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@cdce8p cdce8p commented Feb 15, 2025

Source commit:
python/typeshed@cc8ca93

Partially revert python/typeshed#13450 to fix mypyc runs.

cdce8p and others added 7 commits February 15, 2025 20:12
This is allegedly causing large performance problems, see 13821

typeshed/8231 had zero hits on mypy_primer, so it's not the worst thing
to undo. Patching this in typeshed also feels weird, since there's a
more general soundness issue. If a typevar has a bound or constraint, we
might not want to solve it to a Literal.

If we can confirm the performance regression or fix the unsoundness
within mypy, I might pursue upstreaming this in typeshed.

(Reminder: add this to the sync_typeshed script once merged)
This was referenced Feb 15, 2025
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Diff from mypy_primer, showing the effect of this PR on open source code:

steam.py (https://github.com/Gobot1234/steam.py)
+ steam/trade.py:189: error: Argument 1 of "__mro_entries__" is incompatible with supertype "GenericAlias"; supertype defines the argument type as "Iterable[object]"  [override]
+ steam/trade.py:189: note: This violates the Liskov substitution principle
+ steam/trade.py:189: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides

django-stubs (https://github.com/typeddjango/django-stubs): 2.04x faster (51.1s -> 25.0s in a single noisy sample)

freqtrade (https://github.com/freqtrade/freqtrade): 1.71x slower (130.0s -> 222.0s in a single noisy sample)

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cdce8p commented Feb 15, 2025

Mypy primer hits

@hauntsaninja hauntsaninja merged commit 52c7735 into python:master Feb 16, 2025
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Thanks for fixing the mypyc builds!

@cdce8p cdce8p deleted the sync-typeshed branch February 16, 2025 09:04
x612skm pushed a commit to x612skm/mypy-dev that referenced this pull request Feb 24, 2025
Source commit:

python/typeshed@cc8ca93

Partially revert python/typeshed#13450 to fix
mypyc runs.
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3 participants