Use pin_project_lite instead for throttle

src/stream/stream/mod.rs

@@ -315,7 +315,6 @@ extension_trait! {
             TakeWhile::new(self, predicate)
         }
 
-        #[cfg(all(feature = "default", feature = "unstable"))]
         #[doc = r#"
             Limit the amount of items yielded per timeslice in a stream.
 
@@ -342,6 +341,8 @@ extension_trait! {
             # }) }
             ```
         "#]
+        #[cfg(all(feature = "default", feature = "unstable"))]
+        #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn throttle(self, d: Duration) -> Throttle<Self>
         where
             Self: Sized,

src/stream/stream/throttle.rs

@@ -3,26 +3,25 @@ use std::pin::Pin;
 use std::time::Duration;
 
 use futures_timer::Delay;
+use pin_project_lite::pin_project;
 
 use crate::stream::Stream;
 use crate::task::{Context, Poll};
 
-/// A stream that only yields one element once every `duration`, and applies backpressure. Does not drop any elements.
-/// #[doc(hidden)]
-#[allow(missing_debug_implementations)]
-pub struct Throttle<S> {
-    stream: S,
-    duration: Duration,
-    delay: Option<Delay>,
+pin_project! {
+    /// A stream that only yields one element once every `duration`, and applies backpressure. Does not drop any elements.
+    #[doc(hidden)]
+    #[allow(missing_debug_implementations)]
+    pub struct Throttle<S> {
+        #[pin]
+        stream: S,
+        duration: Duration,
+        #[pin]
+        delay: Option<Delay>,
+    }
 }
 
-impl<S: Unpin> Unpin for Throttle<S> {}
-
 impl<S: Stream> Throttle<S> {
-    pin_utils::unsafe_pinned!(stream: S);
-    pin_utils::unsafe_unpinned!(duration: Duration);
-    pin_utils::unsafe_pinned!(delay: Option<Delay>);
-
     pub(super) fn new(stream: S, duration: Duration) -> Self {
         Throttle {
             stream,
@@ -35,23 +34,24 @@ impl<S: Stream> Throttle<S> {
 impl<S: Stream> Stream for Throttle<S> {
     type Item = S::Item;
 
-    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<S::Item>> {
-        if let Some(d) = self.as_mut().delay().as_pin_mut() {
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<S::Item>> {
+        let mut this = self.project();
+        if let Some(d) = this.delay.as_mut().as_pin_mut() {
             if d.poll(cx).is_ready() {
-                *self.as_mut().delay() = None;
+                this.delay.set(None);
             } else {
                 return Poll::Pending;
             }
         }
 
-        match self.as_mut().stream().poll_next(cx) {
+        match this.stream.poll_next(cx) {
             Poll::Pending => {
                 cx.waker().wake_by_ref(); // Continue driving even though emitting Pending
                 Poll::Pending
             }
             Poll::Ready(None) => Poll::Ready(None),
             Poll::Ready(Some(v)) => {
-                *self.as_mut().delay() = Some(Delay::new(self.duration));
+                this.delay.set(Some(Delay::new(*this.duration)));
                 Poll::Ready(Some(v))
             }
         }