diff --git a/src/libcore/pin.rs b/src/libcore/pin.rs index ff10c33681d22..f9f20dcea9e2e 100644 --- a/src/libcore/pin.rs +++ b/src/libcore/pin.rs @@ -380,10 +380,13 @@ impl<P: Deref> Pin<P> { /// use std::pin::Pin; /// /// fn move_pinned_ref<T>(mut a: T, mut b: T) { - /// unsafe { let p = Pin::new_unchecked(&mut a); } // should mean `a` can never move again + /// unsafe { + /// let p: Pin<&mut T> = Pin::new_unchecked(&mut a); + /// // This should mean the pointee `a` can never move again. + /// } /// mem::swap(&mut a, &mut b); /// // The address of `a` changed to `b`'s stack slot, so `a` got moved even - /// // though we have previously pinned it! + /// // though we have previously pinned it! We have violated the pinning API contract. /// } /// ``` /// A value, once pinned, must remain pinned forever (unless its type implements `Unpin`). @@ -396,12 +399,15 @@ impl<P: Deref> Pin<P> { /// /// fn move_pinned_rc<T>(mut x: Rc<T>) { /// let pinned = unsafe { Pin::new_unchecked(x.clone()) }; - /// { let p: Pin<&T> = pinned.as_ref(); } // should mean the pointee can never move again + /// { + /// let p: Pin<&T> = pinned.as_ref(); + /// // This should mean the pointee can never move again. + /// } /// drop(pinned); /// let content = Rc::get_mut(&mut x).unwrap(); /// // Now, if `x` was the only reference, we have a mutable reference to /// // data that we pinned above, which we could use to move it as we have - /// // seen in the previous example. + /// // seen in the previous example. We have violated the pinning API contract. /// } /// ``` ///