1 files changed, 18 insertions, 1 deletions
diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index e11873218e8..7d3b2656a7b 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -7,6 +7,7 @@
 //! [arc]: struct.Arc.html
 
 use core::any::Any;
+use core::array::LengthAtMost32;
 use core::sync::atomic;
 use core::sync::atomic::Ordering::{Acquire, Relaxed, Release, SeqCst};
 use core::borrow;
@@ -21,7 +22,7 @@ use core::ptr::{self, NonNull};
 use core::marker::{Unpin, Unsize, PhantomData};
 use core::hash::{Hash, Hasher};
 use core::{isize, usize};
-use core::convert::From;
+use core::convert::{From, TryFrom};
 use core::slice::{self, from_raw_parts_mut};
 
 use crate::alloc::{Global, Alloc, Layout, box_free, handle_alloc_error};
@@ -1826,6 +1827,22 @@ impl<T> From<Vec<T>> for Arc<[T]> {
     }
 }
 
+#[unstable(feature = "boxed_slice_try_from", issue = "0")]
+impl<T, const N: usize> TryFrom<Arc<[T]>> for Arc<[T; N]>
+where
+    [T; N]: LengthAtMost32,
+{
+    type Error = Arc<[T]>;
+
+    fn try_from(boxed_slice: Arc<[T]>) -> Result<Self, Self::Error> {
+        if boxed_slice.len() == N {
+            Ok(unsafe { Arc::from_raw(Arc::into_raw(boxed_slice) as *mut [T; N]) })
+        } else {
+            Err(boxed_slice)
+        }
+    }
+}
+
 #[stable(feature = "shared_from_iter", since = "1.37.0")]
 impl<T> iter::FromIterator<T> for Arc<[T]> {
     /// Takes each element in the `Iterator` and collects it into an `Arc<[T]>`.