Add KClass.sealedSubclasses to get direct subclasses of sealed class

#KT-14657 Fixed

compiler/testData/codegen/box/reflection/classes/sealedSubclasses.kt

@@ -0,0 +1,41 @@
+// IGNORE_BACKEND: JS, JS_IR, JVM_IR, NATIVE
+// WITH_REFLECT
+
+import kotlin.reflect.KClass
+import kotlin.reflect.jvm.*
+import kotlin.test.assertEquals
+
+// --
+
+sealed class SealedClassWithTopLevelSubclasses {
+    class NotASealedSubclass : TL2()
+}
+object TL1 : SealedClassWithTopLevelSubclasses()
+open class TL2 : SealedClassWithTopLevelSubclasses()
+
+// --
+
+sealed class SealedClassWithNestedSubclasses {
+    data class N1(val x: Unit) : SealedClassWithNestedSubclasses()
+    object N2 : SealedClassWithNestedSubclasses()
+}
+
+// --
+
+sealed class SealedClassWithNoSubclasses
+
+// --
+
+fun sealedSubclassNames(c: KClass<*>) = c.sealedSubclasses.map { it.simpleName ?: throw AssertionError("Unnamed class: ${it.java}") }.sorted()
+
+fun box(): String {
+    assertEquals(listOf("TL1", "TL2"), sealedSubclassNames(SealedClassWithTopLevelSubclasses::class))
+    assertEquals(listOf("N1", "N2"), sealedSubclassNames(SealedClassWithNestedSubclasses::class))
+    assertEquals(emptyList(), sealedSubclassNames(SealedClassWithNoSubclasses::class))
+
+    assertEquals(emptyList(), sealedSubclassNames(String::class))
+    assertEquals(emptyList(), sealedSubclassNames(Thread::class))
+    assertEquals(emptyList(), sealedSubclassNames(FloatArray::class))
+
+    return "OK"
+}

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -17844,6 +17844,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 runTest("compiler/testData/codegen/box/reflection/classes/qualifiedNameOfStandardClasses.kt");
             }
 
+            @TestMetadata("sealedSubclasses.kt")
+            public void testSealedSubclasses() throws Exception {
+                runTest("compiler/testData/codegen/box/reflection/classes/sealedSubclasses.kt");
+            }
+
             @TestMetadata("starProjectedType.kt")
             public void testStarProjectedType() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/classes/starProjectedType.kt");

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -17844,6 +17844,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                 runTest("compiler/testData/codegen/box/reflection/classes/qualifiedNameOfStandardClasses.kt");
             }
 
+            @TestMetadata("sealedSubclasses.kt")
+            public void testSealedSubclasses() throws Exception {
+                runTest("compiler/testData/codegen/box/reflection/classes/sealedSubclasses.kt");
+            }
+
             @TestMetadata("starProjectedType.kt")
             public void testStarProjectedType() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/classes/starProjectedType.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -17844,6 +17844,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                 runTest("compiler/testData/codegen/box/reflection/classes/qualifiedNameOfStandardClasses.kt");
             }
 
+            @TestMetadata("sealedSubclasses.kt")
+            public void testSealedSubclasses() throws Exception {
+                runTest("compiler/testData/codegen/box/reflection/classes/sealedSubclasses.kt");
+            }
+
             @TestMetadata("starProjectedType.kt")
             public void testStarProjectedType() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/classes/starProjectedType.kt");

core/builtins/src/kotlin/reflect/KClass.kt

@@ -76,6 +76,12 @@ public interface KClass<T : Any> : KDeclarationContainer, KAnnotatedElement, KCl
     @SinceKotlin("1.1")
     public val supertypes: List<KType>
 
+    /**
+     * The list of the immediate subclasses if this class is a sealed class, or an empty list otherwise.
+     */
+    @SinceKotlin("1.3")
+    public val sealedSubclasses: List<KClass<out T>>
+
     /**
      * Visibility of this class, or `null` if its visibility cannot be represented in Kotlin.
      */

core/reflection.jvm/src/kotlin/reflect/jvm/internal/KClassImpl.kt

@@ -147,6 +147,14 @@ internal class KClassImpl<T : Any>(override val jClass: Class<T>) : KDeclaration
             result.compact()
         }
 
+        val sealedSubclasses: List<KClass<out T>> by ReflectProperties.lazySoft {
+            descriptor.sealedSubclasses.mapNotNull { subclass ->
+                @Suppress("UNCHECKED_CAST")
+                val jClass = (subclass as ClassDescriptor).toJavaClass() as Class<out T>?
+                jClass?.let { KClassImpl(it) }
+            }
+        }
+
         val declaredNonStaticMembers: Collection<KCallableImpl<*>>
                 by ReflectProperties.lazySoft { getMembers(memberScope, DECLARED) }
         private val declaredStaticMembers: Collection<KCallableImpl<*>>
@@ -239,6 +247,11 @@ internal class KClassImpl<T : Any>(override val jClass: Class<T>) : KDeclaration
 
     override val supertypes: List<KType> get() = data().supertypes
 
+    /**
+     * The list of the immediate subclasses if this class is a sealed class, or an empty list otherwise.
+     */
+    override val sealedSubclasses: List<KClass<out T>> get() = data().sealedSubclasses
+
     override val visibility: KVisibility?
         get() = descriptor.visibility.toKVisibility()
 

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/IrJsCodegenBoxTestGenerated.java

@@ -16009,6 +16009,11 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
                 runTest("compiler/testData/codegen/box/reflection/classes/qualifiedNameOfStandardClasses.kt");
             }
 
+            @TestMetadata("sealedSubclasses.kt")
+            public void testSealedSubclasses() throws Exception {
+                runTest("compiler/testData/codegen/box/reflection/classes/sealedSubclasses.kt");
+            }
+
             @TestMetadata("starProjectedType.kt")
             public void testStarProjectedType() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/classes/starProjectedType.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -17069,6 +17069,11 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
                 runTest("compiler/testData/codegen/box/reflection/classes/qualifiedNameOfStandardClasses.kt");
             }
 
+            @TestMetadata("sealedSubclasses.kt")
+            public void testSealedSubclasses() throws Exception {
+                runTest("compiler/testData/codegen/box/reflection/classes/sealedSubclasses.kt");
+            }
+
             @TestMetadata("starProjectedType.kt")
             public void testStarProjectedType() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/classes/starProjectedType.kt");

libraries/stdlib/js/src/kotlin/reflect/KClassImpl.kt

@@ -40,6 +40,8 @@ internal abstract class KClassImpl<T : Any>(
         get() = TODO()
     override val typeParameters: List<KTypeParameter>
         get() = TODO()
+    override val sealedSubclasses: List<KClass<out T>>
+        get() = TODO()
     override val visibility: KVisibility?
         get() = TODO()
 

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/ClassReference.kt

@@ -40,6 +40,10 @@ public class ClassReference(override val jClass: Class<*>) : KClass<Any>, ClassB
     override val supertypes: List<KType>
         get() = error()
 
+    @SinceKotlin("1.3")
+    override val sealedSubclasses: List<KClass<out Any>>
+        get() = error()
+
     @SinceKotlin("1.1")
     override val visibility: KVisibility?
         get() = error()

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

@@ -455,6 +455,7 @@ public final class kotlin/jvm/internal/ClassReference : kotlin/jvm/internal/Clas
 	public fun getNestedClasses ()Ljava/util/Collection;
 	public fun getObjectInstance ()Ljava/lang/Object;
 	public fun getQualifiedName ()Ljava/lang/String;
+	public fun getSealedSubclasses ()Ljava/util/List;
 	public fun getSimpleName ()Ljava/lang/String;
 	public fun getSupertypes ()Ljava/util/List;
 	public fun getTypeParameters ()Ljava/util/List;
@@ -1173,6 +1174,7 @@ public abstract interface class kotlin/reflect/KClass : kotlin/reflect/KAnnotate
 	public abstract fun getNestedClasses ()Ljava/util/Collection;
 	public abstract fun getObjectInstance ()Ljava/lang/Object;
 	public abstract fun getQualifiedName ()Ljava/lang/String;
+	public abstract fun getSealedSubclasses ()Ljava/util/List;
 	public abstract fun getSimpleName ()Ljava/lang/String;
 	public abstract fun getSupertypes ()Ljava/util/List;
 	public abstract fun getTypeParameters ()Ljava/util/List;

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

@@ -3293,6 +3293,7 @@ public final class kotlin/jvm/internal/ClassReference : kotlin/jvm/internal/Clas
 	public fun getNestedClasses ()Ljava/util/Collection;
 	public fun getObjectInstance ()Ljava/lang/Object;
 	public fun getQualifiedName ()Ljava/lang/String;
+	public fun getSealedSubclasses ()Ljava/util/List;
 	public fun getSimpleName ()Ljava/lang/String;
 	public fun getSupertypes ()Ljava/util/List;
 	public fun getTypeParameters ()Ljava/util/List;
@@ -4292,6 +4293,7 @@ public abstract interface class kotlin/reflect/KClass : kotlin/reflect/KAnnotate
 	public abstract fun getNestedClasses ()Ljava/util/Collection;
 	public abstract fun getObjectInstance ()Ljava/lang/Object;
 	public abstract fun getQualifiedName ()Ljava/lang/String;
+	public abstract fun getSealedSubclasses ()Ljava/util/List;
 	public abstract fun getSimpleName ()Ljava/lang/String;
 	public abstract fun getSupertypes ()Ljava/util/List;
 	public abstract fun getTypeParameters ()Ljava/util/List;