Rust - beginner display

use std::fmt;
use std::fmt::Display;

struct A<T: Display> {
    value: T
}

impl<T> fmt::Display for A<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "I have the value {}", self.value);
    }
}

fn main() {
    let a = A { value: 55 };
    println!("{}", a);
}