Macro dot 

macro_rules! dot {
    (@internal [$($code:tt)*], $model:literal) => { ... };
    (@internal [$($code:tt)*], $model:expr) => { ... };
    (@internal [$($code:tt)*]) => { ... };
    (@internal [$($code:tt)*] $next:tt $($rest:tt)*) => { ... };
    ($($all_tokens:tt)+) => { ... };
}