| A stability attribute has been used outside of the standard library. | |
| Erroneous code example: | |
| ```compile_fail,E0734 | |
| #[stable(feature = "a", since = "b")] // invalid | |
| #[unstable(feature = "b", issue = "none")] // invalid | |
| fn foo(){} | |
| ``` | |
| These attributes are meant to only be used by the standard library and are | |
| rejected in your own crates. |