diff options
| -rw-r--r-- | library/core/src/future/poll_fn.rs | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/library/core/src/future/poll_fn.rs b/library/core/src/future/poll_fn.rs index db2a523323b..90cb797391a 100644 --- a/library/core/src/future/poll_fn.rs +++ b/library/core/src/future/poll_fn.rs @@ -5,7 +5,9 @@ use crate::task::{Context, Poll}; /// Creates a future that wraps a function returning [`Poll`]. /// -/// Polling the future delegates to the wrapped function. +/// Polling the future delegates to the wrapped function. If the returned future is pinned, then the +/// captured environment of the wrapped function is also pinned in-place, so as long as the closure +/// does not move out of its captures it can soundly create pinned references to them. /// /// # Examples /// @@ -41,7 +43,7 @@ pub struct PollFn<F> { } #[stable(feature = "future_poll_fn", since = "1.64.0")] -impl<F> Unpin for PollFn<F> {} +impl<F: Unpin> Unpin for PollFn<F> {} #[stable(feature = "future_poll_fn", since = "1.64.0")] impl<F> fmt::Debug for PollFn<F> { @@ -57,7 +59,8 @@ where { type Output = T; - fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> { - (&mut self.f)(cx) + fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> { + // SAFETY: We are not moving out of the pinned field. + (unsafe { &mut self.get_unchecked_mut().f })(cx) } } |