1 files changed, 13 insertions, 15 deletions
diff --git a/tokio/src/io/util/flush.rs b/tokio/src/io/util/flush.rs
index 534a5160..88d60b86 100644
--- a/tokio/src/io/util/flush.rs
+++ b/tokio/src/io/util/flush.rs
@@ -1,18 +1,24 @@
 use crate::io::AsyncWrite;
 
+use pin_project_lite::pin_project;
 use std::future::Future;
 use std::io;
+use std::marker::PhantomPinned;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
-cfg_io_util! {
+pin_project! {
     /// A future used to fully flush an I/O object.
     ///
     /// Created by the [`AsyncWriteExt::flush`][flush] function.
     /// [flush]: crate::io::AsyncWriteExt::flush
     #[derive(Debug)]
+    #[must_use = "futures do nothing unless you `.await` or poll them"]
     pub struct Flush<'a, A: ?Sized> {
         a: &'a mut A,
+        // Make this future `!Unpin` for compatibility with async trait methods.
+        #[pin]
+        _pin: PhantomPinned,
     }
 }
 
@@ -21,7 +27,10 @@ pub(super) fn flush<A>(a: &mut A) -> Flush<'_, A>
 where
     A: AsyncWrite + Unpin + ?Sized,
 {
-    Flush { a }
+    Flush {
+        a,
+        _pin: PhantomPinned,
+    }
 }
 
 impl<A> Future for Flush<'_, A>
@@ -30,19 +39,8 @@ where
 {
     type Output = io::Result<()>;
 
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        let me = &mut *self;
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let me = self.project();
         Pin::new(&mut *me.a).poll_flush(cx)
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn assert_unpin() {
-        use std::marker::PhantomPinned;
-        crate::is_unpin::<Flush<'_, PhantomPinned>>();
-    }
-}