diff -r 5c8177fd1295 -r 8e6c973003c8 src/HOL/Library/adhoc_overloading.ML
--- a/src/HOL/Library/adhoc_overloading.ML	Wed Oct 20 17:11:46 2021 +0200
+++ b/src/HOL/Library/adhoc_overloading.ML	Wed Oct 20 18:13:17 2021 +0200
@@ -65,7 +65,6 @@
     {variants : (term * typ) list Symtab.table,
      oconsts : string Termtab.table};
   val empty = {variants = Symtab.empty, oconsts = Termtab.empty};
-  val extend = I;
 
   fun merge
     ({variants = vtab1, oconsts = otab1},