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>

polkadot/node/network/statement-distribution/src/lib.rs

@@ -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()