patch 8.0.0074
Problem:    Cannot make Vim fail on an internal error.
Solution:   Add IEMSG() and IEMSG2(). (Domenique Pelle)  Avoid reporting an
            internal error without mentioning where.
diff --git a/src/hangulin.c b/src/hangulin.c
index 1b5604b..60b3577 100644
--- a/src/hangulin.c
+++ b/src/hangulin.c
@@ -590,7 +590,7 @@
 	    return AUTOMATA_CORRECT_NEW;
 
 	default:
-	    EMSG(_("E256: Hangul automata ERROR"));
+	    IEMSG(_("E256: Hangul automata ERROR"));
 	    break;
     }
     return AUTOMATA_ERROR; /* RrEeAaLlLlYy EeRrRrOoRr */