refactor: inconsistent BalanceConversion fn (paritytech#13610)

* refactor: inconsistent BalanceConversion fn

* Revert "refactor: inconsistent BalanceConversion fn"

This reverts commit 1177877.

* refactor: rename BalanceConversion trait

* feat: add ConversionFromAssetBalance

frame/assets/src/tests.rs

@@ -1162,7 +1162,7 @@ fn set_min_balance_should_work() {
 #[test]
 fn balance_conversion_should_work() {
 	new_test_ext().execute_with(|| {
-		use frame_support::traits::tokens::BalanceConversion;
+		use frame_support::traits::tokens::ConversionToAssetBalance;
 
 		let id = 42;
 		assert_ok!(Assets::force_create(RuntimeOrigin::root(), id, 1, true, 10));

frame/assets/src/types.rs

@@ -20,7 +20,7 @@
 use super::*;
 use frame_support::{
 	pallet_prelude::*,
-	traits::{fungible, tokens::BalanceConversion},
+	traits::{fungible, tokens::ConversionToAssetBalance},
 };
 use sp_runtime::{traits::Convert, FixedPointNumber, FixedPointOperand, FixedU128};
 
@@ -228,7 +228,7 @@ type BalanceOf<F, T> = <F as fungible::Inspect<AccountIdOf<T>>>::Balance;
 /// Converts a balance value into an asset balance based on the ratio between the fungible's
 /// minimum balance and the minimum asset balance.
 pub struct BalanceToAssetBalance<F, T, CON, I = ()>(PhantomData<(F, T, CON, I)>);
-impl<F, T, CON, I> BalanceConversion<BalanceOf<F, T>, AssetIdOf<T, I>, AssetBalanceOf<T, I>>
+impl<F, T, CON, I> ConversionToAssetBalance<BalanceOf<F, T>, AssetIdOf<T, I>, AssetBalanceOf<T, I>>
 	for BalanceToAssetBalance<F, T, CON, I>
 where
 	F: fungible::Inspect<AccountIdOf<T>>,

frame/support/src/traits/tokens.rs

@@ -29,8 +29,8 @@ pub mod nonfungibles_v2;
 pub use imbalance::Imbalance;
 pub mod pay;
 pub use misc::{
-	AssetId, Balance, BalanceConversion, BalanceStatus, ConvertRank, DepositConsequence,
-	ExistenceRequirement, Fortitude, GetSalary, Locker, Precision, Preservation, Provenance,
-	Restriction, WithdrawConsequence, WithdrawReasons,
+	AssetId, Balance, BalanceStatus, ConversionFromAssetBalance, ConversionToAssetBalance,
+	ConvertRank, DepositConsequence, ExistenceRequirement, Fortitude, GetSalary, Locker, Precision,
+	Preservation, Provenance, Restriction, WithdrawConsequence, WithdrawReasons,
 };
 pub use pay::{Pay, PayFromAccount, PaymentStatus};

frame/support/src/traits/tokens/misc.rs

@@ -244,9 +244,19 @@ impl<
 }
 
 /// Converts a balance value into an asset balance.
-pub trait BalanceConversion<InBalance, AssetId, OutBalance> {
+pub trait ConversionToAssetBalance<InBalance, AssetId, AssetBalance> {
 	type Error;
-	fn to_asset_balance(balance: InBalance, asset_id: AssetId) -> Result<OutBalance, Self::Error>;
+	fn to_asset_balance(balance: InBalance, asset_id: AssetId)
+		-> Result<AssetBalance, Self::Error>;
+}
+
+/// Converts an asset balance value into balance.
+pub trait ConversionFromAssetBalance<AssetBalance, AssetId, OutBalance> {
+	type Error;
+	fn from_asset_balance(
+		balance: AssetBalance,
+		asset_id: AssetId,
+	) -> Result<OutBalance, Self::Error>;
 }
 
 /// Trait to handle asset locking mechanism to ensure interactions with the asset can be implemented

frame/transaction-payment/asset-tx-payment/src/payment.rs

@@ -22,7 +22,8 @@ use frame_support::{
 	traits::{
 		fungibles::{Balanced, Credit, Inspect},
 		tokens::{
-			Balance, BalanceConversion, Fortitude::Polite, Precision::Exact, Preservation::Protect,
+			Balance, ConversionToAssetBalance, Fortitude::Polite, Precision::Exact,
+			Preservation::Protect,
 		},
 	},
 	unsigned::TransactionValidityError,
@@ -87,7 +88,7 @@ impl<A, B: Balanced<A>> HandleCredit<A, B> for () {
 }
 
 /// Implements the asset transaction for a balance to asset converter (implementing
-/// [`BalanceConversion`]) and a credit handler (implementing [`HandleCredit`]).
+/// [`ConversionToAssetBalance`]) and a credit handler (implementing [`HandleCredit`]).
 ///
 /// The credit handler is given the complete fee in terms of the asset used for the transaction.
 pub struct FungiblesAdapter<CON, HC>(PhantomData<(CON, HC)>);
@@ -97,7 +98,7 @@ pub struct FungiblesAdapter<CON, HC>(PhantomData<(CON, HC)>);
 impl<T, CON, HC> OnChargeAssetTransaction<T> for FungiblesAdapter<CON, HC>
 where
 	T: Config,
-	CON: BalanceConversion<BalanceOf<T>, AssetIdOf<T>, AssetBalanceOf<T>>,
+	CON: ConversionToAssetBalance<BalanceOf<T>, AssetIdOf<T>, AssetBalanceOf<T>>,
 	HC: HandleCredit<T::AccountId, T::Fungibles>,
 	AssetIdOf<T>: FullCodec + Copy + MaybeSerializeDeserialize + Debug + Default + Eq + TypeInfo,
 {