commit f2005d3de64f9230c6b43b4f4da1866d999446c8
author Richard Smith <richard-llvm@metafoo.co.uk> Tue Dec 29 23:34:32 2015 +0000
committer Richard Smith <richard-llvm@metafoo.co.uk> Tue Dec 29 23:34:32 2015 +0000
tree fbeca65132ed366aae5a8e69cfac59bd1061bf2a
parent 0315920629da8a51b717cbaff05dcd2af42ea5d5

Model NamespaceAliasDecls as having their nominated namespace as an underlying
declaration. This fixes an issue where we would reject (due to a claimed
ambiguity) a case where lookup finds multiple NamespaceAliasDecls from
different scopes that nominate the same namespace.

The C++ standard doesn't make it clear that such a case is in fact valid (which
I'm working on fixing), but there are no relevant rules that distinguish using
declarations and namespace alias declarations here, so it makes sense to treat
them the same way.

llvm-svn: 256601

clang/lib/Sema/SemaDeclCXX.cpp

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 634e699..b4d6175 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -7198,7 +7198,8 @@
     // as if by qualified name lookup.
     LookupResult R(*this, II, IdentLoc, LookupOrdinaryName, ForRedeclaration);
     LookupQualifiedName(R, CurContext->getRedeclContext());
-    NamedDecl *PrevDecl = R.getAsSingle<NamedDecl>();
+    NamedDecl *PrevDecl =
+        R.isSingleResult() ? R.getRepresentativeDecl() : nullptr;
     PrevNS = dyn_cast_or_null<NamespaceDecl>(PrevDecl);
 
     if (PrevNS) {
@@ -7579,9 +7580,9 @@
   }
   
   if (!R.empty()) {
-    NamedDecl *Named = R.getFoundDecl();
-    assert((isa<NamespaceDecl>(Named) || isa<NamespaceAliasDecl>(Named))
-        && "expected namespace decl");
+    NamedDecl *Named = R.getRepresentativeDecl();
+    NamespaceDecl *NS = R.getAsSingle<NamespaceDecl>();
+    assert(NS && "expected namespace decl");
 
     // The use of a nested name specifier may trigger deprecation warnings.
     DiagnoseUseOfDecl(Named, IdentLoc);
@@ -7598,7 +7599,6 @@
 
     // Find enclosing context containing both using-directive and
     // nominated namespace.
-    NamespaceDecl *NS = getNamespaceDecl(Named);
     DeclContext *CommonAncestor = cast<DeclContext>(NS);
     while (CommonAncestor && !CommonAncestor->Encloses(CurContext))
       CommonAncestor = CommonAncestor->getParent();
@@ -8669,7 +8669,7 @@
     }
   }
   assert(!R.isAmbiguous() && !R.empty());
-  NamedDecl *ND = R.getFoundDecl();
+  NamedDecl *ND = R.getRepresentativeDecl();
 
   // Check if we have a previous declaration with the same name.
   LookupResult PrevR(*this, Alias, AliasLoc, LookupOrdinaryName,
@@ -8689,7 +8689,8 @@
   // Find the previous declaration and check that we can redeclare it.
   NamespaceAliasDecl *Prev = nullptr; 
   if (NamedDecl *PrevDecl = PrevR.getAsSingle<NamedDecl>()) {
-    if (NamespaceAliasDecl *AD = dyn_cast<NamespaceAliasDecl>(PrevDecl)) {
+    if (NamespaceAliasDecl *AD =
+            dyn_cast<NamespaceAliasDecl>(PrevR.getRepresentativeDecl())) {
       // We already have an alias with the same name that points to the same
       // namespace; check that it matches.
       if (AD->getNamespace()->Equals(getNamespaceDecl(ND))) {
@@ -8697,7 +8698,7 @@
       } else if (isVisible(PrevDecl)) {
         Diag(AliasLoc, diag::err_redefinition_different_namespace_alias)
           << Alias;
-        Diag(PrevDecl->getLocation(), diag::note_previous_namespace_alias)
+        Diag(AD->getLocation(), diag::note_previous_namespace_alias)
           << AD->getNamespace();
         return nullptr;
       }