docs(tower): moved docs from private tower::util::boxed module (tow…

…er-rs#684)

Now they're on the public `BoxService` struct that referenced them.

Fixes tower-rs#683.

tower/src/util/boxed/mod.rs

@@ -1,37 +1,3 @@
-//! Trait object [`Service`] instances
-//!
-//! Dynamically dispatched [`Service`] objects allow for erasing the underlying
-//! [`Service`] type and using the `Service` instances as opaque handles. This can
-//! be useful when the service instance cannot be explicitly named for whatever
-//! reason.
-//!
-//! There are two variants of service objects. [`BoxService`] requires both the
-//! service and the response future to be [`Send`]. These values can move freely
-//! across threads. [`UnsyncBoxService`] requires both the service and the
-//! response future to remain on the current thread. This is useful for
-//! representing services that are backed by [`Rc`] or other non-[`Send`] types.
-//!
-//! # Examples
-//!
-//! ```
-//! use futures_util::future::ready;
-//! # use tower_service::Service;
-//! # use tower::util::{BoxService, service_fn};
-//! // Respond to requests using a closure, but closures cannot be named...
-//! # pub fn main() {
-//! let svc = service_fn(|mut request: String| {
-//!     request.push_str(" response");
-//!     ready(Ok(request))
-//! });
-//!
-//! let service: BoxService<String, String, ()> = BoxService::new(svc);
-//! # drop(service);
-//! }
-//! ```
-//!
-//! [`Service`]: crate::Service
-//! [`Rc`]: std::rc::Rc
-
 mod layer;
 mod sync;
 mod unsync;

tower/src/util/boxed/sync.rs

@@ -18,7 +18,31 @@ use std::{
 /// If you need a boxed [`Service`] that implements [`Clone`] consider using
 /// [`BoxCloneService`](crate::util::BoxCloneService).
 ///
-/// See module level documentation for more details.
+/// Dynamically dispatched [`Service`] objects allow for erasing the underlying
+/// [`Service`] type and using the `Service` instances as opaque handles. This can
+/// be useful when the service instance cannot be explicitly named for whatever
+/// reason.
+///
+/// # Examples
+///
+/// ```
+/// use futures_util::future::ready;
+/// # use tower_service::Service;
+/// # use tower::util::{BoxService, service_fn};
+/// // Respond to requests using a closure, but closures cannot be named...
+/// # pub fn main() {
+/// let svc = service_fn(|mut request: String| {
+///     request.push_str(" response");
+///     ready(Ok(request))
+/// });
+///
+/// let service: BoxService<String, String, ()> = BoxService::new(svc);
+/// # drop(service);
+/// }
+/// ```
+///
+/// [`Service`]: crate::Service
+/// [`Rc`]: std::rc::Rc
 pub struct BoxService<T, U, E> {
     inner: Box<dyn Service<T, Response = U, Error = E, Future = BoxFuture<U, E>> + Send>,
 }