mcs/mcs/namespace.cs

   1 //
   2 // namespace.cs: Tracks namespaces
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@seznam.cz)
   7 //
   8 // (C) 2001 Ximian, Inc.
   9 //
  10 using System;
  11 using System.Collections;
  12 using System.Collections.Specialized;
  13 using System.Reflection;
  14
  15 namespace Mono.CSharp {
  16
  17         public class RootNamespace : Namespace {
  18                 static MethodInfo get_namespaces_method;
  19
  20                 string alias_name;
  21                 Assembly referenced_assembly;
  22
  23                 Hashtable all_namespaces;
  24
  25                 static Hashtable root_namespaces;
  26                 public static GlobalRootNamespace Global;
  27
  28                 static RootNamespace ()
  29                 {
  30                         get_namespaces_method = typeof (Assembly).GetMethod ("GetNamespaces", BindingFlags.Instance | BindingFlags.NonPublic);
  31
  32                         Reset ();
  33                 }
  34
  35                 public static void Reset ()
  36                 {
  37                         root_namespaces = new Hashtable ();
  38                         Global = new GlobalRootNamespace ();
  39                         root_namespaces ["global"] = Global;
  40                 }
  41
  42                 protected RootNamespace (string alias_name, Assembly assembly)
  43                         : base (null, String.Empty)
  44                 {
  45                         this.alias_name = alias_name;
  46                         referenced_assembly = assembly;
  47
  48                         all_namespaces = new Hashtable ();
  49                         all_namespaces.Add ("", this);
  50
  51                         if (referenced_assembly != null)
  52                                 ComputeNamespaces (this.referenced_assembly);
  53                 }
  54
  55                 public static void DefineRootNamespace (string name, Assembly assembly)
  56                 {
  57                         if (name == "global") {
  58                                 // FIXME: Add proper error number
  59                                 Report.Error (-42, "Cannot define an external alias named `global'");
  60                                 return;
  61                         }
  62                         RootNamespace retval = GetRootNamespace (name);
  63                         if (retval == null || retval.referenced_assembly != assembly)
  64                                 root_namespaces [name] = new RootNamespace (name, assembly);
  65                 }
  66
  67                 public static RootNamespace GetRootNamespace (string name)
  68                 {
  69                         return (RootNamespace) root_namespaces [name];
  70                 }
  71
  72                 public virtual Type LookupTypeReflection (string name, Location loc)
  73                 {
  74                         return GetTypeInAssembly (referenced_assembly, name);
  75                 }
  76
  77                 public void RegisterNamespace (Namespace child)
  78                 {
  79                         if (child != this)
  80                                 all_namespaces.Add (child.Name, child);
  81                 }
  82
  83                 public bool IsNamespace (string name)
  84                 {
  85                         return all_namespaces.Contains (name);
  86                 }
  87
  88                 protected void EnsureNamespace (string dotted_name)
  89                 {
  90                         if (dotted_name != null && dotted_name.Length != 0 && ! IsNamespace (dotted_name))
  91                                 GetNamespace (dotted_name, true);
  92                 }
  93
  94                 protected void ComputeNamespaces (Assembly assembly)
  95                 {
  96                         if (get_namespaces_method != null) {
  97                                 string [] namespaces = (string []) get_namespaces_method.Invoke (assembly, null);
  98                                 foreach (string ns in namespaces)
  99                                         EnsureNamespace (ns);
 100                                 return;
 101                         }
 102
 103                         foreach (Type t in assembly.GetExportedTypes ())
 104                                 EnsureNamespace (t.Namespace);
 105                 }
 106
 107                 protected static Type GetTypeInAssembly (Assembly assembly, string name)
 108                 {
 109                         Type t = assembly.GetType (name);
 110                         if (t == null)
 111                                 return null;
 112
 113                         if (t.IsPointer)
 114                                 throw new InternalErrorException ("Use GetPointerType() to get a pointer");
 115
 116                         TypeAttributes ta = t.Attributes & TypeAttributes.VisibilityMask;
 117                         if (ta == TypeAttributes.NotPublic ||
 118                             ta == TypeAttributes.NestedPrivate ||
 119                             ta == TypeAttributes.NestedAssembly ||
 120                             ta == TypeAttributes.NestedFamANDAssem)
 121                                 return null;
 122
 123                         return t;
 124                 }
 125
 126                 public override string ToString ()
 127                 {
 128                         return String.Format ("RootNamespace ({0}::)", alias_name);
 129                 }
 130
 131                 public override string GetSignatureForError ()
 132                 {
 133                         return alias_name + "::";
 134                 }
 135         }
 136
 137         public class GlobalRootNamespace : RootNamespace {
 138                 Assembly [] assemblies;
 139                 Module [] modules;
 140
 141                 public GlobalRootNamespace ()
 142                         : base ("global", null)
 143                 {
 144                         assemblies = new Assembly [0];
 145                 }
 146
 147                 public Assembly [] Assemblies {
 148                         get { return assemblies; }
 149                 }
 150
 151                 public Module [] Modules {
 152                         get { return modules; }
 153                 }
 154
 155                 public void AddAssemblyReference (Assembly a)
 156                 {
 157                         foreach (Assembly assembly in assemblies) {
 158                                 if (a == assembly)
 159                                         return;
 160                         }
 161
 162                         int top = assemblies.Length;
 163                         Assembly [] n = new Assembly [top + 1];
 164                         assemblies.CopyTo (n, 0);
 165                         n [top] = a;
 166                         assemblies = n;
 167
 168                         ComputeNamespaces (a);
 169                 }
 170
 171                 public void AddModuleReference (Module m)
 172                 {
 173                         int top = modules != null ? modules.Length : 0;
 174                         Module [] n = new Module [top + 1];
 175                         if (modules != null)
 176                                 modules.CopyTo (n, 0);
 177                         n [top] = m;
 178                         modules = n;
 179
 180                         if (m == CodeGen.Module.Builder)
 181                                 return;
 182
 183                         foreach (Type t in m.GetTypes ())
 184                                 EnsureNamespace (t.Namespace);
 185                 }
 186
 187                 public override Type LookupTypeReflection (string name, Location loc)
 188                 {
 189                         Type found_type = null;
 190
 191                         foreach (Assembly a in assemblies) {
 192                                 Type t = GetTypeInAssembly (a, name);
 193                                 if (t == null)
 194                                         continue;
 195
 196                                 if (found_type == null) {
 197                                         found_type = t;
 198                                         continue;
 199                                 }
 200
 201                                 Report.SymbolRelatedToPreviousError (found_type);
 202                                 Report.SymbolRelatedToPreviousError (t);
 203                                 Report.Error (433, loc, "The imported type `{0}' is defined multiple times", name);
 204
 205                                 return found_type;
 206                         }
 207
 208                         if (modules != null) {
 209                                 foreach (Module module in modules) {
 210                                         Type t = module.GetType (name);
 211                                         if (t == null)
 212                                                 continue;
 213
 214                                         if (found_type == null) {
 215                                                 found_type = t;
 216                                                 continue;
 217                                         }
 218
 219                                         Report.SymbolRelatedToPreviousError (t);
 220                                         Report.SymbolRelatedToPreviousError (found_type);
 221                                         Report.Warning (436, 2, loc, "Ignoring imported type `{0}' since the current assembly already has a declaration with the same name",
 222                                                 TypeManager.CSharpName (t));
 223                                         return t;
 224                                 }
 225                         }
 226
 227                         return found_type;
 228                 }
 229         }
 230
 231         /// <summary>
 232         ///   Keeps track of the namespaces defined in the C# code.
 233         ///
 234         ///   This is an Expression to allow it to be referenced in the
 235         ///   compiler parse/intermediate tree during name resolution.
 236         /// </summary>
 237         public class Namespace : FullNamedExpression {
 238
 239                 Namespace parent;
 240                 string fullname;
 241                 Hashtable namespaces;
 242                 IDictionary declspaces;
 243                 Hashtable cached_types;
 244                 RootNamespace root;
 245
 246                 public readonly MemberName MemberName;
 247
 248                 /// <summary>
 249                 ///   Constructor Takes the current namespace and the
 250                 ///   name.  This is bootstrapped with parent == null
 251                 ///   and name = ""
 252                 /// </summary>
 253                 public Namespace (Namespace parent, string name)
 254                 {
 255                         // Expression members.
 256                         this.eclass = ExprClass.Namespace;
 257                         this.Type = null;
 258                         this.loc = Location.Null;
 259
 260                         this.parent = parent;
 261
 262                         if (parent != null)
 263                                 this.root = parent.root;
 264                         else
 265                                 this.root = this as RootNamespace;
 266
 267                         if (this.root == null)
 268                                 throw new InternalErrorException ("Root namespaces must be created using RootNamespace");
 269
 270                         string pname = parent != null ? parent.Name : "";
 271
 272                         if (pname == "")
 273                                 fullname = name;
 274                         else
 275                                 fullname = parent.Name + "." + name;
 276
 277                         if (fullname == null)
 278                                 throw new InternalErrorException ("Namespace has a null fullname");
 279
 280                         if (parent != null && parent.MemberName != MemberName.Null)
 281                                 MemberName = new MemberName (parent.MemberName, name);
 282                         else if (name.Length == 0)
 283                                 MemberName = MemberName.Null;
 284                         else
 285                                 MemberName = new MemberName (name);
 286
 287                         namespaces = new Hashtable ();
 288                         cached_types = new Hashtable ();
 289
 290                         root.RegisterNamespace (this);
 291                 }
 292
 293                 public override Expression DoResolve (EmitContext ec)
 294                 {
 295                         return this;
 296                 }
 297
 298                 public override void Emit (EmitContext ec)
 299                 {
 300                         throw new InternalErrorException ("Expression tree referenced namespace " + fullname + " during Emit ()");
 301                 }
 302
 303                 public override string GetSignatureForError ()
 304                 {
 305                         return Name;
 306                 }
 307
 308                 public Namespace GetNamespace (string name, bool create)
 309                 {
 310                         int pos = name.IndexOf ('.');
 311
 312                         Namespace ns;
 313                         string first;
 314                         if (pos >= 0)
 315                                 first = name.Substring (0, pos);
 316                         else
 317                                 first = name;
 318
 319                         ns = (Namespace) namespaces [first];
 320                         if (ns == null) {
 321                                 if (!create)
 322                                         return null;
 323
 324                                 ns = new Namespace (this, first);
 325                                 namespaces.Add (first, ns);
 326                         }
 327
 328                         if (pos >= 0)
 329                                 ns = ns.GetNamespace (name.Substring (pos + 1), create);
 330
 331                         return ns;
 332                 }
 333
 334                 TypeExpr LookupType (string name, Location loc)
 335                 {
 336                         if (cached_types.Contains (name))
 337                                 return cached_types [name] as TypeExpr;
 338
 339                         Type t = null;
 340                         if (declspaces != null) {
 341                                 DeclSpace tdecl = declspaces [name] as DeclSpace;
 342                                 if (tdecl != null) {
 343                                         //
 344                                         // Note that this is not:
 345                                         //
 346                                         //   t = tdecl.DefineType ()
 347                                         //
 348                                         // This is to make it somewhat more useful when a DefineType
 349                                         // fails due to problems in nested types (more useful in the sense
 350                                         // of fewer misleading error messages)
 351                                         //
 352                                         tdecl.DefineType ();
 353                                         t = tdecl.TypeBuilder;
 354                                 }
 355                         }
 356                         string lookup = t != null ? t.FullName : (fullname.Length == 0 ? name : fullname + "." + name);
 357                         Type rt = root.LookupTypeReflection (lookup, loc);
 358                         if (t == null)
 359                                 t = rt;
 360
 361                         TypeExpr te = t == null ? null : new TypeExpression (t, Location.Null);
 362                         cached_types [name] = te;
 363                         return te;
 364                 }
 365
 366                 public FullNamedExpression Lookup (DeclSpace ds, string name, Location loc)
 367                 {
 368                         if (namespaces.Contains (name))
 369                                 return (Namespace) namespaces [name];
 370
 371                         TypeExpr te = LookupType (name, loc);
 372                         if (te == null || !ds.CheckAccessLevel (te.Type))
 373                                 return null;
 374
 375                         return te;
 376                 }
 377
 378                 public void AddDeclSpace (string name, DeclSpace ds)
 379                 {
 380                         if (declspaces == null)
 381                                 declspaces = new HybridDictionary ();
 382                         declspaces.Add (name, ds);
 383                 }
 384
 385                 /// <summary>
 386                 ///   The qualified name of the current namespace
 387                 /// </summary>
 388                 public string Name {
 389                         get { return fullname; }
 390                 }
 391
 392                 public override string FullName {
 393                         get { return fullname; }
 394                 }
 395
 396                 /// <summary>
 397                 ///   The parent of this namespace, used by the parser to "Pop"
 398                 ///   the current namespace declaration
 399                 /// </summary>
 400                 public Namespace Parent {
 401                         get { return parent; }
 402                 }
 403
 404                 public override string ToString ()
 405                 {
 406                         return String.Format ("Namespace ({0})", Name);
 407                 }
 408         }
 409
 410         public class NamespaceEntry {
 411                 Namespace ns;
 412                 NamespaceEntry parent, implicit_parent;
 413                 SourceFile file;
 414                 int symfile_id;
 415                 Hashtable aliases;
 416                 ArrayList using_clauses;
 417                 public bool DeclarationFound = false;
 418                 bool UsingFound;
 419
 420                 ListDictionary extern_aliases;
 421
 422                 static ArrayList entries = new ArrayList ();
 423
 424                 public static void Reset ()
 425                 {
 426                         entries = new ArrayList ();
 427                 }
 428
 429                 //
 430                 // This class holds the location where a using definition is
 431                 // done, and whether it has been used by the program or not.
 432                 //
 433                 // We use this to flag using clauses for namespaces that do not
 434                 // exist.
 435                 //
 436                 public class UsingEntry {
 437                         public readonly MemberName Name;
 438                         readonly Expression Expr;
 439                         readonly NamespaceEntry NamespaceEntry;
 440                         readonly Location Location;
 441
 442                         public UsingEntry (NamespaceEntry entry, MemberName name, Location loc)
 443                         {
 444                                 Name = name;
 445                                 Expr = name.GetTypeExpression ();
 446                                 NamespaceEntry = entry;
 447                                 Location = loc;
 448                         }
 449
 450                         internal Namespace resolved;
 451
 452                         public Namespace Resolve ()
 453                         {
 454                                 if (resolved != null)
 455                                         return resolved;
 456
 457                                 DeclSpace root = RootContext.Tree.Types;
 458                                 root.NamespaceEntry = NamespaceEntry;
 459                                 FullNamedExpression fne = Expr.ResolveAsTypeStep (root, false);
 460                                 root.NamespaceEntry = null;
 461
 462                                 if (fne == null) {
 463                                         Error_NamespaceNotFound (Location, Name.ToString ());
 464                                         return null;
 465                                 }
 466
 467                                 resolved = fne as Namespace;
 468                                 if (resolved == null) {
 469                                         Report.Error (138, Location,
 470                                                 "`{0} is a type not a namespace. A using namespace directive can only be applied to namespaces", Name.ToString ());
 471                                 }
 472                                 return resolved;
 473                         }
 474                 }
 475
 476                 public abstract class AliasEntry {
 477                         public readonly string Name;
 478                         public readonly NamespaceEntry NamespaceEntry;
 479                         public readonly Location Location;
 480
 481                         protected AliasEntry (NamespaceEntry entry, string name, Location loc)
 482                         {
 483                                 Name = name;
 484                                 NamespaceEntry = entry;
 485                                 Location = loc;
 486                         }
 487
 488                         protected FullNamedExpression resolved;
 489                         bool error;
 490
 491                         public FullNamedExpression Resolve ()
 492                         {
 493                                 if (resolved != null || error)
 494                                         return resolved;
 495                                 resolved = DoResolve ();
 496                                 if (resolved == null)
 497                                         error = true;
 498                                 return resolved;
 499                         }
 500
 501                         protected abstract FullNamedExpression DoResolve ();
 502                 }
 503
 504                 public class LocalAliasEntry : AliasEntry
 505                 {
 506                         public readonly Expression Alias;
 507
 508                         public LocalAliasEntry (NamespaceEntry entry, string name, MemberName alias, Location loc) :
 509                                 base (entry, name, loc)
 510                         {
 511                                 Alias = alias.GetTypeExpression ();
 512                         }
 513
 514                         protected override FullNamedExpression DoResolve ()
 515                         {
 516                                 DeclSpace root = RootContext.Tree.Types;
 517                                 root.NamespaceEntry = NamespaceEntry;
 518                                 resolved = Alias.ResolveAsTypeStep (root, false);
 519                                 root.NamespaceEntry = null;
 520
 521                                 if (resolved == null)
 522                                         return null;
 523
 524                                 if (resolved.Type != null) {
 525                                         TypeAttributes attr = resolved.Type.Attributes & TypeAttributes.VisibilityMask;
 526                                         if (attr == TypeAttributes.NestedPrivate || attr == TypeAttributes.NestedFamily ||
 527                                                 ((attr == TypeAttributes.NestedFamORAssem || attr == TypeAttributes.NestedAssembly) &&
 528                                                 TypeManager.LookupDeclSpace (resolved.Type) == null)) {
 529                                                 Expression.ErrorIsInaccesible (Alias.Location, Alias.ToString ());
 530                                                 return null;
 531                                         }
 532                                 }
 533
 534                                 return resolved;
 535                         }
 536                 }
 537
 538                 public class ExternAliasEntry : AliasEntry
 539                 {
 540                         public ExternAliasEntry (NamespaceEntry entry, string name, Location loc) :
 541                                 base (entry, name, loc)
 542                         {
 543                         }
 544
 545                         protected override FullNamedExpression DoResolve ()
 546                         {
 547                                 resolved = RootNamespace.GetRootNamespace (Name);
 548                                 if (resolved == null)
 549                                         Report.Error (430, Location, "The extern alias '" + Name +
 550                                                                         "' was not specified in a /reference option");
 551
 552                                 return resolved;
 553                         }
 554                 }
 555
 556                 public NamespaceEntry (NamespaceEntry parent, SourceFile file, string name)
 557                 {
 558                         this.parent = parent;
 559                         this.file = file;
 560                         entries.Add (this);
 561                         this.ID = entries.Count;
 562
 563                         if (parent != null)
 564                                 ns = parent.NS.GetNamespace (name, true);
 565                         else if (name != null)
 566                                 ns = RootNamespace.Global.GetNamespace (name, true);
 567                         else
 568                                 ns = RootNamespace.Global;
 569                 }
 570
 571                 private NamespaceEntry (NamespaceEntry parent, SourceFile file, Namespace ns)
 572                 {
 573                         this.parent = parent;
 574                         this.file = file;
 575                         // no need to add self to 'entries', since we don't have any aliases or using entries.
 576                         this.ID = -1;
 577                         this.IsImplicit = true;
 578                         this.ns = ns;
 579                 }
 580
 581                 //
 582                 // According to section 16.3.1 (using-alias-directive), the namespace-or-type-name is
 583                 // resolved as if the immediately containing namespace body has no using-directives.
 584                 //
 585                 // Section 16.3.2 says that the same rule is applied when resolving the namespace-name
 586                 // in the using-namespace-directive.
 587                 //
 588                 // To implement these rules, the expressions in the using directives are resolved using
 589                 // the "doppelganger" (ghostly bodiless duplicate).
 590                 //
 591                 NamespaceEntry doppelganger;
 592                 NamespaceEntry Doppelganger {
 593                         get {
 594                                 if (!IsImplicit && doppelganger == null)
 595                                         doppelganger = new NamespaceEntry (ImplicitParent, file, ns);
 596                                 return doppelganger;
 597                         }
 598                 }
 599
 600                 public readonly int ID;
 601                 public readonly bool IsImplicit;
 602
 603                 public Namespace NS {
 604                         get { return ns; }
 605                 }
 606
 607                 public NamespaceEntry Parent {
 608                         get { return parent; }
 609                 }
 610
 611                 public NamespaceEntry ImplicitParent {
 612                         get {
 613                                 if (parent == null)
 614                                         return null;
 615                                 if (implicit_parent == null) {
 616                                         implicit_parent = (parent.NS == ns.Parent)
 617                                                 ? parent
 618                                                 : new NamespaceEntry (parent, file, ns.Parent);
 619                                 }
 620                                 return implicit_parent;
 621                         }
 622                 }
 623
 624                 /// <summary>
 625                 ///   Records a new namespace for resolving name references
 626                 /// </summary>
 627                 public void Using (MemberName name, Location loc)
 628                 {
 629                         if (DeclarationFound){
 630                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 631                                 return;
 632                         }
 633
 634                         UsingFound = true;
 635
 636                         if (name.Equals (ns.MemberName))
 637                                 return;
 638
 639                         if (using_clauses == null)
 640                                 using_clauses = new ArrayList ();
 641
 642                         foreach (UsingEntry old_entry in using_clauses) {
 643                                 if (name.Equals (old_entry.Name)) {
 644                                         Report.Warning (105, 3, loc, "The using directive for `{0}' appeared previously in this namespace", name.GetName ());
 645                                         return;
 646                                 }
 647                         }
 648
 649                         UsingEntry ue = new UsingEntry (Doppelganger, name, loc);
 650                         using_clauses.Add (ue);
 651                 }
 652
 653                 public void UsingAlias (string name, MemberName alias, Location loc)
 654                 {
 655                         if (DeclarationFound){
 656                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 657                                 return;
 658                         }
 659
 660                         UsingFound = true;
 661
 662                         if (aliases == null)
 663                                 aliases = new Hashtable ();
 664
 665                         if (aliases.Contains (name)) {
 666                                 AliasEntry ae = (AliasEntry) aliases [name];
 667                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 668                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 669                                 return;
 670                         }
 671
 672                         if (RootContext.Version == LanguageVersion.Default &&
 673                             name == "global" && RootContext.WarningLevel >= 2)
 674                                 Report.Warning (440, 2, loc, "An alias named `global' will not be used when resolving 'global::';" +
 675                                         " the global namespace will be used instead");
 676
 677                         // FIXME: get correct error number.  See if the above check can be merged
 678                         if (extern_aliases != null && extern_aliases.Contains (name)) {
 679                                 AliasEntry ae = (AliasEntry) extern_aliases [name];
 680                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 681                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 682                                 return;
 683                         }
 684
 685                         aliases [name] = new LocalAliasEntry (Doppelganger, name, alias, loc);
 686                 }
 687
 688                 public void UsingExternalAlias (string name, Location loc)
 689                 {
 690                         if (UsingFound || DeclarationFound) {
 691                                 Report.Error (439, loc, "An extern alias declaration must precede all other elements");
 692                                 return;
 693                         }
 694
 695                         // Share the extern_aliases field with the Doppelganger
 696                         if (extern_aliases == null) {
 697                                 extern_aliases = new ListDictionary ();
 698                                 Doppelganger.extern_aliases = extern_aliases;
 699                         }
 700
 701                         if (extern_aliases.Contains (name)) {
 702                                 AliasEntry ae = (AliasEntry) extern_aliases [name];
 703                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 704                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 705                                 return;
 706                         }
 707
 708                         if (name == "global") {
 709                                 Report.Error (1681, loc, "You cannot redefine the global extern alias");
 710                                 return;
 711                         }
 712
 713                         // Register the alias in aliases and extern_aliases, since we need both of them
 714                         // to keep things simple (different resolution scenarios)
 715                         ExternAliasEntry alias = new ExternAliasEntry (Doppelganger, name, loc);
 716                         extern_aliases [name] = alias;
 717                 }
 718
 719                 public FullNamedExpression LookupNamespaceOrType (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 720                 {
 721                         // Precondition: Only simple names (no dots) will be looked up with this function.
 722                         FullNamedExpression resolved = null;
 723                         for (NamespaceEntry curr_ns = this; curr_ns != null; curr_ns = curr_ns.ImplicitParent) {
 724                                 if ((resolved = curr_ns.Lookup (ds, name, loc, ignore_cs0104)) != null)
 725                                         break;
 726                         }
 727                         return resolved;
 728                 }
 729
 730                 static void Error_AmbiguousTypeReference (Location loc, string name, FullNamedExpression t1, FullNamedExpression t2)
 731                 {
 732                         Report.Error (104, loc, "`{0}' is an ambiguous reference between `{1}' and `{2}'",
 733                                 name, t1.FullName, t2.FullName);
 734                 }
 735
 736                 // Looks-up a alias named @name in this and surrounding namespace declarations
 737                 public FullNamedExpression LookupAlias (string name)
 738                 {
 739                         AliasEntry entry = null;
 740                         for (NamespaceEntry n = this; n != null; n = n.ImplicitParent) {
 741                                 if (n.extern_aliases != null && (entry = n.extern_aliases [name] as AliasEntry) != null)
 742                                         break;
 743                                 if (n.aliases != null && (entry = n.aliases [name] as AliasEntry) != null)
 744                                         break;
 745                         }
 746                         return entry == null ? null : entry.Resolve ();
 747                 }
 748
 749                 private FullNamedExpression Lookup (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 750                 {
 751                         //
 752                         // Check whether it's in the namespace.
 753                         //
 754                         FullNamedExpression fne = NS.Lookup (ds, name, loc);
 755                         if (fne != null)
 756                                 return fne;
 757
 758                         if (extern_aliases != null) {
 759                                 AliasEntry entry = extern_aliases [name] as AliasEntry;
 760                                 if (entry != null)
 761                                         return entry.Resolve ();
 762                         }
 763
 764                         if (IsImplicit)
 765                                 return null;
 766
 767                         //
 768                         // Check aliases.
 769                         //
 770                         if (aliases != null) {
 771                                 AliasEntry entry = aliases [name] as AliasEntry;
 772                                 if (entry != null)
 773                                         return entry.Resolve ();
 774                         }
 775
 776                         //
 777                         // Check using entries.
 778                         //
 779                         FullNamedExpression match = null;
 780                         foreach (Namespace using_ns in GetUsingTable ()) {
 781                                 match = using_ns.Lookup (ds, name, loc);
 782                                 if (match == null || !(match is TypeExpr))
 783                                         continue;
 784                                 if (fne != null) {
 785                                         if (!ignore_cs0104)
 786                                                 Error_AmbiguousTypeReference (loc, name, fne, match);
 787                                         return null;
 788                                 }
 789                                 fne = match;
 790                         }
 791
 792                         return fne;
 793                 }
 794
 795                 // Our cached computation.
 796                 readonly Namespace [] empty_namespaces = new Namespace [0];
 797                 Namespace [] namespace_using_table;
 798                 Namespace [] GetUsingTable ()
 799                 {
 800                         if (namespace_using_table != null)
 801                                 return namespace_using_table;
 802
 803                         if (using_clauses == null) {
 804                                 namespace_using_table = empty_namespaces;
 805                                 return namespace_using_table;
 806                         }
 807
 808                         ArrayList list = new ArrayList (using_clauses.Count);
 809
 810                         foreach (UsingEntry ue in using_clauses) {
 811                                 Namespace using_ns = ue.Resolve ();
 812                                 if (using_ns == null)
 813                                         continue;
 814
 815                                 list.Add (using_ns);
 816                         }
 817
 818                         namespace_using_table = new Namespace [list.Count];
 819                         list.CopyTo (namespace_using_table, 0);
 820                         return namespace_using_table;
 821                 }
 822
 823                 readonly string [] empty_using_list = new string [0];
 824
 825                 public int SymbolFileID {
 826                         get {
 827                                 if (symfile_id == 0 && file.SourceFileEntry != null) {
 828                                         int parent_id = parent == null ? 0 : parent.SymbolFileID;
 829
 830                                         string [] using_list = empty_using_list;
 831                                         if (using_clauses != null) {
 832                                                 using_list = new string [using_clauses.Count];
 833                                                 for (int i = 0; i < using_clauses.Count; i++)
 834                                                         using_list [i] = ((UsingEntry) using_clauses [i]).Name.ToString ();
 835                                         }
 836
 837                                         symfile_id = CodeGen.SymbolWriter.DefineNamespace (ns.Name, file.SourceFileEntry, using_list, parent_id);
 838                                 }
 839                                 return symfile_id;
 840                         }
 841                 }
 842
 843                 static void MsgtryRef (string s)
 844                 {
 845                         Console.WriteLine ("    Try using -r:" + s);
 846                 }
 847
 848                 static void MsgtryPkg (string s)
 849                 {
 850                         Console.WriteLine ("    Try using -pkg:" + s);
 851                 }
 852
 853                 public static void Error_NamespaceNotFound (Location loc, string name)
 854                 {
 855                         Report.Error (246, loc, "The type or namespace name `{0}' could not be found. Are you missing a using directive or an assembly reference?",
 856                                 name);
 857
 858                         switch (name) {
 859                         case "Gtk": case "GtkSharp":
 860                                 MsgtryPkg ("gtk-sharp");
 861                                 break;
 862
 863                         case "Gdk": case "GdkSharp":
 864                                 MsgtryPkg ("gdk-sharp");
 865                                 break;
 866
 867                         case "Glade": case "GladeSharp":
 868                                 MsgtryPkg ("glade-sharp");
 869                                 break;
 870
 871                         case "System.Drawing":
 872                         case "System.Web.Services":
 873                         case "System.Web":
 874                         case "System.Data":
 875                         case "System.Windows.Forms":
 876                                 MsgtryRef (name);
 877                                 break;
 878                         }
 879                 }
 880
 881                 /// <summary>
 882                 ///   Used to validate that all the using clauses are correct
 883                 ///   after we are finished parsing all the files.
 884                 /// </summary>
 885                 void VerifyUsing ()
 886                 {
 887                         if (extern_aliases != null) {
 888                                 foreach (DictionaryEntry de in extern_aliases)
 889                                         ((AliasEntry) de.Value).Resolve ();
 890                         }
 891
 892                         if (using_clauses != null) {
 893                                 foreach (UsingEntry ue in using_clauses)
 894                                         ue.Resolve ();
 895                         }
 896
 897                         if (aliases != null) {
 898                                 foreach (DictionaryEntry de in aliases)
 899                                         ((AliasEntry) de.Value).Resolve ();
 900                         }
 901                 }
 902
 903                 /// <summary>
 904                 ///   Used to validate that all the using clauses are correct
 905                 ///   after we are finished parsing all the files.
 906                 /// </summary>
 907                 static public void VerifyAllUsing ()
 908                 {
 909                         foreach (NamespaceEntry entry in entries)
 910                                 entry.VerifyUsing ();
 911                 }
 912
 913                 public string GetSignatureForError ()
 914                 {
 915                         return ns.GetSignatureForError ();
 916                 }
 917
 918                 public override string ToString ()
 919                 {
 920                         return ns.ToString ();
 921                 }
 922         }
 923 }