error[E0658]: use of unstable library feature 'issue_52489_unstable' --> $DIR/issue-52489.rs:5:5 | LL | use issue_52489; | ^^^^^^^^^^^ | = help: add `#![feature(issue_52489_unstable)]` to the crate attributes to enable error: aborting due to previous error For more information about this error, try `rustc --explain E0658`.