1 The lang attribute is intended for marking special items that are built-in to
2 Rust itself. This includes special traits (like `Copy` and `Sized`) that affect
3 how the compiler behaves, as well as special functions that may be automatically
4 invoked (such as the handler for out-of-bounds accesses when indexing a slice).
5 Erroneous code example:
8 #![feature(lang_items)]
11 fn cookie() -> ! { // error: definition of an unknown language item: `cookie`