1use core::borrow::Borrow;
2
3/// Key equivalence trait.
4///
5/// This trait allows hash table lookup to be customized.
6/// It has one blanket implementation that uses the regular `Borrow` solution,
7/// just like `HashMap` and `BTreeMap` do, so that you can pass `&str` to lookup
8/// into a map with `String` keys and so on.
9///
10/// # Contract
11///
12/// The implementor **must** hash like `K`, if it is hashable.
13pub trait Equivalent<K: ?Sized> {
14 /// Compare self to `key` and return `true` if they are equal.
15 fn equivalent(&self, key: &K) -> bool;
16}
17
18impl<Q: ?Sized, K: ?Sized> Equivalent<K> for Q
19where
20 Q: Eq,
21 K: Borrow<Q>,
22{
23 #[inline]
24 fn equivalent(&self, key: &K) -> bool {
25 *self == *key.borrow()
26 }
27}
28