Issue #1721812: Binary operations and copy operations on set/frozenset
subclasses need to return the base type, not the subclass itself.
diff --git a/Misc/NEWS b/Misc/NEWS
index 035867c..874f27b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -13,6 +13,11 @@
Core and Builtins
-----------------
+- Issue #1721812: Binary set operations and copy() returned the input type
+ instead of the appropriate base type. This was incorrect because set
+ subclasses would be created without their __init__() method being called.
+ The corrected behavior brings sets into line with lists and dicts.
+
- Issue #4296: Fix PyObject_RichCompareBool so that "x in [x]" evaluates to
True, even when x doesn't compare equal to itself. This was a regression
from 2.6.