Stop relying on Hash{Set,Map}::from_iter directly

In the next commit we'll bump the `hashbrown` version, which no
longer randomizes its hasher by default. Thus, we'll need to call
a different constructor in no-std builds from std builds.

Here we do a quick prefactor to use wrappers for `FromIterator`
constructors instead of calling the tables directly to make the
version bump changeset smaller.

Author: TheBlueMatt

lightning/src/chain/chainmonitor.rs

@@ -42,7 +42,6 @@ use crate::ln::channelmanager::ChannelDetails;
 
 use crate::prelude::*;
 use crate::sync::{RwLock, RwLockReadGuard, Mutex, MutexGuard};
-use core::iter::FromIterator;
 use core::ops::Deref;
 use core::sync::atomic::{AtomicUsize, Ordering};
 use bitcoin::secp256k1::PublicKey;
@@ -317,7 +316,7 @@ where C::Target: chain::Filter,
 		FN: Fn(&ChannelMonitor<ChannelSigner>, &TransactionData) -> Vec<TransactionOutputs>
 	{
 		let err_str = "ChannelMonitor[Update] persistence failed unrecoverably. This indicates we cannot continue normal operation and must shut down.";
-		let funding_outpoints: HashSet<OutPoint> = HashSet::from_iter(self.monitors.read().unwrap().keys().cloned());
+		let funding_outpoints = hash_set_from_iter(self.monitors.read().unwrap().keys().cloned());
 		for funding_outpoint in funding_outpoints.iter() {
 			let monitor_lock = self.monitors.read().unwrap();
 			if let Some(monitor_state) = monitor_lock.get(funding_outpoint) {
@@ -482,9 +481,15 @@ where C::Target: chain::Filter,
 	#[cfg(not(c_bindings))]
 	/// Lists the pending updates for each [`ChannelMonitor`] (by `OutPoint` being monitored).
 	pub fn list_pending_monitor_updates(&self) -> HashMap<OutPoint, Vec<MonitorUpdateId>> {
-		self.monitors.read().unwrap().iter().map(|(outpoint, holder)| {
+		let monitors = self.monitors.read().unwrap();
+		let mut updates = hash_map_with_capacity(monitors.len());
+		let pending_updates = monitors.iter().map(|(outpoint, holder)| {
 			(*outpoint, holder.pending_monitor_updates.lock().unwrap().clone())
-		}).collect()
+		});
+		for (funding_txo, chan_updates) in pending_updates {
+			updates.insert(funding_txo, chan_updates);
+		}
+		updates
 	}
 
 	#[cfg(c_bindings)]

lightning/src/lib.rs

@@ -201,6 +201,9 @@ mod prelude {
 	pub(crate) fn hash_set_with_capacity<K: core::hash::Hash + Eq>(cap: usize) -> HashSet<K> {
 		HashSet::with_capacity(cap)
 	}
+	pub(crate) fn hash_set_from_iter<K: core::hash::Hash + Eq, I: IntoIterator<Item = K>>(iter: I) -> HashSet<K> {
+		HashSet::from_iter(iter)
+	}
 
 	pub use alloc::borrow::ToOwned;
 	pub use alloc::string::ToString;

lightning/src/ln/channelmanager.rs

@@ -10727,7 +10727,7 @@ where
 										retry_strategy: None,
 										attempts: PaymentAttempts::new(),
 										payment_params: None,
-										session_privs: [session_priv_bytes].iter().map(|a| *a).collect(),
+										session_privs: hash_set_from_iter([session_priv_bytes]),
 										payment_hash: htlc.payment_hash,
 										payment_secret: None, // only used for retries, and we'll never retry on startup
 										payment_metadata: None, // only used for retries, and we'll never retry on startup