Rust channel sender error

error.log

error[E0308]: mismatched types
  --> src/lib.rs:15:24
   |
15 |         self.chan.send(w);
   |                        ^ expected type parameter, found a different type parameter
   |
   = note: expected type `A`
              found type `W`

error: aborting due to previous error

lib.rs

use std::io;
use std::sync::mpsc;

// A trait like this is already defined in an external crate.
trait Send {
    fn send<W: io::Write>(&self, w: W);
}

struct ChannelSender<A> {
    chan: mpsc::SyncSender<A>,
}

impl<A> Send for ChannelSender<A> {
    fn send<W: io::Write>(&self, w: W) {
        self.chan.send(w);
    }
}