From 6f31f05aaf8e89f87e01052ba61fa04613b0a090 Mon Sep 17 00:00:00 2001
From: Elichai Turkel <elichai.turkel@gmail.com>
Date: Wed, 22 Apr 2020 12:39:29 +0300
Subject: Add a function to turn Box<T> into Box<[T]> (into_boxed_slice)

---
 src/liballoc/boxed.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'src/liballoc')

diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index db7420954a0..5419491fc23 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -239,6 +239,16 @@ impl<T> Box<T> {
     pub fn pin(x: T) -> Pin<Box<T>> {
         (box x).into()
     }
+
+    /// Converts a `Box<T>` into a `Box<[T]>`
+    ///
+    /// This conversion does not allocate on the heap and happens in place.
+    ///
+    #[unstable(feature = "box_into_boxed_slice", issue = "71582")]
+    pub fn into_boxed_slice(boxed: Box<T>) -> Box<[T]> {
+        // *mut T and *mut [T; 1] have the same size and alignment
+        unsafe { Box::from_raw(Box::into_raw(boxed) as *mut [T; 1] as *mut [T]) }
+    }
 }
 
 impl<T> Box<[T]> {
-- 
cgit 1.4.1-3-g733a5