Introduction Auto traits are no longer intended to be stabilized and made available to the general public^1. They should remain solely an implementation detail of blessed libraries like core and std. Proposal To reflect this new status of auto traits, I hereby propose to remove the syntax auto trait alongside the feature auto_traits it is gated behind and to introduce the attribute #[rustc_auto_trait] as part of the internal feature rustc_attrs. #![feature(auto_traits)] auto trait Trait {}