update docs/comments

crates/bevy_ecs/src/system/commands/command_queue.rs

@@ -25,7 +25,7 @@ pub(crate) struct CommandQueueInner {
 // SAFE: All commands [`Command`] implement [`Send`]
 unsafe impl Send for CommandQueueInner {}
 
-// SAFE: All commands [`Command`] implement [`Sync`]
+// SAFE: `&CommandQueueInner` never gives access to the inner commands.
 unsafe impl Sync for CommandQueueInner {}
 
 impl CommandQueueInner {
@@ -64,13 +64,7 @@ impl CommandQueueInner {
     }
 
     /// Invoke each command `func` for each inserted value with `world`
-    /// and then clears the internal bytes/metas vectors.
-    ///
-    /// # Warning
-    ///
-    /// This does not [`drop`] the pushed commands.
-    /// If the command should be dropped, the initially provided `func`
-    /// should ensure any necessary cleanup occurs.
+    /// and then clears the internal bytes/metas command vectors.
     pub fn apply(&mut self, world: &mut World) {
         let byte_ptr = self.bytes.as_mut_ptr();
         for meta in self.metas.iter() {

crates/bevy_ecs/src/system/commands/mod.rs

@@ -11,6 +11,10 @@ use command_queue::CommandQueueInner;
 use std::marker::PhantomData;
 
 /// A [`World`] mutation.
+//
+// NOTE: `CommandQueueInner` is `Send` because `Command` is send.
+// If the `Command` trait gets reworked to be non-send, `CommandQueueInner`
+// should be reworked.
 pub trait Command: Send + Sync + 'static {
     fn write(self, world: &mut World);
 }