Macro ecs_multi_impl 

macro_rules! ecs_multi_impl {
    (
        $ecs:ident {
            $($world_name:ident {
                $($(#[$comp_attr:meta])* $name:ident: $type:ty => $mask:ident),* $(,)?
            })+
        }
        Tags {
            $($tag_name:ident => $tag_mask:ident),* $(,)?
        }
        Events {
            $($event_name:ident: $event_type:ty),* $(,)?
        }
        $resources:ident {
            $($(#[$attr:meta])* $resource_name:ident: $resource_type:ty),* $(,)?
        }
    ) => { ... };
}