Implement DR 373 "Lookup on namespace qualified name in using-directive"

Summary:
3.4.6 [basic.lookup.udir] paragraph 1:
In a using-directive or namespace-alias-definition, during the lookup for a namespace-name or for a name in a nested-name-specifier, only namespace names are considered.

Reviewers: rsmith, aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D30848

llvm-svn: 298126

1 files changed, 16 insertions, 15 deletions

diff --git a/clang/lib/Sema/SemaCXXScopeSpec.cpp b/clang/lib/Sema/SemaCXXScopeSpec.cpp
index ee4317fe887..6f1b8d2e96c 100644
--- a/clang/lib/Sema/SemaCXXScopeSpec.cpp
+++ b/clang/lib/Sema/SemaCXXScopeSpec.cpp
@@ -461,6 +461,7 @@ class NestedNameSpecifierValidatorCCC : public CorrectionCandidateCallback {
 ///        are allowed.  The bool value pointed by this parameter is set to
 ///       'true' if the identifier is treated as if it was followed by ':',
 ///        not '::'.
+/// \param OnlyNamespace If true, only considers namespaces in lookup.
 ///
 /// This routine differs only slightly from ActOnCXXNestedNameSpecifier, in
 /// that it contains an extra parameter \p ScopeLookupResult, which provides
@@ -473,15 +474,15 @@ class NestedNameSpecifierValidatorCCC : public CorrectionCandidateCallback {
 /// scope if it *knows* that the result is correct.  It should not return in a
 /// dependent context, for example. Nor will it extend \p SS with the scope
 /// specifier.
-bool Sema::BuildCXXNestedNameSpecifier(Scope *S,
-                                       NestedNameSpecInfo &IdInfo,
-                                       bool EnteringContext,
-                                       CXXScopeSpec &SS,
+bool Sema::BuildCXXNestedNameSpecifier(Scope *S, NestedNameSpecInfo &IdInfo,
+                                       bool EnteringContext, CXXScopeSpec &SS,
                                        NamedDecl *ScopeLookupResult,
                                        bool ErrorRecoveryLookup,
-                                       bool *IsCorrectedToColon) {
+                                       bool *IsCorrectedToColon,
+                                       bool OnlyNamespace) {
   LookupResult Found(*this, IdInfo.Identifier, IdInfo.IdentifierLoc,
-                     LookupNestedNameSpecifierName);
+                     OnlyNamespace ? LookupNamespaceName
+                                   : LookupNestedNameSpecifierName);
   QualType ObjectType = GetTypeFromParser(IdInfo.ObjectType);
 
   // Determine where to perform name lookup
@@ -594,7 +595,9 @@ bool Sema::BuildCXXNestedNameSpecifier(Scope *S,
         return true;
       }
       // Replacement '::' -> ':' is not allowed, just issue respective error.
-      Diag(R.getNameLoc(), diag::err_expected_class_or_namespace)
+      Diag(R.getNameLoc(), OnlyNamespace
+                               ? diag::err_expected_namespace_name
+                               : diag::err_expected_class_or_namespace)
           << IdInfo.Identifier << getLangOpts().CPlusPlus;
       if (NamedDecl *ND = R.getAsSingle<NamedDecl>())
         Diag(ND->getLocation(), diag::note_entity_declared_at)
@@ -819,19 +822,17 @@ bool Sema::BuildCXXNestedNameSpecifier(Scope *S,
   return true;
 }
 
-bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
-                                       NestedNameSpecInfo &IdInfo,
-                                       bool EnteringContext,
-                                       CXXScopeSpec &SS,
+bool Sema::ActOnCXXNestedNameSpecifier(Scope *S, NestedNameSpecInfo &IdInfo,
+                                       bool EnteringContext, CXXScopeSpec &SS,
                                        bool ErrorRecoveryLookup,
-                                       bool *IsCorrectedToColon) {
+                                       bool *IsCorrectedToColon,
+                                       bool OnlyNamespace) {
   if (SS.isInvalid())
     return true;
 
-  return BuildCXXNestedNameSpecifier(S, IdInfo,
-                                     EnteringContext, SS,
+  return BuildCXXNestedNameSpecifier(S, IdInfo, EnteringContext, SS,
                                      /*ScopeLookupResult=*/nullptr, false,
-                                     IsCorrectedToColon);
+                                     IsCorrectedToColon, OnlyNamespace);
 }
 
 bool Sema::ActOnCXXNestedNameSpecifierDecltype(CXXScopeSpec &SS,