From aaa01c07877746c48ca602d4e6bde8936482b90a Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Sun, 25 May 2025 16:26:14 +0200
Subject: [PATCH] backport to 0.15: remove reliance on a trait solver bug
 (#19360)

A backport of https://github.com/bevyengine/bevy/pull/18840 to version
0.15.3. I was unsure whether I should also update the versions of all
crates. Looking at previous backports this was not done.

The code which relies on the old solver behavior was introduced in
https://github.com/bevyengine/bevy/pull/15184 which is from version
0.15. So this is the only version which needs a backport.

cc @mockersf
---
 crates/bevy_ecs/src/system/exclusive_function_system.rs | 3 ++-
 crates/bevy_ecs/src/system/function_system.rs           | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_ecs/src/system/exclusive_function_system.rs b/crates/bevy_ecs/src/system/exclusive_function_system.rs
index 8b1a06fb3a..3edd381954 100644
--- a/crates/bevy_ecs/src/system/exclusive_function_system.rs
+++ b/crates/bevy_ecs/src/system/exclusive_function_system.rs
@@ -269,6 +269,7 @@ macro_rules! impl_exclusive_system_function {
                 // is a function, potentially because of the multiple impls of `FnMut`
                 #[allow(clippy::too_many_arguments)]
                 fn call_inner<In: SystemInput, Out, $($param,)*>(
+                    _: PhantomData<In>,
                     mut f: impl FnMut(In::Param<'_>, &mut World, $($param,)*) -> Out,
                     input: In::Inner<'_>,
                     world: &mut World,
@@ -277,7 +278,7 @@ macro_rules! impl_exclusive_system_function {
                     f(In::wrap(input), world, $($param,)*)
                 }
                 let ($($param,)*) = param_value;
-                call_inner(self, input, world, $($param),*)
+                call_inner(PhantomData::<In>, self, input, world, $($param),*)
             }
         }
     };
diff --git a/crates/bevy_ecs/src/system/function_system.rs b/crates/bevy_ecs/src/system/function_system.rs
index 7f2b7dd667..a7b0639c69 100644
--- a/crates/bevy_ecs/src/system/function_system.rs
+++ b/crates/bevy_ecs/src/system/function_system.rs
@@ -1023,6 +1023,7 @@ macro_rules! impl_system_function {
             fn run(&mut self, input: In::Inner<'_>, param_value: SystemParamItem< ($($param,)*)>) -> Out {
                 #[allow(clippy::too_many_arguments)]
                 fn call_inner<In: SystemInput, Out, $($param,)*>(
+                    _: PhantomData<In>,
                     mut f: impl FnMut(In::Param<'_>, $($param,)*)->Out,
                     input: In::Inner<'_>,
                     $($param: $param,)*
@@ -1030,7 +1031,7 @@ macro_rules! impl_system_function {
                     f(In::wrap(input), $($param,)*)
                 }
                 let ($($param,)*) = param_value;
-                call_inner(self, input, $($param),*)
+                call_inner(PhantomData::<In>, self, input, $($param),*)
             }
         }
     };