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};
    match x {
      @{f: ref 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));
      }
    }
}