Add derivation of LiftIO from LiftValue

Author: NthPortal

core/shared/src/main/scala/cats/effect/LiftIO.scala

@@ -19,12 +19,13 @@ package cats.effect
 import cats.{~>, Applicative, FlatMap, Functor}
 import cats.data.{ContT, EitherT, IorT, Kleisli, OptionT, ReaderWriterStateT, StateT, WriterT}
 import cats.kernel.Monoid
+import cats.mtl.LiftValue
 
 trait LiftIO[F[_]] {
   def liftIO[A](ioa: IO[A]): F[A]
 }
 
-object LiftIO {
+object LiftIO extends LiftIOInstances0 {
 
   def apply[F[_]](implicit F: LiftIO[F]): F.type = F
 
@@ -155,3 +156,10 @@ object LiftIO {
       Resource.eval(F0.liftIO(ioa))
   }
 }
+
+private[effect] sealed trait LiftIOInstances0 {
+  implicit def catsEffectLiftIOFromLiftValue[F[_]](implicit lift: LiftValue[IO, F]): LiftIO[F] =
+    new LiftIO[F] {
+      override def liftIO[A](ioa: IO[A]): F[A] = lift(ioa)
+    }
+}

tests/shared/src/test/scala/cats/effect/LiftIOSuite.scala

@@ -0,0 +1,17 @@
+package cats.effect
+
+import cats.Applicative
+import cats.data.IdT
+import cats.mtl.LiftValue
+
+class LiftIOSuite extends BaseSuite {
+  ticked("LiftIO from LiftValue") { implicit ticker =>
+    implicit val lift: LiftValue[IO, IdT[IO, *]] =
+      new LiftValue[IO, IdT[IO, *]] {
+        def applicativeF: Applicative[IO] = implicitly
+        def applicativeG: Applicative[IdT[IO, *]] = implicitly
+        def apply[A](fa: IO[A]): IdT[IO, A] = IdT(fa)
+      }
+    assertCompleteAs(IO.pure(42).to[IdT[IO, *]].value, 42)
+  }
+}