[ty] Avoid emitting cascading diagnostics when parsing invalid type expressions by AlexWaygood · Pull Request #24326 · astral-sh/ruff

AlexWaygood · 2026-03-31T12:08:31Z

Summary

In lots of places in our type-expression parsing, we continue to call self.infer_type_expression() on sub-expressions in the AST even after we've already determined that the type expression is invalid. I think that's generally a mistake; it often leads to us emitting many diagnostics on a single type expression when one would really be sufficient. This PR switches many callsites from infer_type_expression to infer_expression, to avoid this phenomenon of cascading diagnostics in error cases.

Test Plan

Mdtests and snapshots updated.

astral-sh-bot · 2026-03-31T12:10:15Z

Typing conformance results improved 🎉

The percentage of diagnostics emitted that were expected errors increased from 86.61% to 86.79%. The percentage of expected errors that received a diagnostic held steady at 81.56%. The number of fully passing files held steady at 70/132.

Summary

How are test cases classified?

Each test case represents one expected error annotation or a group of annotations sharing a tag. Counts are per test case, not per diagnostic — multiple diagnostics on the same line count as one. Required annotations (E) are true positives when ty flags the expected location and false negatives when it does not. Optional annotations (E?) are true positives when flagged but true negatives (not false negatives) when not. Tagged annotations (E[tag]) require ty to flag exactly one of the tagged lines; tagged multi-annotations (E[tag+]) allow any number up to the tag count. Flagging unexpected locations counts as a false positive.

Metric	Old	New	Diff	Outcome
True Positives	867	867	+0
False Positives	134	132	-2	⏬ (✅)
False Negatives	196	196	+0
Total Diagnostics	1064	1054	-10	⏬
Precision	86.61%	86.79%	+0.17%	⏫ (✅)
Recall	81.56%	81.56%	+0.00%
Passing Files	70/132	70/132	+0

Test file breakdown

2 files altered

File	True Positives	False Positives	False Negatives	Status
generics_defaults.py	5	8 (-1) ✅	1	📈 Improving
generics_typevartuple_specialization.py	2	15 (-1) ✅	4	📈 Improving
Total (all files)	867	132 (-2) ✅	196	70/132

False positives removed (2)

2 diagnostics

Test case

Diff

generics_defaults.py:203

-error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `list[bytes]`?

generics_typevartuple_specialization.py:52

-error[invalid-type-form] Tuple literals are not allowed in this context in a type expression: Did you mean `tuple[()]`?

True positives changed (14)

14 diagnostics

Test case	Diff
aliases_type_statement.py:38	-error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] List literals are not allowed in this context in a type expression
aliases_type_statement.py:39	-error[invalid-type-form] Tuple literals are not allowed in this context in a type expression -error[invalid-type-form] Tuple literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] Tuple literals are not allowed in this context in a type expression
aliases_type_statement.py:43	-error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression -error[invalid-type-form] Int literals are not allowed in this context in a type expression +error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression
aliases_typealiastype.py:53	-error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] List literals are not allowed in this context in a type expression
aliases_typealiastype.py:54	-error[invalid-type-form] Tuple literals are not allowed in this context in a type expression -error[invalid-type-form] Tuple literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] Tuple literals are not allowed in this context in a type expression
aliases_typealiastype.py:58	-error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression -error[invalid-type-form] Int literals are not allowed in this context in a type expression +error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression
annotations_forward_refs.py:42	-error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] List literals are not allowed in this context in a type expression
annotations_forward_refs.py:47	-error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression -error[invalid-type-form] Int literals are not allowed in this context in a type expression +error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression
annotations_typeexpr.py:89	-error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] List literals are not allowed in this context in a type expression
annotations_typeexpr.py:94	-error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression -error[invalid-type-form] Int literals are not allowed in this context in a type expression +error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression
generics_syntax_declarations.py:48	-error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `tuple[str, int]`? +error[invalid-type-form] List literals are not allowed in this context in a type expression
qualifiers_annotated.py:38	-error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] List literals are not allowed in this context in a type expression
qualifiers_annotated.py:39	-error[invalid-type-form] Tuple literals are not allowed in this context in a type expression -error[invalid-type-form] Tuple literals are not allowed in this context in a type expression: Did you mean `tuple[int, str]`? +error[invalid-type-form] Tuple literals are not allowed in this context in a type expression
qualifiers_annotated.py:43	-error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression -error[invalid-type-form] Int literals are not allowed in this context in a type expression +error[invalid-type-form] Invalid subscript of object of type `list[<class 'int'>]` in type expression

astral-sh-bot · 2026-03-31T12:11:04Z

Memory usage report

Summary

Project	Old	New	Diff	Outcome
trio	117.72MB	117.72MB	+0.00% (313.00B)	⏫
flake8	47.98MB	47.98MB	-	✅
sphinx	264.60MB	264.60MB	-0.00% (472.00B)	⬇️
prefect	716.58MB	716.49MB	-0.01% (92.85kB)	⬇️

Significant changes

Click to expand detailed breakdown

trio

Name	Old	New	Diff	Outcome
`is_redundant_with_impl::interned_arguments`	537.62kB	536.77kB	-0.16% (880.00B)	⏫
`check_file_impl`	1.82MB	1.82MB	+0.05% (861.00B)	⏫
`Type<'db>::class_member_with_policy_`	2.00MB	2.00MB	+0.03% (608.00B)	⏫
`infer_deferred_types`	2.38MB	2.38MB	-0.02% (564.00B)	⏫
`is_redundant_with_impl`	473.21kB	472.70kB	-0.11% (528.00B)	⏫
`FunctionType<'db>::last_definition_signature_`	241.23kB	240.75kB	-0.20% (496.00B)	⏫
`infer_expression_types_impl`	7.08MB	7.08MB	+0.01% (496.00B)	⏫
`infer_definition_types`	7.73MB	7.73MB	-0.01% (492.00B)	⏫
`UnionType`	304.73kB	304.28kB	-0.15% (464.00B)	⏫
`BoundTypeVarInstance`	163.27kB	162.98kB	-0.17% (288.00B)	⏫
`place_by_id`	550.84kB	551.08kB	+0.04% (248.00B)	⏫
`Type<'db>::member_lookup_with_policy_`	1.81MB	1.81MB	+0.01% (224.00B)	⏫
`StaticClassLiteral<'db>::implicit_attribute_inner_`	750.54kB	750.76kB	+0.03% (224.00B)	⏫
`StaticClassLiteral<'db>::try_metaclass_`	126.79kB	127.00kB	+0.16% (208.00B)	⏫
`Type<'db>::class_member_with_policy_::interned_arguments`	1.11MB	1.11MB	+0.02% (208.00B)	⏫
...			16 more

sphinx

Name	Old	New	Diff	Outcome
`infer_deferred_types`	5.61MB	5.61MB	-0.00% (248.00B)	⬇️
`TupleType`	568.55kB	568.42kB	-0.02% (128.00B)	⬇️
`infer_definition_types`	23.98MB	23.98MB	-0.00% (96.00B)	⬇️

prefect

Name	Old	New	Diff	Outcome
`infer_deferred_types`	14.75MB	14.72MB	-0.22% (32.62kB)	⬇️
`check_file_impl`	17.97MB	17.96MB	-0.08% (14.25kB)	⬇️
`infer_scope_types_impl`	54.24MB	54.22MB	-0.02% (13.06kB)	⬇️
`TupleType`	717.94kB	711.33kB	-0.92% (6.61kB)	⬇️
`infer_definition_types`	89.94MB	89.93MB	-0.01% (5.43kB)	⬇️
`Specialization`	2.50MB	2.50MB	-0.13% (3.38kB)	⬇️
`Type<'db>::class_member_with_policy_`	17.76MB	17.76MB	-0.02% (3.07kB)	⬇️
`Type<'db>::member_lookup_with_policy_`	16.22MB	16.21MB	-0.01% (2.03kB)	⬇️
`GenericAlias`	1.16MB	1.15MB	-0.14% (1.69kB)	⬇️
`place_by_id`	4.60MB	4.60MB	-0.03% (1.62kB)	⬇️
`BoundTypeVarInstance`	1.38MB	1.38MB	-0.10% (1.48kB)	⬇️
`Type<'db>::apply_specialization_::interned_arguments`	2.89MB	2.89MB	-0.04% (1.09kB)	⬇️
`place_by_id::interned_arguments`	3.39MB	3.39MB	-0.03% (1.05kB)	⬇️
`Type<'db>::class_member_with_policy_::interned_arguments`	9.61MB	9.61MB	-0.01% (1.02kB)	⬇️
`Type<'db>::member_lookup_with_policy_::interned_arguments`	5.78MB	5.78MB	-0.02% (1.02kB)	⬇️
...			13 more

astral-sh-bot · 2026-03-31T12:13:14Z

`ecosystem-analyzer` results

Lint rule	Added	Removed	Changed
`invalid-type-form`	0	135	1
`invalid-await`	0	40	0
`not-subscriptable`	13	0	0
`possibly-missing-submodule`	0	4	0
`unsupported-operator`	3	0	0
`invalid-return-type`	0	1	0
`unbound-type-variable`	0	1	0
Total	16	181	1

Changes in flaky projects detected. Raw diff output excludes flaky projects; see the HTML report for details.

Raw diff (157 changes)

django-stubs (https://github.com/typeddjango/django-stubs)
- django-stubs/contrib/gis/gdal/geometries.pyi:120:55 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:123:31 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:123:44 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:123:50 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/gdal/geometries.pyi:123:31 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
- django-stubs/contrib/gis/gdal/geometries.pyi:125:30 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:125:43 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:125:49 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/gdal/geometries.pyi:125:30 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
- django-stubs/contrib/gis/gdal/geometries.pyi:145:31 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:145:37 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:145:50 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:145:56 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:145:62 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/gdal/geometries.pyi:145:31 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
+ django-stubs/contrib/gis/gdal/geometries.pyi:145:37 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
- django-stubs/contrib/gis/gdal/geometries.pyi:147:30 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:147:36 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:147:49 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/gdal/geometries.pyi:147:30 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
+ django-stubs/contrib/gis/gdal/geometries.pyi:147:36 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
- django-stubs/contrib/gis/gdal/geometries.pyi:163:36 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/gdal/geometries.pyi:165:35 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/geos/collections.pyi:11:36 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/geos/collections.pyi:13:35 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/geos/coordseq.pyi:10:49 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/geos/coordseq.pyi:32:35 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/geos/linestring.pyi:9:49 error[invalid-type-form] `...` is not allowed in this context in a type expression
- django-stubs/contrib/gis/geos/linestring.pyi:12:31 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/geos/linestring.pyi:12:44 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/geos/linestring.pyi:12:31 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
- django-stubs/contrib/gis/geos/linestring.pyi:14:30 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/geos/linestring.pyi:14:43 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/geos/linestring.pyi:14:30 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
- django-stubs/contrib/gis/geos/polygon.pyi:18:31 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/geos/polygon.pyi:18:37 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/geos/polygon.pyi:18:50 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/geos/polygon.pyi:18:31 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
+ django-stubs/contrib/gis/geos/polygon.pyi:18:37 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
- django-stubs/contrib/gis/geos/polygon.pyi:20:30 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/geos/polygon.pyi:20:36 error[invalid-type-form] Invalid subscript of object of type `property` in type expression
- django-stubs/contrib/gis/geos/polygon.pyi:20:49 error[invalid-type-form] `...` is not allowed in this context in a type expression
+ django-stubs/contrib/gis/geos/polygon.pyi:20:30 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method
+ django-stubs/contrib/gis/geos/polygon.pyi:20:36 error[not-subscriptable] Cannot subscript object of type `property` with no `__getitem__` method

egglog-python (https://github.com/egraphs-good/egglog-python)
- python/egglog/builtins.py:542:95 error[invalid-type-form] Int literals are not allowed in this context in a type expression
- python/egglog/builtins.py:666:105 error[invalid-type-form] Int literals are not allowed in this context in a type expression
- python/egglog/builtins.py:1060:99 error[invalid-type-form] Int literals are not allowed in this context in a type expression
- python/egglog/thunk.py:41:37 error[unbound-type-variable] Type variable `T` is not bound to any outer generic context
- python/tests/test_convert.py:117:51 error[invalid-type-form] Int literals are not allowed in this context in a type expression
- python/tests/test_convert.py:140:49 error[invalid-type-form] Int literals are not allowed in this context in a type expression

mypy (https://github.com/python/mypy)
- mypy/typeshed/stdlib/typing.pyi:529:36 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:535:36 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:540:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:564:37 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:564:49 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:564:64 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:581:48 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:618:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:623:38 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:624:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:628:48 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:635:30 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:640:30 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:661:68 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:666:36 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:667:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:677:75 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:683:69 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:693:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:697:41 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:705:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:705:65 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:710:66 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:712:66 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:726:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:728:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:758:36 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:769:36 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:788:34 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:788:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:789:32 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:790:36 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:905:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:909:36 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:911:31 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:418:53 error[invalid-type-form] Bare ParamSpec `_P` is not valid in this context in a type expression
- mypy/typeshed/stdlib/typing.pyi:418:57 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:418:74 error[invalid-type-form] Bare ParamSpec `_P` is not valid in this context in a type expression
- mypy/typeshed/stdlib/typing.pyi:418:78 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:630:69 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:711:41 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:711:64 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:711:72 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
+ mypy/typeshed/stdlib/typing.pyi:711:64 error[unsupported-operator] Operator `|` is not supported between two objects of type `TypeVar`
- mypy/typeshed/stdlib/typing.pyi:713:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:713:65 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:713:73 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
+ mypy/typeshed/stdlib/typing.pyi:713:65 error[unsupported-operator] Operator `|` is not supported between two objects of type `TypeVar`
- mypy/typeshed/stdlib/typing.pyi:739:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:741:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:744:38 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:745:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:747:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:748:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:749:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:754:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:756:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:759:38 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:760:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:762:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:763:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:764:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:814:41 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypy/typeshed/stdlib/typing.pyi:814:46 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
+ mypy/typeshed/stdlib/typing.pyi:814:46 error[unsupported-operator] Operator `|` is not supported between objects of type `TypeVar` and `None`
- mypy/typeshed/stdlib/typing_extensions.pyi:647:25 error[invalid-type-form] Variable of type `Literal[Format.STRING]` is not allowed in a type expression
- mypy/typeshed/stdlib/typing_extensions.pyi:656:25 error[invalid-type-form] Variable of type `Literal[Format.FORWARDREF]` is not allowed in a type expression
- mypy/typeshed/stdlib/typing_extensions.pyi:675:25 error[invalid-type-form] Variable of type `Literal[Format.STRING]` is not allowed in a type expression
- mypy/typeshed/stdlib/typing_extensions.pyi:686:25 error[invalid-type-form] Variable of type `Literal[Format.FORWARDREF]` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:64:37 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:82:38 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:82:41 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:82:44 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:86:38 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:95:35 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:98:44 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:98:47 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:103:38 error[invalid-type-form] Variable of type `object` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:103:43 error[invalid-type-form] Variable of type `object` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:103:48 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:121:43 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:125:43 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:127:38 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:134:32 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:140:34 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:89:44 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:92:74 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:137:37 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:139:40 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:139:46 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:139:59 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:139:65 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:141:33 error[invalid-type-form] Invalid subscript of object of type `Literal[0]` in type expression
- mypyc/test-data/fixtures/typing-full.pyi:141:39 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
- mypyc/test-data/fixtures/typing-full.pyi:141:42 error[invalid-type-form] Variable of type `TypeVar` is not allowed in a type expression
+ mypyc/test-data/fixtures/typing-full.pyi:141:33 error[not-subscriptable] Cannot subscript object of type `Literal[0]` with no `__getitem__` method

pandas (https://github.com/pandas-dev/pandas)
- pandas/core/series.py:324:21 error[invalid-type-form] Variable of type `Accessor` is not allowed in a type expression

pydantic (https://github.com/pydantic/pydantic)
- pydantic/v1/annotated_types.py:13:50 error[invalid-type-form] The special form `typing.TypedDict` is not allowed in type expressions
- pydantic/v1/annotated_types.py:24:26 error[invalid-type-form] The special form `typing.TypedDict` is not allowed in type expressions
- pydantic/v1/validators.py:621:26 error[invalid-type-form] The special form `typing.TypedDict` is not allowed in type expressions

spack (https://github.com/spack/spack)
- lib/spack/spack/detection/path.py:228:45 warning[possibly-missing-submodule] Submodule `package_base` might not have been imported
- lib/spack/spack/detection/path.py:254:29 warning[possibly-missing-submodule] Submodule `package_base` might not have been imported
- lib/spack/spack/detection/path.py:360:45 warning[possibly-missing-submodule] Submodule `package_base` might not have been imported
- lib/spack/spack/detection/path.py:386:45 warning[possibly-missing-submodule] Submodule `package_base` might not have been imported

static-frame (https://github.com/static-frame/static-frame)
- static_frame/test/unit/test_type_clinic.py:459:21 error[invalid-type-form] List literals are not allowed in this context in a type expression: Did you mean `tuple[int, int]`?
+ static_frame/test/unit/test_type_clinic.py:459:21 error[invalid-type-form] List literals are not allowed in this context in a type expression

xarray (https://github.com/pydata/xarray)
- xarray/core/indexing.py:427:40 error[invalid-type-form] `...` is not allowed in this context in a type expression
- xarray/core/indexing.py:433:35 error[invalid-type-form] `...` is not allowed in this context in a type expression

Full report with detailed diff (timing results)

carljm

Results look good. I would like to understand the subscript change better.

crates/ty_python_semantic/src/types/infer/builder/subscript.rs

carljm · 2026-03-31T14:32:46Z

crates/ty_python_semantic/src/types/infer/builder/subscript.rs

+            if matches!(
+                &*subscript.value,
+                ast::Expr::Name(_) | ast::Expr::Attribute(_)
+            ) {
+                builder.infer_type_expression(expr)
+            } else {
+                builder.infer_expression(expr, TypeContext::default())
+            }


This seems deserving of a comment to explain the rationale for why different expressions should be treated differently. This doesn't seem to match the logic described in the PR summary, in that we aren't deciding to stop using infer_type_expression here due to an outer invalid-type-expression error.

Unless the rationale here is that a subscript should always be a name/attribute, and anything else will be an error? But if that's it, then couldn't this cause us to miss emitting an error we should emit?

There's also a similar (non-?)issue here as in other places, where we'll now emit value-expression errors on the subscript expression that we wouldn't have before, e.g. unresolved-reference in def f(x: "list[int][foo()]") -> None: ....

Unless the rationale here is that a subscript should always be a name/attribute, and anything else will be an error? But if that's it, then couldn't this cause us to miss emitting an error we should emit?

I think that's what we should be doing, yes (see #24329).

I'm inclined to rip this change out of this PR for now, though, and maybe include it as part of #24329 instead.

I've ripped out all changes to builder/subscript.rs for now.

crates/ty_python_semantic/src/types/infer/builder/subscript.rs

crates/ty_python_semantic/src/types/infer/builder/type_expression.rs

carljm · 2026-03-31T14:44:32Z

crates/ty_python_semantic/src/types/infer/builder/type_expression.rs

-                    .iter()
-                    .map(|element| self.infer_type_expression(element))
-                    .collect();
+                self.infer_list_expression(list, TypeContext::default());


In some scenarios this adds new diagnostics that we don't emit on main, e.g.

def f(x: "[foo()]") -> None: ...

This PR emits both the "list literal not allowed" message and "foo not defined" -- the latter is not emitted on main. But main does emit an additional "call not allowed", which this PR omits.

I think that's fine?

I've changed it so that we skip the infer_expression() calls entirely if we're inside a stringized annotation. That means that we still get errors about unresolved references inside invalid-in-type-expression AST nodes (which I think is desirable), but we avoid false-positive diagnostics like that inside stringized annotations

carljm · 2026-03-31T14:46:57Z

crates/ty_python_semantic/src/types/infer/builder/type_expression.rs

            | SpecialFormType::AlwaysTruthy
            | SpecialFormType::AlwaysFalsy => {
-                self.infer_type_expression(arguments_slice);
+                self.infer_expression(arguments_slice, TypeContext::default());


Similar to above, now def f(x: "Any[foo()]") -> None: ... emits an unresolved-reference on foo that main doesn't emit. But I think that's OK.

carljm · 2026-03-31T14:50:59Z

crates/ty_python_semantic/src/types/infer/builder/subscript.rs

+        ) -> Type<'db> {
+            if matches!(
+                &*subscript.value,
+                ast::Expr::Name(_) | ast::Expr::Attribute(_)


What if the subscript is a string-quoted name/attribute expression?

that's an invalid type expression -- you should quote the whole subscript expression, not just the value. "list"[int] is going to fail at runtime on Python <3.14, there's no reason to write that even on newer Python versions, and it's not permitted by the grammar at https://typing.python.org/en/latest/spec/annotations.html#type-and-annotation-expressions. Just write "list[int]" instead.

I was actually confused about whether this was checking the "value" or the "slice" expression -- that makes sense.

AlexWaygood added ty Multi-file analysis & type inference diagnostics Related to reporting of diagnostics. labels Mar 31, 2026

AlexWaygood marked this pull request as ready for review March 31, 2026 12:13

AlexWaygood requested review from carljm, dcreager, ibraheemdev and sharkdp as code owners March 31, 2026 12:13

astral-sh-bot bot assigned carljm Mar 31, 2026

carljm approved these changes Mar 31, 2026

View reviewed changes

AlexWaygood force-pushed the alex/cascading-type-expr-diagnostics branch from ae1f280 to 06909e8 Compare April 1, 2026 10:42

AlexWaygood added 6 commits April 1, 2026 11:56

avoid cascading diagnostics in error cases

99d65a3

more

921c8a3

mostly address review

3d984f8

add another test

4d5cc39

revert semantic changes to builder/subscript.rs

389cba5

revert other changes to infer/builder/subscript.rs

9ddda47

AlexWaygood force-pushed the alex/cascading-type-expr-diagnostics branch from a18198c to 9ddda47 Compare April 1, 2026 10:56

AlexWaygood merged commit ab032bf into main Apr 1, 2026
51 checks passed

AlexWaygood deleted the alex/cascading-type-expr-diagnostics branch April 1, 2026 11:09

AlexWaygood mentioned this pull request Apr 1, 2026

[ty] Improve consistency and quality of diagnostics relating to invalid type forms #24325

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