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>

consensus/state_processing/src/per_block_processing/signature_sets.rs

@@ -156,14 +156,14 @@ where
             get_pubkey(proposer_index)
                 .ok_or_else(|| Error::ValidatorUnknown(proposer_index as u64))?,
             spec,
-        )?,
+        ),
         block_header_signature_set(
             state,
             &proposer_slashing.signed_header_2,
             get_pubkey(proposer_index)
                 .ok_or_else(|| Error::ValidatorUnknown(proposer_index as u64))?,
             spec,
-        )?,
+        ),
     ))
 }
 
@@ -173,7 +173,7 @@ fn block_header_signature_set<'a, T: EthSpec>(
     signed_header: &'a SignedBeaconBlockHeader,
     pubkey: Cow<'a, PublicKey>,
     spec: &'a ChainSpec,
-) -> Result<SignatureSet<'a>> {
+) -> SignatureSet<'a> {
     let domain = spec.get_domain(
         signed_header.message.slot.epoch(T::slots_per_epoch()),
         Domain::BeaconProposer,
@@ -183,11 +183,7 @@ fn block_header_signature_set<'a, T: EthSpec>(
 
     let message = signed_header.message.signing_root(domain);
 
-    Ok(SignatureSet::single_pubkey(
-        &signed_header.signature,
-        pubkey,
-        message,
-    ))
+    SignatureSet::single_pubkey(&signed_header.signature, pubkey, message)
 }
 
 /// Returns the signature set for the given `indexed_attestation`.

consensus/swap_or_not_shuffle/src/compute_shuffled_index.rs

@@ -35,18 +35,22 @@ pub fn compute_shuffled_index(
     let mut index = index;
     for round in 0..shuffle_round_count {
         let pivot = bytes_to_int64(&hash_with_round(seed, round)[..]) as usize % list_size;
-        index = do_round(seed, index, pivot, round, list_size)?;
+        index = do_round(seed, index, pivot, round, list_size);
     }
     Some(index)
 }
 
-fn do_round(seed: &[u8], index: usize, pivot: usize, round: u8, list_size: usize) -> Option<usize> {
+fn do_round(seed: &[u8], index: usize, pivot: usize, round: u8, list_size: usize) -> usize {
     let flip = (pivot + (list_size - index)) % list_size;
     let position = max(index, flip);
     let source = hash_with_round_and_position(seed, round, position);
     let byte = source[(position % 256) / 8];
     let bit = (byte >> (position % 8)) % 2;
-    Some(if bit == 1 { flip } else { index })
+    if bit == 1 {
+        flip
+    } else {
+        index
+    }
 }
 
 fn hash_with_round_and_position(seed: &[u8], round: u8, position: usize) -> Hash256 {

consensus/types/src/attester_slashing.rs

@@ -10,7 +10,9 @@ use tree_hash_derive::TreeHash;
 ///
 /// Spec v0.12.1
 #[cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))]
-#[derive(Derivative, Debug, Clone, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom)]
+#[derive(
+    Derivative, Debug, Clone, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom,
+)]
 #[derivative(PartialEq, Eq, Hash(bound = "T: EthSpec"))]
 #[serde(bound = "T: EthSpec")]
 pub struct AttesterSlashing<T: EthSpec> {

consensus/types/src/indexed_attestation.rs

@@ -13,7 +13,9 @@ use tree_hash_derive::TreeHash;
 ///
 /// Spec v0.12.1
 #[cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))]
-#[derive(Derivative, Debug, Clone, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom)]
+#[derive(
+    Derivative, Debug, Clone, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom,
+)]
 #[derivative(PartialEq, Eq)] // to satisfy Clippy's lint about `Hash`
 #[serde(bound = "T: EthSpec")]
 pub struct IndexedAttestation<T: EthSpec> {

consensus/types/src/signed_beacon_block_header.rs

@@ -14,7 +14,9 @@ use tree_hash_derive::TreeHash;
 ///
 /// Spec v0.12.1
 #[cfg_attr(feature = "arbitrary-fuzz", derive(arbitrary::Arbitrary))]
-#[derive(Derivative, Debug, Clone, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom)]
+#[derive(
+    Derivative, Debug, Clone, Serialize, Deserialize, Encode, Decode, TreeHash, TestRandom,
+)]
 #[derivative(PartialEq, Eq)]
 pub struct SignedBeaconBlockHeader {
     pub message: BeaconBlockHeader,