TypedDict 'in' narrowing w/o @final#15698
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Positive effect in Rapptz/discord.py: |
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@hauntsaninja since you approved #13838, can take a look? |
| d_final: DFinal | ||
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| if 'spam' in d_final: | ||
| spam = 'ham' # E: Statement is unreachable |
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Is this test really useless? E.g. this seems useful and I'm not sure where else it is tested
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Good point, brought it back in a68b87a (and also removed more @finals).
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@hauntsaninja another review? |
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Diff from mypy_primer, showing the effect of this PR on open source code: discord.py (https://github.com/Rapptz/discord.py)
- discord/audit_logs.py:251: error: Argument "allow_list" to "AutoModTrigger" has incompatible type "object"; expected "list[str] | None" [arg-type]
- discord/audit_logs.py:257: error: Argument "allow_list" to "AutoModTrigger" has incompatible type "object"; expected "list[str] | None" [arg-type]
- discord/audit_logs.py:258: error: Argument "regex_patterns" to "AutoModTrigger" has incompatible type "object"; expected "list[str] | None" [arg-type]
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This issue recently came up on another forum, and it seems the fix is stuck in limbo. The diff seems fairly innocuous, the build/tests pass, and the discussion elsewhere seemed to conclude that this is the correct fix. Further, pyright merged the equivalent fix. Is it possible for this to be revisited? |
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@hauntsaninja Can we revisit this? |
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I think it would be good to try and get whatever behaviour is desired here into the typing spec. Would you or gandhis1 be willing to follow the steps here? https://github.com/python/typing-council#decisions |
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We shouldn't require
T1andT2to be final, to have'foo' in Union[TD1, TD2]narrowing take place. We previously (#13838) thought we should, but @erictraut made a good point that TypedDicts are structured types (like interfaces in TypeScript) and we shouldn't consider class hierarchy when type-matching but rather just the structure.Fixes #15697.