error[E0038]: the trait `std::cmp::Eq` cannot be made into an object --> $DIR/trait-alias-object-fail.rs:7:13 | LL | let _: &dyn EqAlias = &123; | ^^^^^^^^^^^ the trait `std::cmp::Eq` cannot be made into an object | = note: the trait cannot use `Self` as a type parameter in the supertraits or where-clauses error[E0191]: the value of the associated type `Item` (from the trait `std::iter::Iterator`) must be specified --> $DIR/trait-alias-object-fail.rs:9:13 | LL | let _: &dyn IteratorAlias = &vec![123].into_iter(); | ^^^^^^^^^^^^^^^^^ associated type `Item` must be specified error: aborting due to 2 previous errors Some errors have detailed explanations: E0038, E0191. For more information about an error, try `rustc --explain E0038`.