Sema: Reject templates in all extern "C" contexts.

Otherwise we'd accept them if the LinkageDecl was not the direct
parent DeclContext. PR17968.

llvm-svn: 200641

1 files changed, 6 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 008ed2755c2..bc66fdedb6b 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -5453,18 +5453,19 @@ Sema::CheckTemplateDeclScope(Scope *S, TemplateParameterList *TemplateParams) {
          (S->getFlags() & Scope::TemplateParamScope) != 0)
     S = S->getParent();
 
-  // C++ [temp]p2:
-  //   A template-declaration can appear only as a namespace scope or
-  //   class scope declaration.
+  // C++ [temp]p4:
+  //   A template [...] shall not have C linkage.
   DeclContext *Ctx = S->getEntity();
-  if (Ctx && isa<LinkageSpecDecl>(Ctx) &&
-      cast<LinkageSpecDecl>(Ctx)->getLanguage() != LinkageSpecDecl::lang_cxx)
+  if (Ctx && Ctx->isExternCContext())
     return Diag(TemplateParams->getTemplateLoc(), diag::err_template_linkage)
              << TemplateParams->getSourceRange();
 
   while (Ctx && isa<LinkageSpecDecl>(Ctx))
     Ctx = Ctx->getParent();
 
+  // C++ [temp]p2:
+  //   A template-declaration can appear only as a namespace scope or
+  //   class scope declaration.
   if (Ctx) {
     if (Ctx->isFileContext())
       return false;