// Copyright 2015 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.

#[derive(Clone, Debug, PartialEq)]
enum Expression {
    Dummy,
    Add(Box<Expression>),
}

use Expression::*;

fn simplify(exp: Expression) -> Expression {
    match exp {
        Add(n) => *n.clone(),
        _ => Dummy
    }
}

fn main() {
    assert_eq!(simplify(Add(Box::new(Dummy))), Dummy);
}