Merging upstream version 127.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

23 files changed, 7119 insertions, 1260 deletions

diff --git a/third_party/rust/hashbrown/src/external_trait_impls/mod.rs b/third_party/rust/hashbrown/src/external_trait_impls/mod.rs
index ef497836cb..01d386b046 100644
--- a/third_party/rust/hashbrown/src/external_trait_impls/mod.rs
+++ b/third_party/rust/hashbrown/src/external_trait_impls/mod.rs
@@ -1,4 +1,6 @@
 #[cfg(feature = "rayon")]
 pub(crate) mod rayon;
+#[cfg(feature = "rkyv")]
+mod rkyv;
 #[cfg(feature = "serde")]
 mod serde;
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rayon/map.rs b/third_party/rust/hashbrown/src/external_trait_impls/rayon/map.rs
index 14d91c220c..2534dc9b2b 100644
--- a/third_party/rust/hashbrown/src/external_trait_impls/rayon/map.rs
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rayon/map.rs
@@ -232,11 +232,11 @@ impl<K: Eq + Hash, V: fmt::Debug> fmt::Debug for ParValuesMut<'_, K, V> {
 /// [`into_par_iter`]: /hashbrown/struct.HashMap.html#method.into_par_iter
 /// [`HashMap`]: /hashbrown/struct.HashMap.html
 /// [`IntoParallelIterator`]: https://docs.rs/rayon/1.0/rayon/iter/trait.IntoParallelIterator.html
-pub struct IntoParIter<K, V, A: Allocator + Clone = Global> {
+pub struct IntoParIter<K, V, A: Allocator = Global> {
     inner: RawIntoParIter<(K, V), A>,
 }
 
-impl<K: Send, V: Send, A: Allocator + Clone + Send> ParallelIterator for IntoParIter<K, V, A> {
+impl<K: Send, V: Send, A: Allocator + Send> ParallelIterator for IntoParIter<K, V, A> {
     type Item = (K, V);
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -248,9 +248,7 @@ impl<K: Send, V: Send, A: Allocator + Clone + Send> ParallelIterator for IntoPar
     }
 }
 
-impl<K: fmt::Debug + Eq + Hash, V: fmt::Debug, A: Allocator + Clone> fmt::Debug
-    for IntoParIter<K, V, A>
-{
+impl<K: fmt::Debug + Eq + Hash, V: fmt::Debug, A: Allocator> fmt::Debug for IntoParIter<K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         ParIter {
             inner: unsafe { self.inner.par_iter() },
@@ -267,11 +265,11 @@ impl<K: fmt::Debug + Eq + Hash, V: fmt::Debug, A: Allocator + Clone> fmt::Debug
 ///
 /// [`par_drain`]: /hashbrown/struct.HashMap.html#method.par_drain
 /// [`HashMap`]: /hashbrown/struct.HashMap.html
-pub struct ParDrain<'a, K, V, A: Allocator + Clone = Global> {
+pub struct ParDrain<'a, K, V, A: Allocator = Global> {
     inner: RawParDrain<'a, (K, V), A>,
 }
 
-impl<K: Send, V: Send, A: Allocator + Clone + Sync> ParallelIterator for ParDrain<'_, K, V, A> {
+impl<K: Send, V: Send, A: Allocator + Sync> ParallelIterator for ParDrain<'_, K, V, A> {
     type Item = (K, V);
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -283,9 +281,7 @@ impl<K: Send, V: Send, A: Allocator + Clone + Sync> ParallelIterator for ParDrai
     }
 }
 
-impl<K: fmt::Debug + Eq + Hash, V: fmt::Debug, A: Allocator + Clone> fmt::Debug
-    for ParDrain<'_, K, V, A>
-{
+impl<K: fmt::Debug + Eq + Hash, V: fmt::Debug, A: Allocator> fmt::Debug for ParDrain<'_, K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         ParIter {
             inner: unsafe { self.inner.par_iter() },
@@ -295,7 +291,7 @@ impl<K: fmt::Debug + Eq + Hash, V: fmt::Debug, A: Allocator + Clone> fmt::Debug
     }
 }
 
-impl<K: Sync, V: Sync, S, A: Allocator + Clone> HashMap<K, V, S, A> {
+impl<K: Sync, V: Sync, S, A: Allocator> HashMap<K, V, S, A> {
     /// Visits (potentially in parallel) immutably borrowed keys in an arbitrary order.
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn par_keys(&self) -> ParKeys<'_, K, V> {
@@ -315,7 +311,7 @@ impl<K: Sync, V: Sync, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     }
 }
 
-impl<K: Send, V: Send, S, A: Allocator + Clone> HashMap<K, V, S, A> {
+impl<K: Send, V: Send, S, A: Allocator> HashMap<K, V, S, A> {
     /// Visits (potentially in parallel) mutably borrowed values in an arbitrary order.
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn par_values_mut(&mut self) -> ParValuesMut<'_, K, V> {
@@ -340,7 +336,7 @@ where
     K: Eq + Hash + Sync,
     V: PartialEq + Sync,
     S: BuildHasher + Sync,
-    A: Allocator + Clone + Sync,
+    A: Allocator + Sync,
 {
     /// Returns `true` if the map is equal to another,
     /// i.e. both maps contain the same keys mapped to the same values.
@@ -354,9 +350,7 @@ where
     }
 }
 
-impl<K: Send, V: Send, S, A: Allocator + Clone + Send> IntoParallelIterator
-    for HashMap<K, V, S, A>
-{
+impl<K: Send, V: Send, S, A: Allocator + Send> IntoParallelIterator for HashMap<K, V, S, A> {
     type Item = (K, V);
     type Iter = IntoParIter<K, V, A>;
 
@@ -368,9 +362,7 @@ impl<K: Send, V: Send, S, A: Allocator + Clone + Send> IntoParallelIterator
     }
 }
 
-impl<'a, K: Sync, V: Sync, S, A: Allocator + Clone> IntoParallelIterator
-    for &'a HashMap<K, V, S, A>
-{
+impl<'a, K: Sync, V: Sync, S, A: Allocator> IntoParallelIterator for &'a HashMap<K, V, S, A> {
     type Item = (&'a K, &'a V);
     type Iter = ParIter<'a, K, V>;
 
@@ -383,9 +375,7 @@ impl<'a, K: Sync, V: Sync, S, A: Allocator + Clone> IntoParallelIterator
     }
 }
 
-impl<'a, K: Sync, V: Send, S, A: Allocator + Clone> IntoParallelIterator
-    for &'a mut HashMap<K, V, S, A>
-{
+impl<'a, K: Sync, V: Send, S, A: Allocator> IntoParallelIterator for &'a mut HashMap<K, V, S, A> {
     type Item = (&'a K, &'a mut V);
     type Iter = ParIterMut<'a, K, V>;
 
@@ -424,7 +414,7 @@ where
     K: Eq + Hash + Send,
     V: Send,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn par_extend<I>(&mut self, par_iter: I)
     where
@@ -440,7 +430,7 @@ where
     K: Copy + Eq + Hash + Sync,
     V: Copy + Sync,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn par_extend<I>(&mut self, par_iter: I)
     where
@@ -456,7 +446,7 @@ where
     K: Eq + Hash,
     S: BuildHasher,
     I: IntoParallelIterator,
-    A: Allocator + Clone,
+    A: Allocator,
     HashMap<K, V, S, A>: Extend<I::Item>,
 {
     let (list, len) = super::helpers::collect(par_iter);
@@ -561,10 +551,7 @@ mod test_par_map {
             assert_eq!(value.load(Ordering::Relaxed), 100);
 
             // retain only half
-            let _v: Vec<_> = hm
-                .into_par_iter()
-                .filter(|&(ref key, _)| key.k < 50)
-                .collect();
+            let _v: Vec<_> = hm.into_par_iter().filter(|(key, _)| key.k < 50).collect();
 
             assert_eq!(key.load(Ordering::Relaxed), 50);
             assert_eq!(value.load(Ordering::Relaxed), 50);
@@ -611,7 +598,7 @@ mod test_par_map {
             assert_eq!(value.load(Ordering::Relaxed), 100);
 
             // retain only half
-            let _v: Vec<_> = hm.drain().filter(|&(ref key, _)| key.k < 50).collect();
+            let _v: Vec<_> = hm.drain().filter(|(key, _)| key.k < 50).collect();
             assert!(hm.is_empty());
 
             assert_eq!(key.load(Ordering::Relaxed), 50);
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rayon/mod.rs b/third_party/rust/hashbrown/src/external_trait_impls/rayon/mod.rs
index 99337a1ce3..61ca69b61d 100644
--- a/third_party/rust/hashbrown/src/external_trait_impls/rayon/mod.rs
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rayon/mod.rs
@@ -2,3 +2,4 @@ mod helpers;
 pub(crate) mod map;
 pub(crate) mod raw;
 pub(crate) mod set;
+pub(crate) mod table;
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rayon/raw.rs b/third_party/rust/hashbrown/src/external_trait_impls/rayon/raw.rs
index 883303e278..612be47a55 100644
--- a/third_party/rust/hashbrown/src/external_trait_impls/rayon/raw.rs
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rayon/raw.rs
@@ -1,7 +1,6 @@
 use crate::raw::Bucket;
 use crate::raw::{Allocator, Global, RawIter, RawIterRange, RawTable};
 use crate::scopeguard::guard;
-use alloc::alloc::dealloc;
 use core::marker::PhantomData;
 use core::mem;
 use core::ptr::NonNull;
@@ -76,18 +75,18 @@ impl<T> UnindexedProducer for ParIterProducer<T> {
 }
 
 /// Parallel iterator which consumes a table and returns elements.
-pub struct RawIntoParIter<T, A: Allocator + Clone = Global> {
+pub struct RawIntoParIter<T, A: Allocator = Global> {
     table: RawTable<T, A>,
 }
 
-impl<T, A: Allocator + Clone> RawIntoParIter<T, A> {
+impl<T, A: Allocator> RawIntoParIter<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     pub(super) unsafe fn par_iter(&self) -> RawParIter<T> {
         self.table.par_iter()
     }
 }
 
-impl<T: Send, A: Allocator + Clone + Send> ParallelIterator for RawIntoParIter<T, A> {
+impl<T: Send, A: Allocator + Send> ParallelIterator for RawIntoParIter<T, A> {
     type Item = T;
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -97,9 +96,9 @@ impl<T: Send, A: Allocator + Clone + Send> ParallelIterator for RawIntoParIter<T
     {
         let iter = unsafe { self.table.iter().iter };
         let _guard = guard(self.table.into_allocation(), |alloc| {
-            if let Some((ptr, layout)) = *alloc {
+            if let Some((ptr, layout, ref alloc)) = *alloc {
                 unsafe {
-                    dealloc(ptr.as_ptr(), layout);
+                    alloc.deallocate(ptr, layout);
                 }
             }
         });
@@ -109,23 +108,23 @@ impl<T: Send, A: Allocator + Clone + Send> ParallelIterator for RawIntoParIter<T
 }
 
 /// Parallel iterator which consumes elements without freeing the table storage.
-pub struct RawParDrain<'a, T, A: Allocator + Clone = Global> {
+pub struct RawParDrain<'a, T, A: Allocator = Global> {
     // We don't use a &'a mut RawTable<T> because we want RawParDrain to be
     // covariant over T.
     table: NonNull<RawTable<T, A>>,
     marker: PhantomData<&'a RawTable<T, A>>,
 }
 
-unsafe impl<T: Send, A: Allocator + Clone> Send for RawParDrain<'_, T, A> {}
+unsafe impl<T: Send, A: Allocator> Send for RawParDrain<'_, T, A> {}
 
-impl<T, A: Allocator + Clone> RawParDrain<'_, T, A> {
+impl<T, A: Allocator> RawParDrain<'_, T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     pub(super) unsafe fn par_iter(&self) -> RawParIter<T> {
         self.table.as_ref().par_iter()
     }
 }
 
-impl<T: Send, A: Allocator + Clone> ParallelIterator for RawParDrain<'_, T, A> {
+impl<T: Send, A: Allocator> ParallelIterator for RawParDrain<'_, T, A> {
     type Item = T;
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -143,7 +142,7 @@ impl<T: Send, A: Allocator + Clone> ParallelIterator for RawParDrain<'_, T, A> {
     }
 }
 
-impl<T, A: Allocator + Clone> Drop for RawParDrain<'_, T, A> {
+impl<T, A: Allocator> Drop for RawParDrain<'_, T, A> {
     fn drop(&mut self) {
         // If drive_unindexed is not called then simply clear the table.
         unsafe {
@@ -204,7 +203,7 @@ impl<T> Drop for ParDrainProducer<T> {
     }
 }
 
-impl<T, A: Allocator + Clone> RawTable<T, A> {
+impl<T, A: Allocator> RawTable<T, A> {
     /// Returns a parallel iterator over the elements in a `RawTable`.
     #[cfg_attr(feature = "inline-more", inline)]
     pub unsafe fn par_iter(&self) -> RawParIter<T> {
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rayon/set.rs b/third_party/rust/hashbrown/src/external_trait_impls/rayon/set.rs
index ee4f6e6693..3de98fccb8 100644
--- a/third_party/rust/hashbrown/src/external_trait_impls/rayon/set.rs
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rayon/set.rs
@@ -16,11 +16,11 @@ use rayon::iter::{FromParallelIterator, IntoParallelIterator, ParallelExtend, Pa
 /// [`into_par_iter`]: /hashbrown/struct.HashSet.html#method.into_par_iter
 /// [`HashSet`]: /hashbrown/struct.HashSet.html
 /// [`IntoParallelIterator`]: https://docs.rs/rayon/1.0/rayon/iter/trait.IntoParallelIterator.html
-pub struct IntoParIter<T, A: Allocator + Clone = Global> {
+pub struct IntoParIter<T, A: Allocator = Global> {
     inner: map::IntoParIter<T, (), A>,
 }
 
-impl<T: Send, A: Allocator + Clone + Send> ParallelIterator for IntoParIter<T, A> {
+impl<T: Send, A: Allocator + Send> ParallelIterator for IntoParIter<T, A> {
     type Item = T;
 
     fn drive_unindexed<C>(self, consumer: C) -> C::Result
@@ -38,11 +38,11 @@ impl<T: Send, A: Allocator + Clone + Send> ParallelIterator for IntoParIter<T, A
 ///
 /// [`par_drain`]: /hashbrown/struct.HashSet.html#method.par_drain
 /// [`HashSet`]: /hashbrown/struct.HashSet.html
-pub struct ParDrain<'a, T, A: Allocator + Clone = Global> {
+pub struct ParDrain<'a, T, A: Allocator = Global> {
     inner: map::ParDrain<'a, T, (), A>,
 }
 
-impl<T: Send, A: Allocator + Clone + Send + Sync> ParallelIterator for ParDrain<'_, T, A> {
+impl<T: Send, A: Allocator + Send + Sync> ParallelIterator for ParDrain<'_, T, A> {
     type Item = T;
 
     fn drive_unindexed<C>(self, consumer: C) -> C::Result
@@ -85,7 +85,7 @@ impl<'a, T: Sync> ParallelIterator for ParIter<'a, T> {
 ///
 /// [`par_difference`]: /hashbrown/struct.HashSet.html#method.par_difference
 /// [`HashSet`]: /hashbrown/struct.HashSet.html
-pub struct ParDifference<'a, T, S, A: Allocator + Clone = Global> {
+pub struct ParDifference<'a, T, S, A: Allocator = Global> {
     a: &'a HashSet<T, S, A>,
     b: &'a HashSet<T, S, A>,
 }
@@ -94,7 +94,7 @@ impl<'a, T, S, A> ParallelIterator for ParDifference<'a, T, S, A>
 where
     T: Eq + Hash + Sync,
     S: BuildHasher + Sync,
-    A: Allocator + Clone + Sync,
+    A: Allocator + Sync,
 {
     type Item = &'a T;
 
@@ -118,7 +118,7 @@ where
 ///
 /// [`par_symmetric_difference`]: /hashbrown/struct.HashSet.html#method.par_symmetric_difference
 /// [`HashSet`]: /hashbrown/struct.HashSet.html
-pub struct ParSymmetricDifference<'a, T, S, A: Allocator + Clone = Global> {
+pub struct ParSymmetricDifference<'a, T, S, A: Allocator = Global> {
     a: &'a HashSet<T, S, A>,
     b: &'a HashSet<T, S, A>,
 }
@@ -127,7 +127,7 @@ impl<'a, T, S, A> ParallelIterator for ParSymmetricDifference<'a, T, S, A>
 where
     T: Eq + Hash + Sync,
     S: BuildHasher + Sync,
-    A: Allocator + Clone + Sync,
+    A: Allocator + Sync,
 {
     type Item = &'a T;
 
@@ -150,7 +150,7 @@ where
 ///
 /// [`par_intersection`]: /hashbrown/struct.HashSet.html#method.par_intersection
 /// [`HashSet`]: /hashbrown/struct.HashSet.html
-pub struct ParIntersection<'a, T, S, A: Allocator + Clone = Global> {
+pub struct ParIntersection<'a, T, S, A: Allocator = Global> {
     a: &'a HashSet<T, S, A>,
     b: &'a HashSet<T, S, A>,
 }
@@ -159,7 +159,7 @@ impl<'a, T, S, A> ParallelIterator for ParIntersection<'a, T, S, A>
 where
     T: Eq + Hash + Sync,
     S: BuildHasher + Sync,
-    A: Allocator + Clone + Sync,
+    A: Allocator + Sync,
 {
     type Item = &'a T;
 
@@ -181,7 +181,7 @@ where
 ///
 /// [`par_union`]: /hashbrown/struct.HashSet.html#method.par_union
 /// [`HashSet`]: /hashbrown/struct.HashSet.html
-pub struct ParUnion<'a, T, S, A: Allocator + Clone = Global> {
+pub struct ParUnion<'a, T, S, A: Allocator = Global> {
     a: &'a HashSet<T, S, A>,
     b: &'a HashSet<T, S, A>,
 }
@@ -190,7 +190,7 @@ impl<'a, T, S, A> ParallelIterator for ParUnion<'a, T, S, A>
 where
     T: Eq + Hash + Sync,
     S: BuildHasher + Sync,
-    A: Allocator + Clone + Sync,
+    A: Allocator + Sync,
 {
     type Item = &'a T;
 
@@ -216,7 +216,7 @@ impl<T, S, A> HashSet<T, S, A>
 where
     T: Eq + Hash + Sync,
     S: BuildHasher + Sync,
-    A: Allocator + Clone + Sync,
+    A: Allocator + Sync,
 {
     /// Visits (potentially in parallel) the values representing the union,
     /// i.e. all the values in `self` or `other`, without duplicates.
@@ -289,7 +289,7 @@ where
 impl<T, S, A> HashSet<T, S, A>
 where
     T: Eq + Hash + Send,
-    A: Allocator + Clone + Send,
+    A: Allocator + Send,
 {
     /// Consumes (potentially in parallel) all values in an arbitrary order,
     /// while preserving the set's allocated memory for reuse.
@@ -301,7 +301,7 @@ where
     }
 }
 
-impl<T: Send, S, A: Allocator + Clone + Send> IntoParallelIterator for HashSet<T, S, A> {
+impl<T: Send, S, A: Allocator + Send> IntoParallelIterator for HashSet<T, S, A> {
     type Item = T;
     type Iter = IntoParIter<T, A>;
 
@@ -313,7 +313,7 @@ impl<T: Send, S, A: Allocator + Clone + Send> IntoParallelIterator for HashSet<T
     }
 }
 
-impl<'a, T: Sync, S, A: Allocator + Clone> IntoParallelIterator for &'a HashSet<T, S, A> {
+impl<'a, T: Sync, S, A: Allocator> IntoParallelIterator for &'a HashSet<T, S, A> {
     type Item = &'a T;
     type Iter = ParIter<'a, T>;
 
@@ -374,7 +374,7 @@ fn extend<T, S, I, A>(set: &mut HashSet<T, S, A>, par_iter: I)
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
     I: IntoParallelIterator,
     HashSet<T, S, A>: Extend<I::Item>,
 {
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rayon/table.rs b/third_party/rust/hashbrown/src/external_trait_impls/rayon/table.rs
new file mode 100644
index 0000000000..e8e50944ad
--- /dev/null
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rayon/table.rs
@@ -0,0 +1,252 @@
+//! Rayon extensions for `HashTable`.
+
+use super::raw::{RawIntoParIter, RawParDrain, RawParIter};
+use crate::hash_table::HashTable;
+use crate::raw::{Allocator, Global};
+use core::fmt;
+use core::marker::PhantomData;
+use rayon::iter::plumbing::UnindexedConsumer;
+use rayon::iter::{IntoParallelIterator, ParallelIterator};
+
+/// Parallel iterator over shared references to entries in a map.
+///
+/// This iterator is created by the [`par_iter`] method on [`HashTable`]
+/// (provided by the [`IntoParallelRefIterator`] trait).
+/// See its documentation for more.
+///
+/// [`par_iter`]: /hashbrown/struct.HashTable.html#method.par_iter
+/// [`HashTable`]: /hashbrown/struct.HashTable.html
+/// [`IntoParallelRefIterator`]: https://docs.rs/rayon/1.0/rayon/iter/trait.IntoParallelRefIterator.html
+pub struct ParIter<'a, T> {
+    inner: RawParIter<T>,
+    marker: PhantomData<&'a T>,
+}
+
+impl<'a, T: Sync> ParallelIterator for ParIter<'a, T> {
+    type Item = &'a T;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.inner
+            .map(|x| unsafe { x.as_ref() })
+            .drive_unindexed(consumer)
+    }
+}
+
+impl<T> Clone for ParIter<'_, T> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for ParIter<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let iter = unsafe { self.inner.iter() }.map(|x| unsafe { x.as_ref() });
+        f.debug_list().entries(iter).finish()
+    }
+}
+
+/// Parallel iterator over mutable references to entries in a map.
+///
+/// This iterator is created by the [`par_iter_mut`] method on [`HashTable`]
+/// (provided by the [`IntoParallelRefMutIterator`] trait).
+/// See its documentation for more.
+///
+/// [`par_iter_mut`]: /hashbrown/struct.HashTable.html#method.par_iter_mut
+/// [`HashTable`]: /hashbrown/struct.HashTable.html
+/// [`IntoParallelRefMutIterator`]: https://docs.rs/rayon/1.0/rayon/iter/trait.IntoParallelRefMutIterator.html
+pub struct ParIterMut<'a, T> {
+    inner: RawParIter<T>,
+    marker: PhantomData<&'a mut T>,
+}
+
+impl<'a, T: Send> ParallelIterator for ParIterMut<'a, T> {
+    type Item = &'a mut T;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.inner
+            .map(|x| unsafe { x.as_mut() })
+            .drive_unindexed(consumer)
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for ParIterMut<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        ParIter {
+            inner: self.inner.clone(),
+            marker: PhantomData,
+        }
+        .fmt(f)
+    }
+}
+
+/// Parallel iterator over entries of a consumed map.
+///
+/// This iterator is created by the [`into_par_iter`] method on [`HashTable`]
+/// (provided by the [`IntoParallelIterator`] trait).
+/// See its documentation for more.
+///
+/// [`into_par_iter`]: /hashbrown/struct.HashTable.html#method.into_par_iter
+/// [`HashTable`]: /hashbrown/struct.HashTable.html
+/// [`IntoParallelIterator`]: https://docs.rs/rayon/1.0/rayon/iter/trait.IntoParallelIterator.html
+pub struct IntoParIter<T, A: Allocator = Global> {
+    inner: RawIntoParIter<T, A>,
+}
+
+impl<T: Send, A: Allocator + Send> ParallelIterator for IntoParIter<T, A> {
+    type Item = T;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.inner.drive_unindexed(consumer)
+    }
+}
+
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoParIter<T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        ParIter {
+            inner: unsafe { self.inner.par_iter() },
+            marker: PhantomData,
+        }
+        .fmt(f)
+    }
+}
+
+/// Parallel draining iterator over entries of a map.
+///
+/// This iterator is created by the [`par_drain`] method on [`HashTable`].
+/// See its documentation for more.
+///
+/// [`par_drain`]: /hashbrown/struct.HashTable.html#method.par_drain
+/// [`HashTable`]: /hashbrown/struct.HashTable.html
+pub struct ParDrain<'a, T, A: Allocator = Global> {
+    inner: RawParDrain<'a, T, A>,
+}
+
+impl<T: Send, A: Allocator + Sync> ParallelIterator for ParDrain<'_, T, A> {
+    type Item = T;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.inner.drive_unindexed(consumer)
+    }
+}
+
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for ParDrain<'_, T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        ParIter {
+            inner: unsafe { self.inner.par_iter() },
+            marker: PhantomData,
+        }
+        .fmt(f)
+    }
+}
+
+impl<T: Send, A: Allocator> HashTable<T, A> {
+    /// Consumes (potentially in parallel) all values in an arbitrary order,
+    /// while preserving the map's allocated memory for reuse.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn par_drain(&mut self) -> ParDrain<'_, T, A> {
+        ParDrain {
+            inner: self.raw.par_drain(),
+        }
+    }
+}
+
+impl<T: Send, A: Allocator + Send> IntoParallelIterator for HashTable<T, A> {
+    type Item = T;
+    type Iter = IntoParIter<T, A>;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn into_par_iter(self) -> Self::Iter {
+        IntoParIter {
+            inner: self.raw.into_par_iter(),
+        }
+    }
+}
+
+impl<'a, T: Sync, A: Allocator> IntoParallelIterator for &'a HashTable<T, A> {
+    type Item = &'a T;
+    type Iter = ParIter<'a, T>;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn into_par_iter(self) -> Self::Iter {
+        ParIter {
+            inner: unsafe { self.raw.par_iter() },
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<'a, T: Send, A: Allocator> IntoParallelIterator for &'a mut HashTable<T, A> {
+    type Item = &'a mut T;
+    type Iter = ParIterMut<'a, T>;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn into_par_iter(self) -> Self::Iter {
+        ParIterMut {
+            inner: unsafe { self.raw.par_iter() },
+            marker: PhantomData,
+        }
+    }
+}
+
+#[cfg(test)]
+mod test_par_table {
+    use alloc::vec::Vec;
+    use core::sync::atomic::{AtomicUsize, Ordering};
+
+    use rayon::prelude::*;
+
+    use crate::{
+        hash_map::{make_hash, DefaultHashBuilder},
+        hash_table::HashTable,
+    };
+
+    #[test]
+    fn test_iterate() {
+        let hasher = DefaultHashBuilder::default();
+        let mut a = HashTable::new();
+        for i in 0..32 {
+            a.insert_unique(make_hash(&hasher, &i), i, |x| make_hash(&hasher, x));
+        }
+        let observed = AtomicUsize::new(0);
+        a.par_iter().for_each(|k| {
+            observed.fetch_or(1 << *k, Ordering::Relaxed);
+        });
+        assert_eq!(observed.into_inner(), 0xFFFF_FFFF);
+    }
+
+    #[test]
+    fn test_move_iter() {
+        let hasher = DefaultHashBuilder::default();
+        let hs = {
+            let mut hs = HashTable::new();
+
+            hs.insert_unique(make_hash(&hasher, &'a'), 'a', |x| make_hash(&hasher, x));
+            hs.insert_unique(make_hash(&hasher, &'b'), 'b', |x| make_hash(&hasher, x));
+
+            hs
+        };
+
+        let v = hs.into_par_iter().collect::<Vec<char>>();
+        assert!(v == ['a', 'b'] || v == ['b', 'a']);
+    }
+}
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rkyv/hash_map.rs b/third_party/rust/hashbrown/src/external_trait_impls/rkyv/hash_map.rs
new file mode 100644
index 0000000000..fae7f76763
--- /dev/null
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rkyv/hash_map.rs
@@ -0,0 +1,125 @@
+use crate::HashMap;
+use core::{
+    borrow::Borrow,
+    hash::{BuildHasher, Hash},
+};
+use rkyv::{
+    collections::hash_map::{ArchivedHashMap, HashMapResolver},
+    ser::{ScratchSpace, Serializer},
+    Archive, Deserialize, Fallible, Serialize,
+};
+
+impl<K: Archive + Hash + Eq, V: Archive, S> Archive for HashMap<K, V, S>
+where
+    K::Archived: Hash + Eq,
+{
+    type Archived = ArchivedHashMap<K::Archived, V::Archived>;
+    type Resolver = HashMapResolver;
+
+    #[inline]
+    unsafe fn resolve(&self, pos: usize, resolver: Self::Resolver, out: *mut Self::Archived) {
+        ArchivedHashMap::resolve_from_len(self.len(), pos, resolver, out);
+    }
+}
+
+impl<K, V, S, RandomState> Serialize<S> for HashMap<K, V, RandomState>
+where
+    K: Serialize<S> + Hash + Eq,
+    K::Archived: Hash + Eq,
+    V: Serialize<S>,
+    S: Serializer + ScratchSpace + ?Sized,
+{
+    #[inline]
+    fn serialize(&self, serializer: &mut S) -> Result<Self::Resolver, S::Error> {
+        unsafe { ArchivedHashMap::serialize_from_iter(self.iter(), serializer) }
+    }
+}
+
+impl<K: Archive + Hash + Eq, V: Archive, D: Fallible + ?Sized, S: Default + BuildHasher>
+    Deserialize<HashMap<K, V, S>, D> for ArchivedHashMap<K::Archived, V::Archived>
+where
+    K::Archived: Deserialize<K, D> + Hash + Eq,
+    V::Archived: Deserialize<V, D>,
+{
+    #[inline]
+    fn deserialize(&self, deserializer: &mut D) -> Result<HashMap<K, V, S>, D::Error> {
+        let mut result = HashMap::with_capacity_and_hasher(self.len(), S::default());
+        for (k, v) in self.iter() {
+            result.insert(k.deserialize(deserializer)?, v.deserialize(deserializer)?);
+        }
+        Ok(result)
+    }
+}
+
+impl<K: Hash + Eq + Borrow<AK>, V, AK: Hash + Eq, AV: PartialEq<V>, S: BuildHasher>
+    PartialEq<HashMap<K, V, S>> for ArchivedHashMap<AK, AV>
+{
+    #[inline]
+    fn eq(&self, other: &HashMap<K, V, S>) -> bool {
+        if self.len() != other.len() {
+            false
+        } else {
+            self.iter()
+                .all(|(key, value)| other.get(key).map_or(false, |v| value.eq(v)))
+        }
+    }
+}
+
+impl<K: Hash + Eq + Borrow<AK>, V, AK: Hash + Eq, AV: PartialEq<V>>
+    PartialEq<ArchivedHashMap<AK, AV>> for HashMap<K, V>
+{
+    #[inline]
+    fn eq(&self, other: &ArchivedHashMap<AK, AV>) -> bool {
+        other.eq(self)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::HashMap;
+    use alloc::string::String;
+    use rkyv::{
+        archived_root, check_archived_root,
+        ser::{serializers::AllocSerializer, Serializer},
+        Deserialize, Infallible,
+    };
+
+    #[test]
+    fn index_map() {
+        let mut value = HashMap::new();
+        value.insert(String::from("foo"), 10);
+        value.insert(String::from("bar"), 20);
+        value.insert(String::from("baz"), 40);
+        value.insert(String::from("bat"), 80);
+
+        let mut serializer = AllocSerializer::<4096>::default();
+        serializer.serialize_value(&value).unwrap();
+        let result = serializer.into_serializer().into_inner();
+        let archived = unsafe { archived_root::<HashMap<String, i32>>(result.as_ref()) };
+
+        assert_eq!(value.len(), archived.len());
+        for (k, v) in value.iter() {
+            let (ak, av) = archived.get_key_value(k.as_str()).unwrap();
+            assert_eq!(k, ak);
+            assert_eq!(v, av);
+        }
+
+        let deserialized: HashMap<String, i32> = archived.deserialize(&mut Infallible).unwrap();
+        assert_eq!(value, deserialized);
+    }
+
+    #[test]
+    fn validate_index_map() {
+        let mut value = HashMap::new();
+        value.insert(String::from("foo"), 10);
+        value.insert(String::from("bar"), 20);
+        value.insert(String::from("baz"), 40);
+        value.insert(String::from("bat"), 80);
+
+        let mut serializer = AllocSerializer::<4096>::default();
+        serializer.serialize_value(&value).unwrap();
+        let result = serializer.into_serializer().into_inner();
+        check_archived_root::<HashMap<String, i32>>(result.as_ref())
+            .expect("failed to validate archived index map");
+    }
+}
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rkyv/hash_set.rs b/third_party/rust/hashbrown/src/external_trait_impls/rkyv/hash_set.rs
new file mode 100644
index 0000000000..c8a69cf4fc
--- /dev/null
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rkyv/hash_set.rs
@@ -0,0 +1,123 @@
+use crate::HashSet;
+use core::{
+    borrow::Borrow,
+    hash::{BuildHasher, Hash},
+};
+use rkyv::{
+    collections::hash_set::{ArchivedHashSet, HashSetResolver},
+    ser::{ScratchSpace, Serializer},
+    Archive, Deserialize, Fallible, Serialize,
+};
+
+impl<K: Archive + Hash + Eq, S> Archive for HashSet<K, S>
+where
+    K::Archived: Hash + Eq,
+{
+    type Archived = ArchivedHashSet<K::Archived>;
+    type Resolver = HashSetResolver;
+
+    #[inline]
+    unsafe fn resolve(&self, pos: usize, resolver: Self::Resolver, out: *mut Self::Archived) {
+        ArchivedHashSet::<K::Archived>::resolve_from_len(self.len(), pos, resolver, out);
+    }
+}
+
+impl<K, S, RS> Serialize<S> for HashSet<K, RS>
+where
+    K::Archived: Hash + Eq,
+    K: Serialize<S> + Hash + Eq,
+    S: ScratchSpace + Serializer + ?Sized,
+{
+    #[inline]
+    fn serialize(&self, serializer: &mut S) -> Result<Self::Resolver, S::Error> {
+        unsafe { ArchivedHashSet::serialize_from_iter(self.iter(), serializer) }
+    }
+}
+
+impl<K, D, S> Deserialize<HashSet<K, S>, D> for ArchivedHashSet<K::Archived>
+where
+    K: Archive + Hash + Eq,
+    K::Archived: Deserialize<K, D> + Hash + Eq,
+    D: Fallible + ?Sized,
+    S: Default + BuildHasher,
+{
+    #[inline]
+    fn deserialize(&self, deserializer: &mut D) -> Result<HashSet<K, S>, D::Error> {
+        let mut result = HashSet::with_hasher(S::default());
+        for k in self.iter() {
+            result.insert(k.deserialize(deserializer)?);
+        }
+        Ok(result)
+    }
+}
+
+impl<K: Hash + Eq + Borrow<AK>, AK: Hash + Eq, S: BuildHasher> PartialEq<HashSet<K, S>>
+    for ArchivedHashSet<AK>
+{
+    #[inline]
+    fn eq(&self, other: &HashSet<K, S>) -> bool {
+        if self.len() != other.len() {
+            false
+        } else {
+            self.iter().all(|key| other.get(key).is_some())
+        }
+    }
+}
+
+impl<K: Hash + Eq + Borrow<AK>, AK: Hash + Eq, S: BuildHasher> PartialEq<ArchivedHashSet<AK>>
+    for HashSet<K, S>
+{
+    #[inline]
+    fn eq(&self, other: &ArchivedHashSet<AK>) -> bool {
+        other.eq(self)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::HashSet;
+    use alloc::string::String;
+    use rkyv::{
+        archived_root, check_archived_root,
+        ser::{serializers::AllocSerializer, Serializer},
+        Deserialize, Infallible,
+    };
+
+    #[test]
+    fn index_set() {
+        let mut value = HashSet::new();
+        value.insert(String::from("foo"));
+        value.insert(String::from("bar"));
+        value.insert(String::from("baz"));
+        value.insert(String::from("bat"));
+
+        let mut serializer = AllocSerializer::<4096>::default();
+        serializer.serialize_value(&value).unwrap();
+        let result = serializer.into_serializer().into_inner();
+        let archived = unsafe { archived_root::<HashSet<String>>(result.as_ref()) };
+
+        assert_eq!(value.len(), archived.len());
+        for k in value.iter() {
+            let ak = archived.get(k.as_str()).unwrap();
+            assert_eq!(k, ak);
+        }
+
+        let deserialized: HashSet<String> = archived.deserialize(&mut Infallible).unwrap();
+        assert_eq!(value, deserialized);
+    }
+
+    #[test]
+    fn validate_index_set() {
+        let mut value = HashSet::new();
+        value.insert(String::from("foo"));
+        value.insert(String::from("bar"));
+        value.insert(String::from("baz"));
+        value.insert(String::from("bat"));
+
+        let mut serializer = AllocSerializer::<4096>::default();
+        serializer.serialize_value(&value).unwrap();
+        let result = serializer.into_serializer().into_inner();
+        check_archived_root::<HashSet<String>>(result.as_ref())
+            .expect("failed to validate archived index set");
+    }
+}
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/rkyv/mod.rs b/third_party/rust/hashbrown/src/external_trait_impls/rkyv/mod.rs
new file mode 100644
index 0000000000..2bde6a0653
--- /dev/null
+++ b/third_party/rust/hashbrown/src/external_trait_impls/rkyv/mod.rs
@@ -0,0 +1,2 @@
+mod hash_map;
+mod hash_set;
diff --git a/third_party/rust/hashbrown/src/external_trait_impls/serde.rs b/third_party/rust/hashbrown/src/external_trait_impls/serde.rs
index 4d62deeb7a..0a76dbec25 100644
--- a/third_party/rust/hashbrown/src/external_trait_impls/serde.rs
+++ b/third_party/rust/hashbrown/src/external_trait_impls/serde.rs
@@ -11,6 +11,7 @@ mod size_hint {
 }
 
 mod map {
+    use crate::raw::Allocator;
     use core::fmt;
     use core::hash::{BuildHasher, Hash};
     use core::marker::PhantomData;
@@ -21,11 +22,12 @@ mod map {
 
     use super::size_hint;
 
-    impl<K, V, H> Serialize for HashMap<K, V, H>
+    impl<K, V, H, A> Serialize for HashMap<K, V, H, A>
     where
         K: Serialize + Eq + Hash,
         V: Serialize,
         H: BuildHasher,
+        A: Allocator,
     {
         #[cfg_attr(feature = "inline-more", inline)]
         fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -36,40 +38,46 @@ mod map {
         }
     }
 
-    impl<'de, K, V, S> Deserialize<'de> for HashMap<K, V, S>
+    impl<'de, K, V, S, A> Deserialize<'de> for HashMap<K, V, S, A>
     where
         K: Deserialize<'de> + Eq + Hash,
         V: Deserialize<'de>,
         S: BuildHasher + Default,
+        A: Allocator + Default,
     {
         fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
         where
             D: Deserializer<'de>,
         {
-            struct MapVisitor<K, V, S> {
-                marker: PhantomData<HashMap<K, V, S>>,
+            struct MapVisitor<K, V, S, A>
+            where
+                A: Allocator,
+            {
+                marker: PhantomData<HashMap<K, V, S, A>>,
             }
 
-            impl<'de, K, V, S> Visitor<'de> for MapVisitor<K, V, S>
+            impl<'de, K, V, S, A> Visitor<'de> for MapVisitor<K, V, S, A>
             where
                 K: Deserialize<'de> + Eq + Hash,
                 V: Deserialize<'de>,
                 S: BuildHasher + Default,
+                A: Allocator + Default,
             {
-                type Value = HashMap<K, V, S>;
+                type Value = HashMap<K, V, S, A>;
 
                 fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
                     formatter.write_str("a map")
                 }
 
                 #[cfg_attr(feature = "inline-more", inline)]
-                fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
+                fn visit_map<M>(self, mut map: M) -> Result<Self::Value, M::Error>
                 where
-                    A: MapAccess<'de>,
+                    M: MapAccess<'de>,
                 {
-                    let mut values = HashMap::with_capacity_and_hasher(
+                    let mut values = HashMap::with_capacity_and_hasher_in(
                         size_hint::cautious(map.size_hint()),
                         S::default(),
+                        A::default(),
                     );
 
                     while let Some((key, value)) = map.next_entry()? {
@@ -89,6 +97,7 @@ mod map {
 }
 
 mod set {
+    use crate::raw::Allocator;
     use core::fmt;
     use core::hash::{BuildHasher, Hash};
     use core::marker::PhantomData;
@@ -99,10 +108,11 @@ mod set {
 
     use super::size_hint;
 
-    impl<T, H> Serialize for HashSet<T, H>
+    impl<T, H, A> Serialize for HashSet<T, H, A>
     where
         T: Serialize + Eq + Hash,
         H: BuildHasher,
+        A: Allocator,
     {
         #[cfg_attr(feature = "inline-more", inline)]
         fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -113,38 +123,44 @@ mod set {
         }
     }
 
-    impl<'de, T, S> Deserialize<'de> for HashSet<T, S>
+    impl<'de, T, S, A> Deserialize<'de> for HashSet<T, S, A>
     where
         T: Deserialize<'de> + Eq + Hash,
         S: BuildHasher + Default,
+        A: Allocator + Default,
     {
         fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
         where
             D: Deserializer<'de>,
         {
-            struct SeqVisitor<T, S> {
-                marker: PhantomData<HashSet<T, S>>,
+            struct SeqVisitor<T, S, A>
+            where
+                A: Allocator,
+            {
+                marker: PhantomData<HashSet<T, S, A>>,
             }
 
-            impl<'de, T, S> Visitor<'de> for SeqVisitor<T, S>
+            impl<'de, T, S, A> Visitor<'de> for SeqVisitor<T, S, A>
             where
                 T: Deserialize<'de> + Eq + Hash,
                 S: BuildHasher + Default,
+                A: Allocator + Default,
             {
-                type Value = HashSet<T, S>;
+                type Value = HashSet<T, S, A>;
 
                 fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
                     formatter.write_str("a sequence")
                 }
 
                 #[cfg_attr(feature = "inline-more", inline)]
-                fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+                fn visit_seq<M>(self, mut seq: M) -> Result<Self::Value, M::Error>
                 where
-                    A: SeqAccess<'de>,
+                    M: SeqAccess<'de>,
                 {
-                    let mut values = HashSet::with_capacity_and_hasher(
+                    let mut values = HashSet::with_capacity_and_hasher_in(
                         size_hint::cautious(seq.size_hint()),
                         S::default(),
+                        A::default(),
                     );
 
                     while let Some(value) = seq.next_element()? {
@@ -166,12 +182,15 @@ mod set {
         where
             D: Deserializer<'de>,
         {
-            struct SeqInPlaceVisitor<'a, T, S>(&'a mut HashSet<T, S>);
+            struct SeqInPlaceVisitor<'a, T, S, A>(&'a mut HashSet<T, S, A>)
+            where
+                A: Allocator;
 
-            impl<'a, 'de, T, S> Visitor<'de> for SeqInPlaceVisitor<'a, T, S>
+            impl<'a, 'de, T, S, A> Visitor<'de> for SeqInPlaceVisitor<'a, T, S, A>
             where
                 T: Deserialize<'de> + Eq + Hash,
                 S: BuildHasher + Default,
+                A: Allocator,
             {
                 type Value = ();
 
@@ -180,9 +199,9 @@ mod set {
                 }
 
                 #[cfg_attr(feature = "inline-more", inline)]
-                fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+                fn visit_seq<M>(self, mut seq: M) -> Result<Self::Value, M::Error>
                 where
-                    A: SeqAccess<'de>,
+                    M: SeqAccess<'de>,
                 {
                     self.0.clear();
                     self.0.reserve(size_hint::cautious(seq.size_hint()));
diff --git a/third_party/rust/hashbrown/src/lib.rs b/third_party/rust/hashbrown/src/lib.rs
index bc1c971303..f03ddb6ad9 100644
--- a/third_party/rust/hashbrown/src/lib.rs
+++ b/third_party/rust/hashbrown/src/lib.rs
@@ -20,9 +20,8 @@
         extend_one,
         allocator_api,
         slice_ptr_get,
-        nonnull_slice_from_raw_parts,
         maybe_uninit_array_assume_init,
-        build_hasher_simple_hash_one
+        strict_provenance
     )
 )]
 #![allow(
@@ -37,6 +36,8 @@
 )]
 #![warn(missing_docs)]
 #![warn(rust_2018_idioms)]
+#![cfg_attr(feature = "nightly", warn(fuzzy_provenance_casts))]
+#![cfg_attr(feature = "nightly", allow(internal_features))]
 
 #[cfg(test)]
 #[macro_use]
@@ -81,6 +82,7 @@ mod map;
 mod rustc_entry;
 mod scopeguard;
 mod set;
+mod table;
 
 pub mod hash_map {
     //! A hash map implemented with quadratic probing and SIMD lookup.
@@ -113,9 +115,63 @@ pub mod hash_set {
         pub use crate::external_trait_impls::rayon::set::*;
     }
 }
+pub mod hash_table {
+    //! A hash table implemented with quadratic probing and SIMD lookup.
+    pub use crate::table::*;
+
+    #[cfg(feature = "rayon")]
+    /// [rayon]-based parallel iterator types for hash tables.
+    /// You will rarely need to interact with it directly unless you have need
+    /// to name one of the iterator types.
+    ///
+    /// [rayon]: https://docs.rs/rayon/1.0/rayon
+    pub mod rayon {
+        pub use crate::external_trait_impls::rayon::table::*;
+    }
+}
 
 pub use crate::map::HashMap;
 pub use crate::set::HashSet;
+pub use crate::table::HashTable;
+
+#[cfg(feature = "equivalent")]
+pub use equivalent::Equivalent;
+
+// This is only used as a fallback when building as part of `std`.
+#[cfg(not(feature = "equivalent"))]
+/// Key equivalence trait.
+///
+/// This trait defines the function used to compare the input value with the
+/// map keys (or set values) during a lookup operation such as [`HashMap::get`]
+/// or [`HashSet::contains`].
+/// It is provided with a blanket implementation based on the
+/// [`Borrow`](core::borrow::Borrow) trait.
+///
+/// # Correctness
+///
+/// Equivalent values must hash to the same value.
+pub trait Equivalent<K: ?Sized> {
+    /// Checks if this value is equivalent to the given key.
+    ///
+    /// Returns `true` if both values are equivalent, and `false` otherwise.
+    ///
+    /// # Correctness
+    ///
+    /// When this function returns `true`, both `self` and `key` must hash to
+    /// the same value.
+    fn equivalent(&self, key: &K) -> bool;
+}
+
+#[cfg(not(feature = "equivalent"))]
+impl<Q: ?Sized, K: ?Sized> Equivalent<K> for Q
+where
+    Q: Eq,
+    K: core::borrow::Borrow<Q>,
+{
+    fn equivalent(&self, key: &K) -> bool {
+        self == key.borrow()
+    }
+}
 
 /// The error type for `try_reserve` methods.
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -130,21 +186,3 @@ pub enum TryReserveError {
         layout: alloc::alloc::Layout,
     },
 }
-
-/// Wrapper around `Bump` which allows it to be used as an allocator for
-/// `HashMap`, `HashSet` and `RawTable`.
-///
-/// `Bump` can be used directly without this wrapper on nightly if you enable
-/// the `allocator-api` feature of the `bumpalo` crate.
-#[cfg(feature = "bumpalo")]
-#[derive(Clone, Copy, Debug)]
-pub struct BumpWrapper<'a>(pub &'a bumpalo::Bump);
-
-#[cfg(feature = "bumpalo")]
-#[test]
-fn test_bumpalo() {
-    use bumpalo::Bump;
-    let bump = Bump::new();
-    let mut map = HashMap::new_in(BumpWrapper(&bump));
-    map.insert(0, 1);
-}
diff --git a/third_party/rust/hashbrown/src/macros.rs b/third_party/rust/hashbrown/src/macros.rs
index f8ef917b14..eaba6bed1f 100644
--- a/third_party/rust/hashbrown/src/macros.rs
+++ b/third_party/rust/hashbrown/src/macros.rs
@@ -37,7 +37,7 @@ macro_rules! cfg_if {
     // semicolon is all the remaining items
     (@__items ($($not:meta,)*) ; ) => {};
     (@__items ($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
-        // Emit all items within one block, applying an approprate #[cfg]. The
+        // Emit all items within one block, applying an appropriate #[cfg]. The
         // #[cfg] will require all `$m` matchers specified and must also negate
         // all previous matchers.
         cfg_if! { @__apply cfg(all($($m,)* not(any($($not),*)))), $($it)* }
diff --git a/third_party/rust/hashbrown/src/map.rs b/third_party/rust/hashbrown/src/map.rs
index a5d3ccb97e..88a826582b 100644
--- a/third_party/rust/hashbrown/src/map.rs
+++ b/third_party/rust/hashbrown/src/map.rs
@@ -1,16 +1,18 @@
-use crate::raw::{Allocator, Bucket, Global, RawDrain, RawIntoIter, RawIter, RawTable};
-use crate::TryReserveError;
+use crate::raw::{
+    Allocator, Bucket, Global, RawDrain, RawExtractIf, RawIntoIter, RawIter, RawTable,
+};
+use crate::{Equivalent, TryReserveError};
 use core::borrow::Borrow;
 use core::fmt::{self, Debug};
 use core::hash::{BuildHasher, Hash};
-use core::iter::{FromIterator, FusedIterator};
+use core::iter::FusedIterator;
 use core::marker::PhantomData;
 use core::mem;
 use core::ops::Index;
 
 /// Default hasher for `HashMap`.
 #[cfg(feature = "ahash")]
-pub type DefaultHashBuilder = ahash::RandomState;
+pub type DefaultHashBuilder = core::hash::BuildHasherDefault<ahash::AHasher>;
 
 /// Dummy default hasher for `HashMap`.
 #[cfg(not(feature = "ahash"))]
@@ -182,10 +184,10 @@ pub enum DefaultHashBuilder {}
 /// use hashbrown::HashMap;
 ///
 /// let timber_resources: HashMap<&str, i32> = [("Norway", 100), ("Denmark", 50), ("Iceland", 10)]
-///     .iter().cloned().collect();
+///     .into_iter().collect();
 /// // use the values stored in map
 /// ```
-pub struct HashMap<K, V, S = DefaultHashBuilder, A: Allocator + Clone = Global> {
+pub struct HashMap<K, V, S = DefaultHashBuilder, A: Allocator = Global> {
     pub(crate) hash_builder: S,
     pub(crate) table: RawTable<(K, V), A>,
 }
@@ -209,13 +211,12 @@ impl<K: Clone, V: Clone, S: Clone, A: Allocator + Clone> Clone for HashMap<K, V,
 /// Ensures that a single closure type across uses of this which, in turn prevents multiple
 /// instances of any functions like RawTable::reserve from being generated
 #[cfg_attr(feature = "inline-more", inline)]
-pub(crate) fn make_hasher<K, Q, V, S>(hash_builder: &S) -> impl Fn(&(Q, V)) -> u64 + '_
+pub(crate) fn make_hasher<Q, V, S>(hash_builder: &S) -> impl Fn(&(Q, V)) -> u64 + '_
 where
-    K: Borrow<Q>,
     Q: Hash,
     S: BuildHasher,
 {
-    move |val| make_hash::<K, Q, S>(hash_builder, &val.0)
+    move |val| make_hash::<Q, S>(hash_builder, &val.0)
 }
 
 /// Ensures that a single closure type across uses of this which, in turn prevents multiple
@@ -223,10 +224,9 @@ where
 #[cfg_attr(feature = "inline-more", inline)]
 fn equivalent_key<Q, K, V>(k: &Q) -> impl Fn(&(K, V)) -> bool + '_
 where
-    K: Borrow<Q>,
-    Q: ?Sized + Eq,
+    Q: ?Sized + Equivalent<K>,
 {
-    move |x| k.eq(x.0.borrow())
+    move |x| k.equivalent(&x.0)
 }
 
 /// Ensures that a single closure type across uses of this which, in turn prevents multiple
@@ -234,17 +234,15 @@ where
 #[cfg_attr(feature = "inline-more", inline)]
 fn equivalent<Q, K>(k: &Q) -> impl Fn(&K) -> bool + '_
 where
-    K: Borrow<Q>,
-    Q: ?Sized + Eq,
+    Q: ?Sized + Equivalent<K>,
 {
-    move |x| k.eq(x.borrow())
+    move |x| k.equivalent(x)
 }
 
 #[cfg(not(feature = "nightly"))]
 #[cfg_attr(feature = "inline-more", inline)]
-pub(crate) fn make_hash<K, Q, S>(hash_builder: &S, val: &Q) -> u64
+pub(crate) fn make_hash<Q, S>(hash_builder: &S, val: &Q) -> u64
 where
-    K: Borrow<Q>,
     Q: Hash + ?Sized,
     S: BuildHasher,
 {
@@ -256,38 +254,14 @@ where
 
 #[cfg(feature = "nightly")]
 #[cfg_attr(feature = "inline-more", inline)]
-pub(crate) fn make_hash<K, Q, S>(hash_builder: &S, val: &Q) -> u64
+pub(crate) fn make_hash<Q, S>(hash_builder: &S, val: &Q) -> u64
 where
-    K: Borrow<Q>,
     Q: Hash + ?Sized,
     S: BuildHasher,
 {
     hash_builder.hash_one(val)
 }
 
-#[cfg(not(feature = "nightly"))]
-#[cfg_attr(feature = "inline-more", inline)]
-pub(crate) fn make_insert_hash<K, S>(hash_builder: &S, val: &K) -> u64
-where
-    K: Hash,
-    S: BuildHasher,
-{
-    use core::hash::Hasher;
-    let mut state = hash_builder.build_hasher();
-    val.hash(&mut state);
-    state.finish()
-}
-
-#[cfg(feature = "nightly")]
-#[cfg_attr(feature = "inline-more", inline)]
-pub(crate) fn make_insert_hash<K, S>(hash_builder: &S, val: &K) -> u64
-where
-    K: Hash,
-    S: BuildHasher,
-{
-    hash_builder.hash_one(val)
-}
-
 #[cfg(feature = "ahash")]
 impl<K, V> HashMap<K, V, DefaultHashBuilder> {
     /// Creates an empty `HashMap`.
@@ -295,6 +269,18 @@ impl<K, V> HashMap<K, V, DefaultHashBuilder> {
     /// The hash map is initially created with a capacity of 0, so it will not allocate until it
     /// is first inserted into.
     ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`], for example with
+    /// [`with_hasher`](HashMap::with_hasher) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -313,6 +299,18 @@ impl<K, V> HashMap<K, V, DefaultHashBuilder> {
     /// The hash map will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash map will not allocate.
     ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`], for example with
+    /// [`with_capacity_and_hasher`](HashMap::with_capacity_and_hasher) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -328,11 +326,46 @@ impl<K, V> HashMap<K, V, DefaultHashBuilder> {
 }
 
 #[cfg(feature = "ahash")]
-impl<K, V, A: Allocator + Clone> HashMap<K, V, DefaultHashBuilder, A> {
+impl<K, V, A: Allocator> HashMap<K, V, DefaultHashBuilder, A> {
     /// Creates an empty `HashMap` using the given allocator.
     ///
     /// The hash map is initially created with a capacity of 0, so it will not allocate until it
     /// is first inserted into.
+    ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`], for example with
+    /// [`with_hasher_in`](HashMap::with_hasher_in) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hashbrown::HashMap;
+    /// use bumpalo::Bump;
+    ///
+    /// let bump = Bump::new();
+    /// let mut map = HashMap::new_in(&bump);
+    ///
+    /// // The created HashMap holds none elements
+    /// assert_eq!(map.len(), 0);
+    ///
+    /// // The created HashMap also doesn't allocate memory
+    /// assert_eq!(map.capacity(), 0);
+    ///
+    /// // Now we insert element inside created HashMap
+    /// map.insert("One", 1);
+    /// // We can see that the HashMap holds 1 element
+    /// assert_eq!(map.len(), 1);
+    /// // And it also allocates some capacity
+    /// assert!(map.capacity() > 1);
+    /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn new_in(alloc: A) -> Self {
         Self::with_hasher_in(DefaultHashBuilder::default(), alloc)
@@ -342,6 +375,46 @@ impl<K, V, A: Allocator + Clone> HashMap<K, V, DefaultHashBuilder, A> {
     ///
     /// The hash map will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash map will not allocate.
+    ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`], for example with
+    /// [`with_capacity_and_hasher_in`](HashMap::with_capacity_and_hasher_in) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hashbrown::HashMap;
+    /// use bumpalo::Bump;
+    ///
+    /// let bump = Bump::new();
+    /// let mut map = HashMap::with_capacity_in(5, &bump);
+    ///
+    /// // The created HashMap holds none elements
+    /// assert_eq!(map.len(), 0);
+    /// // But it can hold at least 5 elements without reallocating
+    /// let empty_map_capacity = map.capacity();
+    /// assert!(empty_map_capacity >= 5);
+    ///
+    /// // Now we insert some 5 elements inside created HashMap
+    /// map.insert("One",   1);
+    /// map.insert("Two",   2);
+    /// map.insert("Three", 3);
+    /// map.insert("Four",  4);
+    /// map.insert("Five",  5);
+    ///
+    /// // We can see that the HashMap holds 5 elements
+    /// assert_eq!(map.len(), 5);
+    /// // But its capacity isn't changed
+    /// assert_eq!(map.capacity(), empty_map_capacity)
+    /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
         Self::with_capacity_and_hasher_in(capacity, DefaultHashBuilder::default(), alloc)
@@ -355,14 +428,21 @@ impl<K, V, S> HashMap<K, V, S> {
     /// The hash map is initially created with a capacity of 0, so it will not
     /// allocate until it is first inserted into.
     ///
-    /// Warning: `hash_builder` is normally randomly generated, and
-    /// is designed to allow HashMaps to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`].
     ///
     /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
     /// the HashMap to be useful, see its documentation for details.
     ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -376,8 +456,6 @@ impl<K, V, S> HashMap<K, V, S> {
     ///
     /// map.insert(1, 2);
     /// ```
-    ///
-    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
     #[cfg_attr(feature = "inline-more", inline)]
     pub const fn with_hasher(hash_builder: S) -> Self {
         Self {
@@ -392,14 +470,21 @@ impl<K, V, S> HashMap<K, V, S> {
     /// The hash map will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash map will not allocate.
     ///
-    /// Warning: `hash_builder` is normally randomly generated, and
-    /// is designed to allow HashMaps to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`].
     ///
     /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
     /// the HashMap to be useful, see its documentation for details.
     ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -413,8 +498,6 @@ impl<K, V, S> HashMap<K, V, S> {
     ///
     /// map.insert(1, 2);
     /// ```
-    ///
-    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> Self {
         Self {
@@ -424,7 +507,7 @@ impl<K, V, S> HashMap<K, V, S> {
     }
 }
 
-impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
+impl<K, V, S, A: Allocator> HashMap<K, V, S, A> {
     /// Returns a reference to the underlying allocator.
     #[inline]
     pub fn allocator(&self) -> &A {
@@ -434,12 +517,19 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     /// Creates an empty `HashMap` which will use the given hash builder to hash
     /// keys. It will be allocated with the given allocator.
     ///
-    /// The created map has the default initial capacity.
+    /// The hash map is initially created with a capacity of 0, so it will not allocate until it
+    /// is first inserted into.
+    ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`].
     ///
-    /// Warning: `hash_builder` is normally randomly generated, and
-    /// is designed to allow HashMaps to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
     ///
     /// # Examples
     ///
@@ -452,7 +542,7 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     /// map.insert(1, 2);
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
-    pub fn with_hasher_in(hash_builder: S, alloc: A) -> Self {
+    pub const fn with_hasher_in(hash_builder: S, alloc: A) -> Self {
         Self {
             hash_builder,
             table: RawTable::new_in(alloc),
@@ -465,10 +555,16 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     /// The hash map will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash map will not allocate.
     ///
-    /// Warning: `hash_builder` is normally randomly generated, and
-    /// is designed to allow HashMaps to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashMap`].
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
     ///
     /// # Examples
     ///
@@ -810,14 +906,11 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     ///
     /// let mut map: HashMap<i32, i32> = (0..8).map(|x|(x, x*10)).collect();
     /// assert_eq!(map.len(), 8);
-    /// let capacity_before_retain = map.capacity();
     ///
     /// map.retain(|&k, _| k % 2 == 0);
     ///
     /// // We can see, that the number of elements inside map is changed.
     /// assert_eq!(map.len(), 4);
-    /// // But map capacity is equal to old one.
-    /// assert_eq!(map.capacity(), capacity_before_retain);
     ///
     /// let mut vec: Vec<(i32, i32)> = map.iter().map(|(&k, &v)| (k, v)).collect();
     /// vec.sort_unstable();
@@ -844,26 +937,25 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     /// In other words, move all pairs `(k, v)` such that `f(&k, &mut v)` returns `true` out
     /// into another iterator.
     ///
-    /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
+    /// Note that `extract_if` lets you mutate every value in the filter closure, regardless of
     /// whether you choose to keep or remove it.
     ///
-    /// When the returned DrainedFilter is dropped, any remaining elements that satisfy
-    /// the predicate are dropped from the table.
-    ///
-    /// It is unspecified how many more elements will be subjected to the closure
-    /// if a panic occurs in the closure, or a panic occurs while dropping an element,
-    /// or if the `DrainFilter` value is leaked.
+    /// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
+    /// or the iteration short-circuits, then the remaining elements will be retained.
+    /// Use [`retain()`] with a negated predicate if you do not need the returned iterator.
     ///
     /// Keeps the allocated memory for reuse.
     ///
+    /// [`retain()`]: HashMap::retain
+    ///
     /// # Examples
     ///
     /// ```
     /// use hashbrown::HashMap;
     ///
     /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
-    /// let capacity_before_drain_filter = map.capacity();
-    /// let drained: HashMap<i32, i32> = map.drain_filter(|k, _v| k % 2 == 0).collect();
+    ///
+    /// let drained: HashMap<i32, i32> = map.extract_if(|k, _v| k % 2 == 0).collect();
     ///
     /// let mut evens = drained.keys().cloned().collect::<Vec<_>>();
     /// let mut odds = map.keys().cloned().collect::<Vec<_>>();
@@ -872,27 +964,24 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     ///
     /// assert_eq!(evens, vec![0, 2, 4, 6]);
     /// assert_eq!(odds, vec![1, 3, 5, 7]);
-    /// // Map capacity is equal to old one.
-    /// assert_eq!(map.capacity(), capacity_before_drain_filter);
     ///
     /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
     ///
     /// {   // Iterator is dropped without being consumed.
-    ///     let d = map.drain_filter(|k, _v| k % 2 != 0);
+    ///     let d = map.extract_if(|k, _v| k % 2 != 0);
     /// }
     ///
-    /// // But the map lens have been reduced by half
-    /// // even if we do not use DrainFilter iterator.
-    /// assert_eq!(map.len(), 4);
+    /// // ExtractIf was not exhausted, therefore no elements were drained.
+    /// assert_eq!(map.len(), 8);
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
-    pub fn drain_filter<F>(&mut self, f: F) -> DrainFilter<'_, K, V, F, A>
+    pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, K, V, F, A>
     where
         F: FnMut(&K, &mut V) -> bool,
     {
-        DrainFilter {
+        ExtractIf {
             f,
-            inner: DrainFilterInner {
+            inner: RawExtractIf {
                 iter: unsafe { self.table.iter() },
                 table: &mut self.table,
             },
@@ -984,7 +1073,7 @@ impl<K, V, S, A> HashMap<K, V, S, A>
 where
     K: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// Reserves capacity for at least `additional` more elements to be inserted
     /// in the `HashMap`. The collection may reserve more space to avoid
@@ -992,9 +1081,12 @@ where
     ///
     /// # Panics
     ///
-    /// Panics if the new allocation size overflows [`usize`].
+    /// Panics if the new capacity exceeds [`isize::MAX`] bytes and [`abort`] the program
+    /// in case of allocation error. Use [`try_reserve`](HashMap::try_reserve) instead
+    /// if you want to handle memory allocation failure.
     ///
-    /// [`usize`]: https://doc.rust-lang.org/std/primitive.usize.html
+    /// [`isize::MAX`]: https://doc.rust-lang.org/std/primitive.isize.html
+    /// [`abort`]: https://doc.rust-lang.org/alloc/alloc/fn.handle_alloc_error.html
     ///
     /// # Examples
     ///
@@ -1012,7 +1104,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn reserve(&mut self, additional: usize) {
         self.table
-            .reserve(additional, make_hasher::<K, _, V, S>(&self.hash_builder));
+            .reserve(additional, make_hasher::<_, V, S>(&self.hash_builder));
     }
 
     /// Tries to reserve capacity for at least `additional` more elements to be inserted
@@ -1062,7 +1154,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
         self.table
-            .try_reserve(additional, make_hasher::<K, _, V, S>(&self.hash_builder))
+            .try_reserve(additional, make_hasher::<_, V, S>(&self.hash_builder))
     }
 
     /// Shrinks the capacity of the map as much as possible. It will drop
@@ -1084,7 +1176,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn shrink_to_fit(&mut self) {
         self.table
-            .shrink_to(0, make_hasher::<K, _, V, S>(&self.hash_builder));
+            .shrink_to(0, make_hasher::<_, V, S>(&self.hash_builder));
     }
 
     /// Shrinks the capacity of the map with a lower limit. It will drop
@@ -1113,7 +1205,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.table
-            .shrink_to(min_capacity, make_hasher::<K, _, V, S>(&self.hash_builder));
+            .shrink_to(min_capacity, make_hasher::<_, V, S>(&self.hash_builder));
     }
 
     /// Gets the given key's corresponding entry in the map for in-place manipulation.
@@ -1137,7 +1229,7 @@ where
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn entry(&mut self, key: K) -> Entry<'_, K, V, S, A> {
-        let hash = make_insert_hash::<K, S>(&self.hash_builder, &key);
+        let hash = make_hash::<K, S>(&self.hash_builder, &key);
         if let Some(elem) = self.table.find(hash, equivalent_key(&key)) {
             Entry::Occupied(OccupiedEntry {
                 hash,
@@ -1174,10 +1266,9 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn entry_ref<'a, 'b, Q: ?Sized>(&'a mut self, key: &'b Q) -> EntryRef<'a, 'b, K, Q, V, S, A>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
-        let hash = make_hash::<K, Q, S>(&self.hash_builder, key);
+        let hash = make_hash::<Q, S>(&self.hash_builder, key);
         if let Some(elem) = self.table.find(hash, equivalent_key(key)) {
             EntryRef::Occupied(OccupiedEntryRef {
                 hash,
@@ -1216,12 +1307,11 @@ where
     #[inline]
     pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.get_inner(k) {
-            Some(&(_, ref v)) => Some(v),
+            Some((_, v)) => Some(v),
             None => None,
         }
     }
@@ -1248,12 +1338,11 @@ where
     #[inline]
     pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.get_inner(k) {
-            Some(&(ref key, ref value)) => Some((key, value)),
+            Some((key, value)) => Some((key, value)),
             None => None,
         }
     }
@@ -1261,13 +1350,12 @@ where
     #[inline]
     fn get_inner<Q: ?Sized>(&self, k: &Q) -> Option<&(K, V)>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         if self.table.is_empty() {
             None
         } else {
-            let hash = make_hash::<K, Q, S>(&self.hash_builder, k);
+            let hash = make_hash::<Q, S>(&self.hash_builder, k);
             self.table.get(hash, equivalent_key(k))
         }
     }
@@ -1298,8 +1386,7 @@ where
     #[inline]
     pub fn get_key_value_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<(&K, &mut V)>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.get_inner_mut(k) {
@@ -1330,8 +1417,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         self.get_inner(k).is_some()
     }
@@ -1362,8 +1448,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.get_inner_mut(k) {
@@ -1375,13 +1460,12 @@ where
     #[inline]
     fn get_inner_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut (K, V)>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         if self.table.is_empty() {
             None
         } else {
-            let hash = make_hash::<K, Q, S>(&self.hash_builder, k);
+            let hash = make_hash::<Q, S>(&self.hash_builder, k);
             self.table.get_mut(hash, equivalent_key(k))
         }
     }
@@ -1431,8 +1515,7 @@ where
     /// ```
     pub fn get_many_mut<Q: ?Sized, const N: usize>(&mut self, ks: [&Q; N]) -> Option<[&'_ mut V; N]>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         self.get_many_mut_inner(ks).map(|res| res.map(|(_, v)| v))
     }
@@ -1487,8 +1570,7 @@ where
         ks: [&Q; N],
     ) -> Option<[&'_ mut V; N]>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         self.get_many_unchecked_mut_inner(ks)
             .map(|res| res.map(|(_, v)| v))
@@ -1543,8 +1625,7 @@ where
         ks: [&Q; N],
     ) -> Option<[(&'_ K, &'_ mut V); N]>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         self.get_many_mut_inner(ks)
             .map(|res| res.map(|(k, v)| (&*k, v)))
@@ -1599,8 +1680,7 @@ where
         ks: [&Q; N],
     ) -> Option<[(&'_ K, &'_ mut V); N]>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         self.get_many_unchecked_mut_inner(ks)
             .map(|res| res.map(|(k, v)| (&*k, v)))
@@ -1611,12 +1691,11 @@ where
         ks: [&Q; N],
     ) -> Option<[&'_ mut (K, V); N]>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         let hashes = self.build_hashes_inner(ks);
         self.table
-            .get_many_mut(hashes, |i, (k, _)| ks[i].eq(k.borrow()))
+            .get_many_mut(hashes, |i, (k, _)| ks[i].equivalent(k))
     }
 
     unsafe fn get_many_unchecked_mut_inner<Q: ?Sized, const N: usize>(
@@ -1624,22 +1703,20 @@ where
         ks: [&Q; N],
     ) -> Option<[&'_ mut (K, V); N]>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         let hashes = self.build_hashes_inner(ks);
         self.table
-            .get_many_unchecked_mut(hashes, |i, (k, _)| ks[i].eq(k.borrow()))
+            .get_many_unchecked_mut(hashes, |i, (k, _)| ks[i].equivalent(k))
     }
 
     fn build_hashes_inner<Q: ?Sized, const N: usize>(&self, ks: [&Q; N]) -> [u64; N]
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         let mut hashes = [0_u64; N];
         for i in 0..N {
-            hashes[i] = make_hash::<K, Q, S>(&self.hash_builder, ks[i]);
+            hashes[i] = make_hash::<Q, S>(&self.hash_builder, ks[i]);
         }
         hashes
     }
@@ -1672,13 +1749,19 @@ where
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn insert(&mut self, k: K, v: V) -> Option<V> {
-        let hash = make_insert_hash::<K, S>(&self.hash_builder, &k);
-        if let Some((_, item)) = self.table.get_mut(hash, equivalent_key(&k)) {
-            Some(mem::replace(item, v))
-        } else {
-            self.table
-                .insert(hash, (k, v), make_hasher::<K, _, V, S>(&self.hash_builder));
-            None
+        let hash = make_hash::<K, S>(&self.hash_builder, &k);
+        let hasher = make_hasher::<_, V, S>(&self.hash_builder);
+        match self
+            .table
+            .find_or_find_insert_slot(hash, equivalent_key(&k), hasher)
+        {
+            Ok(bucket) => Some(mem::replace(unsafe { &mut bucket.as_mut().1 }, v)),
+            Err(slot) => {
+                unsafe {
+                    self.table.insert_in_slot(hash, slot, (k, v));
+                }
+                None
+            }
         }
     }
 
@@ -1733,10 +1816,10 @@ where
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn insert_unique_unchecked(&mut self, k: K, v: V) -> (&K, &mut V) {
-        let hash = make_insert_hash::<K, S>(&self.hash_builder, &k);
+        let hash = make_hash::<K, S>(&self.hash_builder, &k);
         let bucket = self
             .table
-            .insert(hash, (k, v), make_hasher::<K, _, V, S>(&self.hash_builder));
+            .insert(hash, (k, v), make_hasher::<_, V, S>(&self.hash_builder));
         let (k_ref, v_ref) = unsafe { bucket.as_mut() };
         (k_ref, v_ref)
     }
@@ -1801,19 +1884,17 @@ where
     /// assert!(map.is_empty() && map.capacity() == 0);
     ///
     /// map.insert(1, "a");
-    /// let capacity_before_remove = map.capacity();
     ///
     /// assert_eq!(map.remove(&1), Some("a"));
     /// assert_eq!(map.remove(&1), None);
     ///
-    /// // Now map holds none elements but capacity is equal to the old one
-    /// assert!(map.len() == 0 && map.capacity() == capacity_before_remove);
+    /// // Now map holds none elements
+    /// assert!(map.is_empty());
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.remove_entry(k) {
@@ -1842,26 +1923,24 @@ where
     /// assert!(map.is_empty() && map.capacity() == 0);
     ///
     /// map.insert(1, "a");
-    /// let capacity_before_remove = map.capacity();
     ///
     /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
     /// assert_eq!(map.remove(&1), None);
     ///
-    /// // Now map hold none elements but capacity is equal to the old one
-    /// assert!(map.len() == 0 && map.capacity() == capacity_before_remove);
+    /// // Now map hold none elements
+    /// assert!(map.is_empty());
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove_entry<Q: ?Sized>(&mut self, k: &Q) -> Option<(K, V)>
     where
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
-        let hash = make_hash::<K, Q, S>(&self.hash_builder, k);
+        let hash = make_hash::<Q, S>(&self.hash_builder, k);
         self.table.remove_entry(hash, equivalent_key(k))
     }
 }
 
-impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
+impl<K, V, S, A: Allocator> HashMap<K, V, S, A> {
     /// Creates a raw entry builder for the HashMap.
     ///
     /// Raw entries provide the lowest level of control for searching and
@@ -2013,19 +2092,31 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
         RawEntryBuilder { map: self }
     }
 
+    /// Returns a reference to the [`RawTable`] used underneath [`HashMap`].
+    /// This function is only available if the `raw` feature of the crate is enabled.
+    ///
+    /// See [`raw_table_mut`] for more.
+    ///
+    /// [`raw_table_mut`]: Self::raw_table_mut
+    #[cfg(feature = "raw")]
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn raw_table(&self) -> &RawTable<(K, V), A> {
+        &self.table
+    }
+
     /// Returns a mutable reference to the [`RawTable`] used underneath [`HashMap`].
     /// This function is only available if the `raw` feature of the crate is enabled.
     ///
     /// # Note
     ///
-    /// Calling the function safe, but using raw hash table API's may require
+    /// Calling this function is safe, but using the raw hash table API may require
     /// unsafe functions or blocks.
     ///
     /// `RawTable` API gives the lowest level of control under the map that can be useful
     /// for extending the HashMap's API, but may lead to *[undefined behavior]*.
     ///
     /// [`HashMap`]: struct.HashMap.html
-    /// [`RawTable`]: raw/struct.RawTable.html
+    /// [`RawTable`]: crate::raw::RawTable
     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     ///
     /// # Examples
@@ -2049,9 +2140,9 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     /// where
     ///     F: Fn(&(K, V)) -> bool,
     /// {
-    ///     let raw_table = map.raw_table();
+    ///     let raw_table = map.raw_table_mut();
     ///     match raw_table.find(hash, is_match) {
-    ///         Some(bucket) => Some(unsafe { raw_table.remove(bucket) }),
+    ///         Some(bucket) => Some(unsafe { raw_table.remove(bucket).0 }),
     ///         None => None,
     ///     }
     /// }
@@ -2070,7 +2161,7 @@ impl<K, V, S, A: Allocator + Clone> HashMap<K, V, S, A> {
     /// ```
     #[cfg(feature = "raw")]
     #[cfg_attr(feature = "inline-more", inline)]
-    pub fn raw_table(&mut self) -> &mut RawTable<(K, V), A> {
+    pub fn raw_table_mut(&mut self) -> &mut RawTable<(K, V), A> {
         &mut self.table
     }
 }
@@ -2080,7 +2171,7 @@ where
     K: Eq + Hash,
     V: PartialEq,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn eq(&self, other: &Self) -> bool {
         if self.len() != other.len() {
@@ -2097,7 +2188,7 @@ where
     K: Eq + Hash,
     V: Eq,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
 }
 
@@ -2105,7 +2196,7 @@ impl<K, V, S, A> Debug for HashMap<K, V, S, A>
 where
     K: Debug,
     V: Debug,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_map().entries(self.iter()).finish()
@@ -2115,7 +2206,7 @@ where
 impl<K, V, S, A> Default for HashMap<K, V, S, A>
 where
     S: Default,
-    A: Default + Allocator + Clone,
+    A: Default + Allocator,
 {
     /// Creates an empty `HashMap<K, V, S, A>`, with the `Default` value for the hasher and allocator.
     ///
@@ -2140,10 +2231,10 @@ where
 
 impl<K, Q: ?Sized, V, S, A> Index<&Q> for HashMap<K, V, S, A>
 where
-    K: Eq + Hash + Borrow<Q>,
-    Q: Eq + Hash,
+    K: Eq + Hash,
+    Q: Hash + Equivalent<K>,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Output = V;
 
@@ -2174,7 +2265,7 @@ where
 impl<K, V, A, const N: usize> From<[(K, V); N]> for HashMap<K, V, DefaultHashBuilder, A>
 where
     K: Eq + Hash,
-    A: Default + Allocator + Clone,
+    A: Default + Allocator,
 {
     /// # Examples
     ///
@@ -2319,11 +2410,11 @@ impl<K, V> IterMut<'_, K, V> {
 /// assert_eq!(iter.next(), None);
 /// assert_eq!(iter.next(), None);
 /// ```
-pub struct IntoIter<K, V, A: Allocator + Clone = Global> {
+pub struct IntoIter<K, V, A: Allocator = Global> {
     inner: RawIntoIter<(K, V), A>,
 }
 
-impl<K, V, A: Allocator + Clone> IntoIter<K, V, A> {
+impl<K, V, A: Allocator> IntoIter<K, V, A> {
     /// Returns a iterator of references over the remaining items.
     #[cfg_attr(feature = "inline-more", inline)]
     pub(super) fn iter(&self) -> Iter<'_, K, V> {
@@ -2363,11 +2454,11 @@ impl<K, V, A: Allocator + Clone> IntoIter<K, V, A> {
 /// assert_eq!(keys.next(), None);
 /// assert_eq!(keys.next(), None);
 /// ```
-pub struct IntoKeys<K, V, A: Allocator + Clone = Global> {
+pub struct IntoKeys<K, V, A: Allocator = Global> {
     inner: IntoIter<K, V, A>,
 }
 
-impl<K, V, A: Allocator + Clone> Iterator for IntoKeys<K, V, A> {
+impl<K, V, A: Allocator> Iterator for IntoKeys<K, V, A> {
     type Item = K;
 
     #[inline]
@@ -2378,18 +2469,26 @@ impl<K, V, A: Allocator + Clone> Iterator for IntoKeys<K, V, A> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[inline]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, |acc, (k, _)| f(acc, k))
+    }
 }
 
-impl<K, V, A: Allocator + Clone> ExactSizeIterator for IntoKeys<K, V, A> {
+impl<K, V, A: Allocator> ExactSizeIterator for IntoKeys<K, V, A> {
     #[inline]
     fn len(&self) -> usize {
         self.inner.len()
     }
 }
 
-impl<K, V, A: Allocator + Clone> FusedIterator for IntoKeys<K, V, A> {}
+impl<K, V, A: Allocator> FusedIterator for IntoKeys<K, V, A> {}
 
-impl<K: Debug, V: Debug, A: Allocator + Clone> fmt::Debug for IntoKeys<K, V, A> {
+impl<K: Debug, V: Debug, A: Allocator> fmt::Debug for IntoKeys<K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list()
             .entries(self.inner.iter().map(|(k, _)| k))
@@ -2425,11 +2524,11 @@ impl<K: Debug, V: Debug, A: Allocator + Clone> fmt::Debug for IntoKeys<K, V, A>
 /// assert_eq!(values.next(), None);
 /// assert_eq!(values.next(), None);
 /// ```
-pub struct IntoValues<K, V, A: Allocator + Clone = Global> {
+pub struct IntoValues<K, V, A: Allocator = Global> {
     inner: IntoIter<K, V, A>,
 }
 
-impl<K, V, A: Allocator + Clone> Iterator for IntoValues<K, V, A> {
+impl<K, V, A: Allocator> Iterator for IntoValues<K, V, A> {
     type Item = V;
 
     #[inline]
@@ -2440,18 +2539,26 @@ impl<K, V, A: Allocator + Clone> Iterator for IntoValues<K, V, A> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[inline]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, |acc, (_, v)| f(acc, v))
+    }
 }
 
-impl<K, V, A: Allocator + Clone> ExactSizeIterator for IntoValues<K, V, A> {
+impl<K, V, A: Allocator> ExactSizeIterator for IntoValues<K, V, A> {
     #[inline]
     fn len(&self) -> usize {
         self.inner.len()
     }
 }
 
-impl<K, V, A: Allocator + Clone> FusedIterator for IntoValues<K, V, A> {}
+impl<K, V, A: Allocator> FusedIterator for IntoValues<K, V, A> {}
 
-impl<K, V: Debug, A: Allocator + Clone> fmt::Debug for IntoValues<K, V, A> {
+impl<K, V: Debug, A: Allocator> fmt::Debug for IntoValues<K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list()
             .entries(self.inner.iter().map(|(_, v)| v))
@@ -2583,11 +2690,11 @@ impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
 /// assert_eq!(drain_iter.next(), None);
 /// assert_eq!(drain_iter.next(), None);
 /// ```
-pub struct Drain<'a, K, V, A: Allocator + Clone = Global> {
+pub struct Drain<'a, K, V, A: Allocator = Global> {
     inner: RawDrain<'a, (K, V), A>,
 }
 
-impl<K, V, A: Allocator + Clone> Drain<'_, K, V, A> {
+impl<K, V, A: Allocator> Drain<'_, K, V, A> {
     /// Returns a iterator of references over the remaining items.
     #[cfg_attr(feature = "inline-more", inline)]
     pub(super) fn iter(&self) -> Iter<'_, K, V> {
@@ -2601,10 +2708,10 @@ impl<K, V, A: Allocator + Clone> Drain<'_, K, V, A> {
 /// A draining iterator over entries of a `HashMap` which don't satisfy the predicate
 /// `f(&k, &mut v)` in arbitrary order. The iterator element type is `(K, V)`.
 ///
-/// This `struct` is created by the [`drain_filter`] method on [`HashMap`]. See its
+/// This `struct` is created by the [`extract_if`] method on [`HashMap`]. See its
 /// documentation for more.
 ///
-/// [`drain_filter`]: struct.HashMap.html#method.drain_filter
+/// [`extract_if`]: struct.HashMap.html#method.extract_if
 /// [`HashMap`]: struct.HashMap.html
 ///
 /// # Examples
@@ -2614,63 +2721,40 @@ impl<K, V, A: Allocator + Clone> Drain<'_, K, V, A> {
 ///
 /// let mut map: HashMap<i32, &str> = [(1, "a"), (2, "b"), (3, "c")].into();
 ///
-/// let mut drain_filter = map.drain_filter(|k, _v| k % 2 != 0);
-/// let mut vec = vec![drain_filter.next(), drain_filter.next()];
+/// let mut extract_if = map.extract_if(|k, _v| k % 2 != 0);
+/// let mut vec = vec![extract_if.next(), extract_if.next()];
 ///
-/// // The `DrainFilter` iterator produces items in arbitrary order, so the
+/// // The `ExtractIf` iterator produces items in arbitrary order, so the
 /// // items must be sorted to test them against a sorted array.
 /// vec.sort_unstable();
 /// assert_eq!(vec, [Some((1, "a")),Some((3, "c"))]);
 ///
 /// // It is fused iterator
-/// assert_eq!(drain_filter.next(), None);
-/// assert_eq!(drain_filter.next(), None);
-/// drop(drain_filter);
+/// assert_eq!(extract_if.next(), None);
+/// assert_eq!(extract_if.next(), None);
+/// drop(extract_if);
 ///
 /// assert_eq!(map.len(), 1);
 /// ```
-pub struct DrainFilter<'a, K, V, F, A: Allocator + Clone = Global>
+#[must_use = "Iterators are lazy unless consumed"]
+pub struct ExtractIf<'a, K, V, F, A: Allocator = Global>
 where
     F: FnMut(&K, &mut V) -> bool,
 {
     f: F,
-    inner: DrainFilterInner<'a, K, V, A>,
-}
-
-impl<'a, K, V, F, A> Drop for DrainFilter<'a, K, V, F, A>
-where
-    F: FnMut(&K, &mut V) -> bool,
-    A: Allocator + Clone,
-{
-    #[cfg_attr(feature = "inline-more", inline)]
-    fn drop(&mut self) {
-        while let Some(item) = self.next() {
-            let guard = ConsumeAllOnDrop(self);
-            drop(item);
-            mem::forget(guard);
-        }
-    }
-}
-
-pub(super) struct ConsumeAllOnDrop<'a, T: Iterator>(pub &'a mut T);
-
-impl<T: Iterator> Drop for ConsumeAllOnDrop<'_, T> {
-    #[cfg_attr(feature = "inline-more", inline)]
-    fn drop(&mut self) {
-        self.0.for_each(drop);
-    }
+    inner: RawExtractIf<'a, (K, V), A>,
 }
 
-impl<K, V, F, A> Iterator for DrainFilter<'_, K, V, F, A>
+impl<K, V, F, A> Iterator for ExtractIf<'_, K, V, F, A>
 where
     F: FnMut(&K, &mut V) -> bool,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Item = (K, V);
 
     #[cfg_attr(feature = "inline-more", inline)]
     fn next(&mut self) -> Option<Self::Item> {
-        self.inner.next(&mut self.f)
+        self.inner.next(|&mut (ref k, ref mut v)| (self.f)(k, v))
     }
 
     #[inline]
@@ -2679,31 +2763,7 @@ where
     }
 }
 
-impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
-
-/// Portions of `DrainFilter` shared with `set::DrainFilter`
-pub(super) struct DrainFilterInner<'a, K, V, A: Allocator + Clone> {
-    pub iter: RawIter<(K, V)>,
-    pub table: &'a mut RawTable<(K, V), A>,
-}
-
-impl<K, V, A: Allocator + Clone> DrainFilterInner<'_, K, V, A> {
-    #[cfg_attr(feature = "inline-more", inline)]
-    pub(super) fn next<F>(&mut self, f: &mut F) -> Option<(K, V)>
-    where
-        F: FnMut(&K, &mut V) -> bool,
-    {
-        unsafe {
-            for item in &mut self.iter {
-                let &mut (ref key, ref mut value) = item.as_mut();
-                if f(key, value) {
-                    return Some(self.table.remove(item));
-                }
-            }
-        }
-        None
-    }
-}
+impl<K, V, F> FusedIterator for ExtractIf<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
 
 /// A mutable iterator over the values of a `HashMap` in arbitrary order.
 /// The iterator element type is `&'a mut V`.
@@ -2791,7 +2851,7 @@ pub struct ValuesMut<'a, K, V> {
 ///
 /// assert_eq!(map.len(), 6);
 /// ```
-pub struct RawEntryBuilderMut<'a, K, V, S, A: Allocator + Clone = Global> {
+pub struct RawEntryBuilderMut<'a, K, V, S, A: Allocator = Global> {
     map: &'a mut HashMap<K, V, S, A>,
 }
 
@@ -2879,7 +2939,7 @@ pub struct RawEntryBuilderMut<'a, K, V, S, A: Allocator + Clone = Global> {
 /// vec.sort_unstable();
 /// assert_eq!(vec, [('a', 10), ('b', 20), ('c', 30), ('d', 40), ('e', 50), ('f', 60)]);
 /// ```
-pub enum RawEntryMut<'a, K, V, S, A: Allocator + Clone = Global> {
+pub enum RawEntryMut<'a, K, V, S, A: Allocator = Global> {
     /// An occupied entry.
     ///
     /// # Examples
@@ -2970,7 +3030,7 @@ pub enum RawEntryMut<'a, K, V, S, A: Allocator + Clone = Global> {
 /// assert_eq!(map.get(&"b"), None);
 /// assert_eq!(map.len(), 1);
 /// ```
-pub struct RawOccupiedEntryMut<'a, K, V, S, A: Allocator + Clone = Global> {
+pub struct RawOccupiedEntryMut<'a, K, V, S, A: Allocator = Global> {
     elem: Bucket<(K, V)>,
     table: &'a mut RawTable<(K, V), A>,
     hash_builder: &'a S,
@@ -2981,7 +3041,7 @@ where
     K: Send,
     V: Send,
     S: Send,
-    A: Send + Allocator + Clone,
+    A: Send + Allocator,
 {
 }
 unsafe impl<K, V, S, A> Sync for RawOccupiedEntryMut<'_, K, V, S, A>
@@ -2989,7 +3049,7 @@ where
     K: Sync,
     V: Sync,
     S: Sync,
-    A: Sync + Allocator + Clone,
+    A: Sync + Allocator,
 {
 }
 
@@ -3041,7 +3101,7 @@ where
 /// }
 /// assert!(map[&"c"] == 30 && map.len() == 3);
 /// ```
-pub struct RawVacantEntryMut<'a, K, V, S, A: Allocator + Clone = Global> {
+pub struct RawVacantEntryMut<'a, K, V, S, A: Allocator = Global> {
     table: &'a mut RawTable<(K, V), A>,
     hash_builder: &'a S,
 }
@@ -3080,11 +3140,11 @@ pub struct RawVacantEntryMut<'a, K, V, S, A: Allocator + Clone = Global> {
 ///     assert_eq!(map.raw_entry().from_key_hashed_nocheck(hash, &k), kv);
 /// }
 /// ```
-pub struct RawEntryBuilder<'a, K, V, S, A: Allocator + Clone = Global> {
+pub struct RawEntryBuilder<'a, K, V, S, A: Allocator = Global> {
     map: &'a HashMap<K, V, S, A>,
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilderMut<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> RawEntryBuilderMut<'a, K, V, S, A> {
     /// Creates a `RawEntryMut` from the given key.
     ///
     /// # Examples
@@ -3103,10 +3163,9 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilderMut<'a, K, V, S, A> {
     pub fn from_key<Q: ?Sized>(self, k: &Q) -> RawEntryMut<'a, K, V, S, A>
     where
         S: BuildHasher,
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
-        let hash = make_hash::<K, Q, S>(&self.map.hash_builder, k);
+        let hash = make_hash::<Q, S>(&self.map.hash_builder, k);
         self.from_key_hashed_nocheck(hash, k)
     }
 
@@ -3136,14 +3195,13 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilderMut<'a, K, V, S, A> {
     #[allow(clippy::wrong_self_convention)]
     pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> RawEntryMut<'a, K, V, S, A>
     where
-        K: Borrow<Q>,
-        Q: Eq,
+        Q: Equivalent<K>,
     {
         self.from_hash(hash, equivalent(k))
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilderMut<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> RawEntryBuilderMut<'a, K, V, S, A> {
     /// Creates a `RawEntryMut` from the given hash and matching function.
     ///
     /// # Examples
@@ -3194,7 +3252,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilderMut<'a, K, V, S, A> {
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilder<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> RawEntryBuilder<'a, K, V, S, A> {
     /// Access an immutable entry by key.
     ///
     /// # Examples
@@ -3211,10 +3269,9 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilder<'a, K, V, S, A> {
     pub fn from_key<Q: ?Sized>(self, k: &Q) -> Option<(&'a K, &'a V)>
     where
         S: BuildHasher,
-        K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<K>,
     {
-        let hash = make_hash::<K, Q, S>(&self.map.hash_builder, k);
+        let hash = make_hash::<Q, S>(&self.map.hash_builder, k);
         self.from_key_hashed_nocheck(hash, k)
     }
 
@@ -3242,8 +3299,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilder<'a, K, V, S, A> {
     #[allow(clippy::wrong_self_convention)]
     pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> Option<(&'a K, &'a V)>
     where
-        K: Borrow<Q>,
-        Q: Eq,
+        Q: Equivalent<K>,
     {
         self.from_hash(hash, equivalent(k))
     }
@@ -3254,7 +3310,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilder<'a, K, V, S, A> {
         F: FnMut(&K) -> bool,
     {
         match self.map.table.get(hash, |(k, _)| is_match(k)) {
-            Some(&(ref key, ref value)) => Some((key, value)),
+            Some((key, value)) => Some((key, value)),
             None => None,
         }
     }
@@ -3289,7 +3345,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryBuilder<'a, K, V, S, A> {
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> RawEntryMut<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> RawEntryMut<'a, K, V, S, A> {
     /// Sets the value of the entry, and returns a RawOccupiedEntryMut.
     ///
     /// # Examples
@@ -3483,7 +3539,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawEntryMut<'a, K, V, S, A> {
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> RawOccupiedEntryMut<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> RawOccupiedEntryMut<'a, K, V, S, A> {
     /// Gets a reference to the key in the entry.
     ///
     /// # Examples
@@ -3650,7 +3706,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawOccupiedEntryMut<'a, K, V, S, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn get_key_value(&self) -> (&K, &V) {
         unsafe {
-            let &(ref key, ref value) = self.elem.as_ref();
+            let (key, value) = self.elem.as_ref();
             (key, value)
         }
     }
@@ -3822,7 +3878,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawOccupiedEntryMut<'a, K, V, S, A> {
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove_entry(self) -> (K, V) {
-        unsafe { self.table.remove(self.elem) }
+        unsafe { self.table.remove(self.elem).0 }
     }
 
     /// Provides shared access to the key and owned access to the value of
@@ -3882,7 +3938,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawOccupiedEntryMut<'a, K, V, S, A> {
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> RawVacantEntryMut<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> RawVacantEntryMut<'a, K, V, S, A> {
     /// Sets the value of the entry with the VacantEntry's key,
     /// and returns a mutable reference to it.
     ///
@@ -3906,7 +3962,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawVacantEntryMut<'a, K, V, S, A> {
         K: Hash,
         S: BuildHasher,
     {
-        let hash = make_insert_hash::<K, S>(self.hash_builder, &key);
+        let hash = make_hash::<K, S>(self.hash_builder, &key);
         self.insert_hashed_nocheck(hash, key, value)
     }
 
@@ -3950,7 +4006,7 @@ impl<'a, K, V, S, A: Allocator + Clone> RawVacantEntryMut<'a, K, V, S, A> {
         let &mut (ref mut k, ref mut v) = self.table.insert_entry(
             hash,
             (key, value),
-            make_hasher::<K, _, V, S>(self.hash_builder),
+            make_hasher::<_, V, S>(self.hash_builder),
         );
         (k, v)
     }
@@ -4014,11 +4070,11 @@ impl<'a, K, V, S, A: Allocator + Clone> RawVacantEntryMut<'a, K, V, S, A> {
         K: Hash,
         S: BuildHasher,
     {
-        let hash = make_insert_hash::<K, S>(self.hash_builder, &key);
+        let hash = make_hash::<K, S>(self.hash_builder, &key);
         let elem = self.table.insert(
             hash,
             (key, value),
-            make_hasher::<K, _, V, S>(self.hash_builder),
+            make_hasher::<_, V, S>(self.hash_builder),
         );
         RawOccupiedEntryMut {
             elem,
@@ -4028,13 +4084,13 @@ impl<'a, K, V, S, A: Allocator + Clone> RawVacantEntryMut<'a, K, V, S, A> {
     }
 }
 
-impl<K, V, S, A: Allocator + Clone> Debug for RawEntryBuilderMut<'_, K, V, S, A> {
+impl<K, V, S, A: Allocator> Debug for RawEntryBuilderMut<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("RawEntryBuilder").finish()
     }
 }
 
-impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for RawEntryMut<'_, K, V, S, A> {
+impl<K: Debug, V: Debug, S, A: Allocator> Debug for RawEntryMut<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             RawEntryMut::Vacant(ref v) => f.debug_tuple("RawEntry").field(v).finish(),
@@ -4043,7 +4099,7 @@ impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for RawEntryMut<'_, K, V
     }
 }
 
-impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for RawOccupiedEntryMut<'_, K, V, S, A> {
+impl<K: Debug, V: Debug, S, A: Allocator> Debug for RawOccupiedEntryMut<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("RawOccupiedEntryMut")
             .field("key", self.key())
@@ -4052,13 +4108,13 @@ impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for RawOccupiedEntryMut<
     }
 }
 
-impl<K, V, S, A: Allocator + Clone> Debug for RawVacantEntryMut<'_, K, V, S, A> {
+impl<K, V, S, A: Allocator> Debug for RawVacantEntryMut<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("RawVacantEntryMut").finish()
     }
 }
 
-impl<K, V, S, A: Allocator + Clone> Debug for RawEntryBuilder<'_, K, V, S, A> {
+impl<K, V, S, A: Allocator> Debug for RawEntryBuilder<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("RawEntryBuilder").finish()
     }
@@ -4109,7 +4165,7 @@ impl<K, V, S, A: Allocator + Clone> Debug for RawEntryBuilder<'_, K, V, S, A> {
 /// ```
 pub enum Entry<'a, K, V, S, A = Global>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// An occupied entry.
     ///
@@ -4142,7 +4198,7 @@ where
     Vacant(VacantEntry<'a, K, V, S, A>),
 }
 
-impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for Entry<'_, K, V, S, A> {
+impl<K: Debug, V: Debug, S, A: Allocator> Debug for Entry<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Entry::Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
@@ -4191,7 +4247,7 @@ impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for Entry<'_, K, V, S, A
 /// assert_eq!(map.get(&"c"), None);
 /// assert_eq!(map.len(), 2);
 /// ```
-pub struct OccupiedEntry<'a, K, V, S, A: Allocator + Clone = Global> {
+pub struct OccupiedEntry<'a, K, V, S = DefaultHashBuilder, A: Allocator = Global> {
     hash: u64,
     key: Option<K>,
     elem: Bucket<(K, V)>,
@@ -4203,7 +4259,7 @@ where
     K: Send,
     V: Send,
     S: Send,
-    A: Send + Allocator + Clone,
+    A: Send + Allocator,
 {
 }
 unsafe impl<K, V, S, A> Sync for OccupiedEntry<'_, K, V, S, A>
@@ -4211,11 +4267,11 @@ where
     K: Sync,
     V: Sync,
     S: Sync,
-    A: Sync + Allocator + Clone,
+    A: Sync + Allocator,
 {
 }
 
-impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for OccupiedEntry<'_, K, V, S, A> {
+impl<K: Debug, V: Debug, S, A: Allocator> Debug for OccupiedEntry<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("OccupiedEntry")
             .field("key", self.key())
@@ -4254,13 +4310,13 @@ impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for OccupiedEntry<'_, K,
 /// }
 /// assert!(map[&"b"] == 20 && map.len() == 2);
 /// ```
-pub struct VacantEntry<'a, K, V, S, A: Allocator + Clone = Global> {
+pub struct VacantEntry<'a, K, V, S = DefaultHashBuilder, A: Allocator = Global> {
     hash: u64,
     key: K,
     table: &'a mut HashMap<K, V, S, A>,
 }
 
-impl<K: Debug, V, S, A: Allocator + Clone> Debug for VacantEntry<'_, K, V, S, A> {
+impl<K: Debug, V, S, A: Allocator> Debug for VacantEntry<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("VacantEntry").field(self.key()).finish()
     }
@@ -4320,7 +4376,7 @@ impl<K: Debug, V, S, A: Allocator + Clone> Debug for VacantEntry<'_, K, V, S, A>
 /// ```
 pub enum EntryRef<'a, 'b, K, Q: ?Sized, V, S, A = Global>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// An occupied entry.
     ///
@@ -4353,7 +4409,7 @@ where
     Vacant(VacantEntryRef<'a, 'b, K, Q, V, S, A>),
 }
 
-impl<K: Borrow<Q>, Q: ?Sized + Debug, V: Debug, S, A: Allocator + Clone> Debug
+impl<K: Borrow<Q>, Q: ?Sized + Debug, V: Debug, S, A: Allocator> Debug
     for EntryRef<'_, '_, K, Q, V, S, A>
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -4431,7 +4487,7 @@ impl<'a, K: Borrow<Q>, Q: ?Sized> AsRef<Q> for KeyOrRef<'a, K, Q> {
 /// assert_eq!(map.get("c"), None);
 /// assert_eq!(map.len(), 2);
 /// ```
-pub struct OccupiedEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone = Global> {
+pub struct OccupiedEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator = Global> {
     hash: u64,
     key: Option<KeyOrRef<'b, K, Q>>,
     elem: Bucket<(K, V)>,
@@ -4444,7 +4500,7 @@ where
     Q: Sync + ?Sized,
     V: Send,
     S: Send,
-    A: Send + Allocator + Clone,
+    A: Send + Allocator,
 {
 }
 unsafe impl<'a, 'b, K, Q, V, S, A> Sync for OccupiedEntryRef<'a, 'b, K, Q, V, S, A>
@@ -4453,16 +4509,16 @@ where
     Q: Sync + ?Sized,
     V: Sync,
     S: Sync,
-    A: Sync + Allocator + Clone,
+    A: Sync + Allocator,
 {
 }
 
-impl<K: Borrow<Q>, Q: ?Sized + Debug, V: Debug, S, A: Allocator + Clone> Debug
+impl<K: Borrow<Q>, Q: ?Sized + Debug, V: Debug, S, A: Allocator> Debug
     for OccupiedEntryRef<'_, '_, K, Q, V, S, A>
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("OccupiedEntryRef")
-            .field("key", &self.key())
+            .field("key", &self.key().borrow())
             .field("value", &self.get())
             .finish()
     }
@@ -4498,13 +4554,13 @@ impl<K: Borrow<Q>, Q: ?Sized + Debug, V: Debug, S, A: Allocator + Clone> Debug
 /// }
 /// assert!(map["b"] == 20 && map.len() == 2);
 /// ```
-pub struct VacantEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone = Global> {
+pub struct VacantEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator = Global> {
     hash: u64,
     key: KeyOrRef<'b, K, Q>,
     table: &'a mut HashMap<K, V, S, A>,
 }
 
-impl<K: Borrow<Q>, Q: ?Sized + Debug, V, S, A: Allocator + Clone> Debug
+impl<K: Borrow<Q>, Q: ?Sized + Debug, V, S, A: Allocator> Debug
     for VacantEntryRef<'_, '_, K, Q, V, S, A>
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -4536,14 +4592,14 @@ impl<K: Borrow<Q>, Q: ?Sized + Debug, V, S, A: Allocator + Clone> Debug
 /// }
 /// assert_eq!(map[&"a"], 100);
 /// ```
-pub struct OccupiedError<'a, K, V, S, A: Allocator + Clone = Global> {
+pub struct OccupiedError<'a, K, V, S, A: Allocator = Global> {
     /// The entry in the map that was already occupied.
     pub entry: OccupiedEntry<'a, K, V, S, A>,
     /// The value which was not inserted, because the entry was already occupied.
     pub value: V,
 }
 
-impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for OccupiedError<'_, K, V, S, A> {
+impl<K: Debug, V: Debug, S, A: Allocator> Debug for OccupiedError<'_, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("OccupiedError")
             .field("key", self.entry.key())
@@ -4553,9 +4609,7 @@ impl<K: Debug, V: Debug, S, A: Allocator + Clone> Debug for OccupiedError<'_, K,
     }
 }
 
-impl<'a, K: Debug, V: Debug, S, A: Allocator + Clone> fmt::Display
-    for OccupiedError<'a, K, V, S, A>
-{
+impl<'a, K: Debug, V: Debug, S, A: Allocator> fmt::Display for OccupiedError<'a, K, V, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
@@ -4567,7 +4621,7 @@ impl<'a, K: Debug, V: Debug, S, A: Allocator + Clone> fmt::Display
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> IntoIterator for &'a HashMap<K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> IntoIterator for &'a HashMap<K, V, S, A> {
     type Item = (&'a K, &'a V);
     type IntoIter = Iter<'a, K, V>;
 
@@ -4599,7 +4653,7 @@ impl<'a, K, V, S, A: Allocator + Clone> IntoIterator for &'a HashMap<K, V, S, A>
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> IntoIterator for &'a mut HashMap<K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> IntoIterator for &'a mut HashMap<K, V, S, A> {
     type Item = (&'a K, &'a mut V);
     type IntoIter = IterMut<'a, K, V>;
 
@@ -4636,7 +4690,7 @@ impl<'a, K, V, S, A: Allocator + Clone> IntoIterator for &'a mut HashMap<K, V, S
     }
 }
 
-impl<K, V, S, A: Allocator + Clone> IntoIterator for HashMap<K, V, S, A> {
+impl<K, V, S, A: Allocator> IntoIterator for HashMap<K, V, S, A> {
     type Item = (K, V);
     type IntoIter = IntoIter<K, V, A>;
 
@@ -4684,6 +4738,17 @@ impl<'a, K, V> Iterator for Iter<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, |acc, x| unsafe {
+            let (k, v) = x.as_ref();
+            f(acc, (k, v))
+        })
+    }
 }
 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
     #[cfg_attr(feature = "inline-more", inline)]
@@ -4712,6 +4777,17 @@ impl<'a, K, V> Iterator for IterMut<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, |acc, x| unsafe {
+            let (k, v) = x.as_mut();
+            f(acc, (k, v))
+        })
+    }
 }
 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
     #[cfg_attr(feature = "inline-more", inline)]
@@ -4731,7 +4807,7 @@ where
     }
 }
 
-impl<K, V, A: Allocator + Clone> Iterator for IntoIter<K, V, A> {
+impl<K, V, A: Allocator> Iterator for IntoIter<K, V, A> {
     type Item = (K, V);
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -4742,16 +4818,24 @@ impl<K, V, A: Allocator + Clone> Iterator for IntoIter<K, V, A> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, f)
+    }
 }
-impl<K, V, A: Allocator + Clone> ExactSizeIterator for IntoIter<K, V, A> {
+impl<K, V, A: Allocator> ExactSizeIterator for IntoIter<K, V, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn len(&self) -> usize {
         self.inner.len()
     }
 }
-impl<K, V, A: Allocator + Clone> FusedIterator for IntoIter<K, V, A> {}
+impl<K, V, A: Allocator> FusedIterator for IntoIter<K, V, A> {}
 
-impl<K: Debug, V: Debug, A: Allocator + Clone> fmt::Debug for IntoIter<K, V, A> {
+impl<K: Debug, V: Debug, A: Allocator> fmt::Debug for IntoIter<K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self.iter()).finish()
     }
@@ -4772,6 +4856,14 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, |acc, (k, _)| f(acc, k))
+    }
 }
 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
     #[cfg_attr(feature = "inline-more", inline)]
@@ -4796,6 +4888,14 @@ impl<'a, K, V> Iterator for Values<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, |acc, (_, v)| f(acc, v))
+    }
 }
 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
     #[cfg_attr(feature = "inline-more", inline)]
@@ -4820,6 +4920,14 @@ impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, |acc, (_, v)| f(acc, v))
+    }
 }
 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
     #[cfg_attr(feature = "inline-more", inline)]
@@ -4837,7 +4945,7 @@ impl<K, V: Debug> fmt::Debug for ValuesMut<'_, K, V> {
     }
 }
 
-impl<'a, K, V, A: Allocator + Clone> Iterator for Drain<'a, K, V, A> {
+impl<'a, K, V, A: Allocator> Iterator for Drain<'a, K, V, A> {
     type Item = (K, V);
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -4848,27 +4956,35 @@ impl<'a, K, V, A: Allocator + Clone> Iterator for Drain<'a, K, V, A> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, f)
+    }
 }
-impl<K, V, A: Allocator + Clone> ExactSizeIterator for Drain<'_, K, V, A> {
+impl<K, V, A: Allocator> ExactSizeIterator for Drain<'_, K, V, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn len(&self) -> usize {
         self.inner.len()
     }
 }
-impl<K, V, A: Allocator + Clone> FusedIterator for Drain<'_, K, V, A> {}
+impl<K, V, A: Allocator> FusedIterator for Drain<'_, K, V, A> {}
 
 impl<K, V, A> fmt::Debug for Drain<'_, K, V, A>
 where
     K: fmt::Debug,
     V: fmt::Debug,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self.iter()).finish()
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> Entry<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> Entry<'a, K, V, S, A> {
     /// Sets the value of the entry, and returns an OccupiedEntry.
     ///
     /// # Examples
@@ -5115,7 +5231,7 @@ impl<'a, K, V, S, A: Allocator + Clone> Entry<'a, K, V, S, A> {
     }
 }
 
-impl<'a, K, V: Default, S, A: Allocator + Clone> Entry<'a, K, V, S, A> {
+impl<'a, K, V: Default, S, A: Allocator> Entry<'a, K, V, S, A> {
     /// Ensures a value is in the entry by inserting the default value if empty,
     /// and returns a mutable reference to the value in the entry.
     ///
@@ -5148,7 +5264,7 @@ impl<'a, K, V: Default, S, A: Allocator + Clone> Entry<'a, K, V, S, A> {
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> OccupiedEntry<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> OccupiedEntry<'a, K, V, S, A> {
     /// Gets a reference to the key in the entry.
     ///
     /// # Examples
@@ -5183,7 +5299,6 @@ impl<'a, K, V, S, A: Allocator + Clone> OccupiedEntry<'a, K, V, S, A> {
     /// assert!(map.is_empty() && map.capacity() == 0);
     ///
     /// map.entry("poneyland").or_insert(12);
-    /// let capacity_before_remove = map.capacity();
     ///
     /// if let Entry::Occupied(o) = map.entry("poneyland") {
     ///     // We delete the entry from the map.
@@ -5191,12 +5306,12 @@ impl<'a, K, V, S, A: Allocator + Clone> OccupiedEntry<'a, K, V, S, A> {
     /// }
     ///
     /// assert_eq!(map.contains_key("poneyland"), false);
-    /// // Now map hold none elements but capacity is equal to the old one
-    /// assert!(map.len() == 0 && map.capacity() == capacity_before_remove);
+    /// // Now map hold none elements
+    /// assert!(map.is_empty());
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove_entry(self) -> (K, V) {
-        unsafe { self.table.table.remove(self.elem) }
+        unsafe { self.table.table.remove(self.elem).0 }
     }
 
     /// Gets a reference to the value in the entry.
@@ -5319,15 +5434,14 @@ impl<'a, K, V, S, A: Allocator + Clone> OccupiedEntry<'a, K, V, S, A> {
     /// assert!(map.is_empty() && map.capacity() == 0);
     ///
     /// map.entry("poneyland").or_insert(12);
-    /// let capacity_before_remove = map.capacity();
     ///
     /// if let Entry::Occupied(o) = map.entry("poneyland") {
     ///     assert_eq!(o.remove(), 12);
     /// }
     ///
     /// assert_eq!(map.contains_key("poneyland"), false);
-    /// // Now map hold none elements but capacity is equal to the old one
-    /// assert!(map.len() == 0 && map.capacity() == capacity_before_remove);
+    /// // Now map hold none elements
+    /// assert!(map.is_empty());
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove(self) -> V {
@@ -5505,7 +5619,7 @@ impl<'a, K, V, S, A: Allocator + Clone> OccupiedEntry<'a, K, V, S, A> {
     }
 }
 
-impl<'a, K, V, S, A: Allocator + Clone> VacantEntry<'a, K, V, S, A> {
+impl<'a, K, V, S, A: Allocator> VacantEntry<'a, K, V, S, A> {
     /// Gets a reference to the key that would be used when inserting a value
     /// through the `VacantEntry`.
     ///
@@ -5567,7 +5681,7 @@ impl<'a, K, V, S, A: Allocator + Clone> VacantEntry<'a, K, V, S, A> {
         let entry = table.insert_entry(
             self.hash,
             (self.key, value),
-            make_hasher::<K, _, V, S>(&self.table.hash_builder),
+            make_hasher::<_, V, S>(&self.table.hash_builder),
         );
         &mut entry.1
     }
@@ -5581,7 +5695,7 @@ impl<'a, K, V, S, A: Allocator + Clone> VacantEntry<'a, K, V, S, A> {
         let elem = self.table.table.insert(
             self.hash,
             (self.key, value),
-            make_hasher::<K, _, V, S>(&self.table.hash_builder),
+            make_hasher::<_, V, S>(&self.table.hash_builder),
         );
         OccupiedEntry {
             hash: self.hash,
@@ -5592,7 +5706,7 @@ impl<'a, K, V, S, A: Allocator + Clone> VacantEntry<'a, K, V, S, A> {
     }
 }
 
-impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V, S, A> {
+impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> EntryRef<'a, 'b, K, Q, V, S, A> {
     /// Sets the value of the entry, and returns an OccupiedEntryRef.
     ///
     /// # Examples
@@ -5682,10 +5796,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V,
 
     /// Ensures a value is in the entry by inserting, if empty, the result of the default function.
     /// This method allows for generating key-derived values for insertion by providing the default
-    /// function a reference to the key that was moved during the `.entry_ref(key)` method call.
-    ///
-    /// The reference to the moved key is provided so that cloning or copying the key is
-    /// unnecessary, unlike with `.or_insert_with(|| ... )`.
+    /// function an access to the borrower form of the key.
     ///
     /// # Examples
     ///
@@ -5737,7 +5848,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V,
         K: Borrow<Q>,
     {
         match *self {
-            EntryRef::Occupied(ref entry) => entry.key(),
+            EntryRef::Occupied(ref entry) => entry.key().borrow(),
             EntryRef::Vacant(ref entry) => entry.key(),
         }
     }
@@ -5833,8 +5944,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V,
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn and_replace_entry_with<F>(self, f: F) -> Self
     where
-        F: FnOnce(&Q, V) -> Option<V>,
-        K: Borrow<Q>,
+        F: FnOnce(&K, V) -> Option<V>,
     {
         match self {
             EntryRef::Occupied(entry) => entry.replace_entry_with(f),
@@ -5843,7 +5953,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V,
     }
 }
 
-impl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V, S, A> {
+impl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator> EntryRef<'a, 'b, K, Q, V, S, A> {
     /// Ensures a value is in the entry by inserting the default value if empty,
     /// and returns a mutable reference to the value in the entry.
     ///
@@ -5876,7 +5986,7 @@ impl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator + Clone> EntryRef<'a, 'b,
     }
 }
 
-impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b, K, Q, V, S, A> {
+impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> OccupiedEntryRef<'a, 'b, K, Q, V, S, A> {
     /// Gets a reference to the key in the entry.
     ///
     /// # Examples
@@ -5893,11 +6003,8 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     /// }
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
-    pub fn key(&self) -> &Q
-    where
-        K: Borrow<Q>,
-    {
-        unsafe { &self.elem.as_ref().0 }.borrow()
+    pub fn key(&self) -> &K {
+        unsafe { &self.elem.as_ref().0 }
     }
 
     /// Take the ownership of the key and value from the map.
@@ -5914,7 +6021,6 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     /// assert!(map.is_empty() && map.capacity() == 0);
     ///
     /// map.entry_ref("poneyland").or_insert(12);
-    /// let capacity_before_remove = map.capacity();
     ///
     /// if let EntryRef::Occupied(o) = map.entry_ref("poneyland") {
     ///     // We delete the entry from the map.
@@ -5923,11 +6029,11 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     ///
     /// assert_eq!(map.contains_key("poneyland"), false);
     /// // Now map hold none elements but capacity is equal to the old one
-    /// assert!(map.len() == 0 && map.capacity() == capacity_before_remove);
+    /// assert!(map.is_empty());
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove_entry(self) -> (K, V) {
-        unsafe { self.table.table.remove(self.elem) }
+        unsafe { self.table.table.remove(self.elem).0 }
     }
 
     /// Gets a reference to the value in the entry.
@@ -6048,7 +6154,6 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     /// assert!(map.is_empty() && map.capacity() == 0);
     ///
     /// map.entry_ref("poneyland").or_insert(12);
-    /// let capacity_before_remove = map.capacity();
     ///
     /// if let EntryRef::Occupied(o) = map.entry_ref("poneyland") {
     ///     assert_eq!(o.remove(), 12);
@@ -6056,7 +6161,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     ///
     /// assert_eq!(map.contains_key("poneyland"), false);
     /// // Now map hold none elements but capacity is equal to the old one
-    /// assert!(map.len() == 0 && map.capacity() == capacity_before_remove);
+    /// assert!(map.is_empty());
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove(self) -> V {
@@ -6068,7 +6173,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     ///
     /// # Panics
     ///
-    /// Will panic if this OccupiedEntry was created through [`EntryRef::insert`].
+    /// Will panic if this OccupiedEntryRef was created through [`EntryRef::insert`].
     ///
     /// # Examples
     ///
@@ -6110,7 +6215,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     ///
     /// # Panics
     ///
-    /// Will panic if this OccupiedEntry was created through [`Entry::insert`].
+    /// Will panic if this OccupiedEntryRef was created through [`EntryRef::insert`].
     ///
     /// # Examples
     ///
@@ -6138,7 +6243,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     /// fn reclaim_memory(map: &mut HashMap<Rc<str>, usize>, keys: &[Rc<str>]) {
     ///     for key in keys {
     ///         if let EntryRef::Occupied(entry) = map.entry_ref(key.as_ref()) {
-    ///         /// Replaces the entry's key with our version of it in `keys`.
+    ///             // Replaces the entry's key with our version of it in `keys`.
     ///             entry.replace_key();
     ///         }
     ///     }
@@ -6204,8 +6309,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn replace_entry_with<F>(self, f: F) -> EntryRef<'a, 'b, K, Q, V, S, A>
     where
-        F: FnOnce(&Q, V) -> Option<V>,
-        K: Borrow<Q>,
+        F: FnOnce(&K, V) -> Option<V>,
     {
         unsafe {
             let mut spare_key = None;
@@ -6213,7 +6317,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
             self.table
                 .table
                 .replace_bucket_with(self.elem.clone(), |(key, value)| {
-                    if let Some(new_value) = f(key.borrow(), value) {
+                    if let Some(new_value) = f(&key, value) {
                         Some((key, new_value))
                     } else {
                         spare_key = Some(KeyOrRef::Owned(key));
@@ -6234,7 +6338,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b,
     }
 }
 
-impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> VacantEntryRef<'a, 'b, K, Q, V, S, A> {
+impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'a, 'b, K, Q, V, S, A> {
     /// Gets a reference to the key that would be used when inserting a value
     /// through the `VacantEntryRef`.
     ///
@@ -6305,7 +6409,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> VacantEntryRef<'a, 'b, K,
         let entry = table.insert_entry(
             self.hash,
             (self.key.into_owned(), value),
-            make_hasher::<K, _, V, S>(&self.table.hash_builder),
+            make_hasher::<_, V, S>(&self.table.hash_builder),
         );
         &mut entry.1
     }
@@ -6319,7 +6423,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> VacantEntryRef<'a, 'b, K,
         let elem = self.table.table.insert(
             self.hash,
             (self.key.into_owned(), value),
-            make_hasher::<K, _, V, S>(&self.table.hash_builder),
+            make_hasher::<_, V, S>(&self.table.hash_builder),
         );
         OccupiedEntryRef {
             hash: self.hash,
@@ -6334,7 +6438,7 @@ impl<K, V, S, A> FromIterator<(K, V)> for HashMap<K, V, S, A>
 where
     K: Eq + Hash,
     S: BuildHasher + Default,
-    A: Default + Allocator + Clone,
+    A: Default + Allocator,
 {
     #[cfg_attr(feature = "inline-more", inline)]
     fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
@@ -6354,7 +6458,7 @@ impl<K, V, S, A> Extend<(K, V)> for HashMap<K, V, S, A>
 where
     K: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// Inserts all new key-values from the iterator to existing `HashMap<K, V, S, A>`.
     /// Replace values with existing keys with new values returned from the iterator.
@@ -6438,7 +6542,7 @@ where
     K: Eq + Hash + Copy,
     V: Copy,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// Inserts all new key-values from the iterator to existing `HashMap<K, V, S, A>`.
     /// Replace values with existing keys with new values returned from the iterator.
@@ -6455,17 +6559,17 @@ where
     /// map.insert(1, 100);
     ///
     /// let arr = [(1, 1), (2, 2)];
-    /// let some_iter = arr.iter().map(|&(k, v)| (k, v));
+    /// let some_iter = arr.iter().map(|(k, v)| (k, v));
     /// map.extend(some_iter);
     /// // Replace values with existing keys with new values returned from the iterator.
     /// // So that the map.get(&1) doesn't return Some(&100).
     /// assert_eq!(map.get(&1), Some(&1));
     ///
     /// let some_vec: Vec<_> = vec![(3, 3), (4, 4)];
-    /// map.extend(some_vec.iter().map(|&(k, v)| (k, v)));
+    /// map.extend(some_vec.iter().map(|(k, v)| (k, v)));
     ///
     /// let some_arr = [(5, 5), (6, 6)];
-    /// map.extend(some_arr.iter().map(|&(k, v)| (k, v)));
+    /// map.extend(some_arr.iter().map(|(k, v)| (k, v)));
     ///
     /// // You can also extend from another HashMap
     /// let mut new_map = HashMap::new();
@@ -6503,7 +6607,7 @@ where
     K: Eq + Hash + Copy,
     V: Copy,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// Inserts all new key-values from the iterator to existing `HashMap<K, V, S, A>`.
     /// Replace values with existing keys with new values returned from the iterator.
@@ -6570,12 +6674,12 @@ fn assert_covariance() {
     fn iter_val<'a, 'new>(v: Iter<'a, u8, &'static str>) -> Iter<'a, u8, &'new str> {
         v
     }
-    fn into_iter_key<'new, A: Allocator + Clone>(
+    fn into_iter_key<'new, A: Allocator>(
         v: IntoIter<&'static str, u8, A>,
     ) -> IntoIter<&'new str, u8, A> {
         v
     }
-    fn into_iter_val<'new, A: Allocator + Clone>(
+    fn into_iter_val<'new, A: Allocator>(
         v: IntoIter<u8, &'static str, A>,
     ) -> IntoIter<u8, &'new str, A> {
         v
@@ -6605,6 +6709,12 @@ mod test_map {
     use super::Entry::{Occupied, Vacant};
     use super::EntryRef;
     use super::{HashMap, RawEntryMut};
+    use alloc::string::{String, ToString};
+    use alloc::sync::Arc;
+    use allocator_api2::alloc::{AllocError, Allocator, Global};
+    use core::alloc::Layout;
+    use core::ptr::NonNull;
+    use core::sync::atomic::{AtomicI8, Ordering};
     use rand::{rngs::SmallRng, Rng, SeedableRng};
     use std::borrow::ToOwned;
     use std::cell::RefCell;
@@ -6695,7 +6805,7 @@ mod test_map {
         assert_eq!(m2.len(), 2);
     }
 
-    thread_local! { static DROP_VECTOR: RefCell<Vec<i32>> = RefCell::new(Vec::new()) }
+    thread_local! { static DROP_VECTOR: RefCell<Vec<i32>> = const { RefCell::new(Vec::new()) } }
 
     #[derive(Hash, PartialEq, Eq)]
     struct Droppable {
@@ -6827,7 +6937,6 @@ mod test_map {
                 }
             });
 
-            #[allow(clippy::let_underscore_drop)] // kind-of a false positive
             for _ in half.by_ref() {}
 
             DROP_VECTOR.with(|v| {
@@ -7155,10 +7264,10 @@ mod test_map {
         map.insert(1, 2);
         map.insert(3, 4);
 
-        let map_str = format!("{:?}", map);
+        let map_str = format!("{map:?}");
 
         assert!(map_str == "{1: 2, 3: 4}" || map_str == "{3: 4, 1: 2}");
-        assert_eq!(format!("{:?}", empty), "{}");
+        assert_eq!(format!("{empty:?}"), "{}");
     }
 
     #[test]
@@ -7474,7 +7583,7 @@ mod test_map {
                               // Test for #19292
         fn check(m: &HashMap<i32, ()>) {
             for k in m.keys() {
-                assert!(m.contains_key(k), "{} is in keys() but not in the map?", k);
+                assert!(m.contains_key(k), "{k} is in keys() but not in the map?");
             }
         }
 
@@ -7510,7 +7619,7 @@ mod test_map {
                               // Test for #19292
         fn check(m: &HashMap<std::string::String, ()>) {
             for k in m.keys() {
-                assert!(m.contains_key(k), "{} is in keys() but not in the map?", k);
+                assert!(m.contains_key(k), "{k} is in keys() but not in the map?");
             }
         }
 
@@ -7559,6 +7668,7 @@ mod test_map {
     }
 
     #[test]
+    #[allow(clippy::needless_borrow)]
     fn test_extend_ref_kv_tuple() {
         use std::ops::AddAssign;
         let mut a = HashMap::new();
@@ -7580,7 +7690,7 @@ mod test_map {
         let vec: Vec<_> = (100..200).map(|i| (i, i)).collect();
         a.extend(iter);
         a.extend(&vec);
-        a.extend(&create_arr::<i32, 100>(200, 1));
+        a.extend(create_arr::<i32, 100>(200, 1));
 
         assert_eq!(a.len(), 300);
 
@@ -7981,7 +8091,7 @@ mod test_map {
                               // Test for #19292
         fn check(m: &HashMap<i32, ()>) {
             for k in m.keys() {
-                assert!(m.contains_key(k), "{} is in keys() but not in the map?", k);
+                assert!(m.contains_key(k), "{k} is in keys() but not in the map?");
             }
         }
 
@@ -8011,7 +8121,7 @@ mod test_map {
                               // Test for #19292
         fn check(m: &HashMap<std::string::String, ()>) {
             for k in m.keys() {
-                assert!(m.contains_key(k), "{} is in keys() but not in the map?", k);
+                assert!(m.contains_key(k), "{k} is in keys() but not in the map?");
             }
         }
 
@@ -8049,10 +8159,10 @@ mod test_map {
     }
 
     #[test]
-    fn test_drain_filter() {
+    fn test_extract_if() {
         {
             let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x * 10)).collect();
-            let drained = map.drain_filter(|&k, _| k % 2 == 0);
+            let drained = map.extract_if(|&k, _| k % 2 == 0);
             let mut out = drained.collect::<Vec<_>>();
             out.sort_unstable();
             assert_eq!(vec![(0, 0), (2, 20), (4, 40), (6, 60)], out);
@@ -8060,7 +8170,7 @@ mod test_map {
         }
         {
             let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x * 10)).collect();
-            drop(map.drain_filter(|&k, _| k % 2 == 0));
+            map.extract_if(|&k, _| k % 2 == 0).for_each(drop);
             assert_eq!(map.len(), 4);
         }
     }
@@ -8070,27 +8180,32 @@ mod test_map {
     fn test_try_reserve() {
         use crate::TryReserveError::{AllocError, CapacityOverflow};
 
-        const MAX_USIZE: usize = usize::MAX;
+        const MAX_ISIZE: usize = isize::MAX as usize;
 
         let mut empty_bytes: HashMap<u8, u8> = HashMap::new();
 
-        if let Err(CapacityOverflow) = empty_bytes.try_reserve(MAX_USIZE) {
+        if let Err(CapacityOverflow) = empty_bytes.try_reserve(usize::MAX) {
         } else {
             panic!("usize::MAX should trigger an overflow!");
         }
 
-        if let Err(AllocError { .. }) = empty_bytes.try_reserve(MAX_USIZE / 16) {
+        if let Err(CapacityOverflow) = empty_bytes.try_reserve(MAX_ISIZE) {
+        } else {
+            panic!("isize::MAX should trigger an overflow!");
+        }
+
+        if let Err(AllocError { .. }) = empty_bytes.try_reserve(MAX_ISIZE / 5) {
         } else {
             // This may succeed if there is enough free memory. Attempt to
             // allocate a few more hashmaps to ensure the allocation will fail.
             let mut empty_bytes2: HashMap<u8, u8> = HashMap::new();
-            let _ = empty_bytes2.try_reserve(MAX_USIZE / 16);
+            let _ = empty_bytes2.try_reserve(MAX_ISIZE / 5);
             let mut empty_bytes3: HashMap<u8, u8> = HashMap::new();
-            let _ = empty_bytes3.try_reserve(MAX_USIZE / 16);
+            let _ = empty_bytes3.try_reserve(MAX_ISIZE / 5);
             let mut empty_bytes4: HashMap<u8, u8> = HashMap::new();
-            if let Err(AllocError { .. }) = empty_bytes4.try_reserve(MAX_USIZE / 16) {
+            if let Err(AllocError { .. }) = empty_bytes4.try_reserve(MAX_ISIZE / 5) {
             } else {
-                panic!("usize::MAX / 8 should trigger an OOM!");
+                panic!("isize::MAX / 5 should trigger an OOM!");
             }
         }
     }
@@ -8104,7 +8219,7 @@ mod test_map {
         let mut map: HashMap<_, _> = xs.iter().copied().collect();
 
         let compute_hash = |map: &HashMap<i32, i32>, k: i32| -> u64 {
-            super::make_insert_hash::<i32, _>(map.hasher(), &k)
+            super::make_hash::<i32, _>(map.hasher(), &k)
         };
 
         // Existing key (insert)
@@ -8266,21 +8381,21 @@ mod test_map {
             loop {
                 // occasionally remove some elements
                 if i < n && rng.gen_bool(0.1) {
-                    let hash_value = super::make_insert_hash(&hash_builder, &i);
+                    let hash_value = super::make_hash(&hash_builder, &i);
 
                     unsafe {
                         let e = map.table.find(hash_value, |q| q.0.eq(&i));
                         if let Some(e) = e {
                             it.reflect_remove(&e);
-                            let t = map.table.remove(e);
+                            let t = map.table.remove(e).0;
                             removed.push(t);
                             left -= 1;
                         } else {
-                            assert!(removed.contains(&(i, 2 * i)), "{} not in {:?}", i, removed);
+                            assert!(removed.contains(&(i, 2 * i)), "{i} not in {removed:?}");
                             let e = map.table.insert(
                                 hash_value,
                                 (i, 2 * i),
-                                super::make_hasher::<usize, _, usize, _>(&hash_builder),
+                                super::make_hasher::<_, usize, _>(&hash_builder),
                             );
                             it.reflect_insert(&e);
                             if let Some(p) = removed.iter().position(|e| e == &(i, 2 * i)) {
@@ -8405,4 +8520,441 @@ mod test_map {
 
         map2.clone_from(&map1);
     }
+
+    #[test]
+    #[should_panic = "panic in clone"]
+    fn test_clone_from_memory_leaks() {
+        use alloc::vec::Vec;
+
+        struct CheckedClone {
+            panic_in_clone: bool,
+            need_drop: Vec<i32>,
+        }
+        impl Clone for CheckedClone {
+            fn clone(&self) -> Self {
+                if self.panic_in_clone {
+                    panic!("panic in clone")
+                }
+                Self {
+                    panic_in_clone: self.panic_in_clone,
+                    need_drop: self.need_drop.clone(),
+                }
+            }
+        }
+        let mut map1 = HashMap::new();
+        map1.insert(
+            1,
+            CheckedClone {
+                panic_in_clone: false,
+                need_drop: vec![0, 1, 2],
+            },
+        );
+        map1.insert(
+            2,
+            CheckedClone {
+                panic_in_clone: false,
+                need_drop: vec![3, 4, 5],
+            },
+        );
+        map1.insert(
+            3,
+            CheckedClone {
+                panic_in_clone: true,
+                need_drop: vec![6, 7, 8],
+            },
+        );
+        let _map2 = map1.clone();
+    }
+
+    struct MyAllocInner {
+        drop_count: Arc<AtomicI8>,
+    }
+
+    #[derive(Clone)]
+    struct MyAlloc {
+        _inner: Arc<MyAllocInner>,
+    }
+
+    impl MyAlloc {
+        fn new(drop_count: Arc<AtomicI8>) -> Self {
+            MyAlloc {
+                _inner: Arc::new(MyAllocInner { drop_count }),
+            }
+        }
+    }
+
+    impl Drop for MyAllocInner {
+        fn drop(&mut self) {
+            println!("MyAlloc freed.");
+            self.drop_count.fetch_sub(1, Ordering::SeqCst);
+        }
+    }
+
+    unsafe impl Allocator for MyAlloc {
+        fn allocate(&self, layout: Layout) -> std::result::Result<NonNull<[u8]>, AllocError> {
+            let g = Global;
+            g.allocate(layout)
+        }
+
+        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+            let g = Global;
+            g.deallocate(ptr, layout)
+        }
+    }
+
+    #[test]
+    fn test_hashmap_into_iter_bug() {
+        let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(1));
+
+        {
+            let mut map = HashMap::with_capacity_in(10, MyAlloc::new(dropped.clone()));
+            for i in 0..10 {
+                map.entry(i).or_insert_with(|| "i".to_string());
+            }
+
+            for (k, v) in map {
+                println!("{}, {}", k, v);
+            }
+        }
+
+        // All allocator clones should already be dropped.
+        assert_eq!(dropped.load(Ordering::SeqCst), 0);
+    }
+
+    #[derive(Debug)]
+    struct CheckedCloneDrop<T> {
+        panic_in_clone: bool,
+        panic_in_drop: bool,
+        dropped: bool,
+        data: T,
+    }
+
+    impl<T> CheckedCloneDrop<T> {
+        fn new(panic_in_clone: bool, panic_in_drop: bool, data: T) -> Self {
+            CheckedCloneDrop {
+                panic_in_clone,
+                panic_in_drop,
+                dropped: false,
+                data,
+            }
+        }
+    }
+
+    impl<T: Clone> Clone for CheckedCloneDrop<T> {
+        fn clone(&self) -> Self {
+            if self.panic_in_clone {
+                panic!("panic in clone")
+            }
+            Self {
+                panic_in_clone: self.panic_in_clone,
+                panic_in_drop: self.panic_in_drop,
+                dropped: self.dropped,
+                data: self.data.clone(),
+            }
+        }
+    }
+
+    impl<T> Drop for CheckedCloneDrop<T> {
+        fn drop(&mut self) {
+            if self.panic_in_drop {
+                self.dropped = true;
+                panic!("panic in drop");
+            }
+            if self.dropped {
+                panic!("double drop");
+            }
+            self.dropped = true;
+        }
+    }
+
+    /// Return hashmap with predefined distribution of elements.
+    /// All elements will be located in the same order as elements
+    /// returned by iterator.
+    ///
+    /// This function does not panic, but returns an error as a `String`
+    /// to distinguish between a test panic and an error in the input data.
+    fn get_test_map<I, T, A>(
+        iter: I,
+        mut fun: impl FnMut(u64) -> T,
+        alloc: A,
+    ) -> Result<HashMap<u64, CheckedCloneDrop<T>, DefaultHashBuilder, A>, String>
+    where
+        I: Iterator<Item = (bool, bool)> + Clone + ExactSizeIterator,
+        A: Allocator,
+        T: PartialEq + core::fmt::Debug,
+    {
+        use crate::scopeguard::guard;
+
+        let mut map: HashMap<u64, CheckedCloneDrop<T>, _, A> =
+            HashMap::with_capacity_in(iter.size_hint().0, alloc);
+        {
+            let mut guard = guard(&mut map, |map| {
+                for (_, value) in map.iter_mut() {
+                    value.panic_in_drop = false
+                }
+            });
+
+            let mut count = 0;
+            // Hash and Key must be equal to each other for controlling the elements placement.
+            for (panic_in_clone, panic_in_drop) in iter.clone() {
+                if core::mem::needs_drop::<T>() && panic_in_drop {
+                    return Err(String::from(
+                        "panic_in_drop can be set with a type that doesn't need to be dropped",
+                    ));
+                }
+                guard.table.insert(
+                    count,
+                    (
+                        count,
+                        CheckedCloneDrop::new(panic_in_clone, panic_in_drop, fun(count)),
+                    ),
+                    |(k, _)| *k,
+                );
+                count += 1;
+            }
+
+            // Let's check that all elements are located as we wanted
+            let mut check_count = 0;
+            for ((key, value), (panic_in_clone, panic_in_drop)) in guard.iter().zip(iter) {
+                if *key != check_count {
+                    return Err(format!(
+                        "key != check_count,\nkey: `{}`,\ncheck_count: `{}`",
+                        key, check_count
+                    ));
+                }
+                if value.dropped
+                    || value.panic_in_clone != panic_in_clone
+                    || value.panic_in_drop != panic_in_drop
+                    || value.data != fun(check_count)
+                {
+                    return Err(format!(
+                        "Value is not equal to expected,\nvalue: `{:?}`,\nexpected: \
+                        `CheckedCloneDrop {{ panic_in_clone: {}, panic_in_drop: {}, dropped: {}, data: {:?} }}`",
+                        value, panic_in_clone, panic_in_drop, false, fun(check_count)
+                    ));
+                }
+                check_count += 1;
+            }
+
+            if guard.len() != check_count as usize {
+                return Err(format!(
+                    "map.len() != check_count,\nmap.len(): `{}`,\ncheck_count: `{}`",
+                    guard.len(),
+                    check_count
+                ));
+            }
+
+            if count != check_count {
+                return Err(format!(
+                    "count != check_count,\ncount: `{}`,\ncheck_count: `{}`",
+                    count, check_count
+                ));
+            }
+            core::mem::forget(guard);
+        }
+        Ok(map)
+    }
+
+    const DISARMED: bool = false;
+    const ARMED: bool = true;
+
+    const ARMED_FLAGS: [bool; 8] = [
+        DISARMED, DISARMED, DISARMED, ARMED, DISARMED, DISARMED, DISARMED, DISARMED,
+    ];
+
+    const DISARMED_FLAGS: [bool; 8] = [
+        DISARMED, DISARMED, DISARMED, DISARMED, DISARMED, DISARMED, DISARMED, DISARMED,
+    ];
+
+    #[test]
+    #[should_panic = "panic in clone"]
+    fn test_clone_memory_leaks_and_double_drop_one() {
+        let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(2));
+
+        {
+            assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
+
+            let map: HashMap<u64, CheckedCloneDrop<Vec<u64>>, DefaultHashBuilder, MyAlloc> =
+                match get_test_map(
+                    ARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
+                    |n| vec![n],
+                    MyAlloc::new(dropped.clone()),
+                ) {
+                    Ok(map) => map,
+                    Err(msg) => panic!("{msg}"),
+                };
+
+            // Clone should normally clone a few elements, and then (when the
+            // clone function panics), deallocate both its own memory, memory
+            // of `dropped: Arc<AtomicI8>` and the memory of already cloned
+            // elements (Vec<i32> memory inside CheckedCloneDrop).
+            let _map2 = map.clone();
+        }
+    }
+
+    #[test]
+    #[should_panic = "panic in drop"]
+    fn test_clone_memory_leaks_and_double_drop_two() {
+        let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(2));
+
+        {
+            assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
+
+            let map: HashMap<u64, CheckedCloneDrop<u64>, DefaultHashBuilder, _> = match get_test_map(
+                DISARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
+                |n| n,
+                MyAlloc::new(dropped.clone()),
+            ) {
+                Ok(map) => map,
+                Err(msg) => panic!("{msg}"),
+            };
+
+            let mut map2 = match get_test_map(
+                DISARMED_FLAGS.into_iter().zip(ARMED_FLAGS),
+                |n| n,
+                MyAlloc::new(dropped.clone()),
+            ) {
+                Ok(map) => map,
+                Err(msg) => panic!("{msg}"),
+            };
+
+            // The `clone_from` should try to drop the elements of `map2` without
+            // double drop and leaking the allocator. Elements that have not been
+            // dropped leak their memory.
+            map2.clone_from(&map);
+        }
+    }
+
+    /// We check that we have a working table if the clone operation from another
+    /// thread ended in a panic (when buckets of maps are equal to each other).
+    #[test]
+    fn test_catch_panic_clone_from_when_len_is_equal() {
+        use std::thread;
+
+        let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(2));
+
+        {
+            assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
+
+            let mut map = match get_test_map(
+                DISARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
+                |n| vec![n],
+                MyAlloc::new(dropped.clone()),
+            ) {
+                Ok(map) => map,
+                Err(msg) => panic!("{msg}"),
+            };
+
+            thread::scope(|s| {
+                let result: thread::ScopedJoinHandle<'_, String> = s.spawn(|| {
+                    let scope_map =
+                        match get_test_map(ARMED_FLAGS.into_iter().zip(DISARMED_FLAGS), |n| vec![n * 2], MyAlloc::new(dropped.clone())) {
+                            Ok(map) => map,
+                            Err(msg) => return msg,
+                        };
+                    if map.table.buckets() != scope_map.table.buckets() {
+                        return format!(
+                            "map.table.buckets() != scope_map.table.buckets(),\nleft: `{}`,\nright: `{}`",
+                            map.table.buckets(), scope_map.table.buckets()
+                        );
+                    }
+                    map.clone_from(&scope_map);
+                    "We must fail the cloning!!!".to_owned()
+                });
+                if let Ok(msg) = result.join() {
+                    panic!("{msg}")
+                }
+            });
+
+            // Let's check that all iterators work fine and do not return elements
+            // (especially `RawIterRange`, which does not depend on the number of
+            // elements in the table, but looks directly at the control bytes)
+            //
+            // SAFETY: We know for sure that `RawTable` will outlive
+            // the returned `RawIter / RawIterRange` iterator.
+            assert_eq!(map.len(), 0);
+            assert_eq!(map.iter().count(), 0);
+            assert_eq!(unsafe { map.table.iter().count() }, 0);
+            assert_eq!(unsafe { map.table.iter().iter.count() }, 0);
+
+            for idx in 0..map.table.buckets() {
+                let idx = idx as u64;
+                assert!(
+                    map.table.find(idx, |(k, _)| *k == idx).is_none(),
+                    "Index: {idx}"
+                );
+            }
+        }
+
+        // All allocator clones should already be dropped.
+        assert_eq!(dropped.load(Ordering::SeqCst), 0);
+    }
+
+    /// We check that we have a working table if the clone operation from another
+    /// thread ended in a panic (when buckets of maps are not equal to each other).
+    #[test]
+    fn test_catch_panic_clone_from_when_len_is_not_equal() {
+        use std::thread;
+
+        let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(2));
+
+        {
+            assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
+
+            let mut map = match get_test_map(
+                [DISARMED].into_iter().zip([DISARMED]),
+                |n| vec![n],
+                MyAlloc::new(dropped.clone()),
+            ) {
+                Ok(map) => map,
+                Err(msg) => panic!("{msg}"),
+            };
+
+            thread::scope(|s| {
+                let result: thread::ScopedJoinHandle<'_, String> = s.spawn(|| {
+                    let scope_map = match get_test_map(
+                        ARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
+                        |n| vec![n * 2],
+                        MyAlloc::new(dropped.clone()),
+                    ) {
+                        Ok(map) => map,
+                        Err(msg) => return msg,
+                    };
+                    if map.table.buckets() == scope_map.table.buckets() {
+                        return format!(
+                            "map.table.buckets() == scope_map.table.buckets(): `{}`",
+                            map.table.buckets()
+                        );
+                    }
+                    map.clone_from(&scope_map);
+                    "We must fail the cloning!!!".to_owned()
+                });
+                if let Ok(msg) = result.join() {
+                    panic!("{msg}")
+                }
+            });
+
+            // Let's check that all iterators work fine and do not return elements
+            // (especially `RawIterRange`, which does not depend on the number of
+            // elements in the table, but looks directly at the control bytes)
+            //
+            // SAFETY: We know for sure that `RawTable` will outlive
+            // the returned `RawIter / RawIterRange` iterator.
+            assert_eq!(map.len(), 0);
+            assert_eq!(map.iter().count(), 0);
+            assert_eq!(unsafe { map.table.iter().count() }, 0);
+            assert_eq!(unsafe { map.table.iter().iter.count() }, 0);
+
+            for idx in 0..map.table.buckets() {
+                let idx = idx as u64;
+                assert!(
+                    map.table.find(idx, |(k, _)| *k == idx).is_none(),
+                    "Index: {idx}"
+                );
+            }
+        }
+
+        // All allocator clones should already be dropped.
+        assert_eq!(dropped.load(Ordering::SeqCst), 0);
+    }
 }
diff --git a/third_party/rust/hashbrown/src/raw/alloc.rs b/third_party/rust/hashbrown/src/raw/alloc.rs
index ba09ea9de7..15299e7b09 100644
--- a/third_party/rust/hashbrown/src/raw/alloc.rs
+++ b/third_party/rust/hashbrown/src/raw/alloc.rs
@@ -1,5 +1,9 @@
 pub(crate) use self::inner::{do_alloc, Allocator, Global};
 
+// Nightly-case.
+// Use unstable `allocator_api` feature.
+// This is compatible with `allocator-api2` which can be enabled or not.
+// This is used when building for `std`.
 #[cfg(feature = "nightly")]
 mod inner {
     use crate::alloc::alloc::Layout;
@@ -7,28 +11,44 @@ mod inner {
     use core::ptr::NonNull;
 
     #[allow(clippy::map_err_ignore)]
-    pub fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
+    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
         match alloc.allocate(layout) {
             Ok(ptr) => Ok(ptr.as_non_null_ptr()),
             Err(_) => Err(()),
         }
     }
+}
 
-    #[cfg(feature = "bumpalo")]
-    unsafe impl Allocator for crate::BumpWrapper<'_> {
-        #[inline]
-        fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, core::alloc::AllocError> {
-            match self.0.try_alloc_layout(layout) {
-                Ok(ptr) => Ok(NonNull::slice_from_raw_parts(ptr, layout.size())),
-                Err(_) => Err(core::alloc::AllocError),
-            }
+// Basic non-nightly case.
+// This uses `allocator-api2` enabled by default.
+// If any crate enables "nightly" in `allocator-api2`,
+// this will be equivalent to the nightly case,
+// since `allocator_api2::alloc::Allocator` would be re-export of
+// `core::alloc::Allocator`.
+#[cfg(all(not(feature = "nightly"), feature = "allocator-api2"))]
+mod inner {
+    use crate::alloc::alloc::Layout;
+    pub use allocator_api2::alloc::{Allocator, Global};
+    use core::ptr::NonNull;
+
+    #[allow(clippy::map_err_ignore)]
+    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
+        match alloc.allocate(layout) {
+            Ok(ptr) => Ok(ptr.cast()),
+            Err(_) => Err(()),
         }
-        #[inline]
-        unsafe fn deallocate(&self, _ptr: NonNull<u8>, _layout: Layout) {}
     }
 }
 
-#[cfg(not(feature = "nightly"))]
+// No-defaults case.
+// When building with default-features turned off and
+// neither `nightly` nor `allocator-api2` is enabled,
+// this will be used.
+// Making it impossible to use any custom allocator with collections defined
+// in this crate.
+// Any crate in build-tree can enable `allocator-api2`,
+// or `nightly` without disturbing users that don't want to use it.
+#[cfg(not(any(feature = "nightly", feature = "allocator-api2")))]
 mod inner {
     use crate::alloc::alloc::{alloc, dealloc, Layout};
     use core::ptr::NonNull;
@@ -41,6 +61,7 @@ mod inner {
 
     #[derive(Copy, Clone)]
     pub struct Global;
+
     unsafe impl Allocator for Global {
         #[inline]
         fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, ()> {
@@ -51,6 +72,7 @@ mod inner {
             dealloc(ptr.as_ptr(), layout);
         }
     }
+
     impl Default for Global {
         #[inline]
         fn default() -> Self {
@@ -58,16 +80,7 @@ mod inner {
         }
     }
 
-    pub fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
+    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
         alloc.allocate(layout)
     }
-
-    #[cfg(feature = "bumpalo")]
-    unsafe impl Allocator for crate::BumpWrapper<'_> {
-        #[allow(clippy::map_err_ignore)]
-        fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, ()> {
-            self.0.try_alloc_layout(layout).map_err(|_| ())
-        }
-        unsafe fn deallocate(&self, _ptr: NonNull<u8>, _layout: Layout) {}
-    }
 }
diff --git a/third_party/rust/hashbrown/src/raw/bitmask.rs b/third_party/rust/hashbrown/src/raw/bitmask.rs
index 7d4f9fc387..6576b3c5c0 100644
--- a/third_party/rust/hashbrown/src/raw/bitmask.rs
+++ b/third_party/rust/hashbrown/src/raw/bitmask.rs
@@ -1,6 +1,6 @@
-use super::imp::{BitMaskWord, BITMASK_MASK, BITMASK_STRIDE};
-#[cfg(feature = "nightly")]
-use core::intrinsics;
+use super::imp::{
+    BitMaskWord, NonZeroBitMaskWord, BITMASK_ITER_MASK, BITMASK_MASK, BITMASK_STRIDE,
+};
 
 /// A bit mask which contains the result of a `Match` operation on a `Group` and
 /// allows iterating through them.
@@ -8,75 +8,55 @@ use core::intrinsics;
 /// The bit mask is arranged so that low-order bits represent lower memory
 /// addresses for group match results.
 ///
-/// For implementation reasons, the bits in the set may be sparsely packed, so
-/// that there is only one bit-per-byte used (the high bit, 7). If this is the
+/// For implementation reasons, the bits in the set may be sparsely packed with
+/// groups of 8 bits representing one element. If any of these bits are non-zero
+/// then this element is considered to true in the mask. If this is the
 /// case, `BITMASK_STRIDE` will be 8 to indicate a divide-by-8 should be
 /// performed on counts/indices to normalize this difference. `BITMASK_MASK` is
 /// similarly a mask of all the actually-used bits.
+///
+/// To iterate over a bit mask, it must be converted to a form where only 1 bit
+/// is set per element. This is done by applying `BITMASK_ITER_MASK` on the
+/// mask bits.
 #[derive(Copy, Clone)]
-pub struct BitMask(pub BitMaskWord);
+pub(crate) struct BitMask(pub(crate) BitMaskWord);
 
 #[allow(clippy::use_self)]
 impl BitMask {
     /// Returns a new `BitMask` with all bits inverted.
     #[inline]
     #[must_use]
-    pub fn invert(self) -> Self {
+    #[allow(dead_code)]
+    pub(crate) fn invert(self) -> Self {
         BitMask(self.0 ^ BITMASK_MASK)
     }
 
-    /// Flip the bit in the mask for the entry at the given index.
-    ///
-    /// Returns the bit's previous state.
-    #[inline]
-    #[allow(clippy::cast_ptr_alignment)]
-    #[cfg(feature = "raw")]
-    pub unsafe fn flip(&mut self, index: usize) -> bool {
-        // NOTE: The + BITMASK_STRIDE - 1 is to set the high bit.
-        let mask = 1 << (index * BITMASK_STRIDE + BITMASK_STRIDE - 1);
-        self.0 ^= mask;
-        // The bit was set if the bit is now 0.
-        self.0 & mask == 0
-    }
-
     /// Returns a new `BitMask` with the lowest bit removed.
     #[inline]
     #[must_use]
-    pub fn remove_lowest_bit(self) -> Self {
+    fn remove_lowest_bit(self) -> Self {
         BitMask(self.0 & (self.0 - 1))
     }
+
     /// Returns whether the `BitMask` has at least one set bit.
     #[inline]
-    pub fn any_bit_set(self) -> bool {
+    pub(crate) fn any_bit_set(self) -> bool {
         self.0 != 0
     }
 
     /// Returns the first set bit in the `BitMask`, if there is one.
     #[inline]
-    pub fn lowest_set_bit(self) -> Option<usize> {
-        if self.0 == 0 {
-            None
+    pub(crate) fn lowest_set_bit(self) -> Option<usize> {
+        if let Some(nonzero) = NonZeroBitMaskWord::new(self.0) {
+            Some(Self::nonzero_trailing_zeros(nonzero))
         } else {
-            Some(unsafe { self.lowest_set_bit_nonzero() })
+            None
         }
     }
 
-    /// Returns the first set bit in the `BitMask`, if there is one. The
-    /// bitmask must not be empty.
-    #[inline]
-    #[cfg(feature = "nightly")]
-    pub unsafe fn lowest_set_bit_nonzero(self) -> usize {
-        intrinsics::cttz_nonzero(self.0) as usize / BITMASK_STRIDE
-    }
-    #[inline]
-    #[cfg(not(feature = "nightly"))]
-    pub unsafe fn lowest_set_bit_nonzero(self) -> usize {
-        self.trailing_zeros()
-    }
-
     /// Returns the number of trailing zeroes in the `BitMask`.
     #[inline]
-    pub fn trailing_zeros(self) -> usize {
+    pub(crate) fn trailing_zeros(self) -> usize {
         // ARM doesn't have a trailing_zeroes instruction, and instead uses
         // reverse_bits (RBIT) + leading_zeroes (CLZ). However older ARM
         // versions (pre-ARMv7) don't have RBIT and need to emulate it
@@ -89,9 +69,21 @@ impl BitMask {
         }
     }
 
+    /// Same as above but takes a `NonZeroBitMaskWord`.
+    #[inline]
+    fn nonzero_trailing_zeros(nonzero: NonZeroBitMaskWord) -> usize {
+        if cfg!(target_arch = "arm") && BITMASK_STRIDE % 8 == 0 {
+            // SAFETY: A byte-swapped non-zero value is still non-zero.
+            let swapped = unsafe { NonZeroBitMaskWord::new_unchecked(nonzero.get().swap_bytes()) };
+            swapped.leading_zeros() as usize / BITMASK_STRIDE
+        } else {
+            nonzero.trailing_zeros() as usize / BITMASK_STRIDE
+        }
+    }
+
     /// Returns the number of leading zeroes in the `BitMask`.
     #[inline]
-    pub fn leading_zeros(self) -> usize {
+    pub(crate) fn leading_zeros(self) -> usize {
         self.0.leading_zeros() as usize / BITMASK_STRIDE
     }
 }
@@ -102,13 +94,32 @@ impl IntoIterator for BitMask {
 
     #[inline]
     fn into_iter(self) -> BitMaskIter {
-        BitMaskIter(self)
+        // A BitMask only requires each element (group of bits) to be non-zero.
+        // However for iteration we need each element to only contain 1 bit.
+        BitMaskIter(BitMask(self.0 & BITMASK_ITER_MASK))
     }
 }
 
 /// Iterator over the contents of a `BitMask`, returning the indices of set
 /// bits.
-pub struct BitMaskIter(BitMask);
+#[derive(Copy, Clone)]
+pub(crate) struct BitMaskIter(pub(crate) BitMask);
+
+impl BitMaskIter {
+    /// Flip the bit in the mask for the entry at the given index.
+    ///
+    /// Returns the bit's previous state.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    #[cfg(feature = "raw")]
+    pub(crate) unsafe fn flip(&mut self, index: usize) -> bool {
+        // NOTE: The + BITMASK_STRIDE - 1 is to set the high bit.
+        let mask = 1 << (index * BITMASK_STRIDE + BITMASK_STRIDE - 1);
+        self.0 .0 ^= mask;
+        // The bit was set if the bit is now 0.
+        self.0 .0 & mask == 0
+    }
+}
 
 impl Iterator for BitMaskIter {
     type Item = usize;
diff --git a/third_party/rust/hashbrown/src/raw/generic.rs b/third_party/rust/hashbrown/src/raw/generic.rs
index b4d31e62c2..c668b0642a 100644
--- a/third_party/rust/hashbrown/src/raw/generic.rs
+++ b/third_party/rust/hashbrown/src/raw/generic.rs
@@ -5,26 +5,29 @@ use core::{mem, ptr};
 // Use the native word size as the group size. Using a 64-bit group size on
 // a 32-bit architecture will just end up being more expensive because
 // shifts and multiplies will need to be emulated.
-#[cfg(any(
-    target_pointer_width = "64",
-    target_arch = "aarch64",
-    target_arch = "x86_64",
-    target_arch = "wasm32",
-))]
-type GroupWord = u64;
-#[cfg(all(
-    target_pointer_width = "32",
-    not(target_arch = "aarch64"),
-    not(target_arch = "x86_64"),
-    not(target_arch = "wasm32"),
-))]
-type GroupWord = u32;
 
-pub type BitMaskWord = GroupWord;
-pub const BITMASK_STRIDE: usize = 8;
+cfg_if! {
+    if #[cfg(any(
+        target_pointer_width = "64",
+        target_arch = "aarch64",
+        target_arch = "x86_64",
+        target_arch = "wasm32",
+    ))] {
+        type GroupWord = u64;
+        type NonZeroGroupWord = core::num::NonZeroU64;
+    } else {
+        type GroupWord = u32;
+        type NonZeroGroupWord = core::num::NonZeroU32;
+    }
+}
+
+pub(crate) type BitMaskWord = GroupWord;
+pub(crate) type NonZeroBitMaskWord = NonZeroGroupWord;
+pub(crate) const BITMASK_STRIDE: usize = 8;
 // We only care about the highest bit of each byte for the mask.
 #[allow(clippy::cast_possible_truncation, clippy::unnecessary_cast)]
-pub const BITMASK_MASK: BitMaskWord = 0x8080_8080_8080_8080_u64 as GroupWord;
+pub(crate) const BITMASK_MASK: BitMaskWord = 0x8080_8080_8080_8080_u64 as GroupWord;
+pub(crate) const BITMASK_ITER_MASK: BitMaskWord = !0;
 
 /// Helper function to replicate a byte across a `GroupWord`.
 #[inline]
@@ -37,7 +40,7 @@ fn repeat(byte: u8) -> GroupWord {
 ///
 /// This implementation uses a word-sized integer.
 #[derive(Copy, Clone)]
-pub struct Group(GroupWord);
+pub(crate) struct Group(GroupWord);
 
 // We perform all operations in the native endianness, and convert to
 // little-endian just before creating a BitMask. The can potentially
@@ -46,14 +49,14 @@ pub struct Group(GroupWord);
 #[allow(clippy::use_self)]
 impl Group {
     /// Number of bytes in the group.
-    pub const WIDTH: usize = mem::size_of::<Self>();
+    pub(crate) const WIDTH: usize = mem::size_of::<Self>();
 
     /// Returns a full group of empty bytes, suitable for use as the initial
     /// value for an empty hash table.
     ///
     /// This is guaranteed to be aligned to the group size.
     #[inline]
-    pub const fn static_empty() -> &'static [u8; Group::WIDTH] {
+    pub(crate) const fn static_empty() -> &'static [u8; Group::WIDTH] {
         #[repr(C)]
         struct AlignedBytes {
             _align: [Group; 0],
@@ -69,7 +72,7 @@ impl Group {
     /// Loads a group of bytes starting at the given address.
     #[inline]
     #[allow(clippy::cast_ptr_alignment)] // unaligned load
-    pub unsafe fn load(ptr: *const u8) -> Self {
+    pub(crate) unsafe fn load(ptr: *const u8) -> Self {
         Group(ptr::read_unaligned(ptr.cast()))
     }
 
@@ -77,7 +80,7 @@ impl Group {
     /// aligned to `mem::align_of::<Group>()`.
     #[inline]
     #[allow(clippy::cast_ptr_alignment)]
-    pub unsafe fn load_aligned(ptr: *const u8) -> Self {
+    pub(crate) unsafe fn load_aligned(ptr: *const u8) -> Self {
         // FIXME: use align_offset once it stabilizes
         debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
         Group(ptr::read(ptr.cast()))
@@ -87,7 +90,7 @@ impl Group {
     /// aligned to `mem::align_of::<Group>()`.
     #[inline]
     #[allow(clippy::cast_ptr_alignment)]
-    pub unsafe fn store_aligned(self, ptr: *mut u8) {
+    pub(crate) unsafe fn store_aligned(self, ptr: *mut u8) {
         // FIXME: use align_offset once it stabilizes
         debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
         ptr::write(ptr.cast(), self.0);
@@ -104,7 +107,7 @@ impl Group {
     /// - This only happens if there is at least 1 true match.
     /// - The chance of this happening is very low (< 1% chance per byte).
     #[inline]
-    pub fn match_byte(self, byte: u8) -> BitMask {
+    pub(crate) fn match_byte(self, byte: u8) -> BitMask {
         // This algorithm is derived from
         // https://graphics.stanford.edu/~seander/bithacks.html##ValueInWord
         let cmp = self.0 ^ repeat(byte);
@@ -114,7 +117,7 @@ impl Group {
     /// Returns a `BitMask` indicating all bytes in the group which are
     /// `EMPTY`.
     #[inline]
-    pub fn match_empty(self) -> BitMask {
+    pub(crate) fn match_empty(self) -> BitMask {
         // If the high bit is set, then the byte must be either:
         // 1111_1111 (EMPTY) or 1000_0000 (DELETED).
         // So we can just check if the top two bits are 1 by ANDing them.
@@ -124,14 +127,14 @@ impl Group {
     /// Returns a `BitMask` indicating all bytes in the group which are
     /// `EMPTY` or `DELETED`.
     #[inline]
-    pub fn match_empty_or_deleted(self) -> BitMask {
+    pub(crate) fn match_empty_or_deleted(self) -> BitMask {
         // A byte is EMPTY or DELETED iff the high bit is set
         BitMask((self.0 & repeat(0x80)).to_le())
     }
 
     /// Returns a `BitMask` indicating all bytes in the group which are full.
     #[inline]
-    pub fn match_full(self) -> BitMask {
+    pub(crate) fn match_full(self) -> BitMask {
         self.match_empty_or_deleted().invert()
     }
 
@@ -140,7 +143,7 @@ impl Group {
     /// - `DELETED => EMPTY`
     /// - `FULL => DELETED`
     #[inline]
-    pub fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
+    pub(crate) fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
         // Map high_bit = 1 (EMPTY or DELETED) to 1111_1111
         // and high_bit = 0 (FULL) to 1000_0000
         //
diff --git a/third_party/rust/hashbrown/src/raw/mod.rs b/third_party/rust/hashbrown/src/raw/mod.rs
index 211b818a5f..c8e8e29122 100644
--- a/third_party/rust/hashbrown/src/raw/mod.rs
+++ b/third_party/rust/hashbrown/src/raw/mod.rs
@@ -4,7 +4,6 @@ use crate::TryReserveError;
 use core::iter::FusedIterator;
 use core::marker::PhantomData;
 use core::mem;
-use core::mem::ManuallyDrop;
 use core::mem::MaybeUninit;
 use core::ptr::NonNull;
 use core::{hint, ptr};
@@ -21,12 +20,21 @@ cfg_if! {
     if #[cfg(all(
         target_feature = "sse2",
         any(target_arch = "x86", target_arch = "x86_64"),
-        not(miri)
+        not(miri),
     ))] {
         mod sse2;
         use sse2 as imp;
+    } else if #[cfg(all(
+        target_arch = "aarch64",
+        target_feature = "neon",
+        // NEON intrinsics are currently broken on big-endian targets.
+        // See https://github.com/rust-lang/stdarch/issues/1484.
+        target_endian = "little",
+        not(miri),
+    ))] {
+        mod neon;
+        use neon as imp;
     } else {
-        #[path = "generic.rs"]
         mod generic;
         use generic as imp;
     }
@@ -37,36 +45,24 @@ pub(crate) use self::alloc::{do_alloc, Allocator, Global};
 
 mod bitmask;
 
-use self::bitmask::{BitMask, BitMaskIter};
+use self::bitmask::BitMaskIter;
 use self::imp::Group;
 
 // Branch prediction hint. This is currently only available on nightly but it
 // consistently improves performance by 10-15%.
+#[cfg(not(feature = "nightly"))]
+use core::convert::identity as likely;
+#[cfg(not(feature = "nightly"))]
+use core::convert::identity as unlikely;
 #[cfg(feature = "nightly")]
 use core::intrinsics::{likely, unlikely};
 
-// On stable we can use #[cold] to get a equivalent effect: this attributes
-// suggests that the function is unlikely to be called
-#[cfg(not(feature = "nightly"))]
-#[inline]
-#[cold]
-fn cold() {}
-
-#[cfg(not(feature = "nightly"))]
-#[inline]
-fn likely(b: bool) -> bool {
-    if !b {
-        cold();
-    }
-    b
-}
-#[cfg(not(feature = "nightly"))]
-#[inline]
-fn unlikely(b: bool) -> bool {
-    if b {
-        cold();
-    }
-    b
+// FIXME: use strict provenance functions once they are stable.
+// Implement it with a transmute for now.
+#[inline(always)]
+#[allow(clippy::useless_transmute)] // clippy is wrong, cast and transmute are different here
+fn invalid_mut<T>(addr: usize) -> *mut T {
+    unsafe { core::mem::transmute(addr) }
 }
 
 #[inline]
@@ -101,6 +97,13 @@ impl Fallibility {
     }
 }
 
+trait SizedTypeProperties: Sized {
+    const IS_ZERO_SIZED: bool = mem::size_of::<Self>() == 0;
+    const NEEDS_DROP: bool = mem::needs_drop::<Self>();
+}
+
+impl<T> SizedTypeProperties for T {}
+
 /// Control byte value for an empty bucket.
 const EMPTY: u8 = 0b1111_1111;
 
@@ -134,6 +137,13 @@ fn h1(hash: u64) -> usize {
     hash as usize
 }
 
+// Constant for h2 function that grabing the top 7 bits of the hash.
+const MIN_HASH_LEN: usize = if mem::size_of::<usize>() < mem::size_of::<u64>() {
+    mem::size_of::<usize>()
+} else {
+    mem::size_of::<u64>()
+};
+
 /// Secondary hash function, saved in the low 7 bits of the control byte.
 #[inline]
 #[allow(clippy::cast_possible_truncation)]
@@ -141,8 +151,8 @@ fn h2(hash: u64) -> u8 {
     // Grab the top 7 bits of the hash. While the hash is normally a full 64-bit
     // value, some hash functions (such as FxHash) produce a usize result
     // instead, which means that the top 32 bits are 0 on 32-bit platforms.
-    let hash_len = usize::min(mem::size_of::<usize>(), mem::size_of::<u64>());
-    let top7 = hash >> (hash_len * 8 - 7);
+    // So we use MIN_HASH_LEN constant to handle this.
+    let top7 = hash >> (MIN_HASH_LEN * 8 - 7);
     (top7 & 0x7f) as u8 // truncation
 }
 
@@ -230,11 +240,15 @@ struct TableLayout {
 
 impl TableLayout {
     #[inline]
-    fn new<T>() -> Self {
+    const fn new<T>() -> Self {
         let layout = Layout::new::<T>();
         Self {
             size: layout.size(),
-            ctrl_align: usize::max(layout.align(), Group::WIDTH),
+            ctrl_align: if layout.align() > Group::WIDTH {
+                layout.align()
+            } else {
+                Group::WIDTH
+            },
         }
     }
 
@@ -248,6 +262,12 @@ impl TableLayout {
             size.checked_mul(buckets)?.checked_add(ctrl_align - 1)? & !(ctrl_align - 1);
         let len = ctrl_offset.checked_add(buckets + Group::WIDTH)?;
 
+        // We need an additional check to ensure that the allocation doesn't
+        // exceed `isize::MAX` (https://github.com/rust-lang/rust/pull/95295).
+        if len > isize::MAX as usize - (ctrl_align - 1) {
+            return None;
+        }
+
         Some((
             unsafe { Layout::from_size_align_unchecked(len, ctrl_align) },
             ctrl_offset,
@@ -255,14 +275,9 @@ impl TableLayout {
     }
 }
 
-/// Returns a Layout which describes the allocation required for a hash table,
-/// and the offset of the control bytes in the allocation.
-/// (the offset is also one past last element of buckets)
-///
-/// Returns `None` if an overflow occurs.
-#[cfg_attr(feature = "inline-more", inline)]
-fn calculate_layout<T>(buckets: usize) -> Option<(Layout, usize)> {
-    TableLayout::new::<T>().calculate_layout_for(buckets)
+/// A reference to an empty bucket into which an can be inserted.
+pub struct InsertSlot {
+    index: usize,
 }
 
 /// A reference to a hash table bucket containing a `T`.
@@ -290,11 +305,79 @@ impl<T> Clone for Bucket<T> {
 }
 
 impl<T> Bucket<T> {
+    /// Creates a [`Bucket`] that contain pointer to the data.
+    /// The pointer calculation is performed by calculating the
+    /// offset from given `base` pointer (convenience for
+    /// `base.as_ptr().sub(index)`).
+    ///
+    /// `index` is in units of `T`; e.g., an `index` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// If the `T` is a ZST, then we instead track the index of the element
+    /// in the table so that `erase` works properly (return
+    /// `NonNull::new_unchecked((index + 1) as *mut T)`)
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the safety rules are directly derived
+    /// from the safety rules for [`<*mut T>::sub`] method of `*mut T` and the safety
+    /// rules of [`NonNull::new_unchecked`] function.
+    ///
+    /// Thus, in order to uphold the safety contracts for the [`<*mut T>::sub`] method
+    /// and [`NonNull::new_unchecked`] function, as well as for the correct
+    /// logic of the work of this crate, the following rules are necessary and
+    /// sufficient:
+    ///
+    /// * the `base` pointer must not be `dangling` and must points to the
+    ///   end of the first `value element` from the `data part` of the table, i.e.
+    ///   must be the pointer that returned by [`RawTable::data_end`] or by
+    ///   [`RawTableInner::data_end<T>`];
+    ///
+    /// * `index` must not be greater than `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)`
+    ///   must be no greater than the number returned by the function
+    ///   [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// If `mem::size_of::<T>() == 0`, then the only requirement is that the
+    /// `index` must not be greater than `RawTableInner.bucket_mask`, i.e.
+    /// `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)`
+    /// must be no greater than the number returned by the function
+    /// [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// [`Bucket`]: crate::raw::Bucket
+    /// [`<*mut T>::sub`]: https://doc.rust-lang.org/core/primitive.pointer.html#method.sub-1
+    /// [`NonNull::new_unchecked`]: https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.new_unchecked
+    /// [`RawTable::data_end`]: crate::raw::RawTable::data_end
+    /// [`RawTableInner::data_end<T>`]: RawTableInner::data_end<T>
+    /// [`RawTable::buckets`]: crate::raw::RawTable::buckets
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
     #[inline]
     unsafe fn from_base_index(base: NonNull<T>, index: usize) -> Self {
-        let ptr = if mem::size_of::<T>() == 0 {
-            // won't overflow because index must be less than length
-            (index + 1) as *mut T
+        // If mem::size_of::<T>() != 0 then return a pointer to an `element` in
+        // the data part of the table (we start counting from "0", so that
+        // in the expression T[last], the "last" index actually one less than the
+        // "buckets" number in the table, i.e. "last = RawTableInner.bucket_mask"):
+        //
+        //                   `from_base_index(base, 1).as_ptr()` returns a pointer that
+        //                   points here in the data part of the table
+        //                   (to the start of T1)
+        //                        |
+        //                        |        `base: NonNull<T>` must point here
+        //                        |         (to the end of T0 or to the start of C0)
+        //                        v         v
+        // [Padding], Tlast, ..., |T1|, T0, |C0, C1, ..., Clast
+        //                           ^
+        //                           `from_base_index(base, 1)` returns a pointer
+        //                           that points here in the data part of the table
+        //                           (to the end of T1)
+        //
+        // where: T0...Tlast - our stored data; C0...Clast - control bytes
+        // or metadata for data.
+        let ptr = if T::IS_ZERO_SIZED {
+            // won't overflow because index must be less than length (bucket_mask)
+            // and bucket_mask is guaranteed to be less than `isize::MAX`
+            // (see TableLayout::calculate_layout_for method)
+            invalid_mut(index + 1)
         } else {
             base.as_ptr().sub(index)
         };
@@ -302,27 +385,183 @@ impl<T> Bucket<T> {
             ptr: NonNull::new_unchecked(ptr),
         }
     }
+
+    /// Calculates the index of a [`Bucket`] as distance between two pointers
+    /// (convenience for `base.as_ptr().offset_from(self.ptr.as_ptr()) as usize`).
+    /// The returned value is in units of T: the distance in bytes divided by
+    /// [`core::mem::size_of::<T>()`].
+    ///
+    /// If the `T` is a ZST, then we return the index of the element in
+    /// the table so that `erase` works properly (return `self.ptr.as_ptr() as usize - 1`).
+    ///
+    /// This function is the inverse of [`from_base_index`].
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the safety rules are directly derived
+    /// from the safety rules for [`<*const T>::offset_from`] method of `*const T`.
+    ///
+    /// Thus, in order to uphold the safety contracts for [`<*const T>::offset_from`]
+    /// method, as well as for the correct logic of the work of this crate, the
+    /// following rules are necessary and sufficient:
+    ///
+    /// * `base` contained pointer must not be `dangling` and must point to the
+    ///   end of the first `element` from the `data part` of the table, i.e.
+    ///   must be a pointer that returns by [`RawTable::data_end`] or by
+    ///   [`RawTableInner::data_end<T>`];
+    ///
+    /// * `self` also must not contain dangling pointer;
+    ///
+    /// * both `self` and `base` must be created from the same [`RawTable`]
+    ///   (or [`RawTableInner`]).
+    ///
+    /// If `mem::size_of::<T>() == 0`, this function is always safe.
+    ///
+    /// [`Bucket`]: crate::raw::Bucket
+    /// [`from_base_index`]: crate::raw::Bucket::from_base_index
+    /// [`RawTable::data_end`]: crate::raw::RawTable::data_end
+    /// [`RawTableInner::data_end<T>`]: RawTableInner::data_end<T>
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`RawTableInner`]: RawTableInner
+    /// [`<*const T>::offset_from`]: https://doc.rust-lang.org/nightly/core/primitive.pointer.html#method.offset_from
     #[inline]
     unsafe fn to_base_index(&self, base: NonNull<T>) -> usize {
-        if mem::size_of::<T>() == 0 {
+        // If mem::size_of::<T>() != 0 then return an index under which we used to store the
+        // `element` in the data part of the table (we start counting from "0", so
+        // that in the expression T[last], the "last" index actually is one less than the
+        // "buckets" number in the table, i.e. "last = RawTableInner.bucket_mask").
+        // For example for 5th element in table calculation is performed like this:
+        //
+        //                        mem::size_of::<T>()
+        //                          |
+        //                          |         `self = from_base_index(base, 5)` that returns pointer
+        //                          |         that points here in tha data part of the table
+        //                          |         (to the end of T5)
+        //                          |           |                    `base: NonNull<T>` must point here
+        //                          v           |                    (to the end of T0 or to the start of C0)
+        //                        /???\         v                      v
+        // [Padding], Tlast, ..., |T10|, ..., T5|, T4, T3, T2, T1, T0, |C0, C1, C2, C3, C4, C5, ..., C10, ..., Clast
+        //                                      \__________  __________/
+        //                                                 \/
+        //                                     `bucket.to_base_index(base)` = 5
+        //                                     (base.as_ptr() as usize - self.ptr.as_ptr() as usize) / mem::size_of::<T>()
+        //
+        // where: T0...Tlast - our stored data; C0...Clast - control bytes or metadata for data.
+        if T::IS_ZERO_SIZED {
+            // this can not be UB
             self.ptr.as_ptr() as usize - 1
         } else {
             offset_from(base.as_ptr(), self.ptr.as_ptr())
         }
     }
+
+    /// Acquires the underlying raw pointer `*mut T` to `data`.
+    ///
+    /// # Note
+    ///
+    /// If `T` is not [`Copy`], do not use `*mut T` methods that can cause calling the
+    /// destructor of `T` (for example the [`<*mut T>::drop_in_place`] method), because
+    /// for properly dropping the data we also need to clear `data` control bytes. If we
+    /// drop data, but do not clear `data control byte` it leads to double drop when
+    /// [`RawTable`] goes out of scope.
+    ///
+    /// If you modify an already initialized `value`, so [`Hash`] and [`Eq`] on the new
+    /// `T` value and its borrowed form *must* match those for the old `T` value, as the map
+    /// will not re-evaluate where the new value should go, meaning the value may become
+    /// "lost" if their location does not reflect their state.
+    ///
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`<*mut T>::drop_in_place`]: https://doc.rust-lang.org/core/primitive.pointer.html#method.drop_in_place
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "raw")]
+    /// # fn test() {
+    /// use core::hash::{BuildHasher, Hash};
+    /// use hashbrown::raw::{Bucket, RawTable};
+    ///
+    /// type NewHashBuilder = core::hash::BuildHasherDefault<ahash::AHasher>;
+    ///
+    /// fn make_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
+    ///     use core::hash::Hasher;
+    ///     let mut state = hash_builder.build_hasher();
+    ///     key.hash(&mut state);
+    ///     state.finish()
+    /// }
+    ///
+    /// let hash_builder = NewHashBuilder::default();
+    /// let mut table = RawTable::new();
+    ///
+    /// let value = ("a", 100);
+    /// let hash = make_hash(&hash_builder, &value.0);
+    ///
+    /// table.insert(hash, value.clone(), |val| make_hash(&hash_builder, &val.0));
+    ///
+    /// let bucket: Bucket<(&str, i32)> = table.find(hash, |(k1, _)| k1 == &value.0).unwrap();
+    ///
+    /// assert_eq!(unsafe { &*bucket.as_ptr() }, &("a", 100));
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "raw")]
+    /// #     test()
+    /// # }
+    /// ```
     #[inline]
     pub fn as_ptr(&self) -> *mut T {
-        if mem::size_of::<T>() == 0 {
+        if T::IS_ZERO_SIZED {
             // Just return an arbitrary ZST pointer which is properly aligned
-            mem::align_of::<T>() as *mut T
+            // invalid pointer is good enough for ZST
+            invalid_mut(mem::align_of::<T>())
         } else {
             unsafe { self.ptr.as_ptr().sub(1) }
         }
     }
+
+    /// Create a new [`Bucket`] that is offset from the `self` by the given
+    /// `offset`. The pointer calculation is performed by calculating the
+    /// offset from `self` pointer (convenience for `self.ptr.as_ptr().sub(offset)`).
+    /// This function is used for iterators.
+    ///
+    /// `offset` is in units of `T`; e.g., a `offset` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the safety rules are directly derived
+    /// from the safety rules for [`<*mut T>::sub`] method of `*mut T` and safety
+    /// rules of [`NonNull::new_unchecked`] function.
+    ///
+    /// Thus, in order to uphold the safety contracts for [`<*mut T>::sub`] method
+    /// and [`NonNull::new_unchecked`] function, as well as for the correct
+    /// logic of the work of this crate, the following rules are necessary and
+    /// sufficient:
+    ///
+    /// * `self` contained pointer must not be `dangling`;
+    ///
+    /// * `self.to_base_index() + ofset` must not be greater than `RawTableInner.bucket_mask`,
+    ///   i.e. `(self.to_base_index() + ofset) <= RawTableInner.bucket_mask` or, in other
+    ///   words, `self.to_base_index() + ofset + 1` must be no greater than the number returned
+    ///   by the function [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// If `mem::size_of::<T>() == 0`, then the only requirement is that the
+    /// `self.to_base_index() + ofset` must not be greater than `RawTableInner.bucket_mask`,
+    /// i.e. `(self.to_base_index() + ofset) <= RawTableInner.bucket_mask` or, in other words,
+    /// `self.to_base_index() + ofset + 1` must be no greater than the number returned by the
+    /// function [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// [`Bucket`]: crate::raw::Bucket
+    /// [`<*mut T>::sub`]: https://doc.rust-lang.org/core/primitive.pointer.html#method.sub-1
+    /// [`NonNull::new_unchecked`]: https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.new_unchecked
+    /// [`RawTable::buckets`]: crate::raw::RawTable::buckets
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
     #[inline]
     unsafe fn next_n(&self, offset: usize) -> Self {
-        let ptr = if mem::size_of::<T>() == 0 {
-            (self.ptr.as_ptr() as usize + offset) as *mut T
+        let ptr = if T::IS_ZERO_SIZED {
+            // invalid pointer is good enough for ZST
+            invalid_mut(self.ptr.as_ptr() as usize + offset)
         } else {
             self.ptr.as_ptr().sub(offset)
         };
@@ -330,26 +569,212 @@ impl<T> Bucket<T> {
             ptr: NonNull::new_unchecked(ptr),
         }
     }
+
+    /// Executes the destructor (if any) of the pointed-to `data`.
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::drop_in_place`] for safety concerns.
+    ///
+    /// You should use [`RawTable::erase`] instead of this function,
+    /// or be careful with calling this function directly, because for
+    /// properly dropping the data we need also clear `data` control bytes.
+    /// If we drop data, but do not erase `data control byte` it leads to
+    /// double drop when [`RawTable`] goes out of scope.
+    ///
+    /// [`ptr::drop_in_place`]: https://doc.rust-lang.org/core/ptr/fn.drop_in_place.html
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`RawTable::erase`]: crate::raw::RawTable::erase
     #[cfg_attr(feature = "inline-more", inline)]
-    pub unsafe fn drop(&self) {
+    pub(crate) unsafe fn drop(&self) {
         self.as_ptr().drop_in_place();
     }
+
+    /// Reads the `value` from `self` without moving it. This leaves the
+    /// memory in `self` unchanged.
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::read`] for safety concerns.
+    ///
+    /// You should use [`RawTable::remove`] instead of this function,
+    /// or be careful with calling this function directly, because compiler
+    /// calls its destructor when readed `value` goes out of scope. It
+    /// can cause double dropping when [`RawTable`] goes out of scope,
+    /// because of not erased `data control byte`.
+    ///
+    /// [`ptr::read`]: https://doc.rust-lang.org/core/ptr/fn.read.html
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`RawTable::remove`]: crate::raw::RawTable::remove
     #[inline]
-    pub unsafe fn read(&self) -> T {
+    pub(crate) unsafe fn read(&self) -> T {
         self.as_ptr().read()
     }
+
+    /// Overwrites a memory location with the given `value` without reading
+    /// or dropping the old value (like [`ptr::write`] function).
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::write`] for safety concerns.
+    ///
+    /// # Note
+    ///
+    /// [`Hash`] and [`Eq`] on the new `T` value and its borrowed form *must* match
+    /// those for the old `T` value, as the map will not re-evaluate where the new
+    /// value should go, meaning the value may become "lost" if their location
+    /// does not reflect their state.
+    ///
+    /// [`ptr::write`]: https://doc.rust-lang.org/core/ptr/fn.write.html
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
     #[inline]
-    pub unsafe fn write(&self, val: T) {
+    pub(crate) unsafe fn write(&self, val: T) {
         self.as_ptr().write(val);
     }
+
+    /// Returns a shared immutable reference to the `value`.
+    ///
+    /// # Safety
+    ///
+    /// See [`NonNull::as_ref`] for safety concerns.
+    ///
+    /// [`NonNull::as_ref`]: https://doc.rust-lang.org/core/ptr/struct.NonNull.html#method.as_ref
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "raw")]
+    /// # fn test() {
+    /// use core::hash::{BuildHasher, Hash};
+    /// use hashbrown::raw::{Bucket, RawTable};
+    ///
+    /// type NewHashBuilder = core::hash::BuildHasherDefault<ahash::AHasher>;
+    ///
+    /// fn make_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
+    ///     use core::hash::Hasher;
+    ///     let mut state = hash_builder.build_hasher();
+    ///     key.hash(&mut state);
+    ///     state.finish()
+    /// }
+    ///
+    /// let hash_builder = NewHashBuilder::default();
+    /// let mut table = RawTable::new();
+    ///
+    /// let value: (&str, String) = ("A pony", "is a small horse".to_owned());
+    /// let hash = make_hash(&hash_builder, &value.0);
+    ///
+    /// table.insert(hash, value.clone(), |val| make_hash(&hash_builder, &val.0));
+    ///
+    /// let bucket: Bucket<(&str, String)> = table.find(hash, |(k, _)| k == &value.0).unwrap();
+    ///
+    /// assert_eq!(
+    ///     unsafe { bucket.as_ref() },
+    ///     &("A pony", "is a small horse".to_owned())
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "raw")]
+    /// #     test()
+    /// # }
+    /// ```
     #[inline]
     pub unsafe fn as_ref<'a>(&self) -> &'a T {
         &*self.as_ptr()
     }
+
+    /// Returns a unique mutable reference to the `value`.
+    ///
+    /// # Safety
+    ///
+    /// See [`NonNull::as_mut`] for safety concerns.
+    ///
+    /// # Note
+    ///
+    /// [`Hash`] and [`Eq`] on the new `T` value and its borrowed form *must* match
+    /// those for the old `T` value, as the map will not re-evaluate where the new
+    /// value should go, meaning the value may become "lost" if their location
+    /// does not reflect their state.
+    ///
+    /// [`NonNull::as_mut`]: https://doc.rust-lang.org/core/ptr/struct.NonNull.html#method.as_mut
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "raw")]
+    /// # fn test() {
+    /// use core::hash::{BuildHasher, Hash};
+    /// use hashbrown::raw::{Bucket, RawTable};
+    ///
+    /// type NewHashBuilder = core::hash::BuildHasherDefault<ahash::AHasher>;
+    ///
+    /// fn make_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
+    ///     use core::hash::Hasher;
+    ///     let mut state = hash_builder.build_hasher();
+    ///     key.hash(&mut state);
+    ///     state.finish()
+    /// }
+    ///
+    /// let hash_builder = NewHashBuilder::default();
+    /// let mut table = RawTable::new();
+    ///
+    /// let value: (&str, String) = ("A pony", "is a small horse".to_owned());
+    /// let hash = make_hash(&hash_builder, &value.0);
+    ///
+    /// table.insert(hash, value.clone(), |val| make_hash(&hash_builder, &val.0));
+    ///
+    /// let bucket: Bucket<(&str, String)> = table.find(hash, |(k, _)| k == &value.0).unwrap();
+    ///
+    /// unsafe {
+    ///     bucket
+    ///         .as_mut()
+    ///         .1
+    ///         .push_str(" less than 147 cm at the withers")
+    /// };
+    /// assert_eq!(
+    ///     unsafe { bucket.as_ref() },
+    ///     &(
+    ///         "A pony",
+    ///         "is a small horse less than 147 cm at the withers".to_owned()
+    ///     )
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "raw")]
+    /// #     test()
+    /// # }
+    /// ```
     #[inline]
     pub unsafe fn as_mut<'a>(&self) -> &'a mut T {
         &mut *self.as_ptr()
     }
+
+    /// Copies `size_of<T>` bytes from `other` to `self`. The source
+    /// and destination may *not* overlap.
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::copy_nonoverlapping`] for safety concerns.
+    ///
+    /// Like [`read`], `copy_nonoverlapping` creates a bitwise copy of `T`, regardless of
+    /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using *both* the values
+    /// in the region beginning at `*self` and the region beginning at `*other` can
+    /// [violate memory safety].
+    ///
+    /// # Note
+    ///
+    /// [`Hash`] and [`Eq`] on the new `T` value and its borrowed form *must* match
+    /// those for the old `T` value, as the map will not re-evaluate where the new
+    /// value should go, meaning the value may become "lost" if their location
+    /// does not reflect their state.
+    ///
+    /// [`ptr::copy_nonoverlapping`]: https://doc.rust-lang.org/core/ptr/fn.copy_nonoverlapping.html
+    /// [`read`]: https://doc.rust-lang.org/core/ptr/fn.read.html
+    /// [violate memory safety]: https://doc.rust-lang.org/std/ptr/fn.read.html#ownership-of-the-returned-value
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
     #[cfg(feature = "raw")]
     #[inline]
     pub unsafe fn copy_from_nonoverlapping(&self, other: &Self) {
@@ -358,15 +783,16 @@ impl<T> Bucket<T> {
 }
 
 /// A raw hash table with an unsafe API.
-pub struct RawTable<T, A: Allocator + Clone = Global> {
-    table: RawTableInner<A>,
+pub struct RawTable<T, A: Allocator = Global> {
+    table: RawTableInner,
+    alloc: A,
     // Tell dropck that we own instances of T.
     marker: PhantomData<T>,
 }
 
 /// Non-generic part of `RawTable` which allows functions to be instantiated only once regardless
 /// of how many different key-value types are used.
-struct RawTableInner<A> {
+struct RawTableInner {
     // Mask to get an index from a hash value. The value is one less than the
     // number of buckets in the table.
     bucket_mask: usize,
@@ -380,8 +806,6 @@ struct RawTableInner<A> {
 
     // Number of elements in the table, only really used by len()
     items: usize,
-
-    alloc: A,
 }
 
 impl<T> RawTable<T, Global> {
@@ -393,7 +817,8 @@ impl<T> RawTable<T, Global> {
     #[inline]
     pub const fn new() -> Self {
         Self {
-            table: RawTableInner::new_in(Global),
+            table: RawTableInner::NEW,
+            alloc: Global,
             marker: PhantomData,
         }
     }
@@ -412,7 +837,9 @@ impl<T> RawTable<T, Global> {
     }
 }
 
-impl<T, A: Allocator + Clone> RawTable<T, A> {
+impl<T, A: Allocator> RawTable<T, A> {
+    const TABLE_LAYOUT: TableLayout = TableLayout::new::<T>();
+
     /// Creates a new empty hash table without allocating any memory, using the
     /// given allocator.
     ///
@@ -420,9 +847,10 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     /// leave the data pointer dangling since that bucket is never written to
     /// due to our load factor forcing us to always have at least 1 free bucket.
     #[inline]
-    pub fn new_in(alloc: A) -> Self {
+    pub const fn new_in(alloc: A) -> Self {
         Self {
-            table: RawTableInner::new_in(alloc),
+            table: RawTableInner::NEW,
+            alloc,
             marker: PhantomData,
         }
     }
@@ -440,73 +868,97 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
 
         Ok(Self {
             table: RawTableInner::new_uninitialized(
-                alloc,
-                TableLayout::new::<T>(),
+                &alloc,
+                Self::TABLE_LAYOUT,
                 buckets,
                 fallibility,
             )?,
+            alloc,
             marker: PhantomData,
         })
     }
 
-    /// Attempts to allocate a new hash table with at least enough capacity
-    /// for inserting the given number of elements without reallocating.
-    fn fallible_with_capacity(
-        alloc: A,
-        capacity: usize,
-        fallibility: Fallibility,
-    ) -> Result<Self, TryReserveError> {
+    /// Attempts to allocate a new hash table using the given allocator, with at least enough
+    /// capacity for inserting the given number of elements without reallocating.
+    #[cfg(feature = "raw")]
+    pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
         Ok(Self {
             table: RawTableInner::fallible_with_capacity(
-                alloc,
-                TableLayout::new::<T>(),
+                &alloc,
+                Self::TABLE_LAYOUT,
                 capacity,
-                fallibility,
+                Fallibility::Fallible,
             )?,
+            alloc,
             marker: PhantomData,
         })
     }
 
-    /// Attempts to allocate a new hash table using the given allocator, with at least enough
-    /// capacity for inserting the given number of elements without reallocating.
-    #[cfg(feature = "raw")]
-    pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
-        Self::fallible_with_capacity(alloc, capacity, Fallibility::Fallible)
-    }
-
     /// Allocates a new hash table using the given allocator, with at least enough capacity for
     /// inserting the given number of elements without reallocating.
     pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
-        // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
-        match Self::fallible_with_capacity(alloc, capacity, Fallibility::Infallible) {
-            Ok(capacity) => capacity,
-            Err(_) => unsafe { hint::unreachable_unchecked() },
+        Self {
+            table: RawTableInner::with_capacity(&alloc, Self::TABLE_LAYOUT, capacity),
+            alloc,
+            marker: PhantomData,
         }
     }
 
     /// Returns a reference to the underlying allocator.
     #[inline]
     pub fn allocator(&self) -> &A {
-        &self.table.alloc
+        &self.alloc
     }
 
-    /// Deallocates the table without dropping any entries.
-    #[cfg_attr(feature = "inline-more", inline)]
-    unsafe fn free_buckets(&mut self) {
-        self.table.free_buckets(TableLayout::new::<T>());
+    /// Returns pointer to one past last `data` element in the table as viewed from
+    /// the start point of the allocation.
+    ///
+    /// The caller must ensure that the `RawTable` outlives the returned [`NonNull<T>`],
+    /// otherwise using it may result in [`undefined behavior`].
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    pub fn data_end(&self) -> NonNull<T> {
+        //                        `self.table.ctrl.cast()` returns pointer that
+        //                        points here (to the end of `T0`)
+        //                          ∨
+        // [Pad], T_n, ..., T1, T0, |CT0, CT1, ..., CT_n|, CTa_0, CTa_1, ..., CTa_m
+        //                           \________  ________/
+        //                                    \/
+        //       `n = buckets - 1`, i.e. `RawTable::buckets() - 1`
+        //
+        // where: T0...T_n  - our stored data;
+        //        CT0...CT_n - control bytes or metadata for `data`.
+        //        CTa_0...CTa_m - additional control bytes, where `m = Group::WIDTH - 1` (so that the search
+        //                        with loading `Group` bytes from the heap works properly, even if the result
+        //                        of `h1(hash) & self.bucket_mask` is equal to `self.bucket_mask`). See also
+        //                        `RawTableInner::set_ctrl` function.
+        //
+        // P.S. `h1(hash) & self.bucket_mask` is the same as `hash as usize % self.buckets()` because the number
+        // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+        self.table.ctrl.cast()
     }
 
-    /// Returns pointer to one past last element of data table.
+    /// Returns pointer to start of data table.
     #[inline]
-    pub unsafe fn data_end(&self) -> NonNull<T> {
-        NonNull::new_unchecked(self.table.ctrl.as_ptr().cast())
+    #[cfg(any(feature = "raw", feature = "nightly"))]
+    pub unsafe fn data_start(&self) -> NonNull<T> {
+        NonNull::new_unchecked(self.data_end().as_ptr().wrapping_sub(self.buckets()))
     }
 
-    /// Returns pointer to start of data table.
+    /// Return the information about memory allocated by the table.
+    ///
+    /// `RawTable` allocates single memory block to store both data and metadata.
+    /// This function returns allocation size and alignment and the beginning of the area.
+    /// These are the arguments which will be passed to `dealloc` when the table is dropped.
+    ///
+    /// This function might be useful for memory profiling.
     #[inline]
-    #[cfg(feature = "nightly")]
-    pub unsafe fn data_start(&self) -> *mut T {
-        self.data_end().as_ptr().wrapping_sub(self.buckets())
+    #[cfg(feature = "raw")]
+    pub fn allocation_info(&self) -> (NonNull<u8>, Layout) {
+        // SAFETY: We use the same `table_layout` that was used to allocate
+        // this table.
+        unsafe { self.table.allocation_info_or_zero(Self::TABLE_LAYOUT) }
     }
 
     /// Returns the index of a bucket from a `Bucket`.
@@ -516,8 +968,55 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     }
 
     /// Returns a pointer to an element in the table.
+    ///
+    /// The caller must ensure that the `RawTable` outlives the returned [`Bucket<T>`],
+    /// otherwise using it may result in [`undefined behavior`].
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the caller of this function must observe the
+    /// following safety rules:
+    ///
+    /// * The table must already be allocated;
+    ///
+    /// * The `index` must not be greater than the number returned by the [`RawTable::buckets`]
+    ///   function, i.e. `(index + 1) <= self.buckets()`.
+    ///
+    /// It is safe to call this function with index of zero (`index == 0`) on a table that has
+    /// not been allocated, but using the returned [`Bucket`] results in [`undefined behavior`].
+    ///
+    /// If `mem::size_of::<T>() == 0`, then the only requirement is that the `index` must
+    /// not be greater than the number returned by the [`RawTable::buckets`] function, i.e.
+    /// `(index + 1) <= self.buckets()`.
+    ///
+    /// [`RawTable::buckets`]: RawTable::buckets
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
     pub unsafe fn bucket(&self, index: usize) -> Bucket<T> {
+        // If mem::size_of::<T>() != 0 then return a pointer to the `element` in the `data part` of the table
+        // (we start counting from "0", so that in the expression T[n], the "n" index actually one less than
+        // the "buckets" number of our `RawTable`, i.e. "n = RawTable::buckets() - 1"):
+        //
+        //           `table.bucket(3).as_ptr()` returns a pointer that points here in the `data`
+        //           part of the `RawTable`, i.e. to the start of T3 (see `Bucket::as_ptr`)
+        //                  |
+        //                  |               `base = self.data_end()` points here
+        //                  |               (to the start of CT0 or to the end of T0)
+        //                  v                 v
+        // [Pad], T_n, ..., |T3|, T2, T1, T0, |CT0, CT1, CT2, CT3, ..., CT_n, CTa_0, CTa_1, ..., CTa_m
+        //                     ^                                              \__________  __________/
+        //        `table.bucket(3)` returns a pointer that points                        \/
+        //         here in the `data` part of the `RawTable` (to              additional control bytes
+        //         the end of T3)                                              `m = Group::WIDTH - 1`
+        //
+        // where: T0...T_n  - our stored data;
+        //        CT0...CT_n - control bytes or metadata for `data`;
+        //        CTa_0...CTa_m - additional control bytes (so that the search with loading `Group` bytes from
+        //                        the heap works properly, even if the result of `h1(hash) & self.table.bucket_mask`
+        //                        is equal to `self.table.bucket_mask`). See also `RawTableInner::set_ctrl` function.
+        //
+        // P.S. `h1(hash) & self.table.bucket_mask` is the same as `hash as usize % self.buckets()` because the number
+        // of buckets is a power of two, and `self.table.bucket_mask = self.buckets() - 1`.
         debug_assert_ne!(self.table.bucket_mask, 0);
         debug_assert!(index < self.buckets());
         Bucket::from_base_index(self.data_end(), index)
@@ -525,8 +1024,7 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
 
     /// Erases an element from the table without dropping it.
     #[cfg_attr(feature = "inline-more", inline)]
-    #[deprecated(since = "0.8.1", note = "use erase or remove instead")]
-    pub unsafe fn erase_no_drop(&mut self, item: &Bucket<T>) {
+    unsafe fn erase_no_drop(&mut self, item: &Bucket<T>) {
         let index = self.bucket_index(item);
         self.table.erase(index);
     }
@@ -534,7 +1032,6 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     /// Erases an element from the table, dropping it in place.
     #[cfg_attr(feature = "inline-more", inline)]
     #[allow(clippy::needless_pass_by_value)]
-    #[allow(deprecated)]
     pub unsafe fn erase(&mut self, item: Bucket<T>) {
         // Erase the element from the table first since drop might panic.
         self.erase_no_drop(&item);
@@ -558,12 +1055,18 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     }
 
     /// Removes an element from the table, returning it.
+    ///
+    /// This also returns an `InsertSlot` pointing to the newly free bucket.
     #[cfg_attr(feature = "inline-more", inline)]
     #[allow(clippy::needless_pass_by_value)]
-    #[allow(deprecated)]
-    pub unsafe fn remove(&mut self, item: Bucket<T>) -> T {
+    pub unsafe fn remove(&mut self, item: Bucket<T>) -> (T, InsertSlot) {
         self.erase_no_drop(&item);
-        item.read()
+        (
+            item.read(),
+            InsertSlot {
+                index: self.bucket_index(&item),
+            },
+        )
     }
 
     /// Finds and removes an element from the table, returning it.
@@ -571,7 +1074,7 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     pub fn remove_entry(&mut self, hash: u64, eq: impl FnMut(&T) -> bool) -> Option<T> {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.find(hash, eq) {
-            Some(bucket) => Some(unsafe { self.remove(bucket) }),
+            Some(bucket) => Some(unsafe { self.remove(bucket).0 }),
             None => None,
         }
     }
@@ -585,18 +1088,17 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     /// Removes all elements from the table without freeing the backing memory.
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn clear(&mut self) {
+        if self.is_empty() {
+            // Special case empty table to avoid surprising O(capacity) time.
+            return;
+        }
         // Ensure that the table is reset even if one of the drops panic
         let mut self_ = guard(self, |self_| self_.clear_no_drop());
         unsafe {
-            self_.drop_elements();
-        }
-    }
-
-    unsafe fn drop_elements(&mut self) {
-        if mem::needs_drop::<T>() && !self.is_empty() {
-            for item in self.iter() {
-                item.drop();
-            }
+            // SAFETY: ScopeGuard sets to zero the `items` field of the table
+            // even in case of panic during the dropping of the elements so
+            // that there will be no double drop of the elements.
+            self_.table.drop_elements::<T>();
         }
     }
 
@@ -607,7 +1109,16 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
         // space for.
         let min_size = usize::max(self.table.items, min_size);
         if min_size == 0 {
-            *self = Self::new_in(self.table.alloc.clone());
+            let mut old_inner = mem::replace(&mut self.table, RawTableInner::NEW);
+            unsafe {
+                // SAFETY:
+                // 1. We call the function only once;
+                // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+                //    and [`TableLayout`] that were used to allocate this table.
+                // 3. If any elements' drop function panics, then there will only be a memory leak,
+                //    because we have replaced the inner table with a new one.
+                old_inner.drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+            }
             return;
         }
 
@@ -624,14 +1135,33 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
         if min_buckets < self.buckets() {
             // Fast path if the table is empty
             if self.table.items == 0 {
-                *self = Self::with_capacity_in(min_size, self.table.alloc.clone());
+                let new_inner =
+                    RawTableInner::with_capacity(&self.alloc, Self::TABLE_LAYOUT, min_size);
+                let mut old_inner = mem::replace(&mut self.table, new_inner);
+                unsafe {
+                    // SAFETY:
+                    // 1. We call the function only once;
+                    // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+                    //    and [`TableLayout`] that were used to allocate this table.
+                    // 3. If any elements' drop function panics, then there will only be a memory leak,
+                    //    because we have replaced the inner table with a new one.
+                    old_inner.drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+                }
             } else {
                 // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
-                if self
-                    .resize(min_size, hasher, Fallibility::Infallible)
-                    .is_err()
-                {
-                    unsafe { hint::unreachable_unchecked() }
+                unsafe {
+                    // SAFETY:
+                    // 1. We know for sure that `min_size >= self.table.items`.
+                    // 2. The [`RawTableInner`] must already have properly initialized control bytes since
+                    //    we will never expose RawTable::new_uninitialized in a public API.
+                    if self
+                        .resize(min_size, hasher, Fallibility::Infallible)
+                        .is_err()
+                    {
+                        // SAFETY: The result of calling the `resize` function cannot be an error
+                        // because `fallibility == Fallibility::Infallible.
+                        hint::unreachable_unchecked()
+                    }
                 }
             }
         }
@@ -641,13 +1171,18 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     /// without reallocation.
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn reserve(&mut self, additional: usize, hasher: impl Fn(&T) -> u64) {
-        if additional > self.table.growth_left {
+        if unlikely(additional > self.table.growth_left) {
             // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
-            if self
-                .reserve_rehash(additional, hasher, Fallibility::Infallible)
-                .is_err()
-            {
-                unsafe { hint::unreachable_unchecked() }
+            unsafe {
+                // SAFETY: The [`RawTableInner`] must already have properly initialized control
+                // bytes since we will never expose RawTable::new_uninitialized in a public API.
+                if self
+                    .reserve_rehash(additional, hasher, Fallibility::Infallible)
+                    .is_err()
+                {
+                    // SAFETY: All allocation errors will be caught inside `RawTableInner::reserve_rehash`.
+                    hint::unreachable_unchecked()
+                }
             }
         }
     }
@@ -661,28 +1196,45 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
         hasher: impl Fn(&T) -> u64,
     ) -> Result<(), TryReserveError> {
         if additional > self.table.growth_left {
-            self.reserve_rehash(additional, hasher, Fallibility::Fallible)
+            // SAFETY: The [`RawTableInner`] must already have properly initialized control
+            // bytes since we will never expose RawTable::new_uninitialized in a public API.
+            unsafe { self.reserve_rehash(additional, hasher, Fallibility::Fallible) }
         } else {
             Ok(())
         }
     }
 
     /// Out-of-line slow path for `reserve` and `try_reserve`.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes,
+    /// otherwise calling this function results in [`undefined behavior`]
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[cold]
     #[inline(never)]
-    fn reserve_rehash(
+    unsafe fn reserve_rehash(
         &mut self,
         additional: usize,
         hasher: impl Fn(&T) -> u64,
         fallibility: Fallibility,
     ) -> Result<(), TryReserveError> {
         unsafe {
+            // SAFETY:
+            // 1. We know for sure that `alloc` and `layout` matches the [`Allocator`] and
+            //    [`TableLayout`] that were used to allocate this table.
+            // 2. The `drop` function is the actual drop function of the elements stored in
+            //    the table.
+            // 3. The caller ensures that the control bytes of the `RawTableInner`
+            //    are already initialized.
             self.table.reserve_rehash_inner(
+                &self.alloc,
                 additional,
                 &|table, index| hasher(table.bucket::<T>(index).as_ref()),
                 fallibility,
-                TableLayout::new::<T>(),
-                if mem::needs_drop::<T>() {
+                Self::TABLE_LAYOUT,
+                if T::NEEDS_DROP {
                     Some(mem::transmute(ptr::drop_in_place::<T> as unsafe fn(*mut T)))
                 } else {
                     None
@@ -693,20 +1245,50 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
 
     /// Allocates a new table of a different size and moves the contents of the
     /// current table into it.
-    fn resize(
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes,
+    /// otherwise calling this function results in [`undefined behavior`]
+    ///
+    /// The caller of this function must ensure that `capacity >= self.table.items`
+    /// otherwise:
+    ///
+    /// * If `self.table.items != 0`, calling of this function with `capacity`
+    ///   equal to 0 (`capacity == 0`) results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) < Group::WIDTH` and
+    ///   `self.table.items > capacity_to_buckets(capacity)`
+    ///   calling this function results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) >= Group::WIDTH` and
+    ///   `self.table.items > capacity_to_buckets(capacity)`
+    ///   calling this function are never return (will go into an
+    ///   infinite loop).
+    ///
+    /// See [`RawTableInner::find_insert_slot`] for more information.
+    ///
+    /// [`RawTableInner::find_insert_slot`]: RawTableInner::find_insert_slot
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    unsafe fn resize(
         &mut self,
         capacity: usize,
         hasher: impl Fn(&T) -> u64,
         fallibility: Fallibility,
     ) -> Result<(), TryReserveError> {
-        unsafe {
-            self.table.resize_inner(
-                capacity,
-                &|table, index| hasher(table.bucket::<T>(index).as_ref()),
-                fallibility,
-                TableLayout::new::<T>(),
-            )
-        }
+        // SAFETY:
+        // 1. The caller of this function guarantees that `capacity >= self.table.items`.
+        // 2. We know for sure that `alloc` and `layout` matches the [`Allocator`] and
+        //    [`TableLayout`] that were used to allocate this table.
+        // 3. The caller ensures that the control bytes of the `RawTableInner`
+        //    are already initialized.
+        self.table.resize_inner(
+            &self.alloc,
+            capacity,
+            &|table, index| hasher(table.bucket::<T>(index).as_ref()),
+            fallibility,
+            Self::TABLE_LAYOUT,
+        )
     }
 
     /// Inserts a new element into the table, and returns its raw bucket.
@@ -715,22 +1297,27 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn insert(&mut self, hash: u64, value: T, hasher: impl Fn(&T) -> u64) -> Bucket<T> {
         unsafe {
-            let mut index = self.table.find_insert_slot(hash);
+            // SAFETY:
+            // 1. The [`RawTableInner`] must already have properly initialized control bytes since
+            //    we will never expose `RawTable::new_uninitialized` in a public API.
+            //
+            // 2. We reserve additional space (if necessary) right after calling this function.
+            let mut slot = self.table.find_insert_slot(hash);
 
-            // We can avoid growing the table once we have reached our load
-            // factor if we are replacing a tombstone. This works since the
-            // number of EMPTY slots does not change in this case.
-            let old_ctrl = *self.table.ctrl(index);
+            // We can avoid growing the table once we have reached our load factor if we are replacing
+            // a tombstone. This works since the number of EMPTY slots does not change in this case.
+            //
+            // SAFETY: The function is guaranteed to return [`InsertSlot`] that contains an index
+            // in the range `0..=self.buckets()`.
+            let old_ctrl = *self.table.ctrl(slot.index);
             if unlikely(self.table.growth_left == 0 && special_is_empty(old_ctrl)) {
                 self.reserve(1, hasher);
-                index = self.table.find_insert_slot(hash);
+                // SAFETY: We know for sure that `RawTableInner` has control bytes
+                // initialized and that there is extra space in the table.
+                slot = self.table.find_insert_slot(hash);
             }
 
-            self.table.record_item_insert_at(index, old_ctrl, hash);
-
-            let bucket = self.bucket(index);
-            bucket.write(value);
-            bucket
+            self.insert_in_slot(hash, slot, value)
         }
     }
 
@@ -796,9 +1383,9 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     {
         let index = self.bucket_index(&bucket);
         let old_ctrl = *self.table.ctrl(index);
-        debug_assert!(is_full(old_ctrl));
+        debug_assert!(self.is_bucket_full(index));
         let old_growth_left = self.table.growth_left;
-        let item = self.remove(bucket);
+        let item = self.remove(bucket).0;
         if let Some(new_item) = f(item) {
             self.table.growth_left = old_growth_left;
             self.table.set_ctrl(index, old_ctrl);
@@ -810,17 +1397,78 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
         }
     }
 
+    /// Searches for an element in the table. If the element is not found,
+    /// returns `Err` with the position of a slot where an element with the
+    /// same hash could be inserted.
+    ///
+    /// This function may resize the table if additional space is required for
+    /// inserting an element.
+    #[inline]
+    pub fn find_or_find_insert_slot(
+        &mut self,
+        hash: u64,
+        mut eq: impl FnMut(&T) -> bool,
+        hasher: impl Fn(&T) -> u64,
+    ) -> Result<Bucket<T>, InsertSlot> {
+        self.reserve(1, hasher);
+
+        unsafe {
+            // SAFETY:
+            // 1. We know for sure that there is at least one empty `bucket` in the table.
+            // 2. The [`RawTableInner`] must already have properly initialized control bytes since we will
+            //    never expose `RawTable::new_uninitialized` in a public API.
+            // 3. The `find_or_find_insert_slot_inner` function returns the `index` of only the full bucket,
+            //    which is in the range `0..self.buckets()` (since there is at least one empty `bucket` in
+            //    the table), so calling `self.bucket(index)` and `Bucket::as_ref` is safe.
+            match self
+                .table
+                .find_or_find_insert_slot_inner(hash, &mut |index| eq(self.bucket(index).as_ref()))
+            {
+                // SAFETY: See explanation above.
+                Ok(index) => Ok(self.bucket(index)),
+                Err(slot) => Err(slot),
+            }
+        }
+    }
+
+    /// Inserts a new element into the table in the given slot, and returns its
+    /// raw bucket.
+    ///
+    /// # Safety
+    ///
+    /// `slot` must point to a slot previously returned by
+    /// `find_or_find_insert_slot`, and no mutation of the table must have
+    /// occurred since that call.
+    #[inline]
+    pub unsafe fn insert_in_slot(&mut self, hash: u64, slot: InsertSlot, value: T) -> Bucket<T> {
+        let old_ctrl = *self.table.ctrl(slot.index);
+        self.table.record_item_insert_at(slot.index, old_ctrl, hash);
+
+        let bucket = self.bucket(slot.index);
+        bucket.write(value);
+        bucket
+    }
+
     /// Searches for an element in the table.
     #[inline]
     pub fn find(&self, hash: u64, mut eq: impl FnMut(&T) -> bool) -> Option<Bucket<T>> {
-        let result = self.table.find_inner(hash, &mut |index| unsafe {
-            eq(self.bucket(index).as_ref())
-        });
-
-        // Avoid `Option::map` because it bloats LLVM IR.
-        match result {
-            Some(index) => Some(unsafe { self.bucket(index) }),
-            None => None,
+        unsafe {
+            // SAFETY:
+            // 1. The [`RawTableInner`] must already have properly initialized control bytes since we
+            //    will never expose `RawTable::new_uninitialized` in a public API.
+            // 1. The `find_inner` function returns the `index` of only the full bucket, which is in
+            //    the range `0..self.buckets()`, so calling `self.bucket(index)` and `Bucket::as_ref`
+            //    is safe.
+            let result = self
+                .table
+                .find_inner(hash, &mut |index| eq(self.bucket(index).as_ref()));
+
+            // Avoid `Option::map` because it bloats LLVM IR.
+            match result {
+                // SAFETY: See explanation above.
+                Some(index) => Some(self.bucket(index)),
+                None => None,
+            }
         }
     }
 
@@ -928,17 +1576,27 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
         self.table.bucket_mask + 1
     }
 
+    /// Checks whether the bucket at `index` is full.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure `index` is less than the number of buckets.
+    #[inline]
+    pub unsafe fn is_bucket_full(&self, index: usize) -> bool {
+        self.table.is_bucket_full(index)
+    }
+
     /// Returns an iterator over every element in the table. It is up to
     /// the caller to ensure that the `RawTable` outlives the `RawIter`.
     /// Because we cannot make the `next` method unsafe on the `RawIter`
     /// struct, we have to make the `iter` method unsafe.
     #[inline]
     pub unsafe fn iter(&self) -> RawIter<T> {
-        let data = Bucket::from_base_index(self.data_end(), 0);
-        RawIter {
-            iter: RawIterRange::new(self.table.ctrl.as_ptr(), data, self.table.buckets()),
-            items: self.table.items,
-        }
+        // SAFETY:
+        // 1. The caller must uphold the safety contract for `iter` method.
+        // 2. The [`RawTableInner`] must already have properly initialized control bytes since
+        //    we will never expose RawTable::new_uninitialized in a public API.
+        self.table.iter()
     }
 
     /// Returns an iterator over occupied buckets that could match a given hash.
@@ -952,7 +1610,7 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     /// `RawIterHash` struct, we have to make the `iter_hash` method unsafe.
     #[cfg_attr(feature = "inline-more", inline)]
     #[cfg(feature = "raw")]
-    pub unsafe fn iter_hash(&self, hash: u64) -> RawIterHash<'_, T, A> {
+    pub unsafe fn iter_hash(&self, hash: u64) -> RawIterHash<T> {
         RawIterHash::new(self, hash)
     }
 
@@ -978,8 +1636,8 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
         debug_assert_eq!(iter.len(), self.len());
         RawDrain {
             iter,
-            table: ManuallyDrop::new(mem::replace(self, Self::new_in(self.table.alloc.clone()))),
-            orig_table: NonNull::from(self),
+            table: mem::replace(&mut self.table, RawTableInner::NEW),
+            orig_table: NonNull::from(&mut self.table),
             marker: PhantomData,
         }
     }
@@ -993,31 +1651,31 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     pub unsafe fn into_iter_from(self, iter: RawIter<T>) -> RawIntoIter<T, A> {
         debug_assert_eq!(iter.len(), self.len());
 
-        let alloc = self.table.alloc.clone();
         let allocation = self.into_allocation();
         RawIntoIter {
             iter,
             allocation,
             marker: PhantomData,
-            alloc,
         }
     }
 
     /// Converts the table into a raw allocation. The contents of the table
     /// should be dropped using a `RawIter` before freeing the allocation.
     #[cfg_attr(feature = "inline-more", inline)]
-    pub(crate) fn into_allocation(self) -> Option<(NonNull<u8>, Layout)> {
+    pub(crate) fn into_allocation(self) -> Option<(NonNull<u8>, Layout, A)> {
         let alloc = if self.table.is_empty_singleton() {
             None
         } else {
             // Avoid `Option::unwrap_or_else` because it bloats LLVM IR.
-            let (layout, ctrl_offset) = match calculate_layout::<T>(self.table.buckets()) {
-                Some(lco) => lco,
-                None => unsafe { hint::unreachable_unchecked() },
-            };
+            let (layout, ctrl_offset) =
+                match Self::TABLE_LAYOUT.calculate_layout_for(self.table.buckets()) {
+                    Some(lco) => lco,
+                    None => unsafe { hint::unreachable_unchecked() },
+                };
             Some((
                 unsafe { NonNull::new_unchecked(self.table.ctrl.as_ptr().sub(ctrl_offset)) },
                 layout,
+                unsafe { ptr::read(&self.alloc) },
             ))
         };
         mem::forget(self);
@@ -1025,41 +1683,62 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
     }
 }
 
-unsafe impl<T, A: Allocator + Clone> Send for RawTable<T, A>
+unsafe impl<T, A: Allocator> Send for RawTable<T, A>
 where
     T: Send,
     A: Send,
 {
 }
-unsafe impl<T, A: Allocator + Clone> Sync for RawTable<T, A>
+unsafe impl<T, A: Allocator> Sync for RawTable<T, A>
 where
     T: Sync,
     A: Sync,
 {
 }
 
-impl<A> RawTableInner<A> {
+impl RawTableInner {
+    const NEW: Self = RawTableInner::new();
+
+    /// Creates a new empty hash table without allocating any memory.
+    ///
+    /// In effect this returns a table with exactly 1 bucket. However we can
+    /// leave the data pointer dangling since that bucket is never accessed
+    /// due to our load factor forcing us to always have at least 1 free bucket.
     #[inline]
-    const fn new_in(alloc: A) -> Self {
+    const fn new() -> Self {
         Self {
             // Be careful to cast the entire slice to a raw pointer.
             ctrl: unsafe { NonNull::new_unchecked(Group::static_empty() as *const _ as *mut u8) },
             bucket_mask: 0,
             items: 0,
             growth_left: 0,
-            alloc,
         }
     }
 }
 
-impl<A: Allocator + Clone> RawTableInner<A> {
+impl RawTableInner {
+    /// Allocates a new [`RawTableInner`] with the given number of buckets.
+    /// The control bytes and buckets are left uninitialized.
+    ///
+    /// # Safety
+    ///
+    /// The caller of this function must ensure that the `buckets` is power of two
+    /// and also initialize all control bytes of the length `self.bucket_mask + 1 +
+    /// Group::WIDTH` with the [`EMPTY`] bytes.
+    ///
+    /// See also [`Allocator`] API for other safety concerns.
+    ///
+    /// [`Allocator`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html
     #[cfg_attr(feature = "inline-more", inline)]
-    unsafe fn new_uninitialized(
-        alloc: A,
+    unsafe fn new_uninitialized<A>(
+        alloc: &A,
         table_layout: TableLayout,
         buckets: usize,
         fallibility: Fallibility,
-    ) -> Result<Self, TryReserveError> {
+    ) -> Result<Self, TryReserveError>
+    where
+        A: Allocator,
+    {
         debug_assert!(buckets.is_power_of_two());
 
         // Avoid `Option::ok_or_else` because it bloats LLVM IR.
@@ -1068,45 +1747,48 @@ impl<A: Allocator + Clone> RawTableInner<A> {
             None => return Err(fallibility.capacity_overflow()),
         };
 
-        // We need an additional check to ensure that the allocation doesn't
-        // exceed `isize::MAX`. We can skip this check on 64-bit systems since
-        // such allocations will never succeed anyways.
-        //
-        // This mirrors what Vec does in the standard library.
-        if mem::size_of::<usize>() < 8 && layout.size() > isize::MAX as usize {
-            return Err(fallibility.capacity_overflow());
-        }
-
-        let ptr: NonNull<u8> = match do_alloc(&alloc, layout) {
+        let ptr: NonNull<u8> = match do_alloc(alloc, layout) {
             Ok(block) => block.cast(),
             Err(_) => return Err(fallibility.alloc_err(layout)),
         };
 
+        // SAFETY: null pointer will be caught in above check
         let ctrl = NonNull::new_unchecked(ptr.as_ptr().add(ctrl_offset));
         Ok(Self {
             ctrl,
             bucket_mask: buckets - 1,
             items: 0,
             growth_left: bucket_mask_to_capacity(buckets - 1),
-            alloc,
         })
     }
 
+    /// Attempts to allocate a new [`RawTableInner`] with at least enough
+    /// capacity for inserting the given number of elements without reallocating.
+    ///
+    /// All the control bytes are initialized with the [`EMPTY`] bytes.
     #[inline]
-    fn fallible_with_capacity(
-        alloc: A,
+    fn fallible_with_capacity<A>(
+        alloc: &A,
         table_layout: TableLayout,
         capacity: usize,
         fallibility: Fallibility,
-    ) -> Result<Self, TryReserveError> {
+    ) -> Result<Self, TryReserveError>
+    where
+        A: Allocator,
+    {
         if capacity == 0 {
-            Ok(Self::new_in(alloc))
+            Ok(Self::NEW)
         } else {
+            // SAFETY: We checked that we could successfully allocate the new table, and then
+            // initialized all control bytes with the constant `EMPTY` byte.
             unsafe {
                 let buckets =
                     capacity_to_buckets(capacity).ok_or_else(|| fallibility.capacity_overflow())?;
 
                 let result = Self::new_uninitialized(alloc, table_layout, buckets, fallibility)?;
+                // SAFETY: We checked that the table is allocated and therefore the table already has
+                // `self.bucket_mask + 1 + Group::WIDTH` number of control bytes (see TableLayout::calculate_layout_for)
+                // so writing `self.num_ctrl_bytes() == bucket_mask + 1 + Group::WIDTH` bytes is safe.
                 result.ctrl(0).write_bytes(EMPTY, result.num_ctrl_bytes());
 
                 Ok(result)
@@ -1114,66 +1796,397 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         }
     }
 
-    /// Searches for an empty or deleted bucket which is suitable for inserting
-    /// a new element and sets the hash for that slot.
+    /// Allocates a new [`RawTableInner`] with at least enough capacity for inserting
+    /// the given number of elements without reallocating.
+    ///
+    /// Panics if the new capacity exceeds [`isize::MAX`] bytes and [`abort`] the program
+    /// in case of allocation error. Use [`fallible_with_capacity`] instead if you want to
+    /// handle memory allocation failure.
+    ///
+    /// All the control bytes are initialized with the [`EMPTY`] bytes.
+    ///
+    /// [`fallible_with_capacity`]: RawTableInner::fallible_with_capacity
+    /// [`abort`]: https://doc.rust-lang.org/alloc/alloc/fn.handle_alloc_error.html
+    fn with_capacity<A>(alloc: &A, table_layout: TableLayout, capacity: usize) -> Self
+    where
+        A: Allocator,
+    {
+        // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
+        match Self::fallible_with_capacity(alloc, table_layout, capacity, Fallibility::Infallible) {
+            Ok(table_inner) => table_inner,
+            // SAFETY: All allocation errors will be caught inside `RawTableInner::new_uninitialized`.
+            Err(_) => unsafe { hint::unreachable_unchecked() },
+        }
+    }
+
+    /// Fixes up an insertion slot returned by the [`RawTableInner::find_insert_slot_in_group`] method.
+    ///
+    /// In tables smaller than the group width (`self.buckets() < Group::WIDTH`), trailing control
+    /// bytes outside the range of the table are filled with [`EMPTY`] entries. These will unfortunately
+    /// trigger a match of [`RawTableInner::find_insert_slot_in_group`] function. This is because
+    /// the `Some(bit)` returned by `group.match_empty_or_deleted().lowest_set_bit()` after masking
+    /// (`(probe_seq.pos + bit) & self.bucket_mask`) may point to a full bucket that is already occupied.
+    /// We detect this situation here and perform a second scan starting at the beginning of the table.
+    /// This second scan is guaranteed to find an empty slot (due to the load factor) before hitting the
+    /// trailing control bytes (containing [`EMPTY`] bytes).
+    ///
+    /// If this function is called correctly, it is guaranteed to return [`InsertSlot`] with an
+    /// index of an empty or deleted bucket in the range `0..self.buckets()` (see `Warning` and
+    /// `Safety`).
+    ///
+    /// # Warning
+    ///
+    /// The table must have at least 1 empty or deleted `bucket`, otherwise if the table is less than
+    /// the group width (`self.buckets() < Group::WIDTH`) this function returns an index outside of the
+    /// table indices range `0..self.buckets()` (`0..=self.bucket_mask`). Attempt to write data at that
+    /// index will cause immediate [`undefined behavior`].
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for [`RawTableInner::ctrl`] method.
+    /// Thus, in order to uphold those safety contracts, as well as for the correct logic of the work
+    /// of this crate, the following rules are necessary and sufficient:
     ///
-    /// There must be at least 1 empty bucket in the table.
+    /// * The [`RawTableInner`] must have properly initialized control bytes otherwise calling this
+    ///   function results in [`undefined behavior`].
+    ///
+    /// * This function must only be used on insertion slots found by [`RawTableInner::find_insert_slot_in_group`]
+    ///   (after the `find_insert_slot_in_group` function, but before insertion into the table).
+    ///
+    /// * The `index` must not be greater than the `self.bucket_mask`, i.e. `(index + 1) <= self.buckets()`
+    ///   (this one is provided by the [`RawTableInner::find_insert_slot_in_group`] function).
+    ///
+    /// Calling this function with an index not provided by [`RawTableInner::find_insert_slot_in_group`]
+    /// may result in [`undefined behavior`] even if the index satisfies the safety rules of the
+    /// [`RawTableInner::ctrl`] function (`index < self.bucket_mask + 1 + Group::WIDTH`).
+    ///
+    /// [`RawTableInner::ctrl`]: RawTableInner::ctrl
+    /// [`RawTableInner::find_insert_slot_in_group`]: RawTableInner::find_insert_slot_in_group
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
-    unsafe fn prepare_insert_slot(&self, hash: u64) -> (usize, u8) {
-        let index = self.find_insert_slot(hash);
+    unsafe fn fix_insert_slot(&self, mut index: usize) -> InsertSlot {
+        // SAFETY: The caller of this function ensures that `index` is in the range `0..=self.bucket_mask`.
+        if unlikely(self.is_bucket_full(index)) {
+            debug_assert!(self.bucket_mask < Group::WIDTH);
+            // SAFETY:
+            //
+            // * Since the caller of this function ensures that the control bytes are properly
+            //   initialized and `ptr = self.ctrl(0)` points to the start of the array of control
+            //   bytes, therefore: `ctrl` is valid for reads, properly aligned to `Group::WIDTH`
+            //   and points to the properly initialized control bytes (see also
+            //   `TableLayout::calculate_layout_for` and `ptr::read`);
+            //
+            // * Because the caller of this function ensures that the index was provided by the
+            //   `self.find_insert_slot_in_group()` function, so for for tables larger than the
+            //   group width (self.buckets() >= Group::WIDTH), we will never end up in the given
+            //   branch, since `(probe_seq.pos + bit) & self.bucket_mask` in `find_insert_slot_in_group`
+            //   cannot return a full bucket index. For tables smaller than the group width, calling
+            //   the `unwrap_unchecked` function is also safe, as the trailing control bytes outside
+            //   the range of the table are filled with EMPTY bytes (and we know for sure that there
+            //   is at least one FULL bucket), so this second scan either finds an empty slot (due to
+            //   the load factor) or hits the trailing control bytes (containing EMPTY).
+            index = Group::load_aligned(self.ctrl(0))
+                .match_empty_or_deleted()
+                .lowest_set_bit()
+                .unwrap_unchecked();
+        }
+        InsertSlot { index }
+    }
+
+    /// Finds the position to insert something in a group.
+    ///
+    /// **This may have false positives and must be fixed up with `fix_insert_slot`
+    /// before it's used.**
+    ///
+    /// The function is guaranteed to return the index of an empty or deleted [`Bucket`]
+    /// in the range `0..self.buckets()` (`0..=self.bucket_mask`).
+    #[inline]
+    fn find_insert_slot_in_group(&self, group: &Group, probe_seq: &ProbeSeq) -> Option<usize> {
+        let bit = group.match_empty_or_deleted().lowest_set_bit();
+
+        if likely(bit.is_some()) {
+            // This is the same as `(probe_seq.pos + bit) % self.buckets()` because the number
+            // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+            Some((probe_seq.pos + bit.unwrap()) & self.bucket_mask)
+        } else {
+            None
+        }
+    }
+
+    /// Searches for an element in the table, or a potential slot where that element could
+    /// be inserted (an empty or deleted [`Bucket`] index).
+    ///
+    /// This uses dynamic dispatch to reduce the amount of code generated, but that is
+    /// eliminated by LLVM optimizations.
+    ///
+    /// This function does not make any changes to the `data` part of the table, or any
+    /// changes to the `items` or `growth_left` field of the table.
+    ///
+    /// The table must have at least 1 empty or deleted `bucket`, otherwise, if the
+    /// `eq: &mut dyn FnMut(usize) -> bool` function does not return `true`, this function
+    /// will never return (will go into an infinite loop) for tables larger than the group
+    /// width, or return an index outside of the table indices range if the table is less
+    /// than the group width.
+    ///
+    /// This function is guaranteed to provide the `eq: &mut dyn FnMut(usize) -> bool`
+    /// function with only `FULL` buckets' indices and return the `index` of the found
+    /// element (as `Ok(index)`). If the element is not found and there is at least 1
+    /// empty or deleted [`Bucket`] in the table, the function is guaranteed to return
+    /// [InsertSlot] with an index in the range `0..self.buckets()`, but in any case,
+    /// if this function returns [`InsertSlot`], it will contain an index in the range
+    /// `0..=self.buckets()`.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes otherwise calling
+    /// this function results in [`undefined behavior`].
+    ///
+    /// Attempt to write data at the [`InsertSlot`] returned by this function when the table is
+    /// less than the group width and if there was not at least one empty or deleted bucket in
+    /// the table will cause immediate [`undefined behavior`]. This is because in this case the
+    /// function will return `self.bucket_mask + 1` as an index due to the trailing [`EMPTY]
+    /// control bytes outside the table range.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn find_or_find_insert_slot_inner(
+        &self,
+        hash: u64,
+        eq: &mut dyn FnMut(usize) -> bool,
+    ) -> Result<usize, InsertSlot> {
+        let mut insert_slot = None;
+
+        let h2_hash = h2(hash);
+        let mut probe_seq = self.probe_seq(hash);
+
+        loop {
+            // SAFETY:
+            // * Caller of this function ensures that the control bytes are properly initialized.
+            //
+            // * `ProbeSeq.pos` cannot be greater than `self.bucket_mask = self.buckets() - 1`
+            //   of the table due to masking with `self.bucket_mask` and also because mumber of
+            //   buckets is a power of two (see `self.probe_seq` function).
+            //
+            // * Even if `ProbeSeq.pos` returns `position == self.bucket_mask`, it is safe to
+            //   call `Group::load` due to the extended control bytes range, which is
+            //  `self.bucket_mask + 1 + Group::WIDTH` (in fact, this means that the last control
+            //   byte will never be read for the allocated table);
+            //
+            // * Also, even if `RawTableInner` is not already allocated, `ProbeSeq.pos` will
+            //   always return "0" (zero), so Group::load will read unaligned `Group::static_empty()`
+            //   bytes, which is safe (see RawTableInner::new).
+            let group = unsafe { Group::load(self.ctrl(probe_seq.pos)) };
+
+            for bit in group.match_byte(h2_hash) {
+                let index = (probe_seq.pos + bit) & self.bucket_mask;
+
+                if likely(eq(index)) {
+                    return Ok(index);
+                }
+            }
+
+            // We didn't find the element we were looking for in the group, try to get an
+            // insertion slot from the group if we don't have one yet.
+            if likely(insert_slot.is_none()) {
+                insert_slot = self.find_insert_slot_in_group(&group, &probe_seq);
+            }
+
+            // Only stop the search if the group contains at least one empty element.
+            // Otherwise, the element that we are looking for might be in a following group.
+            if likely(group.match_empty().any_bit_set()) {
+                // We must have found a insert slot by now, since the current group contains at
+                // least one. For tables smaller than the group width, there will still be an
+                // empty element in the current (and only) group due to the load factor.
+                unsafe {
+                    // SAFETY:
+                    // * Caller of this function ensures that the control bytes are properly initialized.
+                    //
+                    // * We use this function with the slot / index found by `self.find_insert_slot_in_group`
+                    return Err(self.fix_insert_slot(insert_slot.unwrap_unchecked()));
+                }
+            }
+
+            probe_seq.move_next(self.bucket_mask);
+        }
+    }
+
+    /// Searches for an empty or deleted bucket which is suitable for inserting a new
+    /// element and sets the hash for that slot. Returns an index of that slot and the
+    /// old control byte stored in the found index.
+    ///
+    /// This function does not check if the given element exists in the table. Also,
+    /// this function does not check if there is enough space in the table to insert
+    /// a new element. Caller of the funtion must make ensure that the table has at
+    /// least 1 empty or deleted `bucket`, otherwise this function will never return
+    /// (will go into an infinite loop) for tables larger than the group width, or
+    /// return an index outside of the table indices range if the table is less than
+    /// the group width.
+    ///
+    /// If there is at least 1 empty or deleted `bucket` in the table, the function is
+    /// guaranteed to return an `index` in the range `0..self.buckets()`, but in any case,
+    /// if this function returns an `index` it will be in the range `0..=self.buckets()`.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for the
+    /// [`RawTableInner::set_ctrl_h2`] and [`RawTableInner::find_insert_slot`] methods.
+    /// Thus, in order to uphold the safety contracts for that methods, as well as for
+    /// the correct logic of the work of this crate, you must observe the following rules
+    /// when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated and has properly initialized
+    ///   control bytes otherwise calling this function results in [`undefined behavior`].
+    ///
+    /// * The caller of this function must ensure that the "data" parts of the table
+    ///   will have an entry in the returned index (matching the given hash) right
+    ///   after calling this function.
+    ///
+    /// Attempt to write data at the `index` returned by this function when the table is
+    /// less than the group width and if there was not at least one empty or deleted bucket in
+    /// the table will cause immediate [`undefined behavior`]. This is because in this case the
+    /// function will return `self.bucket_mask + 1` as an index due to the trailing [`EMPTY]
+    /// control bytes outside the table range.
+    ///
+    /// The caller must independently increase the `items` field of the table, and also,
+    /// if the old control byte was [`EMPTY`], then decrease the table's `growth_left`
+    /// field, and do not change it if the old control byte was [`DELETED`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`RawTableInner::ctrl`]: RawTableInner::ctrl
+    /// [`RawTableInner::set_ctrl_h2`]: RawTableInner::set_ctrl_h2
+    /// [`RawTableInner::find_insert_slot`]: RawTableInner::find_insert_slot
+    #[inline]
+    unsafe fn prepare_insert_slot(&mut self, hash: u64) -> (usize, u8) {
+        // SAFETY: Caller of this function ensures that the control bytes are properly initialized.
+        let index: usize = self.find_insert_slot(hash).index;
+        // SAFETY:
+        // 1. The `find_insert_slot` function either returns an `index` less than or
+        //    equal to `self.buckets() = self.bucket_mask + 1` of the table, or never
+        //    returns if it cannot find an empty or deleted slot.
+        // 2. The caller of this function guarantees that the table has already been
+        //    allocated
         let old_ctrl = *self.ctrl(index);
         self.set_ctrl_h2(index, hash);
         (index, old_ctrl)
     }
 
     /// Searches for an empty or deleted bucket which is suitable for inserting
-    /// a new element.
+    /// a new element, returning the `index` for the new [`Bucket`].
+    ///
+    /// This function does not make any changes to the `data` part of the table, or any
+    /// changes to the `items` or `growth_left` field of the table.
+    ///
+    /// The table must have at least 1 empty or deleted `bucket`, otherwise this function
+    /// will never return (will go into an infinite loop) for tables larger than the group
+    /// width, or return an index outside of the table indices range if the table is less
+    /// than the group width.
+    ///
+    /// If there is at least 1 empty or deleted `bucket` in the table, the function is
+    /// guaranteed to return [`InsertSlot`] with an index in the range `0..self.buckets()`,
+    /// but in any case, if this function returns [`InsertSlot`], it will contain an index
+    /// in the range `0..=self.buckets()`.
     ///
-    /// There must be at least 1 empty bucket in the table.
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes otherwise calling
+    /// this function results in [`undefined behavior`].
+    ///
+    /// Attempt to write data at the [`InsertSlot`] returned by this function when the table is
+    /// less than the group width and if there was not at least one empty or deleted bucket in
+    /// the table will cause immediate [`undefined behavior`]. This is because in this case the
+    /// function will return `self.bucket_mask + 1` as an index due to the trailing [`EMPTY]
+    /// control bytes outside the table range.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
-    fn find_insert_slot(&self, hash: u64) -> usize {
+    unsafe fn find_insert_slot(&self, hash: u64) -> InsertSlot {
         let mut probe_seq = self.probe_seq(hash);
         loop {
-            unsafe {
-                let group = Group::load(self.ctrl(probe_seq.pos));
-                if let Some(bit) = group.match_empty_or_deleted().lowest_set_bit() {
-                    let result = (probe_seq.pos + bit) & self.bucket_mask;
-
-                    // In tables smaller than the group width, trailing control
-                    // bytes outside the range of the table are filled with
-                    // EMPTY entries. These will unfortunately trigger a
-                    // match, but once masked may point to a full bucket that
-                    // is already occupied. We detect this situation here and
-                    // perform a second scan starting at the beginning of the
-                    // table. This second scan is guaranteed to find an empty
-                    // slot (due to the load factor) before hitting the trailing
-                    // control bytes (containing EMPTY).
-                    if unlikely(is_full(*self.ctrl(result))) {
-                        debug_assert!(self.bucket_mask < Group::WIDTH);
-                        debug_assert_ne!(probe_seq.pos, 0);
-                        return Group::load_aligned(self.ctrl(0))
-                            .match_empty_or_deleted()
-                            .lowest_set_bit_nonzero();
-                    }
+            // SAFETY:
+            // * Caller of this function ensures that the control bytes are properly initialized.
+            //
+            // * `ProbeSeq.pos` cannot be greater than `self.bucket_mask = self.buckets() - 1`
+            //   of the table due to masking with `self.bucket_mask` and also because mumber of
+            //   buckets is a power of two (see `self.probe_seq` function).
+            //
+            // * Even if `ProbeSeq.pos` returns `position == self.bucket_mask`, it is safe to
+            //   call `Group::load` due to the extended control bytes range, which is
+            //  `self.bucket_mask + 1 + Group::WIDTH` (in fact, this means that the last control
+            //   byte will never be read for the allocated table);
+            //
+            // * Also, even if `RawTableInner` is not already allocated, `ProbeSeq.pos` will
+            //   always return "0" (zero), so Group::load will read unaligned `Group::static_empty()`
+            //   bytes, which is safe (see RawTableInner::new).
+            let group = unsafe { Group::load(self.ctrl(probe_seq.pos)) };
 
-                    return result;
+            let index = self.find_insert_slot_in_group(&group, &probe_seq);
+            if likely(index.is_some()) {
+                // SAFETY:
+                // * Caller of this function ensures that the control bytes are properly initialized.
+                //
+                // * We use this function with the slot / index found by `self.find_insert_slot_in_group`
+                unsafe {
+                    return self.fix_insert_slot(index.unwrap_unchecked());
                 }
             }
             probe_seq.move_next(self.bucket_mask);
         }
     }
 
-    /// Searches for an element in the table. This uses dynamic dispatch to reduce the amount of
-    /// code generated, but it is eliminated by LLVM optimizations.
-    #[inline]
-    fn find_inner(&self, hash: u64, eq: &mut dyn FnMut(usize) -> bool) -> Option<usize> {
+    /// Searches for an element in a table, returning the `index` of the found element.
+    /// This uses dynamic dispatch to reduce the amount of code generated, but it is
+    /// eliminated by LLVM optimizations.
+    ///
+    /// This function does not make any changes to the `data` part of the table, or any
+    /// changes to the `items` or `growth_left` field of the table.
+    ///
+    /// The table must have at least 1 empty `bucket`, otherwise, if the
+    /// `eq: &mut dyn FnMut(usize) -> bool` function does not return `true`,
+    /// this function will also never return (will go into an infinite loop).
+    ///
+    /// This function is guaranteed to provide the `eq: &mut dyn FnMut(usize) -> bool`
+    /// function with only `FULL` buckets' indices and return the `index` of the found
+    /// element as `Some(index)`, so the index will always be in the range
+    /// `0..self.buckets()`.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes otherwise calling
+    /// this function results in [`undefined behavior`].
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline(always)]
+    unsafe fn find_inner(&self, hash: u64, eq: &mut dyn FnMut(usize) -> bool) -> Option<usize> {
         let h2_hash = h2(hash);
         let mut probe_seq = self.probe_seq(hash);
 
         loop {
+            // SAFETY:
+            // * Caller of this function ensures that the control bytes are properly initialized.
+            //
+            // * `ProbeSeq.pos` cannot be greater than `self.bucket_mask = self.buckets() - 1`
+            //   of the table due to masking with `self.bucket_mask`.
+            //
+            // * Even if `ProbeSeq.pos` returns `position == self.bucket_mask`, it is safe to
+            //   call `Group::load` due to the extended control bytes range, which is
+            //  `self.bucket_mask + 1 + Group::WIDTH` (in fact, this means that the last control
+            //   byte will never be read for the allocated table);
+            //
+            // * Also, even if `RawTableInner` is not already allocated, `ProbeSeq.pos` will
+            //   always return "0" (zero), so Group::load will read unaligned `Group::static_empty()`
+            //   bytes, which is safe (see RawTableInner::new_in).
             let group = unsafe { Group::load(self.ctrl(probe_seq.pos)) };
 
             for bit in group.match_byte(h2_hash) {
+                // This is the same as `(probe_seq.pos + bit) % self.buckets()` because the number
+                // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
                 let index = (probe_seq.pos + bit) & self.bucket_mask;
 
                 if likely(eq(index)) {
@@ -1189,12 +2202,52 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         }
     }
 
+    /// Prepares for rehashing data in place (that is, without allocating new memory).
+    /// Converts all full index `control bytes` to `DELETED` and all `DELETED` control
+    /// bytes to `EMPTY`, i.e. performs the following conversion:
+    ///
+    /// - `EMPTY` control bytes   -> `EMPTY`;
+    /// - `DELETED` control bytes -> `EMPTY`;
+    /// - `FULL` control bytes    -> `DELETED`.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// You must observe the following safety rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The caller of this function must convert the `DELETED` bytes back to `FULL`
+    ///   bytes when re-inserting them into their ideal position (which was impossible
+    ///   to do during the first insert due to tombstones). If the caller does not do
+    ///   this, then calling this function may result in a memory leak.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes otherwise
+    ///   calling this function results in [`undefined behavior`].
+    ///
+    /// Calling this function on a table that has not been allocated results in
+    /// [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[allow(clippy::mut_mut)]
     #[inline]
     unsafe fn prepare_rehash_in_place(&mut self) {
-        // Bulk convert all full control bytes to DELETED, and all DELETED
-        // control bytes to EMPTY. This effectively frees up all buckets
-        // containing a DELETED entry.
+        // Bulk convert all full control bytes to DELETED, and all DELETED control bytes to EMPTY.
+        // This effectively frees up all buckets containing a DELETED entry.
+        //
+        // SAFETY:
+        // 1. `i` is guaranteed to be within bounds since we are iterating from zero to `buckets - 1`;
+        // 2. Even if `i` will be `i == self.bucket_mask`, it is safe to call `Group::load_aligned`
+        //    due to the extended control bytes range, which is `self.bucket_mask + 1 + Group::WIDTH`;
+        // 3. The caller of this function guarantees that [`RawTableInner`] has already been allocated;
+        // 4. We can use `Group::load_aligned` and `Group::store_aligned` here since we start from 0
+        //    and go to the end with a step equal to `Group::WIDTH` (see TableLayout::calculate_layout_for).
         for i in (0..self.buckets()).step_by(Group::WIDTH) {
             let group = Group::load_aligned(self.ctrl(i));
             let group = group.convert_special_to_empty_and_full_to_deleted();
@@ -1203,15 +2256,245 @@ impl<A: Allocator + Clone> RawTableInner<A> {
 
         // Fix up the trailing control bytes. See the comments in set_ctrl
         // for the handling of tables smaller than the group width.
-        if self.buckets() < Group::WIDTH {
+        //
+        // SAFETY: The caller of this function guarantees that [`RawTableInner`]
+        // has already been allocated
+        if unlikely(self.buckets() < Group::WIDTH) {
+            // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of control bytes,
+            // so copying `self.buckets() == self.bucket_mask + 1` bytes with offset equal to
+            // `Group::WIDTH` is safe
             self.ctrl(0)
                 .copy_to(self.ctrl(Group::WIDTH), self.buckets());
         } else {
+            // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of
+            // control bytes,so copying `Group::WIDTH` bytes with offset equal
+            // to `self.buckets() == self.bucket_mask + 1` is safe
             self.ctrl(0)
                 .copy_to(self.ctrl(self.buckets()), Group::WIDTH);
         }
     }
 
+    /// Returns an iterator over every element in the table.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result
+    /// is [`undefined behavior`]:
+    ///
+    /// * The caller has to ensure that the `RawTableInner` outlives the
+    ///   `RawIter`. Because we cannot make the `next` method unsafe on
+    ///   the `RawIter` struct, we have to make the `iter` method unsafe.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// The type `T` must be the actual type of the elements stored in the table,
+    /// otherwise using the returned [`RawIter`] results in [`undefined behavior`].
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn iter<T>(&self) -> RawIter<T> {
+        // SAFETY:
+        // 1. Since the caller of this function ensures that the control bytes
+        //    are properly initialized and `self.data_end()` points to the start
+        //    of the array of control bytes, therefore: `ctrl` is valid for reads,
+        //    properly aligned to `Group::WIDTH` and points to the properly initialized
+        //    control bytes.
+        // 2. `data` bucket index in the table is equal to the `ctrl` index (i.e.
+        //    equal to zero).
+        // 3. We pass the exact value of buckets of the table to the function.
+        //
+        //                         `ctrl` points here (to the start
+        //                         of the first control byte `CT0`)
+        //                          ∨
+        // [Pad], T_n, ..., T1, T0, |CT0, CT1, ..., CT_n|, CTa_0, CTa_1, ..., CTa_m
+        //                           \________  ________/
+        //                                    \/
+        //       `n = buckets - 1`, i.e. `RawTableInner::buckets() - 1`
+        //
+        // where: T0...T_n  - our stored data;
+        //        CT0...CT_n - control bytes or metadata for `data`.
+        //        CTa_0...CTa_m - additional control bytes, where `m = Group::WIDTH - 1` (so that the search
+        //                        with loading `Group` bytes from the heap works properly, even if the result
+        //                        of `h1(hash) & self.bucket_mask` is equal to `self.bucket_mask`). See also
+        //                        `RawTableInner::set_ctrl` function.
+        //
+        // P.S. `h1(hash) & self.bucket_mask` is the same as `hash as usize % self.buckets()` because the number
+        // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+        let data = Bucket::from_base_index(self.data_end(), 0);
+        RawIter {
+            // SAFETY: See explanation above
+            iter: RawIterRange::new(self.ctrl.as_ptr(), data, self.buckets()),
+            items: self.items,
+        }
+    }
+
+    /// Executes the destructors (if any) of the values stored in the table.
+    ///
+    /// # Note
+    ///
+    /// This function does not erase the control bytes of the table and does
+    /// not make any changes to the `items` or `growth_left` fields of the
+    /// table. If necessary, the caller of this function must manually set
+    /// up these table fields, for example using the [`clear_no_drop`] function.
+    ///
+    /// Be careful during calling this function, because drop function of
+    /// the elements can panic, and this can leave table in an inconsistent
+    /// state.
+    ///
+    /// # Safety
+    ///
+    /// The type `T` must be the actual type of the elements stored in the table,
+    /// otherwise calling this function may result in [`undefined behavior`].
+    ///
+    /// If `T` is a type that should be dropped and **the table is not empty**,
+    /// calling this function more than once results in [`undefined behavior`].
+    ///
+    /// If `T` is not [`Copy`], attempting to use values stored in the table after
+    /// calling this function may result in [`undefined behavior`].
+    ///
+    /// It is safe to call this function on a table that has not been allocated,
+    /// on a table with uninitialized control bytes, and on a table with no actual
+    /// data but with `Full` control bytes if `self.items == 0`.
+    ///
+    /// See also [`Bucket::drop`] / [`Bucket::as_ptr`] methods, for more information
+    /// about of properly removing or saving `element` from / into the [`RawTable`] /
+    /// [`RawTableInner`].
+    ///
+    /// [`Bucket::drop`]: Bucket::drop
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`clear_no_drop`]: RawTableInner::clear_no_drop
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    unsafe fn drop_elements<T>(&mut self) {
+        // Check that `self.items != 0`. Protects against the possibility
+        // of creating an iterator on an table with uninitialized control bytes.
+        if T::NEEDS_DROP && self.items != 0 {
+            // SAFETY: We know for sure that RawTableInner will outlive the
+            // returned `RawIter` iterator, and the caller of this function
+            // must uphold the safety contract for `drop_elements` method.
+            for item in self.iter::<T>() {
+                // SAFETY: The caller must uphold the safety contract for
+                // `drop_elements` method.
+                item.drop();
+            }
+        }
+    }
+
+    /// Executes the destructors (if any) of the values stored in the table and than
+    /// deallocates the table.
+    ///
+    /// # Note
+    ///
+    /// Calling this function automatically makes invalid (dangling) all instances of
+    /// buckets ([`Bucket`]) and makes invalid (dangling) the `ctrl` field of the table.
+    ///
+    /// This function does not make any changes to the `bucket_mask`, `items` or `growth_left`
+    /// fields of the table. If necessary, the caller of this function must manually set
+    /// up these table fields.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is [`undefined behavior`]:
+    ///
+    /// * Calling this function more than once;
+    ///
+    /// * The type `T` must be the actual type of the elements stored in the table.
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` that was used
+    ///   to allocate this table.
+    ///
+    /// * The `table_layout` must be the same [`TableLayout`] as the `TableLayout` that
+    ///   was used to allocate this table.
+    ///
+    /// The caller of this function should pay attention to the possibility of the
+    /// elements' drop function panicking, because this:
+    ///
+    ///    * May leave the table in an inconsistent state;
+    ///
+    ///    * Memory is never deallocated, so a memory leak may occur.
+    ///
+    /// Attempt to use the `ctrl` field of the table (dereference) after calling this
+    /// function results in [`undefined behavior`].
+    ///
+    /// It is safe to call this function on a table that has not been allocated,
+    /// on a table with uninitialized control bytes, and on a table with no actual
+    /// data but with `Full` control bytes if `self.items == 0`.
+    ///
+    /// See also [`RawTableInner::drop_elements`] or [`RawTableInner::free_buckets`]
+    /// for more  information.
+    ///
+    /// [`RawTableInner::drop_elements`]: RawTableInner::drop_elements
+    /// [`RawTableInner::free_buckets`]: RawTableInner::free_buckets
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    unsafe fn drop_inner_table<T, A: Allocator>(&mut self, alloc: &A, table_layout: TableLayout) {
+        if !self.is_empty_singleton() {
+            unsafe {
+                // SAFETY: The caller must uphold the safety contract for `drop_inner_table` method.
+                self.drop_elements::<T>();
+                // SAFETY:
+                // 1. We have checked that our table is allocated.
+                // 2. The caller must uphold the safety contract for `drop_inner_table` method.
+                self.free_buckets(alloc, table_layout);
+            }
+        }
+    }
+
+    /// Returns a pointer to an element in the table (convenience for
+    /// `Bucket::from_base_index(self.data_end::<T>(), index)`).
+    ///
+    /// The caller must ensure that the `RawTableInner` outlives the returned [`Bucket<T>`],
+    /// otherwise using it may result in [`undefined behavior`].
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the safety rules are directly derived from the
+    /// safety rules of the [`Bucket::from_base_index`] function. Therefore, when calling
+    /// this function, the following safety rules must be observed:
+    ///
+    /// * The table must already be allocated;
+    ///
+    /// * The `index` must not be greater than the number returned by the [`RawTableInner::buckets`]
+    ///   function, i.e. `(index + 1) <= self.buckets()`.
+    ///
+    /// * The type `T` must be the actual type of the elements stored in the table, otherwise
+    ///   using the returned [`Bucket`] may result in [`undefined behavior`].
+    ///
+    /// It is safe to call this function with index of zero (`index == 0`) on a table that has
+    /// not been allocated, but using the returned [`Bucket`] results in [`undefined behavior`].
+    ///
+    /// If `mem::size_of::<T>() == 0`, then the only requirement is that the `index` must
+    /// not be greater than the number returned by the [`RawTable::buckets`] function, i.e.
+    /// `(index + 1) <= self.buckets()`.
+    ///
+    /// ```none
+    /// If mem::size_of::<T>() != 0 then return a pointer to the `element` in the `data part` of the table
+    /// (we start counting from "0", so that in the expression T[n], the "n" index actually one less than
+    /// the "buckets" number of our `RawTableInner`, i.e. "n = RawTableInner::buckets() - 1"):
+    ///
+    ///           `table.bucket(3).as_ptr()` returns a pointer that points here in the `data`
+    ///           part of the `RawTableInner`, i.e. to the start of T3 (see [`Bucket::as_ptr`])
+    ///                  |
+    ///                  |               `base = table.data_end::<T>()` points here
+    ///                  |               (to the start of CT0 or to the end of T0)
+    ///                  v                 v
+    /// [Pad], T_n, ..., |T3|, T2, T1, T0, |CT0, CT1, CT2, CT3, ..., CT_n, CTa_0, CTa_1, ..., CTa_m
+    ///                     ^                                              \__________  __________/
+    ///        `table.bucket(3)` returns a pointer that points                        \/
+    ///         here in the `data` part of the `RawTableInner`             additional control bytes
+    ///         (to the end of T3)                                          `m = Group::WIDTH - 1`
+    ///
+    /// where: T0...T_n  - our stored data;
+    ///        CT0...CT_n - control bytes or metadata for `data`;
+    ///        CTa_0...CTa_m - additional control bytes (so that the search with loading `Group` bytes from
+    ///                        the heap works properly, even if the result of `h1(hash) & self.bucket_mask`
+    ///                        is equal to `self.bucket_mask`). See also `RawTableInner::set_ctrl` function.
+    ///
+    /// P.S. `h1(hash) & self.bucket_mask` is the same as `hash as usize % self.buckets()` because the number
+    /// of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+    /// ```
+    ///
+    /// [`Bucket::from_base_index`]: Bucket::from_base_index
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
     unsafe fn bucket<T>(&self, index: usize) -> Bucket<T> {
         debug_assert_ne!(self.bucket_mask, 0);
@@ -1219,6 +2502,52 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         Bucket::from_base_index(self.data_end(), index)
     }
 
+    /// Returns a raw `*mut u8` pointer to the start of the `data` element in the table
+    /// (convenience for `self.data_end::<u8>().as_ptr().sub((index + 1) * size_of)`).
+    ///
+    /// The caller must ensure that the `RawTableInner` outlives the returned `*mut u8`,
+    /// otherwise using it may result in [`undefined behavior`].
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is [`undefined behavior`]:
+    ///
+    /// * The table must already be allocated;
+    ///
+    /// * The `index` must not be greater than the number returned by the [`RawTableInner::buckets`]
+    ///   function, i.e. `(index + 1) <= self.buckets()`;
+    ///
+    /// * The `size_of` must be equal to the size of the elements stored in the table;
+    ///
+    /// ```none
+    /// If mem::size_of::<T>() != 0 then return a pointer to the `element` in the `data part` of the table
+    /// (we start counting from "0", so that in the expression T[n], the "n" index actually one less than
+    /// the "buckets" number of our `RawTableInner`, i.e. "n = RawTableInner::buckets() - 1"):
+    ///
+    ///           `table.bucket_ptr(3, mem::size_of::<T>())` returns a pointer that points here in the
+    ///           `data` part of the `RawTableInner`, i.e. to the start of T3
+    ///                  |
+    ///                  |               `base = table.data_end::<u8>()` points here
+    ///                  |               (to the start of CT0 or to the end of T0)
+    ///                  v                 v
+    /// [Pad], T_n, ..., |T3|, T2, T1, T0, |CT0, CT1, CT2, CT3, ..., CT_n, CTa_0, CTa_1, ..., CTa_m
+    ///                                                                    \__________  __________/
+    ///                                                                               \/
+    ///                                                                    additional control bytes
+    ///                                                                     `m = Group::WIDTH - 1`
+    ///
+    /// where: T0...T_n  - our stored data;
+    ///        CT0...CT_n - control bytes or metadata for `data`;
+    ///        CTa_0...CTa_m - additional control bytes (so that the search with loading `Group` bytes from
+    ///                        the heap works properly, even if the result of `h1(hash) & self.bucket_mask`
+    ///                        is equal to `self.bucket_mask`). See also `RawTableInner::set_ctrl` function.
+    ///
+    /// P.S. `h1(hash) & self.bucket_mask` is the same as `hash as usize % self.buckets()` because the number
+    /// of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+    /// ```
+    ///
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
     unsafe fn bucket_ptr(&self, index: usize, size_of: usize) -> *mut u8 {
         debug_assert_ne!(self.bucket_mask, 0);
@@ -1227,9 +2556,44 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         base.sub((index + 1) * size_of)
     }
 
+    /// Returns pointer to one past last `data` element in the table as viewed from
+    /// the start point of the allocation (convenience for `self.ctrl.cast()`).
+    ///
+    /// This function actually returns a pointer to the end of the `data element` at
+    /// index "0" (zero).
+    ///
+    /// The caller must ensure that the `RawTableInner` outlives the returned [`NonNull<T>`],
+    /// otherwise using it may result in [`undefined behavior`].
+    ///
+    /// # Note
+    ///
+    /// The type `T` must be the actual type of the elements stored in the table, otherwise
+    /// using the returned [`NonNull<T>`] may result in [`undefined behavior`].
+    ///
+    /// ```none
+    ///                        `table.data_end::<T>()` returns pointer that points here
+    ///                        (to the end of `T0`)
+    ///                          ∨
+    /// [Pad], T_n, ..., T1, T0, |CT0, CT1, ..., CT_n|, CTa_0, CTa_1, ..., CTa_m
+    ///                           \________  ________/
+    ///                                    \/
+    ///       `n = buckets - 1`, i.e. `RawTableInner::buckets() - 1`
+    ///
+    /// where: T0...T_n  - our stored data;
+    ///        CT0...CT_n - control bytes or metadata for `data`.
+    ///        CTa_0...CTa_m - additional control bytes, where `m = Group::WIDTH - 1` (so that the search
+    ///                        with loading `Group` bytes from the heap works properly, even if the result
+    ///                        of `h1(hash) & self.bucket_mask` is equal to `self.bucket_mask`). See also
+    ///                        `RawTableInner::set_ctrl` function.
+    ///
+    /// P.S. `h1(hash) & self.bucket_mask` is the same as `hash as usize % self.buckets()` because the number
+    /// of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+    /// ```
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
-    unsafe fn data_end<T>(&self) -> NonNull<T> {
-        NonNull::new_unchecked(self.ctrl.as_ptr().cast())
+    fn data_end<T>(&self) -> NonNull<T> {
+        self.ctrl.cast()
     }
 
     /// Returns an iterator-like object for a probe sequence on the table.
@@ -1240,6 +2604,8 @@ impl<A: Allocator + Clone> RawTableInner<A> {
     #[inline]
     fn probe_seq(&self, hash: u64) -> ProbeSeq {
         ProbeSeq {
+            // This is the same as `hash as usize % self.buckets()` because the number
+            // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
             pos: h1(hash) & self.bucket_mask,
             stride: 0,
         }
@@ -1250,7 +2616,7 @@ impl<A: Allocator + Clone> RawTableInner<A> {
     #[cfg(feature = "raw")]
     #[inline]
     unsafe fn prepare_insert_no_grow(&mut self, hash: u64) -> Result<usize, ()> {
-        let index = self.find_insert_slot(hash);
+        let index = self.find_insert_slot(hash).index;
         let old_ctrl = *self.ctrl(index);
         if unlikely(self.growth_left == 0 && special_is_empty(old_ctrl)) {
             Err(())
@@ -1277,13 +2643,68 @@ impl<A: Allocator + Clone> RawTableInner<A> {
 
     /// Sets a control byte to the hash, and possibly also the replicated control byte at
     /// the end of the array.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for [`RawTableInner::set_ctrl`]
+    /// method. Thus, in order to uphold the safety contracts for the method, you must observe the
+    /// following rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::set_ctrl`]: RawTableInner::set_ctrl
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
-    unsafe fn set_ctrl_h2(&self, index: usize, hash: u64) {
+    unsafe fn set_ctrl_h2(&mut self, index: usize, hash: u64) {
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::set_ctrl_h2`]
         self.set_ctrl(index, h2(hash));
     }
 
+    /// Replaces the hash in the control byte at the given index with the provided one,
+    /// and possibly also replicates the new control byte at the end of the array of control
+    /// bytes, returning the old control byte.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for [`RawTableInner::set_ctrl_h2`]
+    /// and [`RawTableInner::ctrl`] methods. Thus, in order to uphold the safety contracts for both
+    /// methods, you must observe the following rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::set_ctrl_h2`]: RawTableInner::set_ctrl_h2
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
-    unsafe fn replace_ctrl_h2(&self, index: usize, hash: u64) -> u8 {
+    unsafe fn replace_ctrl_h2(&mut self, index: usize, hash: u64) -> u8 {
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::replace_ctrl_h2`]
         let prev_ctrl = *self.ctrl(index);
         self.set_ctrl_h2(index, hash);
         prev_ctrl
@@ -1291,10 +2712,35 @@ impl<A: Allocator + Clone> RawTableInner<A> {
 
     /// Sets a control byte, and possibly also the replicated control byte at
     /// the end of the array.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// You must observe the following safety rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
-    unsafe fn set_ctrl(&self, index: usize, ctrl: u8) {
+    unsafe fn set_ctrl(&mut self, index: usize, ctrl: u8) {
         // Replicate the first Group::WIDTH control bytes at the end of
-        // the array without using a branch:
+        // the array without using a branch. If the tables smaller than
+        // the group width (self.buckets() < Group::WIDTH),
+        // `index2 = Group::WIDTH + index`, otherwise `index2` is:
+        //
         // - If index >= Group::WIDTH then index == index2.
         // - Otherwise index2 == self.bucket_mask + 1 + index.
         //
@@ -1311,16 +2757,43 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         // ---------------------------------------------
         // | [A] | [B] | [EMPTY] | [EMPTY] | [A] | [B] |
         // ---------------------------------------------
+
+        // This is the same as `(index.wrapping_sub(Group::WIDTH)) % self.buckets() + Group::WIDTH`
+        // because the number of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
         let index2 = ((index.wrapping_sub(Group::WIDTH)) & self.bucket_mask) + Group::WIDTH;
 
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::set_ctrl`]
         *self.ctrl(index) = ctrl;
         *self.ctrl(index2) = ctrl;
     }
 
     /// Returns a pointer to a control byte.
+    ///
+    /// # Safety
+    ///
+    /// For the allocated [`RawTableInner`], the result is [`Undefined Behavior`],
+    /// if the `index` is greater than the `self.bucket_mask + 1 + Group::WIDTH`.
+    /// In that case, calling this function with `index == self.bucket_mask + 1 + Group::WIDTH`
+    /// will return a pointer to the end of the allocated table and it is useless on its own.
+    ///
+    /// Calling this function with `index >= self.bucket_mask + 1 + Group::WIDTH` on a
+    /// table that has not been allocated results in [`Undefined Behavior`].
+    ///
+    /// So to satisfy both requirements you should always follow the rule that
+    /// `index < self.bucket_mask + 1 + Group::WIDTH`
+    ///
+    /// Calling this function on [`RawTableInner`] that are not already allocated is safe
+    /// for read-only purpose.
+    ///
+    /// See also [`Bucket::as_ptr()`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`Bucket::as_ptr()`]: Bucket::as_ptr()
+    /// [`Undefined Behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
     unsafe fn ctrl(&self, index: usize) -> *mut u8 {
         debug_assert!(index < self.num_ctrl_bytes());
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::ctrl`]
         self.ctrl.as_ptr().add(index)
     }
 
@@ -1329,6 +2802,17 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         self.bucket_mask + 1
     }
 
+    /// Checks whether the bucket at `index` is full.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure `index` is less than the number of buckets.
+    #[inline]
+    unsafe fn is_bucket_full(&self, index: usize) -> bool {
+        debug_assert!(index < self.buckets());
+        is_full(*self.ctrl(index))
+    }
+
     #[inline]
     fn num_ctrl_bytes(&self) -> usize {
         self.bucket_mask + 1 + Group::WIDTH
@@ -1339,25 +2823,45 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         self.bucket_mask == 0
     }
 
+    /// Attempts to allocate a new hash table with at least enough capacity
+    /// for inserting the given number of elements without reallocating,
+    /// and return it inside ScopeGuard to protect against panic in the hash
+    /// function.
+    ///
+    /// # Note
+    ///
+    /// It is recommended (but not required):
+    ///
+    /// * That the new table's `capacity` be greater than or equal to `self.items`.
+    ///
+    /// * The `alloc` is the same [`Allocator`] as the `Allocator` used
+    ///   to allocate this table.
+    ///
+    /// * The `table_layout` is the same [`TableLayout`] as the `TableLayout` used
+    ///   to allocate this table.
+    ///
+    /// If `table_layout` does not match the `TableLayout` that was used to allocate
+    /// this table, then using `mem::swap` with the `self` and the new table returned
+    /// by this function results in [`undefined behavior`].
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[allow(clippy::mut_mut)]
     #[inline]
-    unsafe fn prepare_resize(
+    fn prepare_resize<'a, A>(
         &self,
+        alloc: &'a A,
         table_layout: TableLayout,
         capacity: usize,
         fallibility: Fallibility,
-    ) -> Result<crate::scopeguard::ScopeGuard<Self, impl FnMut(&mut Self)>, TryReserveError> {
+    ) -> Result<crate::scopeguard::ScopeGuard<Self, impl FnMut(&mut Self) + 'a>, TryReserveError>
+    where
+        A: Allocator,
+    {
         debug_assert!(self.items <= capacity);
 
         // Allocate and initialize the new table.
-        let mut new_table = RawTableInner::fallible_with_capacity(
-            self.alloc.clone(),
-            table_layout,
-            capacity,
-            fallibility,
-        )?;
-        new_table.growth_left -= self.items;
-        new_table.items = self.items;
+        let new_table =
+            RawTableInner::fallible_with_capacity(alloc, table_layout, capacity, fallibility)?;
 
         // The hash function may panic, in which case we simply free the new
         // table without dropping any elements that may have been copied into
@@ -1367,7 +2871,11 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         // the comment at the bottom of this function.
         Ok(guard(new_table, move |self_| {
             if !self_.is_empty_singleton() {
-                self_.free_buckets(table_layout);
+                // SAFETY:
+                // 1. We have checked that our table is allocated.
+                // 2. We know for sure that the `alloc` and `table_layout` matches the
+                //    [`Allocator`] and [`TableLayout`] used to allocate this table.
+                unsafe { self_.free_buckets(alloc, table_layout) };
             }
         }))
     }
@@ -1376,16 +2884,38 @@ impl<A: Allocator + Clone> RawTableInner<A> {
     ///
     /// This uses dynamic dispatch to reduce the amount of
     /// code generated, but it is eliminated by LLVM optimizations when inlined.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`undefined behavior`]:
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` used
+    ///   to allocate this table.
+    ///
+    /// * The `layout` must be the same [`TableLayout`] as the `TableLayout`
+    ///   used to allocate this table.
+    ///
+    /// * The `drop` function (`fn(*mut u8)`) must be the actual drop function of
+    ///   the elements stored in the table.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[allow(clippy::inline_always)]
     #[inline(always)]
-    unsafe fn reserve_rehash_inner(
+    unsafe fn reserve_rehash_inner<A>(
         &mut self,
+        alloc: &A,
         additional: usize,
         hasher: &dyn Fn(&mut Self, usize) -> u64,
         fallibility: Fallibility,
         layout: TableLayout,
         drop: Option<fn(*mut u8)>,
-    ) -> Result<(), TryReserveError> {
+    ) -> Result<(), TryReserveError>
+    where
+        A: Allocator,
+    {
         // Avoid `Option::ok_or_else` because it bloats LLVM IR.
         let new_items = match self.items.checked_add(additional) {
             Some(new_items) => new_items,
@@ -1395,12 +2925,30 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         if new_items <= full_capacity / 2 {
             // Rehash in-place without re-allocating if we have plenty of spare
             // capacity that is locked up due to DELETED entries.
+
+            // SAFETY:
+            // 1. We know for sure that `[`RawTableInner`]` has already been allocated
+            //    (since new_items <= full_capacity / 2);
+            // 2. The caller ensures that `drop` function is the actual drop function of
+            //    the elements stored in the table.
+            // 3. The caller ensures that `layout` matches the [`TableLayout`] that was
+            //    used to allocate this table.
+            // 4. The caller ensures that the control bytes of the `RawTableInner`
+            //    are already initialized.
             self.rehash_in_place(hasher, layout.size, drop);
             Ok(())
         } else {
             // Otherwise, conservatively resize to at least the next size up
             // to avoid churning deletes into frequent rehashes.
+            //
+            // SAFETY:
+            // 1. We know for sure that `capacity >= self.items`.
+            // 2. The caller ensures that `alloc` and `layout` matches the [`Allocator`] and
+            //    [`TableLayout`] that were used to allocate this table.
+            // 3. The caller ensures that the control bytes of the `RawTableInner`
+            //    are already initialized.
             self.resize_inner(
+                alloc,
                 usize::max(new_items, full_capacity + 1),
                 hasher,
                 fallibility,
@@ -1409,48 +2957,160 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         }
     }
 
+    /// Returns an iterator over full buckets indices in the table.
+    ///
+    /// # Safety
+    ///
+    /// Behavior is undefined if any of the following conditions are violated:
+    ///
+    /// * The caller has to ensure that the `RawTableInner` outlives the
+    ///   `FullBucketsIndices`. Because we cannot make the `next` method
+    ///   unsafe on the `FullBucketsIndices` struct, we have to make the
+    ///   `full_buckets_indices` method unsafe.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    #[inline(always)]
+    unsafe fn full_buckets_indices(&self) -> FullBucketsIndices {
+        // SAFETY:
+        // 1. Since the caller of this function ensures that the control bytes
+        //    are properly initialized and `self.ctrl(0)` points to the start
+        //    of the array of control bytes, therefore: `ctrl` is valid for reads,
+        //    properly aligned to `Group::WIDTH` and points to the properly initialized
+        //    control bytes.
+        // 2. The value of `items` is equal to the amount of data (values) added
+        //    to the table.
+        //
+        //                         `ctrl` points here (to the start
+        //                         of the first control byte `CT0`)
+        //                          ∨
+        // [Pad], T_n, ..., T1, T0, |CT0, CT1, ..., CT_n|, Group::WIDTH
+        //                           \________  ________/
+        //                                    \/
+        //       `n = buckets - 1`, i.e. `RawTableInner::buckets() - 1`
+        //
+        // where: T0...T_n  - our stored data;
+        //        CT0...CT_n - control bytes or metadata for `data`.
+        let ctrl = NonNull::new_unchecked(self.ctrl(0));
+
+        FullBucketsIndices {
+            // Load the first group
+            // SAFETY: See explanation above.
+            current_group: Group::load_aligned(ctrl.as_ptr()).match_full().into_iter(),
+            group_first_index: 0,
+            ctrl,
+            items: self.items,
+        }
+    }
+
     /// Allocates a new table of a different size and moves the contents of the
     /// current table into it.
     ///
     /// This uses dynamic dispatch to reduce the amount of
     /// code generated, but it is eliminated by LLVM optimizations when inlined.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`undefined behavior`]:
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` used
+    ///   to allocate this table;
+    ///
+    /// * The `layout` must be the same [`TableLayout`] as the `TableLayout`
+    ///   used to allocate this table;
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// The caller of this function must ensure that `capacity >= self.items`
+    /// otherwise:
+    ///
+    /// * If `self.items != 0`, calling of this function with `capacity == 0`
+    ///   results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) < Group::WIDTH` and
+    ///   `self.items > capacity_to_buckets(capacity)` calling this function
+    ///   results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) >= Group::WIDTH` and
+    ///   `self.items > capacity_to_buckets(capacity)` calling this function
+    ///   are never return (will go into an infinite loop).
+    ///
+    /// Note: It is recommended (but not required) that the new table's `capacity`
+    /// be greater than or equal to `self.items`. In case if `capacity <= self.items`
+    /// this function can never return. See [`RawTableInner::find_insert_slot`] for
+    /// more information.
+    ///
+    /// [`RawTableInner::find_insert_slot`]: RawTableInner::find_insert_slot
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[allow(clippy::inline_always)]
     #[inline(always)]
-    unsafe fn resize_inner(
+    unsafe fn resize_inner<A>(
         &mut self,
+        alloc: &A,
         capacity: usize,
         hasher: &dyn Fn(&mut Self, usize) -> u64,
         fallibility: Fallibility,
         layout: TableLayout,
-    ) -> Result<(), TryReserveError> {
-        let mut new_table = self.prepare_resize(layout, capacity, fallibility)?;
-
-        // Copy all elements to the new table.
-        for i in 0..self.buckets() {
-            if !is_full(*self.ctrl(i)) {
-                continue;
-            }
-
+    ) -> Result<(), TryReserveError>
+    where
+        A: Allocator,
+    {
+        // SAFETY: We know for sure that `alloc` and `layout` matches the [`Allocator`] and [`TableLayout`]
+        // that were used to allocate this table.
+        let mut new_table = self.prepare_resize(alloc, layout, capacity, fallibility)?;
+
+        // SAFETY: We know for sure that RawTableInner will outlive the
+        // returned `FullBucketsIndices` iterator, and the caller of this
+        // function ensures that the control bytes are properly initialized.
+        for full_byte_index in self.full_buckets_indices() {
             // This may panic.
-            let hash = hasher(self, i);
+            let hash = hasher(self, full_byte_index);
 
+            // SAFETY:
             // We can use a simpler version of insert() here since:
-            // - there are no DELETED entries.
-            // - we know there is enough space in the table.
-            // - all elements are unique.
-            let (index, _) = new_table.prepare_insert_slot(hash);
-
+            // 1. There are no DELETED entries.
+            // 2. We know there is enough space in the table.
+            // 3. All elements are unique.
+            // 4. The caller of this function guarantees that `capacity > 0`
+            //    so `new_table` must already have some allocated memory.
+            // 5. We set `growth_left` and `items` fields of the new table
+            //    after the loop.
+            // 6. We insert into the table, at the returned index, the data
+            //    matching the given hash immediately after calling this function.
+            let (new_index, _) = new_table.prepare_insert_slot(hash);
+
+            // SAFETY:
+            //
+            // * `src` is valid for reads of `layout.size` bytes, since the
+            //   table is alive and the `full_byte_index` is guaranteed to be
+            //   within bounds (see `FullBucketsIndices::next_impl`);
+            //
+            // * `dst` is valid for writes of `layout.size` bytes, since the
+            //   caller ensures that `table_layout` matches the [`TableLayout`]
+            //   that was used to allocate old table and we have the `new_index`
+            //   returned by `prepare_insert_slot`.
+            //
+            // * Both `src` and `dst` are properly aligned.
+            //
+            // * Both `src` and `dst` point to different region of memory.
             ptr::copy_nonoverlapping(
-                self.bucket_ptr(i, layout.size),
-                new_table.bucket_ptr(index, layout.size),
+                self.bucket_ptr(full_byte_index, layout.size),
+                new_table.bucket_ptr(new_index, layout.size),
                 layout.size,
             );
         }
 
+        // The hash function didn't panic, so we can safely set the
+        // `growth_left` and `items` fields of the new table.
+        new_table.growth_left -= self.items;
+        new_table.items = self.items;
+
         // We successfully copied all elements without panicking. Now replace
         // self with the new table. The old table will have its memory freed but
         // the items will not be dropped (since they have been moved into the
         // new table).
+        // SAFETY: The caller ensures that `table_layout` matches the [`TableLayout`]
+        // that was used to allocate this table.
         mem::swap(self, &mut new_table);
 
         Ok(())
@@ -1463,6 +3123,21 @@ impl<A: Allocator + Clone> RawTableInner<A> {
     ///
     /// This uses dynamic dispatch to reduce the amount of
     /// code generated, but it is eliminated by LLVM optimizations when inlined.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is [`undefined behavior`]:
+    ///
+    /// * The `size_of` must be equal to the size of the elements stored in the table;
+    ///
+    /// * The `drop` function (`fn(*mut u8)`) must be the actual drop function of
+    ///   the elements stored in the table.
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[allow(clippy::inline_always)]
     #[cfg_attr(feature = "inline-more", inline(always))]
     #[cfg_attr(not(feature = "inline-more"), inline)]
@@ -1506,8 +3181,10 @@ impl<A: Allocator + Clone> RawTableInner<A> {
                 let hash = hasher(*guard, i);
 
                 // Search for a suitable place to put it
-                let new_i = guard.find_insert_slot(hash);
-                let new_i_p = guard.bucket_ptr(new_i, size_of);
+                //
+                // SAFETY: Caller of this function ensures that the control bytes
+                // are properly initialized.
+                let new_i = guard.find_insert_slot(hash).index;
 
                 // Probing works by scanning through all of the control
                 // bytes in groups, which may not be aligned to the group
@@ -1519,6 +3196,8 @@ impl<A: Allocator + Clone> RawTableInner<A> {
                     continue 'outer;
                 }
 
+                let new_i_p = guard.bucket_ptr(new_i, size_of);
+
                 // We are moving the current item to a new position. Write
                 // our H2 to the control byte of the new position.
                 let prev_ctrl = guard.replace_ctrl_h2(new_i, hash);
@@ -1545,17 +3224,107 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         mem::forget(guard);
     }
 
+    /// Deallocates the table without dropping any entries.
+    ///
+    /// # Note
+    ///
+    /// This function must be called only after [`drop_elements`](RawTableInner::drop_elements),
+    /// else it can lead to leaking of memory. Also calling this function automatically
+    /// makes invalid (dangling) all instances of buckets ([`Bucket`]) and makes invalid
+    /// (dangling) the `ctrl` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is [`Undefined Behavior`]:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` that was used
+    ///   to allocate this table.
+    ///
+    /// * The `table_layout` must be the same [`TableLayout`] as the `TableLayout` that was used
+    ///   to allocate this table.
+    ///
+    /// See also [`GlobalAlloc::dealloc`] or [`Allocator::deallocate`] for more  information.
+    ///
+    /// [`Undefined Behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`GlobalAlloc::dealloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc
+    /// [`Allocator::deallocate`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html#tymethod.deallocate
+    #[inline]
+    unsafe fn free_buckets<A>(&mut self, alloc: &A, table_layout: TableLayout)
+    where
+        A: Allocator,
+    {
+        // SAFETY: The caller must uphold the safety contract for `free_buckets`
+        // method.
+        let (ptr, layout) = self.allocation_info(table_layout);
+        alloc.deallocate(ptr, layout);
+    }
+
+    /// Returns a pointer to the allocated memory and the layout that was used to
+    /// allocate the table.
+    ///
+    /// # Safety
+    ///
+    /// Caller of this function must observe the following safety rules:
+    ///
+    /// * The [`RawTableInner`] has already been allocated, otherwise
+    ///   calling this function results in [`undefined behavior`]
+    ///
+    /// * The `table_layout` must be the same [`TableLayout`] as the `TableLayout`
+    ///   that was used to allocate this table. Failure to comply with this condition
+    ///   may result in [`undefined behavior`].
+    ///
+    /// See also [`GlobalAlloc::dealloc`] or [`Allocator::deallocate`] for more  information.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`GlobalAlloc::dealloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc
+    /// [`Allocator::deallocate`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html#tymethod.deallocate
     #[inline]
-    unsafe fn free_buckets(&mut self, table_layout: TableLayout) {
+    unsafe fn allocation_info(&self, table_layout: TableLayout) -> (NonNull<u8>, Layout) {
+        debug_assert!(
+            !self.is_empty_singleton(),
+            "this function can only be called on non-empty tables"
+        );
+
         // Avoid `Option::unwrap_or_else` because it bloats LLVM IR.
         let (layout, ctrl_offset) = match table_layout.calculate_layout_for(self.buckets()) {
             Some(lco) => lco,
-            None => hint::unreachable_unchecked(),
+            None => unsafe { hint::unreachable_unchecked() },
         };
-        self.alloc.deallocate(
-            NonNull::new_unchecked(self.ctrl.as_ptr().sub(ctrl_offset)),
+        (
+            // SAFETY: The caller must uphold the safety contract for `allocation_info` method.
+            unsafe { NonNull::new_unchecked(self.ctrl.as_ptr().sub(ctrl_offset)) },
             layout,
-        );
+        )
+    }
+
+    /// Returns a pointer to the allocated memory and the layout that was used to
+    /// allocate the table. If [`RawTableInner`] has not been allocated, this
+    /// function return `dangling` pointer and `()` (unit) layout.
+    ///
+    /// # Safety
+    ///
+    /// The `table_layout` must be the same [`TableLayout`] as the `TableLayout`
+    /// that was used to allocate this table. Failure to comply with this condition
+    /// may result in [`undefined behavior`].
+    ///
+    /// See also [`GlobalAlloc::dealloc`] or [`Allocator::deallocate`] for more  information.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`GlobalAlloc::dealloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc
+    /// [`Allocator::deallocate`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html#tymethod.deallocate
+    #[cfg(feature = "raw")]
+    unsafe fn allocation_info_or_zero(&self, table_layout: TableLayout) -> (NonNull<u8>, Layout) {
+        if self.is_empty_singleton() {
+            (NonNull::dangling(), Layout::new::<()>())
+        } else {
+            // SAFETY:
+            // 1. We have checked that our table is allocated.
+            // 2. The caller ensures that `table_layout` matches the [`TableLayout`]
+            // that was used to allocate this table.
+            unsafe { self.allocation_info(table_layout) }
+        }
     }
 
     /// Marks all table buckets as empty without dropping their contents.
@@ -1570,27 +3339,95 @@ impl<A: Allocator + Clone> RawTableInner<A> {
         self.growth_left = bucket_mask_to_capacity(self.bucket_mask);
     }
 
+    /// Erases the [`Bucket`]'s control byte at the given index so that it does not
+    /// triggered as full, decreases the `items` of the table and, if it can be done,
+    /// increases `self.growth_left`.
+    ///
+    /// This function does not actually erase / drop the [`Bucket`] itself, i.e. it
+    /// does not make any changes to the `data` parts of the table. The caller of this
+    /// function must take care to properly drop the `data`, otherwise calling this
+    /// function may result in a memory leak.
+    ///
+    /// # Safety
+    ///
+    /// You must observe the following safety rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * It must be the full control byte at the given position;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// Calling this function on a table with no elements is unspecified, but calling subsequent
+    /// functions is likely to result in [`undefined behavior`] due to overflow subtraction
+    /// (`self.items -= 1 cause overflow when self.items == 0`).
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[inline]
     unsafe fn erase(&mut self, index: usize) {
-        debug_assert!(is_full(*self.ctrl(index)));
+        debug_assert!(self.is_bucket_full(index));
+
+        // This is the same as `index.wrapping_sub(Group::WIDTH) % self.buckets()` because
+        // the number of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
         let index_before = index.wrapping_sub(Group::WIDTH) & self.bucket_mask;
+        // SAFETY:
+        // - The caller must uphold the safety contract for `erase` method;
+        // - `index_before` is guaranteed to be in range due to masking with `self.bucket_mask`
         let empty_before = Group::load(self.ctrl(index_before)).match_empty();
         let empty_after = Group::load(self.ctrl(index)).match_empty();
 
-        // If we are inside a continuous block of Group::WIDTH full or deleted
-        // cells then a probe window may have seen a full block when trying to
-        // insert. We therefore need to keep that block non-empty so that
-        // lookups will continue searching to the next probe window.
+        // Inserting and searching in the map is performed by two key functions:
+        //
+        // - The `find_insert_slot` function that looks up the index of any `EMPTY` or `DELETED`
+        //   slot in a group to be able to insert. If it doesn't find an `EMPTY` or `DELETED`
+        //   slot immediately in the first group, it jumps to the next `Group` looking for it,
+        //   and so on until it has gone through all the groups in the control bytes.
+        //
+        // - The `find_inner` function that looks for the index of the desired element by looking
+        //   at all the `FULL` bytes in the group. If it did not find the element right away, and
+        //   there is no `EMPTY` byte in the group, then this means that the `find_insert_slot`
+        //   function may have found a suitable slot in the next group. Therefore, `find_inner`
+        //   jumps further, and if it does not find the desired element and again there is no `EMPTY`
+        //   byte, then it jumps further, and so on. The search stops only if `find_inner` function
+        //   finds the desired element or hits an `EMPTY` slot/byte.
+        //
+        // Accordingly, this leads to two consequences:
         //
-        // Note that in this context `leading_zeros` refers to the bytes at the
-        // end of a group, while `trailing_zeros` refers to the bytes at the
-        // beginning of a group.
+        // - The map must have `EMPTY` slots (bytes);
+        //
+        // - You can't just mark the byte to be erased as `EMPTY`, because otherwise the `find_inner`
+        //   function may stumble upon an `EMPTY` byte before finding the desired element and stop
+        //   searching.
+        //
+        // Thus it is necessary to check all bytes after and before the erased element. If we are in
+        // a contiguous `Group` of `FULL` or `DELETED` bytes (the number of `FULL` or `DELETED` bytes
+        // before and after is greater than or equal to `Group::WIDTH`), then we must mark our byte as
+        // `DELETED` in order for the `find_inner` function to go further. On the other hand, if there
+        // is at least one `EMPTY` slot in the `Group`, then the `find_inner` function will still stumble
+        // upon an `EMPTY` byte, so we can safely mark our erased byte as `EMPTY` as well.
+        //
+        // Finally, since `index_before == (index.wrapping_sub(Group::WIDTH) & self.bucket_mask) == index`
+        // and given all of the above, tables smaller than the group width (self.buckets() < Group::WIDTH)
+        // cannot have `DELETED` bytes.
+        //
+        // Note that in this context `leading_zeros` refers to the bytes at the end of a group, while
+        // `trailing_zeros` refers to the bytes at the beginning of a group.
         let ctrl = if empty_before.leading_zeros() + empty_after.trailing_zeros() >= Group::WIDTH {
             DELETED
         } else {
             self.growth_left += 1;
             EMPTY
         };
+        // SAFETY: the caller must uphold the safety contract for `erase` method.
         self.set_ctrl(index, ctrl);
         self.items -= 1;
     }
@@ -1599,12 +3436,16 @@ impl<A: Allocator + Clone> RawTableInner<A> {
 impl<T: Clone, A: Allocator + Clone> Clone for RawTable<T, A> {
     fn clone(&self) -> Self {
         if self.table.is_empty_singleton() {
-            Self::new_in(self.table.alloc.clone())
+            Self::new_in(self.alloc.clone())
         } else {
             unsafe {
                 // Avoid `Result::ok_or_else` because it bloats LLVM IR.
-                let new_table = match Self::new_uninitialized(
-                    self.table.alloc.clone(),
+                //
+                // SAFETY: This is safe as we are taking the size of an already allocated table
+                // and therefore сapacity overflow cannot occur, `self.table.buckets()` is power
+                // of two and all allocator errors will be caught inside `RawTableInner::new_uninitialized`.
+                let mut new_table = match Self::new_uninitialized(
+                    self.alloc.clone(),
                     self.table.buckets(),
                     Fallibility::Infallible,
                 ) {
@@ -1612,24 +3453,32 @@ impl<T: Clone, A: Allocator + Clone> Clone for RawTable<T, A> {
                     Err(_) => hint::unreachable_unchecked(),
                 };
 
-                // If cloning fails then we need to free the allocation for the
-                // new table. However we don't run its drop since its control
-                // bytes are not initialized yet.
-                let mut guard = guard(ManuallyDrop::new(new_table), |new_table| {
-                    new_table.free_buckets();
-                });
-
-                guard.clone_from_spec(self);
-
-                // Disarm the scope guard and return the newly created table.
-                ManuallyDrop::into_inner(ScopeGuard::into_inner(guard))
+                // Cloning elements may fail (the clone function may panic). But we don't
+                // need to worry about uninitialized control bits, since:
+                // 1. The number of items (elements) in the table is zero, which means that
+                //    the control bits will not be readed by Drop function.
+                // 2. The `clone_from_spec` method will first copy all control bits from
+                //    `self` (thus initializing them). But this will not affect the `Drop`
+                //    function, since the `clone_from_spec` function sets `items` only after
+                //    successfully clonning all elements.
+                new_table.clone_from_spec(self);
+                new_table
             }
         }
     }
 
     fn clone_from(&mut self, source: &Self) {
         if source.table.is_empty_singleton() {
-            *self = Self::new_in(self.table.alloc.clone());
+            let mut old_inner = mem::replace(&mut self.table, RawTableInner::NEW);
+            unsafe {
+                // SAFETY:
+                // 1. We call the function only once;
+                // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+                //    and [`TableLayout`] that were used to allocate this table.
+                // 3. If any elements' drop function panics, then there will only be a memory leak,
+                //    because we have replaced the inner table with a new one.
+                old_inner.drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+            }
         } else {
             unsafe {
                 // Make sure that if any panics occurs, we clear the table and
@@ -1644,27 +3493,38 @@ impl<T: Clone, A: Allocator + Clone> Clone for RawTable<T, A> {
                 //
                 // This leak is unavoidable: we can't try dropping more elements
                 // since this could lead to another panic and abort the process.
-                self_.drop_elements();
+                //
+                // SAFETY: If something gets wrong we clear our table right after
+                // dropping the elements, so there is no double drop, since `items`
+                // will be equal to zero.
+                self_.table.drop_elements::<T>();
 
                 // If necessary, resize our table to match the source.
                 if self_.buckets() != source.buckets() {
-                    // Skip our drop by using ptr::write.
-                    if !self_.table.is_empty_singleton() {
-                        self_.free_buckets();
+                    let new_inner = match RawTableInner::new_uninitialized(
+                        &self_.alloc,
+                        Self::TABLE_LAYOUT,
+                        source.buckets(),
+                        Fallibility::Infallible,
+                    ) {
+                        Ok(table) => table,
+                        Err(_) => hint::unreachable_unchecked(),
+                    };
+                    // Replace the old inner with new uninitialized one. It's ok, since if something gets
+                    // wrong `ScopeGuard` will initialize all control bytes and leave empty table.
+                    let mut old_inner = mem::replace(&mut self_.table, new_inner);
+                    if !old_inner.is_empty_singleton() {
+                        // SAFETY:
+                        // 1. We have checked that our table is allocated.
+                        // 2. We know for sure that `alloc` and `table_layout` matches
+                        // the [`Allocator`] and [`TableLayout`] that were used to allocate this table.
+                        old_inner.free_buckets(&self_.alloc, Self::TABLE_LAYOUT);
                     }
-                    (&mut **self_ as *mut Self).write(
-                        // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
-                        match Self::new_uninitialized(
-                            self_.table.alloc.clone(),
-                            source.buckets(),
-                            Fallibility::Infallible,
-                        ) {
-                            Ok(table) => table,
-                            Err(_) => hint::unreachable_unchecked(),
-                        },
-                    );
                 }
 
+                // Cloning elements may fail (the clone function may panic), but the `ScopeGuard`
+                // inside the `clone_from_impl` function will take care of that, dropping all
+                // cloned elements if necessary. Our `ScopeGuard` will clear the table.
                 self_.clone_from_spec(source);
 
                 // Disarm the scope guard if cloning was successful.
@@ -1696,7 +3556,8 @@ impl<T: Copy, A: Allocator + Clone> RawTableClone for RawTable<T, A> {
             .copy_to_nonoverlapping(self.table.ctrl(0), self.table.num_ctrl_bytes());
         source
             .data_start()
-            .copy_to_nonoverlapping(self.data_start(), self.table.buckets());
+            .as_ptr()
+            .copy_to_nonoverlapping(self.data_start().as_ptr(), self.table.buckets());
 
         self.table.items = source.table.items;
         self.table.growth_left = source.table.growth_left;
@@ -1720,9 +3581,9 @@ impl<T: Clone, A: Allocator + Clone> RawTable<T, A> {
         // to make sure we drop only the elements that have been
         // cloned so far.
         let mut guard = guard((0, &mut *self), |(index, self_)| {
-            if mem::needs_drop::<T>() && !self_.is_empty() {
-                for i in 0..=*index {
-                    if is_full(*self_.table.ctrl(i)) {
+            if T::NEEDS_DROP {
+                for i in 0..*index {
+                    if self_.is_bucket_full(i) {
                         self_.bucket(i).drop();
                     }
                 }
@@ -1735,7 +3596,7 @@ impl<T: Clone, A: Allocator + Clone> RawTable<T, A> {
             to.write(from.as_ref().clone());
 
             // Update the index in case we need to unwind.
-            guard.0 = index;
+            guard.0 = index + 1;
         }
 
         // Successfully cloned all items, no need to clean up.
@@ -1757,7 +3618,7 @@ impl<T: Clone, A: Allocator + Clone> RawTable<T, A> {
         {
             self.clear();
 
-            let guard_self = guard(&mut *self, |self_| {
+            let mut guard_self = guard(&mut *self, |self_| {
                 // Clear the partially copied table if a panic occurs, otherwise
                 // items and growth_left will be out of sync with the contents
                 // of the table.
@@ -1790,7 +3651,7 @@ impl<T: Clone, A: Allocator + Clone> RawTable<T, A> {
     }
 }
 
-impl<T, A: Allocator + Clone + Default> Default for RawTable<T, A> {
+impl<T, A: Allocator + Default> Default for RawTable<T, A> {
     #[inline]
     fn default() -> Self {
         Self::new_in(Default::default())
@@ -1798,31 +3659,41 @@ impl<T, A: Allocator + Clone + Default> Default for RawTable<T, A> {
 }
 
 #[cfg(feature = "nightly")]
-unsafe impl<#[may_dangle] T, A: Allocator + Clone> Drop for RawTable<T, A> {
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawTable<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
-        if !self.table.is_empty_singleton() {
-            unsafe {
-                self.drop_elements();
-                self.free_buckets();
-            }
+        unsafe {
+            // SAFETY:
+            // 1. We call the function only once;
+            // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+            //    and [`TableLayout`] that were used to allocate this table.
+            // 3. If the drop function of any elements fails, then only a memory leak will occur,
+            //    and we don't care because we are inside the `Drop` function of the `RawTable`,
+            //    so there won't be any table left in an inconsistent state.
+            self.table
+                .drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
         }
     }
 }
 #[cfg(not(feature = "nightly"))]
-impl<T, A: Allocator + Clone> Drop for RawTable<T, A> {
+impl<T, A: Allocator> Drop for RawTable<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
-        if !self.table.is_empty_singleton() {
-            unsafe {
-                self.drop_elements();
-                self.free_buckets();
-            }
+        unsafe {
+            // SAFETY:
+            // 1. We call the function only once;
+            // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+            //    and [`TableLayout`] that were used to allocate this table.
+            // 3. If the drop function of any elements fails, then only a memory leak will occur,
+            //    and we don't care because we are inside the `Drop` function of the `RawTable`,
+            //    so there won't be any table left in an inconsistent state.
+            self.table
+                .drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
         }
     }
 }
 
-impl<T, A: Allocator + Clone> IntoIterator for RawTable<T, A> {
+impl<T, A: Allocator> IntoIterator for RawTable<T, A> {
     type Item = T;
     type IntoIter = RawIntoIter<T, A>;
 
@@ -1840,7 +3711,7 @@ impl<T, A: Allocator + Clone> IntoIterator for RawTable<T, A> {
 pub(crate) struct RawIterRange<T> {
     // Mask of full buckets in the current group. Bits are cleared from this
     // mask as each element is processed.
-    current_group: BitMask,
+    current_group: BitMaskIter,
 
     // Pointer to the buckets for the current group.
     data: Bucket<T>,
@@ -1856,19 +3727,44 @@ pub(crate) struct RawIterRange<T> {
 impl<T> RawIterRange<T> {
     /// Returns a `RawIterRange` covering a subset of a table.
     ///
-    /// The control byte address must be aligned to the group size.
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`undefined behavior`]:
+    ///
+    /// * `ctrl` must be [valid] for reads, i.e. table outlives the `RawIterRange`;
+    ///
+    /// * `ctrl` must be properly aligned to the group size (Group::WIDTH);
+    ///
+    /// * `ctrl` must point to the array of properly initialized control bytes;
+    ///
+    /// * `data` must be the [`Bucket`] at the `ctrl` index in the table;
+    ///
+    /// * the value of `len` must be less than or equal to the number of table buckets,
+    ///   and the returned value of `ctrl.as_ptr().add(len).offset_from(ctrl.as_ptr())`
+    ///   must be positive.
+    ///
+    /// * The `ctrl.add(len)` pointer must be either in bounds or one
+    ///   byte past the end of the same [allocated table].
+    ///
+    /// * The `len` must be a power of two.
+    ///
+    /// [valid]: https://doc.rust-lang.org/std/ptr/index.html#safety
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     #[cfg_attr(feature = "inline-more", inline)]
     unsafe fn new(ctrl: *const u8, data: Bucket<T>, len: usize) -> Self {
         debug_assert_ne!(len, 0);
         debug_assert_eq!(ctrl as usize % Group::WIDTH, 0);
+        // SAFETY: The caller must uphold the safety rules for the [`RawIterRange::new`]
         let end = ctrl.add(len);
 
         // Load the first group and advance ctrl to point to the next group
+        // SAFETY: The caller must uphold the safety rules for the [`RawIterRange::new`]
         let current_group = Group::load_aligned(ctrl).match_full();
         let next_ctrl = ctrl.add(Group::WIDTH);
 
         Self {
-            current_group,
+            current_group: current_group.into_iter(),
             data,
             next_ctrl,
             end,
@@ -1925,8 +3821,7 @@ impl<T> RawIterRange<T> {
     #[cfg_attr(feature = "inline-more", inline)]
     unsafe fn next_impl<const DO_CHECK_PTR_RANGE: bool>(&mut self) -> Option<Bucket<T>> {
         loop {
-            if let Some(index) = self.current_group.lowest_set_bit() {
-                self.current_group = self.current_group.remove_lowest_bit();
+            if let Some(index) = self.current_group.next() {
                 return Some(self.data.next_n(index));
             }
 
@@ -1939,7 +3834,86 @@ impl<T> RawIterRange<T> {
             // than the group size where the trailing control bytes are all
             // EMPTY. On larger tables self.end is guaranteed to be aligned
             // to the group size (since tables are power-of-two sized).
-            self.current_group = Group::load_aligned(self.next_ctrl).match_full();
+            self.current_group = Group::load_aligned(self.next_ctrl).match_full().into_iter();
+            self.data = self.data.next_n(Group::WIDTH);
+            self.next_ctrl = self.next_ctrl.add(Group::WIDTH);
+        }
+    }
+
+    /// Folds every element into an accumulator by applying an operation,
+    /// returning the final result.
+    ///
+    /// `fold_impl()` takes three arguments: the number of items remaining in
+    /// the iterator, an initial value, and a closure with two arguments: an
+    /// 'accumulator', and an element. The closure returns the value that the
+    /// accumulator should have for the next iteration.
+    ///
+    /// The initial value is the value the accumulator will have on the first call.
+    ///
+    /// After applying this closure to every element of the iterator, `fold_impl()`
+    /// returns the accumulator.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`Undefined Behavior`]:
+    ///
+    /// * The [`RawTableInner`] / [`RawTable`] must be alive and not moved,
+    ///   i.e. table outlives the `RawIterRange`;
+    ///
+    /// * The provided `n` value must match the actual number of items
+    ///   in the table.
+    ///
+    /// [`Undefined Behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[allow(clippy::while_let_on_iterator)]
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn fold_impl<F, B>(mut self, mut n: usize, mut acc: B, mut f: F) -> B
+    where
+        F: FnMut(B, Bucket<T>) -> B,
+    {
+        loop {
+            while let Some(index) = self.current_group.next() {
+                // The returned `index` will always be in the range `0..Group::WIDTH`,
+                // so that calling `self.data.next_n(index)` is safe (see detailed explanation below).
+                debug_assert!(n != 0);
+                let bucket = self.data.next_n(index);
+                acc = f(acc, bucket);
+                n -= 1;
+            }
+
+            if n == 0 {
+                return acc;
+            }
+
+            // SAFETY: The caller of this function ensures that:
+            //
+            // 1. The provided `n` value matches the actual number of items in the table;
+            // 2. The table is alive and did not moved.
+            //
+            // Taking the above into account, we always stay within the bounds, because:
+            //
+            // 1. For tables smaller than the group width (self.buckets() <= Group::WIDTH),
+            //    we will never end up in the given branch, since we should have already
+            //    yielded all the elements of the table.
+            //
+            // 2. For tables larger than the group width. The number of buckets is a
+            //    power of two (2 ^ n), Group::WIDTH is also power of two (2 ^ k). Since
+            //    `(2 ^ n) > (2 ^ k)`, than `(2 ^ n) % (2 ^ k) = 0`. As we start from the
+            //    start of the array of control bytes, and never try to iterate after
+            //    getting all the elements, the last `self.current_group` will read bytes
+            //    from the `self.buckets() - Group::WIDTH` index.  We know also that
+            //    `self.current_group.next()` will always retun indices within the range
+            //    `0..Group::WIDTH`.
+            //
+            //    Knowing all of the above and taking into account that we are synchronizing
+            //    the `self.data` index with the index we used to read the `self.current_group`,
+            //    the subsequent `self.data.next_n(index)` will always return a bucket with
+            //    an index number less than `self.buckets()`.
+            //
+            //    The last `self.next_ctrl`, whose index would be `self.buckets()`, will never
+            //    actually be read, since we should have already yielded all the elements of
+            //    the table.
+            self.current_group = Group::load_aligned(self.next_ctrl).match_full().into_iter();
             self.data = self.data.next_n(Group::WIDTH);
             self.next_ctrl = self.next_ctrl.add(Group::WIDTH);
         }
@@ -2016,7 +3990,7 @@ impl<T> RawIter<T> {
     /// This method should be called _before_ the removal is made. It is not necessary to call this
     /// method if you are removing an item that this iterator yielded in the past.
     #[cfg(feature = "raw")]
-    pub fn reflect_remove(&mut self, b: &Bucket<T>) {
+    pub unsafe fn reflect_remove(&mut self, b: &Bucket<T>) {
         self.reflect_toggle_full(b, false);
     }
 
@@ -2030,36 +4004,76 @@ impl<T> RawIter<T> {
     ///
     /// This method should be called _after_ the given insert is made.
     #[cfg(feature = "raw")]
-    pub fn reflect_insert(&mut self, b: &Bucket<T>) {
+    pub unsafe fn reflect_insert(&mut self, b: &Bucket<T>) {
         self.reflect_toggle_full(b, true);
     }
 
     /// Refresh the iterator so that it reflects a change to the state of the given bucket.
     #[cfg(feature = "raw")]
-    fn reflect_toggle_full(&mut self, b: &Bucket<T>, is_insert: bool) {
-        unsafe {
-            if b.as_ptr() > self.iter.data.as_ptr() {
-                // The iterator has already passed the bucket's group.
-                // So the toggle isn't relevant to this iterator.
-                return;
+    unsafe fn reflect_toggle_full(&mut self, b: &Bucket<T>, is_insert: bool) {
+        if b.as_ptr() > self.iter.data.as_ptr() {
+            // The iterator has already passed the bucket's group.
+            // So the toggle isn't relevant to this iterator.
+            return;
+        }
+
+        if self.iter.next_ctrl < self.iter.end
+            && b.as_ptr() <= self.iter.data.next_n(Group::WIDTH).as_ptr()
+        {
+            // The iterator has not yet reached the bucket's group.
+            // We don't need to reload anything, but we do need to adjust the item count.
+
+            if cfg!(debug_assertions) {
+                // Double-check that the user isn't lying to us by checking the bucket state.
+                // To do that, we need to find its control byte. We know that self.iter.data is
+                // at self.iter.next_ctrl - Group::WIDTH, so we work from there:
+                let offset = offset_from(self.iter.data.as_ptr(), b.as_ptr());
+                let ctrl = self.iter.next_ctrl.sub(Group::WIDTH).add(offset);
+                // This method should be called _before_ a removal, or _after_ an insert,
+                // so in both cases the ctrl byte should indicate that the bucket is full.
+                assert!(is_full(*ctrl));
             }
 
-            if self.iter.next_ctrl < self.iter.end
-                && b.as_ptr() <= self.iter.data.next_n(Group::WIDTH).as_ptr()
-            {
-                // The iterator has not yet reached the bucket's group.
-                // We don't need to reload anything, but we do need to adjust the item count.
+            if is_insert {
+                self.items += 1;
+            } else {
+                self.items -= 1;
+            }
 
-                if cfg!(debug_assertions) {
-                    // Double-check that the user isn't lying to us by checking the bucket state.
-                    // To do that, we need to find its control byte. We know that self.iter.data is
-                    // at self.iter.next_ctrl - Group::WIDTH, so we work from there:
-                    let offset = offset_from(self.iter.data.as_ptr(), b.as_ptr());
-                    let ctrl = self.iter.next_ctrl.sub(Group::WIDTH).add(offset);
-                    // This method should be called _before_ a removal, or _after_ an insert,
-                    // so in both cases the ctrl byte should indicate that the bucket is full.
-                    assert!(is_full(*ctrl));
-                }
+            return;
+        }
+
+        // The iterator is at the bucket group that the toggled bucket is in.
+        // We need to do two things:
+        //
+        //  - Determine if the iterator already yielded the toggled bucket.
+        //    If it did, we're done.
+        //  - Otherwise, update the iterator cached group so that it won't
+        //    yield a to-be-removed bucket, or _will_ yield a to-be-added bucket.
+        //    We'll also need to update the item count accordingly.
+        if let Some(index) = self.iter.current_group.0.lowest_set_bit() {
+            let next_bucket = self.iter.data.next_n(index);
+            if b.as_ptr() > next_bucket.as_ptr() {
+                // The toggled bucket is "before" the bucket the iterator would yield next. We
+                // therefore don't need to do anything --- the iterator has already passed the
+                // bucket in question.
+                //
+                // The item count must already be correct, since a removal or insert "prior" to
+                // the iterator's position wouldn't affect the item count.
+            } else {
+                // The removed bucket is an upcoming bucket. We need to make sure it does _not_
+                // get yielded, and also that it's no longer included in the item count.
+                //
+                // NOTE: We can't just reload the group here, both since that might reflect
+                // inserts we've already passed, and because that might inadvertently unset the
+                // bits for _other_ removals. If we do that, we'd have to also decrement the
+                // item count for those other bits that we unset. But the presumably subsequent
+                // call to reflect for those buckets might _also_ decrement the item count.
+                // Instead, we _just_ flip the bit for the particular bucket the caller asked
+                // us to reflect.
+                let our_bit = offset_from(self.iter.data.as_ptr(), b.as_ptr());
+                let was_full = self.iter.current_group.flip(our_bit);
+                debug_assert_ne!(was_full, is_insert);
 
                 if is_insert {
                     self.items += 1;
@@ -2067,65 +4081,23 @@ impl<T> RawIter<T> {
                     self.items -= 1;
                 }
 
-                return;
-            }
-
-            // The iterator is at the bucket group that the toggled bucket is in.
-            // We need to do two things:
-            //
-            //  - Determine if the iterator already yielded the toggled bucket.
-            //    If it did, we're done.
-            //  - Otherwise, update the iterator cached group so that it won't
-            //    yield a to-be-removed bucket, or _will_ yield a to-be-added bucket.
-            //    We'll also need to update the item count accordingly.
-            if let Some(index) = self.iter.current_group.lowest_set_bit() {
-                let next_bucket = self.iter.data.next_n(index);
-                if b.as_ptr() > next_bucket.as_ptr() {
-                    // The toggled bucket is "before" the bucket the iterator would yield next. We
-                    // therefore don't need to do anything --- the iterator has already passed the
-                    // bucket in question.
-                    //
-                    // The item count must already be correct, since a removal or insert "prior" to
-                    // the iterator's position wouldn't affect the item count.
-                } else {
-                    // The removed bucket is an upcoming bucket. We need to make sure it does _not_
-                    // get yielded, and also that it's no longer included in the item count.
-                    //
-                    // NOTE: We can't just reload the group here, both since that might reflect
-                    // inserts we've already passed, and because that might inadvertently unset the
-                    // bits for _other_ removals. If we do that, we'd have to also decrement the
-                    // item count for those other bits that we unset. But the presumably subsequent
-                    // call to reflect for those buckets might _also_ decrement the item count.
-                    // Instead, we _just_ flip the bit for the particular bucket the caller asked
-                    // us to reflect.
-                    let our_bit = offset_from(self.iter.data.as_ptr(), b.as_ptr());
-                    let was_full = self.iter.current_group.flip(our_bit);
-                    debug_assert_ne!(was_full, is_insert);
-
-                    if is_insert {
-                        self.items += 1;
+                if cfg!(debug_assertions) {
+                    if b.as_ptr() == next_bucket.as_ptr() {
+                        // The removed bucket should no longer be next
+                        debug_assert_ne!(self.iter.current_group.0.lowest_set_bit(), Some(index));
                     } else {
-                        self.items -= 1;
-                    }
-
-                    if cfg!(debug_assertions) {
-                        if b.as_ptr() == next_bucket.as_ptr() {
-                            // The removed bucket should no longer be next
-                            debug_assert_ne!(self.iter.current_group.lowest_set_bit(), Some(index));
-                        } else {
-                            // We should not have changed what bucket comes next.
-                            debug_assert_eq!(self.iter.current_group.lowest_set_bit(), Some(index));
-                        }
+                        // We should not have changed what bucket comes next.
+                        debug_assert_eq!(self.iter.current_group.0.lowest_set_bit(), Some(index));
                     }
                 }
-            } else {
-                // We must have already iterated past the removed item.
             }
+        } else {
+            // We must have already iterated past the removed item.
         }
     }
 
     unsafe fn drop_elements(&mut self) {
-        if mem::needs_drop::<T>() && self.len() != 0 {
+        if T::NEEDS_DROP && self.items != 0 {
             for item in self {
                 item.drop();
             }
@@ -2159,9 +4131,8 @@ impl<T> Iterator for RawIter<T> {
             self.iter.next_impl::<false>()
         };
 
-        if nxt.is_some() {
-            self.items -= 1;
-        }
+        debug_assert!(nxt.is_some());
+        self.items -= 1;
 
         nxt
     }
@@ -2170,33 +4141,160 @@ impl<T> Iterator for RawIter<T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.items, Some(self.items))
     }
+
+    #[inline]
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        unsafe { self.iter.fold_impl(self.items, init, f) }
+    }
 }
 
 impl<T> ExactSizeIterator for RawIter<T> {}
 impl<T> FusedIterator for RawIter<T> {}
 
+/// Iterator which returns an index of every full bucket in the table.
+///
+/// For maximum flexibility this iterator is not bound by a lifetime, but you
+/// must observe several rules when using it:
+/// - You must not free the hash table while iterating (including via growing/shrinking).
+/// - It is fine to erase a bucket that has been yielded by the iterator.
+/// - Erasing a bucket that has not yet been yielded by the iterator may still
+///   result in the iterator yielding index of that bucket.
+/// - It is unspecified whether an element inserted after the iterator was
+///   created will be yielded by that iterator.
+/// - The order in which the iterator yields indices of the buckets is unspecified
+///   and may change in the future.
+pub(crate) struct FullBucketsIndices {
+    // Mask of full buckets in the current group. Bits are cleared from this
+    // mask as each element is processed.
+    current_group: BitMaskIter,
+
+    // Initial value of the bytes' indices of the current group (relative
+    // to the start of the control bytes).
+    group_first_index: usize,
+
+    // Pointer to the current group of control bytes,
+    // Must be aligned to the group size (Group::WIDTH).
+    ctrl: NonNull<u8>,
+
+    // Number of elements in the table.
+    items: usize,
+}
+
+impl FullBucketsIndices {
+    /// Advances the iterator and returns the next value.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`Undefined Behavior`]:
+    ///
+    /// * The [`RawTableInner`] / [`RawTable`] must be alive and not moved,
+    ///   i.e. table outlives the `FullBucketsIndices`;
+    ///
+    /// * It never tries to iterate after getting all elements.
+    ///
+    /// [`Undefined Behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline(always)]
+    unsafe fn next_impl(&mut self) -> Option<usize> {
+        loop {
+            if let Some(index) = self.current_group.next() {
+                // The returned `self.group_first_index + index` will always
+                // be in the range `0..self.buckets()`. See explanation below.
+                return Some(self.group_first_index + index);
+            }
+
+            // SAFETY: The caller of this function ensures that:
+            //
+            // 1. It never tries to iterate after getting all the elements;
+            // 2. The table is alive and did not moved;
+            // 3. The first `self.ctrl` pointed to the start of the array of control bytes.
+            //
+            // Taking the above into account, we always stay within the bounds, because:
+            //
+            // 1. For tables smaller than the group width (self.buckets() <= Group::WIDTH),
+            //    we will never end up in the given branch, since we should have already
+            //    yielded all the elements of the table.
+            //
+            // 2. For tables larger than the group width. The number of buckets is a
+            //    power of two (2 ^ n), Group::WIDTH is also power of two (2 ^ k). Since
+            //    `(2 ^ n) > (2 ^ k)`, than `(2 ^ n) % (2 ^ k) = 0`. As we start from the
+            //    the start of the array of control bytes, and never try to iterate after
+            //    getting all the elements, the last `self.ctrl` will be equal to
+            //    the `self.buckets() - Group::WIDTH`, so `self.current_group.next()`
+            //    will always contains indices within the range `0..Group::WIDTH`,
+            //    and subsequent `self.group_first_index + index` will always return a
+            //    number less than `self.buckets()`.
+            self.ctrl = NonNull::new_unchecked(self.ctrl.as_ptr().add(Group::WIDTH));
+
+            // SAFETY: See explanation above.
+            self.current_group = Group::load_aligned(self.ctrl.as_ptr())
+                .match_full()
+                .into_iter();
+            self.group_first_index += Group::WIDTH;
+        }
+    }
+}
+
+impl Iterator for FullBucketsIndices {
+    type Item = usize;
+
+    /// Advances the iterator and returns the next value. It is up to
+    /// the caller to ensure that the `RawTable` outlives the `FullBucketsIndices`,
+    /// because we cannot make the `next` method unsafe.
+    #[inline(always)]
+    fn next(&mut self) -> Option<usize> {
+        // Return if we already yielded all items.
+        if self.items == 0 {
+            return None;
+        }
+
+        let nxt = unsafe {
+            // SAFETY:
+            // 1. We check number of items to yield using `items` field.
+            // 2. The caller ensures that the table is alive and has not moved.
+            self.next_impl()
+        };
+
+        debug_assert!(nxt.is_some());
+        self.items -= 1;
+
+        nxt
+    }
+
+    #[inline(always)]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.items, Some(self.items))
+    }
+}
+
+impl ExactSizeIterator for FullBucketsIndices {}
+impl FusedIterator for FullBucketsIndices {}
+
 /// Iterator which consumes a table and returns elements.
-pub struct RawIntoIter<T, A: Allocator + Clone = Global> {
+pub struct RawIntoIter<T, A: Allocator = Global> {
     iter: RawIter<T>,
-    allocation: Option<(NonNull<u8>, Layout)>,
+    allocation: Option<(NonNull<u8>, Layout, A)>,
     marker: PhantomData<T>,
-    alloc: A,
 }
 
-impl<T, A: Allocator + Clone> RawIntoIter<T, A> {
+impl<T, A: Allocator> RawIntoIter<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn iter(&self) -> RawIter<T> {
         self.iter.clone()
     }
 }
 
-unsafe impl<T, A: Allocator + Clone> Send for RawIntoIter<T, A>
+unsafe impl<T, A: Allocator> Send for RawIntoIter<T, A>
 where
     T: Send,
     A: Send,
 {
 }
-unsafe impl<T, A: Allocator + Clone> Sync for RawIntoIter<T, A>
+unsafe impl<T, A: Allocator> Sync for RawIntoIter<T, A>
 where
     T: Sync,
     A: Sync,
@@ -2204,7 +4302,7 @@ where
 }
 
 #[cfg(feature = "nightly")]
-unsafe impl<#[may_dangle] T, A: Allocator + Clone> Drop for RawIntoIter<T, A> {
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawIntoIter<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
         unsafe {
@@ -2212,14 +4310,14 @@ unsafe impl<#[may_dangle] T, A: Allocator + Clone> Drop for RawIntoIter<T, A> {
             self.iter.drop_elements();
 
             // Free the table
-            if let Some((ptr, layout)) = self.allocation {
-                self.alloc.deallocate(ptr, layout);
+            if let Some((ptr, layout, ref alloc)) = self.allocation {
+                alloc.deallocate(ptr, layout);
             }
         }
     }
 }
 #[cfg(not(feature = "nightly"))]
-impl<T, A: Allocator + Clone> Drop for RawIntoIter<T, A> {
+impl<T, A: Allocator> Drop for RawIntoIter<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
         unsafe {
@@ -2227,14 +4325,14 @@ impl<T, A: Allocator + Clone> Drop for RawIntoIter<T, A> {
             self.iter.drop_elements();
 
             // Free the table
-            if let Some((ptr, layout)) = self.allocation {
-                self.alloc.deallocate(ptr, layout);
+            if let Some((ptr, layout, ref alloc)) = self.allocation {
+                alloc.deallocate(ptr, layout);
             }
         }
     }
 }
 
-impl<T, A: Allocator + Clone> Iterator for RawIntoIter<T, A> {
+impl<T, A: Allocator> Iterator for RawIntoIter<T, A> {
     type Item = T;
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -2248,45 +4346,45 @@ impl<T, A: Allocator + Clone> Iterator for RawIntoIter<T, A> {
     }
 }
 
-impl<T, A: Allocator + Clone> ExactSizeIterator for RawIntoIter<T, A> {}
-impl<T, A: Allocator + Clone> FusedIterator for RawIntoIter<T, A> {}
+impl<T, A: Allocator> ExactSizeIterator for RawIntoIter<T, A> {}
+impl<T, A: Allocator> FusedIterator for RawIntoIter<T, A> {}
 
 /// Iterator which consumes elements without freeing the table storage.
-pub struct RawDrain<'a, T, A: Allocator + Clone = Global> {
+pub struct RawDrain<'a, T, A: Allocator = Global> {
     iter: RawIter<T>,
 
     // The table is moved into the iterator for the duration of the drain. This
     // ensures that an empty table is left if the drain iterator is leaked
     // without dropping.
-    table: ManuallyDrop<RawTable<T, A>>,
-    orig_table: NonNull<RawTable<T, A>>,
+    table: RawTableInner,
+    orig_table: NonNull<RawTableInner>,
 
     // We don't use a &'a mut RawTable<T> because we want RawDrain to be
     // covariant over T.
     marker: PhantomData<&'a RawTable<T, A>>,
 }
 
-impl<T, A: Allocator + Clone> RawDrain<'_, T, A> {
+impl<T, A: Allocator> RawDrain<'_, T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn iter(&self) -> RawIter<T> {
         self.iter.clone()
     }
 }
 
-unsafe impl<T, A: Allocator + Copy> Send for RawDrain<'_, T, A>
+unsafe impl<T, A: Allocator> Send for RawDrain<'_, T, A>
 where
     T: Send,
     A: Send,
 {
 }
-unsafe impl<T, A: Allocator + Copy> Sync for RawDrain<'_, T, A>
+unsafe impl<T, A: Allocator> Sync for RawDrain<'_, T, A>
 where
     T: Sync,
     A: Sync,
 {
 }
 
-impl<T, A: Allocator + Clone> Drop for RawDrain<'_, T, A> {
+impl<T, A: Allocator> Drop for RawDrain<'_, T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
         unsafe {
@@ -2300,12 +4398,12 @@ impl<T, A: Allocator + Clone> Drop for RawDrain<'_, T, A> {
             // Move the now empty table back to its original location.
             self.orig_table
                 .as_ptr()
-                .copy_from_nonoverlapping(&*self.table, 1);
+                .copy_from_nonoverlapping(&self.table, 1);
         }
     }
 }
 
-impl<T, A: Allocator + Clone> Iterator for RawDrain<'_, T, A> {
+impl<T, A: Allocator> Iterator for RawDrain<'_, T, A> {
     type Item = T;
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -2322,21 +4420,36 @@ impl<T, A: Allocator + Clone> Iterator for RawDrain<'_, T, A> {
     }
 }
 
-impl<T, A: Allocator + Clone> ExactSizeIterator for RawDrain<'_, T, A> {}
-impl<T, A: Allocator + Clone> FusedIterator for RawDrain<'_, T, A> {}
+impl<T, A: Allocator> ExactSizeIterator for RawDrain<'_, T, A> {}
+impl<T, A: Allocator> FusedIterator for RawDrain<'_, T, A> {}
 
 /// Iterator over occupied buckets that could match a given hash.
 ///
 /// `RawTable` only stores 7 bits of the hash value, so this iterator may return
 /// items that have a hash value different than the one provided. You should
 /// always validate the returned values before using them.
-pub struct RawIterHash<'a, T, A: Allocator + Clone = Global> {
-    inner: RawIterHashInner<'a, A>,
+///
+/// For maximum flexibility this iterator is not bound by a lifetime, but you
+/// must observe several rules when using it:
+/// - You must not free the hash table while iterating (including via growing/shrinking).
+/// - It is fine to erase a bucket that has been yielded by the iterator.
+/// - Erasing a bucket that has not yet been yielded by the iterator may still
+///   result in the iterator yielding that bucket.
+/// - It is unspecified whether an element inserted after the iterator was
+///   created will be yielded by that iterator.
+/// - The order in which the iterator yields buckets is unspecified and may
+///   change in the future.
+pub struct RawIterHash<T> {
+    inner: RawIterHashInner,
     _marker: PhantomData<T>,
 }
 
-struct RawIterHashInner<'a, A: Allocator + Clone> {
-    table: &'a RawTableInner<A>,
+struct RawIterHashInner {
+    // See `RawTableInner`'s corresponding fields for details.
+    // We can't store a `*const RawTableInner` as it would get
+    // invalidated by the user calling `&mut` methods on `RawTable`.
+    bucket_mask: usize,
+    ctrl: NonNull<u8>,
 
     // The top 7 bits of the hash.
     h2_hash: u8,
@@ -2350,71 +4463,105 @@ struct RawIterHashInner<'a, A: Allocator + Clone> {
     bitmask: BitMaskIter,
 }
 
-impl<'a, T, A: Allocator + Clone> RawIterHash<'a, T, A> {
+impl<T> RawIterHash<T> {
     #[cfg_attr(feature = "inline-more", inline)]
     #[cfg(feature = "raw")]
-    fn new(table: &'a RawTable<T, A>, hash: u64) -> Self {
+    unsafe fn new<A: Allocator>(table: &RawTable<T, A>, hash: u64) -> Self {
         RawIterHash {
             inner: RawIterHashInner::new(&table.table, hash),
             _marker: PhantomData,
         }
     }
 }
-impl<'a, A: Allocator + Clone> RawIterHashInner<'a, A> {
+impl RawIterHashInner {
     #[cfg_attr(feature = "inline-more", inline)]
     #[cfg(feature = "raw")]
-    fn new(table: &'a RawTableInner<A>, hash: u64) -> Self {
-        unsafe {
-            let h2_hash = h2(hash);
-            let probe_seq = table.probe_seq(hash);
-            let group = Group::load(table.ctrl(probe_seq.pos));
-            let bitmask = group.match_byte(h2_hash).into_iter();
-
-            RawIterHashInner {
-                table,
-                h2_hash,
-                probe_seq,
-                group,
-                bitmask,
-            }
+    unsafe fn new(table: &RawTableInner, hash: u64) -> Self {
+        let h2_hash = h2(hash);
+        let probe_seq = table.probe_seq(hash);
+        let group = Group::load(table.ctrl(probe_seq.pos));
+        let bitmask = group.match_byte(h2_hash).into_iter();
+
+        RawIterHashInner {
+            bucket_mask: table.bucket_mask,
+            ctrl: table.ctrl,
+            h2_hash,
+            probe_seq,
+            group,
+            bitmask,
         }
     }
 }
 
-impl<'a, T, A: Allocator + Clone> Iterator for RawIterHash<'a, T, A> {
+impl<T> Iterator for RawIterHash<T> {
     type Item = Bucket<T>;
 
     fn next(&mut self) -> Option<Bucket<T>> {
         unsafe {
             match self.inner.next() {
-                Some(index) => Some(self.inner.table.bucket(index)),
+                Some(index) => {
+                    // Can't use `RawTable::bucket` here as we don't have
+                    // an actual `RawTable` reference to use.
+                    debug_assert!(index <= self.inner.bucket_mask);
+                    let bucket = Bucket::from_base_index(self.inner.ctrl.cast(), index);
+                    Some(bucket)
+                }
                 None => None,
             }
         }
     }
 }
 
-impl<'a, A: Allocator + Clone> Iterator for RawIterHashInner<'a, A> {
+impl Iterator for RawIterHashInner {
     type Item = usize;
 
     fn next(&mut self) -> Option<Self::Item> {
         unsafe {
             loop {
                 if let Some(bit) = self.bitmask.next() {
-                    let index = (self.probe_seq.pos + bit) & self.table.bucket_mask;
+                    let index = (self.probe_seq.pos + bit) & self.bucket_mask;
                     return Some(index);
                 }
                 if likely(self.group.match_empty().any_bit_set()) {
                     return None;
                 }
-                self.probe_seq.move_next(self.table.bucket_mask);
-                self.group = Group::load(self.table.ctrl(self.probe_seq.pos));
+                self.probe_seq.move_next(self.bucket_mask);
+
+                // Can't use `RawTableInner::ctrl` here as we don't have
+                // an actual `RawTableInner` reference to use.
+                let index = self.probe_seq.pos;
+                debug_assert!(index < self.bucket_mask + 1 + Group::WIDTH);
+                let group_ctrl = self.ctrl.as_ptr().add(index);
+
+                self.group = Group::load(group_ctrl);
                 self.bitmask = self.group.match_byte(self.h2_hash).into_iter();
             }
         }
     }
 }
 
+pub(crate) struct RawExtractIf<'a, T, A: Allocator> {
+    pub iter: RawIter<T>,
+    pub table: &'a mut RawTable<T, A>,
+}
+
+impl<T, A: Allocator> RawExtractIf<'_, T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub(crate) fn next<F>(&mut self, mut f: F) -> Option<T>
+    where
+        F: FnMut(&mut T) -> bool,
+    {
+        unsafe {
+            for item in &mut self.iter {
+                if f(item.as_mut()) {
+                    return Some(self.table.remove(item).0);
+                }
+            }
+        }
+        None
+    }
+}
+
 #[cfg(test)]
 mod test_map {
     use super::*;
@@ -2457,4 +4604,214 @@ mod test_map {
             assert!(table.find(i + 100, |x| *x == i + 100).is_none());
         }
     }
+
+    /// CHECKING THAT WE ARE NOT TRYING TO READ THE MEMORY OF
+    /// AN UNINITIALIZED TABLE DURING THE DROP
+    #[test]
+    fn test_drop_uninitialized() {
+        use ::alloc::vec::Vec;
+
+        let table = unsafe {
+            // SAFETY: The `buckets` is power of two and we're not
+            // trying to actually use the returned RawTable.
+            RawTable::<(u64, Vec<i32>)>::new_uninitialized(Global, 8, Fallibility::Infallible)
+                .unwrap()
+        };
+        drop(table);
+    }
+
+    /// CHECKING THAT WE DON'T TRY TO DROP DATA IF THE `ITEMS`
+    /// ARE ZERO, EVEN IF WE HAVE `FULL` CONTROL BYTES.
+    #[test]
+    fn test_drop_zero_items() {
+        use ::alloc::vec::Vec;
+        unsafe {
+            // SAFETY: The `buckets` is power of two and we're not
+            // trying to actually use the returned RawTable.
+            let table =
+                RawTable::<(u64, Vec<i32>)>::new_uninitialized(Global, 8, Fallibility::Infallible)
+                    .unwrap();
+
+            // WE SIMULATE, AS IT WERE, A FULL TABLE.
+
+            // SAFETY: We checked that the table is allocated and therefore the table already has
+            // `self.bucket_mask + 1 + Group::WIDTH` number of control bytes (see TableLayout::calculate_layout_for)
+            // so writing `table.table.num_ctrl_bytes() == bucket_mask + 1 + Group::WIDTH` bytes is safe.
+            table
+                .table
+                .ctrl(0)
+                .write_bytes(EMPTY, table.table.num_ctrl_bytes());
+
+            // SAFETY: table.capacity() is guaranteed to be smaller than table.buckets()
+            table.table.ctrl(0).write_bytes(0, table.capacity());
+
+            // Fix up the trailing control bytes. See the comments in set_ctrl
+            // for the handling of tables smaller than the group width.
+            if table.buckets() < Group::WIDTH {
+                // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of control bytes,
+                // so copying `self.buckets() == self.bucket_mask + 1` bytes with offset equal to
+                // `Group::WIDTH` is safe
+                table
+                    .table
+                    .ctrl(0)
+                    .copy_to(table.table.ctrl(Group::WIDTH), table.table.buckets());
+            } else {
+                // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of
+                // control bytes,so copying `Group::WIDTH` bytes with offset equal
+                // to `self.buckets() == self.bucket_mask + 1` is safe
+                table
+                    .table
+                    .ctrl(0)
+                    .copy_to(table.table.ctrl(table.table.buckets()), Group::WIDTH);
+            }
+            drop(table);
+        }
+    }
+
+    /// CHECKING THAT WE DON'T TRY TO DROP DATA IF THE `ITEMS`
+    /// ARE ZERO, EVEN IF WE HAVE `FULL` CONTROL BYTES.
+    #[test]
+    fn test_catch_panic_clone_from() {
+        use ::alloc::sync::Arc;
+        use ::alloc::vec::Vec;
+        use allocator_api2::alloc::{AllocError, Allocator, Global};
+        use core::sync::atomic::{AtomicI8, Ordering};
+        use std::thread;
+
+        struct MyAllocInner {
+            drop_count: Arc<AtomicI8>,
+        }
+
+        #[derive(Clone)]
+        struct MyAlloc {
+            _inner: Arc<MyAllocInner>,
+        }
+
+        impl Drop for MyAllocInner {
+            fn drop(&mut self) {
+                println!("MyAlloc freed.");
+                self.drop_count.fetch_sub(1, Ordering::SeqCst);
+            }
+        }
+
+        unsafe impl Allocator for MyAlloc {
+            fn allocate(&self, layout: Layout) -> std::result::Result<NonNull<[u8]>, AllocError> {
+                let g = Global;
+                g.allocate(layout)
+            }
+
+            unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+                let g = Global;
+                g.deallocate(ptr, layout)
+            }
+        }
+
+        const DISARMED: bool = false;
+        const ARMED: bool = true;
+
+        struct CheckedCloneDrop {
+            panic_in_clone: bool,
+            dropped: bool,
+            need_drop: Vec<u64>,
+        }
+
+        impl Clone for CheckedCloneDrop {
+            fn clone(&self) -> Self {
+                if self.panic_in_clone {
+                    panic!("panic in clone")
+                }
+                Self {
+                    panic_in_clone: self.panic_in_clone,
+                    dropped: self.dropped,
+                    need_drop: self.need_drop.clone(),
+                }
+            }
+        }
+
+        impl Drop for CheckedCloneDrop {
+            fn drop(&mut self) {
+                if self.dropped {
+                    panic!("double drop");
+                }
+                self.dropped = true;
+            }
+        }
+
+        let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(2));
+
+        let mut table = RawTable::new_in(MyAlloc {
+            _inner: Arc::new(MyAllocInner {
+                drop_count: dropped.clone(),
+            }),
+        });
+
+        for (idx, panic_in_clone) in core::iter::repeat(DISARMED).take(7).enumerate() {
+            let idx = idx as u64;
+            table.insert(
+                idx,
+                (
+                    idx,
+                    CheckedCloneDrop {
+                        panic_in_clone,
+                        dropped: false,
+                        need_drop: vec![idx],
+                    },
+                ),
+                |(k, _)| *k,
+            );
+        }
+
+        assert_eq!(table.len(), 7);
+
+        thread::scope(|s| {
+            let result = s.spawn(|| {
+                let armed_flags = [
+                    DISARMED, DISARMED, ARMED, DISARMED, DISARMED, DISARMED, DISARMED,
+                ];
+                let mut scope_table = RawTable::new_in(MyAlloc {
+                    _inner: Arc::new(MyAllocInner {
+                        drop_count: dropped.clone(),
+                    }),
+                });
+                for (idx, &panic_in_clone) in armed_flags.iter().enumerate() {
+                    let idx = idx as u64;
+                    scope_table.insert(
+                        idx,
+                        (
+                            idx,
+                            CheckedCloneDrop {
+                                panic_in_clone,
+                                dropped: false,
+                                need_drop: vec![idx + 100],
+                            },
+                        ),
+                        |(k, _)| *k,
+                    );
+                }
+                table.clone_from(&scope_table);
+            });
+            assert!(result.join().is_err());
+        });
+
+        // Let's check that all iterators work fine and do not return elements
+        // (especially `RawIterRange`, which does not depend on the number of
+        // elements in the table, but looks directly at the control bytes)
+        //
+        // SAFETY: We know for sure that `RawTable` will outlive
+        // the returned `RawIter / RawIterRange` iterator.
+        assert_eq!(table.len(), 0);
+        assert_eq!(unsafe { table.iter().count() }, 0);
+        assert_eq!(unsafe { table.iter().iter.count() }, 0);
+
+        for idx in 0..table.buckets() {
+            let idx = idx as u64;
+            assert!(
+                table.find(idx, |(k, _)| *k == idx).is_none(),
+                "Index: {idx}"
+            );
+        }
+
+        // All allocator clones should already be dropped.
+        assert_eq!(dropped.load(Ordering::SeqCst), 1);
+    }
 }
diff --git a/third_party/rust/hashbrown/src/raw/neon.rs b/third_party/rust/hashbrown/src/raw/neon.rs
new file mode 100644
index 0000000000..44e82d57d5
--- /dev/null
+++ b/third_party/rust/hashbrown/src/raw/neon.rs
@@ -0,0 +1,124 @@
+use super::bitmask::BitMask;
+use super::EMPTY;
+use core::arch::aarch64 as neon;
+use core::mem;
+use core::num::NonZeroU64;
+
+pub(crate) type BitMaskWord = u64;
+pub(crate) type NonZeroBitMaskWord = NonZeroU64;
+pub(crate) const BITMASK_STRIDE: usize = 8;
+pub(crate) const BITMASK_MASK: BitMaskWord = !0;
+pub(crate) const BITMASK_ITER_MASK: BitMaskWord = 0x8080_8080_8080_8080;
+
+/// Abstraction over a group of control bytes which can be scanned in
+/// parallel.
+///
+/// This implementation uses a 64-bit NEON value.
+#[derive(Copy, Clone)]
+pub(crate) struct Group(neon::uint8x8_t);
+
+#[allow(clippy::use_self)]
+impl Group {
+    /// Number of bytes in the group.
+    pub(crate) const WIDTH: usize = mem::size_of::<Self>();
+
+    /// Returns a full group of empty bytes, suitable for use as the initial
+    /// value for an empty hash table.
+    ///
+    /// This is guaranteed to be aligned to the group size.
+    #[inline]
+    pub(crate) const fn static_empty() -> &'static [u8; Group::WIDTH] {
+        #[repr(C)]
+        struct AlignedBytes {
+            _align: [Group; 0],
+            bytes: [u8; Group::WIDTH],
+        }
+        const ALIGNED_BYTES: AlignedBytes = AlignedBytes {
+            _align: [],
+            bytes: [EMPTY; Group::WIDTH],
+        };
+        &ALIGNED_BYTES.bytes
+    }
+
+    /// Loads a group of bytes starting at the given address.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)] // unaligned load
+    pub(crate) unsafe fn load(ptr: *const u8) -> Self {
+        Group(neon::vld1_u8(ptr))
+    }
+
+    /// Loads a group of bytes starting at the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn load_aligned(ptr: *const u8) -> Self {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        Group(neon::vld1_u8(ptr))
+    }
+
+    /// Stores the group of bytes to the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn store_aligned(self, ptr: *mut u8) {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        neon::vst1_u8(ptr, self.0);
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which *may*
+    /// have the given value.
+    #[inline]
+    pub(crate) fn match_byte(self, byte: u8) -> BitMask {
+        unsafe {
+            let cmp = neon::vceq_u8(self.0, neon::vdup_n_u8(byte));
+            BitMask(neon::vget_lane_u64(neon::vreinterpret_u64_u8(cmp), 0))
+        }
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY`.
+    #[inline]
+    pub(crate) fn match_empty(self) -> BitMask {
+        self.match_byte(EMPTY)
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY` or `DELETED`.
+    #[inline]
+    pub(crate) fn match_empty_or_deleted(self) -> BitMask {
+        unsafe {
+            let cmp = neon::vcltz_s8(neon::vreinterpret_s8_u8(self.0));
+            BitMask(neon::vget_lane_u64(neon::vreinterpret_u64_u8(cmp), 0))
+        }
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are full.
+    #[inline]
+    pub(crate) fn match_full(self) -> BitMask {
+        unsafe {
+            let cmp = neon::vcgez_s8(neon::vreinterpret_s8_u8(self.0));
+            BitMask(neon::vget_lane_u64(neon::vreinterpret_u64_u8(cmp), 0))
+        }
+    }
+
+    /// Performs the following transformation on all bytes in the group:
+    /// - `EMPTY => EMPTY`
+    /// - `DELETED => EMPTY`
+    /// - `FULL => DELETED`
+    #[inline]
+    pub(crate) fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
+        // Map high_bit = 1 (EMPTY or DELETED) to 1111_1111
+        // and high_bit = 0 (FULL) to 1000_0000
+        //
+        // Here's this logic expanded to concrete values:
+        //   let special = 0 > byte = 1111_1111 (true) or 0000_0000 (false)
+        //   1111_1111 | 1000_0000 = 1111_1111
+        //   0000_0000 | 1000_0000 = 1000_0000
+        unsafe {
+            let special = neon::vcltz_s8(neon::vreinterpret_s8_u8(self.0));
+            Group(neon::vorr_u8(special, neon::vdup_n_u8(0x80)))
+        }
+    }
+}
diff --git a/third_party/rust/hashbrown/src/raw/sse2.rs b/third_party/rust/hashbrown/src/raw/sse2.rs
index a0bf6da804..956ba5d265 100644
--- a/third_party/rust/hashbrown/src/raw/sse2.rs
+++ b/third_party/rust/hashbrown/src/raw/sse2.rs
@@ -1,28 +1,31 @@
 use super::bitmask::BitMask;
 use super::EMPTY;
 use core::mem;
+use core::num::NonZeroU16;
 
 #[cfg(target_arch = "x86")]
 use core::arch::x86;
 #[cfg(target_arch = "x86_64")]
 use core::arch::x86_64 as x86;
 
-pub type BitMaskWord = u16;
-pub const BITMASK_STRIDE: usize = 1;
-pub const BITMASK_MASK: BitMaskWord = 0xffff;
+pub(crate) type BitMaskWord = u16;
+pub(crate) type NonZeroBitMaskWord = NonZeroU16;
+pub(crate) const BITMASK_STRIDE: usize = 1;
+pub(crate) const BITMASK_MASK: BitMaskWord = 0xffff;
+pub(crate) const BITMASK_ITER_MASK: BitMaskWord = !0;
 
 /// Abstraction over a group of control bytes which can be scanned in
 /// parallel.
 ///
 /// This implementation uses a 128-bit SSE value.
 #[derive(Copy, Clone)]
-pub struct Group(x86::__m128i);
+pub(crate) struct Group(x86::__m128i);
 
 // FIXME: https://github.com/rust-lang/rust-clippy/issues/3859
 #[allow(clippy::use_self)]
 impl Group {
     /// Number of bytes in the group.
-    pub const WIDTH: usize = mem::size_of::<Self>();
+    pub(crate) const WIDTH: usize = mem::size_of::<Self>();
 
     /// Returns a full group of empty bytes, suitable for use as the initial
     /// value for an empty hash table.
@@ -30,7 +33,7 @@ impl Group {
     /// This is guaranteed to be aligned to the group size.
     #[inline]
     #[allow(clippy::items_after_statements)]
-    pub const fn static_empty() -> &'static [u8; Group::WIDTH] {
+    pub(crate) const fn static_empty() -> &'static [u8; Group::WIDTH] {
         #[repr(C)]
         struct AlignedBytes {
             _align: [Group; 0],
@@ -46,7 +49,7 @@ impl Group {
     /// Loads a group of bytes starting at the given address.
     #[inline]
     #[allow(clippy::cast_ptr_alignment)] // unaligned load
-    pub unsafe fn load(ptr: *const u8) -> Self {
+    pub(crate) unsafe fn load(ptr: *const u8) -> Self {
         Group(x86::_mm_loadu_si128(ptr.cast()))
     }
 
@@ -54,7 +57,7 @@ impl Group {
     /// aligned to `mem::align_of::<Group>()`.
     #[inline]
     #[allow(clippy::cast_ptr_alignment)]
-    pub unsafe fn load_aligned(ptr: *const u8) -> Self {
+    pub(crate) unsafe fn load_aligned(ptr: *const u8) -> Self {
         // FIXME: use align_offset once it stabilizes
         debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
         Group(x86::_mm_load_si128(ptr.cast()))
@@ -64,7 +67,7 @@ impl Group {
     /// aligned to `mem::align_of::<Group>()`.
     #[inline]
     #[allow(clippy::cast_ptr_alignment)]
-    pub unsafe fn store_aligned(self, ptr: *mut u8) {
+    pub(crate) unsafe fn store_aligned(self, ptr: *mut u8) {
         // FIXME: use align_offset once it stabilizes
         debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
         x86::_mm_store_si128(ptr.cast(), self.0);
@@ -73,7 +76,7 @@ impl Group {
     /// Returns a `BitMask` indicating all bytes in the group which have
     /// the given value.
     #[inline]
-    pub fn match_byte(self, byte: u8) -> BitMask {
+    pub(crate) fn match_byte(self, byte: u8) -> BitMask {
         #[allow(
             clippy::cast_possible_wrap, // byte: u8 as i8
             // byte: i32 as u16
@@ -91,14 +94,14 @@ impl Group {
     /// Returns a `BitMask` indicating all bytes in the group which are
     /// `EMPTY`.
     #[inline]
-    pub fn match_empty(self) -> BitMask {
+    pub(crate) fn match_empty(self) -> BitMask {
         self.match_byte(EMPTY)
     }
 
     /// Returns a `BitMask` indicating all bytes in the group which are
     /// `EMPTY` or `DELETED`.
     #[inline]
-    pub fn match_empty_or_deleted(self) -> BitMask {
+    pub(crate) fn match_empty_or_deleted(self) -> BitMask {
         #[allow(
             // byte: i32 as u16
             //   note: _mm_movemask_epi8 returns a 16-bit mask in a i32, the
@@ -114,7 +117,7 @@ impl Group {
 
     /// Returns a `BitMask` indicating all bytes in the group which are full.
     #[inline]
-    pub fn match_full(&self) -> BitMask {
+    pub(crate) fn match_full(&self) -> BitMask {
         self.match_empty_or_deleted().invert()
     }
 
@@ -123,7 +126,7 @@ impl Group {
     /// - `DELETED => EMPTY`
     /// - `FULL => DELETED`
     #[inline]
-    pub fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
+    pub(crate) fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
         // Map high_bit = 1 (EMPTY or DELETED) to 1111_1111
         // and high_bit = 0 (FULL) to 1000_0000
         //
diff --git a/third_party/rust/hashbrown/src/rustc_entry.rs b/third_party/rust/hashbrown/src/rustc_entry.rs
index 2e84595269..defbd4bb88 100644
--- a/third_party/rust/hashbrown/src/rustc_entry.rs
+++ b/third_party/rust/hashbrown/src/rustc_entry.rs
@@ -1,5 +1,5 @@
 use self::RustcEntry::*;
-use crate::map::{make_insert_hash, Drain, HashMap, IntoIter, Iter, IterMut};
+use crate::map::{make_hash, Drain, HashMap, IntoIter, Iter, IterMut};
 use crate::raw::{Allocator, Bucket, Global, RawTable};
 use core::fmt::{self, Debug};
 use core::hash::{BuildHasher, Hash};
@@ -9,7 +9,7 @@ impl<K, V, S, A> HashMap<K, V, S, A>
 where
     K: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// Gets the given key's corresponding entry in the map for in-place manipulation.
     ///
@@ -32,7 +32,7 @@ where
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn rustc_entry(&mut self, key: K) -> RustcEntry<'_, K, V, A> {
-        let hash = make_insert_hash(&self.hash_builder, &key);
+        let hash = make_hash(&self.hash_builder, &key);
         if let Some(elem) = self.table.find(hash, |q| q.0.eq(&key)) {
             RustcEntry::Occupied(RustcOccupiedEntry {
                 key: Some(key),
@@ -62,7 +62,7 @@ where
 /// [`rustc_entry`]: struct.HashMap.html#method.rustc_entry
 pub enum RustcEntry<'a, K, V, A = Global>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// An occupied entry.
     Occupied(RustcOccupiedEntry<'a, K, V, A>),
@@ -71,7 +71,7 @@ where
     Vacant(RustcVacantEntry<'a, K, V, A>),
 }
 
-impl<K: Debug, V: Debug, A: Allocator + Clone> Debug for RustcEntry<'_, K, V, A> {
+impl<K: Debug, V: Debug, A: Allocator> Debug for RustcEntry<'_, K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
@@ -86,7 +86,7 @@ impl<K: Debug, V: Debug, A: Allocator + Clone> Debug for RustcEntry<'_, K, V, A>
 /// [`RustcEntry`]: enum.RustcEntry.html
 pub struct RustcOccupiedEntry<'a, K, V, A = Global>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     key: Option<K>,
     elem: Bucket<(K, V)>,
@@ -97,18 +97,18 @@ unsafe impl<K, V, A> Send for RustcOccupiedEntry<'_, K, V, A>
 where
     K: Send,
     V: Send,
-    A: Allocator + Clone + Send,
+    A: Allocator + Send,
 {
 }
 unsafe impl<K, V, A> Sync for RustcOccupiedEntry<'_, K, V, A>
 where
     K: Sync,
     V: Sync,
-    A: Allocator + Clone + Sync,
+    A: Allocator + Sync,
 {
 }
 
-impl<K: Debug, V: Debug, A: Allocator + Clone> Debug for RustcOccupiedEntry<'_, K, V, A> {
+impl<K: Debug, V: Debug, A: Allocator> Debug for RustcOccupiedEntry<'_, K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("OccupiedEntry")
             .field("key", self.key())
@@ -123,20 +123,20 @@ impl<K: Debug, V: Debug, A: Allocator + Clone> Debug for RustcOccupiedEntry<'_,
 /// [`RustcEntry`]: enum.RustcEntry.html
 pub struct RustcVacantEntry<'a, K, V, A = Global>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     hash: u64,
     key: K,
     table: &'a mut RawTable<(K, V), A>,
 }
 
-impl<K: Debug, V, A: Allocator + Clone> Debug for RustcVacantEntry<'_, K, V, A> {
+impl<K: Debug, V, A: Allocator> Debug for RustcVacantEntry<'_, K, V, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("VacantEntry").field(self.key()).finish()
     }
 }
 
-impl<'a, K, V, A: Allocator + Clone> RustcEntry<'a, K, V, A> {
+impl<'a, K, V, A: Allocator> RustcEntry<'a, K, V, A> {
     /// Sets the value of the entry, and returns a RustcOccupiedEntry.
     ///
     /// # Examples
@@ -265,7 +265,7 @@ impl<'a, K, V, A: Allocator + Clone> RustcEntry<'a, K, V, A> {
     }
 }
 
-impl<'a, K, V: Default, A: Allocator + Clone> RustcEntry<'a, K, V, A> {
+impl<'a, K, V: Default, A: Allocator> RustcEntry<'a, K, V, A> {
     /// Ensures a value is in the entry by inserting the default value if empty,
     /// and returns a mutable reference to the value in the entry.
     ///
@@ -293,7 +293,7 @@ impl<'a, K, V: Default, A: Allocator + Clone> RustcEntry<'a, K, V, A> {
     }
 }
 
-impl<'a, K, V, A: Allocator + Clone> RustcOccupiedEntry<'a, K, V, A> {
+impl<'a, K, V, A: Allocator> RustcOccupiedEntry<'a, K, V, A> {
     /// Gets a reference to the key in the entry.
     ///
     /// # Examples
@@ -330,7 +330,7 @@ impl<'a, K, V, A: Allocator + Clone> RustcOccupiedEntry<'a, K, V, A> {
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove_entry(self) -> (K, V) {
-        unsafe { self.table.remove(self.elem) }
+        unsafe { self.table.remove(self.elem).0 }
     }
 
     /// Gets a reference to the value in the entry.
@@ -518,7 +518,7 @@ impl<'a, K, V, A: Allocator + Clone> RustcOccupiedEntry<'a, K, V, A> {
     }
 }
 
-impl<'a, K, V, A: Allocator + Clone> RustcVacantEntry<'a, K, V, A> {
+impl<'a, K, V, A: Allocator> RustcVacantEntry<'a, K, V, A> {
     /// Gets a reference to the key that would be used when inserting a value
     /// through the `RustcVacantEntry`.
     ///
diff --git a/third_party/rust/hashbrown/src/scopeguard.rs b/third_party/rust/hashbrown/src/scopeguard.rs
index f85e6ab0ed..382d06043e 100644
--- a/third_party/rust/hashbrown/src/scopeguard.rs
+++ b/third_party/rust/hashbrown/src/scopeguard.rs
@@ -1,6 +1,6 @@
 // Extracted from the scopeguard crate
 use core::{
-    mem,
+    mem::ManuallyDrop,
     ops::{Deref, DerefMut},
     ptr,
 };
@@ -28,15 +28,13 @@ where
     #[inline]
     pub fn into_inner(guard: Self) -> T {
         // Cannot move out of Drop-implementing types, so
-        // ptr::read the value and forget the guard.
+        // ptr::read the value out of a ManuallyDrop<Self>
+        // Don't use mem::forget as that might invalidate value
+        let guard = ManuallyDrop::new(guard);
         unsafe {
             let value = ptr::read(&guard.value);
-            // read the closure so that it is dropped, and assign it to a local
-            // variable to ensure that it is only dropped after the guard has
-            // been forgotten. (In case the Drop impl of the closure, or that
-            // of any consumed captured variable, panics).
-            let _dropfn = ptr::read(&guard.dropfn);
-            mem::forget(guard);
+            // read the closure so that it is dropped
+            let _ = ptr::read(&guard.dropfn);
             value
         }
     }
diff --git a/third_party/rust/hashbrown/src/set.rs b/third_party/rust/hashbrown/src/set.rs
index 2a4dcea52c..2125a7ac81 100644
--- a/third_party/rust/hashbrown/src/set.rs
+++ b/third_party/rust/hashbrown/src/set.rs
@@ -1,14 +1,14 @@
-use crate::TryReserveError;
+#[cfg(feature = "raw")]
+use crate::raw::RawTable;
+use crate::{Equivalent, TryReserveError};
 use alloc::borrow::ToOwned;
-use core::borrow::Borrow;
 use core::fmt;
 use core::hash::{BuildHasher, Hash};
-use core::iter::{Chain, FromIterator, FusedIterator};
-use core::mem;
+use core::iter::{Chain, FusedIterator};
 use core::ops::{BitAnd, BitOr, BitXor, Sub};
 
-use super::map::{self, ConsumeAllOnDrop, DefaultHashBuilder, DrainFilterInner, HashMap, Keys};
-use crate::raw::{Allocator, Global};
+use super::map::{self, DefaultHashBuilder, HashMap, Keys};
+use crate::raw::{Allocator, Global, RawExtractIf};
 
 // Future Optimization (FIXME!)
 // =============================
@@ -102,7 +102,7 @@ use crate::raw::{Allocator, Global};
 /// use hashbrown::HashSet;
 ///
 /// let viking_names: HashSet<&'static str> =
-///     [ "Einar", "Olaf", "Harald" ].iter().cloned().collect();
+///     [ "Einar", "Olaf", "Harald" ].into_iter().collect();
 /// // use the values stored in the set
 /// ```
 ///
@@ -112,7 +112,7 @@ use crate::raw::{Allocator, Global};
 /// [`HashMap`]: struct.HashMap.html
 /// [`PartialEq`]: https://doc.rust-lang.org/std/cmp/trait.PartialEq.html
 /// [`RefCell`]: https://doc.rust-lang.org/std/cell/struct.RefCell.html
-pub struct HashSet<T, S = DefaultHashBuilder, A: Allocator + Clone = Global> {
+pub struct HashSet<T, S = DefaultHashBuilder, A: Allocator = Global> {
     pub(crate) map: HashMap<T, (), S, A>,
 }
 
@@ -135,6 +135,18 @@ impl<T> HashSet<T, DefaultHashBuilder> {
     /// The hash set is initially created with a capacity of 0, so it will not allocate until it
     /// is first inserted into.
     ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`], for example with
+    /// [`with_hasher`](HashSet::with_hasher) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -153,6 +165,18 @@ impl<T> HashSet<T, DefaultHashBuilder> {
     /// The hash set will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash set will not allocate.
     ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`], for example with
+    /// [`with_capacity_and_hasher`](HashSet::with_capacity_and_hasher) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -169,12 +193,24 @@ impl<T> HashSet<T, DefaultHashBuilder> {
 }
 
 #[cfg(feature = "ahash")]
-impl<T: Hash + Eq, A: Allocator + Clone> HashSet<T, DefaultHashBuilder, A> {
+impl<T: Hash + Eq, A: Allocator> HashSet<T, DefaultHashBuilder, A> {
     /// Creates an empty `HashSet`.
     ///
     /// The hash set is initially created with a capacity of 0, so it will not allocate until it
     /// is first inserted into.
     ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`], for example with
+    /// [`with_hasher_in`](HashSet::with_hasher_in) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -193,6 +229,18 @@ impl<T: Hash + Eq, A: Allocator + Clone> HashSet<T, DefaultHashBuilder, A> {
     /// The hash set will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash set will not allocate.
     ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`], for example with
+    /// [`with_capacity_and_hasher_in`](HashSet::with_capacity_and_hasher_in) method.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -208,7 +256,7 @@ impl<T: Hash + Eq, A: Allocator + Clone> HashSet<T, DefaultHashBuilder, A> {
     }
 }
 
-impl<T, S, A: Allocator + Clone> HashSet<T, S, A> {
+impl<T, S, A: Allocator> HashSet<T, S, A> {
     /// Returns the number of elements the set can hold without reallocating.
     ///
     /// # Examples
@@ -287,7 +335,7 @@ impl<T, S, A: Allocator + Clone> HashSet<T, S, A> {
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let mut set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
+    /// let mut set: HashSet<_> = [1, 2, 3].into_iter().collect();
     /// assert!(!set.is_empty());
     ///
     /// // print 1, 2, 3 in an arbitrary order
@@ -314,7 +362,7 @@ impl<T, S, A: Allocator + Clone> HashSet<T, S, A> {
     /// use hashbrown::HashSet;
     ///
     /// let xs = [1,2,3,4,5,6];
-    /// let mut set: HashSet<i32> = xs.iter().cloned().collect();
+    /// let mut set: HashSet<i32> = xs.into_iter().collect();
     /// set.retain(|&k| k % 2 == 0);
     /// assert_eq!(set.len(), 3);
     /// ```
@@ -331,8 +379,11 @@ impl<T, S, A: Allocator + Clone> HashSet<T, S, A> {
     /// In other words, move all elements `e` such that `f(&e)` returns `true` out
     /// into another iterator.
     ///
-    /// When the returned DrainedFilter is dropped, any remaining elements that satisfy
-    /// the predicate are dropped from the set.
+    /// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
+    /// or the iteration short-circuits, then the remaining elements will be retained.
+    /// Use [`retain()`] with a negated predicate if you do not need the returned iterator.
+    ///
+    /// [`retain()`]: HashSet::retain
     ///
     /// # Examples
     ///
@@ -340,7 +391,7 @@ impl<T, S, A: Allocator + Clone> HashSet<T, S, A> {
     /// use hashbrown::HashSet;
     ///
     /// let mut set: HashSet<i32> = (0..8).collect();
-    /// let drained: HashSet<i32> = set.drain_filter(|v| v % 2 == 0).collect();
+    /// let drained: HashSet<i32> = set.extract_if(|v| v % 2 == 0).collect();
     ///
     /// let mut evens = drained.into_iter().collect::<Vec<_>>();
     /// let mut odds = set.into_iter().collect::<Vec<_>>();
@@ -351,13 +402,13 @@ impl<T, S, A: Allocator + Clone> HashSet<T, S, A> {
     /// assert_eq!(odds, vec![1, 3, 5, 7]);
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
-    pub fn drain_filter<F>(&mut self, f: F) -> DrainFilter<'_, T, F, A>
+    pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, T, F, A>
     where
         F: FnMut(&T) -> bool,
     {
-        DrainFilter {
+        ExtractIf {
             f,
-            inner: DrainFilterInner {
+            inner: RawExtractIf {
                 iter: unsafe { self.map.table.iter() },
                 table: &mut self.map.table,
             },
@@ -386,16 +437,23 @@ impl<T, S> HashSet<T, S, Global> {
     /// Creates a new empty hash set which will use the given hasher to hash
     /// keys.
     ///
-    /// The hash set is also created with the default initial capacity.
+    /// The hash set is initially created with a capacity of 0, so it will not
+    /// allocate until it is first inserted into.
+    ///
+    /// # HashDoS resistance
     ///
-    /// Warning: `hasher` is normally randomly generated, and
-    /// is designed to allow `HashSet`s to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`].
     ///
     /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
-    /// the HashMap to be useful, see its documentation for details.
+    /// the HashSet to be useful, see its documentation for details.
     ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
     ///
     /// # Examples
     ///
@@ -407,8 +465,6 @@ impl<T, S> HashSet<T, S, Global> {
     /// let mut set = HashSet::with_hasher(s);
     /// set.insert(2);
     /// ```
-    ///
-    /// [`BuildHasher`]: ../../std/hash/trait.BuildHasher.html
     #[cfg_attr(feature = "inline-more", inline)]
     pub const fn with_hasher(hasher: S) -> Self {
         Self {
@@ -422,13 +478,20 @@ impl<T, S> HashSet<T, S, Global> {
     /// The hash set will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash set will not allocate.
     ///
-    /// Warning: `hasher` is normally randomly generated, and
-    /// is designed to allow `HashSet`s to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`].
     ///
     /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
-    /// the HashMap to be useful, see its documentation for details.
+    /// the HashSet to be useful, see its documentation for details.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
     ///
     /// # Examples
     ///
@@ -440,8 +503,6 @@ impl<T, S> HashSet<T, S, Global> {
     /// let mut set = HashSet::with_capacity_and_hasher(10, s);
     /// set.insert(1);
     /// ```
-    ///
-    /// [`BuildHasher`]: ../../std/hash/trait.BuildHasher.html
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> Self {
         Self {
@@ -452,7 +513,7 @@ impl<T, S> HashSet<T, S, Global> {
 
 impl<T, S, A> HashSet<T, S, A>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// Returns a reference to the underlying allocator.
     #[inline]
@@ -463,12 +524,23 @@ where
     /// Creates a new empty hash set which will use the given hasher to hash
     /// keys.
     ///
-    /// The hash set is also created with the default initial capacity.
+    /// The hash set is initially created with a capacity of 0, so it will not
+    /// allocate until it is first inserted into.
+    ///
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`].
+    ///
+    /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
+    /// the HashSet to be useful, see its documentation for details.
     ///
-    /// Warning: `hasher` is normally randomly generated, and
-    /// is designed to allow `HashSet`s to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
     ///
     /// # Examples
     ///
@@ -481,7 +553,7 @@ where
     /// set.insert(2);
     /// ```
     #[cfg_attr(feature = "inline-more", inline)]
-    pub fn with_hasher_in(hasher: S, alloc: A) -> Self {
+    pub const fn with_hasher_in(hasher: S, alloc: A) -> Self {
         Self {
             map: HashMap::with_hasher_in(hasher, alloc),
         }
@@ -493,10 +565,20 @@ where
     /// The hash set will be able to hold at least `capacity` elements without
     /// reallocating. If `capacity` is 0, the hash set will not allocate.
     ///
-    /// Warning: `hasher` is normally randomly generated, and
-    /// is designed to allow `HashSet`s to be resistant to attacks that
-    /// cause many collisions and very poor performance. Setting it
-    /// manually using this function can expose a DoS attack vector.
+    /// # HashDoS resistance
+    ///
+    /// The `hash_builder` normally use a fixed key by default and that does
+    /// not allow the `HashSet` to be protected against attacks such as [`HashDoS`].
+    /// Users who require HashDoS resistance should explicitly use
+    /// [`ahash::RandomState`] or [`std::collections::hash_map::RandomState`]
+    /// as the hasher when creating a [`HashSet`].
+    ///
+    /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
+    /// the HashSet to be useful, see its documentation for details.
+    ///
+    /// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
+    /// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
+    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
     ///
     /// # Examples
     ///
@@ -539,7 +621,7 @@ impl<T, S, A> HashSet<T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// Reserves capacity for at least `additional` more elements to be inserted
     /// in the `HashSet`. The collection may reserve more space to avoid
@@ -547,7 +629,12 @@ where
     ///
     /// # Panics
     ///
-    /// Panics if the new allocation size overflows `usize`.
+    /// Panics if the new capacity exceeds [`isize::MAX`] bytes and [`abort`] the program
+    /// in case of allocation error. Use [`try_reserve`](HashSet::try_reserve) instead
+    /// if you want to handle memory allocation failure.
+    ///
+    /// [`isize::MAX`]: https://doc.rust-lang.org/std/primitive.isize.html
+    /// [`abort`]: https://doc.rust-lang.org/alloc/alloc/fn.handle_alloc_error.html
     ///
     /// # Examples
     ///
@@ -637,8 +724,8 @@ where
     ///
     /// ```
     /// use hashbrown::HashSet;
-    /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
-    /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
+    /// let a: HashSet<_> = [1, 2, 3].into_iter().collect();
+    /// let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();
     ///
     /// // Can be seen as `a - b`.
     /// for x in a.difference(&b) {
@@ -668,8 +755,8 @@ where
     ///
     /// ```
     /// use hashbrown::HashSet;
-    /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
-    /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
+    /// let a: HashSet<_> = [1, 2, 3].into_iter().collect();
+    /// let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();
     ///
     /// // Print 1, 4 in arbitrary order.
     /// for x in a.symmetric_difference(&b) {
@@ -696,8 +783,8 @@ where
     ///
     /// ```
     /// use hashbrown::HashSet;
-    /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
-    /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
+    /// let a: HashSet<_> = [1, 2, 3].into_iter().collect();
+    /// let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();
     ///
     /// // Print 2, 3 in arbitrary order.
     /// for x in a.intersection(&b) {
@@ -727,8 +814,8 @@ where
     ///
     /// ```
     /// use hashbrown::HashSet;
-    /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
-    /// let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();
+    /// let a: HashSet<_> = [1, 2, 3].into_iter().collect();
+    /// let b: HashSet<_> = [4, 2, 3, 4].into_iter().collect();
     ///
     /// // Print 1, 2, 3, 4 in arbitrary order.
     /// for x in a.union(&b) {
@@ -763,7 +850,7 @@ where
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
+    /// let set: HashSet<_> = [1, 2, 3].into_iter().collect();
     /// assert_eq!(set.contains(&1), true);
     /// assert_eq!(set.contains(&4), false);
     /// ```
@@ -773,8 +860,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool
     where
-        T: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<T>,
     {
         self.map.contains_key(value)
     }
@@ -790,7 +876,7 @@ where
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
+    /// let set: HashSet<_> = [1, 2, 3].into_iter().collect();
     /// assert_eq!(set.get(&2), Some(&2));
     /// assert_eq!(set.get(&4), None);
     /// ```
@@ -800,8 +886,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn get<Q: ?Sized>(&self, value: &Q) -> Option<&T>
     where
-        T: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<T>,
     {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.map.get_key_value(value) {
@@ -818,7 +903,7 @@ where
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let mut set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
+    /// let mut set: HashSet<_> = [1, 2, 3].into_iter().collect();
     /// assert_eq!(set.len(), 3);
     /// assert_eq!(set.get_or_insert(2), &2);
     /// assert_eq!(set.get_or_insert(100), &100);
@@ -856,8 +941,7 @@ where
     #[inline]
     pub fn get_or_insert_owned<Q: ?Sized>(&mut self, value: &Q) -> &T
     where
-        T: Borrow<Q>,
-        Q: Hash + Eq + ToOwned<Owned = T>,
+        Q: Hash + Equivalent<T> + ToOwned<Owned = T>,
     {
         // Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with
         // `get`. Key mutation is "raw" because you're not supposed to affect `Eq` or `Hash`.
@@ -889,8 +973,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn get_or_insert_with<Q: ?Sized, F>(&mut self, value: &Q, f: F) -> &T
     where
-        T: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<T>,
         F: FnOnce(&Q) -> T,
     {
         // Although the raw entry gives us `&mut T`, we only return `&T` to be consistent with
@@ -951,7 +1034,7 @@ where
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
+    /// let a: HashSet<_> = [1, 2, 3].into_iter().collect();
     /// let mut b = HashSet::new();
     ///
     /// assert_eq!(a.is_disjoint(&b), true);
@@ -972,7 +1055,7 @@ where
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let sup: HashSet<_> = [1, 2, 3].iter().cloned().collect();
+    /// let sup: HashSet<_> = [1, 2, 3].into_iter().collect();
     /// let mut set = HashSet::new();
     ///
     /// assert_eq!(set.is_subset(&sup), true);
@@ -993,7 +1076,7 @@ where
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let sub: HashSet<_> = [1, 2].iter().cloned().collect();
+    /// let sub: HashSet<_> = [1, 2].into_iter().collect();
     /// let mut set = HashSet::new();
     ///
     /// assert_eq!(set.is_superset(&sub), false);
@@ -1106,8 +1189,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool
     where
-        T: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<T>,
     {
         self.map.remove(value).is_some()
     }
@@ -1123,7 +1205,7 @@ where
     /// ```
     /// use hashbrown::HashSet;
     ///
-    /// let mut set: HashSet<_> = [1, 2, 3].iter().cloned().collect();
+    /// let mut set: HashSet<_> = [1, 2, 3].into_iter().collect();
     /// assert_eq!(set.take(&2), Some(2));
     /// assert_eq!(set.take(&2), None);
     /// ```
@@ -1133,8 +1215,7 @@ where
     #[cfg_attr(feature = "inline-more", inline)]
     pub fn take<Q: ?Sized>(&mut self, value: &Q) -> Option<T>
     where
-        T: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Equivalent<T>,
     {
         // Avoid `Option::map` because it bloats LLVM IR.
         match self.map.remove_entry(value) {
@@ -1144,11 +1225,53 @@ where
     }
 }
 
+impl<T, S, A: Allocator> HashSet<T, S, A> {
+    /// Returns a reference to the [`RawTable`] used underneath [`HashSet`].
+    /// This function is only available if the `raw` feature of the crate is enabled.
+    ///
+    /// # Note
+    ///
+    /// Calling this function is safe, but using the raw hash table API may require
+    /// unsafe functions or blocks.
+    ///
+    /// `RawTable` API gives the lowest level of control under the set that can be useful
+    /// for extending the HashSet's API, but may lead to *[undefined behavior]*.
+    ///
+    /// [`HashSet`]: struct.HashSet.html
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[cfg(feature = "raw")]
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn raw_table(&self) -> &RawTable<(T, ()), A> {
+        self.map.raw_table()
+    }
+
+    /// Returns a mutable reference to the [`RawTable`] used underneath [`HashSet`].
+    /// This function is only available if the `raw` feature of the crate is enabled.
+    ///
+    /// # Note
+    ///
+    /// Calling this function is safe, but using the raw hash table API may require
+    /// unsafe functions or blocks.
+    ///
+    /// `RawTable` API gives the lowest level of control under the set that can be useful
+    /// for extending the HashSet's API, but may lead to *[undefined behavior]*.
+    ///
+    /// [`HashSet`]: struct.HashSet.html
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[cfg(feature = "raw")]
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn raw_table_mut(&mut self) -> &mut RawTable<(T, ()), A> {
+        self.map.raw_table_mut()
+    }
+}
+
 impl<T, S, A> PartialEq for HashSet<T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn eq(&self, other: &Self) -> bool {
         if self.len() != other.len() {
@@ -1163,14 +1286,14 @@ impl<T, S, A> Eq for HashSet<T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
 }
 
 impl<T, S, A> fmt::Debug for HashSet<T, S, A>
 where
     T: fmt::Debug,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_set().entries(self.iter()).finish()
@@ -1179,7 +1302,7 @@ where
 
 impl<T, S, A> From<HashMap<T, (), S, A>> for HashSet<T, S, A>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn from(map: HashMap<T, (), S, A>) -> Self {
         Self { map }
@@ -1190,7 +1313,7 @@ impl<T, S, A> FromIterator<T> for HashSet<T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher + Default,
-    A: Default + Allocator + Clone,
+    A: Default + Allocator,
 {
     #[cfg_attr(feature = "inline-more", inline)]
     fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
@@ -1205,7 +1328,7 @@ where
 impl<T, A, const N: usize> From<[T; N]> for HashSet<T, DefaultHashBuilder, A>
 where
     T: Eq + Hash,
-    A: Default + Allocator + Clone,
+    A: Default + Allocator,
 {
     /// # Examples
     ///
@@ -1225,7 +1348,7 @@ impl<T, S, A> Extend<T> for HashSet<T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     #[cfg_attr(feature = "inline-more", inline)]
     fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
@@ -1249,7 +1372,7 @@ impl<'a, T, S, A> Extend<&'a T> for HashSet<T, S, A>
 where
     T: 'a + Eq + Hash + Copy,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     #[cfg_attr(feature = "inline-more", inline)]
     fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
@@ -1272,7 +1395,7 @@ where
 impl<T, S, A> Default for HashSet<T, S, A>
 where
     S: Default,
-    A: Default + Allocator + Clone,
+    A: Default + Allocator,
 {
     /// Creates an empty `HashSet<T, S>` with the `Default` value for the hasher.
     #[cfg_attr(feature = "inline-more", inline)]
@@ -1287,7 +1410,7 @@ impl<T, S, A> BitOr<&HashSet<T, S, A>> for &HashSet<T, S, A>
 where
     T: Eq + Hash + Clone,
     S: BuildHasher + Default,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Output = HashSet<T, S>;
 
@@ -1320,7 +1443,7 @@ impl<T, S, A> BitAnd<&HashSet<T, S, A>> for &HashSet<T, S, A>
 where
     T: Eq + Hash + Clone,
     S: BuildHasher + Default,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Output = HashSet<T, S>;
 
@@ -1431,7 +1554,7 @@ pub struct Iter<'a, K> {
 ///
 /// [`HashSet`]: struct.HashSet.html
 /// [`into_iter`]: struct.HashSet.html#method.into_iter
-pub struct IntoIter<K, A: Allocator + Clone = Global> {
+pub struct IntoIter<K, A: Allocator = Global> {
     iter: map::IntoIter<K, (), A>,
 }
 
@@ -1442,23 +1565,24 @@ pub struct IntoIter<K, A: Allocator + Clone = Global> {
 ///
 /// [`HashSet`]: struct.HashSet.html
 /// [`drain`]: struct.HashSet.html#method.drain
-pub struct Drain<'a, K, A: Allocator + Clone = Global> {
+pub struct Drain<'a, K, A: Allocator = Global> {
     iter: map::Drain<'a, K, (), A>,
 }
 
 /// A draining iterator over entries of a `HashSet` which don't satisfy the predicate `f`.
 ///
-/// This `struct` is created by the [`drain_filter`] method on [`HashSet`]. See its
+/// This `struct` is created by the [`extract_if`] method on [`HashSet`]. See its
 /// documentation for more.
 ///
-/// [`drain_filter`]: struct.HashSet.html#method.drain_filter
+/// [`extract_if`]: struct.HashSet.html#method.extract_if
 /// [`HashSet`]: struct.HashSet.html
-pub struct DrainFilter<'a, K, F, A: Allocator + Clone = Global>
+#[must_use = "Iterators are lazy unless consumed"]
+pub struct ExtractIf<'a, K, F, A: Allocator = Global>
 where
     F: FnMut(&K) -> bool,
 {
     f: F,
-    inner: DrainFilterInner<'a, K, (), A>,
+    inner: RawExtractIf<'a, (K, ()), A>,
 }
 
 /// A lazy iterator producing elements in the intersection of `HashSet`s.
@@ -1468,7 +1592,7 @@ where
 ///
 /// [`HashSet`]: struct.HashSet.html
 /// [`intersection`]: struct.HashSet.html#method.intersection
-pub struct Intersection<'a, T, S, A: Allocator + Clone = Global> {
+pub struct Intersection<'a, T, S, A: Allocator = Global> {
     // iterator of the first set
     iter: Iter<'a, T>,
     // the second set
@@ -1482,7 +1606,7 @@ pub struct Intersection<'a, T, S, A: Allocator + Clone = Global> {
 ///
 /// [`HashSet`]: struct.HashSet.html
 /// [`difference`]: struct.HashSet.html#method.difference
-pub struct Difference<'a, T, S, A: Allocator + Clone = Global> {
+pub struct Difference<'a, T, S, A: Allocator = Global> {
     // iterator of the first set
     iter: Iter<'a, T>,
     // the second set
@@ -1496,7 +1620,7 @@ pub struct Difference<'a, T, S, A: Allocator + Clone = Global> {
 ///
 /// [`HashSet`]: struct.HashSet.html
 /// [`symmetric_difference`]: struct.HashSet.html#method.symmetric_difference
-pub struct SymmetricDifference<'a, T, S, A: Allocator + Clone = Global> {
+pub struct SymmetricDifference<'a, T, S, A: Allocator = Global> {
     iter: Chain<Difference<'a, T, S, A>, Difference<'a, T, S, A>>,
 }
 
@@ -1507,11 +1631,11 @@ pub struct SymmetricDifference<'a, T, S, A: Allocator + Clone = Global> {
 ///
 /// [`HashSet`]: struct.HashSet.html
 /// [`union`]: struct.HashSet.html#method.union
-pub struct Union<'a, T, S, A: Allocator + Clone = Global> {
+pub struct Union<'a, T, S, A: Allocator = Global> {
     iter: Chain<Iter<'a, T>, Difference<'a, T, S, A>>,
 }
 
-impl<'a, T, S, A: Allocator + Clone> IntoIterator for &'a HashSet<T, S, A> {
+impl<'a, T, S, A: Allocator> IntoIterator for &'a HashSet<T, S, A> {
     type Item = &'a T;
     type IntoIter = Iter<'a, T>;
 
@@ -1521,7 +1645,7 @@ impl<'a, T, S, A: Allocator + Clone> IntoIterator for &'a HashSet<T, S, A> {
     }
 }
 
-impl<T, S, A: Allocator + Clone> IntoIterator for HashSet<T, S, A> {
+impl<T, S, A: Allocator> IntoIterator for HashSet<T, S, A> {
     type Item = T;
     type IntoIter = IntoIter<T, A>;
 
@@ -1572,6 +1696,14 @@ impl<'a, K> Iterator for Iter<'a, K> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, f)
+    }
 }
 impl<'a, K> ExactSizeIterator for Iter<'a, K> {
     #[cfg_attr(feature = "inline-more", inline)]
@@ -1587,7 +1719,7 @@ impl<K: fmt::Debug> fmt::Debug for Iter<'_, K> {
     }
 }
 
-impl<K, A: Allocator + Clone> Iterator for IntoIter<K, A> {
+impl<K, A: Allocator> Iterator for IntoIter<K, A> {
     type Item = K;
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -1602,23 +1734,31 @@ impl<K, A: Allocator + Clone> Iterator for IntoIter<K, A> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, |acc, (k, ())| f(acc, k))
+    }
 }
-impl<K, A: Allocator + Clone> ExactSizeIterator for IntoIter<K, A> {
+impl<K, A: Allocator> ExactSizeIterator for IntoIter<K, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn len(&self) -> usize {
         self.iter.len()
     }
 }
-impl<K, A: Allocator + Clone> FusedIterator for IntoIter<K, A> {}
+impl<K, A: Allocator> FusedIterator for IntoIter<K, A> {}
 
-impl<K: fmt::Debug, A: Allocator + Clone> fmt::Debug for IntoIter<K, A> {
+impl<K: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<K, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let entries_iter = self.iter.iter().map(|(k, _)| k);
         f.debug_list().entries(entries_iter).finish()
     }
 }
 
-impl<K, A: Allocator + Clone> Iterator for Drain<'_, K, A> {
+impl<K, A: Allocator> Iterator for Drain<'_, K, A> {
     type Item = K;
 
     #[cfg_attr(feature = "inline-more", inline)]
@@ -1633,37 +1773,31 @@ impl<K, A: Allocator + Clone> Iterator for Drain<'_, K, A> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, |acc, (k, ())| f(acc, k))
+    }
 }
-impl<K, A: Allocator + Clone> ExactSizeIterator for Drain<'_, K, A> {
+impl<K, A: Allocator> ExactSizeIterator for Drain<'_, K, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn len(&self) -> usize {
         self.iter.len()
     }
 }
-impl<K, A: Allocator + Clone> FusedIterator for Drain<'_, K, A> {}
+impl<K, A: Allocator> FusedIterator for Drain<'_, K, A> {}
 
-impl<K: fmt::Debug, A: Allocator + Clone> fmt::Debug for Drain<'_, K, A> {
+impl<K: fmt::Debug, A: Allocator> fmt::Debug for Drain<'_, K, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let entries_iter = self.iter.iter().map(|(k, _)| k);
         f.debug_list().entries(entries_iter).finish()
     }
 }
 
-impl<'a, K, F, A: Allocator + Clone> Drop for DrainFilter<'a, K, F, A>
-where
-    F: FnMut(&K) -> bool,
-{
-    #[cfg_attr(feature = "inline-more", inline)]
-    fn drop(&mut self) {
-        while let Some(item) = self.next() {
-            let guard = ConsumeAllOnDrop(self);
-            drop(item);
-            mem::forget(guard);
-        }
-    }
-}
-
-impl<K, F, A: Allocator + Clone> Iterator for DrainFilter<'_, K, F, A>
+impl<K, F, A: Allocator> Iterator for ExtractIf<'_, K, F, A>
 where
     F: FnMut(&K) -> bool,
 {
@@ -1671,9 +1805,9 @@ where
 
     #[cfg_attr(feature = "inline-more", inline)]
     fn next(&mut self) -> Option<Self::Item> {
-        let f = &mut self.f;
-        let (k, _) = self.inner.next(&mut |k, _| f(k))?;
-        Some(k)
+        self.inner
+            .next(|&mut (ref k, ())| (self.f)(k))
+            .map(|(k, ())| k)
     }
 
     #[inline]
@@ -1682,12 +1816,9 @@ where
     }
 }
 
-impl<K, F, A: Allocator + Clone> FusedIterator for DrainFilter<'_, K, F, A> where
-    F: FnMut(&K) -> bool
-{
-}
+impl<K, F, A: Allocator> FusedIterator for ExtractIf<'_, K, F, A> where F: FnMut(&K) -> bool {}
 
-impl<T, S, A: Allocator + Clone> Clone for Intersection<'_, T, S, A> {
+impl<T, S, A: Allocator> Clone for Intersection<'_, T, S, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn clone(&self) -> Self {
         Intersection {
@@ -1701,7 +1832,7 @@ impl<'a, T, S, A> Iterator for Intersection<'a, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Item = &'a T;
 
@@ -1720,13 +1851,27 @@ where
         let (_, upper) = self.iter.size_hint();
         (0, upper)
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, |acc, elt| {
+            if self.other.contains(elt) {
+                f(acc, elt)
+            } else {
+                acc
+            }
+        })
+    }
 }
 
 impl<T, S, A> fmt::Debug for Intersection<'_, T, S, A>
 where
     T: fmt::Debug + Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self.clone()).finish()
@@ -1737,11 +1882,11 @@ impl<T, S, A> FusedIterator for Intersection<'_, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
 }
 
-impl<T, S, A: Allocator + Clone> Clone for Difference<'_, T, S, A> {
+impl<T, S, A: Allocator> Clone for Difference<'_, T, S, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn clone(&self) -> Self {
         Difference {
@@ -1755,7 +1900,7 @@ impl<'a, T, S, A> Iterator for Difference<'a, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Item = &'a T;
 
@@ -1774,13 +1919,27 @@ where
         let (_, upper) = self.iter.size_hint();
         (0, upper)
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, |acc, elt| {
+            if self.other.contains(elt) {
+                acc
+            } else {
+                f(acc, elt)
+            }
+        })
+    }
 }
 
 impl<T, S, A> FusedIterator for Difference<'_, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
 }
 
@@ -1788,14 +1947,14 @@ impl<T, S, A> fmt::Debug for Difference<'_, T, S, A>
 where
     T: fmt::Debug + Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self.clone()).finish()
     }
 }
 
-impl<T, S, A: Allocator + Clone> Clone for SymmetricDifference<'_, T, S, A> {
+impl<T, S, A: Allocator> Clone for SymmetricDifference<'_, T, S, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn clone(&self) -> Self {
         SymmetricDifference {
@@ -1808,7 +1967,7 @@ impl<'a, T, S, A> Iterator for SymmetricDifference<'a, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Item = &'a T;
 
@@ -1820,13 +1979,21 @@ where
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, f)
+    }
 }
 
 impl<T, S, A> FusedIterator for SymmetricDifference<'_, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
 }
 
@@ -1834,14 +2001,14 @@ impl<T, S, A> fmt::Debug for SymmetricDifference<'_, T, S, A>
 where
     T: fmt::Debug + Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self.clone()).finish()
     }
 }
 
-impl<T, S, A: Allocator + Clone> Clone for Union<'_, T, S, A> {
+impl<T, S, A: Allocator> Clone for Union<'_, T, S, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn clone(&self) -> Self {
         Union {
@@ -1854,7 +2021,7 @@ impl<T, S, A> FusedIterator for Union<'_, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
 }
 
@@ -1862,7 +2029,7 @@ impl<T, S, A> fmt::Debug for Union<'_, T, S, A>
 where
     T: fmt::Debug + Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self.clone()).finish()
@@ -1873,7 +2040,7 @@ impl<'a, T, S, A> Iterator for Union<'a, T, S, A>
 where
     T: Eq + Hash,
     S: BuildHasher,
-    A: Allocator + Clone,
+    A: Allocator,
 {
     type Item = &'a T;
 
@@ -1885,6 +2052,14 @@ where
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, f)
+    }
 }
 
 /// A view into a single entry in a set, which may either be vacant or occupied.
@@ -1925,7 +2100,7 @@ where
 /// ```
 pub enum Entry<'a, T, S, A = Global>
 where
-    A: Allocator + Clone,
+    A: Allocator,
 {
     /// An occupied entry.
     ///
@@ -1958,7 +2133,7 @@ where
     Vacant(VacantEntry<'a, T, S, A>),
 }
 
-impl<T: fmt::Debug, S, A: Allocator + Clone> fmt::Debug for Entry<'_, T, S, A> {
+impl<T: fmt::Debug, S, A: Allocator> fmt::Debug for Entry<'_, T, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Entry::Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
@@ -2003,11 +2178,11 @@ impl<T: fmt::Debug, S, A: Allocator + Clone> fmt::Debug for Entry<'_, T, S, A> {
 /// assert_eq!(set.get(&"c"), None);
 /// assert_eq!(set.len(), 2);
 /// ```
-pub struct OccupiedEntry<'a, T, S, A: Allocator + Clone = Global> {
+pub struct OccupiedEntry<'a, T, S, A: Allocator = Global> {
     inner: map::OccupiedEntry<'a, T, (), S, A>,
 }
 
-impl<T: fmt::Debug, S, A: Allocator + Clone> fmt::Debug for OccupiedEntry<'_, T, S, A> {
+impl<T: fmt::Debug, S, A: Allocator> fmt::Debug for OccupiedEntry<'_, T, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("OccupiedEntry")
             .field("value", self.get())
@@ -2041,17 +2216,17 @@ impl<T: fmt::Debug, S, A: Allocator + Clone> fmt::Debug for OccupiedEntry<'_, T,
 /// }
 /// assert!(set.contains("b") && set.len() == 2);
 /// ```
-pub struct VacantEntry<'a, T, S, A: Allocator + Clone = Global> {
+pub struct VacantEntry<'a, T, S, A: Allocator = Global> {
     inner: map::VacantEntry<'a, T, (), S, A>,
 }
 
-impl<T: fmt::Debug, S, A: Allocator + Clone> fmt::Debug for VacantEntry<'_, T, S, A> {
+impl<T: fmt::Debug, S, A: Allocator> fmt::Debug for VacantEntry<'_, T, S, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("VacantEntry").field(self.get()).finish()
     }
 }
 
-impl<'a, T, S, A: Allocator + Clone> Entry<'a, T, S, A> {
+impl<'a, T, S, A: Allocator> Entry<'a, T, S, A> {
     /// Sets the value of the entry, and returns an OccupiedEntry.
     ///
     /// # Examples
@@ -2128,7 +2303,7 @@ impl<'a, T, S, A: Allocator + Clone> Entry<'a, T, S, A> {
     }
 }
 
-impl<T, S, A: Allocator + Clone> OccupiedEntry<'_, T, S, A> {
+impl<T, S, A: Allocator> OccupiedEntry<'_, T, S, A> {
     /// Gets a reference to the value in the entry.
     ///
     /// # Examples
@@ -2215,7 +2390,7 @@ impl<T, S, A: Allocator + Clone> OccupiedEntry<'_, T, S, A> {
     }
 }
 
-impl<'a, T, S, A: Allocator + Clone> VacantEntry<'a, T, S, A> {
+impl<'a, T, S, A: Allocator> VacantEntry<'a, T, S, A> {
     /// Gets a reference to the value that would be used when inserting
     /// through the `VacantEntry`.
     ///
@@ -2295,34 +2470,30 @@ fn assert_covariance() {
     fn iter<'a, 'new>(v: Iter<'a, &'static str>) -> Iter<'a, &'new str> {
         v
     }
-    fn into_iter<'new, A: Allocator + Clone>(
-        v: IntoIter<&'static str, A>,
-    ) -> IntoIter<&'new str, A> {
+    fn into_iter<'new, A: Allocator>(v: IntoIter<&'static str, A>) -> IntoIter<&'new str, A> {
         v
     }
-    fn difference<'a, 'new, A: Allocator + Clone>(
+    fn difference<'a, 'new, A: Allocator>(
         v: Difference<'a, &'static str, DefaultHashBuilder, A>,
     ) -> Difference<'a, &'new str, DefaultHashBuilder, A> {
         v
     }
-    fn symmetric_difference<'a, 'new, A: Allocator + Clone>(
+    fn symmetric_difference<'a, 'new, A: Allocator>(
         v: SymmetricDifference<'a, &'static str, DefaultHashBuilder, A>,
     ) -> SymmetricDifference<'a, &'new str, DefaultHashBuilder, A> {
         v
     }
-    fn intersection<'a, 'new, A: Allocator + Clone>(
+    fn intersection<'a, 'new, A: Allocator>(
         v: Intersection<'a, &'static str, DefaultHashBuilder, A>,
     ) -> Intersection<'a, &'new str, DefaultHashBuilder, A> {
         v
     }
-    fn union<'a, 'new, A: Allocator + Clone>(
+    fn union<'a, 'new, A: Allocator>(
         v: Union<'a, &'static str, DefaultHashBuilder, A>,
     ) -> Union<'a, &'new str, DefaultHashBuilder, A> {
         v
     }
-    fn drain<'new, A: Allocator + Clone>(
-        d: Drain<'static, &'static str, A>,
-    ) -> Drain<'new, &'new str, A> {
+    fn drain<'new, A: Allocator>(d: Drain<'static, &'static str, A>) -> Drain<'new, &'new str, A> {
         d
     }
 }
@@ -2613,10 +2784,10 @@ mod test_set {
         set.insert(1);
         set.insert(2);
 
-        let set_str = format!("{:?}", set);
+        let set_str = format!("{set:?}");
 
         assert!(set_str == "{1, 2}" || set_str == "{2, 1}");
-        assert_eq!(format!("{:?}", empty), "{}");
+        assert_eq!(format!("{empty:?}"), "{}");
     }
 
     #[test]
@@ -2649,7 +2820,7 @@ mod test_set {
                 assert_eq!(last_i, 49);
             }
 
-            for _ in &s {
+            if !s.is_empty() {
                 panic!("s should be empty!");
             }
 
@@ -2663,6 +2834,7 @@ mod test_set {
         use core::hash;
 
         #[derive(Debug)]
+        #[allow(dead_code)]
         struct Foo(&'static str, i32);
 
         impl PartialEq for Foo {
@@ -2691,11 +2863,12 @@ mod test_set {
     }
 
     #[test]
+    #[allow(clippy::needless_borrow)]
     fn test_extend_ref() {
         let mut a = HashSet::new();
         a.insert(1);
 
-        a.extend(&[2, 3, 4]);
+        a.extend([2, 3, 4]);
 
         assert_eq!(a.len(), 4);
         assert!(a.contains(&1));
@@ -2730,10 +2903,10 @@ mod test_set {
     }
 
     #[test]
-    fn test_drain_filter() {
+    fn test_extract_if() {
         {
             let mut set: HashSet<i32> = (0..8).collect();
-            let drained = set.drain_filter(|&k| k % 2 == 0);
+            let drained = set.extract_if(|&k| k % 2 == 0);
             let mut out = drained.collect::<Vec<_>>();
             out.sort_unstable();
             assert_eq!(vec![0, 2, 4, 6], out);
@@ -2741,7 +2914,7 @@ mod test_set {
         }
         {
             let mut set: HashSet<i32> = (0..8).collect();
-            drop(set.drain_filter(|&k| k % 2 == 0));
+            set.extract_if(|&k| k % 2 == 0).for_each(drop);
             assert_eq!(set.len(), 4, "Removes non-matching items on drop");
         }
     }
@@ -2787,4 +2960,11 @@ mod test_set {
             set.insert(i);
         }
     }
+
+    #[test]
+    fn collect() {
+        // At the time of writing, this hits the ZST case in from_base_index
+        // (and without the `map`, it does not).
+        let mut _set: HashSet<_> = (0..3).map(|_| ()).collect();
+    }
 }
diff --git a/third_party/rust/hashbrown/src/table.rs b/third_party/rust/hashbrown/src/table.rs
new file mode 100644
index 0000000000..faf8a6330f
--- /dev/null
+++ b/third_party/rust/hashbrown/src/table.rs
@@ -0,0 +1,2070 @@
+use core::{fmt, iter::FusedIterator, marker::PhantomData};
+
+use crate::{
+    raw::{
+        Allocator, Bucket, Global, InsertSlot, RawDrain, RawExtractIf, RawIntoIter, RawIter,
+        RawTable,
+    },
+    TryReserveError,
+};
+
+/// Low-level hash table with explicit hashing.
+///
+/// The primary use case for this type over [`HashMap`] or [`HashSet`] is to
+/// support types that do not implement the [`Hash`] and [`Eq`] traits, but
+/// instead require additional data not contained in the key itself to compute a
+/// hash and compare two elements for equality.
+///
+/// Examples of when this can be useful include:
+/// - An `IndexMap` implementation where indices into a `Vec` are stored as
+///   elements in a `HashTable<usize>`. Hashing and comparing the elements
+///   requires indexing the associated `Vec` to get the actual value referred to
+///   by the index.
+/// - Avoiding re-computing a hash when it is already known.
+/// - Mutating the key of an element in a way that doesn't affect its hash.
+///
+/// To achieve this, `HashTable` methods that search for an element in the table
+/// require a hash value and equality function to be explicitly passed in as
+/// arguments. The method will then iterate over the elements with the given
+/// hash and call the equality function on each of them, until a match is found.
+///
+/// In most cases, a `HashTable` will not be exposed directly in an API. It will
+/// instead be wrapped in a helper type which handles the work of calculating
+/// hash values and comparing elements.
+///
+/// Due to its low-level nature, this type provides fewer guarantees than
+/// [`HashMap`] and [`HashSet`]. Specifically, the API allows you to shoot
+/// yourself in the foot by having multiple elements with identical keys in the
+/// table. The table itself will still function correctly and lookups will
+/// arbitrarily return one of the matching elements. However you should avoid
+/// doing this because it changes the runtime of hash table operations from
+/// `O(1)` to `O(k)` where `k` is the number of duplicate entries.
+///
+/// [`HashMap`]: super::HashMap
+/// [`HashSet`]: super::HashSet
+pub struct HashTable<T, A = Global>
+where
+    A: Allocator,
+{
+    pub(crate) raw: RawTable<T, A>,
+}
+
+impl<T> HashTable<T, Global> {
+    /// Creates an empty `HashTable`.
+    ///
+    /// The hash table is initially created with a capacity of 0, so it will not allocate until it
+    /// is first inserted into.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hashbrown::HashTable;
+    /// let mut table: HashTable<&str> = HashTable::new();
+    /// assert_eq!(table.len(), 0);
+    /// assert_eq!(table.capacity(), 0);
+    /// ```
+    pub const fn new() -> Self {
+        Self {
+            raw: RawTable::new(),
+        }
+    }
+
+    /// Creates an empty `HashTable` with the specified capacity.
+    ///
+    /// The hash table will be able to hold at least `capacity` elements without
+    /// reallocating. If `capacity` is 0, the hash table will not allocate.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hashbrown::HashTable;
+    /// let mut table: HashTable<&str> = HashTable::with_capacity(10);
+    /// assert_eq!(table.len(), 0);
+    /// assert!(table.capacity() >= 10);
+    /// ```
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self {
+            raw: RawTable::with_capacity(capacity),
+        }
+    }
+}
+
+impl<T, A> HashTable<T, A>
+where
+    A: Allocator,
+{
+    /// Creates an empty `HashTable` using the given allocator.
+    ///
+    /// The hash table is initially created with a capacity of 0, so it will not allocate until it
+    /// is first inserted into.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use bumpalo::Bump;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let bump = Bump::new();
+    /// let mut table = HashTable::new_in(&bump);
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// // The created HashTable holds none elements
+    /// assert_eq!(table.len(), 0);
+    ///
+    /// // The created HashTable also doesn't allocate memory
+    /// assert_eq!(table.capacity(), 0);
+    ///
+    /// // Now we insert element inside created HashTable
+    /// table.insert_unique(hasher(&"One"), "One", hasher);
+    /// // We can see that the HashTable holds 1 element
+    /// assert_eq!(table.len(), 1);
+    /// // And it also allocates some capacity
+    /// assert!(table.capacity() > 1);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub const fn new_in(alloc: A) -> Self {
+        Self {
+            raw: RawTable::new_in(alloc),
+        }
+    }
+
+    /// Creates an empty `HashTable` with the specified capacity using the given allocator.
+    ///
+    /// The hash table will be able to hold at least `capacity` elements without
+    /// reallocating. If `capacity` is 0, the hash table will not allocate.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use bumpalo::Bump;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let bump = Bump::new();
+    /// let mut table = HashTable::with_capacity_in(5, &bump);
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// // The created HashTable holds none elements
+    /// assert_eq!(table.len(), 0);
+    /// // But it can hold at least 5 elements without reallocating
+    /// let empty_map_capacity = table.capacity();
+    /// assert!(empty_map_capacity >= 5);
+    ///
+    /// // Now we insert some 5 elements inside created HashTable
+    /// table.insert_unique(hasher(&"One"), "One", hasher);
+    /// table.insert_unique(hasher(&"Two"), "Two", hasher);
+    /// table.insert_unique(hasher(&"Three"), "Three", hasher);
+    /// table.insert_unique(hasher(&"Four"), "Four", hasher);
+    /// table.insert_unique(hasher(&"Five"), "Five", hasher);
+    ///
+    /// // We can see that the HashTable holds 5 elements
+    /// assert_eq!(table.len(), 5);
+    /// // But its capacity isn't changed
+    /// assert_eq!(table.capacity(), empty_map_capacity)
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
+        Self {
+            raw: RawTable::with_capacity_in(capacity, alloc),
+        }
+    }
+
+    /// Returns a reference to the underlying allocator.
+    pub fn allocator(&self) -> &A {
+        self.raw.allocator()
+    }
+
+    /// Returns a reference to an entry in the table with the given hash and
+    /// which satisfies the equality function passed.
+    ///
+    /// This method will call `eq` for all entries with the given hash, but may
+    /// also call it for entries with a different hash. `eq` should only return
+    /// true for the desired entry, at which point the search is stopped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&1), 1, hasher);
+    /// table.insert_unique(hasher(&2), 2, hasher);
+    /// table.insert_unique(hasher(&3), 3, hasher);
+    /// assert_eq!(table.find(hasher(&2), |&val| val == 2), Some(&2));
+    /// assert_eq!(table.find(hasher(&4), |&val| val == 4), None);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn find(&self, hash: u64, eq: impl FnMut(&T) -> bool) -> Option<&T> {
+        self.raw.get(hash, eq)
+    }
+
+    /// Returns a mutable reference to an entry in the table with the given hash
+    /// and which satisfies the equality function passed.
+    ///
+    /// This method will call `eq` for all entries with the given hash, but may
+    /// also call it for entries with a different hash. `eq` should only return
+    /// true for the desired entry, at which point the search is stopped.
+    ///
+    /// When mutating an entry, you should ensure that it still retains the same
+    /// hash value as when it was inserted, otherwise lookups of that entry may
+    /// fail to find it.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&1), (1, "a"), |val| hasher(&val.0));
+    /// if let Some(val) = table.find_mut(hasher(&1), |val| val.0 == 1) {
+    ///     val.1 = "b";
+    /// }
+    /// assert_eq!(table.find(hasher(&1), |val| val.0 == 1), Some(&(1, "b")));
+    /// assert_eq!(table.find(hasher(&2), |val| val.0 == 2), None);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn find_mut(&mut self, hash: u64, eq: impl FnMut(&T) -> bool) -> Option<&mut T> {
+        self.raw.get_mut(hash, eq)
+    }
+
+    /// Returns an `OccupiedEntry` for an entry in the table with the given hash
+    /// and which satisfies the equality function passed.
+    ///
+    /// This can be used to remove the entry from the table. Call
+    /// [`HashTable::entry`] instead if you wish to insert an entry if the
+    /// lookup fails.
+    ///
+    /// This method will call `eq` for all entries with the given hash, but may
+    /// also call it for entries with a different hash. `eq` should only return
+    /// true for the desired entry, at which point the search is stopped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&1), (1, "a"), |val| hasher(&val.0));
+    /// if let Ok(entry) = table.find_entry(hasher(&1), |val| val.0 == 1) {
+    ///     entry.remove();
+    /// }
+    /// assert_eq!(table.find(hasher(&1), |val| val.0 == 1), None);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn find_entry(
+        &mut self,
+        hash: u64,
+        eq: impl FnMut(&T) -> bool,
+    ) -> Result<OccupiedEntry<'_, T, A>, AbsentEntry<'_, T, A>> {
+        match self.raw.find(hash, eq) {
+            Some(bucket) => Ok(OccupiedEntry {
+                hash,
+                bucket,
+                table: self,
+            }),
+            None => Err(AbsentEntry { table: self }),
+        }
+    }
+
+    /// Returns an `Entry` for an entry in the table with the given hash
+    /// and which satisfies the equality function passed.
+    ///
+    /// This can be used to remove the entry from the table, or insert a new
+    /// entry with the given hash if one doesn't already exist.
+    ///
+    /// This method will call `eq` for all entries with the given hash, but may
+    /// also call it for entries with a different hash. `eq` should only return
+    /// true for the desired entry, at which point the search is stopped.
+    ///
+    /// This method may grow the table in preparation for an insertion. Call
+    /// [`HashTable::find_entry`] if this is undesirable.
+    ///
+    /// `hasher` is called if entries need to be moved or copied to a new table.
+    /// This must return the same hash value that each entry was inserted with.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&1), (1, "a"), |val| hasher(&val.0));
+    /// if let Entry::Occupied(entry) = table.entry(hasher(&1), |val| val.0 == 1, |val| hasher(&val.0))
+    /// {
+    ///     entry.remove();
+    /// }
+    /// if let Entry::Vacant(entry) = table.entry(hasher(&2), |val| val.0 == 2, |val| hasher(&val.0)) {
+    ///     entry.insert((2, "b"));
+    /// }
+    /// assert_eq!(table.find(hasher(&1), |val| val.0 == 1), None);
+    /// assert_eq!(table.find(hasher(&2), |val| val.0 == 2), Some(&(2, "b")));
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn entry(
+        &mut self,
+        hash: u64,
+        eq: impl FnMut(&T) -> bool,
+        hasher: impl Fn(&T) -> u64,
+    ) -> Entry<'_, T, A> {
+        match self.raw.find_or_find_insert_slot(hash, eq, hasher) {
+            Ok(bucket) => Entry::Occupied(OccupiedEntry {
+                hash,
+                bucket,
+                table: self,
+            }),
+            Err(insert_slot) => Entry::Vacant(VacantEntry {
+                hash,
+                insert_slot,
+                table: self,
+            }),
+        }
+    }
+
+    /// Inserts an element into the `HashTable` with the given hash value, but
+    /// without checking whether an equivalent element already exists within the
+    /// table.
+    ///
+    /// `hasher` is called if entries need to be moved or copied to a new table.
+    /// This must return the same hash value that each entry was inserted with.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut v = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// v.insert_unique(hasher(&1), 1, hasher);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn insert_unique(
+        &mut self,
+        hash: u64,
+        value: T,
+        hasher: impl Fn(&T) -> u64,
+    ) -> OccupiedEntry<'_, T, A> {
+        let bucket = self.raw.insert(hash, value, hasher);
+        OccupiedEntry {
+            hash,
+            bucket,
+            table: self,
+        }
+    }
+
+    /// Clears the table, removing all values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut v = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// v.insert_unique(hasher(&1), 1, hasher);
+    /// v.clear();
+    /// assert!(v.is_empty());
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn clear(&mut self) {
+        self.raw.clear();
+    }
+
+    /// Shrinks the capacity of the table as much as possible. It will drop
+    /// down as much as possible while maintaining the internal rules
+    /// and possibly leaving some space in accordance with the resize policy.
+    ///
+    /// `hasher` is called if entries need to be moved or copied to a new table.
+    /// This must return the same hash value that each entry was inserted with.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::with_capacity(100);
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&1), 1, hasher);
+    /// table.insert_unique(hasher(&2), 2, hasher);
+    /// assert!(table.capacity() >= 100);
+    /// table.shrink_to_fit(hasher);
+    /// assert!(table.capacity() >= 2);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn shrink_to_fit(&mut self, hasher: impl Fn(&T) -> u64) {
+        self.raw.shrink_to(self.len(), hasher)
+    }
+
+    /// Shrinks the capacity of the table with a lower limit. It will drop
+    /// down no lower than the supplied limit while maintaining the internal rules
+    /// and possibly leaving some space in accordance with the resize policy.
+    ///
+    /// `hasher` is called if entries need to be moved or copied to a new table.
+    /// This must return the same hash value that each entry was inserted with.
+    ///
+    /// Panics if the current capacity is smaller than the supplied
+    /// minimum capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::with_capacity(100);
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&1), 1, hasher);
+    /// table.insert_unique(hasher(&2), 2, hasher);
+    /// assert!(table.capacity() >= 100);
+    /// table.shrink_to(10, hasher);
+    /// assert!(table.capacity() >= 10);
+    /// table.shrink_to(0, hasher);
+    /// assert!(table.capacity() >= 2);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn shrink_to(&mut self, min_capacity: usize, hasher: impl Fn(&T) -> u64) {
+        self.raw.shrink_to(min_capacity, hasher);
+    }
+
+    /// Reserves capacity for at least `additional` more elements to be inserted
+    /// in the `HashTable`. The collection may reserve more space to avoid
+    /// frequent reallocations.
+    ///
+    /// `hasher` is called if entries need to be moved or copied to a new table.
+    /// This must return the same hash value that each entry was inserted with.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the new capacity exceeds [`isize::MAX`] bytes and [`abort`] the program
+    /// in case of allocation error. Use [`try_reserve`](HashTable::try_reserve) instead
+    /// if you want to handle memory allocation failure.
+    ///
+    /// [`isize::MAX`]: https://doc.rust-lang.org/std/primitive.isize.html
+    /// [`abort`]: https://doc.rust-lang.org/alloc/alloc/fn.handle_alloc_error.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<i32> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.reserve(10, hasher);
+    /// assert!(table.capacity() >= 10);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn reserve(&mut self, additional: usize, hasher: impl Fn(&T) -> u64) {
+        self.raw.reserve(additional, hasher)
+    }
+
+    /// Tries to reserve capacity for at least `additional` more elements to be inserted
+    /// in the given `HashTable`. The collection may reserve more space to avoid
+    /// frequent reallocations.
+    ///
+    /// `hasher` is called if entries need to be moved or copied to a new table.
+    /// This must return the same hash value that each entry was inserted with.
+    ///
+    /// # Errors
+    ///
+    /// If the capacity overflows, or the allocator reports a failure, then an error
+    /// is returned.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<i32> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table
+    ///     .try_reserve(10, hasher)
+    ///     .expect("why is the test harness OOMing on 10 bytes?");
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn try_reserve(
+        &mut self,
+        additional: usize,
+        hasher: impl Fn(&T) -> u64,
+    ) -> Result<(), TryReserveError> {
+        self.raw.try_reserve(additional, hasher)
+    }
+
+    /// Returns the number of elements the table can hold without reallocating.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use hashbrown::HashTable;
+    /// let table: HashTable<i32> = HashTable::with_capacity(100);
+    /// assert!(table.capacity() >= 100);
+    /// ```
+    pub fn capacity(&self) -> usize {
+        self.raw.capacity()
+    }
+
+    /// Returns the number of elements in the table.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// let mut v = HashTable::new();
+    /// assert_eq!(v.len(), 0);
+    /// v.insert_unique(hasher(&1), 1, hasher);
+    /// assert_eq!(v.len(), 1);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn len(&self) -> usize {
+        self.raw.len()
+    }
+
+    /// Returns `true` if the set contains no elements.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// let mut v = HashTable::new();
+    /// assert!(v.is_empty());
+    /// v.insert_unique(hasher(&1), 1, hasher);
+    /// assert!(!v.is_empty());
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn is_empty(&self) -> bool {
+        self.raw.is_empty()
+    }
+
+    /// An iterator visiting all elements in arbitrary order.
+    /// The iterator element type is `&'a T`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&"a"), "b", hasher);
+    /// table.insert_unique(hasher(&"b"), "b", hasher);
+    ///
+    /// // Will print in an arbitrary order.
+    /// for x in table.iter() {
+    ///     println!("{}", x);
+    /// }
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn iter(&self) -> Iter<'_, T> {
+        Iter {
+            inner: unsafe { self.raw.iter() },
+            marker: PhantomData,
+        }
+    }
+
+    /// An iterator visiting all elements in arbitrary order,
+    /// with mutable references to the elements.
+    /// The iterator element type is `&'a mut T`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&1), 1, hasher);
+    /// table.insert_unique(hasher(&2), 2, hasher);
+    /// table.insert_unique(hasher(&3), 3, hasher);
+    ///
+    /// // Update all values
+    /// for val in table.iter_mut() {
+    ///     *val *= 2;
+    /// }
+    ///
+    /// assert_eq!(table.len(), 3);
+    /// let mut vec: Vec<i32> = Vec::new();
+    ///
+    /// for val in &table {
+    ///     println!("val: {}", val);
+    ///     vec.push(*val);
+    /// }
+    ///
+    /// // The `Iter` iterator produces items in arbitrary order, so the
+    /// // items must be sorted to test them against a sorted array.
+    /// vec.sort_unstable();
+    /// assert_eq!(vec, [2, 4, 6]);
+    ///
+    /// assert_eq!(table.len(), 3);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn iter_mut(&mut self) -> IterMut<'_, T> {
+        IterMut {
+            inner: unsafe { self.raw.iter() },
+            marker: PhantomData,
+        }
+    }
+
+    /// Retains only the elements specified by the predicate.
+    ///
+    /// In other words, remove all elements `e` such that `f(&e)` returns `false`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// for x in 1..=6 {
+    ///     table.insert_unique(hasher(&x), x, hasher);
+    /// }
+    /// table.retain(|&mut x| x % 2 == 0);
+    /// assert_eq!(table.len(), 3);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn retain(&mut self, mut f: impl FnMut(&mut T) -> bool) {
+        // Here we only use `iter` as a temporary, preventing use-after-free
+        unsafe {
+            for item in self.raw.iter() {
+                if !f(item.as_mut()) {
+                    self.raw.erase(item);
+                }
+            }
+        }
+    }
+
+    /// Clears the set, returning all elements in an iterator.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// for x in 1..=3 {
+    ///     table.insert_unique(hasher(&x), x, hasher);
+    /// }
+    /// assert!(!table.is_empty());
+    ///
+    /// // print 1, 2, 3 in an arbitrary order
+    /// for i in table.drain() {
+    ///     println!("{}", i);
+    /// }
+    ///
+    /// assert!(table.is_empty());
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn drain(&mut self) -> Drain<'_, T, A> {
+        Drain {
+            inner: self.raw.drain(),
+        }
+    }
+
+    /// Drains elements which are true under the given predicate,
+    /// and returns an iterator over the removed items.
+    ///
+    /// In other words, move all elements `e` such that `f(&e)` returns `true` out
+    /// into another iterator.
+    ///
+    /// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
+    /// or the iteration short-circuits, then the remaining elements will be retained.
+    /// Use [`retain()`] with a negated predicate if you do not need the returned iterator.
+    ///
+    /// [`retain()`]: HashTable::retain
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// for x in 0..8 {
+    ///     table.insert_unique(hasher(&x), x, hasher);
+    /// }
+    /// let drained: Vec<i32> = table.extract_if(|&mut v| v % 2 == 0).collect();
+    ///
+    /// let mut evens = drained.into_iter().collect::<Vec<_>>();
+    /// let mut odds = table.into_iter().collect::<Vec<_>>();
+    /// evens.sort();
+    /// odds.sort();
+    ///
+    /// assert_eq!(evens, vec![0, 2, 4, 6]);
+    /// assert_eq!(odds, vec![1, 3, 5, 7]);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, T, F, A>
+    where
+        F: FnMut(&mut T) -> bool,
+    {
+        ExtractIf {
+            f,
+            inner: RawExtractIf {
+                iter: unsafe { self.raw.iter() },
+                table: &mut self.raw,
+            },
+        }
+    }
+
+    /// Attempts to get mutable references to `N` values in the map at once.
+    ///
+    /// The `eq` argument should be a closure such that `eq(i, k)` returns true if `k` is equal to
+    /// the `i`th key to be looked up.
+    ///
+    /// Returns an array of length `N` with the results of each query. For soundness, at most one
+    /// mutable reference will be returned to any value. `None` will be returned if any of the
+    /// keys are duplicates or missing.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut libraries: HashTable<(&str, u32)> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// for (k, v) in [
+    ///     ("Bodleian Library", 1602),
+    ///     ("Athenæum", 1807),
+    ///     ("Herzogin-Anna-Amalia-Bibliothek", 1691),
+    ///     ("Library of Congress", 1800),
+    /// ] {
+    ///     libraries.insert_unique(hasher(&k), (k, v), |(k, _)| hasher(&k));
+    /// }
+    ///
+    /// let keys = ["Athenæum", "Library of Congress"];
+    /// let got = libraries.get_many_mut(keys.map(|k| hasher(&k)), |i, val| keys[i] == val.0);
+    /// assert_eq!(
+    ///     got,
+    ///     Some([&mut ("Athenæum", 1807), &mut ("Library of Congress", 1800),]),
+    /// );
+    ///
+    /// // Missing keys result in None
+    /// let keys = ["Athenæum", "New York Public Library"];
+    /// let got = libraries.get_many_mut(keys.map(|k| hasher(&k)), |i, val| keys[i] == val.0);
+    /// assert_eq!(got, None);
+    ///
+    /// // Duplicate keys result in None
+    /// let keys = ["Athenæum", "Athenæum"];
+    /// let got = libraries.get_many_mut(keys.map(|k| hasher(&k)), |i, val| keys[i] == val.0);
+    /// assert_eq!(got, None);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn get_many_mut<const N: usize>(
+        &mut self,
+        hashes: [u64; N],
+        eq: impl FnMut(usize, &T) -> bool,
+    ) -> Option<[&'_ mut T; N]> {
+        self.raw.get_many_mut(hashes, eq)
+    }
+
+    /// Attempts to get mutable references to `N` values in the map at once, without validating that
+    /// the values are unique.
+    ///
+    /// The `eq` argument should be a closure such that `eq(i, k)` returns true if `k` is equal to
+    /// the `i`th key to be looked up.
+    ///
+    /// Returns an array of length `N` with the results of each query. `None` will be returned if
+    /// any of the keys are missing.
+    ///
+    /// For a safe alternative see [`get_many_mut`](`HashTable::get_many_mut`).
+    ///
+    /// # Safety
+    ///
+    /// Calling this method with overlapping keys is *[undefined behavior]* even if the resulting
+    /// references are not used.
+    ///
+    /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut libraries: HashTable<(&str, u32)> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// for (k, v) in [
+    ///     ("Bodleian Library", 1602),
+    ///     ("Athenæum", 1807),
+    ///     ("Herzogin-Anna-Amalia-Bibliothek", 1691),
+    ///     ("Library of Congress", 1800),
+    /// ] {
+    ///     libraries.insert_unique(hasher(&k), (k, v), |(k, _)| hasher(&k));
+    /// }
+    ///
+    /// let keys = ["Athenæum", "Library of Congress"];
+    /// let got = libraries.get_many_mut(keys.map(|k| hasher(&k)), |i, val| keys[i] == val.0);
+    /// assert_eq!(
+    ///     got,
+    ///     Some([&mut ("Athenæum", 1807), &mut ("Library of Congress", 1800),]),
+    /// );
+    ///
+    /// // Missing keys result in None
+    /// let keys = ["Athenæum", "New York Public Library"];
+    /// let got = libraries.get_many_mut(keys.map(|k| hasher(&k)), |i, val| keys[i] == val.0);
+    /// assert_eq!(got, None);
+    ///
+    /// // Duplicate keys result in None
+    /// let keys = ["Athenæum", "Athenæum"];
+    /// let got = libraries.get_many_mut(keys.map(|k| hasher(&k)), |i, val| keys[i] == val.0);
+    /// assert_eq!(got, None);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub unsafe fn get_many_unchecked_mut<const N: usize>(
+        &mut self,
+        hashes: [u64; N],
+        eq: impl FnMut(usize, &T) -> bool,
+    ) -> Option<[&'_ mut T; N]> {
+        self.raw.get_many_unchecked_mut(hashes, eq)
+    }
+}
+
+impl<T, A> IntoIterator for HashTable<T, A>
+where
+    A: Allocator,
+{
+    type Item = T;
+    type IntoIter = IntoIter<T, A>;
+
+    fn into_iter(self) -> IntoIter<T, A> {
+        IntoIter {
+            inner: self.raw.into_iter(),
+        }
+    }
+}
+
+impl<'a, T, A> IntoIterator for &'a HashTable<T, A>
+where
+    A: Allocator,
+{
+    type Item = &'a T;
+    type IntoIter = Iter<'a, T>;
+
+    fn into_iter(self) -> Iter<'a, T> {
+        self.iter()
+    }
+}
+
+impl<'a, T, A> IntoIterator for &'a mut HashTable<T, A>
+where
+    A: Allocator,
+{
+    type Item = &'a mut T;
+    type IntoIter = IterMut<'a, T>;
+
+    fn into_iter(self) -> IterMut<'a, T> {
+        self.iter_mut()
+    }
+}
+
+impl<T, A> Default for HashTable<T, A>
+where
+    A: Allocator + Default,
+{
+    fn default() -> Self {
+        Self {
+            raw: Default::default(),
+        }
+    }
+}
+
+impl<T, A> Clone for HashTable<T, A>
+where
+    T: Clone,
+    A: Allocator + Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            raw: self.raw.clone(),
+        }
+    }
+}
+
+impl<T, A> fmt::Debug for HashTable<T, A>
+where
+    T: fmt::Debug,
+    A: Allocator,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_set().entries(self.iter()).finish()
+    }
+}
+
+/// A view into a single entry in a table, which may either be vacant or occupied.
+///
+/// This `enum` is constructed from the [`entry`] method on [`HashTable`].
+///
+/// [`HashTable`]: struct.HashTable.html
+/// [`entry`]: struct.HashTable.html#method.entry
+///
+/// # Examples
+///
+/// ```
+/// # #[cfg(feature = "nightly")]
+/// # fn test() {
+/// use ahash::AHasher;
+/// use hashbrown::hash_table::{Entry, HashTable, OccupiedEntry};
+/// use std::hash::{BuildHasher, BuildHasherDefault};
+///
+/// let mut table = HashTable::new();
+/// let hasher = BuildHasherDefault::<AHasher>::default();
+/// let hasher = |val: &_| hasher.hash_one(val);
+/// for x in ["a", "b", "c"] {
+///     table.insert_unique(hasher(&x), x, hasher);
+/// }
+/// assert_eq!(table.len(), 3);
+///
+/// // Existing value (insert)
+/// let entry: Entry<_> = table.entry(hasher(&"a"), |&x| x == "a", hasher);
+/// let _raw_o: OccupiedEntry<_, _> = entry.insert("a");
+/// assert_eq!(table.len(), 3);
+/// // Nonexistent value (insert)
+/// table.entry(hasher(&"d"), |&x| x == "d", hasher).insert("d");
+///
+/// // Existing value (or_insert)
+/// table
+///     .entry(hasher(&"b"), |&x| x == "b", hasher)
+///     .or_insert("b");
+/// // Nonexistent value (or_insert)
+/// table
+///     .entry(hasher(&"e"), |&x| x == "e", hasher)
+///     .or_insert("e");
+///
+/// println!("Our HashTable: {:?}", table);
+///
+/// let mut vec: Vec<_> = table.iter().copied().collect();
+/// // The `Iter` iterator produces items in arbitrary order, so the
+/// // items must be sorted to test them against a sorted array.
+/// vec.sort_unstable();
+/// assert_eq!(vec, ["a", "b", "c", "d", "e"]);
+/// # }
+/// # fn main() {
+/// #     #[cfg(feature = "nightly")]
+/// #     test()
+/// # }
+/// ```
+pub enum Entry<'a, T, A = Global>
+where
+    A: Allocator,
+{
+    /// An occupied entry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::{Entry, HashTable, OccupiedEntry};
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// for x in ["a", "b"] {
+    ///     table.insert_unique(hasher(&x), x, hasher);
+    /// }
+    ///
+    /// match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
+    ///     Entry::Vacant(_) => unreachable!(),
+    ///     Entry::Occupied(_) => {}
+    /// }
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    Occupied(OccupiedEntry<'a, T, A>),
+
+    /// A vacant entry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::{Entry, HashTable, OccupiedEntry};
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table = HashTable::<&str>::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
+    ///     Entry::Vacant(_) => {}
+    ///     Entry::Occupied(_) => unreachable!(),
+    /// }
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    Vacant(VacantEntry<'a, T, A>),
+}
+
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for Entry<'_, T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            Entry::Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
+            Entry::Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
+        }
+    }
+}
+
+impl<'a, T, A> Entry<'a, T, A>
+where
+    A: Allocator,
+{
+    /// Sets the value of the entry, replacing any existing value if there is
+    /// one, and returns an [`OccupiedEntry`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<&str> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// let entry = table
+    ///     .entry(hasher(&"horseyland"), |&x| x == "horseyland", hasher)
+    ///     .insert("horseyland");
+    ///
+    /// assert_eq!(entry.get(), &"horseyland");
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn insert(self, value: T) -> OccupiedEntry<'a, T, A> {
+        match self {
+            Entry::Occupied(mut entry) => {
+                *entry.get_mut() = value;
+                entry
+            }
+            Entry::Vacant(entry) => entry.insert(value),
+        }
+    }
+
+    /// Ensures a value is in the entry by inserting if it was vacant.
+    ///
+    /// Returns an [`OccupiedEntry`] pointing to the now-occupied entry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<&str> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// // nonexistent key
+    /// table
+    ///     .entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher)
+    ///     .or_insert("poneyland");
+    /// assert!(table
+    ///     .find(hasher(&"poneyland"), |&x| x == "poneyland")
+    ///     .is_some());
+    ///
+    /// // existing key
+    /// table
+    ///     .entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher)
+    ///     .or_insert("poneyland");
+    /// assert!(table
+    ///     .find(hasher(&"poneyland"), |&x| x == "poneyland")
+    ///     .is_some());
+    /// assert_eq!(table.len(), 1);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn or_insert(self, default: T) -> OccupiedEntry<'a, T, A> {
+        match self {
+            Entry::Occupied(entry) => entry,
+            Entry::Vacant(entry) => entry.insert(default),
+        }
+    }
+
+    /// Ensures a value is in the entry by inserting the result of the default function if empty..
+    ///
+    /// Returns an [`OccupiedEntry`] pointing to the now-occupied entry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<String> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// table
+    ///     .entry(hasher("poneyland"), |x| x == "poneyland", |val| hasher(val))
+    ///     .or_insert_with(|| "poneyland".to_string());
+    ///
+    /// assert!(table
+    ///     .find(hasher(&"poneyland"), |x| x == "poneyland")
+    ///     .is_some());
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn or_insert_with(self, default: impl FnOnce() -> T) -> OccupiedEntry<'a, T, A> {
+        match self {
+            Entry::Occupied(entry) => entry,
+            Entry::Vacant(entry) => entry.insert(default()),
+        }
+    }
+
+    /// Provides in-place mutable access to an occupied entry before any
+    /// potential inserts into the table.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<(&str, u32)> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// table
+    ///     .entry(
+    ///         hasher(&"poneyland"),
+    ///         |&(x, _)| x == "poneyland",
+    ///         |(k, _)| hasher(&k),
+    ///     )
+    ///     .and_modify(|(_, v)| *v += 1)
+    ///     .or_insert(("poneyland", 42));
+    /// assert_eq!(
+    ///     table.find(hasher(&"poneyland"), |&(k, _)| k == "poneyland"),
+    ///     Some(&("poneyland", 42))
+    /// );
+    ///
+    /// table
+    ///     .entry(
+    ///         hasher(&"poneyland"),
+    ///         |&(x, _)| x == "poneyland",
+    ///         |(k, _)| hasher(&k),
+    ///     )
+    ///     .and_modify(|(_, v)| *v += 1)
+    ///     .or_insert(("poneyland", 42));
+    /// assert_eq!(
+    ///     table.find(hasher(&"poneyland"), |&(k, _)| k == "poneyland"),
+    ///     Some(&("poneyland", 43))
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn and_modify(self, f: impl FnOnce(&mut T)) -> Self {
+        match self {
+            Entry::Occupied(mut entry) => {
+                f(entry.get_mut());
+                Entry::Occupied(entry)
+            }
+            Entry::Vacant(entry) => Entry::Vacant(entry),
+        }
+    }
+}
+
+/// A view into an occupied entry in a `HashTable`.
+/// It is part of the [`Entry`] enum.
+///
+/// [`Entry`]: enum.Entry.html
+///
+/// # Examples
+///
+/// ```
+/// # #[cfg(feature = "nightly")]
+/// # fn test() {
+/// use ahash::AHasher;
+/// use hashbrown::hash_table::{Entry, HashTable, OccupiedEntry};
+/// use std::hash::{BuildHasher, BuildHasherDefault};
+///
+/// let mut table = HashTable::new();
+/// let hasher = BuildHasherDefault::<AHasher>::default();
+/// let hasher = |val: &_| hasher.hash_one(val);
+/// for x in ["a", "b", "c"] {
+///     table.insert_unique(hasher(&x), x, hasher);
+/// }
+/// assert_eq!(table.len(), 3);
+///
+/// let _entry_o: OccupiedEntry<_, _> = table.find_entry(hasher(&"a"), |&x| x == "a").unwrap();
+/// assert_eq!(table.len(), 3);
+///
+/// // Existing key
+/// match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
+///     Entry::Vacant(_) => unreachable!(),
+///     Entry::Occupied(view) => {
+///         assert_eq!(view.get(), &"a");
+///     }
+/// }
+///
+/// assert_eq!(table.len(), 3);
+///
+/// // Existing key (take)
+/// match table.entry(hasher(&"c"), |&x| x == "c", hasher) {
+///     Entry::Vacant(_) => unreachable!(),
+///     Entry::Occupied(view) => {
+///         assert_eq!(view.remove().0, "c");
+///     }
+/// }
+/// assert_eq!(table.find(hasher(&"c"), |&x| x == "c"), None);
+/// assert_eq!(table.len(), 2);
+/// # }
+/// # fn main() {
+/// #     #[cfg(feature = "nightly")]
+/// #     test()
+/// # }
+/// ```
+pub struct OccupiedEntry<'a, T, A = Global>
+where
+    A: Allocator,
+{
+    hash: u64,
+    bucket: Bucket<T>,
+    table: &'a mut HashTable<T, A>,
+}
+
+unsafe impl<T, A> Send for OccupiedEntry<'_, T, A>
+where
+    T: Send,
+    A: Send + Allocator,
+{
+}
+unsafe impl<T, A> Sync for OccupiedEntry<'_, T, A>
+where
+    T: Sync,
+    A: Sync + Allocator,
+{
+}
+
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for OccupiedEntry<'_, T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("OccupiedEntry")
+            .field("value", self.get())
+            .finish()
+    }
+}
+
+impl<'a, T, A> OccupiedEntry<'a, T, A>
+where
+    A: Allocator,
+{
+    /// Takes the value out of the entry, and returns it along with a
+    /// `VacantEntry` that can be used to insert another value with the same
+    /// hash as the one that was just removed.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<&str> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// // The table is empty
+    /// assert!(table.is_empty() && table.capacity() == 0);
+    ///
+    /// table.insert_unique(hasher(&"poneyland"), "poneyland", hasher);
+    /// let capacity_before_remove = table.capacity();
+    ///
+    /// if let Entry::Occupied(o) = table.entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher) {
+    ///     assert_eq!(o.remove().0, "poneyland");
+    /// }
+    ///
+    /// assert!(table
+    ///     .find(hasher(&"poneyland"), |&x| x == "poneyland")
+    ///     .is_none());
+    /// // Now table hold none elements but capacity is equal to the old one
+    /// assert!(table.len() == 0 && table.capacity() == capacity_before_remove);
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn remove(self) -> (T, VacantEntry<'a, T, A>) {
+        let (val, slot) = unsafe { self.table.raw.remove(self.bucket) };
+        (
+            val,
+            VacantEntry {
+                hash: self.hash,
+                insert_slot: slot,
+                table: self.table,
+            },
+        )
+    }
+
+    /// Gets a reference to the value in the entry.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<&str> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&"poneyland"), "poneyland", hasher);
+    ///
+    /// match table.entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher) {
+    ///     Entry::Vacant(_) => panic!(),
+    ///     Entry::Occupied(entry) => assert_eq!(entry.get(), &"poneyland"),
+    /// }
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[inline]
+    pub fn get(&self) -> &T {
+        unsafe { self.bucket.as_ref() }
+    }
+
+    /// Gets a mutable reference to the value in the entry.
+    ///
+    /// If you need a reference to the `OccupiedEntry` which may outlive the
+    /// destruction of the `Entry` value, see [`into_mut`].
+    ///
+    /// [`into_mut`]: #method.into_mut
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<(&str, u32)> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&"poneyland"), ("poneyland", 12), |(k, _)| hasher(&k));
+    ///
+    /// assert_eq!(
+    ///     table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
+    ///     Some(&("poneyland", 12))
+    /// );
+    ///
+    /// if let Entry::Occupied(mut o) = table.entry(
+    ///     hasher(&"poneyland"),
+    ///     |&(x, _)| x == "poneyland",
+    ///     |(k, _)| hasher(&k),
+    /// ) {
+    ///     o.get_mut().1 += 10;
+    ///     assert_eq!(o.get().1, 22);
+    ///
+    ///     // We can use the same Entry multiple times.
+    ///     o.get_mut().1 += 2;
+    /// }
+    ///
+    /// assert_eq!(
+    ///     table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
+    ///     Some(&("poneyland", 24))
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[inline]
+    pub fn get_mut(&mut self) -> &mut T {
+        unsafe { self.bucket.as_mut() }
+    }
+
+    /// Converts the OccupiedEntry into a mutable reference to the value in the entry
+    /// with a lifetime bound to the table itself.
+    ///
+    /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
+    ///
+    /// [`get_mut`]: #method.get_mut
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<(&str, u32)> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    /// table.insert_unique(hasher(&"poneyland"), ("poneyland", 12), |(k, _)| hasher(&k));
+    ///
+    /// assert_eq!(
+    ///     table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
+    ///     Some(&("poneyland", 12))
+    /// );
+    ///
+    /// let value: &mut (&str, u32);
+    /// match table.entry(
+    ///     hasher(&"poneyland"),
+    ///     |&(x, _)| x == "poneyland",
+    ///     |(k, _)| hasher(&k),
+    /// ) {
+    ///     Entry::Occupied(entry) => value = entry.into_mut(),
+    ///     Entry::Vacant(_) => panic!(),
+    /// }
+    /// value.1 += 10;
+    ///
+    /// assert_eq!(
+    ///     table.find(hasher(&"poneyland"), |&(x, _)| x == "poneyland",),
+    ///     Some(&("poneyland", 22))
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    pub fn into_mut(self) -> &'a mut T {
+        unsafe { self.bucket.as_mut() }
+    }
+
+    /// Converts the OccupiedEntry into a mutable reference to the underlying
+    /// table.
+    pub fn into_table(self) -> &'a mut HashTable<T, A> {
+        self.table
+    }
+}
+
+/// A view into a vacant entry in a `HashTable`.
+/// It is part of the [`Entry`] enum.
+///
+/// [`Entry`]: enum.Entry.html
+///
+/// # Examples
+///
+/// ```
+/// # #[cfg(feature = "nightly")]
+/// # fn test() {
+/// use ahash::AHasher;
+/// use hashbrown::hash_table::{Entry, HashTable, VacantEntry};
+/// use std::hash::{BuildHasher, BuildHasherDefault};
+///
+/// let mut table: HashTable<&str> = HashTable::new();
+/// let hasher = BuildHasherDefault::<AHasher>::default();
+/// let hasher = |val: &_| hasher.hash_one(val);
+///
+/// let entry_v: VacantEntry<_, _> = match table.entry(hasher(&"a"), |&x| x == "a", hasher) {
+///     Entry::Vacant(view) => view,
+///     Entry::Occupied(_) => unreachable!(),
+/// };
+/// entry_v.insert("a");
+/// assert!(table.find(hasher(&"a"), |&x| x == "a").is_some() && table.len() == 1);
+///
+/// // Nonexistent key (insert)
+/// match table.entry(hasher(&"b"), |&x| x == "b", hasher) {
+///     Entry::Vacant(view) => {
+///         view.insert("b");
+///     }
+///     Entry::Occupied(_) => unreachable!(),
+/// }
+/// assert!(table.find(hasher(&"b"), |&x| x == "b").is_some() && table.len() == 2);
+/// # }
+/// # fn main() {
+/// #     #[cfg(feature = "nightly")]
+/// #     test()
+/// # }
+/// ```
+pub struct VacantEntry<'a, T, A = Global>
+where
+    A: Allocator,
+{
+    hash: u64,
+    insert_slot: InsertSlot,
+    table: &'a mut HashTable<T, A>,
+}
+
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for VacantEntry<'_, T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("VacantEntry")
+    }
+}
+
+impl<'a, T, A> VacantEntry<'a, T, A>
+where
+    A: Allocator,
+{
+    /// Inserts a new element into the table with the hash that was used to
+    /// obtain the `VacantEntry`.
+    ///
+    /// An `OccupiedEntry` is returned for the newly inserted element.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "nightly")]
+    /// # fn test() {
+    /// use ahash::AHasher;
+    /// use hashbrown::hash_table::Entry;
+    /// use hashbrown::HashTable;
+    /// use std::hash::{BuildHasher, BuildHasherDefault};
+    ///
+    /// let mut table: HashTable<&str> = HashTable::new();
+    /// let hasher = BuildHasherDefault::<AHasher>::default();
+    /// let hasher = |val: &_| hasher.hash_one(val);
+    ///
+    /// if let Entry::Vacant(o) = table.entry(hasher(&"poneyland"), |&x| x == "poneyland", hasher) {
+    ///     o.insert("poneyland");
+    /// }
+    /// assert_eq!(
+    ///     table.find(hasher(&"poneyland"), |&x| x == "poneyland"),
+    ///     Some(&"poneyland")
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "nightly")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[inline]
+    pub fn insert(self, value: T) -> OccupiedEntry<'a, T, A> {
+        let bucket = unsafe {
+            self.table
+                .raw
+                .insert_in_slot(self.hash, self.insert_slot, value)
+        };
+        OccupiedEntry {
+            hash: self.hash,
+            bucket,
+            table: self.table,
+        }
+    }
+
+    /// Converts the VacantEntry into a mutable reference to the underlying
+    /// table.
+    pub fn into_table(self) -> &'a mut HashTable<T, A> {
+        self.table
+    }
+}
+
+/// Type representing the absence of an entry, as returned by [`HashTable::find_entry`].
+///
+/// This type only exists due to [limitations] in Rust's NLL borrow checker. In
+/// the future, `find_entry` will return an `Option<OccupiedEntry>` and this
+/// type will be removed.
+///
+/// [limitations]: https://smallcultfollowing.com/babysteps/blog/2018/06/15/mir-based-borrow-check-nll-status-update/#polonius
+///
+/// # Examples
+///
+/// ```
+/// # #[cfg(feature = "nightly")]
+/// # fn test() {
+/// use ahash::AHasher;
+/// use hashbrown::hash_table::{AbsentEntry, Entry, HashTable};
+/// use std::hash::{BuildHasher, BuildHasherDefault};
+///
+/// let mut table: HashTable<&str> = HashTable::new();
+/// let hasher = BuildHasherDefault::<AHasher>::default();
+/// let hasher = |val: &_| hasher.hash_one(val);
+///
+/// let entry_v: AbsentEntry<_, _> = table.find_entry(hasher(&"a"), |&x| x == "a").unwrap_err();
+/// entry_v
+///     .into_table()
+///     .insert_unique(hasher(&"a"), "a", hasher);
+/// assert!(table.find(hasher(&"a"), |&x| x == "a").is_some() && table.len() == 1);
+///
+/// // Nonexistent key (insert)
+/// match table.entry(hasher(&"b"), |&x| x == "b", hasher) {
+///     Entry::Vacant(view) => {
+///         view.insert("b");
+///     }
+///     Entry::Occupied(_) => unreachable!(),
+/// }
+/// assert!(table.find(hasher(&"b"), |&x| x == "b").is_some() && table.len() == 2);
+/// # }
+/// # fn main() {
+/// #     #[cfg(feature = "nightly")]
+/// #     test()
+/// # }
+/// ```
+pub struct AbsentEntry<'a, T, A = Global>
+where
+    A: Allocator,
+{
+    table: &'a mut HashTable<T, A>,
+}
+
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for AbsentEntry<'_, T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("AbsentEntry")
+    }
+}
+
+impl<'a, T, A> AbsentEntry<'a, T, A>
+where
+    A: Allocator,
+{
+    /// Converts the AbsentEntry into a mutable reference to the underlying
+    /// table.
+    pub fn into_table(self) -> &'a mut HashTable<T, A> {
+        self.table
+    }
+}
+
+/// An iterator over the entries of a `HashTable` in arbitrary order.
+/// The iterator element type is `&'a T`.
+///
+/// This `struct` is created by the [`iter`] method on [`HashTable`]. See its
+/// documentation for more.
+///
+/// [`iter`]: struct.HashTable.html#method.iter
+/// [`HashTable`]: struct.HashTable.html
+pub struct Iter<'a, T> {
+    inner: RawIter<T>,
+    marker: PhantomData<&'a T>,
+}
+
+impl<'a, T> Iterator for Iter<'a, T> {
+    type Item = &'a T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // Avoid `Option::map` because it bloats LLVM IR.
+        match self.inner.next() {
+            Some(bucket) => Some(unsafe { bucket.as_ref() }),
+            None => None,
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner
+            .fold(init, |acc, bucket| unsafe { f(acc, bucket.as_ref()) })
+    }
+}
+
+impl<T> ExactSizeIterator for Iter<'_, T> {
+    fn len(&self) -> usize {
+        self.inner.len()
+    }
+}
+
+impl<T> FusedIterator for Iter<'_, T> {}
+
+/// A mutable iterator over the entries of a `HashTable` in arbitrary order.
+/// The iterator element type is `&'a mut T`.
+///
+/// This `struct` is created by the [`iter_mut`] method on [`HashTable`]. See its
+/// documentation for more.
+///
+/// [`iter_mut`]: struct.HashTable.html#method.iter_mut
+/// [`HashTable`]: struct.HashTable.html
+pub struct IterMut<'a, T> {
+    inner: RawIter<T>,
+    marker: PhantomData<&'a mut T>,
+}
+
+impl<'a, T> Iterator for IterMut<'a, T> {
+    type Item = &'a mut T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // Avoid `Option::map` because it bloats LLVM IR.
+        match self.inner.next() {
+            Some(bucket) => Some(unsafe { bucket.as_mut() }),
+            None => None,
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner
+            .fold(init, |acc, bucket| unsafe { f(acc, bucket.as_mut()) })
+    }
+}
+
+impl<T> ExactSizeIterator for IterMut<'_, T> {
+    fn len(&self) -> usize {
+        self.inner.len()
+    }
+}
+
+impl<T> FusedIterator for IterMut<'_, T> {}
+
+/// An owning iterator over the entries of a `HashTable` in arbitrary order.
+/// The iterator element type is `T`.
+///
+/// This `struct` is created by the [`into_iter`] method on [`HashTable`]
+/// (provided by the [`IntoIterator`] trait). See its documentation for more.
+/// The table cannot be used after calling that method.
+///
+/// [`into_iter`]: struct.HashTable.html#method.into_iter
+/// [`HashTable`]: struct.HashTable.html
+/// [`IntoIterator`]: https://doc.rust-lang.org/core/iter/trait.IntoIterator.html
+pub struct IntoIter<T, A = Global>
+where
+    A: Allocator,
+{
+    inner: RawIntoIter<T, A>,
+}
+
+impl<T, A> Iterator for IntoIter<T, A>
+where
+    A: Allocator,
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next()
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner.fold(init, f)
+    }
+}
+
+impl<T, A> ExactSizeIterator for IntoIter<T, A>
+where
+    A: Allocator,
+{
+    fn len(&self) -> usize {
+        self.inner.len()
+    }
+}
+
+impl<T, A> FusedIterator for IntoIter<T, A> where A: Allocator {}
+
+/// A draining iterator over the items of a `HashTable`.
+///
+/// This `struct` is created by the [`drain`] method on [`HashTable`].
+/// See its documentation for more.
+///
+/// [`HashTable`]: struct.HashTable.html
+/// [`drain`]: struct.HashTable.html#method.drain
+pub struct Drain<'a, T, A: Allocator = Global> {
+    inner: RawDrain<'a, T, A>,
+}
+
+impl<T, A: Allocator> Drain<'_, T, A> {
+    /// Returns a iterator of references over the remaining items.
+    fn iter(&self) -> Iter<'_, T> {
+        Iter {
+            inner: self.inner.iter(),
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<T, A: Allocator> Iterator for Drain<'_, T, A> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<T> {
+        self.inner.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+}
+impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {
+    fn len(&self) -> usize {
+        self.inner.len()
+    }
+}
+impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}
+
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for Drain<'_, T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_list().entries(self.iter()).finish()
+    }
+}
+
+/// A draining iterator over entries of a `HashTable` which don't satisfy the predicate `f`.
+///
+/// This `struct` is created by [`HashTable::extract_if`]. See its
+/// documentation for more.
+#[must_use = "Iterators are lazy unless consumed"]
+pub struct ExtractIf<'a, T, F, A: Allocator = Global>
+where
+    F: FnMut(&mut T) -> bool,
+{
+    f: F,
+    inner: RawExtractIf<'a, T, A>,
+}
+
+impl<T, F, A: Allocator> Iterator for ExtractIf<'_, T, F, A>
+where
+    F: FnMut(&mut T) -> bool,
+{
+    type Item = T;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next(|val| (self.f)(val))
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, self.inner.iter.size_hint().1)
+    }
+}
+
+impl<T, F, A: Allocator> FusedIterator for ExtractIf<'_, T, F, A> where F: FnMut(&mut T) -> bool {}