https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80507
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- I'm not sure if the PR 59123 change was meant to apply to static data members. The example in PR 59123 is valid C++, but your code is not. In any case, the change in semantics is almost certainly due to the support for C++17 inline variables.
