Copy-edit and add test (python#541)

Co-authored-by: Alex Waygood <[email protected]>

Author: JelleZijlstra

CHANGELOG.md

@@ -39,7 +39,7 @@ Bugfixes and changed features:
 - Backport CPython PR [#124795](https://github.com/python/cpython/pull/124795):
   fix `TypeAliasType` not raising an error on non-tuple inputs for `type_params`.
   Patch by [Daraan](https://github.com/Daraan).
-- Fix that lists and ... could not be used for parameter expressions for `TypeAliasType`
+- Fix that lists and `...` could not be used for parameter expressions for `TypeAliasType`
   instances before Python 3.11.
   Patch by [Daraan](https://github.com/Daraan).
 - Fix error on Python 3.10 when using `typing.Concatenate` and
@@ -48,9 +48,9 @@ Bugfixes and changed features:
   to reflect Python 3.13+ behavior: A value assigned to `__total__` in the class body of a
   `TypedDict` will be overwritten by the `total` argument of the `TypedDict` constructor.
   Patch by [Daraan](https://github.com/Daraan), backporting a CPython PR by Jelle Zijlstra.
-- Fix for Python 3.11 that now `isinstance(typing_extensions.Unpack[...], TypeVar)`
-  evaluates to `False`, however still `True` for <3.11.
-  Patch by [Daraan](https://github.com/Daraan)
+- `isinstance(typing_extensions.Unpack[...], TypeVar)` now evaluates to `False` on Python 3.11
+  and newer, but remains `True` on versions before 3.11.
+  Patch by [Daraan](https://github.com/Daraan).
 
 # Release 4.12.2 (June 7, 2024)
 

src/test_typing_extensions.py

@@ -5045,6 +5045,14 @@ def test_backwards_compatibility(self):
         self.assertIs(TD.__extra_items__, NoExtraItems)
         self.assertEqual(TD.__annotations__, {"extra_items": int})
 
+    def test_cannot_combine_closed_and_extra_items(self):
+        with self.assertRaisesRegex(
+            TypeError,
+            "Cannot combine closed=True and extra_items"
+        ):
+            class TD(TypedDict, closed=True, extra_items=range):
+                x: str
+
 
 class AnnotatedTests(BaseTestCase):