Small syntax changes for staking and elections code (#9688)

* Simplify stake map creation in `OnChainSequentialPhragmen::elect`

* Use or_else

* More or_else

* trivial;

* revert

substrate/frame/election-provider-support/src/onchain.rs

@@ -73,11 +73,10 @@ impl<T: Config> ElectionProvider<T::AccountId, T::BlockNumber> for OnChainSequen
 		let targets = Self::DataProvider::targets(None).map_err(Error::DataProvider)?;
 		let desired_targets = Self::DataProvider::desired_targets().map_err(Error::DataProvider)?;
 
-		let mut stake_map: BTreeMap<T::AccountId, VoteWeight> = BTreeMap::new();
-
-		voters.iter().for_each(|(v, s, _)| {
-			stake_map.insert(v.clone(), *s);
-		});
+		let stake_map: BTreeMap<T::AccountId, VoteWeight> = voters
+			.iter()
+			.map(|(validator, vote_weight, _)| (validator.clone(), *vote_weight))
+			.collect();
 
 		let stake_of =
 			|w: &T::AccountId| -> VoteWeight { stake_map.get(w).cloned().unwrap_or_default() };

substrate/frame/staking/src/pallet/impls.rs

@@ -78,10 +78,10 @@ impl<T: Config> Pallet<T> {
 		era: EraIndex,
 	) -> DispatchResultWithPostInfo {
 		// Validate input data
-		let current_era = CurrentEra::<T>::get().ok_or(
+		let current_era = CurrentEra::<T>::get().ok_or_else(|| {
 			Error::<T>::InvalidEraToReward
-				.with_weight(T::WeightInfo::payout_stakers_alive_staked(0)),
-		)?;
+				.with_weight(T::WeightInfo::payout_stakers_alive_staked(0))
+		})?;
 		let history_depth = Self::history_depth();
 		ensure!(
 			era <= current_era && era >= current_era.saturating_sub(history_depth),
@@ -96,10 +96,10 @@ impl<T: Config> Pallet<T> {
 				.with_weight(T::WeightInfo::payout_stakers_alive_staked(0))
 		})?;
 
-		let controller = Self::bonded(&validator_stash).ok_or(
-			Error::<T>::NotStash.with_weight(T::WeightInfo::payout_stakers_alive_staked(0)),
-		)?;
-		let mut ledger = <Ledger<T>>::get(&controller).ok_or_else(|| Error::<T>::NotController)?;
+		let controller = Self::bonded(&validator_stash).ok_or_else(|| {
+			Error::<T>::NotStash.with_weight(T::WeightInfo::payout_stakers_alive_staked(0))
+		})?;
+		let mut ledger = <Ledger<T>>::get(&controller).ok_or(Error::<T>::NotController)?;
 
 		ledger
 			.claimed_rewards
@@ -891,7 +891,7 @@ impl<T: Config> frame_election_provider_support::ElectionDataProvider<T::Account
 		targets.into_iter().for_each(|v| {
 			let stake: BalanceOf<T> = target_stake
 				.and_then(|w| <BalanceOf<T>>::try_from(w).ok())
-				.unwrap_or(MinNominatorBond::<T>::get() * 100u32.into());
+				.unwrap_or_else(|| MinNominatorBond::<T>::get() * 100u32.into());
 			<Bonded<T>>::insert(v.clone(), v.clone());
 			<Ledger<T>>::insert(
 				v.clone(),