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