Staking: chill_other takes stash instead of controller (paritytech#…

…2501)

The `chill_other` call is the only staking call that explicitly requires
`controller` in its signature. This PR changes the controller arg to be
the stash instead, with `StakingLedger` then fetching the controller
from storage.

This is not a breaking change per se - the call types do not change, but
is noteworthy as UIs will now want to pass the stash account into
`chill_other` calls, & metadata will reflect this.

Note: This is very low impact. `chill_other` has [hardly ever been
used](https://polkadot.subscan.io/extrinsic?address=&module=staking&call=chill_other&result=all&signedChecked=signed%20only&startDate=&endDate=&startBlock=&timeType=date&version=9431&endBlock=)
on Polkadot - notwithstanding the one called 11 days ago at block
18177457 that was a part of test I did, the last call was made 493 days
ago. Only 2 calls have ever been successful.

Addresses controller deprecation paritytech#2500

---------

Co-authored-by: command-bot <>
Co-authored-by: Gonçalo Pestana <g6pestana@gmail.com>

substrate/frame/staking/src/benchmarking.rs

@@ -873,7 +873,7 @@ benchmarks! {
 		)?;
 
 		let caller = whitelisted_caller();
-	}: _(RawOrigin::Signed(caller), controller)
+	}: _(RawOrigin::Signed(caller), stash.clone())
 	verify {
 		assert!(!T::VoterList::contains(&stash));
 	}

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

@@ -1327,7 +1327,7 @@ pub mod pallet {
 			// (temporary) passive migration.
 			Self::ledger(StakingAccount::Stash(stash.clone())).map(|ledger| {
 				let controller = ledger.controller()
-                    .defensive_proof("ledger was fetched used the StakingInterface, so controller field must exist; qed.")
+                    .defensive_proof("Ledger's controller field didn't exist. The controller should have been fetched using StakingLedger.")
                     .ok_or(Error::<T>::NotController)?;
 
 				if controller == stash {
@@ -1764,11 +1764,16 @@ pub mod pallet {
 		/// who do not satisfy these requirements.
 		#[pallet::call_index(23)]
 		#[pallet::weight(T::WeightInfo::chill_other())]
-		pub fn chill_other(origin: OriginFor<T>, controller: T::AccountId) -> DispatchResult {
+		pub fn chill_other(origin: OriginFor<T>, stash: T::AccountId) -> DispatchResult {
 			// Anyone can call this function.
 			let caller = ensure_signed(origin)?;
-			let ledger = Self::ledger(Controller(controller.clone()))?;
-			let stash = ledger.stash;
+			let ledger = Self::ledger(Stash(stash.clone()))?;
+			let controller = ledger
+				.controller()
+				.defensive_proof(
+					"Ledger's controller field didn't exist. The controller should have been fetched using StakingLedger.",
+				)
+				.ok_or(Error::<T>::NotController)?;
 
 			// In order for one user to chill another user, the following conditions must be met:
 			//