| use crate::bounds::Bounds; |
| use crate::collect::ItemCtxt; |
| use crate::constrained_generic_params as cgp; |
| use crate::hir_ty_lowering::{HirTyLowerer, OnlySelfBounds, PredicateFilter}; |
| use hir::{HirId, Node}; |
| use rustc_data_structures::fx::FxIndexSet; |
| use rustc_hir as hir; |
| use rustc_hir::def::DefKind; |
| use rustc_hir::def_id::{DefId, LocalDefId}; |
| use rustc_hir::intravisit::{self, Visitor}; |
| use rustc_middle::ty::{self, Ty, TyCtxt}; |
| use rustc_middle::ty::{GenericPredicates, ImplTraitInTraitData, ToPredicate}; |
| use rustc_span::symbol::Ident; |
| use rustc_span::{Span, DUMMY_SP}; |
| |
| /// Returns a list of all type predicates (explicit and implicit) for the definition with |
| /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus |
| /// `Self: Trait` predicates for traits. |
| pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> { |
| let mut result = tcx.predicates_defined_on(def_id); |
| |
| if tcx.is_trait(def_id) { |
| // For traits, add `Self: Trait` predicate. This is |
| // not part of the predicates that a user writes, but it |
| // is something that one must prove in order to invoke a |
| // method or project an associated type. |
| // |
| // In the chalk setup, this predicate is not part of the |
| // "predicates" for a trait item. But it is useful in |
| // rustc because if you directly (e.g.) invoke a trait |
| // method like `Trait::method(...)`, you must naturally |
| // prove that the trait applies to the types that were |
| // used, and adding the predicate into this list ensures |
| // that this is done. |
| // |
| // We use a DUMMY_SP here as a way to signal trait bounds that come |
| // from the trait itself that *shouldn't* be shown as the source of |
| // an obligation and instead be skipped. Otherwise we'd use |
| // `tcx.def_span(def_id);` |
| let span = DUMMY_SP; |
| |
| result.predicates = |
| tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once(( |
| ty::TraitRef::identity(tcx, def_id).to_predicate(tcx), |
| span, |
| )))); |
| } |
| debug!("predicates_of(def_id={:?}) = {:?}", def_id, result); |
| result |
| } |
| |
| /// Returns a list of user-specified type predicates for the definition with ID `def_id`. |
| /// N.B., this does not include any implied/inferred constraints. |
| #[instrument(level = "trace", skip(tcx), ret)] |
| fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::GenericPredicates<'_> { |
| use rustc_hir::*; |
| |
| match tcx.opt_rpitit_info(def_id.to_def_id()) { |
| Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) => { |
| let mut predicates = Vec::new(); |
| |
| // RPITITs should inherit the predicates of their parent. This is |
| // both to ensure that the RPITITs are only instantiated when the |
| // parent predicates would hold, and also so that the param-env |
| // inherits these predicates as assumptions. |
| let identity_args = ty::GenericArgs::identity_for_item(tcx, def_id); |
| predicates |
| .extend(tcx.explicit_predicates_of(fn_def_id).instantiate_own(tcx, identity_args)); |
| |
| // We also install bidirectional outlives predicates for the RPITIT |
| // to keep the duplicates lifetimes from opaque lowering in sync. |
| // We only need to compute bidirectional outlives for the duplicated |
| // opaque lifetimes, which explains the slicing below. |
| compute_bidirectional_outlives_predicates( |
| tcx, |
| &tcx.generics_of(def_id.to_def_id()).params |
| [tcx.generics_of(fn_def_id).params.len()..], |
| &mut predicates, |
| ); |
| |
| return ty::GenericPredicates { |
| parent: Some(tcx.parent(def_id.to_def_id())), |
| predicates: tcx.arena.alloc_from_iter(predicates), |
| }; |
| } |
| |
| Some(ImplTraitInTraitData::Impl { fn_def_id }) => { |
| let assoc_item = tcx.associated_item(def_id); |
| let trait_assoc_predicates = |
| tcx.explicit_predicates_of(assoc_item.trait_item_def_id.unwrap()); |
| |
| let impl_assoc_identity_args = ty::GenericArgs::identity_for_item(tcx, def_id); |
| let impl_def_id = tcx.parent(fn_def_id); |
| let impl_trait_ref_args = |
| tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity().args; |
| |
| let impl_assoc_args = |
| impl_assoc_identity_args.rebase_onto(tcx, impl_def_id, impl_trait_ref_args); |
| |
| let impl_predicates = trait_assoc_predicates.instantiate_own(tcx, impl_assoc_args); |
| |
| return ty::GenericPredicates { |
| parent: Some(impl_def_id), |
| predicates: tcx.arena.alloc_from_iter(impl_predicates), |
| }; |
| } |
| |
| None => {} |
| } |
| |
| let hir_id = tcx.local_def_id_to_hir_id(def_id); |
| let node = tcx.hir_node(hir_id); |
| |
| let mut is_trait = None; |
| let mut is_default_impl_trait = None; |
| |
| // FIXME: Should ItemCtxt take a LocalDefId? |
| let icx = ItemCtxt::new(tcx, def_id); |
| |
| const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty(); |
| |
| // We use an `IndexSet` to preserve order of insertion. |
| // Preserving the order of insertion is important here so as not to break UI tests. |
| let mut predicates: FxIndexSet<(ty::Clause<'_>, Span)> = FxIndexSet::default(); |
| |
| let hir_generics = node.generics().unwrap_or(NO_GENERICS); |
| if let Node::Item(item) = node { |
| match item.kind { |
| ItemKind::Impl(impl_) => { |
| if impl_.defaultness.is_default() { |
| is_default_impl_trait = tcx |
| .impl_trait_ref(def_id) |
| .map(|t| ty::Binder::dummy(t.instantiate_identity())); |
| } |
| } |
| |
| ItemKind::Trait(_, _, _, self_bounds, ..) | ItemKind::TraitAlias(_, self_bounds) => { |
| is_trait = Some(self_bounds); |
| } |
| _ => {} |
| } |
| }; |
| |
| let generics = tcx.generics_of(def_id); |
| |
| // Below we'll consider the bounds on the type parameters (including `Self`) |
| // and the explicit where-clauses, but to get the full set of predicates |
| // on a trait we must also consider the bounds that follow the trait's name, |
| // like `trait Foo: A + B + C`. |
| if let Some(self_bounds) = is_trait { |
| predicates.extend( |
| icx.lowerer() |
| .lower_mono_bounds(tcx.types.self_param, self_bounds, PredicateFilter::All) |
| .clauses(), |
| ); |
| } |
| |
| // In default impls, we can assume that the self type implements |
| // the trait. So in: |
| // |
| // default impl Foo for Bar { .. } |
| // |
| // we add a default where clause `Bar: Foo`. We do a similar thing for traits |
| // (see below). Recall that a default impl is not itself an impl, but rather a |
| // set of defaults that can be incorporated into another impl. |
| if let Some(trait_ref) = is_default_impl_trait { |
| predicates.insert((trait_ref.to_predicate(tcx), tcx.def_span(def_id))); |
| } |
| |
| // Collect the predicates that were written inline by the user on each |
| // type parameter (e.g., `<T: Foo>`). Also add `ConstArgHasType` predicates |
| // for each const parameter. |
| for param in hir_generics.params { |
| match param.kind { |
| // We already dealt with early bound lifetimes above. |
| GenericParamKind::Lifetime { .. } => (), |
| GenericParamKind::Type { .. } => { |
| let param_ty = icx.lowerer().lower_ty_param(param.hir_id); |
| let mut bounds = Bounds::default(); |
| // Params are implicitly sized unless a `?Sized` bound is found |
| icx.lowerer().add_sized_bound( |
| &mut bounds, |
| param_ty, |
| &[], |
| Some((param.def_id, hir_generics.predicates)), |
| param.span, |
| ); |
| trace!(?bounds); |
| predicates.extend(bounds.clauses()); |
| trace!(?predicates); |
| } |
| hir::GenericParamKind::Const { .. } => { |
| let ct_ty = tcx |
| .type_of(param.def_id.to_def_id()) |
| .no_bound_vars() |
| .expect("const parameters cannot be generic"); |
| let ct = icx.lowerer().lower_const_param(param.hir_id, ct_ty); |
| predicates.insert(( |
| ty::ClauseKind::ConstArgHasType(ct, ct_ty).to_predicate(tcx), |
| param.span, |
| )); |
| } |
| } |
| } |
| |
| trace!(?predicates); |
| // Add in the bounds that appear in the where-clause. |
| for predicate in hir_generics.predicates { |
| match predicate { |
| hir::WherePredicate::BoundPredicate(bound_pred) => { |
| let ty = icx.lower_ty(bound_pred.bounded_ty); |
| let bound_vars = tcx.late_bound_vars(bound_pred.hir_id); |
| // Keep the type around in a dummy predicate, in case of no bounds. |
| // That way, `where Ty:` is not a complete noop (see #53696) and `Ty` |
| // is still checked for WF. |
| if bound_pred.bounds.is_empty() { |
| if let ty::Param(_) = ty.kind() { |
| // This is a `where T:`, which can be in the HIR from the |
| // transformation that moves `?Sized` to `T`'s declaration. |
| // We can skip the predicate because type parameters are |
| // trivially WF, but also we *should*, to avoid exposing |
| // users who never wrote `where Type:,` themselves, to |
| // compiler/tooling bugs from not handling WF predicates. |
| } else { |
| let span = bound_pred.bounded_ty.span; |
| let predicate = ty::Binder::bind_with_vars( |
| ty::ClauseKind::WellFormed(ty.into()), |
| bound_vars, |
| ); |
| predicates.insert((predicate.to_predicate(tcx), span)); |
| } |
| } |
| |
| let mut bounds = Bounds::default(); |
| icx.lowerer().lower_poly_bounds( |
| ty, |
| bound_pred.bounds.iter(), |
| &mut bounds, |
| bound_vars, |
| OnlySelfBounds(false), |
| ); |
| predicates.extend(bounds.clauses()); |
| } |
| |
| hir::WherePredicate::RegionPredicate(region_pred) => { |
| let r1 = icx.lowerer().lower_lifetime(region_pred.lifetime, None); |
| predicates.extend(region_pred.bounds.iter().map(|bound| { |
| let (r2, span) = match bound { |
| hir::GenericBound::Outlives(lt) => { |
| (icx.lowerer().lower_lifetime(lt, None), lt.ident.span) |
| } |
| bound => { |
| span_bug!( |
| bound.span(), |
| "lifetime param bounds must be outlives, but found {bound:?}" |
| ) |
| } |
| }; |
| let pred = ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(r1, r2)) |
| .to_predicate(tcx); |
| (pred, span) |
| })) |
| } |
| |
| hir::WherePredicate::EqPredicate(..) => { |
| // FIXME(#20041) |
| } |
| } |
| } |
| |
| if tcx.features().generic_const_exprs { |
| predicates.extend(const_evaluatable_predicates_of(tcx, def_id)); |
| } |
| |
| let mut predicates: Vec<_> = predicates.into_iter().collect(); |
| |
| // Subtle: before we store the predicates into the tcx, we |
| // sort them so that predicates like `T: Foo<Item=U>` come |
| // before uses of `U`. This avoids false ambiguity errors |
| // in trait checking. See `setup_constraining_predicates` |
| // for details. |
| if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node { |
| let self_ty = tcx.type_of(def_id).instantiate_identity(); |
| let trait_ref = tcx.impl_trait_ref(def_id).map(ty::EarlyBinder::instantiate_identity); |
| cgp::setup_constraining_predicates( |
| tcx, |
| &mut predicates, |
| trait_ref, |
| &mut cgp::parameters_for_impl(tcx, self_ty, trait_ref), |
| ); |
| } |
| |
| // Opaque types duplicate some of their generic parameters. |
| // We create bi-directional Outlives predicates between the original |
| // and the duplicated parameter, to ensure that they do not get out of sync. |
| if let Node::Item(&Item { kind: ItemKind::OpaqueTy(..), .. }) = node { |
| let opaque_ty_node = tcx.parent_hir_node(hir_id); |
| let Node::Ty(&Ty { kind: TyKind::OpaqueDef(_, lifetimes, _), .. }) = opaque_ty_node else { |
| bug!("unexpected {opaque_ty_node:?}") |
| }; |
| debug!(?lifetimes); |
| |
| compute_bidirectional_outlives_predicates(tcx, &generics.params, &mut predicates); |
| debug!(?predicates); |
| } |
| |
| ty::GenericPredicates { |
| parent: generics.parent, |
| predicates: tcx.arena.alloc_from_iter(predicates), |
| } |
| } |
| |
| /// Opaques have duplicated lifetimes and we need to compute bidirectional outlives predicates to |
| /// enforce that these lifetimes stay in sync. |
| fn compute_bidirectional_outlives_predicates<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| opaque_own_params: &[ty::GenericParamDef], |
| predicates: &mut Vec<(ty::Clause<'tcx>, Span)>, |
| ) { |
| for param in opaque_own_params { |
| let orig_lifetime = tcx.map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local()); |
| if let ty::ReEarlyParam(..) = *orig_lifetime { |
| let dup_lifetime = ty::Region::new_early_param( |
| tcx, |
| ty::EarlyParamRegion { def_id: param.def_id, index: param.index, name: param.name }, |
| ); |
| let span = tcx.def_span(param.def_id); |
| predicates.push(( |
| ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(orig_lifetime, dup_lifetime)) |
| .to_predicate(tcx), |
| span, |
| )); |
| predicates.push(( |
| ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(dup_lifetime, orig_lifetime)) |
| .to_predicate(tcx), |
| span, |
| )); |
| } |
| } |
| } |
| |
| fn const_evaluatable_predicates_of( |
| tcx: TyCtxt<'_>, |
| def_id: LocalDefId, |
| ) -> FxIndexSet<(ty::Clause<'_>, Span)> { |
| struct ConstCollector<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| preds: FxIndexSet<(ty::Clause<'tcx>, Span)>, |
| } |
| |
| impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> { |
| fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) { |
| let ct = ty::Const::from_anon_const(self.tcx, c.def_id); |
| if let ty::ConstKind::Unevaluated(_) = ct.kind() { |
| let span = self.tcx.def_span(c.def_id); |
| self.preds |
| .insert((ty::ClauseKind::ConstEvaluatable(ct).to_predicate(self.tcx), span)); |
| } |
| } |
| |
| fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) { |
| // Do not look into const param defaults, |
| // these get checked when they are actually instantiated. |
| // |
| // We do not want the following to error: |
| // |
| // struct Foo<const N: usize, const M: usize = { N + 1 }>; |
| // struct Bar<const N: usize>(Foo<N, 3>); |
| } |
| } |
| |
| let hir_id = tcx.local_def_id_to_hir_id(def_id); |
| let node = tcx.hir_node(hir_id); |
| |
| let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() }; |
| if let hir::Node::Item(item) = node |
| && let hir::ItemKind::Impl(impl_) = item.kind |
| { |
| if let Some(of_trait) = &impl_.of_trait { |
| debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id); |
| collector.visit_trait_ref(of_trait); |
| } |
| |
| debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id); |
| collector.visit_ty(impl_.self_ty); |
| } |
| |
| if let Some(generics) = node.generics() { |
| debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id); |
| collector.visit_generics(generics); |
| } |
| |
| if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) { |
| debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id); |
| collector.visit_fn_decl(fn_sig.decl); |
| } |
| debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds); |
| |
| collector.preds |
| } |
| |
| pub(super) fn trait_explicit_predicates_and_bounds( |
| tcx: TyCtxt<'_>, |
| def_id: LocalDefId, |
| ) -> ty::GenericPredicates<'_> { |
| assert_eq!(tcx.def_kind(def_id), DefKind::Trait); |
| gather_explicit_predicates_of(tcx, def_id) |
| } |
| |
| pub(super) fn explicit_predicates_of<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| def_id: LocalDefId, |
| ) -> ty::GenericPredicates<'tcx> { |
| let def_kind = tcx.def_kind(def_id); |
| if let DefKind::Trait = def_kind { |
| // Remove bounds on associated types from the predicates, they will be |
| // returned by `explicit_item_bounds`. |
| let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id); |
| let trait_identity_args = ty::GenericArgs::identity_for_item(tcx, def_id); |
| |
| let is_assoc_item_ty = |ty: Ty<'tcx>| { |
| // For a predicate from a where clause to become a bound on an |
| // associated type: |
| // * It must use the identity args of the item. |
| // * We're in the scope of the trait, so we can't name any |
| // parameters of the GAT. That means that all we need to |
| // check are that the args of the projection are the |
| // identity args of the trait. |
| // * It must be an associated type for this trait (*not* a |
| // supertrait). |
| if let ty::Alias(ty::Projection, projection) = ty.kind() { |
| projection.args == trait_identity_args |
| // FIXME(return_type_notation): This check should be more robust |
| && !tcx.is_impl_trait_in_trait(projection.def_id) |
| && tcx.associated_item(projection.def_id).container_id(tcx) |
| == def_id.to_def_id() |
| } else { |
| false |
| } |
| }; |
| |
| let predicates: Vec<_> = predicates_and_bounds |
| .predicates |
| .iter() |
| .copied() |
| .filter(|(pred, _)| match pred.kind().skip_binder() { |
| ty::ClauseKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()), |
| ty::ClauseKind::Projection(proj) => !is_assoc_item_ty(proj.projection_ty.self_ty()), |
| ty::ClauseKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0), |
| _ => true, |
| }) |
| .collect(); |
| if predicates.len() == predicates_and_bounds.predicates.len() { |
| predicates_and_bounds |
| } else { |
| ty::GenericPredicates { |
| parent: predicates_and_bounds.parent, |
| predicates: tcx.arena.alloc_slice(&predicates), |
| } |
| } |
| } else { |
| if matches!(def_kind, DefKind::AnonConst) && tcx.features().generic_const_exprs { |
| let hir_id = tcx.local_def_id_to_hir_id(def_id); |
| let parent_def_id = tcx.hir().get_parent_item(hir_id); |
| |
| if let Some(defaulted_param_def_id) = |
| tcx.hir().opt_const_param_default_param_def_id(hir_id) |
| { |
| // In `generics_of` we set the generics' parent to be our parent's parent which means that |
| // we lose out on the predicates of our actual parent if we dont return those predicates here. |
| // (See comment in `generics_of` for more information on why the parent shenanigans is necessary) |
| // |
| // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait; |
| // ^^^ ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling |
| // ^^^ explicit_predicates_of on |
| // parent item we dont have set as the |
| // parent of generics returned by `generics_of` |
| // |
| // In the above code we want the anon const to have predicates in its param env for `T: Trait` |
| // and we would be calling `explicit_predicates_of(Foo)` here |
| let parent_preds = tcx.explicit_predicates_of(parent_def_id); |
| |
| // If we dont filter out `ConstArgHasType` predicates then every single defaulted const parameter |
| // will ICE because of #106994. FIXME(generic_const_exprs): remove this when a more general solution |
| // to #106994 is implemented. |
| let filtered_predicates = parent_preds |
| .predicates |
| .into_iter() |
| .filter(|(pred, _)| { |
| if let ty::ClauseKind::ConstArgHasType(ct, _) = pred.kind().skip_binder() { |
| match ct.kind() { |
| ty::ConstKind::Param(param_const) => { |
| let defaulted_param_idx = tcx |
| .generics_of(parent_def_id) |
| .param_def_id_to_index[&defaulted_param_def_id.to_def_id()]; |
| param_const.index < defaulted_param_idx |
| } |
| _ => bug!( |
| "`ConstArgHasType` in `predicates_of`\ |
| that isn't a `Param` const" |
| ), |
| } |
| } else { |
| true |
| } |
| }) |
| .cloned(); |
| return GenericPredicates { |
| parent: parent_preds.parent, |
| predicates: { tcx.arena.alloc_from_iter(filtered_predicates) }, |
| }; |
| } |
| |
| let parent_def_kind = tcx.def_kind(parent_def_id); |
| if matches!(parent_def_kind, DefKind::OpaqueTy) { |
| // In `instantiate_identity` we inherit the predicates of our parent. |
| // However, opaque types do not have a parent (see `gather_explicit_predicates_of`), which means |
| // that we lose out on the predicates of our actual parent if we dont return those predicates here. |
| // |
| // |
| // fn foo<T: Trait>() -> impl Iterator<Output = Another<{ <T as Trait>::ASSOC }> > { todo!() } |
| // ^^^^^^^^^^^^^^^^^^^ the def id we are calling |
| // explicit_predicates_of on |
| // |
| // In the above code we want the anon const to have predicates in its param env for `T: Trait`. |
| // However, the anon const cannot inherit predicates from its parent since it's opaque. |
| // |
| // To fix this, we call `explicit_predicates_of` directly on `foo`, the parent's parent. |
| |
| // In the above example this is `foo::{opaque#0}` or `impl Iterator` |
| let parent_hir_id = tcx.local_def_id_to_hir_id(parent_def_id.def_id); |
| |
| // In the above example this is the function `foo` |
| let item_def_id = tcx.hir().get_parent_item(parent_hir_id); |
| |
| // In the above code example we would be calling `explicit_predicates_of(foo)` here |
| return tcx.explicit_predicates_of(item_def_id); |
| } |
| } |
| gather_explicit_predicates_of(tcx, def_id) |
| } |
| } |
| |
| /// Ensures that the super-predicates of the trait with a `DefId` |
| /// of `trait_def_id` are lowered and stored. This also ensures that |
| /// the transitive super-predicates are lowered. |
| pub(super) fn super_predicates_of( |
| tcx: TyCtxt<'_>, |
| trait_def_id: LocalDefId, |
| ) -> ty::GenericPredicates<'_> { |
| implied_predicates_with_filter(tcx, trait_def_id.to_def_id(), PredicateFilter::SelfOnly) |
| } |
| |
| pub(super) fn super_predicates_that_define_assoc_item( |
| tcx: TyCtxt<'_>, |
| (trait_def_id, assoc_name): (DefId, Ident), |
| ) -> ty::GenericPredicates<'_> { |
| implied_predicates_with_filter(tcx, trait_def_id, PredicateFilter::SelfThatDefines(assoc_name)) |
| } |
| |
| pub(super) fn implied_predicates_of( |
| tcx: TyCtxt<'_>, |
| trait_def_id: LocalDefId, |
| ) -> ty::GenericPredicates<'_> { |
| implied_predicates_with_filter( |
| tcx, |
| trait_def_id.to_def_id(), |
| if tcx.is_trait_alias(trait_def_id.to_def_id()) { |
| PredicateFilter::All |
| } else { |
| PredicateFilter::SelfAndAssociatedTypeBounds |
| }, |
| ) |
| } |
| |
| /// Ensures that the super-predicates of the trait with a `DefId` |
| /// of `trait_def_id` are lowered and stored. This also ensures that |
| /// the transitive super-predicates are lowered. |
| pub(super) fn implied_predicates_with_filter( |
| tcx: TyCtxt<'_>, |
| trait_def_id: DefId, |
| filter: PredicateFilter, |
| ) -> ty::GenericPredicates<'_> { |
| let Some(trait_def_id) = trait_def_id.as_local() else { |
| // if `assoc_name` is None, then the query should've been redirected to an |
| // external provider |
| assert!(matches!(filter, PredicateFilter::SelfThatDefines(_))); |
| return tcx.super_predicates_of(trait_def_id); |
| }; |
| |
| let Node::Item(item) = tcx.hir_node_by_def_id(trait_def_id) else { |
| bug!("trait_def_id {trait_def_id:?} is not an item"); |
| }; |
| |
| let (generics, bounds) = match item.kind { |
| hir::ItemKind::Trait(.., generics, supertraits, _) => (generics, supertraits), |
| hir::ItemKind::TraitAlias(generics, supertraits) => (generics, supertraits), |
| _ => span_bug!(item.span, "super_predicates invoked on non-trait"), |
| }; |
| |
| let icx = ItemCtxt::new(tcx, trait_def_id); |
| |
| let self_param_ty = tcx.types.self_param; |
| let superbounds = icx.lowerer().lower_mono_bounds(self_param_ty, bounds, filter); |
| |
| let where_bounds_that_match = icx.probe_ty_param_bounds_in_generics( |
| generics, |
| item.owner_id.def_id, |
| self_param_ty, |
| filter, |
| ); |
| |
| // Combine the two lists to form the complete set of superbounds: |
| let implied_bounds = |
| &*tcx.arena.alloc_from_iter(superbounds.clauses().chain(where_bounds_that_match)); |
| debug!(?implied_bounds); |
| |
| // Now require that immediate supertraits are lowered, which will, in |
| // turn, reach indirect supertraits, so we detect cycles now instead of |
| // overflowing during elaboration. Same for implied predicates, which |
| // make sure we walk into associated type bounds. |
| match filter { |
| PredicateFilter::SelfOnly => { |
| for &(pred, span) in implied_bounds { |
| debug!("superbound: {:?}", pred); |
| if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder() |
| && bound.polarity == ty::PredicatePolarity::Positive |
| { |
| tcx.at(span).super_predicates_of(bound.def_id()); |
| } |
| } |
| } |
| PredicateFilter::SelfAndAssociatedTypeBounds => { |
| for &(pred, span) in implied_bounds { |
| debug!("superbound: {:?}", pred); |
| if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder() |
| && bound.polarity == ty::PredicatePolarity::Positive |
| { |
| tcx.at(span).implied_predicates_of(bound.def_id()); |
| } |
| } |
| } |
| _ => {} |
| } |
| |
| ty::GenericPredicates { parent: None, predicates: implied_bounds } |
| } |
| |
| /// Returns the predicates defined on `item_def_id` of the form |
| /// `X: Foo` where `X` is the type parameter `def_id`. |
| #[instrument(level = "trace", skip(tcx))] |
| pub(super) fn type_param_predicates( |
| tcx: TyCtxt<'_>, |
| (item_def_id, def_id, assoc_name): (LocalDefId, LocalDefId, Ident), |
| ) -> ty::GenericPredicates<'_> { |
| use rustc_hir::*; |
| use rustc_middle::ty::Ty; |
| |
| // In the HIR, bounds can derive from two places. Either |
| // written inline like `<T: Foo>` or in a where-clause like |
| // `where T: Foo`. |
| |
| let param_id = tcx.local_def_id_to_hir_id(def_id); |
| let param_owner = tcx.hir().ty_param_owner(def_id); |
| let generics = tcx.generics_of(param_owner); |
| let index = generics.param_def_id_to_index[&def_id.to_def_id()]; |
| let ty = Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id)); |
| |
| // Don't look for bounds where the type parameter isn't in scope. |
| let parent = if item_def_id == param_owner { |
| None |
| } else { |
| tcx.generics_of(item_def_id).parent.map(|def_id| def_id.expect_local()) |
| }; |
| |
| let mut result = parent |
| .map(|parent| { |
| let icx = ItemCtxt::new(tcx, parent); |
| icx.probe_ty_param_bounds(DUMMY_SP, def_id, assoc_name) |
| }) |
| .unwrap_or_default(); |
| let mut extend = None; |
| |
| let item_hir_id = tcx.local_def_id_to_hir_id(item_def_id); |
| |
| let hir_node = tcx.hir_node(item_hir_id); |
| let Some(hir_generics) = hir_node.generics() else { return result }; |
| if let Node::Item(item) = hir_node |
| && let ItemKind::Trait(..) = item.kind |
| // Implied `Self: Trait` and supertrait bounds. |
| && param_id == item_hir_id |
| { |
| let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id.to_def_id()); |
| extend = Some((identity_trait_ref.to_predicate(tcx), item.span)); |
| } |
| |
| let icx = ItemCtxt::new(tcx, item_def_id); |
| let extra_predicates = extend.into_iter().chain( |
| icx.probe_ty_param_bounds_in_generics( |
| hir_generics, |
| def_id, |
| ty, |
| PredicateFilter::SelfThatDefines(assoc_name), |
| ) |
| .into_iter() |
| .filter(|(predicate, _)| match predicate.kind().skip_binder() { |
| ty::ClauseKind::Trait(data) => data.self_ty().is_param(index), |
| _ => false, |
| }), |
| ); |
| result.predicates = |
| tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates)); |
| result |
| } |
| |
| impl<'tcx> ItemCtxt<'tcx> { |
| /// Finds bounds from `hir::Generics`. |
| /// |
| /// This requires scanning through the HIR. |
| /// We do this to avoid having to lower *all* the bounds, which would create artificial cycles. |
| /// Instead, we can only lower the bounds for a type parameter `X` if `X::Foo` is used. |
| #[instrument(level = "trace", skip(self, hir_generics))] |
| fn probe_ty_param_bounds_in_generics( |
| &self, |
| hir_generics: &'tcx hir::Generics<'tcx>, |
| param_def_id: LocalDefId, |
| ty: Ty<'tcx>, |
| filter: PredicateFilter, |
| ) -> Vec<(ty::Clause<'tcx>, Span)> { |
| let mut bounds = Bounds::default(); |
| |
| for predicate in hir_generics.predicates { |
| let hir::WherePredicate::BoundPredicate(predicate) = predicate else { |
| continue; |
| }; |
| |
| let (only_self_bounds, assoc_name) = match filter { |
| PredicateFilter::All | PredicateFilter::SelfAndAssociatedTypeBounds => { |
| (OnlySelfBounds(false), None) |
| } |
| PredicateFilter::SelfOnly => (OnlySelfBounds(true), None), |
| PredicateFilter::SelfThatDefines(assoc_name) => { |
| (OnlySelfBounds(true), Some(assoc_name)) |
| } |
| }; |
| |
| // Subtle: If we're collecting `SelfAndAssociatedTypeBounds`, then we |
| // want to only consider predicates with `Self: ...`, but we don't want |
| // `OnlySelfBounds(true)` since we want to collect the nested associated |
| // type bound as well. |
| let bound_ty = if predicate.is_param_bound(param_def_id.to_def_id()) { |
| ty |
| } else if matches!(filter, PredicateFilter::All) { |
| self.lower_ty(predicate.bounded_ty) |
| } else { |
| continue; |
| }; |
| |
| let bound_vars = self.tcx.late_bound_vars(predicate.hir_id); |
| self.lowerer().lower_poly_bounds( |
| bound_ty, |
| predicate.bounds.iter().filter(|bound| { |
| assoc_name |
| .map_or(true, |assoc_name| self.bound_defines_assoc_item(bound, assoc_name)) |
| }), |
| &mut bounds, |
| bound_vars, |
| only_self_bounds, |
| ); |
| } |
| |
| bounds.clauses().collect() |
| } |
| |
| #[instrument(level = "trace", skip(self))] |
| fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool { |
| match b { |
| hir::GenericBound::Trait(poly_trait_ref, _) => { |
| let trait_ref = &poly_trait_ref.trait_ref; |
| if let Some(trait_did) = trait_ref.trait_def_id() { |
| self.tcx.trait_may_define_assoc_item(trait_did, assoc_name) |
| } else { |
| false |
| } |
| } |
| _ => false, |
| } |
| } |
| } |
