name(n1:string, _: NToken, n2:string, _: NToken, n3:string, n4: option[(NToken*string)]):string 
    {
        n1+";"+n2+";"+n3+";"+
        match(n4)
        {
            | None => "";
            | Some((_,n5)) => n5;
        } + ";"
    }

Ошибка 3 typing fails on finding the operator op_UnaryPlus(string)
на строку + ";"