fn demo_mut_advanced_unique(mut our: Box<i32>) -> i32 {
  unknown_code_1(&*our);

  // This "re-asserts" uniqueness of the reference: After writing, we know
  // our tag is at the top of the stack.
  *our = 5;

  unknown_code_2();

  // We know this will return 5
  *our //~ ERROR does not exist on the borrow stack
}

// Now comes the evil context
use std::ptr;

static mut LEAK: *mut i32 = ptr::null_mut();

fn unknown_code_1(x: &i32) { unsafe {
    LEAK = x as *const _ as *mut _;
} }

fn unknown_code_2() { unsafe {
    *LEAK = 7;
} }

fn main() {
    demo_mut_advanced_unique(Box::new(0));
}