`HashMap` and `HashSet` should provide a getter for their hashers

[apasel422]

impl<K: Eq + Hash, V, S: BuildHasher> HashMap<K, V, S> {
    pub fn hasher(&self) -> &S { &self.hash_builder }
}

impl<T: Eq + Hash, S: BuildHasher> HashSet<T, S> {
    pub fn hasher(&self) -> &S { self.map.hasher() }
}

This would let us close contain-rs/linked-hash-map#3, and likely has other (niche) uses for code that needs to reproduce hashes.

[rthomas]

I'd be interested in taking this one on.

[rthomas]

As per @gankro s suggestion I've put this behind an unstable feature flag hashmap_public_hasher.

[rthomas]

This has been merged, this issue can now be closed.

[apasel422]

@rthomas This actually needs to stay open to track the stability of the newly added methods.

[alexcrichton]

🔔 This issue is now entering its cycle-long final comment period for stabilization in 1.9 🔔