ecs: fix issue with Entities query returning the incorrect entity ids

lyra-ecs/src/query/entities.rs

@@ -2,21 +2,20 @@ use crate::{archetype::Archetype, World, Entity};
 
 use super::{Fetch, Query, AsQuery};
 
-pub struct EntitiesFetch {
-    entities: Vec<Entity>,
+pub struct EntitiesFetch<'a> {
+    archetype_entities: Option<&'a [Entity]>,
 }
 
-impl<'a> Fetch<'a> for EntitiesFetch {
+impl<'a> Fetch<'a> for EntitiesFetch<'a> {
     type Item = Entity;
 
     unsafe fn get_item(&mut self, entity: crate::world::ArchetypeEntityId) -> Self::Item {
-        let e = *self.entities.get_unchecked(entity.0 as usize);
-        e
+        self.archetype_entities.unwrap()[entity.0 as usize]
     }
 
     fn dangling() -> Self {
         Self {
-            entities: vec![],
+            archetype_entities: None,
         }
     }
 }
@@ -27,7 +26,7 @@ pub struct Entities;
 impl Query for Entities {
     type Item<'a> = Entity;
     
-    type Fetch<'a> = EntitiesFetch;
+    type Fetch<'a> = EntitiesFetch<'a>;
 
     fn new() -> Self {
         Entities
@@ -41,7 +40,7 @@ impl Query for Entities {
     unsafe fn fetch<'a>(&self, _world: &'a World, archetype: &'a Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
         let _ = tick; // ignore unused warnings
         EntitiesFetch {
-            entities: archetype.entity_ids.keys().cloned().collect::<Vec<Entity>>(),
+            archetype_entities: Some(&archetype.entities),
         }
     }
 }