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 // Copyright 2001 Ximian, Inc.
   9 // Copyright 2003-2008 Novell, Inc.
  10 // Copyright 2011 Xamarin Inc
  11 //
  12 using System;
  13 using System.Collections.Generic;
  14 using System.Linq;
  15 using Mono.CompilerServices.SymbolWriter;
  16
  17 namespace Mono.CSharp {
  18
  19         public class RootNamespace : Namespace {
  20
  21                 readonly string alias_name;
  22                 readonly Dictionary<string, Namespace> all_namespaces;
  23
  24                 public RootNamespace (string alias_name)
  25                         : base ()
  26                 {
  27                         this.alias_name = alias_name;
  28                         RegisterNamespace (this);
  29
  30                         all_namespaces = new Dictionary<string, Namespace> ();
  31                         all_namespaces.Add ("", this);
  32                 }
  33
  34                 public string Alias {
  35                         get {
  36                                 return alias_name;
  37                         }
  38                 }
  39
  40                 public static void Error_GlobalNamespaceRedefined (Report report, Location loc)
  41                 {
  42                         report.Error (1681, loc, "The global extern alias cannot be redefined");
  43                 }
  44
  45                 //
  46                 // For better error reporting where we try to guess missing using directive
  47                 //
  48                 public List<string> FindTypeNamespaces (IMemberContext ctx, string name, int arity)
  49                 {
  50                         List<string> res = null;
  51
  52                         foreach (var ns in all_namespaces) {
  53                                 var type = ns.Value.LookupType (ctx, name, arity, LookupMode.Normal, Location.Null);
  54                                 if (type != null) {
  55                                         if (res == null)
  56                                                 res = new List<string> ();
  57
  58                                         res.Add (ns.Key);
  59                                 }
  60                         }
  61
  62                         return res;
  63                 }
  64
  65                 //
  66                 // For better error reporting where compiler tries to guess missing using directive
  67                 //
  68                 public List<string> FindExtensionMethodNamespaces (IMemberContext ctx, string name, int arity)
  69                 {
  70                         List<string> res = null;
  71
  72                         foreach (var ns in all_namespaces) {
  73                                 if (ns.Key.Length == 0)
  74                                         continue;
  75
  76                                 var methods = ns.Value.LookupExtensionMethod (ctx, name, arity);
  77                                 if (methods != null) {
  78                                         if (res == null)
  79                                                 res = new List<string> ();
  80
  81                                         res.Add (ns.Key);
  82                                 }
  83                         }
  84
  85                         return res;
  86                 }
  87
  88                 public void RegisterNamespace (Namespace child)
  89                 {
  90                         if (child != this)
  91                                 all_namespaces.Add (child.Name, child);
  92                 }
  93
  94                 public override string GetSignatureForError ()
  95                 {
  96                         return alias_name + "::";
  97                 }
  98         }
  99
 100         public sealed class GlobalRootNamespace : RootNamespace
 101         {
 102                 public GlobalRootNamespace ()
 103                         : base ("global")
 104                 {
 105                 }
 106         }
 107
 108         //
 109         // Namespace cache for imported and compiled namespaces
 110         //
 111         public class Namespace
 112         {
 113                 readonly Namespace parent;
 114                 string fullname;
 115                 protected Dictionary<string, Namespace> namespaces;
 116                 protected Dictionary<string, IList<TypeSpec>> types;
 117                 List<TypeSpec> extension_method_types;
 118                 Dictionary<string, TypeSpec> cached_types;
 119                 bool cls_checked;
 120
 121                 /// <summary>
 122                 ///   Constructor Takes the current namespace and the
 123                 ///   name.  This is bootstrapped with parent == null
 124                 ///   and name = ""
 125                 /// </summary>
 126                 public Namespace (Namespace parent, string name)
 127                         : this ()
 128                 {
 129                         if (name == null)
 130                                 throw new ArgumentNullException ("name");
 131
 132                         this.parent = parent;
 133
 134                         string pname = parent != null ? parent.fullname : null;
 135
 136                         if (pname == null)
 137                                 fullname = name;
 138                         else
 139                                 fullname = pname + "." + name;
 140
 141                         while (parent.parent != null)
 142                                 parent = parent.parent;
 143
 144                         var root = parent as RootNamespace;
 145                         if (root == null)
 146                                 throw new InternalErrorException ("Root namespaces must be created using RootNamespace");
 147
 148                         root.RegisterNamespace (this);
 149                 }
 150
 151                 protected Namespace ()
 152                 {
 153                         namespaces = new Dictionary<string, Namespace> ();
 154                         cached_types = new Dictionary<string, TypeSpec> ();
 155                 }
 156
 157                 #region Properties
 158
 159                 /// <summary>
 160                 ///   The qualified name of the current namespace
 161                 /// </summary>
 162                 public string Name {
 163                         get { return fullname; }
 164                 }
 165
 166                 /// <summary>
 167                 ///   The parent of this namespace, used by the parser to "Pop"
 168                 ///   the current namespace declaration
 169                 /// </summary>
 170                 public Namespace Parent {
 171                         get { return parent; }
 172                 }
 173
 174                 #endregion
 175
 176                 public Namespace AddNamespace (MemberName name)
 177                 {
 178                         var ns_parent = name.Left == null ? this : AddNamespace (name.Left);
 179                         return ns_parent.TryAddNamespace (name.Basename);
 180                 }
 181
 182                 Namespace TryAddNamespace (string name)
 183                 {
 184                         Namespace ns;
 185
 186                         if (!namespaces.TryGetValue (name, out ns)) {
 187                                 ns = new Namespace (this, name);
 188                                 namespaces.Add (name, ns);
 189                         }
 190
 191                         return ns;
 192                 }
 193
 194                 public bool TryGetNamespace (string name, out Namespace ns)
 195                 {
 196                         return namespaces.TryGetValue (name, out ns);
 197                 }
 198
 199                 // TODO: Replace with CreateNamespace where MemberName is created for the method call
 200                 public Namespace GetNamespace (string name, bool create)
 201                 {
 202                         int pos = name.IndexOf ('.');
 203
 204                         Namespace ns;
 205                         string first;
 206                         if (pos >= 0)
 207                                 first = name.Substring (0, pos);
 208                         else
 209                                 first = name;
 210
 211                         if (!namespaces.TryGetValue (first, out ns)) {
 212                                 if (!create)
 213                                         return null;
 214
 215                                 ns = new Namespace (this, first);
 216                                 namespaces.Add (first, ns);
 217                         }
 218
 219                         if (pos >= 0)
 220                                 ns = ns.GetNamespace (name.Substring (pos + 1), create);
 221
 222                         return ns;
 223                 }
 224
 225                 public IList<TypeSpec> GetAllTypes (string name)
 226                 {
 227                         IList<TypeSpec> found;
 228                         if (types == null || !types.TryGetValue (name, out found))
 229                                 return null;
 230
 231                         return found;
 232                 }
 233
 234                 public virtual string GetSignatureForError ()
 235                 {
 236                         return fullname;
 237                 }
 238
 239                 public TypeSpec LookupType (IMemberContext ctx, string name, int arity, LookupMode mode, Location loc)
 240                 {
 241                         if (types == null)
 242                                 return null;
 243
 244                         TypeSpec best = null;
 245                         if (arity == 0 && cached_types.TryGetValue (name, out best)) {
 246                                 if (best != null || mode != LookupMode.IgnoreAccessibility)
 247                                         return best;
 248                         }
 249
 250                         IList<TypeSpec> found;
 251                         if (!types.TryGetValue (name, out found))
 252                                 return null;
 253
 254                         foreach (var ts in found) {
 255                                 if (ts.Arity == arity) {
 256                                         if (best == null) {
 257                                                 if ((ts.Modifiers & Modifiers.INTERNAL) != 0 && !ts.MemberDefinition.IsInternalAsPublic (ctx.Module.DeclaringAssembly) && mode != LookupMode.IgnoreAccessibility)
 258                                                         continue;
 259
 260                                                 best = ts;
 261                                                 continue;
 262                                         }
 263
 264                                         if (best.MemberDefinition.IsImported && ts.MemberDefinition.IsImported) {
 265                                                 if (ts.Kind == MemberKind.MissingType)
 266                                                         continue;
 267
 268                                                 if (best.Kind == MemberKind.MissingType) {
 269                                                         best = ts;
 270                                                         continue;
 271                                                 }
 272
 273                                                 if (mode == LookupMode.Normal) {
 274                                                         ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (best);
 275                                                         ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (ts);
 276                                                         ctx.Module.Compiler.Report.Error (433, loc, "The imported type `{0}' is defined multiple times", ts.GetSignatureForError ());
 277                                                 }
 278
 279                                                 break;
 280                                         }
 281
 282                                         if (best.MemberDefinition.IsImported)
 283                                                 best = ts;
 284
 285                                         if ((best.Modifiers & Modifiers.INTERNAL) != 0 && !best.MemberDefinition.IsInternalAsPublic (ctx.Module.DeclaringAssembly))
 286                                                 continue;
 287
 288                                         if (mode != LookupMode.Normal)
 289                                                 continue;
 290
 291                                         if (ts.MemberDefinition.IsImported) {
 292                                                 ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (best);
 293                                                 ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (ts);
 294                                         }
 295
 296                                         ctx.Module.Compiler.Report.Warning (436, 2, loc,
 297                                                 "The type `{0}' conflicts with the imported type of same name'. Ignoring the imported type definition",
 298                                                 best.GetSignatureForError ());
 299                                 }
 300
 301                                 //
 302                                 // Lookup for the best candidate with the closest arity match
 303                                 //
 304                                 if (arity < 0) {
 305                                         if (best == null) {
 306                                                 best = ts;
 307                                         } else if (System.Math.Abs (ts.Arity + arity) < System.Math.Abs (best.Arity + arity)) {
 308                                                 best = ts;
 309                                         }
 310                                 }
 311                         }
 312
 313                         // TODO MemberCache: Cache more
 314                         if (arity == 0 && mode == LookupMode.Normal)
 315                                 cached_types.Add (name, best);
 316
 317                         if (best != null) {
 318                                 var dep = best.GetMissingDependencies ();
 319                                 if (dep != null)
 320                                         ImportedTypeDefinition.Error_MissingDependency (ctx, dep, loc);
 321                         }
 322
 323                         return best;
 324                 }
 325
 326                 public FullNamedExpression LookupTypeOrNamespace (IMemberContext ctx, string name, int arity, LookupMode mode, Location loc)
 327                 {
 328                         var texpr = LookupType (ctx, name, arity, mode, loc);
 329
 330                         Namespace ns;
 331                         if (arity == 0 && namespaces.TryGetValue (name, out ns)) {
 332                                 if (texpr == null)
 333                                         return new NamespaceExpression (ns, loc);
 334
 335                                 if (mode != LookupMode.Probing) {
 336                                         //ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (texpr.Type);
 337                                         // ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (ns.loc, "");
 338                                         ctx.Module.Compiler.Report.Warning (437, 2, loc,
 339                                                 "The type `{0}' conflicts with the imported namespace `{1}'. Using the definition found in the source file",
 340                                                 texpr.GetSignatureForError (), ns.GetSignatureForError ());
 341                                 }
 342
 343                                 if (texpr.MemberDefinition.IsImported)
 344                                         return new NamespaceExpression (ns, loc);
 345                         }
 346
 347                         if (texpr == null)
 348                                 return null;
 349
 350                         return new TypeExpression (texpr, loc);
 351                 }
 352
 353                 //
 354                 // Completes types with the given `prefix'
 355                 //
 356                 public IEnumerable<string> CompletionGetTypesStartingWith (string prefix)
 357                 {
 358                         if (types == null)
 359                                 return Enumerable.Empty<string> ();
 360
 361                         var res = from item in types
 362                                           where item.Key.StartsWith (prefix) && item.Value.Any (l => (l.Modifiers & Modifiers.PUBLIC) != 0)
 363                                           select item.Key;
 364
 365                         if (namespaces != null)
 366                                 res = res.Concat (from item in namespaces where item.Key.StartsWith (prefix) select item.Key);
 367
 368                         return res;
 369                 }
 370
 371                 //
 372                 // Looks for extension method in this namespace
 373                 //
 374                 public List<MethodSpec> LookupExtensionMethod (IMemberContext invocationContext, string name, int arity)
 375                 {
 376                         if (extension_method_types == null)
 377                                 return null;
 378
 379                         List<MethodSpec> found = null;
 380                         for (int i = 0; i < extension_method_types.Count; ++i) {
 381                                 var ts = extension_method_types[i];
 382
 383                                 //
 384                                 // When the list was built we didn't know what members the type
 385                                 // contains
 386                                 //
 387                                 if ((ts.Modifiers & Modifiers.METHOD_EXTENSION) == 0) {
 388                                         if (extension_method_types.Count == 1) {
 389                                                 extension_method_types = null;
 390                                                 return found;
 391                                         }
 392
 393                                         extension_method_types.RemoveAt (i--);
 394                                         continue;
 395                                 }
 396
 397                                 var res = ts.MemberCache.FindExtensionMethods (invocationContext, name, arity);
 398                                 if (res == null)
 399                                         continue;
 400
 401                                 if (found == null) {
 402                                         found = res;
 403                                 } else {
 404                                         found.AddRange (res);
 405                                 }
 406                         }
 407
 408                         return found;
 409                 }
 410
 411                 public void AddType (ModuleContainer module, TypeSpec ts)
 412                 {
 413                         if (types == null) {
 414                                 types = new Dictionary<string, IList<TypeSpec>> (64);
 415                         }
 416
 417                         if (ts.IsClass && ts.Arity == 0) {
 418                                 var extension_method_allowed = ts.MemberDefinition.IsImported ? (ts.Modifiers & Modifiers.METHOD_EXTENSION) != 0 : (ts.IsStatic || ts.MemberDefinition.IsPartial);
 419                                 if (extension_method_allowed) {
 420                                         if (extension_method_types == null)
 421                                                 extension_method_types = new List<TypeSpec> ();
 422
 423                                         extension_method_types.Add (ts);
 424                                 }
 425                         }
 426
 427                         var name = ts.Name;
 428                         IList<TypeSpec> existing;
 429                         if (types.TryGetValue (name, out existing)) {
 430                                 TypeSpec better_type;
 431                                 TypeSpec found;
 432                                 if (existing.Count == 1) {
 433                                         found = existing[0];
 434                                         if (ts.Arity == found.Arity) {
 435                                                 better_type = IsImportedTypeOverride (module, ts, found);
 436                                                 if (better_type == found)
 437                                                         return;
 438
 439                                                 if (better_type != null) {
 440                                                         existing [0] = better_type;
 441                                                         return;
 442                                                 }
 443                                         }
 444
 445                                         existing = new List<TypeSpec> ();
 446                                         existing.Add (found);
 447                                         types[name] = existing;
 448                                 } else {
 449                                         for (int i = 0; i < existing.Count; ++i) {
 450                                                 found = existing[i];
 451                                                 if (ts.Arity != found.Arity)
 452                                                         continue;
 453
 454                                                 better_type = IsImportedTypeOverride (module, ts, found);
 455                                                 if (better_type == found)
 456                                                         return;
 457
 458                                                 if (better_type != null) {
 459                                                         existing.RemoveAt (i);
 460                                                         --i;
 461                                                         continue;
 462                                                 }
 463                                         }
 464                                 }
 465
 466                                 existing.Add (ts);
 467                         } else {
 468                                 types.Add (name, new TypeSpec[] { ts });
 469                         }
 470                 }
 471
 472                 //
 473                 // We import any types but in the situation there are same types
 474                 // but one has better visibility (either public or internal with friend)
 475                 // the less visible type is removed from the namespace cache
 476                 //
 477                 public static TypeSpec IsImportedTypeOverride (ModuleContainer module, TypeSpec ts, TypeSpec found)
 478                 {
 479                         var ts_accessible = (ts.Modifiers & Modifiers.PUBLIC) != 0 || ts.MemberDefinition.IsInternalAsPublic (module.DeclaringAssembly);
 480                         var found_accessible = (found.Modifiers & Modifiers.PUBLIC) != 0 || found.MemberDefinition.IsInternalAsPublic (module.DeclaringAssembly);
 481
 482                         if (ts_accessible && !found_accessible)
 483                                 return ts;
 484
 485                         // found is better always better for accessible or inaccessible ts
 486                         if (!ts_accessible)
 487                                 return found;
 488
 489                         return null;
 490                 }
 491
 492                 public void RemoveContainer (TypeContainer tc)
 493                 {
 494                         IList<TypeSpec> found;
 495                         if (types.TryGetValue (tc.MemberName.Name, out found)) {
 496                                 for (int i = 0; i < found.Count; ++i) {
 497                                         if (tc.MemberName.Arity != found [i].Arity)
 498                                                 continue;
 499
 500                                         if (found.Count == 1)
 501                                                 types.Remove (tc.MemberName.Name);
 502                                         else
 503                                                 found.RemoveAt (i);
 504
 505                                         break;
 506                                 }
 507                         }
 508
 509                         cached_types.Remove (tc.MemberName.Basename);
 510                 }
 511
 512                 public void SetBuiltinType (BuiltinTypeSpec pts)
 513                 {
 514                         var found = types[pts.Name];
 515                         cached_types.Remove (pts.Name);
 516                         if (found.Count == 1) {
 517                                 types[pts.Name][0] = pts;
 518                         } else {
 519                                 throw new NotImplementedException ();
 520                         }
 521                 }
 522
 523                 public void VerifyClsCompliance ()
 524                 {
 525                         if (types == null || cls_checked)
 526                                 return;
 527
 528                         cls_checked = true;
 529
 530                         // TODO: This is quite ugly way to check for CLS compliance at namespace level
 531
 532                         var locase_types = new Dictionary<string, List<TypeSpec>> (StringComparer.OrdinalIgnoreCase);
 533                         foreach (var tgroup in types.Values) {
 534                                 foreach (var tm in tgroup) {
 535                                         if ((tm.Modifiers & Modifiers.PUBLIC) == 0 || !tm.IsCLSCompliant ())
 536                                                 continue;
 537
 538                                         List<TypeSpec> found;
 539                                         if (!locase_types.TryGetValue (tm.Name, out found)) {
 540                                                 found = new List<TypeSpec> ();
 541                                                 locase_types.Add (tm.Name, found);
 542                                         }
 543
 544                                         found.Add (tm);
 545                                 }
 546                         }
 547
 548                         foreach (var locase in locase_types.Values) {
 549                                 if (locase.Count < 2)
 550                                         continue;
 551
 552                                 bool all_same = true;
 553                                 foreach (var notcompliant in locase) {
 554                                         all_same = notcompliant.Name == locase[0].Name;
 555                                         if (!all_same)
 556                                                 break;
 557                                 }
 558
 559                                 if (all_same)
 560                                         continue;
 561
 562                                 TypeContainer compiled = null;
 563                                 foreach (var notcompliant in locase) {
 564                                         if (!notcompliant.MemberDefinition.IsImported) {
 565                                                 if (compiled != null)
 566                                                         compiled.Compiler.Report.SymbolRelatedToPreviousError (compiled);
 567
 568                                                 compiled = notcompliant.MemberDefinition as TypeContainer;
 569                                         } else {
 570                                                 compiled.Compiler.Report.SymbolRelatedToPreviousError (notcompliant);
 571                                         }
 572                                 }
 573
 574                                 compiled.Compiler.Report.Warning (3005, 1, compiled.Location,
 575                                         "Identifier `{0}' differing only in case is not CLS-compliant", compiled.GetSignatureForError ());
 576                         }
 577                 }
 578         }
 579
 580         public class CompilationSourceFile : NamespaceContainer
 581         {
 582                 readonly SourceFile file;
 583                 CompileUnitEntry comp_unit;
 584                 Dictionary<string, SourceFile> include_files;
 585                 Dictionary<string, bool> conditionals;
 586
 587                 public CompilationSourceFile (ModuleContainer parent, SourceFile sourceFile)
 588                         : this (parent)
 589                 {
 590                         this.file = sourceFile;
 591                 }
 592
 593                 public CompilationSourceFile (ModuleContainer parent)
 594                         : base (parent)
 595                 {
 596                 }
 597
 598                 public CompileUnitEntry SymbolUnitEntry {
 599                         get {
 600                                 return comp_unit;
 601                         }
 602                 }
 603
 604                 public string FileName {
 605                         get {
 606                                 return file.Name;
 607                         }
 608                 }
 609
 610                 public SourceFile SourceFile {
 611                         get {
 612                                 return file;
 613                         }
 614                 }
 615
 616                 public void AddIncludeFile (SourceFile file)
 617                 {
 618                         if (file == this.file)
 619                                 return;
 620
 621                         if (include_files == null)
 622                                 include_files = new Dictionary<string, SourceFile> ();
 623
 624                         if (!include_files.ContainsKey (file.FullPathName))
 625                                 include_files.Add (file.FullPathName, file);
 626                 }
 627
 628                 public void AddDefine (string value)
 629                 {
 630                         if (conditionals == null)
 631                                 conditionals = new Dictionary<string, bool> (2);
 632
 633                         conditionals[value] = true;
 634                 }
 635
 636                 public void AddUndefine (string value)
 637                 {
 638                         if (conditionals == null)
 639                                 conditionals = new Dictionary<string, bool> (2);
 640
 641                         conditionals[value] = false;
 642                 }
 643
 644                 public override void PrepareEmit ()
 645                 {
 646                         var sw = Module.DeclaringAssembly.SymbolWriter;
 647                         if (sw != null) {
 648                                 CreateUnitSymbolInfo (sw);
 649                         }
 650
 651                         base.PrepareEmit ();
 652                 }
 653
 654                 //
 655                 // Creates symbol file index in debug symbol file
 656                 //
 657                 void CreateUnitSymbolInfo (MonoSymbolFile symwriter)
 658                 {
 659                         var si = file.CreateSymbolInfo (symwriter);
 660                         comp_unit = new CompileUnitEntry (symwriter, si);
 661
 662                         if (include_files != null) {
 663                                 foreach (SourceFile include in include_files.Values) {
 664                                         si = include.CreateSymbolInfo (symwriter);
 665                                         comp_unit.AddFile (si);
 666                                 }
 667                         }
 668                 }
 669
 670                 public bool IsConditionalDefined (string value)
 671                 {
 672                         if (conditionals != null) {
 673                                 bool res;
 674                                 if (conditionals.TryGetValue (value, out res))
 675                                         return res;
 676
 677                                 // When conditional was undefined
 678                                 if (conditionals.ContainsKey (value))
 679                                         return false;
 680                         }
 681
 682                         return Compiler.Settings.IsConditionalSymbolDefined (value);
 683                 }
 684
 685                 public override void Accept (StructuralVisitor visitor)
 686                 {
 687                         visitor.Visit (this);
 688                 }
 689         }
 690
 691
 692         //
 693         // Namespace block as created by the parser
 694         //
 695         public class NamespaceContainer : TypeContainer, IMemberContext
 696         {
 697                 static readonly Namespace[] empty_namespaces = new Namespace[0];
 698
 699                 readonly Namespace ns;
 700
 701                 public new readonly NamespaceContainer Parent;
 702
 703                 List<UsingClause> clauses;
 704
 705                 // Used by parsed to check for parser errors
 706                 public bool DeclarationFound;
 707
 708                 Namespace[] namespace_using_table;
 709                 TypeSpec[] types_using_table;
 710                 Dictionary<string, UsingAliasNamespace> aliases;
 711
 712                 public NamespaceContainer (MemberName name, NamespaceContainer parent)
 713                         : base (parent, name, null, MemberKind.Namespace)
 714                 {
 715                         this.Parent = parent;
 716                         this.ns = parent.NS.AddNamespace (name);
 717
 718                         containers = new List<TypeContainer> ();
 719                 }
 720
 721                 protected NamespaceContainer (ModuleContainer parent)
 722                         : base (parent, null, null, MemberKind.Namespace)
 723                 {
 724                         ns = parent.GlobalRootNamespace;
 725                         containers = new List<TypeContainer> (2);
 726                 }
 727
 728                 #region Properties
 729
 730                 public override AttributeTargets AttributeTargets {
 731                         get {
 732                                 throw new NotSupportedException ();
 733                         }
 734                 }
 735
 736                 public override string DocCommentHeader {
 737                         get {
 738                                 throw new NotSupportedException ();
 739                         }
 740                 }
 741
 742                 public Namespace NS {
 743                         get {
 744                                 return ns;
 745                         }
 746                 }
 747
 748                 public List<UsingClause> Usings {
 749                         get {
 750                                 return clauses;
 751                         }
 752                 }
 753
 754                 public override string[] ValidAttributeTargets {
 755                         get {
 756                                 throw new NotSupportedException ();
 757                         }
 758                 }
 759
 760                 #endregion
 761
 762                 public void AddUsing (UsingClause un)
 763                 {
 764                         if (DeclarationFound){
 765                                 Compiler.Report.Error (1529, un.Location, "A using clause must precede all other namespace elements except extern alias declarations");
 766                         }
 767
 768                         if (clauses == null)
 769                                 clauses = new List<UsingClause> ();
 770
 771                         clauses.Add (un);
 772                 }
 773
 774                 public void AddUsing (UsingAliasNamespace un)
 775                 {
 776                         if (DeclarationFound){
 777                                 Compiler.Report.Error (1529, un.Location, "A using clause must precede all other namespace elements except extern alias declarations");
 778                         }
 779
 780                         AddAlias (un);
 781                 }
 782
 783                 void AddAlias (UsingAliasNamespace un)
 784                 {
 785                         if (clauses == null) {
 786                                 clauses = new List<UsingClause> ();
 787                         } else {
 788                                 foreach (var entry in clauses) {
 789                                         var a = entry as UsingAliasNamespace;
 790                                         if (a != null && a.Alias.Value == un.Alias.Value) {
 791                                                 Compiler.Report.SymbolRelatedToPreviousError (a.Location, "");
 792                                                 Compiler.Report.Error (1537, un.Location,
 793                                                         "The using alias `{0}' appeared previously in this namespace", un.Alias.Value);
 794                                         }
 795                                 }
 796                         }
 797
 798                         clauses.Add (un);
 799                 }
 800
 801                 public override void AddPartial (TypeDefinition next_part)
 802                 {
 803                         var existing = ns.LookupType (this, next_part.MemberName.Name, next_part.MemberName.Arity, LookupMode.Probing, Location.Null);
 804                         var td = existing != null ? existing.MemberDefinition as TypeDefinition : null;
 805                         AddPartial (next_part, td);
 806                 }
 807
 808                 public override void AddTypeContainer (TypeContainer tc)
 809                 {
 810                         var mn = tc.MemberName;
 811                         var name = mn.Basename;
 812                         while (mn.Left != null) {
 813                                 mn = mn.Left;
 814                                 name = mn.Name;
 815                         }
 816
 817                         var names_container = Parent == null ? Module : (TypeContainer) this;
 818
 819                         MemberCore mc;
 820                         if (names_container.DefinedNames.TryGetValue (name, out mc)) {
 821                                 if (tc is NamespaceContainer && mc is NamespaceContainer) {
 822                                         AddTypeContainerMember (tc);
 823                                         return;
 824                                 }
 825
 826                                 Report.SymbolRelatedToPreviousError (mc);
 827                                 if ((mc.ModFlags & Modifiers.PARTIAL) != 0 && (tc is ClassOrStruct || tc is Interface)) {
 828                                         Error_MissingPartialModifier (tc);
 829                                 } else {
 830                                         Report.Error (101, tc.Location, "The namespace `{0}' already contains a definition for `{1}'",
 831                                                 GetSignatureForError (), mn.GetSignatureForError ());
 832                                 }
 833                         } else {
 834                                 names_container.DefinedNames.Add (name, tc);
 835
 836                                 var tdef = tc.PartialContainer;
 837                                 if (tdef != null) {
 838                                         //
 839                                         // Same name conflict in different namespace containers
 840                                         //
 841                                         var conflict = ns.GetAllTypes (name);
 842                                         if (conflict != null) {
 843                                                 foreach (var e in conflict) {
 844                                                         if (e.Arity == mn.Arity) {
 845                                                                 mc = (MemberCore) e.MemberDefinition;
 846                                                                 break;
 847                                                         }
 848                                                 }
 849                                         }
 850
 851                                         if (mc != null) {
 852                                                 Report.SymbolRelatedToPreviousError (mc);
 853                                                 Report.Error (101, tc.Location, "The namespace `{0}' already contains a definition for `{1}'",
 854                                                         GetSignatureForError (), mn.GetSignatureForError ());
 855                                         } else {
 856                                                 ns.AddType (Module, tdef.Definition);
 857                                         }
 858                                 }
 859                         }
 860
 861                         base.AddTypeContainer (tc);
 862                 }
 863
 864                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
 865                 {
 866                         throw new NotSupportedException ();
 867                 }
 868
 869                 public override void EmitContainer ()
 870                 {
 871                         VerifyClsCompliance ();
 872
 873                         base.EmitContainer ();
 874                 }
 875
 876                 public ExtensionMethodCandidates LookupExtensionMethod (IMemberContext invocationContext, string name, int arity, int position)
 877                 {
 878                         //
 879                         // Here we try to resume the search for extension method at the point
 880                         // where the last bunch of candidates was found. It's more tricky than
 881                         // it seems as we have to check both namespace containers and namespace
 882                         // in correct order.
 883                         //
 884                         // Consider:
 885                         //
 886                         // namespace A {
 887                         //      using N1;
 888                         //  namespace B.C.D {
 889                         //              <our first search found candidates in A.B.C.D
 890                         //  }
 891                         // }
 892                         //
 893                         // In the example above namespace A.B.C.D, A.B.C and A.B have to be
 894                         // checked before we hit A.N1 using
 895                         //
 896                         ExtensionMethodCandidates candidates;
 897                         var container = this;
 898                         do {
 899                                 candidates = container.LookupExtensionMethodCandidates (invocationContext, name, arity, ref position);
 900                                 if (candidates != null || container.MemberName == null)
 901                                         return candidates;
 902
 903                                 var container_ns = container.ns.Parent;
 904                                 var mn = container.MemberName.Left;
 905                                 int already_checked = position - 2;
 906                                 while (already_checked-- > 0) {
 907                                         mn = mn.Left;
 908                                         container_ns = container_ns.Parent;
 909                                 }
 910
 911                                 while (mn != null) {
 912                                         ++position;
 913
 914                                         var methods = container_ns.LookupExtensionMethod (invocationContext, name, arity);
 915                                         if (methods != null) {
 916                                                 return new ExtensionMethodCandidates (invocationContext, methods, container, position);
 917                                         }
 918
 919                                         mn = mn.Left;
 920                                         container_ns = container_ns.Parent;
 921                                 }
 922
 923                                 position = 0;
 924                                 container = container.Parent;
 925                         } while (container != null);
 926
 927                         return null;
 928                 }
 929
 930                 ExtensionMethodCandidates LookupExtensionMethodCandidates (IMemberContext invocationContext, string name, int arity, ref int position)
 931                 {
 932                         List<MethodSpec> candidates = null;
 933
 934                         if (position == 0) {
 935                                 ++position;
 936
 937                                 candidates = ns.LookupExtensionMethod (invocationContext, name, arity);
 938                                 if (candidates != null) {
 939                                         return new ExtensionMethodCandidates (invocationContext, candidates, this, position);
 940                                 }
 941                         }
 942
 943                         if (position == 1) {
 944                                 ++position;
 945
 946                                 foreach (Namespace n in namespace_using_table) {
 947                                         var a = n.LookupExtensionMethod (invocationContext, name, arity);
 948                                         if (a == null)
 949                                                 continue;
 950
 951                                         if (candidates == null)
 952                                                 candidates = a;
 953                                         else
 954                                                 candidates.AddRange (a);
 955                                 }
 956
 957                                 if (types_using_table != null) {
 958                                         foreach (var t in types_using_table) {
 959
 960                                                 var res = t.MemberCache.FindExtensionMethods (invocationContext, name, arity);
 961                                                 if (res == null)
 962                                                         continue;
 963
 964                                                 if (candidates == null)
 965                                                         candidates = res;
 966                                                 else
 967                                                         candidates.AddRange (res);
 968                                         }
 969                                 }
 970
 971                                 if (candidates != null)
 972                                         return new ExtensionMethodCandidates (invocationContext, candidates, this, position);
 973                         }
 974
 975                         return null;
 976                 }
 977
 978                 public override FullNamedExpression LookupNamespaceOrType (string name, int arity, LookupMode mode, Location loc)
 979                 {
 980                         //
 981                         // Only simple names (no dots) will be looked up with this function
 982                         //
 983                         FullNamedExpression resolved;
 984                         for (NamespaceContainer container = this; container != null; container = container.Parent) {
 985                                 resolved = container.Lookup (name, arity, mode, loc);
 986                                 if (resolved != null || container.MemberName == null)
 987                                         return resolved;
 988
 989                                 var container_ns = container.ns.Parent;
 990                                 var mn = container.MemberName.Left;
 991                                 while (mn != null) {
 992                                         resolved = container_ns.LookupTypeOrNamespace (this, name, arity, mode, loc);
 993                                         if (resolved != null)
 994                                                 return resolved;
 995
 996                                         mn = mn.Left;
 997                                         container_ns = container_ns.Parent;
 998                                 }
 999                         }
1000
1001                         return null;
1002                 }
1003
1004                 public override void GetCompletionStartingWith (string prefix, List<string> results)
1005                 {
1006                         if (Usings == null)
1007                                 return;
1008
1009                         foreach (var un in Usings) {
1010                                 if (un.Alias != null)
1011                                         continue;
1012
1013                                 var name = un.NamespaceExpression.Name;
1014                                 if (name.StartsWith (prefix))
1015                                         results.Add (name);
1016                         }
1017
1018
1019                         IEnumerable<string> all = Enumerable.Empty<string> ();
1020
1021                         foreach (Namespace using_ns in namespace_using_table) {
1022                                 if (prefix.StartsWith (using_ns.Name)) {
1023                                         int ld = prefix.LastIndexOf ('.');
1024                                         if (ld != -1) {
1025                                                 string rest = prefix.Substring (ld + 1);
1026
1027                                                 all = all.Concat (using_ns.CompletionGetTypesStartingWith (rest));
1028                                         }
1029                                 }
1030                                 all = all.Concat (using_ns.CompletionGetTypesStartingWith (prefix));
1031                         }
1032
1033                         results.AddRange (all);
1034
1035                         base.GetCompletionStartingWith (prefix, results);
1036                 }
1037
1038
1039                 //
1040                 // Looks-up a alias named @name in this and surrounding namespace declarations
1041                 //
1042                 public FullNamedExpression LookupExternAlias (string name)
1043                 {
1044                         if (aliases == null)
1045                                 return null;
1046
1047                         UsingAliasNamespace uan;
1048                         if (aliases.TryGetValue (name, out uan) && uan is UsingExternAlias)
1049                                 return uan.ResolvedExpression;
1050
1051                         return null;
1052                 }
1053
1054                 //
1055                 // Looks-up a alias named @name in this and surrounding namespace declarations
1056                 //
1057                 public override FullNamedExpression LookupNamespaceAlias (string name)
1058                 {
1059                         for (NamespaceContainer n = this; n != null; n = n.Parent) {
1060                                 if (n.aliases == null)
1061                                         continue;
1062
1063                                 UsingAliasNamespace uan;
1064                                 if (n.aliases.TryGetValue (name, out uan))
1065                                         return uan.ResolvedExpression;
1066                         }
1067
1068                         return null;
1069                 }
1070
1071                 FullNamedExpression Lookup (string name, int arity, LookupMode mode, Location loc)
1072                 {
1073                         //
1074                         // Check whether it's in the namespace.
1075                         //
1076                         FullNamedExpression fne = ns.LookupTypeOrNamespace (this, name, arity, mode, loc);
1077
1078                         //
1079                         // Check aliases.
1080                         //
1081                         if (aliases != null && arity == 0) {
1082                                 UsingAliasNamespace uan;
1083                                 if (aliases.TryGetValue (name, out uan)) {
1084                                         if (fne != null && mode != LookupMode.Probing) {
1085                                                 // TODO: Namespace has broken location
1086                                                 //Report.SymbolRelatedToPreviousError (fne.Location, null);
1087                                                 Compiler.Report.SymbolRelatedToPreviousError (uan.Location, null);
1088                                                 Compiler.Report.Error (576, loc,
1089                                                         "Namespace `{0}' contains a definition with same name as alias `{1}'",
1090                                                         GetSignatureForError (), name);
1091                                         }
1092
1093                                         return uan.ResolvedExpression;
1094                                 }
1095                         }
1096
1097                         if (fne != null)
1098                                 return fne;
1099
1100                         //
1101                         // Lookup can be called before the namespace is defined from different namespace using alias clause
1102                         //
1103                         if (namespace_using_table == null) {
1104                                 DoDefineNamespace ();
1105                         }
1106
1107                         //
1108                         // Check using entries.
1109                         //
1110                         FullNamedExpression match = null;
1111                         foreach (Namespace using_ns in namespace_using_table) {
1112                                 //
1113                                 // A using directive imports only types contained in the namespace, it
1114                                 // does not import any nested namespaces
1115                                 //
1116                                 var t = using_ns.LookupType (this, name, arity, mode, loc);
1117                                 if (t == null)
1118                                         continue;
1119
1120                                 fne = new TypeExpression (t, loc);
1121                                 if (match == null) {
1122                                         match = fne;
1123                                         continue;
1124                                 }
1125
1126                                 // Prefer types over namespaces
1127                                 var texpr_fne = fne as TypeExpr;
1128                                 var texpr_match = match as TypeExpr;
1129                                 if (texpr_fne != null && texpr_match == null) {
1130                                         match = fne;
1131                                         continue;
1132                                 } else if (texpr_fne == null) {
1133                                         continue;
1134                                 }
1135
1136                                 // It can be top level accessibility only
1137                                 var better = Namespace.IsImportedTypeOverride (Module, texpr_match.Type, texpr_fne.Type);
1138                                 if (better == null) {
1139                                         if (mode == LookupMode.Normal) {
1140                                                 Compiler.Report.SymbolRelatedToPreviousError (texpr_match.Type);
1141                                                 Compiler.Report.SymbolRelatedToPreviousError (texpr_fne.Type);
1142                                                 Compiler.Report.Error (104, loc, "`{0}' is an ambiguous reference between `{1}' and `{2}'",
1143                                                         name, texpr_match.GetSignatureForError (), texpr_fne.GetSignatureForError ());
1144                                         }
1145
1146                                         return match;
1147                                 }
1148
1149                                 if (better == texpr_fne.Type)
1150                                         match = texpr_fne;
1151                         }
1152
1153                         return match;
1154                 }
1155
1156                 public static Expression LookupStaticUsings (IMemberContext mc, string name, int arity, Location loc)
1157                 {
1158                         for (var m = mc.CurrentMemberDefinition; m != null; m = m.Parent) {
1159
1160                                 var nc = m as NamespaceContainer;
1161                                 if (nc == null)
1162                                         continue;
1163
1164                                 List<MemberSpec> candidates = null;
1165                                 if (nc.types_using_table != null) {
1166                                         foreach (var using_type in nc.types_using_table) {
1167                                                 var members = MemberCache.FindMembers (using_type, name, true);
1168                                                 if (members != null) {
1169                                                         foreach (var member in members) {
1170                                                                 if ((member.Kind & MemberKind.NestedMask) != 0) {
1171                                                                         // non-static nested type is included with using static
1172                                                                 } else {
1173                                                                         if ((member.Modifiers & Modifiers.STATIC) == 0)
1174                                                                                 continue;
1175
1176                                                                         if ((member.Modifiers & Modifiers.METHOD_EXTENSION) != 0)
1177                                                                                 continue;
1178                                                                 }
1179
1180                                                                 if (arity > 0 && member.Arity != arity)
1181                                                                         continue;
1182
1183                                                                 if (candidates == null)
1184                                                                         candidates = new List<MemberSpec> ();
1185
1186                                                                 candidates.Add (member);
1187                                                         }
1188                                                 }
1189                                         }
1190                                 }
1191
1192                                 if (candidates != null) {
1193                                         var expr = Expression.MemberLookupToExpression (mc, candidates, false, null, name, arity, Expression.MemberLookupRestrictions.None, loc);
1194                                         if (expr != null)
1195                                                 return expr;
1196                                 }
1197                         }
1198
1199                         return null;
1200                 }
1201
1202                 protected override void DefineNamespace ()
1203                 {
1204                         if (namespace_using_table == null)
1205                                 DoDefineNamespace ();
1206
1207                         base.DefineNamespace ();
1208                 }
1209
1210                 void DoDefineNamespace ()
1211                 {
1212                         namespace_using_table = empty_namespaces;
1213
1214                         if (clauses != null) {
1215                                 List<Namespace> namespaces = null;
1216                                 List<TypeSpec> types = null;
1217
1218                                 bool post_process_using_aliases = false;
1219
1220                                 for (int i = 0; i < clauses.Count; ++i) {
1221                                         var entry = clauses[i];
1222
1223                                         if (entry.Alias != null) {
1224                                                 if (aliases == null)
1225                                                         aliases = new Dictionary<string, UsingAliasNamespace> ();
1226
1227                                                 //
1228                                                 // Aliases are not available when resolving using section
1229                                                 // except extern aliases
1230                                                 //
1231                                                 if (entry is UsingExternAlias) {
1232                                                         entry.Define (this);
1233                                                         if (entry.ResolvedExpression != null)
1234                                                                 aliases.Add (entry.Alias.Value, (UsingExternAlias) entry);
1235
1236                                                         clauses.RemoveAt (i--);
1237                                                 } else {
1238                                                         post_process_using_aliases = true;
1239                                                 }
1240
1241                                                 continue;
1242                                         }
1243
1244                                         entry.Define (this);
1245
1246                                         //
1247                                         // It's needed for repl only, when using clause cannot be resolved don't hold it in
1248                                         // global list which is resolved for each evaluation
1249                                         //
1250                                         if (entry.ResolvedExpression == null) {
1251                                                 clauses.RemoveAt (i--);
1252                                                 continue;
1253                                         }
1254
1255                                         var using_ns = entry.ResolvedExpression as NamespaceExpression;
1256                                         if (using_ns == null) {
1257
1258                                                 var type = entry.ResolvedExpression.Type;
1259
1260                                                 if (types == null)
1261                                                         types = new List<TypeSpec> ();
1262
1263                                                 if (types.Contains (type)) {
1264                                                         Warning_DuplicateEntry (entry);
1265                                                 } else {
1266                                                         types.Add (type);
1267                                                 }
1268                                         } else {
1269                                                 if (namespaces == null)
1270                                                         namespaces = new List<Namespace> ();
1271
1272                                                 if (namespaces.Contains (using_ns.Namespace)) {
1273                                                         // Ensure we don't report the warning multiple times in repl
1274                                                         clauses.RemoveAt (i--);
1275
1276                                                         Warning_DuplicateEntry (entry);
1277                                                 } else {
1278                                                         namespaces.Add (using_ns.Namespace);
1279                                                 }
1280                                         }
1281                                 }
1282
1283                                 namespace_using_table = namespaces == null ? new Namespace [0] : namespaces.ToArray ();
1284                                 if (types != null)
1285                                         types_using_table = types.ToArray ();
1286
1287                                 if (post_process_using_aliases) {
1288                                         for (int i = 0; i < clauses.Count; ++i) {
1289                                                 var entry = clauses[i];
1290                                                 if (entry.Alias != null) {
1291                                                         entry.Define (this);
1292                                                         if (entry.ResolvedExpression != null) {
1293                                                                 aliases.Add (entry.Alias.Value, (UsingAliasNamespace) entry);
1294                                                         }
1295
1296                                                         clauses.RemoveAt (i--);
1297                                                 }
1298                                         }
1299                                 }
1300                         }
1301                 }
1302
1303                 public void EnableRedefinition ()
1304                 {
1305                         is_defined = false;
1306                         namespace_using_table = null;
1307                 }
1308
1309                 internal override void GenerateDocComment (DocumentationBuilder builder)
1310                 {
1311                         if (containers != null) {
1312                                 foreach (var tc in containers)
1313                                         tc.GenerateDocComment (builder);
1314                         }
1315                 }
1316
1317                 public override string GetSignatureForError ()
1318                 {
1319                         return MemberName == null ? "global::" : base.GetSignatureForError ();
1320                 }
1321
1322                 public override void RemoveContainer (TypeContainer cont)
1323                 {
1324                         base.RemoveContainer (cont);
1325                         NS.RemoveContainer (cont);
1326                 }
1327
1328                 protected override bool VerifyClsCompliance ()
1329                 {
1330                         if (Module.IsClsComplianceRequired ()) {
1331                                 if (MemberName != null && MemberName.Name[0] == '_') {
1332                                         Warning_IdentifierNotCompliant ();
1333                                 }
1334
1335                                 ns.VerifyClsCompliance ();
1336                                 return true;
1337                         }
1338
1339                         return false;
1340                 }
1341
1342                 void Warning_DuplicateEntry (UsingClause entry)
1343                 {
1344                         Compiler.Report.Warning (105, 3, entry.Location,
1345                                 "The using directive for `{0}' appeared previously in this namespace",
1346                                 entry.ResolvedExpression.GetSignatureForError ());
1347                 }
1348
1349                 public override void Accept (StructuralVisitor visitor)
1350                 {
1351                         visitor.Visit (this);
1352                 }
1353         }
1354
1355         public class UsingNamespace : UsingClause
1356         {
1357                 public UsingNamespace (ATypeNameExpression expr, Location loc)
1358                         : base (expr, loc)
1359                 {
1360                 }
1361
1362                 public override void Define (NamespaceContainer ctx)
1363                 {
1364                         base.Define (ctx);
1365
1366                         var ns = resolved as NamespaceExpression;
1367                         if (ns != null)
1368                                 return;
1369
1370                         if (resolved != null) {
1371                                 var compiler = ctx.Module.Compiler;
1372                                 var type = resolved.Type;
1373
1374                                 compiler.Report.SymbolRelatedToPreviousError (type);
1375                                 compiler.Report.Error (138, Location,
1376                                         "A `using' directive can only be applied to namespaces but `{0}' denotes a type. Consider using a `using static' instead",
1377                                         type.GetSignatureForError ());
1378                         }
1379                 }
1380         }
1381
1382         public class UsingType : UsingClause
1383         {
1384                 public UsingType (ATypeNameExpression expr, Location loc)
1385                         : base (expr, loc)
1386                 {
1387                 }
1388
1389                 public override void Define (NamespaceContainer ctx)
1390                 {
1391                         base.Define (ctx);
1392
1393                         if (resolved == null)
1394                                 return;
1395
1396                         var ns = resolved as NamespaceExpression;
1397                         if (ns != null) {
1398                                 var compiler = ctx.Module.Compiler;
1399                                 compiler.Report.Error (7007, Location,
1400                                         "A 'using static' directive can only be applied to types but `{0}' denotes a namespace. Consider using a `using' directive instead",
1401                                         ns.GetSignatureForError ());
1402                                 return;
1403                         }
1404
1405                         // TODO: Need to move it to post_process_using_aliases
1406                         //ObsoleteAttribute obsolete_attr = resolved.Type.GetAttributeObsolete ();
1407                         //if (obsolete_attr != null) {
1408                         //      AttributeTester.Report_ObsoleteMessage (obsolete_attr, resolved.GetSignatureForError (), Location, ctx.Compiler.Report);
1409                         //}
1410                 }
1411         }
1412
1413         public class UsingClause
1414         {
1415                 readonly ATypeNameExpression expr;
1416                 readonly Location loc;
1417                 protected FullNamedExpression resolved;
1418
1419                 public UsingClause (ATypeNameExpression expr, Location loc)
1420                 {
1421                         this.expr = expr;
1422                         this.loc = loc;
1423                 }
1424
1425                 #region Properties
1426
1427                 public virtual SimpleMemberName Alias {
1428                         get {
1429                                 return null;
1430                         }
1431                 }
1432
1433                 public Location Location {
1434                         get {
1435                                 return loc;
1436                         }
1437                 }
1438
1439                 public ATypeNameExpression NamespaceExpression  {
1440                         get {
1441                                 return expr;
1442                         }
1443                 }
1444
1445                 public FullNamedExpression ResolvedExpression {
1446                         get {
1447                                 return resolved;
1448                         }
1449                 }
1450
1451                 #endregion
1452
1453                 public string GetSignatureForError ()
1454                 {
1455                         return expr.GetSignatureForError ();
1456                 }
1457
1458                 public virtual void Define (NamespaceContainer ctx)
1459                 {
1460                         resolved = expr.ResolveAsTypeOrNamespace (ctx, false);
1461                 }
1462
1463                 public override string ToString()
1464                 {
1465                         return resolved.ToString();
1466                 }
1467         }
1468
1469         public class UsingExternAlias : UsingAliasNamespace
1470         {
1471                 public UsingExternAlias (SimpleMemberName alias, Location loc)
1472                         : base (alias, null, loc)
1473                 {
1474                 }
1475
1476                 public override void Define (NamespaceContainer ctx)
1477                 {
1478                         var ns = ctx.Module.GetRootNamespace (Alias.Value);
1479                         if (ns == null) {
1480                                 ctx.Module.Compiler.Report.Error (430, Location,
1481                                         "The extern alias `{0}' was not specified in -reference option",
1482                                         Alias.Value);
1483                                 return;
1484                         }
1485
1486                         resolved = new NamespaceExpression (ns, Location);
1487                 }
1488         }
1489
1490         public class UsingAliasNamespace : UsingNamespace
1491         {
1492                 readonly SimpleMemberName alias;
1493
1494                 public struct AliasContext : IMemberContext
1495                 {
1496                         readonly NamespaceContainer ns;
1497
1498                         public AliasContext (NamespaceContainer ns)
1499                         {
1500                                 this.ns = ns;
1501                         }
1502
1503                         public TypeSpec CurrentType {
1504                                 get {
1505                                         return null;
1506                                 }
1507                         }
1508
1509                         public TypeParameters CurrentTypeParameters {
1510                                 get {
1511                                         return null;
1512                                 }
1513                         }
1514
1515                         public MemberCore CurrentMemberDefinition {
1516                                 get {
1517                                         return null;
1518                                 }
1519                         }
1520
1521                         public bool IsObsolete {
1522                                 get {
1523                                         return false;
1524                                 }
1525                         }
1526
1527                         public bool IsUnsafe {
1528                                 get {
1529                                         throw new NotImplementedException ();
1530                                 }
1531                         }
1532
1533                         public bool IsStatic {
1534                                 get {
1535                                         throw new NotImplementedException ();
1536                                 }
1537                         }
1538
1539                         public ModuleContainer Module {
1540                                 get {
1541                                         return ns.Module;
1542                                 }
1543                         }
1544
1545                         public string GetSignatureForError ()
1546                         {
1547                                 throw new NotImplementedException ();
1548                         }
1549
1550                         public ExtensionMethodCandidates LookupExtensionMethod (string name, int arity)
1551                         {
1552                                 return null;
1553                         }
1554
1555                         public FullNamedExpression LookupNamespaceOrType (string name, int arity, LookupMode mode, Location loc)
1556                         {
1557                                 var fne = ns.NS.LookupTypeOrNamespace (ns, name, arity, mode, loc);
1558                                 if (fne != null)
1559                                         return fne;
1560
1561                                 //
1562                                 // Only extern aliases are allowed in this context
1563                                 //
1564                                 fne = ns.LookupExternAlias (name);
1565                                 if (fne != null || ns.MemberName == null)
1566                                         return fne;
1567
1568                                 var container_ns = ns.NS.Parent;
1569                                 var mn = ns.MemberName.Left;
1570                                 while (mn != null) {
1571                                         fne = container_ns.LookupTypeOrNamespace (this, name, arity, mode, loc);
1572                                         if (fne != null)
1573                                                 return fne;
1574
1575                                         mn = mn.Left;
1576                                         container_ns = container_ns.Parent;
1577                                 }
1578
1579                                 if (ns.Parent != null)
1580                                         return ns.Parent.LookupNamespaceOrType (name, arity, mode, loc);
1581
1582                                 return null;
1583                         }
1584
1585                         public FullNamedExpression LookupNamespaceAlias (string name)
1586                         {
1587                                 return ns.LookupNamespaceAlias (name);
1588                         }
1589                 }
1590
1591                 public UsingAliasNamespace (SimpleMemberName alias, ATypeNameExpression expr, Location loc)
1592                         : base (expr, loc)
1593                 {
1594                         this.alias = alias;
1595                 }
1596
1597                 public override SimpleMemberName Alias {
1598                         get {
1599                                 return alias;
1600                         }
1601                 }
1602
1603                 public override void Define (NamespaceContainer ctx)
1604                 {
1605                         //
1606                         // The namespace-or-type-name of a using-alias-directive is resolved as if
1607                         // the immediately containing compilation unit or namespace body had no
1608                         // using-directives. A using-alias-directive may however be affected
1609                         // by extern-alias-directives in the immediately containing compilation
1610                         // unit or namespace body
1611                         //
1612                         // We achieve that by introducing alias-context which redirect any local
1613                         // namespace or type resolve calls to parent namespace
1614                         //
1615                         resolved = NamespaceExpression.ResolveAsTypeOrNamespace (new AliasContext (ctx), false);
1616                 }
1617         }
1618 }