diff --git a/src/tools/build_helper/src/ci.rs b/src/tools/build_helper/src/ci.rs
index cdd8c809015cf..09489b0d9b7da 100644
--- a/src/tools/build_helper/src/ci.rs
+++ b/src/tools/build_helper/src/ci.rs
@@ -30,7 +30,7 @@ impl CiEnv {
             // The explicit `TERM=xterm` environment is needed for
             // `--color always` to actually work. This env var was lost when
             // compiling through the Makefile. Very strange.
-            cmd.env("TERM", "xterm").args(["--color", "always"]);
+            cmd.env("TERM", "xterm").args(&["--color", "always"]);
         }
     }
 }
diff --git a/src/tools/build_helper/src/git.rs b/src/tools/build_helper/src/git.rs
index 1c50e73249089..a3c857b0268c9 100644
--- a/src/tools/build_helper/src/git.rs
+++ b/src/tools/build_helper/src/git.rs
@@ -21,7 +21,7 @@ fn output_result(cmd: &mut Command) -> Result<String, String> {
             String::from_utf8(output.stderr).map_err(|err| format!("{err:?}"))?
         ));
     }
-    String::from_utf8(output.stdout).map_err(|err| format!("{err:?}"))
+    Ok(String::from_utf8(output.stdout).map_err(|err| format!("{err:?}"))?)
 }
 
 /// Finds the remote for rust-lang/rust.
diff --git a/src/tools/clippy/declare_clippy_lint/src/lib.rs b/src/tools/clippy/declare_clippy_lint/src/lib.rs
index 37e9b753adb0f..25b2fc9395cd9 100644
--- a/src/tools/clippy/declare_clippy_lint/src/lib.rs
+++ b/src/tools/clippy/declare_clippy_lint/src/lib.rs
@@ -144,7 +144,7 @@ pub fn declare_clippy_lint(input: TokenStream) -> TokenStream {
 
     let info_name = format_ident!("{name}_INFO");
 
-    category[0..1].make_ascii_uppercase();
+    (&mut category[0..1]).make_ascii_uppercase();
     let category_variant = format_ident!("{category}");
 
     let output = quote! {
diff --git a/src/tools/miropt-test-tools/src/lib.rs b/src/tools/miropt-test-tools/src/lib.rs
index 5ab053258e20b..4317f23a82219 100644
--- a/src/tools/miropt-test-tools/src/lib.rs
+++ b/src/tools/miropt-test-tools/src/lib.rs
@@ -51,7 +51,7 @@ pub fn files_for_miropt_test(
     panic_strategy: PanicStrategy,
 ) -> MiroptTest {
     let mut out = Vec::new();
-    let test_file_contents = fs::read_to_string(testfile).unwrap();
+    let test_file_contents = fs::read_to_string(&testfile).unwrap();
 
     let test_dir = testfile.parent().unwrap();
     let test_crate = testfile.file_stem().unwrap().to_str().unwrap().replace('-', "_");
diff --git a/src/tools/rustfmt/build.rs b/src/tools/rustfmt/build.rs
index 9a8bb77a8ed19..e7b1e1b854c07 100644
--- a/src/tools/rustfmt/build.rs
+++ b/src/tools/rustfmt/build.rs
@@ -40,7 +40,7 @@ fn channel() -> String {
 
 fn commit_hash() -> Option<String> {
     Command::new("git")
-        .args(["rev-parse", "--short", "HEAD"])
+        .args(&["rev-parse", "--short", "HEAD"])
         .output()
         .ok()
         .and_then(|r| String::from_utf8(r.stdout).ok())
@@ -48,7 +48,7 @@ fn commit_hash() -> Option<String> {
 
 fn commit_date() -> Option<String> {
     Command::new("git")
-        .args(["log", "-1", "--date=short", "--pretty=format:%cd"])
+        .args(&["log", "-1", "--date=short", "--pretty=format:%cd"])
         .output()
         .ok()
         .and_then(|r| String::from_utf8(r.stdout).ok())
diff --git a/src/tools/rustfmt/config_proc_macro/src/attrs.rs b/src/tools/rustfmt/config_proc_macro/src/attrs.rs
index 13a39ddf45b21..d8de9aae088d7 100644
--- a/src/tools/rustfmt/config_proc_macro/src/attrs.rs
+++ b/src/tools/rustfmt/config_proc_macro/src/attrs.rs
@@ -51,24 +51,24 @@ pub fn is_unstable_variant(attr: &syn::Attribute) -> bool {
 }
 
 fn is_attr_name_value(attr: &syn::Attribute, name: &str) -> bool {
-    matches!(&attr.meta,
-        syn::Meta::NameValue(syn::MetaNameValue { path, .. }) if path.is_ident(name))
+    match &attr.meta {
+        syn::Meta::NameValue(syn::MetaNameValue { path, .. }) if path.is_ident(name) => true,
+        _ => false,
+    }
 }
 
 fn is_attr_path(attr: &syn::Attribute, name: &str) -> bool {
-    matches!(&attr.meta,
-        syn::Meta::Path(path) if path.is_ident(name))
+    match &attr.meta {
+        syn::Meta::Path(path) if path.is_ident(name) => true,
+        _ => false,
+    }
 }
 
 fn get_name_value_str_lit(attr: &syn::Attribute, name: &str) -> Option<String> {
     match &attr.meta {
         syn::Meta::NameValue(syn::MetaNameValue {
             path,
-            value:
-                syn::Expr::Lit(syn::ExprLit {
-                    lit: syn::Lit::Str(lit_str),
-                    ..
-                }),
+            value: syn::Expr::Lit(syn::ExprLit { lit: syn::Lit::Str(lit_str), .. }),
             ..
         }) if path.is_ident(name) => Some(lit_str.value()),
         _ => None,
diff --git a/src/tools/rustfmt/config_proc_macro/src/item_enum.rs b/src/tools/rustfmt/config_proc_macro/src/item_enum.rs
index 069b2b53286ac..731a7ea06077b 100644
--- a/src/tools/rustfmt/config_proc_macro/src/item_enum.rs
+++ b/src/tools/rustfmt/config_proc_macro/src/item_enum.rs
@@ -75,7 +75,7 @@ fn impl_doc_hint(ident: &syn::Ident, variants: &Variants) -> TokenStream {
 
     let variant_stables = variants
         .iter()
-        .map(|v| (&v.ident, fields_in_variant(v), !unstable_of_variant(v)));
+        .map(|v| (&v.ident, fields_in_variant(&v), !unstable_of_variant(v)));
     let match_patterns = fold_quote(variant_stables, |(v, fields, stable)| {
         quote! {
             #ident::#v #fields => #stable,
@@ -150,7 +150,7 @@ fn impl_from_str(ident: &syn::Ident, variants: &Variants) -> TokenStream {
 
 fn doc_hint_of_variant(variant: &syn::Variant) -> String {
     let mut text = find_doc_hint(&variant.attrs).unwrap_or(variant.ident.to_string());
-    if unstable_of_variant(variant) {
+    if unstable_of_variant(&variant) {
         text.push_str(" (unstable)")
     };
     text
diff --git a/src/tools/rustfmt/config_proc_macro/src/utils.rs b/src/tools/rustfmt/config_proc_macro/src/utils.rs
index 05c8dc171af0a..f5cba87b07b67 100644
--- a/src/tools/rustfmt/config_proc_macro/src/utils.rs
+++ b/src/tools/rustfmt/config_proc_macro/src/utils.rs
@@ -13,7 +13,10 @@ where
 }
 
 pub fn is_unit(v: &syn::Variant) -> bool {
-    v.fields == syn::Fields::Unit
+    match v.fields {
+        syn::Fields::Unit => true,
+        _ => false,
+    }
 }
 
 #[cfg(feature = "debug-with-rustfmt")]