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
   | |
   | recursive type has infinite size
   |
help: insert some indirection to make `E2` representable
   |
LL | enum E2<T> { V2(Box<E2<E1>>, marker::PhantomData<T>), }
   |                 ^^^^      ^
LL | enum E2<T> { V2(Rc<E2<E1>>, marker::PhantomData<T>), }
   |                 ^^^      ^
LL | enum E2<T> { V2(&E2<E1>, marker::PhantomData<T>), }
   |                 ^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0072`.