return 3;
    }

    @Override
    public char charAt(int index) {
      return "foo".charAt(index);
    }

    @Override
    public CharSequence subSequence(int start, int end) {
      return "foo".subSequence(start, end);
    }

    @Override
    public String toString() {
      throw new AssertionFailedError("shouldn't be invoked");
    }
  }

  // Don't do this.

      return 3;
    }

    @Override
    public char charAt(int index) {
      return "foo".charAt(index);
    }

    @Override
    public CharSequence subSequence(int start, int end) {
      return "foo".subSequence(start, end);
    }

    @Override
    public String toString() {
      throw new AssertionFailedError("shouldn't be invoked");
    }
  }

  // Don't do this.