Debloat the binary by using less AsRef arguments

Using `impl AsRef<str>` as the argument instead of `&str` makes it
possible to call the function with `&str`, `String` and other types
that implement `AsRef` trait.

The cost of it is that compiled binary contains mulitple versions of
the same function, one for each variant of types. If function contains
multiple generic `impl AsRef` arguments, the number of versions possibly
compiled into binary grows exponentially with the number of arguments.

Simple way to avoid it is to call `.as_ref()` on the caller side to
convert the argument to `&str`. In most cases even adding a `&` and
relying on `Deref` coercion is sufficient.

This patch changes many functions that accepted `impl AsRef<str>` and
`impl AsRef<Path>` to accept `&str` and `&Path` instead.

In some places `.clone()` calls are removed. Calling `.clone()` on
`String` and passing `String` to a function accepting `impl
AsRef<str>` is completely unnecessary as `&str` reference could be
passed instead. There is no clippy warning against it yet, but
changing argument type to `&str` allowed to find these cases.

The result of debloating is not impressive, several hundred kilobytes
are saved, which is about 3% of the `.so` binary, but the code is
cleaner too.

src/imap/client.rs

@@ -32,10 +32,10 @@ impl DerefMut for Client {
 }
 
 impl Client {
-    pub async fn login<U: AsRef<str>, P: AsRef<str>>(
+    pub async fn login(
         self,
-        username: U,
-        password: P,
+        username: &str,
+        password: &str,
     ) -> std::result::Result<Session, (ImapError, Self)> {
         let Client { inner, is_secure } = self;
         let session = inner
@@ -53,10 +53,10 @@ impl Client {
         Ok(Session { inner: session })
     }
 
-    pub async fn authenticate<A: async_imap::Authenticator, S: AsRef<str>>(
+    pub async fn authenticate(
         self,
-        auth_type: S,
-        authenticator: A,
+        auth_type: &str,
+        authenticator: impl async_imap::Authenticator,
     ) -> std::result::Result<Session, (ImapError, Self)> {
         let Client { inner, is_secure } = self;
         let session =
@@ -75,15 +75,14 @@ impl Client {
         Ok(Session { inner: session })
     }
 
-    pub async fn connect_secure<A: net::ToSocketAddrs, S: AsRef<str>>(
-        addr: A,
-        domain: S,
+    pub async fn connect_secure(
+        addr: impl net::ToSocketAddrs,
+        domain: &str,
         strict_tls: bool,
     ) -> ImapResult<Self> {
         let stream = TcpStream::connect(addr).await?;
         let tls = dc_build_tls(strict_tls);
-        let tls_stream: Box<dyn SessionStream> =
-            Box::new(tls.connect(domain.as_ref(), stream).await?);
+        let tls_stream: Box<dyn SessionStream> = Box::new(tls.connect(domain, stream).await?);
         let mut client = ImapClient::new(tls_stream);
 
         let _greeting = client
@@ -97,7 +96,7 @@ impl Client {
         })
     }
 
-    pub async fn connect_insecure<A: net::ToSocketAddrs>(addr: A) -> ImapResult<Self> {
+    pub async fn connect_insecure(addr: impl net::ToSocketAddrs) -> ImapResult<Self> {
         let stream: Box<dyn SessionStream> = Box::new(TcpStream::connect(addr).await?);
 
         let mut client = ImapClient::new(stream);
@@ -112,7 +111,7 @@ impl Client {
         })
     }
 
-    pub async fn secure<S: AsRef<str>>(self, domain: S, strict_tls: bool) -> ImapResult<Client> {
+    pub async fn secure(self, domain: &str, strict_tls: bool) -> ImapResult<Client> {
         if self.is_secure {
             Ok(self)
         } else {
@@ -121,7 +120,7 @@ impl Client {
             inner.run_command_and_check_ok("STARTTLS", None).await?;
 
             let stream = inner.into_inner();
-            let ssl_stream = tls.connect(domain.as_ref(), stream).await?;
+            let ssl_stream = tls.connect(domain, stream).await?;
             let boxed: Box<dyn SessionStream> = Box::new(ssl_stream);
 
             Ok(Client {

src/imap/idle.rs

@@ -27,7 +27,7 @@ impl Imap {
         }
         self.setup_handle(context).await?;
 
-        self.select_folder(context, watch_folder.clone()).await?;
+        self.select_folder(context, watch_folder.as_deref()).await?;
 
         let timeout = Duration::from_secs(23 * 60);
         let mut info = Default::default();

src/imap/select_folder.rs

@@ -62,10 +62,10 @@ impl Imap {
     /// select a folder, possibly update uid_validity and, if needed,
     /// expunge the folder to remove delete-marked messages.
     /// Returns whether a new folder was selected.
-    pub(super) async fn select_folder<S: AsRef<str>>(
+    pub(super) async fn select_folder(
         &mut self,
         context: &Context,
-        folder: Option<S>,
+        folder: Option<&str>,
     ) -> Result<NewlySelected> {
         if self.session.is_none() {
             self.config.selected_folder = None;
@@ -76,9 +76,9 @@ impl Imap {
 
         // if there is a new folder and the new folder is equal to the selected one, there's nothing to do.
         // if there is _no_ new folder, we continue as we might want to expunge below.
-        if let Some(ref folder) = folder {
+        if let Some(folder) = folder {
             if let Some(ref selected_folder) = self.config.selected_folder {
-                if folder.as_ref() == selected_folder {
+                if folder == selected_folder {
                     return Ok(NewlySelected::No);
                 }
             }
@@ -88,7 +88,7 @@ impl Imap {
         self.maybe_close_folder(context).await?;
 
         // select new folder
-        if let Some(ref folder) = folder {
+        if let Some(folder) = folder {
             if let Some(ref mut session) = &mut self.session {
                 let res = session.select(folder).await;
 
@@ -98,7 +98,7 @@ impl Imap {
 
                 match res {
                     Ok(mailbox) => {
-                        self.config.selected_folder = Some(folder.as_ref().to_string());
+                        self.config.selected_folder = Some(folder.to_string());
                         self.config.selected_mailbox = Some(mailbox);
                         Ok(NewlySelected::Yes)
                     }
@@ -108,7 +108,7 @@ impl Imap {
                         Err(Error::ConnectionLost)
                     }
                     Err(async_imap::error::Error::Validate(_)) => {
-                        Err(Error::BadFolderName(folder.as_ref().to_string()))
+                        Err(Error::BadFolderName(folder.to_string()))
                     }
                     Err(err) => {
                         self.config.selected_folder = None;