only fast-path fromkeys() when the constructor returns a empty dict (closes #16345)
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 18f7ce6..0840f59 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -254,6 +254,14 @@
d = dict(zip(range(6), range(6)))
self.assertEqual(dict.fromkeys(d, 0), dict(zip(range(6), [0]*6)))
+ class baddict3(dict):
+ def __new__(cls):
+ return d
+ d = {i : i for i in range(10)}
+ res = d.copy()
+ res.update(a=None, b=None, c=None)
+ self.assertEqual(baddict3.fromkeys({"a", "b", "c"}), res)
+
def test_copy(self):
d = {1:1, 2:2, 3:3}
self.assertEqual(d.copy(), {1:1, 2:2, 3:3})