sequencing List[Future[A \/ B]]

gistfile1.scala

  type FutureEither[A, B] = EitherT[Future, A, B]
  
  implicit class SequenceOverFutureEither[F[_], A, B](v: F[FutureEither[A, B]])(implicit F0: Traverse[F]) {
    def sequenceR() = v.sequence[({ type λ[R] = FutureEither[A, R] })#λ, B]
  }

I don't see F0 used in the body there, so it seems you could also write that using "context bound" syntax, as F[_] : Traverse. And if you wanted to avoid that type lambda, you could specify it on a seperate line.
Together, that would give you something that looked like:

implicit class SequenceOverFutureEither[F[_] : Traverse, A, B](v: F[FutureEither[A, B]]) {
  type FutureEitherA[R] = FutureEither[A, R]
  def sequenceR() = v.sequence[FutureEitherA, B]
}

Maybe I should just get more used to those type lambdas, though... :/