clean up safety comments

Author: jakobhellermann

crates/bevy_ecs/src/world/entity_ref.rs

@@ -139,7 +139,7 @@ impl<'w> EntityRef<'w> {
     ///
     /// # Safety
     ///
-    /// - The returned reference must never alias a mutable borrow of this component.
+    /// - The returned reference must never alias another reference to this component
     /// - The returned reference must not be used after this component is moved which
     ///   may happen from **any** `insert_component`, `remove_component` or `despawn`
     ///   operation on this world (non-exhaustive list).
@@ -149,7 +149,8 @@ impl<'w> EntityRef<'w> {
         component_id: ComponentId,
     ) -> Option<MutUntyped<'w>> {
         self.world.components().get_info(component_id)?;
-        // SAFETY: entity_location is valid, component_id is valid as checked by the line above, world access is promised by the caller
+        // SAFETY: entity_location is valid, component_id is valid as checked by the line above,
+        // the caller promises that they can uniquely access this component
         get_mut_by_id(self.world, self.entity, self.location, component_id)
     }
 }

crates/bevy_ecs/src/world/mod.rs

@@ -1480,14 +1480,16 @@ impl World {
         let ticks = Ticks {
             // SAFETY:
             // - index is in-bounds because the column is initialized and non-empty
-            // - no other reference to the ticks of the same row can exist at the same time
+            // - the caller of this function has to ensure that they can mutably access this
+            // component for the duration of the `'_` lifetime. This includes access to the `ComponentTicks`
             component_ticks: ticks.deref_mut(),
             last_change_tick: self.last_change_tick(),
             change_tick: self.read_change_tick(),
         };
 
         Some(MutUntyped {
-            // SAFETY: This function has exclusive access to the world so nothing aliases `ptr`.
+            // SAFETY: the caller of this function has to ensure that they can mutably access this
+            // component for the duration of the `'_` lifetime
             value: ptr.assert_unique(),
             ticks,
         })