bpo-36669: add matmul support to weakref.proxy (GH-12932)

diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst
index 7f3d267..80a908b 100644
--- a/Doc/library/weakref.rst
+++ b/Doc/library/weakref.rst
@@ -139,6 +139,10 @@
    prevent their use as dictionary keys.  *callback* is the same as the parameter
    of the same name to the :func:`ref` function.
 
+   .. versionchanged:: 3.8
+      Extended the operator support on proxy objects to include the matrix
+      multiplication operators ``@`` and ``@=``.
+
 
 .. function:: getweakrefcount(object)
 
diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst
index 2270334..4cb9c4f 100644
--- a/Doc/whatsnew/3.8.rst
+++ b/Doc/whatsnew/3.8.rst
@@ -450,6 +450,13 @@
   activating virtual environments under PowerShell Core 6.1.
   (Contributed by Brett Cannon in :issue:`32718`.)
 
+weakref
+-------
+
+* The proxy objects returned by :func:`weakref.proxy` now support the matrix
+  multiplication operators ``@`` and ``@=`` in addition to the other
+  numeric operators. (Contributed by Mark Dickinson in :issue:`36669`.)
+
 xml
 ---