remove UnsafeCell from WorldCell cache

Author: BoxyUwU

crates/bevy_ecs/src/world/mod.rs

@@ -23,7 +23,6 @@ use bevy_ptr::{OwningPtr, Ptr};
 use bevy_utils::tracing::warn;
 use std::{
     any::TypeId,
-    cell::UnsafeCell,
     fmt,
     sync::atomic::{AtomicU32, Ordering},
 };
@@ -61,7 +60,7 @@ pub struct World {
     pub(crate) bundles: Bundles,
     pub(crate) removed_components: SparseSet<ComponentId, Vec<Entity>>,
     /// Access cache used by [WorldCell]. Is only accessed in the `Drop` impl of `WorldCell`.
-    pub(crate) archetype_component_access: UnsafeCell<ArchetypeComponentAccess>,
+    pub(crate) archetype_component_access: ArchetypeComponentAccess,
     pub(crate) change_tick: AtomicU32,
     pub(crate) last_change_tick: u32,
     pub(crate) last_check_tick: u32,

crates/bevy_ecs/src/world/world_cell.rs

@@ -80,10 +80,10 @@ impl<'w> Drop for WorldCell<'w> {
         let mut access = self.access.borrow_mut();
 
         {
-            // SAFETY: we only swap `archetype_component_access`
-            let world = unsafe { self.world.world() };
-            // SAFETY: the WorldCell has exclusive world access
-            let world_cached_access = unsafe { &mut *world.archetype_component_access.get() };
+            // SAFETY: `WorldCell` does not hand out `UnsafeWorldCell` to anywhere else so this is the only
+            // `UnsafeWorldCell` and we have exclusive access to it.
+            let world = unsafe { self.world.world_mut() };
+            let world_cached_access = &mut world.archetype_component_access;
 
             // give world ArchetypeComponentAccess back to reuse allocations
             std::mem::swap(world_cached_access, &mut *access);
@@ -185,7 +185,7 @@ impl<'w> WorldCell<'w> {
     pub(crate) fn new(world: &'w mut World) -> Self {
         // this is cheap because ArchetypeComponentAccess::new() is const / allocation free
         let access = std::mem::replace(
-            world.archetype_component_access.get_mut(),
+            &mut world.archetype_component_access,
             ArchetypeComponentAccess::new(),
         );
         // world's ArchetypeComponentAccess is recycled to cut down on allocations
@@ -435,11 +435,10 @@ mod tests {
         let u32_archetype_component_id = world
             .get_resource_archetype_component_id(u32_component_id)
             .unwrap();
-        assert_eq!(world.archetype_component_access.get_mut().access.len(), 1);
+        assert_eq!(world.archetype_component_access.access.len(), 1);
         assert_eq!(
             world
                 .archetype_component_access
-                .get_mut()
                 .access
                 .get(u32_archetype_component_id),
             Some(&BASE_ACCESS),