rust dynamic dispatch

trait Foo {
    fn method(&self) -> String;
}
struct S1 {
    a: u8,
}
struct S2 {
    a: String,
}
impl Foo for S1 {
    fn method(&self) -> String { format!("u8: {}", self.a) }
}

impl Foo for S2 {
    fn method(&self) -> String { format!("string: {}", self.a) }
}
fn do_something(x: &Box<dyn Foo>) {
    println!("{}",x.method());
}

fn main() {

    //let x = &S1{a:5u8};
    //let y = &S2{a:"Hello".to_string()};

    let list_of_foo:Vec<Box<dyn Foo>> = vec![
        Box::new(S1{a:5u8}),
        Box::new(S2{a:"Hello".to_string()})];
    for i in list_of_foo.iter() {

        do_something(i);
    }

    println!("Hello, world!");
}