Use associated type bounds for iter_many and friends (#15040)

# Objective

Make the bounds for these query methods less intimidating.
Continuation of #14107

<sub>My last pr was back in february 💀

Author: tim-blackbird

crates/bevy_ecs/src/query/state.rs

@@ -1174,14 +1174,11 @@ impl<D: QueryData, F: QueryFilter> QueryState<D, F> {
     ///
     /// - [`iter_many_mut`](Self::iter_many_mut) to get mutable query items.
     #[inline]
-    pub fn iter_many<'w, 's, EntityList: IntoIterator>(
+    pub fn iter_many<'w, 's, EntityList: IntoIterator<Item: Borrow<Entity>>>(
         &'s mut self,
         world: &'w World,
         entities: EntityList,
-    ) -> QueryManyIter<'w, 's, D::ReadOnly, F, EntityList::IntoIter>
-    where
-        EntityList::Item: Borrow<Entity>,
-    {
+    ) -> QueryManyIter<'w, 's, D::ReadOnly, F, EntityList::IntoIter> {
         self.update_archetypes(world);
         // SAFETY: query is read only
         unsafe {
@@ -1209,14 +1206,11 @@ impl<D: QueryData, F: QueryFilter> QueryState<D, F> {
     /// - [`iter_many`](Self::iter_many) to update archetypes.
     /// - [`iter_manual`](Self::iter_manual) to iterate over all query items.
     #[inline]
-    pub fn iter_many_manual<'w, 's, EntityList: IntoIterator>(
+    pub fn iter_many_manual<'w, 's, EntityList: IntoIterator<Item: Borrow<Entity>>>(
         &'s self,
         world: &'w World,
         entities: EntityList,
-    ) -> QueryManyIter<'w, 's, D::ReadOnly, F, EntityList::IntoIter>
-    where
-        EntityList::Item: Borrow<Entity>,
-    {
+    ) -> QueryManyIter<'w, 's, D::ReadOnly, F, EntityList::IntoIter> {
         self.validate_world(world.id());
         // SAFETY: query is read only, world id is validated
         unsafe {
@@ -1234,14 +1228,11 @@ impl<D: QueryData, F: QueryFilter> QueryState<D, F> {
     /// Items are returned in the order of the list of entities.
     /// Entities that don't match the query are skipped.
     #[inline]
-    pub fn iter_many_mut<'w, 's, EntityList: IntoIterator>(
+    pub fn iter_many_mut<'w, 's, EntityList: IntoIterator<Item: Borrow<Entity>>>(
         &'s mut self,
         world: &'w mut World,
         entities: EntityList,
-    ) -> QueryManyIter<'w, 's, D, F, EntityList::IntoIter>
-    where
-        EntityList::Item: Borrow<Entity>,
-    {
+    ) -> QueryManyIter<'w, 's, D, F, EntityList::IntoIter> {
         self.update_archetypes(world);
         let change_tick = world.change_tick();
         let last_change_tick = world.last_change_tick();
@@ -1334,15 +1325,15 @@ impl<D: QueryData, F: QueryFilter> QueryState<D, F> {
     /// This does not validate that `world.id()` matches `self.world_id`. Calling this on a `world`
     /// with a mismatched [`WorldId`] is unsound.
     #[inline]
-    pub(crate) unsafe fn iter_many_unchecked_manual<'w, 's, EntityList: IntoIterator>(
+    pub(crate) unsafe fn iter_many_unchecked_manual<'w, 's, EntityList>(
         &'s self,
         entities: EntityList,
         world: UnsafeWorldCell<'w>,
         last_run: Tick,
         this_run: Tick,
     ) -> QueryManyIter<'w, 's, D, F, EntityList::IntoIter>
     where
-        EntityList::Item: Borrow<Entity>,
+        EntityList: IntoIterator<Item: Borrow<Entity>>,
     {
         QueryManyIter::new(world, self, entities, last_run, this_run)
     }

crates/bevy_ecs/src/system/query.rs

@@ -616,13 +616,10 @@ impl<'w, 's, D: QueryData, F: QueryFilter> Query<'w, 's, D, F> {
     ///
     /// - [`iter_many_mut`](Self::iter_many_mut) to get mutable query items.
     #[inline]
-    pub fn iter_many<EntityList: IntoIterator>(
+    pub fn iter_many<EntityList: IntoIterator<Item: Borrow<Entity>>>(
         &self,
         entities: EntityList,
-    ) -> QueryManyIter<'_, 's, D::ReadOnly, F, EntityList::IntoIter>
-    where
-        EntityList::Item: Borrow<Entity>,
-    {
+    ) -> QueryManyIter<'_, 's, D::ReadOnly, F, EntityList::IntoIter> {
         // SAFETY:
         // - `self.world` has permission to access the required components.
         // - The query is read-only, so it can be aliased even if it was originally mutable.
@@ -670,13 +667,10 @@ impl<'w, 's, D: QueryData, F: QueryFilter> Query<'w, 's, D, F> {
     /// # bevy_ecs::system::assert_is_system(system);
     /// ```
     #[inline]
-    pub fn iter_many_mut<EntityList: IntoIterator>(
+    pub fn iter_many_mut<EntityList: IntoIterator<Item: Borrow<Entity>>>(
         &mut self,
         entities: EntityList,
-    ) -> QueryManyIter<'_, 's, D, F, EntityList::IntoIter>
-    where
-        EntityList::Item: Borrow<Entity>,
-    {
+    ) -> QueryManyIter<'_, 's, D, F, EntityList::IntoIter> {
         // SAFETY: `self.world` has permission to access the required components.
         unsafe {
             self.state.iter_many_unchecked_manual(
@@ -752,13 +746,10 @@ impl<'w, 's, D: QueryData, F: QueryFilter> Query<'w, 's, D, F> {
     /// # See also
     ///
     /// - [`iter_many_mut`](Self::iter_many_mut) to safely access the query items.
-    pub unsafe fn iter_many_unsafe<EntityList: IntoIterator>(
+    pub unsafe fn iter_many_unsafe<EntityList: IntoIterator<Item: Borrow<Entity>>>(
         &self,
         entities: EntityList,
-    ) -> QueryManyIter<'_, 's, D, F, EntityList::IntoIter>
-    where
-        EntityList::Item: Borrow<Entity>,
-    {
+    ) -> QueryManyIter<'_, 's, D, F, EntityList::IntoIter> {
         // SAFETY:
         // - `self.world` has permission to access the required components.
         // - The caller ensures that this operation will not result in any aliased mutable accesses.