implement UniqueEntitySlice

crates/bevy_ecs/src/entity/entity_set.rs

@@ -13,7 +13,7 @@ use core::{
     option, result,
 };
 
-use super::Entity;
+use super::{Entity, UniqueEntitySlice};
 
 use bevy_platform_support::sync::Arc;
 
@@ -350,6 +350,7 @@ impl<I: EntitySetIterator> UniqueEntityIter<I> {
         Self { iter }
     }
 }
+
 impl<I: Iterator<Item: TrustedEntityBorrow>> UniqueEntityIter<I> {
     /// Constructs a [`UniqueEntityIter`] from an iterator unsafely.
     ///
@@ -359,6 +360,26 @@ impl<I: Iterator<Item: TrustedEntityBorrow>> UniqueEntityIter<I> {
     pub unsafe fn from_iterator_unchecked(iter: I) -> Self {
         Self { iter }
     }
+
+    /// Returns the inner `I`.
+    pub fn into_inner(self) -> I {
+        self.iter
+    }
+
+    /// Returns a reference to the inner `I`.
+    pub fn as_inner(&self) -> &I {
+        &self.iter
+    }
+
+    /// Returns a mutable reference to the inner `I`.
+    ///
+    /// # Safety
+    ///
+    /// `self` must always contain an iterator that yields unique elements,
+    /// even while this reference is live.
+    pub unsafe fn as_mut_inner(&mut self) -> &mut I {
+        &mut self.iter
+    }
 }
 
 impl<I: Iterator<Item: TrustedEntityBorrow>> Iterator for UniqueEntityIter<I> {
@@ -394,6 +415,24 @@ impl<T, I: Iterator<Item: TrustedEntityBorrow> + AsRef<[T]>> AsRef<[T]> for Uniq
     }
 }
 
+impl<T: TrustedEntityBorrow, I: Iterator<Item: TrustedEntityBorrow> + AsRef<[T]>>
+    AsRef<UniqueEntitySlice<T>> for UniqueEntityIter<I>
+{
+    fn as_ref(&self) -> &UniqueEntitySlice<T> {
+        // SAFETY: All elements in the original slice are unique.
+        unsafe { UniqueEntitySlice::from_slice_unchecked(self.iter.as_ref()) }
+    }
+}
+
+impl<T: TrustedEntityBorrow, I: Iterator<Item: TrustedEntityBorrow> + AsMut<[T]>>
+    AsMut<UniqueEntitySlice<T>> for UniqueEntityIter<I>
+{
+    fn as_mut(&mut self) -> &mut UniqueEntitySlice<T> {
+        // SAFETY: All elements in the original slice are unique.
+        unsafe { UniqueEntitySlice::from_slice_unchecked_mut(self.iter.as_mut()) }
+    }
+}
+
 // Default does not guarantee uniqueness, meaning `I` needs to be EntitySetIterator.
 impl<I: EntitySetIterator + Default> Default for UniqueEntityIter<I> {
     fn default() -> Self {

crates/bevy_ecs/src/entity/mod.rs

@@ -66,6 +66,10 @@ mod index_set;
 pub use index_map::EntityIndexMap;
 pub use index_set::EntityIndexSet;
 
+mod unique_slice;
+
+pub use unique_slice::*;
+
 use crate::{
     archetype::{ArchetypeId, ArchetypeRow},
     identifier::{