docs: function findFatArrow(stream, state) {
      if (state.fatArrowAt) state.fatArrowAt = null;
      var arrow = stream.string.indexOf("=>", stream.start);
      if (arrow < 0) return;
  
      var depth = 0, sawSomething = false;
      for (var pos = arrow - 1; pos >= 0; --pos) {
        var ch = stream.string.charAt(pos);
        var bracket = brackets.indexOf(ch);
        if (bracket >= 0 && bracket < 3) {
          if (!depth) { ++pos; break; }
          if (--depth == 0) break;
        } else if (bracket >= 3 && bracket < 6) {
          ++depth;
        } else if (wordRE.test(ch)) {
          sawSomething = true;
        } else if (/["'\/]/.test(ch)) {
          return;
        } else if (sawSomething && !depth) {
          ++pos;
          break;
        }
      }
      if (sawSomething && !depth) state.fatArrowAt = pos;
    }