Macro do_keys

macro_rules! do_keys {
    ( $count:literal: $(
        $(#[$meta:meta])*
        $tag:ident
        $(-? $otp:ty;)?
        $(@ $tp:ty)?
        =$val:literal
        $(+ $($other:ident),+ ;)?
        $(>> $($children:ident),+ ;)?
        $(&>> $($nchildren:ident),+ ;)?
        $(<= $($parents:ident),+ ;)?
        $(- $($req:ident),+ ;)?
        $(! $only:literal;)?
        $(-! $not:literal;)?
    )*
    ) => { ... };
}