[rustc.git] / vendor / ordermap / src / equivalent.rs


use std::borrow::Borrow;

/// Key equivalence trait.
///
/// This trait allows hash table lookup to be customized.
/// It has one blanket implementation that uses the regular `Borrow` solution,
/// just like `HashMap` and `BTreeMap` do, so that you can pass `&str` to lookup
/// into a map with `String` keys and so on.
///
/// # Contract
///
/// The implementor **must** hash like `K`, if it is hashable.
pub trait Equivalent<K: ?Sized> {
    /// Compare self to `key` and return `true` if they are equal.
    fn equivalent(&self, key: &K) -> bool;
}

impl<Q: ?Sized, K: ?Sized> Equivalent<K> for Q
    where Q: Eq,
          K: Borrow<Q>,
{
    #[inline]
    fn equivalent(&self, key: &K) -> bool {
        *self == *key.borrow()
    }
}
Commit	Line	Data
f9f354fc XL	1
	2	use std::borrow::Borrow;
	3
	4	/// Key equivalence trait.
	5	///
	6	/// This trait allows hash table lookup to be customized.
	7	/// It has one blanket implementation that uses the regular `Borrow` solution,
	8	/// just like `HashMap` and `BTreeMap` do, so that you can pass `&str` to lookup
	9	/// into a map with `String` keys and so on.
	10	///
	11	/// # Contract
	12	///
	13	/// The implementor must hash like `K`, if it is hashable.
	14	pub trait Equivalent<K: ?Sized> {
	15	/// Compare self to `key` and return `true` if they are equal.
	16	fn equivalent(&self, key: &K) -> bool;
	17	}
	18
	19	impl<Q: ?Sized, K: ?Sized> Equivalent<K> for Q
	20	where Q: Eq,
	21	K: Borrow<Q>,
	22	{
	23	#[inline]
	24	fn equivalent(&self, key: &K) -> bool {
	25	self == key.borrow()
	26	}
	27	}