diff --git a/clippy_lints/src/cognitive_complexity.rs b/clippy_lints/src/cognitive_complexity.rs
index 8f1c02965244..8f95c63a854f 100644
--- a/clippy_lints/src/cognitive_complexity.rs
+++ b/clippy_lints/src/cognitive_complexity.rs
@@ -56,7 +56,7 @@ impl_lint_pass!(CognitiveComplexity => [COGNITIVE_COMPLEXITY]);
 
 impl CognitiveComplexity {
     fn check<'tcx>(
-        &mut self,
+        &self,
         cx: &LateContext<'tcx>,
         kind: FnKind<'tcx>,
         decl: &'tcx FnDecl<'_>,
diff --git a/clippy_lints/src/manual_let_else.rs b/clippy_lints/src/manual_let_else.rs
index 1f9a943f13dc..5a7967bbf946 100644
--- a/clippy_lints/src/manual_let_else.rs
+++ b/clippy_lints/src/manual_let_else.rs
@@ -49,7 +49,7 @@ declare_clippy_lint! {
 }
 
 impl<'tcx> QuestionMark {
-    pub(crate) fn check_manual_let_else(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'tcx>) {
+    pub(crate) fn check_manual_let_else(&self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'tcx>) {
         if let StmtKind::Let(local) = stmt.kind
             && let Some(init) = local.init
             && local.els.is_none()
diff --git a/clippy_lints/src/matches/match_str_case_mismatch.rs b/clippy_lints/src/matches/match_str_case_mismatch.rs
index 8b4c17000519..eb8b16e1561b 100644
--- a/clippy_lints/src/matches/match_str_case_mismatch.rs
+++ b/clippy_lints/src/matches/match_str_case_mismatch.rs
@@ -54,7 +54,7 @@ impl<'tcx> Visitor<'tcx> for MatchExprVisitor<'_, 'tcx> {
 }
 
 impl MatchExprVisitor<'_, '_> {
-    fn case_altered(&mut self, segment_ident: Symbol, receiver: &Expr<'_>) -> ControlFlow<CaseMethod> {
+    fn case_altered(&self, segment_ident: Symbol, receiver: &Expr<'_>) -> ControlFlow<CaseMethod> {
         if let Some(case_method) = get_case_method(segment_ident) {
             let ty = self.cx.typeck_results().expr_ty(receiver).peel_refs();
 
diff --git a/clippy_lints/src/methods/filter_map.rs b/clippy_lints/src/methods/filter_map.rs
index 4dd54cf19745..5b8457bdd164 100644
--- a/clippy_lints/src/methods/filter_map.rs
+++ b/clippy_lints/src/methods/filter_map.rs
@@ -106,7 +106,7 @@ enum CheckResult<'tcx> {
 
 impl<'tcx> OffendingFilterExpr<'tcx> {
     pub fn check_map_call(
-        &mut self,
+        &self,
         cx: &LateContext<'tcx>,
         map_body: &'tcx Body<'tcx>,
         map_param_id: HirId,
@@ -413,7 +413,7 @@ fn is_find_or_filter<'a>(
         }
 
         && let PatKind::Binding(_, filter_param_id, _, None) = filter_pat.kind
-        && let Some(mut offending_expr) = OffendingFilterExpr::hir(cx, filter_body.value, filter_param_id)
+        && let Some(offending_expr) = OffendingFilterExpr::hir(cx, filter_body.value, filter_param_id)
 
         && let ExprKind::Closure(&Closure { body: map_body_id, .. }) = map_arg.kind
         && let map_body = cx.tcx.hir_body(map_body_id)
diff --git a/clippy_lints/src/mixed_read_write_in_expression.rs b/clippy_lints/src/mixed_read_write_in_expression.rs
index a489c0a4a5a1..3b44d4b60d32 100644
--- a/clippy_lints/src/mixed_read_write_in_expression.rs
+++ b/clippy_lints/src/mixed_read_write_in_expression.rs
@@ -134,7 +134,7 @@ impl<'tcx> DivergenceVisitor<'_, 'tcx> {
         }
     }
 
-    fn report_diverging_sub_expr(&mut self, e: &Expr<'_>) {
+    fn report_diverging_sub_expr(&self, e: &Expr<'_>) {
         if let Some(macro_call) = root_macro_call_first_node(self.cx, e)
             && self.cx.tcx.is_diagnostic_item(sym::todo_macro, macro_call.def_id)
         {
diff --git a/clippy_lints/src/only_used_in_recursion.rs b/clippy_lints/src/only_used_in_recursion.rs
index ba8f6354d976..a42763172f56 100644
--- a/clippy_lints/src/only_used_in_recursion.rs
+++ b/clippy_lints/src/only_used_in_recursion.rs
@@ -173,7 +173,7 @@ impl Params {
     }
 
     /// Sets the `apply_lint` flag on each parameter.
-    fn flag_for_linting(&mut self) {
+    fn flag_for_linting(&self) {
         // Stores the list of parameters currently being resolved. Needed to avoid cycles.
         let mut eval_stack = Vec::new();
         for param in &self.params {
diff --git a/clippy_lints/src/operators/arithmetic_side_effects.rs b/clippy_lints/src/operators/arithmetic_side_effects.rs
index 466beb04b074..ea5b81aec31e 100644
--- a/clippy_lints/src/operators/arithmetic_side_effects.rs
+++ b/clippy_lints/src/operators/arithmetic_side_effects.rs
@@ -325,7 +325,7 @@ impl ArithmeticSideEffects {
         self.issue_lint(cx, expr);
     }
 
-    fn should_skip_expr<'tcx>(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'tcx>) -> bool {
+    fn should_skip_expr<'tcx>(&self, cx: &LateContext<'tcx>, expr: &hir::Expr<'tcx>) -> bool {
         is_lint_allowed(cx, ARITHMETIC_SIDE_EFFECTS, expr.hir_id)
             || self.expr_span.is_some()
             || self.const_span.is_some_and(|sp| sp.contains(expr.span))
diff --git a/clippy_lints/src/operators/numeric_arithmetic.rs b/clippy_lints/src/operators/numeric_arithmetic.rs
index e6be536ca0f4..9b1b063c4737 100644
--- a/clippy_lints/src/operators/numeric_arithmetic.rs
+++ b/clippy_lints/src/operators/numeric_arithmetic.rs
@@ -13,7 +13,7 @@ pub struct Context {
     const_span: Option<Span>,
 }
 impl Context {
-    fn skip_expr(&mut self, e: &hir::Expr<'_>) -> bool {
+    fn skip_expr(&self, e: &hir::Expr<'_>) -> bool {
         self.expr_id.is_some() || self.const_span.is_some_and(|span| span.contains(e.span))
     }
 
diff --git a/clippy_lints/src/pass_by_ref_or_value.rs b/clippy_lints/src/pass_by_ref_or_value.rs
index d7b4a03aa537..1b1e77bbea8f 100644
--- a/clippy_lints/src/pass_by_ref_or_value.rs
+++ b/clippy_lints/src/pass_by_ref_or_value.rs
@@ -120,7 +120,7 @@ impl PassByRefOrValue {
         }
     }
 
-    fn check_poly_fn(&mut self, cx: &LateContext<'_>, def_id: LocalDefId, decl: &FnDecl<'_>, span: Option<Span>) {
+    fn check_poly_fn(&self, cx: &LateContext<'_>, def_id: LocalDefId, decl: &FnDecl<'_>, span: Option<Span>) {
         if self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(def_id) {
             return;
         }
diff --git a/clippy_lints/src/raw_strings.rs b/clippy_lints/src/raw_strings.rs
index 6a79cae32a59..943e662479e9 100644
--- a/clippy_lints/src/raw_strings.rs
+++ b/clippy_lints/src/raw_strings.rs
@@ -103,15 +103,7 @@ impl EarlyLintPass for RawStrings {
 }
 
 impl RawStrings {
-    fn check_raw_string(
-        &mut self,
-        cx: &EarlyContext<'_>,
-        str: &str,
-        lit_span: Span,
-        prefix: &str,
-        max: u8,
-        descr: &str,
-    ) {
+    fn check_raw_string(&self, cx: &EarlyContext<'_>, str: &str, lit_span: Span, prefix: &str, max: u8, descr: &str) {
         if !str.contains(['\\', '"']) {
             span_lint_and_then(
                 cx,
diff --git a/clippy_lints/src/swap.rs b/clippy_lints/src/swap.rs
index 5ecbb56925ec..76ab3cdae22e 100644
--- a/clippy_lints/src/swap.rs
+++ b/clippy_lints/src/swap.rs
@@ -380,7 +380,7 @@ impl<'tcx> IndexBinding<'_, 'tcx> {
         }
     }
 
-    fn is_used_other_than_swapping(&mut self, idx_ident: Ident) -> bool {
+    fn is_used_other_than_swapping(&self, idx_ident: Ident) -> bool {
         if Self::is_used_slice_indexed(self.swap1_idx, idx_ident)
             || Self::is_used_slice_indexed(self.swap2_idx, idx_ident)
         {
@@ -389,7 +389,7 @@ impl<'tcx> IndexBinding<'_, 'tcx> {
         self.is_used_after_swap(idx_ident)
     }
 
-    fn is_used_after_swap(&mut self, idx_ident: Ident) -> bool {
+    fn is_used_after_swap(&self, idx_ident: Ident) -> bool {
         let mut v = IndexBindingVisitor {
             idx: idx_ident,
             suggest_span: self.suggest_span,
diff --git a/clippy_lints/src/unnecessary_box_returns.rs b/clippy_lints/src/unnecessary_box_returns.rs
index 2b7d3dc0c90a..6e3e41f08ee5 100644
--- a/clippy_lints/src/unnecessary_box_returns.rs
+++ b/clippy_lints/src/unnecessary_box_returns.rs
@@ -55,7 +55,7 @@ impl UnnecessaryBoxReturns {
         }
     }
 
-    fn check_fn_item(&mut self, cx: &LateContext<'_>, decl: &FnDecl<'_>, def_id: LocalDefId, name: Symbol) {
+    fn check_fn_item(&self, cx: &LateContext<'_>, decl: &FnDecl<'_>, def_id: LocalDefId, name: Symbol) {
         // we don't want to tell someone to break an exported function if they ask us not to
         if self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(def_id) {
             return;
diff --git a/clippy_utils/src/hir_utils.rs b/clippy_utils/src/hir_utils.rs
index f0d7fb89c446..8160443f4132 100644
--- a/clippy_utils/src/hir_utils.rs
+++ b/clippy_utils/src/hir_utils.rs
@@ -258,7 +258,7 @@ impl HirEqInterExpr<'_, '_, '_> {
         })
     }
 
-    fn should_ignore(&mut self, expr: &Expr<'_>) -> bool {
+    fn should_ignore(&self, expr: &Expr<'_>) -> bool {
         macro_backtrace(expr.span).last().is_some_and(|macro_call| {
             matches!(
                 self.inner.cx.tcx.get_diagnostic_name(macro_call.def_id),