[Bug c/115729] case label does not reduce to an integer constant

[stsp at users dot sourceforge.net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115729

--- Comment #2 from Stas Sergeev <stsp at users dot sourceforge.net> ---
> rejects-valid

You meant accepts-invalid?

Anyway, constexpr makes it consistent, thanks!