code: private Node tryFoldGetElem(Node n, Node left, Node right) {
      checkArgument(n.isGetElem());
  
      if (left.isObjectLit()) {
        return tryFoldObjectPropAccess(n, left, right);
      }
  
      if (left.isArrayLit()) {
        return tryFoldArrayAccess(n, left, right);
      }
  
      if (left.isString()) {
        return tryFoldStringArrayAccess(n, left, right);
      }
      return n;
    }
docs: Try to fold array-element. e.g [1, 2, 3][10];