Use TypeIs in is_dataclass

Author: NeilGirdhar

requirements-tests.txt

@@ -7,7 +7,7 @@ flake8-noqa==1.4.0       # must match .pre-commit-config.yaml
 flake8-pyi==24.4.1       # must match .pre-commit-config.yaml
 mypy==1.10.0
 pre-commit-hooks==4.5.0  # must match .pre-commit-config.yaml
-pyright==1.1.363
+pyright==1.1.364
 pytype==2024.4.11; platform_system != "Windows" and python_version < "3.12"
 ruff==0.3.7              # must match .pre-commit-config.yaml
 

stdlib/dataclasses.pyi

@@ -5,7 +5,7 @@ from _typeshed import DataclassInstance
 from builtins import type as Type  # alias to avoid name clashes with fields named "type"
 from collections.abc import Callable, Iterable, Mapping
 from typing import Any, Generic, Literal, Protocol, TypeVar, overload
-from typing_extensions import TypeAlias, TypeGuard
+from typing_extensions import TypeAlias, TypeIs
 
 if sys.version_info >= (3, 9):
     from types import GenericAlias
@@ -214,11 +214,9 @@ else:
 
 def fields(class_or_instance: DataclassInstance | type[DataclassInstance]) -> tuple[Field[Any], ...]: ...
 @overload
-def is_dataclass(obj: DataclassInstance) -> Literal[True]: ...
+def is_dataclass(obj: type) -> TypeIs[type[DataclassInstance]]: ...
 @overload
-def is_dataclass(obj: type) -> TypeGuard[type[DataclassInstance]]: ...
-@overload
-def is_dataclass(obj: object) -> TypeGuard[DataclassInstance | type[DataclassInstance]]: ...
+def is_dataclass(obj: object) -> TypeIs[DataclassInstance | type[DataclassInstance]]: ...
 
 class FrozenInstanceError(AttributeError): ...