error[E0038]: the trait `Baz` cannot be made into an object --> $DIR/object-safety-supertrait-mentions-Self.rs:15:31 | LL | fn make_baz(t: &T) -> &dyn Baz { | ^^^^^^^ `Baz` cannot be made into an object | note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit --> $DIR/object-safety-supertrait-mentions-Self.rs:8:13 | LL | trait Baz : Bar { | --- ^^^^^^^^^ ...because it uses `Self` as a type parameter | | | this trait cannot be made into an object... error: aborting due to previous error For more information about this error, try `rustc --explain E0038`.