import java.util.Comparator; import java.util.List; class IdeaBugTest { public void foo(List base) { MyCollection.fun(base, new SubComparator()); } } class Base { } class Sub extends Base { } class SubComparator implements Comparator { public int compare(Sub o1, Sub o2) { return 0; } } class MyCollection { public static void fun(List list, Comparator comp) { } }