Add KClass.isFun modifier to reflection

#KT-38881 Fixed

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

@@ -1,8 +1,7 @@
-// IGNORE_BACKEND: JS_IR
+// TARGET_BACKEND: JVM
-// TODO: muted automatically, investigate should it be ran for JS or not
+// IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JS, NATIVE
-
 // WITH_REFLECT
+// FILE: box.kt
 
 import kotlin.test.assertTrue
 import kotlin.test.assertFalse
@@ -12,6 +11,7 @@ sealed class S {
     inner class InnerClass
     companion object
     object NonCompanionObject
+    fun interface FunInterface { fun invoke() }
 }
 
 fun box(): String {
@@ -22,26 +22,49 @@ fun box(): String {
     assertFalse(S::class.isData)
     assertFalse(S::class.isInner)
     assertFalse(S::class.isCompanion)
+    assertFalse(S::class.isFun)
 
     assertFalse(S.DataClass::class.isSealed)
     assertTrue(S.DataClass::class.isData)
     assertFalse(S.DataClass::class.isInner)
     assertFalse(S.DataClass::class.isCompanion)
+    assertFalse(S.DataClass::class.isFun)
 
     assertFalse(S.InnerClass::class.isSealed)
     assertFalse(S.InnerClass::class.isData)
     assertTrue(S.InnerClass::class.isInner)
     assertFalse(S.InnerClass::class.isCompanion)
+    assertFalse(S.InnerClass::class.isFun)
 
     assertFalse(S.Companion::class.isSealed)
     assertFalse(S.Companion::class.isData)
     assertFalse(S.Companion::class.isInner)
     assertTrue(S.Companion::class.isCompanion)
+    assertFalse(S.Companion::class.isFun)
 
     assertFalse(S.NonCompanionObject::class.isSealed)
     assertFalse(S.NonCompanionObject::class.isData)
     assertFalse(S.NonCompanionObject::class.isInner)
     assertFalse(S.NonCompanionObject::class.isCompanion)
+    assertFalse(S.NonCompanionObject::class.isFun)
+
+    assertFalse(S.FunInterface::class.isSealed)
+    assertFalse(S.FunInterface::class.isData)
+    assertFalse(S.FunInterface::class.isInner)
+    assertFalse(S.FunInterface::class.isCompanion)
+    assertTrue(S.FunInterface::class.isFun)
+
+    assertFalse(JavaInterface::class.isSealed)
+    assertFalse(JavaInterface::class.isData)
+    assertFalse(JavaInterface::class.isInner)
+    assertFalse(JavaInterface::class.isCompanion)
+    assertFalse(JavaInterface::class.isFun)
 
     return "OK"
 }
+
+// FILE: JavaInterface.java
+
+public interface JavaInterface {
+    int invoke(String s);
+}

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

@@ -279,6 +279,10 @@ internal class KClassImpl<T : Any>(override val jClass: Class<T>) : KDeclaration
     override val isCompanion: Boolean
         get() = descriptor.isCompanionObject
 
+    @Suppress("NOTHING_TO_OVERRIDE") // Temporary workaround for the JPS build until bootstrap
+    override val isFun: Boolean
+        get() = descriptor.isFun
+
     override fun equals(other: Any?): Boolean =
         other is KClassImpl<*> && javaObjectType == other.javaObjectType
 

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

@@ -21766,11 +21766,6 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
                 runTest("compiler/testData/codegen/box/reflection/modifiers/classVisibility.kt");
             }
 
-            @TestMetadata("classes.kt")
-            public void testClasses() throws Exception {
-                runTest("compiler/testData/codegen/box/reflection/modifiers/classes.kt");
-            }
-
             @TestMetadata("functions.kt")
             public void testFunctions() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/modifiers/functions.kt");

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

@@ -21781,11 +21781,6 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
                 runTest("compiler/testData/codegen/box/reflection/modifiers/classVisibility.kt");
             }
 
-            @TestMetadata("classes.kt")
-            public void testClasses() throws Exception {
-                runTest("compiler/testData/codegen/box/reflection/modifiers/classes.kt");
-            }
-
             @TestMetadata("functions.kt")
             public void testFunctions() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/modifiers/functions.kt");

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

@@ -77,6 +77,10 @@ public class ClassReference(override val jClass: Class<*>) : KClass<Any>, ClassB
     override val isCompanion: Boolean
         get() = error()
 
+    @SinceKotlin("1.4")
+    override val isFun: Boolean
+        get() = error()
+
     private fun error(): Nothing = throw KotlinReflectionNotSupportedError()
 
     override fun equals(other: Any?) =

libraries/stdlib/jvm/src/kotlin/reflect/KClass.kt

@@ -127,6 +127,12 @@ public actual interface KClass<T : Any> : KDeclarationContainer, KAnnotatedEleme
     @SinceKotlin("1.1")
     public val isCompanion: Boolean
 
+    /**
+     * `true` if this class is a Kotlin functional interface.
+     */
+    @SinceKotlin("1.4")
+    public val isFun: Boolean
+
     /**
      * Returns `true` if this [KClass] instance represents the same Kotlin class as the class represented by [other].
      * On JVM this means that all of the following conditions are satisfied:

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

@@ -3450,6 +3450,7 @@ public final class kotlin/jvm/internal/ClassReference : kotlin/jvm/internal/Clas
 	public fun isCompanion ()Z
 	public fun isData ()Z
 	public fun isFinal ()Z
+	public fun isFun ()Z
 	public fun isInner ()Z
 	public fun isInstance (Ljava/lang/Object;)Z
 	public fun isOpen ()Z
@@ -4593,6 +4594,7 @@ public abstract interface class kotlin/reflect/KClass : kotlin/reflect/KAnnotate
 	public abstract fun isCompanion ()Z
 	public abstract fun isData ()Z
 	public abstract fun isFinal ()Z
+	public abstract fun isFun ()Z
 	public abstract fun isInner ()Z
 	public abstract fun isInstance (Ljava/lang/Object;)Z
 	public abstract fun isOpen ()Z