Cargo features are required to be additive, so enabling a feature cannot result in an impl being removed.

Thanks!

For the cfg(feature = "preserve_order") case, maybe a better performing implementation would be to hash each entry individually and xor them together. This would make the hash insensitive to order.

use std::hash::{BuildHasher, RandomState};
use std::sync::OnceLock;

static RANDOM_STATE: OnceLock<RandomState> = OnceLock::new();
let random_state = RANDOM_STATE.get_or_init(RandomState::new);
self.map
    .iter()
    .map(|entry| random_state.hash_one(entry))
    .fold(0, |xor, next| xor ^ next)
    .hash(state);

I would be interested to see a benchmark comparing this approach.