From d09457b158254620ff1df0467070cb06e61d5961 Mon Sep 17 00:00:00 2001
From: HongWeipeng <hongweichen8888@sina.com>
Date: Mon, 26 Aug 2019 02:41:55 +0800
Subject: [PATCH 1/2] Fix infinite recursion with typing.get_type_hints.

---
 Lib/typing.py                                              | 7 +++++--
 .../next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst  | 2 ++
 2 files changed, 7 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst

diff --git a/Lib/typing.py b/Lib/typing.py
index 5f1a0ad3d63743..52553eeb7b9a0a 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -491,7 +491,7 @@ class ForwardRef(_Final, _root=True):
 
     __slots__ = ('__forward_arg__', '__forward_code__',
                  '__forward_evaluated__', '__forward_value__',
-                 '__forward_is_argument__')
+                 '__forward_is_argument__', '__hash')
 
     def __init__(self, arg, is_argument=True):
         if not isinstance(arg, str):
@@ -505,6 +505,7 @@ def __init__(self, arg, is_argument=True):
         self.__forward_evaluated__ = False
         self.__forward_value__ = None
         self.__forward_is_argument__ = is_argument
+        self.__hash = None
 
     def _evaluate(self, globalns, localns):
         if not self.__forward_evaluated__ or localns is not globalns:
@@ -528,7 +529,9 @@ def __eq__(self, other):
                 self.__forward_value__ == other.__forward_value__)
 
     def __hash__(self):
-        return hash((self.__forward_arg__, self.__forward_value__))
+        if self.__hash is None:
+            self.__hash = hash((self.__forward_arg__, self.__forward_value__))
+        return self.__hash
 
     def __repr__(self):
         return f'ForwardRef({self.__forward_arg__!r})'
diff --git a/Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst b/Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst
new file mode 100644
index 00000000000000..64a1f0fbf25b42
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst
@@ -0,0 +1,2 @@
+Fix infinite recursion with typing.get_type_hints.
+Patch by hongweipeng.

From b727c2a114d9ad840876070607f60203791cf557 Mon Sep 17 00:00:00 2001
From: hongweipeng <961365124@qq.com>
Date: Mon, 26 Aug 2019 09:09:11 +0800
Subject: [PATCH 2/2] code review

---
 .../next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst      | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst b/Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst
index 64a1f0fbf25b42..50853efd7ace40 100644
--- a/Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst
+++ b/Misc/NEWS.d/next/Library/2019-08-26-02-29-14.bpo-37806.wR83qu.rst
@@ -1,2 +1 @@
-Fix infinite recursion with typing.get_type_hints.
-Patch by hongweipeng.
+Fix infinite recursion from :func:`typing.get_type_hints`. Patch by hongweipeng.