[Bug libstdc++/86398] [8/9 Regression] is_trivially_constructible always returns true even when is_constructible returns false

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86398

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Arthur O'Dwyer from comment #0)
> This actually looks like a duplicate of PR80682, but that one was closed as
> "fixed" a while back, and the bug is still present.

Definitely not a dup. The testcase for PR 80682 no longer fails, and the
testcase for  this one didn't fail until the fix for 80682 was committed. So
it's caused by it, and so can't possibly be a dup.