Merging upstream version 1.66.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 144 insertions, 59 deletions

diff --git a/src/tools/clippy/clippy_lints/src/dereference.rs b/src/tools/clippy/clippy_lints/src/dereference.rs
index 88e28018e..a37ee82d4 100644
--- a/src/tools/clippy/clippy_lints/src/dereference.rs
+++ b/src/tools/clippy/clippy_lints/src/dereference.rs
@@ -1,4 +1,5 @@
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
+use clippy_utils::mir::{enclosing_mir, expr_local, local_assignments, used_exactly_once, PossibleBorrowerMap};
 use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
 use clippy_utils::sugg::has_enclosing_paren;
 use clippy_utils::ty::{expr_sig, is_copy, peel_mid_ty_refs, ty_sig, variant_of_res};
@@ -11,21 +12,24 @@ use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::{walk_ty, Visitor};
 use rustc_hir::{
-    self as hir, def_id::DefId, BindingAnnotation, Body, BodyId, BorrowKind, Closure, Expr, ExprKind, FnRetTy,
-    GenericArg, HirId, ImplItem, ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind,
-    Path, QPath, TraitItem, TraitItemKind, TyKind, UnOp,
+    self as hir,
+    def_id::{DefId, LocalDefId},
+    BindingAnnotation, Body, BodyId, BorrowKind, Closure, Expr, ExprKind, FnRetTy, GenericArg, HirId, ImplItem,
+    ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind, Path, QPath, TraitItem,
+    TraitItemKind, TyKind, UnOp,
 };
 use rustc_index::bit_set::BitSet;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::mir::{Rvalue, StatementKind};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
 use rustc_middle::ty::{
-    self, subst::Subst, Binder, BoundVariableKind, EarlyBinder, FnSig, GenericArgKind, List, ParamTy, PredicateKind,
+    self, Binder, BoundVariableKind, EarlyBinder, FnSig, GenericArgKind, List, ParamTy, PredicateKind,
     ProjectionPredicate, Ty, TyCtxt, TypeVisitable, TypeckResults,
 };
 use rustc_semver::RustcVersion;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
-use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
+use rustc_span::{symbol::sym, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::traits::{query::evaluate_obligation::InferCtxtExt as _, Obligation, ObligationCause};
 use std::collections::VecDeque;
@@ -135,13 +139,13 @@ declare_clippy_lint! {
     /// let x = String::new();
     /// let y: &str = &x;
     /// ```
-    #[clippy::version = "1.60.0"]
+    #[clippy::version = "1.64.0"]
     pub EXPLICIT_AUTO_DEREF,
     complexity,
     "dereferencing when the compiler would automatically dereference"
 }
 
-impl_lint_pass!(Dereferencing => [
+impl_lint_pass!(Dereferencing<'_> => [
     EXPLICIT_DEREF_METHODS,
     NEEDLESS_BORROW,
     REF_BINDING_TO_REFERENCE,
@@ -149,7 +153,7 @@ impl_lint_pass!(Dereferencing => [
 ]);
 
 #[derive(Default)]
-pub struct Dereferencing {
+pub struct Dereferencing<'tcx> {
     state: Option<(State, StateData)>,
 
     // While parsing a `deref` method call in ufcs form, the path to the function is itself an
@@ -170,11 +174,16 @@ pub struct Dereferencing {
     /// e.g. `m!(x) | Foo::Bar(ref x)`
     ref_locals: FxIndexMap<HirId, Option<RefPat>>,
 
+    /// Stack of (body owner, `PossibleBorrowerMap`) pairs. Used by
+    /// `needless_borrow_impl_arg_position` to determine when a borrowed expression can instead
+    /// be moved.
+    possible_borrowers: Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
+
     // `IntoIterator` for arrays requires Rust 1.53.
     msrv: Option<RustcVersion>,
 }
 
-impl Dereferencing {
+impl<'tcx> Dereferencing<'tcx> {
     #[must_use]
     pub fn new(msrv: Option<RustcVersion>) -> Self {
         Self {
@@ -184,6 +193,7 @@ impl Dereferencing {
     }
 }
 
+#[derive(Debug)]
 struct StateData {
     /// Span of the top level expression
     span: Span,
@@ -191,12 +201,14 @@ struct StateData {
     position: Position,
 }
 
+#[derive(Debug)]
 struct DerefedBorrow {
     count: usize,
     msg: &'static str,
     snip_expr: Option<HirId>,
 }
 
+#[derive(Debug)]
 enum State {
     // Any number of deref method calls.
     DerefMethod {
@@ -241,7 +253,7 @@ struct RefPat {
     hir_id: HirId,
 }
 
-impl<'tcx> LateLintPass<'tcx> for Dereferencing {
+impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
     #[expect(clippy::too_many_lines)]
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         // Skip path expressions from deref calls. e.g. `Deref::deref(e)`
@@ -275,11 +287,13 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
         match (self.state.take(), kind) {
             (None, kind) => {
                 let expr_ty = typeck.expr_ty(expr);
-                let (position, adjustments) = walk_parents(cx, expr, self.msrv);
-
+                let (position, adjustments) = walk_parents(cx, &mut self.possible_borrowers, expr, self.msrv);
                 match kind {
                     RefOp::Deref => {
-                        if let Position::FieldAccess(name) = position
+                        if let Position::FieldAccess {
+                            name,
+                            of_union: false,
+                        } = position
                             && !ty_contains_field(typeck.expr_ty(sub_expr), name)
                         {
                             self.state = Some((
@@ -297,13 +311,10 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
                         if !is_lint_allowed(cx, EXPLICIT_DEREF_METHODS, expr.hir_id)
                             && position.lint_explicit_deref() =>
                     {
+                        let ty_changed_count = usize::from(!deref_method_same_type(expr_ty, typeck.expr_ty(sub_expr)));
                         self.state = Some((
                             State::DerefMethod {
-                                ty_changed_count: if deref_method_same_type(expr_ty, typeck.expr_ty(sub_expr)) {
-                                    0
-                                } else {
-                                    1
-                                },
+                                ty_changed_count,
                                 is_final_ufcs: matches!(expr.kind, ExprKind::Call(..)),
                                 target_mut,
                             },
@@ -454,7 +465,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
             (Some((State::DerefedBorrow(state), data)), RefOp::Deref) => {
                 let position = data.position;
                 report(cx, expr, State::DerefedBorrow(state), data);
-                if let Position::FieldAccess(name) = position
+                if let Position::FieldAccess{name, ..} = position
                     && !ty_contains_field(typeck.expr_ty(sub_expr), name)
                 {
                     self.state = Some((
@@ -548,6 +559,12 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
     }
 
     fn check_body_post(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
+        if self.possible_borrowers.last().map_or(false, |&(local_def_id, _)| {
+            local_def_id == cx.tcx.hir().body_owner_def_id(body.id())
+        }) {
+            self.possible_borrowers.pop();
+        }
+
         if Some(body.id()) == self.current_body {
             for pat in self.ref_locals.drain(..).filter_map(|(_, x)| x) {
                 let replacements = pat.replacements;
@@ -619,14 +636,17 @@ fn deref_method_same_type<'tcx>(result_ty: Ty<'tcx>, arg_ty: Ty<'tcx>) -> bool {
 }
 
 /// The position of an expression relative to it's parent.
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Debug)]
 enum Position {
     MethodReceiver,
     /// The method is defined on a reference type. e.g. `impl Foo for &T`
     MethodReceiverRefImpl,
     Callee,
     ImplArg(HirId),
-    FieldAccess(Symbol),
+    FieldAccess {
+        name: Symbol,
+        of_union: bool,
+    }, // union fields cannot be auto borrowed
     Postfix,
     Deref,
     /// Any other location which will trigger auto-deref to a specific time.
@@ -648,7 +668,10 @@ impl Position {
     }
 
     fn can_auto_borrow(self) -> bool {
-        matches!(self, Self::MethodReceiver | Self::FieldAccess(_) | Self::Callee)
+        matches!(
+            self,
+            Self::MethodReceiver | Self::FieldAccess { of_union: false, .. } | Self::Callee
+        )
     }
 
     fn lint_explicit_deref(self) -> bool {
@@ -660,7 +683,7 @@ impl Position {
             Self::MethodReceiver
             | Self::MethodReceiverRefImpl
             | Self::Callee
-            | Self::FieldAccess(_)
+            | Self::FieldAccess { .. }
             | Self::Postfix => PREC_POSTFIX,
             Self::ImplArg(_) | Self::Deref => PREC_PREFIX,
             Self::DerefStable(p, _) | Self::ReborrowStable(p) | Self::Other(p) => p,
@@ -674,6 +697,7 @@ impl Position {
 #[expect(clippy::too_many_lines)]
 fn walk_parents<'tcx>(
     cx: &LateContext<'tcx>,
+    possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
     e: &'tcx Expr<'_>,
     msrv: Option<RustcVersion>,
 ) -> (Position, &'tcx [Adjustment<'tcx>]) {
@@ -691,47 +715,47 @@ fn walk_parents<'tcx>(
             },
             Node::Item(&Item {
                 kind: ItemKind::Static(..) | ItemKind::Const(..),
-                def_id,
+                owner_id,
                 span,
                 ..
             })
             | Node::TraitItem(&TraitItem {
                 kind: TraitItemKind::Const(..),
-                def_id,
+                owner_id,
                 span,
                 ..
             })
             | Node::ImplItem(&ImplItem {
                 kind: ImplItemKind::Const(..),
-                def_id,
+                owner_id,
                 span,
                 ..
             }) if span.ctxt() == ctxt => {
-                let ty = cx.tcx.type_of(def_id);
+                let ty = cx.tcx.type_of(owner_id.def_id);
                 Some(ty_auto_deref_stability(cx, ty, precedence).position_for_result(cx))
             },
 
             Node::Item(&Item {
                 kind: ItemKind::Fn(..),
-                def_id,
+                owner_id,
                 span,
                 ..
             })
             | Node::TraitItem(&TraitItem {
                 kind: TraitItemKind::Fn(..),
-                def_id,
+                owner_id,
                 span,
                 ..
             })
             | Node::ImplItem(&ImplItem {
                 kind: ImplItemKind::Fn(..),
-                def_id,
+                owner_id,
                 span,
                 ..
             }) if span.ctxt() == ctxt => {
                 let output = cx
                     .tcx
-                    .erase_late_bound_regions(cx.tcx.fn_sig(def_id.to_def_id()).output());
+                    .erase_late_bound_regions(cx.tcx.fn_sig(owner_id.to_def_id()).output());
                 Some(ty_auto_deref_stability(cx, output, precedence).position_for_result(cx))
             },
 
@@ -788,7 +812,16 @@ fn walk_parents<'tcx>(
                             Some(hir_ty) => binding_ty_auto_deref_stability(cx, hir_ty, precedence, ty.bound_vars()),
                             None => {
                                 if let ty::Param(param_ty) = ty.skip_binder().kind() {
-                                    needless_borrow_impl_arg_position(cx, parent, i, *param_ty, e, precedence, msrv)
+                                    needless_borrow_impl_arg_position(
+                                        cx,
+                                        possible_borrowers,
+                                        parent,
+                                        i,
+                                        *param_ty,
+                                        e,
+                                        precedence,
+                                        msrv,
+                                    )
                                 } else {
                                     ty_auto_deref_stability(cx, cx.tcx.erase_late_bound_regions(ty), precedence)
                                         .position_for_arg()
@@ -823,11 +856,10 @@ fn walk_parents<'tcx>(
                                 // Trait methods taking `self`
                                 arg_ty
                             } && impl_ty.is_ref()
-                            && cx.tcx.infer_ctxt().enter(|infcx|
-                                infcx
-                                    .type_implements_trait(trait_id, impl_ty, subs, cx.param_env)
-                                    .must_apply_modulo_regions()
-                            )
+                            && let infcx = cx.tcx.infer_ctxt().build()
+                            && infcx
+                                .type_implements_trait(trait_id, impl_ty, subs, cx.param_env)
+                                .must_apply_modulo_regions()
                         {
                             return Some(Position::MethodReceiverRefImpl)
                         }
@@ -836,7 +868,16 @@ fn walk_parents<'tcx>(
                     args.iter().position(|arg| arg.hir_id == child_id).map(|i| {
                         let ty = cx.tcx.fn_sig(id).skip_binder().inputs()[i + 1];
                         if let ty::Param(param_ty) = ty.kind() {
-                            needless_borrow_impl_arg_position(cx, parent, i + 1, *param_ty, e, precedence, msrv)
+                            needless_borrow_impl_arg_position(
+                                cx,
+                                possible_borrowers,
+                                parent,
+                                i + 1,
+                                *param_ty,
+                                e,
+                                precedence,
+                                msrv,
+                            )
                         } else {
                             ty_auto_deref_stability(
                                 cx,
@@ -847,7 +888,10 @@ fn walk_parents<'tcx>(
                         }
                     })
                 },
-                ExprKind::Field(child, name) if child.hir_id == e.hir_id => Some(Position::FieldAccess(name.name)),
+                ExprKind::Field(child, name) if child.hir_id == e.hir_id => Some(Position::FieldAccess {
+                    name: name.name,
+                    of_union: is_union(cx.typeck_results(), child),
+                }),
                 ExprKind::Unary(UnOp::Deref, child) if child.hir_id == e.hir_id => Some(Position::Deref),
                 ExprKind::Match(child, _, MatchSource::TryDesugar | MatchSource::AwaitDesugar)
                 | ExprKind::Index(child, _)
@@ -868,6 +912,13 @@ fn walk_parents<'tcx>(
     (position, adjustments)
 }
 
+fn is_union<'tcx>(typeck: &'tcx TypeckResults<'_>, path_expr: &'tcx Expr<'_>) -> bool {
+    typeck
+        .expr_ty_adjusted(path_expr)
+        .ty_adt_def()
+        .map_or(false, rustc_middle::ty::AdtDef::is_union)
+}
+
 fn closure_result_position<'tcx>(
     cx: &LateContext<'tcx>,
     closure: &'tcx Closure<'_>,
@@ -939,7 +990,7 @@ fn binding_ty_auto_deref_stability<'tcx>(
                                 cx.typeck_results().node_type(ty.ty.hir_id),
                                 binder_args,
                             ))
-                            .is_sized(cx.tcx.at(DUMMY_SP), cx.param_env.without_caller_bounds()),
+                            .is_sized(cx.tcx, cx.param_env.without_caller_bounds()),
                     )
                 }
             },
@@ -954,7 +1005,7 @@ fn binding_ty_auto_deref_stability<'tcx>(
                         cx.typeck_results().node_type(ty.ty.hir_id),
                         binder_args,
                     ))
-                    .is_sized(cx.tcx.at(DUMMY_SP), cx.param_env.without_caller_bounds()),
+                    .is_sized(cx.tcx, cx.param_env.without_caller_bounds()),
             ),
             TyKind::OpaqueDef(..) | TyKind::Infer | TyKind::Typeof(..) | TyKind::TraitObject(..) | TyKind::Err => {
                 Position::ReborrowStable(precedence)
@@ -1000,8 +1051,10 @@ fn ty_contains_infer(ty: &hir::Ty<'_>) -> bool {
 // If the conditions are met, returns `Some(Position::ImplArg(..))`; otherwise, returns `None`.
 //   The "is copyable" condition is to avoid the case where removing the `&` means `e` would have to
 // be moved, but it cannot be.
+#[expect(clippy::too_many_arguments)]
 fn needless_borrow_impl_arg_position<'tcx>(
     cx: &LateContext<'tcx>,
+    possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
     parent: &Expr<'tcx>,
     arg_index: usize,
     param_ty: ParamTy,
@@ -1064,10 +1117,13 @@ fn needless_borrow_impl_arg_position<'tcx>(
     // elements are modified each time `check_referent` is called.
     let mut substs_with_referent_ty = substs_with_expr_ty.to_vec();
 
-    let mut check_referent = |referent| {
+    let mut check_reference_and_referent = |reference, referent| {
         let referent_ty = cx.typeck_results().expr_ty(referent);
 
-        if !is_copy(cx, referent_ty) {
+        if !is_copy(cx, referent_ty)
+            && (referent_ty.has_significant_drop(cx.tcx, cx.param_env)
+                || !referent_used_exactly_once(cx, possible_borrowers, reference))
+        {
             return false;
         }
 
@@ -1101,15 +1157,14 @@ fn needless_borrow_impl_arg_position<'tcx>(
 
             let predicate = EarlyBinder(predicate).subst(cx.tcx, &substs_with_referent_ty);
             let obligation = Obligation::new(ObligationCause::dummy(), cx.param_env, predicate);
-            cx.tcx
-                .infer_ctxt()
-                .enter(|infcx| infcx.predicate_must_hold_modulo_regions(&obligation))
+            let infcx = cx.tcx.infer_ctxt().build();
+            infcx.predicate_must_hold_modulo_regions(&obligation)
         })
     };
 
     let mut needless_borrow = false;
     while let ExprKind::AddrOf(_, _, referent) = expr.kind {
-        if !check_referent(referent) {
+        if !check_reference_and_referent(expr, referent) {
             break;
         }
         expr = referent;
@@ -1137,6 +1192,36 @@ fn has_ref_mut_self_method(cx: &LateContext<'_>, trait_def_id: DefId) -> bool {
         })
 }
 
+fn referent_used_exactly_once<'tcx>(
+    cx: &LateContext<'tcx>,
+    possible_borrowers: &mut Vec<(LocalDefId, PossibleBorrowerMap<'tcx, 'tcx>)>,
+    reference: &Expr<'tcx>,
+) -> bool {
+    let mir = enclosing_mir(cx.tcx, reference.hir_id);
+    if let Some(local) = expr_local(cx.tcx, reference)
+        && let [location] = *local_assignments(mir, local).as_slice()
+        && let Some(statement) = mir.basic_blocks[location.block].statements.get(location.statement_index)
+        && let StatementKind::Assign(box (_, Rvalue::Ref(_, _, place))) = statement.kind
+        && !place.has_deref()
+    {
+        let body_owner_local_def_id = cx.tcx.hir().enclosing_body_owner(reference.hir_id);
+        if possible_borrowers
+            .last()
+            .map_or(true, |&(local_def_id, _)| local_def_id != body_owner_local_def_id)
+        {
+            possible_borrowers.push((body_owner_local_def_id, PossibleBorrowerMap::new(cx, mir)));
+        }
+        let possible_borrower = &mut possible_borrowers.last_mut().unwrap().1;
+        // If `only_borrowers` were used here, the `copyable_iterator::warn` test would fail. The reason is
+        // that `PossibleBorrowerVisitor::visit_terminator` considers `place.local` a possible borrower of
+        // itself. See the comment in that method for an explanation as to why.
+        possible_borrower.bounded_borrowers(&[local], &[local, place.local], place.local, location)
+            && used_exactly_once(mir, place.local).unwrap_or(false)
+    } else {
+        false
+    }
+}
+
 // Iteratively replaces `param_ty` with `new_ty` in `substs`, and similarly for each resulting
 // projected type that is a type parameter. Returns `false` if replacing the types would have an
 // effect on the function signature beyond substituting `new_ty` for `param_ty`.
@@ -1212,7 +1297,7 @@ impl<'tcx> TyPosition<'tcx> {
     fn position_for_result(self, cx: &LateContext<'tcx>) -> Position {
         match (self.position, self.ty) {
             (Position::ReborrowStable(precedence), Some(ty)) => {
-                Position::DerefStable(precedence, ty.is_sized(cx.tcx.at(DUMMY_SP), cx.param_env))
+                Position::DerefStable(precedence, ty.is_sized(cx.tcx, cx.param_env))
             },
             (position, _) => position,
         }
@@ -1241,7 +1326,7 @@ fn ty_auto_deref_stability<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, precedenc
             ty::Adt(..) if ty.has_placeholders() || ty.has_opaque_types() => {
                 Position::ReborrowStable(precedence).into()
             },
-            ty::Adt(_, substs) if substs.has_param_types_or_consts() => {
+            ty::Adt(_, substs) if substs.has_non_region_param() => {
                 TyPosition::new_deref_stable_for_result(precedence, ty)
             },
             ty::Bool
@@ -1263,7 +1348,7 @@ fn ty_auto_deref_stability<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, precedenc
             | ty::Tuple(_)
             | ty::Projection(_) => Position::DerefStable(
                 precedence,
-                ty.is_sized(cx.tcx.at(DUMMY_SP), cx.param_env.without_caller_bounds()),
+                ty.is_sized(cx.tcx, cx.param_env.without_caller_bounds()),
             )
             .into(),
         };
@@ -1311,7 +1396,7 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
             };
 
             let expr_str = if !expr_is_macro_call && is_final_ufcs && expr.precedence().order() < PREC_PREFIX {
-                format!("({})", expr_str)
+                format!("({expr_str})")
             } else {
                 expr_str.into_owned()
             };
@@ -1325,7 +1410,7 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
                     Mutability::Mut => "explicit `deref_mut` method call",
                 },
                 "try this",
-                format!("{}{}{}", addr_of_str, deref_str, expr_str),
+                format!("{addr_of_str}{deref_str}{expr_str}"),
                 app,
             );
         },
@@ -1339,7 +1424,7 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
                     && !has_enclosing_paren(&snip)
                     && (expr.precedence().order() < data.position.precedence() || calls_field)
                 {
-                    format!("({})", snip)
+                    format!("({snip})")
                 } else {
                     snip.into()
                 };
@@ -1382,9 +1467,9 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
                     let (snip, snip_is_macro) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app);
                     let sugg =
                         if !snip_is_macro && expr.precedence().order() < precedence && !has_enclosing_paren(&snip) {
-                            format!("{}({})", prefix, snip)
+                            format!("{prefix}({snip})")
                         } else {
-                            format!("{}{}", prefix, snip)
+                            format!("{prefix}{snip}")
                         };
                     diag.span_suggestion(data.span, "try this", sugg, app);
                 },
@@ -1421,8 +1506,8 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
     }
 }
 
-impl Dereferencing {
-    fn check_local_usage<'tcx>(&mut self, cx: &LateContext<'tcx>, e: &Expr<'tcx>, local: HirId) {
+impl<'tcx> Dereferencing<'tcx> {
+    fn check_local_usage(&mut self, cx: &LateContext<'tcx>, e: &Expr<'tcx>, local: HirId) {
         if let Some(outer_pat) = self.ref_locals.get_mut(&local) {
             if let Some(pat) = outer_pat {
                 // Check for auto-deref
@@ -1463,14 +1548,14 @@ impl Dereferencing {
                             } else {
                                 pat.always_deref = false;
                                 let snip = snippet_with_context(cx, e.span, parent.span.ctxt(), "..", &mut pat.app).0;
-                                pat.replacements.push((e.span, format!("&{}", snip)));
+                                pat.replacements.push((e.span, format!("&{snip}")));
                             }
                         },
                         _ if !e.span.from_expansion() => {
                             // Double reference might be needed at this point.
                             pat.always_deref = false;
                             let snip = snippet_with_applicability(cx, e.span, "..", &mut pat.app);
-                            pat.replacements.push((e.span, format!("&{}", snip)));
+                            pat.replacements.push((e.span, format!("&{snip}")));
                         },
                         // Edge case for macros. The span of the identifier will usually match the context of the
                         // binding, but not if the identifier was created in a macro. e.g. `concat_idents` and proc