#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(clone_to_uninit)]
use std::rc::Rc;
trait Foo: std::fmt::Debug + std::clone::CloneToUninit {
    fn modify(&mut self);
    fn value(&self) -> i32;
}
impl Foo for i32 {
    fn modify(&mut self) {
        *self *= 10;
    }
    fn value(&self) -> i32 {
        *self
    }
}
fn main() {
    let first: Rc<dyn Foo> = Rc::new(1234);
    let mut second = first.clone();
    Rc::make_mut(&mut second).modify();
    assert_eq!(first.value(), 1234);
    assert_eq!(second.value(), 12340);
}