--- a/NEWS Wed Oct 20 17:11:46 2021 +0200
+++ b/NEWS Wed Oct 20 18:13:17 2021 +0200
@@ -37,6 +37,9 @@
now work uniformly in Isabelle/Haskell vs. Isabelle/ML vs.
Isabelle/Scala/PIDE.
+* Theory_Data / Generic_Data: "val extend = I" has been removed;
+obsolete since Isabelle2021.
+
*** Isar ***