Trivially replace Box::pin with pin! in a few places

Now that our MSRV is above 1.68 we can use the `pin!` macro to
avoid having to `Box` various futures, avoiding some allocations,
especially in `lightning-net-tokio`, which happens in a tight loop.

Author: TheBlueMatt

lightning-liquidity/src/lsps2/service.rs

@@ -9,14 +9,14 @@
 
 //! Contains the main bLIP-52 / LSPS2 server-side object, [`LSPS2ServiceHandler`].
 
-use alloc::boxed::Box;
 use alloc::string::{String, ToString};
 use alloc::vec::Vec;
 use lightning::util::persist::KVStore;
 
 use core::cmp::Ordering as CmpOrdering;
 use core::future::Future as StdFuture;
 use core::ops::Deref;
+use core::pin::pin;
 use core::sync::atomic::{AtomicUsize, Ordering};
 use core::task;
 
@@ -2169,7 +2169,7 @@ where
 		&self, counterparty_node_id: &PublicKey, request_id: LSPSRequestId, intercept_scid: u64,
 		cltv_expiry_delta: u32, client_trusts_lsp: bool, user_channel_id: u128,
 	) -> Result<(), APIError> {
-		let mut fut = Box::pin(self.inner.invoice_parameters_generated(
+		let mut fut = pin!(self.inner.invoice_parameters_generated(
 			counterparty_node_id,
 			request_id,
 			intercept_scid,
@@ -2198,7 +2198,7 @@ where
 		&self, intercept_scid: u64, intercept_id: InterceptId, expected_outbound_amount_msat: u64,
 		payment_hash: PaymentHash,
 	) -> Result<(), APIError> {
-		let mut fut = Box::pin(self.inner.htlc_intercepted(
+		let mut fut = pin!(self.inner.htlc_intercepted(
 			intercept_scid,
 			intercept_id,
 			expected_outbound_amount_msat,
@@ -2224,7 +2224,7 @@ where
 	pub fn htlc_handling_failed(
 		&self, failure_type: HTLCHandlingFailureType,
 	) -> Result<(), APIError> {
-		let mut fut = Box::pin(self.inner.htlc_handling_failed(failure_type));
+		let mut fut = pin!(self.inner.htlc_handling_failed(failure_type));
 
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
@@ -2245,7 +2245,7 @@ where
 	pub fn payment_forwarded(
 		&self, next_channel_id: ChannelId, skimmed_fee_msat: u64,
 	) -> Result<(), APIError> {
-		let mut fut = Box::pin(self.inner.payment_forwarded(next_channel_id, skimmed_fee_msat));
+		let mut fut = pin!(self.inner.payment_forwarded(next_channel_id, skimmed_fee_msat));
 
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
@@ -2286,7 +2286,7 @@ where
 		&self, counterparty_node_id: &PublicKey, user_channel_id: u128,
 	) -> Result<(), APIError> {
 		let mut fut =
-			Box::pin(self.inner.channel_open_abandoned(counterparty_node_id, user_channel_id));
+			pin!(self.inner.channel_open_abandoned(counterparty_node_id, user_channel_id));
 
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
@@ -2305,8 +2305,7 @@ where
 	pub fn channel_open_failed(
 		&self, counterparty_node_id: &PublicKey, user_channel_id: u128,
 	) -> Result<(), APIError> {
-		let mut fut =
-			Box::pin(self.inner.channel_open_failed(counterparty_node_id, user_channel_id));
+		let mut fut = pin!(self.inner.channel_open_failed(counterparty_node_id, user_channel_id));
 
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
@@ -2328,7 +2327,7 @@ where
 		&self, user_channel_id: u128, channel_id: &ChannelId, counterparty_node_id: &PublicKey,
 	) -> Result<(), APIError> {
 		let mut fut =
-			Box::pin(self.inner.channel_ready(user_channel_id, channel_id, counterparty_node_id));
+			pin!(self.inner.channel_ready(user_channel_id, channel_id, counterparty_node_id));
 
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);

lightning-liquidity/src/manager.rs

@@ -7,7 +7,6 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
-use alloc::boxed::Box;
 use alloc::string::ToString;
 use alloc::vec::Vec;
 
@@ -61,6 +60,7 @@ use bitcoin::secp256k1::PublicKey;
 
 use core::future::Future as StdFuture;
 use core::ops::Deref;
+use core::pin::pin;
 use core::task;
 
 const LSPS_FEATURE_BIT: usize = 729;
@@ -1106,7 +1106,7 @@ where
 	) -> Result<Self, lightning::io::Error> {
 		let kv_store = KVStoreSyncWrapper(kv_store_sync);
 
-		let mut fut = Box::pin(LiquidityManager::new(
+		let mut fut = pin!(LiquidityManager::new(
 			entropy_source,
 			node_signer,
 			channel_manager,
@@ -1159,7 +1159,7 @@ where
 		client_config: Option<LiquidityClientConfig>, time_provider: TP,
 	) -> Result<Self, lightning::io::Error> {
 		let kv_store = KVStoreSyncWrapper(kv_store_sync);
-		let mut fut = Box::pin(LiquidityManager::new_with_custom_time_provider(
+		let mut fut = pin!(LiquidityManager::new_with_custom_time_provider(
 			entropy_source,
 			node_signer,
 			channel_manager,
@@ -1289,7 +1289,7 @@ where
 	pub fn persist(&self) -> Result<(), lightning::io::Error> {
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
-		match Box::pin(self.inner.persist()).as_mut().poll(&mut ctx) {
+		match pin!(self.inner.persist()).as_mut().poll(&mut ctx) {
 			task::Poll::Ready(result) => result,
 			task::Poll::Pending => {
 				// In a sync context, we can't wait for the future to complete.

lightning-net-tokio/src/lib.rs

@@ -43,7 +43,7 @@ use std::hash::Hash;
 use std::net::SocketAddr;
 use std::net::TcpStream as StdTcpStream;
 use std::ops::Deref;
-use std::pin::Pin;
+use std::pin::{pin, Pin};
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, Mutex};
 use std::task::{self, Poll};
@@ -205,18 +205,17 @@ impl Connection {
 				}
 				us_lock.read_paused
 			};
-			// TODO: Drop the Box'ing of the futures once Rust has pin-on-stack support.
 			let select_result = if read_paused {
 				TwoSelector {
-					a: Box::pin(write_avail_receiver.recv()),
-					b: Box::pin(read_wake_receiver.recv()),
+					a: pin!(write_avail_receiver.recv()),
+					b: pin!(read_wake_receiver.recv()),
 				}
 				.await
 			} else {
 				ThreeSelector {
-					a: Box::pin(write_avail_receiver.recv()),
-					b: Box::pin(read_wake_receiver.recv()),
-					c: Box::pin(reader.readable()),
+					a: pin!(write_avail_receiver.recv()),
+					b: pin!(read_wake_receiver.recv()),
+					c: pin!(reader.readable()),
 				}
 				.await
 			};

lightning/src/events/bump_transaction/sync.rs

@@ -11,6 +11,7 @@
 
 use core::future::Future;
 use core::ops::Deref;
+use core::pin::pin;
 use core::task;
 
 use crate::chain::chaininterface::BroadcasterInterface;
@@ -220,7 +221,7 @@ where
 
 	/// Handles all variants of [`BumpTransactionEvent`].
 	pub fn handle_event(&self, event: &BumpTransactionEvent) {
-		let mut fut = Box::pin(self.bump_transaction_event_handler.handle_event(event));
+		let mut fut = pin!(self.bump_transaction_event_handler.handle_event(event));
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
 		match fut.as_mut().poll(&mut ctx) {

lightning/src/util/persist.rs

@@ -19,7 +19,7 @@ use bitcoin::{BlockHash, Txid};
 use core::future::Future;
 use core::mem;
 use core::ops::Deref;
-use core::pin::Pin;
+use core::pin::{pin, Pin};
 use core::str::FromStr;
 use core::task;
 
@@ -413,8 +413,7 @@ impl FutureSpawner for PanicingSpawner {
 fn poll_sync_future<F: Future>(future: F) -> F::Output {
 	let mut waker = dummy_waker();
 	let mut ctx = task::Context::from_waker(&mut waker);
-	// TODO A future MSRV bump to 1.68 should allow for the pin macro
-	match Pin::new(&mut Box::pin(future)).poll(&mut ctx) {
+	match pin!(future).poll(&mut ctx) {
 		task::Poll::Ready(result) => result,
 		task::Poll::Pending => {
 			// In a sync context, we can't wait for the future to complete.

lightning/src/util/sweep.rs

@@ -35,6 +35,7 @@ use bitcoin::{BlockHash, ScriptBuf, Transaction, Txid};
 
 use core::future::Future;
 use core::ops::Deref;
+use core::pin::pin;
 use core::sync::atomic::{AtomicBool, Ordering};
 use core::task;
 
@@ -930,7 +931,7 @@ where
 		&self, output_descriptors: Vec<SpendableOutputDescriptor>, channel_id: Option<ChannelId>,
 		exclude_static_outputs: bool, delay_until_height: Option<u32>,
 	) -> Result<(), ()> {
-		let mut fut = Box::pin(self.sweeper.track_spendable_outputs(
+		let mut fut = pin!(self.sweeper.track_spendable_outputs(
 			output_descriptors,
 			channel_id,
 			exclude_static_outputs,
@@ -961,7 +962,7 @@ where
 	/// Regenerates and broadcasts the spending transaction for any outputs that are pending. Wraps
 	/// [`OutputSweeper::regenerate_and_broadcast_spend_if_necessary`].
 	pub fn regenerate_and_broadcast_spend_if_necessary(&self) -> Result<(), ()> {
-		let mut fut = Box::pin(self.sweeper.regenerate_and_broadcast_spend_if_necessary());
+		let mut fut = pin!(self.sweeper.regenerate_and_broadcast_spend_if_necessary());
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
 		match fut.as_mut().poll(&mut ctx) {