[Bug libstdc++/117858] [15 regression] std::optional with a constructor template ctor(T)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117858

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> struct Focus
> {
>     template<typename T>
>     constexpr explicit Focus(T newValue, int t = 0)     {    }

This is not a reasonable constructor, it's going to interfere with all kinds of
type traits that want to check constructibility.