Macro lib_enum

macro_rules! lib_enum {
    (
        $(#[$enum_meta:meta])+
        $enum_ty:ident: $base_ty:ident {
            default: $default_variant:ident,
            error: $err_ty:ident,
            $(
                $(#[$var_doc:meta])*
                $variant:ident = $value:literal$(,)?
            )+
        }
    ) => { ... };
}

Convenience macro to define a library enum.