android/guava/src/com/google/common/collect/ForwardingSortedSet.java
@SuppressWarnings("unchecked")
  private int unsafeCompare(@NullableDecl Object o1, @NullableDecl Object o2) {
    Comparator<? super E> comparator = comparator();
    return (comparator == null)
        ? ((Comparable<Object>) o1).compareTo(o2)
        : ((Comparator<Object>) comparator).compare(o1, o2);
  }
@SuppressWarnings("unchecked")
  private int unsafeCompare(@NullableDecl Object o1, @NullableDecl Object o2) {
    Comparator<? super E> comparator = comparator();
    return (comparator == null)
        ? ((Comparable<Object>) o1).compareTo(o2)
        : ((Comparator<Object>) comparator).compare(o1, o2);
  }
unsafe, but worst case is a CCE is thrown, which callers will be expecting