Extended BorrowDecode for HashMap to support custom hashers (#585)

src/features/impl_std.rs

@@ -444,16 +444,18 @@ where
         Ok(map)
     }
 }
-impl<'de, K, V> BorrowDecode<'de> for HashMap<K, V>
+impl<'de, K, V, S> BorrowDecode<'de> for HashMap<K, V, S>
 where
     K: BorrowDecode<'de> + Eq + std::hash::Hash,
     V: BorrowDecode<'de>,
+    S: std::hash::BuildHasher + Default,
 {
     fn borrow_decode<D: BorrowDecoder<'de>>(decoder: &mut D) -> Result<Self, DecodeError> {
         let len = crate::de::decode_slice_len(decoder)?;
         decoder.claim_container_read::<(K, V)>(len)?;
 
-        let mut map = HashMap::with_capacity(len);
+        let hash_builder: S = Default::default();
+        let mut map = HashMap::with_capacity_and_hasher(len, hash_builder);
         for _ in 0..len {
             // See the documentation on `unclaim_bytes_read` as to why we're doing this here
             decoder.unclaim_bytes_read(core::mem::size_of::<(K, V)>());