Merge pull request #1105 from peterneyens/nested-unapply

Add an Unapply with the signature of Nested.
typelevel · Jun 9, 2016 · 8b2c42c · 8b2c42c
2 parents e78666f + b02af7d
commit 8b2c42c
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diff --git a/core/src/main/scala/cats/Unapply.scala b/core/src/main/scala/cats/Unapply.scala
@@ -168,4 +168,16 @@ private[cats] sealed abstract class Unapply3Instances {
      def TC: TC[F[AA, B, ?]] = tc
      def subst: F[AA, B, C] => M[A] = identity
    }
+
+  type Aux3Nested[TC[_[_]], MA, F[_[_], _[_], _], AA[_], BB[_], C] = Unapply[TC, MA] {
+    type M[X] = F[AA, BB, X]
+    type A = C
+  }
+
+  implicit def unapply3Nested[TC[_[_]], MA, F[_[_], _[_], _], AA[_], BB[_], C](implicit tc: TC[F[AA, BB, ?]]): Aux3Nested[TC, F[AA, BB, C], F, AA, BB, C] = new Unapply[TC, F[AA, BB, C]] {
+    type M[X] = F[AA, BB, X]
+    type A = C
+    def TC: TC[F[AA, BB, ?]] = tc
+    def subst: F[AA, BB, C] => M[C] = identity
+  }
 }
diff --git a/tests/src/test/scala/cats/tests/UnapplyTests.scala b/tests/src/test/scala/cats/tests/UnapplyTests.scala
@@ -29,4 +29,11 @@ class UnapplyTests extends CatsSuite {
   }
 
   checkAll("Unapply[Functor, Option[String]]", SerializableTests.serializable(Unapply[Functor, Option[String]]))
+
+  test("Unapply works for F[_[_], _[_], _]") {
+    val x: List[Option[Int]] = List(Option(1), Option(2))
+    val y: Nested[List, Option, Int] = Nested(x)
+
+    y.map(_ + 1).value should === (x.map(_.map(_ + 1)))
+  }
 }