Update mypy-dev to 1.12.0a3 (home-assistant#124939)

* Update mypy-dev to 1.12.0a3

* Fix

homeassistant/runner.py

@@ -175,7 +175,7 @@ def _enable_posix_spawn() -> None:
     # less efficient. This is a workaround to force posix_spawn()
     # when using musl since cpython is not aware its supported.
     tag = next(packaging.tags.sys_tags())
-    subprocess._USE_POSIX_SPAWN = "musllinux" in tag.platform  # noqa: SLF001
+    subprocess._USE_POSIX_SPAWN = "musllinux" in tag.platform  # type: ignore[misc]  # noqa: SLF001
 
 
 def run(runtime_config: RuntimeConfig) -> int:

homeassistant/util/frozen_dataclass_compat.py

@@ -8,7 +8,10 @@
 
 import dataclasses
 import sys
-from typing import Any, dataclass_transform
+from typing import TYPE_CHECKING, Any, cast, dataclass_transform
+
+if TYPE_CHECKING:
+    from _typeshed import DataclassInstance
 
 
 def _class_fields(cls: type, kw_only: bool) -> list[tuple[str, Any, Any]]:
@@ -111,6 +114,8 @@ def __new__(*args: Any, **kwargs: Any) -> object:
             """
             cls, *_args = args
             if dataclasses.is_dataclass(cls):
+                if TYPE_CHECKING:
+                    cls = cast(type[DataclassInstance], cls)
                 return object.__new__(cls)
             return cls._dataclass(*_args, **kwargs)
 

requirements_test.txt

@@ -11,7 +11,7 @@ astroid==3.2.4
 coverage==7.6.0
 freezegun==1.5.1
 mock-open==1.4.0
-mypy-dev==1.12.0a2
+mypy-dev==1.12.0a3
 pre-commit==3.7.1
 pydantic==1.10.17
 pylint==3.2.6