Auto merge of #46952 - SimonSapin:nonnull, r=alexcrichton

Rename std::ptr::Shared to NonNull and stabilize it

This implements the changes proposed at https://github.com/rust-lang/rust/issues/27730#issuecomment-352800629:

> * Rename `Shared<T>` to `NonNull<T>` and stabilize it. (Being in the `ptr` module is enough to say that it’s a pointer. I’m not very attached to this specific name though.)
> * Rename `Box<T>` methods ~~`from_unique`~~/`into_unique` to ~~`from_nonnull`~~/`into_nonnull` (or whatever names are deemed appropriate), replace `Unique<T>` with `NonNull<T>` in their signatures, and stabilize them.
> *  Replace `Unique<T>` with `NonNull<T>` in the signatures of methods of the `Alloc` trait.
> * Mark `Unique` “permanently-unstable” by replacing remaining occurrences of `#[unstable(feature = "unique", issue = "27730")]` with:
>
>   ```rust
>   #[unstable(feature = "ptr_internals", issue = "0", reason = "\
>       use NonNull instead and consider PhantomData<T> (if you also use #[may_dangle]), \
>       Send, and/or Sync")]
>   ```
>
>   (Maybe the `reason` string is only useful on the struct definition.) Ideally it would be made private to some crate instead, but it needs to be used in both liballoc and libstd.
> * (Leave `NonZero` and `Zeroable` unstable for now, and subject to future bikeshedding.)

22 files changed, 181 insertions, 196 deletions

diff --git a/src/doc/nomicon b/src/doc/nomicon
-Subproject 2f7b05fd5939aa49d52c4ab309b9a47776ba7bd
+Subproject fec3182d0b0a3cf8122e192b3270064a5b19be5
diff --git a/src/liballoc/allocator.rs b/src/liballoc/allocator.rs
index c2a8f5f8ff9..55e8c0b430f 100644
--- a/src/liballoc/allocator.rs
+++ b/src/liballoc/allocator.rs
@@ -19,7 +19,7 @@ use core::cmp;
 use core::fmt;
 use core::mem;
 use core::usize;
-use core::ptr::{self, Unique};
+use core::ptr::{self, NonNull};
 
 /// Represents the combination of a starting address and
 /// a total capacity of the returned block.
@@ -895,12 +895,12 @@ pub unsafe trait Alloc {
     /// Clients wishing to abort computation in response to an
     /// allocation error are encouraged to call the allocator's `oom`
     /// method, rather than directly invoking `panic!` or similar.
-    fn alloc_one<T>(&mut self) -> Result<Unique<T>, AllocErr>
+    fn alloc_one<T>(&mut self) -> Result<NonNull<T>, AllocErr>
         where Self: Sized
     {
         let k = Layout::new::<T>();
         if k.size() > 0 {
-            unsafe { self.alloc(k).map(|p| Unique::new_unchecked(p as *mut T)) }
+            unsafe { self.alloc(k).map(|p| NonNull::new_unchecked(p as *mut T)) }
         } else {
             Err(AllocErr::invalid_input("zero-sized type invalid for alloc_one"))
         }
@@ -923,7 +923,7 @@ pub unsafe trait Alloc {
     /// * `ptr` must denote a block of memory currently allocated via this allocator
     ///
     /// * the layout of `T` must *fit* that block of memory.
-    unsafe fn dealloc_one<T>(&mut self, ptr: Unique<T>)
+    unsafe fn dealloc_one<T>(&mut self, ptr: NonNull<T>)
         where Self: Sized
     {
         let raw_ptr = ptr.as_ptr() as *mut u8;
@@ -963,7 +963,7 @@ pub unsafe trait Alloc {
     /// Clients wishing to abort computation in response to an
     /// allocation error are encouraged to call the allocator's `oom`
     /// method, rather than directly invoking `panic!` or similar.
-    fn alloc_array<T>(&mut self, n: usize) -> Result<Unique<T>, AllocErr>
+    fn alloc_array<T>(&mut self, n: usize) -> Result<NonNull<T>, AllocErr>
         where Self: Sized
     {
         match Layout::array::<T>(n) {
@@ -971,7 +971,7 @@ pub unsafe trait Alloc {
                 unsafe {
                     self.alloc(layout.clone())
                         .map(|p| {
-                            Unique::new_unchecked(p as *mut T)
+                            NonNull::new_unchecked(p as *mut T)
                         })
                 }
             }
@@ -1012,15 +1012,15 @@ pub unsafe trait Alloc {
     /// reallocation error are encouraged to call the allocator's `oom`
     /// method, rather than directly invoking `panic!` or similar.
     unsafe fn realloc_array<T>(&mut self,
-                               ptr: Unique<T>,
+                               ptr: NonNull<T>,
                                n_old: usize,
-                               n_new: usize) -> Result<Unique<T>, AllocErr>
+                               n_new: usize) -> Result<NonNull<T>, AllocErr>
         where Self: Sized
     {
         match (Layout::array::<T>(n_old), Layout::array::<T>(n_new), ptr.as_ptr()) {
             (Some(ref k_old), Some(ref k_new), ptr) if k_old.size() > 0 && k_new.size() > 0 => {
                 self.realloc(ptr as *mut u8, k_old.clone(), k_new.clone())
-                    .map(|p|Unique::new_unchecked(p as *mut T))
+                    .map(|p| NonNull::new_unchecked(p as *mut T))
             }
             _ => {
                 Err(AllocErr::invalid_input("invalid layout for realloc_array"))
@@ -1048,7 +1048,7 @@ pub unsafe trait Alloc {
     /// constraints.
     ///
     /// Always returns `Err` on arithmetic overflow.
-    unsafe fn dealloc_array<T>(&mut self, ptr: Unique<T>, n: usize) -> Result<(), AllocErr>
+    unsafe fn dealloc_array<T>(&mut self, ptr: NonNull<T>, n: usize) -> Result<(), AllocErr>
         where Self: Sized
     {
         let raw_ptr = ptr.as_ptr() as *mut u8;
diff --git a/src/liballoc/arc.rs b/src/liballoc/arc.rs
index 185af8835d1..6a77bf64bae 100644
--- a/src/liballoc/arc.rs
+++ b/src/liballoc/arc.rs
@@ -25,7 +25,7 @@ use core::intrinsics::abort;
 use core::mem::{self, align_of_val, size_of_val, uninitialized};
 use core::ops::Deref;
 use core::ops::CoerceUnsized;
-use core::ptr::{self, Shared};
+use core::ptr::{self, NonNull};
 use core::marker::{Unsize, PhantomData};
 use core::hash::{Hash, Hasher};
 use core::{isize, usize};
@@ -197,7 +197,7 @@ const MAX_REFCOUNT: usize = (isize::MAX) as usize;
 /// [rc_examples]: ../../std/rc/index.html#examples
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Arc<T: ?Sized> {
-    ptr: Shared<ArcInner<T>>,
+    ptr: NonNull<ArcInner<T>>,
     phantom: PhantomData<T>,
 }
 
@@ -234,7 +234,7 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Arc<U>> for Arc<T> {}
 /// [`None`]: ../../std/option/enum.Option.html#variant.None
 #[stable(feature = "arc_weak", since = "1.4.0")]
 pub struct Weak<T: ?Sized> {
-    ptr: Shared<ArcInner<T>>,
+    ptr: NonNull<ArcInner<T>>,
 }
 
 #[stable(feature = "arc_weak", since = "1.4.0")]
@@ -286,7 +286,7 @@ impl<T> Arc<T> {
             weak: atomic::AtomicUsize::new(1),
             data,
         };
-        Arc { ptr: Shared::from(Box::into_unique(x)), phantom: PhantomData }
+        Arc { ptr: Box::into_raw_non_null(x), phantom: PhantomData }
     }
 
     /// Returns the contained value, if the `Arc` has exactly one strong reference.
@@ -397,7 +397,7 @@ impl<T: ?Sized> Arc<T> {
         let arc_ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
 
         Arc {
-            ptr: Shared::new_unchecked(arc_ptr),
+            ptr: NonNull::new_unchecked(arc_ptr),
             phantom: PhantomData,
         }
     }
@@ -582,7 +582,7 @@ impl<T: ?Sized> Arc<T> {
             // Free the allocation without dropping its contents
             box_free(bptr);
 
-            Arc { ptr: Shared::new_unchecked(ptr), phantom: PhantomData }
+            Arc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }
     }
 }
@@ -609,7 +609,7 @@ impl<T> Arc<[T]> {
             &mut (*ptr).data as *mut [T] as *mut T,
             v.len());
 
-        Arc { ptr: Shared::new_unchecked(ptr), phantom: PhantomData }
+        Arc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
     }
 }
 
@@ -669,7 +669,7 @@ impl<T: Clone> ArcFromSlice<T> for Arc<[T]> {
             // All clear. Forget the guard so it doesn't free the new ArcInner.
             mem::forget(guard);
 
-            Arc { ptr: Shared::new_unchecked(ptr), phantom: PhantomData }
+            Arc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }
     }
 }
@@ -991,11 +991,11 @@ impl<T> Weak<T> {
     pub fn new() -> Weak<T> {
         unsafe {
             Weak {
-                ptr: Shared::from(Box::into_unique(box ArcInner {
+                ptr: Box::into_raw_non_null(box ArcInner {
                     strong: atomic::AtomicUsize::new(0),
                     weak: atomic::AtomicUsize::new(1),
                     data: uninitialized(),
-                })),
+                }),
             }
         }
     }
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 6f125cdba81..bfe23ddeca3 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -68,7 +68,7 @@ use core::marker::{self, Unsize};
 use core::mem;
 use core::ops::{CoerceUnsized, Deref, DerefMut, Generator, GeneratorState};
 use core::ops::{BoxPlace, Boxed, InPlace, Place, Placer};
-use core::ptr::{self, Unique};
+use core::ptr::{self, NonNull, Unique};
 use core::convert::From;
 use str::from_boxed_utf8_unchecked;
 
@@ -269,38 +269,7 @@ impl<T: ?Sized> Box<T> {
     #[stable(feature = "box_raw", since = "1.4.0")]
     #[inline]
     pub unsafe fn from_raw(raw: *mut T) -> Self {
-        Box::from_unique(Unique::new_unchecked(raw))
-    }
-
-    /// Constructs a `Box` from a `Unique<T>` pointer.
-    ///
-    /// After calling this function, the memory is owned by a `Box` and `T` can
-    /// then be destroyed and released upon drop.
-    ///
-    /// # Safety
-    ///
-    /// A `Unique<T>` can be safely created via [`Unique::new`] and thus doesn't
-    /// necessarily own the data pointed to nor is the data guaranteed to live
-    /// as long as the pointer.
-    ///
-    /// [`Unique::new`]: ../../core/ptr/struct.Unique.html#method.new
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(unique)]
-    ///
-    /// fn main() {
-    ///     let x = Box::new(5);
-    ///     let ptr = Box::into_unique(x);
-    ///     let x = unsafe { Box::from_unique(ptr) };
-    /// }
-    /// ```
-    #[unstable(feature = "unique", reason = "needs an RFC to flesh out design",
-               issue = "27730")]
-    #[inline]
-    pub unsafe fn from_unique(u: Unique<T>) -> Self {
-        Box(u)
+        Box(Unique::new_unchecked(raw))
     }
 
     /// Consumes the `Box`, returning the wrapped raw pointer.
@@ -326,40 +295,42 @@ impl<T: ?Sized> Box<T> {
     #[stable(feature = "box_raw", since = "1.4.0")]
     #[inline]
     pub fn into_raw(b: Box<T>) -> *mut T {
-        Box::into_unique(b).as_ptr()
+        Box::into_raw_non_null(b).as_ptr()
     }
 
-    /// Consumes the `Box`, returning the wrapped pointer as `Unique<T>`.
+    /// Consumes the `Box`, returning the wrapped pointer as `NonNull<T>`.
     ///
     /// After calling this function, the caller is responsible for the
     /// memory previously managed by the `Box`. In particular, the
     /// caller should properly destroy `T` and release the memory. The
-    /// proper way to do so is to either convert the `Unique<T>` pointer:
-    ///
-    /// - Into a `Box` with the [`Box::from_unique`] function.
-    ///
-    /// - Into a raw pointer and back into a `Box` with the [`Box::from_raw`]
-    ///   function.
+    /// proper way to do so is to convert the `NonNull<T>` pointer
+    /// into a raw pointer and back into a `Box` with the [`Box::from_raw`]
+    /// function.
     ///
     /// Note: this is an associated function, which means that you have
-    /// to call it as `Box::into_unique(b)` instead of `b.into_unique()`. This
+    /// to call it as `Box::into_raw_non_null(b)`
+    /// instead of `b.into_raw_non_null()`. This
     /// is so that there is no conflict with a method on the inner type.
     ///
-    /// [`Box::from_unique`]: struct.Box.html#method.from_unique
     /// [`Box::from_raw`]: struct.Box.html#method.from_raw
     ///
     /// # Examples
     ///
     /// ```
-    /// #![feature(unique)]
+    /// #![feature(box_into_raw_non_null)]
     ///
     /// fn main() {
     ///     let x = Box::new(5);
-    ///     let ptr = Box::into_unique(x);
+    ///     let ptr = Box::into_raw_non_null(x);
     /// }
     /// ```
-    #[unstable(feature = "unique", reason = "needs an RFC to flesh out design",
-               issue = "27730")]
+    #[unstable(feature = "box_into_raw_non_null", issue = "47336")]
+    #[inline]
+    pub fn into_raw_non_null(b: Box<T>) -> NonNull<T> {
+        Box::into_unique(b).into()
+    }
+
+    #[unstable(feature = "ptr_internals", issue = "0", reason = "use into_raw_non_null instead")]
     #[inline]
     pub fn into_unique(b: Box<T>) -> Unique<T> {
         let unique = b.0;
diff --git a/src/liballoc/heap.rs b/src/liballoc/heap.rs
index b2bd9d7d8fa..37af9ea5295 100644
--- a/src/liballoc/heap.rs
+++ b/src/liballoc/heap.rs
@@ -232,7 +232,7 @@ unsafe impl Alloc for Heap {
 ///
 /// This preserves the non-null invariant for types like `Box<T>`. The address
 /// may overlap with non-zero-size memory allocations.
-#[rustc_deprecated(since = "1.19", reason = "Use Unique/Shared::empty() instead")]
+#[rustc_deprecated(since = "1.19", reason = "Use Unique/NonNull::empty() instead")]
 #[unstable(feature = "heap_api", issue = "27700")]
 pub const EMPTY: *mut () = 1 as *mut ();
 
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 6ee4f802802..5139e54b560 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -84,6 +84,7 @@
 #![cfg_attr(test, feature(rand, test))]
 #![feature(allow_internal_unstable)]
 #![feature(ascii_ctype)]
+#![feature(box_into_raw_non_null)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(cfg_target_has_atomic)]
@@ -109,8 +110,8 @@
 #![feature(pattern)]
 #![feature(placement_in_syntax)]
 #![feature(placement_new_protocol)]
+#![feature(ptr_internals)]
 #![feature(rustc_attrs)]
-#![feature(shared)]
 #![feature(slice_get_slice)]
 #![feature(slice_patterns)]
 #![feature(slice_rsplit)]
@@ -120,7 +121,6 @@
 #![feature(trusted_len)]
 #![feature(unboxed_closures)]
 #![feature(unicode)]
-#![feature(unique)]
 #![feature(unsize)]
 #![feature(allocator_internals)]
 #![feature(on_unimplemented)]
diff --git a/src/liballoc/linked_list.rs b/src/liballoc/linked_list.rs
index 3ac5a85d721..3cc810a055f 100644
--- a/src/liballoc/linked_list.rs
+++ b/src/liballoc/linked_list.rs
@@ -29,7 +29,7 @@ use core::iter::{FromIterator, FusedIterator};
 use core::marker::PhantomData;
 use core::mem;
 use core::ops::{BoxPlace, InPlace, Place, Placer};
-use core::ptr::{self, Shared};
+use core::ptr::{self, NonNull};
 
 use boxed::{Box, IntermediateBox};
 use super::SpecExtend;
@@ -44,15 +44,15 @@ use super::SpecExtend;
 /// more memory efficient and make better use of CPU cache.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct LinkedList<T> {
-    head: Option<Shared<Node<T>>>,
-    tail: Option<Shared<Node<T>>>,
+    head: Option<NonNull<Node<T>>>,
+    tail: Option<NonNull<Node<T>>>,
     len: usize,
     marker: PhantomData<Box<Node<T>>>,
 }
 
 struct Node<T> {
-    next: Option<Shared<Node<T>>>,
-    prev: Option<Shared<Node<T>>>,
+    next: Option<NonNull<Node<T>>>,
+    prev: Option<NonNull<Node<T>>>,
     element: T,
 }
 
@@ -65,8 +65,8 @@ struct Node<T> {
 /// [`LinkedList`]: struct.LinkedList.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Iter<'a, T: 'a> {
-    head: Option<Shared<Node<T>>>,
-    tail: Option<Shared<Node<T>>>,
+    head: Option<NonNull<Node<T>>>,
+    tail: Option<NonNull<Node<T>>>,
     len: usize,
     marker: PhantomData<&'a Node<T>>,
 }
@@ -98,8 +98,8 @@ impl<'a, T> Clone for Iter<'a, T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IterMut<'a, T: 'a> {
     list: &'a mut LinkedList<T>,
-    head: Option<Shared<Node<T>>>,
-    tail: Option<Shared<Node<T>>>,
+    head: Option<NonNull<Node<T>>>,
+    tail: Option<NonNull<Node<T>>>,
     len: usize,
 }
 
@@ -157,7 +157,7 @@ impl<T> LinkedList<T> {
         unsafe {
             node.next = self.head;
             node.prev = None;
-            let node = Some(Shared::from(Box::into_unique(node)));
+            let node = Some(Box::into_raw_non_null(node));
 
             match self.head {
                 None => self.tail = node,
@@ -192,7 +192,7 @@ impl<T> LinkedList<T> {
         unsafe {
             node.next = None;
             node.prev = self.tail;
-            let node = Some(Shared::from(Box::into_unique(node)));
+            let node = Some(Box::into_raw_non_null(node));
 
             match self.tail {
                 None => self.head = node,
@@ -225,7 +225,7 @@ impl<T> LinkedList<T> {
     ///
     /// Warning: this will not check that the provided node belongs to the current list.
     #[inline]
-    unsafe fn unlink_node(&mut self, mut node: Shared<Node<T>>) {
+    unsafe fn unlink_node(&mut self, mut node: NonNull<Node<T>>) {
         let node = node.as_mut();
 
         match node.prev {
@@ -986,11 +986,11 @@ impl<'a, T> IterMut<'a, T> {
                     Some(prev) => prev,
                 };
 
-                let node = Some(Shared::from(Box::into_unique(box Node {
+                let node = Some(Box::into_raw_non_null(box Node {
                     next: Some(head),
                     prev: Some(prev),
                     element,
-                })));
+                }));
 
                 prev.as_mut().next = node;
                 head.as_mut().prev = node;
@@ -1038,7 +1038,7 @@ pub struct DrainFilter<'a, T: 'a, F: 'a>
     where F: FnMut(&mut T) -> bool,
 {
     list: &'a mut LinkedList<T>,
-    it: Option<Shared<Node<T>>>,
+    it: Option<NonNull<Node<T>>>,
     pred: F,
     idx: usize,
     old_len: usize,
diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index dbf1fb1367d..621e1906961 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -322,7 +322,7 @@ impl<T, A: Alloc> RawVec<T, A> {
                     // would cause overflow
                     let new_cap = if elem_size > (!0) / 8 { 1 } else { 4 };
                     match self.a.alloc_array::<T>(new_cap) {
-                        Ok(ptr) => (new_cap, ptr),
+                        Ok(ptr) => (new_cap, ptr.into()),
                         Err(e) => self.a.oom(e),
                     }
                 }
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 59079f9ba76..1fa5d34cb57 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -256,7 +256,7 @@ use core::marker::{Unsize, PhantomData};
 use core::mem::{self, align_of_val, forget, size_of_val, uninitialized};
 use core::ops::Deref;
 use core::ops::CoerceUnsized;
-use core::ptr::{self, Shared};
+use core::ptr::{self, NonNull};
 use core::convert::From;
 
 use heap::{Heap, Alloc, Layout, box_free};
@@ -282,7 +282,7 @@ struct RcBox<T: ?Sized> {
 /// [get_mut]: #method.get_mut
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Rc<T: ?Sized> {
-    ptr: Shared<RcBox<T>>,
+    ptr: NonNull<RcBox<T>>,
     phantom: PhantomData<T>,
 }
 
@@ -311,11 +311,11 @@ impl<T> Rc<T> {
             // pointers, which ensures that the weak destructor never frees
             // the allocation while the strong destructor is running, even
             // if the weak pointer is stored inside the strong one.
-            ptr: Shared::from(Box::into_unique(box RcBox {
+            ptr: Box::into_raw_non_null(box RcBox {
                 strong: Cell::new(1),
                 weak: Cell::new(1),
                 value,
-            })),
+            }),
             phantom: PhantomData,
         }
     }
@@ -428,7 +428,7 @@ impl<T: ?Sized> Rc<T> {
         let rc_ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
 
         Rc {
-            ptr: Shared::new_unchecked(rc_ptr),
+            ptr: NonNull::new_unchecked(rc_ptr),
             phantom: PhantomData,
         }
     }
@@ -649,7 +649,7 @@ impl Rc<Any> {
                 let raw: *const RcBox<Any> = self.ptr.as_ptr();
                 forget(self);
                 Ok(Rc {
-                    ptr: Shared::new_unchecked(raw as *const RcBox<T> as *mut _),
+                    ptr: NonNull::new_unchecked(raw as *const RcBox<T> as *mut _),
                     phantom: PhantomData,
                 })
             }
@@ -695,7 +695,7 @@ impl<T: ?Sized> Rc<T> {
             // Free the allocation without dropping its contents
             box_free(bptr);
 
-            Rc { ptr: Shared::new_unchecked(ptr), phantom: PhantomData }
+            Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }
     }
 }
@@ -722,7 +722,7 @@ impl<T> Rc<[T]> {
             &mut (*ptr).value as *mut [T] as *mut T,
             v.len());
 
-        Rc { ptr: Shared::new_unchecked(ptr), phantom: PhantomData }
+        Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
     }
 }
 
@@ -781,7 +781,7 @@ impl<T: Clone> RcFromSlice<T> for Rc<[T]> {
             // All clear. Forget the guard so it doesn't free the new RcBox.
             forget(guard);
 
-            Rc { ptr: Shared::new_unchecked(ptr), phantom: PhantomData }
+            Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }
     }
 }
@@ -1160,7 +1160,7 @@ impl<T> From<Vec<T>> for Rc<[T]> {
 /// [`None`]: ../../std/option/enum.Option.html#variant.None
 #[stable(feature = "rc_weak", since = "1.4.0")]
 pub struct Weak<T: ?Sized> {
-    ptr: Shared<RcBox<T>>,
+    ptr: NonNull<RcBox<T>>,
 }
 
 #[stable(feature = "rc_weak", since = "1.4.0")]
@@ -1190,11 +1190,11 @@ impl<T> Weak<T> {
     pub fn new() -> Weak<T> {
         unsafe {
             Weak {
-                ptr: Shared::from(Box::into_unique(box RcBox {
+                ptr: Box::into_raw_non_null(box RcBox {
                     strong: Cell::new(0),
                     weak: Cell::new(1),
                     value: uninitialized(),
-                })),
+                }),
             }
         }
     }
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index 301e44632b8..b14b9d74765 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -78,7 +78,7 @@ use core::num::Float;
 use core::ops::{InPlace, Index, IndexMut, Place, Placer};
 use core::ops;
 use core::ptr;
-use core::ptr::Shared;
+use core::ptr::NonNull;
 use core::slice;
 
 use borrow::ToOwned;
@@ -1124,7 +1124,7 @@ impl<T> Vec<T> {
                 tail_start: end,
                 tail_len: len - end,
                 iter: range_slice.iter(),
-                vec: Shared::from(self),
+                vec: NonNull::from(self),
             }
         }
     }
@@ -1745,7 +1745,7 @@ impl<T> IntoIterator for Vec<T> {
             let cap = self.buf.cap();
             mem::forget(self);
             IntoIter {
-                buf: Shared::new_unchecked(begin),
+                buf: NonNull::new_unchecked(begin),
                 phantom: PhantomData,
                 cap,
                 ptr: begin,
@@ -2267,7 +2267,7 @@ impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone {
 /// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<T> {
-    buf: Shared<T>,
+    buf: NonNull<T>,
     phantom: PhantomData<T>,
     cap: usize,
     ptr: *const T,
@@ -2442,7 +2442,7 @@ pub struct Drain<'a, T: 'a> {
     tail_len: usize,
     /// Current remaining range to remove
     iter: slice::Iter<'a, T>,
-    vec: Shared<Vec<T>>,
+    vec: NonNull<Vec<T>>,
 }
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
diff --git a/src/liballoc/vec_deque.rs b/src/liballoc/vec_deque.rs
index f56aa23a4eb..8f05a69c5f3 100644
--- a/src/liballoc/vec_deque.rs
+++ b/src/liballoc/vec_deque.rs
@@ -23,7 +23,7 @@ use core::iter::{repeat, FromIterator, FusedIterator};
 use core::mem;
 use core::ops::{Index, IndexMut, Place, Placer, InPlace};
 use core::ptr;
-use core::ptr::Shared;
+use core::ptr::NonNull;
 use core::slice;
 
 use core::hash::{Hash, Hasher};
@@ -895,7 +895,7 @@ impl<T> VecDeque<T> {
         self.head = drain_tail;
 
         Drain {
-            deque: Shared::from(&mut *self),
+            deque: NonNull::from(&mut *self),
             after_tail: drain_head,
             after_head: head,
             iter: Iter {
@@ -2154,7 +2154,7 @@ pub struct Drain<'a, T: 'a> {
     after_tail: usize,
     after_head: usize,
     iter: Iter<'a, T>,
-    deque: Shared<VecDeque<T>>,
+    deque: NonNull<VecDeque<T>>,
 }
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs
index 7f7246df8f2..fab5832d905 100644
--- a/src/libcore/ptr.rs
+++ b/src/libcore/ptr.rs
@@ -2321,7 +2321,7 @@ impl<T: ?Sized> PartialOrd for *mut T {
 /// its owning Unique.
 ///
 /// If you're uncertain of whether it's correct to use `Unique` for your purposes,
-/// consider using `Shared`, which has weaker semantics.
+/// consider using `NonNull`, which has weaker semantics.
 ///
 /// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
 /// is never dereferenced. This is so that enums may use this forbidden value
@@ -2330,9 +2330,9 @@ impl<T: ?Sized> PartialOrd for *mut T {
 ///
 /// Unlike `*mut T`, `Unique<T>` is covariant over `T`. This should always be correct
 /// for any type which upholds Unique's aliasing requirements.
-#[allow(missing_debug_implementations)]
-#[unstable(feature = "unique", reason = "needs an RFC to flesh out design",
-           issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0",
+           reason = "use NonNull instead and consider PhantomData<T> \
+                     (if you also use #[may_dangle]), Send, and/or Sync")]
 pub struct Unique<T: ?Sized> {
     pointer: NonZero<*const T>,
     // NOTE: this marker has no consequences for variance, but is necessary
@@ -2343,26 +2343,34 @@ pub struct Unique<T: ?Sized> {
     _marker: PhantomData<T>,
 }
 
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> fmt::Debug for Unique<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Pointer::fmt(&self.as_ptr(), f)
+    }
+}
+
 /// `Unique` pointers are `Send` if `T` is `Send` because the data they
 /// reference is unaliased. Note that this aliasing invariant is
 /// unenforced by the type system; the abstraction using the
 /// `Unique` must enforce it.
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 unsafe impl<T: Send + ?Sized> Send for Unique<T> { }
 
 /// `Unique` pointers are `Sync` if `T` is `Sync` because the data they
 /// reference is unaliased. Note that this aliasing invariant is
 /// unenforced by the type system; the abstraction using the
 /// `Unique` must enforce it.
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 unsafe impl<T: Sync + ?Sized> Sync for Unique<T> { }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<T: Sized> Unique<T> {
     /// Creates a new `Unique` that is dangling, but well-aligned.
     ///
     /// This is useful for initializing types which lazily allocate, like
     /// `Vec::new` does.
+    // FIXME: rename to dangling() to match NonNull?
     pub fn empty() -> Self {
         unsafe {
             let ptr = mem::align_of::<T>() as *mut T;
@@ -2371,14 +2379,13 @@ impl<T: Sized> Unique<T> {
     }
 }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<T: ?Sized> Unique<T> {
     /// Creates a new `Unique`.
     ///
     /// # Safety
     ///
     /// `ptr` must be non-null.
-    #[unstable(feature = "unique", issue = "27730")]
     pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
         Unique { pointer: NonZero::new_unchecked(ptr), _marker: PhantomData }
     }
@@ -2397,7 +2404,7 @@ impl<T: ?Sized> Unique<T> {
     ///
     /// The resulting lifetime is bound to self so this behaves "as if"
     /// it were actually an instance of T that is getting borrowed. If a longer
-    /// (unbound) lifetime is needed, use `&*my_ptr.ptr()`.
+    /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
     pub unsafe fn as_ref(&self) -> &T {
         &*self.as_ptr()
     }
@@ -2406,112 +2413,130 @@ impl<T: ?Sized> Unique<T> {
     ///
     /// The resulting lifetime is bound to self so this behaves "as if"
     /// it were actually an instance of T that is getting borrowed. If a longer
-    /// (unbound) lifetime is needed, use `&mut *my_ptr.ptr()`.
+    /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
     pub unsafe fn as_mut(&mut self) -> &mut T {
         &mut *self.as_ptr()
     }
 }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<T: ?Sized> Clone for Unique<T> {
     fn clone(&self) -> Self {
         *self
     }
 }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<T: ?Sized> Copy for Unique<T> { }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<T: ?Sized, U: ?Sized> CoerceUnsized<Unique<U>> for Unique<T> where T: Unsize<U> { }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<T: ?Sized> fmt::Pointer for Unique<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         fmt::Pointer::fmt(&self.as_ptr(), f)
     }
 }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<'a, T: ?Sized> From<&'a mut T> for Unique<T> {
     fn from(reference: &'a mut T) -> Self {
         Unique { pointer: NonZero::from(reference), _marker: PhantomData }
     }
 }
 
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<'a, T: ?Sized> From<&'a T> for Unique<T> {
     fn from(reference: &'a T) -> Self {
         Unique { pointer: NonZero::from(reference), _marker: PhantomData }
     }
 }
 
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<'a, T: ?Sized> From<NonNull<T>> for Unique<T> {
+    fn from(p: NonNull<T>) -> Self {
+        Unique { pointer: p.pointer, _marker: PhantomData }
+    }
+}
+
+/// Previous name of `NonNull`.
+#[rustc_deprecated(since = "1.24", reason = "renamed to `NonNull`")]
+#[unstable(feature = "shared", issue = "27730")]
+pub type Shared<T> = NonNull<T>;
+
 /// `*mut T` but non-zero and covariant.
 ///
 /// This is often the correct thing to use when building data structures using
 /// raw pointers, but is ultimately more dangerous to use because of its additional
-/// properties. If you're not sure if you should use `Shared<T>`, just use `*mut T`!
+/// properties. If you're not sure if you should use `NonNull<T>`, just use `*mut T`!
 ///
 /// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
 /// is never dereferenced. This is so that enums may use this forbidden value
-/// as a discriminant -- `Option<Shared<T>>` has the same size as `Shared<T>`.
+/// as a discriminant -- `Option<NonNull<T>>` has the same size as `NonNull<T>`.
 /// However the pointer may still dangle if it isn't dereferenced.
 ///
-/// Unlike `*mut T`, `Shared<T>` is covariant over `T`. If this is incorrect
+/// Unlike `*mut T`, `NonNull<T>` is covariant over `T`. If this is incorrect
 /// for your use case, you should include some PhantomData in your type to
 /// provide invariance, such as `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
 /// Usually this won't be necessary; covariance is correct for most safe abstractions,
 /// such as Box, Rc, Arc, Vec, and LinkedList. This is the case because they
 /// provide a public API that follows the normal shared XOR mutable rules of Rust.
-#[allow(missing_debug_implementations)]
-#[unstable(feature = "shared", reason = "needs an RFC to flesh out design",
-           issue = "27730")]
-pub struct Shared<T: ?Sized> {
+#[stable(feature = "nonnull", since = "1.24.0")]
+pub struct NonNull<T: ?Sized> {
     pointer: NonZero<*const T>,
 }
 
-/// `Shared` pointers are not `Send` because the data they reference may be aliased.
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized> fmt::Debug for NonNull<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Pointer::fmt(&self.as_ptr(), f)
+    }
+}
+
+/// `NonNull` pointers are not `Send` because the data they reference may be aliased.
 // NB: This impl is unnecessary, but should provide better error messages.
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized> !Send for Shared<T> { }
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized> !Send for NonNull<T> { }
 
-/// `Shared` pointers are not `Sync` because the data they reference may be aliased.
+/// `NonNull` pointers are not `Sync` because the data they reference may be aliased.
 // NB: This impl is unnecessary, but should provide better error messages.
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized> !Sync for Shared<T> { }
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized> !Sync for NonNull<T> { }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: Sized> Shared<T> {
-    /// Creates a new `Shared` that is dangling, but well-aligned.
+impl<T: Sized> NonNull<T> {
+    /// Creates a new `NonNull` that is dangling, but well-aligned.
     ///
     /// This is useful for initializing types which lazily allocate, like
     /// `Vec::new` does.
-    pub fn empty() -> Self {
+    #[stable(feature = "nonnull", since = "1.24.0")]
+    pub fn dangling() -> Self {
         unsafe {
             let ptr = mem::align_of::<T>() as *mut T;
-            Shared::new_unchecked(ptr)
+            NonNull::new_unchecked(ptr)
         }
     }
 }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized> Shared<T> {
-    /// Creates a new `Shared`.
+impl<T: ?Sized> NonNull<T> {
+    /// Creates a new `NonNull`.
     ///
     /// # Safety
     ///
     /// `ptr` must be non-null.
-    #[unstable(feature = "shared", issue = "27730")]
+    #[stable(feature = "nonnull", since = "1.24.0")]
     pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
-        Shared { pointer: NonZero::new_unchecked(ptr) }
+        NonNull { pointer: NonZero::new_unchecked(ptr) }
     }
 
-    /// Creates a new `Shared` if `ptr` is non-null.
+    /// Creates a new `NonNull` if `ptr` is non-null.
+    #[stable(feature = "nonnull", since = "1.24.0")]
     pub fn new(ptr: *mut T) -> Option<Self> {
-        NonZero::new(ptr as *const T).map(|nz| Shared { pointer: nz })
+        NonZero::new(ptr as *const T).map(|nz| NonNull { pointer: nz })
     }
 
     /// Acquires the underlying `*mut` pointer.
+    #[stable(feature = "nonnull", since = "1.24.0")]
     pub fn as_ptr(self) -> *mut T {
         self.pointer.get() as *mut T
     }
@@ -2520,7 +2545,8 @@ impl<T: ?Sized> Shared<T> {
     ///
     /// The resulting lifetime is bound to self so this behaves "as if"
     /// it were actually an instance of T that is getting borrowed. If a longer
-    /// (unbound) lifetime is needed, use `&*my_ptr.ptr()`.
+    /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
+    #[stable(feature = "nonnull", since = "1.24.0")]
     pub unsafe fn as_ref(&self) -> &T {
         &*self.as_ptr()
     }
@@ -2529,56 +2555,50 @@ impl<T: ?Sized> Shared<T> {
     ///
     /// The resulting lifetime is bound to self so this behaves "as if"
     /// it were actually an instance of T that is getting borrowed. If a longer
-    /// (unbound) lifetime is needed, use `&mut *my_ptr.ptr_mut()`.
+    /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
+    #[stable(feature = "nonnull", since = "1.24.0")]
     pub unsafe fn as_mut(&mut self) -> &mut T {
         &mut *self.as_ptr()
     }
-
-    /// Acquires the underlying pointer as a `*mut` pointer.
-    #[rustc_deprecated(since = "1.19", reason = "renamed to `as_ptr` for ergonomics/consistency")]
-    #[unstable(feature = "shared", issue = "27730")]
-    pub unsafe fn as_mut_ptr(&self) -> *mut T {
-        self.as_ptr()
-    }
 }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized> Clone for Shared<T> {
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized> Clone for NonNull<T> {
     fn clone(&self) -> Self {
         *self
     }
 }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized> Copy for Shared<T> { }
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized> Copy for NonNull<T> { }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized, U: ?Sized> CoerceUnsized<Shared<U>> for Shared<T> where T: Unsize<U> { }
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized, U: ?Sized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> { }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized> fmt::Pointer for Shared<T> {
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized> fmt::Pointer for NonNull<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         fmt::Pointer::fmt(&self.as_ptr(), f)
     }
 }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: ?Sized> From<Unique<T>> for Shared<T> {
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
     fn from(unique: Unique<T>) -> Self {
-        Shared { pointer: unique.pointer }
+        NonNull { pointer: unique.pointer }
     }
 }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<'a, T: ?Sized> From<&'a mut T> for Shared<T> {
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<'a, T: ?Sized> From<&'a mut T> for NonNull<T> {
     fn from(reference: &'a mut T) -> Self {
-        Shared { pointer: NonZero::from(reference) }
+        NonNull { pointer: NonZero::from(reference) }
     }
 }
 
-#[unstable(feature = "shared", issue = "27730")]
-impl<'a, T: ?Sized> From<&'a T> for Shared<T> {
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<'a, T: ?Sized> From<&'a T> for NonNull<T> {
     fn from(reference: &'a T) -> Self {
-        Shared { pointer: NonZero::from(reference) }
+        NonNull { pointer: NonZero::from(reference) }
     }
 }
diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs
index 2c0009569d7..1c32452f846 100644
--- a/src/libcore/tests/lib.rs
+++ b/src/libcore/tests/lib.rs
@@ -41,7 +41,6 @@
 #![feature(trusted_len)]
 #![feature(try_from)]
 #![feature(try_trait)]
-#![feature(unique)]
 #![feature(exact_chunks)]
 
 extern crate core;
diff --git a/src/libcore/tests/ptr.rs b/src/libcore/tests/ptr.rs
index 98436f0e1d1..00f87336f3c 100644
--- a/src/libcore/tests/ptr.rs
+++ b/src/libcore/tests/ptr.rs
@@ -249,9 +249,9 @@ fn test_set_memory() {
 }
 
 #[test]
-fn test_unsized_unique() {
+fn test_unsized_nonnull() {
     let xs: &[i32] = &[1, 2, 3];
-    let ptr = unsafe { Unique::new_unchecked(xs as *const [i32] as *mut [i32]) };
+    let ptr = unsafe { NonNull::new_unchecked(xs as *const [i32] as *mut [i32]) };
     let ys = unsafe { ptr.as_ref() };
     let zs: &[i32] = &[1, 2, 3];
     assert!(ys == zs);
diff --git a/src/librustc_data_structures/array_vec.rs b/src/librustc_data_structures/array_vec.rs
index 57fc78ef531..511c407d45a 100644
--- a/src/librustc_data_structures/array_vec.rs
+++ b/src/librustc_data_structures/array_vec.rs
@@ -12,7 +12,7 @@
 
 use std::marker::Unsize;
 use std::iter::Extend;
-use std::ptr::{self, drop_in_place, Shared};
+use std::ptr::{self, drop_in_place, NonNull};
 use std::ops::{Deref, DerefMut, Range};
 use std::hash::{Hash, Hasher};
 use std::slice;
@@ -146,7 +146,7 @@ impl<A: Array> ArrayVec<A> {
                 tail_start: end,
                 tail_len: len - end,
                 iter: range_slice.iter(),
-                array_vec: Shared::from(self),
+                array_vec: NonNull::from(self),
             }
         }
     }
@@ -232,7 +232,7 @@ pub struct Drain<'a, A: Array>
     tail_start: usize,
     tail_len: usize,
     iter: slice::Iter<'a, ManuallyDrop<A::Element>>,
-    array_vec: Shared<ArrayVec<A>>,
+    array_vec: NonNull<ArrayVec<A>>,
 }
 
 impl<'a, A: Array> Iterator for Drain<'a, A> {
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index 24048e606df..a35ef2f7ce7 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -21,7 +21,6 @@
       html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![deny(warnings)]
 
-#![feature(shared)]
 #![feature(collections_range)]
 #![feature(nonzero)]
 #![feature(unboxed_closures)]
diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index 96f98efe4aa..73bd5747c10 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -16,7 +16,7 @@ use marker;
 use mem::{align_of, size_of, needs_drop};
 use mem;
 use ops::{Deref, DerefMut};
-use ptr::{self, Unique, Shared};
+use ptr::{self, Unique, NonNull};
 
 use self::BucketState::*;
 
@@ -873,7 +873,7 @@ impl<K, V> RawTable<K, V> {
                 elems_left,
                 marker: marker::PhantomData,
             },
-            table: Shared::from(self),
+            table: NonNull::from(self),
             marker: marker::PhantomData,
         }
     }
@@ -1020,7 +1020,7 @@ impl<K, V> IntoIter<K, V> {
 
 /// Iterator over the entries in a table, clearing the table.
 pub struct Drain<'a, K: 'a, V: 'a> {
-    table: Shared<RawTable<K, V>>,
+    table: NonNull<RawTable<K, V>>,
     iter: RawBuckets<'static, K, V>,
     marker: marker::PhantomData<&'a RawTable<K, V>>,
 }
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index bb38fc55091..91cc6d25cce 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -293,11 +293,11 @@
 #![feature(placement_in_syntax)]
 #![feature(placement_new_protocol)]
 #![feature(prelude_import)]
+#![feature(ptr_internals)]
 #![feature(rand)]
 #![feature(raw)]
 #![feature(repr_align)]
 #![feature(rustc_attrs)]
-#![feature(shared)]
 #![feature(sip_hash_13)]
 #![feature(slice_bytes)]
 #![feature(slice_concat_ext)]
@@ -315,7 +315,6 @@
 #![feature(try_from)]
 #![feature(unboxed_closures)]
 #![feature(unicode)]
-#![feature(unique)]
 #![feature(untagged_unions)]
 #![feature(unwind_attributes)]
 #![feature(vec_push_all)]
diff --git a/src/libstd/panic.rs b/src/libstd/panic.rs
index 53c2211745c..560876006d3 100644
--- a/src/libstd/panic.rs
+++ b/src/libstd/panic.rs
@@ -17,7 +17,7 @@ use cell::UnsafeCell;
 use fmt;
 use ops::{Deref, DerefMut};
 use panicking;
-use ptr::{Unique, Shared};
+use ptr::{Unique, NonNull};
 use rc::Rc;
 use sync::{Arc, Mutex, RwLock, atomic};
 use thread::Result;
@@ -196,10 +196,10 @@ impl<'a, T: RefUnwindSafe + ?Sized> UnwindSafe for &'a T {}
 impl<T: RefUnwindSafe + ?Sized> UnwindSafe for *const T {}
 #[stable(feature = "catch_unwind", since = "1.9.0")]
 impl<T: RefUnwindSafe + ?Sized> UnwindSafe for *mut T {}
-#[unstable(feature = "unique", issue = "27730")]
+#[unstable(feature = "ptr_internals", issue = "0")]
 impl<T: UnwindSafe + ?Sized> UnwindSafe for Unique<T> {}
-#[unstable(feature = "shared", issue = "27730")]
-impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Shared<T> {}
+#[stable(feature = "nonnull", since = "1.24.0")]
+impl<T: RefUnwindSafe + ?Sized> UnwindSafe for NonNull<T> {}
 #[stable(feature = "catch_unwind", since = "1.9.0")]
 impl<T: ?Sized> UnwindSafe for Mutex<T> {}
 #[stable(feature = "catch_unwind", since = "1.9.0")]
diff --git a/src/test/run-pass/allocator-alloc-one.rs b/src/test/run-pass/allocator-alloc-one.rs
index 712fa2d6001..eaa5bc90805 100644
--- a/src/test/run-pass/allocator-alloc-one.rs
+++ b/src/test/run-pass/allocator-alloc-one.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(allocator_api, unique)]
+#![feature(allocator_api, nonnull)]
 
 use std::heap::{Heap, Alloc};
 
diff --git a/src/test/run-pass/issue-23433.rs b/src/test/run-pass/issue-23433.rs
index aa13d6fad47..7af732f561d 100644
--- a/src/test/run-pass/issue-23433.rs
+++ b/src/test/run-pass/issue-23433.rs
@@ -10,13 +10,11 @@
 
 // Don't fail if we encounter a NonZero<*T> where T is an unsized type
 
-#![feature(unique)]
-
-use std::ptr::Unique;
+use std::ptr::NonNull;
 
 fn main() {
     let mut a = [0u8; 5];
-    let b: Option<Unique<[u8]>> = Some(Unique::from(&mut a));
+    let b: Option<NonNull<[u8]>> = Some(NonNull::from(&mut a));
     match b {
         Some(_) => println!("Got `Some`"),
         None => panic!("Unexpected `None`"),
diff --git a/src/test/rustdoc-js/from_u.js b/src/test/rustdoc-js/from_u.js
index 920620a9aee..0296788f7a0 100644
--- a/src/test/rustdoc-js/from_u.js
+++ b/src/test/rustdoc-js/from_u.js
@@ -15,7 +15,6 @@ const EXPECTED = {
         { 'path': 'std::char', 'name': 'from_u32' },
         { 'path': 'std::str', 'name': 'from_utf8' },
         { 'path': 'std::string::String', 'name': 'from_utf8' },
-        { 'path': 'std::boxed::Box', 'name': 'from_unique' },
         { 'path': 'std::i32', 'name': 'from_unsigned' },
         { 'path': 'std::i128', 'name': 'from_unsigned' },
     ],