rust/src/test/run-pass/autoderef-method-twice-but-not-thrice.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.

trait double {
    fn double() -> uint;
}

impl @@uint: double {
    fn double() -> uint { **self * 2u }
}

fn main() {
    let x = @@@@@3u;
    assert x.double() == 6u;
}