tower-rs · davidpdrsn · Nov 15, 2021 · Oct 4, 2021
diff --git a/examples/tonic-key-value-store/src/main.rs b/examples/tonic-key-value-store/src/main.rs
@@ -280,7 +280,7 @@ async fn make_client(
         // Decompress response bodies
         .layer(DecompressionLayer::new())
         // Set a `User-Agent` header
-        .layer(SetRequestHeaderLayer::<_, Request<BoxBody>>::overriding(
+        .layer(SetRequestHeaderLayer::overriding(
             header::USER_AGENT,
             HeaderValue::from_static("tonic-key-value-store"),
         ))

diff --git a/examples/warp-key-value-store/src/main.rs b/examples/warp-key-value-store/src/main.rs
@@ -2,7 +2,7 @@ use bytes::Bytes;
 use hyper::{
     body::HttpBody,
     header::{self, HeaderValue},
-    Body, Request, Response, Server, StatusCode,
+    Body, Response, Server, StatusCode,
 };
 use std::collections::HashMap;
 use std::net::SocketAddr;
@@ -89,7 +89,7 @@ async fn serve_forever(listener: TcpListener) -> Result<(), hyper::Error> {
             content_length_from_response,
         ))
         // Set a `Content-Type` if there isn't one already.
-        .layer(SetResponseHeaderLayer::<_, Request<Body>>::if_not_present(
+        .layer(SetResponseHeaderLayer::if_not_present(
             header::CONTENT_TYPE,
             HeaderValue::from_static("application/octet-stream"),
         ))

diff --git a/tower-http/CHANGELOG.md b/tower-http/CHANGELOG.md
@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - `ServeDir` and `ServeFile`: Ability to serve precompressed files ([#156])
 - `Trace`: Add `DefaultMakeSpan::level` to make log level of tracing spans easily configurable ([#124])
+- `SetRequestHeaderLayer`, `SetResponseHeaderLayer`: Remove unnecessary generic parameter ([#148])
+
+  This removes the need (and possibility) to specify a body type for these layers.
 
 [#124]: https://github.com/tower-rs/tower-http/pull/124
 [#156]: https://github.com/tower-rs/tower-http/pull/156

diff --git a/tower-http/src/lib.rs b/tower-http/src/lib.rs
@@ -110,7 +110,7 @@
 //!             StatusInRangeAsFailures::new(400..=599).into_make_classifier()
 //!         ))
 //!         // Set a `User-Agent` header on all requests.
-//!         .layer(SetRequestHeaderLayer::<_, Body>::overriding(
+//!         .layer(SetRequestHeaderLayer::overriding(
 //!             USER_AGENT,
 //!             HeaderValue::from_static("tower-http demo")
 //!         ))

diff --git a/tower-http/src/set_header/request.rs b/tower-http/src/set_header/request.rs
@@ -24,12 +24,9 @@
 //!     .layer(
 //!         // Layer that sets `User-Agent: my very cool app` on requests.
 //!         //
-//!         // We have to add `::<_, Body>` since Rust cannot infer the body type when
-//!         // we don't use a closure to produce the header value.
-//!         //
 //!         // `if_not_present` will only insert the header if it does not already
 //!         // have a value.
-//!         SetRequestHeaderLayer::<_, Body>::if_not_present(
+//!         SetRequestHeaderLayer::if_not_present(
 //!             header::USER_AGENT,
 //!             HeaderValue::from_static("my very cool app"),
 //!         )
@@ -87,7 +84,6 @@
 
 use super::{InsertHeaderMode, MakeHeaderValue};
 use http::{header::HeaderName, Request};
-use std::marker::PhantomData;
 use std::{
     fmt,
     task::{Context, Poll},
@@ -98,15 +94,13 @@ use tower_service::Service;
 /// Layer that applies [`SetRequestHeader`] which adds a request header.
 ///
 /// See [`SetRequestHeader`] for more details.
-pub struct SetRequestHeaderLayer<M, T> {
+pub struct SetRequestHeaderLayer<M> {
     header_name: HeaderName,
     make: M,
     mode: InsertHeaderMode,
-    // Covariant over T, no dropping of T
-    _marker: PhantomData<fn() -> T>,
 }
 
-impl<M, T> fmt::Debug for SetRequestHeaderLayer<M, T> {
+impl<M> fmt::Debug for SetRequestHeaderLayer<M> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("SetRequestHeaderLayer")
             .field("header_name", &self.header_name)
@@ -116,10 +110,7 @@ impl<M, T> fmt::Debug for SetRequestHeaderLayer<M, T> {
     }
 }
 
-impl<M, T> SetRequestHeaderLayer<M, T>
-where
-    M: MakeHeaderValue<T>,
-{
+impl<M> SetRequestHeaderLayer<M> {
     /// Create a new [`SetRequestHeaderLayer`].
     ///
     /// If a previous value exists for the same header, it is removed and replaced with the new
@@ -148,12 +139,11 @@ where
             make,
             header_name,
             mode,
-            _marker: PhantomData,
         }
     }
 }
 
-impl<T, S, M> Layer<S> for SetRequestHeaderLayer<M, T>
+impl<S, M> Layer<S> for SetRequestHeaderLayer<M>
 where
     M: Clone,
 {
@@ -169,7 +159,7 @@ where
     }
 }
 
-impl<M, T> Clone for SetRequestHeaderLayer<M, T>
+impl<M> Clone for SetRequestHeaderLayer<M>
 where
     M: Clone,
 {
@@ -178,7 +168,6 @@ where
             make: self.make.clone(),
             header_name: self.header_name.clone(),
             mode: self.mode,
-            _marker: PhantomData,
         }
     }
 }

diff --git a/tower-http/src/set_header/response.rs b/tower-http/src/set_header/response.rs
@@ -24,12 +24,9 @@
 //!     .layer(
 //!         // Layer that sets `Content-Type: text/html` on responses.
 //!         //
-//!         // We have to add `::<_, Body>` since Rust cannot infer the body type when
-//!         // we don't use a closure to produce the header value.
-//!         //
 //!         // `if_not_present` will only insert the header if it does not already
 //!         // have a value.
-//!         SetResponseHeaderLayer::<_, Body>::if_not_present(
+//!         SetResponseHeaderLayer::if_not_present(
 //!             header::CONTENT_TYPE,
 //!             HeaderValue::from_static("text/html"),
 //!         )
@@ -101,25 +98,23 @@ use http::{header::HeaderName, Response};
 use pin_project::pin_project;
 use std::{
     fmt,
+    future::Future,
     pin::Pin,
     task::{Context, Poll},
 };
-use std::{future::Future, marker::PhantomData};
 use tower_layer::Layer;
 use tower_service::Service;
 
 /// Layer that applies [`SetResponseHeader`] which adds a response header.
 ///
 /// See [`SetResponseHeader`] for more details.
-pub struct SetResponseHeaderLayer<M, T> {
+pub struct SetResponseHeaderLayer<M> {
     header_name: HeaderName,
     make: M,
     mode: InsertHeaderMode,
-    // Covariant over T, no dropping of T
-    _marker: PhantomData<fn() -> T>,
 }
 
-impl<M, T> fmt::Debug for SetResponseHeaderLayer<M, T> {
+impl<M> fmt::Debug for SetResponseHeaderLayer<M> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("SetResponseHeaderLayer")
             .field("header_name", &self.header_name)
@@ -129,10 +124,7 @@ impl<M, T> fmt::Debug for SetResponseHeaderLayer<M, T> {
     }
 }
 
-impl<M, T> SetResponseHeaderLayer<M, T>
-where
-    M: MakeHeaderValue<T>,
-{
+impl<M> SetResponseHeaderLayer<M> {
     /// Create a new [`SetResponseHeaderLayer`].
     ///
     /// If a previous value exists for the same header, it is removed and replaced with the new
@@ -161,12 +153,11 @@ where
             make,
             header_name,
             mode,
-            _marker: PhantomData,
         }
     }
 }
 
-impl<T, S, M> Layer<S> for SetResponseHeaderLayer<M, T>
+impl<S, M> Layer<S> for SetResponseHeaderLayer<M>
 where
     M: Clone,
 {
@@ -182,7 +173,7 @@ where
     }
 }
 
-impl<M, T> Clone for SetResponseHeaderLayer<M, T>
+impl<M> Clone for SetResponseHeaderLayer<M>
 where
     M: Clone,
 {
@@ -191,7 +182,6 @@ where
             make: self.make.clone(),
             header_name: self.header_name.clone(),
             mode: self.mode,
-            _marker: PhantomData,
         }
     }
 }