bpo-43923: Add support for generic typing.NamedTuple (#92027)

Lib/test/test_typing.py

@@ -5678,6 +5678,45 @@ class NamedTupleTests(BaseTestCase):
         with self.assertRaises(TypeError):
             class X(NamedTuple, A):
                 x: int
+        with self.assertRaises(TypeError):
+            class X(NamedTuple, tuple):
+                x: int
+        with self.assertRaises(TypeError):
+            class X(NamedTuple, NamedTuple):
+                x: int
+        class A(NamedTuple):
+            x: int
+        with self.assertRaises(TypeError):
+            class X(NamedTuple, A):
+                y: str
+
+    def test_generic(self):
+        class X(NamedTuple, Generic[T]):
+            x: T
+        self.assertEqual(X.__bases__, (tuple, Generic))
+        self.assertEqual(X.__orig_bases__, (NamedTuple, Generic[T]))
+        self.assertEqual(X.__mro__, (X, tuple, Generic, object))
+
+        class Y(Generic[T], NamedTuple):
+            x: T
+        self.assertEqual(Y.__bases__, (Generic, tuple))
+        self.assertEqual(Y.__orig_bases__, (Generic[T], NamedTuple))
+        self.assertEqual(Y.__mro__, (Y, Generic, tuple, object))
+
+        for G in X, Y:
+            with self.subTest(type=G):
+                self.assertEqual(G.__parameters__, (T,))
+                A = G[int]
+                self.assertIs(A.__origin__, G)
+                self.assertEqual(A.__args__, (int,))
+                self.assertEqual(A.__parameters__, ())
+
+                a = A(3)
+                self.assertIs(type(a), G)
+                self.assertEqual(a.x, 3)
+
+                with self.assertRaises(TypeError):
+                    G[int, str]
 
     def test_namedtuple_keyword_usage(self):
         LocalEmployee = NamedTuple("LocalEmployee", name=str, age=int)