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         {
  18                 static MethodInfo get_namespaces_method;
  19
  20                 Assembly referenced_assembly;
  21                 Hashtable cached_namespaces;
  22
  23                 static RootNamespace ()
  24                 {
  25                         get_namespaces_method = typeof (Assembly).GetMethod ("GetNamespaces", BindingFlags.Instance | BindingFlags.NonPublic);
  26                 }
  27
  28                 //
  29                 // We access GlobalRoot here to beautify the code
  30                 //
  31                 public static GlobalRootNamespace Global {
  32                         get {
  33                                 return GlobalRootNamespace.GlobalRoot;
  34                         }
  35                 }
  36
  37                 public RootNamespace (Assembly assembly) : base (null, String.Empty)
  38                 {
  39                         this.referenced_assembly = assembly;
  40                         this.cached_namespaces = new Hashtable ();
  41                         this.cached_namespaces.Add ("", null);
  42
  43                         if (this.referenced_assembly != null)
  44                                 ComputeNamespacesForAssembly (this.referenced_assembly);
  45                 }
  46
  47                 public virtual Type LookupTypeReflection (string name, Location loc)
  48                 {
  49                         return GetTypeInAssembly (referenced_assembly, name);
  50                 }
  51
  52                 public virtual void RegisterNamespace (Namespace ns)
  53                 {
  54                         // Do nothing.
  55                 }
  56
  57                 protected void ComputeNamespacesForAssembly (Assembly assembly)
  58                 {
  59                         if (get_namespaces_method != null) {
  60                                 string [] namespaces = (string []) get_namespaces_method.Invoke (assembly, null);
  61                                 foreach (string ns in namespaces) {
  62                                         if (ns.Length == 0)
  63                                                 continue;
  64
  65                                         // Method from parent class Namespace
  66                                         GetNamespace (ns, true);
  67                                 }
  68                         } else {
  69                                 //cached_namespaces.Add ("", null);
  70                                 foreach (Type t in assembly.GetExportedTypes ()) {
  71                                         string ns = t.Namespace;
  72                                         if (ns == null || cached_namespaces.Contains (ns))
  73                                                 continue;
  74
  75                                         // Method from parent class Namespace
  76                                         GetNamespace (ns, true);
  77                                         cached_namespaces.Add (ns, null);
  78                                 }
  79                         }
  80                 }
  81
  82                 protected Type GetTypeInAssembly (Assembly assembly, string name)
  83                 {
  84                         Type t = assembly.GetType (name);
  85                         if (t == null)
  86                                 return null;
  87
  88                         if (t.IsPointer)
  89                                 throw new InternalErrorException ("Use GetPointerType() to get a pointer");
  90
  91                         TypeAttributes ta = t.Attributes & TypeAttributes.VisibilityMask;
  92                         if (ta != TypeAttributes.NotPublic && ta != TypeAttributes.NestedPrivate &&
  93                                         ta != TypeAttributes.NestedAssembly && ta != TypeAttributes.NestedFamANDAssem)
  94                                 return t;
  95
  96                         return null;
  97                 }
  98
  99                 protected Hashtable CachedNamespaces {
 100                         get {
 101                                 return cached_namespaces;
 102                         }
 103                 }
 104
 105         }
 106
 107         public class GlobalRootNamespace : RootNamespace
 108         {
 109                 static ArrayList all_namespaces;
 110                 static Hashtable namespaces_map;
 111                 static Hashtable root_namespaces;
 112                 internal static GlobalRootNamespace GlobalRoot;
 113
 114                 Assembly [] assemblies;
 115                 Module [] modules;
 116
 117                 public static void Reset ()
 118                 {
 119                         all_namespaces = new ArrayList ();
 120                         namespaces_map = new Hashtable ();
 121                         root_namespaces = new Hashtable ();
 122                         GlobalRoot = new GlobalRootNamespace ();
 123                 }
 124
 125                 static GlobalRootNamespace ()
 126                 {
 127                         Reset ();
 128                 }
 129
 130                 public GlobalRootNamespace () : base (null)
 131                 {
 132                         assemblies = new Assembly [0];
 133                         modules = new Module [0];
 134                 }
 135
 136                 public void AddAssemblyReference (Assembly assembly)
 137                 {
 138                         Assembly [] tmp = new Assembly [assemblies.Length + 1];
 139                         Array.Copy (assemblies, 0, tmp, 0, assemblies.Length);
 140                         tmp [assemblies.Length] = assembly;
 141
 142                         assemblies = tmp;
 143                         ComputeNamespacesForAssembly (assembly);
 144                 }
 145
 146                 public void AddModuleReference (Module module)
 147                 {
 148                         Module [] tmp = new Module [modules.Length + 1];
 149                         Array.Copy (modules, 0, tmp, 0, modules.Length);
 150                         tmp [modules.Length] = module;
 151
 152                         modules = tmp;
 153
 154                         if (module != CodeGen.Module.Builder)
 155                                 ComputeNamespacesForModule (module);
 156                 }
 157
 158                 void ComputeNamespacesForModule (Module module)
 159                 {
 160                         foreach (Type t in module.GetTypes ()) {
 161                                 string ns = t.Namespace;
 162                                 if (ns == null || CachedNamespaces.Contains (ns))
 163                                         continue;
 164
 165                                 GetNamespace (ns, true);
 166                                 CachedNamespaces.Add (ns, null);
 167                         }
 168                 }
 169
 170                 public override Type LookupTypeReflection (string name, Location loc)
 171                 {
 172                         Type found_type = null;
 173
 174                         foreach (Assembly a in assemblies) {
 175                                 Type t = GetTypeInAssembly (a, name);
 176                                 if (t == null)
 177                                         continue;
 178
 179                                 if (found_type == null) {
 180                                         found_type = t;
 181                                         continue;
 182                                 }
 183
 184                                 Report.SymbolRelatedToPreviousError (found_type);
 185                                 Report.SymbolRelatedToPreviousError (t);
 186                                 Report.Error (433, loc, "The imported type `{0}' is defined multiple times", name);
 187
 188                                 return found_type;
 189                         }
 190
 191                         foreach (Module module in modules) {
 192                                 Type t = module.GetType (name);
 193                                 if (t == null)
 194                                         continue;
 195
 196                                 if (found_type == null) {
 197                                         found_type = t;
 198                                         continue;
 199                                 }
 200
 201                                 Report.SymbolRelatedToPreviousError (t);
 202                                 Report.SymbolRelatedToPreviousError (found_type);
 203                                 Report.Warning (436, 2, loc, "Ignoring imported type `{0}' since the current assembly already has a declaration with the same name",
 204                                                         TypeManager.CSharpName (t));
 205                                 return t;
 206                         }
 207
 208                         return found_type;
 209                 }
 210
 211                 public override void RegisterNamespace (Namespace child)
 212                 {
 213                         all_namespaces.Add (child);
 214                         if (namespaces_map.Contains (child.Name))
 215                                 return;
 216                         namespaces_map [child.Name] = true;
 217                 }
 218
 219                 public static RootNamespace DefineRootNamespace (string name, Assembly assembly)
 220                 {
 221                         RootNamespace retval = (RootNamespace) root_namespaces [name];
 222                         if (retval != null)
 223                                 return retval;
 224
 225                         retval = new RootNamespace (assembly);
 226                         return retval;
 227                 }
 228
 229                 public static bool IsNamespace (string name)
 230                 {
 231                         return namespaces_map [name] != null;
 232                 }
 233
 234                 public static ArrayList UserDefinedNamespaces {
 235                         get { return all_namespaces; }
 236                 }
 237
 238                 public static void VerifyUsingForAll ()
 239                 {
 240                         foreach (Namespace ns in all_namespaces)
 241                                 ns.VerifyUsing ();
 242                 }
 243
 244                 public static void DefineNamespacesForAll (SymbolWriter symwriter)
 245                 {
 246                         foreach (Namespace ns in all_namespaces)
 247                                 ns.DefineNamespaces (symwriter);
 248                 }
 249
 250                 public override string ToString ()
 251                 {
 252                         return "Namespace (<root>)";
 253                 }
 254
 255                 public override string GetSignatureForError ()
 256                 {
 257                         return "global::";
 258                 }
 259
 260         }
 261
 262         /// <summary>
 263         ///   Keeps track of the namespaces defined in the C# code.
 264         ///
 265         ///   This is an Expression to allow it to be referenced in the
 266         ///   compiler parse/intermediate tree during name resolution.
 267         /// </summary>
 268         public class Namespace : FullNamedExpression {
 269
 270                 Namespace parent;
 271                 string fullname;
 272                 ArrayList entries;
 273                 Hashtable namespaces;
 274                 IDictionary declspaces;
 275                 Hashtable cached_types;
 276                 RootNamespace root;
 277
 278                 public readonly MemberName MemberName;
 279
 280                 /// <summary>
 281                 ///   Constructor Takes the current namespace and the
 282                 ///   name.  This is bootstrapped with parent == null
 283                 ///   and name = ""
 284                 /// </summary>
 285                 public Namespace (Namespace parent, string name)
 286                 {
 287                         // Expression members.
 288                         this.eclass = ExprClass.Namespace;
 289                         this.Type = null;
 290                         this.loc = Location.Null;
 291
 292                         this.parent = parent;
 293
 294                         if (parent != null)
 295                                 this.root = parent.root;
 296                         else
 297                                 this.root = this as RootNamespace;
 298
 299                         if (this.root == null)
 300                                 throw new InternalErrorException ("Root namespaces must be created using RootNamespace");
 301
 302                         string pname = parent != null ? parent.Name : "";
 303
 304                         if (pname == "")
 305                                 fullname = name;
 306                         else
 307                                 fullname = parent.Name + "." + name;
 308
 309                         if (fullname == null)
 310                                 throw new InternalErrorException ("Namespace has a null fullname");
 311
 312                         if (parent != null && parent.MemberName != MemberName.Null)
 313                                 MemberName = new MemberName (
 314                                         parent.MemberName, name, parent.MemberName.Location);
 315                         else if (name == "")
 316                                 MemberName = MemberName.Null;
 317                         else
 318                                 MemberName = new MemberName (name, Location.Null);
 319
 320                         entries = new ArrayList ();
 321                         namespaces = new Hashtable ();
 322                         cached_types = new Hashtable ();
 323
 324                         root.RegisterNamespace (this);
 325                 }
 326
 327                 public override Expression DoResolve (EmitContext ec)
 328                 {
 329                         return this;
 330                 }
 331
 332                 public override void Emit (EmitContext ec)
 333                 {
 334                         throw new InternalErrorException ("Expression tree referenced namespace " + fullname + " during Emit ()");
 335                 }
 336
 337                 public override string GetSignatureForError ()
 338                 {
 339                         return Name;
 340                 }
 341
 342                 public Namespace GetNamespace (string name, bool create)
 343                 {
 344                         int pos = name.IndexOf ('.');
 345
 346                         Namespace ns;
 347                         string first;
 348                         if (pos >= 0)
 349                                 first = name.Substring (0, pos);
 350                         else
 351                                 first = name;
 352
 353                         ns = (Namespace) namespaces [first];
 354                         if (ns == null) {
 355                                 if (!create)
 356                                         return null;
 357
 358                                 ns = new Namespace (this, first);
 359                                 namespaces.Add (first, ns);
 360                         }
 361
 362                         if (pos >= 0)
 363                                 ns = ns.GetNamespace (name.Substring (pos + 1), create);
 364
 365                         return ns;
 366                 }
 367
 368                 TypeExpr LookupType (string name, Location loc)
 369                 {
 370                         if (cached_types.Contains (name))
 371                                 return cached_types [name] as TypeExpr;
 372
 373                         Type t = null;
 374                         if (declspaces != null) {
 375                                 DeclSpace tdecl = declspaces [name] as DeclSpace;
 376                                 if (tdecl != null) {
 377                                         //
 378                                         // Note that this is not:
 379                                         //
 380                                         //   t = tdecl.DefineType ()
 381                                         //
 382                                         // This is to make it somewhat more useful when a DefineType
 383                                         // fails due to problems in nested types (more useful in the sense
 384                                         // of fewer misleading error messages)
 385                                         //
 386                                         tdecl.DefineType ();
 387                                         t = tdecl.TypeBuilder;
 388                                 }
 389                         }
 390                         string lookup = t != null ? t.FullName : (fullname == "" ? name : fullname + "." + name);
 391                         Type rt = root.LookupTypeReflection (lookup, loc);
 392                         if (t == null)
 393                                 t = rt;
 394
 395                         TypeExpr te = t == null ? null : new TypeExpression (t, Location.Null);
 396                         cached_types [name] = te;
 397                         return te;
 398                 }
 399
 400                 public FullNamedExpression Lookup (DeclSpace ds, string name, Location loc)
 401                 {
 402                         Namespace ns = GetNamespace (name, false);
 403                         if (ns != null)
 404                                 return ns;
 405
 406                         TypeExpr te = LookupType (name, loc);
 407                         if (te == null || !ds.CheckAccessLevel (te.Type))
 408                                 return null;
 409
 410                         return te;
 411                 }
 412
 413                 public void AddNamespaceEntry (NamespaceEntry entry)
 414                 {
 415                         entries.Add (entry);
 416                 }
 417
 418                 public void AddDeclSpace (string name, DeclSpace ds)
 419                 {
 420                         if (declspaces == null)
 421                                 declspaces = new HybridDictionary ();
 422                         declspaces.Add (name, ds);
 423                 }
 424
 425                 /// <summary>
 426                 ///   Used to validate that all the using clauses are correct
 427                 ///   after we are finished parsing all the files.
 428                 /// </summary>
 429                 public void VerifyUsing ()
 430                 {
 431                         foreach (NamespaceEntry entry in entries)
 432                                 entry.VerifyUsing ();
 433                 }
 434
 435                 public void DefineNamespaces (SymbolWriter symwriter)
 436                 {
 437                         foreach (NamespaceEntry entry in entries)
 438                                 entry.DefineNamespace (symwriter);
 439                 }
 440
 441                 /// <summary>
 442                 ///   The qualified name of the current namespace
 443                 /// </summary>
 444                 public string Name {
 445                         get { return fullname; }
 446                 }
 447
 448                 public override string FullName {
 449                         get { return fullname; }
 450                 }
 451
 452                 /// <summary>
 453                 ///   The parent of this namespace, used by the parser to "Pop"
 454                 ///   the current namespace declaration
 455                 /// </summary>
 456                 public Namespace Parent {
 457                         get { return parent; }
 458                 }
 459
 460                 public override string ToString ()
 461                 {
 462                         return String.Format ("Namespace ({0})", Name);
 463                 }
 464         }
 465
 466         public class NamespaceEntry
 467         {
 468                 Namespace ns;
 469                 NamespaceEntry parent, implicit_parent;
 470                 SourceFile file;
 471                 int symfile_id;
 472                 Hashtable aliases;
 473                 ArrayList using_clauses;
 474                 public bool DeclarationFound = false;
 475                 public bool UsingFound = false;
 476
 477                 //
 478                 // This class holds the location where a using definition is
 479                 // done, and whether it has been used by the program or not.
 480                 //
 481                 // We use this to flag using clauses for namespaces that do not
 482                 // exist.
 483                 //
 484                 public class UsingEntry {
 485                         public readonly MemberName Name;
 486                         readonly Expression Expr;
 487                         readonly NamespaceEntry NamespaceEntry;
 488                         readonly Location Location;
 489
 490                         public UsingEntry (NamespaceEntry entry, MemberName name, Location loc)
 491                         {
 492                                 Name = name;
 493                                 Expr = name.GetTypeExpression ();
 494                                 NamespaceEntry = entry;
 495                                 Location = loc;
 496                         }
 497
 498                         internal Namespace resolved;
 499
 500                         public Namespace Resolve ()
 501                         {
 502                                 if (resolved != null)
 503                                         return resolved;
 504
 505                                 DeclSpace root = RootContext.Tree.Types;
 506                                 root.NamespaceEntry = NamespaceEntry;
 507                                 FullNamedExpression fne = Expr.ResolveAsTypeStep (root.EmitContext, false);
 508                                 root.NamespaceEntry = null;
 509
 510                                 if (fne == null) {
 511                                         Error_NamespaceNotFound (Location, Name.ToString ());
 512                                         return null;
 513                                 }
 514
 515                                 resolved = fne as Namespace;
 516                                 if (resolved == null) {
 517                                         Report.Error (138, Location,
 518                                                 "`{0} is a type not a namespace. A using namespace directive can only be applied to namespaces", Name.ToString ());
 519                                 }
 520                                 return resolved;
 521                         }
 522                 }
 523
 524                 public abstract class AliasEntry {
 525                         public readonly string Name;
 526                         public readonly NamespaceEntry NamespaceEntry;
 527                         public readonly Location Location;
 528
 529                         protected AliasEntry (NamespaceEntry entry, string name, Location loc)
 530                         {
 531                                 Name = name;
 532                                 NamespaceEntry = entry;
 533                                 Location = loc;
 534                         }
 535
 536                         protected FullNamedExpression resolved;
 537
 538                         public abstract FullNamedExpression Resolve ();
 539                 }
 540
 541                 public class LocalAliasEntry : AliasEntry
 542                 {
 543                         public readonly Expression Alias;
 544
 545                         public LocalAliasEntry (NamespaceEntry entry, string name, MemberName alias, Location loc) :
 546                                 base (entry, name, loc)
 547                         {
 548                                 Alias = alias.GetTypeExpression ();
 549                         }
 550
 551                         public override FullNamedExpression Resolve ()
 552                         {
 553                                 if (resolved != null)
 554                                         return resolved;
 555
 556                                 DeclSpace root = RootContext.Tree.Types;
 557                                 root.NamespaceEntry = NamespaceEntry;
 558                                 resolved = Alias.ResolveAsTypeStep (root.EmitContext, false);
 559                                 root.NamespaceEntry = null;
 560
 561                                 return resolved;
 562                         }
 563                 }
 564
 565                 public class ExternAliasEntry : AliasEntry
 566                 {
 567                         public ExternAliasEntry (NamespaceEntry entry, string name, Location loc) :
 568                                 base (entry, name, loc)
 569                         {
 570                         }
 571
 572                         public override FullNamedExpression Resolve ()
 573                         {
 574                                 if (resolved != null)
 575                                         return resolved;
 576
 577                                 resolved = TypeManager.ComputeNamespacesForAlias (Name);
 578                                 if (resolved == null) {
 579                                         Report.Error (430, Location, "The extern alias '" + Name +
 580                                                                         "' was not specified in a /reference option");
 581                                 }
 582
 583                                 return resolved;
 584                         }
 585                 }
 586
 587                 public NamespaceEntry (NamespaceEntry parent, SourceFile file, string name, Location loc)
 588                 {
 589                         this.parent = parent;
 590                         this.file = file;
 591                         this.IsImplicit = false;
 592                         this.ID = ++next_id;
 593
 594                         if (parent != null)
 595                                 ns = parent.NS.GetNamespace (name, true);
 596                         else if (name != null)
 597                                 ns = RootNamespace.Global.GetNamespace (name, true);
 598                         else
 599                                 ns = RootNamespace.Global;
 600
 601                         ns.AddNamespaceEntry (this);
 602                 }
 603
 604
 605                 private NamespaceEntry (NamespaceEntry parent, SourceFile file, Namespace ns)
 606                 {
 607                         this.parent = parent;
 608                         this.file = file;
 609                         this.IsImplicit = true;
 610                         this.ID = ++next_id;
 611                         this.ns = ns;
 612                 }
 613
 614                 //
 615                 // According to section 16.3.1 (using-alias-directive), the namespace-or-type-name is
 616                 // resolved as if the immediately containing namespace body has no using-directives.
 617                 //
 618                 // Section 16.3.2 says that the same rule is applied when resolving the namespace-name
 619                 // in the using-namespace-directive.
 620                 //
 621                 // To implement these rules, the expressions in the using directives are resolved using
 622                 // the "doppelganger" (ghostly bodiless duplicate).
 623                 //
 624                 NamespaceEntry doppelganger;
 625                 NamespaceEntry Doppelganger {
 626                         get {
 627                                 if (!IsImplicit && doppelganger == null)
 628                                         doppelganger = new NamespaceEntry (ImplicitParent, file, ns);
 629                                 return doppelganger;
 630                         }
 631                 }
 632
 633                 static int next_id = 0;
 634                 public readonly int ID;
 635                 public readonly bool IsImplicit;
 636
 637                 public Namespace NS {
 638                         get { return ns; }
 639                 }
 640
 641                 public NamespaceEntry Parent {
 642                         get { return parent; }
 643                 }
 644
 645                 public NamespaceEntry ImplicitParent {
 646                         get {
 647                                 if (parent == null)
 648                                         return null;
 649                                 if (implicit_parent == null) {
 650                                         implicit_parent = (parent.NS == ns.Parent)
 651                                                 ? parent
 652                                                 : new NamespaceEntry (parent, file, ns.Parent);
 653                                 }
 654                                 return implicit_parent;
 655                         }
 656                 }
 657
 658                 /// <summary>
 659                 ///   Records a new namespace for resolving name references
 660                 /// </summary>
 661                 public void Using (MemberName name, Location loc)
 662                 {
 663                         if (DeclarationFound){
 664                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 665                                 return;
 666                         }
 667
 668                         if (name.Equals (ns.MemberName))
 669                                 return;
 670
 671                         if (using_clauses == null)
 672                                 using_clauses = new ArrayList ();
 673
 674                         foreach (UsingEntry old_entry in using_clauses) {
 675                                 if (name.Equals (old_entry.Name)) {
 676                                         if (RootContext.WarningLevel >= 3)
 677                                                 Report.Warning (105, loc, "The using directive for `{0}' appeared previously in this namespace", name);
 678                                                 return;
 679                                         }
 680                                 }
 681
 682
 683                         UsingEntry ue = new UsingEntry (Doppelganger, name, loc);
 684                         using_clauses.Add (ue);
 685                 }
 686
 687                 public void UsingAlias (string name, MemberName alias, Location loc)
 688                 {
 689                         if (DeclarationFound){
 690                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 691                                 return;
 692                         }
 693
 694                         if (aliases == null)
 695                                 aliases = new Hashtable ();
 696
 697                         if (aliases.Contains (name)) {
 698                                 AliasEntry ae = (AliasEntry)aliases [name];
 699                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 700                                 Report.Error (1537, loc, "The using alias `" + name +
 701                                               "' appeared previously in this namespace");
 702                                 return;
 703                         }
 704
 705                         if (RootContext.Version == LanguageVersion.Default &&
 706                             name == "global" && RootContext.WarningLevel >= 2)
 707                                 Report.Warning (440, loc, "An alias named `global' will not be used when resolving 'global::';" +
 708                                         " the global namespace will be used instead");
 709
 710                         aliases [name] = new LocalAliasEntry (Doppelganger, name, alias, loc);
 711                 }
 712
 713                 public void UsingExternalAlias (string name, Location loc)
 714                 {
 715                         if (UsingFound || DeclarationFound) {
 716                                 Report.Error (439, loc, "An extern alias declaration must precede all other elements");
 717                                 return;
 718                         }
 719
 720                         if (aliases == null)
 721                                 aliases = new Hashtable ();
 722
 723                         if (aliases.Contains (name)) {
 724                                 AliasEntry ae = (AliasEntry) aliases [name];
 725                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 726                                 Report.Error (1537, loc, "The using alias `" + name +
 727                                               "' appeared previously in this namespace");
 728                                 return;
 729                         }
 730
 731                         if (name == "global") {
 732                                 Report.Error (1681, loc, "You cannot redefine the global extern alias");
 733                                 return;
 734                         }
 735
 736                         aliases [name] = new ExternAliasEntry (Doppelganger, name, loc);
 737                 }
 738
 739                 public FullNamedExpression LookupNamespaceOrType (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 740                 {
 741                         // Precondition: Only simple names (no dots) will be looked up with this function.
 742                         FullNamedExpression resolved = null;
 743                         for (NamespaceEntry curr_ns = this; curr_ns != null; curr_ns = curr_ns.ImplicitParent) {
 744                                 if ((resolved = curr_ns.Lookup (ds, name, loc, ignore_cs0104)) != null)
 745                                         break;
 746                         }
 747                         return resolved;
 748                 }
 749
 750                 static void Error_AmbiguousTypeReference (Location loc, string name, FullNamedExpression t1, FullNamedExpression t2)
 751                 {
 752                         Report.Error (104, loc, "`{0}' is an ambiguous reference between `{1}' and `{2}'",
 753                                 name, t1.FullName, t2.FullName);
 754                 }
 755
 756                 // Looks-up a alias named @name in this and surrounding namespace declarations
 757                 public FullNamedExpression LookupAlias (string name)
 758                 {
 759                         AliasEntry entry = null;
 760                         // We use Parent rather than ImplicitParent since we know implicit namespace declarations
 761                         // cannot have using entries.
 762                         for (NamespaceEntry n = this; n != null; n = n.Parent) {
 763                                 if (n.aliases == null)
 764                                         continue;
 765                                 entry = n.aliases [name] as AliasEntry;
 766                                 if (entry != null)
 767                                         return entry.Resolve ();
 768                         }
 769                         return null;
 770                 }
 771
 772                 private FullNamedExpression Lookup (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 773                 {
 774                         //
 775                         // Check whether it's in the namespace.
 776                         //
 777                         FullNamedExpression fne = NS.Lookup (ds, name, loc);
 778                         if (fne != null)
 779                                 return fne;
 780
 781                         if (IsImplicit)
 782                                 return null;
 783
 784                         //
 785                         // Check aliases.
 786                         //
 787                         if (aliases != null) {
 788                                 AliasEntry entry = aliases [name] as AliasEntry;
 789                                 if (entry != null)
 790                                         return entry.Resolve ();
 791                         }
 792
 793                         //
 794                         // Check using entries.
 795                         //
 796                         FullNamedExpression match = null;
 797                         foreach (Namespace using_ns in GetUsingTable ()) {
 798                                 match = using_ns.Lookup (ds, name, loc);
 799                                 if (match == null || !(match is TypeExpr))
 800                                         continue;
 801                                 if (fne != null) {
 802                                         if (!ignore_cs0104)
 803                                                 Error_AmbiguousTypeReference (loc, name, fne, match);
 804                                         return null;
 805                                 }
 806                                 fne = match;
 807                         }
 808
 809                         return fne;
 810                 }
 811
 812                 // Our cached computation.
 813                 readonly Namespace [] empty_namespaces = new Namespace [0];
 814                 Namespace [] namespace_using_table;
 815                 Namespace [] GetUsingTable ()
 816                 {
 817                         if (namespace_using_table != null)
 818                                 return namespace_using_table;
 819
 820                         if (using_clauses == null) {
 821                                 namespace_using_table = empty_namespaces;
 822                                 return namespace_using_table;
 823                         }
 824
 825                         ArrayList list = new ArrayList (using_clauses.Count);
 826
 827                         foreach (UsingEntry ue in using_clauses) {
 828                                 Namespace using_ns = ue.Resolve ();
 829                                 if (using_ns == null)
 830                                         continue;
 831
 832                                 list.Add (using_ns);
 833                         }
 834
 835                         namespace_using_table = new Namespace [list.Count];
 836                         list.CopyTo (namespace_using_table, 0);
 837                         return namespace_using_table;
 838                 }
 839
 840                 readonly string [] empty_using_list = new string [0];
 841
 842                 public void DefineNamespace (SymbolWriter symwriter)
 843                 {
 844                         if (symfile_id != 0)
 845                                 return;
 846                         if (parent != null)
 847                                 parent.DefineNamespace (symwriter);
 848
 849                         string [] using_list = empty_using_list;
 850                         if (using_clauses != null) {
 851                                 using_list = new string [using_clauses.Count];
 852                                 for (int i = 0; i < using_clauses.Count; i++)
 853                                         using_list [i] = ((UsingEntry) using_clauses [i]).Name.ToString ();
 854                         }
 855
 856                         int parent_id = parent != null ? parent.symfile_id : 0;
 857                         if (file.SourceFileEntry == null)
 858                                 return;
 859
 860                         symfile_id = symwriter.DefineNamespace (
 861                                 ns.Name, file.SourceFileEntry, using_list, parent_id);
 862                 }
 863
 864                 public int SymbolFileID {
 865                         get { return symfile_id; }
 866                 }
 867
 868                 static void MsgtryRef (string s)
 869                 {
 870                         Console.WriteLine ("    Try using -r:" + s);
 871                 }
 872
 873                 static void MsgtryPkg (string s)
 874                 {
 875                         Console.WriteLine ("    Try using -pkg:" + s);
 876                 }
 877
 878                 public static void Error_NamespaceNotFound (Location loc, string name)
 879                 {
 880                         Report.Error (246, loc, "The type or namespace name `{0}' could not be found. Are you missing a using directive or an assembly reference?",
 881                                 name);
 882
 883                         switch (name) {
 884                         case "Gtk": case "GtkSharp":
 885                                 MsgtryPkg ("gtk-sharp");
 886                                 break;
 887
 888                         case "Gdk": case "GdkSharp":
 889                                 MsgtryPkg ("gdk-sharp");
 890                                 break;
 891
 892                         case "Glade": case "GladeSharp":
 893                                 MsgtryPkg ("glade-sharp");
 894                                 break;
 895
 896                         case "System.Drawing":
 897                         case "System.Web.Services":
 898                         case "System.Web":
 899                         case "System.Data":
 900                         case "System.Windows.Forms":
 901                                 MsgtryRef (name);
 902                                 break;
 903                         }
 904                 }
 905
 906                 /// <summary>
 907                 ///   Used to validate that all the using clauses are correct
 908                 ///   after we are finished parsing all the files.
 909                 /// </summary>
 910                 public void VerifyUsing ()
 911                 {
 912                         if (using_clauses != null) {
 913                                 foreach (UsingEntry ue in using_clauses)
 914                                         ue.Resolve ();
 915                         }
 916
 917                         if (aliases != null) {
 918                                 foreach (DictionaryEntry de in aliases) {
 919                                         AliasEntry alias = (AliasEntry) de.Value;
 920                                         if (alias.Resolve () == null)
 921                                                 if (alias is LocalAliasEntry) {
 922                                                         LocalAliasEntry local = alias as LocalAliasEntry;
 923                                                         Error_NamespaceNotFound (local.Location, local.Alias.ToString ());
 924                                                 }
 925                                 }
 926                         }
 927                 }
 928
 929                 public string GetSignatureForError ()
 930                 {
 931                         return ns.GetSignatureForError ();
 932                 }
 933
 934                 public override string ToString ()
 935                 {
 936                         return ns.ToString ();
 937                 }
 938         }
 939 }