diff options
Diffstat (limited to 'compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs')
| -rw-r--r-- | compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs | 332 |
1 files changed, 332 insertions, 0 deletions
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs new file mode 100644 index 000000000..d9e0e87eb --- /dev/null +++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs @@ -0,0 +1,332 @@ +use rustc_data_structures::fx::FxIndexSet; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; +use rustc_infer::infer::{outlives::env::OutlivesEnvironment, TyCtxtInferExt}; +use rustc_lint_defs::builtin::REFINING_IMPL_TRAIT; +use rustc_middle::traits::{ObligationCause, Reveal}; +use rustc_middle::ty::{ + self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperVisitable, TypeVisitable, TypeVisitor, +}; +use rustc_span::{Span, DUMMY_SP}; +use rustc_trait_selection::traits::{ + elaborate, normalize_param_env_or_error, outlives_bounds::InferCtxtExt, ObligationCtxt, +}; +use std::ops::ControlFlow; + +/// Check that an implementation does not refine an RPITIT from a trait method signature. +pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>( + tcx: TyCtxt<'tcx>, + impl_m: ty::AssocItem, + trait_m: ty::AssocItem, + impl_trait_ref: ty::TraitRef<'tcx>, +) { + if !tcx.impl_method_has_trait_impl_trait_tys(impl_m.def_id) { + return; + } + // crate-private traits don't have any library guarantees, there's no need to do this check. + if !tcx.visibility(trait_m.container_id(tcx)).is_public() { + return; + } + + // If a type in the trait ref is private, then there's also no reason to to do this check. + let impl_def_id = impl_m.container_id(tcx); + for arg in impl_trait_ref.args { + if let Some(ty) = arg.as_type() + && let Some(self_visibility) = type_visibility(tcx, ty) + && !self_visibility.is_public() + { + return; + } + } + + let impl_m_args = ty::GenericArgs::identity_for_item(tcx, impl_m.def_id); + let trait_m_to_impl_m_args = impl_m_args.rebase_onto(tcx, impl_def_id, impl_trait_ref.args); + let bound_trait_m_sig = tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_m_to_impl_m_args); + let trait_m_sig = tcx.liberate_late_bound_regions(impl_m.def_id, bound_trait_m_sig); + // replace the self type of the trait ref with `Self` so that diagnostics render better. + let trait_m_sig_with_self_for_diag = tcx.liberate_late_bound_regions( + impl_m.def_id, + tcx.fn_sig(trait_m.def_id).instantiate( + tcx, + tcx.mk_args_from_iter( + [tcx.types.self_param.into()] + .into_iter() + .chain(trait_m_to_impl_m_args.iter().skip(1)), + ), + ), + ); + + let Ok(hidden_tys) = tcx.collect_return_position_impl_trait_in_trait_tys(impl_m.def_id) else { + // Error already emitted, no need to delay another. + return; + }; + + let mut collector = ImplTraitInTraitCollector { tcx, types: FxIndexSet::default() }; + trait_m_sig.visit_with(&mut collector); + + // Bound that we find on RPITITs in the trait signature. + let mut trait_bounds = vec![]; + // Bounds that we find on the RPITITs in the impl signature. + let mut impl_bounds = vec![]; + + for trait_projection in collector.types.into_iter().rev() { + let impl_opaque_args = trait_projection.args.rebase_onto(tcx, trait_m.def_id, impl_m_args); + let hidden_ty = hidden_tys[&trait_projection.def_id].instantiate(tcx, impl_opaque_args); + + // If the hidden type is not an opaque, then we have "refined" the trait signature. + let ty::Alias(ty::Opaque, impl_opaque) = *hidden_ty.kind() else { + report_mismatched_rpitit_signature( + tcx, + trait_m_sig_with_self_for_diag, + trait_m.def_id, + impl_m.def_id, + None, + ); + return; + }; + + // This opaque also needs to be from the impl method -- otherwise, + // it's a refinement to a TAIT. + if !tcx.hir().get_if_local(impl_opaque.def_id).map_or(false, |node| { + matches!( + node.expect_item().expect_opaque_ty().origin, + hir::OpaqueTyOrigin::AsyncFn(def_id) | hir::OpaqueTyOrigin::FnReturn(def_id) + if def_id == impl_m.def_id.expect_local() + ) + }) { + report_mismatched_rpitit_signature( + tcx, + trait_m_sig_with_self_for_diag, + trait_m.def_id, + impl_m.def_id, + None, + ); + return; + } + + trait_bounds.extend( + tcx.item_bounds(trait_projection.def_id).iter_instantiated(tcx, trait_projection.args), + ); + impl_bounds.extend(elaborate( + tcx, + tcx.explicit_item_bounds(impl_opaque.def_id) + .iter_instantiated_copied(tcx, impl_opaque.args), + )); + } + + let hybrid_preds = tcx + .predicates_of(impl_def_id) + .instantiate_identity(tcx) + .into_iter() + .chain(tcx.predicates_of(trait_m.def_id).instantiate_own(tcx, trait_m_to_impl_m_args)) + .map(|(clause, _)| clause); + let param_env = ty::ParamEnv::new(tcx.mk_clauses_from_iter(hybrid_preds), Reveal::UserFacing); + let param_env = normalize_param_env_or_error(tcx, param_env, ObligationCause::dummy()); + + let ref infcx = tcx.infer_ctxt().build(); + let ocx = ObligationCtxt::new(infcx); + + // Normalize the bounds. This has two purposes: + // + // 1. Project the RPITIT projections from the trait to the opaques on the impl, + // which means that they don't need to be mapped manually. + // + // 2. Project any other projections that show up in the bound. That makes sure that + // we don't consider `tests/ui/async-await/in-trait/async-associated-types.rs` + // to be refining. + let (trait_bounds, impl_bounds) = + ocx.normalize(&ObligationCause::dummy(), param_env, (trait_bounds, impl_bounds)); + + // Since we've normalized things, we need to resolve regions, since we'll + // possibly have introduced region vars during projection. We don't expect + // this resolution to have incurred any region errors -- but if we do, then + // just delay a bug. + let mut implied_wf_types = FxIndexSet::default(); + implied_wf_types.extend(trait_m_sig.inputs_and_output); + implied_wf_types.extend(ocx.normalize( + &ObligationCause::dummy(), + param_env, + trait_m_sig.inputs_and_output, + )); + if !ocx.select_all_or_error().is_empty() { + tcx.sess.delay_span_bug( + DUMMY_SP, + "encountered errors when checking RPITIT refinement (selection)", + ); + return; + } + let outlives_env = OutlivesEnvironment::with_bounds( + param_env, + infcx.implied_bounds_tys(param_env, impl_m.def_id.expect_local(), implied_wf_types), + ); + let errors = infcx.resolve_regions(&outlives_env); + if !errors.is_empty() { + tcx.sess.delay_span_bug( + DUMMY_SP, + "encountered errors when checking RPITIT refinement (regions)", + ); + return; + } + // Resolve any lifetime variables that may have been introduced during normalization. + let Ok((trait_bounds, impl_bounds)) = infcx.fully_resolve((trait_bounds, impl_bounds)) else { + tcx.sess.delay_span_bug( + DUMMY_SP, + "encountered errors when checking RPITIT refinement (resolution)", + ); + return; + }; + + // For quicker lookup, use an `IndexSet` (we don't use one earlier because + // it's not foldable..). + // Also, We have to anonymize binders in these types because they may contain + // `BrNamed` bound vars, which contain unique `DefId`s which correspond to syntax + // locations that we don't care about when checking bound equality. + let trait_bounds = FxIndexSet::from_iter(trait_bounds.fold_with(&mut Anonymize { tcx })); + let impl_bounds = impl_bounds.fold_with(&mut Anonymize { tcx }); + + // Find any clauses that are present in the impl's RPITITs that are not + // present in the trait's RPITITs. This will trigger on trivial predicates, + // too, since we *do not* use the trait solver to prove that the RPITIT's + // bounds are not stronger -- we're doing a simple, syntactic compatibility + // check between bounds. This is strictly forwards compatible, though. + for (clause, span) in impl_bounds { + if !trait_bounds.contains(&clause) { + report_mismatched_rpitit_signature( + tcx, + trait_m_sig_with_self_for_diag, + trait_m.def_id, + impl_m.def_id, + Some(span), + ); + return; + } + } +} + +struct ImplTraitInTraitCollector<'tcx> { + tcx: TyCtxt<'tcx>, + types: FxIndexSet<ty::AliasTy<'tcx>>, +} + +impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitCollector<'tcx> { + type BreakTy = !; + + fn visit_ty(&mut self, ty: Ty<'tcx>) -> std::ops::ControlFlow<Self::BreakTy> { + if let ty::Alias(ty::Projection, proj) = *ty.kind() + && self.tcx.is_impl_trait_in_trait(proj.def_id) + { + if self.types.insert(proj) { + for (pred, _) in self + .tcx + .explicit_item_bounds(proj.def_id) + .iter_instantiated_copied(self.tcx, proj.args) + { + pred.visit_with(self)?; + } + } + ControlFlow::Continue(()) + } else { + ty.super_visit_with(self) + } + } +} + +fn report_mismatched_rpitit_signature<'tcx>( + tcx: TyCtxt<'tcx>, + trait_m_sig: ty::FnSig<'tcx>, + trait_m_def_id: DefId, + impl_m_def_id: DefId, + unmatched_bound: Option<Span>, +) { + let mapping = std::iter::zip( + tcx.fn_sig(trait_m_def_id).skip_binder().bound_vars(), + tcx.fn_sig(impl_m_def_id).skip_binder().bound_vars(), + ) + .filter_map(|(impl_bv, trait_bv)| { + if let ty::BoundVariableKind::Region(impl_bv) = impl_bv + && let ty::BoundVariableKind::Region(trait_bv) = trait_bv + { + Some((impl_bv, trait_bv)) + } else { + None + } + }) + .collect(); + + let mut return_ty = + trait_m_sig.output().fold_with(&mut super::RemapLateBound { tcx, mapping: &mapping }); + + if tcx.asyncness(impl_m_def_id).is_async() && tcx.asyncness(trait_m_def_id).is_async() { + let ty::Alias(ty::Projection, future_ty) = return_ty.kind() else { + bug!(); + }; + let Some(future_output_ty) = tcx + .explicit_item_bounds(future_ty.def_id) + .iter_instantiated_copied(tcx, future_ty.args) + .find_map(|(clause, _)| match clause.kind().no_bound_vars()? { + ty::ClauseKind::Projection(proj) => proj.term.ty(), + _ => None, + }) + else { + bug!() + }; + return_ty = future_output_ty; + } + + let (span, impl_return_span, pre, post) = + match tcx.hir().get_by_def_id(impl_m_def_id.expect_local()).fn_decl().unwrap().output { + hir::FnRetTy::DefaultReturn(span) => (tcx.def_span(impl_m_def_id), span, "-> ", " "), + hir::FnRetTy::Return(ty) => (ty.span, ty.span, "", ""), + }; + let trait_return_span = + tcx.hir().get_if_local(trait_m_def_id).map(|node| match node.fn_decl().unwrap().output { + hir::FnRetTy::DefaultReturn(_) => tcx.def_span(trait_m_def_id), + hir::FnRetTy::Return(ty) => ty.span, + }); + + let span = unmatched_bound.unwrap_or(span); + tcx.emit_spanned_lint( + REFINING_IMPL_TRAIT, + tcx.local_def_id_to_hir_id(impl_m_def_id.expect_local()), + span, + crate::errors::ReturnPositionImplTraitInTraitRefined { + impl_return_span, + trait_return_span, + pre, + post, + return_ty, + unmatched_bound, + }, + ); +} + +fn type_visibility<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<ty::Visibility<DefId>> { + match *ty.kind() { + ty::Ref(_, ty, _) => type_visibility(tcx, ty), + ty::Adt(def, args) => { + if def.is_fundamental() { + type_visibility(tcx, args.type_at(0)) + } else { + Some(tcx.visibility(def.did())) + } + } + _ => None, + } +} + +struct Anonymize<'tcx> { + tcx: TyCtxt<'tcx>, +} + +impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Anonymize<'tcx> { + fn interner(&self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T> + where + T: TypeFoldable<TyCtxt<'tcx>>, + { + self.tcx.anonymize_bound_vars(t) + } +} |