[Bug libstdc++/111568] std::not_fn can accept non-movable function

[hewillk at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111568

--- Comment #1 from 康桓瑋 <hewillk at gmail dot com> ---
bind_front also seems to missing Mandates:

https://godbolt.org/z/8WPxc44h6

#include <functional>

struct OnlyMovableFun {
  OnlyMovableFun() = default;
  OnlyMovableFun(const OnlyMovableFun&) = delete;
  OnlyMovableFun(OnlyMovableFun&&) = default;
  bool operator()(auto) const;
};

int main() {
  OnlyMovableFun f;
  auto nf = std::bind_front(f); // should be static_assert?
}