Migrate fee payment from Currency to fungible (#2292)

Part of https://github.com/paritytech/polkadot-sdk/issues/226 
Related https://github.com/paritytech/polkadot-sdk/issues/1833

- Deprecate `CurrencyAdapter` and introduce `FungibleAdapter`
- Deprecate `ToStakingPot` and replace usage with `ResolveTo`
- Required creating a new `StakingPotAccountId` struct that implements
`TypedGet` for the staking pot account ID
- Update parachain common utils `DealWithFees`, `ToAuthor` and
`AssetsToBlockAuthor` implementations to use `fungible`
- Update runtime XCM Weight Traders to use `ResolveTo` instead of
`ToStakingPot`
- Update runtime Transaction Payment pallets to use `FungibleAdapter`
instead of `CurrencyAdapter`
- [x] Blocked by https://github.com/paritytech/polkadot-sdk/pull/1296,
needs the `Unbalanced::decrease_balance` fix

polkadot/runtime/common/src/crowdloan/mod.rs

@@ -83,10 +83,6 @@ type CurrencyOf<T> = <<T as Config>::Auctioneer as Auctioneer<BlockNumberFor<T>>
 type LeasePeriodOf<T> = <<T as Config>::Auctioneer as Auctioneer<BlockNumberFor<T>>>::LeasePeriod;
 type BalanceOf<T> = <CurrencyOf<T> as Currency<<T as frame_system::Config>::AccountId>>::Balance;
 
-#[allow(dead_code)]
-type NegativeImbalanceOf<T> =
-	<CurrencyOf<T> as Currency<<T as frame_system::Config>::AccountId>>::NegativeImbalance;
-
 type FundIndex = u32;
 
 pub trait WeightInfo {

polkadot/runtime/common/src/impls.rs

@@ -16,8 +16,12 @@
 
 //! Auxiliary `struct`/`enum`s for polkadot runtime.
 
-use crate::NegativeImbalance;
-use frame_support::traits::{Currency, Imbalance, OnUnbalanced};
+use frame_support::traits::{
+	fungible::{Balanced, Credit},
+	tokens::imbalance::ResolveTo,
+	Imbalance, OnUnbalanced,
+};
+use pallet_treasury::TreasuryAccountId;
 use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use primitives::Balance;
 use sp_runtime::{traits::TryConvert, Perquintill, RuntimeDebug};
@@ -25,28 +29,31 @@ use xcm::VersionedLocation;
 
 /// Logic for the author to get a portion of fees.
 pub struct ToAuthor<R>(sp_std::marker::PhantomData<R>);
-impl<R> OnUnbalanced<NegativeImbalance<R>> for ToAuthor<R>
+impl<R> OnUnbalanced<Credit<R::AccountId, pallet_balances::Pallet<R>>> for ToAuthor<R>
 where
 	R: pallet_balances::Config + pallet_authorship::Config,
 	<R as frame_system::Config>::AccountId: From<primitives::AccountId>,
 	<R as frame_system::Config>::AccountId: Into<primitives::AccountId>,
 {
-	fn on_nonzero_unbalanced(amount: NegativeImbalance<R>) {
+	fn on_nonzero_unbalanced(
+		amount: Credit<<R as frame_system::Config>::AccountId, pallet_balances::Pallet<R>>,
+	) {
 		if let Some(author) = <pallet_authorship::Pallet<R>>::author() {
-			<pallet_balances::Pallet<R>>::resolve_creating(&author, amount);
+			let _ = <pallet_balances::Pallet<R>>::resolve(&author, amount);
 		}
 	}
 }
 
 pub struct DealWithFees<R>(sp_std::marker::PhantomData<R>);
-impl<R> OnUnbalanced<NegativeImbalance<R>> for DealWithFees<R>
+impl<R> OnUnbalanced<Credit<R::AccountId, pallet_balances::Pallet<R>>> for DealWithFees<R>
 where
-	R: pallet_balances::Config + pallet_treasury::Config + pallet_authorship::Config,
-	pallet_treasury::Pallet<R>: OnUnbalanced<NegativeImbalance<R>>,
+	R: pallet_balances::Config + pallet_authorship::Config + pallet_treasury::Config,
 	<R as frame_system::Config>::AccountId: From<primitives::AccountId>,
 	<R as frame_system::Config>::AccountId: Into<primitives::AccountId>,
 {
-	fn on_unbalanceds<B>(mut fees_then_tips: impl Iterator<Item = NegativeImbalance<R>>) {
+	fn on_unbalanceds<B>(
+		mut fees_then_tips: impl Iterator<Item = Credit<R::AccountId, pallet_balances::Pallet<R>>>,
+	) {
 		if let Some(fees) = fees_then_tips.next() {
 			// for fees, 80% to treasury, 20% to author
 			let mut split = fees.ration(80, 20);
@@ -54,8 +61,7 @@ where
 				// for tips, if any, 100% to author
 				tips.merge_into(&mut split.1);
 			}
-			use pallet_treasury::Pallet as Treasury;
-			<Treasury<R> as OnUnbalanced<_>>::on_unbalanced(split.0);
+			ResolveTo::<TreasuryAccountId<R>, pallet_balances::Pallet<R>>::on_unbalanced(split.0);
 			<ToAuthor<R> as OnUnbalanced<_>>::on_unbalanced(split.1);
 		}
 	}
@@ -366,8 +372,14 @@ mod tests {
 	#[test]
 	fn test_fees_and_tip_split() {
 		new_test_ext().execute_with(|| {
-			let fee = Balances::issue(10);
-			let tip = Balances::issue(20);
+			let fee =
+				<pallet_balances::Pallet<Test> as frame_support::traits::fungible::Balanced<
+					AccountId,
+				>>::issue(10);
+			let tip =
+				<pallet_balances::Pallet<Test> as frame_support::traits::fungible::Balanced<
+					AccountId,
+				>>::issue(20);
 
 			assert_eq!(Balances::free_balance(Treasury::account_id()), 0);
 			assert_eq!(Balances::free_balance(TEST_ACCOUNT), 0);

polkadot/runtime/common/src/lib.rs

@@ -63,6 +63,9 @@ pub use sp_runtime::BuildStorage;
 /// Implementations of some helper traits passed into runtime modules as associated types.
 pub use impls::ToAuthor;
 
+#[deprecated(
+	note = "Please use fungible::Credit instead. This type will be removed some time after March 2024."
+)]
 pub type NegativeImbalance<T> = <pallet_balances::Pallet<T> as Currency<
 	<T as frame_system::Config>::AccountId,
 >>::NegativeImbalance;

polkadot/runtime/rococo/src/lib.rs

@@ -79,7 +79,7 @@ use frame_system::{EnsureRoot, EnsureSigned};
 use pallet_grandpa::{fg_primitives, AuthorityId as GrandpaId};
 use pallet_identity::legacy::IdentityInfo;
 use pallet_session::historical as session_historical;
-use pallet_transaction_payment::{CurrencyAdapter, FeeDetails, RuntimeDispatchInfo};
+use pallet_transaction_payment::{FeeDetails, FungibleAdapter, RuntimeDispatchInfo};
 use sp_core::{ConstU128, OpaqueMetadata, H256};
 use sp_runtime::{
 	create_runtime_str, generic, impl_opaque_keys,
@@ -324,7 +324,7 @@ parameter_types! {
 
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Balances, ToAuthor<Runtime>>;
+	type OnChargeTransaction = FungibleAdapter<Balances, ToAuthor<Runtime>>;
 	type OperationalFeeMultiplier = OperationalFeeMultiplier;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;

polkadot/runtime/test-runtime/src/lib.rs

@@ -20,7 +20,7 @@
 // `construct_runtime!` does a lot of recursion and requires us to increase the limit to 256.
 #![recursion_limit = "256"]
 
-use pallet_transaction_payment::CurrencyAdapter;
+use pallet_transaction_payment::FungibleAdapter;
 use parity_scale_codec::Encode;
 use sp_std::{collections::btree_map::BTreeMap, prelude::*};
 
@@ -233,7 +233,7 @@ parameter_types! {
 
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
+	type OnChargeTransaction = FungibleAdapter<Balances, ()>;
 	type OperationalFeeMultiplier = OperationalFeeMultiplier;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = frame_support::weights::ConstantMultiplier<Balance, TransactionByteFee>;

polkadot/runtime/westend/src/lib.rs

@@ -42,7 +42,7 @@ use frame_system::{EnsureRoot, EnsureSigned};
 use pallet_grandpa::{fg_primitives, AuthorityId as GrandpaId};
 use pallet_identity::legacy::IdentityInfo;
 use pallet_session::historical as session_historical;
-use pallet_transaction_payment::{CurrencyAdapter, FeeDetails, RuntimeDispatchInfo};
+use pallet_transaction_payment::{FeeDetails, FungibleAdapter, RuntimeDispatchInfo};
 use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use primitives::{
 	slashing, AccountId, AccountIndex, ApprovalVotingParams, Balance, BlockNumber, CandidateEvent,
@@ -377,7 +377,7 @@ parameter_types! {
 
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Balances, ToAuthor<Runtime>>;
+	type OnChargeTransaction = FungibleAdapter<Balances, ToAuthor<Runtime>>;
 	type OperationalFeeMultiplier = OperationalFeeMultiplier;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;