[k1/K2]: Mark @SubclassOptInRequired as an experimental

At the moment, SubclassOptInRequired is marked with the
ExperimentalSubclassOptIn annotation. However, it does not work
as expected due to a missing opt-in error. To use SubclassOptInRequired,
an explicit opt-in is necessary because SubclassOptInRequired is an
unstable feature now.

^KT-64739

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java

@@ -42229,6 +42229,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                     runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/CorrectApplicability.kt");
                 }
 
+                @Test
+                @TestMetadata("Experimentality.kt")
+                public void testExperimentality() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Experimentality.kt");
+                }
+
                 @Test
                 @TestMetadata("IncorrectApplicability.kt")
                 public void testIncorrectApplicability() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java

@@ -42229,6 +42229,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                     runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/CorrectApplicability.kt");
                 }
 
+                @Test
+                @TestMetadata("Experimentality.kt")
+                public void testExperimentality() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Experimentality.kt");
+                }
+
                 @Test
                 @TestMetadata("IncorrectApplicability.kt")
                 public void testIncorrectApplicability() throws Exception {

compiler/fir/analysis-tests/testData/builtIns/kotlin.txt

@@ -601,7 +601,7 @@ public abstract class Enum<E : R|kotlin/Enum<E>|> : R|kotlin/Comparable<E>|, R|j
 
 }
 
-@R|kotlin/annotation/Target|(allowedTargets = <implicitArrayOf>(R|kotlin/annotation/AnnotationTarget.CLASS|)) @R|kotlin/annotation/Retention|(value = R|kotlin/annotation/AnnotationRetention.BINARY|) @R|kotlin/SinceKotlin|(version = String(1.8)) public final annotation class ExperimentalSubclassOptIn : R|kotlin/Annotation| {
+@R|kotlin/annotation/Target|(allowedTargets = <implicitArrayOf>(R|kotlin/annotation/AnnotationTarget.CLASS|)) @R|kotlin/annotation/Retention|(value = R|kotlin/annotation/AnnotationRetention.BINARY|) @R|kotlin/SinceKotlin|(version = String(1.8)) @R|kotlin/RequiresOptIn|() public final annotation class ExperimentalSubclassOptIn : R|kotlin/Annotation| {
     public constructor(): R|kotlin/ExperimentalSubclassOptIn|
 
 }

compiler/fir/analysis-tests/testData/resolveWithStdlib/ClassIdDiagnosticRendering.fir.txt

@@ -1,4 +1,5 @@
 FILE: ClassIdDiagnosticRendering.kt
+    @FILE:R|kotlin/OptIn|(markerClass = vararg(<getClass>(Q|kotlin/ExperimentalSubclassOptIn|)))
     package a.b.c
 
     @R|kotlin/RequiresOptIn|() public final annotation class Marker : R|kotlin/Annotation| {

compiler/fir/analysis-tests/testData/resolveWithStdlib/ClassIdDiagnosticRendering.kt

@@ -1,4 +1,5 @@
 // WITH_EXTENDED_CHECKERS
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 package a.b.c
 

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java

@@ -39943,6 +39943,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                     runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/CorrectApplicability.kt");
                 }
 
+                @Test
+                @TestMetadata("Experimentality.kt")
+                public void testExperimentality() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Experimentality.kt");
+                }
+
                 @Test
                 @TestMetadata("IncorrectApplicability.kt")
                 public void testIncorrectApplicability() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java

@@ -40063,6 +40063,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                     runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/CorrectApplicability.kt");
                 }
 
+                @Test
+                @TestMetadata("Experimentality.kt")
+                public void testExperimentality() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Experimentality.kt");
+                }
+
                 @Test
                 @TestMetadata("IncorrectApplicability.kt")
                 public void testIncorrectApplicability() throws Exception {

compiler/testData/builtin-classes/default/kotlin.txt

@@ -347,7 +347,7 @@ public abstract class Enum</*0*/ E : kotlin.Enum<E>> : kotlin.Comparable<E> {
     /*primary*/ 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 {
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS}) @kotlin.annotation.Retention(value = AnnotationRetention.BINARY) @kotlin.SinceKotlin(version = "1.8") @kotlin.RequiresOptIn public final annotation class ExperimentalSubclassOptIn : kotlin.Annotation {
     /*primary*/ public constructor ExperimentalSubclassOptIn()
 }
 

compiler/testData/builtin-classes/java6/kotlin.txt

@@ -362,7 +362,7 @@ public abstract class Enum</*0*/ E : kotlin.Enum<E>> : kotlin.Comparable<E>, jav
     /*primary*/ 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 {
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS}) @kotlin.annotation.Retention(value = AnnotationRetention.BINARY) @kotlin.SinceKotlin(version = "1.8") @kotlin.RequiresOptIn public final annotation class ExperimentalSubclassOptIn : kotlin.Annotation {
     /*primary*/ public constructor ExperimentalSubclassOptIn()
 }
 

compiler/testData/builtin-classes/java8/kotlin.txt

@@ -364,7 +364,7 @@ public abstract class Enum</*0*/ E : kotlin.Enum<E>> : kotlin.Comparable<E>, jav
     /*primary*/ 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 {
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS}) @kotlin.annotation.Retention(value = AnnotationRetention.BINARY) @kotlin.SinceKotlin(version = "1.8") @kotlin.RequiresOptIn public final annotation class ExperimentalSubclassOptIn : kotlin.Annotation {
     /*primary*/ public constructor ExperimentalSubclassOptIn()
 }
 

compiler/testData/builtin-classes/newMethods/kotlin.txt

@@ -362,7 +362,7 @@ public abstract class Enum</*0*/ E : kotlin.Enum<E>> : kotlin.Comparable<E>, jav
     /*primary*/ 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 {
+@kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS}) @kotlin.annotation.Retention(value = AnnotationRetention.BINARY) @kotlin.SinceKotlin(version = "1.8") @kotlin.RequiresOptIn public final annotation class ExperimentalSubclassOptIn : kotlin.Annotation {
     /*primary*/ public constructor ExperimentalSubclassOptIn()
 }
 

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/CorrectApplicability.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Experimentality.kt

@@ -0,0 +1,7 @@
+// FIR_IDENTICAL
+
+@RequiresOptIn
+annotation class ApiMarker
+
+@<!OPT_IN_USAGE_ERROR!>SubclassOptInRequired<!>(ApiMarker::class)
+open class OpenKlass

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/IncorrectApplicability.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/InheritingByLocalClassifiers.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/InheritingDifferentOptInLevels.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/InnerAndNestedClasses.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class Api

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/InnerClasses.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class Boom

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/NestedClasses.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class Boom

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/NotApiMarkerAsArgument.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 annotation class DummyAnnotation
 

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Typealias.fir.kt

@@ -1,3 +1,5 @@
+@file:OptIn(ExperimentalSubclassOptIn::class)
+
 @RequiresOptIn
 annotation class ApiMarker
 

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Typealias.kt

@@ -1,3 +1,5 @@
+@file:OptIn(ExperimentalSubclassOptIn::class)
+
 @RequiresOptIn
 annotation class ApiMarker
 

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/UsageOptInIsNotImplied.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/WithAbstractClasses.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/WithInheritanceByDelegation.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/WithInterfaces.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/WithOpenClasses.kt

@@ -1,4 +1,5 @@
 // FIR_IDENTICAL
+@file:OptIn(ExperimentalSubclassOptIn::class)
 
 @RequiresOptIn
 annotation class ApiMarker

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -42229,6 +42229,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/CorrectApplicability.kt");
                 }
 
+                @Test
+                @TestMetadata("Experimentality.kt")
+                public void testExperimentality() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/Experimentality.kt");
+                }
+
                 @Test
                 @TestMetadata("IncorrectApplicability.kt")
                 public void testIncorrectApplicability() throws Exception {

libraries/stdlib/api/js/kotlin.kt

@@ -1599,6 +1599,7 @@ public final annotation class ExperimentalStdlibApi : kotlin.Annotation {
 @kotlin.annotation.Target(allowedTargets = {AnnotationTarget.CLASS})
 @kotlin.annotation.Retention(value = AnnotationRetention.BINARY)
 @kotlin.SinceKotlin(version = "1.8")
+@kotlin.RequiresOptIn
 public final annotation class ExperimentalSubclassOptIn : kotlin.Annotation {
     public constructor ExperimentalSubclassOptIn()
 }

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

@@ -144,6 +144,7 @@ public annotation class OptIn(
 @Target(CLASS)
 @Retention(BINARY)
 @SinceKotlin("1.8")
+@RequiresOptIn
 public annotation class ExperimentalSubclassOptIn
 
 /**