src/Pure/Pure.thy

--- a/src/Pure/Pure.thy	Sun Sep 29 21:20:36 2024 +0200
+++ b/src/Pure/Pure.thy	Sun Sep 29 21:40:37 2024 +0200
@@ -404,7 +404,7 @@
 
 val syntax_consts =
   Parse.and_list1
-    ((Scan.repeat1 Parse.name_position --| (\<^keyword>\<open>\<rightleftharpoons>\<close> || \<^keyword>\<open>==\<close>)) --
+    (Scan.optional (Scan.repeat1 Parse.name_position --| (\<^keyword>\<open>\<rightleftharpoons>\<close> || \<^keyword>\<open>==\<close>)) [] --
       Parse.!!! (Scan.repeat1 Parse.name_position));
 
 val _ =