From 0d4d66236abba5e45ed9203aafa21d35e714b979 Mon Sep 17 00:00:00 2001
From: JoJoJet <21144246+JoJoJet@users.noreply.github.com>
Date: Fri, 3 Feb 2023 10:04:02 -0500
Subject: [PATCH 1/2] remove `ExclusiveSystemParam::apply`

---
 crates/bevy_ecs/src/system/exclusive_function_system.rs | 5 +----
 crates/bevy_ecs/src/system/exclusive_system_param.rs    | 8 --------
 2 files changed, 1 insertion(+), 12 deletions(-)

diff --git a/crates/bevy_ecs/src/system/exclusive_function_system.rs b/crates/bevy_ecs/src/system/exclusive_function_system.rs
index 1d5c7fca36781..6928e284dde22 100644
--- a/crates/bevy_ecs/src/system/exclusive_function_system.rs
+++ b/crates/bevy_ecs/src/system/exclusive_function_system.rs
@@ -132,10 +132,7 @@ where
     }
 
     #[inline]
-    fn apply_buffers(&mut self, world: &mut World) {
-        let param_state = self.param_state.as_mut().expect(PARAM_MESSAGE);
-        Param::apply(param_state, world);
-    }
+    fn apply_buffers(&mut self, _world: &mut World) {}
 
     #[inline]
     fn initialize(&mut self, world: &mut World) {
diff --git a/crates/bevy_ecs/src/system/exclusive_system_param.rs b/crates/bevy_ecs/src/system/exclusive_system_param.rs
index 7f5b25f77fba3..4d77049e317e2 100644
--- a/crates/bevy_ecs/src/system/exclusive_system_param.rs
+++ b/crates/bevy_ecs/src/system/exclusive_system_param.rs
@@ -12,8 +12,6 @@ pub trait ExclusiveSystemParam: Sized {
     type Item<'s>: ExclusiveSystemParam<State = Self::State>;
 
     fn init(world: &mut World, system_meta: &mut SystemMeta) -> Self::State;
-    #[inline]
-    fn apply(_state: &mut Self::State, _world: &mut World) {}
 
     fn get_param<'s>(state: &'s mut Self::State, system_meta: &SystemMeta) -> Self::Item<'s>;
 }
@@ -74,12 +72,6 @@ macro_rules! impl_exclusive_system_param_tuple {
                 (($($param::init(_world, _system_meta),)*))
             }
 
-            #[inline]
-            fn apply(state: &mut Self::State, _world: &mut World) {
-                let ($($param,)*) = state;
-                $($param::apply($param, _world);)*
-            }
-
             #[inline]
             #[allow(clippy::unused_unit)]
             fn get_param<'s>(

From d1cda8c7faf22d479015d0f9fb57cedae54a725b Mon Sep 17 00:00:00 2001
From: JoJoJet <21144246+JoJoJet@users.noreply.github.com>
Date: Fri, 3 Feb 2023 11:58:42 -0500
Subject: [PATCH 2/2] explain why `ExlusiveFunctionSystem::apply_buffers` does
 nothing

---
 crates/bevy_ecs/src/system/exclusive_function_system.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_ecs/src/system/exclusive_function_system.rs b/crates/bevy_ecs/src/system/exclusive_function_system.rs
index 6928e284dde22..c224dd2e46c15 100644
--- a/crates/bevy_ecs/src/system/exclusive_function_system.rs
+++ b/crates/bevy_ecs/src/system/exclusive_function_system.rs
@@ -132,7 +132,11 @@ where
     }
 
     #[inline]
-    fn apply_buffers(&mut self, _world: &mut World) {}
+    fn apply_buffers(&mut self, _world: &mut World) {
+        // "pure" exclusive systems do not have any buffers to apply.
+        // Systems made by piping a normal system with an exclusive system
+        // might have buffers to apply, but this is handled by `PipeSystem`.
+    }
 
     #[inline]
     fn initialize(&mut self, world: &mut World) {