Why am I getting an error message?

Question

I am writing a chat server using mio (0.5.1) following this tutorial . With it, I wrote the following handler:

const SERVER_TOKEN: Token = Token(0);

impl Handler for WebSocketServer {
    type Timeout = usize;
    type Message = ();

    fn ready(&mut self, event_loop: &mut EventLoop<WebSocketServer>,
             token: Token, events: EventSet)
    {
        match token {
            SERVER_TOKEN => {
                let client_socket = match self.socket.accept() {
                    Err(e) => {
                        println!("Accept error: {}", e);
                        return;
                    },
                    Ok(None) => unreachable!("Accept has returned 'None'"),
                    Ok(Some((sock, addr))) => sock,
                };

                self.token_counter += 1;
                let new_token = Token(self.token_counter);

                self.clients.insert(new_token, client_socket);
                event_loop.register(&self.clients[&new_token],
                                    new_token, EventSet::readable(),
                                    PollOpt::edge() | PollOpt::oneshot()).unwrap();
            }
        }
    }
}

However, trying to compile it, I get an error message:

error[E0004]: non-exhaustive patterns: `Token(_)` not covered
  --> src/main.rs:23:15
   |
23 |         match token {
   |               ^^^^^ pattern `Token(_)` not covered

error: aborting due to previous error

Although I understand that this should mean that mine matchdoes not cover all possible cases, I do not see how true it is.

Why am I getting this error and how to fix it?

Answer 1

Here SERVER_TOKENis a constant equal Token(0), so simplify the correspondence:

match token {
    Token(0) => { },
}

, , , , Token(1). panic. , , - .

match token {
    SERVER_TOKEN => { },
    x => panic!("Unexpected invalid token {:?}", x),
}

, Token Debug.