Add aliasers to westend chains (#6814)

`InitiateTransfer`, the new instruction introduced in XCMv5, allows
preserving the origin after a cross-chain transfer via the usage of the
`AliasOrigin` instruction. The receiving chain needs to be configured to
allow such this instruction to have its intended effect and not just
throw an error.

In this PR, I add the alias rules specified in the [RFC for origin
preservation](https://github.com/polkadot-fellows/RFCs/blob/main/text/0122-alias-origin-on-asset-transfers.md)
to westend chains so we can test these scenarios in the testnet.

The new scenarios include:
- Sending a cross-chain transfer from one system chain to another and
doing a Transact on the same message (1 hop)
- Sending a reserve asset transfer from one chain to another going
through asset hub and doing Transact on the same message (2 hops)

The updated chains are:
- Relay: added `AliasChildLocation`
- Collectives: added `AliasChildLocation` and
`AliasOriginRootUsingFilter<AssetHubLocation, Everything>`
- People: added `AliasChildLocation` and
`AliasOriginRootUsingFilter<AssetHubLocation, Everything>`
- Coretime: added `AliasChildLocation` and
`AliasOriginRootUsingFilter<AssetHubLocation, Everything>`

AssetHub already has `AliasChildLocation` and doesn't need the other
config item.
BridgeHub is not intended to be used by end users so I didn't add any
config item.
Only added `AliasChildOrigin` to the relay since we intend for it to be
used less.

---------

Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: command-bot <>

cumulus/parachains/runtimes/collectives/collectives-westend/src/xcm_config.rs

@@ -35,7 +35,8 @@ use polkadot_runtime_common::xcm_sender::ExponentialPrice;
 use westend_runtime_constants::xcm as xcm_constants;
 use xcm::latest::{prelude::*, WESTEND_GENESIS_HASH};
 use xcm_builder::{
-	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
+	AccountId32Aliases, AliasChildLocation, AliasOriginRootUsingFilter,
+	AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
 	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
 	EnsureXcmOrigin, FixedWeightBounds, FrameTransactionalProcessor, FungibleAdapter,
@@ -191,6 +192,10 @@ pub type WaivedLocations = (
 /// - DOT with the parent Relay Chain and sibling parachains.
 pub type TrustedTeleporters = ConcreteAssetFromSystem<WndLocation>;
 
+/// We allow locations to alias into their own child locations, as well as
+/// AssetHub to alias into anything.
+pub type Aliasers = (AliasChildLocation, AliasOriginRootUsingFilter<AssetHub, Everything>);
+
 pub struct XcmConfig;
 impl xcm_executor::Config for XcmConfig {
 	type RuntimeCall = RuntimeCall;
@@ -227,7 +232,7 @@ impl xcm_executor::Config for XcmConfig {
 	type UniversalAliases = Nothing;
 	type CallDispatcher = RuntimeCall;
 	type SafeCallFilter = Everything;
-	type Aliasers = Nothing;
+	type Aliasers = Aliasers;
 	type TransactionalProcessor = FrameTransactionalProcessor;
 	type HrmpNewChannelOpenRequestHandler = ();
 	type HrmpChannelAcceptedHandler = ();

cumulus/parachains/runtimes/coretime/coretime-westend/src/lib.rs

@@ -1126,7 +1126,9 @@ impl_runtime_apis! {
 				}
 
 				fn alias_origin() -> Result<(Location, Location), BenchmarkError> {
-					Err(BenchmarkError::Skip)
+					let origin = Location::new(1, [Parachain(1000)]);
+					let target = Location::new(1, [Parachain(1000), AccountId32 { id: [128u8; 32], network: None }]);
+					Ok((origin, target))
 				}
 			}
 

cumulus/parachains/runtimes/coretime/coretime-westend/src/weights/xcm/mod.rs

@@ -261,8 +261,7 @@ impl<Call> XcmWeightInfo<Call> for CoretimeWestendXcmWeight<Call> {
 		XcmGeneric::<Runtime>::clear_topic()
 	}
 	fn alias_origin(_: &Location) -> Weight {
-		// XCM Executor does not currently support alias origin operations
-		Weight::MAX
+		XcmGeneric::<Runtime>::alias_origin()
 	}
 	fn unpaid_execution(_: &WeightLimit, _: &Option<Location>) -> Weight {
 		XcmGeneric::<Runtime>::unpaid_execution()