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