I am trying to map an HList
of Xor
to an HList
of ValidatedNel
and got an error:
scala> type Result[A] = Xor[String, A]
defined type alias Result
scala> type Validation[A] = ValidatedNel[String, A]
defined type alias Validation
scala> val r0 = Xor.right(0)
r0: cats.data.Xor[Nothing,Int] = Right(0)
scala> val r1 = Xor.left("xxx")
r1: cats.data.Xor[String,Nothing] = Left(xxx)
scala> import shapeless._
import shapeless._
scala> val rs = r0 :: r1 :: HNil
rs: shapeless.::[cats.data.Xor[Nothing,Int],shapeless.::[cats.data.Xor[String,Nothing],shapeless.HNil]] = Right(0) :: Left(xxx) :: HNil
scala> object toValidation extends (Result ~> Validation) { def apply[T](r: Result[T]): Validation[T] = r.toValidatedNel }
defined object toValidation
scala> rs map toValidation
<console>:41: error: type mismatch;
found : toValidation.type
required: shapeless.Poly
rs map toValidation
What's wrong with the code above and how to fix it ?
Could you double check your imports?
I suspect that ~>
references the natural transformation from cats
instead of Poly from shapeless
.
Importing shapeless.poly._
before defining the toValidation
object should get rid of that error.