[FIR] Fix Java sealed class inheritors

This fixes NO_ELSE_IN_WHEN diagnostics when using java sealed
classes in an exhaustive when.

#KT-58216 Fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/services/LLFirSealedClassInheritorsProcessorFactoryForTests.kt

@@ -10,6 +10,8 @@ import org.jetbrains.kotlin.analysis.low.level.api.fir.project.structure.llFirMo
 import org.jetbrains.kotlin.analysis.project.structure.KtModule
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.SealedClassInheritorsProvider
+import org.jetbrains.kotlin.fir.declarations.SealedClassInheritorsProviderInternals
+import org.jetbrains.kotlin.fir.declarations.sealedInheritorsAttr
 import org.jetbrains.kotlin.fir.declarations.utils.classId
 import org.jetbrains.kotlin.name.ClassId
 
@@ -28,10 +30,11 @@ internal class LLFirSealedClassInheritorsProcessorFactoryForTests : FirSealedCla
 private class SealedClassInheritorsProviderForTests(
     private val inheritorsByModule: Map<KtModule, Map<ClassId, List<ClassId>>>
 ) : SealedClassInheritorsProvider() {
+    @OptIn(SealedClassInheritorsProviderInternals::class)
     override fun getSealedClassInheritors(firClass: FirRegularClass): List<ClassId> {
         val ktModule = firClass.llFirModuleData.ktModule
         val inheritorsForModuleMap = inheritorsByModule.getValue(ktModule)
-        return inheritorsForModuleMap[firClass.classId].orEmpty()
+        return inheritorsForModuleMap[firClass.classId] ?: firClass.sealedInheritorsAttr?.value ?: emptyList()
     }
 
-}
+}

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/FirJavaFacade.kt

@@ -394,7 +394,7 @@ abstract class FirJavaFacade(
                 setSealedClassInheritors {
                     permittedTypes.mapNotNull { classifierType ->
                         val classifier = classifierType.classifier as? JavaClass
-                        classifier?.let { JavaToKotlinClassMap.mapJavaToKotlin(it.fqName!!) }
+                        classifier?.let { JavaToKotlinClassMap.mapJavaToKotlin(it.fqName!!) ?: it.classId }
                     }
                 }
             }

compiler/testData/diagnostics/tests/testsWithJava17/sealedClasses/javaSealedClassExhaustiveness.fir.kt

@@ -1,44 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_VARIABLE
-// ISSUE: KT-41215, KT-43551
-
-// FILE: Base.java
-public sealed class Base permits A, B {}
-
-// FILE: A.java
-public final class A extends Base {}
-
-// FILE: B.java
-public sealed class B extends Base permits B.C, B.D {
-    public static final class C implements B {}
-
-    public static non-sealed class D extends B {}
-}
-
-// FILE: main.kt
-fun test_ok_1(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B -> 2
-    }
-}
-
-fun test_ok_2(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B.C -> 2
-        is B.D -> 3
-    }
-}
-
-fun test_error_1(base: Base) {
-    val x = when (base) {
-        is A -> 1
-    }
-}
-
-fun test_error_2(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B.C -> 2
-    }
-}

compiler/testData/diagnostics/tests/testsWithJava17/sealedClasses/javaSealedClassExhaustiveness.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 // ISSUE: KT-41215, KT-43551
 

compiler/testData/diagnostics/tests/testsWithJava17/sealedClasses/javaSealedInterfaceExhaustiveness.fir.kt

@@ -1,64 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_VARIABLE
-// ISSUE: KT-41215, KT-43551
-
-// FILE: Base.java
-public sealed interface Base permits A, B, E {}
-
-// FILE: A.java
-public non-sealed interface A extends Base {}
-
-// FILE: B.java
-public sealed interface B extends Base permits B.C, B.D {
-    public static final class C implements B {}
-
-    public static non-sealed interface D extends B {}
-}
-
-// FILE: E.java
-public enum E implements Base {
-    First, Second
-}
-
-// FILE: main.kt
-fun test_ok_1(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B -> 2
-        is E -> 3
-    }
-}
-
-fun test_ok_2(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B.C -> 2
-        is B.D -> 3
-        E.First -> 4
-        E.Second -> 5
-    }
-}
-
-fun test_error_1(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B -> 2
-    }
-}
-
-fun test_error_2(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B.C -> 2
-        is B.D -> 3
-        E.Second -> 5
-    }
-}
-
-fun test_error_3(base: Base) {
-    val x = when (base) {
-        is A -> 1
-        is B.C -> 2
-        E.First -> 4
-        E.Second -> 5
-    }
-}

compiler/testData/diagnostics/tests/testsWithJava17/sealedClasses/javaSealedInterfaceExhaustiveness.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 // ISSUE: KT-41215, KT-43551