#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::fmt;
struct Foo(f32);
impl fmt::Display for Foo {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        if let Some(precision) = formatter.precision() {
            write!(formatter, "Foo({1:.*})", precision, self.0)
        } else {
            write!(formatter, "Foo({:.2})", self.0)
        }
    }
}
fn main() {
    assert_eq!(format!("{:.4}", Foo(23.2)), "Foo(23.2000)");
    assert_eq!(format!("{}", Foo(23.2)), "Foo(23.20)");
}