1 A `#[marker]` trait contained an associated item.
3 Erroneous code example:
6 #![feature(marker_trait_attr)]
7 #![feature(associated_type_defaults)]
11 const N: usize; // error!
17 The items of marker traits cannot be overridden, so there's no need to have them
18 when they cannot be changed per-type anyway. If you wanted them for ergonomic
19 reasons, consider making an extension trait instead.