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// This file is part of Substrate.
// Copyright (C) 2019-2021 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! A slashing implementation for NPoS systems.
//!
//! For the purposes of the economic model, it is easiest to think of each validator as a nominator
//! which nominates only its own identity.
//! The act of nomination signals intent to unify economic identity with the validator - to take
//! part in the rewards of a job well done, and to take part in the punishment of a job done badly.
//!
//! There are 3 main difficulties to account for with slashing in NPoS:
//! - A nominator can nominate multiple validators and be slashed via any of them.
//! - Until slashed, stake is reused from era to era. Nominating with N coins for E eras in a row
//! does not mean you have N*E coins to be slashed - you've only ever had N.
//! - Slashable offences can be found after the fact and out of order.
//!
//! The algorithm implemented in this module tries to balance these 3 difficulties.
//!
//! First, we only slash participants for the _maximum_ slash they receive in some time period,
//! rather than the sum. This ensures a protection from overslashing.
//!
//! Second, we do not want the time period (or "span") that the maximum is computed
//! over to last indefinitely. That would allow participants to begin acting with
//! impunity after some point, fearing no further repercussions. For that reason, we
//! automatically "chill" validators and withdraw a nominator's nomination after a slashing event,
//! requiring them to re-enlist voluntarily (acknowledging the slash) and begin a new
//! slashing span.
//!
//! Typically, you will have a single slashing event per slashing span. Only in the case
//! where a validator releases many misbehaviors at once, or goes "back in time" to misbehave in
//! eras that have already passed, would you encounter situations where a slashing span
//! has multiple misbehaviors. However, accounting for such cases is necessary
//! to deter a class of "rage-quit" attacks.
//!
//! Based on research at <https://w3f-research.readthedocs.io/en/latest/polkadot/slashing/npos.html>
use crate::{
BalanceOf, Config, EraIndex, Error, Exposure, NegativeImbalanceOf, Pallet, Perbill,
SessionInterface, Store, UnappliedSlash,
use codec::{Decode, Encode};
traits::{Currency, Imbalance, OnUnbalanced},
};
use sp_runtime::{
traits::{Saturating, Zero},
DispatchResult, RuntimeDebug,
use sp_std::vec::Vec;
/// The proportion of the slashing reward to be paid out on the first slashing detection.
/// This is f_1 in the paper.
const REWARD_F1: Perbill = Perbill::from_percent(50);
/// The index of a slashing span - unique to each stash.
// A range of start..end eras for a slashing span.
#[derive(Encode, Decode)]
#[cfg_attr(test, derive(Debug, PartialEq))]
pub(crate) struct SlashingSpan {
pub(crate) index: SpanIndex,
pub(crate) start: EraIndex,
pub(crate) length: Option<EraIndex>, // the ongoing slashing span has indeterminate length.
}
impl SlashingSpan {
fn contains_era(&self, era: EraIndex) -> bool {
self.start <= era && self.length.map_or(true, |l| self.start + l > era)
}
}
/// An encoding of all of a nominator's slashing spans.
#[derive(Encode, Decode, RuntimeDebug)]
pub struct SlashingSpans {
// the index of the current slashing span of the nominator. different for
// every stash, resets when the account hits free balance 0.
span_index: SpanIndex,
// the start era of the most recent (ongoing) slashing span.
last_start: EraIndex,
// the last era at which a non-zero slash occurred.
last_nonzero_slash: EraIndex,
// all prior slashing spans' start indices, in reverse order (most recent first)
// encoded as offsets relative to the slashing span after it.
prior: Vec<EraIndex>,
}
impl SlashingSpans {
// creates a new record of slashing spans for a stash, starting at the beginning
// of the bonding period, relative to now.
pub(crate) fn new(window_start: EraIndex) -> Self {
SlashingSpans {
span_index: 0,
last_start: window_start,
// initialize to zero, as this structure is lazily created until
// the first slash is applied. setting equal to `window_start` would
// put a time limit on nominations.
last_nonzero_slash: 0,
prior: Vec::new(),
}
}
// update the slashing spans to reflect the start of a new span at the era after `now`
// returns `true` if a new span was started, `false` otherwise. `false` indicates
// that internal state is unchanged.
pub(crate) fn end_span(&mut self, now: EraIndex) -> bool {
if next_start <= self.last_start {
return false
}
let last_length = next_start - self.last_start;
self.prior.insert(0, last_length);
self.last_start = next_start;
self.span_index += 1;
true
}
// an iterator over all slashing spans in _reverse_ order - most recent first.
pub(crate) fn iter(&'_ self) -> impl Iterator<Item = SlashingSpan> + '_ {
let mut last_start = self.last_start;
let mut index = self.span_index;
let last = SlashingSpan { index, start: last_start, length: None };
let prior = self.prior.iter().cloned().map(move |length| {
let start = last_start - length;
last_start = start;
index -= 1;
SlashingSpan { index, start, length: Some(length) }
});
sp_std::iter::once(last).chain(prior)
/// Yields the era index where the most recent non-zero slash occurred.
pub fn last_nonzero_slash(&self) -> EraIndex {
self.last_nonzero_slash
}
// prune the slashing spans against a window, whose start era index is given.
//
// If this returns `Some`, then it includes a range start..end of all the span
// indices which were pruned.
fn prune(&mut self, window_start: EraIndex) -> Option<(SpanIndex, SpanIndex)> {
let old_idx = self
.iter()
.skip(1) // skip ongoing span.
.position(|span| span.length.map_or(false, |len| span.start + len <= window_start));
let earliest_span_index = self.span_index - self.prior.len() as SpanIndex;
let pruned = match old_idx {
Some(o) => {
self.prior.truncate(o);
let new_earliest = self.span_index - self.prior.len() as SpanIndex;
Some((earliest_span_index, new_earliest))
None => None,
};
// readjust the ongoing span, if it started before the beginning of the window.
self.last_start = sp_std::cmp::max(self.last_start, window_start);
pruned
}
}
/// A slashing-span record for a particular stash.
#[derive(Encode, Decode, Default)]
pub(crate) struct SpanRecord<Balance> {
slashed: Balance,
paid_out: Balance,
}
impl<Balance> SpanRecord<Balance> {
/// The value of stash balance slashed in this span.
#[cfg(test)]
pub(crate) fn amount_slashed(&self) -> &Balance {
&self.slashed
}
}
/// Parameters for performing a slash.
#[derive(Clone)]
pub(crate) struct SlashParams<'a, T: 'a + Config> {
/// The stash account being slashed.
pub(crate) stash: &'a T::AccountId,
/// The proportion of the slash.
pub(crate) slash: Perbill,
/// The exposure of the stash and all nominators.
pub(crate) exposure: &'a Exposure<T::AccountId, BalanceOf<T>>,
/// The era where the offence occurred.
pub(crate) slash_era: EraIndex,
/// The first era in the current bonding period.
pub(crate) window_start: EraIndex,
/// The current era.
pub(crate) now: EraIndex,
/// The maximum percentage of a slash that ever gets paid out.
/// This is f_inf in the paper.
pub(crate) reward_proportion: Perbill,
}
/// Computes a slash of a validator and nominators. It returns an unapplied
/// record to be applied at some later point. Slashing metadata is updated in storage,
/// since unapplied records are only rarely intended to be dropped.
///
/// The pending slash record returned does not have initialized reporters. Those have
/// to be set at a higher level, if any.
pub(crate) fn compute_slash<T: Config>(
params: SlashParams<T>,
) -> Option<UnappliedSlash<T::AccountId, BalanceOf<T>>> {
let SlashParams { stash, slash, exposure, slash_era, window_start, now, reward_proportion } =
params.clone();
let mut reward_payout = Zero::zero();
let mut val_slashed = Zero::zero();
// is the slash amount here a maximum for the era?
let own_slash = slash * exposure.own;
if slash * exposure.total == Zero::zero() {
// kick out the validator even if they won't be slashed,
// as long as the misbehavior is from their most recent slashing span.
kick_out_if_recent::<T>(params);
let (prior_slash_p, _era_slash) =
<Pallet<T> as Store>::ValidatorSlashInEra::get(&slash_era, stash)
.unwrap_or((Perbill::zero(), Zero::zero()));
// compare slash proportions rather than slash values to avoid issues due to rounding
// error.
if slash.deconstruct() > prior_slash_p.deconstruct() {
<Pallet<T> as Store>::ValidatorSlashInEra::insert(&slash_era, stash, &(slash, own_slash));
} else {
// we slash based on the max in era - this new event is not the max,
// so neither the validator or any nominators will need an update.
//
// this does lead to a divergence of our system from the paper, which
// pays out some reward even if the latest report is not max-in-era.
// we opt to avoid the nominator lookups and edits and leave more rewards
// for more drastic misbehavior.
}
// apply slash to validator.
{
let mut spans = fetch_spans::<T>(
stash,
window_start,
&mut reward_payout,
&mut val_slashed,
reward_proportion,
);
let target_span = spans.compare_and_update_span_slash(slash_era, own_slash);
if target_span == Some(spans.span_index()) {
// misbehavior occurred within the current slashing span - take appropriate
// actions.
// chill the validator - it misbehaved in the current span and should
// not continue in the next election. also end the slashing span.
spans.end_span(now);
<Pallet<T>>::chill_stash(stash);
// make sure to disable validator till the end of this session
if T::SessionInterface::disable_validator(stash).unwrap_or(false) {
// force a new era, to select a new validator set
<Pallet<T>>::ensure_new_era()
}
}
}
let mut nominators_slashed = Vec::new();
reward_payout += slash_nominators::<T>(params, prior_slash_p, &mut nominators_slashed);
Some(UnappliedSlash {
validator: stash.clone(),
own: val_slashed,
others: nominators_slashed,
reporters: Vec::new(),
payout: reward_payout,
})
}
// doesn't apply any slash, but kicks out the validator if the misbehavior is from
// the most recent slashing span.
fn kick_out_if_recent<T: Config>(params: SlashParams<T>) {
// these are not updated by era-span or end-span.
let mut reward_payout = Zero::zero();
let mut val_slashed = Zero::zero();
let mut spans = fetch_spans::<T>(
params.stash,
params.window_start,
&mut reward_payout,
&mut val_slashed,
params.reward_proportion,
);
if spans.era_span(params.slash_era).map(|s| s.index) == Some(spans.span_index()) {
spans.end_span(params.now);
<Pallet<T>>::chill_stash(params.stash);
// make sure to disable validator till the end of this session
if T::SessionInterface::disable_validator(params.stash).unwrap_or(false) {
// force a new era, to select a new validator set
<Pallet<T>>::ensure_new_era()
}
}
}
/// Slash nominators. Accepts general parameters and the prior slash percentage of the validator.
///
/// Returns the amount of reward to pay out.
fn slash_nominators<T: Config>(
params: SlashParams<T>,
prior_slash_p: Perbill,
nominators_slashed: &mut Vec<(T::AccountId, BalanceOf<T>)>,
) -> BalanceOf<T> {
let SlashParams { stash: _, slash, exposure, slash_era, window_start, now, reward_proportion } =
params;
let mut reward_payout = Zero::zero();
nominators_slashed.reserve(exposure.others.len());
for nominator in &exposure.others {
let stash = &nominator.who;
let mut nom_slashed = Zero::zero();
// the era slash of a nominator always grows, if the validator
// had a new max slash for the era.
let era_slash = {
let own_slash_prior = prior_slash_p * nominator.value;
let own_slash_by_validator = slash * nominator.value;
let own_slash_difference = own_slash_by_validator.saturating_sub(own_slash_prior);
let mut era_slash = <Pallet<T> as Store>::NominatorSlashInEra::get(&slash_era, stash)
.unwrap_or_else(|| Zero::zero());
era_slash += own_slash_difference;
<Pallet<T> as Store>::NominatorSlashInEra::insert(&slash_era, stash, &era_slash);
era_slash
};
// compare the era slash against other eras in the same span.
{
let mut spans = fetch_spans::<T>(
stash,
window_start,
&mut reward_payout,
&mut nom_slashed,
reward_proportion,
);
let target_span = spans.compare_and_update_span_slash(slash_era, era_slash);
if target_span == Some(spans.span_index()) {
// End the span, but don't chill the nominator. its nomination
// on this validator will be ignored in the future.
spans.end_span(now);
}
}
nominators_slashed.push((stash.clone(), nom_slashed));
}
reward_payout
}
// helper struct for managing a set of spans we are currently inspecting.
// writes alterations to disk on drop, but only if a slash has been carried out.
//
// NOTE: alterations to slashing metadata should not be done after this is dropped.
// dropping this struct applies any necessary slashes, which can lead to free balance
// being 0, and the account being garbage-collected -- a dead account should get no new
// metadata.
struct InspectingSpans<'a, T: Config + 'a> {
dirty: bool,
window_start: EraIndex,
stash: &'a T::AccountId,
spans: SlashingSpans,
paid_out: &'a mut BalanceOf<T>,
slash_of: &'a mut BalanceOf<T>,
reward_proportion: Perbill,
_marker: sp_std::marker::PhantomData<T>,
}
// fetches the slashing spans record for a stash account, initializing it if necessary.
fn fetch_spans<'a, T: Config + 'a>(
stash: &'a T::AccountId,
window_start: EraIndex,
paid_out: &'a mut BalanceOf<T>,
slash_of: &'a mut BalanceOf<T>,
reward_proportion: Perbill,
) -> InspectingSpans<'a, T> {
let spans = <Pallet<T> as Store>::SlashingSpans::get(stash).unwrap_or_else(|| {
let spans = SlashingSpans::new(window_start);
<Pallet<T> as Store>::SlashingSpans::insert(stash, &spans);
spans
});
InspectingSpans {
dirty: false,
window_start,
stash,
spans,
slash_of,
paid_out,
reward_proportion,
_marker: sp_std::marker::PhantomData,
impl<'a, T: 'a + Config> InspectingSpans<'a, T> {
fn span_index(&self) -> SpanIndex {
self.spans.span_index
}
fn end_span(&mut self, now: EraIndex) {
self.dirty = self.spans.end_span(now) || self.dirty;
}
// add some value to the slash of the staker.
// invariant: the staker is being slashed for non-zero value here
// although `amount` may be zero, as it is only a difference.
fn add_slash(&mut self, amount: BalanceOf<T>, slash_era: EraIndex) {
self.spans.last_nonzero_slash = sp_std::cmp::max(self.spans.last_nonzero_slash, slash_era);
}
// find the span index of the given era, if covered.
fn era_span(&self, era: EraIndex) -> Option<SlashingSpan> {
self.spans.iter().find(|span| span.contains_era(era))
}
// compares the slash in an era to the overall current span slash.
// if it's higher, applies the difference of the slashes and then updates the span on disk.
//
// returns the span index of the era where the slash occurred, if any.
fn compare_and_update_span_slash(
&mut self,
slash_era: EraIndex,
slash: BalanceOf<T>,
) -> Option<SpanIndex> {
let target_span = self.era_span(slash_era)?;
let span_slash_key = (self.stash.clone(), target_span.index);
let mut span_record = <Pallet<T> as Store>::SpanSlash::get(&span_slash_key);
let mut changed = false;
let reward = if span_record.slashed < slash {
// new maximum span slash. apply the difference.
let difference = slash - span_record.slashed;
span_record.slashed = slash;
// compute reward.
let reward =
REWARD_F1 * (self.reward_proportion * slash).saturating_sub(span_record.paid_out);
self.add_slash(difference, slash_era);
changed = true;
reward
} else if span_record.slashed == slash {
// compute reward. no slash difference to apply.
REWARD_F1 * (self.reward_proportion * slash).saturating_sub(span_record.paid_out)
} else {
Zero::zero()
};
if !reward.is_zero() {
changed = true;
span_record.paid_out += reward;
*self.paid_out += reward;
}
if changed {
self.dirty = true;
<Pallet<T> as Store>::SpanSlash::insert(&span_slash_key, &span_record);
}
Some(target_span.index)
}
}
impl<'a, T: 'a + Config> Drop for InspectingSpans<'a, T> {
fn drop(&mut self) {
// only update on disk if we slashed this account.
if !self.dirty {
return
}
if let Some((start, end)) = self.spans.prune(self.window_start) {
for span_index in start..end {
<Pallet<T> as Store>::SpanSlash::remove(&(self.stash.clone(), span_index));
<Pallet<T> as Store>::SlashingSpans::insert(self.stash, &self.spans);
}
}
/// Clear slashing metadata for an obsolete era.
pub(crate) fn clear_era_metadata<T: Config>(obsolete_era: EraIndex) {
<Pallet<T> as Store>::ValidatorSlashInEra::remove_prefix(&obsolete_era, None);
<Pallet<T> as Store>::NominatorSlashInEra::remove_prefix(&obsolete_era, None);
}
/// Clear slashing metadata for a dead account.
pub(crate) fn clear_stash_metadata<T: Config>(
stash: &T::AccountId,
num_slashing_spans: u32,
) -> DispatchResult {
let spans = match <Pallet<T> as Store>::SlashingSpans::get(stash) {
ensure!(
num_slashing_spans as usize >= spans.iter().count(),
Error::<T>::IncorrectSlashingSpans
);
<Pallet<T> as Store>::SlashingSpans::remove(stash);
// kill slashing-span metadata for account.
//
// this can only happen while the account is staked _if_ they are completely slashed.
// in that case, they may re-bond, but it would count again as span 0. Further ancient
// slashes would slash into this new bond, since metadata has now been cleared.
for span in spans.iter() {
<Pallet<T> as Store>::SpanSlash::remove(&(stash.clone(), span.index));
}
// apply the slash to a stash account, deducting any missing funds from the reward
// payout, saturating at 0. this is mildly unfair but also an edge-case that
// can only occur when overlapping locked funds have been slashed.
pub fn do_slash<T: Config>(
stash: &T::AccountId,
value: BalanceOf<T>,
reward_payout: &mut BalanceOf<T>,
slashed_imbalance: &mut NegativeImbalanceOf<T>,
) {
let controller = match <Pallet<T>>::bonded(stash) {
None => return, // defensive: should always exist.
Some(c) => c,
};
let mut ledger = match <Pallet<T>>::ledger(&controller) {
Some(ledger) => ledger,
None => return, // nothing to do.
};
let value = ledger.slash(value, T::Currency::minimum_balance());
if !value.is_zero() {
let (imbalance, missing) = T::Currency::slash(stash, value);
slashed_imbalance.subsume(imbalance);
if !missing.is_zero() {
// deduct overslash from the reward payout
*reward_payout = reward_payout.saturating_sub(missing);
}
<Pallet<T>>::update_ledger(&controller, &ledger);
<Pallet<T>>::deposit_event(super::Event::<T>::Slash(stash.clone(), value));
}
}
/// Apply a previously-unapplied slash.
pub(crate) fn apply_slash<T: Config>(unapplied_slash: UnappliedSlash<T::AccountId, BalanceOf<T>>) {
let mut slashed_imbalance = NegativeImbalanceOf::<T>::zero();
let mut reward_payout = unapplied_slash.payout;
do_slash::<T>(
&unapplied_slash.validator,
unapplied_slash.own,
&mut reward_payout,
&mut slashed_imbalance,
);
for &(ref nominator, nominator_slash) in &unapplied_slash.others {
do_slash::<T>(&nominator, nominator_slash, &mut reward_payout, &mut slashed_imbalance);
}
pay_reporters::<T>(reward_payout, slashed_imbalance, &unapplied_slash.reporters);
}
/// Apply a reward payout to some reporters, paying the rewards out of the slashed imbalance.
fn pay_reporters<T: Config>(
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reward_payout: BalanceOf<T>,
slashed_imbalance: NegativeImbalanceOf<T>,
reporters: &[T::AccountId],
) {
if reward_payout.is_zero() || reporters.is_empty() {
// nobody to pay out to or nothing to pay;
// just treat the whole value as slashed.
T::Slash::on_unbalanced(slashed_imbalance);
return
}
// take rewards out of the slashed imbalance.
let reward_payout = reward_payout.min(slashed_imbalance.peek());
let (mut reward_payout, mut value_slashed) = slashed_imbalance.split(reward_payout);
let per_reporter = reward_payout.peek() / (reporters.len() as u32).into();
for reporter in reporters {
let (reporter_reward, rest) = reward_payout.split(per_reporter);
reward_payout = rest;
// this cancels out the reporter reward imbalance internally, leading
// to no change in total issuance.
T::Currency::resolve_creating(reporter, reporter_reward);
}
// the rest goes to the on-slash imbalance handler (e.g. treasury)
value_slashed.subsume(reward_payout); // remainder of reward division remains.
T::Slash::on_unbalanced(value_slashed);
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn span_contains_era() {
// unbounded end
let span = SlashingSpan { index: 0, start: 1000, length: None };
assert!(!span.contains_era(0));
assert!(!span.contains_era(999));
assert!(span.contains_era(1000));
assert!(span.contains_era(1001));
assert!(span.contains_era(10000));
// bounded end - non-inclusive range.
let span = SlashingSpan { index: 0, start: 1000, length: Some(10) };
assert!(!span.contains_era(0));
assert!(!span.contains_era(999));
assert!(span.contains_era(1000));
assert!(span.contains_era(1001));
assert!(span.contains_era(1009));
assert!(!span.contains_era(1010));
assert!(!span.contains_era(1011));
}
#[test]
fn single_slashing_span() {
let spans = SlashingSpans {
span_index: 0,
last_start: 1000,
last_nonzero_slash: 0,
prior: Vec::new(),
};
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![SlashingSpan { index: 0, start: 1000, length: None }],
);
}
#[test]
fn many_prior_spans() {
let spans = SlashingSpans {
span_index: 10,
last_start: 1000,
last_nonzero_slash: 0,
prior: vec![10, 9, 8, 10],
};
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![
SlashingSpan { index: 10, start: 1000, length: None },
SlashingSpan { index: 9, start: 990, length: Some(10) },
SlashingSpan { index: 8, start: 981, length: Some(9) },
SlashingSpan { index: 7, start: 973, length: Some(8) },
SlashingSpan { index: 6, start: 963, length: Some(10) },
],
)
}
#[test]
fn pruning_spans() {
let mut spans = SlashingSpans {
span_index: 10,
last_start: 1000,
last_nonzero_slash: 0,
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prior: vec![10, 9, 8, 10],
};
assert_eq!(spans.prune(981), Some((6, 8)));
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![
SlashingSpan { index: 10, start: 1000, length: None },
SlashingSpan { index: 9, start: 990, length: Some(10) },
SlashingSpan { index: 8, start: 981, length: Some(9) },
],
);
assert_eq!(spans.prune(982), None);
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![
SlashingSpan { index: 10, start: 1000, length: None },
SlashingSpan { index: 9, start: 990, length: Some(10) },
SlashingSpan { index: 8, start: 981, length: Some(9) },
],
);
assert_eq!(spans.prune(989), None);
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![
SlashingSpan { index: 10, start: 1000, length: None },
SlashingSpan { index: 9, start: 990, length: Some(10) },
SlashingSpan { index: 8, start: 981, length: Some(9) },
],
);
assert_eq!(spans.prune(1000), Some((8, 10)));
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![SlashingSpan { index: 10, start: 1000, length: None },],
);
assert_eq!(spans.prune(2000), None);
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![SlashingSpan { index: 10, start: 2000, length: None },],
);
// now all in one shot.
let mut spans = SlashingSpans {
span_index: 10,
last_start: 1000,
last_nonzero_slash: 0,
prior: vec![10, 9, 8, 10],
};
assert_eq!(spans.prune(2000), Some((6, 10)));
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![SlashingSpan { index: 10, start: 2000, length: None },],
);
}
#[test]
fn ending_span() {
let mut spans = SlashingSpans {
span_index: 1,
last_start: 10,
last_nonzero_slash: 0,
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
prior: Vec::new(),
};
assert!(spans.end_span(10));
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![
SlashingSpan { index: 2, start: 11, length: None },
SlashingSpan { index: 1, start: 10, length: Some(1) },
],
);
assert!(spans.end_span(15));
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![
SlashingSpan { index: 3, start: 16, length: None },
SlashingSpan { index: 2, start: 11, length: Some(5) },
SlashingSpan { index: 1, start: 10, length: Some(1) },
],
);
// does nothing if not a valid end.
assert!(!spans.end_span(15));
assert_eq!(
spans.iter().collect::<Vec<_>>(),
vec![
SlashingSpan { index: 3, start: 16, length: None },
SlashingSpan { index: 2, start: 11, length: Some(5) },
SlashingSpan { index: 1, start: 10, length: Some(1) },
],
);
}
}