From d92d5e794dfd2f66f4f49c9878c6739793545777 Mon Sep 17 00:00:00 2001
From: JoJoJet <21144246+JoJoJet@users.noreply.github.com>
Date: Tue, 10 Jan 2023 18:31:15 +0000
Subject: [PATCH] Fix a miscompilation with `#[derive(SystemParam)]` (#7105)

# Objective

- Fix #7103.
- The issue is caused because I forgot to add a where clause to a generated struct in #7056.

## Solution

- Add the where clause.
---
 crates/bevy_ecs/macros/src/lib.rs          | 3 ++-
 crates/bevy_ecs/src/system/system_param.rs | 9 +++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_ecs/macros/src/lib.rs b/crates/bevy_ecs/macros/src/lib.rs
index 1990f89107774f..3d8a10b3af68ec 100644
--- a/crates/bevy_ecs/macros/src/lib.rs
+++ b/crates/bevy_ecs/macros/src/lib.rs
@@ -465,7 +465,8 @@ pub fn derive_system_param(input: TokenStream) -> TokenStream {
         // <EventReader<'static, 'static, T> as SystemParam>::State
         const _: () = {
             #[doc(hidden)]
-            #state_struct_visibility struct FetchState <'w, 's, #(#lifetimeless_generics,)*> {
+            #state_struct_visibility struct FetchState <'w, 's, #(#lifetimeless_generics,)*>
+            #where_clause {
                 state: (#(<#tuple_types as #path::system::SystemParam>::State,)*),
                 marker: std::marker::PhantomData<(
                     <#path::prelude::Query<'w, 's, ()> as #path::system::SystemParam>::State,
diff --git a/crates/bevy_ecs/src/system/system_param.rs b/crates/bevy_ecs/src/system/system_param.rs
index 289d597335617b..b253f68e28aa93 100644
--- a/crates/bevy_ecs/src/system/system_param.rs
+++ b/crates/bevy_ecs/src/system/system_param.rs
@@ -1546,4 +1546,13 @@ mod tests {
 
     #[derive(SystemParam)]
     pub struct EncapsulatedParam<'w>(Res<'w, PrivateResource>);
+
+    // regression test for https://github.com/bevyengine/bevy/issues/7103.
+    #[derive(SystemParam)]
+    pub struct WhereParam<'w, 's, Q>
+    where
+        Q: 'static + WorldQuery,
+    {
+        _q: Query<'w, 's, Q, ()>,
+    }
 }