# Objective
The type `SyncCell<T>` (added in #5483) is used to force any wrapped type to be `Sync`, by only allowing exclusive access to the wrapped value. This restriction is unnecessary for types which are already `Sync`.
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## Changelog
+ Added the method `read` to `SyncCell`, which allows shared access to values that already implement the `Sync` trait.
# Objective
Partially address #3492.
## Solution
Document the remaining undocumented members of `bevy_utils` and set `warn(missing_docs)` on the crate level. Also enabled `clippy::undocumented_unsafe_blocks` as a warning on the crate to keep it in sync with `bevy_ecs`'s warnings.
# Objective
Currently, `Local` has a `Sync` bound. Theoretically this is unnecessary as a local can only ever be accessed from its own system, ensuring exclusive access on one thread. This PR removes this restriction.
## Solution
- By removing the `Resource` bound from `Local` and adding the new `SyncCell` threading primative, `Local` can have the `Sync` bound removed.
## Changelog
### Added
- Added `SyncCell` to `bevy_utils`
### Changed
- Removed `Resource` bound from `Local`
- `Local` is now wrapped in a `SyncCell`
## Migration Guide
- Any code relying on `Local<T>` having `T: Resource` may have to be changed, but this is unlikely.
Co-authored-by: PROMETHIA-27 <42193387+PROMETHIA-27@users.noreply.github.com>
