Bug deriving Either decoder using generic.auto in Circe. (Run w/ Ammonite)

r.sc

import $ivy.`io.circe::circe-core:0.6.1`
import $ivy.`io.circe::circe-generic:0.6.1`
import $ivy.`io.circe::circe-parser:0.6.1`

import io.circe._
import io.circe.syntax._
import io.circe.parser._
import io.circe.generic.auto._

case class Hi(s: Either[Long, String])
case class S(s:  String)


//Fails
assert(decode[Hi]("""{"s":"some"}""").isLeft)

//Fails
assert(decode[Hi]("""{"s":44}""").isLeft)

//works
assert(decode[S]("""{"s":"some"}""").isRight)

I was able to resolve with

implicit def h[A,B](implicit a: Decoder[A], b: Decoder[B]): Decoder[Either[A,B]] = {
        val l: Decoder[Either[A,B]]= a.map(Left.apply)
        val r: Decoder[Either[A,B]]= b.map(Right.apply)
        l or r
    }