message: Use mem::drop instead of assigning to _.
diff: @@ -408,6 +408,8 @@ fn round_participation<'a, C: Context>(
  #[allow(unused_qualifications)] // This is to suppress warnings originating in the test macros.
  #[cfg(test)]
  mod tests {
  + use std::mem;
  +
  use super::{
  super::state::{tests::*, State, BLOCK_REWARD, REWARD_DELAY},
  *,
  @@ -548,7 +550,7 @@ mod tests {
  add_vote(48, 3u8, Some(2))?; // Proposal
  let w48 = add_vote(53, 3u8, None)?; // Witness
  - let _ = add_vote; // Drop add_vote, so state is not borrowed anymore.
  + mem::drop(add_vote); // Drop add_vote, so state is not borrowed anymore.
  let rp = |time: u64| round_participation(&state, &obs, Timestamp::from(time));
  assert_eq!(RoundParticipation::Yes(&w0), rp(0));
  @@ -653,7 +655,7 @@ mod tests {
  pan[CAROL] = Observation::Faulty;
  let pay16f = add_vote(payday16_lead, pan, payday16, 3u8, Some(0x16))?;
  - let _ = add_vote; // Drop add_vote, so state is not borrowed anymore.
  + mem::drop(add_vote); // Drop add_vote, so state is not borrowed anymore.
  // Round 0: Alice and Bob have quorum 9, Carol 6.
  let expected0 = ValidatorMap::from(vec![
  