Strict semiauto derivation for Scala 3

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

@@ -30,11 +30,10 @@ object Derived:
     extension [I[f[_[_, _]], t[_, _]] <: K2.Instances[f, t], F[_[_, _]], T[_, _]](inst: I[Or2[F], T])
       @targetName("unifyK2") def unify: I[F, T] = inst
 
-  abstract private[derived] class Lazy[A](f: () => A) extends Serializable:
+  private[derived] class Lazy[A](f: () => A) extends Serializable:
     final protected lazy val delegate: A = f()
 
 sealed abstract class OrInstances:
-  inline given [A]: Derived.Or[A] = summonFrom {
+  inline given [A]: Derived.Or[A] = summonFrom:
     case instance: A => Derived.Or(instance)
     case derived: Derived[A] => Derived.Or(derived.instance)
-  }

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

@@ -20,22 +20,32 @@ object DerivedApplicative:
     import DerivedApplicative.given
     summonInline[DerivedApplicative[F]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[F[_]]: Applicative[F] =
+    import Strict.given
+    summonInline[DerivedApplicative[F]].instance
+
   given [T](using T: Monoid[T]): DerivedApplicative[Const[T]] = new Applicative[Const[T]]:
     def pure[A](x: A): T = T.empty
     def ap[A, B](ff: T)(fa: T): T = T.combine(ff, fa)
 
   given nested[F[_], G[_]](using F: => Or[F], G: => Or[G]): DerivedApplicative[[x] =>> F[G[x]]] =
-    new Derived.Lazy(() => F.unify.compose(G.unify)) with Applicative[[x] =>> F[G[x]]]:
+    new Derived.Lazy(() => F.unify.compose(using G.unify)) with Applicative[[x] =>> F[G[x]]]:
       export delegate.*
 
   given [F[_]](using inst: => K1.ProductInstances[Or, F]): DerivedApplicative[F] =
-    given K1.ProductInstances[Applicative, F] = inst.unify
-    new Product[Applicative, F] with DerivedApply.Product[Applicative, F] {}
+    Strict.product(using inst.unify)
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedApplicative_F[F[_]: Or, G[_]: Or]: DerivedApplicative[[x] =>> F[G[x]]] = summon
+  protected given [F[_]: Or, G[_]: Or]: DerivedApplicative[[x] =>> F[G[x]]] = nested
 
   trait Product[T[f[_]] <: Applicative[f], F[_]](using inst: K1.ProductInstances[T, F])
       extends Applicative[F],
         DerivedApply.Product[T, F]:
-    final override def pure[A](x: A): F[A] = inst.construct([f[_]] => (F: T[f]) => F.pure[A](x))
+
+    final override def pure[A](x: A): F[A] =
+      inst.construct([f[_]] => (F: T[f]) => F.pure[A](x))
+
+  object Strict:
+    given product[F[_]](using K1.ProductInstances[Applicative, F]): DerivedApplicative[F] =
+      new Product[Applicative, F] with DerivedApply.Product[Applicative, F] {}

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

@@ -20,23 +20,31 @@ object DerivedApply:
     import DerivedApply.given
     summonInline[DerivedApply[F]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[F[_]]: Apply[F] =
+    import Strict.given
+    summonInline[DerivedApply[F]].instance
+
   given [T](using T: Semigroup[T]): DerivedApply[Const[T]] = new Apply[Const[T]]:
     def ap[A, B](ff: T)(fa: T): T = T.combine(ff, fa)
     def map[A, B](fa: T)(f: A => B): T = fa
 
   given nested[F[_], G[_]](using F: => Or[F], G: => Or[G]): DerivedApply[[x] =>> F[G[x]]] =
-    new Derived.Lazy(() => F.unify.compose(G.unify)) with Apply[[x] =>> F[G[x]]]:
+    new Derived.Lazy(() => F.unify.compose(using G.unify)) with Apply[[x] =>> F[G[x]]]:
       export delegate.*
 
   given [F[_]](using inst: => K1.ProductInstances[Or, F]): DerivedApply[F] =
-    given K1.ProductInstances[Apply, F] = inst.unify
-    new Product[Apply, F] {}
+    Strict.product(using inst.unify)
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedApply_F[F[_]: Or, G[_]: Or]: DerivedApply[[x] =>> F[G[x]]] = summon
+  protected given [F[_]: Or, G[_]: Or]: DerivedApply[[x] =>> F[G[x]]] = nested
 
   trait Product[T[f[_]] <: Apply[f], F[_]](using inst: K1.ProductInstances[T, F]) extends Apply[F]:
     private lazy val F = new DerivedFunctor.Generic[T, F] {}
     final override def map[A, B](fa: F[A])(f: A => B): F[B] = F.map(fa)(f)
     final override def ap[A, B](ff: F[A => B])(fa: F[A]): F[B] =
       inst.map2(ff, fa)([f[_]] => (F: T[f], ff: f[A => B], fa: f[A]) => F.ap(ff)(fa))
+
+  object Strict:
+    given product[F[_]](using K1.ProductInstances[Apply, F]): DerivedApply[F] =
+      new Product[Apply, F] {}

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

@@ -17,10 +17,18 @@ object DerivedCommutativeMonoid:
     import DerivedCommutativeMonoid.given
     summonInline[DerivedCommutativeMonoid[A]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[A]: CommutativeMonoid[A] =
+    import Strict.given
+    summonInline[DerivedCommutativeMonoid[A]].instance
+
   given [A](using inst: => K0.ProductInstances[Or, A]): DerivedCommutativeMonoid[A] =
-    given K0.ProductInstances[CommutativeMonoid, A] = inst.unify
-    new Product[CommutativeMonoid, A] {}
+    Strict.product(using inst.unify)
 
   trait Product[F[x] <: CommutativeMonoid[x], A](using @unused inst: K0.ProductInstances[F, A])
       extends DerivedMonoid.Product[F, A],
         CommutativeMonoid[A]
+
+  object Strict:
+    given product[A](using K0.ProductInstances[CommutativeMonoid, A]): DerivedCommutativeMonoid[A] =
+      new Product[CommutativeMonoid, A] {}

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

@@ -17,10 +17,18 @@ object DerivedCommutativeSemigroup:
     import DerivedCommutativeSemigroup.given
     summonInline[DerivedCommutativeSemigroup[A]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[A]: CommutativeSemigroup[A] =
+    import Strict.given
+    summonInline[DerivedCommutativeSemigroup[A]].instance
+
   given [A](using inst: => K0.ProductInstances[Or, A]): DerivedCommutativeSemigroup[A] =
-    given K0.ProductInstances[CommutativeSemigroup, A] = inst.unify
-    new Product[CommutativeSemigroup, A] {}
+    Strict.product(using inst.unify)
 
   trait Product[F[x] <: CommutativeSemigroup[x], A](using @unused inst: K0.ProductInstances[F, A])
       extends DerivedSemigroup.Product[F, A],
         CommutativeSemigroup[A]
+
+  object Strict:
+    given product[A](using K0.ProductInstances[CommutativeSemigroup, A]): DerivedCommutativeSemigroup[A] =
+      new Product[CommutativeSemigroup, A] {}

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

@@ -21,21 +21,32 @@ object DerivedContravariant:
     import DerivedContravariant.given
     summonInline[DerivedContravariant[F]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[F[_]]: Contravariant[F] =
+    import Strict.given
+    summonInline[DerivedContravariant[F]].instance
+
   given [T]: DerivedContravariant[Const[T]] = new Contravariant[Const[T]]:
     def contramap[A, B](fa: T)(f: B => A): T = fa
 
   given nested[F[_], G[_]](using F: DerivedFunctor.Or[F], G: => Or[G]): DerivedContravariant[[x] =>> F[G[x]]] =
-    new Derived.Lazy(() => F.unify.composeContravariant(G.unify)) with Contravariant[[x] =>> F[G[x]]]:
+    new Derived.Lazy(() => F.unify.composeContravariant(using G.unify)) with Contravariant[[x] =>> F[G[x]]]:
       export delegate.*
 
   given [F[_]](using inst: => K1.Instances[Or, F]): DerivedContravariant[F] =
-    given K1.Instances[Contravariant, F] = inst.unify
-    new Generic[Contravariant, F] {}
+    generic(using inst.unify)
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedContravariant_F[F[_]: DerivedFunctor.Or, G[_]: Or]
-      : DerivedContravariant[[x] =>> F[G[x]]] = summon
+  protected given [F[_]: DerivedFunctor.Or, G[_]: Or]: DerivedContravariant[[x] =>> F[G[x]]] = nested
+
+  private def generic[F[_]](using K1.Instances[Contravariant, F]): DerivedContravariant[F] =
+    new Generic[Contravariant, F] {}
 
   trait Generic[T[f[_]] <: Contravariant[f], F[_]](using inst: K1.Instances[T, F]) extends Contravariant[F]:
     final override def contramap[A, B](fa: F[A])(f: B => A): F[B] =
       inst.map(fa)([f[_]] => (T: T[f], fa: f[A]) => T.contramap(fa)(f))
+
+  object Strict:
+    given product[F[_]](using K1.ProductInstances[Contravariant, F]): DerivedContravariant[F] = generic
+    given coproduct[F[_]](using inst: => K1.CoproductInstances[Or, F]): DerivedContravariant[F] =
+      generic(using inst.unify)

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

@@ -19,8 +19,17 @@ object DerivedEmpty:
     import DerivedEmpty.given
     summonInline[DerivedEmpty[A]].instance
 
-  given product[A](using inst: K0.ProductInstances[Or, A]): DerivedEmpty[A] =
-    Empty(inst.unify.construct([a] => (_: Empty[a]).empty))
+  @nowarn("msg=unused import")
+  inline def strict[A]: Empty[A] =
+    import Strict.given
+    summonInline[DerivedEmpty[A]].instance
+
+  given product[A](using inst: K0.ProductInstances[Or, A]): DerivedEmpty[A] = Strict.product(using inst.unify)
+  inline given coproduct[A](using gen: K0.CoproductGeneric[A]): DerivedEmpty[A] = Strict.coproduct
+
+  object Strict:
+    given product[A](using inst: K0.ProductInstances[Empty, A]): DerivedEmpty[A] =
+      Empty(inst.construct([a] => (A: Empty[a]) => A.empty))
 
-  inline given coproduct[A](using gen: K0.CoproductGeneric[A]): DerivedEmpty[A] =
-    Empty(gen.withOnly[Or, A]([a <: A] => (_: Or[a]).unify.empty))
+    inline given coproduct[A](using gen: K0.CoproductGeneric[A]): DerivedEmpty[A] =
+      Empty(gen.withOnly[Or, A]([a <: A] => (A: Or[a]) => A.unify.empty))

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

@@ -23,32 +23,43 @@ object DerivedEmptyK:
     import DerivedEmptyK.given
     summonInline[DerivedEmptyK[F]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[F[_]]: EmptyK[F] =
+    import Strict.given
+    summonInline[DerivedEmptyK[F]].instance
+
   given [T](using T: Empty[T]): DerivedEmptyK[Const[T]] = new EmptyK[Const[T]]:
     def empty[A]: T = T.empty
 
-  given nested[F[_], G[_]](using F: => Or[F]): DerivedEmptyK[[x] =>> F[G[x]]] = new EmptyK[[x] =>> F[G[x]]]:
-    lazy val f = F.unify
-    def empty[A]: F[G[A]] = f.empty
+  given nested[F[_], G[_]](using F: => Or[F]): DerivedEmptyK[[x] =>> F[G[x]]] =
+    new EmptyK[[x] =>> F[G[x]]]:
+      lazy val f = F.unify
+      def empty[A]: F[G[A]] = f.empty
 
-  given nested[F[_], G[_]](using NotGiven[Or[F]])(using
-      F: DerivedPure.Or[F],
-      G: => Or[G]
-  ): DerivedEmptyK[[x] =>> F[G[x]]] = new EmptyK[[x] =>> F[G[x]]]:
-    val f = F.unify
-    lazy val g = G.unify
-    def empty[A]: F[G[A]] = f.pure(g.empty)
+  given nested[F[_], G[_]](using
+      NotGiven[Or[F]]
+  )(using F: DerivedPure.Or[F], G: => Or[G]): DerivedEmptyK[[x] =>> F[G[x]]] =
+    new EmptyK[[x] =>> F[G[x]]]:
+      val f = F.unify
+      lazy val g = G.unify
+      def empty[A]: F[G[A]] = f.pure(g.empty)
 
-  given product[F[_]](using inst: K1.ProductInstances[Or, F]): DerivedEmptyK[F] = new EmptyK[F]:
-    val f = inst.unify
-    def empty[A]: F[A] = f.construct([f[_]] => (F: EmptyK[f]) => F.empty[A])
-
-  inline given coproduct[F[_]](using gen: K1.CoproductGeneric[F]): DerivedEmptyK[F] =
-    gen.withOnly[Or, EmptyK[F]]([f[x] <: F[x]] => (F: Or[f]) => F.unify.asInstanceOf[EmptyK[F]])
+  given product[F[_]](using inst: K1.ProductInstances[Or, F]): DerivedEmptyK[F] = Strict.product(using inst.unify)
+  inline given coproduct[F[_]](using K1.CoproductGeneric[F]): DerivedEmptyK[F] = Strict.coproduct
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedEmptyK_F[F[_]: Or, G[_]]: DerivedEmptyK[[x] =>> F[G[x]]] = summon
+  protected given [F[_], G[_]](using F: Or[F]): DerivedEmptyK[[x] =>> F[G[x]]] =
+    nested(using F)
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedEmptyK_F[F[_]: DerivedPure.Or, G[_]: Or](
+  protected given [F[_], G[_]](using
       ev: NotGiven[Or[F]]
-  ): DerivedEmptyK[[x] =>> F[G[x]]] = nested(using ev)
+  )(using DerivedPure.Or[F], Or[G]): DerivedEmptyK[[x] =>> F[G[x]]] =
+    nested(using ev)
+
+  object Strict:
+    given product[F[_]](using inst: K1.ProductInstances[EmptyK, F]): DerivedEmptyK[F] = new EmptyK[F]:
+      def empty[A]: F[A] = inst.construct([f[_]] => (F: EmptyK[f]) => F.empty[A])
+
+    inline given coproduct[F[_]](using gen: K1.CoproductGeneric[F]): DerivedEmptyK[F] =
+      gen.withOnly[Or, EmptyK[F]]([f[x] <: F[x]] => (F: Or[f]) => F.unify.asInstanceOf[EmptyK[F]])

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

@@ -19,12 +19,16 @@ object DerivedEq:
     import DerivedEq.given
     summonInline[DerivedEq[A]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[A]: Eq[A] =
+    import Strict.given
+    summonInline[DerivedEq[A]].instance
+
   given singleton[A <: Singleton: ValueOf]: DerivedEq[A] =
     Eq.allEqual
 
   given product[A](using inst: => K0.ProductInstances[Or, A]): DerivedEq[A] =
-    given K0.ProductInstances[Eq, A] = inst.unify
-    new Product[Eq, A] {}
+    Strict.product(using inst.unify)
 
   given coproduct[A](using inst: => K0.CoproductInstances[Or, A]): DerivedEq[A] =
     given K0.CoproductInstances[Eq, A] = inst.unify
@@ -37,3 +41,8 @@ object DerivedEq:
   trait Coproduct[F[x] <: Eq[x], A](using inst: K0.CoproductInstances[F, A]) extends Eq[A]:
     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)
+
+  object Strict:
+    export DerivedEq.coproduct
+    given product[A](using K0.ProductInstances[Eq, A]): DerivedEq[A] =
+      new Product[Eq, A] {}

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

@@ -21,24 +21,24 @@ object DerivedFoldable:
     import DerivedFoldable.given
     summonInline[DerivedFoldable[F]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[F[_]]: Foldable[F] =
+    import Strict.given
+    summonInline[DerivedFoldable[F]].instance
+
   given [T]: DerivedFoldable[Const[T]] = new Foldable[Const[T]]:
     def foldLeft[A, B](fa: T, b: B)(f: (B, A) => B): B = b
     def foldRight[A, B](fa: T, lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] = lb
 
   given nested[F[_], G[_]](using F: => Or[F], G: => Or[G]): DerivedFoldable[[x] =>> F[G[x]]] =
-    new Derived.Lazy(() => F.unify.compose(G.unify)) with Foldable[[x] =>> F[G[x]]]:
+    new Derived.Lazy(() => F.unify.compose(using G.unify)) with Foldable[[x] =>> F[G[x]]]:
       export delegate.*
 
-  given [F[_]](using inst: K1.ProductInstances[Or, F]): DerivedFoldable[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] {}
+  given [F[_]](using inst: K1.ProductInstances[Or, F]): DerivedFoldable[F] = Strict.product(using inst.unify)
+  given [F[_]](using => K1.CoproductInstances[Or, F]): DerivedFoldable[F] = Strict.coproduct
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedFoldable_F[F[_]: Or, G[_]: Or]: DerivedFoldable[[x] =>> F[G[x]]] = summon
+  protected given [F[_]: Or, G[_]: Or]: DerivedFoldable[[x] =>> F[G[x]]] = nested
 
   trait Product[T[f[_]] <: Foldable[f], 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 =
@@ -54,3 +54,11 @@ object DerivedFoldable:
 
     final override def foldRight[A, B](fa: F[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
       inst.fold(fa)([f[_]] => (F: T[f], fa: f[A]) => Eval.defer(F.foldRight(fa, lb)(f)))
+
+  object Strict:
+    given product[F[_]](using K1.ProductInstances[Foldable, F]): DerivedFoldable[F] =
+      new Product[Foldable, F] {}
+
+    given coproduct[F[_]](using inst: => K1.CoproductInstances[Or, F]): DerivedFoldable[F] =
+      given K1.CoproductInstances[Foldable, F] = inst.unify
+      new Coproduct[Foldable, F] {}

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

@@ -22,33 +22,45 @@ object DerivedFunctor:
     import DerivedFunctor.given
     summonInline[DerivedFunctor[F]].instance
 
+  @nowarn("msg=unused import")
+  inline def strict[F[_]]: Functor[F] =
+    import Strict.given
+    summonInline[DerivedFunctor[F]].instance
+
   given [T]: DerivedFunctor[Const[T]] = new Functor[Const[T]]:
     def map[A, B](fa: T)(f: A => B): T = fa
 
   given nested[F[_], G[_]](using F: => Or[F], G: => Or[G]): DerivedFunctor[[x] =>> F[G[x]]] =
-    new Derived.Lazy(() => F.unify.compose(G.unify)) with Functor[[x] =>> F[G[x]]]:
+    new Derived.Lazy(() => F.unify.compose(using G.unify)) with Functor[[x] =>> F[G[x]]]:
       export delegate.*
 
   given nested[F[_], G[_]](using
       F: DerivedContravariant.Or[F],
       G: DerivedContravariant.Or[G]
   ): DerivedFunctor[[x] =>> F[G[x]]] =
-    F.unify.compose(G.unify)
+    F.unify.compose(using G.unify)
 
   given [F[_]](using inst: => K1.Instances[Or, F]): DerivedFunctor[F] =
-    given K1.Instances[Functor, F] = inst.unify
-    new Generic[Functor, F] {}
+    generic(using inst.unify)
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedFunctor_F[F[_], G[_]](using F: Or[F], G: Or[G]): DerivedFunctor[[x] =>> F[G[x]]] =
+  protected given [F[_], G[_]](using F: Or[F], G: Or[G]): DerivedFunctor[[x] =>> F[G[x]]] =
     nested(using F, G)
 
   @deprecated("Kept for binary compatibility", "3.2.0")
-  private[derived] def given_DerivedFunctor_F[F[_], G[_]](using
+  protected given [F[_], G[_]](using
       F: DerivedContravariant.Or[F],
       G: DerivedContravariant.Or[G]
-  ): DerivedFunctor[[x] =>> F[G[x]]] = nested(using F, G)
+  ): DerivedFunctor[[x] =>> F[G[x]]] =
+    nested(using F, G)
+
+  private def generic[F[_]](using K1.Instances[Functor, F]): DerivedFunctor[F] =
+    new Generic[Functor, F] {}
 
   trait Generic[T[f[_]] <: Functor[f], 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[_]] => (F: T[f], fa: f[A]) => F.map(fa)(f))
+
+  object Strict:
+    given product[F[_]](using K1.ProductInstances[Functor, F]): DerivedFunctor[F] = generic
+    given coproduct[F[_]](using inst: => K1.CoproductInstances[Or, F]): DerivedFunctor[F] = generic(using inst.unify)