## Keyboard shortcuts

Press `←` or `→` to navigate between chapters

Press `S` or `/` to search in the book

Press `?` to show this help

Press `Esc` to hide this help

# Error code E0734

A stability attribute has been used outside of the standard library.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    #[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.