Auto merge of #71593 - Dylan-DPC:rollup-ms7j94u, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #71421 (Add a function to turn Box<T> into Box<[T]>)
 - #71537 (Remove support for self-opening)
 - #71551 (Minor refactoring around IndexVec usage in generator transformation)
 - #71569 ([miri] Throw UB if target size and data size don't match)
 - #71576 (check that `AsRef` and `AsMut` are inlined)

Failed merges:

 - #71558 (Cleanup and document `-Z tls-model` )

r? @ghost

1 files changed, 10 insertions, 0 deletions

diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 3d657396a9f..b3a771a721d 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]> {