aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/clang14/lib/Sema/SemaCXXScopeSpec.cpp
blob: 4781d71080c9847c40d6758275be727e469422f9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
//===--- SemaCXXScopeSpec.cpp - Semantic Analysis for C++ scope specifiers-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements C++ semantic analysis for scope specifiers.
//
//===----------------------------------------------------------------------===//

#include "TypeLocBuilder.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/NestedNameSpecifier.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/Template.h"
#include "llvm/ADT/STLExtras.h"
using namespace clang;

/// Find the current instantiation that associated with the given type.
static CXXRecordDecl *getCurrentInstantiationOf(QualType T,
                                                DeclContext *CurContext) {
  if (T.isNull())
    return nullptr;

  const Type *Ty = T->getCanonicalTypeInternal().getTypePtr();
  if (const RecordType *RecordTy = dyn_cast<RecordType>(Ty)) {
    CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());
    if (!Record->isDependentContext() ||
        Record->isCurrentInstantiation(CurContext))
      return Record;

    return nullptr;
  } else if (isa<InjectedClassNameType>(Ty))
    return cast<InjectedClassNameType>(Ty)->getDecl();
  else
    return nullptr;
}

/// Compute the DeclContext that is associated with the given type.
///
/// \param T the type for which we are attempting to find a DeclContext.
///
/// \returns the declaration context represented by the type T,
/// or NULL if the declaration context cannot be computed (e.g., because it is
/// dependent and not the current instantiation).
DeclContext *Sema::computeDeclContext(QualType T) {
  if (!T->isDependentType())
    if (const TagType *Tag = T->getAs<TagType>())
      return Tag->getDecl();

  return ::getCurrentInstantiationOf(T, CurContext);
}

/// Compute the DeclContext that is associated with the given
/// scope specifier.
///
/// \param SS the C++ scope specifier as it appears in the source
///
/// \param EnteringContext when true, we will be entering the context of
/// this scope specifier, so we can retrieve the declaration context of a
/// class template or class template partial specialization even if it is
/// not the current instantiation.
///
/// \returns the declaration context represented by the scope specifier @p SS,
/// or NULL if the declaration context cannot be computed (e.g., because it is
/// dependent and not the current instantiation).
DeclContext *Sema::computeDeclContext(const CXXScopeSpec &SS,
                                      bool EnteringContext) {
  if (!SS.isSet() || SS.isInvalid())
    return nullptr;

  NestedNameSpecifier *NNS = SS.getScopeRep();
  if (NNS->isDependent()) {
    // If this nested-name-specifier refers to the current
    // instantiation, return its DeclContext.
    if (CXXRecordDecl *Record = getCurrentInstantiationOf(NNS))
      return Record;

    if (EnteringContext) {
      const Type *NNSType = NNS->getAsType();
      if (!NNSType) {
        return nullptr;
      }

      // Look through type alias templates, per C++0x [temp.dep.type]p1.
      NNSType = Context.getCanonicalType(NNSType);
      if (const TemplateSpecializationType *SpecType
            = NNSType->getAs<TemplateSpecializationType>()) {
        // We are entering the context of the nested name specifier, so try to
        // match the nested name specifier to either a primary class template
        // or a class template partial specialization.
        if (ClassTemplateDecl *ClassTemplate
              = dyn_cast_or_null<ClassTemplateDecl>(
                            SpecType->getTemplateName().getAsTemplateDecl())) {
          QualType ContextType
            = Context.getCanonicalType(QualType(SpecType, 0));

          // If the type of the nested name specifier is the same as the
          // injected class name of the named class template, we're entering
          // into that class template definition.
          QualType Injected
            = ClassTemplate->getInjectedClassNameSpecialization();
          if (Context.hasSameType(Injected, ContextType))
            return ClassTemplate->getTemplatedDecl();

          // If the type of the nested name specifier is the same as the
          // type of one of the class template's class template partial
          // specializations, we're entering into the definition of that
          // class template partial specialization.
          if (ClassTemplatePartialSpecializationDecl *PartialSpec
                = ClassTemplate->findPartialSpecialization(ContextType)) {
            // A declaration of the partial specialization must be visible.
            // We can always recover here, because this only happens when we're
            // entering the context, and that can't happen in a SFINAE context.
            assert(!isSFINAEContext() &&
                   "partial specialization scope specifier in SFINAE context?");
            if (!hasVisibleDeclaration(PartialSpec))
              diagnoseMissingImport(SS.getLastQualifierNameLoc(), PartialSpec,
                                    MissingImportKind::PartialSpecialization,
                                    /*Recover*/true);
            return PartialSpec;
          }
        }
      } else if (const RecordType *RecordT = NNSType->getAs<RecordType>()) {
        // The nested name specifier refers to a member of a class template.
        return RecordT->getDecl();
      }
    }

    return nullptr;
  }

  switch (NNS->getKind()) {
  case NestedNameSpecifier::Identifier:
    llvm_unreachable("Dependent nested-name-specifier has no DeclContext");

  case NestedNameSpecifier::Namespace:
    return NNS->getAsNamespace();

  case NestedNameSpecifier::NamespaceAlias:
    return NNS->getAsNamespaceAlias()->getNamespace();

  case NestedNameSpecifier::TypeSpec:
  case NestedNameSpecifier::TypeSpecWithTemplate: {
    const TagType *Tag = NNS->getAsType()->getAs<TagType>();
    assert(Tag && "Non-tag type in nested-name-specifier");
    return Tag->getDecl();
  }

  case NestedNameSpecifier::Global:
    return Context.getTranslationUnitDecl();

  case NestedNameSpecifier::Super:
    return NNS->getAsRecordDecl();
  }

  llvm_unreachable("Invalid NestedNameSpecifier::Kind!");
}

bool Sema::isDependentScopeSpecifier(const CXXScopeSpec &SS) {
  if (!SS.isSet() || SS.isInvalid())
    return false;

  return SS.getScopeRep()->isDependent();
}

/// If the given nested name specifier refers to the current
/// instantiation, return the declaration that corresponds to that
/// current instantiation (C++0x [temp.dep.type]p1).
///
/// \param NNS a dependent nested name specifier.
CXXRecordDecl *Sema::getCurrentInstantiationOf(NestedNameSpecifier *NNS) {
  assert(getLangOpts().CPlusPlus && "Only callable in C++");
  assert(NNS->isDependent() && "Only dependent nested-name-specifier allowed");

  if (!NNS->getAsType())
    return nullptr;

  QualType T = QualType(NNS->getAsType(), 0);
  return ::getCurrentInstantiationOf(T, CurContext);
}

/// Require that the context specified by SS be complete.
///
/// If SS refers to a type, this routine checks whether the type is
/// complete enough (or can be made complete enough) for name lookup
/// into the DeclContext. A type that is not yet completed can be
/// considered "complete enough" if it is a class/struct/union/enum
/// that is currently being defined. Or, if we have a type that names
/// a class template specialization that is not a complete type, we
/// will attempt to instantiate that class template.
bool Sema::RequireCompleteDeclContext(CXXScopeSpec &SS,
                                      DeclContext *DC) {
  assert(DC && "given null context");

  TagDecl *tag = dyn_cast<TagDecl>(DC);

  // If this is a dependent type, then we consider it complete.
  // FIXME: This is wrong; we should require a (visible) definition to
  // exist in this case too.
  if (!tag || tag->isDependentContext())
    return false;

  // Grab the tag definition, if there is one.
  QualType type = Context.getTypeDeclType(tag);
  tag = type->getAsTagDecl();

  // If we're currently defining this type, then lookup into the
  // type is okay: don't complain that it isn't complete yet.
  if (tag->isBeingDefined())
    return false;

  SourceLocation loc = SS.getLastQualifierNameLoc();
  if (loc.isInvalid()) loc = SS.getRange().getBegin();

  // The type must be complete.
  if (RequireCompleteType(loc, type, diag::err_incomplete_nested_name_spec,
                          SS.getRange())) {
    SS.SetInvalid(SS.getRange());
    return true;
  }

  if (auto *EnumD = dyn_cast<EnumDecl>(tag))
    // Fixed enum types and scoped enum instantiations are complete, but they
    // aren't valid as scopes until we see or instantiate their definition.
    return RequireCompleteEnumDecl(EnumD, loc, &SS);

  return false;
}

/// Require that the EnumDecl is completed with its enumerators defined or
/// instantiated. SS, if provided, is the ScopeRef parsed.
///
bool Sema::RequireCompleteEnumDecl(EnumDecl *EnumD, SourceLocation L,
                                   CXXScopeSpec *SS) {
  if (EnumD->isCompleteDefinition()) {
    // If we know about the definition but it is not visible, complain.
    NamedDecl *SuggestedDef = nullptr;
    if (!hasVisibleDefinition(EnumD, &SuggestedDef,
                              /*OnlyNeedComplete*/false)) {
      // If the user is going to see an error here, recover by making the
      // definition visible.
      bool TreatAsComplete = !isSFINAEContext();
      diagnoseMissingImport(L, SuggestedDef, MissingImportKind::Definition,
                            /*Recover*/ TreatAsComplete);
      return !TreatAsComplete;
    }
    return false;
  }

  // Try to instantiate the definition, if this is a specialization of an
  // enumeration temploid.
  if (EnumDecl *Pattern = EnumD->getInstantiatedFromMemberEnum()) {
    MemberSpecializationInfo *MSI = EnumD->getMemberSpecializationInfo();
    if (MSI->getTemplateSpecializationKind() != TSK_ExplicitSpecialization) {
      if (InstantiateEnum(L, EnumD, Pattern,
                          getTemplateInstantiationArgs(EnumD),
                          TSK_ImplicitInstantiation)) {
        if (SS)
          SS->SetInvalid(SS->getRange());
        return true;
      }
      return false;
    }
  }

  if (SS) {
    Diag(L, diag::err_incomplete_nested_name_spec)
        << QualType(EnumD->getTypeForDecl(), 0) << SS->getRange();
    SS->SetInvalid(SS->getRange());
  } else {
    Diag(L, diag::err_incomplete_enum) << QualType(EnumD->getTypeForDecl(), 0);
    Diag(EnumD->getLocation(), diag::note_declared_at);
  }

  return true;
}

bool Sema::ActOnCXXGlobalScopeSpecifier(SourceLocation CCLoc,
                                        CXXScopeSpec &SS) {
  SS.MakeGlobal(Context, CCLoc);
  return false;
}

bool Sema::ActOnSuperScopeSpecifier(SourceLocation SuperLoc,
                                    SourceLocation ColonColonLoc,
                                    CXXScopeSpec &SS) {
  CXXRecordDecl *RD = nullptr;
  for (Scope *S = getCurScope(); S; S = S->getParent()) {
    if (S->isFunctionScope()) {
      if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(S->getEntity()))
        RD = MD->getParent();
      break;
    }
    if (S->isClassScope()) {
      RD = cast<CXXRecordDecl>(S->getEntity());
      break;
    }
  }

  if (!RD) {
    Diag(SuperLoc, diag::err_invalid_super_scope);
    return true;
  } else if (RD->isLambda()) {
    Diag(SuperLoc, diag::err_super_in_lambda_unsupported);
    return true;
  } else if (RD->getNumBases() == 0) {
    Diag(SuperLoc, diag::err_no_base_classes) << RD->getName();
    return true;
  }

  SS.MakeSuper(Context, RD, SuperLoc, ColonColonLoc);
  return false;
}

/// Determines whether the given declaration is an valid acceptable
/// result for name lookup of a nested-name-specifier.
/// \param SD Declaration checked for nested-name-specifier.
/// \param IsExtension If not null and the declaration is accepted as an
/// extension, the pointed variable is assigned true.
bool Sema::isAcceptableNestedNameSpecifier(const NamedDecl *SD,
                                           bool *IsExtension) {
  if (!SD)
    return false;

  SD = SD->getUnderlyingDecl();

  // Namespace and namespace aliases are fine.
  if (isa<NamespaceDecl>(SD))
    return true;

  if (!isa<TypeDecl>(SD))
    return false;

  // Determine whether we have a class (or, in C++11, an enum) or
  // a typedef thereof. If so, build the nested-name-specifier.
  QualType T = Context.getTypeDeclType(cast<TypeDecl>(SD));
  if (T->isDependentType())
    return true;
  if (const TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(SD)) {
    if (TD->getUnderlyingType()->isRecordType())
      return true;
    if (TD->getUnderlyingType()->isEnumeralType()) {
      if (Context.getLangOpts().CPlusPlus11)
        return true;
      if (IsExtension)
        *IsExtension = true;
    }
  } else if (isa<RecordDecl>(SD)) {
    return true;
  } else if (isa<EnumDecl>(SD)) {
    if (Context.getLangOpts().CPlusPlus11)
      return true;
    if (IsExtension)
      *IsExtension = true;
  }

  return false;
}

/// If the given nested-name-specifier begins with a bare identifier
/// (e.g., Base::), perform name lookup for that identifier as a
/// nested-name-specifier within the given scope, and return the result of that
/// name lookup.
NamedDecl *Sema::FindFirstQualifierInScope(Scope *S, NestedNameSpecifier *NNS) {
  if (!S || !NNS)
    return nullptr;

  while (NNS->getPrefix())
    NNS = NNS->getPrefix();

  if (NNS->getKind() != NestedNameSpecifier::Identifier)
    return nullptr;

  LookupResult Found(*this, NNS->getAsIdentifier(), SourceLocation(),
                     LookupNestedNameSpecifierName);
  LookupName(Found, S);
  assert(!Found.isAmbiguous() && "Cannot handle ambiguities here yet");

  if (!Found.isSingleResult())
    return nullptr;

  NamedDecl *Result = Found.getFoundDecl();
  if (isAcceptableNestedNameSpecifier(Result))
    return Result;

  return nullptr;
}

bool Sema::isNonTypeNestedNameSpecifier(Scope *S, CXXScopeSpec &SS,
                                        NestedNameSpecInfo &IdInfo) {
  QualType ObjectType = GetTypeFromParser(IdInfo.ObjectType);
  LookupResult Found(*this, IdInfo.Identifier, IdInfo.IdentifierLoc,
                     LookupNestedNameSpecifierName);

  // Determine where to perform name lookup
  DeclContext *LookupCtx = nullptr;
  bool isDependent = false;
  if (!ObjectType.isNull()) {
    // This nested-name-specifier occurs in a member access expression, e.g.,
    // x->B::f, and we are looking into the type of the object.
    assert(!SS.isSet() && "ObjectType and scope specifier cannot coexist");
    LookupCtx = computeDeclContext(ObjectType);
    isDependent = ObjectType->isDependentType();
  } else if (SS.isSet()) {
    // This nested-name-specifier occurs after another nested-name-specifier,
    // so long into the context associated with the prior nested-name-specifier.
    LookupCtx = computeDeclContext(SS, false);
    isDependent = isDependentScopeSpecifier(SS);
    Found.setContextRange(SS.getRange());
  }

  if (LookupCtx) {
    // Perform "qualified" name lookup into the declaration context we
    // computed, which is either the type of the base of a member access
    // expression or the declaration context associated with a prior
    // nested-name-specifier.

    // The declaration context must be complete.
    if (!LookupCtx->isDependentContext() &&
        RequireCompleteDeclContext(SS, LookupCtx))
      return false;

    LookupQualifiedName(Found, LookupCtx);
  } else if (isDependent) {
    return false;
  } else {
    LookupName(Found, S);
  }
  Found.suppressDiagnostics();

  return Found.getAsSingle<NamespaceDecl>();
}

namespace {

// Callback to only accept typo corrections that can be a valid C++ member
// initializer: either a non-static field member or a base class.
class NestedNameSpecifierValidatorCCC final
    : public CorrectionCandidateCallback {
public:
  explicit NestedNameSpecifierValidatorCCC(Sema &SRef)
      : SRef(SRef) {}

  bool ValidateCandidate(const TypoCorrection &candidate) override {
    return SRef.isAcceptableNestedNameSpecifier(candidate.getCorrectionDecl());
  }

  std::unique_ptr<CorrectionCandidateCallback> clone() override {
    return std::make_unique<NestedNameSpecifierValidatorCCC>(*this);
  }

 private:
  Sema &SRef;
};

}

/// Build a new nested-name-specifier for "identifier::", as described
/// by ActOnCXXNestedNameSpecifier.
///
/// \param S Scope in which the nested-name-specifier occurs.
/// \param IdInfo Parser information about an identifier in the
///        nested-name-spec.
/// \param EnteringContext If true, enter the context specified by the
///        nested-name-specifier.
/// \param SS Optional nested name specifier preceding the identifier.
/// \param ScopeLookupResult Provides the result of name lookup within the
///        scope of the nested-name-specifier that was computed at template
///        definition time.
/// \param ErrorRecoveryLookup Specifies if the method is called to improve
///        error recovery and what kind of recovery is performed.
/// \param IsCorrectedToColon If not null, suggestion of replace '::' -> ':'
///        are allowed.  The bool value pointed by this parameter is set to
///       'true' if the identifier is treated as if it was followed by ':',
///        not '::'.
/// \param OnlyNamespace If true, only considers namespaces in lookup.
///
/// This routine differs only slightly from ActOnCXXNestedNameSpecifier, in
/// that it contains an extra parameter \p ScopeLookupResult, which provides
/// the result of name lookup within the scope of the nested-name-specifier
/// that was computed at template definition time.
///
/// If ErrorRecoveryLookup is true, then this call is used to improve error
/// recovery.  This means that it should not emit diagnostics, it should
/// just return true on failure.  It also means it should only return a valid
/// scope if it *knows* that the result is correct.  It should not return in a
/// dependent context, for example. Nor will it extend \p SS with the scope
/// specifier.
bool Sema::BuildCXXNestedNameSpecifier(Scope *S, NestedNameSpecInfo &IdInfo,
                                       bool EnteringContext, CXXScopeSpec &SS,
                                       NamedDecl *ScopeLookupResult,
                                       bool ErrorRecoveryLookup,
                                       bool *IsCorrectedToColon,
                                       bool OnlyNamespace) {
  if (IdInfo.Identifier->isEditorPlaceholder())
    return true;
  LookupResult Found(*this, IdInfo.Identifier, IdInfo.IdentifierLoc,
                     OnlyNamespace ? LookupNamespaceName
                                   : LookupNestedNameSpecifierName);
  QualType ObjectType = GetTypeFromParser(IdInfo.ObjectType);

  // Determine where to perform name lookup
  DeclContext *LookupCtx = nullptr;
  bool isDependent = false;
  if (IsCorrectedToColon)
    *IsCorrectedToColon = false;
  if (!ObjectType.isNull()) {
    // This nested-name-specifier occurs in a member access expression, e.g.,
    // x->B::f, and we are looking into the type of the object.
    assert(!SS.isSet() && "ObjectType and scope specifier cannot coexist");
    LookupCtx = computeDeclContext(ObjectType);
    isDependent = ObjectType->isDependentType();
  } else if (SS.isSet()) {
    // This nested-name-specifier occurs after another nested-name-specifier,
    // so look into the context associated with the prior nested-name-specifier.
    LookupCtx = computeDeclContext(SS, EnteringContext);
    isDependent = isDependentScopeSpecifier(SS);
    Found.setContextRange(SS.getRange());
  }

  bool ObjectTypeSearchedInScope = false;
  if (LookupCtx) {
    // Perform "qualified" name lookup into the declaration context we
    // computed, which is either the type of the base of a member access
    // expression or the declaration context associated with a prior
    // nested-name-specifier.

    // The declaration context must be complete.
    if (!LookupCtx->isDependentContext() &&
        RequireCompleteDeclContext(SS, LookupCtx))
      return true;

    LookupQualifiedName(Found, LookupCtx);

    if (!ObjectType.isNull() && Found.empty()) {
      // C++ [basic.lookup.classref]p4:
      //   If the id-expression in a class member access is a qualified-id of
      //   the form
      //
      //        class-name-or-namespace-name::...
      //
      //   the class-name-or-namespace-name following the . or -> operator is
      //   looked up both in the context of the entire postfix-expression and in
      //   the scope of the class of the object expression. If the name is found
      //   only in the scope of the class of the object expression, the name
      //   shall refer to a class-name. If the name is found only in the
      //   context of the entire postfix-expression, the name shall refer to a
      //   class-name or namespace-name. [...]
      //
      // Qualified name lookup into a class will not find a namespace-name,
      // so we do not need to diagnose that case specifically. However,
      // this qualified name lookup may find nothing. In that case, perform
      // unqualified name lookup in the given scope (if available) or
      // reconstruct the result from when name lookup was performed at template
      // definition time.
      if (S)
        LookupName(Found, S);
      else if (ScopeLookupResult)
        Found.addDecl(ScopeLookupResult);

      ObjectTypeSearchedInScope = true;
    }
  } else if (!isDependent) {
    // Perform unqualified name lookup in the current scope.
    LookupName(Found, S);
  }

  if (Found.isAmbiguous())
    return true;

  // If we performed lookup into a dependent context and did not find anything,
  // that's fine: just build a dependent nested-name-specifier.
  if (Found.empty() && isDependent &&
      !(LookupCtx && LookupCtx->isRecord() &&
        (!cast<CXXRecordDecl>(LookupCtx)->hasDefinition() ||
         !cast<CXXRecordDecl>(LookupCtx)->hasAnyDependentBases()))) {
    // Don't speculate if we're just trying to improve error recovery.
    if (ErrorRecoveryLookup)
      return true;

    // We were not able to compute the declaration context for a dependent
    // base object type or prior nested-name-specifier, so this
    // nested-name-specifier refers to an unknown specialization. Just build
    // a dependent nested-name-specifier.
    SS.Extend(Context, IdInfo.Identifier, IdInfo.IdentifierLoc, IdInfo.CCLoc);
    return false;
  }

  if (Found.empty() && !ErrorRecoveryLookup) {
    // If identifier is not found as class-name-or-namespace-name, but is found
    // as other entity, don't look for typos.
    LookupResult R(*this, Found.getLookupNameInfo(), LookupOrdinaryName);
    if (LookupCtx)
      LookupQualifiedName(R, LookupCtx);
    else if (S && !isDependent)
      LookupName(R, S);
    if (!R.empty()) {
      // Don't diagnose problems with this speculative lookup.
      R.suppressDiagnostics();
      // The identifier is found in ordinary lookup. If correction to colon is
      // allowed, suggest replacement to ':'.
      if (IsCorrectedToColon) {
        *IsCorrectedToColon = true;
        Diag(IdInfo.CCLoc, diag::err_nested_name_spec_is_not_class)
            << IdInfo.Identifier << getLangOpts().CPlusPlus
            << FixItHint::CreateReplacement(IdInfo.CCLoc, ":");
        if (NamedDecl *ND = R.getAsSingle<NamedDecl>())
          Diag(ND->getLocation(), diag::note_declared_at);
        return true;
      }
      // Replacement '::' -> ':' is not allowed, just issue respective error.
      Diag(R.getNameLoc(), OnlyNamespace
                               ? unsigned(diag::err_expected_namespace_name)
                               : unsigned(diag::err_expected_class_or_namespace))
          << IdInfo.Identifier << getLangOpts().CPlusPlus;
      if (NamedDecl *ND = R.getAsSingle<NamedDecl>())
        Diag(ND->getLocation(), diag::note_entity_declared_at)
            << IdInfo.Identifier;
      return true;
    }
  }

  if (Found.empty() && !ErrorRecoveryLookup && !getLangOpts().MSVCCompat) {
    // We haven't found anything, and we're not recovering from a
    // different kind of error, so look for typos.
    DeclarationName Name = Found.getLookupName();
    Found.clear();
    NestedNameSpecifierValidatorCCC CCC(*this);
    if (TypoCorrection Corrected = CorrectTypo(
            Found.getLookupNameInfo(), Found.getLookupKind(), S, &SS, CCC,
            CTK_ErrorRecovery, LookupCtx, EnteringContext)) {
      if (LookupCtx) {
        bool DroppedSpecifier =
            Corrected.WillReplaceSpecifier() &&
            Name.getAsString() == Corrected.getAsString(getLangOpts());
        if (DroppedSpecifier)
          SS.clear();
        diagnoseTypo(Corrected, PDiag(diag::err_no_member_suggest)
                                  << Name << LookupCtx << DroppedSpecifier
                                  << SS.getRange());
      } else
        diagnoseTypo(Corrected, PDiag(diag::err_undeclared_var_use_suggest)
                                  << Name);

      if (Corrected.getCorrectionSpecifier())
        SS.MakeTrivial(Context, Corrected.getCorrectionSpecifier(),
                       SourceRange(Found.getNameLoc()));

      if (NamedDecl *ND = Corrected.getFoundDecl())
        Found.addDecl(ND);
      Found.setLookupName(Corrected.getCorrection());
    } else {
      Found.setLookupName(IdInfo.Identifier);
    }
  }

  NamedDecl *SD =
      Found.isSingleResult() ? Found.getRepresentativeDecl() : nullptr;
  bool IsExtension = false;
  bool AcceptSpec = isAcceptableNestedNameSpecifier(SD, &IsExtension);
  if (!AcceptSpec && IsExtension) {
    AcceptSpec = true;
    Diag(IdInfo.IdentifierLoc, diag::ext_nested_name_spec_is_enum);
  }
  if (AcceptSpec) {
    if (!ObjectType.isNull() && !ObjectTypeSearchedInScope &&
        !getLangOpts().CPlusPlus11) {
      // C++03 [basic.lookup.classref]p4:
      //   [...] If the name is found in both contexts, the
      //   class-name-or-namespace-name shall refer to the same entity.
      //
      // We already found the name in the scope of the object. Now, look
      // into the current scope (the scope of the postfix-expression) to
      // see if we can find the same name there. As above, if there is no
      // scope, reconstruct the result from the template instantiation itself.
      //
      // Note that C++11 does *not* perform this redundant lookup.
      NamedDecl *OuterDecl;
      if (S) {
        LookupResult FoundOuter(*this, IdInfo.Identifier, IdInfo.IdentifierLoc,
                                LookupNestedNameSpecifierName);
        LookupName(FoundOuter, S);
        OuterDecl = FoundOuter.getAsSingle<NamedDecl>();
      } else
        OuterDecl = ScopeLookupResult;

      if (isAcceptableNestedNameSpecifier(OuterDecl) &&
          OuterDecl->getCanonicalDecl() != SD->getCanonicalDecl() &&
          (!isa<TypeDecl>(OuterDecl) || !isa<TypeDecl>(SD) ||
           !Context.hasSameType(
                            Context.getTypeDeclType(cast<TypeDecl>(OuterDecl)),
                               Context.getTypeDeclType(cast<TypeDecl>(SD))))) {
        if (ErrorRecoveryLookup)
          return true;

         Diag(IdInfo.IdentifierLoc,
              diag::err_nested_name_member_ref_lookup_ambiguous)
           << IdInfo.Identifier;
         Diag(SD->getLocation(), diag::note_ambig_member_ref_object_type)
           << ObjectType;
         Diag(OuterDecl->getLocation(), diag::note_ambig_member_ref_scope);

         // Fall through so that we'll pick the name we found in the object
         // type, since that's probably what the user wanted anyway.
       }
    }

    if (auto *TD = dyn_cast_or_null<TypedefNameDecl>(SD))
      MarkAnyDeclReferenced(TD->getLocation(), TD, /*OdrUse=*/false);

    // If we're just performing this lookup for error-recovery purposes,
    // don't extend the nested-name-specifier. Just return now.
    if (ErrorRecoveryLookup)
      return false;

    // The use of a nested name specifier may trigger deprecation warnings.
    DiagnoseUseOfDecl(SD, IdInfo.CCLoc);

    if (NamespaceDecl *Namespace = dyn_cast<NamespaceDecl>(SD)) {
      SS.Extend(Context, Namespace, IdInfo.IdentifierLoc, IdInfo.CCLoc);
      return false;
    }

    if (NamespaceAliasDecl *Alias = dyn_cast<NamespaceAliasDecl>(SD)) {
      SS.Extend(Context, Alias, IdInfo.IdentifierLoc, IdInfo.CCLoc);
      return false;
    }

    QualType T =
        Context.getTypeDeclType(cast<TypeDecl>(SD->getUnderlyingDecl()));

    if (T->isEnumeralType())
      Diag(IdInfo.IdentifierLoc, diag::warn_cxx98_compat_enum_nested_name_spec);

    TypeLocBuilder TLB;
    if (const auto *USD = dyn_cast<UsingShadowDecl>(SD)) {
      T = Context.getUsingType(USD, T);
      TLB.pushTypeSpec(T).setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<InjectedClassNameType>(T)) {
      InjectedClassNameTypeLoc InjectedTL
        = TLB.push<InjectedClassNameTypeLoc>(T);
      InjectedTL.setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<RecordType>(T)) {
      RecordTypeLoc RecordTL = TLB.push<RecordTypeLoc>(T);
      RecordTL.setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<TypedefType>(T)) {
      TypedefTypeLoc TypedefTL = TLB.push<TypedefTypeLoc>(T);
      TypedefTL.setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<EnumType>(T)) {
      EnumTypeLoc EnumTL = TLB.push<EnumTypeLoc>(T);
      EnumTL.setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<TemplateTypeParmType>(T)) {
      TemplateTypeParmTypeLoc TemplateTypeTL
        = TLB.push<TemplateTypeParmTypeLoc>(T);
      TemplateTypeTL.setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<UnresolvedUsingType>(T)) {
      UnresolvedUsingTypeLoc UnresolvedTL
        = TLB.push<UnresolvedUsingTypeLoc>(T);
      UnresolvedTL.setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<SubstTemplateTypeParmType>(T)) {
      SubstTemplateTypeParmTypeLoc TL
        = TLB.push<SubstTemplateTypeParmTypeLoc>(T);
      TL.setNameLoc(IdInfo.IdentifierLoc);
    } else if (isa<SubstTemplateTypeParmPackType>(T)) {
      SubstTemplateTypeParmPackTypeLoc TL
        = TLB.push<SubstTemplateTypeParmPackTypeLoc>(T);
      TL.setNameLoc(IdInfo.IdentifierLoc);
    } else {
      llvm_unreachable("Unhandled TypeDecl node in nested-name-specifier");
    }

    SS.Extend(Context, SourceLocation(), TLB.getTypeLocInContext(Context, T),
              IdInfo.CCLoc);
    return false;
  }

  // Otherwise, we have an error case.  If we don't want diagnostics, just
  // return an error now.
  if (ErrorRecoveryLookup)
    return true;

  // If we didn't find anything during our lookup, try again with
  // ordinary name lookup, which can help us produce better error
  // messages.
  if (Found.empty()) {
    Found.clear(LookupOrdinaryName);
    LookupName(Found, S);
  }

  // In Microsoft mode, if we are within a templated function and we can't
  // resolve Identifier, then extend the SS with Identifier. This will have
  // the effect of resolving Identifier during template instantiation.
  // The goal is to be able to resolve a function call whose
  // nested-name-specifier is located inside a dependent base class.
  // Example:
  //
  // class C {
  // public:
  //    static void foo2() {  }
  // };
  // template <class T> class A { public: typedef C D; };
  //
  // template <class T> class B : public A<T> {
  // public:
  //   void foo() { D::foo2(); }
  // };
  if (getLangOpts().MSVCCompat) {
    DeclContext *DC = LookupCtx ? LookupCtx : CurContext;
    if (DC->isDependentContext() && DC->isFunctionOrMethod()) {
      CXXRecordDecl *ContainingClass = dyn_cast<CXXRecordDecl>(DC->getParent());
      if (ContainingClass && ContainingClass->hasAnyDependentBases()) {
        Diag(IdInfo.IdentifierLoc,
             diag::ext_undeclared_unqual_id_with_dependent_base)
            << IdInfo.Identifier << ContainingClass;
        SS.Extend(Context, IdInfo.Identifier, IdInfo.IdentifierLoc,
                  IdInfo.CCLoc);
        return false;
      }
    }
  }

  if (!Found.empty()) {
    if (TypeDecl *TD = Found.getAsSingle<TypeDecl>())
      Diag(IdInfo.IdentifierLoc, diag::err_expected_class_or_namespace)
          << Context.getTypeDeclType(TD) << getLangOpts().CPlusPlus;
    else {
      Diag(IdInfo.IdentifierLoc, diag::err_expected_class_or_namespace)
          << IdInfo.Identifier << getLangOpts().CPlusPlus;
      if (NamedDecl *ND = Found.getAsSingle<NamedDecl>())
        Diag(ND->getLocation(), diag::note_entity_declared_at)
            << IdInfo.Identifier;
    }
  } else if (SS.isSet())
    Diag(IdInfo.IdentifierLoc, diag::err_no_member) << IdInfo.Identifier
        << LookupCtx << SS.getRange();
  else
    Diag(IdInfo.IdentifierLoc, diag::err_undeclared_var_use)
        << IdInfo.Identifier;

  return true;
}

bool Sema::ActOnCXXNestedNameSpecifier(Scope *S, NestedNameSpecInfo &IdInfo,
                                       bool EnteringContext, CXXScopeSpec &SS,
                                       bool ErrorRecoveryLookup,
                                       bool *IsCorrectedToColon,
                                       bool OnlyNamespace) {
  if (SS.isInvalid())
    return true;

  return BuildCXXNestedNameSpecifier(S, IdInfo, EnteringContext, SS,
                                     /*ScopeLookupResult=*/nullptr, false,
                                     IsCorrectedToColon, OnlyNamespace);
}

bool Sema::ActOnCXXNestedNameSpecifierDecltype(CXXScopeSpec &SS,
                                               const DeclSpec &DS,
                                               SourceLocation ColonColonLoc) {
  if (SS.isInvalid() || DS.getTypeSpecType() == DeclSpec::TST_error)
    return true;

  assert(DS.getTypeSpecType() == DeclSpec::TST_decltype);

  QualType T = BuildDecltypeType(DS.getRepAsExpr());
  if (T.isNull())
    return true;

  if (!T->isDependentType() && !T->getAs<TagType>()) {
    Diag(DS.getTypeSpecTypeLoc(), diag::err_expected_class_or_namespace)
      << T << getLangOpts().CPlusPlus;
    return true;
  }

  TypeLocBuilder TLB;
  DecltypeTypeLoc DecltypeTL = TLB.push<DecltypeTypeLoc>(T);
  DecltypeTL.setDecltypeLoc(DS.getTypeSpecTypeLoc());
  DecltypeTL.setRParenLoc(DS.getTypeofParensRange().getEnd());
  SS.Extend(Context, SourceLocation(), TLB.getTypeLocInContext(Context, T),
            ColonColonLoc);
  return false;
}

/// IsInvalidUnlessNestedName - This method is used for error recovery
/// purposes to determine whether the specified identifier is only valid as
/// a nested name specifier, for example a namespace name.  It is
/// conservatively correct to always return false from this method.
///
/// The arguments are the same as those passed to ActOnCXXNestedNameSpecifier.
bool Sema::IsInvalidUnlessNestedName(Scope *S, CXXScopeSpec &SS,
                                     NestedNameSpecInfo &IdInfo,
                                     bool EnteringContext) {
  if (SS.isInvalid())
    return false;

  return !BuildCXXNestedNameSpecifier(S, IdInfo, EnteringContext, SS,
                                      /*ScopeLookupResult=*/nullptr, true);
}

bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
                                       CXXScopeSpec &SS,
                                       SourceLocation TemplateKWLoc,
                                       TemplateTy OpaqueTemplate,
                                       SourceLocation TemplateNameLoc,
                                       SourceLocation LAngleLoc,
                                       ASTTemplateArgsPtr TemplateArgsIn,
                                       SourceLocation RAngleLoc,
                                       SourceLocation CCLoc,
                                       bool EnteringContext) {
  if (SS.isInvalid())
    return true;

  TemplateName Template = OpaqueTemplate.get();

  // Translate the parser's template argument list in our AST format.
  TemplateArgumentListInfo TemplateArgs(LAngleLoc, RAngleLoc);
  translateTemplateArguments(TemplateArgsIn, TemplateArgs);

  DependentTemplateName *DTN = Template.getAsDependentTemplateName();
  if (DTN && DTN->isIdentifier()) {
    // Handle a dependent template specialization for which we cannot resolve
    // the template name.
    assert(DTN->getQualifier() == SS.getScopeRep());
    QualType T = Context.getDependentTemplateSpecializationType(ETK_None,
                                                          DTN->getQualifier(),
                                                          DTN->getIdentifier(),
                                                                TemplateArgs);

    // Create source-location information for this type.
    TypeLocBuilder Builder;
    DependentTemplateSpecializationTypeLoc SpecTL
      = Builder.push<DependentTemplateSpecializationTypeLoc>(T);
    SpecTL.setElaboratedKeywordLoc(SourceLocation());
    SpecTL.setQualifierLoc(SS.getWithLocInContext(Context));
    SpecTL.setTemplateKeywordLoc(TemplateKWLoc);
    SpecTL.setTemplateNameLoc(TemplateNameLoc);
    SpecTL.setLAngleLoc(LAngleLoc);
    SpecTL.setRAngleLoc(RAngleLoc);
    for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
      SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());

    SS.Extend(Context, TemplateKWLoc, Builder.getTypeLocInContext(Context, T),
              CCLoc);
    return false;
  }

  // If we assumed an undeclared identifier was a template name, try to
  // typo-correct it now.
  if (Template.getAsAssumedTemplateName() &&
      resolveAssumedTemplateNameAsType(S, Template, TemplateNameLoc))
    return true;

  TemplateDecl *TD = Template.getAsTemplateDecl();
  if (Template.getAsOverloadedTemplate() || DTN ||
      isa<FunctionTemplateDecl>(TD) || isa<VarTemplateDecl>(TD)) {
    SourceRange R(TemplateNameLoc, RAngleLoc);
    if (SS.getRange().isValid())
      R.setBegin(SS.getRange().getBegin());

    Diag(CCLoc, diag::err_non_type_template_in_nested_name_specifier)
      << (TD && isa<VarTemplateDecl>(TD)) << Template << R;
    NoteAllFoundTemplates(Template);
    return true;
  }

  // We were able to resolve the template name to an actual template.
  // Build an appropriate nested-name-specifier.
  QualType T = CheckTemplateIdType(Template, TemplateNameLoc, TemplateArgs);
  if (T.isNull())
    return true;

  // Alias template specializations can produce types which are not valid
  // nested name specifiers.
  if (!T->isDependentType() && !T->getAs<TagType>()) {
    Diag(TemplateNameLoc, diag::err_nested_name_spec_non_tag) << T;
    NoteAllFoundTemplates(Template);
    return true;
  }

  // Provide source-location information for the template specialization type.
  TypeLocBuilder Builder;
  TemplateSpecializationTypeLoc SpecTL
    = Builder.push<TemplateSpecializationTypeLoc>(T);
  SpecTL.setTemplateKeywordLoc(TemplateKWLoc);
  SpecTL.setTemplateNameLoc(TemplateNameLoc);
  SpecTL.setLAngleLoc(LAngleLoc);
  SpecTL.setRAngleLoc(RAngleLoc);
  for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
    SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());


  SS.Extend(Context, TemplateKWLoc, Builder.getTypeLocInContext(Context, T),
            CCLoc);
  return false;
}

namespace {
  /// A structure that stores a nested-name-specifier annotation,
  /// including both the nested-name-specifier
  struct NestedNameSpecifierAnnotation {
    NestedNameSpecifier *NNS;
  };
}

void *Sema::SaveNestedNameSpecifierAnnotation(CXXScopeSpec &SS) {
  if (SS.isEmpty() || SS.isInvalid())
    return nullptr;

  void *Mem = Context.Allocate(
      (sizeof(NestedNameSpecifierAnnotation) + SS.location_size()),
      alignof(NestedNameSpecifierAnnotation));
  NestedNameSpecifierAnnotation *Annotation
    = new (Mem) NestedNameSpecifierAnnotation;
  Annotation->NNS = SS.getScopeRep();
  memcpy(Annotation + 1, SS.location_data(), SS.location_size());
  return Annotation;
}

void Sema::RestoreNestedNameSpecifierAnnotation(void *AnnotationPtr,
                                                SourceRange AnnotationRange,
                                                CXXScopeSpec &SS) {
  if (!AnnotationPtr) {
    SS.SetInvalid(AnnotationRange);
    return;
  }

  NestedNameSpecifierAnnotation *Annotation
    = static_cast<NestedNameSpecifierAnnotation *>(AnnotationPtr);
  SS.Adopt(NestedNameSpecifierLoc(Annotation->NNS, Annotation + 1));
}

bool Sema::ShouldEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
  assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");

  // Don't enter a declarator context when the current context is an Objective-C
  // declaration.
  if (isa<ObjCContainerDecl>(CurContext) || isa<ObjCMethodDecl>(CurContext))
    return false;

  NestedNameSpecifier *Qualifier = SS.getScopeRep();

  // There are only two places a well-formed program may qualify a
  // declarator: first, when defining a namespace or class member
  // out-of-line, and second, when naming an explicitly-qualified
  // friend function.  The latter case is governed by
  // C++03 [basic.lookup.unqual]p10:
  //   In a friend declaration naming a member function, a name used
  //   in the function declarator and not part of a template-argument
  //   in a template-id is first looked up in the scope of the member
  //   function's class. If it is not found, or if the name is part of
  //   a template-argument in a template-id, the look up is as
  //   described for unqualified names in the definition of the class
  //   granting friendship.
  // i.e. we don't push a scope unless it's a class member.

  switch (Qualifier->getKind()) {
  case NestedNameSpecifier::Global:
  case NestedNameSpecifier::Namespace:
  case NestedNameSpecifier::NamespaceAlias:
    // These are always namespace scopes.  We never want to enter a
    // namespace scope from anything but a file context.
    return CurContext->getRedeclContext()->isFileContext();

  case NestedNameSpecifier::Identifier:
  case NestedNameSpecifier::TypeSpec:
  case NestedNameSpecifier::TypeSpecWithTemplate:
  case NestedNameSpecifier::Super:
    // These are never namespace scopes.
    return true;
  }

  llvm_unreachable("Invalid NestedNameSpecifier::Kind!");
}

/// ActOnCXXEnterDeclaratorScope - Called when a C++ scope specifier (global
/// scope or nested-name-specifier) is parsed, part of a declarator-id.
/// After this method is called, according to [C++ 3.4.3p3], names should be
/// looked up in the declarator-id's scope, until the declarator is parsed and
/// ActOnCXXExitDeclaratorScope is called.
/// The 'SS' should be a non-empty valid CXXScopeSpec.
bool Sema::ActOnCXXEnterDeclaratorScope(Scope *S, CXXScopeSpec &SS) {
  assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");

  if (SS.isInvalid()) return true;

  DeclContext *DC = computeDeclContext(SS, true);
  if (!DC) return true;

  // Before we enter a declarator's context, we need to make sure that
  // it is a complete declaration context.
  if (!DC->isDependentContext() && RequireCompleteDeclContext(SS, DC))
    return true;

  EnterDeclaratorContext(S, DC);

  // Rebuild the nested name specifier for the new scope.
  if (DC->isDependentContext())
    RebuildNestedNameSpecifierInCurrentInstantiation(SS);

  return false;
}

/// ActOnCXXExitDeclaratorScope - Called when a declarator that previously
/// invoked ActOnCXXEnterDeclaratorScope(), is finished. 'SS' is the same
/// CXXScopeSpec that was passed to ActOnCXXEnterDeclaratorScope as well.
/// Used to indicate that names should revert to being looked up in the
/// defining scope.
void Sema::ActOnCXXExitDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
  assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
  if (SS.isInvalid())
    return;
  assert(!SS.isInvalid() && computeDeclContext(SS, true) &&
         "exiting declarator scope we never really entered");
  ExitDeclaratorContext(S);
}