test_sane_c_specifier should be renamed as there's no "sane" c specifier now. Oh, it also tests the c specifier for char type, which makes it half-sane.

Maybe keep the format(STR("{:^c}"), true) and format(STR("{:c}"), true) tests, but change to use throw_helper?

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

Thanks for implementing this LWG issue resolution that prevents this wacky combination! 🤪 😺 🎉