[Bug c++/106759] New: __has_builtin doesn't report __is_nothrow_constructible as supported

[nikolasklauser at berlin dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106759

            Bug ID: 106759
           Summary: __has_builtin doesn't report
                    __is_nothrow_constructible as supported
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nikolasklauser at berlin dot de
  Target Milestone: ---

__has_builtin normally reports if builtin type traits are supported, but
__has_builtin(__is_nothrow_constructible) is false.

Reproducer: (Godbolt: https://godbolt.org/z/T6d7M6jx7)

#if __has_builtin(__is_nothrow_constructible)
#  error "has builtin" // should error here, but doesn't
#endif

int main() { return __is_nothrow_constructible(int); }