trait Red {}

struct Ball<'a> {
    diameter: &'a i32,
}

impl<'a> Red for Ball<'a> {}

struct StrWrap<'a>(&'a str);

fn foo(string: &str) -> StrWrap<'_> { // Anonymous lifetime
    StrWrap(string)
}

fn main() {
    let num = 5;

    let obj = Box::new(Ball { diameter: &num}) as Box<dyn Red>;
}