Some other clippy suggestions

Author: Mingun

src/escape.rs

@@ -2183,7 +2183,8 @@ mod normalization {
                     if ch == '\u{0085}' {
                         assert_eq!(normalize_xml11_eols(input), "\n", "{}", description);
                     } else {
-                        let mut expected = utf8.clone();
+                        // utf8 is copied, because [u8; 3] implements Copy
+                        let mut expected = utf8;
                         expected[0] = b'\n';
                         let expected = std::str::from_utf8(&expected).expect(&description);
                         assert_eq!(normalize_xml11_eols(input), expected, "{}", description);

src/reader/state.rs

@@ -239,7 +239,7 @@ impl ReaderState {
     ///
     /// Returns `Decl` or `PI` event
     pub fn emit_question_mark<'b>(&mut self, buf: &'b [u8]) -> Result<Event<'b>> {
-        debug_assert!(buf.len() > 0);
+        debug_assert!(!buf.is_empty());
         debug_assert_eq!(buf[0], b'?');
 
         let len = buf.len();

src/se/element.rs

@@ -551,7 +551,7 @@ impl<'w, 'k, W: Write> SerializeMap for Map<'w, 'k, W> {
     where
         T: ?Sized + Serialize,
     {
-        if let Some(_) = self.key.take() {
+        if self.key.take().is_some() {
             return Err(SeError::Custom(
                 "calling `serialize_key` twice without `serialize_value`".to_string(),
             ));

src/se/mod.rs

@@ -638,7 +638,7 @@ impl<'w, 'r, W: Write> Serializer<'w, 'r, W> {
                 allow_primitive: true,
                 expand_empty_elements: false,
             },
-            root_tag: root_tag.map(|tag| XmlName::try_from(tag)).transpose()?,
+            root_tag: root_tag.map(XmlName::try_from).transpose()?,
         })
     }
 

src/se/simple_type.rs

@@ -61,7 +61,7 @@ where
             if let Some(part) = it.next() {
                 writer.write_str(part)?;
             }
-            while let Some(part) = it.next() {
+            for part in it {
                 writer.write_str("]]><![CDATA[")?;
                 writer.write_str(part)?;
             }

tests/serde_helpers/mod.rs

@@ -17,7 +17,7 @@ where
     let result = T::deserialize(&mut de);
 
     // If type was deserialized, the whole XML document should be consumed
-    if let Ok(_) = result {
+    if result.is_ok() {
         de.check_eof_reached();
     }