type annotate the tests (using monkeytype and manual fixes)

docs/versionhistory.rst

@@ -6,8 +6,6 @@ This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
 **UNRELEASED**
 
 - Fixed the type annotation of ``open_signal_receiver()`` as a synchronous context manager
-- Fixed the type annotations of ``AsyncFile.__aiter__``, ``readline``, ``write` to also accept/return ``str``
-  and also fixed ``AsyncFile.writelines`` to take an ``Iterable[str|bytes]`` rather than ``bytes``
 - Fixed the type annotation of ``DeprecatedAwaitable(|List|Float).__await__`` to match the ``typing.Awaitable`` protocol
 
 **3.1.0**

src/anyio/_core/_fileio.py

@@ -1,6 +1,6 @@
 import os
 from os import PathLike
-from typing import Any, AsyncIterator, Callable, Generic, Iterable, List, Optional, TypeVar, Union
+from typing import Any, AsyncIterator, Callable, Generic, Optional, TypeVar, Union
 
 from .. import to_thread
 from ..abc import AsyncResource
@@ -51,7 +51,7 @@ def wrapped(self) -> T_Fp:
         """The wrapped file object."""
         return self._fp
 
-    async def __aiter__(self) -> AsyncIterator[Union[bytes, str]]:
+    async def __aiter__(self) -> AsyncIterator[bytes]:
         while True:
             line = await self.readline()
             if line:
@@ -68,10 +68,10 @@ async def read(self, size: int = -1) -> Union[bytes, str]:
     async def read1(self, size: int = -1) -> Union[bytes, str]:
         return await to_thread.run_sync(self._fp.read1, size)
 
-    async def readline(self) -> Union[bytes, str]:
+    async def readline(self) -> bytes:
         return await to_thread.run_sync(self._fp.readline)
 
-    async def readlines(self) -> List[Union[bytes, str]]:
+    async def readlines(self) -> bytes:
         return await to_thread.run_sync(self._fp.readlines)
 
     async def readinto(self, b: Union[bytes, memoryview]) -> bytes:
@@ -80,10 +80,10 @@ async def readinto(self, b: Union[bytes, memoryview]) -> bytes:
     async def readinto1(self, b: Union[bytes, memoryview]) -> bytes:
         return await to_thread.run_sync(self._fp.readinto1, b)
 
-    async def write(self, b: Union[bytes, str]) -> None:
+    async def write(self, b: bytes) -> None:
         return await to_thread.run_sync(self._fp.write, b)
 
-    async def writelines(self, lines: Iterable[Union[bytes, str]]) -> None:
+    async def writelines(self, lines: bytes) -> None:
         return await to_thread.run_sync(self._fp.writelines, lines)
 
     async def truncate(self, size: Optional[int] = None) -> int:

tests/test_fileio.py

@@ -47,4 +47,4 @@ async def test_async_iteration(tmp_path: PosixPath) -> None:
     async with await open_file(str(testpath)) as f:
         lines_i = iter(lines)
         async for line in f:
-            assert line == next(lines_i)
+            assert line == next(lines_i)  # type: ignore[comparison-overlap]