vendors/tempy.js/makeRe
    function makeRe() {
      if (this.regexp || this.regexp === false)
        return this.regexp;
      var set = this.set;
      if (!set.length) {
        this.regexp = false;
        return this.regexp;
      }
      var options = this.options;
      var twoStar = options.noglobstar ? star : options.dot ? twoStarDot : twoStarNoDot;
      var flags = options.nocase ? "i" : "";
      var re = set.map(function(pattern) {
        return pattern.map(function(p) {
          return p === GLOBSTAR ? twoStar : typeof p === "string" ? regExpEscape(p) : p._src;
        }).join("\\/");
      }).join("|");
      re = "^(?:" + re + ")$";
      if (this.negate)
        re = "^(?!" + re + ").*$";
      try {
        this.regexp = new RegExp(re, flags);
      } catch (ex) {
        this.regexp = false;
      }
      return this.regexp;
    }