Static rustc_lint::unit_bindings::UNIT_BINDINGS

pub static UNIT_BINDINGS: &Lint

The unit_bindings lint detects cases where bindings are useless because they have the unit type () as their inferred type. The lint is suppressed if the user explicitly annotates the let binding with the unit type (), or if the let binding uses an underscore wildcard pattern, i.e. let _ = expr, or if the binding is produced from macro expansions.

Example

#![deny(unit_bindings)]

fn foo() {
    println!("do work");
}

pub fn main() {
    let x = foo(); // useless binding
}

{{produces}}

Explanation

Creating a local binding with the unit type () does not do much and can be a sign of a user error, such as in this example:

fn main() {
    let mut x = [1, 2, 3];
    x[0] = 5;
    let y = x.sort(); // useless binding as `sort` returns `()` and not the sorted array.
    println!("{:?}", y); // prints "()"
}