问C++ broken_promise异常

EN

int main()
{
    std::promise<int> prom;
    std::future<int> fut = prom.get_future();
    auto retFut = std::async(std::launch::async, [prom = std::move(prom)] () mutable {
        cout << "In child" << endl;
        //prom.set_value(4); <-- Shouldn't not having this line cause the exception
    });

    int childValue = fut.get();
    cout << "Child has set the value: " << childValue << endl;
    return 0;
}

void DoSomething(std::future<int>&& fut)
{
    cout << "Waiting for parent to send a value " << endl;
    int val = fut.get();

    cout << "Parent sent value " << val << endl;
}

int main()
{
    std::promise<int> prom;
    std::future<int> fut = prom.get_future();
    auto retFut = std::async(std::launch::async, DoSomething, std::move(fut));
    // prom.set_value(3); <-- This should cause the exception?
    return 0;
}