Protect SubclassOptInRequired with opt-in marker

libraries/stdlib/api/js-v1/kotlin.kt

@@ -1649,6 +1649,13 @@ public final annotation class ExperimentalStdlibApi : kotlin.Annotation {
 /*∆*/     public constructor ExperimentalStdlibApi()
 /*∆*/ }
 /*∆*/ 
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS})
+@kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
+@kotlin.SinceKotlin(version = "1.8")
+public final annotation class ExperimentalSubclassOptIn : kotlin.Annotation {
+    public constructor ExperimentalSubclassOptIn()
+}
+
 @kotlin.RequiresOptIn(level = Level.WARNING)
 @kotlin.annotation.MustBeDocumented
 @kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS, AnnotationTarget.ANNOTATION_CLASS, AnnotationTarget.PROPERTY, AnnotationTarget.FIELD, AnnotationTarget.LOCAL_VARIABLE, AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.CONSTRUCTOR, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER, AnnotationTarget.TYPEALIAS})
@@ -2758,6 +2765,7 @@ public final class String : kotlin.Comparable<kotlin.String>, kotlin.CharSequenc
 @kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS})
 @kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
 @kotlin.SinceKotlin(version = "1.8")
+@kotlin.ExperimentalSubclassOptIn
 public final annotation class SubclassOptInRequired : kotlin.Annotation {
     public constructor SubclassOptInRequired(markerClass: kotlin.reflect.KClass<out kotlin.Annotation>)
 

libraries/stdlib/api/js/kotlin.kt

@@ -1485,6 +1485,13 @@ public final annotation class ExperimentalStdlibApi : kotlin.Annotation {
     public constructor ExperimentalStdlibApi()
 }
 
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS})
+@kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
+@kotlin.SinceKotlin(version = "1.8")
+public final annotation class ExperimentalSubclassOptIn : kotlin.Annotation {
+    public constructor ExperimentalSubclassOptIn()
+}
+
 @kotlin.RequiresOptIn(level = Level.WARNING)
 @kotlin.annotation.MustBeDocumented
 @kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS, AnnotationTarget.ANNOTATION_CLASS, AnnotationTarget.PROPERTY, AnnotationTarget.FIELD, AnnotationTarget.LOCAL_VARIABLE, AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.CONSTRUCTOR, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER, AnnotationTarget.TYPEALIAS})
@@ -2392,6 +2399,7 @@ public final class String : kotlin.Comparable<kotlin.String>, kotlin.CharSequenc
 @kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS})
 @kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
 @kotlin.SinceKotlin(version = "1.8")
+@kotlin.ExperimentalSubclassOptIn
 public final annotation class SubclassOptInRequired : kotlin.Annotation {
     public constructor SubclassOptInRequired(markerClass: kotlin.reflect.KClass<out kotlin.Annotation>)
 

libraries/stdlib/src/kotlin/annotations/OptIn.kt

@@ -5,8 +5,7 @@
 
 package kotlin
 
-import kotlin.annotation.AnnotationRetention.BINARY
-import kotlin.annotation.AnnotationRetention.SOURCE
+import kotlin.annotation.AnnotationRetention.*
 import kotlin.annotation.AnnotationTarget.*
 import kotlin.internal.RequireKotlin
 import kotlin.internal.RequireKotlinVersionKind
@@ -57,7 +56,15 @@ public annotation class OptIn(
 )
 
 /**
- * Forbids creation of subclasses/sub-interfaces from the annotated class/interface without explicit OptIn.
+ * Opt-in marker annotation which allows to use [SubclassOptInRequired].
+ */
+@Target(CLASS)
+@Retention(BINARY)
+@SinceKotlin("1.8")
+public annotation class ExperimentalSubclassOptIn
+
+/**
+ * Forbids creation of subclasses/sub-interfaces from the annotated class/interface without explicit [OptIn].
  *
  * This annotation is devoted to specific case when we want subclassing to be experimental.
  * In this case we annotated the base class or interface with [SubclassOptInRequired].
@@ -76,6 +83,7 @@ public annotation class OptIn(
 @Target(CLASS)
 @Retention(BINARY)
 @SinceKotlin("1.8")
+@ExperimentalSubclassOptIn
 public annotation class SubclassOptInRequired(
     val markerClass: KClass<out Annotation>
 )

libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib-runtime-merged.txt

@@ -66,6 +66,9 @@ public abstract interface annotation class kotlin/ExperimentalMultiplatform : ja
 public abstract interface annotation class kotlin/ExperimentalStdlibApi : java/lang/annotation/Annotation {
 }
 
+public abstract interface annotation class kotlin/ExperimentalSubclassOptIn : java/lang/annotation/Annotation {
+}
+
 public abstract interface annotation class kotlin/ExperimentalUnsignedTypes : java/lang/annotation/Annotation {
 }