From 0499005db5b60c622fa9498fdd2c0e2f2e082cbd Mon Sep 17 00:00:00 2001
From: Mark Thom <markjordanthom@gmail.com>
Date: Sat, 11 Apr 2020 22:40:29 -0600
Subject: [PATCH] throw error when trying to use partial lists as DCG
 terminal-sequence (#286)

---
 src/prolog/lib/dcgs.pl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/prolog/lib/dcgs.pl b/src/prolog/lib/dcgs.pl
index bd35575d..33210f19 100644
--- a/src/prolog/lib/dcgs.pl
+++ b/src/prolog/lib/dcgs.pl
@@ -3,6 +3,7 @@
 		 phrase/2,
 		 phrase/3]).
 
+:- use_module(library(error)).
 :- use_module(library(lists), [append/3]).
 
 user:term_expansion(Term0, Term) :-
@@ -108,6 +109,7 @@ dcg_constr((_->_)). % 7.14.12 - if-then (existence implementation dep.)
 % the construct to be expanded.
 dcg_cbody([], S0, S, S0 = S).
 dcg_cbody([T|Ts], S0, S, Goal) :-
+    must_be(list, [T|Ts]),
     dcg_terminals([T|Ts], S0, S, Goal).
 dcg_cbody(( GRFirst, GRSecond ), S0, S, ( First, Second )) :-
     dcg_body(GRFirst, S0, S1, First),
-- 
2.54.0