fieldOrdinal

In Java it was possible to define this interface in such a way that the ordinal() method was abstract and implemented by each specific Enum, but Kotlin breaks this mechanism. BUT – we're able to cast this to Enum to get to that field. I believe this code gets copied down into each specific Enum subclass, so the dynamic type check for the cast is trivially eliminated in each case. And worst case, Hotspot will be able to inline calls to this from sites that are known to be Enums.