gh-118772: Allow TypeVars without a default to follow those with a default when constructing aliases by JelleZijlstra · Pull Request #118774 · python/cpython · GitHub
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gh-118772: Allow TypeVars without a default to follow those with a default when constructing aliases - #118774

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JelleZijlstra merged 2 commits into
python:mainfrom
JelleZijlstra:relaxdefailt
May 8, 2024
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gh-118772: Allow TypeVars without a default to follow those with a default when constructing aliases#118774
JelleZijlstra merged 2 commits into
python:mainfrom
JelleZijlstra:relaxdefailt

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@JelleZijlstra

@JelleZijlstra JelleZijlstra commented May 8, 2024 •
edited by bedevere-app Bot
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@JelleZijlstra JelleZijlstra added the needs backport to 3.13 bugs and security fixes label May 8, 2024
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JelleZijlstra requested a review from AlexWaygood as a code owner May 8, 2024 16:23
@bedevere-app bedevere-app Bot mentioned this pull request May 8, 2024
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JelleZijlstra merged commit aac6b01 into python:main May 8, 2024
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miss-islington-app Bot commented May 8, 2024

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JelleZijlstra deleted the relaxdefailt branch May 8, 2024 16:54
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bedevere-app Bot commented May 8, 2024

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GH-118776 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.13 bugs and security fixes label May 8, 2024
JelleZijlstra added a commit that referenced this pull request May 8, 2024
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[3.13] gh-118772: Allow TypeVars without a default to follow those wi…
c6680cd 
…th a default when constructing aliases (GH-118774) (#118776)

(cherry picked from commit aac6b01)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
@AlexWaygood

AlexWaygood commented May 13, 2024

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Unfortunately I think it's infeasible to backport this to typing_extensions, unless we can think of some other approach to implement the same behaviour at typing_extensions. Here's the beginnings of a typing_extensions patch: https://github.com/python/typing_extensions/compare/main...AlexWaygood:typing_extensions:646-default-before-nondefault?expand=1. It passes tests on Python 3.11 and 3.12, but starts interfering with the typing.py internals in some quite fundamental ways on lower versions of Python due to the extensiveness of the monkeypatching. It's plausibly fixable, but it would require even more invasive monkeypatching, and I think it would make the code too fragile.

@AlexWaygood AlexWaygood mentioned this pull request May 14, 2024
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AlexWaygood commented May 14, 2024

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@JelleZijlstra JelleZijlstra mentioned this pull request May 28, 2024
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JelleZijlstra restored the relaxdefailt branch September 10, 2024 23:37
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