[Bug c++/101557] the value of '' is not usable in a constant expression

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101557

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Federico Kircheis from comment #2)
> clang does not reject it:
> 
> https://godbolt.org/z/8Mq1e3o3j

clang 11 does reject it but clang 12 does NOT reject it.