remove responsebody indirection from response (#2201)

src/middleware/compat.rs

@@ -1,12 +1,13 @@
 //! For middleware documentation, see [`Compat`].
 
 use std::{
+    error::Error as StdError,
     future::Future,
     pin::Pin,
     task::{Context, Poll},
 };
 
-use actix_http::body::{Body, MessageBody, ResponseBody};
+use actix_http::body::{Body, MessageBody};
 use actix_service::{Service, Transform};
 use futures_core::{future::LocalBoxFuture, ready};
 
@@ -116,10 +117,10 @@ pub trait MapServiceResponseBody {
 impl<B> MapServiceResponseBody for ServiceResponse<B>
 where
     B: MessageBody + Unpin + 'static,
-    B::Error: Into<Error>,
+    B::Error: Into<Box<dyn StdError + 'static>>,
 {
     fn map_body(self) -> ServiceResponse {
-        self.map_body(|_, body| ResponseBody::Other(Body::from_message(body)))
+        self.map_body(|_, body| Body::from_message(body))
     }
 }