regression: return-type inference rejects valid code

import java.util.Comparator;
import java.util.List;

class Test {
   <T extends Comparable<? super T>> Comparator<List<T>> comparator() { return null; }
   static <T extends Comparable<? super T>> void f() {
      Comparator<List<T>> comparator = comparator(); // [*]
   }
}


this program is rejected with the following error message:

 type parameters of <T>java.util.Comparator<java.util.List<T>> cannot be determined;
    no unique maximal instance exists for type variable T with upper bounds java.lang.Comparable<? super T>



See also http://www.netbeans.org/issues/show_bug.cgi?id=163967
http://www.netbeans.org/issues/show_bug.cgi?id=163969