private function forExpr(ForNode $parent, $terminator, $property_name, $is_last = FALSE, $terminator_name = NULL) {
    if ($this->tryMatch($terminator, $parent)) {
      $parent->addChild(new CommaListNode(), $property_name);
      return;
    }
    $parent->addChild($this->exprList(), $property_name);
    $this->mustMatch($terminator, $parent, $terminator_name, $is_last, FALSE);
  }