refactor: eliminate indexing and slicing

src/codec.rs

@@ -53,12 +53,14 @@ impl ClientCodec {
                     }
                     if self.escape_count == 3 {
                         self.escape_count = 0;
-                        buf.write_all(&frame[start..idx]).await?;
+                        buf.write_all(frame.get(start..idx).unwrap_or_default())
+                            .await?;
                         buf.write_all(b".").await?;
                         start = idx;
                     }
                 }
-                buf.write_all(&frame[start..]).await?;
+                buf.write_all(frame.get(start..).unwrap_or_default())
+                    .await?;
                 Ok(())
             }
         }

src/extension.rs

@@ -144,7 +144,7 @@ impl ServerInfo {
                     features.insert(Extension::StartTls);
                 }
                 Some("AUTH") => {
-                    for &mechanism in &split[1..] {
+                    for &mechanism in split.iter().skip(1) {
                         match mechanism {
                             "PLAIN" => {
                                 features.insert(Extension::Authentication(Mechanism::Plain));

src/lib.rs

@@ -21,7 +21,11 @@
     unused_import_braces,
     missing_debug_implementations,
     missing_docs,
-    clippy::explicit_iter_loop
+    clippy::explicit_iter_loop,
+    clippy::unwrap_used,
+    clippy::expect_used,
+    clippy::indexing_slicing,
+    clippy::string_slice
 )]
 
 #[cfg(not(any(feature = "runtime-tokio", feature = "runtime-async-std")))]

src/util.rs

@@ -10,22 +10,14 @@ pub struct XText<'a>(pub &'a str);
 
 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 == '=') {
-            let (start, end) = rest.split_at(idx);
-            f.write_str(start)?;
-
-            let mut end_iter = end.char_indices();
-            let (_, c) = end_iter.next().expect("char");
-            write!(f, "+{:X}", c as u8)?;
-
-            if let Some((idx, _)) = end_iter.next() {
-                rest = &end[idx..];
+        for c in self.0.chars() {
+            if c < '!' || c == '+' || c == '=' {
+                write!(f, "+{:X}", c as u8)?;
             } else {
-                rest = "";
+                write!(f, "{c}")?;
             }
         }
-        f.write_str(rest)
+        Ok(())
     }
 }