% mmc -O0 --deforestation -C deforest_bug.m
%
% Uncaught Mercury exception:
% Software Error: ll_backend.code_gen:
% predicate `ll_backend.code_gen.generate_goal'/5:
% Unexpected: nondet model in det/semidet context

:- module deforest_bug.
:- interface.

:- type bool
    --->    no
    ;       yes.

:- pred foo(bool, int).
:- mode foo(in, out) is det.

:- implementation.

:- type maybe(T)
    --->    no
    ;       yes(T).

foo(B, X) :-
    bar(X0),
    ( if quux(B, no, _) then
	X = X0
    else
	X = X0
    ).

:- pred bar(int).
:- mode bar(out) is det.

bar(0).

:- pred quux(bool, maybe(int), int).
:- mode quux(in, in, out) is semidet.

quux(B, R, Q) :-
    (
	B = yes
    ;
	R = yes(_)
    ),
    (
	R = yes(Q)
    ;
	R = no,
	Q = 0
    ).