gh-99535: Add test for inheritance of annotations and update documentation (#99990)

Lib/test/test_grammar.py

@@ -415,6 +415,28 @@ class GrammarTests(unittest.TestCase):
                 x: int
                 x.y: list = []
 
+    def test_annotations_inheritance(self):
+        # Check that annotations are not inherited by derived classes
+        class A:
+            attr: int
+        class B(A):
+            pass
+        class C(A):
+            attr: str
+        class D:
+            attr2: int
+        class E(A, D):
+            pass
+        class F(C, A):
+            pass
+        self.assertEqual(A.__annotations__, {"attr": int})
+        self.assertEqual(B.__annotations__, {})
+        self.assertEqual(C.__annotations__, {"attr" : str})
+        self.assertEqual(D.__annotations__, {"attr2" : int})
+        self.assertEqual(E.__annotations__, {})
+        self.assertEqual(F.__annotations__, {})
+
+
     def test_var_annot_metaclass_semantics(self):
         class CMeta(type):
             @classmethod