How to create UnionType with 3+ sub-types?

[brandonkelly]

There are a few places I need to add union type declarations via AddPropertyTypeDeclarationRector, which include 3 or more sub-types, for example:

- public $plugin = null;
+ public PluginInterface|string|null $plugin = null;

However PHPStan\Type\UnionType is throwing a ShouldNotHappenException from its constructor immediately when attempting to instantiate a UnionType with more than two sub-types:

use PHPStan\Type\NullType;
use PHPStan\Type\ObjectType;
use PHPStan\Type\StringType;
use PHPStan\Type\UnionType;

$pluginType = new ObjectType('craft\base\PluginInterface');
$stringType = new StringType();
$nullType = new NullType();

// causes ShouldNotHappenException exception:
$unionType = new UnionType([$pluginType, $stringType, $nullType]);

Is there a different way I could go about this with Rector? Or does this just need to be fixed in PHPStan first?

[TomasVotruba]

At the moment it's limitation of PHPStan UnionType object.

We go around it like this:
https://github.com/rectorphp/rector-symfony/blob/91fd3f3882171c6f0c7e60c44e689e8d7d8ad0a4/config/sets/symfony/symfony6/symfony-return-types.php#L56-L63

[brandonkelly]

Thanks! Works like a charm.