Turning Off Warnings

This code produce the two warnings and one error on the previous page.

fn main() {
  let alfa = 7;
  alfa = 9;
}

All we care about right now is the error message. Rust provides as way to suppress warnings (TODO: find the name of these things, "directives", maybe?)

There are several directives available. (TODO: link to the other directives). The one we're
interested in right now is #[allow(unused)]

(TODO: Update based on the one with the ! as well and talk about the difference i.e. #![allow(unused)]

It's applied like this. Give it a shot to see the error message.

SOURCE

#[allow(unused)]
fn main() {
  let alfa = 7;
  alfa = 9;
}

CODE RUNNER