Remove outpoint_to_peer map in ChannelManager

Now that we require `ChannelMonitor`s to track the channel's
counterparty node ID, we can remove the `outpoint_to_peer` map that was
used throughout `MonitorEvent` handling. This is a big win for a
post-splicing future, as we'll no longer have to bother updating this
map when a splice is proposed.

Some existing tests providing coverage have been removed as a result.

Author: wpaulino

lightning/src/ln/async_signer_tests.rs

@@ -18,7 +18,6 @@ use bitcoin::transaction::Version;
 
 use crate::chain::channelmonitor::LATENCY_GRACE_PERIOD_BLOCKS;
 use crate::chain::ChannelMonitorUpdateStatus;
-use crate::chain::transaction::OutPoint;
 use crate::events::bump_transaction::WalletSource;
 use crate::events::{ClosureReason, Event};
 use crate::ln::chan_utils::ClosingTransaction;
@@ -1091,9 +1090,4 @@ fn do_test_closing_signed(extra_closing_signed: bool, reconnect: bool) {
 	assert!(nodes[1].node.list_channels().is_empty());
 	check_closed_event!(nodes[0], 1, ClosureReason::LocallyInitiatedCooperativeClosure, [nodes[1].node.get_our_node_id()], 100000);
 	check_closed_event!(nodes[1], 1, ClosureReason::CounterpartyInitiatedCooperativeClosure, [nodes[0].node.get_our_node_id()], 100000);
-
-	// Check that our maps have been updated after async signing channel closure.
-	let funding_outpoint = OutPoint { txid: funding_tx.compute_txid(), index: 0 };
-	assert!(nodes[0].node().outpoint_to_peer.lock().unwrap().get(&funding_outpoint).is_none());
-	assert!(nodes[1].node().outpoint_to_peer.lock().unwrap().get(&funding_outpoint).is_none());
 }

lightning/src/ln/channel.rs

@@ -3453,6 +3453,24 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
 			!matches!(self.channel_state, ChannelState::AwaitingChannelReady(flags) if flags.is_set(AwaitingChannelReadyFlags::WAITING_FOR_BATCH))
 	}
 
+	/// Unsets the existing funding information.
+	///
+	/// This must only be used if the channel has not yet completed funding and has not been used.
+	///
+	/// Further, the channel must be immediately shut down after this with a call to
+	/// [`ChannelContext::force_shutdown`].
+	pub fn unset_funding_info(&mut self, funding: &mut FundingScope) {
+		debug_assert!(
+			matches!(self.channel_state, ChannelState::FundingNegotiated)
+				|| matches!(self.channel_state, ChannelState::AwaitingChannelReady(_))
+		);
+		funding.channel_transaction_parameters.funding_outpoint = None;
+		self.channel_id = self.temporary_channel_id.expect(
+			"temporary_channel_id should be set since unset_funding_info is only called on funded \
+			 channels that were unfunded immediately beforehand"
+		);
+	}
+
 	/// Transaction nomenclature is somewhat confusing here as there are many different cases - a
 	/// transaction is referred to as "a's transaction" implying that a will be able to broadcast
 	/// the transaction. Thus, b will generally be sending a signature over such a transaction to
@@ -5165,23 +5183,6 @@ impl<SP: Deref> FundedChannel<SP> where
 		self.context.channel_state.clear_waiting_for_batch();
 	}
 
-	/// Unsets the existing funding information.
-	///
-	/// This must only be used if the channel has not yet completed funding and has not been used.
-	///
-	/// Further, the channel must be immediately shut down after this with a call to
-	/// [`ChannelContext::force_shutdown`].
-	pub fn unset_funding_info(&mut self) {
-		debug_assert!(matches!(
-			self.context.channel_state, ChannelState::AwaitingChannelReady(_)
-		));
-		self.funding.channel_transaction_parameters.funding_outpoint = None;
-		self.context.channel_id = self.context.temporary_channel_id.expect(
-			"temporary_channel_id should be set since unset_funding_info is only called on funded \
-			 channels that were unfunded immediately beforehand"
-		);
-	}
-
 	/// Handles a channel_ready message from our peer. If we've already sent our channel_ready
 	/// and the channel is now usable (and public), this may generate an announcement_signatures to
 	/// reply with.