A #[marker]
trait contained an associated item.
Erroneous code example:
#![feature(marker_trait_attr)]
#![feature(associated_type_defaults)]
#[marker]
trait MarkerConst {
const N: usize; // error!
}
fn main() {}
RunThe items of marker traits cannot be overridden, so there’s no need to have them when they cannot be changed per-type anyway. If you wanted them for ergonomic reasons, consider making an extension trait instead.