either sequence

EitherUtils.scala

package app.utils

import scala.collection.generic.CanBuildFrom
import scala.language.higherKinds

object EitherUtils {
  def sequence[
    OuterTraversable[X1] <: TraversableOnce[X1],
    InnerTraversable[X2] <: TraversableOnce[X2],
    A, B
  ](
    eithers: OuterTraversable[Either[A, InnerTraversable[B]]]
  )(implicit cbf: CanBuildFrom[Nothing, B, InnerTraversable[B]]): Either[A, InnerTraversable[B]] = {
    val builder = cbf()
    eithers.foreach {
      case Left(a) => return Left(a)
      case Right(cc2) => cc2.foreach { builder += _ }
    }
    Right(builder.result())
  }
}