#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(clone_to_uninit)]
use std::clone::CloneToUninit;
use std::mem::offset_of;
use std::rc::Rc;
#[derive(PartialEq)]
struct MyDst<T: ?Sized> {
    label: String,
    contents: T,
}
unsafe impl<T: ?Sized + CloneToUninit> CloneToUninit for MyDst<T> {
    unsafe fn clone_to_uninit(&self, dest: *mut u8) {
        let offset_of_contents = unsafe {
            (&raw const self.contents).byte_offset_from_unsigned(self)
        };
        let label = self.label.clone();
        unsafe {
            self.contents.clone_to_uninit(dest.add(offset_of_contents));
            dest.add(offset_of!(Self, label)).cast::<String>().write(label);
        }
    }
}
fn main() {
    let first: Rc<MyDst<[u8]>> = Rc::new(MyDst {
        label: String::from("hello"),
        contents: [1, 2, 3, 4],
    });
    let mut second = first.clone();
    for elem in Rc::make_mut(&mut second).contents.iter_mut() {
        *elem *= 10;
    }
    assert_eq!(first.contents, [1, 2, 3, 4]);
    assert_eq!(second.contents, [10, 20, 30, 40]);
    assert_eq!(second.label, "hello");
}