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 }