Inginious error

local Producer Consumer Filter in
    fun {Producer N}
        fun {Aux X}
            if X==N then X|nil
            else X|{Aux X+1}
            end
        end
    in
        {Aux 1}
    end

    fun {Consumer S}
        fun {Aux S Sum}
            case S
            of H|T then {Aux T Sum+H}
            [] nil then Sum
            end
        end
    in
        {Aux S 0}
    end

    fun {Filter S}
        case S
        of H|T then
            if H mod 2 == 0 then {Filter T}
            else H|{Filter T}
            end
        [] nil then nil
        end
    end

    local S I R in
        thread S = {Producer 20} end
        thread I = {Filter S} end
        thread R = {Consumer I} end
        {Browse R}
    end
end