| //===--- SemaCXXScopeSpec.cpp - Semantic Analysis for C++ scope specifiers-===// | 
 | // | 
 | //                     The LLVM Compiler Infrastructure | 
 | // | 
 | // This file is distributed under the University of Illinois Open Source | 
 | // License. See LICENSE.TXT for details. | 
 | // | 
 | //===----------------------------------------------------------------------===// | 
 | // | 
 | // This file implements C++ semantic analysis for scope specifiers. | 
 | // | 
 | //===----------------------------------------------------------------------===// | 
 |  | 
 | #include "Sema.h" | 
 | #include "Lookup.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/Parse/DeclSpec.h" | 
 | #include "llvm/ADT/STLExtras.h" | 
 | #include "llvm/Support/raw_ostream.h" | 
 | using namespace clang; | 
 |  | 
 | /// \brief Find the current instantiation that associated with the given type. | 
 | static CXXRecordDecl *getCurrentInstantiationOf(QualType T) { | 
 |   if (T.isNull()) | 
 |     return 0; | 
 |  | 
 |   const Type *Ty = T->getCanonicalTypeInternal().getTypePtr(); | 
 |   if (isa<RecordType>(Ty)) | 
 |     return cast<CXXRecordDecl>(cast<RecordType>(Ty)->getDecl()); | 
 |   else if (isa<InjectedClassNameType>(Ty)) | 
 |     return cast<InjectedClassNameType>(Ty)->getDecl(); | 
 |   else | 
 |     return 0; | 
 | } | 
 |  | 
 | /// \brief 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 (const TagType *Tag = T->getAs<TagType>()) | 
 |     return Tag->getDecl(); | 
 |  | 
 |   return ::getCurrentInstantiationOf(T); | 
 | } | 
 |  | 
 | /// \brief 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 0; | 
 |  | 
 |   NestedNameSpecifier *NNS | 
 |     = static_cast<NestedNameSpecifier *>(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) { | 
 |         // do nothing, fall out | 
 |       } else 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(Context); | 
 |           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)) | 
 |             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 0; | 
 |   } | 
 |  | 
 |   switch (NNS->getKind()) { | 
 |   case NestedNameSpecifier::Identifier: | 
 |     assert(false && "Dependent nested-name-specifier has no DeclContext"); | 
 |     break; | 
 |  | 
 |   case NestedNameSpecifier::Namespace: | 
 |     return NNS->getAsNamespace(); | 
 |  | 
 |   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(); | 
 |   } break; | 
 |  | 
 |   case NestedNameSpecifier::Global: | 
 |     return Context.getTranslationUnitDecl(); | 
 |   } | 
 |  | 
 |   // Required to silence a GCC warning. | 
 |   return 0; | 
 | } | 
 |  | 
 | bool Sema::isDependentScopeSpecifier(const CXXScopeSpec &SS) { | 
 |   if (!SS.isSet() || SS.isInvalid()) | 
 |     return false; | 
 |  | 
 |   NestedNameSpecifier *NNS | 
 |     = static_cast<NestedNameSpecifier *>(SS.getScopeRep()); | 
 |   return NNS->isDependent(); | 
 | } | 
 |  | 
 | // \brief Determine whether this C++ scope specifier refers to an | 
 | // unknown specialization, i.e., a dependent type that is not the | 
 | // current instantiation. | 
 | bool Sema::isUnknownSpecialization(const CXXScopeSpec &SS) { | 
 |   if (!isDependentScopeSpecifier(SS)) | 
 |     return false; | 
 |  | 
 |   NestedNameSpecifier *NNS | 
 |     = static_cast<NestedNameSpecifier *>(SS.getScopeRep()); | 
 |   return getCurrentInstantiationOf(NNS) == 0; | 
 | } | 
 |  | 
 | /// \brief 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(getLangOptions().CPlusPlus && "Only callable in C++"); | 
 |   assert(NNS->isDependent() && "Only dependent nested-name-specifier allowed"); | 
 |  | 
 |   if (!NNS->getAsType()) | 
 |     return 0; | 
 |  | 
 |   QualType T = QualType(NNS->getAsType(), 0); | 
 |   return ::getCurrentInstantiationOf(T); | 
 | } | 
 |  | 
 | /// \brief 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 != 0 && "given null context"); | 
 |  | 
 |   if (TagDecl *Tag = dyn_cast<TagDecl>(DC)) { | 
 |     // If this is a dependent type, then we consider it complete. | 
 |     if (Tag->isDependentContext()) | 
 |       return false; | 
 |  | 
 |     // If we're currently defining this type, then lookup into the | 
 |     // type is okay: don't complain that it isn't complete yet. | 
 |     const TagType *TagT = Context.getTypeDeclType(Tag)->getAs<TagType>(); | 
 |     if (TagT && TagT->isBeingDefined()) | 
 |       return false; | 
 |  | 
 |     // The type must be complete. | 
 |     if (RequireCompleteType(SS.getRange().getBegin(), | 
 |                             Context.getTypeDeclType(Tag), | 
 |                             PDiag(diag::err_incomplete_nested_name_spec) | 
 |                               << SS.getRange())) { | 
 |       SS.setScopeRep(0);  // Mark the ScopeSpec invalid. | 
 |       return true; | 
 |     } | 
 |   } | 
 |  | 
 |   return false; | 
 | } | 
 |  | 
 | /// ActOnCXXGlobalScopeSpecifier - Return the object that represents the | 
 | /// global scope ('::'). | 
 | Sema::CXXScopeTy *Sema::ActOnCXXGlobalScopeSpecifier(Scope *S, | 
 |                                                      SourceLocation CCLoc) { | 
 |   return NestedNameSpecifier::GlobalSpecifier(Context); | 
 | } | 
 |  | 
 | /// \brief Determines whether the given declaration is an valid acceptable | 
 | /// result for name lookup of a nested-name-specifier. | 
 | bool Sema::isAcceptableNestedNameSpecifier(NamedDecl *SD) { | 
 |   if (!SD) | 
 |     return false; | 
 |  | 
 |   // Namespace and namespace aliases are fine. | 
 |   if (isa<NamespaceDecl>(SD) || isa<NamespaceAliasDecl>(SD)) | 
 |     return true; | 
 |  | 
 |   if (!isa<TypeDecl>(SD)) | 
 |     return false; | 
 |  | 
 |   // Determine whether we have a class (or, in C++0x, 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; | 
 |   else if (TypedefDecl *TD = dyn_cast<TypedefDecl>(SD)) { | 
 |     if (TD->getUnderlyingType()->isRecordType() || | 
 |         (Context.getLangOptions().CPlusPlus0x && | 
 |          TD->getUnderlyingType()->isEnumeralType())) | 
 |       return true; | 
 |   } else if (isa<RecordDecl>(SD) || | 
 |              (Context.getLangOptions().CPlusPlus0x && isa<EnumDecl>(SD))) | 
 |     return true; | 
 |  | 
 |   return false; | 
 | } | 
 |  | 
 | /// \brief 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 0; | 
 |  | 
 |   while (NNS->getPrefix()) | 
 |     NNS = NNS->getPrefix(); | 
 |  | 
 |   if (NNS->getKind() != NestedNameSpecifier::Identifier) | 
 |     return 0; | 
 |  | 
 |   LookupResult Found(*this, NNS->getAsIdentifier(), SourceLocation(), | 
 |                      LookupNestedNameSpecifierName); | 
 |   LookupName(Found, S); | 
 |   assert(!Found.isAmbiguous() && "Cannot handle ambiguities here yet"); | 
 |  | 
 |   if (!Found.isSingleResult()) | 
 |     return 0; | 
 |  | 
 |   NamedDecl *Result = Found.getFoundDecl(); | 
 |   if (isAcceptableNestedNameSpecifier(Result)) | 
 |     return Result; | 
 |  | 
 |   return 0; | 
 | } | 
 |  | 
 | bool Sema::isNonTypeNestedNameSpecifier(Scope *S, CXXScopeSpec &SS, | 
 |                                         SourceLocation IdLoc, | 
 |                                         IdentifierInfo &II, | 
 |                                         TypeTy *ObjectTypePtr) { | 
 |   QualType ObjectType = GetTypeFromParser(ObjectTypePtr); | 
 |   LookupResult Found(*this, &II, IdLoc, LookupNestedNameSpecifierName); | 
 |    | 
 |   // Determine where to perform name lookup | 
 |   DeclContext *LookupCtx = 0; | 
 |   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(); | 
 |    | 
 |   if (NamedDecl *ND = Found.getAsSingle<NamedDecl>()) | 
 |     return isa<NamespaceDecl>(ND) || isa<NamespaceAliasDecl>(ND); | 
 |    | 
 |   return false; | 
 | } | 
 |  | 
 | /// \brief Build a new nested-name-specifier for "identifier::", as described | 
 | /// by ActOnCXXNestedNameSpecifier. | 
 | /// | 
 | /// 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 null 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. | 
 | Sema::CXXScopeTy *Sema::BuildCXXNestedNameSpecifier(Scope *S, | 
 |                                                     CXXScopeSpec &SS, | 
 |                                                     SourceLocation IdLoc, | 
 |                                                     SourceLocation CCLoc, | 
 |                                                     IdentifierInfo &II, | 
 |                                                     QualType ObjectType, | 
 |                                                   NamedDecl *ScopeLookupResult, | 
 |                                                     bool EnteringContext, | 
 |                                                     bool ErrorRecoveryLookup) { | 
 |   NestedNameSpecifier *Prefix | 
 |     = static_cast<NestedNameSpecifier *>(SS.getScopeRep()); | 
 |  | 
 |   LookupResult Found(*this, &II, IdLoc, LookupNestedNameSpecifierName); | 
 |  | 
 |   // Determine where to perform name lookup | 
 |   DeclContext *LookupCtx = 0; | 
 |   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, 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 0; | 
 |  | 
 |     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 diagnoste 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) { | 
 |     // Don't speculate if we're just trying to improve error recovery. | 
 |     if (ErrorRecoveryLookup) | 
 |       return 0; | 
 |      | 
 |     // 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. | 
 |     if (!Prefix) | 
 |       return NestedNameSpecifier::Create(Context, &II); | 
 |  | 
 |     return NestedNameSpecifier::Create(Context, Prefix, &II); | 
 |   } else { | 
 |     // Perform unqualified name lookup in the current scope. | 
 |     LookupName(Found, S); | 
 |   } | 
 |  | 
 |   // FIXME: Deal with ambiguities cleanly. | 
 |  | 
 |   if (Found.empty() && !ErrorRecoveryLookup) { | 
 |     // We haven't found anything, and we're not recovering from a | 
 |     // different kind of error, so look for typos. | 
 |     DeclarationName Name = Found.getLookupName(); | 
 |     if (CorrectTypo(Found, S, &SS, LookupCtx, EnteringContext,   | 
 |                     CTC_NoKeywords) && | 
 |         Found.isSingleResult() && | 
 |         isAcceptableNestedNameSpecifier(Found.getAsSingle<NamedDecl>())) { | 
 |       if (LookupCtx) | 
 |         Diag(Found.getNameLoc(), diag::err_no_member_suggest) | 
 |           << Name << LookupCtx << Found.getLookupName() << SS.getRange() | 
 |           << FixItHint::CreateReplacement(Found.getNameLoc(), | 
 |                                           Found.getLookupName().getAsString()); | 
 |       else | 
 |         Diag(Found.getNameLoc(), diag::err_undeclared_var_use_suggest) | 
 |           << Name << Found.getLookupName() | 
 |           << FixItHint::CreateReplacement(Found.getNameLoc(), | 
 |                                           Found.getLookupName().getAsString()); | 
 |        | 
 |       if (NamedDecl *ND = Found.getAsSingle<NamedDecl>()) | 
 |         Diag(ND->getLocation(), diag::note_previous_decl) | 
 |           << ND->getDeclName(); | 
 |     } else { | 
 |       Found.clear(); | 
 |       Found.setLookupName(&II); | 
 |     } | 
 |   } | 
 |  | 
 |   NamedDecl *SD = Found.getAsSingle<NamedDecl>(); | 
 |   if (isAcceptableNestedNameSpecifier(SD)) { | 
 |     if (!ObjectType.isNull() && !ObjectTypeSearchedInScope) { | 
 |       // C++ [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. | 
 |       NamedDecl *OuterDecl; | 
 |       if (S) { | 
 |         LookupResult FoundOuter(*this, &II, IdLoc, 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 0; | 
 |               | 
 |              Diag(IdLoc, diag::err_nested_name_member_ref_lookup_ambiguous) | 
 |                << &II; | 
 |              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 (NamespaceDecl *Namespace = dyn_cast<NamespaceDecl>(SD)) | 
 |       return NestedNameSpecifier::Create(Context, Prefix, Namespace); | 
 |  | 
 |     // FIXME: It would be nice to maintain the namespace alias name, then | 
 |     // see through that alias when resolving the nested-name-specifier down to | 
 |     // a declaration context. | 
 |     if (NamespaceAliasDecl *Alias = dyn_cast<NamespaceAliasDecl>(SD)) | 
 |       return NestedNameSpecifier::Create(Context, Prefix, | 
 |  | 
 |                                          Alias->getNamespace()); | 
 |  | 
 |     QualType T = Context.getTypeDeclType(cast<TypeDecl>(SD)); | 
 |     return NestedNameSpecifier::Create(Context, Prefix, false, | 
 |                                        T.getTypePtr()); | 
 |   } | 
 |  | 
 |   // Otherwise, we have an error case.  If we don't want diagnostics, just | 
 |   // return an error now. | 
 |   if (ErrorRecoveryLookup) | 
 |     return 0; | 
 |  | 
 |   // 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); | 
 |   } | 
 |  | 
 |   unsigned DiagID; | 
 |   if (!Found.empty()) | 
 |     DiagID = diag::err_expected_class_or_namespace; | 
 |   else if (SS.isSet()) { | 
 |     Diag(IdLoc, diag::err_no_member) << &II << LookupCtx << SS.getRange(); | 
 |     return 0; | 
 |   } else | 
 |     DiagID = diag::err_undeclared_var_use; | 
 |  | 
 |   if (SS.isSet()) | 
 |     Diag(IdLoc, DiagID) << &II << SS.getRange(); | 
 |   else | 
 |     Diag(IdLoc, DiagID) << &II; | 
 |  | 
 |   return 0; | 
 | } | 
 |  | 
 | /// ActOnCXXNestedNameSpecifier - Called during parsing of a | 
 | /// nested-name-specifier. e.g. for "foo::bar::" we parsed "foo::" and now | 
 | /// we want to resolve "bar::". 'SS' is empty or the previously parsed | 
 | /// nested-name part ("foo::"), 'IdLoc' is the source location of 'bar', | 
 | /// 'CCLoc' is the location of '::' and 'II' is the identifier for 'bar'. | 
 | /// Returns a CXXScopeTy* object representing the C++ scope. | 
 | Sema::CXXScopeTy *Sema::ActOnCXXNestedNameSpecifier(Scope *S, | 
 |                                                     CXXScopeSpec &SS, | 
 |                                                     SourceLocation IdLoc, | 
 |                                                     SourceLocation CCLoc, | 
 |                                                     IdentifierInfo &II, | 
 |                                                     TypeTy *ObjectTypePtr, | 
 |                                                     bool EnteringContext) { | 
 |   return BuildCXXNestedNameSpecifier(S, SS, IdLoc, CCLoc, II, | 
 |                                      QualType::getFromOpaquePtr(ObjectTypePtr), | 
 |                                      /*ScopeLookupResult=*/0, EnteringContext, | 
 |                                      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, | 
 |                                      IdentifierInfo &II, TypeTy *ObjectType, | 
 |                                      bool EnteringContext) { | 
 |   return BuildCXXNestedNameSpecifier(S, SS, SourceLocation(), SourceLocation(), | 
 |                                      II, QualType::getFromOpaquePtr(ObjectType), | 
 |                                      /*ScopeLookupResult=*/0, EnteringContext, | 
 |                                      true); | 
 | } | 
 |  | 
 | Sema::CXXScopeTy *Sema::ActOnCXXNestedNameSpecifier(Scope *S, | 
 |                                                     const CXXScopeSpec &SS, | 
 |                                                     TypeTy *Ty, | 
 |                                                     SourceRange TypeRange, | 
 |                                                     SourceLocation CCLoc) { | 
 |   NestedNameSpecifier *Prefix | 
 |     = static_cast<NestedNameSpecifier *>(SS.getScopeRep()); | 
 |   QualType T = GetTypeFromParser(Ty); | 
 |   return NestedNameSpecifier::Create(Context, Prefix, /*FIXME:*/false, | 
 |                                      T.getTypePtr()); | 
 | } | 
 |  | 
 | bool Sema::ShouldEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS) { | 
 |   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec."); | 
 |  | 
 |   NestedNameSpecifier *Qualifier = | 
 |     static_cast<NestedNameSpecifier*>(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: | 
 |     // These are always namespace scopes.  We never want to enter a | 
 |     // namespace scope from anything but a file context. | 
 |     return CurContext->getLookupContext()->isFileContext(); | 
 |  | 
 |   case NestedNameSpecifier::Identifier: | 
 |   case NestedNameSpecifier::TypeSpec: | 
 |   case NestedNameSpecifier::TypeSpecWithTemplate: | 
 |     // These are never namespace scopes. | 
 |     return true; | 
 |   } | 
 |  | 
 |   // Silence bogus warning. | 
 |   return false; | 
 | } | 
 |  | 
 | /// 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); | 
 | } |