error[E0658]: the `#[marker]` attribute is an experimental feature --> $DIR/feature-gate-marker_trait_attr.rs:3:1 | LL | #[marker] trait ExplicitMarker {} | ^^^^^^^^^ | = note: see issue #29864 for more information = help: add `#![feature(marker_trait_attr)]` to the crate attributes to enable error: aborting due to previous error For more information about this error, try `rustc --explain E0658`.