semiauto-sealed-trait-option3.scala

semiauto-sealed-trait-option3.scala

sealed trait Test1
object Test1 {
  case object Member extends Test1
}

sealed trait Test2
object Test2 {
  sealed trait SubTrait extends Test2
  case object Member extends SubTrait
}

sealed trait Test3
object Test3 {
  case class Member() extends Test3
}

// this succeeds and derives a `Decoder[Member.type]` automatically
io.circe.Decoder.derived[Test1]
// this succeeds and derives a `Decoder[SubTrait]` automatically
io.circe.Decoder.derived[Test2]
// this fails because there is no `Decoder[Member]`
io.circe.Decoder.derived[Test3]