The basic problem is that superTypeReader and superTypeWriter were triggering for Types T and V which were identical, meaning it was getting used even when not necessary due to import upickle.default.given increasing its implicit priority.
This PR adds a : SumOf implicit requirement to V, ensuring that superTypeReader and superTypeWriter only trigger when V is a parent sealed trait/class/enum type, won't trigger when T =:= V as a case class, and thus the .asInstanceOf[TaggedReader[T]] cast is valid
Fixes https://github.com/com-lihaoyi/upickle/issues/469
The basic problem is that
superTypeReaderandsuperTypeWriterwere triggering for TypesTandVwhich were identical, meaning it was getting used even when not necessary due toimport upickle.default.givenincreasing its implicit priority.This PR adds a
: SumOfimplicit requirement toV, ensuring thatsuperTypeReaderandsuperTypeWriteronly trigger whenVis a parentsealed trait/class/enumtype, won't trigger whenT =:= Vas acase class, and thus the.asInstanceOf[TaggedReader[T]]cast is valid