Macro stelar::rule_rhs

macro_rules! rule_rhs {
    (@impl ($($stack:expr,)*), ($e:expr), $($rest:tt)*) => { ... };
    (@impl ($($stack:expr,)*), $e:expr, $($rest:tt)*) => { ... };
    (@impl ($($stack:expr,)*), $(,)?) => { ... };
    (@impl ($($stack:expr,)*), $($rest:tt)*) => { ... };
    ($($rest:tt)*) => { ... };
}