error[E0072]: recursive type `E2` has infinite size --> $DIR/issue-3008-3.rs:4:1 | LL | enum E2<T> { V2(E2<E1>, marker::PhantomData<T>), } | ^^^^^^^^^^ ------ recursive without indirection | help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle | LL | enum E2<T> { V2(Box<E2<E1>>, marker::PhantomData<T>), } | ++++ + error: aborting due to previous error For more information about this error, try `rustc --explain E0072`.