collection_is_never_read misfires on #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]

[RobertGauld]

Summary

The following line causes the collection_is_never_read lint to highlight serde::Deserialize

#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]

Lint Name

collection_is_never_read

Reproducer

I tried this code:

pub enum Payload {
    /// An initialization packet should be the first one sent to a node.
    /// It is used to configure the node's parameters.
    Initialization {
        /// The type of the node being initialized.
        #[cfg_attr(feature = "serde", serde(flatten))]
        node_sort: NodeSort
    },

    /// The poll request packet is sent to a node to cause a receive data packet to be sent.
    PollRequest,

    /// A receive data packet is sent by a node (in response to a poll request packet)
    /// and is used to send the node's input states to the controller.
    ReceiveData {
        /// The data which was read from the inputs.
        data: Data
    },

    /// A transmit data packet is sent to a node to cause it's output states to be changed.
    TransmitData {
        /// The data to be written to the outputs.
        data: Data
    },

    #[cfg(feature = "experimenter")]
    #[cfg_attr(any(docrs, toolchain = "nightly"), doc(cfg(feature = "experimenter")))]
    #[cfg_attr(not(toolchain = "nightly"), doc = "**Available on crate feature experimenter only.**\n\n")]
    /// An unknown message type.
    Unknown {
        /// The packet's message type.
        message_type: u8,
        /// The packet's body.
        body: Data
    }
}

I saw this happen:

warning: collection is never read
 --> cmri/src/packet/payload.rs:7:56
  |
7 | #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
  |                                                        ^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#collection_is_never_read
  = note: this warning originates in the derive macro `serde::Deserialize` (in Nightly builds, run with -Z macro-backtrace for more info)

I expected to see this happen:
No output since removing serde::Deserialize causes tests to start failing since it is needed.

Version

rustc 1.78.0-nightly (98aa3624b 2024-02-08)
binary: rustc
commit-hash: 98aa3624be70462d6a25ed5544333e3df62f4c66
commit-date: 2024-02-08
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 17.0.6

Additional Labels

No response