`while let`

A while let loop is a combination of a while loop and a let statement. It allows you to execute the loop body only if the pattern matches.

    let mut option = Option::Some(0_usize);
 
    // "while `let` destructures `option` into `Some(i)`,
    // evaluate the block (`{}`), else `break`
    while let Option::Some(i) = option {
        if i > 0 {
            option = Option::None;
        } else {
            option = Option::Some(i + 1);
        }
    }

See also