[Bug c++/67238] [C++11][C++14]cc1plus crash for nested decltype expression in parameter pack in trailing return type when '-g' enabled

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67238

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Let's add the testcase and close the bug as fixed for 6.0.