this should compile, right?

foo9.rs

pub trait Even {
    fn say(&self);
}

impl <'a, E: Even> Even for &'a mut E {
    fn say(&self) { }
}

pub trait Odd {
    fn say(&self);
}

fn print_odd<O: Odd>(o: &mut O) {
    o.say();
}

fn main() { }

Fails with:

foo9.rs:14:5: 14:12 error: failed to find an implementation of trait Even for O
foo9.rs:14     o.say();
               ^~~~~~~