KT-29340 Provide effective modality for enum class in IR

* if enum class has abstract members, then it is ABSTRACT
* otherwise, if enum class has entries with members, then it is OPEN
* otherwise, it is FINAL.

core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.java

@@ -5,6 +5,8 @@
 
 package org.jetbrains.kotlin.resolve;
 
+import kotlin.collections.CollectionsKt;
+import kotlin.jvm.functions.Function1;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
@@ -30,6 +32,7 @@ import java.util.*;
 import static org.jetbrains.kotlin.builtins.KotlinBuiltIns.isAny;
 import static org.jetbrains.kotlin.builtins.KotlinBuiltIns.isNullableAny;
 import static org.jetbrains.kotlin.descriptors.CallableMemberDescriptor.Kind.*;
+import static org.jetbrains.kotlin.descriptors.Modality.ABSTRACT;
 import static org.jetbrains.kotlin.resolve.descriptorUtil.DescriptorUtilsKt.getBuiltIns;
 
 public class DescriptorUtils {
@@ -331,6 +334,16 @@ public class DescriptorUtils {
         return descriptor instanceof ClassDescriptor && ((ClassDescriptor) descriptor).getKind() == classKind;
     }
 
+    public static boolean hasAbstractMembers(@NotNull ClassDescriptor classDescriptor) {
+        for (DeclarationDescriptor member : getAllDescriptors(classDescriptor.getDefaultType().getMemberScope())) {
+            if (member instanceof CallableMemberDescriptor &&
+                ((CallableMemberDescriptor) member).getModality() == ABSTRACT) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     @NotNull
     public static List<ClassDescriptor> getSuperclassDescriptors(@NotNull ClassDescriptor classDescriptor) {
         Collection<KotlinType> superclassTypes = classDescriptor.getTypeConstructor().getSupertypes();