KT-880 Overload resolution ambiguity

#KT-880 Fixed

compiler/testData/diagnostics/tests/override/kt880.kt

@@ -0,0 +1,16 @@
+// KT-880 Overload resolution ambiguity
+
+public trait I {
+    open fun test() : Unit
+}
+
+abstract public class A() {
+    open public fun test() : Unit {
+    }
+}
+
+public open class T() : A(), I {
+    open fun main() : Unit {
+        test() // Test no "Overload resolution ambiguity" is here
+    }
+}