Auto merge of #25767 - mystor:patch-1, r=Gankro

By the same logic that `mem::forget` is safe, `boxed::into_raw` is actually a safe function.

Fixes #25755.

src/liballoc/boxed.rs

@@ -139,24 +139,20 @@ impl<T : ?Sized> Box<T> {
 /// convert pointer back to `Box` with `Box::from_raw` function, because
 /// `Box` does not specify, how memory is allocated.
 ///
-/// Function is unsafe, because result of this function is no longer
-/// automatically managed that may lead to memory or other resource
-/// leak.
-///
 /// # Examples
 /// ```
 /// # #![feature(alloc)]
 /// use std::boxed;
 ///
 /// let seventeen = Box::new(17u32);
-/// let raw = unsafe { boxed::into_raw(seventeen) };
+/// let raw = boxed::into_raw(seventeen);
 /// let boxed_again = unsafe { Box::from_raw(raw) };
 /// ```
 #[unstable(feature = "alloc",
            reason = "may be renamed")]
 #[inline]
-pub unsafe fn into_raw<T : ?Sized>(b: Box<T>) -> *mut T {
-    mem::transmute(b)
+pub fn into_raw<T : ?Sized>(b: Box<T>) -> *mut T {
+    unsafe { mem::transmute(b) }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]

src/libstd/sync/mpsc/spsc_queue.rs

@@ -80,12 +80,10 @@ unsafe impl<T: Send> Sync for Queue<T> { }
 
 impl<T> Node<T> {
     fn new() -> *mut Node<T> {
-        unsafe {
-            boxed::into_raw(box Node {
-                value: None,
-                next: AtomicPtr::new(ptr::null_mut::<Node<T>>()),
-            })
-        }
+        boxed::into_raw(box Node {
+            value: None,
+            next: AtomicPtr::new(ptr::null_mut::<Node<T>>()),
+        })
     }
 }