Astrac
commented
7 years ago Also affects 2.11.11 of typelevel-4; this is how I can recreate it using circe: https://github.com/circe/circe/issues/710
It also happens in other situations, not necessarily using the deriveEncoder function:
import io.circe.Encoder
case class Bar[C]()
trait Foo[T]
object Bar {
implicit def e0[T](implicit ev: Foo[Encoder[T]]): Encoder[T] = Encoder[Unit].contramap(_ => ())
implicit def e2[C]: Encoder[Bar[C]] = Encoder[Unit].contramap(_ => ())
implicit val e1: Encoder[Bar[String]] = Encoder[Unit].contramap(_ => ())
}
object Test {
implicitly[Encoder[Bar[String]]]
}Removing any of e1, e2 or e3 will fix the issue but moving any combination of them in a LowPriority trait won't. I tried replacing Encoder with a dummy typeclass but it didn't crash so I suspect that the issue must be caused by some more complex clash involving also the implicits already defined in the Encoder companion object.
travisbrown
TLS version: 2.12.2-bin-typelevel-4
Looks like this is the line with the error.