| An unknown external lang item was used. | |
| Erroneous code example: | |
| ```compile_fail,E0264 | |
| #![feature(lang_items)] | |
| #![allow(internal_features)] | |
| extern "C" { | |
| #[lang = "cake"] // error: unknown external lang item: `cake` | |
| fn cake(); | |
| } | |
| ``` | |
| A list of available external lang items is available in | |
| `compiler/rustc_hir/src/weak_lang_items.rs`. Example: | |
| ``` | |
| #![feature(lang_items)] | |
| #![allow(internal_features)] | |
| extern "C" { | |
| #[lang = "panic_impl"] // ok! | |
| fn cake(); | |
| } | |
| ``` |