https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107022
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Yes, and the standard says that instantiating std::unordered_map with incomplete types is undefined.
redi at gcc dot gnu.org via Gcc-bugs Fri, 23 Sep 2022 15:14:55 -0700
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107022
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Yes, and the standard says that instantiating std::unordered_map with incomplete types is undefined.