Fix an assertion introduced by my previous refactoring.

Add back the test that was triggering the assertion (which I removed mistakenly thinking it was triggering just a warning and not an assertion).  My error was brought to my attention by Rafael (Thanks!).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196721 91177308-0d34-0410-b5e6-96231b3b80d8