From f91e5afde0fcee904edc60f759025a048d437fbd Mon Sep 17 00:00:00 2001
From: ira <JustTheCoolDude@gmail.com>
Date: Mon, 24 Oct 2022 21:01:08 +0000
Subject: [PATCH] Implement IntoIterator for ECS wrapper types. (#5096)

# Objective

Improve ergonomics by passing on the `IntoIterator` impl of the underlying type to wrapper types.

## Solution

Implement `IntoIterator` for ECS wrapper types (Mut, Local, Res, etc.).

Co-authored-by: devil-ira <justthecooldude@gmail.com>
---
 crates/bevy_ecs/src/change_detection.rs    | 50 ++++++++++++++++++++++
 crates/bevy_ecs/src/system/system_param.rs | 36 ++++++++++++++++
 crates/bevy_pbr/src/light.rs               |  4 +-
 3 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_ecs/src/change_detection.rs b/crates/bevy_ecs/src/change_detection.rs
index f808106a0be00..b8d1f7c196d35 100644
--- a/crates/bevy_ecs/src/change_detection.rs
+++ b/crates/bevy_ecs/src/change_detection.rs
@@ -245,6 +245,31 @@ pub struct ResMut<'a, T: ?Sized + Resource> {
     pub(crate) ticks: Ticks<'a>,
 }
 
+impl<'w, 'a, T: Resource> IntoIterator for &'a ResMut<'w, T>
+where
+    &'a T: IntoIterator,
+{
+    type Item = <&'a T as IntoIterator>::Item;
+    type IntoIter = <&'a T as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.value.into_iter()
+    }
+}
+
+impl<'w, 'a, T: Resource> IntoIterator for &'a mut ResMut<'w, T>
+where
+    &'a mut T: IntoIterator,
+{
+    type Item = <&'a mut T as IntoIterator>::Item;
+    type IntoIter = <&'a mut T as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.set_changed();
+        self.value.into_iter()
+    }
+}
+
 change_detection_impl!(ResMut<'a, T>, T, Resource);
 impl_methods!(ResMut<'a, T>, T, Resource);
 impl_debug!(ResMut<'a, T>, Resource);
@@ -298,6 +323,31 @@ pub struct Mut<'a, T: ?Sized> {
     pub(crate) ticks: Ticks<'a>,
 }
 
+impl<'w, 'a, T> IntoIterator for &'a Mut<'w, T>
+where
+    &'a T: IntoIterator,
+{
+    type Item = <&'a T as IntoIterator>::Item;
+    type IntoIter = <&'a T as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.value.into_iter()
+    }
+}
+
+impl<'w, 'a, T> IntoIterator for &'a mut Mut<'w, T>
+where
+    &'a mut T: IntoIterator,
+{
+    type Item = <&'a mut T as IntoIterator>::Item;
+    type IntoIter = <&'a mut T as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.set_changed();
+        self.value.into_iter()
+    }
+}
+
 change_detection_impl!(Mut<'a, T>, T,);
 impl_methods!(Mut<'a, T>, T,);
 impl_debug!(Mut<'a, T>,);
diff --git a/crates/bevy_ecs/src/system/system_param.rs b/crates/bevy_ecs/src/system/system_param.rs
index d064198c61aee..3e19653278375 100644
--- a/crates/bevy_ecs/src/system/system_param.rs
+++ b/crates/bevy_ecs/src/system/system_param.rs
@@ -344,6 +344,18 @@ impl<'w, T: Resource> From<ResMut<'w, T>> for Res<'w, T> {
     }
 }
 
+impl<'w, 'a, T: Resource> IntoIterator for &'a Res<'w, T>
+where
+    &'a T: IntoIterator,
+{
+    type Item = <&'a T as IntoIterator>::Item;
+    type IntoIter = <&'a T as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.value.into_iter()
+    }
+}
+
 /// The [`SystemParamState`] of [`Res<T>`].
 #[doc(hidden)]
 pub struct ResState<T> {
@@ -719,6 +731,30 @@ impl<'a, T: FromWorld + Send + Sync + 'static> DerefMut for Local<'a, T> {
     }
 }
 
+impl<'w, 'a, T: FromWorld + Send + 'static> IntoIterator for &'a Local<'w, T>
+where
+    &'a T: IntoIterator,
+{
+    type Item = <&'a T as IntoIterator>::Item;
+    type IntoIter = <&'a T as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+impl<'w, 'a, T: FromWorld + Send + 'static> IntoIterator for &'a mut Local<'w, T>
+where
+    &'a mut T: IntoIterator,
+{
+    type Item = <&'a mut T as IntoIterator>::Item;
+    type IntoIter = <&'a mut T as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
 /// The [`SystemParamState`] of [`Local<T>`].
 #[doc(hidden)]
 pub struct LocalState<T: Send + 'static>(pub(crate) SyncCell<T>);
diff --git a/crates/bevy_pbr/src/light.rs b/crates/bevy_pbr/src/light.rs
index 4d2fc0dca26db..344fff88cb358 100644
--- a/crates/bevy_pbr/src/light.rs
+++ b/crates/bevy_pbr/src/light.rs
@@ -971,7 +971,7 @@ pub(crate) fn assign_lights_to_clusters(
 
         if config.dynamic_resizing() {
             let mut cluster_index_estimate = 0.0;
-            for light in lights.iter() {
+            for light in &lights {
                 let light_sphere = light.sphere();
 
                 // Check if the light is within the view frustum
@@ -1126,7 +1126,7 @@ pub(crate) fn assign_lights_to_clusters(
         }
 
         let mut update_from_light_intersections = |visible_lights: &mut Vec<Entity>| {
-            for light in lights.iter() {
+            for light in &lights {
                 let light_sphere = light.sphere();
 
                 // Check if the light is within the view frustum