| warning: `auto` traits are unstable |
| --> $DIR/pre-cfg.rs:4:1 |
| | |
| LL | auto trait Foo {} |
| | ^^^^ |
| | |
| = note: see issue #13231 <https://github.com/rust-lang/rust/issues/13231> for more information |
| = help: add `#![feature(auto_traits)]` to the crate attributes to enable |
| = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date |
| = warning: unstable syntax can change at any point in the future, causing a hard error! |
| = note: for more information, see issue #65860 <https://github.com/rust-lang/rust/issues/65860> |
| |
| warning: 1 warning emitted |
| |
