EntityRef as WorldQuery is unsound.

[joseph-gio]

Bevy version

Main branch.

What you did

    #[test]
    fn unsound_disjoint_mutable_access() {
        fn unsound_system(
            mut query: Query<(Entity, &mut TestComponent)>,
            refs: Query<super::EntityRef, Without<TestComponent>>,
        ) {
            let (id, mut c) = query.iter_mut().next().unwrap();
            let world = refs.iter().next().unwrap().world();

            // We now have mutable and shared access to the same component at the same time.
            let c2 = world.entity(id).get::<TestComponent>().unwrap();
            *c = TestComponent(1);
            println!("{c2:?}");
        }

        let mut world = World::new();
        world.spawn(TestComponent(0));
        world.spawn_empty();

        let mut schedule = Schedule::new();
        schedule.add_systems(unsound_system);

        schedule.run(&mut world);
    }

What went wrong

This should panic at runtime since the accesses of the two system params conflict. Instead, it runs and allows aliased mutable access.

[james7132]

EntityRef::world was supposed to be removed in #6960 to make this impossible. Apparently it wasn't. Probably the result of a bad merge or rebase.

[joseph-gio]

Ah, looks like it snuck back in during this merge: 0c91c16