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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 "TypeLocBuilder.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 "clang/Sema/Lookup.h"
     23 #include "clang/Sema/Template.h"
     24 #include "llvm/ADT/STLExtras.h"
     25 #include "llvm/Support/raw_ostream.h"
     26 using namespace clang;
     27 
     28 /// \brief Find the current instantiation that associated with the given type.
     29 static CXXRecordDecl *getCurrentInstantiationOf(QualType T,
     30                                                 DeclContext *CurContext) {
     31   if (T.isNull())
     32     return 0;
     33 
     34   const Type *Ty = T->getCanonicalTypeInternal().getTypePtr();
     35   if (const RecordType *RecordTy = dyn_cast<RecordType>(Ty)) {
     36     CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());
     37     if (!Record->isDependentContext() ||
     38         Record->isCurrentInstantiation(CurContext))
     39       return Record;
     40 
     41     return 0;
     42   } else if (isa<InjectedClassNameType>(Ty))
     43     return cast<InjectedClassNameType>(Ty)->getDecl();
     44   else
     45     return 0;
     46 }
     47 
     48 /// \brief Compute the DeclContext that is associated with the given type.
     49 ///
     50 /// \param T the type for which we are attempting to find a DeclContext.
     51 ///
     52 /// \returns the declaration context represented by the type T,
     53 /// or NULL if the declaration context cannot be computed (e.g., because it is
     54 /// dependent and not the current instantiation).
     55 DeclContext *Sema::computeDeclContext(QualType T) {
     56   if (!T->isDependentType())
     57     if (const TagType *Tag = T->getAs<TagType>())
     58       return Tag->getDecl();
     59 
     60   return ::getCurrentInstantiationOf(T, CurContext);
     61 }
     62 
     63 /// \brief Compute the DeclContext that is associated with the given
     64 /// scope specifier.
     65 ///
     66 /// \param SS the C++ scope specifier as it appears in the source
     67 ///
     68 /// \param EnteringContext when true, we will be entering the context of
     69 /// this scope specifier, so we can retrieve the declaration context of a
     70 /// class template or class template partial specialization even if it is
     71 /// not the current instantiation.
     72 ///
     73 /// \returns the declaration context represented by the scope specifier @p SS,
     74 /// or NULL if the declaration context cannot be computed (e.g., because it is
     75 /// dependent and not the current instantiation).
     76 DeclContext *Sema::computeDeclContext(const CXXScopeSpec &SS,
     77                                       bool EnteringContext) {
     78   if (!SS.isSet() || SS.isInvalid())
     79     return 0;
     80 
     81   NestedNameSpecifier *NNS = SS.getScopeRep();
     82   if (NNS->isDependent()) {
     83     // If this nested-name-specifier refers to the current
     84     // instantiation, return its DeclContext.
     85     if (CXXRecordDecl *Record = getCurrentInstantiationOf(NNS))
     86       return Record;
     87 
     88     if (EnteringContext) {
     89       const Type *NNSType = NNS->getAsType();
     90       if (!NNSType) {
     91         return 0;
     92       }
     93 
     94       // Look through type alias templates, per C++0x [temp.dep.type]p1.
     95       NNSType = Context.getCanonicalType(NNSType);
     96       if (const TemplateSpecializationType *SpecType
     97             = NNSType->getAs<TemplateSpecializationType>()) {
     98         // We are entering the context of the nested name specifier, so try to
     99         // match the nested name specifier to either a primary class template
    100         // or a class template partial specialization.
    101         if (ClassTemplateDecl *ClassTemplate
    102               = dyn_cast_or_null<ClassTemplateDecl>(
    103                             SpecType->getTemplateName().getAsTemplateDecl())) {
    104           QualType ContextType
    105             = Context.getCanonicalType(QualType(SpecType, 0));
    106 
    107           // If the type of the nested name specifier is the same as the
    108           // injected class name of the named class template, we're entering
    109           // into that class template definition.
    110           QualType Injected
    111             = ClassTemplate->getInjectedClassNameSpecialization();
    112           if (Context.hasSameType(Injected, ContextType))
    113             return ClassTemplate->getTemplatedDecl();
    114 
    115           // If the type of the nested name specifier is the same as the
    116           // type of one of the class template's class template partial
    117           // specializations, we're entering into the definition of that
    118           // class template partial specialization.
    119           if (ClassTemplatePartialSpecializationDecl *PartialSpec
    120                 = ClassTemplate->findPartialSpecialization(ContextType))
    121             return PartialSpec;
    122         }
    123       } else if (const RecordType *RecordT = NNSType->getAs<RecordType>()) {
    124         // The nested name specifier refers to a member of a class template.
    125         return RecordT->getDecl();
    126       }
    127     }
    128 
    129     return 0;
    130   }
    131 
    132   switch (NNS->getKind()) {
    133   case NestedNameSpecifier::Identifier:
    134     llvm_unreachable("Dependent nested-name-specifier has no DeclContext");
    135 
    136   case NestedNameSpecifier::Namespace:
    137     return NNS->getAsNamespace();
    138 
    139   case NestedNameSpecifier::NamespaceAlias:
    140     return NNS->getAsNamespaceAlias()->getNamespace();
    141 
    142   case NestedNameSpecifier::TypeSpec:
    143   case NestedNameSpecifier::TypeSpecWithTemplate: {
    144     const TagType *Tag = NNS->getAsType()->getAs<TagType>();
    145     assert(Tag && "Non-tag type in nested-name-specifier");
    146     return Tag->getDecl();
    147   }
    148 
    149   case NestedNameSpecifier::Global:
    150     return Context.getTranslationUnitDecl();
    151   }
    152 
    153   llvm_unreachable("Invalid NestedNameSpecifier::Kind!");
    154 }
    155 
    156 bool Sema::isDependentScopeSpecifier(const CXXScopeSpec &SS) {
    157   if (!SS.isSet() || SS.isInvalid())
    158     return false;
    159 
    160   return SS.getScopeRep()->isDependent();
    161 }
    162 
    163 /// \brief If the given nested name specifier refers to the current
    164 /// instantiation, return the declaration that corresponds to that
    165 /// current instantiation (C++0x [temp.dep.type]p1).
    166 ///
    167 /// \param NNS a dependent nested name specifier.
    168 CXXRecordDecl *Sema::getCurrentInstantiationOf(NestedNameSpecifier *NNS) {
    169   assert(getLangOpts().CPlusPlus && "Only callable in C++");
    170   assert(NNS->isDependent() && "Only dependent nested-name-specifier allowed");
    171 
    172   if (!NNS->getAsType())
    173     return 0;
    174 
    175   QualType T = QualType(NNS->getAsType(), 0);
    176   return ::getCurrentInstantiationOf(T, CurContext);
    177 }
    178 
    179 /// \brief Require that the context specified by SS be complete.
    180 ///
    181 /// If SS refers to a type, this routine checks whether the type is
    182 /// complete enough (or can be made complete enough) for name lookup
    183 /// into the DeclContext. A type that is not yet completed can be
    184 /// considered "complete enough" if it is a class/struct/union/enum
    185 /// that is currently being defined. Or, if we have a type that names
    186 /// a class template specialization that is not a complete type, we
    187 /// will attempt to instantiate that class template.
    188 bool Sema::RequireCompleteDeclContext(CXXScopeSpec &SS,
    189                                       DeclContext *DC) {
    190   assert(DC != 0 && "given null context");
    191 
    192   TagDecl *tag = dyn_cast<TagDecl>(DC);
    193 
    194   // If this is a dependent type, then we consider it complete.
    195   if (!tag || tag->isDependentContext())
    196     return false;
    197 
    198   // If we're currently defining this type, then lookup into the
    199   // type is okay: don't complain that it isn't complete yet.
    200   QualType type = Context.getTypeDeclType(tag);
    201   const TagType *tagType = type->getAs<TagType>();
    202   if (tagType && tagType->isBeingDefined())
    203     return false;
    204 
    205   SourceLocation loc = SS.getLastQualifierNameLoc();
    206   if (loc.isInvalid()) loc = SS.getRange().getBegin();
    207 
    208   // The type must be complete.
    209   if (RequireCompleteType(loc, type, diag::err_incomplete_nested_name_spec,
    210                           SS.getRange())) {
    211     SS.SetInvalid(SS.getRange());
    212     return true;
    213   }
    214 
    215   // Fixed enum types are complete, but they aren't valid as scopes
    216   // until we see a definition, so awkwardly pull out this special
    217   // case.
    218   const EnumType *enumType = dyn_cast_or_null<EnumType>(tagType);
    219   if (!enumType || enumType->getDecl()->isCompleteDefinition())
    220     return false;
    221 
    222   // Try to instantiate the definition, if this is a specialization of an
    223   // enumeration temploid.
    224   EnumDecl *ED = enumType->getDecl();
    225   if (EnumDecl *Pattern = ED->getInstantiatedFromMemberEnum()) {
    226     MemberSpecializationInfo *MSI = ED->getMemberSpecializationInfo();
    227     if (MSI->getTemplateSpecializationKind() != TSK_ExplicitSpecialization) {
    228       if (InstantiateEnum(loc, ED, Pattern, getTemplateInstantiationArgs(ED),
    229                           TSK_ImplicitInstantiation)) {
    230         SS.SetInvalid(SS.getRange());
    231         return true;
    232       }
    233       return false;
    234     }
    235   }
    236 
    237   Diag(loc, diag::err_incomplete_nested_name_spec)
    238     << type << SS.getRange();
    239   SS.SetInvalid(SS.getRange());
    240   return true;
    241 }
    242 
    243 bool Sema::ActOnCXXGlobalScopeSpecifier(Scope *S, SourceLocation CCLoc,
    244                                         CXXScopeSpec &SS) {
    245   SS.MakeGlobal(Context, CCLoc);
    246   return false;
    247 }
    248 
    249 /// \brief Determines whether the given declaration is an valid acceptable
    250 /// result for name lookup of a nested-name-specifier.
    251 bool Sema::isAcceptableNestedNameSpecifier(const NamedDecl *SD) {
    252   if (!SD)
    253     return false;
    254 
    255   // Namespace and namespace aliases are fine.
    256   if (isa<NamespaceDecl>(SD) || isa<NamespaceAliasDecl>(SD))
    257     return true;
    258 
    259   if (!isa<TypeDecl>(SD))
    260     return false;
    261 
    262   // Determine whether we have a class (or, in C++11, an enum) or
    263   // a typedef thereof. If so, build the nested-name-specifier.
    264   QualType T = Context.getTypeDeclType(cast<TypeDecl>(SD));
    265   if (T->isDependentType())
    266     return true;
    267   else if (const TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(SD)) {
    268     if (TD->getUnderlyingType()->isRecordType() ||
    269         (Context.getLangOpts().CPlusPlus11 &&
    270          TD->getUnderlyingType()->isEnumeralType()))
    271       return true;
    272   } else if (isa<RecordDecl>(SD) ||
    273              (Context.getLangOpts().CPlusPlus11 && isa<EnumDecl>(SD)))
    274     return true;
    275 
    276   return false;
    277 }
    278 
    279 /// \brief If the given nested-name-specifier begins with a bare identifier
    280 /// (e.g., Base::), perform name lookup for that identifier as a
    281 /// nested-name-specifier within the given scope, and return the result of that
    282 /// name lookup.
    283 NamedDecl *Sema::FindFirstQualifierInScope(Scope *S, NestedNameSpecifier *NNS) {
    284   if (!S || !NNS)
    285     return 0;
    286 
    287   while (NNS->getPrefix())
    288     NNS = NNS->getPrefix();
    289 
    290   if (NNS->getKind() != NestedNameSpecifier::Identifier)
    291     return 0;
    292 
    293   LookupResult Found(*this, NNS->getAsIdentifier(), SourceLocation(),
    294                      LookupNestedNameSpecifierName);
    295   LookupName(Found, S);
    296   assert(!Found.isAmbiguous() && "Cannot handle ambiguities here yet");
    297 
    298   if (!Found.isSingleResult())
    299     return 0;
    300 
    301   NamedDecl *Result = Found.getFoundDecl();
    302   if (isAcceptableNestedNameSpecifier(Result))
    303     return Result;
    304 
    305   return 0;
    306 }
    307 
    308 bool Sema::isNonTypeNestedNameSpecifier(Scope *S, CXXScopeSpec &SS,
    309                                         SourceLocation IdLoc,
    310                                         IdentifierInfo &II,
    311                                         ParsedType ObjectTypePtr) {
    312   QualType ObjectType = GetTypeFromParser(ObjectTypePtr);
    313   LookupResult Found(*this, &II, IdLoc, LookupNestedNameSpecifierName);
    314 
    315   // Determine where to perform name lookup
    316   DeclContext *LookupCtx = 0;
    317   bool isDependent = false;
    318   if (!ObjectType.isNull()) {
    319     // This nested-name-specifier occurs in a member access expression, e.g.,
    320     // x->B::f, and we are looking into the type of the object.
    321     assert(!SS.isSet() && "ObjectType and scope specifier cannot coexist");
    322     LookupCtx = computeDeclContext(ObjectType);
    323     isDependent = ObjectType->isDependentType();
    324   } else if (SS.isSet()) {
    325     // This nested-name-specifier occurs after another nested-name-specifier,
    326     // so long into the context associated with the prior nested-name-specifier.
    327     LookupCtx = computeDeclContext(SS, false);
    328     isDependent = isDependentScopeSpecifier(SS);
    329     Found.setContextRange(SS.getRange());
    330   }
    331 
    332   if (LookupCtx) {
    333     // Perform "qualified" name lookup into the declaration context we
    334     // computed, which is either the type of the base of a member access
    335     // expression or the declaration context associated with a prior
    336     // nested-name-specifier.
    337 
    338     // The declaration context must be complete.
    339     if (!LookupCtx->isDependentContext() &&
    340         RequireCompleteDeclContext(SS, LookupCtx))
    341       return false;
    342 
    343     LookupQualifiedName(Found, LookupCtx);
    344   } else if (isDependent) {
    345     return false;
    346   } else {
    347     LookupName(Found, S);
    348   }
    349   Found.suppressDiagnostics();
    350 
    351   if (NamedDecl *ND = Found.getAsSingle<NamedDecl>())
    352     return isa<NamespaceDecl>(ND) || isa<NamespaceAliasDecl>(ND);
    353 
    354   return false;
    355 }
    356 
    357 namespace {
    358 
    359 // Callback to only accept typo corrections that can be a valid C++ member
    360 // intializer: either a non-static field member or a base class.
    361 class NestedNameSpecifierValidatorCCC : public CorrectionCandidateCallback {
    362  public:
    363   explicit NestedNameSpecifierValidatorCCC(Sema &SRef)
    364       : SRef(SRef) {}
    365 
    366   virtual bool ValidateCandidate(const TypoCorrection &candidate) {
    367     return SRef.isAcceptableNestedNameSpecifier(candidate.getCorrectionDecl());
    368   }
    369 
    370  private:
    371   Sema &SRef;
    372 };
    373 
    374 }
    375 
    376 /// \brief Build a new nested-name-specifier for "identifier::", as described
    377 /// by ActOnCXXNestedNameSpecifier.
    378 ///
    379 /// This routine differs only slightly from ActOnCXXNestedNameSpecifier, in
    380 /// that it contains an extra parameter \p ScopeLookupResult, which provides
    381 /// the result of name lookup within the scope of the nested-name-specifier
    382 /// that was computed at template definition time.
    383 ///
    384 /// If ErrorRecoveryLookup is true, then this call is used to improve error
    385 /// recovery.  This means that it should not emit diagnostics, it should
    386 /// just return true on failure.  It also means it should only return a valid
    387 /// scope if it *knows* that the result is correct.  It should not return in a
    388 /// dependent context, for example. Nor will it extend \p SS with the scope
    389 /// specifier.
    390 bool Sema::BuildCXXNestedNameSpecifier(Scope *S,
    391                                        IdentifierInfo &Identifier,
    392                                        SourceLocation IdentifierLoc,
    393                                        SourceLocation CCLoc,
    394                                        QualType ObjectType,
    395                                        bool EnteringContext,
    396                                        CXXScopeSpec &SS,
    397                                        NamedDecl *ScopeLookupResult,
    398                                        bool ErrorRecoveryLookup) {
    399   LookupResult Found(*this, &Identifier, IdentifierLoc,
    400                      LookupNestedNameSpecifierName);
    401 
    402   // Determine where to perform name lookup
    403   DeclContext *LookupCtx = 0;
    404   bool isDependent = false;
    405   if (!ObjectType.isNull()) {
    406     // This nested-name-specifier occurs in a member access expression, e.g.,
    407     // x->B::f, and we are looking into the type of the object.
    408     assert(!SS.isSet() && "ObjectType and scope specifier cannot coexist");
    409     LookupCtx = computeDeclContext(ObjectType);
    410     isDependent = ObjectType->isDependentType();
    411   } else if (SS.isSet()) {
    412     // This nested-name-specifier occurs after another nested-name-specifier,
    413     // so look into the context associated with the prior nested-name-specifier.
    414     LookupCtx = computeDeclContext(SS, EnteringContext);
    415     isDependent = isDependentScopeSpecifier(SS);
    416     Found.setContextRange(SS.getRange());
    417   }
    418 
    419 
    420   bool ObjectTypeSearchedInScope = false;
    421   if (LookupCtx) {
    422     // Perform "qualified" name lookup into the declaration context we
    423     // computed, which is either the type of the base of a member access
    424     // expression or the declaration context associated with a prior
    425     // nested-name-specifier.
    426 
    427     // The declaration context must be complete.
    428     if (!LookupCtx->isDependentContext() &&
    429         RequireCompleteDeclContext(SS, LookupCtx))
    430       return true;
    431 
    432     LookupQualifiedName(Found, LookupCtx);
    433 
    434     if (!ObjectType.isNull() && Found.empty()) {
    435       // C++ [basic.lookup.classref]p4:
    436       //   If the id-expression in a class member access is a qualified-id of
    437       //   the form
    438       //
    439       //        class-name-or-namespace-name::...
    440       //
    441       //   the class-name-or-namespace-name following the . or -> operator is
    442       //   looked up both in the context of the entire postfix-expression and in
    443       //   the scope of the class of the object expression. If the name is found
    444       //   only in the scope of the class of the object expression, the name
    445       //   shall refer to a class-name. If the name is found only in the
    446       //   context of the entire postfix-expression, the name shall refer to a
    447       //   class-name or namespace-name. [...]
    448       //
    449       // Qualified name lookup into a class will not find a namespace-name,
    450       // so we do not need to diagnose that case specifically. However,
    451       // this qualified name lookup may find nothing. In that case, perform
    452       // unqualified name lookup in the given scope (if available) or
    453       // reconstruct the result from when name lookup was performed at template
    454       // definition time.
    455       if (S)
    456         LookupName(Found, S);
    457       else if (ScopeLookupResult)
    458         Found.addDecl(ScopeLookupResult);
    459 
    460       ObjectTypeSearchedInScope = true;
    461     }
    462   } else if (!isDependent) {
    463     // Perform unqualified name lookup in the current scope.
    464     LookupName(Found, S);
    465   }
    466 
    467   // If we performed lookup into a dependent context and did not find anything,
    468   // that's fine: just build a dependent nested-name-specifier.
    469   if (Found.empty() && isDependent &&
    470       !(LookupCtx && LookupCtx->isRecord() &&
    471         (!cast<CXXRecordDecl>(LookupCtx)->hasDefinition() ||
    472          !cast<CXXRecordDecl>(LookupCtx)->hasAnyDependentBases()))) {
    473     // Don't speculate if we're just trying to improve error recovery.
    474     if (ErrorRecoveryLookup)
    475       return true;
    476 
    477     // We were not able to compute the declaration context for a dependent
    478     // base object type or prior nested-name-specifier, so this
    479     // nested-name-specifier refers to an unknown specialization. Just build
    480     // a dependent nested-name-specifier.
    481     SS.Extend(Context, &Identifier, IdentifierLoc, CCLoc);
    482     return false;
    483   }
    484 
    485   // FIXME: Deal with ambiguities cleanly.
    486 
    487   if (Found.empty() && !ErrorRecoveryLookup) {
    488     // We haven't found anything, and we're not recovering from a
    489     // different kind of error, so look for typos.
    490     DeclarationName Name = Found.getLookupName();
    491     NestedNameSpecifierValidatorCCC Validator(*this);
    492     TypoCorrection Corrected;
    493     Found.clear();
    494     if ((Corrected = CorrectTypo(Found.getLookupNameInfo(),
    495                                  Found.getLookupKind(), S, &SS, Validator,
    496                                  LookupCtx, EnteringContext))) {
    497       std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
    498       std::string CorrectedQuotedStr(Corrected.getQuoted(getLangOpts()));
    499       bool droppedSpecifier = Corrected.WillReplaceSpecifier() &&
    500                               Name.getAsString() == CorrectedStr;
    501       if (LookupCtx)
    502         Diag(Found.getNameLoc(), diag::err_no_member_suggest)
    503           << Name << LookupCtx << droppedSpecifier << CorrectedQuotedStr
    504           << SS.getRange()
    505           << FixItHint::CreateReplacement(Corrected.getCorrectionRange(),
    506                                           CorrectedStr);
    507       else
    508         Diag(Found.getNameLoc(), diag::err_undeclared_var_use_suggest)
    509           << Name << CorrectedQuotedStr
    510           << FixItHint::CreateReplacement(Corrected.getCorrectionRange(),
    511                                           CorrectedStr);
    512 
    513       if (NamedDecl *ND = Corrected.getCorrectionDecl()) {
    514         Diag(ND->getLocation(), diag::note_previous_decl) << CorrectedQuotedStr;
    515         Found.addDecl(ND);
    516       }
    517       Found.setLookupName(Corrected.getCorrection());
    518     } else {
    519       Found.setLookupName(&Identifier);
    520     }
    521   }
    522 
    523   NamedDecl *SD = Found.getAsSingle<NamedDecl>();
    524   if (isAcceptableNestedNameSpecifier(SD)) {
    525     if (!ObjectType.isNull() && !ObjectTypeSearchedInScope &&
    526         !getLangOpts().CPlusPlus11) {
    527       // C++03 [basic.lookup.classref]p4:
    528       //   [...] If the name is found in both contexts, the
    529       //   class-name-or-namespace-name shall refer to the same entity.
    530       //
    531       // We already found the name in the scope of the object. Now, look
    532       // into the current scope (the scope of the postfix-expression) to
    533       // see if we can find the same name there. As above, if there is no
    534       // scope, reconstruct the result from the template instantiation itself.
    535       //
    536       // Note that C++11 does *not* perform this redundant lookup.
    537       NamedDecl *OuterDecl;
    538       if (S) {
    539         LookupResult FoundOuter(*this, &Identifier, IdentifierLoc,
    540                                 LookupNestedNameSpecifierName);
    541         LookupName(FoundOuter, S);
    542         OuterDecl = FoundOuter.getAsSingle<NamedDecl>();
    543       } else
    544         OuterDecl = ScopeLookupResult;
    545 
    546       if (isAcceptableNestedNameSpecifier(OuterDecl) &&
    547           OuterDecl->getCanonicalDecl() != SD->getCanonicalDecl() &&
    548           (!isa<TypeDecl>(OuterDecl) || !isa<TypeDecl>(SD) ||
    549            !Context.hasSameType(
    550                             Context.getTypeDeclType(cast<TypeDecl>(OuterDecl)),
    551                                Context.getTypeDeclType(cast<TypeDecl>(SD))))) {
    552          if (ErrorRecoveryLookup)
    553            return true;
    554 
    555          Diag(IdentifierLoc,
    556               diag::err_nested_name_member_ref_lookup_ambiguous)
    557            << &Identifier;
    558          Diag(SD->getLocation(), diag::note_ambig_member_ref_object_type)
    559            << ObjectType;
    560          Diag(OuterDecl->getLocation(), diag::note_ambig_member_ref_scope);
    561 
    562          // Fall through so that we'll pick the name we found in the object
    563          // type, since that's probably what the user wanted anyway.
    564        }
    565     }
    566 
    567     // If we're just performing this lookup for error-recovery purposes,
    568     // don't extend the nested-name-specifier. Just return now.
    569     if (ErrorRecoveryLookup)
    570       return false;
    571 
    572     if (NamespaceDecl *Namespace = dyn_cast<NamespaceDecl>(SD)) {
    573       SS.Extend(Context, Namespace, IdentifierLoc, CCLoc);
    574       return false;
    575     }
    576 
    577     if (NamespaceAliasDecl *Alias = dyn_cast<NamespaceAliasDecl>(SD)) {
    578       SS.Extend(Context, Alias, IdentifierLoc, CCLoc);
    579       return false;
    580     }
    581 
    582     QualType T = Context.getTypeDeclType(cast<TypeDecl>(SD));
    583     TypeLocBuilder TLB;
    584     if (isa<InjectedClassNameType>(T)) {
    585       InjectedClassNameTypeLoc InjectedTL
    586         = TLB.push<InjectedClassNameTypeLoc>(T);
    587       InjectedTL.setNameLoc(IdentifierLoc);
    588     } else if (isa<RecordType>(T)) {
    589       RecordTypeLoc RecordTL = TLB.push<RecordTypeLoc>(T);
    590       RecordTL.setNameLoc(IdentifierLoc);
    591     } else if (isa<TypedefType>(T)) {
    592       TypedefTypeLoc TypedefTL = TLB.push<TypedefTypeLoc>(T);
    593       TypedefTL.setNameLoc(IdentifierLoc);
    594     } else if (isa<EnumType>(T)) {
    595       EnumTypeLoc EnumTL = TLB.push<EnumTypeLoc>(T);
    596       EnumTL.setNameLoc(IdentifierLoc);
    597     } else if (isa<TemplateTypeParmType>(T)) {
    598       TemplateTypeParmTypeLoc TemplateTypeTL
    599         = TLB.push<TemplateTypeParmTypeLoc>(T);
    600       TemplateTypeTL.setNameLoc(IdentifierLoc);
    601     } else if (isa<UnresolvedUsingType>(T)) {
    602       UnresolvedUsingTypeLoc UnresolvedTL
    603         = TLB.push<UnresolvedUsingTypeLoc>(T);
    604       UnresolvedTL.setNameLoc(IdentifierLoc);
    605     } else if (isa<SubstTemplateTypeParmType>(T)) {
    606       SubstTemplateTypeParmTypeLoc TL
    607         = TLB.push<SubstTemplateTypeParmTypeLoc>(T);
    608       TL.setNameLoc(IdentifierLoc);
    609     } else if (isa<SubstTemplateTypeParmPackType>(T)) {
    610       SubstTemplateTypeParmPackTypeLoc TL
    611         = TLB.push<SubstTemplateTypeParmPackTypeLoc>(T);
    612       TL.setNameLoc(IdentifierLoc);
    613     } else {
    614       llvm_unreachable("Unhandled TypeDecl node in nested-name-specifier");
    615     }
    616 
    617     if (T->isEnumeralType())
    618       Diag(IdentifierLoc, diag::warn_cxx98_compat_enum_nested_name_spec);
    619 
    620     SS.Extend(Context, SourceLocation(), TLB.getTypeLocInContext(Context, T),
    621               CCLoc);
    622     return false;
    623   }
    624 
    625   // Otherwise, we have an error case.  If we don't want diagnostics, just
    626   // return an error now.
    627   if (ErrorRecoveryLookup)
    628     return true;
    629 
    630   // If we didn't find anything during our lookup, try again with
    631   // ordinary name lookup, which can help us produce better error
    632   // messages.
    633   if (Found.empty()) {
    634     Found.clear(LookupOrdinaryName);
    635     LookupName(Found, S);
    636   }
    637 
    638   // In Microsoft mode, if we are within a templated function and we can't
    639   // resolve Identifier, then extend the SS with Identifier. This will have
    640   // the effect of resolving Identifier during template instantiation.
    641   // The goal is to be able to resolve a function call whose
    642   // nested-name-specifier is located inside a dependent base class.
    643   // Example:
    644   //
    645   // class C {
    646   // public:
    647   //    static void foo2() {  }
    648   // };
    649   // template <class T> class A { public: typedef C D; };
    650   //
    651   // template <class T> class B : public A<T> {
    652   // public:
    653   //   void foo() { D::foo2(); }
    654   // };
    655   if (getLangOpts().MicrosoftExt) {
    656     DeclContext *DC = LookupCtx ? LookupCtx : CurContext;
    657     if (DC->isDependentContext() && DC->isFunctionOrMethod()) {
    658       SS.Extend(Context, &Identifier, IdentifierLoc, CCLoc);
    659       return false;
    660     }
    661   }
    662 
    663   unsigned DiagID;
    664   if (!Found.empty())
    665     DiagID = diag::err_expected_class_or_namespace;
    666   else if (SS.isSet()) {
    667     Diag(IdentifierLoc, diag::err_no_member)
    668       << &Identifier << LookupCtx << SS.getRange();
    669     return true;
    670   } else
    671     DiagID = diag::err_undeclared_var_use;
    672 
    673   if (SS.isSet())
    674     Diag(IdentifierLoc, DiagID) << &Identifier << SS.getRange();
    675   else
    676     Diag(IdentifierLoc, DiagID) << &Identifier;
    677 
    678   return true;
    679 }
    680 
    681 bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
    682                                        IdentifierInfo &Identifier,
    683                                        SourceLocation IdentifierLoc,
    684                                        SourceLocation CCLoc,
    685                                        ParsedType ObjectType,
    686                                        bool EnteringContext,
    687                                        CXXScopeSpec &SS) {
    688   if (SS.isInvalid())
    689     return true;
    690 
    691   return BuildCXXNestedNameSpecifier(S, Identifier, IdentifierLoc, CCLoc,
    692                                      GetTypeFromParser(ObjectType),
    693                                      EnteringContext, SS,
    694                                      /*ScopeLookupResult=*/0, false);
    695 }
    696 
    697 bool Sema::ActOnCXXNestedNameSpecifierDecltype(CXXScopeSpec &SS,
    698                                                const DeclSpec &DS,
    699                                                SourceLocation ColonColonLoc) {
    700   if (SS.isInvalid() || DS.getTypeSpecType() == DeclSpec::TST_error)
    701     return true;
    702 
    703   assert(DS.getTypeSpecType() == DeclSpec::TST_decltype);
    704 
    705   QualType T = BuildDecltypeType(DS.getRepAsExpr(), DS.getTypeSpecTypeLoc());
    706   if (!T->isDependentType() && !T->getAs<TagType>()) {
    707     Diag(DS.getTypeSpecTypeLoc(), diag::err_expected_class)
    708       << T << getLangOpts().CPlusPlus;
    709     return true;
    710   }
    711 
    712   TypeLocBuilder TLB;
    713   DecltypeTypeLoc DecltypeTL = TLB.push<DecltypeTypeLoc>(T);
    714   DecltypeTL.setNameLoc(DS.getTypeSpecTypeLoc());
    715   SS.Extend(Context, SourceLocation(), TLB.getTypeLocInContext(Context, T),
    716             ColonColonLoc);
    717   return false;
    718 }
    719 
    720 /// IsInvalidUnlessNestedName - This method is used for error recovery
    721 /// purposes to determine whether the specified identifier is only valid as
    722 /// a nested name specifier, for example a namespace name.  It is
    723 /// conservatively correct to always return false from this method.
    724 ///
    725 /// The arguments are the same as those passed to ActOnCXXNestedNameSpecifier.
    726 bool Sema::IsInvalidUnlessNestedName(Scope *S, CXXScopeSpec &SS,
    727                                      IdentifierInfo &Identifier,
    728                                      SourceLocation IdentifierLoc,
    729                                      SourceLocation ColonLoc,
    730                                      ParsedType ObjectType,
    731                                      bool EnteringContext) {
    732   if (SS.isInvalid())
    733     return false;
    734 
    735   return !BuildCXXNestedNameSpecifier(S, Identifier, IdentifierLoc, ColonLoc,
    736                                       GetTypeFromParser(ObjectType),
    737                                       EnteringContext, SS,
    738                                       /*ScopeLookupResult=*/0, true);
    739 }
    740 
    741 bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
    742                                        CXXScopeSpec &SS,
    743                                        SourceLocation TemplateKWLoc,
    744                                        TemplateTy Template,
    745                                        SourceLocation TemplateNameLoc,
    746                                        SourceLocation LAngleLoc,
    747                                        ASTTemplateArgsPtr TemplateArgsIn,
    748                                        SourceLocation RAngleLoc,
    749                                        SourceLocation CCLoc,
    750                                        bool EnteringContext) {
    751   if (SS.isInvalid())
    752     return true;
    753 
    754   // Translate the parser's template argument list in our AST format.
    755   TemplateArgumentListInfo TemplateArgs(LAngleLoc, RAngleLoc);
    756   translateTemplateArguments(TemplateArgsIn, TemplateArgs);
    757 
    758   if (DependentTemplateName *DTN = Template.get().getAsDependentTemplateName()){
    759     // Handle a dependent template specialization for which we cannot resolve
    760     // the template name.
    761     assert(DTN->getQualifier() == SS.getScopeRep());
    762     QualType T = Context.getDependentTemplateSpecializationType(ETK_None,
    763                                                           DTN->getQualifier(),
    764                                                           DTN->getIdentifier(),
    765                                                                 TemplateArgs);
    766 
    767     // Create source-location information for this type.
    768     TypeLocBuilder Builder;
    769     DependentTemplateSpecializationTypeLoc SpecTL
    770       = Builder.push<DependentTemplateSpecializationTypeLoc>(T);
    771     SpecTL.setElaboratedKeywordLoc(SourceLocation());
    772     SpecTL.setQualifierLoc(SS.getWithLocInContext(Context));
    773     SpecTL.setTemplateKeywordLoc(TemplateKWLoc);
    774     SpecTL.setTemplateNameLoc(TemplateNameLoc);
    775     SpecTL.setLAngleLoc(LAngleLoc);
    776     SpecTL.setRAngleLoc(RAngleLoc);
    777     for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
    778       SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());
    779 
    780     SS.Extend(Context, TemplateKWLoc, Builder.getTypeLocInContext(Context, T),
    781               CCLoc);
    782     return false;
    783   }
    784 
    785 
    786   if (Template.get().getAsOverloadedTemplate() ||
    787       isa<FunctionTemplateDecl>(Template.get().getAsTemplateDecl())) {
    788     SourceRange R(TemplateNameLoc, RAngleLoc);
    789     if (SS.getRange().isValid())
    790       R.setBegin(SS.getRange().getBegin());
    791 
    792     Diag(CCLoc, diag::err_non_type_template_in_nested_name_specifier)
    793       << Template.get() << R;
    794     NoteAllFoundTemplates(Template.get());
    795     return true;
    796   }
    797 
    798   // We were able to resolve the template name to an actual template.
    799   // Build an appropriate nested-name-specifier.
    800   QualType T = CheckTemplateIdType(Template.get(), TemplateNameLoc,
    801                                    TemplateArgs);
    802   if (T.isNull())
    803     return true;
    804 
    805   // Alias template specializations can produce types which are not valid
    806   // nested name specifiers.
    807   if (!T->isDependentType() && !T->getAs<TagType>()) {
    808     Diag(TemplateNameLoc, diag::err_nested_name_spec_non_tag) << T;
    809     NoteAllFoundTemplates(Template.get());
    810     return true;
    811   }
    812 
    813   // Provide source-location information for the template specialization type.
    814   TypeLocBuilder Builder;
    815   TemplateSpecializationTypeLoc SpecTL
    816     = Builder.push<TemplateSpecializationTypeLoc>(T);
    817   SpecTL.setTemplateKeywordLoc(TemplateKWLoc);
    818   SpecTL.setTemplateNameLoc(TemplateNameLoc);
    819   SpecTL.setLAngleLoc(LAngleLoc);
    820   SpecTL.setRAngleLoc(RAngleLoc);
    821   for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
    822     SpecTL.setArgLocInfo(I, TemplateArgs[I].getLocInfo());
    823 
    824 
    825   SS.Extend(Context, TemplateKWLoc, Builder.getTypeLocInContext(Context, T),
    826             CCLoc);
    827   return false;
    828 }
    829 
    830 namespace {
    831   /// \brief A structure that stores a nested-name-specifier annotation,
    832   /// including both the nested-name-specifier
    833   struct NestedNameSpecifierAnnotation {
    834     NestedNameSpecifier *NNS;
    835   };
    836 }
    837 
    838 void *Sema::SaveNestedNameSpecifierAnnotation(CXXScopeSpec &SS) {
    839   if (SS.isEmpty() || SS.isInvalid())
    840     return 0;
    841 
    842   void *Mem = Context.Allocate((sizeof(NestedNameSpecifierAnnotation) +
    843                                                         SS.location_size()),
    844                                llvm::alignOf<NestedNameSpecifierAnnotation>());
    845   NestedNameSpecifierAnnotation *Annotation
    846     = new (Mem) NestedNameSpecifierAnnotation;
    847   Annotation->NNS = SS.getScopeRep();
    848   memcpy(Annotation + 1, SS.location_data(), SS.location_size());
    849   return Annotation;
    850 }
    851 
    852 void Sema::RestoreNestedNameSpecifierAnnotation(void *AnnotationPtr,
    853                                                 SourceRange AnnotationRange,
    854                                                 CXXScopeSpec &SS) {
    855   if (!AnnotationPtr) {
    856     SS.SetInvalid(AnnotationRange);
    857     return;
    858   }
    859 
    860   NestedNameSpecifierAnnotation *Annotation
    861     = static_cast<NestedNameSpecifierAnnotation *>(AnnotationPtr);
    862   SS.Adopt(NestedNameSpecifierLoc(Annotation->NNS, Annotation + 1));
    863 }
    864 
    865 bool Sema::ShouldEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
    866   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
    867 
    868   NestedNameSpecifier *Qualifier = SS.getScopeRep();
    869 
    870   // There are only two places a well-formed program may qualify a
    871   // declarator: first, when defining a namespace or class member
    872   // out-of-line, and second, when naming an explicitly-qualified
    873   // friend function.  The latter case is governed by
    874   // C++03 [basic.lookup.unqual]p10:
    875   //   In a friend declaration naming a member function, a name used
    876   //   in the function declarator and not part of a template-argument
    877   //   in a template-id is first looked up in the scope of the member
    878   //   function's class. If it is not found, or if the name is part of
    879   //   a template-argument in a template-id, the look up is as
    880   //   described for unqualified names in the definition of the class
    881   //   granting friendship.
    882   // i.e. we don't push a scope unless it's a class member.
    883 
    884   switch (Qualifier->getKind()) {
    885   case NestedNameSpecifier::Global:
    886   case NestedNameSpecifier::Namespace:
    887   case NestedNameSpecifier::NamespaceAlias:
    888     // These are always namespace scopes.  We never want to enter a
    889     // namespace scope from anything but a file context.
    890     return CurContext->getRedeclContext()->isFileContext();
    891 
    892   case NestedNameSpecifier::Identifier:
    893   case NestedNameSpecifier::TypeSpec:
    894   case NestedNameSpecifier::TypeSpecWithTemplate:
    895     // These are never namespace scopes.
    896     return true;
    897   }
    898 
    899   llvm_unreachable("Invalid NestedNameSpecifier::Kind!");
    900 }
    901 
    902 /// ActOnCXXEnterDeclaratorScope - Called when a C++ scope specifier (global
    903 /// scope or nested-name-specifier) is parsed, part of a declarator-id.
    904 /// After this method is called, according to [C++ 3.4.3p3], names should be
    905 /// looked up in the declarator-id's scope, until the declarator is parsed and
    906 /// ActOnCXXExitDeclaratorScope is called.
    907 /// The 'SS' should be a non-empty valid CXXScopeSpec.
    908 bool Sema::ActOnCXXEnterDeclaratorScope(Scope *S, CXXScopeSpec &SS) {
    909   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
    910 
    911   if (SS.isInvalid()) return true;
    912 
    913   DeclContext *DC = computeDeclContext(SS, true);
    914   if (!DC) return true;
    915 
    916   // Before we enter a declarator's context, we need to make sure that
    917   // it is a complete declaration context.
    918   if (!DC->isDependentContext() && RequireCompleteDeclContext(SS, DC))
    919     return true;
    920 
    921   EnterDeclaratorContext(S, DC);
    922 
    923   // Rebuild the nested name specifier for the new scope.
    924   if (DC->isDependentContext())
    925     RebuildNestedNameSpecifierInCurrentInstantiation(SS);
    926 
    927   return false;
    928 }
    929 
    930 /// ActOnCXXExitDeclaratorScope - Called when a declarator that previously
    931 /// invoked ActOnCXXEnterDeclaratorScope(), is finished. 'SS' is the same
    932 /// CXXScopeSpec that was passed to ActOnCXXEnterDeclaratorScope as well.
    933 /// Used to indicate that names should revert to being looked up in the
    934 /// defining scope.
    935 void Sema::ActOnCXXExitDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
    936   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
    937   if (SS.isInvalid())
    938     return;
    939   assert(!SS.isInvalid() && computeDeclContext(SS, true) &&
    940          "exiting declarator scope we never really entered");
    941   ExitDeclaratorContext(S);
    942 }
    943