Rollup merge of #56939 - cramertj:pin-stabilization, r=alexcrichton

Pin stabilization

This implements the changes suggested in https://github.com/rust-lang/rust/issues/55766#issue-378417538 and stabilizes the `pin` feature. @alexcrichton also listed several "blockers" in that issue, but then in [this comment](https://github.com/rust-lang/rust/issues/55766#issuecomment-445074980) mentioned that they're more "TODO items":
>  In that vein I think it's fine for a stabilization PR to be posted at any time now with FCP lapsed for a week or so now. The final points about self/pin/pinned can be briefly discussed there (if even necessary, they could be left as the proposal above).

Let's settle these last bits here and get this thing stabilized! :)

r? @alexcrichton
cc @withoutboats

4 files changed, 16 insertions, 11 deletions

diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index f1581310b48..7438f3e6c9d 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -111,9 +111,11 @@ impl<T> Box<T> {
         box x
     }
 
-    #[unstable(feature = "pin", issue = "49150")]
+    /// Constructs a new `Pin<Box<T>>`. If `T` does not implement `Unpin`, then
+    /// `x` will be pinned in memory and unable to be moved.
+    #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
-    pub fn pinned(x: T) -> Pin<Box<T>> {
+    pub fn pin(x: T) -> Pin<Box<T>> {
         (box x).into()
     }
 }
@@ -446,7 +448,7 @@ impl<T> From<T> for Box<T> {
     }
 }
 
-#[unstable(feature = "pin", issue = "49150")]
+#[stable(feature = "pin", since = "1.33.0")]
 impl<T> From<Box<T>> for Pin<Box<T>> {
     fn from(boxed: Box<T>) -> Self {
         // It's not possible to move or replace the insides of a `Pin<Box<T>>`
@@ -813,7 +815,7 @@ impl<T: ?Sized> AsMut<T> for Box<T> {
  *  implementation of `Unpin` (where `T: Unpin`) would be valid/safe, and
  *  could have a method to project a Pin<T> from it.
  */
-#[unstable(feature = "pin", issue = "49150")]
+#[stable(feature = "pin", since = "1.33.0")]
 impl<T: ?Sized> Unpin for Box<T> { }
 
 #[unstable(feature = "generator_trait", issue = "43122")]
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index afa7a6f919d..8a66cafc001 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -102,7 +102,6 @@
 #![feature(nll)]
 #![feature(optin_builtin_traits)]
 #![feature(pattern)]
-#![feature(pin)]
 #![feature(ptr_internals)]
 #![feature(ptr_offset_from)]
 #![feature(rustc_attrs)]
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 65a610b9d1e..af316b0b61b 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -325,8 +325,10 @@ impl<T> Rc<T> {
         }
     }
 
-    #[unstable(feature = "pin", issue = "49150")]
-    pub fn pinned(value: T) -> Pin<Rc<T>> {
+    /// Constructs a new `Pin<Rc<T>>`. If `T` does not implement `Unpin`, then
+    /// `value` will be pinned in memory and unable to be moved.
+    #[stable(feature = "pin", since = "1.33.0")]
+    pub fn pin(value: T) -> Pin<Rc<T>> {
         unsafe { Pin::new_unchecked(Rc::new(value)) }
     }
 
@@ -1934,5 +1936,5 @@ impl<T: ?Sized> AsRef<T> for Rc<T> {
     }
 }
 
-#[unstable(feature = "pin", issue = "49150")]
+#[stable(feature = "pin", since = "1.33.0")]
 impl<T: ?Sized> Unpin for Rc<T> { }
diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index 948c36117a3..7b8afb1943c 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -303,8 +303,10 @@ impl<T> Arc<T> {
         Arc { ptr: Box::into_raw_non_null(x), phantom: PhantomData }
     }
 
-    #[unstable(feature = "pin", issue = "49150")]
-    pub fn pinned(data: T) -> Pin<Arc<T>> {
+    /// Constructs a new `Pin<Arc<T>>`. If `T` does not implement `Unpin`, then
+    /// `data` will be pinned in memory and unable to be moved.
+    #[stable(feature = "pin", since = "1.33.0")]
+    pub fn pin(data: T) -> Pin<Arc<T>> {
         unsafe { Pin::new_unchecked(Arc::new(data)) }
     }
 
@@ -2050,5 +2052,5 @@ impl<T: ?Sized> AsRef<T> for Arc<T> {
     }
 }
 
-#[unstable(feature = "pin", issue = "49150")]
+#[stable(feature = "pin", since = "1.33.0")]
 impl<T: ?Sized> Unpin for Arc<T> { }