Function get_ptr

3rd/nlohmann_json/include/nlohmann/json.hpp:3019–3023

                   std::is_pointer<PointerType>::value&&
                   std::is_const<typename std::remove_pointer<PointerType>::type>::value, int >::type = 0 >
    constexpr auto get_ptr() const noexcept -> decltype(std::declval<const basic_json_t&>().get_impl_ptr(std::declval<PointerType>()))
    {
        // delegate the call to get_impl_ptr<>() const
        return get_impl_ptr(static_cast<PointerType>(nullptr));
    }

  private:
    /*!