Conditionalize cancel-safety on Future cancel safety

futures-util/src/stream/futures_unordered/mod.rs

@@ -56,10 +56,11 @@ use self::ready_to_run_queue::{Dequeue, ReadyToRunQueue};
 ///
 /// # Cancel safety
 ///
-/// This type is cancellation-safe. If [`poll_next`](Stream::poll_next) is
-/// called (either directly or via [`crate::StreamExt::next`]) and it returns
-/// [`Poll::Pending`], no values will be dropped if `poll_next` is not called
-/// again.
+/// This type is cancellation-safe when the inner [`Future`] is
+/// cancellation-safe. If the future type is cancellation-safe, and
+/// [`poll_next`](Stream::poll_next) is called (either directly or via
+/// [`crate::StreamExt::next`]) and returns [`Poll::Pending`], no values will be
+/// dropped if `poll_next` is not called again.
 #[must_use = "streams do nothing unless polled"]
 pub struct FuturesUnordered<Fut> {
     ready_to_run_queue: Arc<ReadyToRunQueue<Fut>>,