Remove several uses of Pin::new_unchecked (#1294)

Most of the relevant struct already had a `#[pin_project]` attribute,
but it wasn't being used.

The remaining uses of `Pin::new_unchecked` all involve going from a
`&mut T` to a `Pin<&mut T>`, without directly observing a `Pin<&mut T>`
first. As such, they cannot be replaced by `pin_project`

Co-authored-by: Yuki Okushi <huyuumi.dev@gmail.com>

actix-http/src/client/pool.rs

@@ -488,10 +488,12 @@ where
     }
 }
 
+#[pin_project::pin_project(PinnedDrop)]
 struct OpenWaitingConnection<F, Io>
 where
     Io: AsyncRead + AsyncWrite + Unpin + 'static,
 {
+    #[pin]
     fut: F,
     key: Key,
     h2: Option<
@@ -525,12 +527,13 @@ where
     }
 }
 
-impl<F, Io> Drop for OpenWaitingConnection<F, Io>
+#[pin_project::pinned_drop]
+impl<F, Io> PinnedDrop for OpenWaitingConnection<F, Io>
 where
     Io: AsyncRead + AsyncWrite + Unpin + 'static,
 {
-    fn drop(&mut self) {
-        if let Some(inner) = self.inner.take() {
+    fn drop(self: Pin<&mut Self>) {
+        if let Some(inner) = self.project().inner.take() {
             let mut inner = inner.as_ref().borrow_mut();
             inner.release();
             inner.check_availibility();
@@ -545,8 +548,8 @@ where
 {
     type Output = ();
 
-    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        let this = unsafe { self.get_unchecked_mut() };
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let this = self.as_mut().project();
 
         if let Some(ref mut h2) = this.h2 {
             return match Pin::new(h2).poll(cx) {
@@ -571,7 +574,7 @@ where
             };
         }
 
-        match unsafe { Pin::new_unchecked(&mut this.fut) }.poll(cx) {
+        match this.fut.poll(cx) {
             Poll::Ready(Err(err)) => {
                 let _ = this.inner.take();
                 if let Some(rx) = this.rx.take() {
@@ -589,8 +592,8 @@ where
                     )));
                     Poll::Ready(())
                 } else {
-                    this.h2 = Some(handshake(io).boxed_local());
-                    unsafe { Pin::new_unchecked(this) }.poll(cx)
+                    *this.h2 = Some(handshake(io).boxed_local());
+                    self.poll(cx)
                 }
             }
             Poll::Pending => Poll::Pending,

actix-http/src/h2/dispatcher.rs

@@ -158,14 +158,16 @@ where
 
 #[pin_project::pin_project]
 struct ServiceResponse<F, I, E, B> {
+    #[pin]
     state: ServiceResponseState<F, B>,
     config: ServiceConfig,
     buffer: Option<Bytes>,
     _t: PhantomData<(I, E)>,
 }
 
+#[pin_project::pin_project]
 enum ServiceResponseState<F, B> {
-    ServiceCall(F, Option<SendResponse<Bytes>>),
+    ServiceCall(#[pin] F, Option<SendResponse<Bytes>>),
     SendPayload(SendStream<Bytes>, ResponseBody<B>),
 }
 
@@ -247,12 +249,14 @@ where
 {
     type Output = ();
 
+    #[pin_project::project]
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let mut this = self.as_mut().project();
 
-        match this.state {
-            ServiceResponseState::ServiceCall(ref mut call, ref mut send) => {
-                match unsafe { Pin::new_unchecked(call) }.poll(cx) {
+        #[project]
+        match this.state.project() {
+            ServiceResponseState::ServiceCall(call, send) => {
+                match call.poll(cx) {
                     Poll::Ready(Ok(res)) => {
                         let (res, body) = res.into().replace_body(());
 
@@ -273,8 +277,7 @@ where
                         if size.is_eof() {
                             Poll::Ready(())
                         } else {
-                            *this.state =
-                                ServiceResponseState::SendPayload(stream, body);
+                            this.state.set(ServiceResponseState::SendPayload(stream, body));
                             self.poll(cx)
                         }
                     }
@@ -300,10 +303,10 @@ where
                         if size.is_eof() {
                             Poll::Ready(())
                         } else {
-                            *this.state = ServiceResponseState::SendPayload(
+                            this.state.set(ServiceResponseState::SendPayload(
                                 stream,
                                 body.into_body(),
-                            );
+                            ));
                             self.poll(cx)
                         }
                     }