code: private function isInvalidInArrayDimFetch($node)
      {
          if (property_exists($node, 'dim') === false) {
              return $this->isInvalidIn($node);
          } elseif ($node->dim instanceof BinaryOp\Concat) {
              return $this->isInvalidInArrayDimFetch($node->dim->left)
              && $this->isInvalidInArrayDimFetch($node->dim->right);
          } else {
              return $this->isInvalidIn($node->dim);
          }
      }
docs: @param unknown $node
  
  @return bool