def join[A, B, C, D, E, F]()

in src/main/scala/com/twitter/stitch/Arrow.scala [2772:2813]
36 lines of code
12 McCabe index (conditional complexity)

  def join[A, B, C, D, E, F](
    a1: Arrow[A, B],
    a2: Arrow[A, C],
    a3: Arrow[A, D],
    a4: Arrow[A, E],
    a5: Arrow[A, F]
  ): Arrow[A, (B, C, D, E, F)] =
    joinMap(a1, a2, a3, a4, a5)((_, _, _, _, _))

  /**
   * `Arrow.joinMap(a1, a2, a3, a4, a5)(k)` is equivalent to
   * `Arrow.join(a1, a2, a3, a4, a5).map(k.tupled)`,
   * but avoids allocating an intermediate tuple.
   */
  def joinMap[A, B, C, D, E, F, Z](
    a1: Arrow[A, B],
    a2: Arrow[A, C],
    a3: Arrow[A, D],
    a4: Arrow[A, E],
    a5: Arrow[A, F]
  )(
    k: (B, C, D, E, F) => Z
  ): Arrow[A, Z] =
    (a1, a2, a3, a4, a5) match {
      case (Const(Throw(e)), _, _, _, _) => exception(e)
      case (_, Const(Throw(e)), _, _, _) => exception(e)
      case (_, _, Const(Throw(e)), _, _) => exception(e)
      case (_, _, _, Const(Throw(e)), _) => exception(e)
      case (_, _, _, _, Const(Throw(e))) => exception(e)
      case (Const(Return(v1)), _, _, _, _) =>
        joinMap(a2, a3, a4, a5) { (v2, v3, v4, v5) => k(v1, v2, v3, v4, v5) }
      case (_, Const(Return(v2)), _, _, _) =>
        joinMap(a1, a3, a4, a5) { (v1, v3, v4, v5) => k(v1, v2, v3, v4, v5) }
      case (_, _, Const(Return(v3)), _, _) =>
        joinMap(a1, a2, a4, a5) { (v1, v2, v4, v5) => k(v1, v2, v3, v4, v5) }
      case (_, _, _, Const(Return(v4)), _) =>
        joinMap(a1, a2, a3, a5) { (v1, v2, v3, v5) => k(v1, v2, v3, v4, v5) }
      case (_, _, _, _, Const(Return(v5))) =>
        joinMap(a1, a2, a3, a4) { (v1, v2, v3, v4) => k(v1, v2, v3, v4, v5) }
      case _ =>
        JoinMap5(a1, a2, a3, a4, a5, k)
    }