No boxing for c types.

:- module test.

:- interface.

:- import_module io.

:- pred main(io::di, io::uo) is det.

:- type foo ---> foo(int).

:- pred is_five(foo::in) is semidet.

:- implementation.

:- pragma foreign_proc("C", is_five(Foo::in),
    [promise_pure, will_not_call_mercury],
"
    SUCCESS_INDICATOR = (Foo == 5);
").

main(!IO) :-
    Foo = foo(5),
    ( is_five(Foo) ->
        print("Foo is five\n", !IO)
    ;
        print("Foo is not five\n", !IO)
    ).