[Bug c++/120306] Copy constructor with requires (!std::copy_constructible) is available

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120306

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This seems clearly undefined nonsense, so what difference does it make whether
it compiles?

copy_constructible<S> depends on an incomplete type, for a start.