Updated type hints

Tests/test_file_ani.py

@@ -4,13 +4,14 @@ from io import BytesIO
 
 import pytest
 
-from PIL import Image
+from PIL import AniImagePlugin, Image
 
 from .helper import assert_image_equal_tofile
 
 
 def test_aero_busy() -> None:
     with Image.open("Tests/images/ani/aero_busy.ani") as im:
+        assert isinstance(im, AniImagePlugin.AniImageFile)
         assert im.size == (64, 64)
         assert im.n_frames == 18
 
@@ -29,6 +30,7 @@ def test_aero_busy() -> None:
 
 def test_posy_busy() -> None:
     with Image.open("Tests/images/ani/posy_busy.ani") as im:
+        assert isinstance(im, AniImagePlugin.AniImageFile)
         assert im.size == (96, 96)
         assert im.n_frames == 77
 
@@ -43,6 +45,7 @@ def test_posy_busy() -> None:
 
 def test_seq_rate() -> None:
     with Image.open("Tests/images/ani/stopwtch.ani") as im:
+        assert isinstance(im, AniImagePlugin.AniImageFile)
         assert im.size == (32, 32)
         assert im.n_frames == 8
 
@@ -122,6 +125,7 @@ def test_save() -> None:
         )
 
         with Image.open(output, formats=["ANI"]) as im:
+            assert isinstance(im, AniImagePlugin.AniImageFile)
             assert im.n_frames == 6
             assert im.info["seq"] == [0, 2, 4, 1, 3, 5, 0, 1, 0, 1]
             assert im.info["rate"] == [1, 2, 3, 1, 2, 3, 1, 2, 3, 4]

Tests/test_file_cur.py

@@ -59,6 +59,7 @@ def test_posy_link() -> None:
         assert im.getpixel((20, 20)) == (0, 0, 0, 255)
         assert im.getpixel((40, 40)) == (255, 255, 255, 255)
 
+        assert isinstance(im, CurImagePlugin.CurImageFile)
         im.size = (32, 32)
         im.load()
         assert im.getpixel((0, 0)) == (0, 0, 0, 0)

src/PIL/AniImagePlugin.py

@@ -283,7 +283,7 @@ def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
 
 
 class AniFile:
-    def __init__(self, fp: BytesIO) -> None:
+    def __init__(self, fp: IO[bytes]) -> None:
         if not _accept(fp.read(4)):
             SyntaxError("Not an ANI file")
 
@@ -394,6 +394,7 @@ class AniImageFile(ImageFile.ImageFile):
     format_description = "Windows Animated Cursor"
 
     def _open(self) -> None:
+        assert self.fp is not None
         self.ani = AniFile(self.fp)
         self.info["seq"] = self.ani.seq
         self.info["rate"] = self.ani.rate