https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111642
--- Comment #8 from Sergei Trofimovich <slyfox at gcc dot gnu.org> --- With https://gcc.gnu.org/PR111647#c1 I'm convinced it's a gcc's source code bug and we should not try to write calls like `poly_int<1, T>(1, 1)` with mismatching arity.