 public MethodBuilder GetMethodBuilder ()
 288                 {
 289                         return method.MethodData.MethodBuilder;
 290                 }
 291
 292                 public bool EmitMethod (EmitContext ec)
 293                 {
 294                         if (!CreateMethodHost (ec, invoke_mb.ReturnType))
 295                                 return false;
 296
 297                         MethodBuilder builder = GetMethodBuilder ();
 298                         ILGenerator ig = builder.GetILGenerator ();
 299                         aec.ig = ig;
 300
 301                         Parameters.LabelParameters (aec, builder, loc);
 302
 303                         //
 304                         // Adjust based on the computed state of the
 305                         // method from CreateMethodHost
 306
 307                         aec.MethodIsStatic = (method_modifiers & Modifiers.STATIC) != 0;
 308
 309                         aec.EmitMeta (Block, amp);
 310                         aec.EmitResolvedTopBlock (Block, unreachable);
 311                         return true;
 312                 }
 313
 314                 public static void Error_AddressOfCapturedVar (string name, Location loc)
 315                 {
 316                         Report.Error (1686, loc,
 317                                       "Variable {0} is captured in an anonymous method and its address is also being taken: they are exclusive", name);
 318                 }
 319         }
 320
 321         //
 322         // This will emit the code for the delegate, as well delegate creation on the host
 323         //
 324         public class AnonymousDelegate : DelegateCreation {
 325                 AnonymousMethod am;
 326
 327                 public AnonymousDelegate (AnonymousMethod am, Type target_type, Location l)
 328                 {
 329                         type = target_type;
 330                         loc = l;
 331                         this.am = am;
 332                 }
 333
 334                 public override Expression DoResolve (EmitContext ec)
 335                 {
 336                         eclass = ExprClass.Value;
 337
 338                         return this;
 339                 }
 340
 341                 public override void Emit (EmitContext ec)
 342                 {
 343                         if (!am.EmitMethod (ec))
 344                                 return;
 345
 346                         //
 347                         // Now emit the delegate creation.
 348                         //
 349                         if ((am.method.ModFlags & Modifiers.STATIC) == 0)
 350                                 delegate_instance_expression = new AnonymousInstance (am);
 351
 352                         Expression ml = Expression.MemberLookup (ec, type, ".ctor", loc);
 353                         constructor_method = ((MethodGroupExpr) ml).Methods [0];
 354                         delegate_method = am.GetMethodBuilder ();
 355                         base.Emit (ec);
 356                 }
 357
 358                 class AnonymousInstance : Expression {
 359                         AnonymousMethod am;
 360
 361                         public AnonymousInstance (AnonymousMethod am)
 362                         {
 363                                 this.am = am;
 364                                 eclass = ExprClass.Value;
 365                         }
 366
 367                         public override Expression DoResolve (EmitContext ec)
 368                         {
 369                                 return this;
 370                         }
 371
 372                         public override void Emit (EmitContext ec)
 373                         {
 374                                 am.aec.EmitMethodHostInstance (ec, am);
 375                         }
 376                 }
 377         }
 378
 379         class CapturedParameter {
 380                 public Type Type;
 381                 public FieldBuilder FieldBuilder;
 382                 public int Idx;
 383
 384                 public CapturedParameter (Type type, int idx)
 385                 {
 386                         Type = type;
 387                         Idx = idx;
 388                 }
 389         }
 390
 391         //
 392         // Here we cluster all the variables captured on a given scope, we also
 393         // keep some extra information that might be required on each scope.
 394         //
 395         public class ScopeInfo {
 396                 public CaptureContext CaptureContext;
 397                 public ScopeInfo ParentScope;
 398                 public Block ScopeBlock;
 399                 public bool NeedThis = false;
 400                 public bool HostsParameters = false;
 401
 402                 // For tracking the number of scopes created.
 403                 public int id;
 404                 static int count;
 405                 bool inited = false;
 406
 407                 ArrayList locals = new ArrayList ();
 408                 ArrayList children = new ArrayList ();
 409
 410                 //
 411                 // The types and fields generated
 412                 //
 413                 public TypeBuilder ScopeTypeBuilder;
 414                 public ConstructorBuilder ScopeConstructor;
 415                 public FieldBuilder THIS;
 416                 public FieldBuilder ParentLink;
 417
 418                 //
 419                 // Points to the object of type `ScopeTypeBuilder' that
 420                 // holds the data for the scope
 421                 //
 422                 public LocalBuilder ScopeInstance;
 423
 424
 425                 public ScopeInfo (CaptureContext cc, Block b)
 426                 {
 427                         CaptureContext = cc;
 428                         ScopeBlock = b;
 429                         id = count++;
 430
 431                         cc.AddScope (this);
 432                 }
 433
 434                 public void AddLocal (LocalInfo li)
 435                 {
 436                         if (locals.Contains (li))
 437                                 return;
 438
 439                         locals.Add (li);
 440                 }
 441
 442                 public bool IsCaptured (LocalInfo li)
 443                 {
 444                         return locals.Contains (li);
 445                 }
 446
 447                 public void AddChild (ScopeInfo si)
 448                 {
 449                         if (children.Contains (si))
 450                                 return;
 451                         children.Add (si);
 452                 }
 453
 454                 static int indent = 0;
 455
 456                 void Pad ()
 457                 {
 458                         for (int i = 0; i < indent; i++)
 459                                 Console.Write ("    ");
 460                 }
 461
 462                 void EmitDebug ()
 463                 {
 464                         //Console.WriteLine (Environment.StackTrace);
 465                         Pad ();
 466                         Console.WriteLine ("START");
 467                         indent++;
 468                         Pad ();
 469                         Console.WriteLine ("NeedThis=" + NeedThis);
 470                         foreach (LocalInfo li in locals){
 471                                 Pad ();
 472                                 Console.WriteLine ("var {0}", li.Name);
 473                         }
 474
 475                         foreach (ScopeInfo si in children)
 476                                 si.EmitDebug ();
 477                         indent--;
 478                         Pad ();
 479                         Console.WriteLine ("END");
 480                 }
 481
 482                 public string MakeHelperName ()
 483                 {
 484                         return String.Format ("<>AnonHelp<{0}>", id);
 485                 }
 486
 487                 public void EmitScopeConstructor ()
 488                 {
 489                         Type [] constructor_types = TypeManager.NoTypes;
 490                         Parameters constructor_parameters = Parameters.EmptyReadOnlyParameters;
 491                         ScopeConstructor = ScopeTypeBuilder.DefineConstructor (
 492                                 MethodAttributes.Public | MethodAttributes.HideBySig |
 493                                 MethodAttributes.SpecialName | MethodAttributes.RTSpecialName,
 494                                 CallingConventions.HasThis, constructor_types);
 495                         InternalParameters parameter_info = new InternalParameters (constructor_types, constructor_parameters);
 496                         TypeManager.RegisterMethod (ScopeConstructor, parameter_info, constructor_types);
 497
 498                         ILGenerator cig = ScopeConstructor.GetILGenerator ();
 499                         cig.Emit (OpCodes.Ldarg_0);
 500                         cig.Emit (OpCodes.Call, TypeManager.object_ctor);
 501                         cig.Emit (OpCodes.Ret);
 502                 }
 503
 504                 public void EmitScopeType (EmitContext ec)
 505                 {
 506                         //EmitDebug ();
 507
 508                         if (ScopeTypeBuilder != null)
 509                                 return;
 510
 511                         TypeBuilder container = ec.TypeContainer.TypeBuilder;
 512
 513                         ScopeTypeBuilder = container.DefineNestedType (
 514                                 MakeHelperName (), TypeAttributes.AutoLayout | TypeAttributes.Class | TypeAttributes.NestedAssembly,
 515                                 TypeManager.object_type, null);
 516
 517                         if (NeedThis)
 518                                 THIS = ScopeTypeBuilder.DefineField ("<>THIS", container, FieldAttributes.Assembly);
 519
 520                         if (ParentScope != null){
 521                                 if (ParentScope.ScopeTypeBuilder == null){
 522                                         throw new Exception (String.Format ("My parent has not been initialized {0} and {1}", ParentScope, this));
 523                                 }
 524
 525                                 ParentLink = ScopeTypeBuilder.DefineField ("<>parent", ParentScope.ScopeTypeBuilder,
 526                                                                            FieldAttributes.Assembly);
 527                         }
 528
 529                         if (NeedThis && ParentScope != null)
 530                                 throw new Exception ("I was not expecting THIS && having a parent");
 531
 532                         foreach (LocalInfo info in locals){
 533                                 info.FieldBuilder = ScopeTypeBuilder.DefineField (
 534                                         info.Name, info.VariableType, FieldAttributes.Assembly);
 535                         }
 536
 537                         if (HostsParameters){
 538                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 539
 540                                 foreach (DictionaryEntry de in captured_parameters){
 541                                         string name = (string) de.Key;
 542                                         CapturedParameter cp = (CapturedParameter) de.Value;
 543                                         FieldBuilder fb;
 544
 545                                         fb = ScopeTypeBuilder.DefineField ("<p:" + name + ">", cp.Type, FieldAttributes.Assembly);
 546                                         cp.FieldBuilder = fb;
 547                                 }
 548                         }
 549
 550                         EmitScopeConstructor ();
 551                         foreach (ScopeInfo si in children){
 552                                 si.EmitScopeType (ec);
 553                         }
 554                 }
 555
 556                 public void CloseTypes ()
 557                 {
 558                         RootContext.RegisterCompilerGeneratedType (ScopeTypeBuilder);
 559                         foreach (ScopeInfo si in children)
 560                                 si.CloseTypes ();
 561                 }
 562
 563                 //
 564                 // Emits the initialization code for the scope
 565                 //
 566                 public void EmitInitScope (EmitContext ec)
 567                 {
 568                         ILGenerator ig = ec.ig;
 569
 570                         if (inited)
 571                                 return;
 572
 573                         ig.Emit (OpCodes.Newobj, (ConstructorInfo) ScopeConstructor);
 574                         ScopeInstance = ig.DeclareLocal (ScopeTypeBuilder);
 575                         ig.Emit (OpCodes.Stloc, ScopeInstance);
 576
 577                         if (THIS != null){
 578                                 ig.Emit (OpCodes.Ldloc, ScopeInstance);
 579                                 ig.Emit (OpCodes.Ldarg_0);
 580                                 ig.Emit (OpCodes.Stfld, THIS);
 581                         }
 582
 583                         //
 584                         // Copy the parameter values, if any
 585                         //
 586                         int extra = ec.IsStatic ? 0 : 1;
 587                         if (HostsParameters){
 588                                 Hashtable captured_parameters = CaptureContext.captured_parameters;
 589
 590                                 foreach (DictionaryEntry de in captured_parameters){
 591                                         CapturedParameter cp = (CapturedParameter) de.Value;
 592
 593                                         ig.Emit (OpCodes.Ldloc, ScopeInstance);
 594                                         ParameterReference.EmitLdArg (ig, cp.Idx + extra);
 595                                         ig.Emit (OpCodes.Stfld, cp.FieldBuilder);
 596                                 }
 597                         }
 598
 599                         if (ParentScope != null){
 600                                 if (!ParentScope.inited)
 601                                         ParentScope.EmitInitScope (ec);
 602
 603                                 //
 604                                 // Only emit initialization in our capturecontext world
 605                                 //
 606                                 if (ParentScope.CaptureContext == CaptureContext){
 607                                         ig.Emit (OpCodes.Ldloc, ScopeInstance);
 608                                         ig.Emit (OpCodes.Ldloc, ParentScope.ScopeInstance);
 609                                         ig.Emit (OpCodes.Stfld, ParentLink);
 610                                 } else {
 611                                         ig.Emit (OpCodes.Ldloc, ScopeInstance);
 612                                         ig.Emit (OpCodes.Ldarg_0);
 613                                         ig.Emit (OpCodes.Stfld, ParentLink);
 614                                 }
 615                         }
 616                         inited = true;
 617                 }
 618
 619                 static void DoPath (StringBuilder sb, ScopeInfo start)
 620                 {
 621                         if (start.ParentScope != null){
 622                                 DoPath (sb, start.ParentScope);
 623                                 sb.Append (", ");
 624                         }
 625                         sb.Append ((start.id).ToString ());
 626                 }
 627
 628                 public override string ToString ()
 629                 {
 630                         StringBuilder sb = new StringBuilder ();
 631
 632                         sb.Append ("{");
 633                         if (CaptureContext != null){
 634                                 sb.Append (CaptureContext.ToString ());
 635                                 sb.Append (":");
 636                         }
 637
 638                         DoPath (sb, this);
 639                         sb.Append ("}");
 640
 641                         return sb.ToString ();
 642                 }
 643         }
 644
 645         //
 646         // CaptureContext objects are created on demand if a method has
 647         // anonymous methods and kept on the ToplevelBlock.
 648         //
 649         // If they exist, all ToplevelBlocks in the containing block are
 650         // linked together (children pointing to their parents).
 651         //
 652         public class CaptureContext {
 653                 public static int count;
 654                 public int cc_id;
 655                 public Location loc;
 656
 657                 //
 658                 // Points to the toplevel block that owns this CaptureContext
 659                 //
 660                 ToplevelBlock toplevel_owner;
 661                 Hashtable scopes = new Hashtable ();
 662                 bool have_captured_vars = false;
 663                 bool referenced_this = false;
 664                 ScopeInfo topmost = null;
 665
 666                 //
 667                 // Captured fields
 668                 //
 669                 Hashtable captured_fields = new Hashtable ();
 670                 Hashtable captured_variables = new Hashtable ();
 671                 public Hashtable captured_parameters = new Hashtable ();
 672                 public AnonymousMethod Host;
 673
 674                 public CaptureContext (ToplevelBlock toplevel_owner, Location loc, AnonymousMethod host)
 675                 {
 676                         cc_id = count++;
 677                         this.toplevel_owner = toplevel_owner;
 678                         this.loc = loc;
 679
 680                         if (host != null)
 681                                 Host = host;
 682                 }
 683
 684                 void DoPath (StringBuilder sb, CaptureContext cc)
 685                 {
 686                         if (cc.ParentCaptureContext != null){
 687                                 DoPath (sb, cc.ParentCaptureContext);
 688                                 sb.Append (".");
 689                         }
 690                         sb.Append (cc_id.ToString ());
 691                 }
 692
 693                 public override string ToString ()
 694                 {
 695                         StringBuilder sb = new StringBuilder ();
 696                         sb.Append ("[");
 697                         DoPath (sb, this);
 698                         sb.Append ("]");
 699                         return sb.ToString ();
 700                 }
 701
 702                 public ToplevelBlock ParentToplevel {
 703                         get {
 704                                 return toplevel_owner.Container;
 705                         }
 706                 }
 707
 708                 public CaptureContext ParentCaptureContext {
 709                         get {
 710                                 ToplevelBlock parent = ParentToplevel;
 711
 712                                 return (parent == null) ? null : parent.CaptureContext;
 713                         }
 714                 }
 715
 716                 // Returns the deepest of two scopes
 717                 public ScopeInfo Deepest (ScopeInfo a, ScopeInfo b)
 718                 {
 719                         ScopeInfo p;
 720
 721                         if (a == null)
 722                                 return b;
 723                         if (b == null)
 724                                 return a;
 725                         if (a == b)
 726                                 return a;
 727
 728                         //
 729                         // If they Scopes are on the same CaptureContext, we do the double
 730                         // checks just so if there is an invariant change in the future,
 731                         // we get the exception at the end
 732                         //
 733                         for (p = a; p != null; p = p.ParentScope)
 734                                 if (p == b)
 735                                         return a;
 736
 737                         for (p = b; p != null; p = p.ParentScope)
 738                                 if (p == a)
 739                                         return b;
 740
 741                         CaptureContext ca = a.CaptureContext;
 742                         CaptureContext cb = b.CaptureContext;
 743
 744                         for (CaptureContext c = ca; c != null; c = c.ParentCaptureContext)
 745                                 if (c == cb)
 746                                         return a;
 747
 748                         for (CaptureContext c = cb; c != null; c = c.ParentCaptureContext)
 749                                 if (c == ca)
 750                                         return b;
 751                         throw new Exception ("Should never be reached");
 752                 }
 753
 754                 void AdjustMethodScope (AnonymousMethod am, ScopeInfo scope)
 755                 {
 756                         am.Scope = Deepest (am.Scope, scope);
 757                 }
 758
 759                 void LinkScope (ScopeInfo scope, int id)
 760                 {
 761                         ScopeInfo parent = (ScopeInfo) scopes [id];
 762                         scope.ParentScope = parent;
 763                         parent.AddChild (scope);
 764
 765                         if (scope == topmost)
 766                                 topmost = parent;
 767                 }
 768
 769                 public void AddLocal (AnonymousMethod am, LocalInfo li)
 770                 {
 771                         if (li.Block.Toplevel != toplevel_owner){
 772                                 ParentCaptureContext.AddLocal (am, li);
 773                                 return;
 774                         }
 775                         int block_id = li.Block.ID;
 776                         ScopeInfo scope;
 777                         if (scopes [block_id] == null){
 778                                 scope = new ScopeInfo (this, li.Block);
 779                                 scopes [block_id] = scope;
 780                         } else
 781                                 scope = (ScopeInfo) scopes [block_id];
 782
 783                         if (topmost == null){
 784                                 topmost = scope;
 785                         } else {
 786                                 // Link to parent
 787                                 for (Block b = scope.ScopeBlock.Parent; b != null; b = b.Parent){
 788                                         if (scopes [b.ID] != null){
 789                                                 LinkScope (scope, b.ID);
 790                                                 break;
 791                                         }
 792                                 }
 793
 794                                 if (scope.ParentScope == null && ParentCaptureContext != null){
 795                                         CaptureContext pcc = ParentCaptureContext;
 796
 797                                         for (Block b = am.ContainingBlock; b != null; b = b.Parent){
 798                                                 if (pcc.scopes [b.ID] != null){
 799                                                         pcc.LinkScope (scope, b.ID);
 800                                                         break;
 801                                                 }
 802                                         }
 803                                 }
 804                         }
 805
 806                         //
 807                         // Adjust the owner
 808                         //
 809                         if (Host != null)
 810                                 AdjustMethodScope (Host, topmost);
 811
 812                         //
 813                         // Adjust the user
 814                         //
 815                         AdjustMethodScope (am, scope);
 816
 817                         if (captured_variables [li] != null)
 818                                 return;
 819
 820                         have_captured_vars = true;
 821                         captured_variables [li] = li;
 822                         scope.AddLocal (li);
 823                 }
 824
 825                 //
 826                 // Retursn the CaptureContext for the block that defines the parameter `name'
 827                 //
 828                 static CaptureContext _ContextForParameter (ToplevelBlock current, string name)
 829                 {
 830                         ToplevelBlock container = current.Container;
 831                         if (container != null){
 832                                 CaptureContext cc = _ContextForParameter (container, name);
 833                                 if (cc != null)
 834                                         return cc;
 835                         }
 836                         if (current.IsParameterReference (name))
 837                                 return current.ToplevelBlockCaptureContext;
 838                         return null;
 839                 }
 840
 841                 static CaptureContext ContextForParameter (ToplevelBlock current, string name)
 842                 {
 843                         CaptureContext cc = _ContextForParameter (current, name);
 844                         if (cc == null)
 845                                 throw new Exception (String.Format ("request for parameteter {0} failed: not found", name));
 846                         return cc;
 847                 }
 848
 849                 //
 850                 // Records the captured parameter at the appropriate CaptureContext
 851                 //
 852                 public void AddParameter (EmitContext ec, AnonymousMethod am, string name, Type t, int idx)
 853                 {
 854                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
 855
 856                         cc.AddParameterToContext (am, name, t, idx);
 857                 }
 858
 859                 //
 860                 // Records the parameters in the context
 861                 //
 862                 void AddParameterToContext (AnonymousMethod am, string name, Type t, int idx)
 863                 {
 864                         if (captured_parameters == null)
 865                                 captured_parameters = new Hashtable ();
 866                         if (captured_parameters [name] != null)
 867                                 return;
 868                         captured_parameters [name] = new CapturedParameter (t, idx);
 869
 870                         if (topmost == null){
 871                                 //
 872                                 // Create one ScopeInfo, if there are none.
 873                                 //
 874                                 topmost = new ScopeInfo (this, toplevel_owner);
 875                                 scopes [toplevel_owner.ID] = topmost;
 876                         } else {
 877                                 //
 878                                 // If the topmost ScopeInfo is not at the topblock level, insert
 879                                 // a new ScopeInfo there.
 880                                 //
 881                                 if (topmost.ScopeBlock != toplevel_owner){
 882                                         ScopeInfo par_si = new ScopeInfo (this, toplevel_owner);
 883                                         scopes [toplevel_owner.ID] = topmost;
 884                                         topmost.ParentScope = par_si;
 885                                         topmost = par_si;
 886                                 }
 887                         }
 888
 889                         topmost.HostsParameters = true;
 890                         AdjustMethodScope (am, topmost);
 891                 }
 892
 893                 //
 894                 // Captured fields are only recorded on the topmost CaptureContext, because that
 895                 // one is the one linked to the owner of instance fields
 896                 //
 897                 public void AddField (FieldExpr fe)
 898                 {
 899                         if (fe.FieldInfo.IsStatic)
 900                                 throw new Exception ("Attempt to register a static field as a captured field");
 901
 902                         CaptureContext parent = ParentCaptureContext;
 903                         if (parent != null)
 904                                 parent.AddField (fe);
 905                         else
 906                                 captured_fields [fe] = fe;
 907                 }
 908
 909                 public void CaptureThis ()
 910                 {
 911                         CaptureContext parent = ParentCaptureContext;
 912                         if (parent != null)
 913                                 parent.CaptureThis ();
 914                         referenced_this = true;
 915                 }
 916
 917                 public bool HaveCapturedVariables {
 918                         get {
 919                                 return have_captured_vars;
 920                         }
 921                 }
 922
 923                 public bool HaveCapturedFields {
 924                         get {
 925                                 CaptureContext parent = ParentCaptureContext;
 926                                 if (parent != null)
 927                                         return parent.HaveCapturedFields;
 928                                 return captured_fields.Count > 0;
 929                         }
 930                 }
 931
 932                 public bool IsCaptured (LocalInfo local)
 933                 {
 934                         foreach (ScopeInfo si in scopes.Values){
 935                                 if (si.IsCaptured (local))
 936                                         return true;
 937                         }
 938                         return false;
 939                 }
 940
 941                 //
 942                 // Returns whether the parameter is captured
 943                 //
 944                 public bool IsParameterCaptured (string name)
 945                 {
 946                         if (ParentCaptureContext != null && ParentCaptureContext.IsParameterCaptured (name))
 947                                 return true;
 948
 949                         if (captured_parameters != null)
 950                                 return captured_parameters [name] != null;
 951                         return false;
 952                 }
 953
 954                 public void EmitAnonymousHelperClasses (EmitContext ec)
 955                 {
 956                         if (topmost != null){
 957                                 topmost.NeedThis = HaveCapturedFields || referenced_this;
 958                                 topmost.EmitScopeType (ec);
 959                         }
 960                 }
 961
 962                 public void CloseAnonymousHelperClasses ()
 963                 {
 964                         if (topmost != null)
 965                                 topmost.CloseTypes ();
 966                 }
 967
 968                 ScopeInfo GetScopeFromBlock (EmitContext ec, Block b)
 969                 {
 970                         ScopeInfo si;
 971
 972                         si = (ScopeInfo) scopes [b.ID];
 973                         if (si == null)
 974                                 throw new Exception ("Si is null for block " + b.ID);
 975                         si.EmitInitScope (ec);
 976
 977                         return si;
 978                 }
 979
 980                 //
 981                 // Emits the opcodes necessary to load the instance of the captured
 982                 // variable in `li'
 983                 //
 984                 public void EmitCapturedVariableInstance (EmitContext ec, LocalInfo li, AnonymousMethod am)
 985                 {
 986                         ILGenerator ig = ec.ig;
 987                         ScopeInfo si;
 988
 989                         if (li.Block.Toplevel == toplevel_owner){
 990                                 si = GetScopeFromBlock (ec, li.Block);
 991                                 ig.Emit (OpCodes.Ldloc, si.ScopeInstance);
 992                                 return;
 993                         }
 994
 995                         si = am.Scope;
 996                         ig.Emit (OpCodes.Ldarg_0);
 997                         if (si != null){
 998                                 while (si.ScopeBlock.ID != li.Block.ID){
 999                                         if (si.ParentLink != null)
1000                                                 ig.Emit (OpCodes.Ldfld, si.ParentLink);
1001                                         si = si.ParentScope;
1002                                         if (si == null)
1003                                                 throw new Exception (
1004                                                              String.Format ("Never found block {0} starting at {1} while looking up {2}",
1005                                                                             li.Block.ID, am.Scope.ScopeBlock.ID, li.Name));
1006                                 }
1007                         }
1008                 }
1009
1010                 //
1011                 // Internal routine that loads the instance to reach parameter `name'
1012                 //
1013                 void EmitParameterInstance (EmitContext ec, string name)
1014                 {
1015                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1016                         if (cc != this){
1017                                 cc.EmitParameterInstance (ec, name);
1018                                 return;
1019                         }
1020
1021                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1022                         if (par_info != null){
1023                                 //
1024                                 // FIXME: implementing this.
1025                                 //
1026                         }
1027                         ILGenerator ig = ec.ig;
1028
1029                         ScopeInfo si;
1030                         if (ec.CurrentBlock == toplevel_owner){
1031                                 si = GetScopeFromBlock (ec, toplevel_owner);
1032                                 ig.Emit (OpCodes.Ldloc, si.ScopeInstance);
1033                                 return;
1034                         }
1035
1036                         si = ec.CurrentAnonymousMethod.Scope;
1037                         ig.Emit (OpCodes.Ldarg_0);
1038                         if (si != null){
1039                                 while (si.ParentLink != null) {
1040                                         ig.Emit (OpCodes.Ldfld, si.ParentLink);
1041                                         si = si.ParentScope;
1042                                 }
1043                         }
1044                 }
1045
1046                 //
1047                 // Emits the code necessary to load the parameter named `name' within
1048                 // an anonymous method.
1049                 //
1050                 public void EmitParameter (EmitContext ec, string name)
1051                 {
1052                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1053                         if (cc != this){
1054                                 cc.EmitParameter (ec, name);
1055                                 return;
1056                         }
1057                         EmitParameterInstance (ec, name);
1058                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1059                         if (par_info != null){
1060                                 //
1061                                 // FIXME: implementing this.
1062                                 //
1063                         }
1064                         ec.ig.Emit (OpCodes.Ldfld, par_info.FieldBuilder);
1065                 }
1066
1067                 //
1068                 // Implements the assignment of `source' to the paramenter named `name' within
1069                 // an anonymous method.
1070                 //
1071                 public void EmitAssignParameter (EmitContext ec, string name, Expression source, bool leave_copy, bool prepare_for_load)
1072                 {
1073                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1074                         if (cc != this){
1075                                 cc.EmitAssignParameter (ec, name, source, leave_copy, prepare_for_load);
1076                                 return;
1077                         }
1078                         ILGenerator ig = ec.ig;
1079                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1080
1081                         EmitParameterInstance (ec, name);
1082                         source.Emit (ec);
1083                         if (leave_copy)
1084                                 ig.Emit (OpCodes.Dup);
1085                         ig.Emit (OpCodes.Stfld, par_info.FieldBuilder);
1086                 }
1087
1088                 //
1089                 // Emits the address for the parameter named `name' within
1090                 // an anonymous method.
1091                 //
1092                 public void EmitAddressOfParameter (EmitContext ec, string name)
1093                 {
1094                         CaptureContext cc = ContextForParameter (ec.CurrentBlock.Toplevel, name);
1095                         if (cc != this){
1096                                 cc.EmitAddressOfParameter (ec, name);
1097                                 return;
1098                         }
1099                         EmitParameterInstance (ec, name);
1100                         CapturedParameter par_info = (CapturedParameter) captured_parameters [name];
1101                         ec.ig.Emit (OpCodes.Ldflda, par_info.FieldBuilder);
1102                 }
1103
1104                 //
1105                 // The following methods are only invoked on the host for the
1106                 // anonymous method.
1107                 //
1108                 public void EmitMethodHostInstance (EmitContext target, AnonymousMethod am)
1109                 {
1110                         ILGenerator ig = target.ig;
1111                         ScopeInfo si = am.Scope;
1112
1113                         if (si == null){
1114                                 ig.Emit (OpCodes.Ldarg_0);
1115                                 return;
1116                         }
1117
1118                         si.EmitInitScope (target);
1119                         ig.Emit (OpCodes.Ldloc, si.ScopeInstance);
1120                 }
1121
1122                 ArrayList all_scopes = new ArrayList ();
1123
1124                 public void AddScope (ScopeInfo si)
1125                 {
1126                         all_scopes.Add (si);
1127                         toplevel_owner.RegisterCaptureContext (this);
1128                 }
1129
1130                 //
1131                 // Links any scopes that were not linked previously
1132                 //
1133                 public void AdjustScopes ()
1134                 {
1135                         foreach (ScopeInfo scope in all_scopes){
1136                                 if (scope.ParentScope != null)
1137                                         continue;
1138
1139                                 for (Block b = scope.ScopeBlock.Parent; b != null; b = b.Parent){
1140                                         if (scopes [b.ID] != null){
1141                                                 LinkScope (scope, b.ID);
1142                                                 break;
1143                                         }
1144                                 }
1145
1146                                 if (scope.ParentScope == null && ParentCaptureContext != null){
1147                                         CaptureContext pcc = ParentCaptureContext;
1148
1149                                         for (Block b = Host.ContainingBlock; b != null; b = b.Parent){
1150                                                 if (pcc.scopes [b.ID] != null){
1151                                                         pcc.LinkScope (scope, b.ID);
1152                                                         break;
1153                                                 }
1154                                         }
1155                                 }
1156                         }
1157                 }
1158         }
1159 }