unit2anyref.scala:2: error: type mismatch;
 found   : Unit
 required: AnyRef
Note: Unit is not implicitly converted to AnyRef.  You can safely
pattern match `x: AnyRef` or cast `x.asInstanceOf[AnyRef]` to do so.
  val x: AnyRef = ()  // this should not succeed.
                  ^
one error found