Minor doc fixes for future::stream.

Author: jimblandy

futures-util/src/stream/mod.rs

@@ -1051,7 +1051,7 @@ pub trait StreamExt: Stream {
     ///
     /// # Panics
     ///
-    /// This method will panic of `capacity` is zero.
+    /// This method will panic if `capacity` is zero.
     #[cfg(feature = "alloc")]
     fn chunks(self, capacity: usize) -> Chunks<Self>
         where Self: Sized

futures-util/src/stream/once.rs

@@ -4,7 +4,7 @@ use futures_core::stream::Stream;
 use futures_core::task::{Context, Poll};
 use pin_utils::unsafe_pinned;
 
-/// Creates a stream of single element
+/// Creates a stream of a single element.
 ///
 /// ```
 /// #![feature(async_await)]

futures-util/src/stream/poll_fn.rs

@@ -13,9 +13,9 @@ pub struct PollFn<F> {
 
 impl<F> Unpin for PollFn<F> {}
 
-/// Creates a new stream wrapping around a function returning `Poll`.
+/// Creates a new stream wrapping a function returning `Poll<Option<T>>`.
 ///
-/// Polling the returned stream delegates to the wrapped function.
+/// Polling the returned stream calls the wrapped function.
 ///
 /// # Examples
 ///