Introduce SyntheticPropertyDescriptor interface

compiler/frontend.java/src/org/jetbrains/kotlin/synthetic/JavaSyntheticPropertiesScope.kt

@@ -44,9 +44,9 @@ fun canBePropertyAccessor(identifier: String): Boolean {
     return identifier.startsWith("get") || identifier.startsWith("is") || identifier.startsWith("set")
 }
 
-interface SyntheticJavaPropertyDescriptor : PropertyDescriptor {
-    val getMethod: FunctionDescriptor
-    val setMethod: FunctionDescriptor?
+interface SyntheticJavaPropertyDescriptor : PropertyDescriptor, SyntheticPropertyDescriptor {
+    override val getMethod: FunctionDescriptor
+    override val setMethod: FunctionDescriptor?
 
     companion object {
         fun findByGetterOrSetter(getterOrSetter: FunctionDescriptor, syntheticScopes: SyntheticScopes): SyntheticJavaPropertyDescriptor? {

core/descriptors/src/org/jetbrains/kotlin/descriptors/SyntheticPropertyDescriptor.kt

@@ -0,0 +1,11 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. 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.descriptors
+
+interface SyntheticPropertyDescriptor {
+    val getMethod: FunctionDescriptor
+    val setMethod: FunctionDescriptor?
+}