| An unstable feature was used. | |
| Erroneous code example: | |
| ```compile_fail,E0658 | |
| use std::intrinsics; // error: use of unstable library feature `core_intrinsics` | |
| ``` | |
| If you're using a stable or a beta version of rustc, you won't be able to use | |
| any unstable features. In order to do so, please switch to a nightly version of | |
| rustc (by using [rustup]). | |
| If you're using a nightly version of rustc, just add the corresponding feature | |
| to be able to use it: | |
| ``` | |
| #![feature(core_intrinsics)] | |
| use std::intrinsics; // ok! | |
| ``` | |
| [rustup]: https://rust-lang.github.io/rustup/concepts/channels.html |