[3.12] gh-118168: Fix Unpack interaction with builtin aliases (GH-118169) (#118178)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index e7cb01a..ffb1425 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -979,6 +979,38 @@ class UnpackTests(BaseTestCase):
         self.assertEqual(repr(foo.__annotations__['kwargs']),
                          f"typing.Unpack[{__name__}.Movie]")
 
+    def test_builtin_tuple(self):
+        Ts = TypeVarTuple("Ts")
+
+        class Old(Generic[*Ts]): ...
+        class New[*Ts]: ...
+
+        PartOld = Old[int, *Ts]
+        self.assertEqual(PartOld[str].__args__, (int, str))
+        self.assertEqual(PartOld[*tuple[str]].__args__, (int, str))
+        self.assertEqual(PartOld[*Tuple[str]].__args__, (int, str))
+        self.assertEqual(PartOld[Unpack[tuple[str]]].__args__, (int, str))
+        self.assertEqual(PartOld[Unpack[Tuple[str]]].__args__, (int, str))
+
+        PartNew = New[int, *Ts]
+        self.assertEqual(PartNew[str].__args__, (int, str))
+        self.assertEqual(PartNew[*tuple[str]].__args__, (int, str))
+        self.assertEqual(PartNew[*Tuple[str]].__args__, (int, str))
+        self.assertEqual(PartNew[Unpack[tuple[str]]].__args__, (int, str))
+        self.assertEqual(PartNew[Unpack[Tuple[str]]].__args__, (int, str))
+
+    def test_unpack_wrong_type(self):
+        Ts = TypeVarTuple("Ts")
+        class Gen[*Ts]: ...
+        PartGen = Gen[int, *Ts]
+
+        bad_unpack_param = re.escape("Unpack[...] must be used with a tuple type")
+        with self.assertRaisesRegex(TypeError, bad_unpack_param):
+            PartGen[Unpack[list[int]]]
+        with self.assertRaisesRegex(TypeError, bad_unpack_param):
+            PartGen[Unpack[List[int]]]
+
+
 class TypeVarTupleTests(BaseTestCase):
 
     def assertEndsWith(self, string, tail):