[ty] Support narrowing on `__class__` checks by charliermarsh · Pull Request #24997 · astral-sh/ruff

charliermarsh · 2026-05-05T02:09:36Z

Summary

This adds support for narrowing based on __class__ identity checks, treating them the same way we already treat type(...) checks. Although these can differ at runtime, AFAICT we already treat these as the same internally (i.e., infer_builtins_type_call calls arg_type.dunder_class(db)).

For example:

from typing import final, reveal_type

class A: ...
class B: ...

@final
class C: ...

def f(x: A | B, y: A | C):
    if x.__class__ is A:
        reveal_type(x)  # revealed: A

    if C is y.__class__:
        reveal_type(y)  # revealed: C
    else:
        reveal_type(y)  # revealed: A

This supports both operand orders, and both is and is not. As with type(x) is C, negative-branch narrowing is only applied when the tested class is final.

astral-sh-bot · 2026-05-05T02:11:17Z

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 89.36%. The percentage of expected errors that received a diagnostic held steady at 85.49%. The number of fully passing files held steady at 88/134.

astral-sh-bot · 2026-05-05T02:11:56Z

Memory usage report

Memory usage unchanged ✅

astral-sh-bot · 2026-05-05T02:13:44Z

`ecosystem-analyzer` results

Failing projects:

Project	Old Status	New Status	Old Return Code	New Return Code
`pywin32`	abnormal exit	abnormal exit	`2`	`2`

Diagnostic changes:

Lint rule	Added	Removed	Changed
`unresolved-attribute`	0	57	0
`unused-type-ignore-comment`	14	9	0
`invalid-argument-type`	2	19	0
`invalid-return-type`	0	4	1
`invalid-assignment`	0	3	0
`no-matching-overload`	2	1	0
`not-iterable`	0	1	2
`unsupported-operator`	0	0	3
`not-subscriptable`	0	2	0
`call-non-callable`	0	1	0
`invalid-declaration`	0	0	1
Total	18	97	7

Raw diff (122 changes)

discord.py (https://github.com/Rapptz/discord.py)
+ discord/state.py:968:64 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive

ibis (https://github.com/ibis-project/ibis)
- ibis/common/patterns.py:936:13 error[unresolved-attribute] Object of type `Pattern` has no attribute `patterns`

pip (https://github.com/pypa/pip)
- src/pip/_internal/utils/misc.py:551:35 error[unresolved-attribute] Object of type `object` has no attribute `secret`

pydantic (https://github.com/pydantic/pydantic)
- pydantic/networks.py:244:16 error[invalid-return-type] Return type does not match returned value: expected `bool`, found `SupportsBool`
- pydantic/networks.py:247:16 error[invalid-return-type] Return type does not match returned value: expected `bool`, found `SupportsBool`
- pydantic/networks.py:250:16 error[invalid-return-type] Return type does not match returned value: expected `bool`, found `SupportsBool`
- pydantic/networks.py:253:16 error[invalid-return-type] Return type does not match returned value: expected `bool`, found `SupportsBool`

pywin32 (https://github.com/mhammond/pywin32)
- FAILED old=abnormal exit(2) new=abnormal exit(2)

spack (https://github.com/spack/spack)
- lib/spack/spack/vendor/jinja2/lexer.py:762:35 error[call-non-callable] Object of type `str` is not callable

static-frame (https://github.com/static-frame/static-frame)
- static_frame/core/container_util.py:1032:20 error[invalid-assignment] Object of type `(ndarray[Any, Any] & ~Frame) | None` is not assignable to `ndarray[Any, Any]`
- static_frame/core/container_util.py:1067:12 error[unresolved-attribute] Object of type `<Protocol with members '__len__'> & ~str` has no attribute `dtype`
- static_frame/core/container_util.py:1070:16 error[no-matching-overload] No overload of function `sort` matches arguments
- static_frame/core/container_util.py:1521:20 error[unresolved-attribute] Object of type `Iterable[Hashable] & ~IndexBase` has no attribute `ndim`
- static_frame/core/container_util.py:1522:73 error[unresolved-attribute] Object of type `Iterable[Hashable] & ~IndexBase` has no attribute `ndim`
- static_frame/core/container_util.py:1534:9 error[invalid-argument-type] Argument to `IMTOAdapter.__init__` is incorrect: Expected `ndarray[Any, Any]`, found `(Iterable[Hashable] & ~IndexBase) | ndarray[Any, Any]`
- static_frame/core/display.py:486:47 error[unresolved-attribute] Attribute `ndim` is not defined on `Sequence[Any]` in union `ndarray[Any, Any] | Sequence[Any]`
- static_frame/core/display.py:489:36 error[invalid-argument-type] Argument to function `array_str` is incorrect: Expected `ndarray[tuple[Any, ...], dtype[Any]]`, found `ndarray[Any, Any] | Sequence[Any]`
- static_frame/core/display.py:520:38 error[unresolved-attribute] Attribute `dtype` is not defined on `Sequence[Any]` in union `ndarray[Any, Any] | Sequence[Any]`
- static_frame/core/frame.py:7203:56 error[invalid-argument-type] Argument to function `len` is incorrect: Expected `Sized`, found `int | integer[Any] | ndarray[Any, Any] | list[int] | slice[Any, Any, Any]`
+ static_frame/core/frame.py:5381:57 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/frame.py:5392:64 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/index.py:253:37 error[invalid-argument-type] Argument to function `immutable_filter` is incorrect: Expected `ndarray[tuple[Any, ...], dtype[Any]]`, found `ndarray[Any, Any] | None`
- static_frame/core/index.py:334:46 error[invalid-argument-type] Argument to function `immutable_filter` is incorrect: Expected `ndarray[tuple[Any, ...], dtype[Any]]`, found `Iterable[Hashable] & ~IndexBase`
- static_frame/core/index.py:460:18 error[unresolved-attribute] Attribute `dtype` is not defined on `Iterable[Hashable] & ~IndexBase & ~ContainerOperand`, `Iterator[Hashable]` in union `(Iterable[Hashable] & ~IndexBase & ~ContainerOperand) | Unknown | Iterator[Hashable] | ndarray[Any, Any]`
- static_frame/core/index.py:484:62 error[unresolved-attribute] Attribute `step` is not defined on `Iterable[Hashable] & ~IndexBase & ~ContainerOperand & ~str`, `Iterator[Hashable] & ~str`, `ndarray[Any, Any] & ~str` in union `(Iterable[Hashable] & ~IndexBase & ~ContainerOperand & ~str) | (Unknown & ~str) | (Iterator[Hashable] & ~str) | (ndarray[Any, Any] & ~str)`
- static_frame/core/index.py:691:46 error[unresolved-attribute] Attribute `dtype` is not defined on `int`, `list[int]`, `slice[Any, Any, Any]` in union `int | integer[Any] | ndarray[Any, Any] | list[int] | slice[Any, Any, Any]`
- static_frame/core/index.py:1119:74 error[invalid-argument-type] Argument to bound method `SortStatus.derive_status_from_slice` is incorrect: Expected `slice[Any, Any, Any]`, found `int | integer[Any] | ndarray[Any, Any] | list[int] | slice[Any, Any, Any]`
- static_frame/core/index.py:1946:25 error[invalid-argument-type] Argument to function `len` is incorrect: Expected `Sized`, found `Iterable[Hashable] & ~IndexBase`
- static_frame/core/index.py:461:26 error[unresolved-attribute] Attribute `astype` is not defined on `Iterable[Hashable] & ~IndexBase & ~ContainerOperand`, `Iterator[Hashable]` in union `(Iterable[Hashable] & ~IndexBase & ~ContainerOperand) | Unknown | Iterator[Hashable] | ndarray[Any, Any]`
+ static_frame/core/index.py:461:26 error[no-matching-overload] No overload of bound method `ndarray.astype` matches arguments
- static_frame/core/index_hierarchy.py:2154:44 error[unresolved-attribute] Object of type `Hashable & ~int & ~Top[integer[Any]] & ~IndexHierarchy` has no attribute `dtype`
- static_frame/core/index_hierarchy.py:2155:20 error[invalid-argument-type] Method `__getitem__` of type `Overload[(key: ndarray[tuple[Any, ...], dtype[integer[Any] | numpy.bool[builtins.bool]]] | tuple[ndarray[tuple[Any, ...], dtype[integer[Any] | numpy.bool[builtins.bool]]], ...], /) -> ndarray[tuple[Any, ...], Any], (key: SupportsIndex | tuple[SupportsIndex, ...], /) -> Any, (key: SupportsIndex | slice[Any, Any, Any] | EllipsisType | ... omitted 5 union elements, /) -> ndarray[tuple[Any, ...], Any], (key: str, /) -> ndarray[Any | tuple[Any, ...], dtype[Any]], (key: list[str], /) -> ndarray[Any | tuple[Any, ...], Unknown]]` cannot be called with key of type `Hashable` on object of type `ndarray[Any, Any]`
- static_frame/core/index_hierarchy.py:2165:44 error[unresolved-attribute] Object of type `Hashable & ~int & ~Top[integer[Any]] & ~IndexHierarchy & ~Top[list[Unknown]]` has no attribute `ndim`
- static_frame/core/index_hierarchy.py:2166:16 error[unresolved-attribute] Object of type `Hashable & ~int & ~Top[integer[Any]] & ~IndexHierarchy & ~Top[list[Unknown]]` has no attribute `dtype`
- static_frame/core/index_hierarchy.py:2169:35 error[invalid-argument-type] Argument to function `view_2d_as_1d` is incorrect: Expected `ndarray[Any, Any]`, found `Hashable & ~int & ~Top[integer[Any]] & ~IndexHierarchy & ~Top[list[Unknown]]`
- static_frame/core/index_hierarchy.py:2177:72 error[not-iterable] Object of type `Hashable & ~int & ~Top[integer[Any]] & ~IndexHierarchy & ~Top[list[Unknown]]` is not iterable
- static_frame/core/index_hierarchy.py:2266:70 error[invalid-argument-type] Argument to bound method `SortStatus.derive_status_from_slice` is incorrect: Expected `slice[Any, Any, Any]`, found `(ndarray[Any, Any] & ~int & ~Top[integer[Any]]) | (list[int] & ~Top[integer[Any]]) | slice[Any, Any, Any]`
+ static_frame/core/index_hierarchy.py:566:41 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/index_hierarchy.py:567:37 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/index_hierarchy.py:568:30 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/index_hierarchy.py:2173:51 error[not-iterable] Object of type `Hashable & ~int & ~Top[integer[Any]] & ~IndexHierarchy & ~Top[list[Unknown]]` is not iterable
+ static_frame/core/index_hierarchy.py:2173:51 error[not-iterable] Object of type `ndarray[tuple[object, ...], dtype[object]] & ~int & ~Top[integer[Any]] & ~IndexHierarchy & ~Top[list[Unknown]]` is not iterable
- static_frame/core/loc_map.py:187:32 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:190:69 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:191:61 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:199:41 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:202:68 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:204:60 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:207:88 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:209:55 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/loc_map.py:210:40 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/pivot.py:248:44 error[unresolved-attribute] Attribute `dtype` is not defined on `list[Any]` in union `list[Any] | ndarray[Any, Any]`
- static_frame/core/pivot.py:249:16 error[unresolved-attribute] Attribute `dtype` is not defined on `list[Any]` in union `list[Any] | ndarray[Any, Any]`
- static_frame/core/pivot.py:252:13 error[invalid-assignment] Invalid subscript assignment with key of type `list[int]` and value of type `Any` on object of type `list[Any]`
- static_frame/core/pivot.py:253:13 error[unresolved-attribute] Attribute `flags` is not defined on `list[Any]` in union `list[Any] | ndarray[Any, Any]`
- static_frame/core/pivot.py:260:13 error[unresolved-attribute] Attribute `flags` is not defined on `list[Any]` in union `list[Any] | ndarray[Any, Any]`
- static_frame/core/pivot.py:250:25 error[unresolved-attribute] Attribute `astype` is not defined on `list[Any]` in union `list[Any] | ndarray[Any, Any]`
+ static_frame/core/pivot.py:250:25 error[no-matching-overload] No overload of bound method `ndarray.astype` matches arguments
- static_frame/core/reduce.py:462:21 error[unresolved-attribute] Attribute `flags` is not defined on `list[Any]` in union `ndarray[tuple[int], dtype[Any]] | list[Any] | ndarray[Any, Any]`
- static_frame/core/reduce.py:463:35 error[invalid-argument-type] Argument to bound method `list.append` is incorrect: Expected `ndarray[Any, Any]`, found `ndarray[tuple[int], dtype[Any]] | list[Any] | ndarray[Any, Any]`
- static_frame/core/reduce.py:486:21 error[unresolved-attribute] Attribute `flags` is not defined on `list[Any]` in union `ndarray[tuple[int], dtype[Any]] | list[Any] | ndarray[Any, Any]`
- static_frame/core/reduce.py:487:35 error[invalid-argument-type] Argument to bound method `list.append` is incorrect: Expected `ndarray[Any, Any]`, found `ndarray[tuple[int], dtype[Any]] | list[Any] | ndarray[Any, Any]`
- static_frame/core/series.py:2130:44 error[unresolved-attribute] Attribute `dtype` is not defined on `int`, `list[int]`, `slice[Any, Any, Any]`, `None` in union `int | integer[Any] | ndarray[Any, Any] | ... omitted 3 union elements`
- static_frame/core/type_blocks.py:1639:36 error[unresolved-attribute] Attribute `start` is not defined on `int` in union `slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1640:35 error[unresolved-attribute] Attribute `stop` is not defined on `int` in union `slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1760:25 error[unresolved-attribute] Attribute `start` is not defined on `int` in union `slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1761:28 error[unresolved-attribute] Attribute `start` is not defined on `int` in union `slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1765:25 error[unresolved-attribute] Attribute `stop` is not defined on `int` in union `slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1765:46 error[unresolved-attribute] Attribute `stop` is not defined on `int` in union `slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1842:40 error[unresolved-attribute] Attribute `start` is not defined on `None`, `int` in union `None | slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1843:39 error[unresolved-attribute] Attribute `stop` is not defined on `None`, `int` in union `None | slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1890:48 error[unresolved-attribute] Attribute `dtype` is not defined on `int`, `list[int]`, `slice[Any, Any, Any]`, `None` in union `int | integer[Any] | ndarray[Any, Any] | ... omitted 3 union elements`
- static_frame/core/type_blocks.py:1892:50 error[invalid-argument-type] Argument to function `len` is incorrect: Expected `Sized`, found `int | integer[Any] | ndarray[Any, Any] | ... omitted 3 union elements`
- static_frame/core/type_blocks.py:1931:40 error[unresolved-attribute] Attribute `start` is not defined on `None`, `int` in union `None | slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:1932:39 error[unresolved-attribute] Attribute `stop` is not defined on `None`, `int` in union `None | slice[Any, Any, Any] | int`
- static_frame/core/type_blocks.py:2377:27 error[unresolved-attribute] Object of type `object` has no attribute `dtype`
- static_frame/core/type_blocks.py:2726:16 error[unresolved-attribute] Attribute `dtype` is not defined on `list[int] & ~Top[integer[Any]]`, `slice[Any, Any, Any]`, `None` in union `(ndarray[Any, Any] & ~int & ~Top[integer[Any]]) | (list[int] & ~Top[integer[Any]]) | slice[Any, Any, Any] | None`
- static_frame/core/type_blocks.py:2727:20 error[unresolved-attribute] Attribute `sum` is not defined on `list[int] & ~Top[integer[Any]]`, `slice[Any, Any, Any]`, `None` in union `(ndarray[Any, Any] & ~int & ~Top[integer[Any]]) | (list[int] & ~Top[integer[Any]]) | slice[Any, Any, Any] | None`
- static_frame/core/type_blocks.py:2729:22 error[invalid-argument-type] Argument to function `len` is incorrect: Expected `Sized`, found `(ndarray[Any, Any] & ~int & ~Top[integer[Any]]) | (list[int] & ~Top[integer[Any]]) | slice[Any, Any, Any] | None`
- static_frame/core/type_blocks.py:3352:16 error[unresolved-attribute] Attribute `ndim` is not defined on `Iterable[Any] & ~TypeBlocks` in union `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3352:36 error[unresolved-attribute] Attribute `ndim` is not defined on `Iterable[Any] & ~TypeBlocks` in union `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3352:60 error[invalid-argument-type] Argument to function `len` is incorrect: Expected `Sized`, found `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3355:34 error[invalid-assignment] Object of type `GeneratorType[(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any], None, None]` is not assignable to `Iterable[ndarray[Any, Any]]`
- static_frame/core/type_blocks.py:3356:18 error[unresolved-attribute] Attribute `ndim` is not defined on `Iterable[Any] & ~TypeBlocks` in union `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3357:38 error[invalid-argument-type] Argument to function `len` is incorrect: Expected `Sized`, found `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3361:40 error[invalid-argument-type] Argument to function `len` is incorrect: Expected `Sized`, found `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3365:107 error[unresolved-attribute] Attribute `shape` is not defined on `Iterable[Any] & ~TypeBlocks` in union `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3367:18 error[unresolved-attribute] Attribute `ndim` is not defined on `Iterable[Any] & ~TypeBlocks` in union `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3367:38 error[unresolved-attribute] Attribute `shape` is not defined on `Iterable[Any] & ~TypeBlocks` in union `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
- static_frame/core/type_blocks.py:3374:111 error[unresolved-attribute] Attribute `shape` is not defined on `Iterable[Any] & ~TypeBlocks` in union `(Iterable[Any] & ~TypeBlocks) | ndarray[Any, Any]`
+ static_frame/core/type_blocks.py:1642:50 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/type_blocks.py:1643:53 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/type_blocks.py:1768:50 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/type_blocks.py:1769:53 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/type_blocks.py:2177:53 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/type_blocks.py:2178:51 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/type_blocks.py:2272:49 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
+ static_frame/core/type_blocks.py:2292:71 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
- static_frame/core/type_blocks.py:2182:30 error[unsupported-operator] Operator `+` is not supported between objects of type `None | slice[Any, Any, Any] | int` and `Literal[1]`
+ static_frame/core/type_blocks.py:2182:30 error[unsupported-operator] Operator `+` is not supported between objects of type `None | int` and `Literal[1]`
- static_frame/core/type_blocks.py:2266:17 error[invalid-declaration] Cannot declare type `int` for inferred type `None | slice[Any, Any, Any] | int | Any`
+ static_frame/core/type_blocks.py:2266:17 error[invalid-declaration] Cannot declare type `int` for inferred type `None | int | Any`
- static_frame/core/type_blocks.py:2275:21 error[unsupported-operator] Operator `>` is not supported between objects of type `None | slice[Any, Any, Any] | int | Any` and `Literal[0] | Unknown`
+ static_frame/core/type_blocks.py:2275:21 error[unsupported-operator] Operator `>` is not supported between objects of type `None | int | Any` and `Literal[0] | Unknown`
- static_frame/core/type_blocks.py:2310:33 error[unsupported-operator] Operator `+` is not supported between objects of type `None | slice[Any, Any, Any] | int | Any` and `Any | Literal[1]`
+ static_frame/core/type_blocks.py:2310:33 error[unsupported-operator] Operator `+` is not supported between objects of type `None | int | Any` and `Any | Literal[1]`
- static_frame/core/type_blocks.py:3360:39 error[not-subscriptable] Cannot subscript object of type `Iterable[Any]` with no `__getitem__` method
+ static_frame/core/type_blocks.py:3360:39 error[invalid-argument-type] Method `__getitem__` of type `Overload[(key: ndarray[tuple[Any, ...], dtype[integer[Any] | numpy.bool[builtins.bool]]] | tuple[ndarray[tuple[Any, ...], dtype[integer[Any] | numpy.bool[builtins.bool]]], ...], /) -> ndarray[tuple[Any, ...], dtype[object]], (key: SupportsIndex | tuple[SupportsIndex, ...], /) -> Any, (key: SupportsIndex | slice[Any, Any, Any] | EllipsisType | ... omitted 5 union elements, /) -> ndarray[tuple[Any, ...], dtype[object]], (key: str, /) -> ndarray[tuple[object, ...], dtype[Any]], (key: list[str], /) -> ndarray[tuple[object, ...], Unknown]]` cannot be called with key of type `slice[Any, Any, Any]` on object of type `ndarray[tuple[object, ...], dtype[object]]`
- static_frame/core/type_blocks.py:3370:21 error[not-subscriptable] Cannot subscript object of type `Iterable[Any]` with no `__getitem__` method
+ static_frame/core/type_blocks.py:3370:21 error[invalid-argument-type] Method `__getitem__` of type `Overload[(key: ndarray[tuple[Any, ...], dtype[integer[Any] | numpy.bool[builtins.bool]]] | tuple[ndarray[tuple[Any, ...], dtype[integer[Any] | numpy.bool[builtins.bool]]], ...], /) -> ndarray[tuple[Any, ...], dtype[object]], (key: SupportsIndex | tuple[SupportsIndex, ...], /) -> Any, (key: SupportsIndex | slice[Any, Any, Any] | EllipsisType | ... omitted 5 union elements, /) -> ndarray[tuple[Any, ...], dtype[object]], (key: str, /) -> ndarray[tuple[object, ...], dtype[Any]], (key: list[str], /) -> ndarray[tuple[object, ...], Unknown]]` cannot be called with key of type `tuple[slice[Any, Any, Any], slice[Any, Any, Any]]` on object of type `ndarray[tuple[object, ...], dtype[object]]`
- static_frame/core/util.py:446:12 error[unresolved-attribute] Attribute `dtype` is not defined on `int`, `list[int]`, `slice[Any, Any, Any]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:448:14 error[unresolved-attribute] Attribute `dtype` is not defined on `int`, `list[int]`, `slice[Any, Any, Any]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:450:14 error[unresolved-attribute] Attribute `dtype` is not defined on `int`, `list[int]`, `slice[Any, Any, Any]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:455:73 error[unresolved-attribute] Attribute `dtype` is not defined on `int`, `list[int]`, `slice[Any, Any, Any]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:457:12 error[unresolved-attribute] Attribute `start` is not defined on `int`, `list[int]`, `ndarray[Any, dtype[signedinteger[_64Bit]]]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:457:56 error[unresolved-attribute] Attribute `start` is not defined on `int`, `list[int]`, `ndarray[Any, dtype[signedinteger[_64Bit]]]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:459:12 error[unresolved-attribute] Attribute `stop` is not defined on `int`, `list[int]`, `ndarray[Any, dtype[signedinteger[_64Bit]]]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:459:55 error[unresolved-attribute] Attribute `stop` is not defined on `int`, `list[int]`, `ndarray[Any, dtype[signedinteger[_64Bit]]]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:461:28 error[unresolved-attribute] Attribute `indices` is not defined on `int`, `list[int]`, `ndarray[Any, dtype[signedinteger[_64Bit]]]` in union `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]`
- static_frame/core/util.py:2098:19 error[unresolved-attribute] Object of type `Iterable[Any]` has no attribute `start`
- static_frame/core/util.py:2099:18 error[unresolved-attribute] Object of type `Iterable[Any]` has no attribute `stop`
- static_frame/core/util.py:2100:18 error[unresolved-attribute] Object of type `Iterable[Any]` has no attribute `step`
- static_frame/core/util.py:451:22 error[not-iterable] Object of type `int | list[int] | slice[Any, Any, Any] | ndarray[Any, dtype[signedinteger[_64Bit]]]` may not be iterable
+ static_frame/core/util.py:451:22 error[not-iterable] Object of type `(int & ndarray[tuple[object, ...], dtype[object]]) | (list[int] & ndarray[tuple[object, ...], dtype[object]]) | (ndarray[Any, dtype[signedinteger[_64Bit]]] & ndarray[tuple[object, ...], dtype[object]])` is not iterable

sympy (https://github.com/sympy/sympy)
- sympy/matrices/matrixbase.py:5706:12 error[invalid-return-type] Return type does not match returned value: expected `tuple[MatrixBase, MatrixBase | Expr, str]`, found `tuple[MatrixBase | Unknown, None | MatrixBase | Expr | Unknown, Literal["invalid_type", "is_matrix", "possible_scalar"]]`
+ sympy/matrices/matrixbase.py:5706:12 error[invalid-return-type] Return type does not match returned value: expected `tuple[MatrixBase, MatrixBase | Expr, str]`, found `tuple[MatrixBase | Unknown, None | Expr | MatrixBase | Unknown, Literal["invalid_type", "is_matrix", "possible_scalar"]]`

werkzeug (https://github.com/pallets/werkzeug)
- src/werkzeug/datastructures/headers.py:107:33 error[unresolved-attribute] Object of type `object` has no attribute `_list`
- tests/test_wrappers.py:368:16 error[unresolved-attribute] Object of type `Response` has no attribute `foo`

xarray (https://github.com/pydata/xarray)
- xarray/indexes/nd_point_index.py:302:38 error[invalid-argument-type] Argument to bound method `TreeAdapter.equals` is incorrect: Argument type `object` does not satisfy upper bound `TreeAdapter` of type variable `Self`
- xarray/indexes/nd_point_index.py:302:38 error[invalid-argument-type] Argument to bound method `TreeAdapter.equals` is incorrect: Expected `T_TreeAdapter@NDPointIndex`, found `object`

Full report with detailed diff (timing results)

codspeed · 2026-05-05T02:53:28Z

Merging this PR will not alter performance

✅ 117 untouched benchmarks

_{Comparing charlie/dunder-class-narrowing (8d51a70) with main (bd66629)}

ibraheemdev

Code looks good to me, but I'll leave the decision on whether we should be narrowing on __class__ for someone else to approve. It looks like pyright does not do this, but mypy does.

AlexWaygood · 2026-05-07T22:22:32Z

I'll leave the decision on whether we should be narrowing on __class__ for someone else to approve. It looks like pyright does not do this, but mypy does.

For me this one makes sense. I think it's reasonably common and just as idiomatic as if type(x) is Foo narrowing, which we already support. The ecosystem results show it has a decent amount of impact for our users.

AlexWaygood · 2026-05-07T22:23:41Z

Although these can differ at runtime, AFAICT we already treat these as the same internally (i.e., infer_builtins_type_call calls arg_type.dunder_class(db)).

(And they can only differ in extremely dynamic cases, which a type checker cannot reasonably be expected to support or understand, so I don't think we need to really worry about that.)

* main: (23 commits) Lazily initialize `UnionBuilder` when transforming a `Union` (#25050) [ty] Speed-up find-references by using multithreading for cross-file searches (#25042) Revert "[ty] Lazily initialize `UnionBuilder` when transforming a union type" (#25049) [ty] Make text-based find-references pre-filter identifier boundary aware (#25036) [ty] Fix cross-file find-references for keyword arguments (#25043) [ty] Include TypedDict type context when inferring mixed constructors (#25039) [ty] Include TypedDict type context when inferring string keys (#25037) [ty] Lazily initialize `UnionBuilder` when transforming a union type (#24929) [ty] Skip global search for references if identifier is not externally visible (#25033) [ty] Support narrowing on `__class__` checks (#24997) [ty] Bump ecosystem-analyzer (#25032) [ty] Include error context for overload consistency diagnostics (#24950) [ty] Check non-generic overload implementations (#24936) Filter overloads based on return type for ParamSpec mapping (#24769) [ty] Add versioned parameters for dataclass decorator (#25029) [ty] Project reachability constraints before narrowing (#24982) [ty] Emit folding ranges from the language server for multi-line block headers. (#24978) [ty] Allow ParamSpec specialization through unioned generic classes (#24826) [ty] Adjust start of block folding range to preserve visible header for character-precise LSP clients. (#24917) [ty] Use `as_i64` when comparing `IntLiteralType` instances (#25023) ...

## Summary This adds support for narrowing based on `__class__` identity checks, treating them the same way we already treat `type(...)` checks. Although these _can_ differ at runtime, AFAICT we already treat these as the same internally (i.e., `infer_builtins_type_call` calls `arg_type.dunder_class(db)`). For example: ```python from typing import final, reveal_type class A: ... class B: ... @Final class C: ... def f(x: A | B, y: A | C): if x.__class__ is A: reveal_type(x) # revealed: A if C is y.__class__: reveal_type(y) # revealed: C else: reveal_type(y) # revealed: A ``` This supports both operand orders, and both `is` and `is not`. As with `type(x) is C`, negative-branch narrowing is only applied when the tested class is final.

charliermarsh added the ty The ty type checker label May 5, 2026

charliermarsh force-pushed the charlie/dunder-class-narrowing branch 3 times, most recently from 39c0f0c to 85b1ba5 Compare May 5, 2026 02:42

charliermarsh changed the base branch from charlie/protocol-recursion to main May 5, 2026 02:42

charliermarsh force-pushed the charlie/dunder-class-narrowing branch from 85b1ba5 to bb72d84 Compare May 5, 2026 02:56

charliermarsh marked this pull request as ready for review May 5, 2026 03:01

charliermarsh requested review from AlexWaygood, carljm, dcreager, ibraheemdev and sharkdp as code owners May 5, 2026 03:01

astral-sh-bot Bot assigned ibraheemdev May 5, 2026

charliermarsh force-pushed the charlie/dunder-class-narrowing branch from bb72d84 to cc95bfa Compare May 6, 2026 20:56

ibraheemdev reviewed May 7, 2026

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Comment thread crates/ty_python_core/src/place.rs

Comment thread crates/ty_python_semantic/src/types/narrow.rs

Comment thread crates/ty_python_semantic/src/types/narrow.rs

charliermarsh added 2 commits May 7, 2026 17:11

[ty] Support narrowing on __class__ checks

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8d51a70

charliermarsh force-pushed the charlie/dunder-class-narrowing branch from cc95bfa to 8d51a70 Compare May 8, 2026 00:14

charliermarsh enabled auto-merge (squash) May 8, 2026 00:17

charliermarsh merged commit 3a49028 into main May 8, 2026
54 of 56 checks passed

charliermarsh deleted the charlie/dunder-class-narrowing branch May 8, 2026 00:18

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[ty] Support narrowing on `class` checks - #24997

[ty] Support narrowing on `class` checks#24997
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