This PR was merged into the 4.4 branch. Discussion ---------- [Serializer] Fix denormalizing union types | Q | A | ------------- | --- | Branch? | 4.4 | Bug fix? | yes | New feature? | no  | Deprecations? | no  | Tickets | Fix #45818 | License | MIT | Doc PR | -  `@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. Commits ------- 98acd62 [Serializer] Fix denormalizing union types

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