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

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// exec-env:RUST_POISON_ON_FREE=1

fn borrow(x: &int, f: fn(x: &int)) {
    let before = *x;
    f(x);
    let after = *x;
    assert before == after;
}

fn main() {
    let mut x = @3;
    do borrow(x) |b_x| {
        assert *b_x == 3;
        assert ptr::addr_of(&(*x)) == ptr::addr_of(&(*b_x));
        x = @22;

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