[BUG]: Incorrect return type hint of Phalcon\Mvc\Model\MetaData::getDI()

[sergeyklay]

The current implementation of Phalcon\Mvc\Model\MetaData::getDI implies that method must return a Phalcon\Di\DiInterface instance:

cphalcon/phalcon/Mvc/Model/MetaData.zep

Lines 279 to 282 in d3e9463

	public function getDI() -> <DiInterface>
	{
	return this->container;
	}

however, MetaData::$container may be NULL:

cphalcon/phalcon/Mvc/Model/MetaData.zep

Lines 65 to 67 in d3e9463

	protected container;

This lead to a fatal error:

use Phalcon\Mvc\Model\MetaData\Memory;

$metadata = new Memory();
$metadata->getDI();

PHP Fatal error:
Return value of Phalcon\Mvc\Model\MetaData::getDI()
must implement interface Phalcon\Di\DiInterface, null returned

The problem also is that this class implement InjectionAwareInterface which does not declare this method as nullable:

cphalcon/phalcon/Di/InjectionAwareInterface.zep

Lines 24 to 27 in d3e9463

	/**
	* Returns the internal dependency injector
	*/
	public function getDI() -> <DiInterface>;

[sergeyklay]

Fixed in 4.0.x branch