Simplify type signature of distinctBy

Author: cybersaurus

core/src/main/scala-2.13+/cats/data/NonEmptyLazyList.scala

@@ -347,10 +347,10 @@ class NonEmptyLazyListOps[A](private val value: NonEmptyLazyList[A])
    */
   override def distinct[AA >: A](implicit O: Order[AA]): NonEmptyLazyList[AA] = distinctBy(identity[AA])
 
-  override def distinctBy[AA >: A, B](f: A => B)(implicit O: Order[B]): NonEmptyLazyList[AA] = {
+  override def distinctBy[B](f: A => B)(implicit O: Order[B]): NonEmptyLazyList[A] = {
     implicit val ord: Ordering[B] = O.toOrdering
 
-    val buf = LazyList.newBuilder[AA]
+    val buf = LazyList.newBuilder[A]
     toLazyList.foldLeft(TreeSet.empty[B]) { (elementsSoFar, a) =>
       val b = f(a)
       if (elementsSoFar(b)) elementsSoFar

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

@@ -605,7 +605,7 @@ class NonEmptyChainOps[A](private val value: NonEmptyChain[A])
   final def distinct[AA >: A](implicit O: Order[AA]): NonEmptyChain[AA] =
     distinctBy(identity[AA])
 
-  final def distinctBy[AA >: A, B](f: A => B)(implicit O: Order[B]): NonEmptyChain[AA] =
+  final def distinctBy[B](f: A => B)(implicit O: Order[B]): NonEmptyChain[A] =
     create(toChain.distinctBy[B](f))
 
   final def sortBy[B](f: A => B)(implicit B: Order[B]): NonEmptyChain[A] = create(toChain.sortBy(f))

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

@@ -52,7 +52,7 @@ private[cats] trait NonEmptyCollection[+A, U[+_], NE[+_]] extends Any {
   def zipWithIndex: NE[(A, Int)]
 
   def distinct[AA >: A](implicit O: Order[AA]): NE[AA]
-  def distinctBy[AA >: A, B](f: A => B)(implicit O: Order[B]): NE[AA]
+  def distinctBy[B](f: A => B)(implicit O: Order[B]): NE[A]
   def sortBy[B](f: A => B)(implicit B: Order[B]): NE[A]
   def sorted[AA >: A](implicit AA: Order[AA]): NE[AA]
   def groupByNem[B](f: A => B)(implicit B: Order[B]): NonEmptyMap[B, NE[A]]

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

@@ -342,10 +342,10 @@ final case class NonEmptyList[+A](head: A, tail: List[A]) extends NonEmptyCollec
    */
   override def distinct[AA >: A](implicit O: Order[AA]): NonEmptyList[AA] = distinctBy(identity[AA])
 
-  override def distinctBy[AA >: A, B](f: A => B)(implicit O: Order[B]): NonEmptyList[AA] = {
+  override def distinctBy[B](f: A => B)(implicit O: Order[B]): NonEmptyList[A] = {
     implicit val ord: Ordering[B] = O.toOrdering
 
-    val buf = ListBuffer.empty[AA]
+    val buf = ListBuffer.empty[A]
     tail.foldLeft(TreeSet(f(head): B)) { (elementsSoFar, a) =>
       val b = f(a)
       if (elementsSoFar(b)) elementsSoFar

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

@@ -238,10 +238,10 @@ final class NonEmptySeq[+A] private (val toSeq: Seq[A]) extends AnyVal with NonE
    */
   override def distinct[AA >: A](implicit O: Order[AA]): NonEmptySeq[AA] = distinctBy(identity[AA])
 
-  override def distinctBy[AA >: A, B](f: A => B)(implicit O: Order[B]): NonEmptySeq[AA] = {
+  override def distinctBy[B](f: A => B)(implicit O: Order[B]): NonEmptySeq[A] = {
     implicit val ord: Ordering[B] = O.toOrdering
 
-    val buf = Seq.newBuilder[AA]
+    val buf = Seq.newBuilder[A]
     tail.foldLeft(TreeSet(f(head): B)) { (elementsSoFar, a) =>
       val b = f(a)
       if (elementsSoFar(b)) elementsSoFar

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

@@ -248,10 +248,10 @@ final class NonEmptyVector[+A] private (val toVector: Vector[A])
    */
   override def distinct[AA >: A](implicit O: Order[AA]): NonEmptyVector[AA] = distinctBy(identity[AA])
 
-  override def distinctBy[AA >: A, B](f: A => B)(implicit O: Order[B]): NonEmptyVector[AA] = {
+  override def distinctBy[B](f: A => B)(implicit O: Order[B]): NonEmptyVector[A] = {
     implicit val ord: Ordering[B] = O.toOrdering
 
-    val buf = Vector.newBuilder[AA]
+    val buf = Vector.newBuilder[A]
     tail.foldLeft(TreeSet(f(head): B)) { (elementsSoFar, a) =>
       val b = f(a)
       if (elementsSoFar(b)) elementsSoFar

tests/shared/src/test/scala-2.13+/cats/tests/NonEmptyLazyListSuite.scala

@@ -49,7 +49,6 @@ class NonEmptyLazyListSuite extends NonEmptyCollectionSuite[LazyList, NonEmptyLa
   checkAll(s"NonEmptyLazyList[Int]", HashTests[NonEmptyLazyList[Int]].hash)
   checkAll(s"Hash[NonEmptyLazyList[Int]]", SerializableTests.serializable(Hash[NonEmptyLazyList[Int]]))
 
-  checkAll("NonEmptyLazyList[Int]", NonEmptyAlternativeTests[NonEmptyLazyList].nonEmptyAlternative[Int, Int, Int])
   checkAll("NonEmptyLazyList[Int]", NonEmptyAlternativeTests[NonEmptyLazyList].nonEmptyAlternative[Int, Int, Int])
   checkAll("NonEmptyAlternative[NonEmptyLazyList]",
            SerializableTests.serializable(NonEmptyAlternative[NonEmptyLazyList])