Remove TryStreamExt::into_async_read Unpin bound (#2599)

Author: khollbach

futures-util/src/stream/try_stream/into_async_read.rs

@@ -1,30 +1,26 @@
-use crate::stream::TryStreamExt;
 use core::pin::Pin;
 use futures_core::ready;
 use futures_core::stream::TryStream;
 use futures_core::task::{Context, Poll};
 use futures_io::{AsyncBufRead, AsyncRead, AsyncWrite};
+use pin_project_lite::pin_project;
 use std::cmp;
 use std::io::{Error, Result};
 
-/// Reader for the [`into_async_read`](super::TryStreamExt::into_async_read) method.
-#[derive(Debug)]
-#[must_use = "readers do nothing unless polled"]
-#[cfg_attr(docsrs, doc(cfg(feature = "io")))]
-pub struct IntoAsyncRead<St>
-where
-    St: TryStream<Error = Error> + Unpin,
-    St::Ok: AsRef<[u8]>,
-{
-    stream: St,
-    state: ReadState<St::Ok>,
-}
-
-impl<St> Unpin for IntoAsyncRead<St>
-where
-    St: TryStream<Error = Error> + Unpin,
-    St::Ok: AsRef<[u8]>,
-{
+pin_project! {
+    /// Reader for the [`into_async_read`](super::TryStreamExt::into_async_read) method.
+    #[derive(Debug)]
+    #[must_use = "readers do nothing unless polled"]
+    #[cfg_attr(docsrs, doc(cfg(feature = "io")))]
+    pub struct IntoAsyncRead<St>
+    where
+        St: TryStream<Error = Error>,
+        St::Ok: AsRef<[u8]>,
+    {
+        #[pin]
+        stream: St,
+        state: ReadState<St::Ok>,
+    }
 }
 
 #[derive(Debug)]
@@ -36,7 +32,7 @@ enum ReadState<T: AsRef<[u8]>> {
 
 impl<St> IntoAsyncRead<St>
 where
-    St: TryStream<Error = Error> + Unpin,
+    St: TryStream<Error = Error>,
     St::Ok: AsRef<[u8]>,
 {
     pub(super) fn new(stream: St) -> Self {
@@ -46,16 +42,18 @@ where
 
 impl<St> AsyncRead for IntoAsyncRead<St>
 where
-    St: TryStream<Error = Error> + Unpin,
+    St: TryStream<Error = Error>,
     St::Ok: AsRef<[u8]>,
 {
     fn poll_read(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         cx: &mut Context<'_>,
         buf: &mut [u8],
     ) -> Poll<Result<usize>> {
+        let mut this = self.project();
+
         loop {
-            match &mut self.state {
+            match this.state {
                 ReadState::Ready { chunk, chunk_start } => {
                     let chunk = chunk.as_ref();
                     let len = cmp::min(buf.len(), chunk.len() - *chunk_start);
@@ -64,23 +62,23 @@ where
                     *chunk_start += len;
 
                     if chunk.len() == *chunk_start {
-                        self.state = ReadState::PendingChunk;
+                        *this.state = ReadState::PendingChunk;
                     }
 
                     return Poll::Ready(Ok(len));
                 }
-                ReadState::PendingChunk => match ready!(self.stream.try_poll_next_unpin(cx)) {
+                ReadState::PendingChunk => match ready!(this.stream.as_mut().try_poll_next(cx)) {
                     Some(Ok(chunk)) => {
                         if !chunk.as_ref().is_empty() {
-                            self.state = ReadState::Ready { chunk, chunk_start: 0 };
+                            *this.state = ReadState::Ready { chunk, chunk_start: 0 };
                         }
                     }
                     Some(Err(err)) => {
-                        self.state = ReadState::Eof;
+                        *this.state = ReadState::Eof;
                         return Poll::Ready(Err(err));
                     }
                     None => {
-                        self.state = ReadState::Eof;
+                        *this.state = ReadState::Eof;
                         return Poll::Ready(Ok(0));
                     }
                 },
@@ -94,51 +92,52 @@ where
 
 impl<St> AsyncWrite for IntoAsyncRead<St>
 where
-    St: TryStream<Error = Error> + AsyncWrite + Unpin,
+    St: TryStream<Error = Error> + AsyncWrite,
     St::Ok: AsRef<[u8]>,
 {
-    fn poll_write(
-        mut self: Pin<&mut Self>,
-        cx: &mut Context<'_>,
-        buf: &[u8],
-    ) -> Poll<Result<usize>> {
-        Pin::new(&mut self.stream).poll_write(cx, buf)
+    fn poll_write(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8]) -> Poll<Result<usize>> {
+        let this = self.project();
+        this.stream.poll_write(cx, buf)
     }
 
-    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
-        Pin::new(&mut self.stream).poll_flush(cx)
+    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
+        let this = self.project();
+        this.stream.poll_flush(cx)
     }
 
-    fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
-        Pin::new(&mut self.stream).poll_close(cx)
+    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>> {
+        let this = self.project();
+        this.stream.poll_close(cx)
     }
 }
 
 impl<St> AsyncBufRead for IntoAsyncRead<St>
 where
-    St: TryStream<Error = Error> + Unpin,
+    St: TryStream<Error = Error>,
     St::Ok: AsRef<[u8]>,
 {
-    fn poll_fill_buf(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>> {
-        while let ReadState::PendingChunk = self.state {
-            match ready!(self.stream.try_poll_next_unpin(cx)) {
+    fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>> {
+        let mut this = self.project();
+
+        while let ReadState::PendingChunk = this.state {
+            match ready!(this.stream.as_mut().try_poll_next(cx)) {
                 Some(Ok(chunk)) => {
                     if !chunk.as_ref().is_empty() {
-                        self.state = ReadState::Ready { chunk, chunk_start: 0 };
+                        *this.state = ReadState::Ready { chunk, chunk_start: 0 };
                     }
                 }
                 Some(Err(err)) => {
-                    self.state = ReadState::Eof;
+                    *this.state = ReadState::Eof;
                     return Poll::Ready(Err(err));
                 }
                 None => {
-                    self.state = ReadState::Eof;
+                    *this.state = ReadState::Eof;
                     return Poll::Ready(Ok(&[]));
                 }
             }
         }
 
-        if let ReadState::Ready { ref chunk, chunk_start } = self.into_ref().get_ref().state {
+        if let &mut ReadState::Ready { ref chunk, chunk_start } = this.state {
             let chunk = chunk.as_ref();
             return Poll::Ready(Ok(&chunk[chunk_start..]));
         }
@@ -147,16 +146,18 @@ where
         Poll::Ready(Ok(&[]))
     }
 
-    fn consume(mut self: Pin<&mut Self>, amount: usize) {
+    fn consume(self: Pin<&mut Self>, amount: usize) {
+        let this = self.project();
+
         // https://github.com/rust-lang/futures-rs/pull/1556#discussion_r281644295
         if amount == 0 {
             return;
         }
-        if let ReadState::Ready { chunk, chunk_start } = &mut self.state {
+        if let ReadState::Ready { chunk, chunk_start } = this.state {
             *chunk_start += amount;
             debug_assert!(*chunk_start <= chunk.as_ref().len());
             if *chunk_start >= chunk.as_ref().len() {
-                self.state = ReadState::PendingChunk;
+                *this.state = ReadState::PendingChunk;
             }
         } else {
             debug_assert!(false, "Attempted to consume from IntoAsyncRead without chunk");

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

@@ -1031,12 +1031,7 @@ pub trait TryStreamExt: TryStream {
         Compat::new(self)
     }
 
-    /// Adapter that converts this stream into an [`AsyncRead`](crate::io::AsyncRead).
-    ///
-    /// Note that because `into_async_read` moves the stream, the [`Stream`](futures_core::stream::Stream) type must be
-    /// [`Unpin`]. If you want to use `into_async_read` with a [`!Unpin`](Unpin) stream, you'll
-    /// first have to pin the stream. This can be done by boxing the stream using [`Box::pin`]
-    /// or pinning it to the stack using the `pin_mut!` macro from the `pin_utils` crate.
+    /// Adapter that converts this stream into an [`AsyncBufRead`](crate::io::AsyncBufRead).
     ///
     /// This method is only available when the `std` feature of this
     /// library is activated, and it is activated by default.
@@ -1048,20 +1043,20 @@ pub trait TryStreamExt: TryStream {
     /// use futures::stream::{self, TryStreamExt};
     /// use futures::io::AsyncReadExt;
     ///
-    /// let stream = stream::iter(vec![Ok(vec![1, 2, 3, 4, 5])]);
+    /// let stream = stream::iter([Ok(vec![1, 2, 3]), Ok(vec![4, 5])]);
     /// let mut reader = stream.into_async_read();
-    /// let mut buf = Vec::new();
     ///
-    /// assert!(reader.read_to_end(&mut buf).await.is_ok());
-    /// assert_eq!(buf, &[1, 2, 3, 4, 5]);
+    /// let mut buf = Vec::new();
+    /// reader.read_to_end(&mut buf).await.unwrap();
+    /// assert_eq!(buf, [1, 2, 3, 4, 5]);
     /// # })
     /// ```
     #[cfg(feature = "io")]
     #[cfg_attr(docsrs, doc(cfg(feature = "io")))]
     #[cfg(feature = "std")]
     fn into_async_read(self) -> IntoAsyncRead<Self>
     where
-        Self: Sized + TryStreamExt<Error = std::io::Error> + Unpin,
+        Self: Sized + TryStreamExt<Error = std::io::Error>,
         Self::Ok: AsRef<[u8]>,
     {
         crate::io::assert_read(IntoAsyncRead::new(self))