feat: Add stream::delay

Author: k-nasa

src/stream/stream/delay.rs

@@ -2,22 +2,24 @@ use std::future::Future;
 use std::pin::Pin;
 use std::time::Duration;
 
+use pin_project_lite::pin_project;
+
 use crate::stream::Stream;
 use crate::task::{Context, Poll};
 
+pin_project! {
 #[doc(hidden)]
 #[allow(missing_debug_implementations)]
-pub struct Delay<S> {
-    stream: S,
-    delay: futures_timer::Delay,
-    delay_done: bool,
+    pub struct Delay<S> {
+        #[pin]
+        stream: S,
+        #[pin]
+        delay: futures_timer::Delay,
+        delay_done: bool,
+    }
 }
 
 impl<S> Delay<S> {
-    pin_utils::unsafe_pinned!(stream: S);
-    pin_utils::unsafe_pinned!(delay: futures_timer::Delay);
-    pin_utils::unsafe_unpinned!(delay_done: bool);
-
     pub(super) fn new(stream: S, dur: Duration) -> Self {
         Delay {
             stream,
@@ -33,12 +35,14 @@ where
 {
     type Item = S::Item;
 
-    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        if !self.delay_done {
-            futures_core::ready!(self.as_mut().delay().poll(cx));
-            *self.as_mut().delay_done() = true;
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.project();
+
+        if !*this.delay_done {
+            futures_core::ready!(this.delay.poll(cx));
+            *this.delay_done = true;
         }
 
-        self.as_mut().stream().poll_next(cx)
+        this.stream.poll_next(cx)
     }
 }