Fix some clippy warnings (#1009)

src/address/serde.rs

@@ -36,7 +36,7 @@ impl<'de> Deserialize<'de> for Address {
             {
                 struct FieldVisitor;
 
-                impl<'de> Visitor<'de> for FieldVisitor {
+                impl Visitor<'_> for FieldVisitor {
                     type Value = Field;
 
                     fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {

src/message/dkim.rs

@@ -345,7 +345,6 @@ fn dkim_canonicalize_headers<'a>(
 
 /// Sign with Dkim a message by adding Dkim-Signature header created with configuration expressed by
 /// dkim_config
-
 pub fn dkim_sign(message: &mut Message, dkim_config: &DkimConfig) {
     dkim_sign_fixed_time(message, dkim_config, SystemTime::now())
 }

src/message/header/content_type.rs

@@ -119,7 +119,7 @@ mod serde {
         {
             struct ContentTypeVisitor;
 
-            impl<'de> Visitor<'de> for ContentTypeVisitor {
+            impl Visitor<'_> for ContentTypeVisitor {
                 type Value = ContentType;
 
                 // The error message which states what the Visitor expects to

src/message/mailbox/serde.rs

@@ -36,7 +36,7 @@ impl<'de> Deserialize<'de> for Mailbox {
             {
                 struct FieldVisitor;
 
-                impl<'de> Visitor<'de> for FieldVisitor {
+                impl Visitor<'_> for FieldVisitor {
                     type Value = Field;
 
                     fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {

src/message/mailbox/types.rs

@@ -174,7 +174,7 @@ impl Mailboxes {
         self
     }
 
-    /// Adds a new [`Mailbox`] to the list, in a Vec::push style pattern.
+    /// Adds a new [`Mailbox`] to the list, in a `Vec::push` style pattern.
     ///
     /// # Examples
     ///

src/message/mod.rs

@@ -345,7 +345,7 @@ impl MessageBuilder {
                 let hostname = hostname::get()
                     .map_err(|_| ())
                     .and_then(|s| s.into_string().map_err(|_| ()))
-                    .unwrap_or_else(|_| DEFAULT_MESSAGE_ID_DOMAIN.to_owned());
+                    .unwrap_or_else(|()| DEFAULT_MESSAGE_ID_DOMAIN.to_owned());
                 #[cfg(not(feature = "hostname"))]
                 let hostname = DEFAULT_MESSAGE_ID_DOMAIN.to_owned();
 

src/transport/smtp/client/net.rs

@@ -119,12 +119,12 @@ impl NetworkStream {
 
                 if let Some(timeout) = timeout {
                     match socket.connect_timeout(&addr.into(), timeout) {
-                        Ok(_) => return Ok(socket.into()),
+                        Ok(()) => return Ok(socket.into()),
                         Err(err) => last_err = Some(err),
                     }
                 } else {
                     match socket.connect(&addr.into()) {
-                        Ok(_) => return Ok(socket.into()),
+                        Ok(()) => return Ok(socket.into()),
                         Err(err) => last_err = Some(err),
                     }
                 }
@@ -369,7 +369,7 @@ impl Write for NetworkStream {
 /// If the local address is set, binds the socket to this address.
 /// If local address is not set, then destination address is required to determine the default
 /// local address on some platforms.
-/// See: https://github.com/hyperium/hyper/blob/faf24c6ad8eee1c3d5ccc9a4d4835717b8e2903f/src/client/connect/http.rs#L560
+/// See: <https://github.com/hyperium/hyper/blob/faf24c6ad8eee1c3d5ccc9a4d4835717b8e2903f/src/client/connect/http.rs#L560>
 fn bind_local_address(
     socket: &socket2::Socket,
     dst_addr: &SocketAddr,

src/transport/smtp/connection_url.rs

@@ -62,7 +62,7 @@ impl TransportBuilder for AsyncSmtpTransportBuilder {
     }
 }
 
-/// Create a new SmtpTransportBuilder or AsyncSmtpTransportBuilder from a connection URL
+/// Create a new `SmtpTransportBuilder` or `AsyncSmtpTransportBuilder` from a connection URL
 pub(crate) fn from_connection_url<B: TransportBuilder>(connection_url: &str) -> Result<B, Error> {
     let connection_url = Url::parse(connection_url).map_err(error::connection)?;
     let tls: Option<String> = connection_url

src/transport/smtp/util.rs

@@ -6,7 +6,7 @@ use std::fmt::{Display, Formatter, Result as FmtResult};
 #[derive(Debug)]
 pub struct XText<'a>(pub &'a str);
 
-impl<'a> Display for XText<'a> {
+impl Display for XText<'_> {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
         let mut rest = self.0;
         while let Some(idx) = rest.find(|c| c < '!' || c == '+' || c == '=') {