// Creating a shared reference does not leak the data to raw pointers,
// not even when interior mutability is involved.

use std::cell::Cell;
use std::ptr;

fn main() { unsafe {
    let x = &mut Cell::new(0);
    let raw = x as *mut Cell<i32>;
    let x = &mut *raw;
    let _shr = &*x;
    // The state here is interesting because the top of the stack is [Unique, SharedReadWrite],
    // just like if we had done `x as *mut _`.
    // If we said that reading from a lower item is fine if the top item is `SharedReadWrite`
    // (one way to maybe preserve a stack discipline), then we could now read from `raw`
    // without invalidating `x`.  That would be bad!  It would mean that creating `shr`
    // leaked `x` to `raw`.
    let _val = ptr::read(raw);
    let _val = *x.get_mut(); //~ ERROR borrow stack
} }