fix more clippy warnings:

clippy::options_as_ref_deref
clippy::or_fun_call
clippy::clone_on_copy
clippy::redundant_clone
clippy::redundant_closure
clippy::needless_return

Author: matthiaskrgr

src/config/file_lines.rs

@@ -332,7 +332,7 @@ impl str::FromStr for FileLines {
         let mut m = HashMap::new();
         for js in v {
             let (s, r) = JsonSpan::into_tuple(js)?;
-            m.entry(s).or_insert_with(|| vec![]).push(r);
+            m.entry(s).or_insert_with(Vec::new).push(r);
         }
         Ok(FileLines::from_ranges(m))
     }

src/format_report_formatter.rs

@@ -68,7 +68,7 @@ impl<'a> Display for FormatReportFormatter<'a> {
                 let slice = Slice {
                     source: error.line_str().unwrap_or(""),
                     line_start: error.line_num().unwrap_or(0),
-                    origin: origin.as_ref().map(|s| s.as_str()),
+                    origin: origin.as_deref(),
                     fold: false,
                     annotations: slice_annotation(error).into_iter().collect(),
                 };

src/formatting.rs

@@ -215,9 +215,9 @@ fn format_file(
     // source map instead of hitting the file system.
     let original_text = match original_snippet {
         Some(snippet) => snippet,
-        None => std::fs::read_to_string(path.as_path().ok_or(OperationError::IoError(
-            std::io::Error::from(std::io::ErrorKind::InvalidInput),
-        ))?)?,
+        None => std::fs::read_to_string(path.as_path().ok_or_else(|| {
+            OperationError::IoError(std::io::Error::from(std::io::ErrorKind::InvalidInput))
+        })?)?,
     };
     apply_newline_style(config.newline_style(), &mut visitor.buffer, &original_text);
 

src/formatting/comment.rs

@@ -885,7 +885,7 @@ fn is_table_item(mut s: &str) -> bool {
     // This function may return false positive, but should get its job done in most cases (i.e.
     // markdown tables with two column delimiters).
     s = s.trim_start();
-    return s.starts_with('|') && !matches!(s.rfind('|'), Some(0) | None);
+    s.starts_with('|') && !matches!(s.rfind('|'), Some(0) | None)
 }
 
 /// Given the span, rewrite the missing comment inside it if available.

src/formatting/expr.rs

@@ -527,7 +527,7 @@ pub(crate) fn rewrite_block_with_visitor(
 
     let inner_attrs = attrs.map(inner_attributes);
     let label_str = rewrite_label(label);
-    visitor.visit_block(block, inner_attrs.as_ref().map(|a| &**a), has_braces);
+    visitor.visit_block(block, inner_attrs.as_deref(), has_braces);
     let visitor_context = visitor.get_context();
     context
         .skipped_range

src/formatting/generated.rs

@@ -12,11 +12,11 @@ pub(super) fn is_generated_file(file_name: &FileName, original_snippet: Option<&
         FileName::Stdin => original_snippet
             .and_then(|s| s.lines().next())
             .map(str::to_owned)
-            .unwrap_or("".to_owned()),
+            .unwrap_or_default(),
         FileName::Real(ref path) => fs::File::open(path)
             .ok()
             .and_then(|f| io::BufReader::new(f).lines().next()?.ok())
-            .unwrap_or("".to_owned()),
+            .unwrap_or_default(),
     };
 
     is_comment_with_generated_notation(&first_line)

src/formatting/imports.rs

@@ -540,7 +540,7 @@ impl UseTree {
     }
 
     fn flatten(self) -> Vec<UseTree> {
-        match self.path.clone().last() {
+        match self.path.last() {
             Some(UseSegment::List(list)) => {
                 if list.len() == 1 && list[0].path.len() == 1 {
                     if let UseSegment::Slf(..) = list[0].path[0] {

src/formatting/report.rs

@@ -65,7 +65,7 @@ impl FormatResult {
 
     /// Return the newline style used to format the result.
     pub fn newline_style(&self) -> NewlineStyle {
-        self.newline_style.clone()
+        self.newline_style
     }
 
     pub fn original_text(&self) -> &str {

src/formatting/syntux/parser.rs

@@ -116,7 +116,7 @@ impl<'a> Parser<'a> {
                     if sess.can_reset_errors() {
                         sess.reset_errors();
                     }
-                    return None;
+                    None
                 }
             }
         }));
@@ -194,8 +194,7 @@ impl<'a> Parser<'a> {
         mac: &'a ast::MacCall,
     ) -> Result<Vec<ast::Item>, &'static str> {
         let token_stream = mac.args.inner_tokens();
-        let mut parser =
-            rustc_parse::stream_to_parser(sess.inner(), token_stream.clone(), Some(""));
+        let mut parser = rustc_parse::stream_to_parser(sess.inner(), token_stream, Some(""));
         let mut items = vec![];
         let mut process_if_cfg = true;
 

src/result.rs

@@ -54,7 +54,7 @@ impl FormatError {
 
     /// Return the content of the line on which this error arose.
     pub fn line_str(&self) -> Option<&str> {
-        self.line_str.as_ref().map(|s| s.as_str())
+        self.line_str.as_deref()
     }
 
     pub(crate) fn new(kind: ErrorKind, line_num: usize, line_str: String) -> Self {