IntCirceEnum

scala> import enumeratum.values._
scala> import cats.syntax.either._
scala> import io.circe._
scala> import io.circe.syntax._

scala> sealed abstract class ShirtSize(val value:Int) extends IntEnumEntry
scala> case object ShirtSize extends IntEnum[ShirtSize] with IntCirceEnum[ShirtSize] {
   |  case object Small  extends ShirtSize(1)
   |  case object Medium extends ShirtSize(2)
   |  case object Large  extends ShirtSize(3)
   |  val values = findValues
   | }

scala> val size: ShirtSize = ShirtSize.Small

scala> size.asJson
res0: Json = 1

scala> Json.fromInt(3).as[ShirtSize]
res1: Decoder.Result[ShirtSize] = Right(Large)

scala> Json.fromInt(10).as[ShirtSize]
res2: Decoder.Result[ShirtSize] = Left(DecodingFailure(10 is not a member of enum ShirtSize, List()))