feat(errors): expose error enums (fixes hyperium#2462)

Author: nox

src/client/dispatch.rs

@@ -317,7 +317,7 @@ mod tests {
             .expect("fulfilled")
             .expect_err("promise should error");
         match (err.0.kind(), err.1) {
-            (&crate::error::Kind::Canceled, Some(_)) => (),
+            (&crate::error::Kind::Canceled(_), Some(_)) => (),
             e => panic!("expected Error::Cancel(_), found {:?}", e),
         }
     }

src/client/service.rs

@@ -55,7 +55,7 @@ where
     fn poll_ready(&mut self, cx: &mut task::Context<'_>) -> Poll<Result<(), Self::Error>> {
         self.inner
             .poll_ready(cx)
-            .map_err(|e| crate::Error::new(crate::error::Kind::Connect).with(e.into()))
+            .map_err(|e| crate::Error::new_connect(e))
     }
 
     fn call(&mut self, req: T) -> Self::Future {
@@ -76,7 +76,7 @@ where
                     Err(e) => Err(e),
                 },
                 Err(e) => {
-                    let err = crate::Error::new(crate::error::Kind::Connect).with(e.into());
+                    let err = crate::Error::new_connect(e);
                     Err(err)
                 }
             }