rust/src/test/run-pass/borrowck-preserve-box-in-discr.rs

// exec-env:RUST_POISON_ON_FREE=1

fn main() {
    let mut x = @{f: ~3};
    alt *x {
      {f: b_x} {
        assert *b_x == 3;
        assert ptr::addr_of(*x.f) == ptr::addr_of(*b_x);

        x = @{f: ~4};

        debug!{"ptr::addr_of(*b_x) = %x", ptr::addr_of(*b_x) as uint};
        assert *b_x == 3;
        assert ptr::addr_of(*x.f) != ptr::addr_of(*b_x);
      }
    }
}