Bevycheck helps debug bevy errors by adding procedural macros which aid the compiler in emitting better compilation errors.

If you get an error like the trait `IntoSystem<(), (), _>` is not implemented for fn item `for<'a> fn(bevy::prelude::ResMut<'a, [type error]>) {system}, simply add #[bevycheck::system] to your function, and a more helpful error messages should appear:

#[bevycheck::system]
fn system(commands: &mut Commands, query: Query<(Entity, &GlobalTransform)>) {
    // ...
}

How does it work?

It works by replacing

fn system(commands: &mut Commands, query: Query<(Entity, &GlobalTransform)>) {
  // ...
}

with

fn system() {
  assert_is_system_param::<&mut Commands>();
  assert_is_system_param::<Query<(Entity, &GlobalTransform)>>();
  panic!("remove bevycheck before running");
}

That way, without parameters the system is a valid system and the add_system call doesn't error anymore, and by asserting that each specific parameter must be a valid system param, rust can figure out which one's the culprit and print a more directed error message.

Bevy support table