fixes suggested by nightly version of clippy

build.rs

@@ -18,7 +18,7 @@ pub fn main() {
 
     let out_dir = env::var("OUT_DIR").unwrap();
     // println!("cargo:warning=out_dir={}", out_dir);
-    let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap().replace("\\", "/");
+    let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap().replace('\\', "/");
     // println!("cargo:warning=manifest_dir={}", manifest_dir);
     let util_tests_dir = format!("{}/tests/by-util", manifest_dir);
     // println!("cargo:warning=util_tests_dir={}", util_tests_dir);

src/uu/ln/src/ln.rs

@@ -462,7 +462,7 @@ fn numbered_backup_path(path: &Path) -> PathBuf {
 }
 
 fn existing_backup_path(path: &Path, suffix: &str) -> PathBuf {
-    let test_path = simple_backup_path(path, &".~1~".to_owned());
+    let test_path = simple_backup_path(path, ".~1~");
     if test_path.exists() {
         return numbered_backup_path(path);
     }

src/uu/numfmt/src/format.rs

@@ -45,13 +45,13 @@ impl<'a> Iterator for WhitespaceSplitter<'a> {
         let (prefix, field) = haystack.split_at(
             haystack
                 .find(|c: char| !c.is_whitespace())
-                .unwrap_or_else(|| haystack.len()),
+                .unwrap_or(haystack.len()),
         );
 
         let (field, rest) = field.split_at(
             field
                 .find(|c: char| c.is_whitespace())
-                .unwrap_or_else(|| field.len()),
+                .unwrap_or(field.len()),
         );
 
         self.s = if !rest.is_empty() { Some(rest) } else { None };
@@ -269,7 +269,7 @@ fn format_and_print_whitespace(s: &str, options: &NumfmtOptions) -> Result<()> {
                 print!(" ");
                 &prefix[1..]
             } else {
-                &prefix
+                prefix
             };
 
             let implicit_padding = if !empty_prefix && options.padding == 0 {

src/uu/paste/src/paste.rs

@@ -151,5 +151,5 @@ fn unescape(s: String) -> String {
     s.replace("\\n", "\n")
         .replace("\\t", "\t")
         .replace("\\\\", "\\")
-        .replace("\\", "")
+        .replace('\\', "")
 }

src/uu/pr/src/pr.rs

@@ -916,8 +916,7 @@ fn read_stream_and_create_pages(
 
     Box::new(
         lines
-            .map(split_lines_if_form_feed)
-            .flatten()
+            .flat_map(split_lines_if_form_feed)
             .enumerate()
             .map(move |(i, line)| FileLine {
                 line_number: i + start_line_number,
@@ -982,20 +981,18 @@ fn mpr(paths: &[String], options: &OutputOptions) -> Result<i32, PrError> {
         .map(|(i, path)| {
             let lines = BufReader::with_capacity(READ_BUFFER_SIZE, open(path).unwrap()).lines();
 
-            read_stream_and_create_pages(options, lines, i)
-                .map(move |(x, line)| {
-                    let file_line = line;
-                    let page_number = x + 1;
-                    file_line
-                        .into_iter()
-                        .map(|fl| FileLine {
-                            page_number,
-                            group_key: page_number * n_files + fl.file_id,
-                            ..fl
-                        })
-                        .collect::<Vec<_>>()
-                })
-                .flatten()
+            read_stream_and_create_pages(options, lines, i).flat_map(move |(x, line)| {
+                let file_line = line;
+                let page_number = x + 1;
+                file_line
+                    .into_iter()
+                    .map(|fl| FileLine {
+                        page_number,
+                        group_key: page_number * n_files + fl.file_id,
+                        ..fl
+                    })
+                    .collect::<Vec<_>>()
+            })
         })
         .kmerge_by(|a, b| {
             if a.group_key == b.group_key {

src/uu/ptx/src/ptx.rs

@@ -526,7 +526,7 @@ fn format_tex_line(
 }
 
 fn format_roff_field(s: &str) -> String {
-    s.replace("\"", "\"\"")
+    s.replace('\"', "\"\"")
 }
 
 fn format_roff_line(

src/uucore/src/lib/features/encoding.rs

@@ -125,11 +125,13 @@ impl<R: Read> Data<R> {
         }
     }
 
+    #[must_use]
     pub fn line_wrap(mut self, wrap: usize) -> Self {
         self.line_wrap = wrap;
         self
     }
 
+    #[must_use]
     pub fn ignore_garbage(mut self, ignore: bool) -> Self {
         self.ignore_garbage = ignore;
         self