docs: private final int scan_negative_for_numeric_type(int c) throws IOException
      {
          assert(c == '-');
          c = read_char();
          int t = scan_for_numeric_type(c);
          if (t == IonTokenConstsX.TOKEN_TIMESTAMP) {
              bad_token(c);
          }
          unread_char(c); // and the caller need to unread the '-'
          return t;
      }