staking: Proportional ledger slashing (#10982)

* staking: Proportional ledger slashing

* Some comment cleanup

* Update frame/staking/src/pallet/mod.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Fix benchmarks

* FMT

* Try fill in all staking configs

* round of feedback and imp from kian

* demonstrate per_thing usage

* Update some tests

* FMT

* Test that era offset works correctly

* Update mocks

* Remove unnescary docs

* Remove unlock_era

* Update frame/staking/src/lib.rs

* Adjust tests to account for only remove when < ED

* Remove stale TODOs

* Remove dupe test

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: kianenigma <kian@parity.io>

substrate/frame/staking/src/pallet/impls.rs

@@ -213,10 +213,7 @@ impl<T: Config> Pallet<T> {
 	/// Update the ledger for a controller.
 	///
 	/// This will also update the stash lock.
-	pub(crate) fn update_ledger(
-		controller: &T::AccountId,
-		ledger: &StakingLedger<T::AccountId, BalanceOf<T>>,
-	) {
+	pub(crate) fn update_ledger(controller: &T::AccountId, ledger: &StakingLedger<T>) {
 		T::Currency::set_lock(STAKING_ID, &ledger.stash, ledger.total, WithdrawReasons::all());
 		<Ledger<T>>::insert(controller, ledger);
 	}
@@ -606,7 +603,7 @@ impl<T: Config> Pallet<T> {
 				for era in (*earliest)..keep_from {
 					let era_slashes = <Self as Store>::UnappliedSlashes::take(&era);
 					for slash in era_slashes {
-						slashing::apply_slash::<T>(slash);
+						slashing::apply_slash::<T>(slash, era);
 					}
 				}
 
@@ -1248,7 +1245,7 @@ where
 				unapplied.reporters = details.reporters.clone();
 				if slash_defer_duration == 0 {
 					// Apply right away.
-					slashing::apply_slash::<T>(unapplied);
+					slashing::apply_slash::<T>(unapplied, slash_era);
 					{
 						let slash_cost = (6, 5);
 						let reward_cost = (2, 2);

substrate/frame/staking/src/pallet/mod.rs

@@ -75,8 +75,22 @@ pub mod pallet {
 	#[pallet::config]
 	pub trait Config: frame_system::Config + SendTransactionTypes<Call<Self>> {
 		/// The staking balance.
-		type Currency: LockableCurrency<Self::AccountId, Moment = Self::BlockNumber>;
-
+		type Currency: LockableCurrency<
+			Self::AccountId,
+			Moment = Self::BlockNumber,
+			Balance = Self::CurrencyBalance,
+		>;
+		/// Just the `Currency::Balance` type; we have this item to allow us to constrain it to
+		/// `From<u64>`.
+		type CurrencyBalance: sp_runtime::traits::AtLeast32BitUnsigned
+			+ codec::FullCodec
+			+ Copy
+			+ MaybeSerializeDeserialize
+			+ sp_std::fmt::Debug
+			+ Default
+			+ From<u64>
+			+ TypeInfo
+			+ MaxEncodedLen;
 		/// Time used for computing era duration.
 		///
 		/// It is guaranteed to start being called from the first `on_finalize`. Thus value at
@@ -177,6 +191,10 @@ pub mod pallet {
 		#[pallet::constant]
 		type MaxUnlockingChunks: Get<u32>;
 
+		/// A hook called when any staker is slashed. Mostly likely this can be a no-op unless
+		/// other pallets exist that are affected by slashing per-staker.
+		type OnStakerSlash: sp_staking::OnStakerSlash<Self::AccountId, BalanceOf<Self>>;
+
 		/// Some parameters of the benchmarking.
 		type BenchmarkingConfig: BenchmarkingConfig;
 
@@ -239,8 +257,7 @@ pub mod pallet {
 	/// Map from all (unlocked) "controller" accounts to the info regarding the staking.
 	#[pallet::storage]
 	#[pallet::getter(fn ledger)]
-	pub type Ledger<T: Config> =
-		StorageMap<_, Blake2_128Concat, T::AccountId, StakingLedger<T::AccountId, BalanceOf<T>>>;
+	pub type Ledger<T: Config> = StorageMap<_, Blake2_128Concat, T::AccountId, StakingLedger<T>>;
 
 	/// Where the reward payment should be made. Keyed by stash.
 	#[pallet::storage]