fn main() {
    let mut i = 0;
    [].iter().for_each(|_: &i32| {
        [].iter().for_each(move |_: &i32| {
            i += 1;
        });
    });
}

warning: variable does not need to be mutable
 --> src/main.rs:3:9
  |
3 |     let mut i = 0;
  |         ----^
  |         |
  |         help: remove this `mut`
  |
  = note: #[warn(unused_mut)] on by default

    Finished dev [unoptimized + debuginfo] target(s) in 1.26s
     Running `target/debug/playground`