Error code E0556

The feature attribute was badly formed.

Erroneous code example:

#![allow(unused)] #![feature(foo_bar_baz, foo(bar), foo = "baz", foo)] // error! #![feature] // error! #![feature = "foo"] // error! fn main() { }

The feature attribute only accept a "feature flag" and can only be used on nightly. Example:

#![feature(flag)]