gh-137065: Unmerge types.UnionType and typing.Union #137069
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serhiy-storchaka
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AlexWaygood and
rhettinger
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Partially revert pythonGH-105499. types.UnionType no longer an alias of typing.Union and no longer subscriptable, but subscribing typing.Union returns an instance of types.UnionType. typing.Union can no longer be used in the isinstance() checks.
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JelleZijlstra
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Jul 25, 2025
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| - Both syntaxes for creating a union now produce the same string representation in | ||
| ``repr()``. For example, ``repr(Union[int, str])`` | ||
| is now ``"int | str"`` instead of ``"typing.Union[int, str]"``. | ||
| - Unions created using the old syntax are no longer cached. Previously, running |
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Not sure why this was removed; the text would seem to still apply under this PR.
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I now think that we need a full revert. See #138967. |
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Partially revert GH-105499.
types.UnionType no longer an alias of typing.Union and no longer subscriptable, but subscribing typing.Union returns an instance of types.UnionType. typing.Union can no longer be used in the isinstance() checks.
typing._UnionGenericAlias, nottyping.Union#137065📚 Documentation preview 📚: https://cpython-previews--137069.org.readthedocs.build/