Addressing feedback.

Author: katzdm

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -269,7 +269,7 @@ def err_expected_semi_after_namespace_name : Error<
 def err_unexpected_namespace_attributes_alias : Error<
   "attributes cannot be specified on namespace alias">;
 def err_unexpected_qualified_namespace_alias : Error<
-  "unexpected nested name specifier in namespace alias definition">;
+  "namespace alias must be a single identifier">;
 def err_unexpected_nested_namespace_attribute : Error<
   "attributes cannot be specified on a nested namespace definition">;
 def err_inline_namespace_alias : Error<"namespace alias cannot be inline">;

clang/lib/Parse/ParseDeclCXX.cpp

@@ -141,7 +141,10 @@ Parser::DeclGroupPtrTy Parser::ParseNamespace(DeclaratorContext Context,
       return nullptr;
     }
     if (!ExtraNSs.empty()) {
-      Diag(IdentLoc, diag::err_unexpected_qualified_namespace_alias);
+      Diag(ExtraNSs.front().NamespaceLoc,
+           diag::err_unexpected_qualified_namespace_alias)
+          << SourceRange(ExtraNSs.front().NamespaceLoc,
+                         ExtraNSs.back().IdentLoc);
       SkipUntil(tok::semi);
       return nullptr;
     }

clang/test/SemaCXX/namespace-alias.cpp

@@ -48,7 +48,7 @@ namespace I {
 
   namespace A2 = A1;
 
-  namespace A3::extra::specifiers = A2;  // expected-error {{unexpected nested name specifier}}
+  namespace A3::extra::specifiers = A2;  // expected-error {{alias must be a single identifier}}
 }
 
 int f() {