error[E0072]: recursive type `Bar` has infinite size
  --> $DIR/issue-3008-1.rs:15:1
   |
LL | enum Bar {
   | ^^^^^^^^ recursive type has infinite size
...
LL |     BarSome(Bar)
   |             ---- recursive without indirection
   |
   = help: insert indirection (e.g., a `Box`, `Rc`, or `&`) at some point to make `Bar` representable

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0072"