Macro enum_meta::meta

macro_rules! meta {
    ($enum_type:ident, $return_type:ty;
     $($enum_variant:ident, $return_value:expr);*
    ) => { ... };
    ($enum_type:ident, $return_type:ty;
     $($enum_variant:ident, $return_value:expr);+ ;
    ) => { ... };
}