Macro event 

macro_rules! event {
    ($event_type:ty { $($evnet_field:tt)* } $(, $($tt:tt)* )?) => { ... };
    ($event_data:expr                       $(, $($tt:tt)* )?) => { ... };
    (@load_known $event_builder:expr, $name:ident: $type:ty) => { ... };
    (@field $event_builder:expr, $name:ident               $(, $($tt:tt)* )?) => { ... };
    (@field $event_builder:expr, $name:ident = Map           { $($build:tt)* } $(, $($tt:tt)* )?) => { ... };
    (@field $event_builder:expr, $name:ident = $struct:ident { $(build:tt)* } $(, $($tt:tt)* )?) => { ... };
    (@field $event_builder:expr, $name:ident = $value:expr $(, $($tt:tt)* )?) => { ... };
    (@field $event_builder:expr $(,)? ) => { ... };
}