box_patterns -

# `box_patterns`

The tracking issue for this feature is: #29641

See also `box_syntax`

Box patterns let you match on `Box<T>`s:

    #![feature(box_patterns)]

    fn main() {
        let b = Some(Box::new(5));
        match b {
            Some(box n) if n < 0 => {
                println!("Box contains negative number {}", n);
            },
            Some(box n) if n >= 0 => {
                println!("Box contains non-negative number {}", n);
            },
            None => {
                println!("No box");
            },
            _ => unreachable!()
        }
    }