Remove MaybeUninit

Author: SpecificProtagonist

crates/bevy_ecs/src/change_detection.rs

@@ -1517,7 +1517,7 @@ impl MaybeLocation {
     /// within a non-tracked function body.
     #[inline]
     #[track_caller]
-    pub fn caller() -> Self {
+    pub const fn caller() -> Self {
         // Note that this cannot use `new_with`, since `FnOnce` invocations cannot be annotated with `#[track_caller]`.
         MaybeLocation {
             #[cfg(feature = "track_location")]

crates/bevy_ecs/src/entity/mod.rs

@@ -81,13 +81,7 @@ use crate::{
 };
 use alloc::vec::Vec;
 use bevy_platform::sync::atomic::Ordering;
-use core::{
-    fmt,
-    hash::Hash,
-    mem::{self, MaybeUninit},
-    num::NonZero,
-    panic::Location,
-};
+use core::{fmt, hash::Hash, mem, num::NonZero, panic::Location};
 use log::warn;
 
 #[cfg(feature = "serialize")]
@@ -928,7 +922,7 @@ impl Entities {
     pub(crate) unsafe fn mark_spawn_despawn(&mut self, index: u32, by: MaybeLocation, at: Tick) {
         // SAFETY: Caller guarantees that `index` a valid entity index
         let meta = unsafe { self.meta.get_unchecked_mut(index as usize) };
-        meta.spawned_or_despawned = MaybeUninit::new(SpawnedOrDespawned { by, at });
+        meta.spawned_or_despawned = SpawnedOrDespawned { by, at };
     }
 
     /// Increments the `generation` of a freed [`Entity`]. The next entity ID allocated with this
@@ -1006,7 +1000,7 @@ impl Entities {
                     Entity::from_raw_and_generation(row, meta.generation),
                     &mut meta.location,
                 );
-                meta.spawned_or_despawned = MaybeUninit::new(SpawnedOrDespawned { by, at });
+                meta.spawned_or_despawned = SpawnedOrDespawned { by, at };
             }
 
             *free_cursor = 0;
@@ -1019,7 +1013,7 @@ impl Entities {
                 Entity::from_raw_and_generation(row, meta.generation),
                 &mut meta.location,
             );
-            meta.spawned_or_despawned = MaybeUninit::new(SpawnedOrDespawned { by, at });
+            meta.spawned_or_despawned = SpawnedOrDespawned { by, at };
         }
     }
 
@@ -1121,10 +1115,7 @@ impl Entities {
             (meta.generation == entity.generation)
             || (meta.location.archetype_id == ArchetypeId::INVALID)
             && (meta.generation == entity.generation.after_versions(1)))
-            .map(|meta| {
-                // SAFETY: valid archetype or non-min generation is proof this is init
-                unsafe { meta.spawned_or_despawned.assume_init() }
-            })
+            .map(|meta| meta.spawned_or_despawned)
     }
 
     /// Returns the source code location from which this entity has last been spawned
@@ -1141,9 +1132,7 @@ impl Entities {
     ) -> (MaybeLocation, Tick) {
         // SAFETY: caller ensures entity is allocated
         let meta = unsafe { self.meta.get_unchecked(entity.index() as usize) };
-        // SAFETY: caller ensures entities of this index were at least spawned
-        let spawned_or_despawned = unsafe { meta.spawned_or_despawned.assume_init() };
-        (spawned_or_despawned.by, spawned_or_despawned.at)
+        (meta.spawned_or_despawned.by, meta.spawned_or_despawned.at)
     }
 
     #[inline]
@@ -1152,9 +1141,7 @@ impl Entities {
             if meta.generation != EntityGeneration::FIRST
                 || meta.location.archetype_id != ArchetypeId::INVALID
             {
-                // SAFETY: non-min generation or valid archetype is proof this is init
-                let spawned_or_despawned = unsafe { meta.spawned_or_despawned.assume_init_mut() };
-                spawned_or_despawned.at.check_tick(change_tick);
+                meta.spawned_or_despawned.at.check_tick(change_tick);
             }
         }
     }
@@ -1219,7 +1206,7 @@ struct EntityMeta {
     /// The current location of the [`EntityRow`].
     pub location: EntityLocation,
     /// Location of the last spawn, despawn or flush of this entity.
-    spawned_or_despawned: MaybeUninit<SpawnedOrDespawned>,
+    spawned_or_despawned: SpawnedOrDespawned,
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -1233,7 +1220,10 @@ impl EntityMeta {
     const EMPTY: EntityMeta = EntityMeta {
         generation: EntityGeneration::FIRST,
         location: EntityLocation::INVALID,
-        spawned_or_despawned: MaybeUninit::uninit(),
+        spawned_or_despawned: SpawnedOrDespawned {
+            by: MaybeLocation::caller(),
+            at: Tick::new(0),
+        },
     };
 }