While Let

• Similar to if let, while let can make awkward match sequences more tolerable

#![allow(unused)]
fn main() {
    // Make `optional` of type `Option<i32>`
    let mut optional = Some(0);

    // Repeatedly try this test.
    loop {
        match optional {
            // If `optional` destructures, evaluate the block.
            Some(i) => {
                if i > 9 {
                    println!("Greater than 9, quit!");
                    optional = None;
                } else {
                    println!("`i` is `{:?}`. Try again.", i);
                    optional = Some(i + 1);
                }
                // ^ Requires 3 indentations!
            }
            // Quit the loop when the destructure fails:
            _ => {
                break;
            } // ^ Why should this be required? There must be a better way!
        }
    }
}