move generics of election trait to associated types

frame/bags-list/remote-tests/src/snapshot.rs

@@ -55,11 +55,8 @@ pub async fn execute<Runtime: crate::RuntimeT, Block: BlockT + DeserializeOwned>
 			<Runtime as pallet_staking::Config>::SortedListProvider::count(),
 		);
 
-		let voters = <pallet_staking::Pallet<Runtime> as ElectionDataProvider<
-			Runtime::AccountId,
-			Runtime::BlockNumber,
-		>>::voters(voter_limit)
-		.unwrap();
+		let voters =
+			<pallet_staking::Pallet<Runtime> as ElectionDataProvider>::voters(voter_limit).unwrap();
 
 		let mut voters_nominator_only = voters
 			.iter()

frame/election-provider-multi-phase/src/benchmarking.rs

@@ -289,7 +289,7 @@ frame_benchmarking::benchmarks! {
 		assert!(<Snapshot<T>>::get().is_some());
 		assert!(<SnapshotMetadata<T>>::get().is_some());
 	}: {
-		assert_ok!(<MultiPhase<T> as ElectionProvider<T::AccountId, T::BlockNumber>>::elect());
+		assert_ok!(<MultiPhase<T> as ElectionProvider>::elect());
 	} verify {
 		assert!(<MultiPhase<T>>::queued_solution().is_none());
 		assert!(<DesiredTargets<T>>::get().is_none());

frame/election-provider-multi-phase/src/lib.rs

@@ -139,7 +139,7 @@
 //! To generate an emergency solution, one must only provide one argument: [`Supports`]. This is
 //! essentially a collection of elected winners for the election, and voters who support them. The
 //! supports can be generated by any means. In the simplest case, it could be manual. For example,
-//! in the case of massive network failure or misbehaviour, [`Config::ForceOrigin`] might decide to
+//! in the case of massive network failure or misbehavior, [`Config::ForceOrigin`] might decide to
 //! select only a small number of emergency winners (which would greatly restrict the next validator
 //! set, if this pallet is used with `pallet-staking`). If the failure is for other technical
 //! reasons, then a simple and safe way to generate supports is using the staking-miner binary
@@ -286,10 +286,7 @@ pub type SolutionTargetIndexOf<T> = <SolutionOf<T> as NposSolution>::TargetIndex
 /// The accuracy of the election, when submitted from offchain. Derived from [`SolutionOf`].
 pub type SolutionAccuracyOf<T> = <SolutionOf<T> as NposSolution>::Accuracy;
 /// The fallback election type.
-pub type FallbackErrorOf<T> = <<T as crate::Config>::Fallback as ElectionProvider<
-	<T as frame_system::Config>::AccountId,
-	<T as frame_system::Config>::BlockNumber,
->>::Error;
+pub type FallbackErrorOf<T> = <<T as crate::Config>::Fallback as ElectionProvider>::Error;
 
 /// Configuration for the benchmarks of the pallet.
 pub trait BenchmarkingConfig {
@@ -312,7 +309,9 @@ pub trait BenchmarkingConfig {
 /// A fallback implementation that transitions the pallet to the emergency phase.
 pub struct NoFallback<T>(sp_std::marker::PhantomData<T>);
 
-impl<T: Config> ElectionProvider<T::AccountId, T::BlockNumber> for NoFallback<T> {
+impl<T: Config> ElectionProvider for NoFallback<T> {
+	type AccountId = T::AccountId;
+	type BlockNumber = T::BlockNumber;
 	type DataProvider = T::DataProvider;
 	type Error = &'static str;
 
@@ -654,7 +653,10 @@ pub mod pallet {
 		type MinerMaxLength: Get<u32>;
 
 		/// Something that will provide the election data.
-		type DataProvider: ElectionDataProvider<Self::AccountId, Self::BlockNumber>;
+		type DataProvider: ElectionDataProvider<
+			AccountId = Self::AccountId,
+			BlockNumber = Self::BlockNumber,
+		>;
 
 		/// The solution type.
 		type Solution: codec::Codec
@@ -669,8 +671,8 @@ pub mod pallet {
 
 		/// Configuration for the fallback
 		type Fallback: ElectionProvider<
-			Self::AccountId,
-			Self::BlockNumber,
+			AccountId = Self::AccountId,
+			BlockNumber = Self::BlockNumber,
 			DataProvider = Self::DataProvider,
 		>;
 
@@ -818,7 +820,7 @@ pub mod pallet {
 			// NOTE that this pallet does not really need to enforce this in runtime. The
 			// solution cannot represent any voters more than `LIMIT` anyhow.
 			assert_eq!(
-				<T::DataProvider as ElectionDataProvider<T::AccountId, T::BlockNumber>>::MAXIMUM_VOTES_PER_VOTER,
+				<T::DataProvider as ElectionDataProvider>::MAXIMUM_VOTES_PER_VOTER,
 				<SolutionOf<T> as NposSolution>::LIMIT as u32,
 			);
 		}
@@ -1492,7 +1494,9 @@ impl<T: Config> Pallet<T> {
 	}
 }
 
-impl<T: Config> ElectionProvider<T::AccountId, T::BlockNumber> for Pallet<T> {
+impl<T: Config> ElectionProvider for Pallet<T> {
+	type AccountId = T::AccountId;
+	type BlockNumber = T::BlockNumber;
 	type Error = ElectionError<T>;
 	type DataProvider = T::DataProvider;
 

frame/election-provider-multi-phase/src/mock.rs

@@ -285,7 +285,9 @@ impl onchain::Config for Runtime {
 }
 
 pub struct MockFallback;
-impl ElectionProvider<AccountId, u64> for MockFallback {
+impl ElectionProvider for MockFallback {
+	type AccountId = AccountId;
+	type BlockNumber = u64;
 	type Error = &'static str;
 	type DataProvider = StakingMock;
 
@@ -438,7 +440,9 @@ pub type Extrinsic = sp_runtime::testing::TestXt<Call, ()>;
 pub struct ExtBuilder {}
 
 pub struct StakingMock;
-impl ElectionDataProvider<AccountId, u64> for StakingMock {
+impl ElectionDataProvider for StakingMock {
+	type AccountId = AccountId;
+	type BlockNumber = u64;
 	const MAXIMUM_VOTES_PER_VOTER: u32 = <TestNposSolution as NposSolution>::LIMIT as u32;
 	fn targets(maybe_max_len: Option<usize>) -> data_provider::Result<Vec<AccountId>> {
 		let targets = Targets::get();

frame/election-provider-support/src/lib.rs

@@ -90,21 +90,24 @@
 //!
 //!     pub trait Config: Sized {
 //!         type ElectionProvider: ElectionProvider<
-//!             AccountId,
-//!             BlockNumber,
-//!             DataProvider = Module<Self>,
+//!             AccountId = AccountId,
+//!             BlockNumber = BlockNumber,
+//!             DataProvider = Pallet<Self>,
 //!         >;
 //!     }
 //!
-//!     pub struct Module<T: Config>(std::marker::PhantomData<T>);
+//!     pub struct Pallet<T: Config>(std::marker::PhantomData<T>);
 //!
-//!     impl<T: Config> ElectionDataProvider<AccountId, BlockNumber> for Module<T> {
+//!     impl<T: Config> ElectionDataProvider for Pallet<T> {
+//!         type AccountId = AccountId;
+//!         type BlockNumber = BlockNumber;
 //!         const MAXIMUM_VOTES_PER_VOTER: u32 = 1;
+//!
 //!         fn desired_targets() -> data_provider::Result<u32> {
 //!             Ok(1)
 //!         }
 //!         fn voters(maybe_max_len: Option<usize>)
-//!         -> data_provider::Result<Vec<(AccountId, VoteWeight, Vec<AccountId>)>>
+//!           -> data_provider::Result<Vec<(AccountId, VoteWeight, Vec<AccountId>)>>
 //!         {
 //!             Ok(Default::default())
 //!         }
@@ -124,10 +127,12 @@
 //!     pub struct GenericElectionProvider<T: Config>(std::marker::PhantomData<T>);
 //!
 //!     pub trait Config {
-//!         type DataProvider: ElectionDataProvider<AccountId, BlockNumber>;
+//!         type DataProvider: ElectionDataProvider<AccountId=AccountId, BlockNumber = BlockNumber>;
 //!     }
 //!
-//!     impl<T: Config> ElectionProvider<AccountId, BlockNumber> for GenericElectionProvider<T> {
+//!     impl<T: Config> ElectionProvider for GenericElectionProvider<T> {
+//!         type AccountId = AccountId;
+//!         type BlockNumber = BlockNumber;
 //!         type Error = &'static str;
 //!         type DataProvider = T::DataProvider;
 //!
@@ -146,7 +151,7 @@
 //!
 //!     struct Runtime;
 //!     impl generic_election_provider::Config for Runtime {
-//!         type DataProvider = data_provider_mod::Module<Runtime>;
+//!         type DataProvider = data_provider_mod::Pallet<Runtime>;
 //!     }
 //!
 //!     impl data_provider_mod::Config for Runtime {
@@ -178,7 +183,13 @@ pub mod data_provider {
 }
 
 /// Something that can provide the data to an [`ElectionProvider`].
-pub trait ElectionDataProvider<AccountId, BlockNumber> {
+pub trait ElectionDataProvider {
+	/// The account identifier type.
+	type AccountId;
+
+	/// The block number type.
+	type BlockNumber;
+
 	/// Maximum number of votes per voter that this data provider is providing.
 	const MAXIMUM_VOTES_PER_VOTER: u32;
 
@@ -189,7 +200,7 @@ pub trait ElectionDataProvider<AccountId, BlockNumber> {
 	///
 	/// This should be implemented as a self-weighing function. The implementor should register its
 	/// appropriate weight at the end of execution with the system pallet directly.
-	fn targets(maybe_max_len: Option<usize>) -> data_provider::Result<Vec<AccountId>>;
+	fn targets(maybe_max_len: Option<usize>) -> data_provider::Result<Vec<Self::AccountId>>;
 
 	/// All possible voters for the election.
 	///
@@ -202,7 +213,7 @@ pub trait ElectionDataProvider<AccountId, BlockNumber> {
 	/// appropriate weight at the end of execution with the system pallet directly.
 	fn voters(
 		maybe_max_len: Option<usize>,
-	) -> data_provider::Result<Vec<(AccountId, VoteWeight, Vec<AccountId>)>>;
+	) -> data_provider::Result<Vec<(Self::AccountId, VoteWeight, Vec<Self::AccountId>)>>;
 
 	/// The number of targets to elect.
 	///
@@ -216,14 +227,14 @@ pub trait ElectionDataProvider<AccountId, BlockNumber> {
 	/// [`ElectionProvider::elect`].
 	///
 	/// This is only useful for stateful election providers.
-	fn next_election_prediction(now: BlockNumber) -> BlockNumber;
+	fn next_election_prediction(now: Self::BlockNumber) -> Self::BlockNumber;
 
 	/// Utility function only to be used in benchmarking scenarios, to be implemented optionally,
 	/// else a noop.
 	#[cfg(any(feature = "runtime-benchmarks", test))]
 	fn put_snapshot(
-		_voters: Vec<(AccountId, VoteWeight, Vec<AccountId>)>,
-		_targets: Vec<AccountId>,
+		_voters: Vec<(Self::AccountId, VoteWeight, Vec<Self::AccountId>)>,
+		_targets: Vec<Self::AccountId>,
 		_target_stake: Option<VoteWeight>,
 	) {
 	}
@@ -233,22 +244,29 @@ pub trait ElectionDataProvider<AccountId, BlockNumber> {
 	///
 	/// Same as `put_snapshot`, but can add a single voter one by one.
 	#[cfg(any(feature = "runtime-benchmarks", test))]
-	fn add_voter(_voter: AccountId, _weight: VoteWeight, _targets: Vec<AccountId>) {}
+	fn add_voter(_voter: Self::AccountId, _weight: VoteWeight, _targets: Vec<Self::AccountId>) {}
 
 	/// Utility function only to be used in benchmarking scenarios, to be implemented optionally,
 	/// else a noop.
 	///
 	/// Same as `put_snapshot`, but can add a single voter one by one.
 	#[cfg(any(feature = "runtime-benchmarks", test))]
-	fn add_target(_target: AccountId) {}
+	fn add_target(_target: Self::AccountId) {}
 
 	/// Clear all voters and targets.
 	#[cfg(any(feature = "runtime-benchmarks", test))]
 	fn clear() {}
 }
 
+/// An election data provider that should only be used for testing.
 #[cfg(feature = "std")]
-impl<AccountId, BlockNumber> ElectionDataProvider<AccountId, BlockNumber> for () {
+pub struct TestDataProvider<X>(sp_std::marker::PhantomData<X>);
+
+#[cfg(feature = "std")]
+impl<AccountId, BlockNumber> ElectionDataProvider for TestDataProvider<(AccountId, BlockNumber)> {
+	type AccountId = AccountId;
+	type BlockNumber = BlockNumber;
+
 	const MAXIMUM_VOTES_PER_VOTER: u32 = 0;
 	fn targets(_maybe_max_len: Option<usize>) -> data_provider::Result<Vec<AccountId>> {
 		Ok(Default::default())
@@ -271,29 +289,44 @@ impl<AccountId, BlockNumber> ElectionDataProvider<AccountId, BlockNumber> for ()
 /// This trait only provides an interface to _request_ an election, i.e.
 /// [`ElectionProvider::elect`]. That data required for the election need to be passed to the
 /// implemented of this trait through [`ElectionProvider::DataProvider`].
-pub trait ElectionProvider<AccountId, BlockNumber> {
+pub trait ElectionProvider {
+	/// The account identifier type.
+	type AccountId;
+
+	/// The block number type.
+	type BlockNumber;
+
 	/// The error type that is returned by the provider.
 	type Error: Debug;
 
 	/// The data provider of the election.
-	type DataProvider: ElectionDataProvider<AccountId, BlockNumber>;
+	type DataProvider: ElectionDataProvider<
+		AccountId = Self::AccountId,
+		BlockNumber = Self::BlockNumber,
+	>;
 
 	/// Elect a new set of winners.
 	///
 	/// The result is returned in a target major format, namely as vector of supports.
 	///
 	/// This should be implemented as a self-weighing function. The implementor should register its
 	/// appropriate weight at the end of execution with the system pallet directly.
-	fn elect() -> Result<Supports<AccountId>, Self::Error>;
+	fn elect() -> Result<Supports<Self::AccountId>, Self::Error>;
 }
 
+/// An election provider to be used only for testing.
 #[cfg(feature = "std")]
-impl<AccountId, BlockNumber> ElectionProvider<AccountId, BlockNumber> for () {
+pub struct NoElection<X>(sp_std::marker::PhantomData<X>);
+
+#[cfg(feature = "std")]
+impl<AccountId, BlockNumber> ElectionProvider for NoElection<(AccountId, BlockNumber)> {
+	type AccountId = AccountId;
+	type BlockNumber = BlockNumber;
 	type Error = &'static str;
-	type DataProvider = ();
+	type DataProvider = TestDataProvider<(AccountId, BlockNumber)>;
 
 	fn elect() -> Result<Supports<AccountId>, Self::Error> {
-		Err("<() as ElectionProvider> cannot do anything.")
+		Err("<NoElection as ElectionProvider> cannot do anything.")
 	}
 }
 

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

@@ -62,10 +62,15 @@ pub trait Config: frame_system::Config {
 	/// The accuracy used to compute the election:
 	type Accuracy: PerThing128;
 	/// Something that provides the data for election.
-	type DataProvider: ElectionDataProvider<Self::AccountId, Self::BlockNumber>;
+	type DataProvider: ElectionDataProvider<
+		AccountId = Self::AccountId,
+		BlockNumber = Self::BlockNumber,
+	>;
 }
 
-impl<T: Config> ElectionProvider<T::AccountId, T::BlockNumber> for OnChainSequentialPhragmen<T> {
+impl<T: Config> ElectionProvider for OnChainSequentialPhragmen<T> {
+	type AccountId = T::AccountId;
+	type BlockNumber = T::BlockNumber;
 	type Error = Error;
 	type DataProvider = T::DataProvider;
 
@@ -160,7 +165,9 @@ mod tests {
 		use crate::data_provider;
 
 		pub struct DataProvider;
-		impl ElectionDataProvider<AccountId, BlockNumber> for DataProvider {
+		impl ElectionDataProvider for DataProvider {
+			type AccountId = AccountId;
+			type BlockNumber = BlockNumber;
 			const MAXIMUM_VOTES_PER_VOTER: u32 = 2;
 			fn voters(
 				_: Option<usize>,

frame/staking/src/pallet/impls.rs

@@ -844,7 +844,9 @@ impl<T: Config> Pallet<T> {
 	}
 }
 
-impl<T: Config> ElectionDataProvider<T::AccountId, BlockNumberFor<T>> for Pallet<T> {
+impl<T: Config> ElectionDataProvider for Pallet<T> {
+	type AccountId = T::AccountId;
+	type BlockNumber = BlockNumberFor<T>;
 	const MAXIMUM_VOTES_PER_VOTER: u32 = T::MAX_NOMINATIONS;
 
 	fn desired_targets() -> data_provider::Result<u32> {

frame/staking/src/pallet/mod.rs

@@ -79,16 +79,16 @@ pub mod pallet {
 
 		/// Something that provides the election functionality.
 		type ElectionProvider: frame_election_provider_support::ElectionProvider<
-			Self::AccountId,
-			Self::BlockNumber,
+			AccountId = Self::AccountId,
+			BlockNumber = Self::BlockNumber,
 			// we only accept an election provider that has staking as data provider.
 			DataProvider = Pallet<Self>,
 		>;
 
 		/// Something that provides the election functionality at genesis.
 		type GenesisElectionProvider: frame_election_provider_support::ElectionProvider<
-			Self::AccountId,
-			Self::BlockNumber,
+			AccountId = Self::AccountId,
+			BlockNumber = Self::BlockNumber,
 			DataProvider = Pallet<Self>,
 		>;
 

frame/staking/src/tests.rs

@@ -4013,7 +4013,7 @@ mod election_data_provider {
 		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Staking::nominators(101).unwrap().targets, vec![11, 21]);
 			assert_eq!(
-				<Staking as ElectionDataProvider<AccountId, BlockNumber>>::voters(None)
+				<Staking as ElectionDataProvider>::voters(None)
 					.unwrap()
 					.iter()
 					.find(|x| x.0 == 101)
@@ -4028,7 +4028,7 @@ mod election_data_provider {
 			// 11 is gone.
 			start_active_era(2);
 			assert_eq!(
-				<Staking as ElectionDataProvider<AccountId, BlockNumber>>::voters(None)
+				<Staking as ElectionDataProvider>::voters(None)
 					.unwrap()
 					.iter()
 					.find(|x| x.0 == 101)
@@ -4040,7 +4040,7 @@ mod election_data_provider {
 			// resubmit and it is back
 			assert_ok!(Staking::nominate(Origin::signed(100), vec![11, 21]));
 			assert_eq!(
-				<Staking as ElectionDataProvider<AccountId, BlockNumber>>::voters(None)
+				<Staking as ElectionDataProvider>::voters(None)
 					.unwrap()
 					.iter()
 					.find(|x| x.0 == 101)