https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115596
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Last reconfirmed| |2024-06-23 --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Confirmed. EDG also rejects it: "<source>", line 3: error: default argument is not allowed concept C = requires(T t = {}) { ^ So GCC is definitely the odd one out here.