Address JDK8/JDK6 issues with computeIfAbsent

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeAttributes.kt

@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.fir.types
 
+import org.jetbrains.kotlin.fir.util.ConeTypeRegistry
 import org.jetbrains.kotlin.util.AttributeArrayOwner
 import org.jetbrains.kotlin.util.TypeRegistry
 import org.jetbrains.kotlin.types.model.AnnotationMarker
@@ -36,7 +37,7 @@ abstract class ConeAttribute<T : ConeAttribute<T>> : AnnotationMarker {
 class ConeAttributes private constructor(attributes: List<ConeAttribute<*>>) : AttributeArrayOwner<ConeAttribute<*>, ConeAttribute<*>>(),
     Iterable<ConeAttribute<*>> {
 
-    companion object : TypeRegistry<ConeAttribute<*>, ConeAttribute<*>>() {
+    companion object : ConeTypeRegistry<ConeAttribute<*>, ConeAttribute<*>>() {
         inline fun <reified T : ConeAttribute<T>> attributeAccessor(): ReadOnlyProperty<ConeAttributes, T?> {
             @Suppress("UNCHECKED_CAST")
             return generateNullableAccessor<ConeAttribute<*>, T>(T::class) as ReadOnlyProperty<ConeAttributes, T?>

compiler/fir/cones/src/org/jetbrains/kotlin/fir/util/ConeTypeRegistry.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.util
+
+import org.jetbrains.kotlin.util.TypeRegistry
+import java.util.concurrent.ConcurrentHashMap
+import kotlin.reflect.KClass
+
+abstract class ConeTypeRegistry<K : Any, V : Any> : TypeRegistry<K, V>() {
+    override fun <T : K> ConcurrentHashMap<KClass<out K>, Int>.customComputeIfAbsent(
+        kClass: KClass<T>,
+        compute: (KClass<out K>) -> Int
+    ): Int {
+        return this.computeIfAbsent(kClass, compute)
+    }
+}