Auto merge of #132301 - compiler-errors:adjust, r=lcnr

Remove region from adjustments

It's not necessary to store this region, because it's only used in THIR and MemCat/ExprUse, both of which already basically only deal with erased regions anyways.

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1525,7 +1525,6 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 matches!(
                     adj.kind,
                     ty::adjustment::Adjust::Borrow(ty::adjustment::AutoBorrow::Ref(
-                        _,
                         ty::adjustment::AutoBorrowMutability::Not
                             | ty::adjustment::AutoBorrowMutability::Mut {
                                 allow_two_phase_borrow: ty::adjustment::AllowTwoPhase::No

compiler/rustc_hir_typeck/src/autoderef.rs

@@ -50,8 +50,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     self.try_overloaded_deref(autoderef.span(), source).and_then(
                         |InferOk { value: method, obligations: o }| {
                             obligations.extend(o);
-                            if let ty::Ref(region, _, mutbl) = *method.sig.output().kind() {
+                            // FIXME: we should assert the sig is &T here... there's no reason for this to be fallible.
-                                Some(OverloadedDeref { region, mutbl, span: autoderef.span() })
+                            if let ty::Ref(_, _, mutbl) = *method.sig.output().kind() {
+                                Some(OverloadedDeref { mutbl, span: autoderef.span() })
                             } else {
                                 None
                             }

compiler/rustc_hir_typeck/src/callee.rs

@@ -307,7 +307,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if borrow {
                     // Check for &self vs &mut self in the method signature. Since this is either
                     // the Fn or FnMut trait, it should be one of those.
-                    let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind() else {
+                    let ty::Ref(_, _, mutbl) = method.sig.inputs()[0].kind() else {
                         bug!("Expected `FnMut`/`Fn` to take receiver by-ref/by-mut")
                     };
 
@@ -317,7 +317,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let mutbl = AutoBorrowMutability::new(*mutbl, AllowTwoPhase::No);
 
                     autoref = Some(Adjustment {
-                        kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
+                        kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                         target: method.sig.inputs()[0],
                     });
                 }

compiler/rustc_hir_typeck/src/coercion.rs

@@ -113,7 +113,7 @@ fn identity(_: Ty<'_>) -> Vec<Adjustment<'_>> {
     vec![]
 }
 
-fn simple<'tcx>(kind: Adjust<'tcx>) -> impl FnOnce(Ty<'tcx>) -> Vec<Adjustment<'tcx>> {
+fn simple<'tcx>(kind: Adjust) -> impl FnOnce(Ty<'tcx>) -> Vec<Adjustment<'tcx>> {
     move |target| vec![Adjustment { kind, target }]
 }
 
@@ -484,14 +484,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
         // Now apply the autoref. We have to extract the region out of
         // the final ref type we got.
-        let ty::Ref(r_borrow, _, _) = ty.kind() else {
+        let ty::Ref(..) = ty.kind() else {
             span_bug!(span, "expected a ref type, got {:?}", ty);
         };
         let mutbl = AutoBorrowMutability::new(mutbl_b, self.allow_two_phase);
-        adjustments.push(Adjustment {
+        adjustments.push(Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)), target: ty });
-            kind: Adjust::Borrow(AutoBorrow::Ref(*r_borrow, mutbl)),
-            target: ty,
-        });
 
         debug!("coerce_borrowed_pointer: succeeded ty={:?} adjustments={:?}", ty, adjustments);
 
@@ -547,7 +544,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                 let mutbl = AutoBorrowMutability::new(mutbl_b, AllowTwoPhase::No);
 
                 Some((Adjustment { kind: Adjust::Deref(None), target: ty_a }, Adjustment {
-                    kind: Adjust::Borrow(AutoBorrow::Ref(r_borrow, mutbl)),
+                    kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                     target: Ty::new_ref(self.tcx, r_borrow, ty_a, mutbl_b),
                 }))
             }
@@ -827,7 +824,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         };
 
         let (pin, a_region, a_ty, mut_a) = extract_pin_mut(a)?;
-        let (_, b_region, _b_ty, mut_b) = extract_pin_mut(b)?;
+        let (_, _, _b_ty, mut_b) = extract_pin_mut(b)?;
 
         coerce_mutbls(mut_a, mut_b)?;
 
@@ -841,7 +838,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         // To complete the reborrow, we need to make sure we can unify the inner types, and if so we
         // add the adjustments.
         self.unify_and(a, b, |_inner_ty| {
-            vec![Adjustment { kind: Adjust::ReborrowPin(b_region, mut_b), target: b }]
+            vec![Adjustment { kind: Adjust::ReborrowPin(mut_b), target: b }]
         })
     }
 
@@ -1321,7 +1318,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let noop = match self.typeck_results.borrow().expr_adjustments(expr) {
                 &[
                     Adjustment { kind: Adjust::Deref(_), .. },
-                    Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(_, mutbl_adj)), .. },
+                    Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(mutbl_adj)), .. },
                 ] => {
                     match *self.node_ty(expr.hir_id).kind() {
                         ty::Ref(_, _, mt_orig) => {

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -781,7 +781,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                     self.walk_autoref(expr, &place_with_id, autoref);
                 }
 
-                adjustment::Adjust::ReborrowPin(_, mutbl) => {
+                adjustment::Adjust::ReborrowPin(mutbl) => {
                     // Reborrowing a Pin is like a combinations of a deref and a borrow, so we do
                     // both.
                     let bk = match mutbl {
@@ -804,7 +804,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
         &self,
         expr: &hir::Expr<'_>,
         base_place: &PlaceWithHirId<'tcx>,
-        autoref: &adjustment::AutoBorrow<'tcx>,
+        autoref: &adjustment::AutoBorrow,
     ) {
         debug!(
             "walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
@@ -812,7 +812,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
         );
 
         match *autoref {
-            adjustment::AutoBorrow::Ref(_, m) => {
+            adjustment::AutoBorrow::Ref(m) => {
                 self.delegate.borrow_mut().borrow(
                     base_place,
                     base_place.hir_id,
@@ -1283,7 +1283,12 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
             adjustment::Adjust::Deref(overloaded) => {
                 // Equivalent to *expr or something similar.
                 let base = if let Some(deref) = overloaded {
-                    let ref_ty = Ty::new_ref(self.cx.tcx(), deref.region, target, deref.mutbl);
+                    let ref_ty = Ty::new_ref(
+                        self.cx.tcx(),
+                        self.cx.tcx().lifetimes.re_erased,
+                        target,
+                        deref.mutbl,
+                    );
                     self.cat_rvalue(expr.hir_id, ref_ty)
                 } else {
                     previous()?

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -264,7 +264,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let autoborrow_mut = adj.iter().any(|adj| {
             matches!(adj, &Adjustment {
-                kind: Adjust::Borrow(AutoBorrow::Ref(_, AutoBorrowMutability::Mut { .. })),
+                kind: Adjust::Borrow(AutoBorrow::Ref(AutoBorrowMutability::Mut { .. })),
                 ..
             })
         });

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -200,10 +200,8 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                 // for two-phase borrows.
                 let mutbl = AutoBorrowMutability::new(mutbl, AllowTwoPhase::Yes);
 
-                adjustments.push(Adjustment {
+                adjustments
-                    kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
+                    .push(Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)), target });
-                    target,
-                });
 
                 if unsize {
                     let unsized_ty = if let ty::Array(elem_ty, _) = base_ty.kind() {
@@ -250,7 +248,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                     _ => bug!("Cannot adjust receiver type for reborrowing pin of {target:?}"),
                 };
 
-                adjustments.push(Adjustment { kind: Adjust::ReborrowPin(region, mutbl), target });
+                adjustments.push(Adjustment { kind: Adjust::ReborrowPin(mutbl), target });
             }
             None => {}
         }

compiler/rustc_hir_typeck/src/op.rs

@@ -256,23 +256,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             Ok(method) => {
                 let by_ref_binop = !op.node.is_by_value();
                 if is_assign == IsAssign::Yes || by_ref_binop {
-                    if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind() {
+                    if let ty::Ref(_, _, mutbl) = method.sig.inputs()[0].kind() {
                         let mutbl = AutoBorrowMutability::new(*mutbl, AllowTwoPhase::Yes);
                         let autoref = Adjustment {
-                            kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
+                            kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                             target: method.sig.inputs()[0],
                         };
                         self.apply_adjustments(lhs_expr, vec![autoref]);
                     }
                 }
                 if by_ref_binop {
-                    if let ty::Ref(region, _, mutbl) = method.sig.inputs()[1].kind() {
+                    if let ty::Ref(_, _, mutbl) = method.sig.inputs()[1].kind() {
                         // Allow two-phase borrows for binops in initial deployment
                         // since they desugar to methods
                         let mutbl = AutoBorrowMutability::new(*mutbl, AllowTwoPhase::Yes);
 
                         let autoref = Adjustment {
-                            kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
+                            kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                             target: method.sig.inputs()[1],
                         };
                         // HACK(eddyb) Bypass checks due to reborrows being in

compiler/rustc_hir_typeck/src/place_op.rs

@@ -29,9 +29,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let ok = self.try_overloaded_deref(expr.span, oprnd_ty)?;
         let method = self.register_infer_ok_obligations(ok);
-        if let ty::Ref(region, _, hir::Mutability::Not) = method.sig.inputs()[0].kind() {
+        if let ty::Ref(_, _, hir::Mutability::Not) = method.sig.inputs()[0].kind() {
             self.apply_adjustments(oprnd_expr, vec![Adjustment {
-                kind: Adjust::Borrow(AutoBorrow::Ref(*region, AutoBorrowMutability::Not)),
+                kind: Adjust::Borrow(AutoBorrow::Ref(AutoBorrowMutability::Not)),
                 target: method.sig.inputs()[0],
             }]);
         } else {
@@ -158,7 +158,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let mut adjustments = self.adjust_steps(autoderef);
                 if let ty::Ref(region, _, hir::Mutability::Not) = method.sig.inputs()[0].kind() {
                     adjustments.push(Adjustment {
-                        kind: Adjust::Borrow(AutoBorrow::Ref(*region, AutoBorrowMutability::Not)),
+                        kind: Adjust::Borrow(AutoBorrow::Ref(AutoBorrowMutability::Not)),
                         target: Ty::new_imm_ref(self.tcx, *region, adjusted_ty),
                     });
                 } else {
@@ -289,9 +289,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         )
                     {
                         let method = self.register_infer_ok_obligations(ok);
-                        if let ty::Ref(region, _, mutbl) = *method.sig.output().kind() {
+                        let ty::Ref(_, _, mutbl) = *method.sig.output().kind() else {
-                            *deref = OverloadedDeref { region, mutbl, span: deref.span };
+                            span_bug!(
-                        }
+                                self.tcx.def_span(method.def_id),
+                                "expected DerefMut to return a &mut"
+                            );
+                        };
+                        *deref = OverloadedDeref { mutbl, span: deref.span };
                         // If this is a union field, also throw an error for `DerefMut` of `ManuallyDrop` (see RFC 2514).
                         // This helps avoid accidental drops.
                         if inside_union
@@ -390,7 +394,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // not the case today.
                         allow_two_phase_borrow: AllowTwoPhase::No,
                     };
-                    adjustment.kind = Adjust::Borrow(AutoBorrow::Ref(*region, mutbl));
+                    adjustment.kind = Adjust::Borrow(AutoBorrow::Ref(mutbl));
                     adjustment.target = Ty::new_ref(self.tcx, *region, source, mutbl.into());
                 }
                 source = adjustment.target;

compiler/rustc_lint/src/unused.rs

@@ -1610,7 +1610,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedAllocation {
         }
 
         for adj in cx.typeck_results().expr_adjustments(e) {
-            if let adjustment::Adjust::Borrow(adjustment::AutoBorrow::Ref(_, m)) = adj.kind {
+            if let adjustment::Adjust::Borrow(adjustment::AutoBorrow::Ref(m)) = adj.kind {
                 match m {
                     adjustment::AutoBorrowMutability::Not => {
                         cx.emit_span_lint(UNUSED_ALLOCATION, e.span, UnusedAllocationDiag);

compiler/rustc_middle/src/ty/adjustment.rs

@@ -82,7 +82,7 @@ pub enum PointerCoercion {
 ///    `Box<[i32]>` is an `Adjust::Unsize` with the target `Box<[i32]>`.
 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Adjustment<'tcx> {
-    pub kind: Adjust<'tcx>,
+    pub kind: Adjust,
     pub target: Ty<'tcx>,
 }
 
@@ -93,20 +93,20 @@ impl<'tcx> Adjustment<'tcx> {
 }
 
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
-pub enum Adjust<'tcx> {
+pub enum Adjust {
     /// Go from ! to any type.
     NeverToAny,
 
     /// Dereference once, producing a place.
-    Deref(Option<OverloadedDeref<'tcx>>),
+    Deref(Option<OverloadedDeref>),
 
     /// Take the address and produce either a `&` or `*` pointer.
-    Borrow(AutoBorrow<'tcx>),
+    Borrow(AutoBorrow),
 
     Pointer(PointerCoercion),
 
     /// Take a pinned reference and reborrow as a `Pin<&mut T>` or `Pin<&T>`.
-    ReborrowPin(ty::Region<'tcx>, hir::Mutability),
+    ReborrowPin(hir::Mutability),
 }
 
 /// An overloaded autoderef step, representing a `Deref(Mut)::deref(_mut)`
@@ -115,17 +115,16 @@ pub enum Adjust<'tcx> {
 /// being those shared by both the receiver and the returned reference.
 #[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct OverloadedDeref<'tcx> {
+pub struct OverloadedDeref {
-    pub region: ty::Region<'tcx>,
     pub mutbl: hir::Mutability,
     /// The `Span` associated with the field access or method call
     /// that triggered this overloaded deref.
     pub span: Span,
 }
 
-impl<'tcx> OverloadedDeref<'tcx> {
+impl OverloadedDeref {
     /// Get the zst function item type for this method call.
-    pub fn method_call(&self, tcx: TyCtxt<'tcx>, source: Ty<'tcx>) -> Ty<'tcx> {
+    pub fn method_call<'tcx>(&self, tcx: TyCtxt<'tcx>, source: Ty<'tcx>) -> Ty<'tcx> {
         let trait_def_id = match self.mutbl {
             hir::Mutability::Not => tcx.require_lang_item(LangItem::Deref, None),
             hir::Mutability::Mut => tcx.require_lang_item(LangItem::DerefMut, None),
@@ -187,9 +186,9 @@ impl From<AutoBorrowMutability> for hir::Mutability {
 
 #[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub enum AutoBorrow<'tcx> {
+pub enum AutoBorrow {
     /// Converts from T to &T.
-    Ref(ty::Region<'tcx>, AutoBorrowMutability),
+    Ref(AutoBorrowMutability),
 
     /// Converts from T to *T.
     RawPtr(hir::Mutability),

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -140,7 +140,7 @@ impl<'tcx> Cx<'tcx> {
 
                 expr = Expr {
                     temp_lifetime,
-                    ty: Ty::new_ref(self.tcx, deref.region, expr.ty, deref.mutbl),
+                    ty: Ty::new_ref(self.tcx, self.tcx.lifetimes.re_erased, expr.ty, deref.mutbl),
                     span,
                     kind: ExprKind::Borrow {
                         borrow_kind: deref.mutbl.to_borrow_kind(),
@@ -152,14 +152,14 @@ impl<'tcx> Cx<'tcx> {
 
                 self.overloaded_place(hir_expr, adjustment.target, Some(call), expr, deref.span)
             }
-            Adjust::Borrow(AutoBorrow::Ref(_, m)) => ExprKind::Borrow {
+            Adjust::Borrow(AutoBorrow::Ref(m)) => ExprKind::Borrow {
                 borrow_kind: m.to_borrow_kind(),
                 arg: self.thir.exprs.push(expr),
             },
             Adjust::Borrow(AutoBorrow::RawPtr(mutability)) => {
                 ExprKind::RawBorrow { mutability, arg: self.thir.exprs.push(expr) }
             }
-            Adjust::ReborrowPin(region, mutbl) => {
+            Adjust::ReborrowPin(mutbl) => {
                 debug!("apply ReborrowPin adjustment");
                 // Rewrite `$expr` as `Pin { __pointer: &(mut)? *($expr).__pointer }`
 
@@ -197,7 +197,8 @@ impl<'tcx> Cx<'tcx> {
                     hir::Mutability::Mut => BorrowKind::Mut { kind: mir::MutBorrowKind::Default },
                     hir::Mutability::Not => BorrowKind::Shared,
                 };
-                let new_pin_target = Ty::new_ref(self.tcx, region, ptr_target_ty, mutbl);
+                let new_pin_target =
+                    Ty::new_ref(self.tcx, self.tcx.lifetimes.re_erased, ptr_target_ty, mutbl);
                 let expr = self.thir.exprs.push(Expr {
                     temp_lifetime,
                     ty: new_pin_target,

compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs

@@ -551,10 +551,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         ] => "",
                         [
                             ..,
-                            Adjustment {
+                            Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(mut_)), target: _ },
-                                kind: Adjust::Borrow(AutoBorrow::Ref(_, mut_)),
-                                target: _,
-                            },
                         ] => hir::Mutability::from(*mut_).ref_prefix_str(),
                         _ => "",
                     };

src/tools/clippy/clippy_lints/src/dereference.rs

@@ -418,7 +418,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                         let (required_refs, msg) = if can_auto_borrow {
                             (1, if deref_count == 1 { borrow_msg } else { deref_msg })
                         } else if let Some(&Adjustment {
-                            kind: Adjust::Borrow(AutoBorrow::Ref(_, mutability)),
+                            kind: Adjust::Borrow(AutoBorrow::Ref(mutability)),
                             ..
                         }) = next_adjust
                             && matches!(mutability, AutoBorrowMutability::Mut { .. })

src/tools/clippy/clippy_lints/src/loops/explicit_into_iter_loop.rs

@@ -53,7 +53,7 @@ pub(super) fn check(cx: &LateContext<'_>, self_arg: &Expr<'_>, call_expr: &Expr<
         [] => AdjustKind::None,
         &[
             Adjustment {
-                kind: Adjust::Borrow(AutoBorrow::Ref(_, mutbl)),
+                kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                 ..
             },
         ] => AdjustKind::borrow(mutbl),
@@ -62,7 +62,7 @@ pub(super) fn check(cx: &LateContext<'_>, self_arg: &Expr<'_>, call_expr: &Expr<
                 kind: Adjust::Deref(_), ..
             },
             Adjustment {
-                kind: Adjust::Borrow(AutoBorrow::Ref(_, mutbl)),
+                kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                 target,
             },
         ] => {

src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs

@@ -199,7 +199,7 @@ fn is_ref_iterable<'tcx>(
                     kind: Adjust::Deref(_), ..
                 },
                 Adjustment {
-                    kind: Adjust::Borrow(AutoBorrow::Ref(_, mutbl)),
+                    kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                     target,
                 },
                 ..,
@@ -236,7 +236,7 @@ fn is_ref_iterable<'tcx>(
             },
             &[
                 Adjustment {
-                    kind: Adjust::Borrow(AutoBorrow::Ref(_, mutbl)),
+                    kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
                     target,
                 },
                 ..,

src/tools/clippy/clippy_lints/src/methods/manual_inspect.rs

@@ -137,7 +137,7 @@ pub(crate) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, arg: &Expr<'_>, name:
                                 _ if matches!(
                                     typeck.expr_adjustments(prev_expr).first(),
                                     Some(Adjustment {
-                                        kind: Adjust::Borrow(AutoBorrow::Ref(_, AutoBorrowMutability::Not))
+                                        kind: Adjust::Borrow(AutoBorrow::Ref(AutoBorrowMutability::Not))
                                             | Adjust::Deref(_),
                                         ..
                                     })
@@ -230,7 +230,7 @@ fn check_use<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (UseKind<'tcx>,
             if use_cx
                 .adjustments
                 .first()
-                .is_some_and(|a| matches!(a.kind, Adjust::Borrow(AutoBorrow::Ref(_, AutoBorrowMutability::Not)))) =>
+                .is_some_and(|a| matches!(a.kind, Adjust::Borrow(AutoBorrow::Ref(AutoBorrowMutability::Not)))) =>
         {
             UseKind::AutoBorrowed
         },

src/tools/clippy/clippy_lints/src/redundant_slicing.rs

@@ -110,7 +110,7 @@ impl<'tcx> LateLintPass<'tcx> for RedundantSlicing {
                 ) || cx.typeck_results().expr_adjustments(expr).first().map_or(false, |a| {
                     matches!(
                         a.kind,
-                        Adjust::Borrow(AutoBorrow::Ref(_, AutoBorrowMutability::Mut { .. }))
+                        Adjust::Borrow(AutoBorrow::Ref(AutoBorrowMutability::Mut { .. }))
                     )
                 }) || (matches!(
                     cx.typeck_results().expr_ty(indexed).ref_mutability(),