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take a bit more space for new_unchecked examples

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RalfJung committed Feb 21, 2019
1 parent 811af42 commit 497439c199131ba65f03c116aec2e9cd5a7e63ff
Showing with 10 additions and 4 deletions.
  1. +10 −4 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.
/// }
/// ```
///

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