'operator' checks

compiler/testData/diagnostics/tests/smartCasts/varnotnull/postfixNotnullClassIncrement.kt

@@ -1,13 +1,12 @@
 class MyClass
 
-// In principle it is not correct, MyClass? is not a subtype of MyClass
-operator fun MyClass.inc(): MyClass? { return null }
+operator fun MyClass.inc(): MyClass { <!UNREACHABLE_CODE!>return<!> null!! }
 
 public fun box() : MyClass? {
-    var i : MyClass? 
+    var i : MyClass?
     i = MyClass()
     // type of j can be inferred as MyClass()
     var j = <!DEBUG_INFO_SMARTCAST!>i<!>++
     <!DEBUG_INFO_SMARTCAST!>j<!>.hashCode()
     return i
-}
+}