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[ty] remove special handling for Any() in match class patterns#23011

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sharkdp merged 1 commit intoastral-sh:mainfrom
abhijeetbodas2001:apb-none-match
Feb 2, 2026
Merged

[ty] remove special handling for Any() in match class patterns#23011
sharkdp merged 1 commit intoastral-sh:mainfrom
abhijeetbodas2001:apb-none-match

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@abhijeetbodas2001 abhijeetbodas2001 commented Feb 1, 2026 •
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Summary

Any does not support isinstance checks and cannot be used in class patterns. If the arm with Any() is hit, it will raise an error at runtime:

[nav] In [1]: from typing import Any
         ...:
         ...: X = Any
         ...:
         ...: def f(obj: object):
         ...:     match obj:
         ...:         case int():
         ...:             ...
         ...:         case X():
         ...:             ...

[ins] In [2]: f("")
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[2], line 1
----> 1 f("")

Cell In[1], line 9, in f(obj)
      7 case int():
      8     ...
----> 9 case X():
     10     ...

# << snipped for brevity >>

TypeError: typing.Any cannot be used with isinstance()

Because this fails at runtime, we should ideally raise a diagnostic on seeing Any() in a match pattern. That could potentially be done as part of astral-sh/ty#2592. But for now, this PR only removes the special support that we have.

The special-case handling does not reduce any diagnostics on jax as of today either.

Test Plan

Removed tests :)

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astral-sh-bot bot commented Feb 1, 2026 •
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Typing conformance results

No changes detected ✅

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astral-sh-bot bot commented Feb 1, 2026 •
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mypy_primer results

Changes were detected when running on open source projects 
pydantic (https://github.com/pydantic/pydantic)
- pydantic/_internal/_core_metadata.py:87:54: error[invalid-assignment] Invalid assignment to key "pydantic_js_extra" with declared type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | ((dict[str, Divergent], type[Any], /) -> None)` on TypedDict `CoreMetadata`: value of type `dict[object, object]`
+ pydantic/_internal/_core_metadata.py:87:54: error[invalid-assignment] Invalid assignment to key "pydantic_js_extra" with declared type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | ((dict[str, int | float | str | ... omitted 3 union elements], type[Any], /) -> None)` on TypedDict `CoreMetadata`: value of type `dict[object, object]`
- pydantic/fields.py:949:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
+ pydantic/fields.py:949:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
- pydantic/fields.py:989:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
+ pydantic/fields.py:989:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
- pydantic/fields.py:1032:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
+ pydantic/fields.py:1032:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
- pydantic/fields.py:1072:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
+ pydantic/fields.py:1072:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
- pydantic/fields.py:1115:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
+ pydantic/fields.py:1115:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
- pydantic/fields.py:1154:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
+ pydantic/fields.py:1154:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
- pydantic/fields.py:1194:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
+ pydantic/fields.py:1194:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
- pydantic/fields.py:1573:13: error[invalid-argument-type] Argument is incorrect: Expected `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`, found `Top[dict[Unknown, Unknown]] | (((dict[str, Divergent], /) -> None) & ~Top[dict[Unknown, Unknown]]) | None`
+ pydantic/fields.py:1573:13: error[invalid-argument-type] Argument is incorrect: Expected `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`, found `Top[dict[Unknown, Unknown]] | (((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) & ~Top[dict[Unknown, Unknown]]) | None`

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:997:32: error[invalid-await] `Unknown | R@FlowRunEngine | Coroutine[Any, Any, R@FlowRunEngine]` is not awaitable
- src/prefect/flow_engine.py:1596:24: error[invalid-await] `Unknown | R@AsyncFlowRunEngine | Coroutine[Any, Any, R@AsyncFlowRunEngine]` is not awaitable
- src/prefect/flow_engine.py:1677:43: 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:1685:21: warning[possibly-missing-attribute] Attribute `throw` may be missing on object of type `Unknown | R@run_generator_flow_sync`
- src/prefect/flow_engine.py:1719:44: warning[possibly-missing-attribute] Attribute `__anext__` may be missing on object of type `Unknown | R@run_generator_flow_async`
- src/prefect/flow_engine.py:1726:25: warning[possibly-missing-attribute] Attribute `throw` may be missing on object of type `Unknown | R@run_generator_flow_async`
- src/prefect/flows.py:285:34: error[unresolved-attribute] Object of type `(**P@Flow) -> R@Flow` has no attribute `__name__`
+ src/prefect/flows.py:285:34: error[unresolved-attribute] Object of type `((**P@Flow) -> R@Flow) & ((*args: object, **kwargs: object) -> object)` has no attribute `__name__`
- src/prefect/flows.py:403:68: error[unresolved-attribute] Object of type `(**P@Flow) -> R@Flow` has no attribute `__name__`
+ src/prefect/flows.py:403:68: error[unresolved-attribute] Object of type `((**P@Flow) -> R@Flow) & ((*args: object, **kwargs: object) -> object)` has no attribute `__name__`
- src/prefect/flows.py:1945:21: error[no-matching-overload] No overload of function `run_coro_as_sync` matches arguments
+ src/prefect/flows.py:1885:53: warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- Found 5371 diagnostics
+ Found 5365 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 47 diagnostics
+ Found 46 diagnostics

core (https://github.com/home-assistant/core)
- homeassistant/util/variance.py:47:12: error[invalid-return-type] Return type does not match returned value: expected `(**_P@ignore_variance) -> _R@ignore_variance`, found `_Wrapped[_P@ignore_variance, int | _R@ignore_variance | float | datetime, _P@ignore_variance, _R@ignore_variance | int | float | datetime]`
- Found 14514 diagnostics
+ Found 14513 diagnostics

No memory usage changes detected ✅

@abhijeetbodas2001 abhijeetbodas2001 changed the title [ty] [DRAFT] remove special Any handling for match class patterns [ty] remove special handling for Any() in match class patterns Feb 1, 2026
@ntBre ntBre added the ty Multi-file analysis & type inference label Feb 1, 2026
@abhijeetbodas2001 abhijeetbodas2001 marked this pull request as ready for review February 2, 2026 10:20
@abhijeetbodas2001 abhijeetbodas2001 mentioned this pull request Feb 2, 2026
Merged
sharkdp
sharkdp reviewed Feb 2, 2026
View reviewed changes
crates/ty_python_semantic/resources/mdtest/narrow/match.md
Comment on lines -121 to -146
## Class patterns where the class pattern does not resolve to a class

In general this does not allow for narrowing, but we make an exception for `Any`. This is to support
[real ecosystem code](https://github.com/jax-ml/jax/blob/d2ce04b6c3d03ae18b145965b8b8b92e09e8009c/jax/_src/pallas/mosaic_gpu/lowering.py#L3372-L3387)
found in `jax`.

```py
from typing import Any

X = Any

def f(obj: object):
match obj:
case int():
reveal_type(obj) # revealed: int
case X():
reveal_type(obj) # revealed: Any & ~int

def g(obj: object, Y: Any):
match obj:
case int():
reveal_type(obj) # revealed: int
case Y():
reveal_type(obj) # revealed: Any & ~int
```

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Link to relevant discussion here: https://github.com/astral-sh/ruff/pull/21150/files#r2749631869

sharkdp
sharkdp approved these changes Feb 2, 2026
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This looks good to me, thank you!

I'll keep the referenced ticket open for now, because I think it makes sense to introduce a new diagnostic.

@sharkdp sharkdp merged commit 9e0189b into astral-sh:main Feb 2, 2026
49 checks passed
@abhijeetbodas2001 abhijeetbodas2001 deleted the apb-none-match branch February 2, 2026 14:01
carljm added a commit that referenced this pull request Feb 2, 2026
@carljm
Merge branch 'main' into claude/fix-issue-1858-UjARA
d330ae7 
* main: (48 commits)
  add info for non_octal permissions (#22972)
  Fix empty body rule rendering (#23039)
  [ty] Infer `ParamSpec` from class constructors for callable protocols (#22853)
  Update NPM Development dependencies (#23030)
  Update CodSpeedHQ/action action to v4.8.2 (#23029)
  [ty] remove special handling for `Any()` in match class patterns (#23011)
  Update Rust crate get-size2 to v0.7.4 (#23022)
  Update Rust crate insta to v1.46.1 (#23023)
  Update taiki-e/install-action action to v2.67.11 (#23033)
  Update Rust crate colored to v3.1.1 (#23031)
  Update cargo-bins/cargo-binstall action to v1.17.3 (#23028)
  Update Rust crate uuid to v1.20.0 (#23032)
  [ty] Avoid using `.node()` for detecting `Self` (#23000)
  Update Rust crate proc-macro2 to v1.0.106 (#23024)
  Update actions/setup-python action to v6.2.0 (#23027)
  [ty] fix query cycles in decorated function with parameter defaults (#23014)
  Update Rust crate quote to v1.0.44 (#23025)
  Update Rust crate thiserror to v2.0.18 (#23026)
  Update Rust crate filetime to v0.2.27 (#23021)
  Update Rust crate clearscreen to v4.0.3 (#23020)
  ...
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@sharkdp sharkdp sharkdp approved these changes

@carljm carljm Awaiting requested review from carljm carljm is a code owner

@AlexWaygood AlexWaygood Awaiting requested review from AlexWaygood AlexWaygood is a code owner

@dcreager dcreager Awaiting requested review from dcreager dcreager is a code owner

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@abhijeetbodas2001 @sharkdp @ntBre