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