commit https://github.com/vim/vim/commit/95f096030ed1a8afea028f2ea295d6f6a70f466f Author: Bram Moolenaar <Bram@vim.org> Date: Thu Nov 10 20:01:45 2016 +0100 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.

--- a/src/hashtab.c
+++ b/src/hashtab.c
@@ -210,7 +210,7 @@ hash_add(hashtab_T *ht, char_u *key)
     hi = hash_lookup(ht, key, hash);
     if (!HASHITEM_EMPTY(hi))
     {
-	EMSG2(_(e_intern2), "hash_add()");
+	internal_error("hash_add()");
 	return FAIL;
     }
     return hash_add_item(ht, hi, key, hash);