Add Parallel instance for Ior

core/src/main/scala/cats/data/Ior.scala

@@ -2,6 +2,7 @@ package cats
 package data
 
 import cats.Bifunctor
+import cats.arrow.FunctionK
 import cats.data.Validated.{Invalid, Valid}
 
 import scala.annotation.tailrec
@@ -203,6 +204,44 @@ private[data] sealed abstract class IorInstances extends IorInstances0 {
     new Bifunctor[Ior] {
       override def bimap[A, B, C, D](fab: A Ior B)(f: A => C, g: B => D): C Ior D = fab.bimap(f, g)
     }
+
+  // scalastyle:off cyclomatic.complexity
+  implicit def parallelForIor[E]
+    (implicit E: Semigroup[E]): Parallel[Ior[E, ?], Ior[E, ?]] = new Parallel[Ior[E, ?], Ior[E, ?]]
+  {
+
+    private[this] val identityK: Ior[E, ?] ~> Ior[E, ?] = FunctionK.id
+
+    def parallel: Ior[E, ?] ~> Ior[E, ?] = identityK
+    def sequential: Ior[E, ?] ~> Ior[E, ?] = identityK
+
+    val applicative: Applicative[Ior[E, ?]] = new Applicative[Ior[E, ?]] {
+      def pure[A](a: A): Ior[E, A] = Ior.right(a)
+      def ap[A, B](ff: Ior[E, A => B])(fa: Ior[E, A]): Ior[E, B] =
+        fa match {
+          case Ior.Right(a) => ff match {
+            case Ior.Right(f) => Ior.Right(f(a))
+            case Ior.Both(e1, f) => Ior.Both(e1, f(a))
+            case Ior.Left(e1) => Ior.Left(e1)
+          }
+          case Ior.Both(e1, a) => ff match {
+            case Ior.Right(f) => Ior.Both(e1, f(a))
+            case Ior.Both(e2, f) => Ior.Both(E.combine(e2, e1), f(a))
+            case Ior.Left(e2) => Ior.Left(E.combine(e2, e1))
+          }
+          case Ior.Left(e1) => ff match {
+            case Ior.Right(f) => Ior.Left(e1)
+            case Ior.Both(e2, f) => Ior.Left(E.combine(e2, e1))
+            case Ior.Left(e2) => Ior.Left(E.combine(e2, e1))
+          }
+        }
+    }
+
+    lazy val monad: Monad[Ior[E, ?]] = Monad[Ior[E, ?]]
+  }
+  // scalastyle:on cyclomatic.complexity
+
+
 }
 
 private[data] sealed abstract class IorInstances0 {

tests/src/test/scala/cats/tests/ParallelSuite.scala

@@ -1,4 +1,3 @@
-
 package cats
 package tests
 
@@ -17,7 +16,7 @@ import scala.collection.immutable.SortedSet
 class ParallelSuite extends CatsSuite with ApplicativeErrorForEitherTest {
 
 
-  test("ParTraversing Either should accumulate errors") {
+  test("ParSequence Either should accumulate errors") {
     forAll { es: List[Either[String, Int]] =>
       val lefts = es.collect {
         case Left(e) => e
@@ -27,6 +26,21 @@ class ParallelSuite extends CatsSuite with ApplicativeErrorForEitherTest {
     }
   }
 
+  test("ParSequence Ior should accumulate errors") {
+    forAll { es: List[Ior[String, Int]] =>
+      val lefts = es.map(_.left).collect {
+        case Some(e) => e
+      }.foldMap(identity)
+      es.parSequence.left.getOrElse(Monoid[String].empty) should === (lefts)
+    }
+  }
+
+  test("ParSequence Ior should sequence values") {
+    forAll { es: List[Ior[String, Int]] =>
+      es.parSequence.right should === (es.map(_.toOption).sequence)
+    }
+  }
+
   test("ParTraverse identity should be equivalent to parSequence") {
     forAll { es: List[Either[String, Int]] =>
       es.parTraverse(identity) should === (es.parSequence)
@@ -156,6 +170,7 @@ class ParallelSuite extends CatsSuite with ApplicativeErrorForEitherTest {
   }
 
   checkAll("Parallel[Either[String, ?], Validated[String, ?]]", ParallelTests[Either[String, ?], Validated[String, ?]].parallel[Int, String])
+  checkAll("Parallel[Ior[String, ?], Ior[String, ?]]", ParallelTests[Ior[String, ?], Ior[String, ?]].parallel[Int, String])
   checkAll("Parallel[OptionT[M, ?], Nested[F, Option, ?]]", ParallelTests[OptionT[Either[String, ?], ?], Nested[Validated[String, ?], Option, ?]].parallel[Int, String])
   checkAll("Parallel[EitherT[M, String, ?], Nested[F, Validated[String, ?], ?]]", ParallelTests[EitherT[Either[String, ?], String, ?], Nested[Validated[String, ?], Validated[String, ?], ?]].parallel[Int, String])
   checkAll("Parallel[EitherT[Option, String, ?], Nested[Option, Validated[String, ?], ?]]", ParallelTests[EitherT[Option, String, ?], Nested[Option, Validated[String, ?], ?]].parallel[Int, String])