Add the XCM primitives crate. (#1760)

Co-authored-by: Gavin Wood <gavin@parity.io>

Co-authored-by: Gavin Wood <gavin@parity.io>

polkadot/xcm/src/v0/traits.rs

@@ -0,0 +1,67 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Cumulus.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Cumulus.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Cross-Consensus Message format data structures.
+
+use core::result;
+use codec::{Encode, Decode};
+
+use super::{MultiLocation, Xcm};
+
+#[derive(Copy, Clone, Encode, Decode, Eq, PartialEq, Ord, PartialOrd, Debug)]
+pub enum Error {
+	Undefined,
+	Unimplemented,
+	UnhandledXcmVersion,
+	UnhandledXcmMessage,
+	UnhandledEffect,
+	EscalationOfPrivilege,
+	UntrustedReserveLocation,
+	UntrustedTeleportLocation,
+	DestinationBufferOverflow,
+	CannotReachDestination,
+	MultiLocationFull,
+	FailedToDecode,
+	BadOrigin,
+}
+
+impl From<()> for Error {
+	fn from(_: ()) -> Self {
+		Self::Undefined
+	}
+}
+
+pub type Result = result::Result<(), Error>;
+
+pub trait ExecuteXcm {
+	fn execute_xcm(origin: MultiLocation, msg: Xcm) -> Result;
+}
+
+impl ExecuteXcm for () {
+	fn execute_xcm(_origin: MultiLocation, _msg: Xcm) -> Result {
+		Err(Error::Unimplemented)
+	}
+}
+
+pub trait SendXcm {
+	fn send_xcm(dest: MultiLocation, msg: Xcm) -> Result;
+}
+
+impl SendXcm for () {
+	fn send_xcm(_dest: MultiLocation, _msg: Xcm) -> Result {
+		Err(Error::Unimplemented)
+	}
+}