select! pattern matching with exclusive references in async expr

[coljnr9]

I find that I frequently want to select! over expressions that

• Return pattern-matchable values and
• Require exclusive references to something

When receiving from a UdpSocket, I'd love to do something like

let mut buf = [0; 64];
select! {
    Ok(n) = socket.recv(&mut buf) => { /* Handle successful rx */ },
    Err(e) = socket.recv(&mut buf) => { /* Handle rx error */ },
     _ = another_future => { /* Handle that */ }
}

but I obviously get an error about the multiple borrow of buf

similarly, when receiving from an mpsc::Receiver

select! {
    Some(msg) = receiver.recv() => { /* Handle message */ },
    None = receiver.recv() =>  { /* Handle channel closed */ },
    _ =>  another_future => { /* Handle it */ }
}

And here I get the (expected) error that receiver is mutably borrowed twice.

Right now I handle this by doing the matching outside of the select!, but I'm curious if there's a trick to use something like the above syntax.

Thanks!

[Darksonn]

Select does not support that, you'll have to match separately from the select.