[ty] Disallow Self in metaclass and static methods by charliermarsh · Pull Request #22755 · astral-sh/ruff

charliermarsh · 2026-01-20T03:50:54Z

Summary

astral-sh-bot · 2026-01-20T03:52:36Z

Typing conformance results improved 🎉

The percentage of diagnostics emitted that were expected errors increased from 83.14% to 83.23%. The percentage of expected errors that received a diagnostic increased from 74.24% to 74.63%.

Summary

Metric	Old	New	Diff	Outcome
True Positives	804	809	+5	⏫ (✅)
False Positives	163	163	+0
False Negatives	279	275	-4	⏬ (✅)
Total Diagnostics	967	972	+5	⏫
Precision	83.14%	83.23%	+0.09%	⏫ (✅)
Recall	74.24%	74.63%	+0.39%	⏫ (✅)

True positives added

Details

Location	Name	Message
generics_self_usage.py:113:19	invalid-type-form	`Self` cannot be used in a static method
generics_self_usage.py:118:31 generics_self_usage.py:118:40	invalid-type-form invalid-type-form	`Self` cannot be used in a static method `Self` cannot be used in a static method
generics_self_usage.py:123:37	invalid-type-form	`Self` cannot be used in a metaclass
generics_self_usage.py:127:42	invalid-type-form	`Self` cannot be used in a metaclass

astral-sh-bot · 2026-01-20T03:53:48Z

`mypy_primer` results

Changes were detected when running on open source projects

porcupine (https://github.com/Akuli/porcupine)
+ porcupine/pluginmanager.py:133:49: error[invalid-argument-type] Argument to function `__new__` is incorrect: Expected `Iterable[Never]`, found `Unknown | str`
- Found 24 diagnostics
+ Found 25 diagnostics

setuptools (https://github.com/pypa/setuptools)
- setuptools/_distutils/command/install.py:719:42: error[invalid-argument-type] Argument to function `__new__` is incorrect: Expected `Iterable[Never]`, found `map[str]`
- Found 1127 diagnostics
+ Found 1126 diagnostics

prefect (https://github.com/PrefectHQ/prefect)
- src/prefect/deployments/runner.py:1017:70: warning[possibly-missing-attribute] Attribute `__name__` may be missing on object of type `Unknown | ((...) -> Any)`
+ src/prefect/deployments/runner.py:1017:70: warning[possibly-missing-attribute] Attribute `__name__` may be missing on object of type `Unknown | (((...) -> Any) & ((*args: object, **kwargs: object) -> object))`
- src/prefect/flow_engine.py:1004:32: error[invalid-await] `Unknown | R@FlowRunEngine | Coroutine[Any, Any, R@FlowRunEngine]` is not awaitable
- src/prefect/flow_engine.py:1610:24: error[invalid-await] `Unknown | R@AsyncFlowRunEngine | Coroutine[Any, Any, R@AsyncFlowRunEngine]` is not awaitable
- src/prefect/flow_engine.py:1691:43: error[invalid-argument-type] Argument to function `next` is incorrect: Expected `SupportsNext[Unknown]`, found `Unknown | R@run_generator_flow_sync`
- src/prefect/flow_engine.py:1699:21: warning[possibly-missing-attribute] Attribute `throw` may be missing on object of type `Unknown | R@run_generator_flow_sync`
- src/prefect/flow_engine.py:1733:44: warning[possibly-missing-attribute] Attribute `__anext__` may be missing on object of type `Unknown | R@run_generator_flow_async`
- src/prefect/flow_engine.py:1740:25: warning[possibly-missing-attribute] Attribute `throw` may be missing on object of type `Unknown | R@run_generator_flow_async`
- src/prefect/flows.py:286:34: error[unresolved-attribute] Object of type `(**P@Flow) -> R@Flow` has no attribute `__name__`
+ src/prefect/flows.py:286:34: error[unresolved-attribute] Object of type `((**P@Flow) -> R@Flow) & ((*args: object, **kwargs: object) -> object)` has no attribute `__name__`
- src/prefect/flows.py:404:68: error[unresolved-attribute] Object of type `(**P@Flow) -> R@Flow` has no attribute `__name__`
+ src/prefect/flows.py:404:68: error[unresolved-attribute] Object of type `((**P@Flow) -> R@Flow) & ((*args: object, **kwargs: object) -> object)` has no attribute `__name__`
- src/prefect/flows.py:1946:21: error[no-matching-overload] No overload of function `run_coro_as_sync` matches arguments
+ src/prefect/flows.py:1886:53: warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- Found 5463 diagnostics
+ Found 5457 diagnostics

scikit-build-core (https://github.com/scikit-build/scikit-build-core)
+ src/scikit_build_core/build/wheel.py:99:20: error[no-matching-overload] No overload of bound method `__init__` matches arguments
- Found 49 diagnostics
+ Found 50 diagnostics

charliermarsh · 2026-01-20T04:02:09Z

(Needs refinement, not ready for review!)

codspeed-hq · 2026-01-20T14:10:48Z

Merging this PR will not alter performance

✅ 24 untouched benchmarks
⏩ 30 skipped benchmarks¹

_{Comparing charlie/self2 (37d02cb) with main (c685810)}

30 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

AlexWaygood · 2026-01-21T08:04:40Z

crates/ty_python_semantic/src/types/class.rs

+    ///
+    /// This is a cheap check that doesn't trigger type inference. A class with no
+    /// explicit bases only inherits from `object`.
+    pub(super) fn has_explicit_bases(self, db: &'db dyn Db) -> bool {


Because this method directly accessed the AST, it needs to be Salsa-tracked to avoid overly eager cache invalidation if it's accessed while inferring types for a different module to the one the class is defined in. But we try not to have too many Salsa-tracked functions/methods, because they increase our memory-usage, so it may be better to use the existing explicit_bases method unless this buys us a lot in terms of performance

AlexWaygood · 2026-01-21T08:10:30Z

crates/ty_python_semantic/resources/mdtest/annotations/self.md

+        pass
+```
+
+## `__new__` is not a static method


The behaviour demonstrated in this test is correct, but the prose describing it seems pretty confused. __new__ is a staticmethod, even if isn't decorated with @staticmethod. But using Self in __new__ is allowed, partly because of the fact that at runtime it is heavily special-cased by the interpreter and behaves in many ways more like you'd usually expect a classmethod to behave. It always receives a cls argument with type type[Self] first, and it often returns an object of type Self.

AlexWaygood · 2026-01-21T08:11:49Z

crates/ty_python_semantic/src/types/infer.rs

 }

+/// Check if a function definition is decorated with `@staticmethod`.
+pub(crate) fn is_function_staticmethod<'db>(db: &'db dyn Db, definition: Definition<'db>) -> bool {


Uff, I think we already have 3 methods for determining if a function is a staticmethod — I'd prefer not to add a fourth 😄

charliermarsh · 2026-01-29T21:41:52Z

I re-did this to track state during traversal rather than re-detecting static methods et al after the fact, because I had a lot of trouble shaking the regression on Altair. I suspect people will have qualms with the approach, open to feedback 😭

astral-sh-bot · 2026-02-10T22:00:25Z

Memory usage report

Summary

Project	Old	New	Diff	Outcome
prefect	679.32MB	683.99MB	+0.7% (4.67MB)	⏫
sphinx	270.11MB	271.50MB	+0.5% (1.39MB)	⏫
trio	118.31MB	118.58MB	+0.2% (273.00kB)	⏫
flake8	49.45MB	49.53MB	+0.2% (78.55kB)	⏫

Significant changes

Click to expand detailed breakdown

prefect

Name	Old	New	Diff	Outcome
`infer_definition_types`	82.75MB	84.72MB	+2.4% (1.97MB)	⏫
`infer_expression_types_impl`	50.97MB	52.16MB	+2.3% (1.19MB)	⏫
`infer_scope_types_impl`	57.19MB	57.91MB	+1.2% (731.62kB)	⏫
`infer_deferred_types`	14.29MB	14.74MB	+3.1% (457.31kB)	⏫
`StaticClassLiteral<'db>::is_metaclass_`	0.00B	335.51kB	+335.51kB (new)	⏫
`infer_expression_type_impl`	10.30MB	10.30MB	+0.1% (9.26kB)	⏫
`StaticClassLiteral<'db>::implicit_attribute_inner_`	9.79MB	9.80MB	+0.0% (4.25kB)	⏫
`Type<'db>::member_lookup_with_policy_`	15.25MB	15.25MB	+0.0% (3.50kB)	⏫
`all_narrowing_constraints_for_expression`	3.48MB	3.48MB	+0.0% (1.29kB)	⏫
`all_negative_narrowing_constraints_for_expression`	1.51MB	1.51MB	+0.1% (804.00B)	⏫
`Type<'db>::class_member_with_policy_`	16.87MB	16.87MB	+0.0% (456.00B)	⏫
`GenericAlias<'db>::variance_of_`	545.19kB	545.50kB	+0.1% (312.00B)	⏫
`FunctionType<'db>::signature_`	4.07MB	4.07MB	+0.0% (180.00B)	⏫
`cached_protocol_interface`	523.76kB	523.90kB	+0.0% (144.00B)	⏫
`infer_unpack_types`	778.97kB	779.11kB	+0.0% (144.00B)	⏫
...			6 more

sphinx

Name	Old	New	Diff	Outcome
`infer_definition_types`	23.34MB	23.90MB	+2.4% (571.17kB)	⏫
`infer_expression_types_impl`	21.26MB	21.72MB	+2.2% (473.71kB)	⏫
`infer_scope_types_impl`	17.47MB	17.60MB	+0.8% (140.39kB)	⏫
`infer_deferred_types`	5.82MB	5.95MB	+2.2% (131.16kB)	⏫
`StaticClassLiteral<'db>::is_metaclass_`	0.00B	96.77kB	+96.77kB (new)	⏫
`infer_expression_type_impl`	2.23MB	2.23MB	+0.1% (2.37kB)	⏫
`Type<'db>::member_lookup_with_policy_`	6.48MB	6.48MB	+0.0% (1.31kB)	⏫
`StaticClassLiteral<'db>::implicit_attribute_inner_`	2.53MB	2.54MB	+0.0% (816.00B)	⏫
`all_narrowing_constraints_for_expression`	1.07MB	1.07MB	+0.0% (360.00B)	⏫
`StaticClassLiteral<'db>::try_mro_`	2.12MB	2.12MB	+0.0% (60.00B)	⏫
`StaticClassLiteral<'db>::is_typed_dict_`	182.19kB	182.25kB	+0.0% (60.00B)	⏫
`all_negative_narrowing_constraints_for_expression`	649.64kB	649.68kB	+0.0% (48.00B)	⏫
`cached_protocol_interface`	200.14kB	200.17kB	+0.0% (24.00B)	⏫
`is_equivalent_to_object_inner`	105.09kB	105.11kB	+0.0% (24.00B)	⏫
`StaticClassLiteral<'db>::try_metaclass_`	351.58kB	351.59kB	+0.0% (12.00B)	⏫
...			1 more

trio

Name	Old	New	Diff	Outcome
`infer_definition_types`	7.19MB	7.30MB	+1.5% (107.24kB)	⏫
`infer_expression_types_impl`	5.60MB	5.67MB	+1.1% (64.31kB)	⏫
`infer_deferred_types`	2.44MB	2.48MB	+1.5% (36.30kB)	⏫
`StaticClassLiteral<'db>::is_metaclass_`	0.00B	33.62kB	+33.62kB (new)	⏫
`infer_scope_types_impl`	5.56MB	5.59MB	+0.5% (28.75kB)	⏫
`infer_expression_type_impl`	709.86kB	711.16kB	+0.2% (1.30kB)	⏫
`Type<'db>::member_lookup_with_policy_`	1.75MB	1.75MB	+0.0% (408.00B)	⏫
`StaticClassLiteral<'db>::implicit_attribute_inner_`	816.06kB	816.40kB	+0.0% (348.00B)	⏫
`cached_protocol_interface`	153.93kB	154.16kB	+0.2% (240.00B)	⏫
`is_equivalent_to_object_inner`	66.01kB	66.24kB	+0.4% (240.00B)	⏫
`all_narrowing_constraints_for_expression`	251.89kB	252.06kB	+0.1% (168.00B)	⏫
`all_negative_narrowing_constraints_for_expression`	111.44kB	111.51kB	+0.1% (72.00B)	⏫
`infer_unpack_types`	163.69kB	163.71kB	+0.0% (24.00B)	⏫
`FunctionType<'db>::signature_`	1.11MB	1.11MB	+0.0% (12.00B)	⏫

flake8

Name	Old	New	Diff	Outcome
`infer_definition_types`	1.85MB	1.88MB	+1.5% (28.23kB)	⏫
`infer_expression_types_impl`	1.06MB	1.08MB	+1.8% (19.96kB)	⏫
`StaticClassLiteral<'db>::is_metaclass_`	0.00B	11.19kB	+11.19kB (new)	⏫
`infer_deferred_types`	717.88kB	728.28kB	+1.4% (10.39kB)	⏫
`infer_scope_types_impl`	1.09MB	1.10MB	+0.7% (8.29kB)	⏫
`infer_expression_type_impl`	119.70kB	119.89kB	+0.2% (192.00B)	⏫
`StaticClassLiteral<'db>::implicit_attribute_inner_`	313.54kB	313.66kB	+0.0% (120.00B)	⏫
`Type<'db>::member_lookup_with_policy_`	422.87kB	422.99kB	+0.0% (120.00B)	⏫
`cached_protocol_interface`	40.96kB	40.98kB	+0.1% (24.00B)	⏫
`is_equivalent_to_object_inner`	23.33kB	23.35kB	+0.1% (24.00B)	⏫
`all_narrowing_constraints_for_expression`	37.64kB	37.66kB	+0.1% (24.00B)	⏫

charliermarsh · 2026-02-11T17:07:56Z

Closing in favor of #23231 which is simpler.

charliermarsh added the ty Multi-file analysis & type inference label Jan 20, 2026

charliermarsh force-pushed the charlie/self2 branch from ac2f05d to e785fba Compare January 20, 2026 13:58

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[ty] Disallow Self in metaclass and static methods

37d02cb

charliermarsh force-pushed the charlie/self2 branch from 0fd45c6 to 37d02cb Compare February 11, 2026 16:02

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[ty] Disallow Self in metaclass and static methods#22755

[ty] Disallow Self in metaclass and static methods#22755
charliermarsh wants to merge 1 commit intomainfrom
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charliermarsh commented Jan 20, 2026

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Typing conformance results improved 🎉

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True positives added

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mypy_primer results

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Merging this PR will not alter performance

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AlexWaygood Jan 21, 2026

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Memory usage report

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Significant changes

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trio

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`mypy_primer` results

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