[Bug c++/86398] New: is_trivially_constructible always returns true even when is_constructible returns false

[arthur.j.odwyer at gmail dot com]

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

            Bug ID: 86398
           Summary: is_trivially_constructible always returns true even
                    when is_constructible returns false
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arthur.j.odwyer at gmail dot com
  Target Milestone: ---

This actually looks like a duplicate of PR80682, but that one was closed as
"fixed" a while back, and the bug is still present.

// https://godbolt.org/g/SfcQiC
#include <type_traits>
int x[] = {
  std::is_trivially_constructible_v<int,void*>,
  std::is_constructible_v<int,void*>,
};
int main() {
    printf("%d %d\n", x[0], x[1]);
}

On Clang this prints "0 0" because `int` is not constructible from `void*`.
On GCC this prints "1 0": `int` is trivially constructible, yet not
constructible, from `void*`.