More Extensible Multiaddress Format (#7380)

* More extensible multiaddress format

* update name

* Don't depend on indices to define multiaddress type

* Use MultiAddress in Node Template too!

* reduce traits, fix build

* support multiple `StaticLookup`

* bump tx version

* feedback

substrate/primitives/runtime/src/multiaddress.rs

@@ -0,0 +1,66 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! MultiAddress type is a wrapper for multiple downstream account formats.
+
+use codec::{Encode, Decode};
+use sp_std::vec::Vec;
+
+/// A multi-format address wrapper for on-chain accounts.
+#[derive(Encode, Decode, PartialEq, Eq, Clone, crate::RuntimeDebug)]
+#[cfg_attr(feature = "std", derive(Hash))]
+pub enum MultiAddress<AccountId, AccountIndex> {
+	/// It's an account ID (pubkey).
+	Id(AccountId),
+	/// It's an account index.
+	Index(#[codec(compact)] AccountIndex),
+	/// It's some arbitrary raw bytes.
+	Raw(Vec<u8>),
+	/// It's a 32 byte representation.
+	Address32([u8; 32]),
+	/// Its a 20 byte representation.
+	Address20([u8; 20]),
+}
+
+#[cfg(feature = "std")]
+impl<AccountId, AccountIndex> std::fmt::Display for MultiAddress<AccountId, AccountIndex>
+where
+	AccountId: std::fmt::Debug,
+	AccountIndex: std::fmt::Debug,
+{
+	fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+		use sp_core::hexdisplay::HexDisplay;
+		match self {
+			MultiAddress::Raw(inner) => write!(f, "MultiAddress::Raw({})", HexDisplay::from(inner)),
+			MultiAddress::Address32(inner) => write!(f, "MultiAddress::Address32({})", HexDisplay::from(inner)),
+			MultiAddress::Address20(inner) => write!(f, "MultiAddress::Address20({})", HexDisplay::from(inner)),
+			_ => write!(f, "{:?}", self),
+		}
+	}
+}
+
+impl<AccountId, AccountIndex> From<AccountId> for MultiAddress<AccountId, AccountIndex> {
+	fn from(a: AccountId) -> Self {
+		MultiAddress::Id(a)
+	}
+}
+
+impl<AccountId: Default, AccountIndex> Default for MultiAddress<AccountId, AccountIndex> {
+	fn default() -> Self {
+		MultiAddress::Id(Default::default())
+	}
+}