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                                 var methods = ns.Value.LookupExtensionMethod (ctx, name, arity);
  74                                 if (methods != null) {
  75                                         if (res == null)
  76                                                 res = new List<string> ();
  77
  78                                         res.Add (ns.Key);
  79                                 }
  80                         }
  81
  82                         return res;
  83                 }
  84
  85                 public void RegisterNamespace (Namespace child)
  86                 {
  87                         if (child != this)
  88                                 all_namespaces.Add (child.Name, child);
  89                 }
  90
  91                 public override string GetSignatureForError ()
  92                 {
  93                         return alias_name + "::";
  94                 }
  95         }
  96
  97         public sealed class GlobalRootNamespace : RootNamespace
  98         {
  99                 public GlobalRootNamespace ()
 100                         : base ("global")
 101                 {
 102                 }
 103         }
 104
 105         //
 106         // Namespace cache for imported and compiled namespaces
 107         //
 108         public class Namespace
 109         {
 110                 readonly Namespace parent;
 111                 string fullname;
 112                 protected Dictionary<string, Namespace> namespaces;
 113                 protected Dictionary<string, IList<TypeSpec>> types;
 114                 List<TypeSpec> extension_method_types;
 115                 Dictionary<string, TypeSpec> cached_types;
 116                 bool cls_checked;
 117
 118                 /// <summary>
 119                 ///   Constructor Takes the current namespace and the
 120                 ///   name.  This is bootstrapped with parent == null
 121                 ///   and name = ""
 122                 /// </summary>
 123                 public Namespace (Namespace parent, string name)
 124                         : this ()
 125                 {
 126                         if (name == null)
 127                                 throw new ArgumentNullException ("name");
 128
 129                         this.parent = parent;
 130
 131                         string pname = parent != null ? parent.fullname : null;
 132
 133                         if (pname == null)
 134                                 fullname = name;
 135                         else
 136                                 fullname = pname + "." + name;
 137
 138                         while (parent.parent != null)
 139                                 parent = parent.parent;
 140
 141                         var root = parent as RootNamespace;
 142                         if (root == null)
 143                                 throw new InternalErrorException ("Root namespaces must be created using RootNamespace");
 144
 145                         root.RegisterNamespace (this);
 146                 }
 147
 148                 protected Namespace ()
 149                 {
 150                         namespaces = new Dictionary<string, Namespace> ();
 151                         cached_types = new Dictionary<string, TypeSpec> ();
 152                 }
 153
 154                 #region Properties
 155
 156                 /// <summary>
 157                 ///   The qualified name of the current namespace
 158                 /// </summary>
 159                 public string Name {
 160                         get { return fullname; }
 161                 }
 162
 163                 /// <summary>
 164                 ///   The parent of this namespace, used by the parser to "Pop"
 165                 ///   the current namespace declaration
 166                 /// </summary>
 167                 public Namespace Parent {
 168                         get { return parent; }
 169                 }
 170
 171                 #endregion
 172
 173                 public Namespace AddNamespace (MemberName name)
 174                 {
 175                         var ns_parent = name.Left == null ? this : AddNamespace (name.Left);
 176                         return ns_parent.TryAddNamespace (name.Basename);
 177                 }
 178
 179                 Namespace TryAddNamespace (string name)
 180                 {
 181                         Namespace ns;
 182
 183                         if (!namespaces.TryGetValue (name, out ns)) {
 184                                 ns = new Namespace (this, name);
 185                                 namespaces.Add (name, ns);
 186                         }
 187
 188                         return ns;
 189                 }
 190
 191                 public bool TryGetNamespace (string name, out Namespace ns)
 192                 {
 193                         return namespaces.TryGetValue (name, out ns);
 194                 }
 195
 196                 // TODO: Replace with CreateNamespace where MemberName is created for the method call
 197                 public Namespace GetNamespace (string name, bool create)
 198                 {
 199                         int pos = name.IndexOf ('.');
 200
 201                         Namespace ns;
 202                         string first;
 203                         if (pos >= 0)
 204                                 first = name.Substring (0, pos);
 205                         else
 206                                 first = name;
 207
 208                         if (!namespaces.TryGetValue (first, out ns)) {
 209                                 if (!create)
 210                                         return null;
 211
 212                                 ns = new Namespace (this, first);
 213                                 namespaces.Add (first, ns);
 214                         }
 215
 216                         if (pos >= 0)
 217                                 ns = ns.GetNamespace (name.Substring (pos + 1), create);
 218
 219                         return ns;
 220                 }
 221
 222                 public IList<TypeSpec> GetAllTypes (string name)
 223                 {
 224                         IList<TypeSpec> found;
 225                         if (types == null || !types.TryGetValue (name, out found))
 226                                 return null;
 227
 228                         return found;
 229                 }
 230
 231                 public virtual string GetSignatureForError ()
 232                 {
 233                         return fullname;
 234                 }
 235
 236                 public TypeSpec LookupType (IMemberContext ctx, string name, int arity, LookupMode mode, Location loc)
 237                 {
 238                         if (types == null)
 239                                 return null;
 240
 241                         TypeSpec best = null;
 242                         if (arity == 0 && cached_types.TryGetValue (name, out best)) {
 243                                 if (best != null || mode != LookupMode.IgnoreAccessibility)
 244                                         return best;
 245                         }
 246
 247                         IList<TypeSpec> found;
 248                         if (!types.TryGetValue (name, out found))
 249                                 return null;
 250
 251                         foreach (var ts in found) {
 252                                 if (ts.Arity == arity || mode == LookupMode.NameOf) {
 253                                         if (best == null) {
 254                                                 if ((ts.Modifiers & Modifiers.INTERNAL) != 0 && !ts.MemberDefinition.IsInternalAsPublic (ctx.Module.DeclaringAssembly) && mode != LookupMode.IgnoreAccessibility)
 255                                                         continue;
 256
 257                                                 best = ts;
 258                                                 continue;
 259                                         }
 260
 261                                         if (best.MemberDefinition.IsImported && ts.MemberDefinition.IsImported) {
 262                                                 if (ts.Kind == MemberKind.MissingType)
 263                                                         continue;
 264
 265                                                 if (best.Kind == MemberKind.MissingType) {
 266                                                         best = ts;
 267                                                         continue;
 268                                                 }
 269
 270                                                 if (mode == LookupMode.Normal) {
 271                                                         ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (best);
 272                                                         ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (ts);
 273                                                         ctx.Module.Compiler.Report.Error (433, loc, "The imported type `{0}' is defined multiple times", ts.GetSignatureForError ());
 274                                                 }
 275
 276                                                 break;
 277                                         }
 278
 279                                         if (best.MemberDefinition.IsImported)
 280                                                 best = ts;
 281
 282                                         if ((best.Modifiers & Modifiers.INTERNAL) != 0 && !best.MemberDefinition.IsInternalAsPublic (ctx.Module.DeclaringAssembly))
 283                                                 continue;
 284
 285                                         if (mode != LookupMode.Normal)
 286                                                 continue;
 287
 288                                         if (ts.MemberDefinition.IsImported) {
 289                                                 ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (best);
 290                                                 ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (ts);
 291                                         }
 292
 293                                         ctx.Module.Compiler.Report.Warning (436, 2, loc,
 294                                                 "The type `{0}' conflicts with the imported type of same name'. Ignoring the imported type definition",
 295                                                 best.GetSignatureForError ());
 296                                 }
 297
 298                                 //
 299                                 // Lookup for the best candidate with the closest arity match
 300                                 //
 301                                 if (arity < 0) {
 302                                         if (best == null) {
 303                                                 best = ts;
 304                                         } else if (System.Math.Abs (ts.Arity + arity) < System.Math.Abs (best.Arity + arity)) {
 305                                                 best = ts;
 306                                         }
 307                                 }
 308                         }
 309
 310                         // TODO MemberCache: Cache more
 311                         if (arity == 0 && mode == LookupMode.Normal)
 312                                 cached_types.Add (name, best);
 313
 314                         if (best != null) {
 315                                 var dep = best.GetMissingDependencies ();
 316                                 if (dep != null)
 317                                         ImportedTypeDefinition.Error_MissingDependency (ctx, dep, loc);
 318                         }
 319
 320                         return best;
 321                 }
 322
 323                 public FullNamedExpression LookupTypeOrNamespace (IMemberContext ctx, string name, int arity, LookupMode mode, Location loc)
 324                 {
 325                         var texpr = LookupType (ctx, name, arity, mode, loc);
 326
 327                         Namespace ns;
 328                         if (arity == 0 && namespaces.TryGetValue (name, out ns)) {
 329                                 if (texpr == null)
 330                                         return new NamespaceExpression (ns, loc);
 331
 332                                 if (mode != LookupMode.Probing) {
 333                                         //ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (texpr.Type);
 334                                         // ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (ns.loc, "");
 335                                         ctx.Module.Compiler.Report.Warning (437, 2, loc,
 336                                                 "The type `{0}' conflicts with the imported namespace `{1}'. Using the definition found in the source file",
 337                                                 texpr.GetSignatureForError (), ns.GetSignatureForError ());
 338                                 }
 339
 340                                 if (texpr.MemberDefinition.IsImported)
 341                                         return new NamespaceExpression (ns, loc);
 342                         }
 343
 344                         if (texpr == null)
 345                                 return null;
 346
 347                         return new TypeExpression (texpr, loc);
 348                 }
 349
 350                 //
 351                 // Completes types with the given `prefix'
 352                 //
 353                 public IEnumerable<string> CompletionGetTypesStartingWith (string prefix)
 354                 {
 355                         if (types == null)
 356                                 return Enumerable.Empty<string> ();
 357
 358                         var res = from item in types
 359                                           where item.Key.StartsWith (prefix) && item.Value.Any (l => (l.Modifiers & Modifiers.PUBLIC) != 0)
 360                                           select item.Key;
 361
 362                         if (namespaces != null)
 363                                 res = res.Concat (from item in namespaces where item.Key.StartsWith (prefix) select item.Key);
 364
 365                         return res;
 366                 }
 367
 368                 //
 369                 // Looks for extension method in this namespace
 370                 //
 371                 public List<MethodSpec> LookupExtensionMethod (IMemberContext invocationContext, string name, int arity)
 372                 {
 373                         if (extension_method_types == null)
 374                                 return null;
 375
 376                         List<MethodSpec> found = null;
 377                         for (int i = 0; i < extension_method_types.Count; ++i) {
 378                                 var ts = extension_method_types[i];
 379
 380                                 //
 381                                 // When the list was built we didn't know what members the type
 382                                 // contains
 383                                 //
 384                                 if ((ts.Modifiers & Modifiers.METHOD_EXTENSION) == 0) {
 385                                         if (extension_method_types.Count == 1) {
 386                                                 extension_method_types = null;
 387                                                 return found;
 388                                         }
 389
 390                                         extension_method_types.RemoveAt (i--);
 391                                         continue;
 392                                 }
 393
 394                                 var res = ts.MemberCache.FindExtensionMethods (invocationContext, name, arity);
 395                                 if (res == null)
 396                                         continue;
 397
 398                                 if (found == null) {
 399                                         found = res;
 400                                 } else {
 401                                         found.AddRange (res);
 402                                 }
 403                         }
 404
 405                         return found;
 406                 }
 407
 408                 public void AddType (ModuleContainer module, TypeSpec ts)
 409                 {
 410                         if (types == null) {
 411                                 types = new Dictionary<string, IList<TypeSpec>> (64);
 412                         }
 413
 414                         if (ts.IsClass && ts.Arity == 0) {
 415                                 var extension_method_allowed = ts.MemberDefinition.IsImported ? (ts.Modifiers & Modifiers.METHOD_EXTENSION) != 0 : (ts.IsStatic || ts.MemberDefinition.IsPartial);
 416                                 if (extension_method_allowed) {
 417                                         if (extension_method_types == null)
 418                                                 extension_method_types = new List<TypeSpec> ();
 419
 420                                         extension_method_types.Add (ts);
 421                                 }
 422                         }
 423
 424                         var name = ts.Name;
 425                         IList<TypeSpec> existing;
 426                         if (types.TryGetValue (name, out existing)) {
 427                                 TypeSpec better_type;
 428                                 TypeSpec found;
 429                                 if (existing.Count == 1) {
 430                                         found = existing[0];
 431                                         if (ts.Arity == found.Arity) {
 432                                                 better_type = IsImportedTypeOverride (module, ts, found);
 433                                                 if (better_type == found)
 434                                                         return;
 435
 436                                                 if (better_type != null) {
 437                                                         existing [0] = better_type;
 438                                                         return;
 439                                                 }
 440                                         }
 441
 442                                         existing = new List<TypeSpec> ();
 443                                         existing.Add (found);
 444                                         types[name] = existing;
 445                                 } else {
 446                                         for (int i = 0; i < existing.Count; ++i) {
 447                                                 found = existing[i];
 448                                                 if (ts.Arity != found.Arity)
 449                                                         continue;
 450
 451                                                 better_type = IsImportedTypeOverride (module, ts, found);
 452                                                 if (better_type == found)
 453                                                         return;
 454
 455                                                 if (better_type != null) {
 456                                                         existing.RemoveAt (i);
 457                                                         --i;
 458                                                         continue;
 459                                                 }
 460                                         }
 461                                 }
 462
 463                                 existing.Add (ts);
 464                         } else {
 465                                 types.Add (name, new TypeSpec[] { ts });
 466                         }
 467                 }
 468
 469                 //
 470                 // We import any types but in the situation there are same types
 471                 // but one has better visibility (either public or internal with friend)
 472                 // the less visible type is removed from the namespace cache
 473                 //
 474                 public static TypeSpec IsImportedTypeOverride (ModuleContainer module, TypeSpec ts, TypeSpec found)
 475                 {
 476                         var ts_accessible = (ts.Modifiers & Modifiers.PUBLIC) != 0 || ts.MemberDefinition.IsInternalAsPublic (module.DeclaringAssembly);
 477                         var found_accessible = (found.Modifiers & Modifiers.PUBLIC) != 0 || found.MemberDefinition.IsInternalAsPublic (module.DeclaringAssembly);
 478
 479                         if (ts_accessible && !found_accessible)
 480                                 return ts;
 481
 482                         // found is better always better for accessible or inaccessible ts
 483                         if (!ts_accessible)
 484                                 return found;
 485
 486                         return null;
 487                 }
 488
 489                 public void RemoveContainer (TypeContainer tc)
 490                 {
 491                         types.Remove (tc.Basename);
 492                         cached_types.Remove (tc.Basename);
 493                 }
 494
 495                 public void SetBuiltinType (BuiltinTypeSpec pts)
 496                 {
 497                         var found = types[pts.Name];
 498                         cached_types.Remove (pts.Name);
 499                         if (found.Count == 1) {
 500                                 types[pts.Name][0] = pts;
 501                         } else {
 502                                 throw new NotImplementedException ();
 503                         }
 504                 }
 505
 506                 public void VerifyClsCompliance ()
 507                 {
 508                         if (types == null || cls_checked)
 509                                 return;
 510
 511                         cls_checked = true;
 512
 513                         // TODO: This is quite ugly way to check for CLS compliance at namespace level
 514
 515                         var locase_types = new Dictionary<string, List<TypeSpec>> (StringComparer.OrdinalIgnoreCase);
 516                         foreach (var tgroup in types.Values) {
 517                                 foreach (var tm in tgroup) {
 518                                         if ((tm.Modifiers & Modifiers.PUBLIC) == 0 || !tm.IsCLSCompliant ())
 519                                                 continue;
 520
 521                                         List<TypeSpec> found;
 522                                         if (!locase_types.TryGetValue (tm.Name, out found)) {
 523                                                 found = new List<TypeSpec> ();
 524                                                 locase_types.Add (tm.Name, found);
 525                                         }
 526
 527                                         found.Add (tm);
 528                                 }
 529                         }
 530
 531                         foreach (var locase in locase_types.Values) {
 532                                 if (locase.Count < 2)
 533                                         continue;
 534
 535                                 bool all_same = true;
 536                                 foreach (var notcompliant in locase) {
 537                                         all_same = notcompliant.Name == locase[0].Name;
 538                                         if (!all_same)
 539                                                 break;
 540                                 }
 541
 542                                 if (all_same)
 543                                         continue;
 544
 545                                 TypeContainer compiled = null;
 546                                 foreach (var notcompliant in locase) {
 547                                         if (!notcompliant.MemberDefinition.IsImported) {
 548                                                 if (compiled != null)
 549                                                         compiled.Compiler.Report.SymbolRelatedToPreviousError (compiled);
 550
 551                                                 compiled = notcompliant.MemberDefinition as TypeContainer;
 552                                         } else {
 553                                                 compiled.Compiler.Report.SymbolRelatedToPreviousError (notcompliant);
 554                                         }
 555                                 }
 556
 557                                 compiled.Compiler.Report.Warning (3005, 1, compiled.Location,
 558                                         "Identifier `{0}' differing only in case is not CLS-compliant", compiled.GetSignatureForError ());
 559                         }
 560                 }
 561         }
 562
 563         public class CompilationSourceFile : NamespaceContainer
 564         {
 565                 readonly SourceFile file;
 566                 CompileUnitEntry comp_unit;
 567                 Dictionary<string, SourceFile> include_files;
 568                 Dictionary<string, bool> conditionals;
 569
 570                 public CompilationSourceFile (ModuleContainer parent, SourceFile sourceFile)
 571                         : this (parent)
 572                 {
 573                         this.file = sourceFile;
 574                 }
 575
 576                 public CompilationSourceFile (ModuleContainer parent)
 577                         : base (parent)
 578                 {
 579                 }
 580
 581                 public CompileUnitEntry SymbolUnitEntry {
 582                         get {
 583                                 return comp_unit;
 584                         }
 585                 }
 586
 587                 public string FileName {
 588                         get {
 589                                 return file.Name;
 590                         }
 591                 }
 592
 593                 public SourceFile SourceFile {
 594                         get {
 595                                 return file;
 596                         }
 597                 }
 598
 599                 public void AddIncludeFile (SourceFile file)
 600                 {
 601                         if (file == this.file)
 602                                 return;
 603
 604                         if (include_files == null)
 605                                 include_files = new Dictionary<string, SourceFile> ();
 606
 607                         if (!include_files.ContainsKey (file.FullPathName))
 608                                 include_files.Add (file.FullPathName, file);
 609                 }
 610
 611                 public void AddDefine (string value)
 612                 {
 613                         if (conditionals == null)
 614                                 conditionals = new Dictionary<string, bool> (2);
 615
 616                         conditionals[value] = true;
 617                 }
 618
 619                 public void AddUndefine (string value)
 620                 {
 621                         if (conditionals == null)
 622                                 conditionals = new Dictionary<string, bool> (2);
 623
 624                         conditionals[value] = false;
 625                 }
 626
 627                 public override void PrepareEmit ()
 628                 {
 629                         var sw = Module.DeclaringAssembly.SymbolWriter;
 630                         if (sw != null) {
 631                                 CreateUnitSymbolInfo (sw);
 632                         }
 633
 634                         base.PrepareEmit ();
 635                 }
 636
 637                 //
 638                 // Creates symbol file index in debug symbol file
 639                 //
 640                 void CreateUnitSymbolInfo (MonoSymbolFile symwriter)
 641                 {
 642                         var si = file.CreateSymbolInfo (symwriter);
 643                         comp_unit = new CompileUnitEntry (symwriter, si);
 644
 645                         if (include_files != null) {
 646                                 foreach (SourceFile include in include_files.Values) {
 647                                         si = include.CreateSymbolInfo (symwriter);
 648                                         comp_unit.AddFile (si);
 649                                 }
 650                         }
 651                 }
 652
 653                 public bool IsConditionalDefined (string value)
 654                 {
 655                         if (conditionals != null) {
 656                                 bool res;
 657                                 if (conditionals.TryGetValue (value, out res))
 658                                         return res;
 659
 660                                 // When conditional was undefined
 661                                 if (conditionals.ContainsKey (value))
 662                                         return false;
 663                         }
 664
 665                         return Compiler.Settings.IsConditionalSymbolDefined (value);
 666                 }
 667
 668                 public override void Accept (StructuralVisitor visitor)
 669                 {
 670                         visitor.Visit (this);
 671                 }
 672         }
 673
 674
 675         //
 676         // Namespace block as created by the parser
 677         //
 678         public class NamespaceContainer : TypeContainer, IMemberContext
 679         {
 680                 static readonly Namespace[] empty_namespaces = new Namespace[0];
 681
 682                 readonly Namespace ns;
 683
 684                 public new readonly NamespaceContainer Parent;
 685
 686                 List<UsingNamespace> clauses;
 687
 688                 // Used by parsed to check for parser errors
 689                 public bool DeclarationFound;
 690
 691                 Namespace[] namespace_using_table;
 692                 TypeSpec[] types_using_table;
 693                 Dictionary<string, UsingAliasNamespace> aliases;
 694
 695                 public NamespaceContainer (MemberName name, NamespaceContainer parent)
 696                         : base (parent, name, null, MemberKind.Namespace)
 697                 {
 698                         this.Parent = parent;
 699                         this.ns = parent.NS.AddNamespace (name);
 700
 701                         containers = new List<TypeContainer> ();
 702                 }
 703
 704                 protected NamespaceContainer (ModuleContainer parent)
 705                         : base (parent, null, null, MemberKind.Namespace)
 706                 {
 707                         ns = parent.GlobalRootNamespace;
 708                         containers = new List<TypeContainer> (2);
 709                 }
 710
 711                 #region Properties
 712
 713                 public override AttributeTargets AttributeTargets {
 714                         get {
 715                                 throw new NotSupportedException ();
 716                         }
 717                 }
 718
 719                 public override string DocCommentHeader {
 720                         get {
 721                                 throw new NotSupportedException ();
 722                         }
 723                 }
 724
 725                 public Namespace NS {
 726                         get {
 727                                 return ns;
 728                         }
 729                 }
 730
 731                 public List<UsingNamespace> Usings {
 732                         get {
 733                                 return clauses;
 734                         }
 735                 }
 736
 737                 public override string[] ValidAttributeTargets {
 738                         get {
 739                                 throw new NotSupportedException ();
 740                         }
 741                 }
 742
 743                 #endregion
 744
 745                 public void AddUsing (UsingNamespace un)
 746                 {
 747                         if (DeclarationFound){
 748                                 Compiler.Report.Error (1529, un.Location, "A using clause must precede all other namespace elements except extern alias declarations");
 749                         }
 750
 751                         if (clauses == null)
 752                                 clauses = new List<UsingNamespace> ();
 753
 754                         clauses.Add (un);
 755                 }
 756
 757                 public void AddUsing (UsingAliasNamespace un)
 758                 {
 759                         if (DeclarationFound){
 760                                 Compiler.Report.Error (1529, un.Location, "A using clause must precede all other namespace elements except extern alias declarations");
 761                         }
 762
 763                         AddAlias (un);
 764                 }
 765
 766                 void AddAlias (UsingAliasNamespace un)
 767                 {
 768                         if (clauses == null) {
 769                                 clauses = new List<UsingNamespace> ();
 770                         } else {
 771                                 foreach (var entry in clauses) {
 772                                         var a = entry as UsingAliasNamespace;
 773                                         if (a != null && a.Alias.Value == un.Alias.Value) {
 774                                                 Compiler.Report.SymbolRelatedToPreviousError (a.Location, "");
 775                                                 Compiler.Report.Error (1537, un.Location,
 776                                                         "The using alias `{0}' appeared previously in this namespace", un.Alias.Value);
 777                                         }
 778                                 }
 779                         }
 780
 781                         clauses.Add (un);
 782                 }
 783
 784                 public override void AddPartial (TypeDefinition next_part)
 785                 {
 786                         var existing = ns.LookupType (this, next_part.MemberName.Name, next_part.MemberName.Arity, LookupMode.Probing, Location.Null);
 787                         var td = existing != null ? existing.MemberDefinition as TypeDefinition : null;
 788                         AddPartial (next_part, td);
 789                 }
 790
 791                 public override void AddTypeContainer (TypeContainer tc)
 792                 {
 793                         string name = tc.Basename;
 794
 795                         var mn = tc.MemberName;
 796                         while (mn.Left != null) {
 797                                 mn = mn.Left;
 798                                 name = mn.Name;
 799                         }
 800
 801                         var names_container = Parent == null ? Module : (TypeContainer) this;
 802
 803                         MemberCore mc;
 804                         if (names_container.DefinedNames.TryGetValue (name, out mc)) {
 805                                 if (tc is NamespaceContainer && mc is NamespaceContainer) {
 806                                         AddTypeContainerMember (tc);
 807                                         return;
 808                                 }
 809
 810                                 Report.SymbolRelatedToPreviousError (mc);
 811                                 if ((mc.ModFlags & Modifiers.PARTIAL) != 0 && (tc is ClassOrStruct || tc is Interface)) {
 812                                         Error_MissingPartialModifier (tc);
 813                                 } else {
 814                                         Report.Error (101, tc.Location, "The namespace `{0}' already contains a definition for `{1}'",
 815                                                 GetSignatureForError (), mn.GetSignatureForError ());
 816                                 }
 817                         } else {
 818                                 names_container.DefinedNames.Add (name, tc);
 819
 820                                 var tdef = tc.PartialContainer;
 821                                 if (tdef != null) {
 822                                         //
 823                                         // Same name conflict in different namespace containers
 824                                         //
 825                                         var conflict = ns.GetAllTypes (name);
 826                                         if (conflict != null) {
 827                                                 foreach (var e in conflict) {
 828                                                         if (e.Arity == mn.Arity) {
 829                                                                 mc = (MemberCore) e.MemberDefinition;
 830                                                                 break;
 831                                                         }
 832                                                 }
 833                                         }
 834
 835                                         if (mc != null) {
 836                                                 Report.SymbolRelatedToPreviousError (mc);
 837                                                 Report.Error (101, tc.Location, "The namespace `{0}' already contains a definition for `{1}'",
 838                                                         GetSignatureForError (), mn.GetSignatureForError ());
 839                                         } else {
 840                                                 ns.AddType (Module, tdef.Definition);
 841                                         }
 842                                 }
 843                         }
 844
 845                         base.AddTypeContainer (tc);
 846                 }
 847
 848                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
 849                 {
 850                         throw new NotSupportedException ();
 851                 }
 852
 853                 public override void EmitContainer ()
 854                 {
 855                         VerifyClsCompliance ();
 856
 857                         base.EmitContainer ();
 858                 }
 859
 860                 public ExtensionMethodCandidates LookupExtensionMethod (IMemberContext invocationContext, TypeSpec extensionType, string name, int arity, int position)
 861                 {
 862                         //
 863                         // Here we try to resume the search for extension method at the point
 864                         // where the last bunch of candidates was found. It's more tricky than
 865                         // it seems as we have to check both namespace containers and namespace
 866                         // in correct order.
 867                         //
 868                         // Consider:
 869                         //
 870                         // namespace A {
 871                         //      using N1;
 872                         //  namespace B.C.D {
 873                         //              <our first search found candidates in A.B.C.D
 874                         //  }
 875                         // }
 876                         //
 877                         // In the example above namespace A.B.C.D, A.B.C and A.B have to be
 878                         // checked before we hit A.N1 using
 879                         //
 880                         ExtensionMethodCandidates candidates;
 881                         var container = this;
 882                         do {
 883                                 candidates = container.LookupExtensionMethodCandidates (invocationContext, name, arity, ref position);
 884                                 if (candidates != null || container.MemberName == null)
 885                                         return candidates;
 886
 887                                 var container_ns = container.ns.Parent;
 888                                 var mn = container.MemberName.Left;
 889                                 int already_checked = position - 2;
 890                                 while (already_checked-- > 0) {
 891                                         mn = mn.Left;
 892                                         container_ns = container_ns.Parent;
 893                                 }
 894
 895                                 while (mn != null) {
 896                                         ++position;
 897
 898                                         var methods = container_ns.LookupExtensionMethod (invocationContext, name, arity);
 899                                         if (methods != null) {
 900                                                 return new ExtensionMethodCandidates (invocationContext, methods, container, position);
 901                                         }
 902
 903                                         mn = mn.Left;
 904                                         container_ns = container_ns.Parent;
 905                                 }
 906
 907                                 position = 0;
 908                                 container = container.Parent;
 909                         } while (container != null);
 910
 911                         return null;
 912                 }
 913
 914                 ExtensionMethodCandidates LookupExtensionMethodCandidates (IMemberContext invocationContext, string name, int arity, ref int position)
 915                 {
 916                         List<MethodSpec> candidates = null;
 917
 918                         if (position == 0) {
 919                                 ++position;
 920
 921                                 candidates = ns.LookupExtensionMethod (invocationContext, name, arity);
 922                                 if (candidates != null) {
 923                                         return new ExtensionMethodCandidates (invocationContext, candidates, this, position);
 924                                 }
 925                         }
 926
 927                         if (position == 1) {
 928                                 ++position;
 929
 930                                 foreach (Namespace n in namespace_using_table) {
 931                                         var a = n.LookupExtensionMethod (invocationContext, name, arity);
 932                                         if (a == null)
 933                                                 continue;
 934
 935                                         if (candidates == null)
 936                                                 candidates = a;
 937                                         else
 938                                                 candidates.AddRange (a);
 939                                 }
 940
 941                                 if (candidates != null)
 942                                         return new ExtensionMethodCandidates (invocationContext, candidates, this, position);
 943                         }
 944
 945                         // LAMESPEC: TODO no spec about priority over normal extension methods yet
 946                         if (types_using_table != null) {
 947                                 foreach (var t in types_using_table) {
 948
 949                                         var res = t.MemberCache.FindExtensionMethods (invocationContext, name, arity);
 950                                         if (res == null)
 951                                                 continue;
 952
 953                                         if (candidates == null)
 954                                                 candidates = res;
 955                                         else
 956                                                 candidates.AddRange (res);
 957                                 }
 958
 959                                 if (candidates != null)
 960                                         return new ExtensionMethodCandidates (invocationContext, candidates, this, position);
 961                         }
 962
 963                         return null;
 964                 }
 965
 966                 public override FullNamedExpression LookupNamespaceOrType (string name, int arity, LookupMode mode, Location loc)
 967                 {
 968                         //
 969                         // Only simple names (no dots) will be looked up with this function
 970                         //
 971                         FullNamedExpression resolved;
 972                         for (NamespaceContainer container = this; container != null; container = container.Parent) {
 973                                 resolved = container.Lookup (name, arity, mode, loc);
 974                                 if (resolved != null || container.MemberName == null)
 975                                         return resolved;
 976
 977                                 var container_ns = container.ns.Parent;
 978                                 var mn = container.MemberName.Left;
 979                                 while (mn != null) {
 980                                         resolved = container_ns.LookupTypeOrNamespace (this, name, arity, mode, loc);
 981                                         if (resolved != null)
 982                                                 return resolved;
 983
 984                                         mn = mn.Left;
 985                                         container_ns = container_ns.Parent;
 986                                 }
 987                         }
 988
 989                         return null;
 990                 }
 991
 992                 public override void GetCompletionStartingWith (string prefix, List<string> results)
 993                 {
 994                         if (Usings == null)
 995                                 return;
 996
 997                         foreach (var un in Usings) {
 998                                 if (un.Alias != null)
 999                                         continue;
1000
1001                                 var name = un.NamespaceExpression.Name;
1002                                 if (name.StartsWith (prefix))
1003                                         results.Add (name);
1004                         }
1005
1006
1007                         IEnumerable<string> all = Enumerable.Empty<string> ();
1008
1009                         foreach (Namespace using_ns in namespace_using_table) {
1010                                 if (prefix.StartsWith (using_ns.Name)) {
1011                                         int ld = prefix.LastIndexOf ('.');
1012                                         if (ld != -1) {
1013                                                 string rest = prefix.Substring (ld + 1);
1014
1015                                                 all = all.Concat (using_ns.CompletionGetTypesStartingWith (rest));
1016                                         }
1017                                 }
1018                                 all = all.Concat (using_ns.CompletionGetTypesStartingWith (prefix));
1019                         }
1020
1021                         results.AddRange (all);
1022
1023                         base.GetCompletionStartingWith (prefix, results);
1024                 }
1025
1026
1027                 //
1028                 // Looks-up a alias named @name in this and surrounding namespace declarations
1029                 //
1030                 public FullNamedExpression LookupExternAlias (string name)
1031                 {
1032                         if (aliases == null)
1033                                 return null;
1034
1035                         UsingAliasNamespace uan;
1036                         if (aliases.TryGetValue (name, out uan) && uan is UsingExternAlias)
1037                                 return uan.ResolvedExpression;
1038
1039                         return null;
1040                 }
1041
1042                 //
1043                 // Looks-up a alias named @name in this and surrounding namespace declarations
1044                 //
1045                 public override FullNamedExpression LookupNamespaceAlias (string name)
1046                 {
1047                         for (NamespaceContainer n = this; n != null; n = n.Parent) {
1048                                 if (n.aliases == null)
1049                                         continue;
1050
1051                                 UsingAliasNamespace uan;
1052                                 if (n.aliases.TryGetValue (name, out uan))
1053                                         return uan.ResolvedExpression;
1054                         }
1055
1056                         return null;
1057                 }
1058
1059                 FullNamedExpression Lookup (string name, int arity, LookupMode mode, Location loc)
1060                 {
1061                         //
1062                         // Check whether it's in the namespace.
1063                         //
1064                         FullNamedExpression fne = ns.LookupTypeOrNamespace (this, name, arity, mode, loc);
1065
1066                         //
1067                         // Check aliases.
1068                         //
1069                         if (aliases != null && arity == 0) {
1070                                 UsingAliasNamespace uan;
1071                                 if (aliases.TryGetValue (name, out uan)) {
1072                                         if (fne != null && mode != LookupMode.Probing) {
1073                                                 // TODO: Namespace has broken location
1074                                                 //Report.SymbolRelatedToPreviousError (fne.Location, null);
1075                                                 Compiler.Report.SymbolRelatedToPreviousError (uan.Location, null);
1076                                                 Compiler.Report.Error (576, loc,
1077                                                         "Namespace `{0}' contains a definition with same name as alias `{1}'",
1078                                                         GetSignatureForError (), name);
1079                                         }
1080
1081                                         return uan.ResolvedExpression;
1082                                 }
1083                         }
1084
1085                         if (fne != null)
1086                                 return fne;
1087
1088                         //
1089                         // Lookup can be called before the namespace is defined from different namespace using alias clause
1090                         //
1091                         if (namespace_using_table == null) {
1092                                 DoDefineNamespace ();
1093                         }
1094
1095                         //
1096                         // Check using entries.
1097                         //
1098                         FullNamedExpression match = null;
1099                         foreach (Namespace using_ns in namespace_using_table) {
1100                                 //
1101                                 // A using directive imports only types contained in the namespace, it
1102                                 // does not import any nested namespaces
1103                                 //
1104                                 var t = using_ns.LookupType (this, name, arity, mode, loc);
1105                                 if (t == null)
1106                                         continue;
1107
1108                                 fne = new TypeExpression (t, loc);
1109                                 if (match == null) {
1110                                         match = fne;
1111                                         continue;
1112                                 }
1113
1114                                 // Prefer types over namespaces
1115                                 var texpr_fne = fne as TypeExpr;
1116                                 var texpr_match = match as TypeExpr;
1117                                 if (texpr_fne != null && texpr_match == null) {
1118                                         match = fne;
1119                                         continue;
1120                                 } else if (texpr_fne == null) {
1121                                         continue;
1122                                 }
1123
1124                                 // It can be top level accessibility only
1125                                 var better = Namespace.IsImportedTypeOverride (Module, texpr_match.Type, texpr_fne.Type);
1126                                 if (better == null) {
1127                                         if (mode == LookupMode.Normal) {
1128                                                 Compiler.Report.SymbolRelatedToPreviousError (texpr_match.Type);
1129                                                 Compiler.Report.SymbolRelatedToPreviousError (texpr_fne.Type);
1130                                                 Compiler.Report.Error (104, loc, "`{0}' is an ambiguous reference between `{1}' and `{2}'",
1131                                                         name, texpr_match.GetSignatureForError (), texpr_fne.GetSignatureForError ());
1132                                         }
1133
1134                                         return match;
1135                                 }
1136
1137                                 if (better == texpr_fne.Type)
1138                                         match = texpr_fne;
1139                         }
1140
1141                         return match;
1142                 }
1143
1144                 public static MethodGroupExpr LookupStaticUsings (IMemberContext mc, string name, int arity, Location loc)
1145                 {
1146                         for (var m = mc.CurrentMemberDefinition; m != null; m = m.Parent) {
1147
1148                                 var nc = m as NamespaceContainer;
1149                                 if (nc == null)
1150                                         continue;
1151
1152                                 List<MemberSpec> candidates = null;
1153                                 if (nc.types_using_table != null) {
1154                                         foreach (var using_type in nc.types_using_table) {
1155                                                 var members = MemberCache.FindMembers (using_type, name, true);
1156                                                 if (members != null) {
1157                                                         foreach (var member in members) {
1158                                                                 if ((member.Modifiers & Modifiers.METHOD_EXTENSION) != 0)
1159                                                                         continue;
1160
1161                                                                 if (arity > 0 && member.Arity != arity)
1162                                                                         continue;
1163
1164                                                                 if (candidates == null)
1165                                                                         candidates = new List<MemberSpec> ();
1166
1167                                                                 candidates.Add (member);
1168                                                         }
1169                                                 }
1170                                         }
1171                                 }
1172
1173                                 if (candidates != null)
1174                                         return new MethodGroupExpr (candidates, null, loc);
1175                         }
1176
1177                         return null;
1178                 }
1179
1180                 protected override void DefineNamespace ()
1181                 {
1182                         if (namespace_using_table == null)
1183                                 DoDefineNamespace ();
1184
1185                         base.DefineNamespace ();
1186                 }
1187
1188                 void DoDefineNamespace ()
1189                 {
1190                         namespace_using_table = empty_namespaces;
1191
1192                         if (clauses != null) {
1193                                 List<Namespace> namespaces = null;
1194                                 List<TypeSpec> types = null;
1195
1196                                 bool post_process_using_aliases = false;
1197
1198                                 for (int i = 0; i < clauses.Count; ++i) {
1199                                         var entry = clauses[i];
1200
1201                                         if (entry.Alias != null) {
1202                                                 if (aliases == null)
1203                                                         aliases = new Dictionary<string, UsingAliasNamespace> ();
1204
1205                                                 //
1206                                                 // Aliases are not available when resolving using section
1207                                                 // except extern aliases
1208                                                 //
1209                                                 if (entry is UsingExternAlias) {
1210                                                         entry.Define (this);
1211                                                         if (entry.ResolvedExpression != null)
1212                                                                 aliases.Add (entry.Alias.Value, (UsingExternAlias) entry);
1213
1214                                                         clauses.RemoveAt (i--);
1215                                                 } else {
1216                                                         post_process_using_aliases = true;
1217                                                 }
1218
1219                                                 continue;
1220                                         }
1221
1222                                         entry.Define (this);
1223
1224                                         //
1225                                         // It's needed for repl only, when using clause cannot be resolved don't hold it in
1226                                         // global list which is resolved for each evaluation
1227                                         //
1228                                         if (entry.ResolvedExpression == null) {
1229                                                 clauses.RemoveAt (i--);
1230                                                 continue;
1231                                         }
1232
1233                                         var using_ns = entry.ResolvedExpression as NamespaceExpression;
1234                                         if (using_ns == null) {
1235
1236                                                 var type = ((TypeExpr)entry.ResolvedExpression).Type;
1237
1238                                                 if (types == null)
1239                                                         types = new List<TypeSpec> ();
1240
1241                                                 if (types.Contains (type)) {
1242                                                         Warning_DuplicateEntry (entry);
1243                                                 } else {
1244                                                         types.Add (type);
1245                                                 }
1246                                         } else {
1247                                                 if (namespaces == null)
1248                                                         namespaces = new List<Namespace> ();
1249
1250                                                 if (namespaces.Contains (using_ns.Namespace)) {
1251                                                         // Ensure we don't report the warning multiple times in repl
1252                                                         clauses.RemoveAt (i--);
1253
1254                                                         Warning_DuplicateEntry (entry);
1255                                                 } else {
1256                                                         namespaces.Add (using_ns.Namespace);
1257                                                 }
1258                                         }
1259                                 }
1260
1261                                 namespace_using_table = namespaces == null ? new Namespace [0] : namespaces.ToArray ();
1262                                 if (types != null)
1263                                         types_using_table = types.ToArray ();
1264
1265                                 if (post_process_using_aliases) {
1266                                         for (int i = 0; i < clauses.Count; ++i) {
1267                                                 var entry = clauses[i];
1268                                                 if (entry.Alias != null) {
1269                                                         entry.Define (this);
1270                                                         if (entry.ResolvedExpression != null) {
1271                                                                 aliases.Add (entry.Alias.Value, (UsingAliasNamespace) entry);
1272                                                         }
1273
1274                                                         clauses.RemoveAt (i--);
1275                                                 }
1276                                         }
1277                                 }
1278                         }
1279                 }
1280
1281                 public void EnableRedefinition ()
1282                 {
1283                         is_defined = false;
1284                         namespace_using_table = null;
1285                 }
1286
1287                 internal override void GenerateDocComment (DocumentationBuilder builder)
1288                 {
1289                         if (containers != null) {
1290                                 foreach (var tc in containers)
1291                                         tc.GenerateDocComment (builder);
1292                         }
1293                 }
1294
1295                 public override string GetSignatureForError ()
1296                 {
1297                         return MemberName == null ? "global::" : base.GetSignatureForError ();
1298                 }
1299
1300                 public override void RemoveContainer (TypeContainer cont)
1301                 {
1302                         base.RemoveContainer (cont);
1303                         NS.RemoveContainer (cont);
1304                 }
1305
1306                 protected override bool VerifyClsCompliance ()
1307                 {
1308                         if (Module.IsClsComplianceRequired ()) {
1309                                 if (MemberName != null && MemberName.Name[0] == '_') {
1310                                         Warning_IdentifierNotCompliant ();
1311                                 }
1312
1313                                 ns.VerifyClsCompliance ();
1314                                 return true;
1315                         }
1316
1317                         return false;
1318                 }
1319
1320                 void Warning_DuplicateEntry (UsingNamespace entry)
1321                 {
1322                         Compiler.Report.Warning (105, 3, entry.Location,
1323                                 "The using directive for `{0}' appeared previously in this namespace",
1324                                 entry.ResolvedExpression.GetSignatureForError ());
1325                 }
1326
1327                 public override void Accept (StructuralVisitor visitor)
1328                 {
1329                         visitor.Visit (this);
1330                 }
1331         }
1332
1333         public class UsingNamespace
1334         {
1335                 readonly ATypeNameExpression expr;
1336                 readonly Location loc;
1337                 protected FullNamedExpression resolved;
1338
1339                 public UsingNamespace (ATypeNameExpression expr, Location loc)
1340                 {
1341                         this.expr = expr;
1342                         this.loc = loc;
1343                 }
1344
1345                 #region Properties
1346
1347                 public virtual SimpleMemberName Alias {
1348                         get {
1349                                 return null;
1350                         }
1351                 }
1352
1353                 public Location Location {
1354                         get {
1355                                 return loc;
1356                         }
1357                 }
1358
1359                 public ATypeNameExpression NamespaceExpression  {
1360                         get {
1361                                 return expr;
1362                         }
1363                 }
1364
1365                 public FullNamedExpression ResolvedExpression {
1366                         get {
1367                                 return resolved;
1368                         }
1369                 }
1370
1371                 #endregion
1372
1373                 public string GetSignatureForError ()
1374                 {
1375                         return expr.GetSignatureForError ();
1376                 }
1377
1378                 public virtual void Define (NamespaceContainer ctx)
1379                 {
1380                         resolved = expr.ResolveAsTypeOrNamespace (ctx, false);
1381                         var ns = resolved as NamespaceExpression;
1382                         if (ns != null)
1383                                 return;
1384
1385                         if (resolved != null) {
1386                                 var compiler = ctx.Module.Compiler;
1387                                 var type = resolved.Type;
1388                                 if (compiler.Settings.Version >= LanguageVersion.V_6) {
1389                                         if (!type.IsClass || !type.IsStatic) {
1390                                                 compiler.Report.SymbolRelatedToPreviousError (type);
1391                                                 compiler.Report.Error (7007, Location,
1392                                                         "`{0}' is not a static class. A using namespace directive can only be applied to static classes or namespace",
1393                                                         GetSignatureForError ());
1394                                         }
1395
1396                                         return;
1397                                 }
1398
1399                                 compiler.Report.SymbolRelatedToPreviousError (type);
1400                                 compiler.Report.Error (138, Location,
1401                                         "`{0}' is a type not a namespace. A using namespace directive can only be applied to namespaces",
1402                                         GetSignatureForError ());
1403                         }
1404                 }
1405
1406                 public override string ToString()
1407                 {
1408                         return resolved.ToString();
1409                 }
1410         }
1411
1412         public class UsingExternAlias : UsingAliasNamespace
1413         {
1414                 public UsingExternAlias (SimpleMemberName alias, Location loc)
1415                         : base (alias, null, loc)
1416                 {
1417                 }
1418
1419                 public override void Define (NamespaceContainer ctx)
1420                 {
1421                         var ns = ctx.Module.GetRootNamespace (Alias.Value);
1422                         if (ns == null) {
1423                                 ctx.Module.Compiler.Report.Error (430, Location,
1424                                         "The extern alias `{0}' was not specified in -reference option",
1425                                         Alias.Value);
1426                                 return;
1427                         }
1428
1429                         resolved = new NamespaceExpression (ns, Location);
1430                 }
1431         }
1432
1433         public class UsingAliasNamespace : UsingNamespace
1434         {
1435                 readonly SimpleMemberName alias;
1436
1437                 public struct AliasContext : IMemberContext
1438                 {
1439                         readonly NamespaceContainer ns;
1440
1441                         public AliasContext (NamespaceContainer ns)
1442                         {
1443                                 this.ns = ns;
1444                         }
1445
1446                         public TypeSpec CurrentType {
1447                                 get {
1448                                         return null;
1449                                 }
1450                         }
1451
1452                         public TypeParameters CurrentTypeParameters {
1453                                 get {
1454                                         return null;
1455                                 }
1456                         }
1457
1458                         public MemberCore CurrentMemberDefinition {
1459                                 get {
1460                                         return null;
1461                                 }
1462                         }
1463
1464                         public bool IsObsolete {
1465                                 get {
1466                                         return false;
1467                                 }
1468                         }
1469
1470                         public bool IsUnsafe {
1471                                 get {
1472                                         throw new NotImplementedException ();
1473                                 }
1474                         }
1475
1476                         public bool IsStatic {
1477                                 get {
1478                                         throw new NotImplementedException ();
1479                                 }
1480                         }
1481
1482                         public ModuleContainer Module {
1483                                 get {
1484                                         return ns.Module;
1485                                 }
1486                         }
1487
1488                         public string GetSignatureForError ()
1489                         {
1490                                 throw new NotImplementedException ();
1491                         }
1492
1493                         public ExtensionMethodCandidates LookupExtensionMethod (TypeSpec extensionType, string name, int arity)
1494                         {
1495                                 return null;
1496                         }
1497
1498                         public FullNamedExpression LookupNamespaceOrType (string name, int arity, LookupMode mode, Location loc)
1499                         {
1500                                 var fne = ns.NS.LookupTypeOrNamespace (ns, name, arity, mode, loc);
1501                                 if (fne != null)
1502                                         return fne;
1503
1504                                 //
1505                                 // Only extern aliases are allowed in this context
1506                                 //
1507                                 fne = ns.LookupExternAlias (name);
1508                                 if (fne != null || ns.MemberName == null)
1509                                         return fne;
1510
1511                                 var container_ns = ns.NS.Parent;
1512                                 var mn = ns.MemberName.Left;
1513                                 while (mn != null) {
1514                                         fne = container_ns.LookupTypeOrNamespace (this, name, arity, mode, loc);
1515                                         if (fne != null)
1516                                                 return fne;
1517
1518                                         mn = mn.Left;
1519                                         container_ns = container_ns.Parent;
1520                                 }
1521
1522                                 if (ns.Parent != null)
1523                                         return ns.Parent.LookupNamespaceOrType (name, arity, mode, loc);
1524
1525                                 return null;
1526                         }
1527
1528                         public FullNamedExpression LookupNamespaceAlias (string name)
1529                         {
1530                                 return ns.LookupNamespaceAlias (name);
1531                         }
1532                 }
1533
1534                 public UsingAliasNamespace (SimpleMemberName alias, ATypeNameExpression expr, Location loc)
1535                         : base (expr, loc)
1536                 {
1537                         this.alias = alias;
1538                 }
1539
1540                 public override SimpleMemberName Alias {
1541                         get {
1542                                 return alias;
1543                         }
1544                 }
1545
1546                 public override void Define (NamespaceContainer ctx)
1547                 {
1548                         //
1549                         // The namespace-or-type-name of a using-alias-directive is resolved as if
1550                         // the immediately containing compilation unit or namespace body had no
1551                         // using-directives. A using-alias-directive may however be affected
1552                         // by extern-alias-directives in the immediately containing compilation
1553                         // unit or namespace body
1554                         //
1555                         // We achieve that by introducing alias-context which redirect any local
1556                         // namespace or type resolve calls to parent namespace
1557                         //
1558                         resolved = NamespaceExpression.ResolveAsTypeOrNamespace (new AliasContext (ctx), false);
1559                 }
1560         }
1561 }