Macro idcontain::derive_flat

macro_rules! derive_flat {
    (
        #[element($element:ident, & $element_ref:ident, &mut $element_ref_mut:ident)]
        #[access(& $access:ident, &mut $access_mut:ident)]
        pub struct $struct_name:ident {
            $(#[element($element_field:ident)]
              pub $field:ident : $field_type:ty,)+
        }
    ) => { ... };
}