def.scala

object Input {
  implicit def inputCodec: CodecJson[Input] = {

    val encoder = {
      case train: Train => Train.trainCodec.encode(train)
      case predict: Predict => Predict.predictCodec.encode(predict)
    }
    val decoder = (json: HCursor) => Predict.predictCodec.decode(json) orElse Train.trainCodec.decode(json)

    CodecJson[Input](encoder, decoder)
  }
}

gistfile1.txt

Error:(38, 19) missing parameter type for expanded function
The argument types of an anonymous function must be fully known. (SLS 8.5)
Expected type was: ?
    val encoder = {
Error:(42, 72) value orElse is not a member of argonaut.DecodeResult[algorithmia.TechSupport.Predict]
    val decoder = (json: HCursor) => Predict.predictCodec.decode(json) orElse Train.trainCodec.decode(json)