From: Mark Thom <markjordanthom@gmail.com>
Date: Thu, 20 Jan 2022 03:19:47 +0000 (-0700)
Subject: throw errors from phrase/{2,3} where expected (#1220)
X-Git-Tag: v0.9.0^2~47
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=1854338ff460c4dd00f91bac12e76f501fc7b94b;p=scryer-prolog.git

throw errors from phrase/{2,3} where expected (#1220)
---

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).