#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::ops::Not;
#[derive(Debug, PartialEq)]
enum Answer {
    Yes,
    No,
}
impl Not for Answer {
    type Output = Self;
    fn not(self) -> Self::Output {
        match self {
            Answer::Yes => Answer::No,
            Answer::No => Answer::Yes,
        }
    }
}
fn main() {
    assert_eq!(! Answer::Yes, Answer::No);
    assert_eq!(! Answer::No, Answer::Yes);
}