Macro StateMachineBuilder

macro_rules! StateMachineBuilder {
    (
        ($d:tt)
        $(#[$($state_macros:tt)*])*
        enum $state_name:ident $(impl $trait:ident)?  {
            $($(#[$($variant_macros:tt)*])*
            $variant_name:ident($state:ty$(,$($aux:ty),+)?) $(-> $override:expr)?),+ $(,)?
        }
    ) => { ... };
    ($($tt:tt)+) => { ... };
}