Create a new error for when a char is needed but event-to-character gives nil lisp/ChangeLog addition: 2015-03-14 Aidan Kehoe <kehoea@parhasard.net> * cmdloop.el (no-character-typed): New error, for those cases when a keystroke is to be treated as a character but has no character equivalent. * cmdloop.el (read-char-1): Use it. * keymap.el (synthesize-keysym): Use it. src/ChangeLog addition: 2015-03-14 Aidan Kehoe <kehoea@parhasard.net> * general-slots.h (Qno_character_typed): New error symbol. * event-stream.c (syms_of_event_stream): Define it. New error, for those cases when a keystroke is to be treated as a character in some context but has no character equivalent. * cmds.c (Fself_insert_command): Use it.

--- a/src/cmds.c	Sat Mar 14 01:16:45 2015 +0000
+++ b/src/cmds.c	Sat Mar 14 01:40:49 2015 +0000
@@ -346,9 +346,9 @@
     c = Fevent_to_character (Vlast_command_event, Qnil, Qnil, Qnil);
 
   if (NILP (c))
-    invalid_operation (
-	    "Last typed key has no character equivalent (that we know of)",
-	    Fcopy_event (Vlast_command_event, Qnil));
+    {
+      Fsignal (Qno_character_typed, Fcopy_event (Vlast_command_event, Qnil));
+    }
 
   CHECK_CHAR_COERCE_INT (c);