From d01628e411752ee6849f862cae66a1c69fe512b7 Mon Sep 17 00:00:00 2001
From: Ethan Smith <ethan@ethanhs.me>
Date: Tue, 14 Apr 2020 16:14:15 -0700
Subject: bpo-39481: PEP 585 for dataclasses, mailbox, contextvars (GH-19425)

---
 Lib/mailbox.py | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'Lib/mailbox.py')

diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index 5b4e86419f..70da07ed2e 100644
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -18,6 +18,7 @@ import email.message
 import email.generator
 import io
 import contextlib
+from types import GenericAlias
 try:
     import fcntl
 except ImportError:
@@ -260,6 +261,8 @@ class Mailbox:
         else:
             raise TypeError('Invalid message type: %s' % type(message))
 
+    __class_getitem__ = classmethod(GenericAlias)
+
 
 class Maildir(Mailbox):
     """A qmail-style Maildir mailbox."""
@@ -2015,6 +2018,8 @@ class _ProxyFile:
             return False
         return self._file.closed
 
+    __class_getitem__ = classmethod(GenericAlias)
+
 
 class _PartialFile(_ProxyFile):
     """A read-only wrapper of part of a file."""
-- 
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