trpl-zh-cn/listings/ch06-enums-and-pattern-matching/no-listing-10-non-exhaustive-match/src/main.rs

fn main() {
    // ANCHOR: here
    fn plus_one(x: Option<i32>) -> Option<i32> {
        match x {
            Some(i) => Some(i + 1),
        }
    }
    // ANCHOR_END: here

    let five = Some(5);
    let six = plus_one(five);
    let none = plus_one(None);
}