Save the type if a subtype is passed to fnmatch.filter/fnmatch.filterfalse.

stdlib/fnmatch.pyi

@@ -1,16 +1,41 @@
 import sys
 from collections.abc import Iterable
 from os import PathLike
-from typing import AnyStr
+from typing import AnyStr, TypeVar, overload
 
 __all__ = ["filter", "fnmatch", "fnmatchcase", "translate"]
 if sys.version_info >= (3, 14):
     __all__ += ["filterfalse"]
 
+_PathT_str = TypeVar("_PathT_str", bound=str | PathLike[str])
+_PathT_bytes = TypeVar("_PathT_bytes", bound=bytes | PathLike[bytes])
+_T_str = TypeVar("_T_str", bound=str)
+_T_bytes = TypeVar("_T_bytes", bound=bytes)
+
 def fnmatch(name: AnyStr | PathLike[AnyStr], pat: AnyStr | PathLike[AnyStr]) -> bool: ...
 def fnmatchcase(name: AnyStr, pat: AnyStr) -> bool: ...
-def filter(names: Iterable[AnyStr | PathLike[AnyStr]], pat: AnyStr | PathLike[AnyStr]) -> list[AnyStr]: ...
+
+if sys.platform == "win32":
+    @overload
+    def filter(names: Iterable[_PathT_str], pat: str | PathLike[str]) -> list[_PathT_str]: ...
+    @overload
+    def filter(names: Iterable[_PathT_bytes], pat: bytes | PathLike[bytes]) -> list[_PathT_bytes]: ...
+else:
+    @overload
+    def filter(names: Iterable[_T_str], pat: str | PathLike[str]) -> list[_T_str]: ...
+    @overload
+    def filter(names: Iterable[_T_bytes], pat: bytes | PathLike[bytes]) -> list[_T_bytes]: ...
+
 def translate(pat: str) -> str: ...
 
 if sys.version_info >= (3, 14):
-    def filterfalse(names: Iterable[AnyStr | PathLike[AnyStr]], pat: AnyStr | PathLike[AnyStr]) -> list[AnyStr]: ...
+    if sys.platform == "win32":
+        @overload
+        def filterfalse(names: Iterable[_PathT_str], pat: str | PathLike[str]) -> list[_PathT_str]: ...
+        @overload
+        def filterfalse(names: Iterable[_PathT_bytes], pat: bytes | PathLike[bytes]) -> list[_PathT_bytes]: ...
+    else:
+        @overload
+        def filterfalse(names: Iterable[_T_str], pat: str | PathLike[str]) -> list[_T_str]: ...
+        @overload
+        def filterfalse(names: Iterable[_T_bytes], pat: bytes | PathLike[bytes]) -> list[_T_bytes]: ...