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.)

1 files changed, 4 insertions, 4 deletions

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")]