docs: public static String keywordToName(int token) {
          switch (token) {
              case Token.BREAK:      return "break";
              case Token.CASE:       return "case";
              case Token.CONTINUE:   return "continue";
              case Token.DEFAULT:    return "default";
              case Token.DELPROP:    return "delete";
              case Token.DO:         return "do";
              case Token.ELSE:       return "else";
              case Token.FALSE:      return "false";
              case Token.FOR:        return "for";
              case Token.FUNCTION:   return "function";
              case Token.IF:         return "if";
              case Token.IN:         return "in";
              case Token.LET:        return "let";
              case Token.NEW:        return "new";
              case Token.NULL:       return "null";
              case Token.RETURN:     return "return";
              case Token.SWITCH:     return "switch";
              case Token.THIS:       return "this";
              case Token.TRUE:       return "true";
              case Token.TYPEOF:     return "typeof";
              case Token.VAR:        return "var";
              case Token.VOID:       return "void";
              case Token.WHILE:      return "while";
              case Token.WITH:       return "with";
              case Token.YIELD:      return "yield";
              case Token.CATCH:      return "catch";
              case Token.CONST:      return "const";
              case Token.DEBUGGER:   return "debugger";
              case Token.FINALLY:    return "finally";
              case Token.INSTANCEOF: return "instanceof";
              case Token.THROW:      return "throw";
              case Token.TRY:        return "try";
              default:               return null;
          }
      }