Why is this an issue?

Returning the unit type from a closure expecting an Ord type is likely a mistake caused by an extra semi-colon. This is because the unit type implements Ord but doesn’t serve the intended sorting purpose, making the code misleading and potentially incorrect.

Code examples

Noncompliant code example

let mut twins = vec![(1, 1), (2, 2)];
twins.sort_by_key(|x| { x.1; }); // Noncompliant: Closure returns unit type due to unnecessary semi-colon.

Compliant solution

let mut twins = vec![(1, 1), (2, 2)];
twins.sort_by_key(|x| x.1); // Compliant: Closure correctly returns an `Ord` type.

Resources

Documentation

• Clippy Lints - https://rust-lang.github.io/rust-clippy/master/index.html#unit_return_expecting_ord