more to core under feature flag

Author: conradludgate

library/alloc/src/collections/btree/cmp.rs

@@ -1,6 +1,5 @@
 mod append;
 mod borrow;
-mod cmp;
 mod dedup_sorted_iter;
 mod fix;
 pub(super) mod map;

library/alloc/src/collections/btree/mod.rs

@@ -1,7 +1,7 @@
+use core::cmp::Comparable;
 use core::ops::RangeBounds;
 use core::{hint, ptr};
 
-use super::cmp::Comparable;
 use super::node::ForceResult::*;
 use super::node::{Handle, NodeRef, marker};
 use super::search::SearchBound;

library/alloc/src/collections/btree/navigate.rs

@@ -1,10 +1,9 @@
-use core::cmp::Ordering;
+use core::cmp::{Comparable, Ordering};
 use core::ops::{Bound, RangeBounds};
 
 use SearchBound::*;
 use SearchResult::*;
 
-use super::cmp::Comparable;
 use super::node::ForceResult::*;
 use super::node::{Handle, NodeRef, marker};
 

library/alloc/src/collections/btree/search.rs

@@ -107,6 +107,7 @@
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]
 #![feature(coerce_unsized)]
+#![feature(comparable_trait)]
 #![feature(const_default)]
 #![feature(const_eval_select)]
 #![feature(const_heap)]

library/alloc/src/lib.rs

@@ -1510,6 +1510,54 @@ pub macro PartialOrd($item:item) {
     /* compiler built-in */
 }
 
+/// Key equivalence trait.
+///
+/// This trait allows hash table lookup to be customized.
+///
+/// # Contract
+///
+/// The implementor **must** hash like `Q`, if it is hashable.
+#[unstable(feature = "comparable_trait", issue = "145986")]
+pub trait Equivalent<Q: ?Sized> {
+    /// Compare self to `key` and return `true` if they are equal.
+    #[unstable(feature = "comparable_trait", issue = "145986")]
+    fn equivalent(&self, key: &Q) -> bool;
+}
+
+#[unstable(feature = "comparable_trait", issue = "145986")]
+impl<K: ?Sized, Q: ?Sized> Equivalent<Q> for K
+where
+    K: crate::borrow::Borrow<Q>,
+    Q: Eq,
+{
+    #[inline]
+    fn equivalent(&self, key: &Q) -> bool {
+        PartialEq::eq(self.borrow(), key)
+    }
+}
+
+/// Key ordering trait.
+///
+/// This trait allows ordered map lookup to be customized.
+#[unstable(feature = "comparable_trait", issue = "145986")]
+pub trait Comparable<Q: ?Sized>: Equivalent<Q> {
+    /// Compare self to `key` and return their ordering.
+    #[unstable(feature = "comparable_trait", issue = "145986")]
+    fn compare(&self, key: &Q) -> Ordering;
+}
+
+#[unstable(feature = "comparable_trait", issue = "145986")]
+impl<K: ?Sized, Q: ?Sized> Comparable<Q> for K
+where
+    K: crate::borrow::Borrow<Q>,
+    Q: Ord,
+{
+    #[inline]
+    fn compare(&self, key: &Q) -> Ordering {
+        Ord::cmp(self.borrow(), key)
+    }
+}
+
 /// Compares and returns the minimum of two values.
 ///
 /// Returns the first argument if the comparison determines them to be equal.