8000 gh-118168: Fix Unpack interaction with builtin aliases by JelleZijlstra · Pull Request #118169 · python/cpython · GitHub
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gh-118168: Fix Unpack interaction with builtin aliases #118169

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Merged
merged 2 commits into from
Apr 23, 2024
Merged

gh-118168: Fix Unpack interaction with builtin aliases #118169

merged 2 commits into from
Apr 23, 2024

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JelleZijlstra
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@JelleZijlstra JelleZijlstra commented Apr 23, 2024 •
edited by bedevere-app bot
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AlexWaygood
AlexWaygood approved these changes Apr 23, 2024
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Lib/typing.py
Comment on lines +1789 to +1791
if isinstance(arg, (_GenericAlias, types.GenericAlias)):
if arg.__origin__ is not tuple:
raise TypeError("Unpack[...] must be used with a tuple type")
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@AlexWaygood AlexWaygood Apr 23, 2024 •
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It feels weirdly inconsistent that we allow nonsensical things with the new syntax, but not with the "backwards-compatible syntax":

>>> from typing import TypeVarTuple, Unpack
>>> class Foo[*Ts]: ...
...
>>> Ts = TypeVarTuple("Ts")
>>> Bar = Foo[int, *Ts]
>>> Bar[*list[str]]
__main__.Foo[int, *list[str]]
>>> Bar[Unpack[list[str]]]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    Bar[Unpack[list[str]]]
    ~~~^^^^^^^^^^^^^^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 394, in inner
    return func(*args, **kwds)
           ~~~~^^^^^^^^^^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 1394, in __getitem__
    args = _unpack_args(args)
           ~~~~~~~~~~~~^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 306, in _unpack_args
    subargs = getattr(arg, '__typing_unpacked_tuple_args__', None)
              ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alexw/dev/cpython/Lib/typing.py", line 1791, in __typing_unpacked_tuple_args__
    raise TypeError("Unpack[...] must be used with a tuple type")
TypeError: Unpack[...] must be used with a tuple type

But I guess that's a preexisting problem, not new to this PR. We previously discussed the issue of "all generic aliases being unpackable" in #103450.

@JelleZijlstra @AlexWaygood
Update Lib/test/test_typing.py
5e82806 
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
@JelleZijlstra
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@AlexWaygood thanks for the review! Do you think this is safe to backport? (I'm leaning yes.)

@AlexWaygood
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@AlexWaygood thanks for the review! Do you think this is safe to backport? (I'm leaning yes.)

yeah, I think should be fine

@AlexWaygood AlexWaygood added the needs backport to 3.12 only security fixes label Apr 23, 2024
@JelleZijlstra JelleZijlstra enabled auto-merge (squash) April 23, 2024 13:19
@JelleZijlstra JelleZijlstra merged commit d0b664e into python:main Apr 23, 2024
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Thanks @JelleZijlstra for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Apr 23, 2024
@JelleZijlstra @AlexWaygood @miss-islington
pythongh-118168: Fix Unpack interaction with builtin aliases (pythonG…
d2bafbe 
…H-118169)

(cherry picked from commit d0b664e)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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bedevere-app bot commented Apr 23, 2024

GH-118178 is a backport of this pull request to the 3.12 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.12 only security fixes label Apr 23, 2024
AlexWaygood added a commit that referenced this pull request Apr 23, 2024
@miss-islington @JelleZijlstra @AlexWaygood
[3.12] gh-118168: Fix Unpack interaction with builtin aliases (GH-118169
741A
30e25d4 
) (#118178)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
@JelleZijlstra JelleZijlstra deleted the unpacktuple branch April 23, 2024 15:15
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