gh-98852: Fix subscription of type aliases (GH-98920)

Fix subscription of type aliases containing bare generic types or types
like TypeVar: for example tuple[A, T][int] and tuple[TypeVar, T][int],
where A is a generic type, and T is a type variable.

1 files changed, 28 insertions, 0 deletions

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 9571d952903..f8168bd19f4 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -3916,6 +3916,34 @@ class GenericTests(BaseTestCase):
         # C version of GenericAlias
         self.assertEqual(list[A()].__parameters__, (T,))
 
+    def test_non_generic_subscript(self):
+        T = TypeVar('T')
+        class G(Generic[T]):
+            pass
+        class A:
+            __parameters__ = (T,)
+
+        for s in (int, G, A, List, list,
+                  TypeVar, TypeVarTuple, ParamSpec,
+                  types.GenericAlias, types.UnionType):
+
+            for t in Tuple, tuple:
+                with self.subTest(tuple=t, sub=s):
+                    self.assertEqual(t[s, T][int], t[s, int])
+                    self.assertEqual(t[T, s][int], t[int, s])
+                    a = t[s]
+                    with self.assertRaises(TypeError):
+                        a[int]
+
+            for c in Callable, collections.abc.Callable:
+                with self.subTest(callable=c, sub=s):
+                    self.assertEqual(c[[s], T][int], c[[s], int])
+                    self.assertEqual(c[[T], s][int], c[[int], s])
+                    a = c[[s], s]
+                    with self.assertRaises(TypeError):
+                        a[int]
+
+
 class ClassVarTests(BaseTestCase):
 
     def test_basics(self):