Drop Deref indirection for UtxoLookup

Reduces generics and verbosity across the codebase, should provide equivalent
behavior.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: valentinewallace

lightning-background-processor/src/lib.rs

@@ -200,11 +200,9 @@ pub enum GossipSync<
 	P: Deref<Target = P2PGossipSync<G, U, L>>,
 	R: Deref<Target = RapidGossipSync<G, L>>,
 	G: Deref<Target = NetworkGraph<L>>,
-	U: Deref,
+	U: UtxoLookup,
 	L: Logger,
-> where
-	U::Target: UtxoLookup,
-{
+> {
 	/// Gossip sync via the lightning peer-to-peer network as defined by BOLT 7.
 	P2P(P),
 	/// Rapid gossip sync from a trusted server.
@@ -217,11 +215,9 @@ impl<
 		P: Deref<Target = P2PGossipSync<G, U, L>>,
 		R: Deref<Target = RapidGossipSync<G, L>>,
 		G: Deref<Target = NetworkGraph<L>>,
-		U: Deref,
+		U: UtxoLookup,
 		L: Logger,
 	> GossipSync<P, R, G, U, L>
-where
-	U::Target: UtxoLookup,
 {
 	fn network_graph(&self) -> Option<&G> {
 		match self {
@@ -258,11 +254,9 @@ where
 impl<
 		P: Deref<Target = P2PGossipSync<G, U, L>>,
 		G: Deref<Target = NetworkGraph<L>>,
-		U: Deref,
+		U: UtxoLookup,
 		L: Logger,
 	> GossipSync<P, &RapidGossipSync<G, L>, G, U, L>
-where
-	U::Target: UtxoLookup,
 {
 	/// Initializes a new [`GossipSync::P2P`] variant.
 	pub fn p2p(gossip_sync: P) -> Self {
@@ -928,7 +922,7 @@ use futures_util::{dummy_waker, Joiner, OptionalSelector, Selector, SelectorOutp
 ///```
 pub async fn process_events_async<
 	'a,
-	UL: Deref,
+	UL: UtxoLookup,
 	CF: chain::Filter,
 	T: BroadcasterInterface,
 	F: FeeEstimator,
@@ -961,7 +955,6 @@ pub async fn process_events_async<
 	sleeper: Sleeper, mobile_interruptable_platform: bool, fetch_time: FetchTime,
 ) -> Result<(), lightning::io::Error>
 where
-	UL::Target: UtxoLookup,
 	P::Target: Persist<<CM::Target as AChannelManager>::Signer>,
 	CM::Target: AChannelManager,
 	OM::Target: AOnionMessenger,
@@ -1422,7 +1415,7 @@ fn check_and_reset_sleeper<
 /// Async events processor that is based on [`process_events_async`] but allows for [`KVStoreSync`] to be used for
 /// synchronous background persistence.
 pub async fn process_events_async_with_kv_store_sync<
-	UL: Deref,
+	UL: UtxoLookup,
 	CF: chain::Filter,
 	T: BroadcasterInterface,
 	F: FeeEstimator,
@@ -1455,7 +1448,6 @@ pub async fn process_events_async_with_kv_store_sync<
 	sleeper: Sleeper, mobile_interruptable_platform: bool, fetch_time: FetchTime,
 ) -> Result<(), lightning::io::Error>
 where
-	UL::Target: UtxoLookup,
 	P::Target: Persist<<CM::Target as AChannelManager>::Signer>,
 	CM::Target: AChannelManager,
 	OM::Target: AOnionMessenger,
@@ -1530,7 +1522,7 @@ impl BackgroundProcessor {
 	/// [`NetworkGraph::write`]: lightning::routing::gossip::NetworkGraph#impl-Writeable
 	pub fn start<
 		'a,
-		UL: 'static + Deref,
+		UL: 'static + UtxoLookup,
 		CF: 'static + chain::Filter,
 		T: 'static + BroadcasterInterface,
 		F: 'static + FeeEstimator + Send,
@@ -1563,7 +1555,6 @@ impl BackgroundProcessor {
 		liquidity_manager: Option<LM>, sweeper: Option<OS>, logger: L, scorer: Option<S>,
 	) -> Self
 	where
-		UL::Target: 'static + UtxoLookup,
 		L::Target: 'static + Logger,
 		P::Target: 'static + Persist<<CM::Target as AChannelManager>::Signer>,
 		ES::Target: 'static + EntropySource,

lightning-block-sync/src/gossip.rs

@@ -239,16 +239,6 @@ where
 	}
 }
 
-impl<S: FutureSpawner, Blocks: Deref + Send + Sync + Clone> Deref for GossipVerifier<S, Blocks>
-where
-	Blocks::Target: UtxoSource,
-{
-	type Target = Self;
-	fn deref(&self) -> &Self {
-		self
-	}
-}
-
 impl<S: FutureSpawner, Blocks: Deref + Send + Sync + Clone> UtxoLookup for GossipVerifier<S, Blocks>
 where
 	Blocks::Target: UtxoSource,

lightning/src/routing/gossip.rs

@@ -319,10 +319,7 @@ impl MaybeReadable for NetworkUpdate {
 /// This network graph is then used for routing payments.
 /// Provides interface to help with initial routing sync by
 /// serving historical announcements.
-pub struct P2PGossipSync<G: Deref<Target = NetworkGraph<L>>, U: Deref, L: Logger>
-where
-	U::Target: UtxoLookup,
-{
+pub struct P2PGossipSync<G: Deref<Target = NetworkGraph<L>>, U: UtxoLookup, L: Logger> {
 	network_graph: G,
 	#[cfg(any(feature = "_test_utils", test))]
 	pub(super) utxo_lookup: Option<U>,
@@ -333,10 +330,7 @@ where
 	logger: L,
 }
 
-impl<G: Deref<Target = NetworkGraph<L>>, U: Deref, L: Logger> P2PGossipSync<G, U, L>
-where
-	U::Target: UtxoLookup,
-{
+impl<G: Deref<Target = NetworkGraph<L>>, U: UtxoLookup, L: Logger> P2PGossipSync<G, U, L> {
 	/// Creates a new tracker of the actual state of the network of channels and nodes,
 	/// assuming an existing [`NetworkGraph`].
 	///
@@ -534,10 +528,8 @@ pub fn verify_channel_announcement<C: Verification>(
 	Ok(())
 }
 
-impl<G: Deref<Target = NetworkGraph<L>>, U: Deref, L: Logger> RoutingMessageHandler
+impl<G: Deref<Target = NetworkGraph<L>>, U: UtxoLookup, L: Logger> RoutingMessageHandler
 	for P2PGossipSync<G, U, L>
-where
-	U::Target: UtxoLookup,
 {
 	fn handle_node_announcement(
 		&self, _their_node_id: Option<PublicKey>, msg: &msgs::NodeAnnouncement,
@@ -761,10 +753,8 @@ where
 	}
 }
 
-impl<G: Deref<Target = NetworkGraph<L>>, U: Deref, L: Logger> BaseMessageHandler
+impl<G: Deref<Target = NetworkGraph<L>>, U: UtxoLookup, L: Logger> BaseMessageHandler
 	for P2PGossipSync<G, U, L>
-where
-	U::Target: UtxoLookup,
 {
 	/// Initiates a stateless sync of routing gossip information with a peer
 	/// using [`gossip_queries`]. The default strategy used by this implementation
@@ -1951,12 +1941,9 @@ impl<L: Logger> NetworkGraph<L> {
 	///
 	/// If a [`UtxoLookup`] object is provided via `utxo_lookup`, it will be called to verify
 	/// the corresponding UTXO exists on chain and is correctly-formatted.
-	pub fn update_channel_from_announcement<U: Deref>(
+	pub fn update_channel_from_announcement<U: UtxoLookup>(
 		&self, msg: &msgs::ChannelAnnouncement, utxo_lookup: &Option<U>,
-	) -> Result<(), LightningError>
-	where
-		U::Target: UtxoLookup,
-	{
+	) -> Result<(), LightningError> {
 		self.pre_channel_announcement_validation_check(&msg.contents, utxo_lookup)?;
 		verify_channel_announcement(msg, &self.secp_ctx)?;
 		self.update_channel_from_unsigned_announcement_intern(&msg.contents, Some(msg), utxo_lookup)
@@ -1981,12 +1968,9 @@ impl<L: Logger> NetworkGraph<L> {
 	///
 	/// If a [`UtxoLookup`] object is provided via `utxo_lookup`, it will be called to verify
 	/// the corresponding UTXO exists on chain and is correctly-formatted.
-	pub fn update_channel_from_unsigned_announcement<U: Deref>(
+	pub fn update_channel_from_unsigned_announcement<U: UtxoLookup>(
 		&self, msg: &msgs::UnsignedChannelAnnouncement, utxo_lookup: &Option<U>,
-	) -> Result<(), LightningError>
-	where
-		U::Target: UtxoLookup,
-	{
+	) -> Result<(), LightningError> {
 		self.pre_channel_announcement_validation_check(&msg, utxo_lookup)?;
 		self.update_channel_from_unsigned_announcement_intern(msg, None, utxo_lookup)
 	}
@@ -2105,12 +2089,9 @@ impl<L: Logger> NetworkGraph<L> {
 	///
 	/// In those cases, this will return an `Err` that we can return immediately. Otherwise it will
 	/// return an `Ok(())`.
-	fn pre_channel_announcement_validation_check<U: Deref>(
+	fn pre_channel_announcement_validation_check<U: UtxoLookup>(
 		&self, msg: &msgs::UnsignedChannelAnnouncement, utxo_lookup: &Option<U>,
-	) -> Result<(), LightningError>
-	where
-		U::Target: UtxoLookup,
-	{
+	) -> Result<(), LightningError> {
 		let channels = self.channels.read().unwrap();
 
 		if let Some(chan) = channels.get(&msg.short_channel_id) {
@@ -2149,13 +2130,10 @@ impl<L: Logger> NetworkGraph<L> {
 	///
 	/// Generally [`Self::pre_channel_announcement_validation_check`] should have been called
 	/// first.
-	fn update_channel_from_unsigned_announcement_intern<U: Deref>(
+	fn update_channel_from_unsigned_announcement_intern<U: UtxoLookup>(
 		&self, msg: &msgs::UnsignedChannelAnnouncement,
 		full_msg: Option<&msgs::ChannelAnnouncement>, utxo_lookup: &Option<U>,
-	) -> Result<(), LightningError>
-	where
-		U::Target: UtxoLookup,
-	{
+	) -> Result<(), LightningError> {
 		if msg.node_id_1 == msg.node_id_2 || msg.bitcoin_key_1 == msg.bitcoin_key_2 {
 			return Err(LightningError {
 				err: "Channel announcement node had a channel with itself".to_owned(),

lightning/src/routing/utxo.rs

@@ -75,6 +75,15 @@ pub trait UtxoLookup {
 	) -> UtxoResult;
 }
 
+impl<T: UtxoLookup + ?Sized, U: Deref<Target = T>> UtxoLookup for U {
+	fn get_utxo(
+		&self, chain_hash: &ChainHash, short_channel_id: u64,
+		async_completion_notifier: Arc<Notifier>,
+	) -> UtxoResult {
+		self.deref().get_utxo(chain_hash, short_channel_id, async_completion_notifier)
+	}
+}
+
 enum ChannelAnnouncement {
 	Full(msgs::ChannelAnnouncement),
 	Unsigned(msgs::UnsignedChannelAnnouncement),
@@ -332,10 +341,10 @@ impl PendingChecks {
 	}
 
 	#[rustfmt::skip]
-	pub(super) fn check_channel_announcement<U: Deref>(&self,
+	pub(super) fn check_channel_announcement<U: UtxoLookup>(&self,
 		utxo_lookup: &Option<U>, msg: &msgs::UnsignedChannelAnnouncement,
 		full_msg: Option<&msgs::ChannelAnnouncement>
-	) -> Result<Option<Amount>, msgs::LightningError> where U::Target: UtxoLookup {
+	) -> Result<Option<Amount>, msgs::LightningError> {
 		let handle_result = |res| {
 			match res {
 				Ok(TxOut { value, script_pubkey }) => {