[FE] Support sealed classes and interfaces from java

KT-43551
KT-41215

core/compiler.common/src/org/jetbrains/kotlin/descriptors/Modality.kt

@@ -15,12 +15,13 @@ enum class Modality {
     ABSTRACT;
 
     companion object {
-
-        // NB: never returns SEALED
-        fun convertFromFlags(abstract: Boolean, open: Boolean): Modality {
-            if (abstract) return ABSTRACT
-            if (open) return OPEN
-            return FINAL
+        fun convertFromFlags(sealed: Boolean, abstract: Boolean, open: Boolean): Modality {
+            return when {
+                sealed -> SEALED
+                abstract -> ABSTRACT
+                open -> OPEN
+                else -> FINAL
+            }
         }
     }
 }

core/descriptors.jvm/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaClassDescriptor.kt

@@ -76,7 +76,7 @@ class LazyJavaClassDescriptor(
 
     private val modality =
         if (jClass.isAnnotationType || jClass.isEnum) Modality.FINAL
-        else Modality.convertFromFlags(jClass.isAbstract || jClass.isInterface, !jClass.isFinal)
+        else Modality.convertFromFlags(jClass.isSealed, jClass.isAbstract || jClass.isInterface, !jClass.isFinal)
 
     private val visibility = jClass.visibility
     private val isInner = jClass.outerClass != null && !jClass.isStatic
@@ -180,7 +180,14 @@ class LazyJavaClassDescriptor(
     fun wasScopeContentRequested() =
         getUnsubstitutedMemberScope().wasContentRequested() || staticScope.wasContentRequested()
 
-    override fun getSealedSubclasses(): Collection<ClassDescriptor> = emptyList()
+    override fun getSealedSubclasses(): Collection<ClassDescriptor> = if (modality == Modality.SEALED) {
+        val attributes = TypeUsage.COMMON.toAttributes()
+        jClass.permittedTypes.mapNotNull {
+            c.typeResolver.transformJavaType(it, attributes).constructor.declarationDescriptor as? ClassDescriptor
+        }
+    } else {
+        emptyList()
+    }
 
     override fun toString() = "Lazy Java class ${this.fqNameUnsafe}"
 

core/descriptors.jvm/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaClassMemberScope.kt

@@ -515,7 +515,7 @@ class LazyJavaClassMemberScope(
             returnType,
             // Those functions are generated as open in bytecode
             // Actually, it should not be important because the class is final anyway, but leaving them open is convenient for consistency
-            Modality.convertFromFlags(abstract = false, open = true),
+            Modality.convertFromFlags(sealed = false, abstract = false, open = true),
             DescriptorVisibilities.PUBLIC,
             null,
         )

core/descriptors.jvm/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaScope.kt

@@ -181,7 +181,7 @@ abstract class LazyJavaScope(
             effectiveSignature.typeParameters,
             effectiveSignature.valueParameters,
             effectiveSignature.returnType,
-            Modality.convertFromFlags(method.isAbstract, !method.isFinal),
+            Modality.convertFromFlags(sealed = false, method.isAbstract, !method.isFinal),
             method.visibility.toDescriptorVisibility(),
             if (effectiveSignature.receiverType != null)
                 mapOf(JavaMethodDescriptor.ORIGINAL_VALUE_PARAMETER_FOR_EXTENSION_RECEIVER to valueParameters.descriptors.first())