Function swap

uspace/lib/cpp/include/__bits/functional/function.hpp:369–372

    template<class R, class... Args>
    void swap(function<R(Args...)>& f1, function<R(Args...)>& f2)
    {
        f1.swap(f2);
    }

    template<class R, class... Args, class Alloc>
    struct uses_allocator<function<R(Args...)>, Alloc>