use std::ptr::NonNull;

fn main() { unsafe {
    let x = &mut 0;
    let mut ptr1 = NonNull::from(x);
    let mut ptr2 = ptr1.clone();
    let raw1 = ptr1.as_mut();
    let _raw2 = ptr2.as_mut();
    let _val = *raw1; //~ ERROR borrow stack
} }