https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126233
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- This is https://cplusplus.github.io/LWG/issue4207 "4207. Point of reference for source_location is not specified when used in an default template argument" (but we should be consistent about whether it's at global scope on line 10 or in main() on line 13)
