Rewrite TowerLevels.

core/descriptors/src/org/jetbrains/kotlin/types/TypeUtils.java

@@ -258,19 +258,31 @@ public class TypeUtils {
 
     @NotNull
     public static List<KotlinType> getImmediateSupertypes(@NotNull KotlinType type) {
-        boolean isNullable = type.isMarkedNullable();
         TypeSubstitutor substitutor = TypeSubstitutor.create(type);
         Collection<KotlinType> originalSupertypes = type.getConstructor().getSupertypes();
         List<KotlinType> result = new ArrayList<KotlinType>(originalSupertypes.size());
         for (KotlinType supertype : originalSupertypes) {
-            KotlinType substitutedType = substitutor.substitute(supertype, Variance.INVARIANT);
+            KotlinType substitutedType = createSubstitutedSupertype(type, supertype, substitutor);
             if (substitutedType != null) {
-                result.add(makeNullableIfNeeded(substitutedType, isNullable));
+                result.add(substitutedType);
             }
         }
         return result;
     }
 
+    @Nullable
+    public static KotlinType createSubstitutedSupertype(
+            @NotNull KotlinType subType,
+            @NotNull KotlinType superType,
+            @NotNull TypeSubstitutor substitutor
+    ) {
+        KotlinType substitutedType = substitutor.substitute(superType, Variance.INVARIANT);
+        if (substitutedType != null) {
+            return makeNullableIfNeeded(substitutedType, subType.isMarkedNullable());
+        }
+        return null;
+    }
+
     private static void collectAllSupertypes(@NotNull KotlinType type, @NotNull Set<KotlinType> result) {
         List<KotlinType> immediateSupertypes = getImmediateSupertypes(type);
         result.addAll(immediateSupertypes);

core/descriptors/src/org/jetbrains/kotlin/types/TypeUtils.kt

@@ -17,11 +17,9 @@
 package org.jetbrains.kotlin.types.typeUtil
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
-import org.jetbrains.kotlin.descriptors.CallableDescriptor
-import org.jetbrains.kotlin.descriptors.ClassDescriptor
-import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
-import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
+import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
+import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
 import org.jetbrains.kotlin.utils.toReadOnlyList
@@ -162,3 +160,14 @@ private fun constituentTypes(result: MutableSet<KotlinType>, types: Collection<K
         }
     }
 }
+
+fun KotlinType.getImmediateSuperclassNotAny(): KotlinType? {
+    val superclasses = constructor.supertypes.filter {
+        val descriptor = it.constructor.declarationDescriptor
+        (DescriptorUtils.isClass(descriptor) || DescriptorUtils.isEnumClass(descriptor)) &&
+        !KotlinBuiltIns.isAnyOrNullableAny(it)
+    }
+    return superclasses.singleOrNull()?.let {
+        TypeUtils.createSubstitutedSupertype(this, it, TypeSubstitutor.create(this))
+    }
+}