XCMv4 (#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 <kungfukeith11@gmail.com>

cumulus/parachains/runtimes/testing/penpal/src/lib.rs

@@ -32,7 +32,6 @@ include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 mod weights;
 pub mod xcm_config;
 
-use assets_common::MultiLocationForAssetId;
 use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use cumulus_primitives_core::{AggregateMessageOrigin, ParaId};
 use frame_support::{
@@ -474,8 +473,8 @@ pub type ForeignAssetsInstance = pallet_assets::Instance2;
 impl pallet_assets::Config<ForeignAssetsInstance> for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type Balance = Balance;
-	type AssetId = MultiLocationForAssetId;
-	type AssetIdParameter = MultiLocationForAssetId;
+	type AssetId = xcm::v3::Location;
+	type AssetIdParameter = xcm::v3::Location;
 	type Currency = Balances;
 	type CreateOrigin = AsEnsureOriginWithArg<EnsureSigned<AccountId>>;
 	type ForceOrigin = EnsureRoot<AccountId>;

cumulus/parachains/runtimes/testing/penpal/src/xcm_config.rs

@@ -29,7 +29,7 @@ use super::{
 };
 use core::marker::PhantomData;
 use frame_support::{
-	match_types, parameter_types,
+	parameter_types,
 	traits::{
 		fungibles::{self, Balanced, Credit},
 		ConstU32, Contains, ContainsPair, Everything, Get, Nothing,
@@ -59,13 +59,13 @@ use xcm_builder::{
 use xcm_executor::{traits::JustTry, XcmExecutor};
 
 parameter_types! {
-	pub const RelayLocation: MultiLocation = MultiLocation::parent();
+	pub const RelayLocation: Location = Location::parent();
 	pub const RelayNetwork: Option<NetworkId> = None;
 	pub RelayChainOrigin: RuntimeOrigin = cumulus_pallet_xcm::Origin::Relay.into();
-	pub UniversalLocation: InteriorMultiLocation = X1(Parachain(ParachainInfo::parachain_id().into()));
+	pub UniversalLocation: InteriorLocation = [Parachain(ParachainInfo::parachain_id().into())].into();
 }
 
-/// Type for specifying how a `MultiLocation` can be converted into an `AccountId`. This is used
+/// Type for specifying how a `Location` can be converted into an `AccountId`. This is used
 /// when determining ownership of accounts for asset transacting and when attempting to use XCM
 /// `Transact` in order to determine the dispatch Origin.
 pub type LocationToAccountId = (
@@ -84,7 +84,7 @@ pub type CurrencyTransactor = CurrencyAdapter<
 	Balances,
 	// Use this currency when it is a fungible asset matching the given location or name:
 	IsConcrete<RelayLocation>,
-	// Do a simple punn to convert an AccountId32 MultiLocation into a native chain account ID:
+	// Do a simple punn to convert an AccountId32 Location into a native chain account ID:
 	LocationToAccountId,
 	// Our chain's account ID type (we can't get away without mentioning it explicitly):
 	AccountId,
@@ -115,7 +115,7 @@ pub type FungiblesTransactor = FungiblesAdapter<
 			JustTry,
 		>,
 	),
-	// Convert an XCM MultiLocation into a local account id:
+	// Convert an XCM Location into a local account id:
 	LocationToAccountId,
 	// Our chain's account ID type (we can't get away without mentioning it explicitly):
 	AccountId,
@@ -180,14 +180,18 @@ parameter_types! {
 	pub const MaxAssetsIntoHolding: u32 = 64;
 }
 
-match_types! {
-	pub type ParentOrParentsExecutivePlurality: impl Contains<MultiLocation> = {
-		MultiLocation { parents: 1, interior: Here } |
-		MultiLocation { parents: 1, interior: X1(Plurality { id: BodyId::Executive, .. }) }
-	};
-	pub type CommonGoodAssetsParachain: impl Contains<MultiLocation> = {
-		MultiLocation { parents: 1, interior: X1(Parachain(1000)) }
-	};
+pub struct ParentOrParentsExecutivePlurality;
+impl Contains<Location> for ParentOrParentsExecutivePlurality {
+	fn contains(location: &Location) -> bool {
+		matches!(location.unpack(), (1, []) | (1, [Plurality { id: BodyId::Executive, .. }]))
+	}
+}
+
+pub struct CommonGoodAssetsParachain;
+impl Contains<Location> for CommonGoodAssetsParachain {
+	fn contains(location: &Location) -> bool {
+		matches!(location.unpack(), (1, [Parachain(1000)]))
+	}
 }
 
 pub type Barrier = TrailingSetTopicAsId<
@@ -224,15 +228,15 @@ pub type AccountIdOf<R> = <R as frame_system::Config>::AccountId;
 
 /// Asset filter that allows all assets from a certain location matching asset id.
 pub struct AssetPrefixFrom<Prefix, Origin>(PhantomData<(Prefix, Origin)>);
-impl<Prefix, Origin> ContainsPair<MultiAsset, MultiLocation> for AssetPrefixFrom<Prefix, Origin>
+impl<Prefix, Origin> ContainsPair<Asset, Location> for AssetPrefixFrom<Prefix, Origin>
 where
-	Prefix: Get<MultiLocation>,
-	Origin: Get<MultiLocation>,
+	Prefix: Get<Location>,
+	Origin: Get<Location>,
 {
-	fn contains(asset: &MultiAsset, origin: &MultiLocation) -> bool {
+	fn contains(asset: &Asset, origin: &Location) -> bool {
 		let loc = Origin::get();
 		&loc == origin &&
-			matches!(asset, MultiAsset { id: AssetId::Concrete(asset_loc), fun: Fungible(_a) }
+			matches!(asset, Asset { id: AssetId(asset_loc), fun: Fungible(_a) }
 			if asset_loc.starts_with(&Prefix::get()))
 	}
 }
@@ -241,12 +245,12 @@ type AssetsFrom<T> = AssetPrefixFrom<T, T>;
 
 /// Asset filter that allows native/relay asset if coming from a certain location.
 pub struct NativeAssetFrom<T>(PhantomData<T>);
-impl<T: Get<MultiLocation>> ContainsPair<MultiAsset, MultiLocation> for NativeAssetFrom<T> {
-	fn contains(asset: &MultiAsset, origin: &MultiLocation) -> bool {
+impl<T: Get<Location>> ContainsPair<Asset, Location> for NativeAssetFrom<T> {
+	fn contains(asset: &Asset, origin: &Location) -> bool {
 		let loc = T::get();
 		&loc == origin &&
-			matches!(asset, MultiAsset { id: AssetId::Concrete(asset_loc), fun: Fungible(_a) }
-			if *asset_loc == MultiLocation::from(Parent))
+			matches!(asset, Asset { id: AssetId(asset_loc), fun: Fungible(_a) }
+			if *asset_loc == Location::from(Parent))
 	}
 }
 
@@ -282,29 +286,34 @@ where
 pub const TELEPORTABLE_ASSET_ID: u32 = 2;
 parameter_types! {
 	/// The location that this chain recognizes as the Relay network's Asset Hub.
-	pub SystemAssetHubLocation: MultiLocation = MultiLocation::new(1, X1(Parachain(1000)));
+	pub SystemAssetHubLocation: Location = Location::new(1, [Parachain(1000)]);
 	// ALWAYS ensure that the index in PalletInstance stays up-to-date with
 	// the Relay Chain's Asset Hub's Assets pallet index
-	pub SystemAssetHubAssetsPalletLocation: MultiLocation =
-		MultiLocation::new(1, X2(Parachain(1000), PalletInstance(50)));
-	pub AssetsPalletLocation: MultiLocation =
-		MultiLocation::new(0, X1(PalletInstance(50)));
+	pub SystemAssetHubAssetsPalletLocation: Location =
+		Location::new(1, [Parachain(1000), PalletInstance(50)]);
+	pub AssetsPalletLocation: Location =
+		Location::new(0, [PalletInstance(50)]);
 	pub CheckingAccount: AccountId = PolkadotXcm::check_account();
-	pub LocalTeleportableToAssetHub: MultiLocation = MultiLocation::new(
+	pub LocalTeleportableToAssetHub: Location = Location::new(
 		0,
-		X2(PalletInstance(50), GeneralIndex(TELEPORTABLE_ASSET_ID.into()))
+		[PalletInstance(50), GeneralIndex(TELEPORTABLE_ASSET_ID.into())]
 	);
-	pub EthereumLocation: MultiLocation = MultiLocation::new(2, X1(GlobalConsensus(EthereumNetwork::get())));
+	pub LocalTeleportableToAssetHubV3: xcm::v3::Location = xcm::v3::Location::new(
+		0,
+		[xcm::v3::Junction::PalletInstance(50), xcm::v3::Junction::GeneralIndex(TELEPORTABLE_ASSET_ID.into())]
+	);
+	pub EthereumLocation: Location = Location::new(2, [GlobalConsensus(EthereumNetwork::get())]);
 }
 
 /// Accepts asset with ID `AssetLocation` and is coming from `Origin` chain.
 pub struct AssetFromChain<AssetLocation, Origin>(PhantomData<(AssetLocation, Origin)>);
-impl<AssetLocation: Get<MultiLocation>, Origin: Get<MultiLocation>>
-	ContainsPair<MultiAsset, MultiLocation> for AssetFromChain<AssetLocation, Origin>
+impl<AssetLocation: Get<Location>, Origin: Get<Location>> ContainsPair<Asset, Location>
+	for AssetFromChain<AssetLocation, Origin>
 {
-	fn contains(asset: &MultiAsset, origin: &MultiLocation) -> bool {
+	fn contains(asset: &Asset, origin: &Location) -> bool {
 		log::trace!(target: "xcm::contains", "AssetFromChain asset: {:?}, origin: {:?}", asset, origin);
-		*origin == Origin::get() && matches!(asset.id, Concrete(id) if id == AssetLocation::get())
+		*origin == Origin::get() &&
+			matches!(asset.id.clone(), AssetId(id) if id == AssetLocation::get())
 	}
 }
 
@@ -398,8 +407,8 @@ impl cumulus_pallet_xcm::Config for Runtime {
 /// Simple conversion of `u32` into an `AssetId` for use in benchmarking.
 pub struct XcmBenchmarkHelper;
 #[cfg(feature = "runtime-benchmarks")]
-impl pallet_assets::BenchmarkHelper<MultiLocation> for XcmBenchmarkHelper {
-	fn create_asset_id_parameter(id: u32) -> MultiLocation {
-		MultiLocation { parents: 1, interior: X1(Parachain(id)) }
+impl pallet_assets::BenchmarkHelper<xcm::v3::Location> for XcmBenchmarkHelper {
+	fn create_asset_id_parameter(id: u32) -> xcm::v3::Location {
+		xcm::v3::Location::new(1, [xcm::v3::Junction::Parachain(id)])
 	}
 }