HttpClient: remove Error type bounds

This makes using HttpClient as a dynamic Trait object, such as in
http-rs/surf#69
substantially more complex.

This complexity can be reduced by having the backing client implementor handle the error translation (which was already required to begin with).

Author: Fishrock123

src/h1.rs

@@ -1,10 +1,10 @@
 //! http-client implementation for async-h1.
 
-use super::{HttpClient, Request, Response};
+use super::{Error, HttpClient, Request, Response};
 
 use async_h1::client;
 use futures::future::BoxFuture;
-use http_types::{Error, StatusCode};
+use http_types::StatusCode;
 
 /// Async-h1 based HTTP Client.
 #[derive(Debug)]
@@ -30,9 +30,7 @@ impl Clone for H1Client {
 }
 
 impl HttpClient for H1Client {
-    type Error = Error;
-
-    fn send(&self, mut req: Request) -> BoxFuture<'static, Result<Response, Self::Error>> {
+    fn send(&self, mut req: Request) -> BoxFuture<'static, Result<Response, Error>> {
         Box::pin(async move {
             // Insert host
             let host = req

src/isahc.rs

@@ -1,6 +1,6 @@
 //! http-client implementation for isahc
 
-use super::{Body, HttpClient, Request, Response};
+use super::{Body, Error, HttpClient, Request, Response};
 
 use async_std::io::BufReader;
 use futures::future::BoxFuture;
@@ -42,9 +42,7 @@ impl Clone for IsahcClient {
 }
 
 impl HttpClient for IsahcClient {
-    type Error = isahc::Error;
-
-    fn send(&self, mut req: Request) -> BoxFuture<'static, Result<Response, Self::Error>> {
+    fn send(&self, mut req: Request) -> BoxFuture<'static, Result<Response, Error>> {
         let client = self.client.clone();
         Box::pin(async move {
             let mut builder = http::Request::builder()
@@ -65,7 +63,7 @@ impl HttpClient for IsahcClient {
             };
 
             let request = builder.body(body).unwrap();
-            let res = client.send_async(request).await?;
+            let res = client.send_async(request).await.map_err(Error::from)?;
             let (parts, body) = res.into_parts();
             let len = body.len().map(|len| len as usize);
             let body = Body::from_reader(BufReader::new(body), len);

src/lib.rs

@@ -53,11 +53,8 @@ pub use http_types;
 /// though middleware for one of its own requests, and in order to do so should be wrapped in an
 /// `Rc`/`Arc` to enable reference cloning.
 pub trait HttpClient: std::fmt::Debug + Unpin + Send + Sync + 'static {
-    /// The associated error type.
-    type Error: Send + Sync + Into<Error>;
-
     /// Perform a request.
-    fn send(&self, req: Request) -> BoxFuture<'static, Result<Response, Self::Error>>;
+    fn send(&self, req: Request) -> BoxFuture<'static, Result<Response, Error>>;
 }
 
 /// The raw body of an http request or response.

src/wasm.rs

@@ -1,6 +1,6 @@
 //! http-client implementation for fetch
 
-use super::{Body, HttpClient, Request, Response};
+use super::{Body, Error, HttpClient, Request, Response};
 
 use futures::future::BoxFuture;
 use futures::prelude::*;
@@ -29,9 +29,7 @@ impl Clone for WasmClient {
 }
 
 impl HttpClient for WasmClient {
-    type Error = std::io::Error;
-
-    fn send(&self, req: Request) -> BoxFuture<'static, Result<Response, Self::Error>> {
+    fn send(&self, req: Request) -> BoxFuture<'static, Result<Response, Error>> {
         let fut = Box::pin(async move {
             let url = format!("{}", req.uri());
             let req = fetch::new(req.method().as_str(), &url);