[Bug libstdc++/108323] combine does not change the locale name

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108323

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Also, locale::combine (and has_facet and use_facet, and locale::global and
locale::classic) should use [[nodiscard]].