f comments

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -916,7 +916,15 @@ macro_rules! handle_chan_restoration_locked {
 			macro_rules! handle_cs { () => {
 				if let Some(monitor_update) = chanmon_update {
 					assert!($order == RAACommitmentOrder::RevokeAndACKFirst);
+					// We only ever broadcast a funding transaction in response to a funding_signed
+					// message and the resulting monitor update. Thus, on channel_reestablish
+					// message handling we can't have a funding transaction to broadcast. When
+					// processing a monitor update finishing resulting in a funding broadcast, we
+					// cannot have a second monitor update, thus this case would indicate a bug.
 					assert!(funding_broadcastable.is_none());
+					// Given we were just reconnected or finished updating a channel monitor, the
+					// only case where we can get a new ChannelMonitorUpdate would be if we also
+					// have some commitment updates to send as well.
 					assert!($commitment_update.is_some());
 					if let Err(e) = $self.chain_monitor.update_channel($channel_entry.get().get_funding_txo().unwrap(), monitor_update) {
 						break handle_monitor_err!($self, e, $channel_state, $channel_entry, RAACommitmentOrder::CommitmentFirst, false, true);