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/traits.rs

@@ -209,6 +209,44 @@ impl<T> Lookup for IdentityLookup<T> {
 	fn lookup(&self, x: T) -> Result<T, LookupError> { Ok(x) }
 }
 
+/// A lookup implementation returning the `AccountId` from a `MultiAddress`.
+pub struct AccountIdLookup<AccountId, AccountIndex>(PhantomData<(AccountId, AccountIndex)>);
+impl<AccountId, AccountIndex> StaticLookup for AccountIdLookup<AccountId, AccountIndex>
+where
+	AccountId: Codec + Clone + PartialEq + Debug,
+	AccountIndex: Codec + Clone + PartialEq + Debug,
+	crate::MultiAddress<AccountId, AccountIndex>: Codec,
+{
+	type Source = crate::MultiAddress<AccountId, AccountIndex>;
+	type Target = AccountId;
+	fn lookup(x: Self::Source) -> Result<Self::Target, LookupError> {
+		match x {
+			crate::MultiAddress::Id(i) => Ok(i),
+			_ => Err(LookupError),
+		}
+	}
+	fn unlookup(x: Self::Target) -> Self::Source {
+		crate::MultiAddress::Id(x)
+	}
+}
+
+/// Perform a StaticLookup where there are multiple lookup sources of the same type.
+impl<A, B> StaticLookup for (A, B)
+where
+	A: StaticLookup,
+	B: StaticLookup<Source = A::Source, Target = A::Target>,
+{
+	type Source = A::Source;
+	type Target = A::Target;
+
+	fn lookup(x: Self::Source) -> Result<Self::Target, LookupError> {
+		A::lookup(x.clone()).or_else(|_| B::lookup(x))
+	}
+	fn unlookup(x: Self::Target) -> Self::Source {
+		A::unlookup(x)
+	}
+}
+
 /// Extensible conversion trait. Generic over both source and destination types.
 pub trait Convert<A, B> {
 	/// Make conversion.