Duplicate codec index in Message

[serban300]

This is related to the Message struct in polkadot-sdk/substrate/client/network/src/protocol/message.rs:

	/// A network message.
	#[derive(Debug, PartialEq, Eq, Clone, Encode, Decode)]
	pub enum Message<Header, Hash, Number, Extrinsic> {
		/// Status packet.
		Status(Status<Hash, Number>),
		/// Block request.
		BlockRequest(BlockRequest<Hash, Number>),
		/// Block response.
		BlockResponse(BlockResponse<Header, Hash, Extrinsic>),
		/// Block announce.
		BlockAnnounce(BlockAnnounce<Header>),
		/// Consensus protocol message.
		// NOTE: index is incremented by 1 due to transaction-related
		// message that was removed
		#[codec(index = 6)]
		Consensus(ConsensusMessage),
		/// Remote method call request.
		RemoteCallRequest(RemoteCallRequest<Hash>),
		/// Remote method call response.
		RemoteCallResponse(RemoteCallResponse),
		/// Remote storage read request.
		RemoteReadRequest(RemoteReadRequest<Hash>),
		/// Remote storage read response.
		RemoteReadResponse(RemoteReadResponse),
		/// Remote header request.
		RemoteHeaderRequest(RemoteHeaderRequest<Number>),
		/// Remote header response.
		RemoteHeaderResponse(RemoteHeaderResponse<Header>),
		/// Remote changes request.
		RemoteChangesRequest(RemoteChangesRequest<Hash>),
		/// Remote changes response.
		RemoteChangesResponse(RemoteChangesResponse<Number, Hash>),
		/// Remote child storage read request.
		RemoteReadChildRequest(RemoteReadChildRequest<Hash>),
		/// Batch of consensus protocol messages.
		// NOTE: index is incremented by 2 due to finality proof related
		// messages that were removed.
		#[codec(index = 17)]
		ConsensusBatch(Vec<ConsensusMessage>),
	}

This encodes to:

                    fn encode_to<__CodecOutputEdqy: ::codec::Output + ?::core::marker::Sized>(
                        &self,
                        __codec_dest_edqy: &mut __CodecOutputEdqy,
                    ) {
                        match *self {
                            Message::Status(ref aa) => {
                                __codec_dest_edqy.push_byte(0usize as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            Message::BlockRequest(ref aa) => {
                                __codec_dest_edqy.push_byte(1usize as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            Message::BlockResponse(ref aa) => {
                                __codec_dest_edqy.push_byte(2usize as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            Message::BlockAnnounce(ref aa) => {
                                __codec_dest_edqy.push_byte(3usize as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            Message::Consensus(ref aa) => {
                                __codec_dest_edqy.push_byte(6u8 as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            Message::RemoteCallRequest(ref aa) => {
                                __codec_dest_edqy.push_byte(5usize as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            Message::RemoteCallResponse(ref aa) => {
                                __codec_dest_edqy.push_byte(6usize as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            Message::RemoteReadRequest(ref aa) => {
                                __codec_dest_edqy.push_byte(7usize as ::core::primitive::u8);
                                ::codec::Encode::encode_to(aa, __codec_dest_edqy);
                            }
                            ...
                        }
                    }
                }

Index 6 is used both for Consensus and for RemoteCallResponse

[serban300]

Uncovered by paritytech/parity-scale-codec#653

We either need to fix this struct or change the parity-scale-codec logic

Related to paritytech/parity-scale-codec#691 as well