foo.rs

trait Foo {
    fn foo(&self);
}

#[deriving(Show)]
enum SomeValue {
    Value(int)
}

struct Bar {
    value: SomeValue
}

impl Bar {
    fn new(value: SomeValue) -> Bar {
        Bar { value: value }
    }
}

impl Foo for Bar {
    fn foo(&self) {
        use_value(self.value);
    }
}

fn use_value(value: SomeValue) {
    println!("{}", value);
}

fn main() {
    let bar = Bar::new(SomeValue::Value(1));
}

// foo.rs:22:19: 22:23 error: cannot move out of dereference of `&`-pointer
// foo.rs:22         use_value(self.value);