Use a function instead of a closure for the add_system_to_stage error path

Author: bjorn3

crates/bevy_ecs/src/schedule/mod.rs

@@ -20,6 +20,8 @@ pub use system_container::*;
 pub use system_descriptor::*;
 pub use system_set::*;
 
+use std::fmt::Debug;
+
 use crate::{
     system::{IntoSystem, System},
     world::World,
@@ -144,14 +146,19 @@ impl Schedule {
         stage_label: impl StageLabel,
         system: impl Into<SystemDescriptor>,
     ) -> &mut Self {
+        // Use a function instead of a closure to ensure that it is codegend inside bevy_ecs instead
+        // of the game. Closures inherit generic parameters from their enclosing function.
+        #[cold]
+        fn stage_not_found(stage_label: &dyn Debug) -> ! {
+            panic!(
+                "Stage '{:?}' does not exist or is not a SystemStage",
+                stage_label
+            )
+        }
+
         let stage = self
             .get_stage_mut::<SystemStage>(&stage_label)
-            .unwrap_or_else(move || {
-                panic!(
-                    "Stage '{:?}' does not exist or is not a SystemStage",
-                    stage_label
-                )
-            });
+            .unwrap_or_else(move || stage_not_found(&stage_label));
         stage.add_system(system);
         self
     }