#[derive(Bundle)] compilation issue in Bevy 0.16

[Zeenobit]

From my testing, the following code doesn't compile anymore:

use bevy::prelude::*;

#[derive(Bundle)]
struct Foo<T: Bundle>(T);

error[E0277]: the trait bound `T: BundleFromComponents` is not satisfied

I understand this requires BundleFromComponent trait bound to work because of the new changes to Bundles.
But this feels like a regression to me, especially since neither Bundle nor BundleFromComponents require each other.
So the user is forced to require both Bundle and BundleFromComponents, and the latter isn't in prelude either:

use bevy::prelude::*;
use bevy::ecs::bundle::BundleFromComponents;

#[derive(Bundle)]
struct Foo<T: Bundle + BundleFromComponents>(T);

I was curious if this API design is intentional, or if we could find a way to improve it.

Is there a reason Bundle doesn't require BundleFromComponent?
Could we introduce a new trait like CompleteBundle (naming TBD) and use #[derive(CompleteBundle)] instead?

[alice-i-cecile]

Yeah, this wasn't an intended regression. It should be documented at the very least, but I think that we should be clearer about our semantics around the Bundle trait more generally and be careful about where we use it versus distinct traits (see #3227).

[Zeenobit]

Let me know if you'd like me to open a new issue on this, or if it's already on radar! :)

[alice-i-cecile]

Please open a new issue :)