:- module unif_bug2.

:- interface.

:- pred foo(X::in, X::out) is semidet <= foo(X).

:- implementation.

:- import_module list.

:- typeclass foo(X) where [].

foo(X, Y) :-
	% The calls to reverse() are necessary so things aren't
	% optimized away...
	promise_equivalent_solutions [Bar] reverse([X], Bar),
	(
		Bar = [], false
	;
		Bar = [Z|L],
		reverse(L, _),
		Y = Z
	).