https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92786
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Yes, this is https://gcc.gnu.org/wiki/VerboseDiagnostics#missing_static_const_definition In C++17 the static member is implicitly 'inline' which means the declaration with an initializer is also a definition.
