[ty] Reject deletingFinal attributes#24508
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charliermarsh merged 1 commit intomainfrom Apr 10, 2026
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Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 87.80%. The percentage of expected errors that received a diagnostic held steady at 82.91%. The number of fully passing files held steady at 76/132. |
Memory usage reportMemory usage unchanged ✅ |
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| Lint rule | Added | Removed | Changed |
|---|---|---|---|
invalid-await |
40 | 0 | 0 |
invalid-return-type |
2 | 0 | 0 |
invalid-assignment |
1 | 0 | 0 |
| Total | 43 | 0 | 0 |
Large timing changes:
| Project | Old Time | New Time | Change |
|---|---|---|---|
pandas |
1.09s | 1.64s | +50% |
Changes in flaky projects detected. Raw diff output excludes flaky projects; see the HTML report for details.
Raw diff:
schema_salad (https://github.com/common-workflow-language/schema_salad)
+ schema_salad/ref_resolver.py:119:13 error[invalid-assignment] Cannot delete final attribute `normalize` on type `Self@__del__`: `Final` attributes cannot be deleted
carljm
approved these changes
Apr 9, 2026
Comment on lines
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| if self.validate_final_attribute_deletion( | ||
| target, | ||
| object_ty, | ||
| attribute, | ||
| emit_diagnostics, | ||
| ) { | ||
| return false; | ||
| } |
Contributor
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Removing this doesn't fail any tests. It's not totally clear to me what behavior is right here. If we have a __delattr__, we don't know what it does internally, so should we assume it's deleting the Final attr of the same name, or not?
Other type checkers that validate deletion of Final attrs do it even if there is a __delattr__, so maybe we should too? In that case we should add a test.
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carljm
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Apr 10, 2026
* main: Bump typing conformance suite commit to latest upstream (#24553) [ty] Reject deleting`Final` attributes (#24508) [ty] Respect property deleters in attribute deletion checks (#24500) [ty] stop unioning Unknown into types of un-annotated attributes (#24531) [ty] Fix bad diagnostic range for incorrect implicit `__init_subclass__` calls (#24541) [ty] Add a `SupportedPythonVersion` enum (#24412) [ty] Ignore unsupported editor-selected Python versions (#24498) [ty] Add snapshots for `__init_subclass__` diagnostics (#24539) [ty] Minor fix in tests (#24538) [ty] Allow `Final` variable assignments in `__post_init__` (#24529) [ty] Expand test suite for assignment errors (#24537) [ty] Use `map`, not `__map`, as the name of the mapping parameter in `TypedDict` `__init__` methods (#24535) [ty] Rework logic for synthesizing `TypedDict` methods (#24534) [flake8-bandit] Fix S103 false positives and negatives in mask analysis (#24424) [ty] mdtest.py: update dependencies (#24533) Rename patterns and arguments source order iterator method (#24532) [ty] Omit invalid keyword arguments from `TypedDict` signature (#24522) [ty] support super() in metaclass methods (#24483) [ty] Synthesize `__init__` for `TypedDict` (#24476)
This was referenced Apr 27, 2026
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Summary
We now error when attempting to delete a
Finalattribute, as in: