# Error code E0551

An invalid meta-item was used inside an attribute.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    #[deprecated(note)] // error!
    fn i_am_deprecated() {}
    }

Meta items are the key-value pairs inside of an attribute. To fix this issue, you need to give a value to the `note` key. Example:

    #![allow(unused)]
    fn main() {
    #[deprecated(note = "because")] // ok!
    fn i_am_deprecated() {}
    }