[Bug c++/118543] Previous forward declaration of enum causes early instantiation of later definition

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118543

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I suspect this code is IFNDR because a non-template form is invalid .
And GCC produces:
<source>:14:25: error: 'static constexpr T S::f(char)' called in a constant
expression before its definition is complete