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      1 //===--- SemaCXXScopeSpec.cpp - Semantic Analysis for C++ scope specifiers-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements C++ semantic analysis for scope specifiers.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "clang/Sema/SemaInternal.h"
     15 #include "clang/Sema/Lookup.h"
     16 #include "clang/AST/ASTContext.h"
     17 #include "clang/AST/DeclTemplate.h"
     18 #include "clang/AST/ExprCXX.h"
     19 #include "clang/AST/NestedNameSpecifier.h"
     20 #include "clang/Basic/PartialDiagnostic.h"
     21 #include "clang/Sema/DeclSpec.h"
     22 #include "TypeLocBuilder.h"
     23 #include "llvm/ADT/STLExtras.h"
     24 #include "llvm/Support/raw_ostream.h"
     25 using namespace clang;
     26 
     27 /// \brief Find the current instantiation that associated with the given type.
     28 static CXXRecordDecl *getCurrentInstantiationOf(QualType T,
     29                                                 DeclContext *CurContext) {
     30   if (T.isNull())
     31     return 0;
     32 
     33   const Type *Ty = T->getCanonicalTypeInternal().getTypePtr();
     34   if (const RecordType *RecordTy = dyn_cast<RecordType>(Ty)) {
     35     CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());
     36     if (!T->isDependentType())
     37       return Record;
     38 
     39     // This may be a member of a class template or class template partial
     40     // specialization. If it's part of the current semantic context, then it's
     41     // an injected-class-name;
     42     for (; !CurContext->isFileContext(); CurContext = CurContext->getParent())
     43       if (CurContext->Equals(Record))
     44         return Record;
     45 
     46     return 0;
     47   } else if (isa<InjectedClassNameType>(Ty))
     48     return cast<InjectedClassNameType>(Ty)->getDecl();
     49   else
     50     return 0;
     51 }
     52 
     53 /// \brief Compute the DeclContext that is associated with the given type.
     54 ///
     55 /// \param T the type for which we are attempting to find a DeclContext.
     56 ///
     57 /// \returns the declaration context represented by the type T,
     58 /// or NULL if the declaration context cannot be computed (e.g., because it is
     59 /// dependent and not the current instantiation).
     60 DeclContext *Sema::computeDeclContext(QualType T) {
     61   if (!T->isDependentType())
     62     if (const TagType *Tag = T->getAs<TagType>())
     63       return Tag->getDecl();
     64 
     65   return ::getCurrentInstantiationOf(T, CurContext);
     66 }
     67 
     68 /// \brief Compute the DeclContext that is associated with the given
     69 /// scope specifier.
     70 ///
     71 /// \param SS the C++ scope specifier as it appears in the source
     72 ///
     73 /// \param EnteringContext when true, we will be entering the context of
     74 /// this scope specifier, so we can retrieve the declaration context of a
     75 /// class template or class template partial specialization even if it is
     76 /// not the current instantiation.
     77 ///
     78 /// \returns the declaration context represented by the scope specifier @p SS,
     79 /// or NULL if the declaration context cannot be computed (e.g., because it is
     80 /// dependent and not the current instantiation).
     81 DeclContext *Sema::computeDeclContext(const CXXScopeSpec &SS,
     82                                       bool EnteringContext) {
     83   if (!SS.isSet() || SS.isInvalid())
     84     return 0;
     85 
     86   NestedNameSpecifier *NNS
     87     = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
     88   if (NNS->isDependent()) {
     89     // If this nested-name-specifier refers to the current
     90     // instantiation, return its DeclContext.
     91     if (CXXRecordDecl *Record = getCurrentInstantiationOf(NNS))
     92       return Record;
     93 
     94     if (EnteringContext) {
     95       const Type *NNSType = NNS->getAsType();
     96       if (!NNSType) {
     97         return 0;
     98       }
     99 
    100       // Look through type alias templates, per C++0x [temp.dep.type]p1.
    101       NNSType = Context.getCanonicalType(NNSType);
    102       if (const TemplateSpecializationType *SpecType
    103             = NNSType->getAs<TemplateSpecializationType>()) {
    104         // We are entering the context of the nested name specifier, so try to
    105         // match the nested name specifier to either a primary class template
    106         // or a class template partial specialization.
    107         if (ClassTemplateDecl *ClassTemplate
    108               = dyn_cast_or_null<ClassTemplateDecl>(
    109                             SpecType->getTemplateName().getAsTemplateDecl())) {
    110           QualType ContextType
    111             = Context.getCanonicalType(QualType(SpecType, 0));
    112 
    113           // If the type of the nested name specifier is the same as the
    114           // injected class name of the named class template, we're entering
    115           // into that class template definition.
    116           QualType Injected
    117             = ClassTemplate->getInjectedClassNameSpecialization();
    118           if (Context.hasSameType(Injected, ContextType))
    119             return ClassTemplate->getTemplatedDecl();
    120 
    121           // If the type of the nested name specifier is the same as the
    122           // type of one of the class template's class template partial
    123           // specializations, we're entering into the definition of that
    124           // class template partial specialization.
    125           if (ClassTemplatePartialSpecializationDecl *PartialSpec
    126                 = ClassTemplate->findPartialSpecialization(ContextType))
    127             return PartialSpec;
    128         }
    129       } else if (const RecordType *RecordT = NNSType->getAs<RecordType>()) {
    130         // The nested name specifier refers to a member of a class template.
    131         return RecordT->getDecl();
    132       }
    133     }
    134 
    135     return 0;
    136   }
    137 
    138   switch (NNS->getKind()) {
    139   case NestedNameSpecifier::Identifier:
    140     assert(false && "Dependent nested-name-specifier has no DeclContext");
    141     break;
    142 
    143   case NestedNameSpecifier::Namespace:
    144     return NNS->getAsNamespace();
    145 
    146   case NestedNameSpecifier::NamespaceAlias:
    147     return NNS->getAsNamespaceAlias()->getNamespace();
    148 
    149   case NestedNameSpecifier::TypeSpec:
    150   case NestedNameSpecifier::TypeSpecWithTemplate: {
    151     const TagType *Tag = NNS->getAsType()->getAs<TagType>();
    152     assert(Tag && "Non-tag type in nested-name-specifier");
    153     return Tag->getDecl();
    154   } break;
    155 
    156   case NestedNameSpecifier::Global:
    157     return Context.getTranslationUnitDecl();
    158   }
    159 
    160   // Required to silence a GCC warning.
    161   return 0;
    162 }
    163 
    164 bool Sema::isDependentScopeSpecifier(const CXXScopeSpec &SS) {
    165   if (!SS.isSet() || SS.isInvalid())
    166     return false;
    167 
    168   NestedNameSpecifier *NNS
    169     = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
    170   return NNS->isDependent();
    171 }
    172 
    173 // \brief Determine whether this C++ scope specifier refers to an
    174 // unknown specialization, i.e., a dependent type that is not the
    175 // current instantiation.
    176 bool Sema::isUnknownSpecialization(const CXXScopeSpec &SS) {
    177   if (!isDependentScopeSpecifier(SS))
    178     return false;
    179 
    180   NestedNameSpecifier *NNS
    181     = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
    182   return getCurrentInstantiationOf(NNS) == 0;
    183 }
    184 
    185 /// \brief If the given nested name specifier refers to the current
    186 /// instantiation, return the declaration that corresponds to that
    187 /// current instantiation (C++0x [temp.dep.type]p1).
    188 ///
    189 /// \param NNS a dependent nested name specifier.
    190 CXXRecordDecl *Sema::getCurrentInstantiationOf(NestedNameSpecifier *NNS) {
    191   assert(getLangOptions().CPlusPlus && "Only callable in C++");
    192   assert(NNS->isDependent() && "Only dependent nested-name-specifier allowed");
    193 
    194   if (!NNS->getAsType())
    195     return 0;
    196 
    197   QualType T = QualType(NNS->getAsType(), 0);
    198   return ::getCurrentInstantiationOf(T, CurContext);
    199 }
    200 
    201 /// \brief Require that the context specified by SS be complete.
    202 ///
    203 /// If SS refers to a type, this routine checks whether the type is
    204 /// complete enough (or can be made complete enough) for name lookup
    205 /// into the DeclContext. A type that is not yet completed can be
    206 /// considered "complete enough" if it is a class/struct/union/enum
    207 /// that is currently being defined. Or, if we have a type that names
    208 /// a class template specialization that is not a complete type, we
    209 /// will attempt to instantiate that class template.
    210 bool Sema::RequireCompleteDeclContext(CXXScopeSpec &SS,
    211                                       DeclContext *DC) {
    212   assert(DC != 0 && "given null context");
    213 
    214   if (TagDecl *tag = dyn_cast<TagDecl>(DC)) {
    215     // If this is a dependent type, then we consider it complete.
    216     if (tag->isDependentContext())
    217       return false;
    218 
    219     // If we're currently defining this type, then lookup into the
    220     // type is okay: don't complain that it isn't complete yet.
    221     QualType type = Context.getTypeDeclType(tag);
    222     const TagType *tagType = type->getAs<TagType>();
    223     if (tagType && tagType->isBeingDefined())
    224       return false;
    225 
    226     SourceLocation loc = SS.getLastQualifierNameLoc();
    227     if (loc.isInvalid()) loc = SS.getRange().getBegin();
    228 
    229     // The type must be complete.
    230     if (RequireCompleteType(loc, type,
    231                             PDiag(diag::err_incomplete_nested_name_spec)
    232                               << SS.getRange())) {
    233       SS.SetInvalid(SS.getRange());
    234       return true;
    235     }
    236 
    237     // Fixed enum types are complete, but they aren't valid as scopes
    238     // until we see a definition, so awkwardly pull out this special
    239     // case.
    240     if (const EnumType *enumType = dyn_cast_or_null<EnumType>(tagType)) {
    241       if (!enumType->getDecl()->isDefinition()) {
    242         Diag(loc, diag::err_incomplete_nested_name_spec)
    243           << type << SS.getRange();
    244         SS.SetInvalid(SS.getRange());
    245         return true;
    246       }
    247     }
    248   }
    249 
    250   return false;
    251 }
    252 
    253 bool Sema::ActOnCXXGlobalScopeSpecifier(Scope *S, SourceLocation CCLoc,
    254                                         CXXScopeSpec &SS) {
    255   SS.MakeGlobal(Context, CCLoc);
    256   return false;
    257 }
    258 
    259 /// \brief Determines whether the given declaration is an valid acceptable
    260 /// result for name lookup of a nested-name-specifier.
    261 bool Sema::isAcceptableNestedNameSpecifier(NamedDecl *SD) {
    262   if (!SD)
    263     return false;
    264 
    265   // Namespace and namespace aliases are fine.
    266   if (isa<NamespaceDecl>(SD) || isa<NamespaceAliasDecl>(SD))
    267     return true;
    268 
    269   if (!isa<TypeDecl>(SD))
    270     return false;
    271 
    272   // Determine whether we have a class (or, in C++0x, an enum) or
    273   // a typedef thereof. If so, build the nested-name-specifier.
    274   QualType T = Context.getTypeDeclType(cast<TypeDecl>(SD));
    275   if (T->isDependentType())
    276     return true;
    277   else if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(SD)) {
    278     if (TD->getUnderlyingType()->isRecordType() ||
    279         (Context.getLangOptions().CPlusPlus0x &&
    280          TD->getUnderlyingType()->isEnumeralType()))
    281       return true;
    282   } else if (isa<RecordDecl>(SD) ||
    283              (Context.getLangOptions().CPlusPlus0x && isa<EnumDecl>(SD)))
    284     return true;
    285 
    286   return false;
    287 }
    288 
    289 /// \brief If the given nested-name-specifier begins with a bare identifier
    290 /// (e.g., Base::), perform name lookup for that identifier as a
    291 /// nested-name-specifier within the given scope, and return the result of that
    292 /// name lookup.
    293 NamedDecl *Sema::FindFirstQualifierInScope(Scope *S, NestedNameSpecifier *NNS) {
    294   if (!S || !NNS)
    295     return 0;
    296 
    297   while (NNS->getPrefix())
    298     NNS = NNS->getPrefix();
    299 
    300   if (NNS->getKind() != NestedNameSpecifier::Identifier)
    301     return 0;
    302 
    303   LookupResult Found(*this, NNS->getAsIdentifier(), SourceLocation(),
    304                      LookupNestedNameSpecifierName);
    305   LookupName(Found, S);
    306   assert(!Found.isAmbiguous() && "Cannot handle ambiguities here yet");
    307 
    308   if (!Found.isSingleResult())
    309     return 0;
    310 
    311   NamedDecl *Result = Found.getFoundDecl();
    312   if (isAcceptableNestedNameSpecifier(Result))
    313     return Result;
    314 
    315   return 0;
    316 }
    317 
    318 bool Sema::isNonTypeNestedNameSpecifier(Scope *S, CXXScopeSpec &SS,
    319                                         SourceLocation IdLoc,
    320                                         IdentifierInfo &II,
    321                                         ParsedType ObjectTypePtr) {
    322   QualType ObjectType = GetTypeFromParser(ObjectTypePtr);
    323   LookupResult Found(*this, &II, IdLoc, LookupNestedNameSpecifierName);
    324 
    325   // Determine where to perform name lookup
    326   DeclContext *LookupCtx = 0;
    327   bool isDependent = false;
    328   if (!ObjectType.isNull()) {
    329     // This nested-name-specifier occurs in a member access expression, e.g.,
    330     // x->B::f, and we are looking into the type of the object.
    331     assert(!SS.isSet() && "ObjectType and scope specifier cannot coexist");
    332     LookupCtx = computeDeclContext(ObjectType);
    333     isDependent = ObjectType->isDependentType();
    334   } else if (SS.isSet()) {
    335     // This nested-name-specifier occurs after another nested-name-specifier,
    336     // so long into the context associated with the prior nested-name-specifier.
    337     LookupCtx = computeDeclContext(SS, false);
    338     isDependent = isDependentScopeSpecifier(SS);
    339     Found.setContextRange(SS.getRange());
    340   }
    341 
    342   if (LookupCtx) {
    343     // Perform "qualified" name lookup into the declaration context we
    344     // computed, which is either the type of the base of a member access
    345     // expression or the declaration context associated with a prior
    346     // nested-name-specifier.
    347 
    348     // The declaration context must be complete.
    349     if (!LookupCtx->isDependentContext() &&
    350         RequireCompleteDeclContext(SS, LookupCtx))
    351       return false;
    352 
    353     LookupQualifiedName(Found, LookupCtx);
    354   } else if (isDependent) {
    355     return false;
    356   } else {
    357     LookupName(Found, S);
    358   }
    359   Found.suppressDiagnostics();
    360 
    361   if (NamedDecl *ND = Found.getAsSingle<NamedDecl>())
    362     return isa<NamespaceDecl>(ND) || isa<NamespaceAliasDecl>(ND);
    363 
    364   return false;
    365 }
    366 
    367 /// \brief Build a new nested-name-specifier for "identifier::", as described
    368 /// by ActOnCXXNestedNameSpecifier.
    369 ///
    370 /// This routine differs only slightly from ActOnCXXNestedNameSpecifier, in
    371 /// that it contains an extra parameter \p ScopeLookupResult, which provides
    372 /// the result of name lookup within the scope of the nested-name-specifier
    373 /// that was computed at template definition time.
    374 ///
    375 /// If ErrorRecoveryLookup is true, then this call is used to improve error
    376 /// recovery.  This means that it should not emit diagnostics, it should
    377 /// just return true on failure.  It also means it should only return a valid
    378 /// scope if it *knows* that the result is correct.  It should not return in a
    379 /// dependent context, for example. Nor will it extend \p SS with the scope
    380 /// specifier.
    381 bool Sema::BuildCXXNestedNameSpecifier(Scope *S,
    382                                        IdentifierInfo &Identifier,
    383                                        SourceLocation IdentifierLoc,
    384                                        SourceLocation CCLoc,
    385                                        QualType ObjectType,
    386                                        bool EnteringContext,
    387                                        CXXScopeSpec &SS,
    388                                        NamedDecl *ScopeLookupResult,
    389                                        bool ErrorRecoveryLookup) {
    390   LookupResult Found(*this, &Identifier, IdentifierLoc,
    391                      LookupNestedNameSpecifierName);
    392 
    393   // Determine where to perform name lookup
    394   DeclContext *LookupCtx = 0;
    395   bool isDependent = false;
    396   if (!ObjectType.isNull()) {
    397     // This nested-name-specifier occurs in a member access expression, e.g.,
    398     // x->B::f, and we are looking into the type of the object.
    399     assert(!SS.isSet() && "ObjectType and scope specifier cannot coexist");
    400     LookupCtx = computeDeclContext(ObjectType);
    401     isDependent = ObjectType->isDependentType();
    402   } else if (SS.isSet()) {
    403     // This nested-name-specifier occurs after another nested-name-specifier,
    404     // so look into the context associated with the prior nested-name-specifier.
    405     LookupCtx = computeDeclContext(SS, EnteringContext);
    406     isDependent = isDependentScopeSpecifier(SS);
    407     Found.setContextRange(SS.getRange());
    408   }
    409 
    410 
    411   bool ObjectTypeSearchedInScope = false;
    412   if (LookupCtx) {
    413     // Perform "qualified" name lookup into the declaration context we
    414     // computed, which is either the type of the base of a member access
    415     // expression or the declaration context associated with a prior
    416     // nested-name-specifier.
    417 
    418     // The declaration context must be complete.
    419     if (!LookupCtx->isDependentContext() &&
    420         RequireCompleteDeclContext(SS, LookupCtx))
    421       return true;
    422 
    423     LookupQualifiedName(Found, LookupCtx);
    424 
    425     if (!ObjectType.isNull() && Found.empty()) {
    426       // C++ [basic.lookup.classref]p4:
    427       //   If the id-expression in a class member access is a qualified-id of
    428       //   the form
    429       //
    430       //        class-name-or-namespace-name::...
    431       //
    432       //   the class-name-or-namespace-name following the . or -> operator is
    433       //   looked up both in the context of the entire postfix-expression and in
    434       //   the scope of the class of the object expression. If the name is found
    435       //   only in the scope of the class of the object expression, the name
    436       //   shall refer to a class-name. If the name is found only in the
    437       //   context of the entire postfix-expression, the name shall refer to a
    438       //   class-name or namespace-name. [...]
    439       //
    440       // Qualified name lookup into a class will not find a namespace-name,
    441       // so we do not need to diagnose that case specifically. However,
    442       // this qualified name lookup may find nothing. In that case, perform
    443       // unqualified name lookup in the given scope (if available) or
    444       // reconstruct the result from when name lookup was performed at template
    445       // definition time.
    446       if (S)
    447         LookupName(Found, S);
    448       else if (ScopeLookupResult)
    449         Found.addDecl(ScopeLookupResult);
    450 
    451       ObjectTypeSearchedInScope = true;
    452     }
    453   } else if (!isDependent) {
    454     // Perform unqualified name lookup in the current scope.
    455     LookupName(Found, S);
    456   }
    457 
    458   // If we performed lookup into a dependent context and did not find anything,
    459   // that's fine: just build a dependent nested-name-specifier.
    460   if (Found.empty() && isDependent &&
    461       !(LookupCtx && LookupCtx->isRecord() &&
    462         (!cast<CXXRecordDecl>(LookupCtx)->hasDefinition() ||
    463          !cast<CXXRecordDecl>(LookupCtx)->hasAnyDependentBases()))) {
    464     // Don't speculate if we're just trying to improve error recovery.
    465     if (ErrorRecoveryLookup)
    466       return true;
    467 
    468     // We were not able to compute the declaration context for a dependent
    469     // base object type or prior nested-name-specifier, so this
    470     // nested-name-specifier refers to an unknown specialization. Just build
    471     // a dependent nested-name-specifier.
    472     SS.Extend(Context, &Identifier, IdentifierLoc, CCLoc);
    473     return false;
    474   }
    475 
    476   // FIXME: Deal with ambiguities cleanly.
    477 
    478   if (Found.empty() && !ErrorRecoveryLookup) {
    479     // We haven't found anything, and we're not recovering from a
    480     // different kind of error, so look for typos.
    481     DeclarationName Name = Found.getLookupName();
    482     TypoCorrection Corrected;
    483     Found.clear();
    484     if ((Corrected = CorrectTypo(Found.getLookupNameInfo(),
    485                                  Found.getLookupKind(), S, &SS, LookupCtx,
    486                                  EnteringContext, CTC_NoKeywords)) &&
    487         isAcceptableNestedNameSpecifier(Corrected.getCorrectionDecl())) {
    488       std::string CorrectedStr(Corrected.getAsString(getLangOptions()));
    489       std::string CorrectedQuotedStr(Corrected.getQuoted(getLangOptions()));
    490       if (LookupCtx)
    491         Diag(Found.getNameLoc(), diag::err_no_member_suggest)
    492           << Name << LookupCtx << CorrectedQuotedStr << SS.getRange()
    493           << FixItHint::CreateReplacement(Found.getNameLoc(), CorrectedStr);
    494       else
    495         Diag(Found.getNameLoc(), diag::err_undeclared_var_use_suggest)
    496           << Name << CorrectedQuotedStr
    497           << FixItHint::CreateReplacement(Found.getNameLoc(), CorrectedStr);
    498 
    499       if (NamedDecl *ND = Corrected.getCorrectionDecl()) {
    500         Diag(ND->getLocation(), diag::note_previous_decl) << CorrectedQuotedStr;
    501         Found.addDecl(ND);
    502       }
    503       Found.setLookupName(Corrected.getCorrection());
    504     } else {
    505       Found.setLookupName(&Identifier);
    506     }
    507   }
    508 
    509   NamedDecl *SD = Found.getAsSingle<NamedDecl>();
    510   if (isAcceptableNestedNameSpecifier(SD)) {
    511     if (!ObjectType.isNull() && !ObjectTypeSearchedInScope) {
    512       // C++ [basic.lookup.classref]p4:
    513       //   [...] If the name is found in both contexts, the
    514       //   class-name-or-namespace-name shall refer to the same entity.
    515       //
    516       // We already found the name in the scope of the object. Now, look
    517       // into the current scope (the scope of the postfix-expression) to
    518       // see if we can find the same name there. As above, if there is no
    519       // scope, reconstruct the result from the template instantiation itself.
    520       NamedDecl *OuterDecl;
    521       if (S) {
    522         LookupResult FoundOuter(*this, &Identifier, IdentifierLoc,
    523                                 LookupNestedNameSpecifierName);
    524         LookupName(FoundOuter, S);
    525         OuterDecl = FoundOuter.getAsSingle<NamedDecl>();
    526       } else
    527         OuterDecl = ScopeLookupResult;
    528 
    529       if (isAcceptableNestedNameSpecifier(OuterDecl) &&
    530           OuterDecl->getCanonicalDecl() != SD->getCanonicalDecl() &&
    531           (!isa<TypeDecl>(OuterDecl) || !isa<TypeDecl>(SD) ||
    532            !Context.hasSameType(
    533                             Context.getTypeDeclType(cast<TypeDecl>(OuterDecl)),
    534                                Context.getTypeDeclType(cast<TypeDecl>(SD))))) {
    535          if (ErrorRecoveryLookup)
    536            return true;
    537 
    538          Diag(IdentifierLoc,
    539               diag::err_nested_name_member_ref_lookup_ambiguous)
    540            << &Identifier;
    541          Diag(SD->getLocation(), diag::note_ambig_member_ref_object_type)
    542            << ObjectType;
    543          Diag(OuterDecl->getLocation(), diag::note_ambig_member_ref_scope);
    544 
    545          // Fall through so that we'll pick the name we found in the object
    546          // type, since that's probably what the user wanted anyway.
    547        }
    548     }
    549 
    550     // If we're just performing this lookup for error-recovery purposes,
    551     // don't extend the nested-name-specifier. Just return now.
    552     if (ErrorRecoveryLookup)
    553       return false;
    554 
    555     if (NamespaceDecl *Namespace = dyn_cast<NamespaceDecl>(SD)) {
    556       SS.Extend(Context, Namespace, IdentifierLoc, CCLoc);
    557       return false;
    558     }
    559 
    560     if (NamespaceAliasDecl *Alias = dyn_cast<NamespaceAliasDecl>(SD)) {
    561       SS.Extend(Context, Alias, IdentifierLoc, CCLoc);
    562       return false;
    563     }
    564 
    565     QualType T = Context.getTypeDeclType(cast<TypeDecl>(SD));
    566     TypeLocBuilder TLB;
    567     if (isa<InjectedClassNameType>(T)) {
    568       InjectedClassNameTypeLoc InjectedTL
    569         = TLB.push<InjectedClassNameTypeLoc>(T);
    570       InjectedTL.setNameLoc(IdentifierLoc);
    571     } else if (isa<RecordType>(T)) {
    572       RecordTypeLoc RecordTL = TLB.push<RecordTypeLoc>(T);
    573       RecordTL.setNameLoc(IdentifierLoc);
    574     } else if (isa<TypedefType>(T)) {
    575       TypedefTypeLoc TypedefTL = TLB.push<TypedefTypeLoc>(T);
    576       TypedefTL.setNameLoc(IdentifierLoc);
    577     } else if (isa<EnumType>(T)) {
    578       EnumTypeLoc EnumTL = TLB.push<EnumTypeLoc>(T);
    579       EnumTL.setNameLoc(IdentifierLoc);
    580     } else if (isa<TemplateTypeParmType>(T)) {
    581       TemplateTypeParmTypeLoc TemplateTypeTL
    582         = TLB.push<TemplateTypeParmTypeLoc>(T);
    583       TemplateTypeTL.setNameLoc(IdentifierLoc);
    584     } else if (isa<UnresolvedUsingType>(T)) {
    585       UnresolvedUsingTypeLoc UnresolvedTL
    586         = TLB.push<UnresolvedUsingTypeLoc>(T);
    587       UnresolvedTL.setNameLoc(IdentifierLoc);
    588     } else if (isa<SubstTemplateTypeParmType>(T)) {
    589       SubstTemplateTypeParmTypeLoc TL
    590         = TLB.push<SubstTemplateTypeParmTypeLoc>(T);
    591       TL.setNameLoc(IdentifierLoc);
    592     } else if (isa<SubstTemplateTypeParmPackType>(T)) {
    593       SubstTemplateTypeParmPackTypeLoc TL
    594         = TLB.push<SubstTemplateTypeParmPackTypeLoc>(T);
    595       TL.setNameLoc(IdentifierLoc);
    596     } else {
    597       llvm_unreachable("Unhandled TypeDecl node in nested-name-specifier");
    598     }
    599 
    600     SS.Extend(Context, SourceLocation(), TLB.getTypeLocInContext(Context, T),
    601               CCLoc);
    602     return false;
    603   }
    604 
    605   // Otherwise, we have an error case.  If we don't want diagnostics, just
    606   // return an error now.
    607   if (ErrorRecoveryLookup)
    608     return true;
    609 
    610   // If we didn't find anything during our lookup, try again with
    611   // ordinary name lookup, which can help us produce better error
    612   // messages.
    613   if (Found.empty()) {
    614     Found.clear(LookupOrdinaryName);
    615     LookupName(Found, S);
    616   }
    617 
    618   unsigned DiagID;
    619   if (!Found.empty())
    620     DiagID = diag::err_expected_class_or_namespace;
    621   else if (SS.isSet()) {
    622     Diag(IdentifierLoc, diag::err_no_member)
    623       << &Identifier << LookupCtx << SS.getRange();
    624     return true;
    625   } else
    626     DiagID = diag::err_undeclared_var_use;
    627 
    628   if (SS.isSet())
    629     Diag(IdentifierLoc, DiagID) << &Identifier << SS.getRange();
    630   else
    631     Diag(IdentifierLoc, DiagID) << &Identifier;
    632 
    633   return true;
    634 }
    635 
    636 bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
    637                                        IdentifierInfo &Identifier,
    638                                        SourceLocation IdentifierLoc,
    639                                        SourceLocation CCLoc,
    640                                        ParsedType ObjectType,
    641                                        bool EnteringContext,
    642                                        CXXScopeSpec &SS) {
    643   if (SS.isInvalid())
    644     return true;
    645 
    646   return BuildCXXNestedNameSpecifier(S, Identifier, IdentifierLoc, CCLoc,
    647                                      GetTypeFromParser(ObjectType),
    648                                      EnteringContext, SS,
    649                                      /*ScopeLookupResult=*/0, false);
    650 }
    651 
    652 /// IsInvalidUnlessNestedName - This method is used for error recovery
    653 /// purposes to determine whether the specified identifier is only valid as
    654 /// a nested name specifier, for example a namespace name.  It is
    655 /// conservatively correct to always return false from this method.
    656 ///
    657 /// The arguments are the same as those passed to ActOnCXXNestedNameSpecifier.
    658 bool Sema::IsInvalidUnlessNestedName(Scope *S, CXXScopeSpec &SS,
    659                                      IdentifierInfo &Identifier,
    660                                      SourceLocation IdentifierLoc,
    661                                      SourceLocation ColonLoc,
    662                                      ParsedType ObjectType,
    663                                      bool EnteringContext) {
    664   if (SS.isInvalid())
    665     return false;
    666 
    667   return !BuildCXXNestedNameSpecifier(S, Identifier, IdentifierLoc, ColonLoc,
    668                                       GetTypeFromParser(ObjectType),
    669                                       EnteringContext, SS,
    670                                       /*ScopeLookupResult=*/0, true);
    671 }
    672 
    673 bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
    674                                        SourceLocation TemplateLoc,
    675                                        CXXScopeSpec &SS,
    676                                        TemplateTy Template,
    677                                        SourceLocation TemplateNameLoc,
    678                                        SourceLocation LAngleLoc,
    679                                        ASTTemplateArgsPtr TemplateArgsIn,
    680                                        SourceLocation RAngleLoc,
    681                                        SourceLocation CCLoc,
    682                                        bool EnteringContext) {
    683   if (SS.isInvalid())
    684     return true;
    685 
    686   // Translate the parser's template argument list in our AST format.
    687   TemplateArgumentListInfo TemplateArgs(LAngleLoc, RAngleLoc);
    688   translateTemplateArguments(TemplateArgsIn, TemplateArgs);
    689 
    690   if (DependentTemplateName *DTN = Template.get().getAsDependentTemplateName()){
    691     // Handle a dependent template specialization for which we cannot resolve
    692     // the template name.
    693     assert(DTN->getQualifier()
    694              == static_cast<NestedNameSpecifier*>(SS.getScopeRep()));
    695     QualType T = Context.getDependentTemplateSpecializationType(ETK_None,
    696                                                           DTN->getQualifier(),
    697                                                           DTN->getIdentifier(),
    698                                                                 TemplateArgs);
    699 
    700     // Create source-location information for this type.
    701     TypeLocBuilder Builder;
    702     DependentTemplateSpecializationTypeLoc SpecTL
    703       = Builder.push<DependentTemplateSpecializationTypeLoc>(T);
    704     SpecTL.setLAngleLoc(LAngleLoc);
    705     SpecTL.setRAngleLoc(RAngleLoc);
    706     SpecTL.setKeywordLoc(SourceLocation());
    707     SpecTL.setNameLoc(TemplateNameLoc);
    708     SpecTL.setQualifierLoc(SS.getWithLocInContext(Context));
    709     for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
    710       SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());
    711 
    712     SS.Extend(Context, TemplateLoc, Builder.getTypeLocInContext(Context, T),
    713               CCLoc);
    714     return false;
    715   }
    716 
    717 
    718   if (Template.get().getAsOverloadedTemplate() ||
    719       isa<FunctionTemplateDecl>(Template.get().getAsTemplateDecl())) {
    720     SourceRange R(TemplateNameLoc, RAngleLoc);
    721     if (SS.getRange().isValid())
    722       R.setBegin(SS.getRange().getBegin());
    723 
    724     Diag(CCLoc, diag::err_non_type_template_in_nested_name_specifier)
    725       << Template.get() << R;
    726     NoteAllFoundTemplates(Template.get());
    727     return true;
    728   }
    729 
    730   // We were able to resolve the template name to an actual template.
    731   // Build an appropriate nested-name-specifier.
    732   QualType T = CheckTemplateIdType(Template.get(), TemplateNameLoc,
    733                                    TemplateArgs);
    734   if (T.isNull())
    735     return true;
    736 
    737   // Alias template specializations can produce types which are not valid
    738   // nested name specifiers.
    739   if (!T->isDependentType() && !T->getAs<TagType>()) {
    740     Diag(TemplateNameLoc, diag::err_nested_name_spec_non_tag) << T;
    741     NoteAllFoundTemplates(Template.get());
    742     return true;
    743   }
    744 
    745   // Provide source-location information for the template specialization
    746   // type.
    747   TypeLocBuilder Builder;
    748   TemplateSpecializationTypeLoc SpecTL
    749     = Builder.push<TemplateSpecializationTypeLoc>(T);
    750 
    751   SpecTL.setLAngleLoc(LAngleLoc);
    752   SpecTL.setRAngleLoc(RAngleLoc);
    753   SpecTL.setTemplateNameLoc(TemplateNameLoc);
    754   for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
    755     SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());
    756 
    757 
    758   SS.Extend(Context, TemplateLoc, Builder.getTypeLocInContext(Context, T),
    759             CCLoc);
    760   return false;
    761 }
    762 
    763 namespace {
    764   /// \brief A structure that stores a nested-name-specifier annotation,
    765   /// including both the nested-name-specifier
    766   struct NestedNameSpecifierAnnotation {
    767     NestedNameSpecifier *NNS;
    768   };
    769 }
    770 
    771 void *Sema::SaveNestedNameSpecifierAnnotation(CXXScopeSpec &SS) {
    772   if (SS.isEmpty() || SS.isInvalid())
    773     return 0;
    774 
    775   void *Mem = Context.Allocate((sizeof(NestedNameSpecifierAnnotation) +
    776                                                         SS.location_size()),
    777                                llvm::alignOf<NestedNameSpecifierAnnotation>());
    778   NestedNameSpecifierAnnotation *Annotation
    779     = new (Mem) NestedNameSpecifierAnnotation;
    780   Annotation->NNS = SS.getScopeRep();
    781   memcpy(Annotation + 1, SS.location_data(), SS.location_size());
    782   return Annotation;
    783 }
    784 
    785 void Sema::RestoreNestedNameSpecifierAnnotation(void *AnnotationPtr,
    786                                                 SourceRange AnnotationRange,
    787                                                 CXXScopeSpec &SS) {
    788   if (!AnnotationPtr) {
    789     SS.SetInvalid(AnnotationRange);
    790     return;
    791   }
    792 
    793   NestedNameSpecifierAnnotation *Annotation
    794     = static_cast<NestedNameSpecifierAnnotation *>(AnnotationPtr);
    795   SS.Adopt(NestedNameSpecifierLoc(Annotation->NNS, Annotation + 1));
    796 }
    797 
    798 bool Sema::ShouldEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
    799   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
    800 
    801   NestedNameSpecifier *Qualifier =
    802     static_cast<NestedNameSpecifier*>(SS.getScopeRep());
    803 
    804   // There are only two places a well-formed program may qualify a
    805   // declarator: first, when defining a namespace or class member
    806   // out-of-line, and second, when naming an explicitly-qualified
    807   // friend function.  The latter case is governed by
    808   // C++03 [basic.lookup.unqual]p10:
    809   //   In a friend declaration naming a member function, a name used
    810   //   in the function declarator and not part of a template-argument
    811   //   in a template-id is first looked up in the scope of the member
    812   //   function's class. If it is not found, or if the name is part of
    813   //   a template-argument in a template-id, the look up is as
    814   //   described for unqualified names in the definition of the class
    815   //   granting friendship.
    816   // i.e. we don't push a scope unless it's a class member.
    817 
    818   switch (Qualifier->getKind()) {
    819   case NestedNameSpecifier::Global:
    820   case NestedNameSpecifier::Namespace:
    821   case NestedNameSpecifier::NamespaceAlias:
    822     // These are always namespace scopes.  We never want to enter a
    823     // namespace scope from anything but a file context.
    824     return CurContext->getRedeclContext()->isFileContext();
    825 
    826   case NestedNameSpecifier::Identifier:
    827   case NestedNameSpecifier::TypeSpec:
    828   case NestedNameSpecifier::TypeSpecWithTemplate:
    829     // These are never namespace scopes.
    830     return true;
    831   }
    832 
    833   // Silence bogus warning.
    834   return false;
    835 }
    836 
    837 /// ActOnCXXEnterDeclaratorScope - Called when a C++ scope specifier (global
    838 /// scope or nested-name-specifier) is parsed, part of a declarator-id.
    839 /// After this method is called, according to [C++ 3.4.3p3], names should be
    840 /// looked up in the declarator-id's scope, until the declarator is parsed and
    841 /// ActOnCXXExitDeclaratorScope is called.
    842 /// The 'SS' should be a non-empty valid CXXScopeSpec.
    843 bool Sema::ActOnCXXEnterDeclaratorScope(Scope *S, CXXScopeSpec &SS) {
    844   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
    845 
    846   if (SS.isInvalid()) return true;
    847 
    848   DeclContext *DC = computeDeclContext(SS, true);
    849   if (!DC) return true;
    850 
    851   // Before we enter a declarator's context, we need to make sure that
    852   // it is a complete declaration context.
    853   if (!DC->isDependentContext() && RequireCompleteDeclContext(SS, DC))
    854     return true;
    855 
    856   EnterDeclaratorContext(S, DC);
    857 
    858   // Rebuild the nested name specifier for the new scope.
    859   if (DC->isDependentContext())
    860     RebuildNestedNameSpecifierInCurrentInstantiation(SS);
    861 
    862   return false;
    863 }
    864 
    865 /// ActOnCXXExitDeclaratorScope - Called when a declarator that previously
    866 /// invoked ActOnCXXEnterDeclaratorScope(), is finished. 'SS' is the same
    867 /// CXXScopeSpec that was passed to ActOnCXXEnterDeclaratorScope as well.
    868 /// Used to indicate that names should revert to being looked up in the
    869 /// defining scope.
    870 void Sema::ActOnCXXExitDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
    871   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
    872   if (SS.isInvalid())
    873     return;
    874   assert(!SS.isInvalid() && computeDeclContext(SS, true) &&
    875          "exiting declarator scope we never really entered");
    876   ExitDeclaratorContext(S);
    877 }
    878