STC: lowed bound wildcard inference produces false positives

class Pogo {
  String x
}
class Sorter implements Comparator<Pogo>, Serializable {
  int compare(Pogo p1, Pogo p2) { p1.x <=> p2.x }
}
@groovy.transform.TypeChecked
void test(Pogo[] pogos) {
  List<String> strings = pogos.sort(true, new Sorter()).collect { Pogo pogo ->
    pogo.x
  }
  print strings
}
test(new Pogo(x:'foo'),new Pogo(x:'bar'))

Incompatible generic argument types. Cannot assign java.util.List<java.lang.Object> to: java.util.List<java.lang.String>
Expected parameter of type java.lang.Object but got Pogo
No such property: x for class: java.lang.Object