Make LayerFn type private

tower-layer/src/layer_fn.rs

@@ -1,21 +1,23 @@
 use super::Layer;
 
-/// Returns a new `LayerFn` with the given closure.
-pub fn layer_fn<T>(f: T) -> LayerFn<T> {
+/// Returns a new `impl Layer` with the given closure.
+pub fn layer_fn<F, S, T>(f: F) -> impl Layer<S, Service = T> + Clone
+where
+    F: Fn(S) -> T + Clone,
+{
     LayerFn { f }
 }
 
-/// A `Layer` implemented by a closure.
 #[derive(Clone, Copy, Debug)]
-pub struct LayerFn<F> {
+struct LayerFn<F> {
     f: F,
 }
 
-impl<F, S, Out> Layer<S> for LayerFn<F>
+impl<F, S, T> Layer<S> for LayerFn<F>
 where
-    F: Fn(S) -> Out,
+    F: Fn(S) -> T,
 {
-    type Service = Out;
+    type Service = T;
 
     fn layer(&self, inner: S) -> Self::Service {
         (self.f)(inner)

tower-layer/src/lib.rs

@@ -17,11 +17,7 @@ mod identity;
 mod layer_fn;
 mod stack;
 
-pub use self::{
-    identity::Identity,
-    layer_fn::{layer_fn, LayerFn},
-    stack::Stack,
-};
+pub use self::{identity::Identity, layer_fn::layer_fn, stack::Stack};
 
 /// Decorates a `Service`, transforming either the request or the response.
 ///