Various minor fixes (#13945)

* Fix: Incorrect implementation of can_reserve check

* Fix: Incorrect migration of consumer counting for existing accounts with frozen amounts

* Fix: Inconsistent implementation between assets can_deposit and new_account

* Fixes

* Fixes

* Another fix

* Update tests.rs

* Update fungible_tests.rs

* Use `can_accrue_consumers` in the body of `can_inc_consumer`

---------

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: parity-processbot <>

substrate/frame/balances/src/impl_currency.rs

@@ -490,7 +490,9 @@ where
 			return true
 		}
 		Self::account(who).free.checked_sub(&value).map_or(false, |new_balance| {
-			Self::ensure_can_withdraw(who, value, WithdrawReasons::RESERVE, new_balance).is_ok()
+			new_balance >= T::ExistentialDeposit::get() &&
+				Self::ensure_can_withdraw(who, value, WithdrawReasons::RESERVE, new_balance)
+					.is_ok()
 		})
 	}
 

substrate/frame/balances/src/lib.rs

@@ -788,7 +788,7 @@ pub mod pallet {
 				return false
 			}
 			a.flags.set_new_logic();
-			if !a.reserved.is_zero() || !a.frozen.is_zero() {
+			if !a.reserved.is_zero() && a.frozen.is_zero() {
 				if system::Pallet::<T>::providers(who) == 0 {
 					// Gah!! We have no provider refs :(
 					// This shouldn't practically happen, but we need a failsafe anyway: let's give

substrate/frame/balances/src/tests/currency_tests.rs

@@ -1180,6 +1180,16 @@ fn named_reserve_should_work() {
 	});
 }
 
+#[test]
+fn reserve_must_succeed_if_can_reserve_does() {
+	ExtBuilder::default().build_and_execute_with(|| {
+		let _ = Balances::deposit_creating(&1, 1);
+		let _ = Balances::deposit_creating(&2, 2);
+		assert!(Balances::can_reserve(&1, 1) == Balances::reserve(&1, 1).is_ok());
+		assert!(Balances::can_reserve(&2, 1) == Balances::reserve(&2, 1).is_ok());
+	});
+}
+
 #[test]
 fn reserved_named_to_yourself_should_work() {
 	ExtBuilder::default().build_and_execute_with(|| {

substrate/frame/balances/src/tests/fungible_tests.rs

@@ -398,6 +398,31 @@ fn unholding_frees_hold_slot() {
 		});
 }
 
+#[test]
+fn sufficients_work_properly_with_reference_counting() {
+	ExtBuilder::default()
+		.existential_deposit(1)
+		.monied(true)
+		.build_and_execute_with(|| {
+			// Only run PoC when the system pallet is enabled, since the underlying bug is in the
+			// system pallet it won't work with BalancesAccountStore
+			if UseSystem::get() {
+				// Start with a balance of 100
+				<Balances as fungible::Mutate<_>>::set_balance(&1, 100);
+				// Emulate a sufficient, in reality this could be reached by transferring a
+				// sufficient asset to the account
+				System::inc_sufficients(&1);
+				// Spend the same balance multiple times
+				assert_ok!(<Balances as fungible::Mutate<_>>::transfer(&1, &1337, 100, Expendable));
+				assert_eq!(Balances::free_balance(&1), 0);
+				assert_noop!(
+					<Balances as fungible::Mutate<_>>::transfer(&1, &1337, 100, Expendable),
+					TokenError::FundsUnavailable
+				);
+			}
+		});
+}
+
 #[test]
 fn emit_events_with_changing_freezes() {
 	ExtBuilder::default().build_and_execute_with(|| {