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use core::hash::{BuildHasher, Hash};
use super::{Bucket, Entries, Equivalent, IndexMap};
/// Opt-in mutable access to [`IndexMap`] keys.
///
/// These methods expose `&mut K`, mutable references to the key as it is stored
/// in the map.
/// You are allowed to modify the keys in the map **if the modification
/// does not change the key’s hash and equality**.
///
/// If keys are modified erroneously, you can no longer look them up.
/// This is sound (memory safe) but a logical error hazard (just like
/// implementing `PartialEq`, `Eq`, or `Hash` incorrectly would be).
///
/// `use` this trait to enable its methods for `IndexMap`.
///
/// This trait is sealed and cannot be implemented for types outside this crate.
pub trait MutableKeys: private::Sealed {
type Key;
type Value;
/// Return item index, mutable reference to key and value
///
/// Computes in **O(1)** time (average).
fn get_full_mut2<Q>(&mut self, key: &Q) -> Option<(usize, &mut Self::Key, &mut Self::Value)>
where
Q: ?Sized + Hash + Equivalent<Self::Key>;
/// Return mutable reference to key and value at an index.
///
/// Valid indices are *0 <= index < self.len()*
///
/// Computes in **O(1)** time.
fn get_index_mut2(&mut self, index: usize) -> Option<(&mut Self::Key, &mut Self::Value)>;
/// Scan through each key-value pair in the map and keep those where the
/// closure `keep` returns `true`.
///
/// The elements are visited in order, and remaining elements keep their
/// order.
///
/// Computes in **O(n)** time (average).
fn retain2<F>(&mut self, keep: F)
where
F: FnMut(&mut Self::Key, &mut Self::Value) -> bool;
}
/// Opt-in mutable access to [`IndexMap`] keys.
///
/// See [`MutableKeys`] for more information.
impl<K, V, S> MutableKeys for IndexMap<K, V, S>
where
S: BuildHasher,
{
type Key = K;
type Value = V;
fn get_full_mut2<Q>(&mut self, key: &Q) -> Option<(usize, &mut K, &mut V)>
where
Q: ?Sized + Hash + Equivalent<K>,
{
if let Some(i) = self.get_index_of(key) {
let entry = &mut self.as_entries_mut()[i];
Some((i, &mut entry.key, &mut entry.value))
} else {
None
}
}
fn get_index_mut2(&mut self, index: usize) -> Option<(&mut K, &mut V)> {
self.as_entries_mut().get_mut(index).map(Bucket::muts)
}
fn retain2<F>(&mut self, keep: F)
where
F: FnMut(&mut K, &mut V) -> bool,
{
self.core.retain_in_order(keep);
}
}
mod private {
pub trait Sealed {}
impl<K, V, S> Sealed for super::IndexMap<K, V, S> {}
}