Error if an extern C declaration matches a previous hidden extern C declaration.

Without this patch we produce an error for

extern "C" {
  void f() {
    extern int b;
  }
}
extern "C" {
  extern float b;
}

but not for

extern "C" {
  void f() {
    extern int b;
  }
}
extern "C" {
  float b;
}

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176867 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 35af7b7..252f94dc 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -5004,10 +5004,7 @@
 
 template<typename T>
 static bool mayConflictWithNonVisibleExternC(const T *ND) {
-  VarDecl::StorageClass SC = ND->getStorageClass();
-  if (ND->isExternC() && (SC == SC_Extern || SC == SC_PrivateExtern))
-    return true;
-  return ND->getDeclContext()->isTranslationUnit();
+  return ND->isExternC() || ND->getDeclContext()->isTranslationUnit();
 }
 
 /// \brief Perform semantic checking on a newly-created variable