This produces an unexpected error:

  class C<T> {}
  <X> void m(C<? super X> arg) {}
  void test(C<?> arg) {
    m(arg);
  }

error: method m in class cannot be applied to given types;
    m(arg);
    ^
  required: C<? super X>
  found: C<CAP#1>
  reason: cannot infer type-variable(s) X
    (argument mismatch; C<CAP#1> cannot be converted to C<? super X>)
  where X is a type-variable:
    X extends Object declared in method <X>m(C<? super X>)
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Object from capture of ?
1 error

The error is the same under both -source 8 and -source 7.

This is a regression: there is also an error in javac 7, but not javac 6.