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gh-140348: Fix using | on unusual objects plus Unions#140383

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JelleZijlstra merged 2 commits intopython:mainfrom
JelleZijlstra:union-nb-or
Nov 3, 2025
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gh-140348: Fix using | on unusual objects plus Unions#140383
JelleZijlstra merged 2 commits intopython:mainfrom
JelleZijlstra:union-nb-or

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@JelleZijlstra JelleZijlstra commented Oct 20, 2025 •
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This restores the 3.13 behavior where Union[A, B] | ... was almost always allowed, rejecting only things that typing._type_check rejects.

It also necessarily means that something like int | str | "float" now works. And if a third-party type implements __ror__ on union objects and does something other than create a union, it may no longer work.

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I havent heavily been involved in unionobject.c or genericaliasobject.c in about 4 years. But from what I recall, LGTM.

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efimov-mikhail commented Oct 21, 2025 •
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CI is red, this PR breaks some tests.
I've prepared slighly changed variant of this:
https://github.com/efimov-mikhail/cpython/tree/issue-140383-union-nb-or

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JelleZijlstra commented Oct 21, 2025

Oops, pushed a new version that does not impact other types.

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efimov-mikhail commented Oct 21, 2025

Is it okay that now we have two variants of __or__ method? For example, will GenericAlias and str objects work together as expected?

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JelleZijlstra commented Oct 21, 2025

They don't, and maybe they should, but the behavior is the same in 3.13 and 3.14, so it's not part of the current issue. This PR focuses only on fixing the regression in 3.14.

$ uvx python3.13 -c 'list[int] | "str"'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    list[int] | "str"
    ~~~~~~~~~~^~~~~~~
TypeError: unsupported operand type(s) for |: 'types.GenericAlias' and 'str'
$ uvx python3.14 -c 'list[int] | "str"'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    list[int] | "str"
    ~~~~~~~~~~^~~~~~~
TypeError: unsupported operand type(s) for |: 'types.GenericAlias' and 'str'

@JelleZijlstra JelleZijlstra added the needs backport to 3.14 bugs and security fixes label Nov 3, 2025
@JelleZijlstra JelleZijlstra merged commit 7a9437d into python:main Nov 3, 2025
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miss-islington-app bot commented Nov 3, 2025

Thanks @JelleZijlstra for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Nov 3, 2025
@JelleZijlstra @miss-islington
pythongh-140348: Fix using | on unusual objects plus Unions (pythonGH…
e6db97a 
…-140383)

(cherry picked from commit 7a9437d)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
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bedevere-app bot commented Nov 3, 2025

GH-140948 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.14 bugs and security fixes label Nov 3, 2025
JelleZijlstra added a commit that referenced this pull request Nov 3, 2025
@miss-islington @JelleZijlstra
[3.14] gh-140348: Fix using | on unusual objects plus Unions (GH-140383…
7881046 
…) (#140948)

gh-140348: Fix using | on unusual objects plus Unions (GH-140383)
(cherry picked from commit 7a9437d)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
StanFromIreland pushed a commit to StanFromIreland/cpython that referenced this pull request Dec 6, 2025
@JelleZijlstra @StanFromIreland
pythongh-140348: Fix using | on unusual objects plus Unions (python#1…
db6d4e7 
…40383)
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@efimov-mikhail efimov-mikhail efimov-mikhail approved these changes

@Fidget-Spinner Fidget-Spinner Fidget-Spinner approved these changes

@AlexWaygood AlexWaygood Awaiting requested review from AlexWaygood AlexWaygood is a code owner

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