#[non_exhaustive]
pub enum Error {
    Message(String),
    Other,
}

let error = Error::Other;
// Non-exhaustive enums can be matched on exhaustively within the defining crate.
match error {
    Error::Message(ref s) => { },
    Error::Other => { },
}

// Create a new channel, dealing with layer 2 packets
let (mut tx, mut rx) = match datalink::channel(&interface, Default::default()) {
    Ok(Ethernet(tx, rx)) => (tx, rx),
    Ok(_) => panic!("Unhandled channel type"),
    Err(e) => panic!("An error occurred when creating the datalink channel: {}", e)
};

pub enum Channel {
    Ethernet(Box<dyn DataLinkSender, Global>, Box<dyn DataLinkReceiver, Global>),
}

error[E0004]: non-exhaustive patterns: `Ok(_)` not covered
  --> src/main.rs:33:31
   |
33 |     let (_tx, mut rx) = match datalink::channel(&interface, Default::default()) {
   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ pattern `Ok(_)` not covered
   |
note: `Result<Channel, std::io::Error>` defined here
...
   |
   = note: not covered
   = note: the matched value is of type `Result<Channel, std::io::Error>`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
   |
38 ~         },
39 +         Ok(_) => todo!()
   |

For more information about this error, try `rustc --explain E0004`.

// https://docs.rs/pnet_datalink/0.34.0/src/pnet_datalink/lib.rs.html#99
/// A channel for sending and receiving at the data link layer.
#[non_exhaustive]
pub enum Channel {
    /// A datalink channel which sends and receives Ethernet packets.
    Ethernet(Box<dyn DataLinkSender>, Box<dyn DataLinkReceiver>),
}