Issue #27985: Implement PEP 526 -- Syntax for Variable Annotations.

Patch by Ivan Levkivskyi.

Lib/test/ann_module3.py

@@ -0,0 +1,18 @@
+"""
+Correct syntax for variable annotation that should fail at runtime
+in a certain manner. More examples are in test_grammar and test_parser.
+"""
+
+def f_bad_ann():
+    __annotations__[1] = 2
+
+class C_OK:
+    def __init__(self, x: int) -> None:
+        self.x: no_such_name = x  # This one is OK as proposed by Guido
+
+class D_bad_ann:
+    def __init__(self, x: int) -> None:
+        sfel.y: int = 0
+
+def g_bad_ann():
+    no_such_name.attr: int = 0