Function try_invoke

dlib/test/constexpr_if.cpp:120–131

    template <typename Func, typename... Args>
    bool try_invoke(Func&& f, Args&&... args)
    {
        return switch_(bools(is_invocable<Func, Args...>{}),
            [&](true_t, auto _) {
                _(std::forward<Func>(f))(std::forward<Args>(args)...);
                return true;
            },
            [](auto...) {
                return false;
            }
        );
    }

    void test_try_invoke()
    {