#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::ops::{Deref, DerefMut};
struct DerefMutExample<T> {
    value: T,
}
impl<T> Deref for DerefMutExample<T> {
    type Target = T;
    fn deref(&self) -> &Self::Target {
        &self.value
    }
}
impl<T> DerefMut for DerefMutExample<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.value
    }
}
fn main() {
    let mut x = DerefMutExample { value: 'a' };
    *x = 'b';
    assert_eq!('b', x.value);
}