Allow unsized writer for copy_{buf_}into

Author: Nemo157

futures-util/src/io/copy_buf_into.rs

@@ -7,15 +7,15 @@ use std::pin::Pin;
 /// Future for the [`copy_buf_into`](super::AsyncBufReadExt::copy_buf_into) method.
 #[derive(Debug)]
 #[must_use = "futures do nothing unless you `.await` or poll them"]
-pub struct CopyBufInto<'a, R, W> {
+pub struct CopyBufInto<'a, R, W: ?Sized> {
     reader: R,
     writer: &'a mut W,
     amt: u64,
 }
 
-impl<R: Unpin, W> Unpin for CopyBufInto<'_, R, W> {}
+impl<R: Unpin, W: ?Sized> Unpin for CopyBufInto<'_, R, W> {}
 
-impl<R, W> CopyBufInto<'_, R, W> {
+impl<R, W: ?Sized> CopyBufInto<'_, R, W> {
     pub(super) fn new(reader: R, writer: &mut W) -> CopyBufInto<'_, R, W> {
         CopyBufInto {
             reader,
@@ -25,7 +25,7 @@ impl<R, W> CopyBufInto<'_, R, W> {
     }
 }
 
-impl<R, W: Unpin> CopyBufInto<'_, R, W> {
+impl<R, W: Unpin + ?Sized> CopyBufInto<'_, R, W> {
     fn project<'b>(self: Pin<&'b mut Self>) -> (Pin<&'b mut R>, Pin<&'b mut W>, &'b mut u64) {
         unsafe {
             let this = self.get_unchecked_mut();
@@ -36,7 +36,7 @@ impl<R, W: Unpin> CopyBufInto<'_, R, W> {
 
 impl<R, W> Future for CopyBufInto<'_, R, W>
     where R: AsyncBufRead,
-          W: AsyncWrite + Unpin,
+          W: AsyncWrite + Unpin + ?Sized,
 {
     type Output = io::Result<u64>;
 

futures-util/src/io/copy_into.rs

@@ -9,13 +9,13 @@ use pin_utils::unsafe_pinned;
 /// Future for the [`copy_into`](super::AsyncReadExt::copy_into) method.
 #[derive(Debug)]
 #[must_use = "futures do nothing unless you `.await` or poll them"]
-pub struct CopyInto<'a, R: AsyncRead, W> {
+pub struct CopyInto<'a, R: AsyncRead, W: ?Sized> {
     inner: CopyBufInto<'a, BufReader<R>, W>,
 }
 
-impl<'a, R: AsyncRead, W> Unpin for CopyInto<'a, R, W> where CopyBufInto<'a, BufReader<R>, W>: Unpin {}
+impl<'a, R: AsyncRead, W: ?Sized> Unpin for CopyInto<'a, R, W> where CopyBufInto<'a, BufReader<R>, W>: Unpin {}
 
-impl<'a, R: AsyncRead, W> CopyInto<'a, R, W> {
+impl<'a, R: AsyncRead, W: ?Sized> CopyInto<'a, R, W> {
     unsafe_pinned!(inner: CopyBufInto<'a, BufReader<R>, W>);
 
     pub(super) fn new(reader: R, writer: &mut W) -> CopyInto<'_, R, W> {
@@ -25,7 +25,7 @@ impl<'a, R: AsyncRead, W> CopyInto<'a, R, W> {
     }
 }
 
-impl<R: AsyncRead, W: AsyncWrite + Unpin> Future for CopyInto<'_, R, W> {
+impl<R: AsyncRead, W: AsyncWrite + Unpin + ?Sized> Future for CopyInto<'_, R, W> {
     type Output = io::Result<u64>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {

futures-util/src/io/mod.rs

@@ -111,7 +111,11 @@ pub trait AsyncReadExt: AsyncRead {
     /// assert_eq!(writer.into_inner(), [1, 2, 3, 4, 0]);
     /// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
     /// ```
-    fn copy_into<W: AsyncWrite + Unpin>(self, writer: &mut W) -> CopyInto<'_, Self, W> where Self: Sized {
+    fn copy_into<W>(self, writer: &mut W) -> CopyInto<'_, Self, W>
+    where
+        Self: Sized,
+        W: AsyncWrite + Unpin + ?Sized,
+    {
         CopyInto::new(self, writer)
     }
 
@@ -470,7 +474,11 @@ pub trait AsyncBufReadExt: AsyncBufRead {
     /// assert_eq!(writer.into_inner(), [1, 2, 3, 4, 0]);
     /// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
     /// ```
-    fn copy_buf_into<W: AsyncWrite + Unpin>(self, writer: &mut W) -> CopyBufInto<'_, Self, W> where Self: Sized {
+    fn copy_buf_into<W>(self, writer: &mut W) -> CopyBufInto<'_, Self, W>
+    where
+        Self: Sized,
+        W: AsyncWrite + Unpin + ?Sized,
+    {
         CopyBufInto::new(self, writer)
     }