Use a more typesafe approach for managing indexed data (#6150)

* Fix for issue #2403 * Nightly fmt * Quick documentation fixes * Default Implementation * iter() function integrated * Implemented iter functionalities * Fmt * small change * updates node-network * updates in dispute-coordinator * Updates * benchmarking fix * minor fix * test fixes in runtime api * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * Removal of [index], shorting of FromIterator, Renaming of GroupValidators to ValidatorGroups * Removal of ops import * documentation fixes for spell check * implementation of generic type * Refactoring * Test and documentation fixes * minor test fix * minor test fix * minor test fix * Update node/network/statement-distribution/src/lib.rs Co-authored-by: Andronik <write@reusable.software> * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * removed IterMut * Update node/core/dispute-coordinator/src/import.rs Co-authored-by: Andronik <write@reusable.software> * Update node/core/dispute-coordinator/src/initialized.rs Co-authored-by: Andronik <write@reusable.software> * Update primitives/src/v2/mod.rs Co-authored-by: Andronik <write@reusable.software> * fmt * IterMut * documentation update Co-authored-by: Andronik <write@reusable.software> * minor adjustments and new TypeIndex trait * spelling fix * TypeIndex fix Co-authored-by: Andronik <write@reusable.software>
2026-06-09 20:11:09 +00:00 · 2022-10-22 09:39:11 +01:00
parent f8cc39a761
commit 8eb1f4617f
28 changed files with 261 additions and 138 deletions
@@ -21,7 +21,8 @@ use polkadot_node_primitives::approval::{
 	self as approval_types, AssignmentCert, AssignmentCertKind, DelayTranche, RelayVRFStory,
 };
 use polkadot_primitives::v2::{
-	AssignmentId, AssignmentPair, CandidateHash, CoreIndex, GroupIndex, SessionInfo, ValidatorIndex,
+	AssignmentId, AssignmentPair, CandidateHash, CoreIndex, GroupIndex, IndexedVec, SessionInfo,
+	ValidatorIndex,
 };
 use sc_keystore::LocalKeystore;
 use sp_application_crypto::ByteArray;
@@ -138,7 +139,7 @@ pub(crate) struct Config {
 	/// The assignment public keys for validators.
 	assignment_keys: Vec<AssignmentId>,
 	/// The groups of validators assigned to each core.
-	validator_groups: Vec<Vec<ValidatorIndex>>,
+	validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>>,
 	/// The number of availability cores used by the protocol during this session.
 	n_cores: u32,
 	/// The zeroth delay tranche width.
@@ -541,11 +542,11 @@ pub(crate) fn check_assignment_cert(
 }

 fn is_in_backing_group(
-	validator_groups: &[Vec<ValidatorIndex>],
+	validator_groups: &IndexedVec<GroupIndex, Vec<ValidatorIndex>>,
 	validator: ValidatorIndex,
 	group: GroupIndex,
 ) -> bool {
-	validator_groups.get(group.0 as usize).map_or(false, |g| g.contains(&validator))
+	validator_groups.get(group).map_or(false, |g| g.contains(&validator))
 }

 #[cfg(test)]
@@ -590,7 +591,10 @@ mod tests {
 			.collect()
 	}

-	fn basic_groups(n_validators: usize, n_groups: usize) -> Vec<Vec<ValidatorIndex>> {
+	fn basic_groups(
+		n_validators: usize,
+		n_groups: usize,
+	) -> IndexedVec<GroupIndex, Vec<ValidatorIndex>> {
 		let size = n_validators / n_groups;
 		let big_groups = n_validators % n_groups;
 		let scraps = n_groups * size;
@@ -631,10 +635,10 @@ mod tests {
 					Sr25519Keyring::Bob,
 					Sr25519Keyring::Charlie,
 				]),
-				validator_groups: vec![
+				validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 					vec![ValidatorIndex(0)],
 					vec![ValidatorIndex(1), ValidatorIndex(2)],
-				],
+				]),
 				n_cores: 2,
 				zeroth_delay_tranche_width: 10,
 				relay_vrf_modulo_samples: 3,
@@ -666,10 +670,10 @@ mod tests {
 					Sr25519Keyring::Bob,
 					Sr25519Keyring::Charlie,
 				]),
-				validator_groups: vec![
+				validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 					vec![ValidatorIndex(0)],
 					vec![ValidatorIndex(1), ValidatorIndex(2)],
-				],
+				]),
 				n_cores: 2,
 				zeroth_delay_tranche_width: 10,
 				relay_vrf_modulo_samples: 3,
@@ -696,7 +700,7 @@ mod tests {
 					Sr25519Keyring::Bob,
 					Sr25519Keyring::Charlie,
 				]),
-				validator_groups: vec![],
+				validator_groups: Default::default(),
 				n_cores: 0,
 				zeroth_delay_tranche_width: 10,
 				relay_vrf_modulo_samples: 3,
@@ -620,7 +620,9 @@ pub(crate) mod tests {
 	use polkadot_node_subsystem::messages::{AllMessages, ApprovalVotingMessage};
 	use polkadot_node_subsystem_test_helpers::make_subsystem_context;
 	use polkadot_node_subsystem_util::database::Database;
-	use polkadot_primitives::v2::{Id as ParaId, SessionInfo, ValidatorIndex};
+	use polkadot_primitives::v2::{
+		Id as ParaId, IndexedVec, SessionInfo, ValidatorId, ValidatorIndex,
+	};
 	pub(crate) use sp_consensus_babe::{
 		digests::{CompatibleDigestItem, PreDigest, SecondaryVRFPreDigest},
 		AllowedSlots, BabeEpochConfiguration, Epoch as BabeEpoch,
@@ -713,10 +715,10 @@ pub(crate) mod tests {

 	fn dummy_session_info(index: SessionIndex) -> SessionInfo {
 		SessionInfo {
-			validators: Vec::new(),
+			validators: Default::default(),
 			discovery_keys: Vec::new(),
 			assignment_keys: Vec::new(),
-			validator_groups: Vec::new(),
+			validator_groups: Default::default(),
 			n_cores: index as _,
 			zeroth_delay_tranche_width: index as _,
 			relay_vrf_modulo_samples: index as _,
@@ -1174,21 +1176,27 @@ pub(crate) mod tests {

 		let session = 5;
 		let irrelevant = 666;
-		let session_info = SessionInfo {
-			validators: vec![Sr25519Keyring::Alice.public().into(); 6],
-			discovery_keys: Vec::new(),
-			assignment_keys: Vec::new(),
-			validator_groups: vec![vec![ValidatorIndex(0); 5], vec![ValidatorIndex(0); 2]],
-			n_cores: 6,
-			needed_approvals: 2,
-			zeroth_delay_tranche_width: irrelevant,
-			relay_vrf_modulo_samples: irrelevant,
-			n_delay_tranches: irrelevant,
-			no_show_slots: irrelevant,
-			active_validator_indices: Vec::new(),
-			dispute_period: 6,
-			random_seed: [0u8; 32],
-		};
+		let session_info =
+			SessionInfo {
+				validators: IndexedVec::<ValidatorIndex, ValidatorId>::from(
+					vec![Sr25519Keyring::Alice.public().into(); 6],
+				),
+				discovery_keys: Vec::new(),
+				assignment_keys: Vec::new(),
+				validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
+					vec![ValidatorIndex(0); 5],
+					vec![ValidatorIndex(0); 2],
+				]),
+				n_cores: 6,
+				needed_approvals: 2,
+				zeroth_delay_tranche_width: irrelevant,
+				relay_vrf_modulo_samples: irrelevant,
+				n_delay_tranches: irrelevant,
+				no_show_slots: irrelevant,
+				active_validator_indices: Vec::new(),
+				dispute_period: 6,
+				random_seed: [0u8; 32],
+			};

 		let slot = Slot::from(10);

@@ -1803,7 +1803,7 @@ fn check_and_import_approval<T>(
 		)),
 	};

-	let pubkey = match session_info.validators.get(approval.validator.0 as usize) {
+	let pubkey = match session_info.validators.get(approval.validator) {
 		Some(k) => k,
 		None => respond_early!(ApprovalCheckResult::Bad(
 			ApprovalCheckError::InvalidValidatorIndex(approval.validator),
@@ -2503,7 +2503,7 @@ async fn issue_approval<Context>(
 		},
 	};

-	let validator_pubkey = match session_info.validators.get(validator_index.0 as usize) {
+	let validator_pubkey = match session_info.validators.get(validator_index) {
 		Some(p) => p,
 		None => {
 			gum::warn!(
@@ -32,7 +32,7 @@ use polkadot_node_subsystem_test_helpers as test_helpers;
 use polkadot_node_subsystem_util::TimeoutExt;
 use polkadot_overseer::HeadSupportsParachains;
 use polkadot_primitives::v2::{
-	CandidateCommitments, CandidateEvent, CoreIndex, GroupIndex, Header, Id as ParaId,
+	CandidateCommitments, CandidateEvent, CoreIndex, GroupIndex, Header, Id as ParaId, IndexedVec,
 	ValidationCode, ValidatorSignature,
 };
 use std::time::Duration;
@@ -739,7 +739,10 @@ fn session_info(keys: &[Sr25519Keyring]) -> SessionInfo {
 		validators: keys.iter().map(|v| v.public().into()).collect(),
 		discovery_keys: keys.iter().map(|v| v.public().into()).collect(),
 		assignment_keys: keys.iter().map(|v| v.public().into()).collect(),
-		validator_groups: vec![vec![ValidatorIndex(0)], vec![ValidatorIndex(1)]],
+		validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
+			vec![ValidatorIndex(0)],
+			vec![ValidatorIndex(1)],
+		]),
 		n_cores: keys.len() as _,
 		needed_approvals: 2,
 		zeroth_delay_tranche_width: 5,
@@ -1552,11 +1555,11 @@ fn subsystem_second_approval_import_only_schedules_wakeups() {
 			Sr25519Keyring::Eve,
 		];
 		let session_info = SessionInfo {
-			validator_groups: vec![
+			validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 				vec![ValidatorIndex(0), ValidatorIndex(1)],
 				vec![ValidatorIndex(2)],
 				vec![ValidatorIndex(3), ValidatorIndex(4)],
-			],
+			]),
 			needed_approvals: 1,
 			..session_info(&validators)
 		};
@@ -1889,11 +1892,11 @@ fn import_checked_approval_updates_entries_and_schedules() {
 			Sr25519Keyring::Eve,
 		];
 		let session_info = SessionInfo {
-			validator_groups: vec![
+			validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 				vec![ValidatorIndex(0), ValidatorIndex(1)],
 				vec![ValidatorIndex(2)],
 				vec![ValidatorIndex(3), ValidatorIndex(4)],
-			],
+			]),
 			..session_info(&validators)
 		};

@@ -2046,11 +2049,11 @@ fn subsystem_import_checked_approval_sets_one_block_bit_at_a_time() {
 			Sr25519Keyring::Eve,
 		];
 		let session_info = SessionInfo {
-			validator_groups: vec![
+			validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 				vec![ValidatorIndex(0), ValidatorIndex(1)],
 				vec![ValidatorIndex(2)],
 				vec![ValidatorIndex(3), ValidatorIndex(4)],
-			],
+			]),
 			..session_info(&validators)
 		};

@@ -2336,11 +2339,11 @@ fn subsystem_validate_approvals_cache() {
 			Sr25519Keyring::Eve,
 		];
 		let session_info = SessionInfo {
-			validator_groups: vec![
+			validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 				vec![ValidatorIndex(0), ValidatorIndex(1)],
 				vec![ValidatorIndex(2)],
 				vec![ValidatorIndex(3), ValidatorIndex(4)],
-			],
+			]),
 			..session_info(&validators)
 		};

@@ -2548,11 +2551,11 @@ where
 			Sr25519Keyring::Ferdie,
 		];
 		let session_info = SessionInfo {
-			validator_groups: vec![
+			validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 				vec![ValidatorIndex(0), ValidatorIndex(1)],
 				vec![ValidatorIndex(2), ValidatorIndex(3)],
 				vec![ValidatorIndex(4), ValidatorIndex(5)],
-			],
+			]),
 			relay_vrf_modulo_samples: 2,
 			no_show_slots,
 			..session_info(&validators)
@@ -2868,11 +2871,11 @@ fn pre_covers_dont_stall_approval() {
 			Sr25519Keyring::One,
 		];
 		let session_info = SessionInfo {
-			validator_groups: vec![
+			validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 				vec![ValidatorIndex(0), ValidatorIndex(1)],
 				vec![ValidatorIndex(2), ValidatorIndex(5)],
 				vec![ValidatorIndex(3), ValidatorIndex(4)],
-			],
+			]),
 			..session_info(&validators)
 		};

@@ -3045,11 +3048,11 @@ fn waits_until_approving_assignments_are_old_enough() {
 			Sr25519Keyring::One,
 		];
 		let session_info = SessionInfo {
-			validator_groups: vec![
+			validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 				vec![ValidatorIndex(0), ValidatorIndex(1)],
 				vec![ValidatorIndex(2), ValidatorIndex(5)],
 				vec![ValidatorIndex(3), ValidatorIndex(4)],
-			],
+			]),
 			..session_info(&validators)
 		};

@@ -31,8 +31,8 @@ use std::collections::{BTreeMap, HashMap, HashSet};
 use polkadot_node_primitives::{CandidateVotes, SignedDisputeStatement};
 use polkadot_node_subsystem_util::rolling_session_window::RollingSessionWindow;
 use polkadot_primitives::v2::{
-	CandidateReceipt, DisputeStatement, SessionIndex, SessionInfo, ValidDisputeStatementKind,
-	ValidatorId, ValidatorIndex, ValidatorPair, ValidatorSignature,
+	CandidateReceipt, DisputeStatement, IndexedVec, SessionIndex, SessionInfo,
+	ValidDisputeStatementKind, ValidatorId, ValidatorIndex, ValidatorPair, ValidatorSignature,
 };
 use sc_keystore::LocalKeystore;

@@ -63,7 +63,7 @@ impl<'a> CandidateEnvironment<'a> {
 	}

 	/// Validators in the candidate's session.
-	pub fn validators(&self) -> &Vec<ValidatorId> {
+	pub fn validators(&self) -> &IndexedVec<ValidatorIndex, ValidatorId> {
 		&self.session.validators
 	}

@@ -229,7 +229,7 @@ impl CandidateVoteState<CandidateVotes> {
 		for (statement, val_index) in statements {
 			if env
 				.validators()
-				.get(val_index.0 as usize)
+				.get(val_index)
 				.map_or(true, |v| v != statement.validator_public())
 			{
 				gum::error!(
@@ -488,7 +488,7 @@ impl ImportResult {
 		for (index, sig) in approval_votes.into_iter() {
 			debug_assert!(
 				{
-					let pub_key = &env.session_info().validators[index.0 as usize];
+					let pub_key = &env.session_info().validators.get(index).expect("indices are validated by approval-voting subsystem; qed");
 					let candidate_hash = votes.candidate_receipt.hash();
 					let session_index = env.session_index();
 					DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalChecking)
@@ -538,7 +538,7 @@ impl ImportResult {
 /// That is all `ValidatorIndex`es we have private keys for. Usually this will only be one.
 fn find_controlled_validator_indices(
 	keystore: &LocalKeystore,
-	validators: &[ValidatorId],
+	validators: &IndexedVec<ValidatorIndex, ValidatorId>,
 ) -> HashSet<ValidatorIndex> {
 	let mut controlled = HashSet::new();
 	for (index, validator) in validators.iter().enumerate() {
@@ -372,7 +372,7 @@ impl Initialized {
 				.filter_map(|(validator_index, attestation)| {
 					let validator_public: ValidatorId = session_info
 						.validators
-						.get(validator_index.0 as usize)
+						.get(validator_index)
 						.or_else(|| {
 							gum::error!(
 								target: LOG_TARGET,
@@ -473,7 +473,7 @@ impl Initialized {

 					let validator_public: ValidatorId = session_info
 						.validators
-						.get(validator_index.0 as usize)
+						.get(validator_index)
 						.or_else(|| {
 							gum::error!(
 								target: LOG_TARGET,
@@ -903,7 +903,7 @@ impl Initialized {
 			let no_votes = Vec::new();
 			let our_approval_votes = new_state.own_approval_votes().unwrap_or(&no_votes);
 			for (validator_index, sig) in our_approval_votes {
-				let pub_key = match env.validators().get(validator_index.0 as usize) {
+				let pub_key = match env.validators().get(*validator_index) {
 					None => {
 						gum::error!(
 							target: LOG_TARGET,
@@ -1097,7 +1097,10 @@ impl Initialized {
 				valid,
 				candidate_hash,
 				session,
-				env.validators()[index.0 as usize].clone(),
+				env.validators()
+					.get(*index)
+					.expect("`controlled_indices` are derived from `validators`; qed")
+					.clone(),
 			)
 			.await;

@@ -1238,7 +1241,7 @@ fn make_dispute_message(
 				our_vote.candidate_hash().clone(),
 				our_vote.session_index(),
 				validators
-					.get(validator_index.0 as usize)
+					.get(*validator_index)
 					.ok_or(DisputeMessageCreationError::InvalidValidatorIndex)?
 					.clone(),
 				validator_signature.clone(),
@@ -1253,7 +1256,7 @@ fn make_dispute_message(
 				our_vote.candidate_hash().clone(),
 				our_vote.session_index(),
 				validators
-					.get(validator_index.0 as usize)
+					.get(*validator_index)
 					.ok_or(DisputeMessageCreationError::InvalidValidatorIndex)?
 					.clone(),
 				validator_signature.clone(),
@@ -58,9 +58,9 @@ use polkadot_node_subsystem::{
 use polkadot_node_subsystem_test_helpers::{make_subsystem_context, TestSubsystemContextHandle};
 use polkadot_primitives::v2::{
 	ApprovalVote, BlockNumber, CandidateCommitments, CandidateHash, CandidateReceipt,
-	DisputeStatement, Hash, Header, MultiDisputeStatementSet, ScrapedOnChainVotes, SessionIndex,
-	SessionInfo, SigningContext, ValidDisputeStatementKind, ValidatorId, ValidatorIndex,
-	ValidatorSignature,
+	DisputeStatement, GroupIndex, Hash, Header, IndexedVec, MultiDisputeStatementSet,
+	ScrapedOnChainVotes, SessionIndex, SessionInfo, SigningContext, ValidDisputeStatementKind,
+	ValidatorId, ValidatorIndex, ValidatorSignature,
 };

 use crate::{
@@ -125,8 +125,8 @@ impl MockClock {

 struct TestState {
 	validators: Vec<Pair>,
-	validator_public: Vec<ValidatorId>,
-	validator_groups: Vec<Vec<ValidatorIndex>>,
+	validator_public: IndexedVec<ValidatorIndex, ValidatorId>,
+	validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>>,
 	master_keystore: Arc<sc_keystore::LocalKeystore>,
 	subsystem_keystore: Arc<sc_keystore::LocalKeystore>,
 	db: Arc<dyn Database>,
@@ -163,11 +163,11 @@ impl Default for TestState {
 			.map(|k| ValidatorId::from(k.0.public()))
 			.collect();

-		let validator_groups = vec![
+		let validator_groups = IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
 			vec![ValidatorIndex(0), ValidatorIndex(1)],
 			vec![ValidatorIndex(2), ValidatorIndex(3)],
 			vec![ValidatorIndex(4), ValidatorIndex(5), ValidatorIndex(6)],
-		];
+		]);

 		let master_keystore = make_keystore(validators.iter().map(|v| v.1.clone())).into();
 		let subsystem_keystore =
@@ -431,7 +431,7 @@ impl TestState {
 		session: SessionIndex,
 		valid: bool,
 	) -> SignedDisputeStatement {
-		let public = self.validator_public[index.0 as usize].clone();
+		let public = self.validator_public.get(index).unwrap().clone();

 		let keystore = self.master_keystore.clone() as SyncCryptoStorePtr;

@@ -522,10 +522,10 @@ fn requests_session_index_for_child() {

 fn dummy_session_info() -> SessionInfo {
 	SessionInfo {
-		validators: vec![],
+		validators: Default::default(),
 		discovery_keys: vec![],
 		assignment_keys: vec![],
-		validator_groups: vec![],
+		validator_groups: Default::default(),
 		n_cores: 4u32,
 		zeroth_delay_tranche_width: 0u32,
 		relay_vrf_modulo_samples: 0u32,
@@ -24,8 +24,8 @@ use polkadot_erasure_coding::{branches, obtain_chunks_v1 as obtain_chunks};
 use polkadot_node_primitives::{AvailableData, BlockData, ErasureChunk, PoV, Proof};
 use polkadot_primitives::v2::{
 	CandidateCommitments, CandidateDescriptor, CandidateHash, CommittedCandidateReceipt,
-	GroupIndex, Hash, HeadData, Id as ParaId, OccupiedCore, PersistedValidationData, SessionInfo,
-	ValidatorIndex,
+	GroupIndex, Hash, HeadData, Id as ParaId, IndexedVec, OccupiedCore, PersistedValidationData,
+	SessionInfo, ValidatorIndex,
 };
 use polkadot_primitives_test_helpers::{
 	dummy_collator, dummy_collator_signature, dummy_hash, dummy_validation_code,
@@ -43,10 +43,11 @@ pub fn make_session_info() -> SessionInfo {
 		Sr25519Keyring::One,
 	];

-	let validator_groups: Vec<Vec<ValidatorIndex>> = [vec![5, 0, 3], vec![1, 6, 2, 4]]
-		.iter()
-		.map(|g| g.into_iter().map(|v| ValidatorIndex(*v)).collect())
-		.collect();
+	let validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>> =
+		[vec![5, 0, 3], vec![1, 6, 2, 4]]
+			.iter()
+			.map(|g| g.into_iter().map(|v| ValidatorIndex(*v)).collect())
+			.collect();

 	SessionInfo {
 		discovery_keys: validators.iter().map(|k| k.public().into()).collect(),
@@ -58,7 +58,7 @@ use polkadot_node_subsystem::{
 use polkadot_node_subsystem_util::request_session_info;
 use polkadot_primitives::v2::{
 	AuthorityDiscoveryId, BlakeTwo256, BlockNumber, CandidateHash, CandidateReceipt, GroupIndex,
-	Hash, HashT, SessionIndex, SessionInfo, ValidatorId, ValidatorIndex,
+	Hash, HashT, IndexedVec, SessionIndex, SessionInfo, ValidatorId, ValidatorIndex,
 };

 mod error;
@@ -134,7 +134,7 @@ struct RecoveryParams {
 	validator_authority_keys: Vec<AuthorityDiscoveryId>,

 	/// Validators relevant to this `RecoveryTask`.
-	validators: Vec<ValidatorId>,
+	validators: IndexedVec<ValidatorIndex, ValidatorId>,

 	/// The number of pieces needed.
 	threshold: usize,
@@ -871,7 +871,7 @@ async fn launch_recovery_task<Context>(
 	};

 	let phase = backing_group
-		.and_then(|g| session_info.validator_groups.get(g.0 as usize))
+		.and_then(|g| session_info.validator_groups.get(g))
 		.map(|group| Source::RequestFromBackers(RequestFromBackers::new(group.clone())))
 		.unwrap_or_else(|| {
 			Source::RequestChunks(RequestChunksFromValidators::new(params.validators.len() as _))
@@ -36,7 +36,9 @@ use polkadot_node_subsystem::{
 };
 use polkadot_node_subsystem_test_helpers::{make_subsystem_context, TestSubsystemContextHandle};
 use polkadot_node_subsystem_util::TimeoutExt;
-use polkadot_primitives::v2::{AuthorityDiscoveryId, Hash, HeadData, PersistedValidationData};
+use polkadot_primitives::v2::{
+	AuthorityDiscoveryId, Hash, HeadData, IndexedVec, PersistedValidationData, ValidatorId,
+};
 use polkadot_primitives_test_helpers::{dummy_candidate_receipt, dummy_hash};

 type VirtualOverseer = TestSubsystemContextHandle<AvailabilityRecoveryMessage>;
@@ -179,7 +181,7 @@ impl Has {
 #[derive(Clone)]
 struct TestState {
 	validators: Vec<Sr25519Keyring>,
-	validator_public: Vec<ValidatorId>,
+	validator_public: IndexedVec<ValidatorIndex, ValidatorId>,
 	validator_authority_id: Vec<AuthorityDiscoveryId>,
 	current: Hash,
 	candidate: CandidateReceipt,
@@ -218,7 +220,7 @@ impl TestState {
 					validators: self.validator_public.clone(),
 					discovery_keys: self.validator_authority_id.clone(),
 					// all validators in the same group.
-					validator_groups: vec![(0..self.validators.len()).map(|i| ValidatorIndex(i as _)).collect()],
+					validator_groups: IndexedVec::<GroupIndex,Vec<ValidatorIndex>>::from(vec![(0..self.validators.len()).map(|i| ValidatorIndex(i as _)).collect()]),
 					assignment_keys: vec![],
 					n_cores: 0,
 					zeroth_delay_tranche_width: 0,
@@ -402,7 +404,7 @@ impl TestState {
 	}
 }

-fn validator_pubkeys(val_ids: &[Sr25519Keyring]) -> Vec<ValidatorId> {
+fn validator_pubkeys(val_ids: &[Sr25519Keyring]) -> IndexedVec<ValidatorIndex, ValidatorId> {
 	val_ids.iter().map(|v| v.public().into()).collect()
 }

@@ -448,10 +448,8 @@ async fn determine_our_validators<Context>(
 	let rotation_info = get_group_rotation_info(ctx.sender(), relay_parent).await?;

 	let current_group_index = rotation_info.group_for_core(core_index, cores);
-	let current_validators = groups
-		.get(current_group_index.0 as usize)
-		.map(|v| v.as_slice())
-		.unwrap_or_default();
+	let current_validators =
+		groups.get(current_group_index).map(|v| v.as_slice()).unwrap_or_default();

 	let validators = &info.discovery_keys;

@@ -44,8 +44,8 @@ use polkadot_node_subsystem::{
 use polkadot_node_subsystem_test_helpers as test_helpers;
 use polkadot_node_subsystem_util::TimeoutExt;
 use polkadot_primitives::v2::{
-	AuthorityDiscoveryId, CollatorPair, GroupRotationInfo, ScheduledCore, SessionIndex,
-	SessionInfo, ValidatorId, ValidatorIndex,
+	AuthorityDiscoveryId, CollatorPair, GroupIndex, GroupRotationInfo, IndexedVec, ScheduledCore,
+	SessionIndex, SessionInfo, ValidatorId, ValidatorIndex,
 };
 use polkadot_primitives_test_helpers::TestCandidateBuilder;

@@ -62,7 +62,7 @@ struct TestState {
 	session_index: SessionIndex,
 }

-fn validator_pubkeys(val_ids: &[Sr25519Keyring]) -> Vec<ValidatorId> {
+fn validator_pubkeys(val_ids: &[Sr25519Keyring]) -> IndexedVec<ValidatorIndex, ValidatorId> {
 	val_ids.iter().map(|v| v.public().into()).collect()
 }

@@ -135,7 +135,7 @@ impl TestState {
 	fn current_group_validator_indices(&self) -> &[ValidatorIndex] {
 		let core_num = self.availability_cores.len();
 		let GroupIndex(group_idx) = self.group_rotation_info.group_for_core(CoreIndex(0), core_num);
-		&self.session_info.validator_groups[group_idx as usize]
+		&self.session_info.validator_groups.get(GroupIndex::from(group_idx)).unwrap()
 	}

 	fn current_session_index(&self) -> SessionIndex {
@@ -367,7 +367,7 @@ async fn distribute_collation(
 			)) => {
 				assert_eq!(relay_parent, test_state.relay_parent);
 				tx.send(Ok((
-					test_state.session_info.validator_groups.clone(),
+					test_state.session_info.validator_groups.to_vec(),
 					test_state.group_rotation_info.clone(),
 				)))
 				.unwrap();
@@ -299,7 +299,7 @@ impl DisputeSender {
 		let valid_public = info
 			.session_info
 			.validators
-			.get(valid_index.0 as usize)
+			.get(*valid_index)
 			.ok_or(JfyiError::InvalidStatementFromCoordinator)?;
 		let valid_signed = SignedDisputeStatement::new_checked(
 			DisputeStatement::Valid(kind.clone()),
@@ -314,7 +314,7 @@ impl DisputeSender {
 		let invalid_public = info
 			.session_info
 			.validators
-			.get(invalid_index.0 as usize)
+			.get(*invalid_index)
 			.ok_or(JfyiError::InvalidValidatorIndexFromCoordinator)?;
 		let invalid_signed = SignedDisputeStatement::new_checked(
 			DisputeStatement::Invalid(kind.clone()),
@@ -84,7 +84,7 @@ pub static ref MOCK_SESSION_INFO: SessionInfo =
 			.map(|k| MOCK_VALIDATORS_DISCOVERY_KEYS.get(&k).unwrap().clone())
 			.collect(),
 		assignment_keys: vec![],
-		validator_groups: vec![],
+		validator_groups: Default::default(),
 		n_cores: 0,
 		zeroth_delay_tranche_width: 0,
 		relay_vrf_modulo_samples: 0,
@@ -104,9 +104,9 @@ pub static ref MOCK_NEXT_SESSION_INFO: SessionInfo =
 				.iter()
 				.map(|k| MOCK_VALIDATORS_DISCOVERY_KEYS.get(&k).unwrap().clone())
 				.collect(),
-		validators: vec![],
+		validators: Default::default(),
 		assignment_keys: vec![],
-		validator_groups: vec![],
+		validator_groups: Default::default(),
 		n_cores: 0,
 		zeroth_delay_tranche_width: 0,
 		relay_vrf_modulo_samples: 0,
@@ -37,6 +37,7 @@ use polkadot_node_subsystem::{
 };
 use polkadot_node_subsystem_test_helpers as test_helpers;
 use polkadot_node_subsystem_util::TimeoutExt as _;
+use polkadot_primitives::v2::{GroupIndex, IndexedVec};
 use test_helpers::mock::make_ferdie_keystore;

 use super::*;
@@ -219,7 +220,9 @@ fn make_session_info() -> SessionInfo {
 		validators: AUTHORITY_KEYRINGS.iter().map(|k| k.public().into()).collect(),
 		discovery_keys: AUTHORITIES.clone(),
 		assignment_keys: AUTHORITY_KEYRINGS.iter().map(|k| k.public().into()).collect(),
-		validator_groups: vec![all_validator_indices],
+		validator_groups: IndexedVec::<GroupIndex, Vec<ValidatorIndex>>::from(vec![
+			all_validator_indices,
+		]),
 		n_cores: 1,
 		zeroth_delay_tranche_width: 1,
 		relay_vrf_modulo_samples: 1,
@@ -47,8 +47,8 @@ use polkadot_node_subsystem::{
 };
 use polkadot_primitives::v2::{
 	AuthorityDiscoveryId, CandidateHash, CommittedCandidateReceipt, CompactStatement, Hash,
-	SignedStatement, SigningContext, UncheckedSignedStatement, ValidatorId, ValidatorIndex,
-	ValidatorSignature,
+	IndexedVec, SignedStatement, SigningContext, UncheckedSignedStatement, ValidatorId,
+	ValidatorIndex, ValidatorSignature,
 };

 use futures::{
@@ -665,7 +665,7 @@ struct ActiveHeadData {
 	/// Large statements we are waiting for with associated meta data.
 	waiting_large_statements: HashMap<CandidateHash, LargeStatementStatus>,
 	/// The parachain validators at the head's child session index.
-	validators: Vec<ValidatorId>,
+	validators: IndexedVec<ValidatorIndex, ValidatorId>,
 	/// The current session index of this fork.
 	session_index: sp_staking::SessionIndex,
 	/// How many `Seconded` statements we've seen per validator.
@@ -676,7 +676,7 @@ struct ActiveHeadData {

 impl ActiveHeadData {
 	fn new(
-		validators: Vec<ValidatorId>,
+		validators: IndexedVec<ValidatorIndex, ValidatorId>,
 		session_index: sp_staking::SessionIndex,
 		span: PerLeafSpan,
 	) -> Self {
@@ -878,7 +878,7 @@ fn check_statement_signature(
 		SigningContext { session_index: head.session_index, parent_hash: relay_parent };

 	head.validators
-		.get(statement.unchecked_validator_index().0 as usize)
+		.get(statement.unchecked_validator_index())
 		.ok_or_else(|| statement.clone())
 		.and_then(|v| statement.try_into_checked(&signing_context, v))
 }
@@ -2072,7 +2072,10 @@ impl<R: rand::Rng> StatementDistributionSubsystem<R> {
 					// directly:
 					let group_peers = {
 						if let Some(our_group) = validator_info.our_group {
-							let our_group = &session_info.validator_groups[our_group.0 as usize];
+							let our_group = &session_info
+								.validator_groups
+								.get(our_group)
+								.expect("`our_group` is derived from `validator_groups`; qed");

 							our_group
 								.into_iter()
@@ -35,7 +35,9 @@ use polkadot_node_subsystem::{
 	ActivatedLeaf, LeafStatus,
 };
 use polkadot_node_subsystem_test_helpers::mock::make_ferdie_keystore;
-use polkadot_primitives::v2::{Hash, Id as ParaId, SessionInfo, ValidationCode};
+use polkadot_primitives::v2::{
+	GroupIndex, Hash, Id as ParaId, IndexedVec, SessionInfo, ValidationCode, ValidatorId,
+};
 use polkadot_primitives_test_helpers::{
 	dummy_committed_candidate_receipt, dummy_hash, AlwaysZeroRng,
 };
@@ -83,7 +85,7 @@ fn active_head_accepts_only_2_seconded_per_validator() {
 	};

 	let mut head_data = ActiveHeadData::new(
-		validators,
+		IndexedVec::<ValidatorIndex, ValidatorId>::from(validators),
 		session_index,
 		PerLeafSpan::new(Arc::new(jaeger::Span::Disabled), "test"),
 	);
@@ -429,7 +431,7 @@ fn peer_view_update_sends_messages() {

 	let new_head_data = {
 		let mut data = ActiveHeadData::new(
-			validators,
+			IndexedVec::<ValidatorIndex, ValidatorId>::from(validators),
 			session_index,
 			PerLeafSpan::new(Arc::new(jaeger::Span::Disabled), "test"),
 		);
@@ -2319,7 +2321,7 @@ fn handle_multiple_seconded_statements() {
 }

 fn make_session_info(validators: Vec<Pair>, groups: Vec<Vec<u32>>) -> SessionInfo {
-	let validator_groups: Vec<Vec<ValidatorIndex>> = groups
+	let validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>> = groups
 		.iter()
 		.map(|g| g.into_iter().map(|v| ValidatorIndex(*v)).collect())
 		.collect();
@@ -135,11 +135,11 @@ impl DisputeMessage {

 		let valid_id = session_info
 			.validators
-			.get(valid_index.0 as usize)
+			.get(valid_index)
 			.ok_or(Error::ValidStatementInvalidValidatorIndex)?;
 		let invalid_id = session_info
 			.validators
-			.get(invalid_index.0 as usize)
+			.get(invalid_index)
 			.ok_or(Error::InvalidStatementInvalidValidatorIndex)?;

 		if valid_id != valid_statement.validator_public() {
@@ -223,8 +223,7 @@ impl UncheckedDisputeMessage {

 		let vote_valid = {
 			let ValidDisputeVote { validator_index, signature, kind } = valid_vote;
-			let validator_public =
-				session_info.validators.get(validator_index.0 as usize).ok_or(())?.clone();
+			let validator_public = session_info.validators.get(validator_index).ok_or(())?.clone();

 			(
 				SignedDisputeStatement::new_checked(
@@ -240,8 +239,7 @@ impl UncheckedDisputeMessage {

 		let vote_invalid = {
 			let InvalidDisputeVote { validator_index, signature, kind } = invalid_vote;
-			let validator_public =
-				session_info.validators.get(validator_index.0 as usize).ok_or(())?.clone();
+			let validator_public = session_info.validators.get(validator_index).ok_or(())?.clone();

 			(
 				SignedDisputeStatement::new_checked(
@@ -399,10 +399,10 @@ mod tests {

 	fn dummy_session_info(index: SessionIndex) -> SessionInfo {
 		SessionInfo {
-			validators: Vec::new(),
+			validators: Default::default(),
 			discovery_keys: Vec::new(),
 			assignment_keys: Vec::new(),
-			validator_groups: Vec::new(),
+			validator_groups: Default::default(),
 			n_cores: index as _,
 			zeroth_delay_tranche_width: index as _,
 			relay_vrf_modulo_samples: index as _,
@@ -27,9 +27,9 @@ use sp_keystore::{CryptoStore, SyncCryptoStorePtr};

 use polkadot_node_subsystem::{messages::RuntimeApiMessage, overseer, SubsystemSender};
 use polkadot_primitives::v2::{
-	CandidateEvent, CoreState, EncodeAs, GroupIndex, GroupRotationInfo, Hash, OccupiedCore,
-	ScrapedOnChainVotes, SessionIndex, SessionInfo, Signed, SigningContext, UncheckedSigned,
-	ValidationCode, ValidationCodeHash, ValidatorId, ValidatorIndex,
+	CandidateEvent, CoreState, EncodeAs, GroupIndex, GroupRotationInfo, Hash, IndexedVec,
+	OccupiedCore, ScrapedOnChainVotes, SessionIndex, SessionInfo, Signed, SigningContext,
+	UncheckedSigned, ValidationCode, ValidationCodeHash, ValidatorId, ValidatorIndex,
 };

 use crate::{
@@ -228,7 +228,10 @@ impl RuntimeInfo {
 	/// Get our `ValidatorIndex`.
 	///
 	/// Returns: None if we are not a validator.
-	async fn get_our_index(&self, validators: &[ValidatorId]) -> Option<ValidatorIndex> {
+	async fn get_our_index(
+		&self,
+		validators: &IndexedVec<ValidatorIndex, ValidatorId>,
+	) -> Option<ValidatorIndex> {
 		let keystore = self.keystore.as_ref()?;
 		for (i, v) in validators.iter().enumerate() {
 			if CryptoStore::has_keys(&**keystore, &[(v.to_raw_vec(), ValidatorId::ID)]).await {
@@ -254,7 +257,7 @@ where

 	session_info
 		.validators
-		.get(signed.unchecked_validator_index().0 as usize)
+		.get(signed.unchecked_validator_index())
 		.ok_or_else(|| signed.clone())
 		.and_then(|v| signed.try_into_checked(&signing_context, v))
 }
@@ -19,7 +19,12 @@
 use bitvec::vec::BitVec;
 use parity_scale_codec::{Decode, Encode};
 use scale_info::TypeInfo;
-use sp_std::prelude::*;
+use sp_std::{
+	marker::PhantomData,
+	prelude::*,
+	slice::{Iter, IterMut},
+	vec::IntoIter,
+};

 use application_crypto::KeyTypeId;
 use inherents::InherentIdentifier;
@@ -123,6 +128,12 @@ impl MallocSizeOf for ValidatorId {
 	}
 }

+/// Trait required for type specific indices e.g. `ValidatorIndex` and `GroupIndex`
+pub trait TypeIndex {
+	/// Returns the index associated to this value.
+	fn type_index(&self) -> usize;
+}
+
 /// Index of the validator is used as a lightweight replacement of the `ValidatorId` when appropriate.
 #[derive(Eq, Ord, PartialEq, PartialOrd, Copy, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
 #[cfg_attr(feature = "std", derive(Serialize, Deserialize, Hash, MallocSizeOf))]
@@ -135,6 +146,12 @@ impl From<u32> for ValidatorIndex {
 	}
 }

+impl TypeIndex for ValidatorIndex {
+	fn type_index(&self) -> usize {
+		self.0 as usize
+	}
+}
+
 application_crypto::with_pair! {
 	/// A Parachain validator keypair.
 	pub type ValidatorPair = validator_app::Pair;
@@ -779,6 +796,12 @@ impl From<u32> for CoreIndex {
 	}
 }

+impl TypeIndex for CoreIndex {
+	fn type_index(&self) -> usize {
+		self.0 as usize
+	}
+}
+
 /// The unique (during session) index of a validator group.
 #[derive(Encode, Decode, Default, Clone, Copy, Debug, PartialEq, Eq, TypeInfo)]
 #[cfg_attr(feature = "std", derive(Hash, MallocSizeOf))]
@@ -790,6 +813,12 @@ impl From<u32> for GroupIndex {
 	}
 }

+impl TypeIndex for GroupIndex {
+	fn type_index(&self) -> usize {
+		self.0 as usize
+	}
+}
+
 /// A claim on authoring the next block for a given parathread.
 #[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
 #[cfg_attr(feature = "std", derive(PartialEq))]
@@ -1569,6 +1598,72 @@ impl CompactStatement {
 	}
 }

+/// `IndexedVec` struct indexed by type specific indices.
+#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
+#[cfg_attr(feature = "std", derive(PartialEq, MallocSizeOf))]
+pub struct IndexedVec<K, V>(Vec<V>, PhantomData<fn(K) -> K>);
+
+impl<K, V> Default for IndexedVec<K, V> {
+	fn default() -> Self {
+		Self(vec![], PhantomData)
+	}
+}
+
+impl<K, V> From<Vec<V>> for IndexedVec<K, V> {
+	fn from(validators: Vec<V>) -> Self {
+		Self(validators, PhantomData)
+	}
+}
+
+impl<K, V> FromIterator<V> for IndexedVec<K, V> {
+	fn from_iter<T: IntoIterator<Item = V>>(iter: T) -> Self {
+		Self(Vec::from_iter(iter), PhantomData)
+	}
+}
+
+impl<K, V> IndexedVec<K, V>
+where
+	V: Clone,
+{
+	/// Returns a reference to an element indexed using `K`.
+	pub fn get(&self, index: K) -> Option<&V>
+	where
+		K: TypeIndex,
+	{
+		self.0.get(index.type_index())
+	}
+
+	/// Returns number of elements in vector.
+	pub fn len(&self) -> usize {
+		self.0.len()
+	}
+
+	/// Returns contained vector.
+	pub fn to_vec(&self) -> Vec<V> {
+		self.0.clone()
+	}
+
+	/// Returns an iterator over the underlying vector.
+	pub fn iter(&self) -> Iter<'_, V> {
+		self.0.iter()
+	}
+
+	/// Returns a mutable iterator over the underlying vector.
+	pub fn iter_mut(&mut self) -> IterMut<'_, V> {
+		self.0.iter_mut()
+	}
+
+	/// Creates a consuming iterator.
+	pub fn into_iter(self) -> IntoIter<V> {
+		self.0.into_iter()
+	}
+
+	/// Returns true if the underlying container is empty.
+	pub fn is_empty(&self) -> bool {
+		self.0.is_empty()
+	}
+}
+
 /// The maximum number of validators `f` which may safely be faulty.
 ///
 /// The total number of validators is `n = 3f + e` where `e in { 1, 2, 3 }`.
@@ -1603,7 +1698,7 @@ pub struct SessionInfo {
 	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148).
 	///
 	/// `SessionInfo::validators` will be limited to to `max_validators` when set.
-	pub validators: Vec<ValidatorId>,
+	pub validators: IndexedVec<ValidatorIndex, ValidatorId>,
 	/// Validators' authority discovery keys for the session in canonical ordering.
 	///
 	/// NOTE: The first `validators.len()` entries will match the corresponding validators in
@@ -1626,7 +1721,7 @@ pub struct SessionInfo {
 	/// Validators in shuffled ordering - these are the validator groups as produced
 	/// by the `Scheduler` module for the session and are typically referred to by
 	/// `GroupIndex`.
-	pub validator_groups: Vec<Vec<ValidatorIndex>>,
+	pub validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>>,
 	/// The number of availability cores used by the protocol during this session.
 	pub n_cores: u32,
 	/// The zeroth delay tranche width.
@@ -1679,7 +1774,7 @@ pub struct OldV1SessionInfo {
 	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148).
 	///
 	/// `SessionInfo::validators` will be limited to to `max_validators` when set.
-	pub validators: Vec<ValidatorId>,
+	pub validators: IndexedVec<ValidatorIndex, ValidatorId>,
 	/// Validators' authority discovery keys for the session in canonical ordering.
 	///
 	/// NOTE: The first `validators.len()` entries will match the corresponding validators in
@@ -1702,7 +1797,7 @@ pub struct OldV1SessionInfo {
 	/// Validators in shuffled ordering - these are the validator groups as produced
 	/// by the `Scheduler` module for the session and are typically referred to by
 	/// `GroupIndex`.
-	pub validator_groups: Vec<Vec<ValidatorIndex>>,
+	pub validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>>,
 	/// The number of availability cores used by the protocol during this session.
 	pub n_cores: u32,
 	/// The zeroth delay tranche width.
@@ -25,9 +25,10 @@ use primitives::v2::{
 	collator_signature_payload, AvailabilityBitfield, BackedCandidate, CandidateCommitments,
 	CandidateDescriptor, CandidateHash, CollatorId, CollatorSignature, CommittedCandidateReceipt,
 	CompactStatement, CoreIndex, CoreOccupied, DisputeStatement, DisputeStatementSet, GroupIndex,
-	HeadData, Id as ParaId, InherentData as ParachainsInherentData, InvalidDisputeStatementKind,
-	PersistedValidationData, SessionIndex, SigningContext, UncheckedSigned,
-	ValidDisputeStatementKind, ValidationCode, ValidatorId, ValidatorIndex, ValidityAttestation,
+	HeadData, Id as ParaId, IndexedVec, InherentData as ParachainsInherentData,
+	InvalidDisputeStatementKind, PersistedValidationData, SessionIndex, SigningContext,
+	UncheckedSigned, ValidDisputeStatementKind, ValidationCode, ValidatorId, ValidatorIndex,
+	ValidityAttestation,
 };
 use sp_core::{sr25519, H256};
 use sp_runtime::{
@@ -65,7 +66,7 @@ fn byte32_slice_from(n: u32) -> [u8; 32] {
 /// Paras inherent `enter` benchmark scenario builder.
 pub(crate) struct BenchBuilder<T: paras_inherent::Config> {
 	/// Active validators. Validators should be declared prior to all other setup.
-	validators: Option<Vec<ValidatorId>>,
+	validators: Option<IndexedVec<ValidatorIndex, ValidatorId>>,
 	/// Starting block number; we expect it to get incremented on session setup.
 	block_number: T::BlockNumber,
 	/// Starting session; we expect it to get incremented on session setup.
@@ -410,7 +411,7 @@ impl<T: paras_inherent::Config> BenchBuilder<T> {
 		assert_eq!(<shared::Pallet<T>>::session_index(), target_session);

 		// We need to refetch validators since they have been shuffled.
-		let validators_shuffled: Vec<_> = session_info::Pallet::<T>::session_info(target_session)
+		let validators_shuffled = session_info::Pallet::<T>::session_info(target_session)
 			.unwrap()
 			.validators
 			.clone();
@@ -549,7 +550,7 @@ impl<T: paras_inherent::Config> BenchBuilder<T> {
 					.iter()
 					.take(*num_votes as usize)
 					.map(|val_idx| {
-						let public = validators.get(val_idx.0 as usize).unwrap();
+						let public = validators.get(*val_idx).unwrap();
 						let sig = UncheckedSigned::<CompactStatement>::benchmark_sign(
 							public,
 							CompactStatement::Valid(candidate_hash.clone()),
@@ -606,7 +607,7 @@ impl<T: paras_inherent::Config> BenchBuilder<T> {
 					self.dispute_statements.get(&seed).cloned().unwrap_or(validators.len() as u32);
 				let statements = (0..statements_len)
 					.map(|validator_index| {
-						let validator_public = &validators.get(validator_index as usize).expect("Test case is not borked. `ValidatorIndex` out of bounds of `ValidatorId`s.");
+						let validator_public = &validators.get(ValidatorIndex::from(validator_index)).expect("Test case is not borked. `ValidatorIndex` out of bounds of `ValidatorId`s.");

 						// We need dispute statements on each side. And we don't want a revert log
 						// so we make sure that we have a super majority with valid statements.
@@ -985,8 +985,7 @@ impl<T: Config> Pallet<T> {
 			let mut importer = DisputeStateImporter::new(dispute_state, now);
 			for (i, (statement, validator_index, signature)) in set.statements.iter().enumerate() {
 				// assure the validator index and is present in the session info
-				let validator_public = match session_info.validators.get(validator_index.0 as usize)
-				{
+				let validator_public = match session_info.validators.get(*validator_index) {
 					None => {
 						filter.remove_index(i);
 						continue
@@ -257,7 +257,7 @@ where

 		let keys = losers
 			.into_iter()
-			.filter_map(|i| session_info.validators.get(i.0 as usize).cloned().map(|id| (i, id)))
+			.filter_map(|i| session_info.validators.get(i).cloned().map(|id| (i, id)))
 			.collect();
 		let unapplied = PendingSlashes { keys, kind };
 		<UnappliedSlashes<T>>::insert(session_index, candidate_hash, unapplied);
@@ -80,7 +80,7 @@ where
 	let session_index = crate::shared::Pallet::<T>::session_index();
 	let session_info = crate::session_info::Pallet::<T>::session_info(session_index);
 	let session_info = session_info.unwrap();
-	let validator_id = session_info.validators[0].clone();
+	let validator_id = session_info.validators.get(ValidatorIndex::from(0)).unwrap().clone();
 	let key = (PARACHAIN_KEY_TYPE_ID, validator_id.clone());
 	let key_owner_proof = pallet_session::historical::Pallet::<T>::prove(key).unwrap();

@@ -126,12 +126,12 @@ impl<T: Config> Pallet<T> {

 		let dispute_period = config.dispute_period;

-		let validators = notification.validators.clone();
+		let validators = notification.validators.clone().into();
 		let discovery_keys = <T as AuthorityDiscoveryConfig>::authorities();
 		let assignment_keys = AssignmentKeysUnsafe::<T>::get();
 		let active_set = <shared::Pallet<T>>::active_validator_indices();

-		let validator_groups = <scheduler::Pallet<T>>::validator_groups();
+		let validator_groups = <scheduler::Pallet<T>>::validator_groups().into();
 		let n_cores = <scheduler::Pallet<T>>::availability_cores().len() as u32;
 		let zeroth_delay_tranche_width = config.zeroth_delay_tranche_width;
 		let relay_vrf_modulo_samples = config.relay_vrf_modulo_samples;
@@ -201,7 +201,7 @@ fn session_info_active_subsets() {
 		});
 		let session = Sessions::<Test>::get(&1).unwrap();

-		assert_eq!(session.validators, validators);
+		assert_eq!(session.validators.to_vec(), validators);
 		assert_eq!(
 			session.discovery_keys,
 			take_active_subset_and_inactive(&active_set, &unscrambled_discovery),