fix: Cargo clippy lints

crates/chain/src/local_chain.rs

@@ -265,7 +265,7 @@ impl Iterator for CheckPointIter {
 
     fn next(&mut self) -> Option<Self::Item> {
         let current = self.current.clone()?;
-        self.current = current.prev.clone();
+        self.current.clone_from(&current.prev);
         Some(CheckPoint(current))
     }
 }
@@ -359,7 +359,7 @@ impl LocalChain {
     /// The [`BTreeMap`] enforces the height order. However, the caller must ensure the blocks are
     /// all of the same chain.
     pub fn from_blocks(blocks: BTreeMap<u32, BlockHash>) -> Result<Self, MissingGenesisError> {
-        if blocks.get(&0).is_none() {
+        if !blocks.contains_key(&0) {
             return Err(MissingGenesisError);
         }
 

crates/chain/src/spk_client.rs

@@ -255,6 +255,9 @@ impl<K: Ord + Clone> FullScanRequest<K> {
         spks: impl IntoIterator<IntoIter = impl Iterator<Item = (u32, ScriptBuf)> + Send + 'static>,
     ) -> Self {
         match self.spks_by_keychain.remove(&keychain) {
+            // clippy here suggests to remove `into_iter` from `spks.into_iter()`, but doing so
+            // results in a compilation error
+            #[allow(clippy::useless_conversion)]
             Some(keychain_spks) => self
                 .spks_by_keychain
                 .insert(keychain, Box::new(keychain_spks.chain(spks.into_iter()))),

crates/chain/src/spk_txout_index.rs

@@ -229,7 +229,7 @@ impl<I: Clone + Ord> SpkTxOutIndex<I> {
     /// Here, "unused" means that after the script pubkey was stored in the index, the index has
     /// never scanned a transaction output with it.
     pub fn is_used(&self, index: &I) -> bool {
-        self.unused.get(index).is_none()
+        !self.unused.contains(index)
     }
 
     /// Marks the script pubkey at `index` as used even though it hasn't seen an output spending to it.