XCMv4 (paritytech#1230)

# Note for reviewer

Most changes are just syntax changes necessary for the new version.
Most important files should be the ones under the `xcm` folder.

# Description 

Added XCMv4.

## Removed `Multi` prefix
The following types have been renamed:
- MultiLocation -> Location
- MultiAsset -> Asset
- MultiAssets -> Assets
- InteriorMultiLocation -> InteriorLocation
- MultiAssetFilter -> AssetFilter
- VersionedMultiAsset -> VersionedAsset
- WildMultiAsset -> WildAsset
- VersionedMultiLocation -> VersionedLocation

In order to fix a name conflict, the `Assets` in `xcm-executor` were
renamed to `HoldingAssets`, as they represent assets in holding.

## Removed `Abstract` asset id

It was not being used anywhere and this simplifies the code.

Now assets are just constructed as follows:

```rust
let asset: Asset = (AssetId(Location::new(1, Here)), 100u128).into();
```

No need for specifying `Concrete` anymore.

## Outcome is now a named fields struct

Instead of

```rust
pub enum Outcome {
  Complete(Weight),
  Incomplete(Weight, Error),
  Error(Error),
}
```

we now have

```rust
pub enum Outcome {
  Complete { used: Weight },
  Incomplete { used: Weight, error: Error },
  Error { error: Error },
}
```

## Added Reanchorable trait

Now both locations and assets implement this trait, making it easier to
reanchor both.

## New syntax for building locations and junctions

Now junctions are built using the following methods:

```rust
let location = Location {
    parents: 1,
    interior: [Parachain(1000), PalletInstance(50), GeneralIndex(1984)].into()
};
```

or

```rust
let location = Location::new(1, [Parachain(1000), PalletInstance(50), GeneralIndex(1984)]);
```

And they are matched like so:

```rust
match location.unpack() {
  (1, [Parachain(id)]) => ...
  (0, Here) => ...,
  (1, [_]) => ...,
}
```

This syntax is mandatory in v4, and has been also implemented for v2 and
v3 for easier migration.

This was needed to make all sizes smaller.

# TODO
- [x] Scaffold v4
- [x] Port github.com/paritytech/polkadot/pull/7236
- [x] Remove `Multi` prefix
- [x] Remove `Abstract` asset id

---------

Co-authored-by: command-bot <>
Co-authored-by: Keith Yeung <[email protected]>

bin/runtime-common/src/messages_benchmarking.rs

@@ -38,7 +38,7 @@ use frame_support::weights::Weight;
 use pallet_bridge_messages::benchmarking::{MessageDeliveryProofParams, MessageProofParams};
 use sp_runtime::traits::{Header, Zero};
 use sp_std::prelude::*;
-use xcm::v3::prelude::*;
+use xcm::latest::prelude::*;
 
 /// Prepare inbound bridge message according to given message proof parameters.
 fn prepare_inbound_message(
@@ -266,19 +266,19 @@ where
 /// Returns callback which generates `BridgeMessage` from Polkadot XCM builder based on
 /// `expected_message_size` for benchmark.
 pub fn generate_xcm_builder_bridge_message_sample(
-	destination: InteriorMultiLocation,
+	destination: InteriorLocation,
 ) -> impl Fn(usize) -> MessagePayload {
 	move |expected_message_size| -> MessagePayload {
 		// For XCM bridge hubs, it is the message that
 		// will be pushed further to some XCM queue (XCMP/UMP)
-		let location = xcm::VersionedInteriorMultiLocation::V3(destination);
+		let location = xcm::VersionedInteriorLocation::V4(destination.clone());
 		let location_encoded_size = location.encoded_size();
 
 		// we don't need to be super-precise with `expected_size` here
 		let xcm_size = expected_message_size.saturating_sub(location_encoded_size);
 		let xcm_data_size = xcm_size.saturating_sub(
 			// minus empty instruction size
-			xcm::v3::Instruction::<()>::ExpectPallet {
+			Instruction::<()>::ExpectPallet {
 				index: 0,
 				name: vec![],
 				module_name: vec![],
@@ -294,8 +294,8 @@ pub fn generate_xcm_builder_bridge_message_sample(
 			expected_message_size, location_encoded_size, xcm_size, xcm_data_size,
 		);
 
-		let xcm = xcm::VersionedXcm::<()>::V3(
-			vec![xcm::v3::Instruction::<()>::ExpectPallet {
+		let xcm = xcm::VersionedXcm::<()>::V4(
+			vec![Instruction::<()>::ExpectPallet {
 				index: 0,
 				name: vec![42; xcm_data_size],
 				module_name: vec![],

bin/runtime-common/src/messages_xcm_extension.rs

@@ -126,14 +126,14 @@ impl<
 #[cfg_attr(feature = "std", derive(Debug, Eq, PartialEq))]
 pub struct SenderAndLane {
 	/// Sending chain relative location.
-	pub location: MultiLocation,
+	pub location: Location,
 	/// Message lane, used by the sending chain.
 	pub lane: LaneId,
 }
 
 impl SenderAndLane {
 	/// Create new object using provided location and lane.
-	pub fn new(location: MultiLocation, lane: LaneId) -> Self {
+	pub fn new(location: Location, lane: LaneId) -> Self {
 		SenderAndLane { location, lane }
 	}
 }
@@ -171,7 +171,7 @@ pub struct XcmBlobHaulerAdapter<XcmBlobHauler, Lanes>(
 
 impl<
 		H: XcmBlobHauler,
-		Lanes: Get<sp_std::vec::Vec<(SenderAndLane, (NetworkId, InteriorMultiLocation))>>,
+		Lanes: Get<sp_std::vec::Vec<(SenderAndLane, (NetworkId, InteriorLocation))>>,
 	> OnMessagesDelivered for XcmBlobHaulerAdapter<H, Lanes>
 {
 	fn on_messages_delivered(lane: LaneId, enqueued_messages: MessageNonce) {
@@ -291,7 +291,7 @@ impl<H: XcmBlobHauler> LocalXcmQueueManager<H> {
 	/// Send congested signal to the `sending_chain_location`.
 	fn send_congested_signal(sender_and_lane: &SenderAndLane) -> Result<(), SendError> {
 		if let Some(msg) = H::CongestedMessage::get() {
-			send_xcm::<H::ToSourceChainSender>(sender_and_lane.location, msg)?;
+			send_xcm::<H::ToSourceChainSender>(sender_and_lane.location.clone(), msg)?;
 			OutboundLanesCongestedSignals::<H::Runtime, H::MessagesInstance>::insert(
 				sender_and_lane.lane,
 				true,
@@ -303,7 +303,7 @@ impl<H: XcmBlobHauler> LocalXcmQueueManager<H> {
 	/// Send `uncongested` signal to the `sending_chain_location`.
 	fn send_uncongested_signal(sender_and_lane: &SenderAndLane) -> Result<(), SendError> {
 		if let Some(msg) = H::UncongestedMessage::get() {
-			send_xcm::<H::ToSourceChainSender>(sender_and_lane.location, msg)?;
+			send_xcm::<H::ToSourceChainSender>(sender_and_lane.location.clone(), msg)?;
 			OutboundLanesCongestedSignals::<H::Runtime, H::MessagesInstance>::remove(
 				sender_and_lane.lane,
 			);
@@ -318,10 +318,10 @@ impl<H: XcmBlobHauler> LocalXcmQueueManager<H> {
 pub struct XcmVersionOfDestAndRemoteBridge<Version, RemoteBridge>(
 	sp_std::marker::PhantomData<(Version, RemoteBridge)>,
 );
-impl<Version: GetVersion, RemoteBridge: Get<MultiLocation>> GetVersion
+impl<Version: GetVersion, RemoteBridge: Get<Location>> GetVersion
 	for XcmVersionOfDestAndRemoteBridge<Version, RemoteBridge>
 {
-	fn get_version_for(dest: &MultiLocation) -> Option<XcmVersion> {
+	fn get_version_for(dest: &Location) -> Option<XcmVersion> {
 		let dest_version = Version::get_version_for(dest);
 		let bridge_hub_version = Version::get_version_for(&RemoteBridge::get());
 
@@ -345,11 +345,11 @@ mod tests {
 
 	parameter_types! {
 		pub TestSenderAndLane: SenderAndLane = SenderAndLane {
-			location: MultiLocation::new(1, X1(Parachain(1000))),
+			location: Location::new(1, [Parachain(1000)]),
 			lane: TEST_LANE_ID,
 		};
-		pub TestLanes: sp_std::vec::Vec<(SenderAndLane, (NetworkId, InteriorMultiLocation))> = sp_std::vec![
-			(TestSenderAndLane::get(), (NetworkId::ByGenesis([0; 32]), InteriorMultiLocation::Here))
+		pub TestLanes: sp_std::vec::Vec<(SenderAndLane, (NetworkId, InteriorLocation))> = sp_std::vec![
+			(TestSenderAndLane::get(), (NetworkId::ByGenesis([0; 32]), InteriorLocation::Here))
 		];
 		pub DummyXcmMessage: Xcm<()> = Xcm::new();
 	}
@@ -366,7 +366,7 @@ mod tests {
 		type Ticket = ();
 
 		fn validate(
-			_destination: &mut Option<MultiLocation>,
+			_destination: &mut Option<Location>,
 			_message: &mut Option<Xcm<()>>,
 		) -> SendResult<Self::Ticket> {
 			Ok(((), Default::default()))

modules/xcm-bridge-hub-router/src/benchmarking.rs

@@ -37,10 +37,10 @@ pub trait Config<I: 'static>: crate::Config<I> {
 	/// Returns destination which is valid for this router instance.
 	/// (Needs to pass `T::Bridges`)
 	/// Make sure that `SendXcm` will pass.
-	fn ensure_bridged_target_destination() -> Result<MultiLocation, BenchmarkError> {
-		Ok(MultiLocation::new(
+	fn ensure_bridged_target_destination() -> Result<Location, BenchmarkError> {
+		Ok(Location::new(
 			Self::UniversalLocation::get().len() as u8,
-			X1(GlobalConsensus(Self::BridgedNetworkId::get().unwrap())),
+			[GlobalConsensus(Self::BridgedNetworkId::get().unwrap())],
 		))
 	}
 }

modules/xcm-bridge-hub-router/src/lib.rs

@@ -80,7 +80,7 @@ pub mod pallet {
 		type WeightInfo: WeightInfo;
 
 		/// Universal location of this runtime.
-		type UniversalLocation: Get<InteriorMultiLocation>;
+		type UniversalLocation: Get<InteriorLocation>;
 		/// The bridged network that this config is for if specified.
 		/// Also used for filtering `Bridges` by `BridgedNetworkId`.
 		/// If not specified, allows all networks pass through.
@@ -235,9 +235,9 @@ type ViaBridgeHubExporter<T, I> = SovereignPaidRemoteExporter<
 impl<T: Config<I>, I: 'static> ExporterFor for Pallet<T, I> {
 	fn exporter_for(
 		network: &NetworkId,
-		remote_location: &InteriorMultiLocation,
+		remote_location: &InteriorLocation,
 		message: &Xcm<()>,
-	) -> Option<(MultiLocation, Option<MultiAsset>)> {
+	) -> Option<(Location, Option<Asset>)> {
 		// ensure that the message is sent to the expected bridged network (if specified).
 		if let Some(bridged_network) = T::BridgedNetworkId::get() {
 			if *network != bridged_network {
@@ -268,7 +268,7 @@ impl<T: Config<I>, I: 'static> ExporterFor for Pallet<T, I> {
 		// take `base_fee` from `T::Brides`, but it has to be the same `T::FeeAsset`
 		let base_fee = match maybe_payment {
 			Some(payment) => match payment {
-				MultiAsset { fun: Fungible(amount), id } if id.eq(&T::FeeAsset::get()) => amount,
+				Asset { fun: Fungible(amount), id } if id.eq(&T::FeeAsset::get()) => amount,
 				invalid_asset => {
 					log::error!(
 						target: LOG_TARGET,
@@ -318,7 +318,7 @@ impl<T: Config<I>, I: 'static> SendXcm for Pallet<T, I> {
 	type Ticket = (u32, <T::ToBridgeHubSender as SendXcm>::Ticket);
 
 	fn validate(
-		dest: &mut Option<MultiLocation>,
+		dest: &mut Option<Location>,
 		xcm: &mut Option<Xcm<()>>,
 	) -> SendResult<Self::Ticket> {
 		// `dest` and `xcm` are required here
@@ -446,7 +446,7 @@ mod tests {
 		run_test(|| {
 			assert_eq!(
 				send_xcm::<XcmBridgeHubRouter>(
-					MultiLocation::new(2, X2(GlobalConsensus(Rococo), Parachain(1000))),
+					Location::new(2, [GlobalConsensus(Rococo), Parachain(1000)]),
 					vec![].into(),
 				),
 				Err(SendError::NotApplicable),
@@ -459,7 +459,7 @@ mod tests {
 		run_test(|| {
 			assert_eq!(
 				send_xcm::<XcmBridgeHubRouter>(
-					MultiLocation::new(2, X2(GlobalConsensus(Rococo), Parachain(1000))),
+					Location::new(2, [GlobalConsensus(Rococo), Parachain(1000)]),
 					vec![ClearOrigin; HARD_MESSAGE_SIZE_LIMIT as usize].into(),
 				),
 				Err(SendError::ExceedsMaxMessageSize),
@@ -483,14 +483,14 @@ mod tests {
 	#[test]
 	fn returns_proper_delivery_price() {
 		run_test(|| {
-			let dest = MultiLocation::new(2, X1(GlobalConsensus(BridgedNetworkId::get())));
+			let dest = Location::new(2, [GlobalConsensus(BridgedNetworkId::get())]);
 			let xcm: Xcm<()> = vec![ClearOrigin].into();
 			let msg_size = xcm.encoded_size();
 
 			// initially the base fee is used: `BASE_FEE + BYTE_FEE * msg_size + HRMP_FEE`
 			let expected_fee = BASE_FEE + BYTE_FEE * (msg_size as u128) + HRMP_FEE;
 			assert_eq!(
-				XcmBridgeHubRouter::validate(&mut Some(dest), &mut Some(xcm.clone()))
+				XcmBridgeHubRouter::validate(&mut Some(dest.clone()), &mut Some(xcm.clone()))
 					.unwrap()
 					.1
 					.get(0),
@@ -518,10 +518,7 @@ mod tests {
 		run_test(|| {
 			let old_bridge = XcmBridgeHubRouter::bridge();
 			assert_ok!(send_xcm::<XcmBridgeHubRouter>(
-				MultiLocation::new(
-					2,
-					X2(GlobalConsensus(BridgedNetworkId::get()), Parachain(1000))
-				),
+				Location::new(2, [GlobalConsensus(BridgedNetworkId::get()), Parachain(1000)]),
 				vec![ClearOrigin].into(),
 			)
 			.map(drop));
@@ -538,10 +535,7 @@ mod tests {
 
 			let old_bridge = XcmBridgeHubRouter::bridge();
 			assert_ok!(send_xcm::<XcmBridgeHubRouter>(
-				MultiLocation::new(
-					2,
-					X2(GlobalConsensus(BridgedNetworkId::get()), Parachain(1000))
-				),
+				Location::new(2, [GlobalConsensus(BridgedNetworkId::get()), Parachain(1000)]),
 				vec![ClearOrigin].into(),
 			)
 			.map(drop));
@@ -560,10 +554,7 @@ mod tests {
 
 			let old_bridge = XcmBridgeHubRouter::bridge();
 			assert_ok!(send_xcm::<XcmBridgeHubRouter>(
-				MultiLocation::new(
-					2,
-					X2(GlobalConsensus(BridgedNetworkId::get()), Parachain(1000))
-				),
+				Location::new(2, [GlobalConsensus(BridgedNetworkId::get()), Parachain(1000)]),
 				vec![ClearOrigin].into(),
 			)
 			.map(drop));

modules/xcm-bridge-hub-router/src/mock.rs

@@ -49,9 +49,9 @@ construct_runtime! {
 parameter_types! {
 	pub ThisNetworkId: NetworkId = Polkadot;
 	pub BridgedNetworkId: NetworkId = Kusama;
-	pub UniversalLocation: InteriorMultiLocation = X2(GlobalConsensus(ThisNetworkId::get()), Parachain(1000));
-	pub SiblingBridgeHubLocation: MultiLocation = ParentThen(X1(Parachain(1002))).into();
-	pub BridgeFeeAsset: AssetId = MultiLocation::parent().into();
+	pub UniversalLocation: InteriorLocation = [GlobalConsensus(ThisNetworkId::get()), Parachain(1000)].into();
+	pub SiblingBridgeHubLocation: Location = ParentThen([Parachain(1002)].into()).into();
+	pub BridgeFeeAsset: AssetId = Location::parent().into();
 	pub BridgeTable: Vec<NetworkExportTableItem>
 		= vec![
 			NetworkExportTableItem::new(
@@ -61,7 +61,7 @@ parameter_types! {
 				Some((BridgeFeeAsset::get(), BASE_FEE).into())
 			)
 		];
-	pub UnknownXcmVersionLocation: MultiLocation = MultiLocation::new(2, X2(GlobalConsensus(BridgedNetworkId::get()), Parachain(9999)));
+	pub UnknownXcmVersionLocation: Location = Location::new(2, [GlobalConsensus(BridgedNetworkId::get()), Parachain(9999)]);
 }
 
 #[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
@@ -87,11 +87,11 @@ impl pallet_xcm_bridge_hub_router::Config<()> for TestRuntime {
 }
 
 pub struct LatestOrNoneForLocationVersionChecker<Location>(sp_std::marker::PhantomData<Location>);
-impl<Location: Contains<MultiLocation>> GetVersion
-	for LatestOrNoneForLocationVersionChecker<Location>
+impl<LocationValue: Contains<Location>> GetVersion
+	for LatestOrNoneForLocationVersionChecker<LocationValue>
 {
-	fn get_version_for(dest: &MultiLocation) -> Option<XcmVersion> {
-		if Location::contains(dest) {
+	fn get_version_for(dest: &Location) -> Option<XcmVersion> {
+		if LocationValue::contains(dest) {
 			return None
 		}
 		Some(XCM_VERSION)
@@ -110,7 +110,7 @@ impl SendXcm for TestToBridgeHubSender {
 	type Ticket = ();
 
 	fn validate(
-		_destination: &mut Option<MultiLocation>,
+		_destination: &mut Option<Location>,
 		_message: &mut Option<Xcm<()>>,
 	) -> SendResult<Self::Ticket> {
 		Ok(((), (BridgeFeeAsset::get(), HRMP_FEE).into()))

modules/xcm-bridge-hub/src/exporter.rs

@@ -53,10 +53,10 @@ where
 	fn validate(
 		network: NetworkId,
 		channel: u32,
-		universal_source: &mut Option<InteriorMultiLocation>,
-		destination: &mut Option<InteriorMultiLocation>,
+		universal_source: &mut Option<InteriorLocation>,
+		destination: &mut Option<InteriorLocation>,
 		message: &mut Option<Xcm<()>>,
-	) -> Result<(Self::Ticket, MultiAssets), SendError> {
+	) -> Result<(Self::Ticket, Assets), SendError> {
 		// Find supported lane_id.
 		let sender_and_lane = Self::lane_for(
 			universal_source.as_ref().ok_or(SendError::MissingArgument)?,
@@ -134,11 +134,11 @@ mod tests {
 	use frame_support::assert_ok;
 	use xcm_executor::traits::export_xcm;
 
-	fn universal_source() -> InteriorMultiLocation {
-		X2(GlobalConsensus(RelayNetwork::get()), Parachain(SIBLING_ASSET_HUB_ID))
+	fn universal_source() -> InteriorLocation {
+		[GlobalConsensus(RelayNetwork::get()), Parachain(SIBLING_ASSET_HUB_ID)].into()
 	}
 
-	fn universal_destination() -> InteriorMultiLocation {
+	fn universal_destination() -> InteriorLocation {
 		BridgedDestination::get()
 	}
 

modules/xcm-bridge-hub/src/lib.rs

@@ -45,25 +45,25 @@ pub mod pallet {
 		BridgeMessagesConfig<Self::BridgeMessagesPalletInstance>
 	{
 		/// Runtime's universal location.
-		type UniversalLocation: Get<InteriorMultiLocation>;
+		type UniversalLocation: Get<InteriorLocation>;
 		// TODO: https://github.com/paritytech/parity-bridges-common/issues/1666 remove `ChainId` and
 		// replace it with the `NetworkId` - then we'll be able to use
 		// `T as pallet_bridge_messages::Config<T::BridgeMessagesPalletInstance>::BridgedChain::NetworkId`
 		/// Bridged network as relative location of bridged `GlobalConsensus`.
 		#[pallet::constant]
-		type BridgedNetwork: Get<MultiLocation>;
+		type BridgedNetwork: Get<Location>;
 		/// Associated messages pallet instance that bridges us with the
 		/// `BridgedNetworkId` consensus.
 		type BridgeMessagesPalletInstance: 'static;
 
 		/// Price of single message export to the bridged consensus (`Self::BridgedNetworkId`).
-		type MessageExportPrice: Get<MultiAssets>;
+		type MessageExportPrice: Get<Assets>;
 		/// Checks the XCM version for the destination.
 		type DestinationVersion: GetVersion;
 
 		/// Get point-to-point links with bridged consensus (`Self::BridgedNetworkId`).
 		/// (this will be replaced with dynamic on-chain bridges - `Bridges V2`)
-		type Lanes: Get<sp_std::vec::Vec<(SenderAndLane, (NetworkId, InteriorMultiLocation))>>;
+		type Lanes: Get<sp_std::vec::Vec<(SenderAndLane, (NetworkId, InteriorLocation))>>;
 		/// Support for point-to-point links
 		/// (this will be replaced with dynamic on-chain bridges - `Bridges V2`)
 		type LanesSupport: XcmBlobHauler;
@@ -86,10 +86,10 @@ pub mod pallet {
 	impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		/// Returns dedicated/configured lane identifier.
 		pub(crate) fn lane_for(
-			source: &InteriorMultiLocation,
-			dest: (&NetworkId, &InteriorMultiLocation),
+			source: &InteriorLocation,
+			dest: (&NetworkId, &InteriorLocation),
 		) -> Option<SenderAndLane> {
-			let source = source.relative_to(&T::UniversalLocation::get());
+			let source = source.clone().relative_to(&T::UniversalLocation::get());
 
 			// Check that we have configured a point-to-point lane for 'source' and `dest`.
 			T::Lanes::get()