Method ~timer

source/timers/timer.cpp:37–39

timer::timer(std::shared_ptr<timer_state_base> timer_impl) noexcept : m_state(std::move(timer_impl)) {}

timer::~timer() noexcept {
    cancel();
}

void timer::throw_if_empty(const char* error_message) const {
    if (static_cast<bool>(m_state)) {