foo.rs

pub(crate) trait Transport<I: Ip> {
    type SocketCollection;
}

pub(crate) enum Udp {}

impl<I: Ip> Transport<I> for Udp {
    type SocketCollection = UdpSocketCollection<I>;
}

pub(crate) struct SocketCollection<T>
where
    T: Transport<Ipv4>,
    T: Transport<Ipv6>,
{
    v4: <T as Transport<Ipv4>>::SocketCollection,
    v6: <T as Transport<Ipv6>>::SocketCollection,
}

impl<T> Default for SocketCollection<T>
where
    T: Transport<Ipv4>,
    T: Transport<Ipv6>,
    <T as Transport<Ipv4>>::SocketCollection: Default,
    <T as Transport<Ipv6>>::SocketCollection: Default,
{
    fn default() -> Self {
        Self { v4: Default::default(), v6: Default::default() }
    }
}

pub(crate) trait SocketCollectionExt<T>: Ip
where
    T: Transport<Ipv4>,
    T: Transport<Ipv6>,
    T: Transport<Self>,
{
    fn get_collection<D: AsRef<SocketCollection<T>>>(
        dispatcher: &D,
    ) -> &<T as Transport<Self>>::SocketCollection;

    fn get_collection_mut<D: AsMut<SocketCollection<T>>>(
        dispatcher: &mut D,
    ) -> &mut <T as Transport<Self>>::SocketCollection;
}

impl<T> SocketCollectionExt<T> for Ipv4
where
    T: Transport<Ipv4>,
    T: Transport<Ipv6>,
{
    fn get_collection<D: AsRef<SocketCollection<T>>>(
        dispatcher: &D,
    ) -> &<T as Transport<Self>>::SocketCollection {
        &dispatcher.as_ref().v4
    }

    fn get_collection_mut<D: AsMut<SocketCollection<T>>>(
        dispatcher: &mut D,
    ) -> &mut <T as Transport<Self>>::SocketCollection {
        &mut dispatcher.as_mut().v4
    }
}

impl<T> SocketCollectionExt<T> for Ipv6
where
    T: Transport<Ipv4>,
    T: Transport<Ipv6>,
{
    fn get_collection<D: AsRef<SocketCollection<T>>>(
        dispatcher: &D,
    ) -> &<T as Transport<Self>>::SocketCollection {
        &dispatcher.as_ref().v6
    }

    fn get_collection_mut<D: AsMut<SocketCollection<T>>>(
        dispatcher: &mut D,
    ) -> &mut <T as Transport<Self>>::SocketCollection {
        &mut dispatcher.as_mut().v6
    }
}

stdout

error[E0311]: the parameter type `T` may not live long enough
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:100:21
    |
100 |         &dispatcher.as_ref().v4
    |                     ^^^^^^
    |
note: the parameter type `T` must be valid for the anonymous lifetime defined here...
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:98:21
    |
98  |         dispatcher: &D,
    |                     ^^
note: ...so that the reference type `&SocketCollection<T>` does not outlive the data it points at
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:100:21
    |
100 |         &dispatcher.as_ref().v4
    |                     ^^^^^^

error[E0311]: the parameter type `T` may not live long enough
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:106:25
    |
106 |         &mut dispatcher.as_mut().v4
    |                         ^^^^^^
    |
note: the parameter type `T` must be valid for the anonymous lifetime defined here...
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:104:21
    |
104 |         dispatcher: &mut D,
    |                     ^^^^^^
note: ...so that the reference type `&mut SocketCollection<T>` does not outlive the data it points at
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:106:25
    |
106 |         &mut dispatcher.as_mut().v4
    |                         ^^^^^^

error[E0311]: the parameter type `T` may not live long enough
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:118:21
    |
118 |         &dispatcher.as_ref().v6
    |                     ^^^^^^
    |
note: the parameter type `T` must be valid for the anonymous lifetime defined here...
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:116:21
    |
116 |         dispatcher: &D,
    |                     ^^
note: ...so that the reference type `&SocketCollection<T>` does not outlive the data it points at
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:118:21
    |
118 |         &dispatcher.as_ref().v6
    |                     ^^^^^^

error[E0311]: the parameter type `T` may not live long enough
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:124:25
    |
124 |         &mut dispatcher.as_mut().v6
    |                         ^^^^^^
    |
note: the parameter type `T` must be valid for the anonymous lifetime defined here...
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:122:21
    |
122 |         dispatcher: &mut D,
    |                     ^^^^^^
note: ...so that the reference type `&mut SocketCollection<T>` does not outlive the data it points at
   --> ../../src/connectivity/network/netstack3/src/bindings/socket/datagram.rs:124:25
    |
124 |         &mut dispatcher.as_mut().v6
    |                         ^^^^^^

error: aborting due to 4 previous errors