Rework narrowing logic for equality and identity #20492
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This was referenced Jan 16, 2026
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This is a follow up to #20492 that is pure refactoring. I separated it out to make that change easier to review. We inline `narrow_identity_equality_comparison`, improve comments, etc. There is some further refactoring later in my commit stack too.
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Requested in #20492 (comment) Regression for the Never's in #18524 (comment)
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This relates to changes made in python#20492
Collaborator
|
Noticed a minor regression in Home Assistant with # mypy: warn-unreachable
from enum import IntFlag
class WeatherFeature(IntFlag):
FORECAST_DAILY = 1
FORECAST_HOURLY = 2
FORECAST_TWICE_DAILY = 4
def func(supported_features: int) -> None:
reveal_type(supported_features)
if (supported_features & WeatherFeature.FORECAST_DAILY) == 0:
print("Hello World") # <-- This should work fine |
Collaborator
Author
|
Thanks, I have a follow up commit that will fix this case |
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Fixes some of the primer regressions from #20492 Fixes #19753 This should also happen to fix the case mentioned by cdce8p in #20492 (comment)
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This relates to changes made in python#20492
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This relates to changes made in python#20492
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This relates to changes made in python#20492
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This relates to changes made in python#20492
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This relates to changes made in python#20492
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This relates to changes made in python#20492
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This relates to changes made in python#20492
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Mypy does not narrow as much as it could, which results in false positives.
We would also like to narrow based on containment. The PR for that was previously reverted due to inconsistencies between narrowing via equality and via containment. This fixes the inconsistency on the equality side and paves the road for adding narrowing via containment. That is, we lay groundwork for fixing #17864 and fixing #17841
Fixes #18524
Fixes #20041
Fixes #17162
Fixes #16830
Fixes #13704
Fixes #7642
Fixes #3964