pallet-referenda: Migrate from Currency reserves to fungible holds

cumulus/parachains/runtimes/assets/asset-hub-westend/src/governance/mod.rs

@@ -88,7 +88,7 @@ impl pallet_referenda::Config for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type RuntimeEvent = RuntimeEvent;
 	type Scheduler = Scheduler;
-	type Currency = Balances;
+	type NativeBalance = Balances;
 	type SubmitOrigin = frame_system::EnsureSigned<AccountId>;
 	type CancelOrigin = EitherOf<EnsureRoot<AccountId>, ReferendumCanceller>;
 	type KillOrigin = EitherOf<EnsureRoot<AccountId>, ReferendumKiller>;

cumulus/parachains/runtimes/collectives/collectives-westend/src/ambassador/mod.rs

@@ -135,7 +135,7 @@ impl pallet_referenda::Config<AmbassadorReferendaInstance> for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type RuntimeEvent = RuntimeEvent;
 	type Scheduler = Scheduler;
-	type Currency = Balances;
+	type NativeBalance = Balances;
 	// A proposal can be submitted by a member of the Ambassador Program of
 	// [ranks::SENIOR_AMBASSADOR_TIER_3] rank or higher.
 	type SubmitOrigin = pallet_ranked_collective::EnsureMember<

cumulus/parachains/runtimes/collectives/collectives-westend/src/fellowship/mod.rs

@@ -80,7 +80,7 @@ impl pallet_referenda::Config<FellowshipReferendaInstance> for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type RuntimeEvent = RuntimeEvent;
 	type Scheduler = Scheduler;
-	type Currency = Balances;
+	type NativeBalance = Balances;
 	// Fellows can submit proposals.
 	type SubmitOrigin = EitherOf<
 		pallet_ranked_collective::EnsureMember<Runtime, FellowshipCollectiveInstance, 3>,

polkadot/runtime/rococo/src/governance/fellowship.rs

@@ -299,7 +299,7 @@ impl pallet_referenda::Config<FellowshipReferendaInstance> for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type RuntimeEvent = RuntimeEvent;
 	type Scheduler = Scheduler;
-	type Currency = Balances;
+	type NativeBalance = Balances;
 	type SubmitOrigin =
 		pallet_ranked_collective::EnsureMember<Runtime, FellowshipCollectiveInstance, 1>;
 	type CancelOrigin = FellowshipExperts;

polkadot/runtime/rococo/src/governance/mod.rs

@@ -79,7 +79,7 @@ impl pallet_referenda::Config for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type RuntimeEvent = RuntimeEvent;
 	type Scheduler = Scheduler;
-	type Currency = Balances;
+	type NativeBalance = Balances;
 	type SubmitOrigin = frame_system::EnsureSigned<AccountId>;
 	type CancelOrigin = EitherOf<EnsureRoot<AccountId>, ReferendumCanceller>;
 	type KillOrigin = EitherOf<EnsureRoot<AccountId>, ReferendumKiller>;

polkadot/runtime/westend/src/governance/mod.rs

@@ -83,7 +83,7 @@ impl pallet_referenda::Config for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type RuntimeEvent = RuntimeEvent;
 	type Scheduler = Scheduler;
-	type Currency = Balances;
+	type NativeBalance = Balances;
 	type SubmitOrigin = frame_system::EnsureSigned<AccountId>;
 	type CancelOrigin = EitherOf<EnsureRoot<AccountId>, ReferendumCanceller>;
 	type KillOrigin = EitherOf<EnsureRoot<AccountId>, ReferendumKiller>;

substrate/bin/node/runtime/src/lib.rs

@@ -1051,7 +1051,7 @@ impl pallet_referenda::Config for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type RuntimeEvent = RuntimeEvent;
 	type Scheduler = Scheduler;
-	type Currency = pallet_balances::Pallet<Self>;
+	type NativeBalance = pallet_balances::Pallet<Self>;
 	type SubmitOrigin = EnsureSigned<AccountId>;
 	type CancelOrigin = EnsureRoot<AccountId>;
 	type KillOrigin = EnsureRoot<AccountId>;

substrate/frame/referenda/src/benchmarking.rs

@@ -26,7 +26,10 @@ use frame_benchmarking::v1::{
 };
 use frame_support::{
 	assert_ok,
-	traits::{Currency, EnsureOrigin, EnsureOriginWithArg, UnfilteredDispatchable},
+	traits::{
+		tokens::{Fortitude, Preservation},
+		EnsureOrigin, EnsureOriginWithArg, UnfilteredDispatchable,
+	},
 };
 use frame_system::RawOrigin;
 use sp_runtime::traits::Bounded as ArithBounded;
@@ -41,9 +44,16 @@ fn assert_last_event<T: Config<I>, I: 'static>(generic_event: <T as Config<I>>::
 	frame_system::Pallet::<T>::assert_last_event(generic_event.into());
 }
 
-fn funded_account<T: Config<I>, I: 'static>(name: &'static str, index: u32) -> T::AccountId {
+fn funded_account<T: Config<I>, I: 'static>(
+	name: &'static str,
+	index: u32,
+	decision_deposit: BalanceOf<T, I>,
+) -> T::AccountId {
 	let caller: T::AccountId = account(name, index, SEED);
-	T::Currency::make_free_balance_be(&caller, BalanceOf::<T, I>::max_value());
+	//Giving enough balance to cover the decision deposit + the submission deposit + buffer for
+	// fees
+	let amount = T::NativeBalance::minimum_balance() + decision_deposit.saturating_mul(2u32.into());
+	T::NativeBalance::set_balance(&caller, amount);
 	caller
 }
 
@@ -55,7 +65,7 @@ fn dummy_call<T: Config<I>, I: 'static>() -> BoundedCallOf<T, I> {
 
 fn create_referendum<T: Config<I>, I: 'static>(origin: T::RuntimeOrigin) -> ReferendumIndex {
 	if let Ok(caller) = frame_system::ensure_signed(origin.clone()) {
-		T::Currency::make_free_balance_be(&caller, BalanceOf::<T, I>::max_value());
+		T::NativeBalance::set_balance(&caller, BalanceOf::<T, I>::max_value() / 2u32.into());
 		whitelist_account!(caller);
 	}
 
@@ -69,8 +79,11 @@ fn create_referendum<T: Config<I>, I: 'static>(origin: T::RuntimeOrigin) -> Refe
 }
 
 fn place_deposit<T: Config<I>, I: 'static>(index: ReferendumIndex) {
-	let caller = funded_account::<T, I>("caller", 0);
+	let track_info = info::<T, I>(index);
+	let decision_deposit = track_info.decision_deposit;
+	let caller = funded_account::<T, I>("caller", 0, decision_deposit);
 	whitelist_account!(caller);
+
 	assert_ok!(Referenda::<T, I>::place_decision_deposit(RawOrigin::Signed(caller).into(), index));
 }
 
@@ -202,7 +215,7 @@ benchmarks_instance_pallet! {
 		let origin =
 			T::SubmitOrigin::try_successful_origin(&RawOrigin::Root.into()).map_err(|_| BenchmarkError::Weightless)?;
 		if let Ok(caller) = frame_system::ensure_signed(origin.clone()) {
-			T::Currency::make_free_balance_be(&caller, BalanceOf::<T, I>::max_value());
+			T::NativeBalance::set_balance(&caller, BalanceOf::<T, I>::max_value()/2u32.into());
 			whitelist_account!(caller);
 		}
 	}: _<T::RuntimeOrigin>(
@@ -291,7 +304,7 @@ benchmarks_instance_pallet! {
 			T::SubmitOrigin::try_successful_origin(&RawOrigin::Root.into()).map_err(|_| BenchmarkError::Weightless)?;
 		let index = create_referendum::<T, I>(origin.clone());
 		let caller = frame_system::ensure_signed(origin.clone()).unwrap();
-		let balance = T::Currency::free_balance(&caller);
+		let balance = T::NativeBalance::reducible_balance(&caller, Preservation::Preserve, Fortitude::Polite);
 		assert_ok!(Referenda::<T, I>::cancel(
 			T::CancelOrigin::try_successful_origin()
 				.expect("CancelOrigin has no successful origin required for the benchmark"),
@@ -301,7 +314,7 @@ benchmarks_instance_pallet! {
 	}: _<T::RuntimeOrigin>(origin, index)
 	verify {
 		assert_matches!(ReferendumInfoFor::<T, I>::get(index), Some(ReferendumInfo::Cancelled(_, None, _)));
-		let new_balance = T::Currency::free_balance(&caller);
+		let new_balance = T::NativeBalance::reducible_balance(&caller, Preservation::Preserve, Fortitude::Polite);
 		// the deposit is zero or make sure it was unreserved.
 		assert!(T::SubmissionDeposit::get().is_zero() || new_balance > balance);
 	}

substrate/frame/referenda/src/lib.rs

@@ -73,12 +73,14 @@ use frame_support::{
 	dispatch::DispatchResult,
 	ensure,
 	traits::{
+		fungible::{Balanced, Inspect, InspectHold, Mutate, MutateHold},
 		schedule::{
 			v3::{Anon as ScheduleAnon, Named as ScheduleNamed},
 			DispatchTime,
 		},
-		Currency, LockIdentifier, OnUnbalanced, OriginTrait, PollStatus, Polling, QueryPreimage,
-		ReservableCurrency, StorePreimage, VoteTally,
+		tokens::{Fortitude, Precision},
+		LockIdentifier, OnUnbalanced, OriginTrait, PollStatus, Polling, QueryPreimage,
+		StorePreimage, VoteTally,
 	},
 	BoundedVec,
 };
@@ -97,11 +99,10 @@ use self::branch::{BeginDecidingBranch, OneFewerDecidingBranch, ServiceBranch};
 pub use self::{
 	pallet::*,
 	types::{
-		BalanceOf, BlockNumberFor, BoundedCallOf, CallOf, ConstTrackInfo, Curve, DecidingStatus,
-		DecidingStatusOf, Deposit, InsertSorted, NegativeImbalanceOf, PalletsOriginOf,
-		ReferendumIndex, ReferendumInfo, ReferendumInfoOf, ReferendumStatus, ReferendumStatusOf,
-		ScheduleAddressOf, StringLike, TallyOf, Track, TrackIdOf, TrackInfo, TrackInfoOf,
-		TracksInfo, VotesOf,
+		BalanceOf, BlockNumberFor, BoundedCallOf, CallOf, ConstTrackInfo, Curve, DebtOf,
+		DecidingStatus, DecidingStatusOf, Deposit, InsertSorted, PalletsOriginOf, ReferendumIndex,
+		ReferendumInfo, ReferendumInfoOf, ReferendumStatus, ReferendumStatusOf, ScheduleAddressOf,
+		StringLike, TallyOf, Track, TrackIdOf, TrackInfo, TrackInfoOf, TracksInfo, VotesOf,
 	},
 	weights::WeightInfo,
 };
@@ -130,12 +131,20 @@ pub mod pallet {
 	};
 
 	/// The in-code storage version.
-	const STORAGE_VERSION: StorageVersion = StorageVersion::new(1);
+	const STORAGE_VERSION: StorageVersion = StorageVersion::new(2);
 
 	#[pallet::pallet]
 	#[pallet::storage_version(STORAGE_VERSION)]
 	pub struct Pallet<T, I = ()>(_);
 
+	/// A reason for holding funds.
+	/// Creates a hold reason for this pallet that is aggregated by `construct_runtime`.
+	#[pallet::composite_enum]
+	pub enum HoldReason<I: 'static = ()> {
+		/// The account has deposited tokens to place a decision deposit.
+		DecisionDeposit,
+	}
+
 	#[pallet::config]
 	pub trait Config<I: 'static = ()>: frame_system::Config + Sized {
 		// System level stuff.
@@ -162,7 +171,11 @@ pub mod pallet {
 				Hasher = Self::Hashing,
 			>;
 		/// Currency type for this pallet.
-		type Currency: ReservableCurrency<Self::AccountId>;
+		type NativeBalance: Inspect<Self::AccountId>
+			+ Mutate<Self::AccountId>
+			+ Balanced<Self::AccountId>
+			+ InspectHold<Self::AccountId, Reason: From<HoldReason<I>>>
+			+ MutateHold<Self::AccountId, Reason: From<HoldReason<I>>>;
 		// Origins and unbalances.
 		/// Origin from which proposals may be submitted.
 		type SubmitOrigin: EnsureOriginWithArg<
@@ -175,7 +188,7 @@ pub mod pallet {
 		/// Origin from which any vote may be killed.
 		type KillOrigin: EnsureOrigin<Self::RuntimeOrigin>;
 		/// Handler for the unbalanced reduction when slashing a preimage deposit.
-		type Slash: OnUnbalanced<NegativeImbalanceOf<Self, I>>;
+		type Slash: OnUnbalanced<DebtOf<Self, I>>;
 		/// The counting type for votes. Usually just balance.
 		type Votes: AtLeast32BitUnsigned + Copy + Parameter + Member + MaxEncodedLen;
 		/// The tallying type.
@@ -569,7 +582,7 @@ pub mod pallet {
 				.take_decision_deposit()
 				.map_err(|_| Error::<T, I>::Unfinished)?
 				.ok_or(Error::<T, I>::NoDeposit)?;
-			Self::refund_deposit(Some(deposit.clone()));
+			Self::refund_deposit(Some(deposit.clone()))?;
 			ReferendumInfoFor::<T, I>::insert(index, info);
 			let e = Event::<T, I>::DecisionDepositRefunded {
 				index,
@@ -621,8 +634,8 @@ pub mod pallet {
 			}
 			Self::note_one_fewer_deciding(status.track);
 			Self::deposit_event(Event::<T, I>::Killed { index, tally: status.tally });
-			Self::slash_deposit(Some(status.submission_deposit.clone()));
-			Self::slash_deposit(status.decision_deposit.clone());
+			Self::slash_deposit(Some(status.submission_deposit.clone()))?;
+			Self::slash_deposit(status.decision_deposit.clone())?;
 			Self::do_clear_metadata(index);
 			let info = ReferendumInfo::Killed(T::BlockNumberProvider::current_block_number());
 			ReferendumInfoFor::<T, I>::insert(index, info);
@@ -707,7 +720,7 @@ pub mod pallet {
 				.take_submission_deposit()
 				.map_err(|_| Error::<T, I>::BadStatus)?
 				.ok_or(Error::<T, I>::NoDeposit)?;
-			Self::refund_deposit(Some(deposit.clone()));
+			Self::refund_deposit(Some(deposit.clone()))?;
 			ReferendumInfoFor::<T, I>::insert(index, info);
 			let e = Event::<T, I>::SubmissionDepositRefunded {
 				index,
@@ -1289,23 +1302,40 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		who: T::AccountId,
 		amount: BalanceOf<T, I>,
 	) -> Result<Deposit<T::AccountId, BalanceOf<T, I>>, DispatchError> {
-		T::Currency::reserve(&who, amount)?;
+		T::NativeBalance::hold(&HoldReason::<I>::DecisionDeposit.into(), &who, amount)?;
 		Ok(Deposit { who, amount })
 	}
 
 	/// Return a deposit, if `Some`.
-	fn refund_deposit(deposit: Option<Deposit<T::AccountId, BalanceOf<T, I>>>) {
+	fn refund_deposit(
+		deposit: Option<Deposit<T::AccountId, BalanceOf<T, I>>>,
+	) -> Result<(), DispatchError> {
 		if let Some(Deposit { who, amount }) = deposit {
-			T::Currency::unreserve(&who, amount);
+			T::NativeBalance::release(
+				&HoldReason::<I>::DecisionDeposit.into(),
+				&who,
+				amount,
+				Precision::BestEffort,
+			)?;
 		}
+		Ok(())
 	}
 
 	/// Slash a deposit, if `Some`.
-	fn slash_deposit(deposit: Option<Deposit<T::AccountId, BalanceOf<T, I>>>) {
+	fn slash_deposit(
+		deposit: Option<Deposit<T::AccountId, BalanceOf<T, I>>>,
+	) -> Result<(), DispatchError> {
 		if let Some(Deposit { who, amount }) = deposit {
-			T::Slash::on_unbalanced(T::Currency::slash_reserved(&who, amount).0);
-			Self::deposit_event(Event::<T, I>::DepositSlashed { who, amount });
+			let amount_burned = T::NativeBalance::burn_held(
+				&HoldReason::<I>::DecisionDeposit.into(),
+				&who,
+				amount,
+				Precision::BestEffort,
+				Fortitude::Force,
+			)?;
+			Self::deposit_event(Event::<T, I>::DepositSlashed { who, amount: amount_burned });
 		}
+		Ok(())
 	}
 
 	/// Determine whether the given `tally` would result in a referendum passing at `elapsed` blocks