1 files changed, 10 insertions, 15 deletions
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index b34a6d3f660..8eee7cff208 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -18,6 +18,7 @@ use core::intrinsics::abort;
 use core::iter;
 use core::marker::{PhantomData, Unsize};
 use core::mem::{self, ManuallyDrop, align_of_val_raw};
+use core::num::NonZeroUsize;
 use core::ops::{CoerceUnsized, Deref, DerefPure, DispatchFromDyn, LegacyReceiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 use core::pin::{Pin, PinCoerceUnsized};
@@ -1396,6 +1397,8 @@ impl<T: ?Sized> Arc<T> {
     /// different types. See [`mem::transmute`][transmute] for more information
     /// on what restrictions apply in this case.
     ///
+    /// The raw pointer must point to a block of memory allocated by the global allocator.
+    ///
     /// The user of `from_raw` has to make sure a specific value of `T` is only
     /// dropped once.
     ///
@@ -1451,7 +1454,8 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// The pointer must have been obtained through `Arc::into_raw`, and the
     /// associated `Arc` instance must be valid (i.e. the strong count must be at
-    /// least 1) for the duration of this method.
+    /// least 1) for the duration of this method, and `ptr` must point to a block of memory
+    /// allocated by the global allocator.
     ///
     /// # Examples
     ///
@@ -1485,7 +1489,8 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// The pointer must have been obtained through `Arc::into_raw`, and the
     /// associated `Arc` instance must be valid (i.e. the strong count must be at
-    /// least 1) when invoking this method. This method can be used to release the final
+    /// least 1) when invoking this method, and `ptr` must point to a block of memory
+    /// allocated by the global allocator. This method can be used to release the final
     /// `Arc` and backing storage, but **should not** be called after the final `Arc` has been
     /// released.
     ///
@@ -2468,7 +2473,7 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     /// let x: Arc<&str> = Arc::new("Hello, world!");
     /// {
     ///     let s = String::from("Oh, no!");
-    ///     let mut y: Arc<&str> = x.clone().into();
+    ///     let mut y: Arc<&str> = x.clone();
     ///     unsafe {
     ///         // this is Undefined Behavior, because x's inner type
     ///         // is &'long str, not &'short str
@@ -2687,12 +2692,7 @@ impl<T> Weak<T> {
     #[rustc_const_stable(feature = "const_weak_new", since = "1.73.0")]
     #[must_use]
     pub const fn new() -> Weak<T> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<ArcInner<T>>(usize::MAX))
-            },
-            alloc: Global,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc: Global }
     }
 }
 
@@ -2717,12 +2717,7 @@ impl<T, A: Allocator> Weak<T, A> {
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
     pub fn new_in(alloc: A) -> Weak<T, A> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<ArcInner<T>>(usize::MAX))
-            },
-            alloc,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc }
     }
 }