3 files changed, 17 insertions, 7 deletions
diff --git a/src/liballoc/alloc.rs b/src/liballoc/alloc.rs
index c0372d24ed5..f59c9f7fd61 100644
--- a/src/liballoc/alloc.rs
+++ b/src/liballoc/alloc.rs
@@ -16,7 +16,7 @@
             issue = "32838")]
 
 use core::intrinsics::{min_align_of_val, size_of_val};
-use core::ptr::NonNull;
+use core::ptr::{NonNull, Unique};
 use core::usize;
 
 #[doc(inline)]
@@ -152,9 +152,17 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
     }
 }
 
-#[cfg_attr(not(test), lang = "box_free")]
+#[cfg(stage0)]
+#[lang = "box_free"]
+#[inline]
+unsafe fn old_box_free<T: ?Sized>(ptr: *mut T) {
+    box_free(Unique::new_unchecked(ptr))
+}
+
+#[cfg_attr(not(any(test, stage0)), lang = "box_free")]
 #[inline]
-pub(crate) unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
+pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
+    let ptr = ptr.as_ptr();
     let size = size_of_val(&*ptr);
     let align = min_align_of_val(&*ptr);
     // We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.
diff --git a/src/liballoc/arc.rs b/src/liballoc/arc.rs
index e52a0216dd3..d0950bff9ce 100644
--- a/src/liballoc/arc.rs
+++ b/src/liballoc/arc.rs
@@ -566,7 +566,8 @@ impl<T: ?Sized> Arc<T> {
 
     fn from_box(v: Box<T>) -> Arc<T> {
         unsafe {
-            let bptr = Box::into_raw(v);
+            let box_unique = Box::into_unique(v);
+            let bptr = box_unique.as_ptr();
 
             let value_size = size_of_val(&*bptr);
             let ptr = Self::allocate_for_ptr(bptr);
@@ -578,7 +579,7 @@ impl<T: ?Sized> Arc<T> {
                 value_size);
 
             // Free the allocation without dropping its contents
-            box_free(bptr);
+            box_free(box_unique);
 
             Arc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 8fb8e111754..d0188c6e828 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -681,7 +681,8 @@ impl<T: ?Sized> Rc<T> {
 
     fn from_box(v: Box<T>) -> Rc<T> {
         unsafe {
-            let bptr = Box::into_raw(v);
+            let box_unique = Box::into_unique(v);
+            let bptr = box_unique.as_ptr();
 
             let value_size = size_of_val(&*bptr);
             let ptr = Self::allocate_for_ptr(bptr);
@@ -693,7 +694,7 @@ impl<T: ?Sized> Rc<T> {
                 value_size);
 
             // Free the allocation without dropping its contents
-            box_free(bptr);
+            box_free(box_unique);
 
             Rc { ptr: NonNull::new_unchecked(ptr), phantom: PhantomData }
         }