rustc_lint/
impl_trait_overcaptures.rs

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1use std::assert_matches::debug_assert_matches;
2use std::cell::LazyCell;
3
4use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
5use rustc_data_structures::unord::UnordSet;
6use rustc_errors::{LintDiagnostic, Subdiagnostic};
7use rustc_hir as hir;
8use rustc_hir::def::DefKind;
9use rustc_hir::def_id::{DefId, LocalDefId};
10use rustc_infer::infer::TyCtxtInferExt;
11use rustc_infer::infer::outlives::env::OutlivesEnvironment;
12use rustc_macros::LintDiagnostic;
13use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
14use rustc_middle::ty::relate::{
15    Relate, RelateResult, TypeRelation, structurally_relate_consts, structurally_relate_tys,
16};
17use rustc_middle::ty::{
18    self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
19};
20use rustc_middle::{bug, span_bug};
21use rustc_session::lint::FutureIncompatibilityReason;
22use rustc_session::{declare_lint, declare_lint_pass};
23use rustc_span::edition::Edition;
24use rustc_span::{Span, Symbol};
25use rustc_trait_selection::errors::{
26    AddPreciseCapturingForOvercapture, impl_trait_overcapture_suggestion,
27};
28use rustc_trait_selection::regions::OutlivesEnvironmentBuildExt;
29use rustc_trait_selection::traits::ObligationCtxt;
30
31use crate::{LateContext, LateLintPass, fluent_generated as fluent};
32
33declare_lint! {
34    /// The `impl_trait_overcaptures` lint warns against cases where lifetime
35    /// capture behavior will differ in edition 2024.
36    ///
37    /// In the 2024 edition, `impl Trait`s will capture all lifetimes in scope,
38    /// rather than just the lifetimes that are mentioned in the bounds of the type.
39    /// Often these sets are equal, but if not, it means that the `impl Trait` may
40    /// cause erroneous borrow-checker errors.
41    ///
42    /// ### Example
43    ///
44    /// ```rust,compile_fail
45    /// # #![deny(impl_trait_overcaptures)]
46    /// # use std::fmt::Display;
47    /// let mut x = vec![];
48    /// x.push(1);
49    ///
50    /// fn test(x: &Vec<i32>) -> impl Display {
51    ///     x[0]
52    /// }
53    ///
54    /// let element = test(&x);
55    /// x.push(2);
56    /// println!("{element}");
57    /// ```
58    ///
59    /// {{produces}}
60    ///
61    /// ### Explanation
62    ///
63    /// In edition < 2024, the returned `impl Display` doesn't capture the
64    /// lifetime from the `&Vec<i32>`, so the vector can be mutably borrowed
65    /// while the `impl Display` is live.
66    ///
67    /// To fix this, we can explicitly state that the `impl Display` doesn't
68    /// capture any lifetimes, using `impl Display + use<>`.
69    pub IMPL_TRAIT_OVERCAPTURES,
70    Allow,
71    "`impl Trait` will capture more lifetimes than possibly intended in edition 2024",
72    @future_incompatible = FutureIncompatibleInfo {
73        reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
74        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/rpit-lifetime-capture.html>",
75    };
76}
77
78declare_lint! {
79    /// The `impl_trait_redundant_captures` lint warns against cases where use of the
80    /// precise capturing `use<...>` syntax is not needed.
81    ///
82    /// In the 2024 edition, `impl Trait`s will capture all lifetimes in scope.
83    /// If precise-capturing `use<...>` syntax is used, and the set of parameters
84    /// that are captures are *equal* to the set of parameters in scope, then
85    /// the syntax is redundant, and can be removed.
86    ///
87    /// ### Example
88    ///
89    /// ```rust,edition2024,compile_fail
90    /// # #![deny(impl_trait_redundant_captures)]
91    /// fn test<'a>(x: &'a i32) -> impl Sized + use<'a> { x }
92    /// ```
93    ///
94    /// {{produces}}
95    ///
96    /// ### Explanation
97    ///
98    /// To fix this, remove the `use<'a>`, since the lifetime is already captured
99    /// since it is in scope.
100    pub IMPL_TRAIT_REDUNDANT_CAPTURES,
101    Allow,
102    "redundant precise-capturing `use<...>` syntax on an `impl Trait`",
103}
104
105declare_lint_pass!(
106    /// Lint for opaque types that will begin capturing in-scope but unmentioned lifetimes
107    /// in edition 2024.
108    ImplTraitOvercaptures => [IMPL_TRAIT_OVERCAPTURES, IMPL_TRAIT_REDUNDANT_CAPTURES]
109);
110
111impl<'tcx> LateLintPass<'tcx> for ImplTraitOvercaptures {
112    fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'tcx>) {
113        match &it.kind {
114            hir::ItemKind::Fn { .. } => check_fn(cx.tcx, it.owner_id.def_id),
115            _ => {}
116        }
117    }
118
119    fn check_impl_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::ImplItem<'tcx>) {
120        match &it.kind {
121            hir::ImplItemKind::Fn(_, _) => check_fn(cx.tcx, it.owner_id.def_id),
122            _ => {}
123        }
124    }
125
126    fn check_trait_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::TraitItem<'tcx>) {
127        match &it.kind {
128            hir::TraitItemKind::Fn(_, _) => check_fn(cx.tcx, it.owner_id.def_id),
129            _ => {}
130        }
131    }
132}
133
134#[derive(PartialEq, Eq, Hash, Debug, Copy, Clone)]
135enum ParamKind {
136    // Early-bound var.
137    Early(Symbol, u32),
138    // Late-bound var on function, not within a binder. We can capture these.
139    Free(DefId, Symbol),
140    // Late-bound var in a binder. We can't capture these yet.
141    Late,
142}
143
144fn check_fn(tcx: TyCtxt<'_>, parent_def_id: LocalDefId) {
145    let sig = tcx.fn_sig(parent_def_id).instantiate_identity();
146
147    let mut in_scope_parameters = FxIndexMap::default();
148    // Populate the in_scope_parameters list first with all of the generics in scope
149    let mut current_def_id = Some(parent_def_id.to_def_id());
150    while let Some(def_id) = current_def_id {
151        let generics = tcx.generics_of(def_id);
152        for param in &generics.own_params {
153            in_scope_parameters.insert(param.def_id, ParamKind::Early(param.name, param.index));
154        }
155        current_def_id = generics.parent;
156    }
157
158    for bound_var in sig.bound_vars() {
159        let ty::BoundVariableKind::Region(ty::BoundRegionKind::Named(def_id, name)) = bound_var
160        else {
161            span_bug!(tcx.def_span(parent_def_id), "unexpected non-lifetime binder on fn sig");
162        };
163
164        in_scope_parameters.insert(def_id, ParamKind::Free(def_id, name));
165    }
166
167    let sig = tcx.liberate_late_bound_regions(parent_def_id.to_def_id(), sig);
168
169    // Then visit the signature to walk through all the binders (incl. the late-bound
170    // vars on the function itself, which we need to count too).
171    sig.visit_with(&mut VisitOpaqueTypes {
172        tcx,
173        parent_def_id,
174        in_scope_parameters,
175        seen: Default::default(),
176        // Lazily compute these two, since they're likely a bit expensive.
177        variances: LazyCell::new(|| {
178            let mut functional_variances = FunctionalVariances {
179                tcx,
180                variances: FxHashMap::default(),
181                ambient_variance: ty::Covariant,
182                generics: tcx.generics_of(parent_def_id),
183            };
184            functional_variances.relate(sig, sig).unwrap();
185            functional_variances.variances
186        }),
187        outlives_env: LazyCell::new(|| {
188            let typing_env = ty::TypingEnv::non_body_analysis(tcx, parent_def_id);
189            let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
190            let ocx = ObligationCtxt::new(&infcx);
191            let assumed_wf_tys = ocx.assumed_wf_types(param_env, parent_def_id).unwrap_or_default();
192            OutlivesEnvironment::new(&infcx, parent_def_id, param_env, assumed_wf_tys)
193        }),
194    });
195}
196
197struct VisitOpaqueTypes<'tcx, VarFn, OutlivesFn> {
198    tcx: TyCtxt<'tcx>,
199    parent_def_id: LocalDefId,
200    in_scope_parameters: FxIndexMap<DefId, ParamKind>,
201    variances: LazyCell<FxHashMap<DefId, ty::Variance>, VarFn>,
202    outlives_env: LazyCell<OutlivesEnvironment<'tcx>, OutlivesFn>,
203    seen: FxIndexSet<LocalDefId>,
204}
205
206impl<'tcx, VarFn, OutlivesFn> TypeVisitor<TyCtxt<'tcx>>
207    for VisitOpaqueTypes<'tcx, VarFn, OutlivesFn>
208where
209    VarFn: FnOnce() -> FxHashMap<DefId, ty::Variance>,
210    OutlivesFn: FnOnce() -> OutlivesEnvironment<'tcx>,
211{
212    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(&mut self, t: &ty::Binder<'tcx, T>) {
213        // When we get into a binder, we need to add its own bound vars to the scope.
214        let mut added = vec![];
215        for arg in t.bound_vars() {
216            let arg: ty::BoundVariableKind = arg;
217            match arg {
218                ty::BoundVariableKind::Region(ty::BoundRegionKind::Named(def_id, ..))
219                | ty::BoundVariableKind::Ty(ty::BoundTyKind::Param(def_id, _)) => {
220                    added.push(def_id);
221                    let unique = self.in_scope_parameters.insert(def_id, ParamKind::Late);
222                    assert_eq!(unique, None);
223                }
224                _ => {
225                    self.tcx.dcx().span_delayed_bug(
226                        self.tcx.def_span(self.parent_def_id),
227                        format!("unsupported bound variable kind: {arg:?}"),
228                    );
229                }
230            }
231        }
232
233        t.super_visit_with(self);
234
235        // And remove them. The `shift_remove` should be `O(1)` since we're popping
236        // them off from the end.
237        for arg in added.into_iter().rev() {
238            self.in_scope_parameters.shift_remove(&arg);
239        }
240    }
241
242    fn visit_ty(&mut self, t: Ty<'tcx>) {
243        if !t.has_aliases() {
244            return;
245        }
246
247        if let ty::Alias(ty::Projection, opaque_ty) = *t.kind()
248            && self.tcx.is_impl_trait_in_trait(opaque_ty.def_id)
249        {
250            // visit the opaque of the RPITIT
251            self.tcx
252                .type_of(opaque_ty.def_id)
253                .instantiate(self.tcx, opaque_ty.args)
254                .visit_with(self)
255        } else if let ty::Alias(ty::Opaque, opaque_ty) = *t.kind()
256            && let Some(opaque_def_id) = opaque_ty.def_id.as_local()
257            // Don't recurse infinitely on an opaque
258            && self.seen.insert(opaque_def_id)
259            // If it's owned by this function
260            && let opaque =
261                self.tcx.hir_node_by_def_id(opaque_def_id).expect_opaque_ty()
262            // We want to recurse into RPITs and async fns, even though the latter
263            // doesn't overcapture on its own, it may mention additional RPITs
264            // in its bounds.
265            && let hir::OpaqueTyOrigin::FnReturn { parent, .. }
266                | hir::OpaqueTyOrigin::AsyncFn { parent, .. } = opaque.origin
267            && parent == self.parent_def_id
268        {
269            let opaque_span = self.tcx.def_span(opaque_def_id);
270            let new_capture_rules = opaque_span.at_least_rust_2024();
271            if !new_capture_rules
272                && !opaque.bounds.iter().any(|bound| matches!(bound, hir::GenericBound::Use(..)))
273            {
274                // Compute the set of args that are captured by the opaque...
275                let mut captured = FxIndexSet::default();
276                let mut captured_regions = FxIndexSet::default();
277                let variances = self.tcx.variances_of(opaque_def_id);
278                let mut current_def_id = Some(opaque_def_id.to_def_id());
279                while let Some(def_id) = current_def_id {
280                    let generics = self.tcx.generics_of(def_id);
281                    for param in &generics.own_params {
282                        // A param is captured if it's invariant.
283                        if variances[param.index as usize] != ty::Invariant {
284                            continue;
285                        }
286
287                        let arg = opaque_ty.args[param.index as usize];
288                        // We need to turn all `ty::Param`/`ConstKind::Param` and
289                        // `ReEarlyParam`/`ReBound` into def ids.
290                        captured.insert(extract_def_id_from_arg(self.tcx, generics, arg));
291
292                        captured_regions.extend(arg.as_region());
293                    }
294                    current_def_id = generics.parent;
295                }
296
297                // Compute the set of in scope params that are not captured.
298                let mut uncaptured_args: FxIndexSet<_> = self
299                    .in_scope_parameters
300                    .iter()
301                    .filter(|&(def_id, _)| !captured.contains(def_id))
302                    .collect();
303                // Remove the set of lifetimes that are in-scope that outlive some other captured
304                // lifetime and are contravariant (i.e. covariant in argument position).
305                uncaptured_args.retain(|&(def_id, kind)| {
306                    let Some(ty::Bivariant | ty::Contravariant) = self.variances.get(def_id) else {
307                        // Keep all covariant/invariant args. Also if variance is `None`,
308                        // then that means it's either not a lifetime, or it didn't show up
309                        // anywhere in the signature.
310                        return true;
311                    };
312                    // We only computed variance of lifetimes...
313                    debug_assert_matches!(self.tcx.def_kind(def_id), DefKind::LifetimeParam);
314                    let uncaptured = match *kind {
315                        ParamKind::Early(name, index) => ty::Region::new_early_param(
316                            self.tcx,
317                            ty::EarlyParamRegion { name, index },
318                        ),
319                        ParamKind::Free(def_id, name) => ty::Region::new_late_param(
320                            self.tcx,
321                            self.parent_def_id.to_def_id(),
322                            ty::LateParamRegionKind::Named(def_id, name),
323                        ),
324                        // Totally ignore late bound args from binders.
325                        ParamKind::Late => return true,
326                    };
327                    // Does this region outlive any captured region?
328                    !captured_regions.iter().any(|r| {
329                        self.outlives_env
330                            .free_region_map()
331                            .sub_free_regions(self.tcx, *r, uncaptured)
332                    })
333                });
334
335                // If we have uncaptured args, and if the opaque doesn't already have
336                // `use<>` syntax on it, and we're < edition 2024, then warn the user.
337                if !uncaptured_args.is_empty() {
338                    let suggestion = impl_trait_overcapture_suggestion(
339                        self.tcx,
340                        opaque_def_id,
341                        self.parent_def_id,
342                        captured,
343                    );
344
345                    let uncaptured_spans: Vec<_> = uncaptured_args
346                        .into_iter()
347                        .map(|(def_id, _)| self.tcx.def_span(def_id))
348                        .collect();
349
350                    self.tcx.emit_node_span_lint(
351                        IMPL_TRAIT_OVERCAPTURES,
352                        self.tcx.local_def_id_to_hir_id(opaque_def_id),
353                        opaque_span,
354                        ImplTraitOvercapturesLint {
355                            self_ty: t,
356                            num_captured: uncaptured_spans.len(),
357                            uncaptured_spans,
358                            suggestion,
359                        },
360                    );
361                }
362            }
363
364            // Otherwise, if we are edition 2024, have `use<>` syntax, and
365            // have no uncaptured args, then we should warn to the user that
366            // it's redundant to capture all args explicitly.
367            if new_capture_rules
368                && let Some((captured_args, capturing_span)) =
369                    opaque.bounds.iter().find_map(|bound| match *bound {
370                        hir::GenericBound::Use(a, s) => Some((a, s)),
371                        _ => None,
372                    })
373            {
374                let mut explicitly_captured = UnordSet::default();
375                for arg in captured_args {
376                    match self.tcx.named_bound_var(arg.hir_id()) {
377                        Some(
378                            ResolvedArg::EarlyBound(def_id) | ResolvedArg::LateBound(_, _, def_id),
379                        ) => {
380                            if self.tcx.def_kind(self.tcx.local_parent(def_id)) == DefKind::OpaqueTy
381                            {
382                                let def_id = self
383                                    .tcx
384                                    .map_opaque_lifetime_to_parent_lifetime(def_id)
385                                    .opt_param_def_id(self.tcx, self.parent_def_id.to_def_id())
386                                    .expect("variable should have been duplicated from parent");
387
388                                explicitly_captured.insert(def_id);
389                            } else {
390                                explicitly_captured.insert(def_id.to_def_id());
391                            }
392                        }
393                        _ => {
394                            self.tcx.dcx().span_delayed_bug(
395                                self.tcx.hir().span(arg.hir_id()),
396                                "no valid for captured arg",
397                            );
398                        }
399                    }
400                }
401
402                if self
403                    .in_scope_parameters
404                    .iter()
405                    .all(|(def_id, _)| explicitly_captured.contains(def_id))
406                {
407                    self.tcx.emit_node_span_lint(
408                        IMPL_TRAIT_REDUNDANT_CAPTURES,
409                        self.tcx.local_def_id_to_hir_id(opaque_def_id),
410                        opaque_span,
411                        ImplTraitRedundantCapturesLint { capturing_span },
412                    );
413                }
414            }
415
416            // Walk into the bounds of the opaque, too, since we want to get nested opaques
417            // in this lint as well. Interestingly, one place that I expect this lint to fire
418            // is for `impl for<'a> Bound<Out = impl Other>`, since `impl Other` will begin
419            // to capture `'a` in e2024 (even though late-bound vars in opaques are not allowed).
420            for clause in
421                self.tcx.item_bounds(opaque_ty.def_id).iter_instantiated(self.tcx, opaque_ty.args)
422            {
423                clause.visit_with(self)
424            }
425        }
426
427        t.super_visit_with(self);
428    }
429}
430
431struct ImplTraitOvercapturesLint<'tcx> {
432    uncaptured_spans: Vec<Span>,
433    self_ty: Ty<'tcx>,
434    num_captured: usize,
435    suggestion: Option<AddPreciseCapturingForOvercapture>,
436}
437
438impl<'a> LintDiagnostic<'a, ()> for ImplTraitOvercapturesLint<'_> {
439    fn decorate_lint<'b>(self, diag: &'b mut rustc_errors::Diag<'a, ()>) {
440        diag.primary_message(fluent::lint_impl_trait_overcaptures);
441        diag.arg("self_ty", self.self_ty.to_string())
442            .arg("num_captured", self.num_captured)
443            .span_note(self.uncaptured_spans, fluent::lint_note)
444            .note(fluent::lint_note2);
445        if let Some(suggestion) = self.suggestion {
446            suggestion.add_to_diag(diag);
447        }
448    }
449}
450
451#[derive(LintDiagnostic)]
452#[diag(lint_impl_trait_redundant_captures)]
453struct ImplTraitRedundantCapturesLint {
454    #[suggestion(lint_suggestion, code = "", applicability = "machine-applicable")]
455    capturing_span: Span,
456}
457
458fn extract_def_id_from_arg<'tcx>(
459    tcx: TyCtxt<'tcx>,
460    generics: &'tcx ty::Generics,
461    arg: ty::GenericArg<'tcx>,
462) -> DefId {
463    match arg.unpack() {
464        ty::GenericArgKind::Lifetime(re) => match *re {
465            ty::ReEarlyParam(ebr) => generics.region_param(ebr, tcx).def_id,
466            ty::ReBound(
467                _,
468                ty::BoundRegion { kind: ty::BoundRegionKind::Named(def_id, ..), .. },
469            )
470            | ty::ReLateParam(ty::LateParamRegion {
471                scope: _,
472                kind: ty::LateParamRegionKind::Named(def_id, ..),
473            }) => def_id,
474            _ => unreachable!(),
475        },
476        ty::GenericArgKind::Type(ty) => {
477            let ty::Param(param_ty) = *ty.kind() else {
478                bug!();
479            };
480            generics.type_param(param_ty, tcx).def_id
481        }
482        ty::GenericArgKind::Const(ct) => {
483            let ty::ConstKind::Param(param_ct) = ct.kind() else {
484                bug!();
485            };
486            generics.const_param(param_ct, tcx).def_id
487        }
488    }
489}
490
491/// Computes the variances of regions that appear in the type, but considering
492/// late-bound regions too, which don't have their variance computed usually.
493///
494/// Like generalization, this is a unary operation implemented on top of the binary
495/// relation infrastructure, mostly because it's much easier to have the relation
496/// track the variance for you, rather than having to do it yourself.
497struct FunctionalVariances<'tcx> {
498    tcx: TyCtxt<'tcx>,
499    variances: FxHashMap<DefId, ty::Variance>,
500    ambient_variance: ty::Variance,
501    generics: &'tcx ty::Generics,
502}
503
504impl<'tcx> TypeRelation<TyCtxt<'tcx>> for FunctionalVariances<'tcx> {
505    fn cx(&self) -> TyCtxt<'tcx> {
506        self.tcx
507    }
508
509    fn relate_with_variance<T: Relate<TyCtxt<'tcx>>>(
510        &mut self,
511        variance: ty::Variance,
512        _: ty::VarianceDiagInfo<TyCtxt<'tcx>>,
513        a: T,
514        b: T,
515    ) -> RelateResult<'tcx, T> {
516        let old_variance = self.ambient_variance;
517        self.ambient_variance = self.ambient_variance.xform(variance);
518        self.relate(a, b).unwrap();
519        self.ambient_variance = old_variance;
520        Ok(a)
521    }
522
523    fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
524        structurally_relate_tys(self, a, b).unwrap();
525        Ok(a)
526    }
527
528    fn regions(
529        &mut self,
530        a: ty::Region<'tcx>,
531        _: ty::Region<'tcx>,
532    ) -> RelateResult<'tcx, ty::Region<'tcx>> {
533        let def_id = match *a {
534            ty::ReEarlyParam(ebr) => self.generics.region_param(ebr, self.tcx).def_id,
535            ty::ReBound(
536                _,
537                ty::BoundRegion { kind: ty::BoundRegionKind::Named(def_id, ..), .. },
538            )
539            | ty::ReLateParam(ty::LateParamRegion {
540                scope: _,
541                kind: ty::LateParamRegionKind::Named(def_id, ..),
542            }) => def_id,
543            _ => {
544                return Ok(a);
545            }
546        };
547
548        if let Some(variance) = self.variances.get_mut(&def_id) {
549            *variance = unify(*variance, self.ambient_variance);
550        } else {
551            self.variances.insert(def_id, self.ambient_variance);
552        }
553
554        Ok(a)
555    }
556
557    fn consts(
558        &mut self,
559        a: ty::Const<'tcx>,
560        b: ty::Const<'tcx>,
561    ) -> RelateResult<'tcx, ty::Const<'tcx>> {
562        structurally_relate_consts(self, a, b).unwrap();
563        Ok(a)
564    }
565
566    fn binders<T>(
567        &mut self,
568        a: ty::Binder<'tcx, T>,
569        b: ty::Binder<'tcx, T>,
570    ) -> RelateResult<'tcx, ty::Binder<'tcx, T>>
571    where
572        T: Relate<TyCtxt<'tcx>>,
573    {
574        self.relate(a.skip_binder(), b.skip_binder()).unwrap();
575        Ok(a)
576    }
577}
578
579/// What is the variance that satisfies the two variances?
580fn unify(a: ty::Variance, b: ty::Variance) -> ty::Variance {
581    match (a, b) {
582        // Bivariance is lattice bottom.
583        (ty::Bivariant, other) | (other, ty::Bivariant) => other,
584        // Invariant is lattice top.
585        (ty::Invariant, _) | (_, ty::Invariant) => ty::Invariant,
586        // If type is required to be covariant and contravariant, then it's invariant.
587        (ty::Contravariant, ty::Covariant) | (ty::Covariant, ty::Contravariant) => ty::Invariant,
588        // Otherwise, co + co = co, contra + contra = contra.
589        (ty::Contravariant, ty::Contravariant) => ty::Contravariant,
590        (ty::Covariant, ty::Covariant) => ty::Covariant,
591    }
592}
rustc_lint/impl_trait_overcaptures.rs

rustc_lint/
impl_trait_overcaptures.rs
