Static rustc_lint_defs::builtin::DEREFERENCING_MUT_BINDING

pub static DEREFERENCING_MUT_BINDING: &Lint

The dereferencing_mut_binding lint detects a mut x pattern that resets the binding mode, as this behavior will change in rust 2024.

Example

let x = Some(123u32);
let _y = match &x {
    Some(mut x) => {
        x += 1;
        x
    }
    None => 0,
};

{{produces}}

Explanation

Without the mut, x would have type &u32. Pre-2024, adding mut makes x have type u32, which was deemed surprising. After edition 2024, adding mut will not change the type of x. This lint warns users of editions before 2024 to update their code.