[Bug c++/123889] [13/14/15 Regression] C++11 diagnostic about non-constexpr functions is useless

[webrown.cpp at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123889

--- Comment #7 from W E Brown <webrown.cpp at gmail dot com> ---
Bug 124100 exhibits a similar "not constant" diagnostic; possibly related?