Add dedup check for events

update_macros/src/update.rs

@@ -181,6 +181,8 @@ fn events_and_systems(update: &Update) -> TokenStream2 {
             P: std::any::Any + Send + Sync,
         {
             fn add_reader(&mut self, func: Func) {
+                #( #verify_dedup )*
+
                 match self.events.get_mut(&TypeId::of::<P>()) {
                     Some((_, listener)) => listener.push(std::sync::Arc::new(move |world, payload| {
                         let typed_payload: &P = payload.downcast_ref().unwrap();