Rust generic constraints

main.rs

trait Wrap {
    fn pass<F>(&self, consumer: F) where F: Fn(&Self) {
        consumer(self)
    }
}

struct Stringy(String);

impl Wrap for Stringy {
}

fn main() {
    let print_stringy = |x: &Stringy| {
        match x {
            Stringy(s) => println!("{}", s)
        }
    };
    print_stringy(&Stringy("hello world".to_string()))
}