1 A `#![feature]` attribute was declared for a feature that is stable in
2 the current edition, but not in all editions.
4 Erroneous code example:
6 ```ignore (limited to a warning during 2018 edition development)
7 #![feature(rust_2018_preview)]
8 #![feature(test_2018_feature)] // error: the feature
9 // `test_2018_feature` is
10 // included in the Rust 2018 edition