Try #7222:

crates/bevy_ecs/src/world/entity_ref.rs

@@ -22,8 +22,13 @@ pub struct EntityRef<'w> {
 }
 
 impl<'w> EntityRef<'w> {
+    /// # Safety
+    ///
+    /// Entity and location _must_ be valid for the provided world.
     #[inline]
-    pub(crate) fn new(world: &'w World, entity: Entity, location: EntityLocation) -> Self {
+    pub(crate) unsafe fn new(world: &'w World, entity: Entity, location: EntityLocation) -> Self {
+        debug_assert!(world.entities().contains(entity));
+
         Self {
             world,
             entity,
@@ -193,7 +198,9 @@ impl<'w> EntityRef<'w> {
 
 impl<'w> From<EntityMut<'w>> for EntityRef<'w> {
     fn from(entity_mut: EntityMut<'w>) -> EntityRef<'w> {
-        EntityRef::new(entity_mut.world, entity_mut.entity, entity_mut.location)
+        // SAFETY: the safety invariants on EntityMut and EntityRef are identical
+        // and EntityMut is promised to be valid by construction.
+        unsafe { EntityRef::new(entity_mut.world, entity_mut.entity, entity_mut.location) }
     }
 }
 
@@ -206,13 +213,16 @@ pub struct EntityMut<'w> {
 
 impl<'w> EntityMut<'w> {
     /// # Safety
-    /// entity and location _must_ be valid
+    ///
+    /// Entity and location _must_ be valid for the provided world.
     #[inline]
     pub(crate) unsafe fn new(
         world: &'w mut World,
         entity: Entity,
         location: EntityLocation,
     ) -> Self {
+        debug_assert!(world.entities().contains(entity));
+
         EntityMut {
             world,
             entity,

crates/bevy_ecs/src/world/mod.rs

@@ -317,7 +317,10 @@ impl World {
     #[inline]
     pub fn get_entity(&self, entity: Entity) -> Option<EntityRef> {
         let location = self.entities.get(entity)?;
-        Some(EntityRef::new(self, entity, location))
+        // SAFETY: if the Entity is invalid, the function returns early.
+        // Additionally, Entities::get(entity) returns the correct EntityLocation if the entity exists.
+        let entity_ref = unsafe { EntityRef::new(self, entity, location) };
+        Some(entity_ref)
     }
 
     /// Returns an [`Entity`] iterator of current entities.