[Bug libstdc++/93923] [10 Regression] std::is_copy_constructible raises compilation error

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93923

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm unsure. What the standard allows here might not be very helpful for users.