zio · hearnadam · Jan 29, 2025 · Jan 28, 2025
diff --git a/core/shared/src/main/scala/zio/IsSubtype.scala b/core/shared/src/main/scala/zio/IsSubtype.scala
@@ -7,23 +7,23 @@ import scala.annotation.implicitNotFound
 @implicitNotFound("\nThis operator requires that the output type be a subtype of ${B}\nBut the actual type was ${A}.")
 sealed abstract class IsSubtypeOfOutput[-A, +B] extends (A => B) with Serializable
 object IsSubtypeOfOutput {
-  implicit def impl[A, B](implicit subtype: A <:< B): IsSubtypeOfOutput[A, B] = new IsSubtypeOfOutput[A, B] {
-    override def apply(a: A): B = subtype(a)
-  }
+  private val instance: IsSubtypeOfOutput[Any, Any] = new IsSubtypeOfOutput[Any, Any] { def apply(a: Any): Any = a }
 
-  implicit def implNothing[B]: IsSubtypeOfOutput[Nothing, B] = new IsSubtypeOfOutput[Nothing, B] {
-    override def apply(a: Nothing): B = a
-  }
+  implicit def impl[A, B](implicit subtype: A <:< B): IsSubtypeOfOutput[A, B] =
+    instance.asInstanceOf[IsSubtypeOfOutput[A, B]]
+
+  implicit def implNothing[B]: IsSubtypeOfOutput[Nothing, B] =
+    instance.asInstanceOf[IsSubtypeOfOutput[Nothing, B]]
 }
 
 @implicitNotFound("\nThis operator requires that the error type be a subtype of ${B}\nBut the actual type was ${A}.")
 sealed abstract class IsSubtypeOfError[-A, +B] extends (A => B) with Serializable
 object IsSubtypeOfError {
-  implicit def impl[A, B](implicit subtype: A <:< B): IsSubtypeOfError[A, B] = new IsSubtypeOfError[A, B] {
-    override def apply(a: A): B = subtype(a)
-  }
+  private val instance: IsSubtypeOfError[Any, Any] = new IsSubtypeOfError[Any, Any] { def apply(a: Any): Any = a }
+
+  implicit def impl[A, B](implicit subtype: A <:< B): IsSubtypeOfError[A, B] =
+    instance.asInstanceOf[IsSubtypeOfError[A, B]]
 
-  implicit def implNothing[B]: IsSubtypeOfError[Nothing, B] = new IsSubtypeOfError[Nothing, B] {
-    override def apply(a: Nothing): B = a
-  }
+  implicit def implNothing[B]: IsSubtypeOfError[Nothing, B] =
+    instance.asInstanceOf[IsSubtypeOfError[Nothing, B]]
 }
diff --git a/core/shared/src/main/scala/zio/ZIO.scala b/core/shared/src/main/scala/zio/ZIO.scala
@@ -5494,15 +5494,12 @@ object ZIO extends ZIOCompanionPlatformSpecific with ZIOCompanionVersionSpecific
   @implicitNotFound(
     "Pattern guards are only supported when the error type is a supertype of NoSuchElementException. However, your effect has ${E} for the error type."
   )
-  abstract class CanFilter[+E] {
+  sealed abstract class CanFilter[+E] {
     def apply(t: NoSuchElementException): E
   }
-
   object CanFilter {
-    implicit def canFilter[E >: NoSuchElementException]: CanFilter[E] =
-      new CanFilter[E] {
-        def apply(t: NoSuchElementException): E = t
-      }
+    private val instance: CanFilter[Any]                              = new CanFilter[Any] { def apply(t: NoSuchElementException): Any = t }
+    implicit def canFilter[E >: NoSuchElementException]: CanFilter[E] = instance.asInstanceOf[CanFilter[E]]
   }
 
   final class Grafter(private val scope: FiberScope) extends AnyVal { self =>

diff --git a/test/shared/src/main/scala-2/zio/test/Eql.scala b/test/shared/src/main/scala-2/zio/test/Eql.scala
@@ -31,11 +31,12 @@ import scala.annotation.implicitNotFound
     "they cannot be equal."
 )
 sealed abstract class Eql[A, B]
-
 object Eql extends EqlLowPriority {
-  implicit final def eqlSubtype1[A <: B, B]: Eql[A, B] = new Eql[A, B] {}
+  implicit final def eqlSubtype1[A <: B, B]: Eql[A, B] = instance.asInstanceOf[Eql[A, B]]
 }
 
 private[test] sealed abstract class EqlLowPriority {
-  implicit final def eqlSubtype2[A, B <: A]: Eql[A, B] = new Eql[A, B] {}
+  protected val instance: Eql[Any, Any] = new Eql[Any, Any] {}
+
+  implicit final def eqlSubtype2[A, B <: A]: Eql[A, B] = instance.asInstanceOf[Eql[A, B]]
 }