Remove useless into_response calls

Route::new applies a `map_response(into_response)` already, so the
service being given to it doesn't have to involve an into_response call
itself.

axum/src/routing/method_routing.rs

@@ -19,7 +19,7 @@ use std::{
     fmt,
     task::{Context, Poll},
 };
-use tower::{service_fn, util::MapResponseLayer};
+use tower::service_fn;
 use tower_layer::Layer;
 use tower_service::Service;
 
@@ -748,7 +748,7 @@ where
     /// requests.
     pub fn new() -> Self {
         let fallback = Route::new(service_fn(|_: Request| async {
-            Ok(StatusCode::METHOD_NOT_ALLOWED.into_response())
+            Ok(StatusCode::METHOD_NOT_ALLOWED)
         }));
 
         Self {
@@ -1016,11 +1016,7 @@ where
             );
         }
 
-        let layer_fn = move |svc| {
-            let svc = layer.layer(svc);
-            let svc = MapResponseLayer::new(IntoResponse::into_response).layer(svc);
-            Route::new(svc)
-        };
+        let layer_fn = move |svc| Route::new(layer.layer(svc));
 
         self.get = self.get.map(layer_fn.clone());
         self.head = self.head.map(layer_fn.clone());

axum/src/routing/route.rs

@@ -67,11 +67,7 @@ impl<E> Route<E> {
         <L::Service as Service<Request>>::Future: Send + 'static,
         NewError: 'static,
     {
-        let layer = (
-            MapErrLayer::new(Into::into),
-            MapResponseLayer::new(IntoResponse::into_response),
-            layer,
-        );
+        let layer = (MapErrLayer::new(Into::into), layer);
 
         Route::new(layer.layer(self))
     }