Rollup merge of rust-lang#69538 - JohnTitor:boxed-slice-try-from, r=Centril

Stabilize `boxed_slice_try_from`

Closes rust-lang#69202

Author: Centril

src/liballoc/boxed.rs

@@ -825,7 +825,7 @@ impl From<Box<str>> for Box<[u8]> {
     }
 }
 
-#[unstable(feature = "boxed_slice_try_from", issue = "none")]
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]>
 where
     [T; N]: LengthAtMost32,

src/liballoc/rc.rs

@@ -1453,7 +1453,7 @@ impl<T> From<Vec<T>> for Rc<[T]> {
     }
 }
 
-#[unstable(feature = "boxed_slice_try_from", issue = "none")]
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Rc<[T]>> for Rc<[T; N]>
 where
     [T; N]: LengthAtMost32,

src/liballoc/sync.rs

@@ -2002,7 +2002,7 @@ impl<T> From<Vec<T>> for Arc<[T]> {
     }
 }
 
-#[unstable(feature = "boxed_slice_try_from", issue = "none")]
+#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Arc<[T]>> for Arc<[T; N]>
 where
     [T; N]: LengthAtMost32,