error[E0072]: recursive type `Bar` has infinite size
  --> $DIR/issue-3008-1.rs:5:1
   |
LL | enum Bar {
   | ^^^^^^^^ recursive type has infinite size
...
LL |     BarSome(Bar)
   |             --- recursive without indirection
   |
help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `Bar` representable
   |
LL |     BarSome(Box<Bar>)
   |             ++++   +

error: aborting due to previous error

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