Order for IorT (#3555)

typelevel · Aug 10, 2020 · a26f161 · a26f161
1 parent 34ff5c2
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diff --git a/core/src/main/scala/cats/data/IorT.scala b/core/src/main/scala/cats/data/IorT.scala
@@ -119,6 +119,9 @@ final case class IorT[F[_], A, B](value: F[Ior[A, B]]) {
   def ===(that: IorT[F, A, B])(implicit eq: Eq[F[Ior[A, B]]]): Boolean =
     eq.eqv(value, that.value)
 
+  def compare(that: IorT[F, A, B])(implicit ord: Order[F[Ior[A, B]]]): Int =
+    ord.compare(value, that.value)
+
   def combine(that: IorT[F, A, B])(implicit F: Apply[F], A: Semigroup[A], B: Semigroup[B]): IorT[F, A, B] =
     IorT(F.map2(this.value, that.value)(_.combine(_)))
 }
@@ -502,6 +505,9 @@ abstract private[data] class IorTInstances1 extends IorTInstances2 {
       lazy val monad: Monad[IorT[F0, E, *]] = Monad[IorT[F0, E, *]]
     }
 
+  implicit def catsDataOrderForIorT[F[_], A, B](implicit F: Order[F[Ior[A, B]]]): Order[IorT[F, A, B]] =
+    new IorTOrder[F, A, B] { val F0: Order[F[Ior[A, B]]] = F }
+
 }
 
 abstract private[data] class IorTInstances2 extends IorTInstances3 {
@@ -535,6 +541,12 @@ sealed private[data] trait IorTEq[F[_], A, B] extends Eq[IorT[F, A, B]] {
   override def eqv(x: IorT[F, A, B], y: IorT[F, A, B]): Boolean = x === y
 }
 
+sealed private[data] trait IorTOrder[F[_], A, B] extends Order[IorT[F, A, B]] {
+  implicit def F0: Order[F[Ior[A, B]]]
+
+  override def compare(x: IorT[F, A, B], y: IorT[F, A, B]): Int = x.compare(y)
+}
+
 sealed private[data] trait IorTMonad[F[_], A] extends Monad[IorT[F, A, *]] with IorTFunctor[F, A] {
   implicit def A0: Semigroup[A]
   implicit override def F0: Monad[F]

diff --git a/tests/src/test/scala/cats/tests/IorTSuite.scala b/tests/src/test/scala/cats/tests/IorTSuite.scala
@@ -2,12 +2,13 @@ package cats.tests
 
 import cats.{~>, Bifunctor, Eval, Foldable, Functor, Id, Monad, MonadError, Traverse}
 import cats.data.{Ior, IorT}
-import cats.kernel.{Eq, Monoid, Semigroup}
+import cats.kernel.{Eq, Monoid, Order, Semigroup}
 import cats.kernel.laws.discipline.{EqTests, MonoidTests, SemigroupTests}
 import cats.laws.discipline._
 import cats.laws.discipline.arbitrary._
 import cats.syntax.eq._
 import org.scalacheck.Prop._
+import cats.kernel.laws.discipline.OrderTests
 
 class IorTSuite extends CatsSuite {
 
@@ -61,6 +62,15 @@ class IorTSuite extends CatsSuite {
     checkAll("Foldable[IorT[ListWrapper, Int, *]]", SerializableTests.serializable(Foldable[IorT[ListWrapper, Int, *]]))
   }
 
+  {
+    implicit val F: Order[ListWrapper[Ior[String, Int]]] = ListWrapper.order[Ior[String, Int]]
+
+    checkAll("IorT[ListWrapper, String, Int]", OrderTests[IorT[ListWrapper, String, Int]].order)
+    checkAll("Order[IorT[ListWrapper, String, Int]]",
+             SerializableTests.serializable(Order[IorT[ListWrapper, String, Int]])
+    )
+  }
+
   {
     implicit val F: Semigroup[ListWrapper[Ior[String, Int]]] = ListWrapper.semigroup[Ior[String, Int]]