Macro exonum::__ex_message

macro_rules! __ex_message {
    {
        $service_id:expr,
        $message_id:expr,

        $(#[$attr:meta])*
        struct $name:ident {
        $(
            $(#[$field_attr:meta])*
            $field_name:ident : $field_type:ty
        ),*
        $(,)*
       }

        $($tt:tt)*
    } => { ... };
    { $service_id:expr, $message_id:expr, } => { ... };
}