Fix bug in finding arity for verify attributes

tests/scryer/cli/issues/compilation_bug.in/b.pl

@@ -0,0 +1,30 @@
+% Issue 2632
+
+% Repro for cycle detection crash
+:- use_module(library(lists)).
+:- use_module(library(clpz)).
+:- use_module(library(error)).
+:- use_module(library(lambda)).
+:- use_module(library(debug)).
+
+clpz:monotonic.
+
+q_r(T/N, T:U) :- 0 #=< #T, 0 #=< #U, #N #= T + U.
+
+qs_Ts_Us(Qs, ΣTs, ΣUs) :-
+    maplist(\Q^T^U^(q_r(Q, T:U)), Qs, Ts, Us),
+    intlist_partsums(Ts, ΣTs),
+    intlist_partsums(Us, ΣUs).
+
+%% Utility predicates used above:
+
+intlist_partsums([X|Xs], [X|Ss]) :-
+    intlist_partsums_acc(Xs, Ss, X).
+
+intlist_partsums_acc([], [], _).
+intlist_partsums_acc([X|Xs], [S|Ss], A) :-
+    #S #= #X + #A,
+    intlist_partsums_acc(Xs, Ss, S).
+
+test_b :-
+    once(qs_Ts_Us(_, [1,3], [5,9])).