mcs/gmcs/namespace.cs

   1 //
   2 // namespace.cs: Tracks namespaces
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //
   7 // (C) 2001 Ximian, Inc.
   8 //
   9 using System;
  10 using System.Collections;
  11 using System.Collections.Specialized;
  12 using System.Reflection;
  13
  14 namespace Mono.CSharp {
  15
  16         public class RootNamespace : Namespace {
  17                 static MethodInfo get_namespaces_method;
  18
  19                 string alias_name;
  20                 Assembly referenced_assembly;
  21
  22                 Hashtable all_namespaces;
  23
  24                 static Hashtable root_namespaces;
  25                 public static GlobalRootNamespace Global;
  26
  27                 static RootNamespace ()
  28                 {
  29                         get_namespaces_method = typeof (Assembly).GetMethod ("GetNamespaces", BindingFlags.Instance | BindingFlags.NonPublic);
  30
  31                         Reset ();
  32                 }
  33
  34                 public static void Reset ()
  35                 {
  36                         root_namespaces = new Hashtable ();
  37                         Global = new GlobalRootNamespace ();
  38                         root_namespaces ["global"] = Global;
  39                 }
  40
  41                 protected RootNamespace (string alias_name, Assembly assembly)
  42                         : base (null, String.Empty)
  43                 {
  44                         this.alias_name = alias_name;
  45                         referenced_assembly = assembly;
  46
  47                         all_namespaces = new Hashtable ();
  48                         all_namespaces.Add ("", this);
  49
  50                         if (referenced_assembly != null)
  51                                 ComputeNamespaces (this.referenced_assembly);
  52                 }
  53
  54                 public static void DefineRootNamespace (string name, Assembly assembly)
  55                 {
  56                         if (name == "global") {
  57                                 // FIXME: Add proper error number
  58                                 Report.Error (-42, "Cannot define an external alias named `global'");
  59                                 return;
  60                         }
  61                         RootNamespace retval = GetRootNamespace (name);
  62                         if (retval == null || retval.referenced_assembly != assembly)
  63                                 root_namespaces [name] = new RootNamespace (name, assembly);
  64                 }
  65
  66                 public static RootNamespace GetRootNamespace (string name)
  67                 {
  68                         return (RootNamespace) root_namespaces [name];
  69                 }
  70
  71                 public virtual Type LookupTypeReflection (string name, Location loc)
  72                 {
  73                         return GetTypeInAssembly (referenced_assembly, name);
  74                 }
  75
  76                 public void RegisterNamespace (Namespace child)
  77                 {
  78                         if (child != this)
  79                                 all_namespaces.Add (child.Name, child);
  80                 }
  81
  82                 public bool IsNamespace (string name)
  83                 {
  84                         return all_namespaces.Contains (name);
  85                 }
  86
  87                 protected void EnsureNamespace (string dotted_name)
  88                 {
  89                         if (dotted_name != null && dotted_name != "" && ! IsNamespace (dotted_name))
  90                                 GetNamespace (dotted_name, true);
  91                 }
  92
  93                 protected void ComputeNamespaces (Assembly assembly)
  94                 {
  95                         if (get_namespaces_method != null) {
  96                                 string [] namespaces = (string []) get_namespaces_method.Invoke (assembly, null);
  97                                 foreach (string ns in namespaces)
  98                                         EnsureNamespace (ns);
  99                                 return;
 100                         }
 101
 102                         foreach (Type t in assembly.GetExportedTypes ())
 103                                 EnsureNamespace (t.Namespace);
 104                 }
 105
 106                 protected static Type GetTypeInAssembly (Assembly assembly, string name)
 107                 {
 108                         Type t = assembly.GetType (name);
 109                         if (t == null)
 110                                 return null;
 111
 112                         if (t.IsPointer)
 113                                 throw new InternalErrorException ("Use GetPointerType() to get a pointer");
 114
 115
 116                         TypeAttributes ta = t.Attributes & TypeAttributes.VisibilityMask;
 117                         if (ta == TypeAttributes.NestedPrivate)
 118                                 return null;
 119
 120                         if (ta == TypeAttributes.NotPublic ||
 121                                         ta == TypeAttributes.NestedAssembly ||
 122                                         ta == TypeAttributes.NestedFamANDAssem)
 123                                 if (!TypeManager.IsFriendAssembly (t.Assembly))
 124                                         return null;
 125
 126                         return t;
 127                 }
 128
 129                 public override string ToString ()
 130                 {
 131                         return String.Format ("RootNamespace ({0}::)", alias_name);
 132                 }
 133
 134                 public override string GetSignatureForError ()
 135                 {
 136                         return alias_name + "::";
 137                 }
 138         }
 139
 140         public class GlobalRootNamespace : RootNamespace {
 141                 Assembly [] assemblies;
 142                 Module [] modules;
 143
 144                 public GlobalRootNamespace ()
 145                         : base ("global", null)
 146                 {
 147                         assemblies = new Assembly [0];
 148                 }
 149
 150                 public Assembly [] Assemblies {
 151                         get { return assemblies; }
 152                 }
 153
 154                 public Module [] Modules {
 155                         get { return modules; }
 156                 }
 157
 158                 public void AddAssemblyReference (Assembly a)
 159                 {
 160                         foreach (Assembly assembly in assemblies) {
 161                                 if (a == assembly)
 162                                         return;
 163                         }
 164
 165                         int top = assemblies.Length;
 166                         Assembly [] n = new Assembly [top + 1];
 167                         assemblies.CopyTo (n, 0);
 168                         n [top] = a;
 169                         assemblies = n;
 170
 171                         ComputeNamespaces (a);
 172                 }
 173
 174                 public void AddModuleReference (Module m)
 175                 {
 176                         int top = modules != null ? modules.Length : 0;
 177                         Module [] n = new Module [top + 1];
 178                         if (modules != null)
 179                                 modules.CopyTo (n, 0);
 180                         n [top] = m;
 181                         modules = n;
 182
 183                         if (m == CodeGen.Module.Builder)
 184                                 return;
 185
 186                         foreach (Type t in m.GetTypes ())
 187                                 EnsureNamespace (t.Namespace);
 188                 }
 189
 190                 public override Type LookupTypeReflection (string name, Location loc)
 191                 {
 192                         Type found_type = null;
 193
 194                         foreach (Assembly a in assemblies) {
 195                                 Type t = GetTypeInAssembly (a, name);
 196                                 if (t == null)
 197                                         continue;
 198
 199                                 if (found_type == null) {
 200                                         found_type = t;
 201                                         continue;
 202                                 }
 203
 204                                 Report.SymbolRelatedToPreviousError (found_type);
 205                                 Report.SymbolRelatedToPreviousError (t);
 206                                 Report.Error (433, loc, "The imported type `{0}' is defined multiple times", name);
 207
 208                                 return found_type;
 209                         }
 210
 211                         if (modules != null) {
 212                                 foreach (Module module in modules) {
 213                                         Type t = module.GetType (name);
 214                                         if (t == null)
 215                                                 continue;
 216
 217                                         if (found_type == null) {
 218                                                 found_type = t;
 219                                                 continue;
 220                                         }
 221
 222                                         Report.SymbolRelatedToPreviousError (t);
 223                                         Report.SymbolRelatedToPreviousError (found_type);
 224                                         Report.Warning (436, 2, loc, "Ignoring imported type `{0}' since the current assembly already has a declaration with the same name",
 225                                                 TypeManager.CSharpName (t));
 226                                         return t;
 227                                 }
 228                         }
 229
 230                         return found_type;
 231                 }
 232         }
 233
 234         /// <summary>
 235         ///   Keeps track of the namespaces defined in the C# code.
 236         ///
 237         ///   This is an Expression to allow it to be referenced in the
 238         ///   compiler parse/intermediate tree during name resolution.
 239         /// </summary>
 240         public class Namespace : FullNamedExpression {
 241
 242                 Namespace parent;
 243                 string fullname;
 244                 Hashtable namespaces;
 245                 IDictionary declspaces;
 246                 Hashtable cached_types;
 247                 RootNamespace root;
 248
 249                 public readonly MemberName MemberName;
 250
 251                 /// <summary>
 252                 ///   Constructor Takes the current namespace and the
 253                 ///   name.  This is bootstrapped with parent == null
 254                 ///   and name = ""
 255                 /// </summary>
 256                 public Namespace (Namespace parent, string name)
 257                 {
 258                         // Expression members.
 259                         this.eclass = ExprClass.Namespace;
 260                         this.Type = null;
 261                         this.loc = Location.Null;
 262
 263                         this.parent = parent;
 264
 265                         if (parent != null)
 266                                 this.root = parent.root;
 267                         else
 268                                 this.root = this as RootNamespace;
 269
 270                         if (this.root == null)
 271                                 throw new InternalErrorException ("Root namespaces must be created using RootNamespace");
 272
 273                         string pname = parent != null ? parent.Name : "";
 274
 275                         if (pname == "")
 276                                 fullname = name;
 277                         else
 278                                 fullname = parent.Name + "." + name;
 279
 280                         if (fullname == null)
 281                                 throw new InternalErrorException ("Namespace has a null fullname");
 282
 283                         if (parent != null && parent.MemberName != MemberName.Null)
 284                                 MemberName = new MemberName (
 285                                         parent.MemberName, name, parent.MemberName.Location);
 286                         else if (name == "")
 287                                 MemberName = MemberName.Null;
 288                         else
 289                                 MemberName = new MemberName (name, Location.Null);
 290
 291                         namespaces = new Hashtable ();
 292                         cached_types = new Hashtable ();
 293
 294                         root.RegisterNamespace (this);
 295                 }
 296
 297                 public override Expression DoResolve (EmitContext ec)
 298                 {
 299                         return this;
 300                 }
 301
 302                 public override void Emit (EmitContext ec)
 303                 {
 304                         throw new InternalErrorException ("Expression tree referenced namespace " + fullname + " during Emit ()");
 305                 }
 306
 307                 public override string GetSignatureForError ()
 308                 {
 309                         return Name;
 310                 }
 311
 312                 public Namespace GetNamespace (string name, bool create)
 313                 {
 314                         int pos = name.IndexOf ('.');
 315
 316                         Namespace ns;
 317                         string first;
 318                         if (pos >= 0)
 319                                 first = name.Substring (0, pos);
 320                         else
 321                                 first = name;
 322
 323                         ns = (Namespace) namespaces [first];
 324                         if (ns == null) {
 325                                 if (!create)
 326                                         return null;
 327
 328                                 ns = new Namespace (this, first);
 329                                 namespaces.Add (first, ns);
 330                         }
 331
 332                         if (pos >= 0)
 333                                 ns = ns.GetNamespace (name.Substring (pos + 1), create);
 334
 335                         return ns;
 336                 }
 337
 338                 TypeExpr LookupType (string name, Location loc)
 339                 {
 340                         if (cached_types.Contains (name))
 341                                 return cached_types [name] as TypeExpr;
 342
 343                         Type t = null;
 344                         if (declspaces != null) {
 345                                 DeclSpace tdecl = declspaces [name] as DeclSpace;
 346                                 if (tdecl != null) {
 347                                         //
 348                                         // Note that this is not:
 349                                         //
 350                                         //   t = tdecl.DefineType ()
 351                                         //
 352                                         // This is to make it somewhat more useful when a DefineType
 353                                         // fails due to problems in nested types (more useful in the sense
 354                                         // of fewer misleading error messages)
 355                                         //
 356                                         tdecl.DefineType ();
 357                                         t = tdecl.TypeBuilder;
 358                                 }
 359                         }
 360                         string lookup = t != null ? t.FullName : (fullname == "" ? name : fullname + "." + name);
 361                         Type rt = root.LookupTypeReflection (lookup, loc);
 362                         if (t == null)
 363                                 t = rt;
 364
 365                         TypeExpr te = t == null ? null : new TypeExpression (t, Location.Null);
 366                         cached_types [name] = te;
 367                         return te;
 368                 }
 369
 370                 public FullNamedExpression Lookup (DeclSpace ds, string name, Location loc)
 371                 {
 372                         if (namespaces.Contains (name))
 373                                 return (Namespace) namespaces [name];
 374
 375                         TypeExpr te = LookupType (name, loc);
 376                         if (te == null || !ds.CheckAccessLevel (te.Type))
 377                                 return null;
 378
 379                         return te;
 380                 }
 381
 382                 public void AddDeclSpace (string name, DeclSpace ds)
 383                 {
 384                         if (declspaces == null)
 385                                 declspaces = new HybridDictionary ();
 386                         declspaces.Add (name, ds);
 387                 }
 388
 389                 /// <summary>
 390                 ///   The qualified name of the current namespace
 391                 /// </summary>
 392                 public string Name {
 393                         get { return fullname; }
 394                 }
 395
 396                 public override string FullName {
 397                         get { return fullname; }
 398                 }
 399
 400                 /// <summary>
 401                 ///   The parent of this namespace, used by the parser to "Pop"
 402                 ///   the current namespace declaration
 403                 /// </summary>
 404                 public Namespace Parent {
 405                         get { return parent; }
 406                 }
 407
 408                 public override string ToString ()
 409                 {
 410                         return String.Format ("Namespace ({0})", Name);
 411                 }
 412         }
 413
 414         public class NamespaceEntry {
 415                 Namespace ns;
 416                 NamespaceEntry parent, implicit_parent;
 417                 SourceFile file;
 418                 int symfile_id;
 419                 Hashtable aliases;
 420                 ArrayList using_clauses;
 421                 public bool DeclarationFound = false;
 422                 bool UsingFound;
 423
 424                 static ArrayList entries = new ArrayList ();
 425
 426                 public static void Reset ()
 427                 {
 428                         entries = new ArrayList ();
 429                 }
 430
 431                 //
 432                 // This class holds the location where a using definition is
 433                 // done, and whether it has been used by the program or not.
 434                 //
 435                 // We use this to flag using clauses for namespaces that do not
 436                 // exist.
 437                 //
 438                 public class UsingEntry {
 439                         public readonly MemberName Name;
 440                         readonly Expression Expr;
 441                         readonly NamespaceEntry NamespaceEntry;
 442                         readonly Location Location;
 443
 444                         public UsingEntry (NamespaceEntry entry, MemberName name, Location loc)
 445                         {
 446                                 Name = name;
 447                                 Expr = name.GetTypeExpression ();
 448                                 NamespaceEntry = entry;
 449                                 Location = loc;
 450                         }
 451
 452                         internal Namespace resolved;
 453
 454                         public Namespace Resolve ()
 455                         {
 456                                 if (resolved != null)
 457                                         return resolved;
 458
 459                                 DeclSpace root = RootContext.Tree.Types;
 460                                 root.NamespaceEntry = NamespaceEntry;
 461                                 FullNamedExpression fne = Expr.ResolveAsTypeStep (root.EmitContext, false);
 462                                 root.NamespaceEntry = null;
 463
 464                                 if (fne == null) {
 465                                         Error_NamespaceNotFound (Location, Name.ToString ());
 466                                         return null;
 467                                 }
 468
 469                                 resolved = fne as Namespace;
 470                                 if (resolved == null) {
 471                                         Report.Error (138, Location,
 472                                                 "`{0} is a type not a namespace. A using namespace directive can only be applied to namespaces", Name.ToString ());
 473                                 }
 474                                 return resolved;
 475                         }
 476                 }
 477
 478                 public abstract class AliasEntry {
 479                         public readonly string Name;
 480                         public readonly NamespaceEntry NamespaceEntry;
 481                         public readonly Location Location;
 482
 483                         protected AliasEntry (NamespaceEntry entry, string name, Location loc)
 484                         {
 485                                 Name = name;
 486                                 NamespaceEntry = entry;
 487                                 Location = loc;
 488                         }
 489
 490                         protected FullNamedExpression resolved;
 491                         bool error;
 492
 493                         public FullNamedExpression Resolve ()
 494                         {
 495                                 if (resolved != null || error)
 496                                         return resolved;
 497                                 resolved = DoResolve ();
 498                                 if (resolved == null)
 499                                         error = true;
 500                                 return resolved;
 501                         }
 502
 503                         protected abstract FullNamedExpression DoResolve ();
 504                 }
 505
 506                 public class LocalAliasEntry : AliasEntry
 507                 {
 508                         public readonly Expression Alias;
 509
 510                         public LocalAliasEntry (NamespaceEntry entry, string name, MemberName alias, Location loc) :
 511                                 base (entry, name, loc)
 512                         {
 513                                 Alias = alias.GetTypeExpression ();
 514                         }
 515
 516                         protected override FullNamedExpression DoResolve ()
 517                         {
 518                                 DeclSpace root = RootContext.Tree.Types;
 519                                 root.NamespaceEntry = NamespaceEntry;
 520                                 resolved = Alias.ResolveAsTypeStep (root.EmitContext, false);
 521                                 root.NamespaceEntry = null;
 522
 523                                 if (resolved == null)
 524                                         Error_NamespaceNotFound (Location, Alias.ToString ());
 525                                 return resolved;
 526                         }
 527                 }
 528
 529                 public class ExternAliasEntry : AliasEntry
 530                 {
 531                         public ExternAliasEntry (NamespaceEntry entry, string name, Location loc) :
 532                                 base (entry, name, loc)
 533                         {
 534                         }
 535
 536                         protected override FullNamedExpression DoResolve ()
 537                         {
 538                                 resolved = RootNamespace.GetRootNamespace (Name);
 539                                 if (resolved == null)
 540                                         Report.Error (430, Location, "The extern alias '" + Name +
 541                                                                         "' was not specified in a /reference option");
 542
 543                                 return resolved;
 544                         }
 545                 }
 546
 547                 public NamespaceEntry (NamespaceEntry parent, SourceFile file, string name, Location loc)
 548                 {
 549                         this.parent = parent;
 550                         this.file = file;
 551                         entries.Add (this);
 552                         this.ID = entries.Count;
 553
 554                         if (parent != null)
 555                                 ns = parent.NS.GetNamespace (name, true);
 556                         else if (name != null)
 557                                 ns = RootNamespace.Global.GetNamespace (name, true);
 558                         else
 559                                 ns = RootNamespace.Global;
 560                 }
 561
 562                 private NamespaceEntry (NamespaceEntry parent, SourceFile file, Namespace ns)
 563                 {
 564                         this.parent = parent;
 565                         this.file = file;
 566                         // no need to add self to 'entries', since we don't have any aliases or using entries.
 567                         this.ID = -1;
 568                         this.IsImplicit = true;
 569                         this.ns = ns;
 570                 }
 571
 572                 //
 573                 // According to section 16.3.1 (using-alias-directive), the namespace-or-type-name is
 574                 // resolved as if the immediately containing namespace body has no using-directives.
 575                 //
 576                 // Section 16.3.2 says that the same rule is applied when resolving the namespace-name
 577                 // in the using-namespace-directive.
 578                 //
 579                 // To implement these rules, the expressions in the using directives are resolved using
 580                 // the "doppelganger" (ghostly bodiless duplicate).
 581                 //
 582                 NamespaceEntry doppelganger;
 583                 NamespaceEntry Doppelganger {
 584                         get {
 585                                 if (!IsImplicit && doppelganger == null)
 586                                         doppelganger = new NamespaceEntry (ImplicitParent, file, ns);
 587                                 return doppelganger;
 588                         }
 589                 }
 590
 591                 public readonly int ID;
 592                 public readonly bool IsImplicit;
 593
 594                 public Namespace NS {
 595                         get { return ns; }
 596                 }
 597
 598                 public NamespaceEntry Parent {
 599                         get { return parent; }
 600                 }
 601
 602                 public NamespaceEntry ImplicitParent {
 603                         get {
 604                                 if (parent == null)
 605                                         return null;
 606                                 if (implicit_parent == null) {
 607                                         implicit_parent = (parent.NS == ns.Parent)
 608                                                 ? parent
 609                                                 : new NamespaceEntry (parent, file, ns.Parent);
 610                                 }
 611                                 return implicit_parent;
 612                         }
 613                 }
 614
 615                 /// <summary>
 616                 ///   Records a new namespace for resolving name references
 617                 /// </summary>
 618                 public void Using (MemberName name, Location loc)
 619                 {
 620                         if (DeclarationFound){
 621                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 622                                 return;
 623                         }
 624
 625                         UsingFound = true;
 626
 627                         if (name.Equals (ns.MemberName))
 628                                 return;
 629
 630                         if (using_clauses == null)
 631                                 using_clauses = new ArrayList ();
 632
 633                         foreach (UsingEntry old_entry in using_clauses) {
 634                                 if (name.Equals (old_entry.Name)) {
 635                                         Report.Warning (105, 3, loc, "The using directive for `{0}' appeared previously in this namespace", name.GetName ());
 636                                                 return;
 637                                         }
 638                                 }
 639
 640                         UsingEntry ue = new UsingEntry (Doppelganger, name, loc);
 641                         using_clauses.Add (ue);
 642                 }
 643
 644                 public void UsingAlias (string name, MemberName alias, Location loc)
 645                 {
 646                         if (DeclarationFound){
 647                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 648                                 return;
 649                         }
 650
 651                         UsingFound = true;
 652
 653                         if (aliases == null)
 654                                 aliases = new Hashtable ();
 655
 656                         if (aliases.Contains (name)) {
 657                                 AliasEntry ae = (AliasEntry)aliases [name];
 658                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 659                                 Report.Error (1537, loc, "The using alias `" + name +
 660                                               "' appeared previously in this namespace");
 661                                 return;
 662                         }
 663
 664                         if (RootContext.Version == LanguageVersion.Default &&
 665                             name == "global" && RootContext.WarningLevel >= 2)
 666                                 Report.Warning (440, 2, loc, "An alias named `global' will not be used when resolving 'global::';" +
 667                                         " the global namespace will be used instead");
 668
 669                         aliases [name] = new LocalAliasEntry (Doppelganger, name, alias, loc);
 670                 }
 671
 672                 public void UsingExternalAlias (string name, Location loc)
 673                 {
 674                         if (UsingFound || DeclarationFound) {
 675                                 Report.Error (439, loc, "An extern alias declaration must precede all other elements");
 676                                 return;
 677                         }
 678
 679                         if (aliases == null)
 680                                 aliases = new Hashtable ();
 681
 682                         if (aliases.Contains (name)) {
 683                                 AliasEntry ae = (AliasEntry) aliases [name];
 684                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 685                                 Report.Error (1537, loc, "The using alias `" + name +
 686                                               "' appeared previously in this namespace");
 687                                 return;
 688                         }
 689
 690                         if (name == "global") {
 691                                 Report.Error (1681, loc, "You cannot redefine the global extern alias");
 692                                 return;
 693                         }
 694
 695                         aliases [name] = new ExternAliasEntry (Doppelganger, name, loc);
 696                 }
 697
 698                 public FullNamedExpression LookupNamespaceOrType (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 699                 {
 700                         // Precondition: Only simple names (no dots) will be looked up with this function.
 701                         FullNamedExpression resolved = null;
 702                         for (NamespaceEntry curr_ns = this; curr_ns != null; curr_ns = curr_ns.ImplicitParent) {
 703                                 if ((resolved = curr_ns.Lookup (ds, name, loc, ignore_cs0104)) != null)
 704                                         break;
 705                         }
 706                         return resolved;
 707                 }
 708
 709                 static void Error_AmbiguousTypeReference (Location loc, string name, FullNamedExpression t1, FullNamedExpression t2)
 710                 {
 711                         Report.Error (104, loc, "`{0}' is an ambiguous reference between `{1}' and `{2}'",
 712                                 name, t1.FullName, t2.FullName);
 713                 }
 714
 715                 // Looks-up a alias named @name in this and surrounding namespace declarations
 716                 public FullNamedExpression LookupAlias (string name)
 717                 {
 718                         AliasEntry entry = null;
 719                         // We use Parent rather than ImplicitParent since we know implicit namespace declarations
 720                         // cannot have using entries.
 721                         for (NamespaceEntry n = this; n != null; n = n.Parent) {
 722                                 if (n.aliases == null)
 723                                         continue;
 724                                 entry = n.aliases [name] as AliasEntry;
 725                                 if (entry != null)
 726                                         return entry.Resolve ();
 727                         }
 728                         return null;
 729                 }
 730
 731                 private FullNamedExpression Lookup (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 732                 {
 733                         //
 734                         // Check whether it's in the namespace.
 735                         //
 736                         FullNamedExpression fne = NS.Lookup (ds, name, loc);
 737                         if (fne != null)
 738                                 return fne;
 739
 740                         if (IsImplicit)
 741                                 return null;
 742
 743                         //
 744                         // Check aliases.
 745                         //
 746                         if (aliases != null) {
 747                                 AliasEntry entry = aliases [name] as AliasEntry;
 748                                 if (entry != null)
 749                                         return entry.Resolve ();
 750                         }
 751
 752                         //
 753                         // Check using entries.
 754                         //
 755                         FullNamedExpression match = null;
 756                         foreach (Namespace using_ns in GetUsingTable ()) {
 757                                 match = using_ns.Lookup (ds, name, loc);
 758                                 if (match == null || !(match is TypeExpr))
 759                                         continue;
 760                                 if (fne != null) {
 761                                         if (!ignore_cs0104)
 762                                                 Error_AmbiguousTypeReference (loc, name, fne, match);
 763                                         return null;
 764                                 }
 765                                 fne = match;
 766                         }
 767
 768                         return fne;
 769                 }
 770
 771                 // Our cached computation.
 772                 readonly Namespace [] empty_namespaces = new Namespace [0];
 773                 Namespace [] namespace_using_table;
 774                 Namespace [] GetUsingTable ()
 775                 {
 776                         if (namespace_using_table != null)
 777                                 return namespace_using_table;
 778
 779                         if (using_clauses == null) {
 780                                 namespace_using_table = empty_namespaces;
 781                                 return namespace_using_table;
 782                         }
 783
 784                         ArrayList list = new ArrayList (using_clauses.Count);
 785
 786                         foreach (UsingEntry ue in using_clauses) {
 787                                 Namespace using_ns = ue.Resolve ();
 788                                 if (using_ns == null)
 789                                         continue;
 790
 791                                 list.Add (using_ns);
 792                         }
 793
 794                         namespace_using_table = new Namespace [list.Count];
 795                         list.CopyTo (namespace_using_table, 0);
 796                         return namespace_using_table;
 797                 }
 798
 799                 readonly string [] empty_using_list = new string [0];
 800
 801                 public int SymbolFileID {
 802                         get {
 803                                 if (symfile_id == 0 && file.SourceFileEntry != null) {
 804                                         int parent_id = parent == null ? 0 : parent.SymbolFileID;
 805
 806                                         string [] using_list = empty_using_list;
 807                                         if (using_clauses != null) {
 808                                                 using_list = new string [using_clauses.Count];
 809                                                 for (int i = 0; i < using_clauses.Count; i++)
 810                                                         using_list [i] = ((UsingEntry) using_clauses [i]).Name.ToString ();
 811                                         }
 812
 813                                         symfile_id = CodeGen.SymbolWriter.DefineNamespace (ns.Name, file.SourceFileEntry, using_list, parent_id);
 814                                 }
 815                                 return symfile_id;
 816                         }
 817                 }
 818
 819                 static void MsgtryRef (string s)
 820                 {
 821                         Console.WriteLine ("    Try using -r:" + s);
 822                 }
 823
 824                 static void MsgtryPkg (string s)
 825                 {
 826                         Console.WriteLine ("    Try using -pkg:" + s);
 827                 }
 828
 829                 public static void Error_NamespaceNotFound (Location loc, string name)
 830                 {
 831                         Report.Error (246, loc, "The type or namespace name `{0}' could not be found. Are you missing a using directive or an assembly reference?",
 832                                 name);
 833
 834                         switch (name) {
 835                         case "Gtk": case "GtkSharp":
 836                                 MsgtryPkg ("gtk-sharp");
 837                                 break;
 838
 839                         case "Gdk": case "GdkSharp":
 840                                 MsgtryPkg ("gdk-sharp");
 841                                 break;
 842
 843                         case "Glade": case "GladeSharp":
 844                                 MsgtryPkg ("glade-sharp");
 845                                 break;
 846
 847                         case "System.Drawing":
 848                         case "System.Web.Services":
 849                         case "System.Web":
 850                         case "System.Data":
 851                         case "System.Windows.Forms":
 852                                 MsgtryRef (name);
 853                                 break;
 854                         }
 855                 }
 856
 857                 /// <summary>
 858                 ///   Used to validate that all the using clauses are correct
 859                 ///   after we are finished parsing all the files.
 860                 /// </summary>
 861                 void VerifyUsing ()
 862                 {
 863                         if (using_clauses != null) {
 864                                 foreach (UsingEntry ue in using_clauses)
 865                                         ue.Resolve ();
 866                         }
 867
 868                         if (aliases != null) {
 869                                 foreach (DictionaryEntry de in aliases)
 870                                         ((AliasEntry) de.Value).Resolve ();
 871                         }
 872                 }
 873
 874                 /// <summary>
 875                 ///   Used to validate that all the using clauses are correct
 876                 ///   after we are finished parsing all the files.
 877                 /// </summary>
 878                 static public void VerifyAllUsing ()
 879                 {
 880                         foreach (NamespaceEntry entry in entries)
 881                                 entry.VerifyUsing ();
 882                 }
 883
 884                 public string GetSignatureForError ()
 885                 {
 886                         return ns.GetSignatureForError ();
 887                 }
 888
 889                 public override string ToString ()
 890                 {
 891                         return ns.ToString ();
 892                 }
 893         }
 894 }