tests/ui/auto-traits/pre-cfg.stderr

   1 warning: `auto` traits are unstable
   2   --> $DIR/pre-cfg.rs:4:1
   3    |
   4 LL | auto trait Foo {}
   5    | ^^^^
   6    |
   7    = note: see issue #13231 <https://github.com/rust-lang/rust/issues/13231> for more information
   8    = help: add `#![feature(auto_traits)]` to the crate attributes to enable
   9    = warning: unstable syntax can change at any point in the future, causing a hard error!
  10    = note: for more information, see issue #65860 <https://github.com/rust-lang/rust/issues/65860>
  11
  12 warning: 1 warning emitted
  13