feat(client): expose hyper::client::connect::Connect trait alias

This is *just* a "trait alias". It is automatically implemented for all
`Service<Uri>`s that have the required bounds. It's purpose being public
is to ease setting trait bounds outside of hyper. Therefore, it doesn't
have any exposed associated types, to prevent otherwise relying on any
super-traits that hyper requires.

src/client/connect/http.rs

@@ -637,10 +637,13 @@ mod tests {
 
     use ::http::Uri;
 
-    use super::super::sealed::Connect;
+    use super::super::sealed::{Connect, ConnectSvc};
     use super::HttpConnector;
 
-    async fn connect<C>(connector: C, dst: Uri) -> Result<C::Transport, C::Error>
+    async fn connect<C>(
+        connector: C,
+        dst: Uri,
+    ) -> Result<<C::_Svc as ConnectSvc>::Connection, <C::_Svc as ConnectSvc>::Error>
     where
         C: Connect,
     {

src/client/connect/mod.rs

@@ -83,6 +83,7 @@ pub mod dns;
 mod http;
 #[cfg(feature = "tcp")]
 pub use self::http::{HttpConnector, HttpInfo};
+pub use self::sealed::Connect;
 
 /// Describes a type returned by a connector.
 pub trait Connection {
@@ -258,26 +259,45 @@ pub(super) mod sealed {
     // The `Sized` bound is to prevent creating `dyn Connect`, since they cannot
     // fit the `Connect` bounds because of the blanket impl for `Service`.
     pub trait Connect: Sealed + Sized {
-        /// The connected IO Stream.
-        type Transport: AsyncRead + AsyncWrite + Connection;
-        /// An error occured when trying to connect.
-        type Error: Into<Box<dyn StdError + Send + Sync>>;
-        /// A Future that will resolve to the connected Transport.
-        type Future: Future<Output = Result<Self::Transport, Self::Error>>;
         #[doc(hidden)]
+        type _Svc: ConnectSvc;
+        #[doc(hidden)]
+        fn connect(self, internal_only: Internal, dst: Uri) -> <Self::_Svc as ConnectSvc>::Future;
+    }
+
+    pub trait ConnectSvc {
+        type Connection: AsyncRead + AsyncWrite + Connection + Unpin + Send + 'static;
+        type Error: Into<Box<dyn StdError + Send + Sync>>;
+        type Future: Future<Output = Result<Self::Connection, Self::Error>> + Unpin + Send + 'static;
+
         fn connect(self, internal_only: Internal, dst: Uri) -> Self::Future;
     }
 
     impl<S, T> Connect for S
     where
-        S: tower_service::Service<Uri, Response = T> + Send,
+        S: tower_service::Service<Uri, Response = T> + Send + 'static,
         S::Error: Into<Box<dyn StdError + Send + Sync>>,
         S::Future: Unpin + Send,
         T: AsyncRead + AsyncWrite + Connection + Unpin + Send + 'static,
     {
-        type Transport = T;
+        type _Svc = S;
+
+        fn connect(self, _: Internal, dst: Uri) -> crate::service::Oneshot<S, Uri> {
+            crate::service::oneshot(self, dst)
+        }
+    }
+
+    impl<S, T> ConnectSvc for S
+    where
+        S: tower_service::Service<Uri, Response = T> + Send + 'static,
+        S::Error: Into<Box<dyn StdError + Send + Sync>>,
+        S::Future: Unpin + Send,
+        T: AsyncRead + AsyncWrite + Connection + Unpin + Send + 'static,
+    {
+        type Connection = T;
         type Error = S::Error;
         type Future = crate::service::Oneshot<S, Uri>;
+
         fn connect(self, _: Internal, dst: Uri) -> Self::Future {
             crate::service::oneshot(self, dst)
         }

src/client/mod.rs

@@ -150,8 +150,6 @@ impl Client<(), Body> {
 impl<C, B> Client<C, B>
 where
     C: Connect + Clone + Send + Sync + 'static,
-    C::Transport: Unpin + Send + 'static,
-    C::Future: Unpin + Send + 'static,
     B: Payload + Send + 'static,
     B::Data: Send,
 {
@@ -548,8 +546,6 @@ where
 impl<C, B> tower_service::Service<Request<B>> for Client<C, B>
 where
     C: Connect + Clone + Send + Sync + 'static,
-    C::Transport: Unpin + Send + 'static,
-    C::Future: Unpin + Send + 'static,
     B: Payload + Send + 'static,
     B::Data: Send,
 {