_ProxyFile is no longer generic

See python/cpython#140838

Author: srittau

stdlib/mailbox.pyi

@@ -5,7 +5,7 @@ from _typeshed import StrPath, SupportsItems, SupportsNoArgReadline, SupportsRea
 from abc import ABCMeta, abstractmethod
 from collections.abc import Callable, Iterable, Iterator, Mapping, Sequence
 from types import GenericAlias, TracebackType
-from typing import Any, AnyStr, Generic, Literal, Protocol, TypeVar, overload, type_check_only
+from typing import Any, Generic, Literal, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 __all__ = [
@@ -29,7 +29,6 @@ __all__ = [
 ]
 
 _T = TypeVar("_T")
-_AnyStr = TypeVar("_AnyStr", str, bytes, default=bytes)
 
 @type_check_only
 class _SupportsReadAndReadline(SupportsRead[bytes], SupportsNoArgReadline[bytes], Protocol): ...
@@ -48,16 +47,16 @@ linesep: bytes
 
 # Common interface for get_file() return types.
 @type_check_only
-class _GetFileReturn(Protocol[_AnyStr]):
-    def __iter__(self) -> Iterator[_AnyStr]: ...
+class _GetFileReturn(Protocol):
+    def __iter__(self) -> Iterator[bytes]: ...
     def __enter__(self) -> Self: ...
     def __exit__(
         self, exc_type: type[BaseException] | None, exc: BaseException | None, tb: TracebackType | None, /
     ) -> bool | None: ...
-    def read(self, size: int | None = None, /) -> _AnyStr: ...
-    def read1(self, size: int | None = None, /) -> _AnyStr: ...
-    def readline(self, size: int | None = None, /) -> _AnyStr: ...
-    def readlines(self, sizehint: int | None = None, /) -> list[_AnyStr]: ...
+    def read(self, size: int | None = None, /) -> bytes: ...
+    def read1(self, size: int | None = None, /) -> bytes: ...
+    def readline(self, size: int | None = None, /) -> bytes: ...
+    def readlines(self, sizehint: int | None = None, /) -> list[bytes]: ...
     def tell(self) -> int: ...
     def seek(self, offset: int, whence: int = 0, /) -> object: ...
     def close(self) -> object: ...
@@ -265,13 +264,14 @@ class BabylMessage(Message):
 
 class MMDFMessage(_mboxMMDFMessage): ...
 
-class _ProxyFile(Generic[AnyStr]):
-    def __init__(self, f: _GetFileReturn[AnyStr], pos: int | None = None) -> None: ...
-    def read(self, size: int | None = None) -> AnyStr: ...
-    def read1(self, size: int | None = None) -> AnyStr: ...
-    def readline(self, size: int | None = None) -> AnyStr: ...
-    def readlines(self, sizehint: int | None = None) -> list[AnyStr]: ...
-    def __iter__(self) -> Iterator[AnyStr]: ...
+# Until Python 3.14, this class was technically - but unnecessarily - generic at runtime.
+class _ProxyFile:
+    def __init__(self, f: _GetFileReturn, pos: int | None = None) -> None: ...
+    def read(self, size: int | None = None) -> bytes: ...
+    def read1(self, size: int | None = None) -> bytes: ...
+    def readline(self, size: int | None = None) -> bytes: ...
+    def readlines(self, sizehint: int | None = None) -> list[bytes]: ...
+    def __iter__(self) -> Iterator[bytes]: ...
     def tell(self) -> int: ...
     def seek(self, offset: int, whence: int = 0) -> None: ...
     def close(self) -> None: ...
@@ -285,8 +285,8 @@ class _ProxyFile(Generic[AnyStr]):
     def closed(self) -> bool: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
-class _PartialFile(_ProxyFile[AnyStr]):
-    def __init__(self, f: _GetFileReturn[AnyStr], start: int | None = None, stop: int | None = None) -> None: ...
+class _PartialFile(_ProxyFile):
+    def __init__(self, f: _GetFileReturn, start: int | None = None, stop: int | None = None) -> None: ...
 
 class Error(Exception): ...
 class NoSuchMailboxError(Error): ...