clippy::reversed_empty_ranges: this range is empty so it will yield no values

What you see

error: this range is empty so it will yield no values
 --> main.rs:2:6
  |
2 |     (10..=0).for_each(|x| println!("{}", x));
  |      ^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#reversed_empty_ranges
  = note: `#[deny(clippy::reversed_empty_ranges)]` on by default
help: consider using the following if you are attempting to iterate over this range in reverse
  |
2 -     (10..=0).for_each(|x| println!("{}", x));
2 +     ((0..=10).rev()).for_each(|x| println!("{}", x));
  |

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

Empty ranges yield no values so iterating them is a no-op. Moreover, trying to use a reversed range to index a slice will panic at run-time.

Code that is almost certainly wrong. Denied by default: the build fails until you fix it or allow it.

How to fix it

Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:

Flagged

fn main() {
    (10..=0).for_each(|x| println!("{}", x));

    let arr = [1, 2, 3, 4, 5];
    let sub = &arr[3..1];
}

Write this instead

fn main() {
    (0..=10).rev().for_each(|x| println!("{}", x));

    let arr = [1, 2, 3, 4, 5];
    let sub = &arr[1..3];
}

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

#[allow(clippy::reversed_empty_ranges)]
fn my_function() { /* ... */ }

[lints.clippy]
reversed_empty_ranges = "allow"

cargo clippy -- -A clippy::reversed-empty-ranges

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.