rtic-sync: improve some more docs

Author: datdenkikniet

rtic-sync/src/channel/channel.rs

@@ -18,10 +18,14 @@ use super::{Receiver, Sender};
 pub(crate) type WaitQueueData = (Waker, FreeSlotPtr);
 pub(crate) type WaitQueue = DoublyLinkedList<WaitQueueData>;
 
+/// A free slot.
 #[derive(Debug)]
 pub(crate) struct FreeSlot(u8);
 
 /// A pointer to a free slot.
+///
+/// This struct exists to enforce lifetime/safety requirements, and to ensure
+/// that [`FreeSlot`]s can only be created/updated by this module.
 #[derive(Clone)]
 pub(crate) struct FreeSlotPtr(*mut Option<FreeSlot>);
 

rtic-sync/src/channel/sender.rs

@@ -171,7 +171,7 @@ impl<T, const N: usize> Sender<'_, T, N> {
 
                         // If our link is popped, then:
                         // 1. We were popped by `return_free_lot` and provided us with a slot.
-                        // 2. We were popped by `Receiver::drop` and it did not provide us with a slot, and the channel is closed.
+                        // 2. We were popped by `drop_receiver` and it did not provide us with a slot, and the channel is closed.
                         if let Some(slot) = slot {
                             Poll::Ready(Ok(slot))
                         } else {