Struct RawVacantEntryMut 

pub struct RawVacantEntryMut<'a, K, V, S, A = Global>
where
    A: Allocator,
{ /* private fields */ }

A view into a vacant entry in a HashMap. It is part of the RawEntryMut enum.

Examples

use core::hash::{BuildHasher, Hash};
use rune::alloc::hash_map::{RawEntryMut, RawVacantEntryMut};
use rune::alloc::HashMap;

let mut map = HashMap::<&str, i32>::new();

fn compute_hash<K, S>(hash_builder: &S, key: &K) -> u64
where
    K: Hash + ?Sized,
    S: BuildHasher,
{
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

let raw_v: RawVacantEntryMut<_, _, _> = match map.raw_entry_mut().from_key(&"a") {
    RawEntryMut::Vacant(view) => view,
    RawEntryMut::Occupied(_) => unreachable!(),
};
raw_v.try_insert("a", 10)?;
assert!(map[&"a"] == 10 && map.len() == 1);

// Nonexistent key (insert and update)
let hash = compute_hash(map.hasher(), &"b");
match map.raw_entry_mut().from_key_hashed_nocheck(hash, &"b") {
    RawEntryMut::Occupied(_) => unreachable!(),
    RawEntryMut::Vacant(view) => {
        let (k, value) = view.try_insert("b", 2)?;
        assert_eq!((*k, *value), ("b", 2));
        *value = 20;
    }
}
assert!(map[&"b"] == 20 && map.len() == 2);

let hash = compute_hash(map.hasher(), &"c");
match map.raw_entry_mut().from_hash(hash, |q| *q == "c") {
    RawEntryMut::Occupied(_) => unreachable!(),
    RawEntryMut::Vacant(view) => {
        assert_eq!(view.try_insert("c", 30)?, (&mut "c", &mut 30));
    }
}
assert!(map[&"c"] == 30 && map.len() == 3);