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/quickfix.c b/src/quickfix.c
index a45faea..a563fa9 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -3231,7 +3231,7 @@
     {
 	if (buf != curbuf)
 	{
-	    EMSG2(_(e_intern2), "qf_fill_buffer()");
+	    internal_error("qf_fill_buffer()");
 	    return;
 	}