Macro gen_choice_last_field_pat

macro_rules! gen_choice_last_field_pat {
    ($pat:pat, ($($stars:tt,)*);) => { ... };
    ($pat:pat, ($($stars:tt,)*); $_:ident $(, $rest:ident)*) => { ... };
}

Generate inj_ord_choice_pat!(*, …, *, p) with |$variant| stars before p