From b67c936b279219dd9a80e6e338d9335bd1a9f714 Mon Sep 17 00:00:00 2001
From: Eric Wieser <wieser.eric@gmail.com>
Date: Tue, 12 May 2020 09:59:38 +0100
Subject: [PATCH] Copy cached_property return type annotations to
 __annotations__

---
 Lib/functools.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Lib/functools.py b/Lib/functools.py
index 87c7d874389..9c8bef2a2de 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -1191,6 +1191,18 @@ class cached_property:
                 f"({self.attrname!r} and {name!r})."
             )
 
+        # copy across the annotation for runtime introspection
+        try:
+            prop_ann = self.fget.__annotations__['return']
+        except KeyError:
+            return
+
+        try:
+            owner_anns = owner.__annotations__
+        except AttributeError:
+            owner_anns = owner.__annotations__ = {}
+        owner_anns[name] = prop_ann
+
     def __get__(self, instance, owner=None):
         if instance is None:
             return self