error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
  --> $DIR/return-cycle-2.rs:6:34
   |
LL |     fn as_ref(_: i32, _: i32) -> _ {
   |                                  ^
   |                                  |
   |                                  not allowed in type signatures
   |                                  help: replace with the correct return type: `Token<&'static T>`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0121`.