Race condition in resume_foreground(DispatcherQueue)

[oldnewthing]

    [[nodiscard]] inline auto resume_foreground(
        Windows::System::DispatcherQueue const& dispatcher,
        Windows::System::DispatcherQueuePriority const priority = Windows::System::DispatcherQueuePriority::Normal) noexcept
    {
        struct awaitable
        {
...
            bool await_suspend(std::experimental::coroutine_handle<> handle)
            {
                m_queued = m_dispatcher.TryEnqueue(m_priority, [handle]
                    {
                        handle();
                    });

                return m_queued;
            }

There is a race condition here: If TryEnqueue succeeds, the coroutine may resume before TryEnqueue returns. In that case, the coroutine has been destructed, and our attempt to use m_queued will AV.

Unit tests randomly fail on my machine due to this bug.