| An invalid meta-item was used inside an attribute. | |
| Erroneous code example: | |
| ```compile_fail,E0551 | |
| #[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: | |
| ``` | |
| #[deprecated(note = "because")] // ok! | |
| fn i_am_deprecated() {} | |
| ``` |