E0522 - Error codes index
Description: Book listing all Rust error codes

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# Error code E0522

The lang attribute was used in an invalid context.

Erroneous code example:

    #![allow(unused)]
    #![feature(lang_items)]

    fn main() {
    #[lang = "cookie"]
    fn cookie() -> ! { // error: definition of an unknown lang item: `cookie`
        loop {}
    }
    }

The lang attribute is intended for marking special items that are built-in to Rust itself. This includes special traits (like `Copy` and `Sized`) that affect how the compiler behaves, as well as special functions that may be automatically invoked (such as the handler for out-of-bounds accesses when indexing a slice).