rust/src/test/compile-fail/mut-cant-alias.rs

// Copyright 2013 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.

use std::cell::RefCell;

fn main() {
    let m = RefCell::new(0);
    let mut b = m.borrow_mut();
    let b1 = b.get();
    let b2 = b.get(); //~ ERROR cannot borrow
}