Fix warnings

src/executor.rs

@@ -134,7 +134,7 @@ impl Executor for Tokio1Executor {
         #[allow(clippy::match_single_binding)]
         let tls_parameters = match tls {
             #[cfg(any(feature = "tokio1-native-tls", feature = "tokio1-rustls-tls"))]
-            Tls::Wrapper(ref tls_parameters) => Some(tls_parameters.clone()),
+            Tls::Wrapper(tls_parameters) => Some(tls_parameters.clone()),
             _ => None,
         };
         #[allow(unused_mut)]
@@ -149,13 +149,13 @@ impl Executor for Tokio1Executor {
 
         #[cfg(any(feature = "tokio1-native-tls", feature = "tokio1-rustls-tls"))]
         match tls {
-            Tls::Opportunistic(ref tls_parameters) => {
+            Tls::Opportunistic(tls_parameters) => {
                 if conn.can_starttls() {
-                    conn.starttls(tls_parameters.clone(), hello_name).await?;
+                    conn = conn.starttls(tls_parameters.clone(), hello_name).await?;
                 }
             }
-            Tls::Required(ref tls_parameters) => {
-                conn.starttls(tls_parameters.clone(), hello_name).await?;
+            Tls::Required(tls_parameters) => {
+                conn = conn.starttls(tls_parameters.clone(), hello_name).await?;
             }
             _ => (),
         }
@@ -231,7 +231,7 @@ impl Executor for AsyncStd1Executor {
         #[allow(clippy::match_single_binding)]
         let tls_parameters = match tls {
             #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
-            Tls::Wrapper(ref tls_parameters) => Some(tls_parameters.clone()),
+            Tls::Wrapper(tls_parameters) => Some(tls_parameters.clone()),
             _ => None,
         };
         #[allow(unused_mut)]
@@ -245,13 +245,13 @@ impl Executor for AsyncStd1Executor {
 
         #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
         match tls {
-            Tls::Opportunistic(ref tls_parameters) => {
+            Tls::Opportunistic(tls_parameters) => {
                 if conn.can_starttls() {
-                    conn.starttls(tls_parameters.clone(), hello_name).await?;
+                    conn = conn.starttls(tls_parameters.clone(), hello_name).await?;
                 }
             }
-            Tls::Required(ref tls_parameters) => {
-                conn.starttls(tls_parameters.clone(), hello_name).await?;
+            Tls::Required(tls_parameters) => {
+                conn = conn.starttls(tls_parameters.clone(), hello_name).await?;
             }
             _ => (),
         }

src/message/dkim.rs

@@ -2,7 +2,6 @@ use std::{
     borrow::Cow,
     error::Error as StdError,
     fmt::{self, Display},
-    iter::IntoIterator,
     time::SystemTime,
 };
 

src/message/mailbox/types.rs

@@ -88,7 +88,7 @@ impl Mailbox {
 
 impl Display for Mailbox {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
-        if let Some(ref name) = self.name {
+        if let Some(name) = &self.name {
             let name = name.trim();
             if !name.is_empty() {
                 write_word(f, name)?;

src/transport/file/error.rs

@@ -54,7 +54,7 @@ impl fmt::Debug for Error {
 
         builder.field("kind", &self.inner.kind);
 
-        if let Some(ref source) = self.inner.source {
+        if let Some(source) = &self.inner.source {
             builder.field("source", source);
         }
 
@@ -70,7 +70,7 @@ impl fmt::Display for Error {
             Kind::Envelope => f.write_str("internal client error")?,
         };
 
-        if let Some(ref e) = self.inner.source {
+        if let Some(e) = &self.inner.source {
             write!(f, ": {e}")?;
         }
 

src/transport/sendmail/error.rs

@@ -52,7 +52,7 @@ impl fmt::Debug for Error {
 
         builder.field("kind", &self.inner.kind);
 
-        if let Some(ref source) = self.inner.source {
+        if let Some(source) = &self.inner.source {
             builder.field("source", source);
         }
 
@@ -67,7 +67,7 @@ impl fmt::Display for Error {
             Kind::Client => f.write_str("internal client error")?,
         };
 
-        if let Some(ref e) = self.inner.source {
+        if let Some(e) = &self.inner.source {
             write!(f, ": {e}")?;
         }
 

src/transport/smtp/client/async_connection.rs

@@ -6,7 +6,7 @@ use futures_util::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
 use super::async_net::AsyncTokioStream;
 #[cfg(feature = "tracing")]
 use super::escape_crlf;
-use super::{AsyncNetworkStream, ClientCodec, TlsParameters};
+use super::{AsyncNetworkStream, ClientCodec, ConnectionState, TlsParameters};
 use crate::{
     transport::smtp::{
         authentication::{Credentials, Mechanism},
@@ -19,25 +19,11 @@ use crate::{
     Envelope,
 };
 
-macro_rules! try_smtp (
-    ($err: expr, $client: ident) => ({
-        match $err {
-            Ok(val) => val,
-            Err(err) => {
-                $client.abort().await;
-                return Err(From::from(err))
-            },
-        }
-    })
-);
-
 /// Structure that implements the SMTP client
 pub struct AsyncSmtpConnection {
     /// TCP stream between client and server
     /// Value is None before connection
     stream: BufReader<AsyncNetworkStream>,
-    /// Panic state
-    panic: bool,
     /// Information about the server
     server_info: ServerInfo,
 }
@@ -126,7 +112,6 @@ impl AsyncSmtpConnection {
         let stream = BufReader::new(stream);
         let mut conn = AsyncSmtpConnection {
             stream,
-            panic: false,
             server_info: ServerInfo::default(),
         };
         // TODO log
@@ -170,30 +155,26 @@ impl AsyncSmtpConnection {
             mail_options.push(MailParameter::Body(MailBodyParameter::EightBitMime));
         }
 
-        try_smtp!(
-            self.command(Mail::new(envelope.from().cloned(), mail_options))
-                .await,
-            self
-        );
+        self.command(Mail::new(envelope.from().cloned(), mail_options))
+            .await?;
 
         // Recipient
         for to_address in envelope.to() {
-            try_smtp!(
-                self.command(Rcpt::new(to_address.clone(), vec![])).await,
-                self
-            );
+            self.command(Rcpt::new(to_address.clone(), vec![])).await?;
         }
 
         // Data
-        try_smtp!(self.command(Data).await, self);
+        self.command(Data).await?;
 
         // Message content
-        let result = try_smtp!(self.message(email).await, self);
-        Ok(result)
+        self.message(email).await
     }
 
     pub fn has_broken(&self) -> bool {
-        self.panic
+        match self.stream.get_ref().state() {
+            ConnectionState::Ok => false,
+            ConnectionState::Broken | ConnectionState::Closed => true,
+        }
     }
 
     pub fn can_starttls(&self) -> bool {
@@ -208,18 +189,20 @@ impl AsyncSmtpConnection {
     /// [rfc8314]: https://www.rfc-editor.org/rfc/rfc8314
     #[allow(unused_variables)]
     pub async fn starttls(
-        &mut self,
+        mut self,
         tls_parameters: TlsParameters,
         hello_name: &ClientId,
-    ) -> Result<(), Error> {
+    ) -> Result<Self, Error> {
         if self.server_info.supports_feature(Extension::StartTls) {
-            try_smtp!(self.command(Starttls).await, self);
-            self.stream.get_mut().upgrade_tls(tls_parameters).await?;
+            self.command(Starttls).await?;
+            let stream = self.stream.into_inner();
+            let stream = stream.upgrade_tls(tls_parameters).await?;
+            self.stream = BufReader::new(stream);
             #[cfg(feature = "tracing")]
             tracing::debug!("connection encrypted");
             // Send EHLO again
-            try_smtp!(self.ehlo(hello_name).await, self);
-            Ok(())
+            self.ehlo(hello_name).await?;
+            Ok(self)
         } else {
             Err(error::client("STARTTLS is not supported on this server"))
         }
@@ -227,22 +210,24 @@ impl AsyncSmtpConnection {
 
     /// Send EHLO and update server info
     async fn ehlo(&mut self, hello_name: &ClientId) -> Result<(), Error> {
-        let ehlo_response = try_smtp!(self.command(Ehlo::new(hello_name.clone())).await, self);
-        self.server_info = try_smtp!(ServerInfo::from_response(&ehlo_response), self);
+        let ehlo_response = self.command(Ehlo::new(hello_name.clone())).await?;
+        self.server_info = ServerInfo::from_response(&ehlo_response)?;
         Ok(())
     }
 
     pub async fn quit(&mut self) -> Result<Response, Error> {
-        Ok(try_smtp!(self.command(Quit).await, self))
+        self.command(Quit).await
     }
 
     pub async fn abort(&mut self) {
-        // Only try to quit if we are not already broken
-        if !self.panic {
-            self.panic = true;
-            let _ = self.command(Quit).await;
+        match self.stream.get_ref().state() {
+            ConnectionState::Ok | ConnectionState::Broken => {
+                let _ = self.command(Quit).await;
+                let _ = self.stream.close().await;
+                self.stream.get_mut().set_state(ConnectionState::Closed);
+            }
+            ConnectionState::Closed => {}
         }
-        let _ = self.stream.close().await;
     }
 
     /// Sets the underlying stream
@@ -279,15 +264,13 @@ impl AsyncSmtpConnection {
 
         while challenges > 0 && response.has_code(334) {
             challenges -= 1;
-            response = try_smtp!(
-                self.command(Auth::new_from_response(
+            response = self
+                .command(Auth::new_from_response(
                     mechanism,
                     credentials.clone(),
                     &response,
                 )?)
-                .await,
-                self
-            );
+                .await?;
         }
 
         if challenges == 0 {
@@ -315,6 +298,9 @@ impl AsyncSmtpConnection {
 
     /// Writes a string to the server
     async fn write(&mut self, string: &[u8]) -> Result<(), Error> {
+        self.stream.get_ref().state().verify()?;
+        self.stream.get_mut().set_state(ConnectionState::Broken);
+
         self.stream
             .get_mut()
             .write_all(string)
@@ -326,6 +312,8 @@ impl AsyncSmtpConnection {
             .await
             .map_err(error::network)?;
 
+        self.stream.get_mut().set_state(ConnectionState::Ok);
+
         #[cfg(feature = "tracing")]
         tracing::debug!("Wrote: {}", escape_crlf(&String::from_utf8_lossy(string)));
         Ok(())
@@ -333,6 +321,9 @@ impl AsyncSmtpConnection {
 
     /// Gets the SMTP response
     pub async fn read_response(&mut self) -> Result<Response, Error> {
+        self.stream.get_ref().state().verify()?;
+        self.stream.get_mut().set_state(ConnectionState::Broken);
+
         let mut buffer = String::with_capacity(100);
 
         while self
@@ -346,6 +337,8 @@ impl AsyncSmtpConnection {
             tracing::debug!("<< {}", escape_crlf(&buffer));
             match parse_response(&buffer) {
                 Ok((_remaining, response)) => {
+                    self.stream.get_mut().set_state(ConnectionState::Ok);
+
                     return if response.is_positive() {
                         Ok(response)
                     } else {
@@ -353,7 +346,7 @@ impl AsyncSmtpConnection {
                             response.code(),
                             Some(response.message().collect()),
                         ))
-                    }
+                    };
                 }
                 Err(nom::Err::Failure(e)) => {
                     return Err(error::response(e.to_string()));

src/transport/smtp/client/async_net.rs

@@ -11,8 +11,7 @@ use async_native_tls::TlsStream as AsyncStd1TlsStream;
 #[cfg(feature = "async-std1")]
 use async_std::net::{TcpStream as AsyncStd1TcpStream, ToSocketAddrs as AsyncStd1ToSocketAddrs};
 use futures_io::{
-    AsyncRead as FuturesAsyncRead, AsyncWrite as FuturesAsyncWrite, Error as IoError, ErrorKind,
-    Result as IoResult,
+    AsyncRead as FuturesAsyncRead, AsyncWrite as FuturesAsyncWrite, Result as IoResult,
 };
 #[cfg(feature = "async-std1-rustls-tls")]
 use futures_rustls::client::TlsStream as AsyncStd1RustlsTlsStream;
@@ -40,7 +39,7 @@ use tokio1_rustls::client::TlsStream as Tokio1RustlsTlsStream;
     feature = "async-std1-rustls-tls"
 ))]
 use super::InnerTlsParameters;
-use super::TlsParameters;
+use super::{ConnectionState, TlsParameters};
 #[cfg(feature = "tokio1")]
 use crate::transport::smtp::client::net::resolved_address_filter;
 use crate::transport::smtp::{error, Error};
@@ -49,6 +48,7 @@ use crate::transport::smtp::{error, Error};
 #[derive(Debug)]
 pub struct AsyncNetworkStream {
     inner: InnerAsyncNetworkStream,
+    state: ConnectionState,
 }
 
 #[cfg(feature = "tokio1")]
@@ -91,45 +91,43 @@ enum InnerAsyncNetworkStream {
     /// Encrypted Tokio 1.x TCP stream
     #[cfg(feature = "async-std1-rustls-tls")]
     AsyncStd1RustlsTls(AsyncStd1RustlsTlsStream<AsyncStd1TcpStream>),
-    /// Can't be built
-    None,
 }
 
 impl AsyncNetworkStream {
     fn new(inner: InnerAsyncNetworkStream) -> Self {
-        if let InnerAsyncNetworkStream::None = inner {
-            debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
+        AsyncNetworkStream {
+            inner,
+            state: ConnectionState::Ok,
         }
+    }
 
-        AsyncNetworkStream { inner }
+    pub(super) fn state(&self) -> ConnectionState {
+        self.state
+    }
+
+    pub(super) fn set_state(&mut self, state: ConnectionState) {
+        self.state = state;
     }
 
     /// Returns peer's address
     pub fn peer_addr(&self) -> IoResult<SocketAddr> {
-        match self.inner {
+        match &self.inner {
             #[cfg(feature = "tokio1")]
-            InnerAsyncNetworkStream::Tokio1Tcp(ref s) => s.peer_addr(),
+            InnerAsyncNetworkStream::Tokio1Tcp(s) => s.peer_addr(),
             #[cfg(feature = "tokio1-native-tls")]
-            InnerAsyncNetworkStream::Tokio1NativeTls(ref s) => {
+            InnerAsyncNetworkStream::Tokio1NativeTls(s) => {
                 s.get_ref().get_ref().get_ref().peer_addr()
             }
             #[cfg(feature = "tokio1-rustls-tls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(ref s) => s.get_ref().0.peer_addr(),
+            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => s.get_ref().0.peer_addr(),
             #[cfg(feature = "tokio1-boring-tls")]
-            InnerAsyncNetworkStream::Tokio1BoringTls(ref s) => s.get_ref().peer_addr(),
+            InnerAsyncNetworkStream::Tokio1BoringTls(s) => s.get_ref().peer_addr(),
             #[cfg(feature = "async-std1")]
-            InnerAsyncNetworkStream::AsyncStd1Tcp(ref s) => s.peer_addr(),
+            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => s.peer_addr(),
             #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref s) => s.get_ref().peer_addr(),
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => s.get_ref().peer_addr(),
             #[cfg(feature = "async-std1-rustls-tls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref s) => s.get_ref().0.peer_addr(),
-            InnerAsyncNetworkStream::None => {
-                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
-                Err(IoError::new(
-                    ErrorKind::Other,
-                    "InnerAsyncNetworkStream::None must never be built",
-                ))
-            }
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => s.get_ref().0.peer_addr(),
         }
     }
 
@@ -199,7 +197,7 @@ impl AsyncNetworkStream {
         let mut stream =
             AsyncNetworkStream::new(InnerAsyncNetworkStream::Tokio1Tcp(Box::new(tcp_stream)));
         if let Some(tls_parameters) = tls_parameters {
-            stream.upgrade_tls(tls_parameters).await?;
+            stream = stream.upgrade_tls(tls_parameters).await?;
         }
         Ok(stream)
     }
@@ -250,13 +248,13 @@ impl AsyncNetworkStream {
 
         let mut stream = AsyncNetworkStream::new(InnerAsyncNetworkStream::AsyncStd1Tcp(tcp_stream));
         if let Some(tls_parameters) = tls_parameters {
-            stream.upgrade_tls(tls_parameters).await?;
+            stream = stream.upgrade_tls(tls_parameters).await?;
         }
         Ok(stream)
     }
 
-    pub async fn upgrade_tls(&mut self, tls_parameters: TlsParameters) -> Result<(), Error> {
-        match &self.inner {
+    pub async fn upgrade_tls(self, tls_parameters: TlsParameters) -> Result<Self, Error> {
+        match self.inner {
             #[cfg(all(
                 feature = "tokio1",
                 not(any(
@@ -275,18 +273,14 @@ impl AsyncNetworkStream {
                 feature = "tokio1-rustls-tls",
                 feature = "tokio1-boring-tls"
             ))]
-            InnerAsyncNetworkStream::Tokio1Tcp(_) => {
-                // get owned TcpStream
-                let tcp_stream = mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);
-                let tcp_stream = match tcp_stream {
-                    InnerAsyncNetworkStream::Tokio1Tcp(tcp_stream) => tcp_stream,
-                    _ => unreachable!(),
-                };
-
-                self.inner = Self::upgrade_tokio1_tls(tcp_stream, tls_parameters)
+            InnerAsyncNetworkStream::Tokio1Tcp(tcp_stream) => {
+                let inner = Self::upgrade_tokio1_tls(tcp_stream, tls_parameters)
                     .await
                     .map_err(error::connection)?;
-                Ok(())
+                Ok(Self {
+                    inner,
+                    state: ConnectionState::Ok,
+                })
             }
             #[cfg(all(
                 feature = "async-std1",
@@ -298,20 +292,16 @@ impl AsyncNetworkStream {
             }
 
             #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
-            InnerAsyncNetworkStream::AsyncStd1Tcp(_) => {
-                // get owned TcpStream
-                let tcp_stream = mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);
-                let tcp_stream = match tcp_stream {
-                    InnerAsyncNetworkStream::AsyncStd1Tcp(tcp_stream) => tcp_stream,
-                    _ => unreachable!(),
-                };
-
-                self.inner = Self::upgrade_asyncstd1_tls(tcp_stream, tls_parameters)
+            InnerAsyncNetworkStream::AsyncStd1Tcp(tcp_stream) => {
+                let inner = Self::upgrade_asyncstd1_tls(tcp_stream, tls_parameters)
                     .await
                     .map_err(error::connection)?;
-                Ok(())
+                Ok(Self {
+                    inner,
+                    state: ConnectionState::Ok,
+                })
             }
-            _ => Ok(()),
+            _ => Ok(self),
         }
     }
 
@@ -445,7 +435,7 @@ impl AsyncNetworkStream {
     }
 
     pub fn is_encrypted(&self) -> bool {
-        match self.inner {
+        match &self.inner {
             #[cfg(feature = "tokio1")]
             InnerAsyncNetworkStream::Tokio1Tcp(_) => false,
             #[cfg(feature = "tokio1-native-tls")]
@@ -460,7 +450,6 @@ impl AsyncNetworkStream {
             InnerAsyncNetworkStream::AsyncStd1NativeTls(_) => true,
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(_) => true,
-            InnerAsyncNetworkStream::None => false,
         }
     }
 
@@ -509,7 +498,6 @@ impl AsyncNetworkStream {
                 .first()
                 .unwrap()
                 .to_vec()),
-            InnerAsyncNetworkStream::None => panic!("InnerNetworkStream::None must never be built"),
         }
     }
 }
@@ -520,9 +508,9 @@ impl FuturesAsyncRead for AsyncNetworkStream {
         cx: &mut Context<'_>,
         buf: &mut [u8],
     ) -> Poll<IoResult<usize>> {
-        match self.inner {
+        match &mut self.inner {
             #[cfg(feature = "tokio1")]
-            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => {
+            InnerAsyncNetworkStream::Tokio1Tcp(s) => {
                 let mut b = Tokio1ReadBuf::new(buf);
                 match Pin::new(s).poll_read(cx, &mut b) {
                     Poll::Ready(Ok(())) => Poll::Ready(Ok(b.filled().len())),
@@ -531,7 +519,7 @@ impl FuturesAsyncRead for AsyncNetworkStream {
                 }
             }
             #[cfg(feature = "tokio1-native-tls")]
-            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => {
+            InnerAsyncNetworkStream::Tokio1NativeTls(s) => {
                 let mut b = Tokio1ReadBuf::new(buf);
                 match Pin::new(s).poll_read(cx, &mut b) {
                     Poll::Ready(Ok(())) => Poll::Ready(Ok(b.filled().len())),
@@ -540,7 +528,7 @@ impl FuturesAsyncRead for AsyncNetworkStream {
                 }
             }
             #[cfg(feature = "tokio1-rustls-tls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => {
+            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => {
                 let mut b = Tokio1ReadBuf::new(buf);
                 match Pin::new(s).poll_read(cx, &mut b) {
                     Poll::Ready(Ok(())) => Poll::Ready(Ok(b.filled().len())),
@@ -549,7 +537,7 @@ impl FuturesAsyncRead for AsyncNetworkStream {
                 }
             }
             #[cfg(feature = "tokio1-boring-tls")]
-            InnerAsyncNetworkStream::Tokio1BoringTls(ref mut s) => {
+            InnerAsyncNetworkStream::Tokio1BoringTls(s) => {
                 let mut b = Tokio1ReadBuf::new(buf);
                 match Pin::new(s).poll_read(cx, &mut b) {
                     Poll::Ready(Ok(())) => Poll::Ready(Ok(b.filled().len())),
@@ -558,19 +546,11 @@ impl FuturesAsyncRead for AsyncNetworkStream {
                 }
             }
             #[cfg(feature = "async-std1")]
-            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_read(cx, buf),
+            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_read(cx, buf),
             #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => {
-                Pin::new(s).poll_read(cx, buf)
-            }
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_read(cx, buf),
             #[cfg(feature = "async-std1-rustls-tls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => {
-                Pin::new(s).poll_read(cx, buf)
-            }
-            InnerAsyncNetworkStream::None => {
-                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
-                Poll::Ready(Ok(0))
-            }
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_read(cx, buf),
         }
     }
 }
@@ -581,75 +561,61 @@ impl FuturesAsyncWrite for AsyncNetworkStream {
         cx: &mut Context<'_>,
         buf: &[u8],
     ) -> Poll<IoResult<usize>> {
-        match self.inner {
+        match &mut self.inner {
             #[cfg(feature = "tokio1")]
-            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            InnerAsyncNetworkStream::Tokio1Tcp(s) => Pin::new(s).poll_write(cx, buf),
             #[cfg(feature = "tokio1-native-tls")]
-            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            InnerAsyncNetworkStream::Tokio1NativeTls(s) => Pin::new(s).poll_write(cx, buf),
             #[cfg(feature = "tokio1-rustls-tls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => Pin::new(s).poll_write(cx, buf),
             #[cfg(feature = "tokio1-boring-tls")]
-            InnerAsyncNetworkStream::Tokio1BoringTls(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            InnerAsyncNetworkStream::Tokio1BoringTls(s) => Pin::new(s).poll_write(cx, buf),
             #[cfg(feature = "async-std1")]
-            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_write(cx, buf),
             #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => {
-                Pin::new(s).poll_write(cx, buf)
-            }
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_write(cx, buf),
             #[cfg(feature = "async-std1-rustls-tls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => {
-                Pin::new(s).poll_write(cx, buf)
-            }
-            InnerAsyncNetworkStream::None => {
-                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
-                Poll::Ready(Ok(0))
-            }
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_write(cx, buf),
         }
     }
 
     fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<IoResult<()>> {
-        match self.inner {
+        match &mut self.inner {
             #[cfg(feature = "tokio1")]
-            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::Tokio1Tcp(s) => Pin::new(s).poll_flush(cx),
             #[cfg(feature = "tokio1-native-tls")]
-            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::Tokio1NativeTls(s) => Pin::new(s).poll_flush(cx),
             #[cfg(feature = "tokio1-rustls-tls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => Pin::new(s).poll_flush(cx),
             #[cfg(feature = "tokio1-boring-tls")]
-            InnerAsyncNetworkStream::Tokio1BoringTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::Tokio1BoringTls(s) => Pin::new(s).poll_flush(cx),
             #[cfg(feature = "async-std1")]
-            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_flush(cx),
             #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_flush(cx),
             #[cfg(feature = "async-std1-rustls-tls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => Pin::new(s).poll_flush(cx),
-            InnerAsyncNetworkStream::None => {
-                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
-                Poll::Ready(Ok(()))
-            }
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_flush(cx),
         }
     }
 
     fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<IoResult<()>> {
-        match self.inner {
+        self.state = ConnectionState::Closed;
+
+        match &mut self.inner {
             #[cfg(feature = "tokio1")]
-            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            InnerAsyncNetworkStream::Tokio1Tcp(s) => Pin::new(s).poll_shutdown(cx),
             #[cfg(feature = "tokio1-native-tls")]
-            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            InnerAsyncNetworkStream::Tokio1NativeTls(s) => Pin::new(s).poll_shutdown(cx),
             #[cfg(feature = "tokio1-rustls-tls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => Pin::new(s).poll_shutdown(cx),
             #[cfg(feature = "tokio1-boring-tls")]
-            InnerAsyncNetworkStream::Tokio1BoringTls(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            InnerAsyncNetworkStream::Tokio1BoringTls(s) => Pin::new(s).poll_shutdown(cx),
             #[cfg(feature = "async-std1")]
-            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_close(cx),
+            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_close(cx),
             #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => Pin::new(s).poll_close(cx),
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_close(cx),
             #[cfg(feature = "async-std1-rustls-tls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => Pin::new(s).poll_close(cx),
-            InnerAsyncNetworkStream::None => {
-                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
-                Poll::Ready(Ok(()))
-            }
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_close(cx),
         }
     }
 }

src/transport/smtp/client/connection.rs

@@ -7,7 +7,7 @@ use std::{
 
 #[cfg(feature = "tracing")]
 use super::escape_crlf;
-use super::{ClientCodec, NetworkStream, TlsParameters};
+use super::{ClientCodec, ConnectionState, NetworkStream, TlsParameters};
 use crate::{
     address::Envelope,
     transport::smtp::{
@@ -20,25 +20,11 @@ use crate::{
     },
 };
 
-macro_rules! try_smtp (
-    ($err: expr, $client: ident) => ({
-        match $err {
-            Ok(val) => val,
-            Err(err) => {
-                $client.abort();
-                return Err(From::from(err))
-            },
-        }
-    })
-);
-
 /// Structure that implements the SMTP client
 pub struct SmtpConnection {
     /// TCP stream between client and server
     /// Value is None before connection
     stream: BufReader<NetworkStream>,
-    /// Panic state
-    panic: bool,
     /// Information about the server
     server_info: ServerInfo,
 }
@@ -65,7 +51,6 @@ impl SmtpConnection {
         let stream = BufReader::new(stream);
         let mut conn = SmtpConnection {
             stream,
-            panic: false,
             server_info: ServerInfo::default(),
         };
         conn.set_timeout(timeout).map_err(error::network)?;
@@ -110,26 +95,25 @@ impl SmtpConnection {
             mail_options.push(MailParameter::Body(MailBodyParameter::EightBitMime));
         }
 
-        try_smtp!(
-            self.command(Mail::new(envelope.from().cloned(), mail_options)),
-            self
-        );
+        self.command(Mail::new(envelope.from().cloned(), mail_options))?;
 
         // Recipient
         for to_address in envelope.to() {
-            try_smtp!(self.command(Rcpt::new(to_address.clone(), vec![])), self);
+            self.command(Rcpt::new(to_address.clone(), vec![]))?;
         }
 
         // Data
-        try_smtp!(self.command(Data), self);
+        self.command(Data)?;
 
         // Message content
-        let result = try_smtp!(self.message(email), self);
-        Ok(result)
+        self.message(email)
     }
 
     pub fn has_broken(&self) -> bool {
-        self.panic
+        match self.stream.get_ref().state() {
+            ConnectionState::Ok => false,
+            ConnectionState::Broken | ConnectionState::Closed => true,
+        }
     }
 
     pub fn can_starttls(&self) -> bool {
@@ -138,20 +122,22 @@ impl SmtpConnection {
 
     #[allow(unused_variables)]
     pub fn starttls(
-        &mut self,
+        mut self,
         tls_parameters: &TlsParameters,
         hello_name: &ClientId,
-    ) -> Result<(), Error> {
+    ) -> Result<Self, Error> {
         if self.server_info.supports_feature(Extension::StartTls) {
             #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
             {
-                try_smtp!(self.command(Starttls), self);
-                self.stream.get_mut().upgrade_tls(tls_parameters)?;
+                self.command(Starttls)?;
+                let stream = self.stream.into_inner();
+                let stream = stream.upgrade_tls(tls_parameters)?;
+                self.stream = BufReader::new(stream);
                 #[cfg(feature = "tracing")]
                 tracing::debug!("connection encrypted");
                 // Send EHLO again
-                try_smtp!(self.ehlo(hello_name), self);
-                Ok(())
+                self.ehlo(hello_name)?;
+                Ok(self)
             }
             #[cfg(not(any(
                 feature = "native-tls",
@@ -168,22 +154,24 @@ impl SmtpConnection {
 
     /// Send EHLO and update server info
     fn ehlo(&mut self, hello_name: &ClientId) -> Result<(), Error> {
-        let ehlo_response = try_smtp!(self.command(Ehlo::new(hello_name.clone())), self);
-        self.server_info = try_smtp!(ServerInfo::from_response(&ehlo_response), self);
+        let ehlo_response = self.command(Ehlo::new(hello_name.clone()))?;
+        self.server_info = ServerInfo::from_response(&ehlo_response)?;
         Ok(())
     }
 
     pub fn quit(&mut self) -> Result<Response, Error> {
-        Ok(try_smtp!(self.command(Quit), self))
+        self.command(Quit)
     }
 
     pub fn abort(&mut self) {
-        // Only try to quit if we are not already broken
-        if !self.panic {
-            self.panic = true;
-            let _ = self.command(Quit);
+        match self.stream.get_ref().state() {
+            ConnectionState::Ok | ConnectionState::Broken => {
+                let _ = self.command(Quit);
+                let _ = self.stream.get_mut().shutdown(std::net::Shutdown::Both);
+                self.stream.get_mut().set_state(ConnectionState::Closed);
+            }
+            ConnectionState::Closed => {}
         }
-        let _ = self.stream.get_mut().shutdown(std::net::Shutdown::Both);
     }
 
     /// Sets the underlying stream
@@ -224,14 +212,11 @@ impl SmtpConnection {
 
         while challenges > 0 && response.has_code(334) {
             challenges -= 1;
-            response = try_smtp!(
-                self.command(Auth::new_from_response(
-                    mechanism,
-                    credentials.clone(),
-                    &response,
-                )?),
-                self
-            );
+            response = self.command(Auth::new_from_response(
+                mechanism,
+                credentials.clone(),
+                &response,
+            )?)?;
         }
 
         if challenges == 0 {
@@ -260,12 +245,17 @@ impl SmtpConnection {
 
     /// Writes a string to the server
     fn write(&mut self, string: &[u8]) -> Result<(), Error> {
+        self.stream.get_ref().state().verify()?;
+        self.stream.get_mut().set_state(ConnectionState::Broken);
+
         self.stream
             .get_mut()
             .write_all(string)
             .map_err(error::network)?;
         self.stream.get_mut().flush().map_err(error::network)?;
 
+        self.stream.get_mut().set_state(ConnectionState::Ok);
+
         #[cfg(feature = "tracing")]
         tracing::debug!("Wrote: {}", escape_crlf(&String::from_utf8_lossy(string)));
         Ok(())
@@ -273,6 +263,9 @@ impl SmtpConnection {
 
     /// Gets the SMTP response
     pub fn read_response(&mut self) -> Result<Response, Error> {
+        self.stream.get_ref().state().verify()?;
+        self.stream.get_mut().set_state(ConnectionState::Broken);
+
         let mut buffer = String::with_capacity(100);
 
         while self.stream.read_line(&mut buffer).map_err(error::network)? > 0 {
@@ -280,6 +273,8 @@ impl SmtpConnection {
             tracing::debug!("<< {}", escape_crlf(&buffer));
             match parse_response(&buffer) {
                 Ok((_remaining, response)) => {
+                    self.stream.get_mut().set_state(ConnectionState::Ok);
+
                     return if response.is_positive() {
                         Ok(response)
                     } else {

src/transport/smtp/client/mod.rs

@@ -40,6 +40,7 @@ pub use self::{
     connection::SmtpConnection,
     tls::{Certificate, CertificateStore, Tls, TlsParameters, TlsParametersBuilder},
 };
+use super::{error, Error};
 
 #[cfg(any(feature = "tokio1", feature = "async-std1"))]
 mod async_connection;
@@ -49,6 +50,23 @@ mod connection;
 mod net;
 mod tls;
 
+#[derive(Debug, Copy, Clone)]
+enum ConnectionState {
+    Ok,
+    Broken,
+    Closed,
+}
+
+impl ConnectionState {
+    fn verify(&mut self) -> Result<(), Error> {
+        match self {
+            Self::Ok => Ok(()),
+            Self::Broken => Err(error::connection("connection broken")),
+            Self::Closed => Err(error::connection("connection closed")),
+        }
+    }
+}
+
 /// The codec used for transparency
 #[derive(Debug)]
 struct ClientCodec {

src/transport/smtp/client/net.rs

@@ -2,8 +2,7 @@
 use std::sync::Arc;
 use std::{
     io::{self, Read, Write},
-    mem,
-    net::{IpAddr, Ipv4Addr, Shutdown, SocketAddr, SocketAddrV4, TcpStream, ToSocketAddrs},
+    net::{IpAddr, Shutdown, SocketAddr, TcpStream, ToSocketAddrs},
     time::Duration,
 };
 
@@ -17,12 +16,13 @@ use socket2::{Domain, Protocol, Type};
 
 #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
 use super::InnerTlsParameters;
-use super::TlsParameters;
+use super::{ConnectionState, TlsParameters};
 use crate::transport::smtp::{error, Error};
 
 /// A network stream
 pub struct NetworkStream {
     inner: InnerNetworkStream,
+    state: ConnectionState,
 }
 
 /// Represents the different types of underlying network streams
@@ -40,53 +40,49 @@ enum InnerNetworkStream {
     RustlsTls(StreamOwned<ClientConnection, TcpStream>),
     #[cfg(feature = "boring-tls")]
     BoringTls(SslStream<TcpStream>),
-    /// Can't be built
-    None,
 }
 
 impl NetworkStream {
     fn new(inner: InnerNetworkStream) -> Self {
-        if let InnerNetworkStream::None = inner {
-            debug_assert!(false, "InnerNetworkStream::None must never be built");
+        NetworkStream {
+            inner,
+            state: ConnectionState::Ok,
         }
+    }
 
-        NetworkStream { inner }
+    pub(super) fn state(&self) -> ConnectionState {
+        self.state
+    }
+
+    pub(super) fn set_state(&mut self, state: ConnectionState) {
+        self.state = state;
     }
 
     /// Returns peer's address
     pub fn peer_addr(&self) -> io::Result<SocketAddr> {
-        match self.inner {
-            InnerNetworkStream::Tcp(ref s) => s.peer_addr(),
+        match &self.inner {
+            InnerNetworkStream::Tcp(s) => s.peer_addr(),
             #[cfg(feature = "native-tls")]
-            InnerNetworkStream::NativeTls(ref s) => s.get_ref().peer_addr(),
+            InnerNetworkStream::NativeTls(s) => s.get_ref().peer_addr(),
             #[cfg(feature = "rustls-tls")]
-            InnerNetworkStream::RustlsTls(ref s) => s.get_ref().peer_addr(),
+            InnerNetworkStream::RustlsTls(s) => s.get_ref().peer_addr(),
             #[cfg(feature = "boring-tls")]
-            InnerNetworkStream::BoringTls(ref s) => s.get_ref().peer_addr(),
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                Ok(SocketAddr::V4(SocketAddrV4::new(
-                    Ipv4Addr::new(127, 0, 0, 1),
-                    80,
-                )))
-            }
+            InnerNetworkStream::BoringTls(s) => s.get_ref().peer_addr(),
         }
     }
 
     /// Shutdowns the connection
-    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
-        match self.inner {
-            InnerNetworkStream::Tcp(ref s) => s.shutdown(how),
+    pub fn shutdown(&mut self, how: Shutdown) -> io::Result<()> {
+        self.state = ConnectionState::Closed;
+
+        match &self.inner {
+            InnerNetworkStream::Tcp(s) => s.shutdown(how),
             #[cfg(feature = "native-tls")]
-            InnerNetworkStream::NativeTls(ref s) => s.get_ref().shutdown(how),
+            InnerNetworkStream::NativeTls(s) => s.get_ref().shutdown(how),
             #[cfg(feature = "rustls-tls")]
-            InnerNetworkStream::RustlsTls(ref s) => s.get_ref().shutdown(how),
+            InnerNetworkStream::RustlsTls(s) => s.get_ref().shutdown(how),
             #[cfg(feature = "boring-tls")]
-            InnerNetworkStream::BoringTls(ref s) => s.get_ref().shutdown(how),
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                Ok(())
-            }
+            InnerNetworkStream::BoringTls(s) => s.get_ref().shutdown(how),
         }
     }
 
@@ -139,13 +135,13 @@ impl NetworkStream {
         let tcp_stream = try_connect(server, timeout, local_addr)?;
         let mut stream = NetworkStream::new(InnerNetworkStream::Tcp(tcp_stream));
         if let Some(tls_parameters) = tls_parameters {
-            stream.upgrade_tls(tls_parameters)?;
+            stream = stream.upgrade_tls(tls_parameters)?;
         }
         Ok(stream)
     }
 
-    pub fn upgrade_tls(&mut self, tls_parameters: &TlsParameters) -> Result<(), Error> {
-        match &self.inner {
+    pub fn upgrade_tls(self, tls_parameters: &TlsParameters) -> Result<Self, Error> {
+        match self.inner {
             #[cfg(not(any(
                 feature = "native-tls",
                 feature = "rustls-tls",
@@ -157,18 +153,14 @@ impl NetworkStream {
             }
 
             #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
-            InnerNetworkStream::Tcp(_) => {
-                // get owned TcpStream
-                let tcp_stream = mem::replace(&mut self.inner, InnerNetworkStream::None);
-                let tcp_stream = match tcp_stream {
-                    InnerNetworkStream::Tcp(tcp_stream) => tcp_stream,
-                    _ => unreachable!(),
-                };
-
-                self.inner = Self::upgrade_tls_impl(tcp_stream, tls_parameters)?;
-                Ok(())
+            InnerNetworkStream::Tcp(tcp_stream) => {
+                let inner = Self::upgrade_tls_impl(tcp_stream, tls_parameters)?;
+                Ok(Self {
+                    inner,
+                    state: ConnectionState::Ok,
+                })
             }
-            _ => Ok(()),
+            _ => Ok(self),
         }
     }
 
@@ -208,7 +200,7 @@ impl NetworkStream {
     }
 
     pub fn is_encrypted(&self) -> bool {
-        match self.inner {
+        match &self.inner {
             InnerNetworkStream::Tcp(_) => false,
             #[cfg(feature = "native-tls")]
             InnerNetworkStream::NativeTls(_) => true,
@@ -216,10 +208,6 @@ impl NetworkStream {
             InnerNetworkStream::RustlsTls(_) => true,
             #[cfg(feature = "boring-tls")]
             InnerNetworkStream::BoringTls(_) => true,
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                false
-            }
         }
     }
 
@@ -249,105 +237,72 @@ impl NetworkStream {
                 .unwrap()
                 .to_der()
                 .map_err(error::tls)?),
-            InnerNetworkStream::None => panic!("InnerNetworkStream::None must never be built"),
         }
     }
 
     pub fn set_read_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
-        match self.inner {
-            InnerNetworkStream::Tcp(ref mut stream) => stream.set_read_timeout(duration),
+        match &mut self.inner {
+            InnerNetworkStream::Tcp(stream) => stream.set_read_timeout(duration),
             #[cfg(feature = "native-tls")]
-            InnerNetworkStream::NativeTls(ref mut stream) => {
-                stream.get_ref().set_read_timeout(duration)
-            }
+            InnerNetworkStream::NativeTls(stream) => stream.get_ref().set_read_timeout(duration),
             #[cfg(feature = "rustls-tls")]
-            InnerNetworkStream::RustlsTls(ref mut stream) => {
-                stream.get_ref().set_read_timeout(duration)
-            }
+            InnerNetworkStream::RustlsTls(stream) => stream.get_ref().set_read_timeout(duration),
             #[cfg(feature = "boring-tls")]
-            InnerNetworkStream::BoringTls(ref mut stream) => {
-                stream.get_ref().set_read_timeout(duration)
-            }
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                Ok(())
-            }
+            InnerNetworkStream::BoringTls(stream) => stream.get_ref().set_read_timeout(duration),
         }
     }
 
     /// Set write timeout for IO calls
     pub fn set_write_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
-        match self.inner {
-            InnerNetworkStream::Tcp(ref mut stream) => stream.set_write_timeout(duration),
+        match &mut self.inner {
+            InnerNetworkStream::Tcp(stream) => stream.set_write_timeout(duration),
 
             #[cfg(feature = "native-tls")]
-            InnerNetworkStream::NativeTls(ref mut stream) => {
-                stream.get_ref().set_write_timeout(duration)
-            }
+            InnerNetworkStream::NativeTls(stream) => stream.get_ref().set_write_timeout(duration),
             #[cfg(feature = "rustls-tls")]
-            InnerNetworkStream::RustlsTls(ref mut stream) => {
-                stream.get_ref().set_write_timeout(duration)
-            }
+            InnerNetworkStream::RustlsTls(stream) => stream.get_ref().set_write_timeout(duration),
             #[cfg(feature = "boring-tls")]
-            InnerNetworkStream::BoringTls(ref mut stream) => {
-                stream.get_ref().set_write_timeout(duration)
-            }
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                Ok(())
-            }
+            InnerNetworkStream::BoringTls(stream) => stream.get_ref().set_write_timeout(duration),
         }
     }
 }
 
 impl Read for NetworkStream {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        match self.inner {
-            InnerNetworkStream::Tcp(ref mut s) => s.read(buf),
+        match &mut self.inner {
+            InnerNetworkStream::Tcp(s) => s.read(buf),
             #[cfg(feature = "native-tls")]
-            InnerNetworkStream::NativeTls(ref mut s) => s.read(buf),
+            InnerNetworkStream::NativeTls(s) => s.read(buf),
             #[cfg(feature = "rustls-tls")]
-            InnerNetworkStream::RustlsTls(ref mut s) => s.read(buf),
+            InnerNetworkStream::RustlsTls(s) => s.read(buf),
             #[cfg(feature = "boring-tls")]
-            InnerNetworkStream::BoringTls(ref mut s) => s.read(buf),
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                Ok(0)
-            }
+            InnerNetworkStream::BoringTls(s) => s.read(buf),
         }
     }
 }
 
 impl Write for NetworkStream {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        match self.inner {
-            InnerNetworkStream::Tcp(ref mut s) => s.write(buf),
+        match &mut self.inner {
+            InnerNetworkStream::Tcp(s) => s.write(buf),
             #[cfg(feature = "native-tls")]
-            InnerNetworkStream::NativeTls(ref mut s) => s.write(buf),
+            InnerNetworkStream::NativeTls(s) => s.write(buf),
             #[cfg(feature = "rustls-tls")]
-            InnerNetworkStream::RustlsTls(ref mut s) => s.write(buf),
+            InnerNetworkStream::RustlsTls(s) => s.write(buf),
             #[cfg(feature = "boring-tls")]
-            InnerNetworkStream::BoringTls(ref mut s) => s.write(buf),
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                Ok(0)
-            }
+            InnerNetworkStream::BoringTls(s) => s.write(buf),
         }
     }
 
     fn flush(&mut self) -> io::Result<()> {
-        match self.inner {
-            InnerNetworkStream::Tcp(ref mut s) => s.flush(),
+        match &mut self.inner {
+            InnerNetworkStream::Tcp(s) => s.flush(),
             #[cfg(feature = "native-tls")]
-            InnerNetworkStream::NativeTls(ref mut s) => s.flush(),
+            InnerNetworkStream::NativeTls(s) => s.flush(),
             #[cfg(feature = "rustls-tls")]
-            InnerNetworkStream::RustlsTls(ref mut s) => s.flush(),
+            InnerNetworkStream::RustlsTls(s) => s.flush(),
             #[cfg(feature = "boring-tls")]
-            InnerNetworkStream::BoringTls(ref mut s) => s.flush(),
-            InnerNetworkStream::None => {
-                debug_assert!(false, "InnerNetworkStream::None must never be built");
-                Ok(())
-            }
+            InnerNetworkStream::BoringTls(s) => s.flush(),
         }
     }
 }

src/transport/smtp/error.rs

@@ -119,7 +119,7 @@ impl fmt::Debug for Error {
 
         builder.field("kind", &self.inner.kind);
 
-        if let Some(ref source) = self.inner.source {
+        if let Some(source) = &self.inner.source {
             builder.field("source", source);
         }
 
@@ -129,22 +129,22 @@ impl fmt::Debug for Error {
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self.inner.kind {
+        match &self.inner.kind {
             Kind::Response => f.write_str("response error")?,
             Kind::Client => f.write_str("internal client error")?,
             Kind::Network => f.write_str("network error")?,
             Kind::Connection => f.write_str("Connection error")?,
             #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
             Kind::Tls => f.write_str("tls error")?,
-            Kind::Transient(ref code) => {
+            Kind::Transient(code) => {
                 write!(f, "transient error ({code})")?;
             }
-            Kind::Permanent(ref code) => {
+            Kind::Permanent(code) => {
                 write!(f, "permanent error ({code})")?;
             }
         };
 
-        if let Some(ref e) = self.inner.source {
+        if let Some(e) = &self.inner.source {
             write!(f, ": {e}")?;
         }
 

src/transport/smtp/extension.rs

@@ -4,7 +4,6 @@ use std::{
     collections::HashSet,
     fmt::{self, Display, Formatter},
     net::{Ipv4Addr, Ipv6Addr},
-    result::Result,
 };
 
 use crate::transport::smtp::{
@@ -53,10 +52,10 @@ impl Default for ClientId {
 
 impl Display for ClientId {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match *self {
-            Self::Domain(ref value) => f.write_str(value),
-            Self::Ipv4(ref value) => write!(f, "[{value}]"),
-            Self::Ipv6(ref value) => write!(f, "[IPv6:{value}]"),
+        match self {
+            Self::Domain(value) => f.write_str(value),
+            Self::Ipv4(value) => write!(f, "[{value}]"),
+            Self::Ipv6(value) => write!(f, "[IPv6:{value}]"),
         }
     }
 }
@@ -93,11 +92,11 @@ pub enum Extension {
 
 impl Display for Extension {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match *self {
+        match self {
             Extension::EightBitMime => f.write_str("8BITMIME"),
             Extension::SmtpUtfEight => f.write_str("SMTPUTF8"),
             Extension::StartTls => f.write_str("STARTTLS"),
-            Extension::Authentication(ref mechanism) => write!(f, "AUTH {mechanism}"),
+            Extension::Authentication(mechanism) => write!(f, "AUTH {mechanism}"),
         }
     }
 }
@@ -227,16 +226,16 @@ pub enum MailParameter {
 
 impl Display for MailParameter {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match *self {
-            MailParameter::Body(ref value) => write!(f, "BODY={value}"),
+        match self {
+            MailParameter::Body(value) => write!(f, "BODY={value}"),
             MailParameter::Size(size) => write!(f, "SIZE={size}"),
             MailParameter::SmtpUtfEight => f.write_str("SMTPUTF8"),
             MailParameter::Other {
-                ref keyword,
-                value: Some(ref value),
+                keyword,
+                value: Some(value),
             } => write!(f, "{}={}", keyword, XText(value)),
             MailParameter::Other {
-                ref keyword,
+                keyword,
                 value: None,
             } => f.write_str(keyword),
         }
@@ -277,13 +276,13 @@ pub enum RcptParameter {
 
 impl Display for RcptParameter {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        match *self {
+        match &self {
             RcptParameter::Other {
-                ref keyword,
-                value: Some(ref value),
+                keyword,
+                value: Some(value),
             } => write!(f, "{keyword}={}", XText(value)),
             RcptParameter::Other {
-                ref keyword,
+                keyword,
                 value: None,
             } => f.write_str(keyword),
         }

src/transport/smtp/response.rs

@@ -5,7 +5,6 @@ use std::{
     fmt::{Display, Formatter, Result},
     result,
     str::FromStr,
-    string::ToString,
 };
 
 use nom::{

src/transport/smtp/transport.rs

@@ -317,9 +317,9 @@ impl SmtpClient {
     /// Handles encryption and authentication
     pub fn connection(&self) -> Result<SmtpConnection, Error> {
         #[allow(clippy::match_single_binding)]
-        let tls_parameters = match self.info.tls {
+        let tls_parameters = match &self.info.tls {
             #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
-            Tls::Wrapper(ref tls_parameters) => Some(tls_parameters),
+            Tls::Wrapper(tls_parameters) => Some(tls_parameters),
             _ => None,
         };
 
@@ -333,14 +333,14 @@ impl SmtpClient {
         )?;
 
         #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
-        match self.info.tls {
-            Tls::Opportunistic(ref tls_parameters) => {
+        match &self.info.tls {
+            Tls::Opportunistic(tls_parameters) => {
                 if conn.can_starttls() {
-                    conn.starttls(tls_parameters, &self.info.hello_name)?;
+                    conn = conn.starttls(tls_parameters, &self.info.hello_name)?;
                 }
             }
-            Tls::Required(ref tls_parameters) => {
-                conn.starttls(tls_parameters, &self.info.hello_name)?;
+            Tls::Required(tls_parameters) => {
+                conn = conn.starttls(tls_parameters, &self.info.hello_name)?;
             }
             _ => (),
         }