more accurate syntax: follow documentation in "isar-ref" (and command 'syntax_consts');

--- a/src/Pure/Pure.thy	Wed Jan 29 11:53:49 2025 +0100
+++ b/src/Pure/Pure.thy	Wed Jan 29 14:43:14 2025 +0100
@@ -1423,7 +1423,8 @@
 local
 
 val adhoc_overloading_args =
-  Parse.and_list1 ((Parse.const --| (\<^keyword>\<open>\<rightleftharpoons>\<close> || \<^keyword>\<open>==\<close>)) -- Scan.repeat Parse.term);
+  Parse.and_list1
+    ((Parse.const --| (\<^keyword>\<open>\<rightleftharpoons>\<close> || \<^keyword>\<open>==\<close>)) -- Parse.!!! (Scan.repeat1 Parse.term));
 
 val _ =
   Outer_Syntax.local_theory \<^command_keyword>\<open>adhoc_overloading\<close>