Function get_impl

3rd/nlohmann_json/include/nlohmann/json.hpp:3111–3115

                   detail::has_non_default_from_json<basic_json_t, ValueType>::value,
                   int > = 0 >
    ValueType get_impl(detail::priority_tag<1> /*unused*/) const noexcept(noexcept(
                JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>())))
    {
        return JSONSerializer<ValueType>::from_json(*this);
    }

    /*!
    @brief get special-case overload