diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index 4ca59144b2990..8c71332bfabb1 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -802,12 +802,9 @@ impl Integer {
     pub fn for_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Option<Integer> {
         let dl = cx.data_layout();
 
-        for candidate in [I8, I16, I32, I64, I128] {
-            if wanted == candidate.align(dl).abi && wanted.bytes() == candidate.size().bytes() {
-                return Some(candidate);
-            }
-        }
-        None
+        [I8, I16, I32, I64, I128].into_iter().find(|&candidate| {
+            wanted == candidate.align(dl).abi && wanted.bytes() == candidate.size().bytes()
+        })
     }
 
     /// Find the largest integer with the given alignment or less.
diff --git a/compiler/rustc_data_structures/src/base_n.rs b/compiler/rustc_data_structures/src/base_n.rs
index 3c7bea2712409..4567759c004da 100644
--- a/compiler/rustc_data_structures/src/base_n.rs
+++ b/compiler/rustc_data_structures/src/base_n.rs
@@ -9,7 +9,7 @@ pub const MAX_BASE: usize = 64;
 pub const ALPHANUMERIC_ONLY: usize = 62;
 pub const CASE_INSENSITIVE: usize = 36;
 
-const BASE_64: &[u8; MAX_BASE as usize] =
+const BASE_64: &[u8; MAX_BASE] =
     b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
 
 #[inline]
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 06bb5edc090f4..0f79bc558bf26 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -802,7 +802,7 @@ impl Diagnostic {
         debug_assert!(
             !(suggestions
                 .iter()
-                .flat_map(|suggs| suggs)
+                .flatten()
                 .any(|(sp, suggestion)| sp.is_empty() && suggestion.is_empty())),
             "Span must not be empty and have no suggestion"
         );
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 4df2198fb0e9b..aaf0699f0dc41 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -1308,7 +1308,7 @@ impl EmitterWriter {
         //                see how it *looks* with
         //                very *weird* formats
         //                see?
-        for &(ref text, ref style) in msg.iter() {
+        for (text, style) in msg.iter() {
             let text = self.translate_message(text, args);
             let lines = text.split('\n').collect::<Vec<_>>();
             if lines.len() > 1 {
@@ -1370,7 +1370,7 @@ impl EmitterWriter {
                 buffer.append(0, ": ", header_style);
                 label_width += 2;
             }
-            for &(ref text, _) in msg.iter() {
+            for (text, _) in msg.iter() {
                 let text = self.translate_message(text, args);
                 // Account for newlines to align output to its label.
                 for (line, text) in normalize_whitespace(&text).lines().enumerate() {
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 8bc022e1e178e..91825c29258ac 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -548,12 +548,7 @@ impl<'hir> Generics<'hir> {
     }
 
     pub fn get_named(&self, name: Symbol) -> Option<&GenericParam<'hir>> {
-        for param in self.params {
-            if name == param.name.ident().name {
-                return Some(param);
-            }
-        }
-        None
+        self.params.iter().find(|&param| name == param.name.ident().name)
     }
 
     pub fn spans(&self) -> MultiSpan {
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index 777112442f010..686cb6dac4962 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -209,7 +209,7 @@ impl<T: Idx> BitSet<T> {
             self.words[start_word_index] |= !(start_mask - 1);
             // And all trailing bits (i.e. from 0..=end) in the end word,
             // including the end.
-            self.words[end_word_index] |= end_mask | end_mask - 1;
+            self.words[end_word_index] |= end_mask | (end_mask - 1);
         } else {
             self.words[start_word_index] |= end_mask | (end_mask - start_mask);
         }
diff --git a/compiler/rustc_lexer/src/unescape.rs b/compiler/rustc_lexer/src/unescape.rs
index e405013dcabf8..87c44638a8de1 100644
--- a/compiler/rustc_lexer/src/unescape.rs
+++ b/compiler/rustc_lexer/src/unescape.rs
@@ -204,14 +204,13 @@ fn scan_escape(chars: &mut Chars<'_>, is_byte: bool) -> Result<char, EscapeError
                         })?;
                     }
                     Some(c) => {
-                        let digit =
+                        let digit: u32 =
                             c.to_digit(16).ok_or(EscapeError::InvalidCharInUnicodeEscape)?;
                         n_digits += 1;
                         if n_digits > 6 {
                             // Stop updating value since we're sure that it's incorrect already.
                             continue;
                         }
-                        let digit = digit as u32;
                         value = value * 16 + digit;
                     }
                 };
diff --git a/compiler/rustc_span/src/source_map.rs b/compiler/rustc_span/src/source_map.rs
index 43a3172270733..a4e0f54d27670 100644
--- a/compiler/rustc_span/src/source_map.rs
+++ b/compiler/rustc_span/src/source_map.rs
@@ -1150,7 +1150,7 @@ impl FilePathMapping {
             // NOTE: We are iterating over the mapping entries from last to first
             //       because entries specified later on the command line should
             //       take precedence.
-            for &(ref from, ref to) in mapping.iter().rev() {
+            for (from, to) in mapping.iter().rev() {
                 debug!("Trying to apply {from:?} => {to:?}");
 
                 if let Ok(rest) = path.strip_prefix(from) {