change lower bound of Option.orNull to nullable

library/src/scala/Option.scala

@@ -220,7 +220,10 @@ sealed abstract class Option[+A] extends IterableOnce[A] with Product with Seria
    *  val textField = new JComponent(initialText.orNull,20)
    *  ```
    */
-  @inline final def orNull[A1 >: A](implicit ev: Null <:< A1): A1 = this getOrElse ev(null)
+  @inline final def orNull: A | Null = this.getOrElse(null)
+
+  // for binary and TASTy backwards compatibility 
+  @deprecated @inline protected final def orNull[A1 >: A](implicit ev: Null <:< A1): A1 = this getOrElse ev(null)
 
   /** Returns a $some containing the result of applying $f to this $option's
    *  value if this $option is nonempty.

project/MiMaFilters.scala

@@ -52,6 +52,7 @@ object MiMaFilters {
         ProblemFilters.exclude[FinalMethodProblem]("scala.jdk.Accumulator.:++"),
         ProblemFilters.exclude[FinalMethodProblem]("scala.jdk.Accumulator.concat"),
         ProblemFilters.exclude[FinalMethodProblem]("scala.jdk.Accumulator.sizeHint$default$2"),
+        ProblemFilters.exclude[DirectMissingMethodProblem]("scala.None.orNull"),
       )
     )
   }

tests/explicit-nulls/pos/option-ornull.scala

@@ -0,0 +1,6 @@
+import java.util.Optional
+
+class CheckResult(result: Option[Unit]):
+  def foo =
+    val x: Optional[Unit] = Optional.ofNullable(result.orNull)
+    42