bpo-33514: Document PEP 492 changes in 3.7 changelog

hroncok · hroncok · commit d4599c29be96 · 2018-05-16T12:55:59.000+02:00
Based on PEP 492, old __aiter__ protocol is no longer supported
and async and await are now keywords.
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst
@@ -684,6 +684,8 @@ can be used to create instance variables with different implementation details.
    :pep:`3129` - Class Decorators
 
 
+.. _async:
+
 Coroutines
 ==========
 
diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
@@ -1157,6 +1157,16 @@ Changes in Python behavior
   exceptions.
   (Contributed by Yury Selivanov in :issue:`32670`.)
 
+* :pep:`492` is fully implemented in Python 3.7, meaning that the old
+  :meth:`__aiter__` protocol is no longer supported: a
+  :exc:`RuntimeError` will be raised if :meth:`__aiter__` returns anything
+  but an asynchronous iterator.
+
+  Since Python 3.7, :keyword:`async` and :keyword:`await` names are proper
+  keywords. If you use them for variable names, you need to rename them in
+  order to make the code work on Python 3.7. Trying to use a keyword as
+  a variable name will raise a :exc:`SyntaxError`.
+
 * Due to an oversight, earlier Python versions erroneously accepted the
   following syntax::
 
