Add {Arc/Rc}::ptr_eq

Author: carols10cents

_posts/2017-04-27-Rust-1.17.md

@@ -168,10 +168,11 @@ See the [detailed release notes][notes] for more.
 
 #### Library stabilizations
 
-17 new bits of API were stabilized this release:
+19 new bits of API were stabilized this release:
 
 * [`Arc::into_raw`] and [`Rc::into_raw`] let you consume an `Arc` or `Rc` and get a raw pointer.
 * [`Arc::from_raw`] and [`Rc::from_raw`] let you take that raw pointer and get an `Arc` or `Rc`.
+* [`Arc::ptr_eq`] and [`Rc::ptr_eq`] return true if the two `Arc`s or two `Rc`s point to the same value (not just values that compare as equal).
 * [`Ordering::then`] lets you chain two `Ordering`s together, and [`Ordering::then_with`] lets you do it with a function.
 * [`BTreeMap::range`] allows you to iterate over a portion of a `BTreeMap`, and [`BTreeMap::range_mut`] lets you do it mutably. [`collections::Bound`] can give you even more control.
 * [`process::abort`] will completely terminate a process in an abnormal fashion.
@@ -184,6 +185,7 @@ See the [detailed release notes][notes] for more.
 
 [`Arc::from_raw`]: https://doc.rust-lang.org/std/sync/struct.Arc.html#method.from_raw
 [`Arc::into_raw`]: https://doc.rust-lang.org/std/sync/struct.Arc.html#method.into_raw
+[`Arc::ptr_eq`]: https://doc.rust-lang.org/std/sync/struct.Arc.html#method.ptr_eq
 [`BTreeMap::range_mut`]: https://doc.rust-lang.org/std/collections/btree_map/struct.BTreeMap.html#method.range_mut
 [`BTreeMap::range`]: https://doc.rust-lang.org/std/collections/btree_map/struct.BTreeMap.html#method.range
 [`Cell::into_inner`]: https://doc.rust-lang.org/std/cell/struct.Cell.html#method.into_inner
@@ -194,6 +196,7 @@ See the [detailed release notes][notes] for more.
 [`Ordering::then`]: https://doc.rust-lang.org/std/cmp/enum.Ordering.html#method.then
 [`Rc::from_raw`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.from_raw
 [`Rc::into_raw`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.into_raw
+[`Rc::ptr_eq`]: https://doc.rust-lang.org/std/rc/struct.Rc.html#method.ptr_eq
 [`Result::expect_err`]: https://doc.rust-lang.org/std/result/enum.Result.html#method.expect_err
 [`collections::Bound`]: https://doc.rust-lang.org/std/collections/enum.Bound.html
 [`process::abort`]: https://doc.rust-lang.org/std/process/fn.abort.html