@nicolas-grekas Replaces: #45824 as I accidentally registerred a lot of people to the notifier list when changing target branch.

Note about difference between docblock vs PHP 8 union types:
With PHP 8 union types, the resolved $types array was always (when I checked) in the same order, no matter the type definition.
So these two things: public null|boolean|DateTime and public DateTime|boolean|null would always generate an array, where the first item was DateTime.

With PHP docblock the $tpyes array order depends of the order of the documentation.
So the * @var \DateTime|bool|null would resolve to an array with DateTime as first item, but the * @var null|bool|\DateTime would resolve to the DateTime being the last element.