mcs/gmcs/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.NestedPrivate)
 118                                 return null;
 119
 120                         if (ta == TypeAttributes.NotPublic ||
 121                             ta == TypeAttributes.NestedAssembly ||
 122                             ta == TypeAttributes.NestedFamANDAssem)
 123                                 if (!TypeManager.IsFriendAssembly (t.Assembly))
 124                                         return null;
 125
 126                         return t;
 127                 }
 128
 129                 public override string ToString ()
 130                 {
 131                         return String.Format ("RootNamespace ({0}::)", alias_name);
 132                 }
 133
 134                 public override string GetSignatureForError ()
 135                 {
 136                         return alias_name + "::";
 137                 }
 138         }
 139
 140         public class GlobalRootNamespace : RootNamespace {
 141                 Assembly [] assemblies;
 142                 Module [] modules;
 143
 144                 public GlobalRootNamespace ()
 145                         : base ("global", null)
 146                 {
 147                         assemblies = new Assembly [0];
 148                 }
 149
 150                 public Assembly [] Assemblies {
 151                         get { return assemblies; }
 152                 }
 153
 154                 public Module [] Modules {
 155                         get { return modules; }
 156                 }
 157
 158                 public void AddAssemblyReference (Assembly a)
 159                 {
 160                         foreach (Assembly assembly in assemblies) {
 161                                 if (a == assembly)
 162                                         return;
 163                         }
 164
 165                         int top = assemblies.Length;
 166                         Assembly [] n = new Assembly [top + 1];
 167                         assemblies.CopyTo (n, 0);
 168                         n [top] = a;
 169                         assemblies = n;
 170
 171                         ComputeNamespaces (a);
 172                 }
 173
 174                 public void AddModuleReference (Module m)
 175                 {
 176                         int top = modules != null ? modules.Length : 0;
 177                         Module [] n = new Module [top + 1];
 178                         if (modules != null)
 179                                 modules.CopyTo (n, 0);
 180                         n [top] = m;
 181                         modules = n;
 182
 183                         if (m == CodeGen.Module.Builder)
 184                                 return;
 185
 186                         foreach (Type t in m.GetTypes ())
 187                                 EnsureNamespace (t.Namespace);
 188                 }
 189
 190                 public override void Error_NamespaceDoesNotExist(Location loc, string name)
 191                 {
 192                         Report.Error (400, loc, "The type or namespace name `{0}' could not be found in the global namespace (are you missing an assembly reference?)",
 193                                 name);
 194                 }
 195
 196                 public override Type LookupTypeReflection (string name, Location loc)
 197                 {
 198                         Type found_type = null;
 199
 200                         foreach (Assembly a in assemblies) {
 201                                 Type t = GetTypeInAssembly (a, name);
 202                                 if (t == null)
 203                                         continue;
 204
 205                                 if (found_type == null) {
 206                                         found_type = t;
 207                                         continue;
 208                                 }
 209
 210                                 Report.SymbolRelatedToPreviousError (found_type);
 211                                 Report.SymbolRelatedToPreviousError (t);
 212                                 Report.Error (433, loc, "The imported type `{0}' is defined multiple times", name);
 213
 214                                 return found_type;
 215                         }
 216
 217                         if (modules != null) {
 218                                 foreach (Module module in modules) {
 219                                         Type t = module.GetType (name);
 220                                         if (t == null)
 221                                                 continue;
 222
 223                                         if (found_type == null) {
 224                                                 found_type = t;
 225                                                 continue;
 226                                         }
 227
 228                                         Report.SymbolRelatedToPreviousError (t);
 229                                         Report.SymbolRelatedToPreviousError (found_type);
 230                                         Report.Warning (436, 2, loc, "Ignoring imported type `{0}' since the current assembly already has a declaration with the same name",
 231                                                 TypeManager.CSharpName (t));
 232                                         return t;
 233                                 }
 234                         }
 235
 236                         return found_type;
 237                 }
 238         }
 239
 240         /// <summary>
 241         ///   Keeps track of the namespaces defined in the C# code.
 242         ///
 243         ///   This is an Expression to allow it to be referenced in the
 244         ///   compiler parse/intermediate tree during name resolution.
 245         /// </summary>
 246         public class Namespace : FullNamedExpression {
 247
 248                 Namespace parent;
 249                 string fullname;
 250                 Hashtable namespaces;
 251                 IDictionary declspaces;
 252                 Hashtable cached_types;
 253                 RootNamespace root;
 254
 255                 public readonly MemberName MemberName;
 256
 257                 /// <summary>
 258                 ///   Constructor Takes the current namespace and the
 259                 ///   name.  This is bootstrapped with parent == null
 260                 ///   and name = ""
 261                 /// </summary>
 262                 public Namespace (Namespace parent, string name)
 263                 {
 264                         // Expression members.
 265                         this.eclass = ExprClass.Namespace;
 266                         this.Type = null;
 267                         this.loc = Location.Null;
 268
 269                         this.parent = parent;
 270
 271                         if (parent != null)
 272                                 this.root = parent.root;
 273                         else
 274                                 this.root = this as RootNamespace;
 275
 276                         if (this.root == null)
 277                                 throw new InternalErrorException ("Root namespaces must be created using RootNamespace");
 278
 279                         string pname = parent != null ? parent.Name : "";
 280
 281                         if (pname == "")
 282                                 fullname = name;
 283                         else
 284                                 fullname = parent.Name + "." + name;
 285
 286                         if (fullname == null)
 287                                 throw new InternalErrorException ("Namespace has a null fullname");
 288
 289                         if (parent != null && parent.MemberName != MemberName.Null)
 290                                 MemberName = new MemberName (parent.MemberName, name, parent.MemberName.Location);
 291                         else if (name.Length == 0)
 292                                 MemberName = MemberName.Null;
 293                         else
 294                                 MemberName = new MemberName (name, Location.Null);
 295
 296                         namespaces = new Hashtable ();
 297                         cached_types = new Hashtable ();
 298
 299                         root.RegisterNamespace (this);
 300                 }
 301
 302                 public override Expression DoResolve (EmitContext ec)
 303                 {
 304                         return this;
 305                 }
 306
 307                 public virtual void Error_NamespaceDoesNotExist (Location loc, string name)
 308                 {
 309                         Report.Error (234, loc, "The type or namespace name `{0}' does not exist in the namespace `{1}'. Are you missing an assembly reference?",
 310                                 name, FullName);
 311                 }
 312
 313                 public override void Emit (EmitContext ec)
 314                 {
 315                         throw new InternalErrorException ("Expression tree referenced namespace " + fullname + " during Emit ()");
 316                 }
 317
 318                 public override string GetSignatureForError ()
 319                 {
 320                         return Name;
 321                 }
 322
 323                 public Namespace GetNamespace (string name, bool create)
 324                 {
 325                         int pos = name.IndexOf ('.');
 326
 327                         Namespace ns;
 328                         string first;
 329                         if (pos >= 0)
 330                                 first = name.Substring (0, pos);
 331                         else
 332                                 first = name;
 333
 334                         ns = (Namespace) namespaces [first];
 335                         if (ns == null) {
 336                                 if (!create)
 337                                         return null;
 338
 339                                 ns = new Namespace (this, first);
 340                                 namespaces.Add (first, ns);
 341                         }
 342
 343                         if (pos >= 0)
 344                                 ns = ns.GetNamespace (name.Substring (pos + 1), create);
 345
 346                         return ns;
 347                 }
 348
 349                 TypeExpr LookupType (string name, Location loc)
 350                 {
 351                         if (cached_types.Contains (name))
 352                                 return cached_types [name] as TypeExpr;
 353
 354                         Type t = null;
 355                         if (declspaces != null) {
 356                                 DeclSpace tdecl = declspaces [name] as DeclSpace;
 357                                 if (tdecl != null) {
 358                                         //
 359                                         // Note that this is not:
 360                                         //
 361                                         //   t = tdecl.DefineType ()
 362                                         //
 363                                         // This is to make it somewhat more useful when a DefineType
 364                                         // fails due to problems in nested types (more useful in the sense
 365                                         // of fewer misleading error messages)
 366                                         //
 367                                         tdecl.DefineType ();
 368                                         t = tdecl.TypeBuilder;
 369                                 }
 370                         }
 371                         string lookup = t != null ? t.FullName : (fullname.Length == 0 ? name : fullname + "." + name);
 372                         Type rt = root.LookupTypeReflection (lookup, loc);
 373                         if (t == null)
 374                                 t = rt;
 375
 376                         TypeExpr te = t == null ? null : new TypeExpression (t, Location.Null);
 377                         cached_types [name] = te;
 378                         return te;
 379                 }
 380
 381                 public FullNamedExpression Lookup (DeclSpace ds, string name, Location loc)
 382                 {
 383                         if (namespaces.Contains (name))
 384                                 return (Namespace) namespaces [name];
 385
 386                         TypeExpr te = LookupType (name, loc);
 387                         if (te == null || !ds.CheckAccessLevel (te.Type))
 388                                 return null;
 389
 390                         return te;
 391                 }
 392
 393                 public void AddDeclSpace (string name, DeclSpace ds)
 394                 {
 395                         if (declspaces == null)
 396                                 declspaces = new HybridDictionary ();
 397                         declspaces.Add (name, ds);
 398                 }
 399
 400                 /// <summary>
 401                 ///   The qualified name of the current namespace
 402                 /// </summary>
 403                 public string Name {
 404                         get { return fullname; }
 405                 }
 406
 407                 public override string FullName {
 408                         get { return fullname; }
 409                 }
 410
 411                 /// <summary>
 412                 ///   The parent of this namespace, used by the parser to "Pop"
 413                 ///   the current namespace declaration
 414                 /// </summary>
 415                 public Namespace Parent {
 416                         get { return parent; }
 417                 }
 418
 419                 public override string ToString ()
 420                 {
 421                         return String.Format ("Namespace ({0})", Name);
 422                 }
 423         }
 424
 425         public class NamespaceEntry {
 426                 Namespace ns;
 427                 NamespaceEntry parent, implicit_parent;
 428                 SourceFile file;
 429                 int symfile_id;
 430                 Hashtable aliases;
 431                 ArrayList using_clauses;
 432                 public bool DeclarationFound = false;
 433                 bool UsingFound;
 434
 435                 public readonly DeclSpace SlaveDeclSpace;
 436
 437                 ListDictionary extern_aliases;
 438
 439                 static ArrayList entries = new ArrayList ();
 440
 441                 public static void Reset ()
 442                 {
 443                         entries = new ArrayList ();
 444                 }
 445
 446                 //
 447                 // This class holds the location where a using definition is
 448                 // done, and whether it has been used by the program or not.
 449                 //
 450                 // We use this to flag using clauses for namespaces that do not
 451                 // exist.
 452                 //
 453                 public class UsingEntry : IResolveContext {
 454                         public readonly MemberName Name;
 455                         readonly Expression Expr;
 456                         readonly NamespaceEntry NamespaceEntry;
 457                         readonly Location Location;
 458
 459                         public UsingEntry (NamespaceEntry entry, MemberName name, Location loc)
 460                         {
 461                                 Name = name;
 462                                 Expr = name.GetTypeExpression ();
 463                                 NamespaceEntry = entry;
 464                                 Location = loc;
 465                         }
 466
 467                         internal Namespace resolved;
 468
 469                         public Namespace Resolve ()
 470                         {
 471                                 if (resolved != null)
 472                                         return resolved;
 473
 474                                 FullNamedExpression fne = Expr.ResolveAsTypeStep (this, false);
 475                                 if (fne == null) {
 476                                         Error_NamespaceNotFound (Location, Name.ToString ());
 477                                         return null;
 478                                 }
 479
 480                                 resolved = fne as Namespace;
 481                                 if (resolved == null) {
 482                                         Report.Error (138, Location,
 483                                                 "`{0} is a type not a namespace. A using namespace directive can only be applied to namespaces", Name.ToString ());
 484                                 }
 485                                 return resolved;
 486                         }
 487
 488                         DeclSpace IResolveContext.DeclContainer {
 489                                 get { return NamespaceEntry.SlaveDeclSpace; }
 490                         }
 491                         DeclSpace IResolveContext.GenericDeclContainer {
 492                                 get { return NamespaceEntry.SlaveDeclSpace; }
 493                         }
 494                         bool IResolveContext.IsInObsoleteScope {
 495                                 get { return false; }
 496                         }
 497                         bool IResolveContext.IsInUnsafeScope {
 498                                 get { return false; }
 499                         }
 500                 }
 501
 502                 public abstract class AliasEntry {
 503                         public readonly string Name;
 504                         public readonly NamespaceEntry NamespaceEntry;
 505                         public readonly Location Location;
 506
 507                         protected AliasEntry (NamespaceEntry entry, string name, Location loc)
 508                         {
 509                                 Name = name;
 510                                 NamespaceEntry = entry;
 511                                 Location = loc;
 512                         }
 513
 514                         protected FullNamedExpression resolved;
 515                         bool error;
 516
 517                         public FullNamedExpression Resolve ()
 518                         {
 519                                 if (resolved != null || error)
 520                                         return resolved;
 521                                 resolved = DoResolve ();
 522                                 if (resolved == null)
 523                                         error = true;
 524                                 return resolved;
 525                         }
 526
 527                         protected abstract FullNamedExpression DoResolve ();
 528                 }
 529
 530                 public class LocalAliasEntry : AliasEntry, IResolveContext {
 531                         public readonly Expression Alias;
 532
 533                         public LocalAliasEntry (NamespaceEntry entry, string name, MemberName alias, Location loc) :
 534                                 base (entry, name, loc)
 535                         {
 536                                 Alias = alias.GetTypeExpression ();
 537                         }
 538
 539                         protected override FullNamedExpression DoResolve ()
 540                         {
 541                                 resolved = Alias.ResolveAsTypeStep (this, false);
 542                                 if (resolved == null)
 543                                         return null;
 544
 545                                 if (resolved.Type != null) {
 546                                         TypeAttributes attr = resolved.Type.Attributes & TypeAttributes.VisibilityMask;
 547                                         if (attr == TypeAttributes.NestedPrivate || attr == TypeAttributes.NestedFamily ||
 548                                                 ((attr == TypeAttributes.NestedFamORAssem || attr == TypeAttributes.NestedAssembly) &&
 549                                                 TypeManager.LookupDeclSpace (resolved.Type) == null)) {
 550                                                 Expression.ErrorIsInaccesible (Alias.Location, Alias.ToString ());
 551                                                 return null;
 552                                         }
 553                                 }
 554
 555                                 return resolved;
 556                         }
 557
 558                         DeclSpace IResolveContext.DeclContainer {
 559                                 get { return NamespaceEntry.SlaveDeclSpace; }
 560                         }
 561                         DeclSpace IResolveContext.GenericDeclContainer {
 562                                 get { return NamespaceEntry.SlaveDeclSpace; }
 563                         }
 564                         bool IResolveContext.IsInObsoleteScope {
 565                                 get { return false; }
 566                         }
 567                         bool IResolveContext.IsInUnsafeScope {
 568                                 get { return false; }
 569                         }
 570                 }
 571
 572                 public class ExternAliasEntry : AliasEntry {
 573                         public ExternAliasEntry (NamespaceEntry entry, string name, Location loc) :
 574                                 base (entry, name, loc)
 575                         {
 576                         }
 577
 578                         protected override FullNamedExpression DoResolve ()
 579                         {
 580                                 resolved = RootNamespace.GetRootNamespace (Name);
 581                                 if (resolved == null)
 582                                         Report.Error (430, Location, "The extern alias '" + Name +
 583                                                                         "' was not specified in a /reference option");
 584
 585                                 return resolved;
 586                         }
 587                 }
 588
 589                 public NamespaceEntry (NamespaceEntry parent, SourceFile file, string name)
 590                 {
 591                         this.parent = parent;
 592                         this.file = file;
 593                         entries.Add (this);
 594                         this.ID = entries.Count;
 595
 596                         if (parent != null)
 597                                 ns = parent.NS.GetNamespace (name, true);
 598                         else if (name != null)
 599                                 ns = RootNamespace.Global.GetNamespace (name, true);
 600                         else
 601                                 ns = RootNamespace.Global;
 602                         SlaveDeclSpace = new RootDeclSpace (this);
 603                 }
 604
 605                 private NamespaceEntry (NamespaceEntry parent, SourceFile file, Namespace ns, bool slave)
 606                 {
 607                         this.parent = parent;
 608                         this.file = file;
 609                         // no need to add self to 'entries', since we don't have any aliases or using entries.
 610                         this.ID = -1;
 611                         this.IsImplicit = true;
 612                         this.ns = ns;
 613                         this.SlaveDeclSpace = slave ? new RootDeclSpace (this) : null;
 614                 }
 615
 616                 //
 617                 // According to section 16.3.1 (using-alias-directive), the namespace-or-type-name is
 618                 // resolved as if the immediately containing namespace body has no using-directives.
 619                 //
 620                 // Section 16.3.2 says that the same rule is applied when resolving the namespace-name
 621                 // in the using-namespace-directive.
 622                 //
 623                 // To implement these rules, the expressions in the using directives are resolved using
 624                 // the "doppelganger" (ghostly bodiless duplicate).
 625                 //
 626                 NamespaceEntry doppelganger;
 627                 NamespaceEntry Doppelganger {
 628                         get {
 629                                 if (!IsImplicit && doppelganger == null)
 630                                         doppelganger = new NamespaceEntry (ImplicitParent, file, ns, true);
 631                                 return doppelganger;
 632                         }
 633                 }
 634
 635                 public readonly int ID;
 636                 public readonly bool IsImplicit;
 637
 638                 public Namespace NS {
 639                         get { return ns; }
 640                 }
 641
 642                 public NamespaceEntry Parent {
 643                         get { return parent; }
 644                 }
 645
 646                 public NamespaceEntry ImplicitParent {
 647                         get {
 648                                 if (parent == null)
 649                                         return null;
 650                                 if (implicit_parent == null) {
 651                                         implicit_parent = (parent.NS == ns.Parent)
 652                                                 ? parent
 653                                                 : new NamespaceEntry (parent, file, ns.Parent, false);
 654                                 }
 655                                 return implicit_parent;
 656                         }
 657                 }
 658
 659                 /// <summary>
 660                 ///   Records a new namespace for resolving name references
 661                 /// </summary>
 662                 public void Using (MemberName name, Location loc)
 663                 {
 664                         if (DeclarationFound){
 665                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 666                                 return;
 667                         }
 668
 669                         UsingFound = true;
 670
 671                         if (name.Equals (ns.MemberName))
 672                                 return;
 673
 674                         if (using_clauses == null)
 675                                 using_clauses = new ArrayList ();
 676
 677                         foreach (UsingEntry old_entry in using_clauses) {
 678                                 if (name.Equals (old_entry.Name)) {
 679                                         Report.Warning (105, 3, loc, "The using directive for `{0}' appeared previously in this namespace", name.GetName ());
 680                                         return;
 681                                 }
 682                         }
 683
 684                         UsingEntry ue = new UsingEntry (Doppelganger, name, loc);
 685                         using_clauses.Add (ue);
 686                 }
 687
 688                 public void UsingAlias (string name, MemberName alias, Location loc)
 689                 {
 690                         if (DeclarationFound){
 691                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 692                                 return;
 693                         }
 694
 695                         UsingFound = true;
 696
 697                         if (aliases == null)
 698                                 aliases = new Hashtable ();
 699
 700                         if (aliases.Contains (name)) {
 701                                 AliasEntry ae = (AliasEntry) aliases [name];
 702                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 703                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 704                                 return;
 705                         }
 706
 707                         if (RootContext.Version == LanguageVersion.Default &&
 708                             name == "global" && RootContext.WarningLevel >= 2)
 709                                 Report.Warning (440, 2, loc, "An alias named `global' will not be used when resolving 'global::';" +
 710                                         " the global namespace will be used instead");
 711
 712                         // FIXME: get correct error number.  See if the above check can be merged
 713                         if (extern_aliases != null && extern_aliases.Contains (name)) {
 714                                 AliasEntry ae = (AliasEntry) extern_aliases [name];
 715                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 716                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 717                                 return;
 718                         }
 719
 720                         aliases [name] = new LocalAliasEntry (Doppelganger, name, alias, loc);
 721                 }
 722
 723                 public void UsingExternalAlias (string name, Location loc)
 724                 {
 725                         if (UsingFound || DeclarationFound) {
 726                                 Report.Error (439, loc, "An extern alias declaration must precede all other elements");
 727                                 return;
 728                         }
 729
 730                         // Share the extern_aliases field with the Doppelganger
 731                         if (extern_aliases == null) {
 732                                 extern_aliases = new ListDictionary ();
 733                                 Doppelganger.extern_aliases = extern_aliases;
 734                         }
 735
 736                         if (extern_aliases.Contains (name)) {
 737                                 AliasEntry ae = (AliasEntry) extern_aliases [name];
 738                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 739                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 740                                 return;
 741                         }
 742
 743                         if (name == "global") {
 744                                 Report.Error (1681, loc, "You cannot redefine the global extern alias");
 745                                 return;
 746                         }
 747
 748                         // Register the alias in aliases and extern_aliases, since we need both of them
 749                         // to keep things simple (different resolution scenarios)
 750                         ExternAliasEntry alias = new ExternAliasEntry (Doppelganger, name, loc);
 751                         extern_aliases [name] = alias;
 752                 }
 753
 754                 public FullNamedExpression LookupNamespaceOrType (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 755                 {
 756                         // Precondition: Only simple names (no dots) will be looked up with this function.
 757                         FullNamedExpression resolved = null;
 758                         for (NamespaceEntry curr_ns = this; curr_ns != null; curr_ns = curr_ns.ImplicitParent) {
 759                                 if ((resolved = curr_ns.Lookup (ds, name, loc, ignore_cs0104)) != null)
 760                                         break;
 761                         }
 762                         return resolved;
 763                 }
 764
 765                 static void Error_AmbiguousTypeReference (Location loc, string name, FullNamedExpression t1, FullNamedExpression t2)
 766                 {
 767                         Report.Error (104, loc, "`{0}' is an ambiguous reference between `{1}' and `{2}'",
 768                                 name, t1.FullName, t2.FullName);
 769                 }
 770
 771                 // Looks-up a alias named @name in this and surrounding namespace declarations
 772                 public FullNamedExpression LookupAlias (string name)
 773                 {
 774                         AliasEntry entry = null;
 775                         for (NamespaceEntry n = this; n != null; n = n.ImplicitParent) {
 776                                 if (n.extern_aliases != null && (entry = n.extern_aliases [name] as AliasEntry) != null)
 777                                         break;
 778                                 if (n.aliases != null && (entry = n.aliases [name] as AliasEntry) != null)
 779                                         break;
 780                         }
 781                         return entry == null ? null : entry.Resolve ();
 782                 }
 783
 784                 private FullNamedExpression Lookup (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 785                 {
 786                         //
 787                         // Check whether it's in the namespace.
 788                         //
 789                         FullNamedExpression fne = NS.Lookup (ds, name, loc);
 790                         if (fne != null)
 791                                 return fne;
 792
 793                         if (extern_aliases != null) {
 794                                 AliasEntry entry = extern_aliases [name] as AliasEntry;
 795                                 if (entry != null)
 796                                         return entry.Resolve ();
 797                         }
 798
 799                         if (IsImplicit)
 800                                 return null;
 801
 802                         //
 803                         // Check aliases.
 804                         //
 805                         if (aliases != null) {
 806                                 AliasEntry entry = aliases [name] as AliasEntry;
 807                                 if (entry != null)
 808                                         return entry.Resolve ();
 809                         }
 810
 811                         //
 812                         // Check using entries.
 813                         //
 814                         FullNamedExpression match = null;
 815                         foreach (Namespace using_ns in GetUsingTable ()) {
 816                                 match = using_ns.Lookup (ds, name, loc);
 817                                 if (match == null || !(match is TypeExpr))
 818                                         continue;
 819                                 if (fne != null) {
 820                                         if (!ignore_cs0104)
 821                                                 Error_AmbiguousTypeReference (loc, name, fne, match);
 822                                         return null;
 823                                 }
 824                                 fne = match;
 825                         }
 826
 827                         return fne;
 828                 }
 829
 830                 // Our cached computation.
 831                 readonly Namespace [] empty_namespaces = new Namespace [0];
 832                 Namespace [] namespace_using_table;
 833                 Namespace [] GetUsingTable ()
 834                 {
 835                         if (namespace_using_table != null)
 836                                 return namespace_using_table;
 837
 838                         if (using_clauses == null) {
 839                                 namespace_using_table = empty_namespaces;
 840                                 return namespace_using_table;
 841                         }
 842
 843                         ArrayList list = new ArrayList (using_clauses.Count);
 844
 845                         foreach (UsingEntry ue in using_clauses) {
 846                                 Namespace using_ns = ue.Resolve ();
 847                                 if (using_ns == null)
 848                                         continue;
 849
 850                                 list.Add (using_ns);
 851                         }
 852
 853                         namespace_using_table = new Namespace [list.Count];
 854                         list.CopyTo (namespace_using_table, 0);
 855                         return namespace_using_table;
 856                 }
 857
 858                 readonly string [] empty_using_list = new string [0];
 859
 860                 public int SymbolFileID {
 861                         get {
 862                                 if (symfile_id == 0 && file.SourceFileEntry != null) {
 863                                         int parent_id = parent == null ? 0 : parent.SymbolFileID;
 864
 865                                         string [] using_list = empty_using_list;
 866                                         if (using_clauses != null) {
 867                                                 using_list = new string [using_clauses.Count];
 868                                                 for (int i = 0; i < using_clauses.Count; i++)
 869                                                         using_list [i] = ((UsingEntry) using_clauses [i]).Name.ToString ();
 870                                         }
 871
 872                                         symfile_id = CodeGen.SymbolWriter.DefineNamespace (ns.Name, file.SourceFileEntry, using_list, parent_id);
 873                                 }
 874                                 return symfile_id;
 875                         }
 876                 }
 877
 878                 static void MsgtryRef (string s)
 879                 {
 880                         Console.WriteLine ("    Try using -r:" + s);
 881                 }
 882
 883                 static void MsgtryPkg (string s)
 884                 {
 885                         Console.WriteLine ("    Try using -pkg:" + s);
 886                 }
 887
 888                 public static void Error_NamespaceNotFound (Location loc, string name)
 889                 {
 890                         Report.Error (246, loc, "The type or namespace name `{0}' could not be found. Are you missing a using directive or an assembly reference?",
 891                                 name);
 892
 893                         switch (name) {
 894                         case "Gtk": case "GtkSharp":
 895                                 MsgtryPkg ("gtk-sharp");
 896                                 break;
 897
 898                         case "Gdk": case "GdkSharp":
 899                                 MsgtryPkg ("gdk-sharp");
 900                                 break;
 901
 902                         case "Glade": case "GladeSharp":
 903                                 MsgtryPkg ("glade-sharp");
 904                                 break;
 905
 906                         case "System.Drawing":
 907                         case "System.Web.Services":
 908                         case "System.Web":
 909                         case "System.Data":
 910                         case "System.Windows.Forms":
 911                                 MsgtryRef (name);
 912                                 break;
 913                         }
 914                 }
 915
 916                 /// <summary>
 917                 ///   Used to validate that all the using clauses are correct
 918                 ///   after we are finished parsing all the files.
 919                 /// </summary>
 920                 void VerifyUsing ()
 921                 {
 922                         if (extern_aliases != null) {
 923                                 foreach (DictionaryEntry de in extern_aliases)
 924                                         ((AliasEntry) de.Value).Resolve ();
 925                         }
 926
 927                         if (using_clauses != null) {
 928                                 foreach (UsingEntry ue in using_clauses)
 929                                         ue.Resolve ();
 930                         }
 931
 932                         if (aliases != null) {
 933                                 foreach (DictionaryEntry de in aliases)
 934                                         ((AliasEntry) de.Value).Resolve ();
 935                         }
 936                 }
 937
 938                 /// <summary>
 939                 ///   Used to validate that all the using clauses are correct
 940                 ///   after we are finished parsing all the files.
 941                 /// </summary>
 942                 static public void VerifyAllUsing ()
 943                 {
 944                         foreach (NamespaceEntry entry in entries)
 945                                 entry.VerifyUsing ();
 946                 }
 947
 948                 public string GetSignatureForError ()
 949                 {
 950                         return ns.GetSignatureForError ();
 951                 }
 952
 953                 public override string ToString ()
 954                 {
 955                         return ns.ToString ();
 956                 }
 957         }
 958 }