Do you know why Validated is covariant on its two type (like Either) but EitherT is invariant?
sealed abstract class Validated[+E, +A]
final case class EitherT[F[_], A, B]
julien-truffaut
👍1
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Wouldn鈥檛 it require F[+_]? Which limits us. Note Functor has widen and Bifunctor has leftWiden which you can use like explicit covariance.
johnynek
on 3 Jul 2018
👍3
@johnynek you're probably right, make sense. I guess it is just annoying that we have to treat Either and EitherT differently in a for comprehension. It doesn't help that intellij doesn't recognize leftWiden (but that's another issue).
julien-truffaut
on 3 Jul 2018
Has anyone got any clue why IntelliJ doesn't recognise leftWiden?
henricook
on 13 Jul 2018
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Most helpful comment
Wouldn鈥檛 it require
F[+_]? Which limits us. Note Functor has widen and Bifunctor has leftWiden which you can use like explicit covariance.