Update for clippy 1.50 (#2193)

## Issue Addressed

NA

## Proposed Changes

Rust 1.50 has landed 🎉

The shiny new `clippy` peers down upon us mere mortals with disgust. Brutish peasants wrapping our `usize`s in superfluous `Option`s... tsk tsk.

I've performed the goat sacrifice and corrected our evil ways in this PR. Tonight we shall pray that Github Actions bestows the almighty green tick upon us.

## Additional Info

NA


Co-authored-by: realbigsean <seananderson33@gmail.com>
Co-authored-by: Michael Sproul <michael@sigmaprime.io>

beacon_node/network/src/attestation_service/mod.rs

@@ -584,13 +584,13 @@ impl<T: BeaconChainTypes> AttestationService<T> {
     /// We don't keep track of a specific validator to random subnet, rather the ratio of active
     /// validators to random subnets. So when a validator goes offline, we can simply remove the
     /// allocated amount of random subnets.
-    fn handle_known_validator_expiry(&mut self) -> Result<(), ()> {
+    fn handle_known_validator_expiry(&mut self) {
         let spec = &self.beacon_chain.spec;
         let subnet_count = spec.attestation_subnet_count;
         let random_subnets_per_validator = spec.random_subnets_per_validator;
         if self.known_validators.len() as u64 * random_subnets_per_validator >= subnet_count {
             // have too many validators, ignore
-            return Ok(());
+            return;
         }
 
         let subscribed_subnets = self.random_subnets.keys().cloned().collect::<Vec<_>>();
@@ -616,7 +616,6 @@ impl<T: BeaconChainTypes> AttestationService<T> {
                 .push_back(AttServiceMessage::EnrRemove(*subnet_id));
             self.random_subnets.remove(subnet_id);
         }
-        Ok(())
     }
 }
 

beacon_node/network/src/attestation_service/tests/mod.rs

@@ -203,7 +203,11 @@ async fn subscribe_current_slot_wait_for_unsubscribe() {
     let events = get_events(&mut attestation_service, None, 1).await;
     assert_matches!(
         events[..3],
-        [AttServiceMessage::DiscoverPeers(_), AttServiceMessage::Subscribe(_any1), AttServiceMessage::EnrAdd(_any3)]
+        [
+            AttServiceMessage::DiscoverPeers(_),
+            AttServiceMessage::Subscribe(_any1),
+            AttServiceMessage::EnrAdd(_any3)
+        ]
     );
 
     // If the long lived and short lived subnets are the same, there should be no more events
@@ -281,7 +285,11 @@ async fn test_same_subnet_unsubscription() {
     let events = get_events(&mut attestation_service, None, 1).await;
     assert_matches!(
         events[..3],
-        [AttServiceMessage::DiscoverPeers(_), AttServiceMessage::Subscribe(_any1), AttServiceMessage::EnrAdd(_any3)]
+        [
+            AttServiceMessage::DiscoverPeers(_),
+            AttServiceMessage::Subscribe(_any1),
+            AttServiceMessage::EnrAdd(_any3)
+        ]
     );
 
     let expected = AttServiceMessage::Subscribe(subnet_id1);

beacon_node/network/src/nat.rs

@@ -52,11 +52,7 @@ pub fn construct_upnp_mappings<T: EthSpec>(
                 // Just use the first IP of the first interface that is not a loopback and not an
                 // ipv6 address.
                 if !interface.is_loopback() {
-                    if let IpAddr::V4(_) = interface.ip() {
-                        Some(interface.ip())
-                    } else {
-                        None
-                    }
+                    interface.ip().is_ipv4().then(|| interface.ip())
                 } else {
                     None
                 }

beacon_node/network/src/service.rs

@@ -219,7 +219,7 @@ impl<T: BeaconChainTypes> NetworkService<T> {
             log: network_log,
         };
 
-        spawn_service(executor, network_service)?;
+        spawn_service(executor, network_service);
 
         Ok((network_globals, network_send))
     }
@@ -228,7 +228,7 @@ impl<T: BeaconChainTypes> NetworkService<T> {
 fn spawn_service<T: BeaconChainTypes>(
     executor: task_executor::TaskExecutor,
     mut service: NetworkService<T>,
-) -> error::Result<()> {
+) {
     let mut exit_rx = executor.exit();
     let mut shutdown_sender = executor.shutdown_sender();
 
@@ -570,8 +570,6 @@ fn spawn_service<T: BeaconChainTypes>(
             metrics::update_bandwidth_metrics(service.libp2p.bandwidth.clone());
         }
     }, "network");
-
-    Ok(())
 }
 
 /// Returns a `Sleep` that triggers shortly after the next change in the beacon chain fork version.