Add various fixes to clippy lints

Thou shalt appease clippy

eth2/fork_choice/src/test_utils.rs

@@ -57,7 +57,7 @@ fn get_chain_of_blocks<T: EthSpec, U: Store>(
 ) -> Vec<(Hash256, BeaconBlock)> {
     let spec = T::default_spec();
     let mut blocks_and_roots: Vec<(Hash256, BeaconBlock)> = vec![];
-    let mut unique_hashes = (0..).into_iter().map(|i| Hash256::from(i));
+    let mut unique_hashes = (0..).map(Hash256::from);
     let mut random_block = BeaconBlock::random_for_test(&mut XorShiftRng::from_seed([42; 16]));
     random_block.previous_block_root = Hash256::zero();
     let beacon_state = get_state::<T>(validator_count);

eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs

@@ -49,7 +49,7 @@ fn verify_indexed_attestation_parametric<T: EthSpec>(
     );
 
     // Check that nobody signed with custody bit 1 (to be removed in phase 1)
-    if custody_bit_1_indices.len() > 0 {
+    if !custody_bit_1_indices.is_empty() {
         invalid!(Invalid::CustodyBitfieldHasSetBits);
     }
 
@@ -96,7 +96,7 @@ where
             state
                 .validator_registry
                 .get(validator_idx as usize)
-                .ok_or(Error::Invalid(Invalid::UnknownValidator(validator_idx)))
+                .ok_or_else(|| Error::Invalid(Invalid::UnknownValidator(validator_idx)))
                 .map(|validator| {
                     aggregate_pubkey.add(&validator.pubkey);
                     aggregate_pubkey

eth2/state_processing/src/per_epoch_processing.rs

@@ -156,7 +156,7 @@ pub fn process_crosslinks<T: EthSpec>(
 
     state.previous_crosslinks = state.current_crosslinks.clone();
 
-    for relative_epoch in vec![RelativeEpoch::Previous, RelativeEpoch::Current] {
+    for &relative_epoch in &[RelativeEpoch::Previous, RelativeEpoch::Current] {
         let epoch = relative_epoch.into_epoch(state.current_epoch());
         for offset in 0..state.get_epoch_committee_count(relative_epoch)? {
             let shard =

eth2/types/src/beacon_state.rs

@@ -422,7 +422,7 @@ impl<T: EthSpec> BeaconState<T> {
             };
             let effective_balance = self.validator_registry[candidate_index].effective_balance;
             if (effective_balance * MAX_RANDOM_BYTE)
-                >= (spec.max_effective_balance * random_byte as u64)
+                >= (spec.max_effective_balance * u64::from(random_byte))
             {
                 break candidate_index;
             }

eth2/types/src/beacon_state/committee_cache.rs

@@ -162,7 +162,6 @@ impl CommitteeCache {
         let i = self.shuffled_position(validator_index)?;
 
         (0..self.committee_count)
-            .into_iter()
             .map(|nth_committee| (nth_committee, self.compute_committee_range(nth_committee)))
             .find(|(_, range)| {
                 if let Some(range) = range {

eth2/types/src/chain_spec.rs

@@ -174,7 +174,7 @@ impl ChainSpec {
             /*
              * Time parameters
              */
-            genesis_time: u32::max_value() as u64,
+            genesis_time: u64::from(u32::max_value()),
             seconds_per_slot: 6,
             min_attestation_inclusion_delay: 4,
             min_seed_lookahead: Epoch::new(1),

eth2/types/src/slot_epoch.rs

@@ -77,7 +77,7 @@ impl Epoch {
     /// Position of some slot inside an epoch, if any.
     ///
     /// E.g., the first `slot` in `epoch` is at position `0`.
-    pub fn position(&self, slot: Slot, slots_per_epoch: u64) -> Option<usize> {
+    pub fn position(self, slot: Slot, slots_per_epoch: u64) -> Option<usize> {
         let start = self.start_slot(slots_per_epoch);
         let end = self.end_slot(slots_per_epoch);
 

eth2/types/src/test_utils/builders/testing_beacon_block_builder.rs

@@ -271,7 +271,7 @@ fn build_proposer_slashing<T: EthSpec>(
         Signature::new(message, domain, secret_key)
     };
 
-    TestingProposerSlashingBuilder::double_vote::<T, _>(validator_index, signer, spec)
+    TestingProposerSlashingBuilder::double_vote::<T, _>(validator_index, signer)
 }
 
 /// Builds an `AttesterSlashing` for some `validator_indices`.

eth2/types/src/test_utils/builders/testing_proposer_slashing_builder.rs

@@ -17,7 +17,7 @@ impl TestingProposerSlashingBuilder {
     /// - `domain: Domain`
     ///
     /// Where domain is a domain "constant" (e.g., `spec.domain_attestation`).
-    pub fn double_vote<T, F>(proposer_index: u64, signer: F, spec: &ChainSpec) -> ProposerSlashing
+    pub fn double_vote<T, F>(proposer_index: u64, signer: F) -> ProposerSlashing
     where
         T: EthSpec,
         F: Fn(u64, &[u8], Epoch, Domain) -> Signature,

eth2/types/src/test_utils/serde_utils.rs

@@ -13,6 +13,7 @@ where
     u8::from_str_radix(&s.as_str()[2..], 16).map_err(D::Error::custom)
 }
 
+#[allow(clippy::trivially_copy_pass_by_ref)] // Serde requires the `byte` to be a ref.
 pub fn u8_to_hex_str<S>(byte: &u8, serializer: S) -> Result<S::Ok, S::Error>
 where
     S: Serializer,

eth2/utils/eth2_config/src/lib.rs

@@ -80,7 +80,7 @@ where
             )
         })?;
         file.write_all(toml_encoded.as_bytes())
-            .expect(&format!("Unable to write to {:?}", path));
+            .unwrap_or_else(|_| panic!("Unable to write to {:?}", path));
     }
 
     Ok(())