private static class WildcardCapturer {

    static final WildcardCapturer INSTANCE = new WildcardCapturer();

    private final AtomicInteger id;

    private WildcardCapturer() {
      this(new AtomicInteger());
    }

    private WildcardCapturer(AtomicInteger id) {
      this.id = id;
    }

    final Type capture(Type type) {