Use the bucket API from hashbrown v0.16.1

This is similar to indexmap-rs/indexmap#424, simplify a lot of code by
using a bucket index in `OccupiedEntry` rather than having to split
references. The effects are a little more pronounced here because our
`RefMut` needed **3** references, due to the extra offset tracking, so
with that gone, now *every* `*Entry` type is reduced in size.

Author: cuviper

Cargo.toml

@@ -15,6 +15,7 @@ bench = false
 
 [dependencies]
 equivalent = { version = "1.0", default-features = false }
+hashbrown = { version = "0.16.1", default-features = false }
 
 arbitrary = { version = "1.0", optional = true, default-features = false }
 quickcheck = { version = "1.0", optional = true, default-features = false }
@@ -23,10 +24,6 @@ borsh = { version = "1.2", optional = true, default-features = false }
 rayon = { version = "1.9", optional = true }
 sval = { version = "2", optional = true, default-features = false }
 
-[dependencies.hashbrown]
-version = "0.16.0"
-default-features = false
-
 # serde v1.0.220 is the first version that released with `serde_core`.
 # This is required to avoid conflict with other `serde` users which may require an older version.
 [target.'cfg(any())'.dependencies]

src/map.rs

@@ -760,7 +760,7 @@ where
     /// Computes in **O(1)** time (amortized average).
     pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
         let hash = self.hash(&key);
-        self.core.entry(hash, key)
+        Entry::new(&mut self.core, hash, key)
     }
 
     /// Creates a splicing iterator that replaces the specified range in the map
@@ -1564,10 +1564,7 @@ impl<K, V, S> RingMap<K, V, S> {
     ///
     /// Computes in **O(1)** time.
     pub fn get_index_entry(&mut self, index: usize) -> Option<IndexedEntry<'_, K, V>> {
-        if index >= self.len() {
-            return None;
-        }
-        Some(IndexedEntry::new(&mut self.core, index))
+        IndexedEntry::new(&mut self.core, index)
     }
 
     /// Get an array of `N` key-value pairs by `N` indices