bpo-46611: add coverage to instance and class checks in `typing.py` (GH-31078)

Lib/test/test_types.py

@@ -703,22 +703,62 @@ class UnionTests(unittest.TestCase):
         self.assertEqual(hash(int | str), hash(str | int))
         self.assertEqual(hash(int | str), hash(typing.Union[int, str]))
 
-    def test_instancecheck(self):
-        x = int | str
-        self.assertIsInstance(1, x)
-        self.assertIsInstance(True, x)
-        self.assertIsInstance('a', x)
-        self.assertNotIsInstance(None, x)
-        self.assertTrue(issubclass(int, x))
-        self.assertTrue(issubclass(bool, x))
-        self.assertTrue(issubclass(str, x))
-        self.assertFalse(issubclass(type(None), x))
-        x = int | None
-        self.assertIsInstance(None, x)
-        self.assertTrue(issubclass(type(None), x))
-        x = int | collections.abc.Mapping
-        self.assertIsInstance({}, x)
-        self.assertTrue(issubclass(dict, x))
+    def test_instancecheck_and_subclasscheck(self):
+        for x in (int | str, typing.Union[int, str]):
+            with self.subTest(x=x):
+                self.assertIsInstance(1, x)
+                self.assertIsInstance(True, x)
+                self.assertIsInstance('a', x)
+                self.assertNotIsInstance(None, x)
+                self.assertTrue(issubclass(int, x))
+                self.assertTrue(issubclass(bool, x))
+                self.assertTrue(issubclass(str, x))
+                self.assertFalse(issubclass(type(None), x))
+
+        for x in (int | None, typing.Union[int, None]):
+            with self.subTest(x=x):
+                self.assertIsInstance(None, x)
+                self.assertTrue(issubclass(type(None), x))
+
+        for x in (
+            int | collections.abc.Mapping,
+            typing.Union[int, collections.abc.Mapping],
+        ):
+            with self.subTest(x=x):
+                self.assertIsInstance({}, x)
+                self.assertNotIsInstance((), x)
+                self.assertTrue(issubclass(dict, x))
+                self.assertFalse(issubclass(list, x))
+
+    def test_instancecheck_and_subclasscheck_order(self):
+        T = typing.TypeVar('T')
+
+        will_resolve = (
+            int | T,
+            typing.Union[int, T],
+        )
+        for x in will_resolve:
+            with self.subTest(x=x):
+                self.assertIsInstance(1, x)
+                self.assertTrue(issubclass(int, x))
+
+        wont_resolve = (
+            T | int,
+            typing.Union[T, int],
+        )
+        for x in wont_resolve:
+            with self.subTest(x=x):
+                with self.assertRaises(TypeError):
+                    issubclass(int, x)
+                with self.assertRaises(TypeError):
+                    isinstance(1, x)
+
+        for x in (*will_resolve, *wont_resolve):
+            with self.subTest(x=x):
+                with self.assertRaises(TypeError):
+                    issubclass(object, x)
+                with self.assertRaises(TypeError):
+                    isinstance(object(), x)
 
     def test_bad_instancecheck(self):
         class BadMeta(type):

Lib/test/test_typing.py

@@ -439,6 +439,8 @@ class TupleTests(BaseTestCase):
         class MyTuple(tuple):
             pass
         self.assertIsSubclass(MyTuple, Tuple)
+        self.assertIsSubclass(Tuple, Tuple)
+        self.assertIsSubclass(tuple, Tuple)
 
     def test_tuple_instance_type_error(self):
         with self.assertRaises(TypeError):
@@ -466,6 +468,7 @@ class BaseCallableTests:
         with self.assertRaises(TypeError):
             issubclass(types.FunctionType, Callable[[int], int])
         self.assertIsSubclass(types.FunctionType, Callable)
+        self.assertIsSubclass(Callable, Callable)
 
     def test_eq_hash(self):
         Callable = self.Callable