@SuppressWarnings("unchecked") // returns default for both F and T
      T defaultConverter = (T) defaultConverter(convertFromType, convertToType);
      return defaultConverter;
    }
    if (type.getRawType().isInterface()) {
      return newDefaultReturningProxy(type);
    }
    return null;
  }

  private <F, T> Converter<F, T> defaultConverter(
      final TypeToken<F> convertFromType, final TypeToken<T> convertToType) {

      @SuppressWarnings("unchecked") // returns default for both F and T
      T defaultConverter = (T) defaultConverter(convertFromType, convertToType);
      return defaultConverter;
    }
    if (type.getRawType().isInterface()) {
      return newDefaultReturningProxy(type);
    }
    return null;
  }

  private <F, T> Converter<F, T> defaultConverter(
      final TypeToken<F> convertFromType, final TypeToken<T> convertToType) {

      Converter<String, Integer> defaultConverter =
          (Converter<String, Integer>) getDefaultParameterValue(0);
      assertEquals(Integer.valueOf(0), defaultConverter.convert("anything"));
      assertEquals("", defaultConverter.reverse().convert(123));
      assertNull(defaultConverter.convert(null));
      assertNull(defaultConverter.reverse().convert(null));
    }
  }