[FIR generator] Deduplicate the logic of needPureAbstractElement

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/implementation.kt

@@ -98,7 +98,7 @@ fun SmartPrinter.printImplementation(implementation: Implementation) {
         }
 
         print(" : ")
-        if (!isInterface && !allParents.any { it.kind == ImplementationKind.AbstractClass || it.kind == ImplementationKind.SealedClass }) {
+        if (needPureAbstractElement) {
             print("${pureAbstractElementType.type}(), ")
         }
         print(allParents.joinToString { "${it.typeWithArguments}${it.kind.braces()}" })

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/utils.kt

@@ -113,10 +113,6 @@ private fun List<String>.filterRedundantImports(
 }
 
 
-val ImplementationKindOwner.needPureAbstractElement: Boolean
-    get() = (kind != ImplementationKind.Interface && kind != ImplementationKind.SealedInterface) && !allParents.any { it.kind == ImplementationKind.AbstractClass || it.kind == ImplementationKind.SealedClass }
-
-
 val Field.isVal: Boolean
     get() = (this is FieldList && !isMutableOrEmpty) || (this is FieldWithDefault && origin is FieldList && !origin.isMutableOrEmpty) || !isMutable
 

compiler/ir/ir.tree/tree-generator/src/org/jetbrains/kotlin/ir/generator/model/Transformations.kt

@@ -160,7 +160,7 @@ private fun markLeaves(elements: List<Element>) {
 
 private fun addAbstractElement(elements: List<Element>) {
     for (el in elements) {
-        if (el.kind!!.typeKind == TypeKind.Class && el.elementParents.none { it.element.kind!!.typeKind == TypeKind.Class }) {
+        if (el.needPureAbstractElement) {
             el.otherParents += elementBaseType
         }
     }

generators/tree-generator-common/src/org/jetbrains/kotlin/generators/tree/ImplementationKindOwner.kt

@@ -8,4 +8,8 @@ package org.jetbrains.kotlin.generators.tree
 interface ImplementationKindOwner : Importable {
     var kind: ImplementationKind?
     val allParents: List<ImplementationKindOwner>
-}
+}
+
+val ImplementationKindOwner.needPureAbstractElement: Boolean
+    get() = !(kind?.isInterface ?: false) &&
+            allParents.none { it.kind == ImplementationKind.AbstractClass || it.kind == ImplementationKind.SealedClass }