Compiling the following program:

interface List<E> {}

class Test {
   <T> void merge(List<T> l1, List<T> l2) {}
   void test(List<? extends Test> list) {
    merge(list, list);
   }
}

produces the following bad output if the compatibility mode flag (-XDoldDiags) is set:

TestX.java:6: method merge in class Test cannot be applied to given types
    merge(list, list);
    ^
  required: List<T>,List<T>
  found: List<capture#0 of ? extends Test>,List<capture#0 of ? extends Test>
1 error

That is, captured var indexes are not generated correctly.