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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Merge 'types.UnionType' with `typing._UnionGenericAlias`, not `typing.Union`","articleBody":"# Bug report\n\nI think #105499 was a mistake. `types.UnionType` was intentionally named so to avoid confusion with `typing.Union` (see #88895). `types.UnionType` should not be subscriptable because it is not generic type (and if it was a generic type, subscription would have different semantic than for `typing.Union`). `types.UnionType` corresponds to `typing._UnionGenericAlias`, not `typing.Union` (see https://github.com/python/cpython/issues/89581#issuecomment-1093932536).\n\nSo we should restore `typing.Union`, make `typing._UnionGenericAlias` an alias of `types.UnionType`, and make `types.UnionType` non-subscriptable again.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-137069\n* gh-138967\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/serhiy-storchaka","@type":"Person","name":"serhiy-storchaka"},"datePublished":"2025-07-24T05:20:20.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":19},"url":"https://github.com/137065/cpython/issues/137065"}