reintroduced e2d08b9c9047, lost in 54e290da6da8 + e13b0c88c798 (clone of f6ffe53387ef);

--- a/src/Tools/adhoc_overloading.ML	Thu Nov 21 22:13:11 2013 +0100
+++ b/src/Tools/adhoc_overloading.ML	Fri Nov 22 21:57:50 2013 +0100
@@ -178,9 +178,9 @@
 fun check ctxt =
   map (fn t => Term.map_aterms (insert_variants ctxt t) t);
 
-fun uncheck ctxt =
-  if Config.get ctxt show_variants then I
-  else map (insert_overloaded ctxt);
+fun uncheck ctxt ts =
+  if Config.get ctxt show_variants orelse exists (is_none o try Term.type_of) ts then ts
+  else map (insert_overloaded ctxt) ts;
 
 fun reject_unresolved ctxt =
   let