[Bug c++/102305] intrinsic __is_constructible is wrong for templated abstract classes

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102305

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It should be backported IMHO.

I don't see how anybody can be relying on is_default_constructible being wrong,
that doesn't make much sense. You check that trait in SFINAE contexts to see if
you can construct the type, but because the answer is wrong any code that tries
to construct it will get a compiler error.