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Refactor Ref#mapK to take Functor[G] constraint instead of Functor[F] #4115

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Refactor Ref#mapK to take Functor[G] constraint instead of Functor[F] #4115

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31 changes: 28 additions & 3 deletions kernel/shared/src/main/scala/cats/effect/kernel/Ref.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ package effect
package kernel

import cats.data.State
import cats.effect.kernel.Ref.TransformedRef
import cats.effect.kernel.Ref.{TransformedRef, TransformedRef2}
import cats.syntax.all._

/**
Expand Down Expand Up @@ -186,8 +186,12 @@ abstract class Ref[F[_], A] extends RefSource[F, A] with RefSink[F, A] {
/**
* Modify the context `F` using transformation `f`.
*/
def mapK[G[_]](f: F ~> G)(implicit F: Functor[F]): Ref[G, A] =
new TransformedRef(this, f)
def mapK[G[_]](f: F ~> G)(implicit G: Functor[G], dummy: DummyImplicit): Ref[G, A] =
new TransformedRef2(this, f)

@deprecated("Use mapK with Functor[G] constraint", "3.6.0")
def mapK[G[_]](f: F ~> G, F: Functor[F]): Ref[G, A] =
new TransformedRef(this, f)(F)
}

object Ref {
Expand Down Expand Up @@ -361,6 +365,27 @@ object Ref {
def empty[A: Monoid]: F[Ref[F, A]] = of(Monoid[A].empty)
}

final private[kernel] class TransformedRef2[F[_], G[_], A](
underlying: Ref[F, A],
trans: F ~> G)(
implicit G: Functor[G]
) extends Ref[G, A] {
override def get: G[A] = trans(underlying.get)
override def set(a: A): G[Unit] = trans(underlying.set(a))
override def getAndSet(a: A): G[A] = trans(underlying.getAndSet(a))
override def tryUpdate(f: A => A): G[Boolean] = trans(underlying.tryUpdate(f))
override def tryModify[B](f: A => (A, B)): G[Option[B]] = trans(underlying.tryModify(f))
override def update(f: A => A): G[Unit] = trans(underlying.update(f))
override def modify[B](f: A => (A, B)): G[B] = trans(underlying.modify(f))
override def tryModifyState[B](state: State[A, B]): G[Option[B]] =
trans(underlying.tryModifyState(state))
override def modifyState[B](state: State[A, B]): G[B] = trans(underlying.modifyState(state))

override def access: G[(A, A => G[Boolean])] =
G.compose[(A, *)].compose[A => *].map(trans(underlying.access))(trans(_))
}

@deprecated("Use TransformedRef2 with Functor[G] constraint", "3.6.0")
final private[kernel] class TransformedRef[F[_], G[_], A](
underlying: Ref[F, A],
trans: F ~> G)(
Expand Down
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