https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120775
--- Comment #29 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
If REFL is non-dependent, then I think we should error even in a template,
because there won't be a valid instantiation?
Fair enough on the second point, but that could be fixed by adding
if (require_constant_expression (refl))
cxx_constant_value (refl);
maybe?
