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