Fix: use contravariance to allow derived index type

softwaremill · Jan 23, 2024 · a6f0a5c · a6f0a5c
1 parent ef445f7
commit a6f0a5c
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/quicklens/src/main/scala-3/com/softwaremill/quicklens/package.scala b/quicklens/src/main/scala-3/com/softwaremill/quicklens/package.scala
@@ -161,7 +161,7 @@ package object quicklens {
     }
   }
 
-  trait QuicklensIndexedFunctor[F[_], I] {
+  trait QuicklensIndexedFunctor[F[_], -I] {
     def at[A](fa: F[A], f: A => A, idx: I): F[A]
     def atOrElse[A](fa: F[A], f: A => A, idx: I, default: => A): F[A]
     def index[A](fa: F[A], f: A => A, idx: I): F[A]