[Bug c++/89781] Misleading error messages when initializing a static data member in-class

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89781

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yeah I guess the diagnostics could be improved for C++17 and up to say that
using 'inline' would make it valid.