lib.rs

					Err(Error::<T, I>::KeepAlive)?
				}
			}

			Self::set_free_balance(transactor, new_from_balance);
			if !<FreeBalance<T, I>>::exists(dest) {
				Self::new_account(dest, new_to_balance);
			}

			// Emit transfer event.
			Self::deposit_event(RawEvent::Transfer(transactor.clone(), dest.clone(), value, fee));

			// Take action on the set_free_balance call.
			// This will emit events that _resulted_ from the transfer.
			Self::set_free_balance(dest, new_to_balance);
			T::TransferPayment::on_unbalanced(NegativeImbalance::new(fee));
		}

		Ok(())
	}

	// Withdraw some free balance from an account, respecting existence requirements.
	// Is a no-op if value to be withdrawn is zero.
	fn withdraw(
		who: &T::AccountId,
		value: Self::Balance,
		reasons: WithdrawReasons,
		liveness: ExistenceRequirement,
	) -> result::Result<Self::NegativeImbalance, DispatchError> {
		if value.is_zero() { return Ok(NegativeImbalance::zero()); }

		let old_balance = Self::free_balance(who);
		if let Some(new_balance) = old_balance.checked_sub(&value) {
			// if we need to keep the account alive...
			if liveness == ExistenceRequirement::KeepAlive
				// ...and it would be dead afterwards...
				&& new_balance < T::ExistentialDeposit::get()
				// ...yet is was alive before
				&& old_balance >= T::ExistentialDeposit::get()
			{
				Err(Error::<T, I>::KeepAlive)?
			}
			Self::ensure_can_withdraw(who, value, reasons, new_balance)?;
			Self::set_free_balance(who, new_balance);
			Ok(NegativeImbalance::new(value))
		} else {
			Err(Error::<T, I>::InsufficientBalance)?
		}
	}

	// Slash an account, returning the negative imbalance created and any left over
	// amount that could not be slashed.
	// Is a no-op if value to be slashed is zero.
	fn slash(
		who: &T::AccountId,
		value: Self::Balance
	) -> (Self::NegativeImbalance, Self::Balance) {
		if value.is_zero() { return (NegativeImbalance::zero(), Zero::zero()) }

		let free_balance = Self::free_balance(who);
		let free_slash = cmp::min(free_balance, value);

		Self::set_free_balance(who, free_balance - free_slash);
		let remaining_slash = value - free_slash;
		// NOTE: `slash()` prefers free balance, but assumes that reserve balance can be drawn
		// from in extreme circumstances. `can_slash()` should be used prior to `slash()` to avoid having
		// to draw from reserved funds, however we err on the side of punishment if things are inconsistent
		// or `can_slash` wasn't used appropriately.
		if !remaining_slash.is_zero() {
			let reserved_balance = Self::reserved_balance(who);
			let reserved_slash = cmp::min(reserved_balance, remaining_slash);
			Self::set_reserved_balance(who, reserved_balance - reserved_slash);
			(NegativeImbalance::new(free_slash + reserved_slash), remaining_slash - reserved_slash)
		} else {
			(NegativeImbalance::new(value), Zero::zero())
		}
	}

	// Deposit some `value` into the free balance of an existing account.
	// Is a no-op if the value to be deposited is zero.
	fn deposit_into_existing(
		who: &T::AccountId,
		value: Self::Balance
	) -> result::Result<Self::PositiveImbalance, DispatchError> {
		if value.is_zero() { return Ok(PositiveImbalance::zero()) }

		if Self::total_balance(who).is_zero() {
			Err(Error::<T, I>::DeadAccount)?
		}
		Self::set_free_balance(who, Self::free_balance(who) + value);
		Ok(PositiveImbalance::new(value))
	}

	// Deposit some `value` into the free balance of `who`, possibly creating a new account.
	// Is a no-op if the value to be deposited is zero.
	fn deposit_creating(
		who: &T::AccountId,
		value: Self::Balance,
	) -> Self::PositiveImbalance {
		if value.is_zero() { return Self::PositiveImbalance::zero() }

		let (imbalance, _) = Self::make_free_balance_be(who, Self::free_balance(who) + value);
		if let SignedImbalance::Positive(p) = imbalance {
			p
		} else {
			// Impossible, but be defensive.
			Self::PositiveImbalance::zero()
		}
	}

	fn make_free_balance_be(who: &T::AccountId, balance: Self::Balance) -> (
		SignedImbalance<Self::Balance, Self::PositiveImbalance>,
		UpdateBalanceOutcome
	) {
		let original = Self::free_balance(who);
		if balance < T::ExistentialDeposit::get() && original.is_zero() {
			// If we're attempting to set an existing account to less than ED, then
			// bypass the entire operation. It's a no-op if you follow it through, but
			// since this is an instance where we might account for a negative imbalance
			// (in the dust cleaner of set_free_balance) before we account for its actual
			// equal and opposite cause (returned as an Imbalance), then in the
			// instance that there's no other accounts on the system at all, we might
			// underflow the issuance and our arithmetic will be off.
			return (
				SignedImbalance::Positive(Self::PositiveImbalance::zero()),
				UpdateBalanceOutcome::AccountKilled,
			)
		}
		let imbalance = if original <= balance {
			SignedImbalance::Positive(PositiveImbalance::new(balance - original))
		} else {
			SignedImbalance::Negative(NegativeImbalance::new(original - balance))
		};
		// If the balance is too low, then the account is reaped.
		// NOTE: There are two balances for every account: `reserved_balance` and
		// `free_balance`. This contract subsystem only cares about the latter: whenever
		// the term "balance" is used *here* it should be assumed to mean "free balance"
		// in the rest of the module.
		// Free balance can never be less than ED. If that happens, it gets reduced to zero
		// and the account information relevant to this subsystem is deleted (i.e. the
		// account is reaped).
		let outcome = if balance < T::ExistentialDeposit::get() {
			Self::set_free_balance(who, balance);
			UpdateBalanceOutcome::AccountKilled
		} else {
			if !<FreeBalance<T, I>>::exists(who) {
				Self::new_account(&who, balance);
			}
			Self::set_free_balance(who, balance);
			UpdateBalanceOutcome::Updated
		};
		(imbalance, outcome)
	}
}

impl<T: Trait<I>, I: Instance> ReservableCurrency<T::AccountId> for Module<T, I>
where
	T::Balance: MaybeSerializeDeserialize + Debug
{
	// Check if `who` can reserve `value` from their free balance.
	// Is a no-op if value to be reserved is zero.
	fn can_reserve(who: &T::AccountId, value: Self::Balance) -> bool {
		if value.is_zero() { return true }
		Self::free_balance(who)
			.checked_sub(&value)
			.map_or(false, |new_balance|
				Self::ensure_can_withdraw(who, value, WithdrawReason::Reserve.into(), new_balance).is_ok()
			)
	}

	fn reserved_balance(who: &T::AccountId) -> Self::Balance {
		<ReservedBalance<T, I>>::get(who)
	}

	// Move `value` from the free balance from `who` to their reserved balance.
	// Is a no-op if value to be reserved is zero.
	fn reserve(who: &T::AccountId, value: Self::Balance) -> result::Result<(), DispatchError> {
		if value.is_zero() { return Ok(()) }
		let b = Self::free_balance(who);
		if b < value {
			Err(Error::<T, I>::InsufficientBalance)?
		}
		let new_balance = b - value;
		Self::ensure_can_withdraw(who, value, WithdrawReason::Reserve.into(), new_balance)?;
		Self::set_reserved_balance(who, Self::reserved_balance(who) + value);
		Self::set_free_balance(who, new_balance);
		Ok(())
	}

	// Unreserve some funds, returning any amount that was unable to be unreserved.
	// Is a no-op if the value to be unreserved is zero.
	fn unreserve(who: &T::AccountId, value: Self::Balance) -> Self::Balance {
		if value.is_zero() { return Zero::zero() }
		let b = Self::reserved_balance(who);
		let actual = cmp::min(b, value);
		Self::set_free_balance(who, Self::free_balance(who) + actual);
		Self::set_reserved_balance(who, b - actual);
		value - actual
	}

	// Slash from reserved balance, returning the negative imbalance created,
	// and any amount that was unable to be slashed.
	// Is a no-op if the value to be slashed is zero.
	fn slash_reserved(
		who: &T::AccountId,
		value: Self::Balance
	) -> (Self::NegativeImbalance, Self::Balance) {
		if value.is_zero() { return (NegativeImbalance::zero(), Zero::zero()) }
		let b = Self::reserved_balance(who);
		let slash = cmp::min(b, value);
		// underflow should never happen, but it if does, there's nothing to be done here.
		Self::set_reserved_balance(who, b - slash);
		(NegativeImbalance::new(slash), value - slash)
	}

	// Move the reserved balance of one account into the free balance of another.
	// Is a no-op if the value to be moved is zero.
	fn repatriate_reserved(
		slashed: &T::AccountId,
		beneficiary: &T::AccountId,
		value: Self::Balance,
	) -> result::Result<Self::Balance, DispatchError> {
		if value.is_zero() { return Ok (Zero::zero()) }
		if Self::total_balance(beneficiary).is_zero() {
			Err(Error::<T, I>::DeadAccount)?
		}
		let b = Self::reserved_balance(slashed);
		let slash = cmp::min(b, value);
		Self::set_free_balance(beneficiary, Self::free_balance(beneficiary) + slash);
		Self::set_reserved_balance(slashed, b - slash);
		Ok(value - slash)
	}
}

impl<T: Trait<I>, I: Instance> LockableCurrency<T::AccountId> for Module<T, I>
where
	T::Balance: MaybeSerializeDeserialize + Debug
{
	type Moment = T::BlockNumber;

	// Set a lock on the balance of `who`.
	// Is a no-op if lock amount is zero.
	fn set_lock(
		id: LockIdentifier,
		who: &T::AccountId,
		amount: T::Balance,
		until: T::BlockNumber,
		reasons: WithdrawReasons,
	) {
		if amount.is_zero() { return }
		let now = <frame_system::Module<T>>::block_number();
		let mut new_lock = Some(BalanceLock { id, amount, until, reasons });
		let mut locks = Self::locks(who).into_iter().filter_map(|l|
			if l.id == id {
				new_lock.take()
			} else if l.until > now {
				Some(l)
			} else {
				None
			}).collect::<Vec<_>>();
		if let Some(lock) = new_lock {
			locks.push(lock)
		}
		<Locks<T, I>>::insert(who, locks);
	}

	fn extend_lock(
		id: LockIdentifier,
		who: &T::AccountId,
		amount: T::Balance,
		until: T::BlockNumber,
		reasons: WithdrawReasons,
	) {
		let now = <frame_system::Module<T>>::block_number();
		let mut new_lock = Some(BalanceLock { id, amount, until, reasons });
		let mut locks = Self::locks(who).into_iter().filter_map(|l|
			if l.id == id {
				new_lock.take().map(|nl| {
					BalanceLock {
						id: l.id,
						amount: l.amount.max(nl.amount),
						until: l.until.max(nl.until),
						reasons: l.reasons | nl.reasons,
					}
				})
			} else if l.until > now {
				Some(l)
			} else {
				None
			}).collect::<Vec<_>>();
		if let Some(lock) = new_lock {
			locks.push(lock)
		}
		<Locks<T, I>>::insert(who, locks);
	}

	fn remove_lock(
		id: LockIdentifier,
		who: &T::AccountId,
	) {
		let now = <frame_system::Module<T>>::block_number();
		let locks = Self::locks(who).into_iter().filter_map(|l|
			if l.until > now && l.id != id {
				Some(l)
			} else {
				None
			}).collect::<Vec<_>>();
		<Locks<T, I>>::insert(who, locks);
	}
}

impl<T: Trait<I>, I: Instance> VestingCurrency<T::AccountId> for Module<T, I>
where
	T::Balance: MaybeSerializeDeserialize + Debug
{
	type Moment = T::BlockNumber;

	/// Get the amount that is currently being vested and cannot be transferred out of this account.
	fn vesting_balance(who: &T::AccountId) -> T::Balance {
		if let Some(v) = Self::vesting(who) {
			Self::free_balance(who)
				.min(v.locked_at(<frame_system::Module<T>>::block_number()))
		} else {
			Zero::zero()
		}
	}

	/// Adds a vesting schedule to a given account.
	///
	/// If there already exists a vesting schedule for the given account, an `Err` is returned
	/// and nothing is updated.
	/// Is a no-op if the amount to be vested is zero.
	fn add_vesting_schedule(
		who: &T::AccountId,
		locked: T::Balance,
		per_block: T::Balance,
		starting_block: T::BlockNumber
	) -> DispatchResult {
		if locked.is_zero() { return Ok(()) }
		if <Vesting<T, I>>::exists(who) {
			Err(Error::<T, I>::ExistingVestingSchedule)?
		}
		let vesting_schedule = VestingSchedule {
			locked,
			per_block,
			starting_block
		};
		<Vesting<T, I>>::insert(who, vesting_schedule);
		Ok(())
	}

	/// Remove a vesting schedule for a given account.
	fn remove_vesting_schedule(who: &T::AccountId) {
		<Vesting<T, I>>::remove(who);
	}
}

impl<T: Trait<I>, I: Instance> IsDeadAccount<T::AccountId> for Module<T, I>
where
	T::Balance: MaybeSerializeDeserialize + Debug
{
	fn is_dead_account(who: &T::AccountId) -> bool {
		Self::total_balance(who).is_zero()
	}
}