only fast-path fromkeys() when the constructor returns a empty dict (closes #16345)
diff --git a/Misc/NEWS b/Misc/NEWS
index f3fd034..fc8c838 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
- Issue #14700: Fix buggy overflow checks for large width and precision
in string formatting operations.
+- Issue #16345: Fix an infinite loop when ``fromkeys`` on a dict subclass
+ recieved a nonempty dict from the constructor.
+
- Issue #6074: Ensure cached bytecode files can always be updated by the
user that created them, even when the source file is read-only.