unused_variables warning on Context

[gdesmott]

#[async_handler]
impl Handler<Msg> for MyActor {
    type Result = usize;

    async fn handle(&mut self, _msg: Msg, ctx: &mut Context<Self>) -> Self::Result {
        dbg!(&ctx);
        self.0 = 30;
        sleep(Duration::from_secs(3)).await;
        self.0 -= 1;
        self.0
    }
}

This raises this warning while ctx is actually used.

warning: unused variable: `ctx`
  --> examples/hello.rs:22:43
   |
22 |     async fn handle(&mut self, _msg: Msg, ctx: &mut Context<Self>) -> Self::Result {
   |                                           ^^^ help: if this is intentional, prefix it with an underscore: `_ctx`
   |
   = note: `#[warn(unused_variables)]` on by default