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# Objective
Label traits such as `ScheduleLabel` currently have a major footgun: the
trait is implemented for `Box<dyn ScheduleLabel>`, but the
implementation does not function as one would expect since `Box<T>` is
considered to be a distinct type from `T`. This is because the behavior
of the `ScheduleLabel` trait is specified mainly through blanket
implementations, which prevents `Box<dyn ScheduleLabel>` from being
properly special-cased.
## Solution
Replace the blanket-implemented behavior with a series of methods
defined on `ScheduleLabel`. This allows us to fully special-case
`Box<dyn ScheduleLabel>` .
---
## Changelog
Fixed a bug where boxed label types (such as `Box<dyn ScheduleLabel>`)
behaved incorrectly when compared with concretely-typed labels.
## Migration Guide
The `ScheduleLabel` trait has been refactored to no longer depend on the
traits `std::any::Any`, `bevy_utils::DynEq`, and `bevy_utils::DynHash`.
Any manual implementations will need to implement new trait methods in
their stead.
```rust
impl ScheduleLabel for MyType {
// Before:
fn dyn_clone(&self) -> Box<dyn ScheduleLabel> { ... }
// After:
fn dyn_clone(&self) -> Box<dyn ScheduleLabel> { ... }
fn as_dyn_eq(&self) -> &dyn DynEq {
self
}
// No, `mut state: &mut` is not a typo.
fn dyn_hash(&self, mut state: &mut dyn Hasher) {
self.hash(&mut state);
// Hashing the TypeId isn't strictly necessary, but it prevents collisions.
TypeId::of::<Self>().hash(&mut state);
}
}
```
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