| use crate::autoderef::Autoderef; |
| use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter}; |
| |
| use rustc_ast as ast; |
| use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet}; |
| use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed}; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::{DefId, LocalDefId}; |
| use rustc_hir::lang_items::LangItem; |
| use rustc_hir::ItemKind; |
| use rustc_infer::infer::outlives::env::{OutlivesEnvironment, RegionBoundPairs}; |
| use rustc_infer::infer::outlives::obligations::TypeOutlives; |
| use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt}; |
| use rustc_middle::mir::ConstraintCategory; |
| use rustc_middle::query::Providers; |
| use rustc_middle::ty::trait_def::TraitSpecializationKind; |
| use rustc_middle::ty::{ |
| self, AdtKind, GenericParamDefKind, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, |
| TypeVisitable, TypeVisitableExt, TypeVisitor, |
| }; |
| use rustc_middle::ty::{GenericArgKind, InternalSubsts}; |
| use rustc_session::parse::feature_err; |
| use rustc_span::symbol::{sym, Ident, Symbol}; |
| use rustc_span::{Span, DUMMY_SP}; |
| use rustc_target::spec::abi::Abi; |
| use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt; |
| use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _; |
| use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _; |
| use rustc_trait_selection::traits::{ |
| self, ObligationCause, ObligationCauseCode, ObligationCtxt, WellFormedLoc, |
| }; |
| |
| use std::cell::LazyCell; |
| use std::ops::{ControlFlow, Deref}; |
| |
| pub(super) struct WfCheckingCtxt<'a, 'tcx> { |
| pub(super) ocx: ObligationCtxt<'a, 'tcx>, |
| span: Span, |
| body_def_id: LocalDefId, |
| param_env: ty::ParamEnv<'tcx>, |
| } |
| impl<'a, 'tcx> Deref for WfCheckingCtxt<'a, 'tcx> { |
| type Target = ObligationCtxt<'a, 'tcx>; |
| fn deref(&self) -> &Self::Target { |
| &self.ocx |
| } |
| } |
| |
| impl<'tcx> WfCheckingCtxt<'_, 'tcx> { |
| fn tcx(&self) -> TyCtxt<'tcx> { |
| self.ocx.infcx.tcx |
| } |
| |
| // Convenience function to normalize during wfcheck. This performs |
| // `ObligationCtxt::normalize`, but provides a nice `ObligationCauseCode`. |
| fn normalize<T>(&self, span: Span, loc: Option<WellFormedLoc>, value: T) -> T |
| where |
| T: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| self.ocx.normalize( |
| &ObligationCause::new(span, self.body_def_id, ObligationCauseCode::WellFormed(loc)), |
| self.param_env, |
| value, |
| ) |
| } |
| |
| fn register_wf_obligation( |
| &self, |
| span: Span, |
| loc: Option<WellFormedLoc>, |
| arg: ty::GenericArg<'tcx>, |
| ) { |
| let cause = traits::ObligationCause::new( |
| span, |
| self.body_def_id, |
| ObligationCauseCode::WellFormed(loc), |
| ); |
| // for a type to be WF, we do not need to check if const trait predicates satisfy. |
| let param_env = self.param_env.without_const(); |
| self.ocx.register_obligation(traits::Obligation::new( |
| self.tcx(), |
| cause, |
| param_env, |
| ty::Binder::dummy(ty::PredicateKind::WellFormed(arg)), |
| )); |
| } |
| } |
| |
| pub(super) fn enter_wf_checking_ctxt<'tcx, F>( |
| tcx: TyCtxt<'tcx>, |
| span: Span, |
| body_def_id: LocalDefId, |
| f: F, |
| ) where |
| F: for<'a> FnOnce(&WfCheckingCtxt<'a, 'tcx>), |
| { |
| let param_env = tcx.param_env(body_def_id); |
| let infcx = &tcx.infer_ctxt().build(); |
| let ocx = ObligationCtxt::new(infcx); |
| |
| let mut wfcx = WfCheckingCtxt { ocx, span, body_def_id, param_env }; |
| |
| if !tcx.features().trivial_bounds { |
| wfcx.check_false_global_bounds() |
| } |
| f(&mut wfcx); |
| |
| let assumed_wf_types = wfcx.ocx.assumed_wf_types(param_env, span, body_def_id); |
| let implied_bounds = infcx.implied_bounds_tys(param_env, body_def_id, assumed_wf_types); |
| |
| let errors = wfcx.select_all_or_error(); |
| if !errors.is_empty() { |
| infcx.err_ctxt().report_fulfillment_errors(&errors); |
| return; |
| } |
| |
| let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds); |
| |
| let _ = wfcx.ocx.resolve_regions_and_report_errors(body_def_id, &outlives_env); |
| } |
| |
| fn check_well_formed(tcx: TyCtxt<'_>, def_id: hir::OwnerId) { |
| let node = tcx.hir().owner(def_id); |
| match node { |
| hir::OwnerNode::Crate(_) => {} |
| hir::OwnerNode::Item(item) => check_item(tcx, item), |
| hir::OwnerNode::TraitItem(item) => check_trait_item(tcx, item), |
| hir::OwnerNode::ImplItem(item) => check_impl_item(tcx, item), |
| hir::OwnerNode::ForeignItem(item) => check_foreign_item(tcx, item), |
| } |
| |
| if let Some(generics) = node.generics() { |
| for param in generics.params { |
| check_param_wf(tcx, param) |
| } |
| } |
| } |
| |
| /// Checks that the field types (in a struct def'n) or argument types (in an enum def'n) are |
| /// well-formed, meaning that they do not require any constraints not declared in the struct |
| /// definition itself. For example, this definition would be illegal: |
| /// |
| /// ```rust |
| /// struct Ref<'a, T> { x: &'a T } |
| /// ``` |
| /// |
| /// because the type did not declare that `T:'a`. |
| /// |
| /// We do this check as a pre-pass before checking fn bodies because if these constraints are |
| /// not included it frequently leads to confusing errors in fn bodies. So it's better to check |
| /// the types first. |
| #[instrument(skip(tcx), level = "debug")] |
| fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) { |
| let def_id = item.owner_id.def_id; |
| |
| debug!( |
| ?item.owner_id, |
| item.name = ? tcx.def_path_str(def_id) |
| ); |
| |
| match item.kind { |
| // Right now we check that every default trait implementation |
| // has an implementation of itself. Basically, a case like: |
| // |
| // impl Trait for T {} |
| // |
| // has a requirement of `T: Trait` which was required for default |
| // method implementations. Although this could be improved now that |
| // there's a better infrastructure in place for this, it's being left |
| // for a follow-up work. |
| // |
| // Since there's such a requirement, we need to check *just* positive |
| // implementations, otherwise things like: |
| // |
| // impl !Send for T {} |
| // |
| // won't be allowed unless there's an *explicit* implementation of `Send` |
| // for `T` |
| hir::ItemKind::Impl(impl_) => { |
| let is_auto = tcx |
| .impl_trait_ref(def_id) |
| .is_some_and(|trait_ref| tcx.trait_is_auto(trait_ref.skip_binder().def_id)); |
| if let (hir::Defaultness::Default { .. }, true) = (impl_.defaultness, is_auto) { |
| let sp = impl_.of_trait.as_ref().map_or(item.span, |t| t.path.span); |
| let mut err = |
| tcx.sess.struct_span_err(sp, "impls of auto traits cannot be default"); |
| err.span_labels(impl_.defaultness_span, "default because of this"); |
| err.span_label(sp, "auto trait"); |
| err.emit(); |
| } |
| // We match on both `ty::ImplPolarity` and `ast::ImplPolarity` just to get the `!` span. |
| match (tcx.impl_polarity(def_id), impl_.polarity) { |
| (ty::ImplPolarity::Positive, _) => { |
| check_impl(tcx, item, impl_.self_ty, &impl_.of_trait, impl_.constness); |
| } |
| (ty::ImplPolarity::Negative, ast::ImplPolarity::Negative(span)) => { |
| // FIXME(#27579): what amount of WF checking do we need for neg impls? |
| if let hir::Defaultness::Default { .. } = impl_.defaultness { |
| let mut spans = vec![span]; |
| spans.extend(impl_.defaultness_span); |
| struct_span_err!( |
| tcx.sess, |
| spans, |
| E0750, |
| "negative impls cannot be default impls" |
| ) |
| .emit(); |
| } |
| } |
| (ty::ImplPolarity::Reservation, _) => { |
| // FIXME: what amount of WF checking do we need for reservation impls? |
| } |
| _ => unreachable!(), |
| } |
| } |
| hir::ItemKind::Fn(ref sig, ..) => { |
| check_item_fn(tcx, def_id, item.ident, item.span, sig.decl); |
| } |
| hir::ItemKind::Static(ty, ..) => { |
| check_item_type(tcx, def_id, ty.span, false); |
| } |
| hir::ItemKind::Const(ty, ..) => { |
| check_item_type(tcx, def_id, ty.span, false); |
| } |
| hir::ItemKind::Struct(_, ast_generics) => { |
| check_type_defn(tcx, item, false); |
| check_variances_for_type_defn(tcx, item, ast_generics); |
| } |
| hir::ItemKind::Union(_, ast_generics) => { |
| check_type_defn(tcx, item, true); |
| check_variances_for_type_defn(tcx, item, ast_generics); |
| } |
| hir::ItemKind::Enum(_, ast_generics) => { |
| check_type_defn(tcx, item, true); |
| check_variances_for_type_defn(tcx, item, ast_generics); |
| } |
| hir::ItemKind::Trait(..) => { |
| check_trait(tcx, item); |
| } |
| hir::ItemKind::TraitAlias(..) => { |
| check_trait(tcx, item); |
| } |
| // `ForeignItem`s are handled separately. |
| hir::ItemKind::ForeignMod { .. } => {} |
| _ => {} |
| } |
| } |
| |
| fn check_foreign_item(tcx: TyCtxt<'_>, item: &hir::ForeignItem<'_>) { |
| let def_id = item.owner_id.def_id; |
| |
| debug!( |
| ?item.owner_id, |
| item.name = ? tcx.def_path_str(def_id) |
| ); |
| |
| match item.kind { |
| hir::ForeignItemKind::Fn(decl, ..) => { |
| check_item_fn(tcx, def_id, item.ident, item.span, decl) |
| } |
| hir::ForeignItemKind::Static(ty, ..) => check_item_type(tcx, def_id, ty.span, true), |
| hir::ForeignItemKind::Type => (), |
| } |
| } |
| |
| fn check_trait_item(tcx: TyCtxt<'_>, trait_item: &hir::TraitItem<'_>) { |
| let def_id = trait_item.owner_id.def_id; |
| |
| let (method_sig, span) = match trait_item.kind { |
| hir::TraitItemKind::Fn(ref sig, _) => (Some(sig), trait_item.span), |
| hir::TraitItemKind::Type(_bounds, Some(ty)) => (None, ty.span), |
| _ => (None, trait_item.span), |
| }; |
| check_object_unsafe_self_trait_by_name(tcx, trait_item); |
| check_associated_item(tcx, def_id, span, method_sig); |
| } |
| |
| /// Require that the user writes where clauses on GATs for the implicit |
| /// outlives bounds involving trait parameters in trait functions and |
| /// lifetimes passed as GAT substs. See `self-outlives-lint` test. |
| /// |
| /// We use the following trait as an example throughout this function: |
| /// ```rust,ignore (this code fails due to this lint) |
| /// trait IntoIter { |
| /// type Iter<'a>: Iterator<Item = Self::Item<'a>>; |
| /// type Item<'a>; |
| /// fn into_iter<'a>(&'a self) -> Self::Iter<'a>; |
| /// } |
| /// ``` |
| fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRef]) { |
| // Associates every GAT's def_id to a list of possibly missing bounds detected by this lint. |
| let mut required_bounds_by_item = FxHashMap::default(); |
| |
| // Loop over all GATs together, because if this lint suggests adding a where-clause bound |
| // to one GAT, it might then require us to an additional bound on another GAT. |
| // In our `IntoIter` example, we discover a missing `Self: 'a` bound on `Iter<'a>`, which |
| // then in a second loop adds a `Self: 'a` bound to `Item` due to the relationship between |
| // those GATs. |
| loop { |
| let mut should_continue = false; |
| for gat_item in associated_items { |
| let gat_def_id = gat_item.id.owner_id; |
| let gat_item = tcx.associated_item(gat_def_id); |
| // If this item is not an assoc ty, or has no substs, then it's not a GAT |
| if gat_item.kind != ty::AssocKind::Type { |
| continue; |
| } |
| let gat_generics = tcx.generics_of(gat_def_id); |
| // FIXME(jackh726): we can also warn in the more general case |
| if gat_generics.params.is_empty() { |
| continue; |
| } |
| |
| // Gather the bounds with which all other items inside of this trait constrain the GAT. |
| // This is calculated by taking the intersection of the bounds that each item |
| // constrains the GAT with individually. |
| let mut new_required_bounds: Option<FxHashSet<ty::Predicate<'_>>> = None; |
| for item in associated_items { |
| let item_def_id = item.id.owner_id; |
| // Skip our own GAT, since it does not constrain itself at all. |
| if item_def_id == gat_def_id { |
| continue; |
| } |
| |
| let param_env = tcx.param_env(item_def_id); |
| |
| let item_required_bounds = match item.kind { |
| // In our example, this corresponds to `into_iter` method |
| hir::AssocItemKind::Fn { .. } => { |
| // For methods, we check the function signature's return type for any GATs |
| // to constrain. In the `into_iter` case, we see that the return type |
| // `Self::Iter<'a>` is a GAT we want to gather any potential missing bounds from. |
| let sig: ty::FnSig<'_> = tcx.liberate_late_bound_regions( |
| item_def_id.to_def_id(), |
| tcx.fn_sig(item_def_id).subst_identity(), |
| ); |
| gather_gat_bounds( |
| tcx, |
| param_env, |
| item_def_id, |
| sig.inputs_and_output, |
| // We also assume that all of the function signature's parameter types |
| // are well formed. |
| &sig.inputs().iter().copied().collect(), |
| gat_def_id.def_id, |
| gat_generics, |
| ) |
| } |
| // In our example, this corresponds to the `Iter` and `Item` associated types |
| hir::AssocItemKind::Type => { |
| // If our associated item is a GAT with missing bounds, add them to |
| // the param-env here. This allows this GAT to propagate missing bounds |
| // to other GATs. |
| let param_env = augment_param_env( |
| tcx, |
| param_env, |
| required_bounds_by_item.get(&item_def_id), |
| ); |
| gather_gat_bounds( |
| tcx, |
| param_env, |
| item_def_id, |
| tcx.explicit_item_bounds(item_def_id) |
| .subst_identity_iter_copied() |
| .collect::<Vec<_>>(), |
| &FxIndexSet::default(), |
| gat_def_id.def_id, |
| gat_generics, |
| ) |
| } |
| hir::AssocItemKind::Const => None, |
| }; |
| |
| if let Some(item_required_bounds) = item_required_bounds { |
| // Take the intersection of the required bounds for this GAT, and |
| // the item_required_bounds which are the ones implied by just |
| // this item alone. |
| // This is why we use an Option<_>, since we need to distinguish |
| // the empty set of bounds from the _uninitialized_ set of bounds. |
| if let Some(new_required_bounds) = &mut new_required_bounds { |
| new_required_bounds.retain(|b| item_required_bounds.contains(b)); |
| } else { |
| new_required_bounds = Some(item_required_bounds); |
| } |
| } |
| } |
| |
| if let Some(new_required_bounds) = new_required_bounds { |
| let required_bounds = required_bounds_by_item.entry(gat_def_id).or_default(); |
| if new_required_bounds.into_iter().any(|p| required_bounds.insert(p)) { |
| // Iterate until our required_bounds no longer change |
| // Since they changed here, we should continue the loop |
| should_continue = true; |
| } |
| } |
| } |
| // We know that this loop will eventually halt, since we only set `should_continue` if the |
| // `required_bounds` for this item grows. Since we are not creating any new region or type |
| // variables, the set of all region and type bounds that we could ever insert are limited |
| // by the number of unique types and regions we observe in a given item. |
| if !should_continue { |
| break; |
| } |
| } |
| |
| for (gat_def_id, required_bounds) in required_bounds_by_item { |
| let gat_item_hir = tcx.hir().expect_trait_item(gat_def_id.def_id); |
| debug!(?required_bounds); |
| let param_env = tcx.param_env(gat_def_id); |
| |
| let mut unsatisfied_bounds: Vec<_> = required_bounds |
| .into_iter() |
| .filter(|clause| match clause.kind().skip_binder() { |
| ty::PredicateKind::Clause(ty::Clause::RegionOutlives(ty::OutlivesPredicate( |
| a, |
| b, |
| ))) => !region_known_to_outlive( |
| tcx, |
| gat_def_id.def_id, |
| param_env, |
| &FxIndexSet::default(), |
| a, |
| b, |
| ), |
| ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate( |
| a, |
| b, |
| ))) => !ty_known_to_outlive( |
| tcx, |
| gat_def_id.def_id, |
| param_env, |
| &FxIndexSet::default(), |
| a, |
| b, |
| ), |
| _ => bug!("Unexpected PredicateKind"), |
| }) |
| .map(|clause| clause.to_string()) |
| .collect(); |
| |
| // We sort so that order is predictable |
| unsatisfied_bounds.sort(); |
| |
| if !unsatisfied_bounds.is_empty() { |
| let plural = pluralize!(unsatisfied_bounds.len()); |
| let mut err = tcx.sess.struct_span_err( |
| gat_item_hir.span, |
| format!("missing required bound{} on `{}`", plural, gat_item_hir.ident), |
| ); |
| |
| let suggestion = format!( |
| "{} {}", |
| gat_item_hir.generics.add_where_or_trailing_comma(), |
| unsatisfied_bounds.join(", "), |
| ); |
| err.span_suggestion( |
| gat_item_hir.generics.tail_span_for_predicate_suggestion(), |
| format!("add the required where clause{plural}"), |
| suggestion, |
| Applicability::MachineApplicable, |
| ); |
| |
| let bound = |
| if unsatisfied_bounds.len() > 1 { "these bounds are" } else { "this bound is" }; |
| err.note(format!( |
| "{} currently required to ensure that impls have maximum flexibility", |
| bound |
| )); |
| err.note( |
| "we are soliciting feedback, see issue #87479 \ |
| <https://github.com/rust-lang/rust/issues/87479> \ |
| for more information", |
| ); |
| |
| err.emit(); |
| } |
| } |
| } |
| |
| /// Add a new set of predicates to the caller_bounds of an existing param_env. |
| fn augment_param_env<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| new_predicates: Option<&FxHashSet<ty::Predicate<'tcx>>>, |
| ) -> ty::ParamEnv<'tcx> { |
| let Some(new_predicates) = new_predicates else { |
| return param_env; |
| }; |
| |
| if new_predicates.is_empty() { |
| return param_env; |
| } |
| |
| let bounds = tcx.mk_predicates_from_iter( |
| param_env.caller_bounds().iter().chain(new_predicates.iter().cloned()), |
| ); |
| // FIXME(compiler-errors): Perhaps there is a case where we need to normalize this |
| // i.e. traits::normalize_param_env_or_error |
| ty::ParamEnv::new(bounds, param_env.reveal(), param_env.constness()) |
| } |
| |
| /// We use the following trait as an example throughout this function. |
| /// Specifically, let's assume that `to_check` here is the return type |
| /// of `into_iter`, and the GAT we are checking this for is `Iter`. |
| /// ```rust,ignore (this code fails due to this lint) |
| /// trait IntoIter { |
| /// type Iter<'a>: Iterator<Item = Self::Item<'a>>; |
| /// type Item<'a>; |
| /// fn into_iter<'a>(&'a self) -> Self::Iter<'a>; |
| /// } |
| /// ``` |
| fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>( |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| item_def_id: hir::OwnerId, |
| to_check: T, |
| wf_tys: &FxIndexSet<Ty<'tcx>>, |
| gat_def_id: LocalDefId, |
| gat_generics: &'tcx ty::Generics, |
| ) -> Option<FxHashSet<ty::Predicate<'tcx>>> { |
| // The bounds we that we would require from `to_check` |
| let mut bounds = FxHashSet::default(); |
| |
| let (regions, types) = GATSubstCollector::visit(gat_def_id.to_def_id(), to_check); |
| |
| // If both regions and types are empty, then this GAT isn't in the |
| // set of types we are checking, and we shouldn't try to do clause analysis |
| // (particularly, doing so would end up with an empty set of clauses, |
| // since the current method would require none, and we take the |
| // intersection of requirements of all methods) |
| if types.is_empty() && regions.is_empty() { |
| return None; |
| } |
| |
| for (region_a, region_a_idx) in ®ions { |
| // Ignore `'static` lifetimes for the purpose of this lint: it's |
| // because we know it outlives everything and so doesn't give meaningful |
| // clues |
| if let ty::ReStatic = **region_a { |
| continue; |
| } |
| // For each region argument (e.g., `'a` in our example), check for a |
| // relationship to the type arguments (e.g., `Self`). If there is an |
| // outlives relationship (`Self: 'a`), then we want to ensure that is |
| // reflected in a where clause on the GAT itself. |
| for (ty, ty_idx) in &types { |
| // In our example, requires that `Self: 'a` |
| if ty_known_to_outlive(tcx, item_def_id.def_id, param_env, &wf_tys, *ty, *region_a) { |
| debug!(?ty_idx, ?region_a_idx); |
| debug!("required clause: {ty} must outlive {region_a}"); |
| // Translate into the generic parameters of the GAT. In |
| // our example, the type was `Self`, which will also be |
| // `Self` in the GAT. |
| let ty_param = gat_generics.param_at(*ty_idx, tcx); |
| let ty_param = tcx.mk_ty_param(ty_param.index, ty_param.name); |
| // Same for the region. In our example, 'a corresponds |
| // to the 'me parameter. |
| let region_param = gat_generics.param_at(*region_a_idx, tcx); |
| let region_param = tcx.mk_re_early_bound(ty::EarlyBoundRegion { |
| def_id: region_param.def_id, |
| index: region_param.index, |
| name: region_param.name, |
| }); |
| // The predicate we expect to see. (In our example, |
| // `Self: 'me`.) |
| let clause = ty::PredicateKind::Clause(ty::Clause::TypeOutlives( |
| ty::OutlivesPredicate(ty_param, region_param), |
| )); |
| let clause = tcx.mk_predicate(ty::Binder::dummy(clause)); |
| bounds.insert(clause); |
| } |
| } |
| |
| // For each region argument (e.g., `'a` in our example), also check for a |
| // relationship to the other region arguments. If there is an outlives |
| // relationship, then we want to ensure that is reflected in the where clause |
| // on the GAT itself. |
| for (region_b, region_b_idx) in ®ions { |
| // Again, skip `'static` because it outlives everything. Also, we trivially |
| // know that a region outlives itself. |
| if ty::ReStatic == **region_b || region_a == region_b { |
| continue; |
| } |
| if region_known_to_outlive( |
| tcx, |
| item_def_id.def_id, |
| param_env, |
| &wf_tys, |
| *region_a, |
| *region_b, |
| ) { |
| debug!(?region_a_idx, ?region_b_idx); |
| debug!("required clause: {region_a} must outlive {region_b}"); |
| // Translate into the generic parameters of the GAT. |
| let region_a_param = gat_generics.param_at(*region_a_idx, tcx); |
| let region_a_param = tcx.mk_re_early_bound(ty::EarlyBoundRegion { |
| def_id: region_a_param.def_id, |
| index: region_a_param.index, |
| name: region_a_param.name, |
| }); |
| // Same for the region. |
| let region_b_param = gat_generics.param_at(*region_b_idx, tcx); |
| let region_b_param = tcx.mk_re_early_bound(ty::EarlyBoundRegion { |
| def_id: region_b_param.def_id, |
| index: region_b_param.index, |
| name: region_b_param.name, |
| }); |
| // The predicate we expect to see. |
| let clause = ty::PredicateKind::Clause(ty::Clause::RegionOutlives( |
| ty::OutlivesPredicate(region_a_param, region_b_param), |
| )); |
| let clause = tcx.mk_predicate(ty::Binder::dummy(clause)); |
| bounds.insert(clause); |
| } |
| } |
| } |
| |
| Some(bounds) |
| } |
| |
| /// Given a known `param_env` and a set of well formed types, can we prove that |
| /// `ty` outlives `region`. |
| fn ty_known_to_outlive<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| id: LocalDefId, |
| param_env: ty::ParamEnv<'tcx>, |
| wf_tys: &FxIndexSet<Ty<'tcx>>, |
| ty: Ty<'tcx>, |
| region: ty::Region<'tcx>, |
| ) -> bool { |
| resolve_regions_with_wf_tys(tcx, id, param_env, &wf_tys, |infcx, region_bound_pairs| { |
| let origin = infer::RelateParamBound(DUMMY_SP, ty, None); |
| let outlives = &mut TypeOutlives::new(infcx, tcx, region_bound_pairs, None, param_env); |
| outlives.type_must_outlive(origin, ty, region, ConstraintCategory::BoringNoLocation); |
| }) |
| } |
| |
| /// Given a known `param_env` and a set of well formed types, can we prove that |
| /// `region_a` outlives `region_b` |
| fn region_known_to_outlive<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| id: LocalDefId, |
| param_env: ty::ParamEnv<'tcx>, |
| wf_tys: &FxIndexSet<Ty<'tcx>>, |
| region_a: ty::Region<'tcx>, |
| region_b: ty::Region<'tcx>, |
| ) -> bool { |
| resolve_regions_with_wf_tys(tcx, id, param_env, &wf_tys, |mut infcx, _| { |
| use rustc_infer::infer::outlives::obligations::TypeOutlivesDelegate; |
| let origin = infer::RelateRegionParamBound(DUMMY_SP); |
| // `region_a: region_b` -> `region_b <= region_a` |
| infcx.push_sub_region_constraint( |
| origin, |
| region_b, |
| region_a, |
| ConstraintCategory::BoringNoLocation, |
| ); |
| }) |
| } |
| |
| /// Given a known `param_env` and a set of well formed types, set up an |
| /// `InferCtxt`, call the passed function (to e.g. set up region constraints |
| /// to be tested), then resolve region and return errors |
| fn resolve_regions_with_wf_tys<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| id: LocalDefId, |
| param_env: ty::ParamEnv<'tcx>, |
| wf_tys: &FxIndexSet<Ty<'tcx>>, |
| add_constraints: impl for<'a> FnOnce(&'a InferCtxt<'tcx>, &'a RegionBoundPairs<'tcx>), |
| ) -> bool { |
| // Unfortunately, we have to use a new `InferCtxt` each call, because |
| // region constraints get added and solved there and we need to test each |
| // call individually. |
| let infcx = tcx.infer_ctxt().build(); |
| let outlives_environment = OutlivesEnvironment::with_bounds( |
| param_env, |
| infcx.implied_bounds_tys(param_env, id, wf_tys.clone()), |
| ); |
| let region_bound_pairs = outlives_environment.region_bound_pairs(); |
| |
| add_constraints(&infcx, region_bound_pairs); |
| |
| let errors = infcx.resolve_regions(&outlives_environment); |
| debug!(?errors, "errors"); |
| |
| // If we were able to prove that the type outlives the region without |
| // an error, it must be because of the implied or explicit bounds... |
| errors.is_empty() |
| } |
| |
| /// TypeVisitor that looks for uses of GATs like |
| /// `<P0 as Trait<P1..Pn>>::GAT<Pn..Pm>` and adds the arguments `P0..Pm` into |
| /// the two vectors, `regions` and `types` (depending on their kind). For each |
| /// parameter `Pi` also track the index `i`. |
| struct GATSubstCollector<'tcx> { |
| gat: DefId, |
| // Which region appears and which parameter index its substituted for |
| regions: FxHashSet<(ty::Region<'tcx>, usize)>, |
| // Which params appears and which parameter index its substituted for |
| types: FxHashSet<(Ty<'tcx>, usize)>, |
| } |
| |
| impl<'tcx> GATSubstCollector<'tcx> { |
| fn visit<T: TypeFoldable<TyCtxt<'tcx>>>( |
| gat: DefId, |
| t: T, |
| ) -> (FxHashSet<(ty::Region<'tcx>, usize)>, FxHashSet<(Ty<'tcx>, usize)>) { |
| let mut visitor = |
| GATSubstCollector { gat, regions: FxHashSet::default(), types: FxHashSet::default() }; |
| t.visit_with(&mut visitor); |
| (visitor.regions, visitor.types) |
| } |
| } |
| |
| impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for GATSubstCollector<'tcx> { |
| type BreakTy = !; |
| |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| match t.kind() { |
| ty::Alias(ty::Projection, p) if p.def_id == self.gat => { |
| for (idx, subst) in p.substs.iter().enumerate() { |
| match subst.unpack() { |
| GenericArgKind::Lifetime(lt) if !lt.is_late_bound() => { |
| self.regions.insert((lt, idx)); |
| } |
| GenericArgKind::Type(t) => { |
| self.types.insert((t, idx)); |
| } |
| _ => {} |
| } |
| } |
| } |
| _ => {} |
| } |
| t.super_visit_with(self) |
| } |
| } |
| |
| fn could_be_self(trait_def_id: LocalDefId, ty: &hir::Ty<'_>) -> bool { |
| match ty.kind { |
| hir::TyKind::TraitObject([trait_ref], ..) => match trait_ref.trait_ref.path.segments { |
| [s] => s.res.opt_def_id() == Some(trait_def_id.to_def_id()), |
| _ => false, |
| }, |
| _ => false, |
| } |
| } |
| |
| /// Detect when an object unsafe trait is referring to itself in one of its associated items. |
| /// When this is done, suggest using `Self` instead. |
| fn check_object_unsafe_self_trait_by_name(tcx: TyCtxt<'_>, item: &hir::TraitItem<'_>) { |
| let (trait_name, trait_def_id) = |
| match tcx.hir().get_by_def_id(tcx.hir().get_parent_item(item.hir_id()).def_id) { |
| hir::Node::Item(item) => match item.kind { |
| hir::ItemKind::Trait(..) => (item.ident, item.owner_id), |
| _ => return, |
| }, |
| _ => return, |
| }; |
| let mut trait_should_be_self = vec![]; |
| match &item.kind { |
| hir::TraitItemKind::Const(ty, _) | hir::TraitItemKind::Type(_, Some(ty)) |
| if could_be_self(trait_def_id.def_id, ty) => |
| { |
| trait_should_be_self.push(ty.span) |
| } |
| hir::TraitItemKind::Fn(sig, _) => { |
| for ty in sig.decl.inputs { |
| if could_be_self(trait_def_id.def_id, ty) { |
| trait_should_be_self.push(ty.span); |
| } |
| } |
| match sig.decl.output { |
| hir::FnRetTy::Return(ty) if could_be_self(trait_def_id.def_id, ty) => { |
| trait_should_be_self.push(ty.span); |
| } |
| _ => {} |
| } |
| } |
| _ => {} |
| } |
| if !trait_should_be_self.is_empty() { |
| if tcx.check_is_object_safe(trait_def_id) { |
| return; |
| } |
| let sugg = trait_should_be_self.iter().map(|span| (*span, "Self".to_string())).collect(); |
| tcx.sess |
| .struct_span_err( |
| trait_should_be_self, |
| "associated item referring to unboxed trait object for its own trait", |
| ) |
| .span_label(trait_name.span, "in this trait") |
| .multipart_suggestion( |
| "you might have meant to use `Self` to refer to the implementing type", |
| sugg, |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| } |
| |
| fn check_impl_item(tcx: TyCtxt<'_>, impl_item: &hir::ImplItem<'_>) { |
| let (method_sig, span) = match impl_item.kind { |
| hir::ImplItemKind::Fn(ref sig, _) => (Some(sig), impl_item.span), |
| // Constrain binding and overflow error spans to `<Ty>` in `type foo = <Ty>`. |
| hir::ImplItemKind::Type(ty) if ty.span != DUMMY_SP => (None, ty.span), |
| _ => (None, impl_item.span), |
| }; |
| |
| check_associated_item(tcx, impl_item.owner_id.def_id, span, method_sig); |
| } |
| |
| fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) { |
| match param.kind { |
| // We currently only check wf of const params here. |
| hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. } => (), |
| |
| // Const parameters are well formed if their type is structural match. |
| hir::GenericParamKind::Const { ty: hir_ty, default: _ } => { |
| let ty = tcx.type_of(param.def_id).subst_identity(); |
| |
| if tcx.features().adt_const_params { |
| if let Some(non_structural_match_ty) = |
| traits::search_for_adt_const_param_violation(param.span, tcx, ty) |
| { |
| // We use the same error code in both branches, because this is really the same |
| // issue: we just special-case the message for type parameters to make it |
| // clearer. |
| match non_structural_match_ty.kind() { |
| ty::Param(_) => { |
| // Const parameters may not have type parameters as their types, |
| // because we cannot be sure that the type parameter derives `PartialEq` |
| // and `Eq` (just implementing them is not enough for `structural_match`). |
| struct_span_err!( |
| tcx.sess, |
| hir_ty.span, |
| E0741, |
| "`{ty}` is not guaranteed to `#[derive(PartialEq, Eq)]`, so may not be \ |
| used as the type of a const parameter", |
| ) |
| .span_label( |
| hir_ty.span, |
| format!("`{ty}` may not derive both `PartialEq` and `Eq`"), |
| ) |
| .note( |
| "it is not currently possible to use a type parameter as the type of a \ |
| const parameter", |
| ) |
| .emit(); |
| } |
| ty::Float(_) => { |
| struct_span_err!( |
| tcx.sess, |
| hir_ty.span, |
| E0741, |
| "`{ty}` is forbidden as the type of a const generic parameter", |
| ) |
| .note("floats do not derive `Eq` or `Ord`, which are required for const parameters") |
| .emit(); |
| } |
| ty::FnPtr(_) => { |
| struct_span_err!( |
| tcx.sess, |
| hir_ty.span, |
| E0741, |
| "using function pointers as const generic parameters is forbidden", |
| ) |
| .emit(); |
| } |
| ty::RawPtr(_) => { |
| struct_span_err!( |
| tcx.sess, |
| hir_ty.span, |
| E0741, |
| "using raw pointers as const generic parameters is forbidden", |
| ) |
| .emit(); |
| } |
| _ => { |
| let mut diag = struct_span_err!( |
| tcx.sess, |
| hir_ty.span, |
| E0741, |
| "`{}` must be annotated with `#[derive(PartialEq, Eq)]` to be used as \ |
| the type of a const parameter", |
| non_structural_match_ty, |
| ); |
| |
| if ty == non_structural_match_ty { |
| diag.span_label( |
| hir_ty.span, |
| format!("`{ty}` doesn't derive both `PartialEq` and `Eq`"), |
| ); |
| } |
| |
| diag.emit(); |
| } |
| } |
| } |
| } else { |
| let err_ty_str; |
| let mut is_ptr = true; |
| |
| let err = match ty.kind() { |
| ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Error(_) => None, |
| ty::FnPtr(_) => Some("function pointers"), |
| ty::RawPtr(_) => Some("raw pointers"), |
| _ => { |
| is_ptr = false; |
| err_ty_str = format!("`{ty}`"); |
| Some(err_ty_str.as_str()) |
| } |
| }; |
| |
| if let Some(unsupported_type) = err { |
| if is_ptr { |
| tcx.sess.span_err( |
| hir_ty.span, |
| format!( |
| "using {unsupported_type} as const generic parameters is forbidden", |
| ), |
| ); |
| } else { |
| let mut err = tcx.sess.struct_span_err( |
| hir_ty.span, |
| format!( |
| "{unsupported_type} is forbidden as the type of a const generic parameter", |
| ), |
| ); |
| err.note("the only supported types are integers, `bool` and `char`"); |
| if tcx.sess.is_nightly_build() { |
| err.help( |
| "more complex types are supported with `#![feature(adt_const_params)]`", |
| ); |
| } |
| err.emit(); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| #[instrument(level = "debug", skip(tcx, span, sig_if_method))] |
| fn check_associated_item( |
| tcx: TyCtxt<'_>, |
| item_id: LocalDefId, |
| span: Span, |
| sig_if_method: Option<&hir::FnSig<'_>>, |
| ) { |
| let loc = Some(WellFormedLoc::Ty(item_id)); |
| enter_wf_checking_ctxt(tcx, span, item_id, |wfcx| { |
| let item = tcx.associated_item(item_id); |
| |
| let self_ty = match item.container { |
| ty::TraitContainer => tcx.types.self_param, |
| ty::ImplContainer => tcx.type_of(item.container_id(tcx)).subst_identity(), |
| }; |
| |
| match item.kind { |
| ty::AssocKind::Const => { |
| let ty = tcx.type_of(item.def_id).subst_identity(); |
| let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty); |
| wfcx.register_wf_obligation(span, loc, ty.into()); |
| } |
| ty::AssocKind::Fn => { |
| let sig = tcx.fn_sig(item.def_id).subst_identity(); |
| let hir_sig = sig_if_method.expect("bad signature for method"); |
| check_fn_or_method( |
| wfcx, |
| item.ident(tcx).span, |
| sig, |
| hir_sig.decl, |
| item.def_id.expect_local(), |
| ); |
| check_method_receiver(wfcx, hir_sig, item, self_ty); |
| } |
| ty::AssocKind::Type => { |
| if let ty::AssocItemContainer::TraitContainer = item.container { |
| check_associated_type_bounds(wfcx, item, span) |
| } |
| if item.defaultness(tcx).has_value() { |
| let ty = tcx.type_of(item.def_id).subst_identity(); |
| let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty); |
| wfcx.register_wf_obligation(span, loc, ty.into()); |
| } |
| } |
| } |
| }) |
| } |
| |
| fn item_adt_kind(kind: &ItemKind<'_>) -> Option<AdtKind> { |
| match kind { |
| ItemKind::Struct(..) => Some(AdtKind::Struct), |
| ItemKind::Union(..) => Some(AdtKind::Union), |
| ItemKind::Enum(..) => Some(AdtKind::Enum), |
| _ => None, |
| } |
| } |
| |
| /// In a type definition, we check that to ensure that the types of the fields are well-formed. |
| fn check_type_defn<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item<'tcx>, all_sized: bool) { |
| let _ = tcx.representability(item.owner_id.def_id); |
| let adt_def = tcx.adt_def(item.owner_id); |
| |
| enter_wf_checking_ctxt(tcx, item.span, item.owner_id.def_id, |wfcx| { |
| let variants = adt_def.variants(); |
| let packed = adt_def.repr().packed(); |
| |
| for variant in variants.iter() { |
| // All field types must be well-formed. |
| for field in &variant.fields { |
| let field_id = field.did.expect_local(); |
| let hir::FieldDef { ty: hir_ty, .. } = |
| tcx.hir().get_by_def_id(field_id).expect_field(); |
| let ty = wfcx.normalize(hir_ty.span, None, tcx.type_of(field.did).subst_identity()); |
| wfcx.register_wf_obligation( |
| hir_ty.span, |
| Some(WellFormedLoc::Ty(field_id)), |
| ty.into(), |
| ) |
| } |
| |
| // For DST, or when drop needs to copy things around, all |
| // intermediate types must be sized. |
| let needs_drop_copy = || { |
| packed && { |
| let ty = tcx.type_of(variant.fields.raw.last().unwrap().did).subst_identity(); |
| let ty = tcx.erase_regions(ty); |
| if ty.has_infer() { |
| tcx.sess |
| .delay_span_bug(item.span, format!("inference variables in {:?}", ty)); |
| // Just treat unresolved type expression as if it needs drop. |
| true |
| } else { |
| ty.needs_drop(tcx, tcx.param_env(item.owner_id)) |
| } |
| } |
| }; |
| // All fields (except for possibly the last) should be sized. |
| let all_sized = all_sized || variant.fields.is_empty() || needs_drop_copy(); |
| let unsized_len = if all_sized { 0 } else { 1 }; |
| for (idx, field) in |
| variant.fields.raw[..variant.fields.len() - unsized_len].iter().enumerate() |
| { |
| let last = idx == variant.fields.len() - 1; |
| let field_id = field.did.expect_local(); |
| let hir::FieldDef { ty: hir_ty, .. } = |
| tcx.hir().get_by_def_id(field_id).expect_field(); |
| let ty = wfcx.normalize(hir_ty.span, None, tcx.type_of(field.did).subst_identity()); |
| wfcx.register_bound( |
| traits::ObligationCause::new( |
| hir_ty.span, |
| wfcx.body_def_id, |
| traits::FieldSized { |
| adt_kind: match item_adt_kind(&item.kind) { |
| Some(i) => i, |
| None => bug!(), |
| }, |
| span: hir_ty.span, |
| last, |
| }, |
| ), |
| wfcx.param_env, |
| ty, |
| tcx.require_lang_item(LangItem::Sized, None), |
| ); |
| } |
| |
| // Explicit `enum` discriminant values must const-evaluate successfully. |
| if let ty::VariantDiscr::Explicit(discr_def_id) = variant.discr { |
| let cause = traits::ObligationCause::new( |
| tcx.def_span(discr_def_id), |
| wfcx.body_def_id, |
| traits::MiscObligation, |
| ); |
| wfcx.register_obligation(traits::Obligation::new( |
| tcx, |
| cause, |
| wfcx.param_env, |
| ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable( |
| ty::Const::from_anon_const(tcx, discr_def_id.expect_local()), |
| )), |
| )); |
| } |
| } |
| |
| check_where_clauses(wfcx, item.span, item.owner_id.def_id); |
| }); |
| } |
| |
| #[instrument(skip(tcx, item))] |
| fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>) { |
| debug!(?item.owner_id); |
| |
| let def_id = item.owner_id.def_id; |
| let trait_def = tcx.trait_def(def_id); |
| if trait_def.is_marker |
| || matches!(trait_def.specialization_kind, TraitSpecializationKind::Marker) |
| { |
| for associated_def_id in &*tcx.associated_item_def_ids(def_id) { |
| struct_span_err!( |
| tcx.sess, |
| tcx.def_span(*associated_def_id), |
| E0714, |
| "marker traits cannot have associated items", |
| ) |
| .emit(); |
| } |
| } |
| |
| enter_wf_checking_ctxt(tcx, item.span, def_id, |wfcx| { |
| check_where_clauses(wfcx, item.span, def_id) |
| }); |
| |
| // Only check traits, don't check trait aliases |
| if let hir::ItemKind::Trait(_, _, _, _, items) = item.kind { |
| check_gat_where_clauses(tcx, items); |
| } |
| } |
| |
| /// Checks all associated type defaults of trait `trait_def_id`. |
| /// |
| /// Assuming the defaults are used, check that all predicates (bounds on the |
| /// assoc type and where clauses on the trait) hold. |
| fn check_associated_type_bounds(wfcx: &WfCheckingCtxt<'_, '_>, item: ty::AssocItem, span: Span) { |
| let bounds = wfcx.tcx().explicit_item_bounds(item.def_id); |
| |
| debug!("check_associated_type_bounds: bounds={:?}", bounds); |
| let wf_obligations = bounds.subst_identity_iter_copied().flat_map(|(bound, bound_span)| { |
| let normalized_bound = wfcx.normalize(span, None, bound); |
| traits::wf::predicate_obligations( |
| wfcx.infcx, |
| wfcx.param_env, |
| wfcx.body_def_id, |
| normalized_bound, |
| bound_span, |
| ) |
| }); |
| |
| wfcx.register_obligations(wf_obligations); |
| } |
| |
| fn check_item_fn( |
| tcx: TyCtxt<'_>, |
| def_id: LocalDefId, |
| ident: Ident, |
| span: Span, |
| decl: &hir::FnDecl<'_>, |
| ) { |
| enter_wf_checking_ctxt(tcx, span, def_id, |wfcx| { |
| let sig = tcx.fn_sig(def_id).subst_identity(); |
| check_fn_or_method(wfcx, ident.span, sig, decl, def_id); |
| }) |
| } |
| |
| fn check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_foreign_ty: bool) { |
| debug!("check_item_type: {:?}", item_id); |
| |
| enter_wf_checking_ctxt(tcx, ty_span, item_id, |wfcx| { |
| let ty = tcx.type_of(item_id).subst_identity(); |
| let item_ty = wfcx.normalize(ty_span, Some(WellFormedLoc::Ty(item_id)), ty); |
| |
| let mut forbid_unsized = true; |
| if allow_foreign_ty { |
| let tail = tcx.struct_tail_erasing_lifetimes(item_ty, wfcx.param_env); |
| if let ty::Foreign(_) = tail.kind() { |
| forbid_unsized = false; |
| } |
| } |
| |
| wfcx.register_wf_obligation(ty_span, Some(WellFormedLoc::Ty(item_id)), item_ty.into()); |
| if forbid_unsized { |
| wfcx.register_bound( |
| traits::ObligationCause::new(ty_span, wfcx.body_def_id, traits::WellFormed(None)), |
| wfcx.param_env, |
| item_ty, |
| tcx.require_lang_item(LangItem::Sized, None), |
| ); |
| } |
| |
| // Ensure that the end result is `Sync` in a non-thread local `static`. |
| let should_check_for_sync = tcx.static_mutability(item_id.to_def_id()) |
| == Some(hir::Mutability::Not) |
| && !tcx.is_foreign_item(item_id.to_def_id()) |
| && !tcx.is_thread_local_static(item_id.to_def_id()); |
| |
| if should_check_for_sync { |
| wfcx.register_bound( |
| traits::ObligationCause::new(ty_span, wfcx.body_def_id, traits::SharedStatic), |
| wfcx.param_env, |
| item_ty, |
| tcx.require_lang_item(LangItem::Sync, Some(ty_span)), |
| ); |
| } |
| }); |
| } |
| |
| #[instrument(level = "debug", skip(tcx, ast_self_ty, ast_trait_ref))] |
| fn check_impl<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| item: &'tcx hir::Item<'tcx>, |
| ast_self_ty: &hir::Ty<'_>, |
| ast_trait_ref: &Option<hir::TraitRef<'_>>, |
| constness: hir::Constness, |
| ) { |
| enter_wf_checking_ctxt(tcx, item.span, item.owner_id.def_id, |wfcx| { |
| match ast_trait_ref { |
| Some(ast_trait_ref) => { |
| // `#[rustc_reservation_impl]` impls are not real impls and |
| // therefore don't need to be WF (the trait's `Self: Trait` predicate |
| // won't hold). |
| let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().subst_identity(); |
| let trait_ref = wfcx.normalize( |
| ast_trait_ref.path.span, |
| Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)), |
| trait_ref, |
| ); |
| let trait_pred = ty::TraitPredicate { |
| trait_ref, |
| constness: match constness { |
| hir::Constness::Const => ty::BoundConstness::ConstIfConst, |
| hir::Constness::NotConst => ty::BoundConstness::NotConst, |
| }, |
| polarity: ty::ImplPolarity::Positive, |
| }; |
| let mut obligations = traits::wf::trait_obligations( |
| wfcx.infcx, |
| wfcx.param_env, |
| wfcx.body_def_id, |
| &trait_pred, |
| ast_trait_ref.path.span, |
| item, |
| ); |
| for obligation in &mut obligations { |
| if let Some(pred) = obligation.predicate.to_opt_poly_trait_pred() |
| && pred.self_ty().skip_binder() == trait_ref.self_ty() |
| { |
| obligation.cause.span = ast_self_ty.span; |
| } |
| } |
| debug!(?obligations); |
| wfcx.register_obligations(obligations); |
| } |
| None => { |
| let self_ty = tcx.type_of(item.owner_id).subst_identity(); |
| let self_ty = wfcx.normalize( |
| item.span, |
| Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)), |
| self_ty, |
| ); |
| wfcx.register_wf_obligation( |
| ast_self_ty.span, |
| Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)), |
| self_ty.into(), |
| ); |
| } |
| } |
| |
| check_where_clauses(wfcx, item.span, item.owner_id.def_id); |
| }); |
| } |
| |
| /// Checks where-clauses and inline bounds that are declared on `def_id`. |
| #[instrument(level = "debug", skip(wfcx))] |
| fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id: LocalDefId) { |
| let infcx = wfcx.infcx; |
| let tcx = wfcx.tcx(); |
| |
| let predicates = tcx.predicates_of(def_id.to_def_id()); |
| let generics = tcx.generics_of(def_id); |
| |
| let is_our_default = |def: &ty::GenericParamDef| match def.kind { |
| GenericParamDefKind::Type { has_default, .. } |
| | GenericParamDefKind::Const { has_default } => { |
| has_default && def.index >= generics.parent_count as u32 |
| } |
| GenericParamDefKind::Lifetime => unreachable!(), |
| }; |
| |
| // Check that concrete defaults are well-formed. See test `type-check-defaults.rs`. |
| // For example, this forbids the declaration: |
| // |
| // struct Foo<T = Vec<[u32]>> { .. } |
| // |
| // Here, the default `Vec<[u32]>` is not WF because `[u32]: Sized` does not hold. |
| for param in &generics.params { |
| match param.kind { |
| GenericParamDefKind::Type { .. } => { |
| if is_our_default(param) { |
| let ty = tcx.type_of(param.def_id).subst_identity(); |
| // Ignore dependent defaults -- that is, where the default of one type |
| // parameter includes another (e.g., `<T, U = T>`). In those cases, we can't |
| // be sure if it will error or not as user might always specify the other. |
| if !ty.has_param() { |
| wfcx.register_wf_obligation( |
| tcx.def_span(param.def_id), |
| Some(WellFormedLoc::Ty(param.def_id.expect_local())), |
| ty.into(), |
| ); |
| } |
| } |
| } |
| GenericParamDefKind::Const { .. } => { |
| if is_our_default(param) { |
| // FIXME(const_generics_defaults): This |
| // is incorrect when dealing with unused substs, for example |
| // for `struct Foo<const N: usize, const M: usize = { 1 - 2 }>` |
| // we should eagerly error. |
| let default_ct = tcx.const_param_default(param.def_id).subst_identity(); |
| if !default_ct.has_param() { |
| wfcx.register_wf_obligation( |
| tcx.def_span(param.def_id), |
| None, |
| default_ct.into(), |
| ); |
| } |
| } |
| } |
| // Doesn't have defaults. |
| GenericParamDefKind::Lifetime => {} |
| } |
| } |
| |
| // Check that trait predicates are WF when params are substituted by their defaults. |
| // We don't want to overly constrain the predicates that may be written but we want to |
| // catch cases where a default my never be applied such as `struct Foo<T: Copy = String>`. |
| // Therefore we check if a predicate which contains a single type param |
| // with a concrete default is WF with that default substituted. |
| // For more examples see tests `defaults-well-formedness.rs` and `type-check-defaults.rs`. |
| // |
| // First we build the defaulted substitution. |
| let substs = InternalSubsts::for_item(tcx, def_id.to_def_id(), |param, _| { |
| match param.kind { |
| GenericParamDefKind::Lifetime => { |
| // All regions are identity. |
| tcx.mk_param_from_def(param) |
| } |
| |
| GenericParamDefKind::Type { .. } => { |
| // If the param has a default, ... |
| if is_our_default(param) { |
| let default_ty = tcx.type_of(param.def_id).subst_identity(); |
| // ... and it's not a dependent default, ... |
| if !default_ty.has_param() { |
| // ... then substitute it with the default. |
| return default_ty.into(); |
| } |
| } |
| |
| tcx.mk_param_from_def(param) |
| } |
| GenericParamDefKind::Const { .. } => { |
| // If the param has a default, ... |
| if is_our_default(param) { |
| let default_ct = tcx.const_param_default(param.def_id).subst_identity(); |
| // ... and it's not a dependent default, ... |
| if !default_ct.has_param() { |
| // ... then substitute it with the default. |
| return default_ct.into(); |
| } |
| } |
| |
| tcx.mk_param_from_def(param) |
| } |
| } |
| }); |
| |
| // Now we build the substituted predicates. |
| let default_obligations = predicates |
| .predicates |
| .iter() |
| .flat_map(|&(pred, sp)| { |
| #[derive(Default)] |
| struct CountParams { |
| params: FxHashSet<u32>, |
| } |
| impl<'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for CountParams { |
| type BreakTy = (); |
| |
| fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if let ty::Param(param) = t.kind() { |
| self.params.insert(param.index); |
| } |
| t.super_visit_with(self) |
| } |
| |
| fn visit_region(&mut self, _: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { |
| ControlFlow::Break(()) |
| } |
| |
| fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { |
| if let ty::ConstKind::Param(param) = c.kind() { |
| self.params.insert(param.index); |
| } |
| c.super_visit_with(self) |
| } |
| } |
| let mut param_count = CountParams::default(); |
| let has_region = pred.visit_with(&mut param_count).is_break(); |
| let substituted_pred = ty::EarlyBinder::new(pred).subst(tcx, substs); |
| // Don't check non-defaulted params, dependent defaults (including lifetimes) |
| // or preds with multiple params. |
| if substituted_pred.has_non_region_param() || param_count.params.len() > 1 || has_region |
| { |
| None |
| } else if predicates.predicates.iter().any(|&(p, _)| p == substituted_pred) { |
| // Avoid duplication of predicates that contain no parameters, for example. |
| None |
| } else { |
| Some((substituted_pred, sp)) |
| } |
| }) |
| .map(|(pred, sp)| { |
| // Convert each of those into an obligation. So if you have |
| // something like `struct Foo<T: Copy = String>`, we would |
| // take that predicate `T: Copy`, substitute to `String: Copy` |
| // (actually that happens in the previous `flat_map` call), |
| // and then try to prove it (in this case, we'll fail). |
| // |
| // Note the subtle difference from how we handle `predicates` |
| // below: there, we are not trying to prove those predicates |
| // to be *true* but merely *well-formed*. |
| let pred = wfcx.normalize(sp, None, pred); |
| let cause = traits::ObligationCause::new( |
| sp, |
| wfcx.body_def_id, |
| traits::ItemObligation(def_id.to_def_id()), |
| ); |
| traits::Obligation::new(tcx, cause, wfcx.param_env, pred) |
| }); |
| |
| let predicates = predicates.instantiate_identity(tcx); |
| |
| let predicates = wfcx.normalize(span, None, predicates); |
| |
| debug!(?predicates.predicates); |
| assert_eq!(predicates.predicates.len(), predicates.spans.len()); |
| let wf_obligations = predicates.into_iter().flat_map(|(p, sp)| { |
| traits::wf::predicate_obligations( |
| infcx, |
| wfcx.param_env.without_const(), |
| wfcx.body_def_id, |
| p, |
| sp, |
| ) |
| }); |
| let obligations: Vec<_> = wf_obligations.chain(default_obligations).collect(); |
| wfcx.register_obligations(obligations); |
| } |
| |
| #[instrument(level = "debug", skip(wfcx, span, hir_decl))] |
| fn check_fn_or_method<'tcx>( |
| wfcx: &WfCheckingCtxt<'_, 'tcx>, |
| span: Span, |
| sig: ty::PolyFnSig<'tcx>, |
| hir_decl: &hir::FnDecl<'_>, |
| def_id: LocalDefId, |
| ) { |
| let tcx = wfcx.tcx(); |
| let mut sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig); |
| |
| // Normalize the input and output types one at a time, using a different |
| // `WellFormedLoc` for each. We cannot call `normalize_associated_types` |
| // on the entire `FnSig`, since this would use the same `WellFormedLoc` |
| // for each type, preventing the HIR wf check from generating |
| // a nice error message. |
| let arg_span = |
| |idx| hir_decl.inputs.get(idx).map_or(hir_decl.output.span(), |arg: &hir::Ty<'_>| arg.span); |
| |
| sig.inputs_and_output = |
| tcx.mk_type_list_from_iter(sig.inputs_and_output.iter().enumerate().map(|(idx, ty)| { |
| wfcx.normalize( |
| arg_span(idx), |
| Some(WellFormedLoc::Param { |
| function: def_id, |
| // Note that the `param_idx` of the output type is |
| // one greater than the index of the last input type. |
| param_idx: idx.try_into().unwrap(), |
| }), |
| ty, |
| ) |
| })); |
| |
| for (idx, ty) in sig.inputs_and_output.iter().enumerate() { |
| wfcx.register_wf_obligation( |
| arg_span(idx), |
| Some(WellFormedLoc::Param { function: def_id, param_idx: idx.try_into().unwrap() }), |
| ty.into(), |
| ); |
| } |
| |
| check_where_clauses(wfcx, span, def_id); |
| |
| check_return_position_impl_trait_in_trait_bounds( |
| wfcx, |
| def_id, |
| sig.output(), |
| hir_decl.output.span(), |
| ); |
| |
| if sig.abi == Abi::RustCall { |
| let span = tcx.def_span(def_id); |
| let has_implicit_self = hir_decl.implicit_self != hir::ImplicitSelfKind::None; |
| let mut inputs = sig.inputs().iter().skip(if has_implicit_self { 1 } else { 0 }); |
| // Check that the argument is a tuple |
| if let Some(ty) = inputs.next() { |
| wfcx.register_bound( |
| ObligationCause::new(span, wfcx.body_def_id, ObligationCauseCode::RustCall), |
| wfcx.param_env, |
| *ty, |
| tcx.require_lang_item(hir::LangItem::Tuple, Some(span)), |
| ); |
| } else { |
| tcx.sess.span_err( |
| hir_decl.inputs.last().map_or(span, |input| input.span), |
| "functions with the \"rust-call\" ABI must take a single non-self tuple argument", |
| ); |
| } |
| // No more inputs other than the `self` type and the tuple type |
| if inputs.next().is_some() { |
| tcx.sess.span_err( |
| hir_decl.inputs.last().map_or(span, |input| input.span), |
| "functions with the \"rust-call\" ABI must take a single non-self tuple argument", |
| ); |
| } |
| } |
| } |
| |
| /// Basically `check_associated_type_bounds`, but separated for now and should be |
| /// deduplicated when RPITITs get lowered into real associated items. |
| #[tracing::instrument(level = "trace", skip(wfcx))] |
| fn check_return_position_impl_trait_in_trait_bounds<'tcx>( |
| wfcx: &WfCheckingCtxt<'_, 'tcx>, |
| fn_def_id: LocalDefId, |
| fn_output: Ty<'tcx>, |
| span: Span, |
| ) { |
| let tcx = wfcx.tcx(); |
| let Some(assoc_item) = tcx.opt_associated_item(fn_def_id.to_def_id()) else { |
| return; |
| }; |
| if assoc_item.container != ty::AssocItemContainer::TraitContainer { |
| return; |
| } |
| fn_output.visit_with(&mut ImplTraitInTraitFinder { |
| wfcx, |
| fn_def_id, |
| depth: ty::INNERMOST, |
| seen: FxHashSet::default(), |
| }); |
| } |
| |
| // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): Even with the new lowering |
| // strategy, we can't just call `check_associated_item` on the new RPITITs, |
| // because tests like `tests/ui/async-await/in-trait/implied-bounds.rs` will fail. |
| // That's because we need to check that the bounds of the RPITIT hold using |
| // the special substs that we create during opaque type lowering, otherwise we're |
| // getting a bunch of early bound and free regions mixed up... Haven't looked too |
| // deep into this, though. |
| struct ImplTraitInTraitFinder<'a, 'tcx> { |
| wfcx: &'a WfCheckingCtxt<'a, 'tcx>, |
| fn_def_id: LocalDefId, |
| depth: ty::DebruijnIndex, |
| seen: FxHashSet<DefId>, |
| } |
| impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> { |
| type BreakTy = !; |
| |
| fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<!> { |
| let tcx = self.wfcx.tcx(); |
| if let ty::Alias(ty::Opaque, unshifted_opaque_ty) = *ty.kind() |
| && self.seen.insert(unshifted_opaque_ty.def_id) |
| && let Some(opaque_def_id) = unshifted_opaque_ty.def_id.as_local() |
| && let opaque = tcx.hir().expect_item(opaque_def_id).expect_opaque_ty() |
| && let hir::OpaqueTyOrigin::FnReturn(source) | hir::OpaqueTyOrigin::AsyncFn(source) = opaque.origin |
| && source == self.fn_def_id |
| { |
| let opaque_ty = tcx.fold_regions(unshifted_opaque_ty, |re, _depth| { |
| match re.kind() { |
| ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReError(_) => re, |
| r => bug!("unexpected region: {r:?}"), |
| } |
| }); |
| for (bound, bound_span) in tcx |
| .explicit_item_bounds(opaque_ty.def_id) |
| .subst_iter_copied(tcx, opaque_ty.substs) |
| { |
| let bound = self.wfcx.normalize(bound_span, None, bound); |
| self.wfcx.register_obligations(traits::wf::predicate_obligations( |
| self.wfcx.infcx, |
| self.wfcx.param_env, |
| self.wfcx.body_def_id, |
| bound, |
| bound_span, |
| )); |
| // Set the debruijn index back to innermost here, since we already eagerly |
| // shifted the substs that we use to generate these bounds. This is unfortunately |
| // subtly different behavior than the `ImplTraitInTraitFinder` we use in `param_env`, |
| // but that function doesn't actually need to normalize the bound it's visiting |
| // (whereas we have to do so here)... |
| let old_depth = std::mem::replace(&mut self.depth, ty::INNERMOST); |
| bound.visit_with(self); |
| self.depth = old_depth; |
| } |
| } |
| ty.super_visit_with(self) |
| } |
| } |
| |
| const HELP_FOR_SELF_TYPE: &str = "consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, \ |
| `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one \ |
| of the previous types except `Self`)"; |
| |
| #[instrument(level = "debug", skip(wfcx))] |
| fn check_method_receiver<'tcx>( |
| wfcx: &WfCheckingCtxt<'_, 'tcx>, |
| fn_sig: &hir::FnSig<'_>, |
| method: ty::AssocItem, |
| self_ty: Ty<'tcx>, |
| ) { |
| let tcx = wfcx.tcx(); |
| |
| if !method.fn_has_self_parameter { |
| return; |
| } |
| |
| let span = fn_sig.decl.inputs[0].span; |
| |
| let sig = tcx.fn_sig(method.def_id).subst_identity(); |
| let sig = tcx.liberate_late_bound_regions(method.def_id, sig); |
| let sig = wfcx.normalize(span, None, sig); |
| |
| debug!("check_method_receiver: sig={:?}", sig); |
| |
| let self_ty = wfcx.normalize(span, None, self_ty); |
| |
| let receiver_ty = sig.inputs()[0]; |
| let receiver_ty = wfcx.normalize(span, None, receiver_ty); |
| |
| if tcx.features().arbitrary_self_types { |
| if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) { |
| // Report error; `arbitrary_self_types` was enabled. |
| e0307(tcx, span, receiver_ty); |
| } |
| } else { |
| if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, false) { |
| if receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) { |
| // Report error; would have worked with `arbitrary_self_types`. |
| feature_err( |
| &tcx.sess.parse_sess, |
| sym::arbitrary_self_types, |
| span, |
| format!( |
| "`{receiver_ty}` cannot be used as the type of `self` without \ |
| the `arbitrary_self_types` feature", |
| ), |
| ) |
| .help(HELP_FOR_SELF_TYPE) |
| .emit(); |
| } else { |
| // Report error; would not have worked with `arbitrary_self_types`. |
| e0307(tcx, span, receiver_ty); |
| } |
| } |
| } |
| } |
| |
| fn e0307(tcx: TyCtxt<'_>, span: Span, receiver_ty: Ty<'_>) { |
| struct_span_err!( |
| tcx.sess.diagnostic(), |
| span, |
| E0307, |
| "invalid `self` parameter type: {receiver_ty}" |
| ) |
| .note("type of `self` must be `Self` or a type that dereferences to it") |
| .help(HELP_FOR_SELF_TYPE) |
| .emit(); |
| } |
| |
| /// Returns whether `receiver_ty` would be considered a valid receiver type for `self_ty`. If |
| /// `arbitrary_self_types` is enabled, `receiver_ty` must transitively deref to `self_ty`, possibly |
| /// through a `*const/mut T` raw pointer. If the feature is not enabled, the requirements are more |
| /// strict: `receiver_ty` must implement `Receiver` and directly implement |
| /// `Deref<Target = self_ty>`. |
| /// |
| /// N.B., there are cases this function returns `true` but causes an error to be emitted, |
| /// particularly when `receiver_ty` derefs to a type that is the same as `self_ty` but has the |
| /// wrong lifetime. Be careful of this if you are calling this function speculatively. |
| fn receiver_is_valid<'tcx>( |
| wfcx: &WfCheckingCtxt<'_, 'tcx>, |
| span: Span, |
| receiver_ty: Ty<'tcx>, |
| self_ty: Ty<'tcx>, |
| arbitrary_self_types_enabled: bool, |
| ) -> bool { |
| let infcx = wfcx.infcx; |
| let tcx = wfcx.tcx(); |
| let cause = |
| ObligationCause::new(span, wfcx.body_def_id, traits::ObligationCauseCode::MethodReceiver); |
| |
| let can_eq_self = |ty| infcx.can_eq(wfcx.param_env, self_ty, ty); |
| |
| // `self: Self` is always valid. |
| if can_eq_self(receiver_ty) { |
| if let Err(err) = wfcx.eq(&cause, wfcx.param_env, self_ty, receiver_ty) { |
| infcx.err_ctxt().report_mismatched_types(&cause, self_ty, receiver_ty, err).emit(); |
| } |
| return true; |
| } |
| |
| let mut autoderef = Autoderef::new(infcx, wfcx.param_env, wfcx.body_def_id, span, receiver_ty); |
| |
| // The `arbitrary_self_types` feature allows raw pointer receivers like `self: *const Self`. |
| if arbitrary_self_types_enabled { |
| autoderef = autoderef.include_raw_pointers(); |
| } |
| |
| // The first type is `receiver_ty`, which we know its not equal to `self_ty`; skip it. |
| autoderef.next(); |
| |
| let receiver_trait_def_id = tcx.require_lang_item(LangItem::Receiver, Some(span)); |
| |
| // Keep dereferencing `receiver_ty` until we get to `self_ty`. |
| loop { |
| if let Some((potential_self_ty, _)) = autoderef.next() { |
| debug!( |
| "receiver_is_valid: potential self type `{:?}` to match `{:?}`", |
| potential_self_ty, self_ty |
| ); |
| |
| if can_eq_self(potential_self_ty) { |
| wfcx.register_obligations(autoderef.into_obligations()); |
| |
| if let Err(err) = wfcx.eq(&cause, wfcx.param_env, self_ty, potential_self_ty) { |
| infcx |
| .err_ctxt() |
| .report_mismatched_types(&cause, self_ty, potential_self_ty, err) |
| .emit(); |
| } |
| |
| break; |
| } else { |
| // Without `feature(arbitrary_self_types)`, we require that each step in the |
| // deref chain implement `receiver` |
| if !arbitrary_self_types_enabled |
| && !receiver_is_implemented( |
| wfcx, |
| receiver_trait_def_id, |
| cause.clone(), |
| potential_self_ty, |
| ) |
| { |
| return false; |
| } |
| } |
| } else { |
| debug!("receiver_is_valid: type `{:?}` does not deref to `{:?}`", receiver_ty, self_ty); |
| // If the receiver already has errors reported due to it, consider it valid to avoid |
| // unnecessary errors (#58712). |
| return receiver_ty.references_error(); |
| } |
| } |
| |
| // Without `feature(arbitrary_self_types)`, we require that `receiver_ty` implements `Receiver`. |
| if !arbitrary_self_types_enabled |
| && !receiver_is_implemented(wfcx, receiver_trait_def_id, cause.clone(), receiver_ty) |
| { |
| return false; |
| } |
| |
| true |
| } |
| |
| fn receiver_is_implemented<'tcx>( |
| wfcx: &WfCheckingCtxt<'_, 'tcx>, |
| receiver_trait_def_id: DefId, |
| cause: ObligationCause<'tcx>, |
| receiver_ty: Ty<'tcx>, |
| ) -> bool { |
| let tcx = wfcx.tcx(); |
| let trait_ref = ty::TraitRef::new(tcx, receiver_trait_def_id, [receiver_ty]); |
| |
| let obligation = traits::Obligation::new(tcx, cause, wfcx.param_env, trait_ref); |
| |
| if wfcx.infcx.predicate_must_hold_modulo_regions(&obligation) { |
| true |
| } else { |
| debug!( |
| "receiver_is_implemented: type `{:?}` does not implement `Receiver` trait", |
| receiver_ty |
| ); |
| false |
| } |
| } |
| |
| fn check_variances_for_type_defn<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| item: &hir::Item<'tcx>, |
| hir_generics: &hir::Generics<'_>, |
| ) { |
| let ty = tcx.type_of(item.owner_id).subst_identity(); |
| if tcx.has_error_field(ty) { |
| return; |
| } |
| |
| let ty_predicates = tcx.predicates_of(item.owner_id); |
| assert_eq!(ty_predicates.parent, None); |
| let variances = tcx.variances_of(item.owner_id); |
| |
| let mut constrained_parameters: FxHashSet<_> = variances |
| .iter() |
| .enumerate() |
| .filter(|&(_, &variance)| variance != ty::Bivariant) |
| .map(|(index, _)| Parameter(index as u32)) |
| .collect(); |
| |
| identify_constrained_generic_params(tcx, ty_predicates, None, &mut constrained_parameters); |
| |
| // Lazily calculated because it is only needed in case of an error. |
| let explicitly_bounded_params = LazyCell::new(|| { |
| let icx = crate::collect::ItemCtxt::new(tcx, item.owner_id.def_id); |
| hir_generics |
| .predicates |
| .iter() |
| .filter_map(|predicate| match predicate { |
| hir::WherePredicate::BoundPredicate(predicate) => { |
| match icx.to_ty(predicate.bounded_ty).kind() { |
| ty::Param(data) => Some(Parameter(data.index)), |
| _ => None, |
| } |
| } |
| _ => None, |
| }) |
| .collect::<FxHashSet<_>>() |
| }); |
| |
| for (index, _) in variances.iter().enumerate() { |
| let parameter = Parameter(index as u32); |
| |
| if constrained_parameters.contains(¶meter) { |
| continue; |
| } |
| |
| let param = &hir_generics.params[index]; |
| |
| match param.name { |
| hir::ParamName::Error => {} |
| _ => { |
| let has_explicit_bounds = explicitly_bounded_params.contains(¶meter); |
| report_bivariance(tcx, param, has_explicit_bounds); |
| } |
| } |
| } |
| } |
| |
| fn report_bivariance( |
| tcx: TyCtxt<'_>, |
| param: &rustc_hir::GenericParam<'_>, |
| has_explicit_bounds: bool, |
| ) -> ErrorGuaranteed { |
| let span = param.span; |
| let param_name = param.name.ident().name; |
| let mut err = error_392(tcx, span, param_name); |
| |
| let suggested_marker_id = tcx.lang_items().phantom_data(); |
| // Help is available only in presence of lang items. |
| let msg = if let Some(def_id) = suggested_marker_id { |
| format!( |
| "consider removing `{}`, referring to it in a field, or using a marker such as `{}`", |
| param_name, |
| tcx.def_path_str(def_id), |
| ) |
| } else { |
| format!("consider removing `{param_name}` or referring to it in a field") |
| }; |
| err.help(msg); |
| |
| if matches!(param.kind, hir::GenericParamKind::Type { .. }) && !has_explicit_bounds { |
| err.help(format!( |
| "if you intended `{0}` to be a const parameter, use `const {0}: usize` instead", |
| param_name |
| )); |
| } |
| err.emit() |
| } |
| |
| impl<'tcx> WfCheckingCtxt<'_, 'tcx> { |
| /// Feature gates RFC 2056 -- trivial bounds, checking for global bounds that |
| /// aren't true. |
| #[instrument(level = "debug", skip(self))] |
| fn check_false_global_bounds(&mut self) { |
| let tcx = self.ocx.infcx.tcx; |
| let mut span = self.span; |
| let empty_env = ty::ParamEnv::empty(); |
| |
| let predicates_with_span = tcx.predicates_of(self.body_def_id).predicates.iter().copied(); |
| // Check elaborated bounds. |
| let implied_obligations = traits::elaborate(tcx, predicates_with_span); |
| |
| for (pred, obligation_span) in implied_obligations { |
| // We lower empty bounds like `Vec<dyn Copy>:` as |
| // `WellFormed(Vec<dyn Copy>)`, which will later get checked by |
| // regular WF checking |
| if let ty::PredicateKind::WellFormed(..) = pred.kind().skip_binder() { |
| continue; |
| } |
| // Match the existing behavior. |
| if pred.is_global() && !pred.has_late_bound_vars() { |
| let pred = self.normalize(span, None, pred); |
| let hir_node = tcx.hir().find_by_def_id(self.body_def_id); |
| |
| // only use the span of the predicate clause (#90869) |
| |
| if let Some(hir::Generics { predicates, .. }) = |
| hir_node.and_then(|node| node.generics()) |
| { |
| span = predicates |
| .iter() |
| // There seems to be no better way to find out which predicate we are in |
| .find(|pred| pred.span().contains(obligation_span)) |
| .map(|pred| pred.span()) |
| .unwrap_or(obligation_span); |
| } |
| |
| let obligation = traits::Obligation::new( |
| tcx, |
| traits::ObligationCause::new(span, self.body_def_id, traits::TrivialBound), |
| empty_env, |
| pred, |
| ); |
| self.ocx.register_obligation(obligation); |
| } |
| } |
| } |
| } |
| |
| fn check_mod_type_wf(tcx: TyCtxt<'_>, module: LocalDefId) { |
| let items = tcx.hir_module_items(module); |
| items.par_items(|item| tcx.ensure().check_well_formed(item.owner_id)); |
| items.par_impl_items(|item| tcx.ensure().check_well_formed(item.owner_id)); |
| items.par_trait_items(|item| tcx.ensure().check_well_formed(item.owner_id)); |
| items.par_foreign_items(|item| tcx.ensure().check_well_formed(item.owner_id)); |
| } |
| |
| fn error_392( |
| tcx: TyCtxt<'_>, |
| span: Span, |
| param_name: Symbol, |
| ) -> DiagnosticBuilder<'_, ErrorGuaranteed> { |
| let mut err = struct_span_err!(tcx.sess, span, E0392, "parameter `{param_name}` is never used"); |
| err.span_label(span, "unused parameter"); |
| err |
| } |
| |
| pub fn provide(providers: &mut Providers) { |
| *providers = Providers { check_mod_type_wf, check_well_formed, ..*providers }; |
| } |
