no-implicit-to-anyref.scala:11: error: type mismatch; found : Int(1) required: AnyRef Note: an implicit exists from scala.Int => java.lang.Integer, but methods inherited from Object are rendered ambiguous. This is to avoid a blanket implicit which would convert any scala.Int to any AnyRef. You may wish to use a type ascription: `x: java.lang.Integer`. 1: AnyRef ^ no-implicit-to-anyref.scala:17: error: type mismatch; found : Any required: AnyRef (null: Any): AnyRef ^ no-implicit-to-anyref.scala:21: error: type mismatch; found : AnyVal required: AnyRef (0: AnyVal): AnyRef ^ no-implicit-to-anyref.scala:27: error: type mismatch; found : Test.AV required: AnyRef Note that AV extends Any, not AnyRef. Such types can participate in value classes, but instances cannot appear in singleton types or in reference comparisons. new AV(0): AnyRef ^ four errors found