add Local[F, Span[F]] instance where F is Kleisli[F, Span[F], *]

typelevel · Jan 27, 2023 · 5d836f5 · 5d836f5
1 parent ab95b63
commit 5d836f5
Showing 1 changed file with 21 additions and 0 deletions.
diff --git a/modules/mtl/shared/src/main/scala/package.scala b/modules/mtl/shared/src/main/scala/package.scala
@@ -4,6 +4,8 @@
 
 package natchez
 
+import cats._
+import cats.data.Kleisli
 import cats.mtl.Local
 import cats.effect.{Trace => _, _}
 
@@ -13,4 +15,23 @@ package object mtl {
       eb: MonadCancel[F, Throwable]
   ): Trace[F] =
     new LocalTrace(ev)
+
+  implicit def localSpanForKleisli[F[_]](implicit
+      F: MonadCancel[F, _]
+  ): Local[Kleisli[F, Span[F], *], Span[Kleisli[F, Span[F], *]]] =
+    new Local[Kleisli[F, Span[F], *], Span[Kleisli[F, Span[F], *]]] {
+      override def local[A](
+          fa: Kleisli[F, Span[F], A]
+      )(f: Span[Kleisli[F, Span[F], *]] => Span[Kleisli[F, Span[F], *]]): Kleisli[F, Span[F], A] =
+        fa.local {
+          f.andThen(_.mapK(Kleisli.applyK(Span.noop[F])))
+            .compose(_.mapK(Kleisli.liftK))
+        }
+
+      override def applicative: Applicative[Kleisli[F, Span[F], *]] =
+        Kleisli.catsDataApplicativeForKleisli
+
+      override def ask[E2 >: Span[Kleisli[F, Span[F], *]]]: Kleisli[F, Span[F], E2] =
+        Kleisli.ask[F, Span[F]].map(_.mapK(Kleisli.liftK))
+    }
 }