Macro newtype_enum 

macro_rules! newtype_enum {
    (
        $(#[$type_attrs:meta])*
        $visibility:vis enum $type:ident : $base_vis:vis $base_integer:ty => $(#[$impl_attrs:meta])* {
            $(
                $(#[$variant_attrs:meta])*
                $variant:ident = $value:expr,
            )*
        }
    ) => { ... };
}