Method final_suspend

tests/Issue679.cpp:18–18

    Promise() = default;
    std::suspend_always initial_suspend() { return {}; }
    std::suspend_always final_suspend() noexcept { return {}; }
    void unhandled_exception() { std::rethrow_exception(std::current_exception()); }

    std::suspend_always yield_value(const char* value) {