[ty] Use `Top` materializations for `TypeIs` special form #20591

AlexWaygood · 2025-09-26T11:40:46Z

Summary

Typeshed has many functions that return TypeIs[SomeCovariantGeneric[Any]]. This is somewhat unfortunate for ty, because for our purposes it's almost always better to intersect with CovariantGeneric[object] for the purposes of type narrowing, but it's somewhat hard to change these in typeshed without creating false-positive diagnostics for users of other type checkers. This PR therefore introduces a workaround for the typeshed issue: under the hood, we convert the type argument passed to TypeIs to its top materialization before intersecting with that type.

Test Plan

I added an mdtest that fails on main without this change. It's similar to the false-positive diagnostics relating to the use of asyncio.iscoroutine that we see going away on homeassistant/core in the mypy_primer report.

Some more ecosystem analysis is found in #20591 (comment).

github-actions · 2025-09-26T11:42:39Z

Diagnostic diff on typing conformance tests

No changes detected when running ty on typing conformance tests ✅

github-actions · 2025-09-26T11:43:50Z

`mypy_primer` results

Changes were detected when running on open source projects

spack (https://github.com/spack/spack)
- lib/spack/spack/llnl/util/filesystem.py:330:21: warning[possibly-missing-attribute] Attribute `replace` on type `(str & ~((...) -> object)) | (((Match[Unknown], /) -> str) & ~((...) -> object))` may be missing
+ lib/spack/spack/llnl/util/filesystem.py:330:21: warning[possibly-missing-attribute] Attribute `replace` on type `(str & ~(() -> object)) | (((Match[Unknown], /) -> str) & ~(() -> object))` may be missing
- lib/spack/spack/vendor/jinja2/runtime.py:734:17: error[invalid-assignment] Object of type `(Unknown & ~((...) -> object)) | bool | (((str | None, /) -> bool) & ~((...) -> object))` is not assignable to `bool | None`
+ lib/spack/spack/vendor/jinja2/runtime.py:734:17: error[invalid-assignment] Object of type `(Unknown & ~(() -> object)) | bool | (((str | None, /) -> bool) & ~(() -> object))` is not assignable to `bool | None`

jinja (https://github.com/pallets/jinja)
- src/jinja2/runtime.py:690:17: error[invalid-assignment] Object of type `(Unknown & ~((...) -> object)) | bool | (((str | None, /) -> bool) & ~((...) -> object))` is not assignable to `bool | None`
+ src/jinja2/runtime.py:690:17: error[invalid-assignment] Object of type `(Unknown & ~(() -> object)) | bool | (((str | None, /) -> bool) & ~(() -> object))` is not assignable to `bool | None`

pytest (https://github.com/pytest-dev/pytest)
- src/_pytest/fixtures.py:1236:29: error[unresolved-attribute] Type `FixtureFunction@__call__ & ~type[Any] & ~FixtureFunctionDefinition` has no attribute `__name__`
+ src/_pytest/fixtures.py:1236:29: error[unresolved-attribute] Type `FixtureFunction@__call__ & ~type & ~FixtureFunctionDefinition` has no attribute `__name__`
+ src/_pytest/fixtures.py:1383:9: error[invalid-argument-type] Argument is incorrect: Expected `tuple[object, ...] | ((Any, /) -> object) | None`, found `None | (Sequence[object] & (() -> object)) | (((Any, /) -> object) & (() -> object)) | Unknown`
- src/_pytest/fixtures.py:1383:70: error[invalid-argument-type] Argument to class `tuple` is incorrect: Expected `Iterable[object]`, found `(Sequence[object] & ~((...) -> object)) | (((Any, /) -> object) & ~((...) -> object))`
+ src/_pytest/fixtures.py:1383:70: error[invalid-argument-type] Argument to class `tuple` is incorrect: Expected `Iterable[object]`, found `(Sequence[object] & ~(() -> object)) | (((Any, /) -> object) & ~(() -> object))`
- src/_pytest/fixtures.py:1658:24: error[invalid-return-type] Return type does not match returned value: expected `Scope`, found `Scope | (Unknown & ~None & ~((...) -> object) & ~str) | (((str, Config, /) -> Unknown) & ~((...) -> object) & ~str) | (Unknown & ~str)`
+ src/_pytest/fixtures.py:1658:24: error[invalid-return-type] Return type does not match returned value: expected `Scope`, found `Scope | (Unknown & ~None & ~(() -> object) & ~str) | (((str, Config, /) -> Unknown) & ~(() -> object) & ~str) | (Unknown & ~str)`
+ src/_pytest/python.py:1389:13: error[invalid-argument-type] Argument is incorrect: Expected `((Any, /) -> object) | None`, found `None | (Iterable[object] & (() -> object)) | (((Any, /) -> object) & (() -> object))`
- Found 485 diagnostics
+ Found 487 diagnostics

beartype (https://github.com/beartype/beartype)
- beartype/_check/metadata/metadecor.py:523:34: error[unresolved-attribute] Type `((...) -> Unknown) & ((...) -> object)` has no attribute `__name__`
+ beartype/_check/metadata/metadecor.py:523:34: error[unresolved-attribute] Type `((...) -> Unknown) & (() -> object)` has no attribute `__name__`
- beartype/_util/cache/utilcachecall.py:180:34: error[unresolved-attribute] Type `CallableT@callable_cached & ((...) -> object)` has no attribute `__name__`
+ beartype/_util/cache/utilcachecall.py:180:34: error[unresolved-attribute] Type `CallableT@callable_cached & (() -> object)` has no attribute `__name__`
- beartype/_util/cache/utilcachecall.py:417:34: error[unresolved-attribute] Type `CallableT@method_cached_arg_by_id & ((...) -> object)` has no attribute `__name__`
+ beartype/_util/cache/utilcachecall.py:417:34: error[unresolved-attribute] Type `CallableT@method_cached_arg_by_id & (() -> object)` has no attribute `__name__`
- beartype/_util/cache/utilcachecall.py:568:44: error[unresolved-attribute] Type `CallableT@property_cached & ((...) -> object)` has no attribute `__name__`
+ beartype/_util/cache/utilcachecall.py:568:44: error[unresolved-attribute] Type `CallableT@property_cached & (() -> object)` has no attribute `__name__`
- beartype/_util/func/utilfuncscope.py:261:29: error[unresolved-attribute] Type `((...) -> Unknown) & ((...) -> object)` has no attribute `__name__`
+ beartype/_util/func/utilfuncscope.py:261:29: error[unresolved-attribute] Type `((...) -> Unknown) & (() -> object)` has no attribute `__name__`
- beartype/_util/func/utilfuncscope.py:320:16: error[unresolved-attribute] Type `((...) -> Unknown) & ((...) -> object)` has no attribute `__qualname__`
+ beartype/_util/func/utilfuncscope.py:320:16: error[unresolved-attribute] Type `((...) -> Unknown) & (() -> object)` has no attribute `__qualname__`
- beartype/_util/func/utilfuncscope.py:334:16: error[unresolved-attribute] Type `((...) -> Unknown) & ((...) -> object)` has no attribute `__qualname__`
+ beartype/_util/func/utilfuncscope.py:334:16: error[unresolved-attribute] Type `((...) -> Unknown) & (() -> object)` has no attribute `__qualname__`
- beartype/_util/func/utilfunctest.py:907:16: error[unresolved-attribute] Type `((...) -> Unknown) & ~((...) -> Unknown)` has no attribute `__qualname__`
+ beartype/_util/func/utilfunctest.py:907:16: error[unresolved-attribute] Type `((...) -> Unknown) & ~(() -> object)` has no attribute `__qualname__`
- beartype/_util/func/utilfunctest.py:1100:16: warning[possibly-missing-attribute] Attribute `__name__` on type `(Any & ~MethodType) | ((...) -> Unknown)` may be missing
+ beartype/_util/func/utilfunctest.py:1100:16: error[unresolved-attribute] Type `(...) -> Unknown` has no attribute `__name__`
- beartype/typing/_typingcache.py:87:34: error[unresolved-attribute] Type `((...) -> Unknown) & ((...) -> object)` has no attribute `__name__`
+ beartype/typing/_typingcache.py:87:34: error[unresolved-attribute] Type `((...) -> Unknown) & (() -> object)` has no attribute `__name__`

werkzeug (https://github.com/pallets/werkzeug)
- src/werkzeug/utils.py:508:12: error[unsupported-operator] Operator `>` is not supported for types `(str | None, /) -> int | None` and `Literal[0]`, in comparing `(int & ~((...) -> object)) | (((str | None, /) -> int | None) & ~((...) -> object)) | (@Todo & ~None)` with `Literal[0]`
+ src/werkzeug/utils.py:508:12: error[unsupported-operator] Operator `>` is not supported for types `(str | None, /) -> int | None` and `Literal[0]`, in comparing `(int & ~(() -> object)) | (((str | None, /) -> int | None) & ~(() -> object)) | (@Todo & ~None)` with `Literal[0]`
- src/werkzeug/utils.py:512:9: error[invalid-assignment] Object of type `(int & ~((...) -> object)) | (((str | None, /) -> int | None) & ~((...) -> object)) | (@Todo & ~None)` is not assignable to attribute `max_age` of type `int | None`
+ src/werkzeug/utils.py:512:9: error[invalid-assignment] Object of type `(int & ~(() -> object)) | (((str | None, /) -> int | None) & ~(() -> object)) | (@Todo & ~None)` is not assignable to attribute `max_age` of type `int | None`
- src/werkzeug/wsgi.py:246:30: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `Iterable[Unknown]`, found `((() -> None) & ~((...) -> object)) | (Iterable[() -> None] & ~((...) -> object))`
- Found 367 diagnostics
+ Found 366 diagnostics

starlette (https://github.com/encode/starlette)
+ starlette/routing.py:67:5: error[invalid-assignment] Object of type `((Request, /) -> Awaitable[Response] | Response) | partial[Unknown]` is not assignable to `(Request, /) -> Awaitable[Response]`
- Found 146 diagnostics
+ Found 147 diagnostics

ignite (https://github.com/pytorch/ignite)
- ignite/handlers/base_logger.py:52:29: error[not-iterable] Object of type `(list[str] & ~((...) -> object)) | (((str, Unknown, /) -> bool) & ~((...) -> object))` may not be iterable
+ ignite/handlers/base_logger.py:52:29: error[not-iterable] Object of type `(list[str] & ~(() -> object)) | (((str, Unknown, /) -> bool) & ~(() -> object))` may not be iterable

poetry (https://github.com/python-poetry/poetry)
- src/poetry/utils/cache.py:149:16: error[invalid-return-type] Return type does not match returned value: expected `T@FileCache`, found `(Unknown & ~None) | @Todo | (T@FileCache & ~((...) -> object)) | ((() -> T@FileCache) & ~((...) -> object))`
- Found 986 diagnostics
+ Found 985 diagnostics

tornado (https://github.com/tornadoweb/tornado)
- tornado/escape.py:336:30: warning[possibly-missing-attribute] Attribute `strip` on type `(str & ~AlwaysFalsy & ~((...) -> object)) | (((str, /) -> str) & ~AlwaysFalsy & ~((...) -> object))` may be missing
+ tornado/escape.py:336:30: warning[possibly-missing-attribute] Attribute `strip` on type `(str & ~AlwaysFalsy & ~(() -> object)) | (((str, /) -> str) & ~AlwaysFalsy & ~(() -> object))` may be missing

vision (https://github.com/pytorch/vision)
- test/datasets_utils.py:835:52: error[invalid-argument-type] Argument to function `create_image_file` is incorrect: Expected `Sequence[int] | int`, found `@Todo | (Sequence[int] & ~((...) -> object)) | (int & ~((...) -> object)) | (((int, /) -> Sequence[int] | int) & ~((...) -> object))`
+ test/datasets_utils.py:835:52: error[invalid-argument-type] Argument to function `create_image_file` is incorrect: Expected `Sequence[int] | int`, found `@Todo | (Sequence[int] & ~(() -> object)) | (int & ~(() -> object)) | (((int, /) -> Sequence[int] | int) & ~(() -> object))`
+ torchvision/transforms/v2/_utils.py:149:16: error[invalid-return-type] Return type does not match returned value: expected `(Any, /) -> Any`, found `(str & (() -> object)) | (((Any, /) -> Any) & (() -> object))`
- Found 1473 diagnostics
+ Found 1474 diagnostics

psycopg (https://github.com/psycopg/psycopg)
+ psycopg_pool/psycopg_pool/_acompat.py:185:12: error[invalid-return-type] Return type does not match returned value: expected `T@ensure_async`, found `object`
- Found 698 diagnostics
+ Found 699 diagnostics

operator (https://github.com/canonical/operator)
+ ops/charm.py:1639:55: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- Found 99 diagnostics
+ Found 100 diagnostics

cki-lib (https://gitlab.com/cki-project/cki-lib)
- cki_lib/messagequeue.py:373:36: error[invalid-type-form] Variable of type `def callable(obj: object, /) -> TypeIs[(...) -> object]` is not allowed in a type expression
+ cki_lib/messagequeue.py:373:36: error[invalid-type-form] Variable of type `def callable(obj: object, /) -> TypeIs[() -> object]` is not allowed in a type expression

sphinx (https://github.com/sphinx-doc/sphinx)
- sphinx/environment/__init__.py:393:13: error[invalid-assignment] Object of type `(str & ((...) -> object)) | (((Node, /) -> bool) & ((...) -> object))` is not assignable to `Literal[False] | ((Node, /) -> bool)`
+ sphinx/environment/__init__.py:393:13: error[invalid-assignment] Object of type `(str & (() -> object)) | (((Node, /) -> bool) & (() -> object))` is not assignable to `Literal[False] | ((Node, /) -> bool)`
- sphinx/environment/__init__.py:397:25: error[invalid-argument-type] Method `__getitem__` of type `bound method dict[str, Literal[False] | ((Node, /) -> bool)].__getitem__(key: str, /) -> Literal[False] | ((Node, /) -> bool)` cannot be called with key of type `(str & ~((...) -> object)) | (((Node, /) -> bool) & ~((...) -> object))` on object of type `dict[str, Literal[False] | ((Node, /) -> bool)]`
+ sphinx/environment/__init__.py:397:25: error[invalid-argument-type] Method `__getitem__` of type `bound method dict[str, Literal[False] | ((Node, /) -> bool)].__getitem__(key: str, /) -> Literal[False] | ((Node, /) -> bool)` cannot be called with key of type `(str & ~(() -> object)) | (((Node, /) -> bool) & ~(() -> object))` on object of type `dict[str, Literal[False] | ((Node, /) -> bool)]`

trio (https://github.com/python-trio/trio)
+ src/trio/_core/_tests/test_ki.py:685:43: error[invalid-argument-type] Argument to function `_consume_async_generator` is incorrect: Expected `AsyncGenerator[None, None]`, found `AsyncGeneratorType[object, Never]`
+ src/trio/_core/_tests/test_ki.py:690:25: error[invalid-argument-type] Argument to bound method `send` is incorrect: Expected `Never`, found `None`
+ src/trio/_core/_tests/test_ki.py:690:25: error[invalid-argument-type] Argument to bound method `send` is incorrect: Expected `Never`, found `None`
- Found 665 diagnostics
+ Found 668 diagnostics

schemathesis (https://github.com/schemathesis/schemathesis)
- src/schemathesis/hooks.py:297:16: error[unresolved-attribute] Type `(str & ((...) -> object)) | (((...) -> Unknown) & ((...) -> object))` has no attribute `__name__`
+ src/schemathesis/hooks.py:297:16: error[unresolved-attribute] Type `(str & (() -> object)) | (((...) -> Unknown) & (() -> object))` has no attribute `__name__`

freqtrade (https://github.com/freqtrade/freqtrade)
- freqtrade/strategy/informative_decorator.py:147:21: warning[possibly-missing-attribute] Attribute `format` on type `(str & ~AlwaysFalsy & ~((...) -> object)) | (((Any, /) -> str) & ~AlwaysFalsy & ~((...) -> object))` may be missing
+ freqtrade/strategy/informative_decorator.py:147:21: warning[possibly-missing-attribute] Attribute `format` on type `(str & ~AlwaysFalsy & ~(() -> object)) | (((Any, /) -> str) & ~AlwaysFalsy & ~(() -> object))` may be missing

prefect (https://github.com/PrefectHQ/prefect)
- src/prefect/concurrency/v1/sync.py:63:58: error[invalid-argument-type] Argument to function `emit_concurrency_acquisition_events` is incorrect: Expected `list[MinimalConcurrencyLimitResponse]`, found `(Unknown & ~Coroutine[Any, Any, Any]) | (Coroutine[Any, Any, Unknown] & ~Coroutine[Any, Any, Any])`
- src/prefect/concurrency/v1/sync.py:72:41: error[invalid-argument-type] Argument to function `emit_concurrency_release_events` is incorrect: Expected `list[MinimalConcurrencyLimitResponse]`, found `(Unknown & ~Coroutine[Any, Any, Any]) | (Coroutine[Any, Any, Unknown] & ~Coroutine[Any, Any, Any])`
- src/prefect/flows.py:288:34: warning[possibly-missing-attribute] Attribute `__name__` on type `(((...) -> R@__init__) & ((...) -> object) & ~classmethod & ~staticmethod) | (@Todo & ((...) -> object) & ~classmethod & ~staticmethod) | (((...) -> R@__init__) & ((...) -> object) & ~staticmethod) | (((...) -> R@__init__) & ((...) -> object))` may be missing
+ src/prefect/flows.py:288:34: warning[possibly-missing-attribute] Attribute `__name__` on type `(((...) -> R@__init__) & (() -> object) & ~classmethod & ~staticmethod) | (@Todo & (() -> object) & ~classmethod & ~staticmethod) | (((...) -> R@__init__) & (() -> object) & ~staticmethod) | (((...) -> R@__init__) & (() -> object))` may be missing
- src/prefect/flows.py:405:68: warning[possibly-missing-attribute] Attribute `__name__` on type `(((...) -> R@__init__) & ((...) -> object) & ~classmethod & ~staticmethod) | (@Todo & ((...) -> object) & ~classmethod & ~staticmethod) | (((...) -> R@__init__) & ((...) -> object) & ~staticmethod) | (((...) -> R@__init__) & ((...) -> object))` may be missing
+ src/prefect/flows.py:405:68: warning[possibly-missing-attribute] Attribute `__name__` on type `(((...) -> R@__init__) & (() -> object) & ~classmethod & ~staticmethod) | (@Todo & (() -> object) & ~classmethod & ~staticmethod) | (((...) -> R@__init__) & (() -> object) & ~staticmethod) | (((...) -> R@__init__) & (() -> object))` may be missing
+ src/prefect/runner/submit.py:174:35: error[invalid-argument-type] Argument to bound method `append` is incorrect: Expected `FlowRun`, found `object`
- Found 3082 diagnostics
+ Found 3081 diagnostics

hydra-zen (https://github.com/mit-ll-responsible-ai/hydra-zen)
+ src/hydra_zen/structured_configs/_implementations.py:2252:47: error[invalid-argument-type] Argument to function `get_target_path` is incorrect: Expected `HasTarget`, found `(() -> object) & type`
- Found 567 diagnostics
+ Found 568 diagnostics

xarray (https://github.com/pydata/xarray)
+ xarray/core/dataarray.py:5269:35: error[too-many-positional-arguments] Too many positional arguments: expected 0, got 1
+ xarray/core/dataset.py:8080:35: error[too-many-positional-arguments] Too many positional arguments: expected 0, got 1
- Found 1619 diagnostics
+ Found 1621 diagnostics

jax (https://github.com/google/jax)
- jax/_src/interpreters/batching.py:1008:37: error[invalid-argument-type] Argument to function `safe_zip` is incorrect: Expected `Iterable[Unknown]`, found `@Todo | ((() -> Sequence[int | None]) & ~((...) -> object))`
- jax/_src/interpreters/batching.py:1010:39: error[invalid-argument-type] Argument to function `safe_zip` is incorrect: Expected `Iterable[Unknown]`, found `@Todo | ((() -> Sequence[int | None]) & ~((...) -> object))`
- jax/_src/xla_bridge.py:532:5: error[no-matching-overload] No overload of bound method `update` matches arguments
- Found 2267 diagnostics
+ Found 2264 diagnostics

aiohttp (https://github.com/aio-libs/aiohttp)
+ aiohttp/web.py:307:9: error[invalid-assignment] Object of type `object` is not assignable to `Application | Awaitable[Application]`
- Found 160 diagnostics
+ Found 161 diagnostics

setuptools (https://github.com/pypa/setuptools)
- setuptools/_vendor/typeguard/_decorators.py:209:29: error[invalid-assignment] Method `__setitem__` of type `bound method dict[str, (@Todo & str) | (@Todo & None)].__setitem__(key: str, value: (@Todo & str) | (@Todo & None), /) -> None` cannot be called with a key of type `Literal["fset", "fget", "fdel"]` and a value of type `FunctionType` on object of type `dict[str, (@Todo & str) | (@Todo & None)]`
+ setuptools/_vendor/typeguard/_decorators.py:209:29: error[invalid-assignment] Method `__setitem__` of type `bound method dict[str, (Unknown & str) | (Unknown & None)].__setitem__(key: str, value: (Unknown & str) | (Unknown & None), /) -> None` cannot be called with a key of type `Literal["fset", "fget", "fdel"]` and a value of type `FunctionType` on object of type `dict[str, (Unknown & str) | (Unknown & None)]`
- setuptools/_vendor/typeguard/_importhook.py:211:33: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `MetaPathFinder`, found `MetaPathFinderProtocol & type[Any]`
+ setuptools/_vendor/typeguard/_importhook.py:211:33: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `MetaPathFinder`, found `MetaPathFinderProtocol & type`
- setuptools/_vendor/typing_extensions.py:2855:17: error[invalid-assignment] Object of type `Unknown` is not assignable to attribute `__deprecated__` on type `_T@__call__ & ((...) -> object) & ~type`
+ setuptools/_vendor/typing_extensions.py:2855:17: error[invalid-assignment] Object of type `Unknown` is not assignable to attribute `__deprecated__` on type `_T@__call__ & (() -> object) & ~type`
- setuptools/config/_apply_pyprojecttoml.py:124:31: error[invalid-argument-type] Argument to function `_set_config` is incorrect: Expected `str`, found `(Unknown & ~((...) -> object)) | (partial[Unknown] & ~((...) -> object))`
+ setuptools/config/_apply_pyprojecttoml.py:124:31: error[invalid-argument-type] Argument to function `_set_config` is incorrect: Expected `str`, found `(Unknown & ~(() -> object)) | (partial[Unknown] & ~(() -> object))`

bokeh (https://github.com/bokeh/bokeh)
- src/bokeh/core/property/bases.py:184:20: error[invalid-return-type] Return type does not match returned value: expected `T@Property`, found `((() -> T@Property) & ~((...) -> object)) | (T@Property & ~((...) -> object))`
- src/bokeh/core/property/bases.py:187:24: error[invalid-return-type] Return type does not match returned value: expected `T@Property`, found `((() -> T@Property) & ((...) -> object)) | (T@Property & ((...) -> object))`
+ src/bokeh/core/property/bases.py:187:24: error[invalid-return-type] Return type does not match returned value: expected `T@Property`, found `(() -> T@Property) | (T@Property & (() -> object))`
- Found 467 diagnostics
+ Found 466 diagnostics

pandas (https://github.com/pandas-dev/pandas)
- pandas/core/groupby/numba_.py:61:57: error[unresolved-attribute] Type `((...) -> Unknown) & ((...) -> object)` has no attribute `__name__`
+ pandas/core/groupby/numba_.py:61:57: error[unresolved-attribute] Type `((...) -> Unknown) & (() -> object)` has no attribute `__name__`
- pandas/io/parsers/base_parser.py:991:12: error[invalid-return-type] Return type does not match returned value: expected `SequenceT@evaluate_callable_usecols | set[int]`, found `(((Hashable, /) -> object) & ~((...) -> object)) | (SequenceT@evaluate_callable_usecols & ~((...) -> object))`
+ pandas/io/parsers/base_parser.py:991:12: error[invalid-return-type] Return type does not match returned value: expected `SequenceT@evaluate_callable_usecols | set[int]`, found `(((Hashable, /) -> object) & ~(() -> object)) | (SequenceT@evaluate_callable_usecols & ~(() -> object))`
- pandas/util/_decorators.py:199:41: warning[possibly-missing-attribute] Attribute `get` on type `(Mapping[Any, Any] & ~((...) -> object)) | (((Any, /) -> Any) & <Protocol with members 'get'> & ~((...) -> object)) | (((Any, /) -> Any) & ((...) -> object) & ~((...) -> object))` may be missing
- Found 3320 diagnostics
+ Found 3319 diagnostics

ibis (https://github.com/ibis-project/ibis)
- ibis/backends/tests/conftest.py:9:35: error[invalid-type-form] Variable of type `def callable(obj: object, /) -> TypeIs[(...) -> object]` is not allowed in a type expression
+ ibis/backends/tests/conftest.py:9:35: error[invalid-type-form] Variable of type `def callable(obj: object, /) -> TypeIs[() -> object]` is not allowed in a type expression
- ibis/expr/types/relations.py:4433:13: warning[possibly-missing-attribute] Attribute `setdefault` on type `(((str, /) -> Value) & Top[Mapping[Unknown, object]]) | Mapping[str, (str, /) -> Value] | Unknown | dict[Unknown, ((str, /) -> Value) & ((...) -> object) & ~Top[Mapping[Unknown, object]]]` may be missing
+ ibis/expr/types/relations.py:4433:13: warning[possibly-missing-attribute] Attribute `setdefault` on type `(((str, /) -> Value) & Top[Mapping[Unknown, object]]) | Mapping[str, (str, /) -> Value] | Unknown | dict[Unknown, ((str, /) -> Value) & (() -> object) & ~Top[Mapping[Unknown, object]]]` may be missing

zulip (https://github.com/zulip/zulip)
- zerver/lib/rest.py:110:20: error[invalid-return-type] Return type does not match returned value: expected `tuple[(...) -> HttpResponse, set[str]] | HttpResponse`, found `tuple[(...) -> object, Top[set[Unknown]]]`
+ zerver/lib/rest.py:110:20: error[invalid-return-type] Return type does not match returned value: expected `tuple[(...) -> HttpResponse, set[str]] | HttpResponse`, found `tuple[() -> object, Top[set[Unknown]]]`
- zerver/lib/rest.py:112:16: error[invalid-return-type] Return type does not match returned value: expected `tuple[(...) -> HttpResponse, set[str]] | HttpResponse`, found `tuple[((...) -> object) & ~tuple[object, ...], set[Unknown]]`
+ zerver/lib/rest.py:112:16: error[invalid-return-type] Return type does not match returned value: expected `tuple[(...) -> HttpResponse, set[str]] | HttpResponse`, found `tuple[(() -> object) & ~tuple[object, ...], set[Unknown]]`
- zerver/tests/test_openapi.py:588:38: error[not-iterable] Object of type `((...) -> Unknown) & ~((...) -> object)` is not iterable
+ zerver/tests/test_openapi.py:588:38: error[not-iterable] Object of type `((...) -> Unknown) & ~(() -> object)` is not iterable
- zerver/tests/test_openapi.py:600:58: warning[possibly-missing-attribute] Attribute `__name__` on type `(Unknown & ((...) -> object) & ~(def get_events(request: HttpRequest, user_profile: UserProfile) -> HttpResponse)) | (((...) -> Unknown) & ((...) -> object) & ~(def get_events(request: HttpRequest, user_profile: UserProfile) -> HttpResponse)) | (Unknown & ~(def get_events(request: HttpRequest, user_profile: UserProfile) -> HttpResponse)) | ((...) -> Unknown)` may be missing
+ zerver/tests/test_openapi.py:600:58: warning[possibly-missing-attribute] Attribute `__name__` on type `(Unknown & (() -> object) & ~(def get_events(request: HttpRequest, user_profile: UserProfile) -> HttpResponse)) | (((...) -> Unknown) & (() -> object) & ~(def get_events(request: HttpRequest, user_profile: UserProfile) -> HttpResponse)) | (Unknown & ~(def get_events(request: HttpRequest, user_profile: UserProfile) -> HttpResponse)) | ((...) -> Unknown)` may be missing

sympy (https://github.com/sympy/sympy)
- sympy/utilities/tests/test_pickling.py:72:17: warning[possibly-missing-attribute] Attribute `loads` on type `(Unknown & ModuleType & ~((...) -> object)) | (((x: _T@copy) -> _T@copy) & ModuleType & ~((...) -> object)) | (((x: _T@deepcopy, memo: dict[int, Any] | None = None, _nil: Any = list[Unknown]) -> _T@deepcopy) & ModuleType & ~((...) -> object))` may be missing
+ sympy/utilities/tests/test_pickling.py:72:17: warning[possibly-missing-attribute] Attribute `loads` on type `(Unknown & ModuleType & ~(() -> object)) | (((x: _T@copy) -> _T@copy) & ModuleType & ~(() -> object)) | (((x: _T@deepcopy, memo: dict[int, Any] | None = None, _nil: Any = list[Unknown]) -> _T@deepcopy) & ModuleType & ~(() -> object))` may be missing
- sympy/utilities/tests/test_pickling.py:72:32: warning[possibly-missing-attribute] Attribute `dumps` on type `(Unknown & ModuleType & ~((...) -> object)) | (((x: _T@copy) -> _T@copy) & ModuleType & ~((...) -> object)) | (((x: _T@deepcopy, memo: dict[int, Any] | None = None, _nil: Any = list[Unknown]) -> _T@deepcopy) & ModuleType & ~((...) -> object))` may be missing
+ sympy/utilities/tests/test_pickling.py:72:32: warning[possibly-missing-attribute] Attribute `dumps` on type `(Unknown & ModuleType & ~(() -> object)) | (((x: _T@copy) -> _T@copy) & ModuleType & ~(() -> object)) | (((x: _T@deepcopy, memo: dict[int, Any] | None = None, _nil: Any = list[Unknown]) -> _T@deepcopy) & ModuleType & ~(() -> object))` may be missing
- sympy/utilities/tests/test_pickling.py:74:46: error[invalid-argument-type] Argument to function `dumps` is incorrect: Expected `int | None`, found `(Unknown & ~((...) -> object) & ~ModuleType) | (int & ~((...) -> object)) | (((x: _T@copy) -> _T@copy) & ~((...) -> object) & ~ModuleType) | (((x: _T@deepcopy, memo: dict[int, Any] | None = None, _nil: Any = list[Unknown]) -> _T@deepcopy) & ~((...) -> object) & ~ModuleType)`
+ sympy/utilities/tests/test_pickling.py:74:46: error[invalid-argument-type] Argument to function `dumps` is incorrect: Expected `int | None`, found `(Unknown & ~(() -> object) & ~ModuleType) | (int & ~(() -> object)) | (((x: _T@copy) -> _T@copy) & ~(() -> object) & ~ModuleType) | (((x: _T@deepcopy, memo: dict[int, Any] | None = None, _nil: Any = list[Unknown]) -> _T@deepcopy) & ~(() -> object) & ~ModuleType)`

dd-trace-py (https://github.com/DataDog/dd-trace-py)
- ddtrace/internal/datadog/profiling/ddup/test/interface.py:53:20: error[invalid-type-form] Variable of type `def callable(obj: object, /) -> TypeIs[(...) -> object]` is not allowed in a type expression
+ ddtrace/internal/datadog/profiling/ddup/test/interface.py:53:20: error[invalid-type-form] Variable of type `def callable(obj: object, /) -> TypeIs[() -> object]` is not allowed in a type expression

core (https://github.com/home-assistant/core)
- homeassistant/components/tomorrowio/sensor.py:349:18: error[unsupported-operator] Operator `*` is unsupported between objects of type `float` and `(((int | float, /) -> int | float) & ~((...) -> object)) | (int & ~((...) -> object)) | (float & ~((...) -> object))`
+ homeassistant/components/tomorrowio/sensor.py:349:18: error[unsupported-operator] Operator `*` is unsupported between objects of type `float` and `(((int | float, /) -> int | float) & ~(() -> object)) | (int & ~(() -> object)) | (float & ~(() -> object))`
- homeassistant/core.py:596:65: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `(...) -> Unknown`, found `(((...) -> Any) & ~Coroutine[Any, Any, Any]) | (Coroutine[Any, Any, Any] & ~Coroutine[Any, Any, Any])`
- homeassistant/core.py:661:49: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `(...) -> Unknown`, found `(((...) -> Coroutine[Any, Any, _R@async_add_job] | _R@async_add_job) & ~Coroutine[Any, Any, Any]) | (Coroutine[Any, Any, _R@async_add_job] & ~Coroutine[Any, Any, Any])`
- homeassistant/core.py:988:48: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `(...) -> Unknown`, found `(((...) -> Coroutine[Any, Any, _R@async_run_job] | _R@async_run_job) & ~Coroutine[Any, Any, Any]) | (Coroutine[Any, Any, _R@async_run_job] & ~Coroutine[Any, Any, Any])`
- homeassistant/data_entry_flow.py:1042:25: error[invalid-argument-type] Argument to bound method `async_show_progress` is incorrect: Expected `Mapping[str, str] | None`, found `None | @Todo | (dict[str, str] & ~((...) -> object)) | (((Any, /) -> dict[str, str]) & ~((...) -> object))`
+ homeassistant/data_entry_flow.py:1042:25: error[invalid-argument-type] Argument to bound method `async_show_progress` is incorrect: Expected `Mapping[str, str] | None`, found `None | @Todo | (dict[str, str] & ~(() -> object)) | (((Any, /) -> dict[str, str]) & ~(() -> object))`
- homeassistant/helpers/schema_config_entry_flow.py:258:13: error[invalid-assignment] Object of type `(((dict[str, Any], /) -> Coroutine[Any, Any, str | None]) & ~((...) -> object)) | (str & ~((...) -> object)) | None` is not assignable to `str | None`
+ homeassistant/helpers/schema_config_entry_flow.py:258:13: error[invalid-assignment] Object of type `(((dict[str, Any], /) -> Coroutine[Any, Any, str | None]) & ~(() -> object)) | (str & ~(() -> object)) | None` is not assignable to `str | None`
- homeassistant/helpers/service.py:807:9: error[invalid-argument-type] Argument to function `_get_permissible_entity_candidates` is incorrect: Expected `dict[str, Entity]`, found `@Todo | (dict[str, Entity] & ~((...) -> object)) | ((() -> dict[str, Entity]) & ~((...) -> object))`
- Found 13731 diagnostics
+ Found 13727 diagnostics

No memory usage changes detected ✅

github-actions · 2025-09-26T13:20:45Z

`ecosystem-analyzer` results

Lint rule	Added	Removed	Changed
`invalid-argument-type`	7	9	7
`unresolved-attribute`	1	0	12
`possibly-missing-attribute`	0	2	9
`invalid-assignment`	2	0	7
`invalid-return-type`	2	2	5
`invalid-type-form`	0	0	3
`not-iterable`	0	0	2
`too-many-positional-arguments`	2	0	0
`unsupported-operator`	0	0	2
`no-matching-overload`	0	1	0
`unused-ignore-comment`	1	0	0
Total	15	14	47

Full report with detailed diff (timing results)

AlexWaygood · 2025-09-26T13:55:39Z

Ecosystem analysis

Overall this PR adds about as many diagnostics as it removes, but I think it makes our narrowing behaviour for TypeIs more consistent with our narrowing behaviour elsewhere, and therefore easier to reason about.

There are several hits that look like true positives: we're now inferring less dynamic types which is allowing us to highlight places where the code arguably is unsound (aiohttp, beartype, prefect, psycopg, trio). I worry that some of these will seem pedantic, overly strict, and possibly confusing to users. But it makes our TypeIs narrowing behaviour more consistent with our isinstance() narrowing behaviour, which will be especially beneficial when #20368 lands.

The new diagnostic on hydra-zen is caused by missing support for TypeGuard.

We have some new false positives in pytest, vision and xarray that are caused by this TODO here, which causes us to incorrectly think that Top[Callable[..., Any]] -> Callable[[], object] (it should really be Callable[Top[...], object], I suppose?

ruff/crates/ty_python_semantic/src/types/signatures.rs

Lines 1286 to 1291 in 57e1ff8

    
           // TODO: This is wrong, the empty Parameters is not a subtype of all materializations. 
        
           // The bottom materialization is not currently representable and implementing it 
        
           // properly requires extending the Parameters struct. 
        
           TypeMapping::Materialize(MaterializationKind::Bottom) if self.is_gradual => { 
        
               Parameters::empty() 
        
           }

We have a new false positive on starlette which is caused by missing support for functools.partial.

carljm · 2025-09-26T16:55:26Z

it should really be Callable[Top[...], object], I suppose?

No, it should be Callable[Bottom[...], object] due to contravariance of arguments.

AlexWaygood · 2025-09-26T16:56:22Z

it should really be Callable[Top[...], object], I suppose?

No, it should be Callable[Bottom[...], object] due to contravariance of arguments.

Right, yes, sorry

carljm

I don't love implicitly transforming a type explicitly written by the user :/ but I do feel like this practically improves the results, given the way TypeIs is currently used in typeshed. Narrowing with a gradual type is just not really very useful, if it's handled precisely (as we do).

I feel like the user intent expressed by -> TypeIs[Foo[Any]] is "the type is some kind of Foo, I don't know which kind" (this is accurately modeled by taking the top materialization), but also then "treat the contained type of Foo as dynamic if I end up using it" -- and this latter part is what we don't do.

I wonder what it would look like if, instead of doing this, we simplified Foo[Any] & Foo[Bar] to Foo[Bar & Any]? I think that's a correct simplification? And I think that would give the same benefits as this PR, but with fewer false positives -- it would better respect the user's intent in writing TypeIs[Foo[Any]]. WDYT?

Edit: I guess then we'd have false negatives compared to other type checkers, who are happy to simplify Foo[Any] & Foo[Bar] to just Foo[Bar]. Which is not correct, but is maybe practically what users expect.

carljm

Going ahead and approving this -- I don't love it, but it seems like a net improvement for now, and it's easy to reverse if we come up with a better idea.

AlexWaygood · 2025-09-26T17:16:20Z

I wonder what it would look like if, instead of doing this, we simplified Foo[Any] & Foo[Bar] to Foo[Bar & Any]? I think that's a correct simplification?

That's only a correct simplification if Foo is covariant, I think? I don't think it's true, for example, that list[Any] & list[int] can be simplified to list[int & Any]

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

* main: (21 commits) [ty] Literal promotion refactor (#20646) [ty] Add tests for nested generic functions (#20631) [`cli`] Add conflict between `--add-noqa` and `--diff` options (#20642) [ty] Ensure first-party search paths always appear in a sensible order (#20629) [ty] Use `typing.Self` for the first parameter of instance methods (#20517) [ty] Remove unnecessary `parsed_module()` calls (#20630) Remove `TextEmitter` (#20595) [ty] Use fully qualified names to distinguish ambiguous protocols in diagnostics (#20627) [ty] Ecosystem analyzer: relax timeout thresholds (#20626) [ty] Apply type mappings to functions eagerly (#20596) [ty] Improve disambiguation of class names in diagnostics (#20603) Add the *The Basics* title back to CONTRIBUTING.md (#20624) [`playground`] Fix quick fixes for empty ranges in playground (#20599) Update dependency ruff to v0.13.2 (#20622) [`ruff`] Fix minor typos in doc comments (#20623) Update dependency PyYAML to v6.0.3 (#20621) Update cargo-bins/cargo-binstall action to v1.15.6 (#20620) Fixed documentation for try_consider_else (#20587) [ty] Use `Top` materializations for `TypeIs` special form (#20591) [ty] Simplify `Any | (Any & T)` to `Any` (#20593) ...

AlexWaygood added the ty Multi-file analysis & type inference label Sep 26, 2025

AlexWaygood force-pushed the alex/typeis-top branch from 3cb9437 to 2afd6a9 Compare September 26, 2025 13:11

AlexWaygood added the ecosystem-analyzer label Sep 26, 2025

AlexWaygood added 2 commits September 26, 2025 17:03

Use Top materializations for TypeIs special form

688bf32

add a test

ad032c5

AlexWaygood force-pushed the alex/typeis-top branch from 2afd6a9 to ad032c5 Compare September 26, 2025 16:04

AlexWaygood added ecosystem-analyzer and removed ecosystem-analyzer labels Sep 26, 2025

AlexWaygood marked this pull request as ready for review September 26, 2025 16:27

AlexWaygood requested review from carljm, dcreager and sharkdp as code owners September 26, 2025 16:27

AlexWaygood changed the title ~~Use Top materializations for TypeIs special form~~ [ty] Use Top materializations for TypeIs special form Sep 26, 2025

carljm reviewed Sep 26, 2025

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carljm approved these changes Sep 26, 2025

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AlexWaygood commented Sep 26, 2025

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AlexWaygood enabled auto-merge (squash) September 26, 2025 17:19

AlexWaygood merged commit 6b3c493 into main Sep 26, 2025
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AlexWaygood deleted the alex/typeis-top branch September 26, 2025 17:24

AlexWaygood mentioned this pull request Oct 8, 2025

[ty] Improve assignability/subtyping between two protocol types #20368

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AlexWaygood mentioned this pull request Oct 23, 2025

Incorrect top materialization of Callable types astral-sh/ty#1426

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