#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::fmt;
struct Foo(i32);
impl fmt::Display for Foo {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        assert!(formatter.sign_aware_zero_pad());
        assert_eq!(formatter.width(), Some(4));
        write!(formatter, "{}", self.0)
    }
}
fn main() {
    assert_eq!(format!("{:04}", Foo(23)), "23");
}