From 1854338ff460c4dd00f91bac12e76f501fc7b94b Mon Sep 17 00:00:00 2001
From: Mark Thom <markjordanthom@gmail.com>
Date: Wed, 19 Jan 2022 20:19:47 -0700
Subject: [PATCH] throw errors from phrase/{2,3} where expected (#1220)

---
 src/lib/dcgs.pl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/lib/dcgs.pl b/src/lib/dcgs.pl
index 5f8543ed..10eab327 100644
--- a/src/lib/dcgs.pl
+++ b/src/lib/dcgs.pl
@@ -72,6 +72,7 @@ phrase_((A -> B), S0, S, M) :-
 phrase_(phrase(NonTerminal), S0, S, M) :-
     phrase(NonTerminal, S0, S, M).
 phrase_([T|Ts], S0, S, _) :-
+    must_be(list, [T|Ts]),
     append([T|Ts], S, S0).
 
 
-- 
2.54.0