diff --git a/src/chain-libs/chain-impl-mockchain/src/multiverse.rs b/src/chain-libs/chain-impl-mockchain/src/multiverse.rs
index 1abf72afca..82d30fdc03 100644
--- a/src/chain-libs/chain-impl-mockchain/src/multiverse.rs
+++ b/src/chain-libs/chain-impl-mockchain/src/multiverse.rs
@@ -110,7 +110,7 @@ impl<State> Multiverse<State> {
     pub fn insert(&mut self, chain_length: ChainLength, k: HeaderId, st: State) -> Ref<State> {
         self.states_by_chain_length
             .entry(chain_length)
-            .or_insert_with(HashSet::new)
+            .or_default()
             .insert(k);
         let state = Arc::new(st);
         self.states_by_hash
diff --git a/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/address.rs b/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/address.rs
index 7ae7cba9f3..7ba72c21c6 100644
--- a/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/address.rs
+++ b/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/address.rs
@@ -106,23 +106,20 @@ impl ArbitraryAddressDataValueVec {
     pub fn utxos(&self) -> Vec<AddressDataValue> {
         self.0
             .iter()
-            .cloned()
-            .filter(|x| matches!(x.address_data.kind(), Kind::Single { .. }))
+            .filter(|&x| matches!(x.address_data.kind(), Kind::Single { .. })).cloned()
             .collect()
     }
     pub fn accounts(&self) -> Vec<AddressDataValue> {
         self.0
             .iter()
-            .cloned()
-            .filter(|x| matches!(x.address_data.kind(), Kind::Account { .. }))
+            .filter(|&x| matches!(x.address_data.kind(), Kind::Account { .. })).cloned()
             .collect()
     }
 
     pub fn delegations(&self) -> Vec<AddressDataValue> {
         self.0
             .iter()
-            .cloned()
-            .filter(|x| matches!(x.address_data.kind(), Kind::Group { .. }))
-            .collect()
+            .filter(|&x| matches!(x.address_data.kind(), Kind::Group { .. }))
+            .cloned().collect()
     }
 }
diff --git a/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/ledger_builder.rs b/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/ledger_builder.rs
index 957d064db5..80a442a749 100644
--- a/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/ledger_builder.rs
+++ b/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/ledger_builder.rs
@@ -23,7 +23,7 @@ impl Arbitrary for LedgerBuilder {
 
         let faucets = WalletCollection::arbitrary(g);
         let splits = utils::split_vec(&faucets.0, g, 3);
-        let stake_pools_owners = splits.get(0).unwrap();
+        let stake_pools_owners = splits.first().unwrap();
         let stake_pools: Vec<StakePool> = stake_pools_owners
             .iter()
             .cloned()
diff --git a/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/transaction.rs b/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/transaction.rs
index 1845f0a14b..badaf7b838 100644
--- a/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/transaction.rs
+++ b/src/chain-libs/chain-impl-mockchain/src/testing/arbitrary/transaction.rs
@@ -190,8 +190,7 @@ impl AccountStatesVerifier {
             .0
             .addresses
             .iter()
-            .cloned()
-            .filter(filter_accounts)
+            .filter(|&x| filter_accounts(x)).cloned()
             .map(|x| find_equal_and_sub(x, inputs))
             .collect();
 
@@ -232,8 +231,7 @@ impl AccountStatesVerifier {
 fn find_equal_and_sub(x: AddressDataValue, collection: &[AddressDataValue]) -> AddressDataValue {
     match collection
         .iter()
-        .cloned()
-        .find(|y| y.address_data == x.address_data)
+        .find(|&y| y.address_data == x.address_data).cloned()
     {
         Some(y) => AddressDataValue::new(x.address_data, (x.value - y.value).unwrap()),
         None => x,
@@ -243,8 +241,7 @@ fn find_equal_and_sub(x: AddressDataValue, collection: &[AddressDataValue]) -> A
 fn find_equal_and_add(x: AddressDataValue, collection: &[AddressDataValue]) -> AddressDataValue {
     match collection
         .iter()
-        .cloned()
-        .find(|y| y.address_data == x.address_data)
+        .find(|&y| y.address_data == x.address_data).cloned()
     {
         Some(y) => AddressDataValue::new(x.address_data, (x.value + y.value).unwrap()),
         None => x,
diff --git a/src/chain-libs/chain-impl-mockchain/src/tokens/minting_policy.rs b/src/chain-libs/chain-impl-mockchain/src/tokens/minting_policy.rs
index 5e2725358c..07209f1d20 100644
--- a/src/chain-libs/chain-impl-mockchain/src/tokens/minting_policy.rs
+++ b/src/chain-libs/chain-impl-mockchain/src/tokens/minting_policy.rs
@@ -49,7 +49,7 @@ impl MintingPolicy {
         if self.0.is_empty() {
             return Err(MintingPolicyViolation::AdditionalMintingNotAllowed);
         }
-
+        #[allow(clippy::never_loop)]
         for _entry in &self.0 {
             unreachable!("implement this when we have actual minting policies");
         }
diff --git a/src/chain-libs/chain-impl-mockchain/src/value.rs b/src/chain-libs/chain-impl-mockchain/src/value.rs
index d57a3ec253..456386bdbb 100644
--- a/src/chain-libs/chain-impl-mockchain/src/value.rs
+++ b/src/chain-libs/chain-impl-mockchain/src/value.rs
@@ -31,7 +31,7 @@ impl Value {
     where
         I: Iterator<Item = Self>,
     {
-        values.fold(Ok(Value::zero()), |acc, v| acc? + v)
+        values.try_fold(Value::zero(), |acc, v| acc? + v)
     }
 
     #[inline]