docs: function createFunctionRule(
    words: string[],
    tokenName: string
  ): ParserContext => ?Token {
    const map = util.createHashMap(words, functionBoundary, false);
    return function(context: ParserContext): ?Token {
      // must be right after a "("
      const token = util.getPreviousNonWsToken(
        context.getAllTokens(),
        context.count()
      );
      if (!token) return null;
  
      if (
        token.name !== "punctuation" ||
        (token.value !== "(" &&
          (token.name !== "operator" || token.value !== "#'"))
      )
        return null;
  
      return util.matchWord(context, map, tokenName);
    };
  }