[3.13] typing: Add missing test case for Protocol inheritance (GH-132597) (#132603)

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

Author: miss-islington

Lib/test/test_typing.py

@@ -2935,6 +2935,23 @@ class E(C, BP): pass
         self.assertNotIsInstance(D(), E)
         self.assertNotIsInstance(E(), D)
 
+    def test_inheritance_from_object(self):
+        # Inheritance from object is specifically allowed, unlike other nominal classes
+        class P(Protocol, object):
+            x: int
+
+        self.assertEqual(typing.get_protocol_members(P), {'x'})
+
+        class OldGeneric(Protocol, Generic[T], object):
+            y: T
+
+        self.assertEqual(typing.get_protocol_members(OldGeneric), {'y'})
+
+        class NewGeneric[T](Protocol, object):
+            z: T
+
+        self.assertEqual(typing.get_protocol_members(NewGeneric), {'z'})
+
     def test_no_instantiation(self):
         class P(Protocol): pass