private function _use() {
    $node = new UseDeclarationStatementNode();
    $this->mustMatch(T_USE, $node);
    $this->tryMatch(T_FUNCTION, $node, 'useFunction') || $this->tryMatch(T_CONST, $node, 'useConst');
    $declarations = new CommaListNode();
    do {
      $declarations->addChild($this->useDeclaration());
    } while ($this->tryMatch(',', $declarations));
    $node->addChild($declarations, 'declarations');
    $this->endStatement($node);
    return $node;
  }