error[E0224]: at least one trait is required for an object type --> $DIR/issue-65673.rs:9:16 | LL | trait Alias = where T: Trait; | -------------- this alias does not contain a trait ... LL | type Ctx = dyn Alias; | ^^^^^^^^^^^^ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0224`.