Add internal docs for ChannelMonitor::payment_preimages

Author: TheBlueMatt

lightning/src/chain/channelmonitor.rs

@@ -655,6 +655,10 @@ pub(crate) struct ChannelMonitorImpl<Signer: Sign> {
 	// deserialization
 	current_holder_commitment_number: u64,
 
+	/// The set of payment hashes from inbound payments for which we know the preimage. Payment
+	/// preimages that are not included in any unrevoked local commitment transaction or unrevoked
+	/// remote commitment transactions are automatically removed when commitment transactions are
+	/// revoked.
 	payment_preimages: HashMap<PaymentHash, PaymentPreimage>,
 
 	// Note that `MonitorEvent`s MUST NOT be generated during update processing, only generated

lightning/src/ln/channel.rs

@@ -1703,11 +1703,11 @@ impl<Signer: Sign> Channel<Signer> {
 		make_funding_redeemscript(&self.get_holder_pubkeys().funding_pubkey, self.counterparty_funding_pubkey())
 	}
 
-	/// Claims an HTLC while we're disconnected from a peer, dropping the ChannelMonitorUpdate
+	/// Claims an HTLC while we're disconnected from a peer, dropping the [`ChannelMonitorUpdate`]
 	/// entirely.
 	///
-	/// The ChannelMonitor for this channel MUST be updated out-of-band with the preimage provided
-	/// (i.e. without calling [`crate::chain::Watch::update_channel`]).
+	/// The [`ChannelMonitor`] for this channel MUST be updated out-of-band with the preimage
+	/// provided (i.e. without calling [`crate::chain::Watch::update_channel`]).
 	///
 	/// The HTLC claim will end up in the holding cell (because the caller must ensure the peer is
 	/// disconnected).

lightning/src/ln/channelmanager.rs

@@ -414,7 +414,9 @@ pub(super) struct ChannelHolder<Signer: Sign> {
 	/// guarantees are made about the existence of a channel with the short id here, nor the short
 	/// ids in the PendingHTLCInfo!
 	pub(super) forward_htlcs: HashMap<u64, Vec<HTLCForwardInfo>>,
-	/// Map from payment hash to any HTLCs which are to us and can be failed/claimed by the user.
+	/// Map from payment hash to the payment data and any HTLCs which are to us and can be
+	/// failed/claimed by the user.
+	///
 	/// Note that while this is held in the same mutex as the channels themselves, no consistency
 	/// guarantees are made about the channels given here actually existing anymore by the time you
 	/// go to read them!