Rust Guide section on enums is confusing since PartialEq, Eq traits are not derived by default

[cdouglass]

The guide gives example code (below) that doesn't compile for this reason, but does not mention deriving anywhere, and I found this confusing.

enum Ordering {
    Less,
    Equal,
    Greater,
}

fn cmp(a: int, b: int) -> Ordering {
    if a < b { Less }
    else if a > b { Greater }
    else { Equal }
}

fn main() {
    let x = 5i;
    let y = 10i;

    let ordering = cmp(x, y);

    if ordering == Less {
        println!("less");
    } else if ordering == Greater {
        println!("greater");
    } else if ordering == Equal {
        println!("equal");
    }
}

[steveklabnik]

As the guide says, the enum is provided by Rust itself. You have re-defined and shadowed the original enum. If you don't, it works just fine.