Extraction Engine: Use original topmost descriptors when validating extracted code (fixes 'mutablyFlexibleType' test which failed after migration to generic contains/remove/etc. members in collections)

core/descriptors/src/org/jetbrains/kotlin/resolve/overridingUtils.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2010-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.resolve
+
+import org.jetbrains.kotlin.descriptors.CallableDescriptor
+import java.util.*
+
+fun CallableDescriptor.getOriginalTopmostOverriddenDescriptors(): Set<CallableDescriptor> {
+    return OverridingUtil.getTopmostOverridenDescriptors(this).mapTo(LinkedHashSet()) { it.original }
+}