[Bug c++/60430] static_assert and reference to const/constexpr

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60430

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
This is fixed in 7.1.0. I'm adding the testcase and closing the bug.