Error code E0705

Note: this error code is no longer emitted by the compiler.

A #![feature] attribute was declared for a feature that is stable in the current edition, but not in all editions.

Erroneous code example:

#![allow(unused)]
#![feature(rust_2018_preview)]
#![feature(test_2018_feature)] // error: the feature
fn main() {
                               // `test_2018_feature` is
                               // included in the Rust 2018 edition
}