From e8dd5bc73eae67fbba0a9cd14388a4a881b3b8f8 Mon Sep 17 00:00:00 2001
From: Kevin King <4kevinking@gmail.com>
Date: Thu, 9 Dec 2021 21:47:29 -0800
Subject: [PATCH] improve error message for attempting to add startup systems
 using add_system_to_stage

Fixes #3250

Notes:
We perform this extra check in bevy_app so that the `StartupStage` type
id is available to us.
---
 crates/bevy_app/src/app.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/crates/bevy_app/src/app.rs b/crates/bevy_app/src/app.rs
index 04024d794a4d3..6fc2efb3e71cc 100644
--- a/crates/bevy_app/src/app.rs
+++ b/crates/bevy_app/src/app.rs
@@ -353,6 +353,10 @@ impl App {
         stage_label: impl StageLabel,
         system: impl IntoSystemDescriptor<Params>,
     ) -> &mut Self {
+        use std::any::TypeId;
+        if stage_label.type_id() == TypeId::of::<StartupStage>() {
+            panic!("add systems to a startup stage using App::add_startup_system_to_stage");
+        }
         self.schedule.add_system_to_stage(stage_label, system);
         self
     }
@@ -383,6 +387,10 @@ impl App {
         stage_label: impl StageLabel,
         system_set: SystemSet,
     ) -> &mut Self {
+        use std::any::TypeId;
+        if stage_label.type_id() == TypeId::of::<StartupStage>() {
+            panic!("add system sets to a startup stage using App::add_startup_system_set_to_stage");
+        }
         self.schedule
             .add_system_set_to_stage(stage_label, system_set);
         self