diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/traits/object_safety.rs')
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/object_safety.rs | 162 |
1 files changed, 114 insertions, 48 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs index c9121212c..4eacb5211 100644 --- a/compiler/rustc_trait_selection/src/traits/object_safety.rs +++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs @@ -18,10 +18,10 @@ use rustc_errors::{DelayDm, FatalError, MultiSpan}; use rustc_hir as hir; use rustc_hir::def_id::DefId; use rustc_middle::ty::subst::{GenericArg, InternalSubsts}; +use rustc_middle::ty::ToPredicate; use rustc_middle::ty::{ self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, }; -use rustc_middle::ty::{Predicate, ToPredicate}; use rustc_session::lint::builtin::WHERE_CLAUSES_OBJECT_SAFETY; use rustc_span::symbol::Symbol; use rustc_span::Span; @@ -62,11 +62,42 @@ fn object_safety_violations(tcx: TyCtxt<'_>, trait_def_id: DefId) -> &'_ [Object ) } +fn check_is_object_safe(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool { + let violations = tcx.object_safety_violations(trait_def_id); + + if violations.is_empty() { + return true; + } + + // If the trait contains any other violations, then let the error reporting path + // report it instead of emitting a warning here. + if violations.iter().all(|violation| { + matches!( + violation, + ObjectSafetyViolation::Method(_, MethodViolationCode::WhereClauseReferencesSelf, _) + ) + }) { + for violation in violations { + if let ObjectSafetyViolation::Method( + _, + MethodViolationCode::WhereClauseReferencesSelf, + span, + ) = violation + { + lint_object_unsafe_trait(tcx, *span, trait_def_id, &violation); + } + } + return true; + } + + false +} + /// We say a method is *vtable safe* if it can be invoked on a trait /// object. Note that object-safe traits can have some /// non-vtable-safe methods, so long as they require `Self: Sized` or /// otherwise ensure that they cannot be used when `Self = Trait`. -pub fn is_vtable_safe_method(tcx: TyCtxt<'_>, trait_def_id: DefId, method: &ty::AssocItem) -> bool { +pub fn is_vtable_safe_method(tcx: TyCtxt<'_>, trait_def_id: DefId, method: ty::AssocItem) -> bool { debug_assert!(tcx.generics_of(trait_def_id).has_self); debug!("is_vtable_safe_method({:?}, {:?})", trait_def_id, method); // Any method that has a `Self: Sized` bound cannot be called. @@ -89,23 +120,10 @@ fn object_safety_violations_for_trait( .associated_items(trait_def_id) .in_definition_order() .filter(|item| item.kind == ty::AssocKind::Fn) - .filter_map(|item| { - object_safety_violation_for_method(tcx, trait_def_id, &item) + .filter_map(|&item| { + object_safety_violation_for_method(tcx, trait_def_id, item) .map(|(code, span)| ObjectSafetyViolation::Method(item.name, code, span)) }) - .filter(|violation| { - if let ObjectSafetyViolation::Method( - _, - MethodViolationCode::WhereClauseReferencesSelf, - span, - ) = violation - { - lint_object_unsafe_trait(tcx, *span, trait_def_id, &violation); - false - } else { - true - } - }) .collect(); // Check the trait itself. @@ -289,7 +307,7 @@ fn predicate_references_self<'tcx>( match predicate.kind().skip_binder() { ty::PredicateKind::Clause(ty::Clause::Trait(ref data)) => { // In the case of a trait predicate, we can skip the "self" type. - if data.trait_ref.substs[1..].iter().any(has_self_ty) { Some(sp) } else { None } + data.trait_ref.substs[1..].iter().any(has_self_ty).then_some(sp) } ty::PredicateKind::Clause(ty::Clause::Projection(ref data)) => { // And similarly for projections. This should be redundant with @@ -307,8 +325,14 @@ fn predicate_references_self<'tcx>( // // This is ALT2 in issue #56288, see that for discussion of the // possible alternatives. - if data.projection_ty.substs[1..].iter().any(has_self_ty) { Some(sp) } else { None } + data.projection_ty.substs[1..].iter().any(has_self_ty).then_some(sp) + } + ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(_ct, ty)) => { + has_self_ty(&ty.into()).then_some(sp) } + + ty::PredicateKind::AliasEq(..) => bug!("`AliasEq` not allowed as assumption"), + ty::PredicateKind::WellFormed(..) | ty::PredicateKind::ObjectSafe(..) | ty::PredicateKind::Clause(ty::Clause::TypeOutlives(..)) @@ -316,6 +340,7 @@ fn predicate_references_self<'tcx>( | ty::PredicateKind::ClosureKind(..) | ty::PredicateKind::Subtype(..) | ty::PredicateKind::Coerce(..) + // FIXME(generic_const_exprs): this can mention `Self` | ty::PredicateKind::ConstEvaluatable(..) | ty::PredicateKind::ConstEquate(..) | ty::PredicateKind::Ambiguous @@ -341,6 +366,7 @@ fn generics_require_sized_self(tcx: TyCtxt<'_>, def_id: DefId) -> bool { trait_pred.def_id() == sized_def_id && trait_pred.self_ty().is_param(0) } ty::PredicateKind::Clause(ty::Clause::Projection(..)) + | ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..)) | ty::PredicateKind::Subtype(..) | ty::PredicateKind::Coerce(..) | ty::PredicateKind::Clause(ty::Clause::RegionOutlives(..)) @@ -350,6 +376,7 @@ fn generics_require_sized_self(tcx: TyCtxt<'_>, def_id: DefId) -> bool { | ty::PredicateKind::Clause(ty::Clause::TypeOutlives(..)) | ty::PredicateKind::ConstEvaluatable(..) | ty::PredicateKind::ConstEquate(..) + | ty::PredicateKind::AliasEq(..) | ty::PredicateKind::Ambiguous | ty::PredicateKind::TypeWellFormedFromEnv(..) => false, } @@ -360,7 +387,7 @@ fn generics_require_sized_self(tcx: TyCtxt<'_>, def_id: DefId) -> bool { fn object_safety_violation_for_method( tcx: TyCtxt<'_>, trait_def_id: DefId, - method: &ty::AssocItem, + method: ty::AssocItem, ) -> Option<(MethodViolationCode, Span)> { debug!("object_safety_violation_for_method({:?}, {:?})", trait_def_id, method); // Any method that has a `Self : Sized` requisite is otherwise @@ -393,9 +420,9 @@ fn object_safety_violation_for_method( fn virtual_call_violation_for_method<'tcx>( tcx: TyCtxt<'tcx>, trait_def_id: DefId, - method: &ty::AssocItem, + method: ty::AssocItem, ) -> Option<MethodViolationCode> { - let sig = tcx.fn_sig(method.def_id); + let sig = tcx.fn_sig(method.def_id).subst_identity(); // The method's first parameter must be named `self` if !method.fn_has_self_parameter { @@ -505,8 +532,7 @@ fn virtual_call_violation_for_method<'tcx>( } } - let trait_object_ty = - object_ty_for_trait(tcx, trait_def_id, tcx.mk_region(ty::ReStatic)); + let trait_object_ty = object_ty_for_trait(tcx, trait_def_id, tcx.lifetimes.re_static); // e.g., `Rc<dyn Trait>` let trait_object_receiver = @@ -529,16 +555,56 @@ fn virtual_call_violation_for_method<'tcx>( // NOTE: This check happens last, because it results in a lint, and not a // hard error. - if tcx - .predicates_of(method.def_id) - .predicates - .iter() - // A trait object can't claim to live more than the concrete type, - // so outlives predicates will always hold. - .cloned() - .filter(|(p, _)| p.to_opt_type_outlives().is_none()) - .any(|pred| contains_illegal_self_type_reference(tcx, trait_def_id, pred)) - { + if tcx.predicates_of(method.def_id).predicates.iter().any(|&(pred, span)| { + // dyn Trait is okay: + // + // trait Trait { + // fn f(&self) where Self: 'static; + // } + // + // because a trait object can't claim to live longer than the concrete + // type. If the lifetime bound holds on dyn Trait then it's guaranteed + // to hold as well on the concrete type. + if pred.to_opt_type_outlives().is_some() { + return false; + } + + // dyn Trait is okay: + // + // auto trait AutoTrait {} + // + // trait Trait { + // fn f(&self) where Self: AutoTrait; + // } + // + // because `impl AutoTrait for dyn Trait` is disallowed by coherence. + // Traits with a default impl are implemented for a trait object if and + // only if the autotrait is one of the trait object's trait bounds, like + // in `dyn Trait + AutoTrait`. This guarantees that trait objects only + // implement auto traits if the underlying type does as well. + if let ty::PredicateKind::Clause(ty::Clause::Trait(ty::TraitPredicate { + trait_ref: pred_trait_ref, + constness: ty::BoundConstness::NotConst, + polarity: ty::ImplPolarity::Positive, + })) = pred.kind().skip_binder() + && pred_trait_ref.self_ty() == tcx.types.self_param + && tcx.trait_is_auto(pred_trait_ref.def_id) + { + // Consider bounds like `Self: Bound<Self>`. Auto traits are not + // allowed to have generic parameters so `auto trait Bound<T> {}` + // would already have reported an error at the definition of the + // auto trait. + if pred_trait_ref.substs.len() != 1 { + tcx.sess.diagnostic().delay_span_bug( + span, + "auto traits cannot have generic parameters", + ); + } + return false; + } + + contains_illegal_self_type_reference(tcx, trait_def_id, pred) + }) { return Some(MethodViolationCode::WhereClauseReferencesSelf); } @@ -588,11 +654,9 @@ fn object_ty_for_trait<'tcx>( debug!(?obligation); let pred = obligation.predicate.to_opt_poly_projection_pred()?; Some(pred.map_bound(|p| { - ty::ExistentialPredicate::Projection(ty::ExistentialProjection { - def_id: p.projection_ty.def_id, - substs: p.projection_ty.substs, - term: p.term, - }) + ty::ExistentialPredicate::Projection(ty::ExistentialProjection::erase_self_ty( + tcx, p, + )) })) }) .collect(); @@ -602,8 +666,9 @@ fn object_ty_for_trait<'tcx>( elaborated_predicates.sort_by(|a, b| a.skip_binder().stable_cmp(tcx, &b.skip_binder())); elaborated_predicates.dedup(); - let existential_predicates = tcx - .mk_poly_existential_predicates(iter::once(trait_predicate).chain(elaborated_predicates)); + let existential_predicates = tcx.mk_poly_existential_predicates_from_iter( + iter::once(trait_predicate).chain(elaborated_predicates), + ); debug!(?existential_predicates); tcx.mk_dynamic(existential_predicates, lifetime, ty::Dyn) @@ -658,7 +723,7 @@ fn object_ty_for_trait<'tcx>( #[allow(dead_code)] fn receiver_is_dispatchable<'tcx>( tcx: TyCtxt<'tcx>, - method: &ty::AssocItem, + method: ty::AssocItem, receiver_ty: Ty<'tcx>, ) -> bool { debug!("receiver_is_dispatchable: method = {:?}, receiver_ty = {:?}", method, receiver_ty); @@ -702,11 +767,11 @@ fn receiver_is_dispatchable<'tcx>( ty::Binder::dummy(tcx.mk_trait_ref(trait_def_id, substs)).to_predicate(tcx) }; - let caller_bounds: Vec<Predicate<'tcx>> = - param_env.caller_bounds().iter().chain([unsize_predicate, trait_predicate]).collect(); + let caller_bounds = + param_env.caller_bounds().iter().chain([unsize_predicate, trait_predicate]); ty::ParamEnv::new( - tcx.intern_predicates(&caller_bounds), + tcx.mk_predicates_from_iter(caller_bounds), param_env.reveal(), param_env.constness(), ) @@ -726,7 +791,7 @@ fn receiver_is_dispatchable<'tcx>( infcx.predicate_must_hold_modulo_regions(&obligation) } -fn contains_illegal_self_type_reference<'tcx, T: TypeVisitable<'tcx>>( +fn contains_illegal_self_type_reference<'tcx, T: TypeVisitable<TyCtxt<'tcx>>>( tcx: TyCtxt<'tcx>, trait_def_id: DefId, value: T, @@ -776,7 +841,7 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeVisitable<'tcx>>( supertraits: Option<Vec<DefId>>, } - impl<'tcx> TypeVisitor<'tcx> for IllegalSelfTypeVisitor<'tcx> { + impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for IllegalSelfTypeVisitor<'tcx> { type BreakTy = (); fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { @@ -866,5 +931,6 @@ pub fn contains_illegal_impl_trait_in_trait<'tcx>( } pub fn provide(providers: &mut ty::query::Providers) { - *providers = ty::query::Providers { object_safety_violations, ..*providers }; + *providers = + ty::query::Providers { object_safety_violations, check_is_object_safe, ..*providers }; } |