diff --git a/src/tools/expand-yaml-anchors/src/main.rs b/src/tools/expand-yaml-anchors/src/main.rs
index d8dad8fc789..f7ff64036a1 100644
--- a/src/tools/expand-yaml-anchors/src/main.rs
+++ b/src/tools/expand-yaml-anchors/src/main.rs
@@ -48,8 +48,8 @@ impl App {
         // Parse CLI arguments
         let args = std::env::args().skip(1).collect::<Vec<_>>();
         let (mode, base) = match args.iter().map(|s| s.as_str()).collect::<Vec<_>>().as_slice() {
-            &["generate", ref base] => (Mode::Generate, PathBuf::from(base)),
-            &["check", ref base] => (Mode::Check, PathBuf::from(base)),
+            ["generate", ref base] => (Mode::Generate, PathBuf::from(base)),
+            ["check", ref base] => (Mode::Check, PathBuf::from(base)),
             _ => {
                 eprintln!("usage: expand-yaml-anchors <source-dir> <dest-dir>");
                 std::process::exit(1);
@@ -138,9 +138,7 @@ fn filter_document(document: Yaml) -> Yaml {
                 .map(|(key, value)| (filter_document(key), filter_document(value)))
                 .collect(),
         ),
-        Yaml::Array(vec) => {
-            Yaml::Array(vec.into_iter().map(|item| filter_document(item)).collect())
-        }
+        Yaml::Array(vec) => Yaml::Array(vec.into_iter().map(filter_document).collect()),
         other => other,
     }
 }
diff --git a/src/tools/linkchecker/main.rs b/src/tools/linkchecker/main.rs
index 194318d7a59..b7ceba1e282 100644
--- a/src/tools/linkchecker/main.rs
+++ b/src/tools/linkchecker/main.rs
@@ -172,10 +172,10 @@ fn check(cache: &mut Cache, root: &Path, file: &Path, errors: &mut bool) -> Opti
         {
             return;
         }
-        let mut parts = url.splitn(2, "#");
+        let mut parts = url.splitn(2, '#');
         let url = parts.next().unwrap();
         let fragment = parts.next();
-        let mut parts = url.splitn(2, "?");
+        let mut parts = url.splitn(2, '?');
         let url = parts.next().unwrap();
 
         // Once we've plucked out the URL, parse it using our base url and
@@ -258,7 +258,7 @@ fn check(cache: &mut Cache, root: &Path, file: &Path, errors: &mut bool) -> Opti
                 }
 
                 // These appear to be broken in mdbook right now?
-                if fragment.starts_with("-") {
+                if fragment.starts_with('-') {
                     return;
                 }
 
@@ -324,7 +324,7 @@ fn load_file(
 }
 
 fn maybe_redirect(source: &str) -> Option<String> {
-    const REDIRECT: &'static str = "<p>Redirecting to <a href=";
+    const REDIRECT: &str = "<p>Redirecting to <a href=";
 
     let mut lines = source.lines();
     let redirect_line = lines.nth(6)?;
@@ -345,11 +345,11 @@ fn with_attrs_in_source<F: FnMut(&str, usize, &str)>(contents: &str, attr: &str,
             // we can get away with using one pass.
             let is_base = line[..j].ends_with("<base");
             line = rest;
-            let pos_equals = match rest.find("=") {
+            let pos_equals = match rest.find('=') {
                 Some(i) => i,
                 None => continue,
             };
-            if rest[..pos_equals].trim_start_matches(" ") != "" {
+            if rest[..pos_equals].trim_start_matches(' ') != "" {
                 continue;
             }
 
@@ -361,7 +361,7 @@ fn with_attrs_in_source<F: FnMut(&str, usize, &str)>(contents: &str, attr: &str,
             };
             let quote_delim = rest.as_bytes()[pos_quote] as char;
 
-            if rest[..pos_quote].trim_start_matches(" ") != "" {
+            if rest[..pos_quote].trim_start_matches(' ') != "" {
                 continue;
             }
             let rest = &rest[pos_quote + 1..];
diff --git a/src/tools/tidy/src/error_codes_check.rs b/src/tools/tidy/src/error_codes_check.rs
index 2fa0f12d7e8..82a5234ac5b 100644
--- a/src/tools/tidy/src/error_codes_check.rs
+++ b/src/tools/tidy/src/error_codes_check.rs
@@ -47,9 +47,7 @@ fn check_error_code_explanation(
     invalid_compile_fail_format
 }
 
-fn check_if_error_code_is_test_in_explanation(f: &str, err_code: &String) -> bool {
-    let mut can_be_ignored = false;
-
+fn check_if_error_code_is_test_in_explanation(f: &str, err_code: &str) -> bool {
     for line in f.lines() {
         let s = line.trim();
         if s.starts_with("#### Note: this error code is no longer emitted by the compiler") {
@@ -58,13 +56,13 @@ fn check_if_error_code_is_test_in_explanation(f: &str, err_code: &String) -> boo
         if s.starts_with("```") {
             if s.contains("compile_fail") && s.contains(err_code) {
                 return true;
-            } else if s.contains("(") {
+            } else if s.contains('(') {
                 // It's very likely that we can't actually make it fail compilation...
-                can_be_ignored = true;
+                return true;
             }
         }
     }
-    can_be_ignored
+    false
 }
 
 macro_rules! some_or_continue {
diff --git a/src/tools/unicode-table-generator/src/main.rs b/src/tools/unicode-table-generator/src/main.rs
index d2d1807b3bb..218e9668df4 100644
--- a/src/tools/unicode-table-generator/src/main.rs
+++ b/src/tools/unicode-table-generator/src/main.rs
@@ -315,7 +315,7 @@ fn version() -> String {
 fn fmt_list<V: std::fmt::Debug>(values: impl IntoIterator<Item = V>) -> String {
     let pieces = values.into_iter().map(|b| format!("{:?}, ", b)).collect::<Vec<_>>();
     let mut out = String::new();
-    let mut line = format!("\n    ");
+    let mut line = String::from("\n    ");
     for piece in pieces {
         if line.len() + piece.len() < 98 {
             line.push_str(&piece);
diff --git a/src/tools/unicode-table-generator/src/raw_emitter.rs b/src/tools/unicode-table-generator/src/raw_emitter.rs
index 63cc29b670f..42e7e5fb406 100644
--- a/src/tools/unicode-table-generator/src/raw_emitter.rs
+++ b/src/tools/unicode-table-generator/src/raw_emitter.rs
@@ -20,7 +20,7 @@ impl RawEmitter {
         if self.file.is_empty() || self.file.ends_with("\n\n") {
             return;
         }
-        writeln!(&mut self.file, "").unwrap();
+        writeln!(&mut self.file).unwrap();
     }
 
     fn emit_bitset(&mut self, ranges: &[Range<u32>]) {
@@ -161,10 +161,10 @@ pub fn emit_codepoints(emitter: &mut RawEmitter, ranges: &[Range<u32>]) {
 
     if bitset.bytes_used <= skiplist.bytes_used {
         *emitter = bitset;
-        emitter.desc = format!("bitset");
+        emitter.desc = String::from("bitset");
     } else {
         *emitter = skiplist;
-        emitter.desc = format!("skiplist");
+        emitter.desc = String::from("skiplist");
     }
 }
 
@@ -289,7 +289,7 @@ impl Canonicalized {
                 // Remove the now-canonicalized word from other mappings,
                 // to ensure that we deprioritize them in the next iteration of
                 // the while loop.
-                for (_, mapped) in &mut mappings {
+                for mapped in mappings.values_mut() {
                     let mut i = 0;
                     while i != mapped.len() {
                         if mapped[i].0 == *from {
@@ -309,7 +309,7 @@ impl Canonicalized {
 
             // Remove the now-canonical word from other mappings, to ensure that
             // we deprioritize them in the next iteration of the while loop.
-            for (_, mapped) in &mut mappings {
+            for mapped in mappings.values_mut() {
                 let mut i = 0;
                 while i != mapped.len() {
                     if mapped[i].0 == to {
diff --git a/src/tools/unstable-book-gen/src/main.rs b/src/tools/unstable-book-gen/src/main.rs
index 11617911446..5d277e1c41f 100644
--- a/src/tools/unstable-book-gen/src/main.rs
+++ b/src/tools/unstable-book-gen/src/main.rs
@@ -94,9 +94,9 @@ fn copy_recursive(from: &Path, to: &Path) {
 }
 
 fn main() {
-    let library_path_str = env::args_os().skip(1).next().expect("library path required");
-    let src_path_str = env::args_os().skip(2).next().expect("source path required");
-    let dest_path_str = env::args_os().skip(3).next().expect("destination path required");
+    let library_path_str = env::args_os().nth(1).expect("library path required");
+    let src_path_str = env::args_os().nth(2).expect("source path required");
+    let dest_path_str = env::args_os().nth(3).expect("destination path required");
     let library_path = Path::new(&library_path_str);
     let src_path = Path::new(&src_path_str);
     let dest_path = Path::new(&dest_path_str);