impls.rs

						match len {
							0 => { /* not supporting this validator at all. */ },
							1 => sum += individual[0].value,
							_ =>
								return Err(
									"nominator cannot back a validator more than once.".into()
								),
						};
						Ok(())
					})
					.collect::<Result<Vec<_>, _>>()?;

				// We take total instead of active as the nominator might have requested to unbond
				// some of their stake that is still exposed in the current era.
				if sum <= Self::ledger(Stash(nominator.clone()))?.total {
					// This can happen when there is a slash in the current era so we only warn.
					log!(warn, "nominator stake exceeds what is bonded.");
				}

				Ok(())
			})
			.collect::<Result<Vec<_>, _>>()?;

		Ok(())
	}

	fn ensure_is_stash(who: &T::AccountId) -> Result<(), &'static str> {
		ensure!(Self::bonded(who).is_some(), "Not a stash.");
		Ok(())
	}

	fn ensure_ledger_consistent(ctrl: T::AccountId) -> Result<(), TryRuntimeError> {
		// ensures ledger.total == ledger.active + sum(ledger.unlocking).
		let ledger = Self::ledger(StakingAccount::Controller(ctrl.clone()))?;

		let real_total: BalanceOf<T> =
			ledger.unlocking.iter().fold(ledger.active, |a, c| a + c.value);
		ensure!(real_total == ledger.total, "ledger.total corrupt");

		Ok(())
	}
}