Module xcm::v2

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XCM Version 2

Version 2 of the Cross-Consensus Message format data structures. The comprehensive list of changes can be found in this PR description.

Changes to be aware of

The biggest change here is the restructuring of XCM messages: instead of having Order and Xcm types, the Xcm type now simply wraps a Vec containing Instructions. However, most changes should still be automatically convertible via the try_from and from conversion functions.

Junction

  • No special attention necessary

MultiLocation

  • No special attention necessary

MultiAsset

  • No special attention necessary

XCM and Order

  • Xcm and Order variants are now combined under a single Instruction enum.
  • Order is now obsolete and replaced entirely by Instruction.
  • Xcm is now a simple wrapper around a Vec<Instruction>.
  • During conversion from Order to Instruction, we do not handle BuyExecutions that have nested XCMs, i.e. if the instructions field in the BuyExecution enum struct variant is not empty, then the conversion will fail. To address this, rewrite the XCM using Instructions in chronological order.
  • During conversion from Xcm to Instruction, we do not handle RelayedFrom messages at all.

XCM Pallet

  • The Weigher configuration item must have sensible weights defined for BuyExecution and DepositAsset instructions. Failing that, dispatch calls to teleport_assets and reserve_transfer_assets will fail with UnweighableMessage.

Modules

  • opaque
  • prelude
    A prelude for importing all types typically used when interacting with XCM messages.

Structs

  • Ancestor
    A unit struct which can be converted into a MultiLocation of the inner parents value.
  • AncestorThen
    A unit struct which can be converted into a MultiLocation of the inner parents value and the inner interior.
  • MultiAsset
  • MultiAssets
    A Vec of MultiAssets. There may be no duplicate fungible items in here and when decoding, they must be sorted.
  • MultiLocation
    A relative path between state-bearing consensus systems.
  • Parent
    A unit struct which can be converted into a MultiLocation of parents value 1.
  • ParentThen
    A tuple struct which can be converted into a MultiLocation of parents value 1 with the inner interior.
  • Xcm

Enums

  • AssetId
    Classification of an asset being concrete or abstract.
  • AssetInstance
    A general identifier for an instance of a non-fungible asset class.
  • BodyId
    An identifier of a pluralistic body.
  • BodyPart
    A part of a pluralistic body.
  • Error
  • Fungibility
    Classification of whether an asset is fungible or not, along with a mandatory amount or instance.
  • Instruction
    Cross-Consensus Message: A message from one consensus system to another.
  • Junction
    A single item in a path to describe the relative location of a consensus system.
  • Junctions
    Non-parent junctions that can be constructed, up to the length of 8. This specific Junctions implementation uses a Rust enum in order to make pattern matching easier.
  • MultiAssetFilter
    MultiAsset collection, either MultiAssets or a single wildcard.
  • NetworkId
    A global identifier of an account-bearing consensus system.
  • OriginKind
    Basically just the XCM (more general) version of ParachainDispatchOrigin.
  • Outcome
    Outcome of an XCM execution.
  • Response
    Response data to a query.
  • SendError
    Error result value when attempting to send an XCM message.
  • WeightLimit
    An optional weight limit.
  • WildFungibility
    Classification of whether an asset is fungible or not.
  • WildMultiAsset
    A wildcard representing a set of assets.

Constants

  • VERSION
    This module’s XCM version.

Traits

Type Definitions

  • InteriorMultiLocation
    A relative location which is constrained to be an interior location of the context.
  • QueryId
    An identifier for a query.
  • Result
  • SendResult
    Result value when attempting to send an XCM message.
  • Weight
    Local weight type; execution time in picoseconds.