fix: Using pin_project!

src/stream/stream/flatten.rs

@@ -1,18 +1,22 @@
 use std::pin::Pin;
+use pin_project_lite::pin_project;
 
 use crate::prelude::*;
 use crate::stream::stream::map::Map;
 use crate::stream::{IntoStream, Stream};
 use crate::task::{Context, Poll};
 
-/// This `struct` is created by the [`flat_map`] method on [`Stream`]. See its
-/// documentation for more.
-///
-/// [`flat_map`]: trait.Stream.html#method.flat_map
-/// [`Stream`]: trait.Stream.html
-#[allow(missing_debug_implementations)]
-pub struct FlatMap<S: Stream, U: IntoStream, F> {
+pin_project! {
+    /// This `struct` is created by the [`flat_map`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`flat_map`]: trait.Stream.html#method.flat_map
+    /// [`Stream`]: trait.Stream.html
+    #[allow(missing_debug_implementations)]
+    pub struct FlatMap<S: Stream, U: IntoStream, F> {
+        #[pin]
         inner: FlattenCompat<Map<S, F, S::Item, U>, U>,
+    }
 }
 
 impl<S, U, F> FlatMap<S, U, F>
@@ -21,7 +25,6 @@ where
     U: IntoStream,
     F: FnMut(S::Item) -> U,
 {
-    pin_utils::unsafe_pinned!(inner: FlattenCompat<Map<S, F, S::Item, U>, U>);
 
     pub fn new(stream: S, f: F) -> FlatMap<S, U, F> {
         FlatMap {
@@ -33,33 +36,33 @@ where
 impl<S, U, F> Stream for FlatMap<S, U, F>
 where
     S: Stream<Item: IntoStream<IntoStream = U, Item = U::Item>> + std::marker::Unpin,
-    S::Item: std::marker::Unpin,
     U: Stream + std::marker::Unpin,
-    F: FnMut(S::Item) -> U + std::marker::Unpin,
+    F: FnMut(S::Item) -> U,
 {
     type Item = U::Item;
 
-    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        self.as_mut().inner().poll_next(cx)
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        self.project().inner.poll_next(cx)
     }
 }
 
-/// This `struct` is created by the [`flatten`] method on [`Stream`]. See its
-/// documentation for more.
-///
-/// [`flatten`]: trait.Stream.html#method.flatten
-/// [`Stream`]: trait.Stream.html
-#[allow(missing_debug_implementations)]
-pub struct Flatten<S: Stream>
-where
+pin_project!{
+    /// This `struct` is created by the [`flatten`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`flatten`]: trait.Stream.html#method.flatten
+    /// [`Stream`]: trait.Stream.html
+    #[allow(missing_debug_implementations)]
+    pub struct Flatten<S: Stream>
+    where
         S::Item: IntoStream,
-{
+    {
+        #[pin]
         inner: FlattenCompat<S, <S::Item as IntoStream>::IntoStream>,
+    }
 }
 
 impl<S: Stream<Item: IntoStream>> Flatten<S> {
-    pin_utils::unsafe_pinned!(inner: FlattenCompat<S, <S::Item as IntoStream>::IntoStream>);
-
     pub fn new(stream: S) -> Flatten<S> {
         Flatten { inner: FlattenCompat::new(stream) }
     }
@@ -72,24 +75,23 @@ where
 {
     type Item = U::Item;
 
-    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        self.as_mut().inner().poll_next(cx)
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        self.project().inner.poll_next(cx)
     }
 }
 
 
-/// Real logic of both `Flatten` and `FlatMap` which simply delegate to
-/// this type.
-#[derive(Clone, Debug)]
-struct FlattenCompat<S, U> {
+pin_project! {
+    /// Real logic of both `Flatten` and `FlatMap` which simply delegate to
+    /// this type.
+    #[derive(Clone, Debug)]
+    struct FlattenCompat<S, U> {
         stream: S,
         frontiter: Option<U>,
+    }
 }
 
 impl<S, U> FlattenCompat<S, U> {
-    pin_utils::unsafe_unpinned!(stream: S);
-    pin_utils::unsafe_unpinned!(frontiter: Option<U>);
-
     /// Adapts an iterator by flattening it, for use in `flatten()` and `flat_map()`.
     pub fn new(stream: S) -> FlattenCompat<S, U> {
         FlattenCompat {
@@ -106,17 +108,18 @@ where
 {
     type Item = U::Item;
 
-    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let mut this = self.project();
         loop {
-            if let Some(ref mut inner) = self.as_mut().frontiter() {
+            if let Some(inner) = this.frontiter {
                 if let item @ Some(_) = futures_core::ready!(Pin::new(inner).poll_next(cx)) {
                     return Poll::Ready(item);
                 }
             }
 
-            match futures_core::ready!(Pin::new(&mut self.stream).poll_next(cx)) {
+            match futures_core::ready!(Pin::new(&mut this.stream).poll_next(cx)) {
                 None => return Poll::Ready(None),
-                Some(inner) => *self.as_mut().frontiter() = Some(inner.into_stream()),
+                Some(inner) => *this.frontiter = Some(inner.into_stream()),
             }
         }
     }