Replace wire::Message's Writeable implementation with unreachable!

Previously, we seemingly implemented `Writeable` for `Message<T>` which
however wasn't ever used. It seems this might have only been addded to
satisfy the `Type: Writeable` trait bound (?). In any case, having this
legit looking implementation that doesn't actually do anything is very confusing.

Here, as a quick fix, we hence simply replace it with an `unreachable!` statement.

Author: tnull

lightning/src/ln/wire.rs

@@ -109,63 +109,8 @@ pub(crate) enum Message<T: core::fmt::Debug + Type + TestEq> {
 }
 
 impl<T: core::fmt::Debug + Type + TestEq> Writeable for Message<T> {
-	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
-		match self {
-			&Message::Init(ref msg) => msg.write(writer),
-			&Message::Error(ref msg) => msg.write(writer),
-			&Message::Warning(ref msg) => msg.write(writer),
-			&Message::Ping(ref msg) => msg.write(writer),
-			&Message::Pong(ref msg) => msg.write(writer),
-			&Message::PeerStorage(ref msg) => msg.write(writer),
-			&Message::PeerStorageRetrieval(ref msg) => msg.write(writer),
-			&Message::OpenChannel(ref msg) => msg.write(writer),
-			&Message::OpenChannelV2(ref msg) => msg.write(writer),
-			&Message::AcceptChannel(ref msg) => msg.write(writer),
-			&Message::AcceptChannelV2(ref msg) => msg.write(writer),
-			&Message::FundingCreated(ref msg) => msg.write(writer),
-			&Message::FundingSigned(ref msg) => msg.write(writer),
-			&Message::Stfu(ref msg) => msg.write(writer),
-			&Message::SpliceInit(ref msg) => msg.write(writer),
-			&Message::SpliceAck(ref msg) => msg.write(writer),
-			&Message::SpliceLocked(ref msg) => msg.write(writer),
-			&Message::TxAddInput(ref msg) => msg.write(writer),
-			&Message::TxAddOutput(ref msg) => msg.write(writer),
-			&Message::TxRemoveInput(ref msg) => msg.write(writer),
-			&Message::TxRemoveOutput(ref msg) => msg.write(writer),
-			&Message::TxComplete(ref msg) => msg.write(writer),
-			&Message::TxSignatures(ref msg) => msg.write(writer),
-			&Message::TxInitRbf(ref msg) => msg.write(writer),
-			&Message::TxAckRbf(ref msg) => msg.write(writer),
-			&Message::TxAbort(ref msg) => msg.write(writer),
-			&Message::ChannelReady(ref msg) => msg.write(writer),
-			&Message::Shutdown(ref msg) => msg.write(writer),
-			&Message::ClosingSigned(ref msg) => msg.write(writer),
-			#[cfg(simple_close)]
-			&Message::ClosingComplete(ref msg) => msg.write(writer),
-			#[cfg(simple_close)]
-			&Message::ClosingSig(ref msg) => msg.write(writer),
-			&Message::OnionMessage(ref msg) => msg.write(writer),
-			&Message::StartBatch(ref msg) => msg.write(writer),
-			&Message::UpdateAddHTLC(ref msg) => msg.write(writer),
-			&Message::UpdateFulfillHTLC(ref msg) => msg.write(writer),
-			&Message::UpdateFailHTLC(ref msg) => msg.write(writer),
-			&Message::UpdateFailMalformedHTLC(ref msg) => msg.write(writer),
-			&Message::CommitmentSigned(ref msg) => msg.write(writer),
-			&Message::RevokeAndACK(ref msg) => msg.write(writer),
-			&Message::UpdateFee(ref msg) => msg.write(writer),
-			&Message::ChannelReestablish(ref msg) => msg.write(writer),
-			&Message::AnnouncementSignatures(ref msg) => msg.write(writer),
-			&Message::ChannelAnnouncement(ref msg) => msg.write(writer),
-			&Message::NodeAnnouncement(ref msg) => msg.write(writer),
-			&Message::ChannelUpdate(ref msg) => msg.write(writer),
-			&Message::QueryShortChannelIds(ref msg) => msg.write(writer),
-			&Message::ReplyShortChannelIdsEnd(ref msg) => msg.write(writer),
-			&Message::QueryChannelRange(ref msg) => msg.write(writer),
-			&Message::ReplyChannelRange(ref msg) => msg.write(writer),
-			&Message::GossipTimestampFilter(ref msg) => msg.write(writer),
-			&Message::Unknown(_) => Ok(()),
-			&Message::Custom(ref msg) => msg.write(writer),
-		}
+	fn write<W: Writer>(&self, _: &mut W) -> Result<(), io::Error> {
+		unreachable!("This is never used");
 	}
 }