Check in LLVM r95781.
diff --git a/test/Parser/cxx-namespace-alias.cpp b/test/Parser/cxx-namespace-alias.cpp
new file mode 100644
index 0000000..2e4d7af
--- /dev/null
+++ b/test/Parser/cxx-namespace-alias.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -parse-noop -verify %s
+
+namespace A = B;
+
+namespace A = !; // expected-error {{expected namespace name}}
+namespace A = A::!; // expected-error {{expected namespace name}}
+
+