Fix some clippy lints (#292)

This commit can be replicated with `cargo +nightly clippy --fix -Z unstable-options`,
plus an edit to fix another `return` missed by clippy.

src/error.rs

@@ -182,7 +182,7 @@ impl Error {
     pub fn kind(&self) -> ErrorKind {
         match self {
             Error::Status(_, _) => ErrorKind::HTTP,
-            Error::Transport(Transport { kind: k, .. }) => k.clone(),
+            Error::Transport(Transport { kind: k, .. }) => *k,
         }
     }
 

src/header.rs

@@ -85,7 +85,7 @@ pub fn add_header(headers: &mut Vec<Header>, header: Header) {
 // tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
 // "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
 fn valid_name(name: &str) -> bool {
-    name.len() > 0 && name.bytes().all(is_tchar)
+    !name.is_empty() && name.bytes().all(is_tchar)
 }
 
 #[inline]

src/lib.rs

@@ -279,19 +279,19 @@ pub fn is_test(is: bool) -> bool {
         IS_TEST.store(true, Ordering::SeqCst);
     }
     let x = IS_TEST.load(Ordering::SeqCst);
-    return x;
+    x
 }
 
 /// Agents are used to hold configuration and keep state between requests.
 pub fn agent() -> Agent {
     #[cfg(not(test))]
     if is_test(false) {
-        return testserver::test_agent();
+        testserver::test_agent()
     } else {
-        return AgentBuilder::new().build();
+        AgentBuilder::new().build()
     }
     #[cfg(test)]
-    return testserver::test_agent();
+    testserver::test_agent()
 }
 
 /// Make a request with the HTTP verb as a parameter.

src/pool.rs

@@ -107,7 +107,7 @@ impl ConnectionPool {
                 let stream = streams.pop_back();
                 let stream = stream.expect("invariant failed: empty VecDeque in `recycle`");
 
-                if streams.len() == 0 {
+                if streams.is_empty() {
                     occupied_entry.remove();
                 }
 
@@ -172,7 +172,7 @@ impl ConnectionPool {
                     .pop_front()
                     .expect("invariant failed: key existed in recycle but no streams available");
                 debug!("dropping oldest stream in pool: {:?}", stream);
-                if streams.len() == 0 {
+                if streams.is_empty() {
                     occupied_entry.remove();
                 }
             }
@@ -214,7 +214,7 @@ impl PoolKey {
             scheme: url.scheme().to_string(),
             hostname: url.host_str().unwrap_or("").to_string(),
             port,
-            proxy: proxy,
+            proxy,
         }
     }
 }

src/response.rs

@@ -414,7 +414,7 @@ impl Response {
         //
         // HTTP/1.1 200 OK\r\n
         let mut stream =
-            stream::DeadlineStream::new(stream, unit.as_ref().and_then(|u| u.deadline.clone()));
+            stream::DeadlineStream::new(stream, unit.as_ref().and_then(|u| u.deadline));
         let status_line = read_next_line(&mut stream)?;
 
         let (index, status) = parse_status_line(status_line.as_str())?;
@@ -559,7 +559,7 @@ impl<'a> Iterator for Hist<'a> {
         };
 
         self.response = response.previous.as_deref();
-        return Some(response);
+        Some(response)
     }
 }
 

src/testserver.rs

@@ -82,10 +82,10 @@ pub struct TestHeaders(Vec<String>);
 impl TestHeaders {
     // Return the path for a request, e.g. /foo from "GET /foo HTTP/1.1"
     pub fn path(&self) -> &str {
-        if self.0.len() == 0 {
+        if self.0.is_empty() {
             ""
         } else {
-            &self.0[0].split(" ").nth(1).unwrap()
+            &self.0[0].split(' ').nth(1).unwrap()
         }
     }
 
@@ -105,7 +105,7 @@ pub fn read_request(stream: &TcpStream) -> TestHeaders {
                 eprintln!("testserver: in read_request: {}", e);
                 break;
             }
-            Ok(line) if line == "" => break,
+            Ok(line) if line.is_empty() => break,
             Ok(line) => results.push(line),
         };
     }

src/unit.rs

@@ -83,7 +83,7 @@ impl Unit {
 
             let username = url.username();
             let password = url.password().unwrap_or("");
-            if (username != "" || password != "") && get_header(&headers, "authorization").is_none()
+            if (!username.is_empty() || !password.is_empty()) && get_header(&headers, "authorization").is_none()
             {
                 let encoded = base64::encode(&format!("{}:{}", username, password));
                 extra.push(Header::new("Authorization", &format!("Basic {}", encoded)));