allow TypedDict as a type argument

Author: JelleZijlstra

CHANGELOG.md

@@ -1,3 +1,9 @@
+# Unreleased
+
+- Fix usage of `typing_extensions.TypedDict` nested inside other types
+  (e.g., `typing.Type[typing_extensions.TypedDict]`). This is not allowed by the
+  type system but worked on older versions, so we maintain support.
+
 # Release 4.14.0 (June 2, 2025)
 
 Changes since 4.14.0rc1:

src/test_typing_extensions.py

@@ -4202,6 +4202,12 @@ def test_basics_functional_syntax(self):
         self.assertEqual(Emp.__annotations__, {'name': str, 'id': int})
         self.assertEqual(Emp.__total__, True)
 
+    def test_allowed_as_type_argument(self):
+        # https://github.com/python/typing_extensions/issues/613
+        obj = typing.Type[typing_extensions.TypedDict]
+        self.assertIs(typing_extensions.get_origin(obj), type)
+        self.assertEqual(typing_extensions.get_args(obj), (typing_extensions.TypedDict,))
+
     @skipIf(sys.version_info < (3, 13), "Change in behavior in 3.13")
     def test_keywords_syntax_raises_on_3_13(self):
         with self.assertRaises(TypeError), self.assertWarns(DeprecationWarning):

src/typing_extensions.py

@@ -1223,7 +1223,50 @@ def _create_typeddict(
         td.__orig_bases__ = (TypedDict,)
         return td
 
-    class _TypedDictSpecialForm(_ExtensionsSpecialForm, _root=True):
+    # Cannot inherit from typing._SpecialForm, because then typing._type_check
+    # would reject TypedDict as a type, and we need that to work for compatibility.
+    if hasattr(typing, "_NotIterable"):
+        _special_form_bases = (typing._Final, typing._NotIterable)
+    else:
+        _special_form_bases = (typing._Final,)
+
+    class _TypedDictSpecialForm(*_special_form_bases, _root=True):
+        __slots__ = ('_name', '__doc__', '_getitem')
+
+        def __init__(self, getitem):
+            self._getitem = getitem
+            self._name = getitem.__name__
+            self.__doc__ = getitem.__doc__
+
+        def __getattr__(self, item):
+            if item in {'__name__', '__qualname__'}:
+                return self._name
+
+            raise AttributeError(item)
+
+        def __repr__(self):
+            return 'typing_extensions.' + self._name
+
+        def __reduce__(self):
+            return self._name
+
+        if sys.version_info >= (3, 10):
+            def __or__(self, other):
+                return typing.Union[self, other]
+
+            def __ror__(self, other):
+                return typing.Union[other, self]
+
+        def __instancecheck__(self, obj):
+            raise TypeError(f"{self} cannot be used with isinstance()")
+
+        def __subclasscheck__(self, cls):
+            raise TypeError(f"{self} cannot be used with issubclass()")
+
+        @typing._tp_cache
+        def __getitem__(self, parameters):
+            return self._getitem(self, parameters)
+
         def __call__(
             self,
             typename,