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wip: allow providing the key at insertion time for EntryRef #579

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wip: allow providing the key at insertion time for EntryRef #579

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54 changes: 45 additions & 9 deletions src/map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2984,10 +2984,10 @@ where
/// }
/// assert!(map["b"] == 20 && map.len() == 2);
/// ```
pub struct VacantEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator = Global> {
pub struct VacantEntryRef<'map, 'key, K, Q: ?Sized, V, S, A: Allocator = Global> {
hash: u64,
key: &'b Q,
table: &'a mut HashMap<K, V, S, A>,
key: &'key Q,
table: &'map mut HashMap<K, V, S, A>,
}

impl<K, Q, V, S, A> Debug for VacantEntryRef<'_, '_, K, Q, V, S, A>
Expand Down Expand Up @@ -4328,7 +4328,25 @@ impl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator> EntryRef<'a, 'b, K, Q, V
}
}

impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'a, 'b, K, Q, V, S, A> {
impl<'map, 'key, K, V, S, A: Allocator> VacantEntryRef<'map, 'key, K, K, V, S, A> {
/// insert, cloing the key
#[cfg_attr(feature = "inline-more", inline)]
pub fn insert_clone(self, value: V) -> &'map mut V
where
K: Hash + Clone,
S: BuildHasher,
{
let table = &mut self.table.table;
let entry = table.insert_entry(
self.hash,
(self.key.clone(), value),
make_hasher::<_, V, S>(&self.table.hash_builder),
);
&mut entry.1
}
}

impl<'map, 'key, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'map, 'key, K, Q, V, S, A> {
/// Gets a reference to the key that would be used when inserting a value
/// through the `VacantEntryRef`.
///
Expand All @@ -4342,7 +4360,7 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'a, 'b, K, Q, V, S
/// assert_eq!(map.entry_ref(key).key(), "poneyland");
/// ```
#[cfg_attr(feature = "inline-more", inline)]
pub fn key(&self) -> &'b Q {
pub fn key(&self) -> &'key Q {
self.key
}

Expand All @@ -4364,9 +4382,9 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'a, 'b, K, Q, V, S
/// assert_eq!(map["poneyland"], 37);
/// ```
#[cfg_attr(feature = "inline-more", inline)]
pub fn insert(self, value: V) -> &'a mut V
pub fn insert(self, value: V) -> &'map mut V
where
K: Hash + From<&'b Q>,
K: Hash + From<&'key Q>,
S: BuildHasher,
{
let table = &mut self.table.table;
Expand All @@ -4378,6 +4396,24 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'a, 'b, K, Q, V, S
&mut entry.1
}

/// provide explicit key at insert-time instead of relying on there being effectively a from &K to K implementation and not working with cloneable values
#[cfg_attr(feature = "inline-more", inline)]
pub fn insert_kv(self, key: K, value: V) -> &'map mut V
where
K: Hash,
for<'k> &'k K: PartialEq<&'key Q>,
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I think this should use Q: Equivalent<K> instead, just like entry_ref did when it was created.

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ah yes that covers exactly what is needed there. had not seen that trait so far and tbh i have not read a lot of hashbrowns code, i just needed one of those methods to avoid either copying my key more than needed or doing a double lookup.

S: BuildHasher,
{
let table = &mut self.table.table;
assert!(&key == self.key);
let entry = table.insert_entry(
self.hash,
(key, value),
make_hasher::<_, V, S>(&self.table.hash_builder),
);
&mut entry.1
}

/// Sets the value of the entry with the [`VacantEntryRef`]'s key,
/// and returns an [`OccupiedEntry`].
///
Expand All @@ -4395,9 +4431,9 @@ impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'a, 'b, K, Q, V, S
/// }
/// ```
#[cfg_attr(feature = "inline-more", inline)]
pub fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V, S, A>
pub fn insert_entry(self, value: V) -> OccupiedEntry<'map, K, V, S, A>
where
K: Hash + From<&'b Q>,
K: Hash + From<&'key Q>,
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Not your problem, but this is an issue too, since downstream Q might implement a bad From<&Q> for K.

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yeah i noticed that too, that was half the reason i asked about the assert

S: BuildHasher,
{
let elem = self.table.table.insert(
Expand Down
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