Remove Unpin requirement for the send Buf

src/codec/framed_write.rs

@@ -281,7 +281,7 @@ impl<T, B> FramedWrite<T, B> {
     }
 }
 
-impl<T: AsyncRead + Unpin, B: Unpin> AsyncRead for FramedWrite<T, B> {
+impl<T: AsyncRead + Unpin, B> AsyncRead for FramedWrite<T, B> {
     unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [std::mem::MaybeUninit<u8>]) -> bool {
         self.inner.prepare_uninitialized_buffer(buf)
     }
@@ -303,6 +303,9 @@ impl<T: AsyncRead + Unpin, B: Unpin> AsyncRead for FramedWrite<T, B> {
     }
 }
 
+// We never project the Pin to `B`.
+impl<T: Unpin, B> Unpin for FramedWrite<T, B> {}
+
 #[cfg(feature = "unstable")]
 mod unstable {
     use super::*;

src/codec/mod.rs

@@ -27,7 +27,7 @@ pub struct Codec<T, B> {
 impl<T, B> Codec<T, B>
 where
     T: AsyncRead + AsyncWrite + Unpin,
-    B: Buf + Unpin,
+    B: Buf,
 {
     /// Returns a new `Codec` with the default max frame size
     #[inline]
@@ -118,7 +118,7 @@ impl<T, B> Codec<T, B> {
 impl<T, B> Codec<T, B>
 where
     T: AsyncWrite + Unpin,
-    B: Buf + Unpin,
+    B: Buf,
 {
     /// Returns `Ready` when the codec can buffer a frame
     pub fn poll_ready(&mut self, cx: &mut Context) -> Poll<io::Result<()>> {
@@ -149,7 +149,6 @@ where
 impl<T, B> Stream for Codec<T, B>
 where
     T: AsyncRead + Unpin,
-    B: Unpin,
 {
     type Item = Result<Frame, RecvError>;
 
@@ -161,7 +160,7 @@ where
 impl<T, B> Sink<Frame<B>> for Codec<T, B>
 where
     T: AsyncWrite + Unpin,
-    B: Buf + Unpin,
+    B: Buf,
 {
     type Error = SendError;