New rust lints for rustc 1.64.0 (#3602)

## Issue Addressed
fixes lints from the last rust release

## Proposed Changes
Fix the lints, most of the lints by `clippy::question-mark` are false positives in the form of https://github.com/rust-lang/rust-clippy/issues/9518 so it's allowed for now

## Additional Info

Makefile

@@ -153,7 +153,8 @@ lint:
 		-A clippy::derive_partial_eq_without_eq \
 		-A clippy::from-over-into \
 		-A clippy::upper-case-acronyms \
-		-A clippy::vec-init-then-push
+		-A clippy::vec-init-then-push \
+	    -A clippy::question-mark
 
 nightly-lint:
 	cp .github/custom/clippy.toml .

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -809,7 +809,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
 
             if let Some(request_root) = request_root_opt {
                 if let Ok(prev_root) = state.get_block_root(prev_slot) {
-                    return Ok(Some((*prev_root != request_root).then(|| request_root)));
+                    return Ok(Some((*prev_root != request_root).then_some(request_root)));
                 }
             }
 
@@ -831,7 +831,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                     slot: curr_slot,
                 });
             }
-            Ok((curr_root != prev_root).then(|| curr_root))
+            Ok((curr_root != prev_root).then_some(curr_root))
         } else {
             Ok(None)
         }
@@ -2871,7 +2871,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 .pubkeys
                 .iter()
                 .zip(sync_aggregate.sync_committee_bits.iter())
-                .filter_map(|(pubkey, bit)| bit.then(|| pubkey))
+                .filter_map(|(pubkey, bit)| bit.then_some(pubkey))
                 .collect::<Vec<_>>();
 
             validator_monitor.register_sync_aggregate_in_block(

beacon_node/beacon_chain/src/schema_change/migration_schema_v7.rs

@@ -212,7 +212,7 @@ fn map_relevant_epochs_to_roots<T: BeaconChainTypes>(
 
         let root = iter
             .find_map(|next| match next {
-                Ok((root, slot)) => (slot == start_slot).then(|| Ok(root)),
+                Ok((root, slot)) => (slot == start_slot).then_some(Ok(root)),
                 Err(e) => Some(Err(format!("{:?}", e))),
             })
             .transpose()?
@@ -286,7 +286,7 @@ fn find_finalized_descendant_heads(
         .filter_map(|(index, node)| {
             (!nodes_referenced_as_parents.contains(&index)
                 && fork_choice.is_descendant(finalized_root, node.root))
-            .then(|| HeadInfo {
+            .then_some(HeadInfo {
                 index,
                 root: node.root,
                 slot: node.slot,
@@ -306,7 +306,7 @@ fn update_store_justified_checkpoint(
         .filter_map(|node| {
             (node.finalized_checkpoint
                 == Some(persisted_fork_choice.fork_choice_store.finalized_checkpoint))
-            .then(|| node.justified_checkpoint)
+            .then_some(node.justified_checkpoint)
             .flatten()
         })
         .max_by_key(|justified_checkpoint| justified_checkpoint.epoch)

beacon_node/beacon_chain/src/sync_committee_verification.rs

@@ -343,7 +343,7 @@ impl<T: BeaconChainTypes> VerifiedSyncContribution<T> {
         let participant_pubkeys = sync_subcommittee_pubkeys
             .into_iter()
             .zip(contribution.aggregation_bits.iter())
-            .filter_map(|(pubkey, bit)| bit.then(|| pubkey))
+            .filter_map(|(pubkey, bit)| bit.then_some(pubkey))
             .collect::<Vec<_>>();
 
         // Ensure that all signatures are valid.

beacon_node/beacon_chain/src/test_utils.rs

@@ -1130,7 +1130,7 @@ where
                             selection_proof
                                 .is_aggregator::<E>()
                                 .expect("should determine aggregator")
-                                .then(|| validator_index)
+                                .then_some(validator_index)
                         })?;
 
                     let default = SyncCommitteeContribution::from_message(

beacon_node/http_api/src/lib.rs

@@ -2531,7 +2531,7 @@ pub fn serve<T: BeaconChainTypes>(
                                         || matches!(validator_status, ValidatorStatus::Active);
 
                                 // Filter out validators who are not 'active' or 'pending'.
-                                is_active_or_pending.then(|| {
+                                is_active_or_pending.then_some({
                                     (
                                         ProposerPreparationData {
                                             validator_index: validator_index as u64,

consensus/merkle_proof/src/lib.rs

@@ -100,9 +100,7 @@ impl MerkleTree {
                     (Leaf(_), Leaf(_)) => return Err(MerkleTreeError::MerkleTreeFull),
                     // There is a right node so insert in right node
                     (Node(_, _, _), Node(_, _, _)) => {
-                        if let Err(e) = right.push_leaf(elem, depth - 1) {
-                            return Err(e);
-                        }
+                        right.push_leaf(elem, depth - 1)?;
                     }
                     // Both branches are zero, insert in left one
                     (Zero(_), Zero(_)) => {

consensus/ssz_types/src/fixed_vector.rs

@@ -326,7 +326,7 @@ mod test {
 
         assert_eq!(fixed[0], 1);
         assert_eq!(&fixed[0..1], &vec[0..1]);
-        assert_eq!((&fixed[..]).len(), 8192);
+        assert_eq!((fixed[..]).len(), 8192);
 
         fixed[1] = 3;
         assert_eq!(fixed[1], 3);

consensus/ssz_types/src/variable_list.rs

@@ -308,7 +308,7 @@ mod test {
 
         assert_eq!(fixed[0], 1);
         assert_eq!(&fixed[0..1], &vec[0..1]);
-        assert_eq!((&fixed[..]).len(), 2);
+        assert_eq!((fixed[..]).len(), 2);
 
         fixed[1] = 3;
         assert_eq!(fixed[1], 3);

validator_client/src/preparation_service.rs

@@ -294,7 +294,7 @@ impl<T: SlotClock + 'static, E: EthSpec> PreparationService<T, E> {
             proposal_data.fee_recipient.and_then(|fee_recipient| {
                 proposal_data
                     .builder_proposals
-                    .then(|| ValidatorRegistrationKey {
+                    .then_some(ValidatorRegistrationKey {
                         fee_recipient,
                         gas_limit: proposal_data.gas_limit,
                         pubkey,