diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs index 3399a9fe880..d0272651c08 100644 --- a/compiler/rustc_hir_typeck/src/demand.rs +++ b/compiler/rustc_hir_typeck/src/demand.rs @@ -917,7 +917,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { [candidate] => format!( "the method of the same name on {} `{}`", match candidate.kind { - probe::CandidateKind::InherentImplCandidate(_) => "the inherent impl for", + probe::CandidateKind::InherentImplCandidate { .. } => "the inherent impl for", _ => "trait", }, self.tcx.def_path_str(candidate.item.container_id(self.tcx)) diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs index 66ff71f729c..7524a1faaa3 100644 --- a/compiler/rustc_hir_typeck/src/method/probe.rs +++ b/compiler/rustc_hir_typeck/src/method/probe.rs @@ -103,7 +103,7 @@ pub(crate) struct Candidate<'tcx> { #[derive(Debug, Clone)] pub(crate) enum CandidateKind<'tcx> { - InherentImplCandidate(DefId), + InherentImplCandidate { impl_def_id: DefId, receiver_steps: usize }, ObjectCandidate(ty::PolyTraitRef<'tcx>), TraitCandidate(ty::PolyTraitRef<'tcx>), WhereClauseCandidate(ty::PolyTraitRef<'tcx>), @@ -171,6 +171,37 @@ struct PickDiagHints<'a, 'tcx> { )>, } +/// Criteria to apply when searching for a given Pick. This is used during +/// the search for potentially shadowed methods to ensure we don't search +/// more candidates than strictly necessary. +#[derive(Debug)] +struct PickConstraintsForShadowed { + autoderefs: usize, + receiver_steps: Option, + def_id: DefId, +} + +impl PickConstraintsForShadowed { + fn may_shadow_based_on_autoderefs(&self, autoderefs: usize) -> bool { + autoderefs == self.autoderefs + } + + fn candidate_may_shadow(&self, candidate: &Candidate<'_>) -> bool { + // An item never shadows itself + candidate.item.def_id != self.def_id + // and we're only concerned about inherent impls doing the shadowing. + // Shadowing can only occur if the shadowed is further along + // the Receiver dereferencing chain than the shadowed. + && match candidate.kind { + CandidateKind::InherentImplCandidate { receiver_steps, .. } => match self.receiver_steps { + Some(shadowed_receiver_steps) => receiver_steps > shadowed_receiver_steps, + _ => false + }, + _ => false + } + } +} + #[derive(Debug, Clone)] pub(crate) struct Pick<'tcx> { pub item: ty::AssocItem, @@ -190,6 +221,11 @@ pub(crate) struct Pick<'tcx> { /// Unstable candidates alongside the stable ones. unstable_candidates: Vec<(Candidate<'tcx>, Symbol)>, + + /// Number of jumps along the `Receiver::Target` chain we followed + /// to identify this method. Used only for deshadowing errors. + /// Only applies for inherent impls. + pub receiver_steps: Option, } #[derive(Clone, Debug, PartialEq, Eq)] @@ -706,12 +742,16 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { fn assemble_inherent_candidates(&mut self) { for step in self.steps.iter() { - self.assemble_probe(&step.self_ty); + self.assemble_probe(&step.self_ty, step.autoderefs); } } #[instrument(level = "debug", skip(self))] - fn assemble_probe(&mut self, self_ty: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>) { + fn assemble_probe( + &mut self, + self_ty: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>, + receiver_steps: usize, + ) { let raw_self_ty = self_ty.value.value; match *raw_self_ty.kind() { ty::Dynamic(data, ..) if let Some(p) = data.principal() => { @@ -736,22 +776,31 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { self.fcx.instantiate_canonical(self.span, self_ty); self.assemble_inherent_candidates_from_object(generalized_self_ty); - self.assemble_inherent_impl_candidates_for_type(p.def_id()); + self.assemble_inherent_impl_candidates_for_type(p.def_id(), receiver_steps); if self.tcx.has_attr(p.def_id(), sym::rustc_has_incoherent_inherent_impls) { - self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty); + self.assemble_inherent_candidates_for_incoherent_ty( + raw_self_ty, + receiver_steps, + ); } } ty::Adt(def, _) => { let def_id = def.did(); - self.assemble_inherent_impl_candidates_for_type(def_id); + self.assemble_inherent_impl_candidates_for_type(def_id, receiver_steps); if self.tcx.has_attr(def_id, sym::rustc_has_incoherent_inherent_impls) { - self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty); + self.assemble_inherent_candidates_for_incoherent_ty( + raw_self_ty, + receiver_steps, + ); } } ty::Foreign(did) => { - self.assemble_inherent_impl_candidates_for_type(did); + self.assemble_inherent_impl_candidates_for_type(did, receiver_steps); if self.tcx.has_attr(did, sym::rustc_has_incoherent_inherent_impls) { - self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty); + self.assemble_inherent_candidates_for_incoherent_ty( + raw_self_ty, + receiver_steps, + ); } } ty::Param(p) => { @@ -768,29 +817,35 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { | ty::RawPtr(_, _) | ty::Ref(..) | ty::Never - | ty::Tuple(..) => self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty), + | ty::Tuple(..) => { + self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty, receiver_steps) + } _ => {} } } - fn assemble_inherent_candidates_for_incoherent_ty(&mut self, self_ty: Ty<'tcx>) { + fn assemble_inherent_candidates_for_incoherent_ty( + &mut self, + self_ty: Ty<'tcx>, + receiver_steps: usize, + ) { let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::InstantiateWithInfer) else { bug!("unexpected incoherent type: {:?}", self_ty) }; for &impl_def_id in self.tcx.incoherent_impls(simp).into_iter() { - self.assemble_inherent_impl_probe(impl_def_id); + self.assemble_inherent_impl_probe(impl_def_id, receiver_steps); } } - fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) { + fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId, receiver_steps: usize) { let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id).into_iter(); for &impl_def_id in impl_def_ids { - self.assemble_inherent_impl_probe(impl_def_id); + self.assemble_inherent_impl_probe(impl_def_id, receiver_steps); } } #[instrument(level = "debug", skip(self))] - fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId) { + fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId, receiver_steps: usize) { if !self.impl_dups.insert(impl_def_id) { return; // already visited } @@ -804,7 +859,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { self.push_candidate( Candidate { item, - kind: InherentImplCandidate(impl_def_id), + kind: InherentImplCandidate { impl_def_id, receiver_steps }, import_ids: smallvec![], }, true, @@ -1198,8 +1253,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { return Some(by_value_pick); } - let autoref_pick = - self.pick_autorefd_method(step, self_ty, hir::Mutability::Not, pick_diag_hints); + let autoref_pick = self.pick_autorefd_method( + step, + self_ty, + hir::Mutability::Not, + pick_diag_hints, + None, + ); // Check for shadowing of a by-mut-ref method by a by-reference method (see comments on check_for_shadowing) if let Some(autoref_pick) = autoref_pick { if let Ok(autoref_pick) = autoref_pick.as_ref() { @@ -1242,9 +1302,15 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { // to avoid such compatibility breaks. // We also don't check for reborrowed pin methods which // may be shadowed; these also seem unlikely to occur. - self.pick_autorefd_method(step, self_ty, hir::Mutability::Mut, pick_diag_hints) - .or_else(|| self.pick_const_ptr_method(step, self_ty, pick_diag_hints)) - .or_else(|| self.pick_reborrow_pin_method(step, self_ty, pick_diag_hints)) + self.pick_autorefd_method( + step, + self_ty, + hir::Mutability::Mut, + pick_diag_hints, + None, + ) + .or_else(|| self.pick_const_ptr_method(step, self_ty, pick_diag_hints)) + .or_else(|| self.pick_reborrow_pin_method(step, self_ty, pick_diag_hints)) }) } @@ -1265,7 +1331,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { /// Report an error in this case. fn check_for_shadowed_autorefd_method( &self, - _possible_shadower: &Pick<'tcx>, + possible_shadower: &Pick<'tcx>, step: &CandidateStep<'tcx>, self_ty: Ty<'tcx>, mutbl: hir::Mutability, @@ -1279,8 +1345,54 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { unstable_candidates: if track_unstable_candidates { Some(Vec::new()) } else { None }, unsatisfied_predicates: &mut Vec::new(), }; - let _potentially_shadowed_pick = - self.pick_autorefd_method(step, self_ty, mutbl, &mut pick_diag_hints); + // Set criteria for how we find methods possibly shadowed by 'possible_shadower' + let pick_constraints = PickConstraintsForShadowed { + // It's the same `self` type... + autoderefs: possible_shadower.autoderefs, + // ... but the method was found in an impl block determined + // by searching further along the Receiver chain than the other, + // showing that it's a smart pointer type causing the problem... + receiver_steps: possible_shadower.receiver_steps, + // ... and they don't end up pointing to the same item in the + // first place (could happen with things like blanket impls for T) + def_id: possible_shadower.item.def_id, + }; + // A note on the autoderefs above. Within pick_by_value_method, an extra + // autoderef may be applied in order to reborrow a reference with + // a different lifetime. That seems as though it would break the + // logic of these constraints, since the number of autoderefs could + // no longer be used to identify the fundamental type of the receiver. + // However, this extra autoderef is applied only to by-value calls + // where the receiver is already a reference. So this situation would + // only occur in cases where the shadowing looks like this: + // ``` + // struct A; + // impl A { + // fn foo(self: &&NonNull) {} + // // note this is by DOUBLE reference + // } + // ``` + // then we've come along and added this method to `NonNull`: + // ``` + // fn foo(&self) // note this is by single reference + // ``` + // and the call is: + // ``` + // let bar = NonNull; + // let bar = &foo; + // bar.foo(); + // ``` + // In these circumstances, the logic is wrong, and we wouldn't spot + // the shadowing, because the autoderef-based maths wouldn't line up. + // This is a niche case and we can live without generating an error + // in the case of such shadowing. + let _potentially_shadowed_pick = self.pick_autorefd_method( + step, + self_ty, + mutbl, + &mut pick_diag_hints, + Some(&pick_constraints), + ); // At the moment, this function does no checks. A future // commit will fill out the body here. @@ -1303,7 +1415,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { return None; } - self.pick_method(self_ty, pick_diag_hints).map(|r| { + self.pick_method(self_ty, pick_diag_hints, None).map(|r| { r.map(|mut pick| { pick.autoderefs = step.autoderefs; @@ -1342,14 +1454,21 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { self_ty: Ty<'tcx>, mutbl: hir::Mutability, pick_diag_hints: &mut PickDiagHints<'_, 'tcx>, + pick_constraints: Option<&PickConstraintsForShadowed>, ) -> Option> { let tcx = self.tcx; + if let Some(pick_constraints) = pick_constraints { + if !pick_constraints.may_shadow_based_on_autoderefs(step.autoderefs) { + return None; + } + } + // In general, during probing we erase regions. let region = tcx.lifetimes.re_erased; let autoref_ty = Ty::new_ref(tcx, region, self_ty, mutbl); - self.pick_method(autoref_ty, pick_diag_hints).map(|r| { + self.pick_method(autoref_ty, pick_diag_hints, pick_constraints).map(|r| { r.map(|mut pick| { pick.autoderefs = step.autoderefs; pick.autoref_or_ptr_adjustment = @@ -1386,7 +1505,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { let region = self.tcx.lifetimes.re_erased; let autopin_ty = Ty::new_pinned_ref(self.tcx, region, inner_ty, hir::Mutability::Not); - self.pick_method(autopin_ty, pick_diag_hints).map(|r| { + self.pick_method(autopin_ty, pick_diag_hints, None).map(|r| { r.map(|mut pick| { pick.autoderefs = step.autoderefs; pick.autoref_or_ptr_adjustment = @@ -1415,7 +1534,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { }; let const_ptr_ty = Ty::new_imm_ptr(self.tcx, ty); - self.pick_method(const_ptr_ty, pick_diag_hints).map(|r| { + self.pick_method(const_ptr_ty, pick_diag_hints, None).map(|r| { r.map(|mut pick| { pick.autoderefs = step.autoderefs; pick.autoref_or_ptr_adjustment = Some(AutorefOrPtrAdjustment::ToConstPtr); @@ -1428,6 +1547,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { &self, self_ty: Ty<'tcx>, pick_diag_hints: &mut PickDiagHints<'_, 'tcx>, + pick_constraints: Option<&PickConstraintsForShadowed>, ) -> Option> { debug!("pick_method(self_ty={})", self.ty_to_string(self_ty)); @@ -1435,19 +1555,23 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { [("inherent", &self.inherent_candidates), ("extension", &self.extension_candidates)] { debug!("searching {} candidates", kind); - let res = self.consider_candidates(self_ty, candidates, pick_diag_hints); + let res = + self.consider_candidates(self_ty, candidates, pick_diag_hints, pick_constraints); if let Some(pick) = res { return Some(pick); } } if self.private_candidate.get().is_none() { - if let Some(Ok(pick)) = - self.consider_candidates(self_ty, &self.private_candidates, &mut PickDiagHints { + if let Some(Ok(pick)) = self.consider_candidates( + self_ty, + &self.private_candidates, + &mut PickDiagHints { unstable_candidates: None, unsatisfied_predicates: &mut vec![], - }) - { + }, + None, + ) { self.private_candidate.set(Some((pick.item.kind.as_def_kind(), pick.item.def_id))); } } @@ -1459,9 +1583,15 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { self_ty: Ty<'tcx>, candidates: &[Candidate<'tcx>], pick_diag_hints: &mut PickDiagHints<'_, 'tcx>, + pick_constraints: Option<&PickConstraintsForShadowed>, ) -> Option> { let mut applicable_candidates: Vec<_> = candidates .iter() + .filter(|candidate| { + pick_constraints + .map(|pick_constraints| pick_constraints.candidate_may_shadow(&candidate)) + .unwrap_or(true) + }) .map(|probe| { ( probe, @@ -1535,6 +1665,7 @@ impl<'tcx> Pick<'tcx> { autoref_or_ptr_adjustment: _, self_ty, unstable_candidates: _, + receiver_steps: _, } = *self; self_ty != other.self_ty || def_id != other.item.def_id } @@ -1610,7 +1741,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { /// so do not use to make a decision that may lead to a successful compilation. fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>) -> CandidateSource { match candidate.kind { - InherentImplCandidate(_) => { + InherentImplCandidate { .. } => { CandidateSource::Impl(candidate.item.container_id(self.tcx)) } ObjectCandidate(_) | WhereClauseCandidate(_) => { @@ -1664,7 +1795,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { let (mut xform_self_ty, mut xform_ret_ty); match probe.kind { - InherentImplCandidate(impl_def_id) => { + InherentImplCandidate { impl_def_id, .. } => { let impl_args = self.fresh_args_for_item(self.span, impl_def_id); let impl_ty = self.tcx.type_of(impl_def_id).instantiate(self.tcx, impl_args); (xform_self_ty, xform_ret_ty) = @@ -1856,7 +1987,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { // We don't normalize the other candidates for perf/backwards-compat reasons... // but `self.return_type` is only set on the diagnostic-path, so we // should be okay doing it here. - if !matches!(probe.kind, InherentImplCandidate(_)) { + if !matches!(probe.kind, InherentImplCandidate { .. }) { xform_ret_ty = ocx.normalize(&cause, self.param_env, xform_ret_ty); } @@ -1934,6 +2065,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { autoref_or_ptr_adjustment: None, self_ty, unstable_candidates: vec![], + receiver_steps: None, }) } @@ -2205,7 +2337,7 @@ impl<'tcx> Candidate<'tcx> { Pick { item: self.item, kind: match self.kind { - InherentImplCandidate(_) => InherentImplPick, + InherentImplCandidate { .. } => InherentImplPick, ObjectCandidate(_) => ObjectPick, TraitCandidate(_) => TraitPick, WhereClauseCandidate(trait_ref) => { @@ -2227,6 +2359,10 @@ impl<'tcx> Candidate<'tcx> { autoref_or_ptr_adjustment: None, self_ty, unstable_candidates, + receiver_steps: match self.kind { + InherentImplCandidate { receiver_steps, .. } => Some(receiver_steps), + _ => None, + }, } } }