Mark owned Repeated & Map types as Send & Sync.

PiperOrigin-RevId: 640063798

rust/map.rs

@@ -64,6 +64,13 @@ pub struct Map<K: ?Sized + Proxied, V: ?Sized + ProxiedInMapValue<K>> {
     _phantom: PhantomData<(PhantomData<K>, PhantomData<V>)>,
 }
 
+// SAFETY: `Map` is Sync because it does not implement interior mutability.
+unsafe impl<K: ?Sized + Proxied, V: ?Sized + ProxiedInMapValue<K>> Sync for Map<K, V> {}
+
+// SAFETY: `Map` is Send because it's not bound to a specific thread e.g.
+// it does not use thread-local data or similar.
+unsafe impl<K: ?Sized + Proxied, V: ?Sized + ProxiedInMapValue<K>> Send for Map<K, V> {}
+
 impl<K: ?Sized + Proxied, V: ?Sized + ProxiedInMapValue<K>> Drop for Map<K, V> {
     fn drop(&mut self) {
         // SAFETY:

rust/repeated.rs

@@ -341,6 +341,13 @@ pub struct Repeated<T: ?Sized + ProxiedInRepeated> {
     _phantom: PhantomData<T>,
 }
 
+// SAFETY: `Repeated` is Sync because it does not implement interior mutability.
+unsafe impl<T: ?Sized + ProxiedInRepeated> Sync for Repeated<T> {}
+
+// SAFETY: `Repeated` is Send because it's not bound to a specific thread e.g.
+// it does not use thread-local data or similar.
+unsafe impl<T: ?Sized + ProxiedInRepeated> Send for Repeated<T> {}
+
 impl<T: ?Sized + ProxiedInRepeated> Repeated<T> {
     pub fn new() -> Self {
         T::repeated_new(Private)
@@ -368,9 +375,6 @@ impl<T: ?Sized + ProxiedInRepeated> Drop for Repeated<T> {
     }
 }
 
-// SAFETY: `Repeated` does not allow for shared mutability.
-unsafe impl<T: ProxiedInRepeated> Sync for Repeated<T> {}
-
 impl<T> Proxied for Repeated<T>
 where
     T: ProxiedInRepeated + ?Sized,