Cleanup Const - it's provided by shapeless

Also use the constant type directly for brevity

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

@@ -1,7 +1,7 @@
 package cats.derived
 
 import alleycats.{Empty, EmptyK}
-import shapeless3.deriving.K1
+import shapeless3.deriving.{Const, K1}
 
 object emptyk extends EmptyKDerivation
 

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

@@ -1,7 +1,7 @@
 package cats.derived
 
 import cats.{Eval, Foldable}
-import shapeless3.deriving.{K1, Continue}
+import shapeless3.deriving.{Const, Continue, K1}
 
 object foldable extends FoldableDerivation
 
@@ -43,6 +43,5 @@ trait FoldableDerivation:
     new CoproductFoldable[Foldable, F]{}
 
   given [X]: Foldable[Const[X]] with
-    def foldLeft[A, B](fa: Const[X][A], b: B)(f: (B, A) => B): B = b
-
-    def foldRight[A, B](fa: Const[X][A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] = lb
+    def foldLeft[A, B](fa: X, b: B)(f: (B, A) => B): B = b
+    def foldRight[A, B](fa: X, lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] = lb

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

@@ -1,11 +1,11 @@
 package cats.derived
 
 import cats.Functor
-import shapeless3.deriving.K1
+import shapeless3.deriving.{Const, K1}
 
 object functor extends FunctorDerivation
 
-trait ProductFunctor[T[x[_]] <: Functor[x], F[_]](using inst: K1.Instances[T, F])
+trait GenericFunctor[T[x[_]] <: Functor[x], F[_]](using inst: K1.Instances[T, F])
     extends Functor[F]:
 
   def map[A, B](fa: F[A])(f: A => B): F[B] =
@@ -16,10 +16,7 @@ trait ProductFunctor[T[x[_]] <: Functor[x], F[_]](using inst: K1.Instances[T, F]
 trait FunctorDerivation:
   extension (F: Functor.type)
     inline def derived[F[_]](using gen: K1.Generic[F]): Functor[F] =
-      new ProductFunctor[Functor, F]{}
-
-  given functorGen[F[_]](using inst: => K1.ProductInstances[Functor, F]): Functor[F] =
-    new ProductFunctor[Functor, F]{}
+      new GenericFunctor[Functor, F]{}
 
   given [X]: Functor[Const[X]] with
-    def map[A, B](fa: Const[X][A])(f: A => B): Const[X][B] = fa
+    def map[A, B](fa: X)(f: A => B): X = fa

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

@@ -1,7 +1,7 @@
 package cats.derived
 
 import cats.{Monoid, MonoidK}
-import shapeless3.deriving.K1
+import shapeless3.deriving.{Const, K1}
 
 object monoidk extends MonoidKDerivation
 
@@ -14,7 +14,5 @@ trait MonoidKDerivation:
     inline def derived[F[_]](using gen: K1.Generic[F]): MonoidK[F] = ???
 
   given [X](using X: Monoid[X]): MonoidK[Const[X]] with
-    def empty[A]: Const[X][A] = X.empty
-
-    def combineK[A](x: Const[X][A], y: Const[X][A]): Const[X][A] =
-      X.combine(x, y)
+    def empty[A]: X = X.empty
+    def combineK[A](x: X, y: X): X = X.combine(x, y)

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

@@ -1,7 +1,7 @@
 package cats.derived
 
 import cats.{Semigroup, SemigroupK}
-import shapeless3.deriving.K1
+import shapeless3.deriving.{Const, K1}
 
 object semigroupk extends SemigroupKDerivation
 
@@ -17,5 +17,5 @@ trait SemigroupKDerivation:
       new ProductSemigroupK[SemigroupK, F]{}
 
   given [X](using X: Semigroup[X]): SemigroupK[Const[X]] with
-    def combineK[A](x: Const[X][A], y: Const[X][A]): Const[X][A] =
+    def combineK[A](x: X, y: X): X =
       X.combine(x, y)

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

@@ -1,20 +1,20 @@
 package cats.derived
 
 import cats.{Applicative, Eval, Traverse}
-import shapeless3.deriving.{K1, Continue}
+import shapeless3.deriving.{Const, Continue, K1}
 
 object traverse extends TraverseDerivation
 
 trait ProductTraverse[T[x[_]] <: Traverse[x], F[_]](using inst: K1.ProductInstances[T, F])
-    extends ProductFunctor[T, F], ProductFoldable[T, F], Traverse[F]:
+    extends GenericFunctor[T, F], ProductFoldable[T, F], Traverse[F]:
 
   def traverse[G[_], A, B](fa: F[A])(f: A => G[B])(using G: Applicative[G]): G[F[B]] =
     inst.traverse[A, G, B](fa)([a,b] => (ga: G[a], f: a => b) => G.map(ga)(f))([a] => (x: a) => G.pure(x))([a,b] => (gf: G[a => b], ga: G[a]) => G.ap(gf)(ga))(
       [t[_]] => (trav: T[t], t0: t[A]) => trav.traverse[G, A, B](t0)(f)
     )
 
 trait CoproductTraverse[T[x[_]] <: Traverse[x], F[_]](using inst: K1.CoproductInstances[T, F])
-    extends ProductFunctor[T, F], CoproductFoldable[T, F], Traverse[F]:
+    extends GenericFunctor[T, F], CoproductFoldable[T, F], Traverse[F]:
 
   def traverse[G[_], A, B](fa: F[A])(f: A => G[B])(using G: Applicative[G]): G[F[B]] =
     inst.traverse[A, G, B](fa)([a,b] => (ga: G[a], f: a => b) => G.map(ga)(f))([a] => (x: a) => G.pure(x))([a,b] => (gf: G[a => b], ga: G[a]) => G.ap(gf)(ga))(
@@ -33,11 +33,7 @@ trait TraverseDerivation:
     new CoproductTraverse[Traverse, F]{}
 
   given [X]: Traverse[Const[X]] with
-    override def map[A, B](fa: Const[X][A])(f: A => B): Const[X][B] = fa
-
-    def foldLeft[A, B](fa: Const[X][A], b: B)(f: (B, A) => B): B = b
-
-    def foldRight[A, B](fa: Const[X][A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] = lb
-
-    def traverse[G[_]: Applicative, A, B](fa: Const[X][A])(f: A => G[B]): G[Const[X][B]] =
-      Applicative[G].pure(fa)
+    override def map[A, B](fa: X)(f: A => B): X = fa
+    def foldLeft[A, B](fa: X, b: B)(f: (B, A) => B): B = b
+    def foldRight[A, B](fa: X, lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] = lb
+    def traverse[G[_]: Applicative, A, B](fa: X)(f: A => G[B]): G[X] = Applicative[G].pure(fa)