Make derived methods final override (#395)

core/src/main/scala-3/cats/derived/DerivedEq.scala

@@ -21,11 +21,11 @@ object DerivedEq:
     new Coproduct[Eq, A] {}
 
   trait Product[F[x] <: Eq[x], A](using inst: K0.ProductInstances[F, A]) extends Eq[A]:
-    def eqv(x: A, y: A): Boolean = inst.foldLeft2(x, y)(true: Boolean)(
+    final override def eqv(x: A, y: A): Boolean = inst.foldLeft2(x, y)(true: Boolean)(
       [t] => (acc: Boolean, eqt: F[t], x: t, y: t) => Complete(!eqt.eqv(x, y))(false)(true)
     )
 
   trait Coproduct[F[x] <: Eq[x], A](using inst: K0.CoproductInstances[F, A]) extends Eq[A]:
-    def eqv(x: A, y: A): Boolean = inst.fold2(x, y)(false)(
+    final override def eqv(x: A, y: A): Boolean = inst.fold2(x, y)(false)(
       [t] => (eqt: F[t], x: t, y: t) => eqt.eqv(x, y)
     )

core/src/main/scala-3/cats/derived/DerivedFoldable.scala

@@ -16,36 +16,28 @@ object DerivedFoldable:
     def foldRight[A, B](fa: T, lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] = lb
 
   given [F[_], G[_]](using F: Or[F], G: Or[G]): DerivedFoldable[[x] =>> F[G[x]]] =
-    F.unify `compose` G.unify
+    F.unify.compose(G.unify)
 
   given [F[_]](using inst: K1.ProductInstances[Or, F]): DerivedFoldable[F] =
-    new Product(using inst.unify) {}
-
-  given [F[_]](using inst: => K1.CoproductInstances[Or, F]): DerivedFoldable[F] = 
-    new Coproduct(using inst.unify) {}
-
-  trait Product[T[x[_]] <: Foldable[x], F[_]](using inst: K1.ProductInstances[T, F])
-    extends Foldable[F]:
-
-    def foldLeft[A, B](fa: F[A], b: B)(f: (B, A) => B): B =
-      inst.foldLeft[A, B](fa)(b) { [f[_]] => (acc: B, tf: T[f], fa: f[A]) => 
-        Continue(tf.foldLeft(fa, acc)(f))
-      }
-
-    def foldRight[A, B](fa: F[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
-      inst.foldRight[A, Eval[B]](fa)(lb) { [f[_]] => (tf: T[f], fa: f[A], acc: Eval[B]) =>
-        Continue(Eval.defer(tf.foldRight(fa, acc)(f)))
-      }
-
-  trait Coproduct[T[x[_]] <: Foldable[x], F[_]](using inst: K1.CoproductInstances[T, F])
-    extends Foldable[F]:
-
-    def foldLeft[A, B](fa: F[A], b: B)(f: (B, A) => B): B =
-      inst.fold[A, B](fa) { [f[_]] => (tf: T[f], fa: f[A]) =>
-        tf.foldLeft(fa, b)(f)
-      }
-
-    def foldRight[A, B](fa: F[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
-      inst.fold[A, Eval[B]](fa) { [f[_]] => (tf: T[f], fa: f[A]) =>
-        Eval.defer(tf.foldRight(fa, lb)(f))
-      }
+    given K1.ProductInstances[Foldable, F] = inst.unify
+    new Product[Foldable, F] {}
+
+  given [F[_]](using inst: => K1.CoproductInstances[Or, F]): DerivedFoldable[F] =
+    given K1.CoproductInstances[Foldable, F] = inst.unify
+    new Coproduct[Foldable, F] {}
+
+  trait Product[T[x[_]] <: Foldable[x], F[_]](using inst: K1.ProductInstances[T, F]) extends Foldable[F]:
+    final override def foldLeft[A, B](fa: F[A], b: B)(f: (B, A) => B): B =
+      inst.foldLeft[A, B](fa)(b)([f[_]] => (acc: B, tf: T[f], fa: f[A]) => Continue(tf.foldLeft(fa, acc)(f)))
+
+    final override def foldRight[A, B](fa: F[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
+      inst.foldRight[A, Eval[B]](fa)(lb)(
+        [f[_]] => (tf: T[f], fa: f[A], acc: Eval[B]) => Continue(Eval.defer(tf.foldRight(fa, acc)(f)))
+      )
+
+  trait Coproduct[T[x[_]] <: Foldable[x], F[_]](using inst: K1.CoproductInstances[T, F]) extends Foldable[F]:
+    final override def foldLeft[A, B](fa: F[A], b: B)(f: (B, A) => B): B =
+      inst.fold[A, B](fa)([f[_]] => (tf: T[f], fa: f[A]) => tf.foldLeft(fa, b)(f))
+
+    final override def foldRight[A, B](fa: F[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
+      inst.fold[A, Eval[B]](fa)([f[_]] => (tf: T[f], fa: f[A]) => Eval.defer(tf.foldRight(fa, lb)(f)))

core/src/main/scala-3/cats/derived/DerivedFunctor.scala

@@ -23,8 +23,8 @@ object DerivedFunctor:
 
   given [F[_]](using inst: => K1.Instances[Or, F]): DerivedFunctor[F] =
     given K1.Instances[Functor, F] = inst.unify
-    new GenericFunctor[Functor, F] {}
+    new Generic[Functor, F] {}
 
-  trait GenericFunctor[T[x[_]] <: Functor[x], F[_]](using inst: K1.Instances[T, F]) extends Functor[F]:
-    override def map[A, B](fa: F[A])(f: A => B): F[B] =
+  trait Generic[T[x[_]] <: Functor[x], F[_]](using inst: K1.Instances[T, F]) extends Functor[F]:
+    final override def map[A, B](fa: F[A])(f: A => B): F[B] =
       inst.map(fa: F[A])([f[_]] => (tf: T[f], fa: f[A]) => tf.map(fa)(f))

core/src/main/scala-3/cats/derived/DerivedHash.scala

@@ -25,7 +25,7 @@ object DerivedHash:
       extends DerivedEq.Product[F, A],
         Hash[A]:
 
-    def hash(x: A): Int =
+    final override def hash(x: A): Int =
       val arity = x.productArity
       val prefix = x.productPrefix.hashCode
       if arity <= 0 then prefix
@@ -41,5 +41,5 @@ object DerivedHash:
       extends DerivedEq.Coproduct[F, A],
         Hash[A]:
 
-    def hash(x: A): Int =
+    final override def hash(x: A): Int =
       inst.fold[Int](x)([t] => (h: F[t], x: t) => h.hash(x))

core/src/main/scala-3/cats/derived/DerivedMonoid.scala

@@ -19,4 +19,4 @@ object DerivedMonoid:
   trait Product[F[x] <: Monoid[x], A](using inst: K0.ProductInstances[F, A])
       extends DerivedSemigroup.Product[F, A],
         Monoid[A]:
-    val empty: A = inst.construct([A] => (F: F[A]) => F.empty)
+    final override val empty: A = inst.construct([A] => (F: F[A]) => F.empty)

core/src/main/scala-3/cats/derived/DerivedNonEmptyTraverse.scala

@@ -20,37 +20,35 @@ object DerivedNonEmptyTraverse:
       inst: K1.ProductInstances[DerivedTraverse.Or, F]
   ): DerivedNonEmptyTraverse[F] =
     given K1.ProductInstances[Traverse, F] = inst.unify
-    new ProductNonEmptyTraverse[Traverse, F](ev) with DerivedReducible.Product[Traverse, F](ev) {}
+    new Product[Traverse, F](ev)
+      with DerivedReducible.Product[Traverse, F](ev)
+      with DerivedTraverse.Product[Traverse, F] {}
 
   inline given [F[_]](using gen: K1.ProductGeneric[F]): DerivedNonEmptyTraverse[F] =
     product(K1.summonFirst[Or, gen.MirroredElemTypes, Const[Any]].unify)
 
   given [F[_]](using inst: => K1.CoproductInstances[Or, F]): DerivedNonEmptyTraverse[F] =
     given K1.CoproductInstances[NonEmptyTraverse, F] = inst.unify
-    new CoproductNonEmptyTraverse[NonEmptyTraverse, F] {}
+    new Coproduct[NonEmptyTraverse, F] {}
 
-  trait ProductNonEmptyTraverse[T[x[_]] <: Traverse[x], F[_]](ev: NonEmptyTraverse[?])(using
+  trait Product[T[x[_]] <: Traverse[x], F[_]](ev: NonEmptyTraverse[?])(using
       inst: K1.ProductInstances[T, F]
   ) extends NonEmptyTraverse[F],
         DerivedReducible.Product[T, F],
-        DerivedTraverse.ProductTraverse[T, F]:
+        DerivedTraverse.Product[T, F]:
 
-    // FIXME: Why is this override necessary?
-    override def traverse[G[_]: Applicative, A, B](fa: F[A])(f: A => G[B]): G[F[B]] =
-      super[ProductTraverse].traverse(fa)(f)
-
-    override def nonEmptyTraverse[G[_]: Apply, A, B](fa: F[A])(f: A => G[B]): G[F[B]] =
+    final override def nonEmptyTraverse[G[_]: Apply, A, B](fa: F[A])(f: A => G[B]): G[F[B]] =
       traverse[Alt[G], A, B](fa)(f.andThen(Left.apply)) match
         case Left(value) => value
         case Right(_) => ???
 
-  trait CoproductNonEmptyTraverse[T[x[_]] <: NonEmptyTraverse[x], F[_]](using
+  trait Coproduct[T[x[_]] <: NonEmptyTraverse[x], F[_]](using
       inst: K1.CoproductInstances[T, F]
   ) extends NonEmptyTraverse[F],
         DerivedReducible.Coproduct[T, F],
-        DerivedTraverse.CoproductTraverse[T, F]:
+        DerivedTraverse.Coproduct[T, F]:
 
-    override def nonEmptyTraverse[G[_]: Apply, A, B](fa: F[A])(f: A => G[B]): G[F[B]] =
+    final override def nonEmptyTraverse[G[_]: Apply, A, B](fa: F[A])(f: A => G[B]): G[F[B]] =
       inst.fold(fa)([f[_]] => (tf: T[f], fa: f[A]) => tf.nonEmptyTraverse(fa)(f).asInstanceOf[G[F[B]]])
 
   private type Alt[F[_]] = [A] =>> Either[F[A], A]

core/src/main/scala-3/cats/derived/DerivedReducible.scala

@@ -13,7 +13,7 @@ object DerivedReducible:
     summonInline[DerivedReducible[F]].instance
 
   given [F[_], G[_]](using F: Or[F], G: Or[G]): DerivedReducible[[x] =>> F[G[x]]] =
-    F.unify `compose` G.unify
+    F.unify.compose(G.unify)
 
   def product[F[_]](ev: Reducible[?])(using inst: K1.ProductInstances[DerivedFoldable.Or, F]): DerivedReducible[F] =
     given K1.ProductInstances[Foldable, F] = inst.unify
@@ -27,36 +27,40 @@ object DerivedReducible:
     new Coproduct[Reducible, F] {}
 
   trait Product[T[x[_]] <: Foldable[x], F[_]](ev: Reducible[?])(using inst: K1.ProductInstances[T, F])
-    extends DerivedFoldable.Product[T, F], Reducible[F]:
+      extends DerivedFoldable.Product[T, F],
+        Reducible[F]:
 
     private val evalNone = Eval.now(None)
 
-    def reduceLeftTo[A, B](fa: F[A])(f: A => B)(g: (B, A) => B): B =
-      inst.foldLeft[A, Option[B]](fa)(None)(
-        [f[_]] => (acc: Option[B], tf: T[f], fa: f[A]) =>
-          acc match 
-            case Some(b) => Continue(Some(tf.foldLeft(fa, b)(g)))
-            case None => Continue(tf.reduceLeftToOption(fa)(f)(g))
-      ).get
-
-    def reduceRightTo[A, B](fa: F[A])(f: A => B)(g: (A, Eval[B]) => Eval[B]): Eval[B] =
-      inst.foldRight[A, Eval[Option[B]]](fa)(evalNone)(
-        [f[_]] => (tf: T[f], fa: f[A], acc: Eval[Option[B]]) =>
-          Continue(acc.flatMap {
-            case Some(b) => tf.foldRight(fa, Eval.now(b))(g).map(Some.apply)
-            case None => tf.reduceRightToOption(fa)(f)(g)
-          })
-      ).map(_.get)
+    final override def reduceLeftTo[A, B](fa: F[A])(f: A => B)(g: (B, A) => B): B =
+      inst
+        .foldLeft[A, Option[B]](fa)(None)(
+          [f[_]] =>
+            (acc: Option[B], tf: T[f], fa: f[A]) =>
+              acc match
+                case Some(b) => Continue(Some(tf.foldLeft(fa, b)(g)))
+                case None => Continue(tf.reduceLeftToOption(fa)(f)(g))
+        )
+        .get
+
+    final override def reduceRightTo[A, B](fa: F[A])(f: A => B)(g: (A, Eval[B]) => Eval[B]): Eval[B] =
+      inst
+        .foldRight[A, Eval[Option[B]]](fa)(evalNone)(
+          [f[_]] =>
+            (tf: T[f], fa: f[A], acc: Eval[Option[B]]) =>
+              Continue(acc.flatMap {
+                case Some(b) => tf.foldRight(fa, Eval.now(b))(g).map(Some.apply)
+                case None => tf.reduceRightToOption(fa)(f)(g)
+              })
+        )
+        .map(_.get)
 
   trait Coproduct[T[x[_]] <: Reducible[x], F[_]](using inst: K1.CoproductInstances[T, F])
-    extends DerivedFoldable.Coproduct[T, F], Reducible[F]:
+      extends DerivedFoldable.Coproduct[T, F],
+        Reducible[F]:
 
-    def reduceLeftTo[A, B](fa: F[A])(f: A => B)(g: (B, A) => B): B =
-      inst.fold[A, B](fa) { [f[_]] => (tf: T[f], fa: f[A]) =>
-        tf.reduceLeftTo(fa)(f)(g)
-      }
+    final override def reduceLeftTo[A, B](fa: F[A])(f: A => B)(g: (B, A) => B): B =
+      inst.fold[A, B](fa)([f[_]] => (tf: T[f], fa: f[A]) => tf.reduceLeftTo(fa)(f)(g))
 
-    def reduceRightTo[A, B](fa: F[A])(f: A => B)(g: (A, Eval[B]) => Eval[B]): Eval[B] =
-      inst.fold[A, Eval[B]](fa) { [f[_]] => (tf: T[f], fa: f[A]) =>
-        Eval.defer(tf.reduceRightTo(fa)(f)(g))
-      }
+    final override def reduceRightTo[A, B](fa: F[A])(f: A => B)(g: (A, Eval[B]) => Eval[B]): Eval[B] =
+      inst.fold[A, Eval[B]](fa)([f[_]] => (tf: T[f], fa: f[A]) => Eval.defer(tf.reduceRightTo(fa)(f)(g)))

core/src/main/scala-3/cats/derived/DerivedSemigroup.scala

@@ -17,4 +17,5 @@ object DerivedSemigroup:
     new Product[Semigroup, A] {}
 
   trait Product[F[x] <: Semigroup[x], A](using inst: K0.ProductInstances[F, A]) extends Semigroup[A]:
-    def combine(x: A, y: A): A = inst.map2(x, y)([A] => (F: F[A], x: A, y: A) => F.combine(x, y))
+    final override def combine(x: A, y: A): A =
+      inst.map2(x, y)([A] => (F: F[A], x: A, y: A) => F.combine(x, y))

core/src/main/scala-3/cats/derived/DerivedTraverse.scala

@@ -23,27 +23,27 @@ object DerivedTraverse:
 
   given [F[_]](using inst: K1.ProductInstances[Or, F]): DerivedTraverse[F] =
     given K1.ProductInstances[Traverse, F] = inst.unify
-    new ProductTraverse[Traverse, F] {}
+    new Product[Traverse, F] {}
 
   given [F[_]](using inst: => K1.CoproductInstances[Or, F]): DerivedTraverse[F] =
     given K1.CoproductInstances[Traverse, F] = inst.unify
-    new CoproductTraverse[Traverse, F] {}
+    new Coproduct[Traverse, F] {}
 
-  trait ProductTraverse[T[x[_]] <: Traverse[x], F[_]](using inst: K1.ProductInstances[T, F])
+  trait Product[T[x[_]] <: Traverse[x], F[_]](using inst: K1.ProductInstances[T, F])
       extends Traverse[F],
-        DerivedFunctor.GenericFunctor[T, F],
+        DerivedFunctor.Generic[T, F],
         DerivedFoldable.Product[T, F]:
 
-    override def traverse[G[_], A, B](fa: F[A])(f: A => G[B])(using G: Applicative[G]): G[F[B]] =
+    final override def traverse[G[_], A, B](fa: F[A])(f: A => G[B])(using G: Applicative[G]): G[F[B]] =
       val pure = [a] => (x: a) => G.pure(x)
       val map = [a, b] => (ga: G[a], f: a => b) => G.map(ga)(f)
       val ap = [a, b] => (gf: G[a => b], ga: G[a]) => G.ap(gf)(ga)
       inst.traverse[A, G, B](fa)(map)(pure)(ap)([f[_]] => (tf: T[f], fa: f[A]) => tf.traverse(fa)(f))
 
-  trait CoproductTraverse[T[x[_]] <: Traverse[x], F[_]](using inst: K1.CoproductInstances[T, F])
+  trait Coproduct[T[x[_]] <: Traverse[x], F[_]](using inst: K1.CoproductInstances[T, F])
       extends Traverse[F],
-        DerivedFunctor.GenericFunctor[T, F],
+        DerivedFunctor.Generic[T, F],
         DerivedFoldable.Coproduct[T, F]:
 
-    override def traverse[G[_]: Applicative, A, B](fa: F[A])(f: A => G[B]): G[F[B]] =
+    final override def traverse[G[_]: Applicative, A, B](fa: F[A])(f: A => G[B]): G[F[B]] =
       inst.fold(fa)([f[_]] => (tf: T[f], fa: f[A]) => tf.traverse(fa)(f).asInstanceOf[G[F[B]]])